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CHEMICAL TECHNOLOGY
BY RUDOLF WAGNER, PH. D.,
PROFESSOR OF CHEMICAL TECHNOLOGY AT THE UNIVERSITY OF WURTZBURG.
Translated and Edited from the Eighth German Edition,
with Extensive Additions,
BY WILLIAM CROOKES, F. R. S.
WITH 336 ILLUSTRATIONS.
NEW YORK:
D. APPLETON AND COMPANY,
549 & 551 Broadway.
1872.
TRANSLATOR'S PREFACE.
THE several Editions of Professor RUDOLF WAGNER'S "Handbuch der Chemischen
Technologie" have succeeded each other so rapidly that no apology is needed in
offering a translation to the public.
There is little to be said as to the arrangement. Improvements in Technological
processes that have appeared since the publication of the Eighth German Edition
have been added during translation. Only when necessary have Foreign weights
and measures been stated in English equivalents; where the point has been one of
comparison, the weights have been left unaltered. The Metrical System has in
some cases been of great service in avoiding the repetition of tiresome distinctions
between English and Prussian grain weights, English and Bavarian foot measure,
&c. The formulæ have been subjected to careful revision, and are molecular
throughout. Indeed, every care has been taken to merit the confidence of the
manufacturer and of the student.
Under the head of Metallurgical Chemistry, the latest methods of preparing Iron,
Cobalt, Nickel, Copper, Copper Salts, Lead and Tin and their Salts, Bismuth, Zinc,
Zinc Salts, Cadmium, Antimony, Arsenic, Mercury, Platinum, Silver, Gold, Man-
ganates, Aluminum, and Magnesium, are described. The various applications of
the Voltaic Current to Electro-Metallurgy follow under this division. The Prepara-
tion of Potash and Soda Salts, the Manufacture of Sulphuric Acid, and the Recovery
of Sulphur from Soda-waste, of course occupy prominent places in the consideration
of chemical manufactures. It is difficult to over-estimate the mercantile value of
Mond's process, as well as the many new and important applications of
Bisulphide of Carbon. The Manufacture of Soap will be found to include much
detail. The Technology of Glass, Stoneware, Limes, and Mortars, will present
much of interest to the builder and engineer. The Technology of Vegetable Fibres
has been considered to include the preparation of Flax, Hemp, Cotton, as well
as Paper Making; while the applications of Vegetable Products will be found
to include Sugar-boiling, Wine and Beer Brewing, the Distillation of Spirits,
the Baking of Bread, the Preparation of Vinegar, the Preservation of Wood, &c.
299705
ነ
TRANSLATOR'S PREFACE.
Dr. WAGNER gives much information in reference to the production of Potash
from Sugar residues. The use of Baryta Salts is also fully described, as well as the
Preparation of Sugar from Beet-roots. Tanning, the Preservation of Meat, Milk,
&c., the Preparation of Phosphorus and Animal Charcoal, are considered as
belonging to the Technology of Animal Products. The Preparation of the Materials
for Dyeing has necessarily required much space; while the final sections of the
book have been devoted to the Technology of Heating and Illumination.
We cannot let this work pass out of our hands without expressing the hope
that, at no distant date, Chairs of Technology will be founded in all our Univer-
sities, and that the subject will be included in the curriculum of every large school
LONDON, May, 1872.
AUTHOR'S PREFACE TO THE EIGHTH EDITION.
THE Eighth Edition of my "Chemischen Technologie" having followed the Seventh
within two years, but few words of introduction are necessary.
The arrangement of the subject-matter in former Editions has essentially been
left unaltered, with the exceptions that I have brought the consideration of the
materials and products of Chemical Industry, and the Technology of Glass and of
Stoneware, in former Editions arranged as one section, under distinct headings
The various processes of Chemical Manufacture have had much detail added. The
descriptions of the Technological Preparation of Alkali and Ammoniacal Salts,
as well as of the Tar-colours, have in consequence of the extended application
of these products, been much enlarged. The Chemical formulæ are molecular.
throughout.
Of the present Edition translations will be made into English by Mr. WILLIAM
CROOKES, of London, and into French by Professor L. GAUTIER, of Melle, Deux-
Sèvres. A translation into Dutch of part of the Seventh Edition that has recently
appeared has been made without my permission or that of my publishers.
The First Edition of this work, written whilst I held the position of Private Tutor
in Chemistry to the Philosophical Faculty to the High-School of Leipsic, appeared
in September, 1850. The Second in May, 1853, and the Third Edition in July,
1856, were presented to the public during my Professorship of Technological
Chemistry in the Imperial Industrial Schools of Nuremburg. The later Editions
appeared-
The Fourth in May, 1859,
Fifth in May, 1862,
""
Sixth in October, 1865,
""
Seventh in March, 1868,
during intervals in my official duties in Wurtzburg; and in these I have been much
assisted by the contributions and suggestions of many friends, to whom I now tender
my sincere thanks.
UNIVERSITY OF WURTZBURG,
December 10th, 1870.
DR. RUDOLF WAGNER.
CONTENTS.
DIVISION I.
CHEMICAL METALLURGY, ALLOYS, AND PREPARATIONS MADE AND OBTAINED FROM
METALS.
*
6.
Ores, 4. Dressing of
The Mixing of the
GENERAL OBSERVATIONS. Meaning of the term Metallurgy, 4.
Ores, 5. Preparation of Ores, 5. Smelting of the Ores,
Smelt, 7.
Products of the Smelting Operation, 7. Slags, 7.
IRON.-Its Occurrence, 8.
PIG OR CRUDE IRON.-Extraction of Iron from its Ores, 9. Theory of the Iron Extraction
Process, 10. Blast-furnace Process, 1o. Description of the Blast-furnace, II. The
Blowing Engine and Blast, 12. Course of the Smelting Process, 13. Chemical Pro-
cess going on in the Interior of the Blast-furnace, 13. Temperature in the Blast-
furnace at Different Points, 15. Blast-furnace Gases, 15. Application of these
Gases to the Manufacture of Sal-ammoniac, 16. Crude Iron, Cast-iron, 16. White
Cast-iron, 16. Grey Cast-iron, 16. Statistics concerning the Production of Crude
Iron, 18. Iron Foundry Work--Re-smelting Crude Cast-iron, 18. Shaft or Cupola
Furnace, 18. Reverberatory Furnace, 18. Making the Moulds, 19. Annealing,
Tempering, 20. Enamelling of Cast-iron, 20.
MALLEABLE, BAR, OR WROUGHT-IRON.-Bar Iron, Refined Iron, 20. German Iron-refining
Process, 21. Swedish Refining Process, 22. The Puddling Process, 22. Puddling
Furnace, 22. Heating with Gases, 24. Refining of Iron by Mechanical Means, 24.
Boiler-plate Rolling, 24. Iron Wire Manufacture, 25. Properties of Bar Iron, 26.
STEEL.-Steel, 26. Rough Steel, 27. Steel Making by Imparting Carbon to Wrought-
iron, 28. Refined Steel, Shear Steel, 29. Cast-steel, 29. Steel made from Malleable
and Crude Cast-iron, 29. Surface Steel Hardening, 29. Properties of Steel, 29.
Tempering, 30. Steel and other Metals, 30. Damascene or Wootz Steel, 30. Sidero-
graphy or Steel Engraving, 31. Statistics of Steel Production, 31.
IRON PREPARATIONS.-Copperas-Green Vitriol, 31. Preparation of Green Vitriol as a By-
product in Alum Works, 32. Preparation of Green Vitriol in Beds, 32. Green
Vitriol from the Residues of Pyrites Distillation, 32. Green Vitriol from Metallic
Iron and Sulphuric Acid, 32. From Spathic Iron Ore, 32. Uses of Green Vitriol, 32.
Iron Minium, 32. Yellow Prussiate of Potassa, 33. Applications of the Yellow
Prussiate, 35. Red Prussiate, 35. Cyanide of Potassium, 35. Berlin Blue, 36. Old
Method of Preparing Prussian Blue, 36. Recent Methods of Preparing Berlin Blue,
36. Turnbull's Blue, 37. Berlin Blue as a By-product of the Manufactures of Coal-
gas and Animal Charcoal, 37. Soluble Berlin-Blue, 37.
COBALT.-Metallic Cobalt, 37. Cobalt Colours, 37. Smalt, 38. Cobalt Speiss, 38. Appli-
cations of Smalt, 38. Cobalt Ultramarine, 38. Cæruleum, 39. Rinmann's or Cobalt
Green, 39. Chemically pure Protoxide of Cobalt, 39. Nitrate of Protoxide of
Cobalt and Potassa, 39. Cobalt Bronze, 39.
NICKEL.—Nickel and its Ores, 39. Preparation of Nickel from its Ores, 40. The Concen-
tration-Smelting of the Nickel Ores, 40. Preparation of Metallic Nickel, or of Alloys
of Nickel and Copper, 41. Properties of Nickel, 43.
COPPER.--Where it Occurs, and How, 43. Ores of Copper, 43. Mode of Treating the
Copper Ores for the Purpose of Extracting the Metal, 44. The Working-up of the
Copper Ores in the Shaft Furnace, 44. Refining the Copper, 46. Refining on the
Hearth, 46. Refining Copper in Large Quantities, 46. Liquation Process, 47.
English Mode of Copper Smelting, 47. Calcining or Roasting the Ores, 48. Smelting
the Ores, 48. Roasting or Calcining the Coarse Metal, 49. Smelting for White
Metal, 49. Blistered or Crude Copper, 49. Refining the Blistered Metal, 49. Mode
of Obtaining Copper from Oxidised Ores, 49. Hydro-Metallurgical Method of Prepa-
ring Copper, 49. Copper obtained by Voltaic Electricity, 50. Properties of Copper,
50. Alloys of Copper, 51. Bronze, 51. Brass, 52. German or Nickel Silver, 53.
Amalgam of Copper, 54.
49
viii
CONTENTS.
PREPARATIONS OF COPPER.-Blue Vitriol, Sulphate of Copper, 54. Preparation of Blue
Vitriol, 54. Double Vitriol, 55. Applications of Blue Vitriol, 56. Copper Pigments, 56.
Brunswick Green, 56. Bremen Blue or Bremen Green, 56. Casselmann's Green, 57.
Mineral Green and Blue, 57. Oil Blue, 57. Schweinfurt Green or Emerald Green,
58. Stannate of Oxide of Copper, 58. Verdigris, 58. Applications of Verdigris, 59.
LEAD.-Occurrence of Lead, 59. Method of Obtaining Lead by Precipitation, 59.
Obtaining Lead by Calcination, 60. Raw Lead, 61. Revivification of Litharge, 61.
Properties of Lead, 62. Applications of Metallic Lead, 62. Manufacture of Shot, 62.
Alloys of Lead, 62.
PREPARATIONS OF LEAD.-Oxide of Lead, 63. Massicot, 63.
Minium, Red-lead, 63.
Superoxide of Lead, 64. Combinations of Oxide of Lead, 64. Acetate of Lead, 64.
Chromate of Lead, 64. Neutral or Yellow Chromate of Potassa, 64. Applications of
the Chromates of Potassa, 65. Chrome Yellow or Chromate of Lead, 66. Chrome
Red, 66. Chrome Oxide or Chrome Green, 67. Chrome Alum, 67. White-lead, 67.
English Method of Manufacturing White-lead, 68. French Method of Preparing White-
lead, 69. Apparatus used in White-lead Manufacture at Clichy, 69. White-lead from
Sulphate of Lead, 70. Theory of Preparing White-lead, 70. White-lead from Chloride
of Lead, 70. Basic Chloride of Lead as a Substitute for White-lead, 71. Properties of
White-lead, 71. Adulteration of White-lead, 72. Applications of White-lead, 72.
TIN.-Occurrence and Mode of Obtaining the Metal, 73. Properties of Tin, 74,
Tinning, 75. Tinning of Copper, Brass, and Malleable Iron, 75. Tinned Sheet-iron,
75. Moiré Metallique, 75.
Tinsalt, 75. Nitrate of
Liquation-Furnace, 76.
PREPARATIONS OF TIN.-Aurum Musivum, Mosaic Gold, 75.
Tin or Physic, 76. Stannate of Soda, 76.
BISMUTH.--Occurrence and Mode of Obtaining, 76. Bismuth
Properties of Bismuth, 77. Applications of Bismuth, 77.
ZINC.-Occurrence of Zinc, 77. Method of Extracting Zinc, 77. Distillation of Zinc in
Muffles, 78. Distillation in Tubes, 79. Distillation of Zinc in Crucibles, 79. Mode
of Obtaining Zinc from Sulphuret of Zinc, the Black-Jack of the English Miners, 79.
Properties of Zinc, 79. Application of Zinc, 80.
PREPARATIONS OF ZINC.-Zinc-white, 80. White Vitriol, Sulphate of Zinc, 81. Chromate
of Zinc, 81. Chloride of Zinc, 81.
CADMIUM, 82.
ANTIMONY.-Antimony, 82. Properties of Antimony, 84.
ANTIMONIAL PREPARATIONS IN TECHNICAL USE.-Oxide of Antimony, 84. Black Sulphuret
of Antimony, 85. Neapolitan Yellow, 85. Antimony Cinnabar, 85.
ARSENIC.-Arsenic, 85. Arsenious Acid, 85. Arsenic Acid, 86. Sulphurets of Arsenic,
86. Realgar, 87. Orpiment, 87. Rusma, 87.
QUICKSILVER OR MERCURY.-Occurrence and Mode of Obtaining Mercury, 87. Method of
Extracting Mercury pursued in Idria, 87. Spanish Method of Extracting Mercury,
89. Method of Decomposing the Ore by the Aid of other Substances, go. Proper-
ties of Mercury, 91. Applications of Mercury, 91.
PREPARATIONS OF MERCURY.-Mercurial Compounds, gr. Chloride of Mercury, 91. Cin-
nabar, 91. Fulminating Mercury, 92. Percussion-Caps, 93.
PLATINUM.-Occurrence of Platinum, 93. Platinum Ores, 93. Wollaston's Method of
Extracting Platinum from its Ores, 94. Method of Deville and Debray, 95. Proper-
ties of Platinum, 95. Black Platinum, Spongy Platinum, 95. Hammered or Cast
Platinum, and its Applications, 95. Platinum Alloys, 96. Elayl-platino-chloride, 96.
SILVER.-Silver and its Occurrence, 96. Extraction of Silver from its Ores, 96. Smelting
for Silver directly, 97. Extraction of Silver by Amalgamation, 97. European
Amalgamation Process, 97. American Amalgamation Process, 98. Augustin's
Method of Silver Extraction, 99. Ziervogel's Method, 99. Sundry Hydro-Metallur-
gical Methods of Extracting Silver, 99. Extraction of Silver by the Dry Process, 100.
Mode of Preparing the Lead-containing Silver, 100. Refining Process, 100. Pattin-
son's Method, 101. Reduction by Means of Zinc, 102. The Ultimate Refining of
Silver, 102. Chemically Pure Silver, 102. Properties of Silver, 102. Alloys of
Silver, 103. Silver Alloy for Plate, &c., 103. Silver Assay, 103. Dry Assay, 103.
Wet Assay, 104. Hydrostatical Assay, 104. Silvering, 104. Igneous or Fire
Silvering, 104. Silvering in the Cold, 104. Silvering by the
Nitrate of Silver, 105. Marking Ink, 105.
GOLD.-Occurrence and Mode of Extracting Gold, 105. Mode of Extracting Gold, 105.
Extraction by Means of Mercury, 106. Smelting for Gold, 106. Treating with
Alkali, 106. Extraction of Gold from other Metallic Ores, 106. Extraction of Gold
from Poor Minerals, 106. Refining Gold, 106. By Means of Sulphuret of Antimony,
106. By the Aid of Sulphur, 107. Cementation Process, 107. Quartation, 107.
Wet Way, 105.
CONTENTS.
ix
Refining Gold by the Aid of Sulphuric Acid, 107. Chemically Pure Gold, 108. Pro-
perties of Gold, 108. Alloys of Gold, 109. Colour of Gold, 109. Testing the Fine-
ness of Gold, 109. Applications of Gold, 110. Gilding, 110. Gilding with Gold-
leaf, 110. Gilding by the Cold Process, 110. Gilding by the Wet Way, 110. Fire-
gilding, 110. Cassius's Purple, 111. Salts of Gold, III.
MANGANESE AND ITS PREPARATIONS.-Manganese, III. Testing the Quality of Manganese,
III.
PERMANGANATE OF POTASSA.-Permanganate of Potassa, 112.
ALUMINIUM. Preparation of Aluminium, 113. Properties of Aluminium, 113. Applica-
tions, 114.
MAGNESIUM.-Magnesium, 114.
ELECTRO-METALLURGY.-Application of Galvanism, 114. Electrolytic Law, 114. Electro-
typing, 115. Reproduction of Copper-plate Engravings, 115. Deposition of Metals,
115. Electro-plating with Gold and Silver, 115. Gold Solution, 116. Silver Solu-
tion, 116. Copper Solution, 116. Zinc and Tin Solution, 116. Etching by Gal-
vanism, 117. Metallochromy, 117. Electro-stereotyping, 117. Glyphography, 117.
Galvanography, 117.
DIVISION II.
CRUDE MATERIALS AND PRODUCTS OF CHEMICAL INDUSTRY.
CARBONATE OF POTASSA.-Sources whence Potassa is Derived, 118. Potassa Salts from the
Stassfurt Salt Minerals, 118. Mode of Obtaining Potassa from Felspar, 122.
Potassa Salts from Sea-water, 122. Potash from the Ashes of Plants, 122. Potash
from Molasses, 125. Potassa Salts from Sea-weeds, 129. Potassa Salts from Suint,
132. Caustic Potassa, 133.
SALTPETRE, NITRATE OF POTASSA.-Saltpetre, 134. Occurrence of Native Saltpetre, 134.
Mode of Obtaining Saltpetre, 135. Treatment of the Ripe Saltpetre Earth, 135.
Preparation of Raw Lye, 136. Breaking up the Raw Lye, 136. Boiling down the
Raw Lye, 136. Refining the Crude Saltpetre, 137. Preparation of Nitrate of
Potassa from Chili Saltpetre, 138. Testing the Saltpetre, 140. Quantitative Estima-
tion of the Nitric Acid in Saltpetre, 140. Uses of Saltpetre, 141. Nitrate of Soda, 141.
NITRIC ACID.—Methods of Manufacturing Nitric Acid, 142. Bleaching Nitric Acid, 143.
Condensation of the Nitric Acid, 144. Other Methods of Nitric Acid Manufacture, 145.
Density of Nitric Acid, 146. Fuming Nitric Acid, 147. Uses of Nitric Acid, 147.
TECHNOLOGY OF THE EXPLOSIVE COMPOUNDs-GunpowdeR, AND THE CHEMISTRY OF FIREWORKS,
OR PYROTECHNY.-On Gunpowder in General, 148. Manufacture of Gunpowder, 148.
Mechanical Operations of Powder Manufacture, 149. Pulverising the Ingredients,
149. Mixing the Ingredients, 149. Caking or Pressing the Powder, 150. Granula-
tion of the Cake and Sorting the Powder, 150. Polishing the Granulated Powder,
150. Drying the Powder, 151. Sifting the Dust from the Powder, 151. Properties
of Gunpowder, 151. Composition of Gunpowder, 152. Products of the Combustion
of Powder, 153. New Kinds of Blasting Powder, 154. Testing the Strength of Gun-
powder, 154. White Gunpowder, 154. Chemical Principles of Pyrotechny, 155.
The more commonly used Firework Mixtures, 156. Gunpowder, 156. Saltpetre and
Sulphur Mixture, 156. Grey-coloured Mixture, 156. Chlorate of Potassa Mixtures,
156. Friction Mixtures, Percussion Powders, 156. Mixture for Igniting the Cart-
ridges of Needle-guns, 157. Heat-producing Mixtures, 157. Coloured Fires, 157.
NITROGLYCERINE.-Nitroglycerine, 158. Nobel's Dynamite, 160.
GUN-COTTON.-Gun-cotton, 160. Properties of Gun-cotton, 161. Gun-cotton as a Substi-
tute for Gunpowder, 162. Other Uses of Gun-cotton, 162. Collodion, 162.
COMMON SALT.-Occurrence, 163. Method of Preparing Common Salt from Sea-water, 163.
Method of Obtaining Common Salt in Salines, 164. By Freezing, 165. By Artificial
Evaporation, 165. Rock-salt, 165. Mode of Working Rock-salt, 167. Mode of
Preparation of Common Salt from Brine, 168.
Enriching by Gradation, 168. Faggot Gradation, 168.
Properties of Common Salt, 169. Uses of Common
Working Salt Springs, 167.
167.
Concentrating the Brine, 168.
Boiling down the Brine, 168.
Salt, 170.
MANUFACTURE OF SODA-NATIVE SODA.-Occurrence of Native Soda, 170.
SODA FROM PLANTS OR SODA-ASH.-Soda from Soda Plants and from Beet-root, 171.
SODA PREPARED BY CHEMICAL PROCESSES. -Soda from Chemical Processes, 172. Leblanc's
Process, 172. Sulphate or Decomposing Furnace, 172. New Decomposition Fur-
nace, 173. Conversion of the Sulphate into Crude Soda, 174. Soda Furnace with
X
CONTENTS.
Rotatory Hearth, 175. Lixiviation of the Crude Soda, 176. Evaporation of the
Ley, 180. Theory of Leblanc's Process, 183. Utilisation of Soda Waste, 184.
Schaffner's Sulphur Regeneration Process, 185. Sundry Methods of Preparing Soda
from Sulphate of Soda, 187. Direct Conversion of Common Salt into Soda, 188.
Soda from Cryolite, 188. Soda from Nitrate of Soda, 189. Caustic Soda, 189. New
Methods of Caustic Soda Manufacture, 189. Bicarbonate of Soda, 190.
PREPARATION OF IODINE AND BROMINE.-Preparation of Iodine, 191. Preparation from
Kelp, 191.
Stanford and Moride's Method of Preparing Iodine from Carbonised Sea-
weed, 192. Preparation of Iodine from Chili Saltpetre, 192. Properties and Uses of
Iodine, 193. Preparation of Bromine, 193.
SULPHUR.-Sulphur, 194. Smelting and Refining Sulphur, 194. Lamy's Refining Appa-
ratus, 196. Roll Sulphur, 197. Flowers of Sulphur, 197. Preparation of Sulphur
from Pyrites, 197. Preparation of Sulphur by Roasting Copper Pyrites, 198. Sul-
phur obtained as a By-product of Gas Manufacture, 198. Sulphur from Soda-
Waste, 198. Production of Sulphur by the Reaction of Sulphuretted Hydrogen upon
Sulphurous Acid, 198. Sulphur obtained by the Reaction of Sulphurous Acid on
Charcoal, 198. By Heating of Sulphuretted Hydrogen, 198. Properties and Uses of
Sulphur, 199.
SULPHUROUS AND HYPOSULPHUROUS ACID.-Sulphurous Acid, 199.
Hyposulphite of Soda, 201.
MANUFACTURE OF SULPHURIC ACID.-Sulphuric Acid, 201. Fuming Sulphuric Acid, 202.
Ordinary or English Sulphuric Acid, 203. Present Manufacture of Sulphuric Acid,
203. Use of Pyrites for the Preparation of Sulphurous Acid, 206. Chamber Acid,
206. Concentration of Sulphuric Acid, 206. Concentration in Leaden Pans, 207.
Concentration in Glass Retorts, 208. Other Methods of Sulphuric Acid Manufac-
ture, 208. Properties of Sulphuric Acid, 209.
Sulphite of Lime, 201.
SULPHIDE OF CARBON.-Sulphide of Carbon, 210. Carbon, 211. Chloride of Sulphur, 211.
HYDROCHLORIC ACID AND GLAUBER'S SALT, OR SULPHATE OF SODA.-Hydrochloric Acid, 211.
Properties of Hydrochloric Acid, 213. Uses of Hydrochloric Acid, 213. Glauber's
Salt, 213.
Uses of Sulphate of Soda, 214. Bisulphate of Soda, 214.
BLEACHING-POWDER AND HYPOCHLORITES.-Chlorine, 214. Preparation of Bleaching-
powder, 214. Preparation of Chlorine without Manganese, 214. Apparatus for Pre-
paring Chlorine, 216. Condensing Apparatus, 217. Utilisation of the Chlorine
Production Residues, 218. Dunlop's Process, 218. Gatty's Process, 219. Hofmann's
Process, 219. Weldon's Process, 219. Other Methods of Utilising the Residues, 219.
Theory of the Formation of Bleaching-powder, 220. Properties of Bleaching-
powder, 220. Chlorimetry, 221. Gay-Lussac's Chlorimetric Method, 221. Perrot's
Test, 221. Dr. Wagner's Method, 222. Chlorimetrical Degrees, 222. Alkaline
Hypochlorites, 223. Chlorate of Potassa, 223.
ALKALIMETRY. — Alkalimetry, 224. Volumetric Method, 224. Mohr's Method, 225.
Gruneberg's Method of Estimating the Value of Potash, 226.
AMMONIA AND AMMONIACAL SALTS.—Ammonia, 226. Preparation of Liquid Ammonia, 227.
Inorganic Sources of Ammonia, 228. Organic Sources of Ammonia, 229. Ammonia
from Gas-water, 230. Mallet's Apparatus, 230. Rose's Apparatus, 232. Lunge's
Apparatus, 232. Ammonia from Lant, 234. Ammonia from Bones, 235. Ammonia
as a By-product of Beet-root Sugar Manufacture, 236. Technically Important
Ammoniacal Salts, 236. Sulphate of Ammonia, 238. Carbonate of Ammonia, 238.
Nitrate of Ammonia, 238.
SOAP MAKING.-Soap, 239. Raw Materials of Soap Boiling, 239. Ley, 242. Theory of Saponi-
fication, 242. Chief Varieties of Soap, 243. Olive Oil Soap, 244. Oleic Acid Soap, 245.
Resin Tallow Soaps, 245. Fulling Soaps, 245. Soft Soap, 246. Various other
Soaps, 247. Toilet Soaps, 247. Transparent Soap, 248. Uses of Soap, 248. Soap
Tests, 248. Insoluble Soap, 249.
BORIC OR BORACIC ACID, AND BORAX.-Theory of the Formation of the Native Boracic Acid,
250. The Production of Boracic Acid, 250. Properties and Uses of Boracic Acid,
251. Borax, 252. Borax from Boracic Acid, 252. Purifying the Borax, 254. Octa-
hedral Borax, 255. Uses of Borax, 255. Diamond Boron or Adamantine, 256.
PRODUCTION OF ALUM, SULPHATES OF ALUMINA, AND ALUMINATES.-Alum, 256. Material of
Alum Manufacture, 256. Preparation of Alum from Alum-stone, 257. Preparation
of Alum from Alum-shale and Alum-earths, 257. Alum-shale, 257. Alum-earths,
257. Preparation of Alum, 257. Roasting the Alum-earths, 257. Lixiviation, 257.
Evaporation of the Ley, 257. Alum Flour, 258. Washing and Re-crystallisation,
258. Preparation of Alum from Clay, 258. Preparation of Alum from Cryolite, 258.
Preparation of Alum from Bauxite, 259. Preparation of Alum from Blast-furnace
Slag, 260. Alum from Felspar, 260. Properties of Alum, 260. Ammonia-alum, 260.
CONTENTS.
xi
Soda-alum, 26г. Sulphate of Alumina, 261. Aluminate of Soda, 262. Uses of
Alum and of Sulphate of Alumina, 263. Acetate of Alumina, 263.
ULTRAMARINE.—Ultramarine, 264. Native Ultramarine, 264.
Raw Materials, 264. Manufacture of Ultramarine, 265.
marine, 266. Preparation of Silica Ultramarine, 267.
267. Properties of Ultramarine, 267.
DIVISION III.
Artificial Ultramarine, 264.
Preparation of Soda Ultra-
Constitution of Ultramarine,
TECHNOLOGY OF GLASS, CERAMIC WARE, GYPSUM, LIME, AND MORTAR
+
GLASS MANUFACTURE. — Definition and General Properties of Glass, 268. Classification
of the Various Kinds of Glass, 268. Raw Materials used in Glass Making, 269.
Utilisation of Refuse Glass, 270. Bleaching, 270. The Melting Vessel, 270. The
Glass Oven, 271.
Preparation of the Material, and Melting, 274. Drying the
Materials, 274. Melting the Glass Material, 275. Clear-melting, 275. Cold-stoking,
275. Defects in Glass, 276. Various Kinds of Glass, 276. Plate or Window Glass,
276. Tools, 277. Crown Glass, 277. Sheet Glass or Cylinder. Glass, 278. Plate
Glass, 279. The Melting and Clearing, 280. Casting and Cooling, 281. Polishing,
281. Silvering, 281. Silvering by Precipitation, 281. Platinising, 282. Bottle
Glass, 282. Pressed and Cast-glass, 283. Water-glass, 283. Stereochromy, 285.
Crystal Glass, 285. Polishing, 286. Optical Glass, 286. Strass, 288. Coloured
Glass and Glass Staining, 289. Glass Painting, 289. Enamel, Bone Glass, Alabaster
Glass, 290. Cryolite Glass, 291. Ice Glass, 291.. Hæmatinon Astralite, 291. Aven-
turin Glass, 291. Glass Relief, 291. Filigree, or Reticulated Glass, 292. Millifiore
Work, 292. Glass Pearls, 292. Blown Pearls, 292. Hyalography, 292.
CERAMIC OR EARTHENWARE MANUFACTURE.-Clays and their Application-Felspar, 293.
Kaolin or Porcelain Clay, 293. The Technically Important Qualities of the Clays, 293.
Colour, 294. Plasticity, 294. Kinds of Clay, 294. Potter's Clay, 295. Walkerite,
295. Marl, 295. Loam, 296. Composition of Kaolin, 296. Kinds of Clay Ware, 296.
I. HARD PORCELAIN.-Grinding and Mixing the Material, 297. Drying the Mass, 298.
Kneading the Dried Mass, 298. The Moulding, 298. The Potter's Wheel, 298.
Moulding in Plaster-of-Paris Forms, 299. Casting, 299. Preparation of Porcelain
Articles without Moulds, 299. Glazing, 299. Drying the Porcelain, 299. Porcelain
Glaze, 300. Applying the Glaze, 300. Immersion, 300. Dusting, 300. Watering,
300. By Volatilisation or Smearing, 300. Lustres and Flowering Colours, 301. The
Capsule or Sagger, 301. The Porcelain Oven, 301. Emptying the Oven and Sorting
the Ware, 302, Faulty Ware, 302. Porcelain Painting, 302. Ornamenting the Por-
celain, 303. Bright Gilding, 303. Silvering and Platinising, 303. Lithophanie, 303.
II. TENDER PORCELAIN.-French Fritte Porcelain, 304. English Fritte Porcelain, 304.
Parian and Carrara, 304.
III. STONEWARE.-Stoneware, 305. Stoneware Ovens, 306. Lacquered Ware, 307.
IV. FAYENCE WARE.-Fayence Ware, 307. Ornamenting Fayence, 308. Flowing Colours,
309. Lustres, 309. Etruscan Vases, 309. Clay Pipes, 309. Water Coolers, 309.
V. COMMON POTTERY.-Common Pottery, 310. Burning, 310.
VI. BRICK AND TILE MAKING, &C.-Bricks, 310. Terra Cotta, 311.
Preparation of the Clays, 311. Moulding the Brick, 312.
Machinery, 312. Bricks from Dried Clay, 314. The Burning
Annular Kilns, 317. Field Burning, 318. Dutch Clinkers, 318.
Tiles, 318. Drain and Gutter Tiles, 318. Floating Bricks, 318. Fire-bricks, 319.
Sanitary Ware, 321. Crucibles, 321.
Brick Material, 311.
Brick Moulding by
of the Bricks, 315.
Roofing and Dutch
LIME AND LIME-BURNING.-Lime, 322. Properties, 322. Lime-Burning, 322. Occasional
or Periodic Kilns, 323. The Continuous Kilns, 324. Kilns for Burning Lime and
Bricks, 325. Properties of Lime, 325. Slaking Lime, 326. Uses of Lime, 326.
MORTAR.-Mortar, 326.
A. COMMON OR AIR-SETTING MORTAR.-Setting of the Mortar, 327.
B. HYDRAULIC MORTAR.-Hydraulic Mortar, 327. Cement, 327. Artificial Cements, 328.
Manufacture of Artificial Cement in Germany, 330. The Setting of Hydraulic
Mortars, 331.
GYPSUM AND ITS PREPARATION.-Occurrence, 333. Nature of Gypsum, 333. The Burning
of Gypsum, 333.
Kilns or Burning Ovens, 334. Grinding the Gypsum, 335. Uses
of Gypsum, 335. Gypsum Casts, 336. Hardening of Gypsum, 336.
xii
CONTENTS.
DIVISION IV.
VEGETABLE FIBRES AND THEIR TECHNICAL APPLICATION.
Water Cleansing, 339.
Tow or Tangled Fibre,
Linen, 340.
THE TECHNOLOGY OF VEGETABLE FIBRE-FLAX.-Flax, 338. Hot
Beating or Batting the Flax, 339. Combing the Flax, 340.
340. Flax Spinning, 340. Weaving the Linen Threads, 340.
HEMP.-Hemp, 340. Its Substitutes, 340.
COTTON.-Cotton, 342. Species of Cotton, 342. Cotton Spinning, 342. Fine Spinning,
343. Yarn, 343. Cotton Fabrics, 343. Substitutes for Cotton, 343. Detecting
Cotton in Linen Fabrics, 343.
PAPER MAKING.-History of Paper, 345. Materials of Paper Manufacture, 346. Sub-
stitute for Rags, 346. Mineral Additions to the Rags, 346. Manufacture of Paper by
Hand, 346. Cutting and Cleaning the Rags, 347. The Separation of the Rags for
Half-stuff and Whole-stuff, 347. Stamp Machine, 347. The Hollander, 347.
Bleaching the Pulp, 349. Antichlore, 349. Blueing, 350. Sizing, 350.
A. HAND PAPER.-Straining the Paper Sheets, 350. Pressing the Paper, 351. Drying the
Paper, 351. Sizing the Paper, 351. Preparing the Paper, 351. The Different
Kinds of Paper, 351.
B. MACHINE PAPER.-Manufacture of Machine Paper, 352. Paper Cutting Machine, 353.
C. PASTEBOARD AND OTHER PAPER. - Making Pasteboard, 353. Coloured Paper, 355.
Parchment Paper, 355.
STARCH.-Nature of Starch, 356. Sources of Starch, 357. Starch from Potatoes, 357.
Drying the Potato Starch, 358. Preparation of Wheat Starch, 358. Constituents
and Uses of Commercial Starch, 360. Rice Starch, Chesnut Starch, Cassava Starch,
Arrow-root, 360. Sago, 361. Dextrine, 361.
SUGAR MANUFACTURE.-History of Sugar, 362. Nature of Sugar, 362.
CANE SUGAR.-Sugar from the Sugar-cane, 364. Components of the Sugar-cane, 364.
Preparing the Raw Sugar from the Sugar-cane, 365. Varieties of Sugar, 366.
Molasses, 366. Refining the Sugar, 366. Production of Raw Sugar, 367.
BEET-ROOT SUGAR.-Its Nature, 367. Species of Beet, 367. Chemical Constituents of
the Beet. 368. Saccharimetry, 369. Mechanical Method, 369. Chemical Method,
369. Ferment Test, 370. Physical Method, 370. Preparation of Sugar from the
Beet, 370. The Residue, 372. Components of the Juice, 373. Other Methods of
De-Liming the Juice, 374. Purifying with Baryta, 374. The Filter, 375. Dumont's
Filter, 375. Evaporation Pans, 375. Vacuum Pans, 377. Evaporating the Juice,
380. Draining the Crystals, 381. The Centrifugal Drier, 381. Removing the Sugar
from the Form, 381. Beet Molasses, 382. Sugar-candy, 382.
Grape Sugar.—Grape Sugar, 383. Preparation of Grape Sugar, 384. Composition of
Starch Sugar, 386. Uses of Grape Sugar, 386.
FERMENTATION.--Fermentation, 386. Vinous Fermentation, 387. Yeast, 387. Condi-
tions of Alcoholic or Vinous Fermentation, 389.
WINE-MAKING.-Wine, 390. The Vine and its Cultivation, 390. Vintage, 390. The Pres-
sing of the Grapes, 391. The Centrifugal Machine, 391. Chemical Constituents of
the Must, 391. The Sugar of the Grape, 392. The Fermentation of the Grape
Juice, 393. Drawing Off and Casking the Wine, 393. Constituents of Wine, 393.
Maladies of Wines, 396. Ageing and Conservation of Wines, 397. Clearing or
Fining the Wine, 399. The Residue or Waste of Wine Making, 399. Effervescing
Wines, 399. The Improving of the Wine Must, 401.
BEER-BREWING.—Beer, 403. Materials of Beer-Brewing, 403. Hops, 404. Quality of the
Hops, 404. Substitutes for Hops, 405. Water, 405. The Ferment, 405. The Pro-
cess of Beer Brewing, 405. The Malting, 4v5. The Bruising of the Malt, 408.
Mashing, 408. Decoction Method, 409. Thick Mash Boiling, 409. Augsburg
Method, 410. Infusion Method, 410. Extractives of the Wort, 411. Boiling the
Wort, 411. Adding the Hops, 412. Cooling the Wort, 413. The Fermentation, 414.
Sedimentary Fermentation, 415. After-Fermentation in the Casks, 416. Surface-
Fermentation, 417. Steam-Brewing, 418. Constituents of Beer, 418. Beer-Testing,
420. Balling's Saccharometrical Beer Test, 420. Fuchs's Beer Test, 422.
By-pro-
ducts of the Brewing Process, 423.
PREPARATION OR DISTILLATION OF SPIRITS.-Alcohol, 424. Alcohol and its Technically
Important Properties, 424. Raw Materials of Spirit Manufacture, 425.
A. PREPARATION OF A VINOUS MASH.-Vinous Mash from Cereals, 426. The Bruising, 426.
The Mixing with Water, 426. The Cooling of the Mash, 426. The Fermentation of
CONTENTS.
xiii
the Mash, 427. Mash from Potatoes, 427. Mash with Sulphuric Acid, 428. The
Fermentation of the Potato Mash, 429. Mash from Roots, 429. Spirits from the
By-products of Sugar Manufacture, 430. Spirits from Wine and Marc, 430.
B. DISTILLATION OF THE VINOUS MASH.-Distillation of the Mash, 431. The Distilling
Apparatus, 432. Improved Distilling Apparatus, 432. Dorn's Apparatus, 433. Pis-
torius's Apparatus, 435.
Gall's Apparatus, 435. Schwarz's Apparatus, 436.
Siemens's Apparatus, 440.
Continuous Distilling Apparatus, 440. Tangier's Appa-
ratus, 443. Removing the Fusel Oils-Defuseling, 445. Yield of Alcohol, 446.
Alcoholometry, 447. Areometer, 447. Relation of Brandy Distilling to Agriculture,
448. The Residue or Wash, 448. Dry Yeast, 449. So-called Artificial Yeast, 450.
Vienna Yeast, 450. Duty on Spirits, 451.
BREAD BAKING.-Modes of Bread Making, 451.
The Details of Bread Baking, 451. The
Mixing of the Dough and the Kneading, 452. Kneading, 452. Kneading Machines,
453. The Oven, 454.
Substitutes for the Ferments, 456. Yield of Bread, 459.
Composition of Bread, 459. Impurities and Adulteration of Bread, 460.
THE MANUFACTURE OF VINEGAR.-Vinegar and its Origin, 460.
A. PREPARATION OF VINEGAR FROM ALCOHOLIC FLUIDS.-Vinegar from Alcohol, 461. Pheno-
mena of Vinegar Formation, 462. The Older Method of Vinegar Making, 462.
Quick Vinegar Making, 463. Vinegar from Sugar-beet, 466. Vinegar with the help
of Mycoderma Aceti, 466. Vinegar with the help of Platinum Black, 467. Testing
Vinegar, 467. Acetometry, 468.
B. PREPARATION OF VINEGAR FROM WOOD VINEGAR.-Wood Vinegar, 469. Purifying Wood
Vinegar, 471. Wood Spirit, 472.
THE PRESERVATION OF WOOD.-On the Durability of Wood in General, 472. Preservation
of Wood in Particular, 474. Drying Wood, 474. Elimination of the Constituents of
the Sap, 474. Air Drains, 475.
Air Drains, 475. Chemical Alteration of the Constituents of the Sap,
475. Mineralising Wood, 476. Boucherie's Method of Impregnation, 477.
TOBACCO.-Tobacco, 477. Chemical Composition of the Tobacco Leaf, 478. Manufacture
of Tobacco, 478. Smoking Tobacco, 479. Snuff, 480.
TECHNOLOGY OF ESSENTIAL OILS AND RESINS.-Essential Oils and Resins, 480. Prepara-
tion of Essential Oils, 481. Preparation of Essential Oils by Pressure, 481. Extrac-
tion of Essential Oils by Means of Fatty Oils, 481. Properties and Uses of
Essential Oils, 481. Perfumery, 481. Chemical Perfumes, 482. Preparation of
Cordials, 482. Resins, 483. Use of Resins as Sealing-wax, 483. Asphalte, 484.
Caoutchouc, 484. Solvents of Caoutchouc, 485. Properties and Use of India-rubber,
486. Vulcanised Caoutchouc, 486. Production and Consumption of Caoutchouc, 486.
Gutta-percha, 486. Solvents of Gutta-percha, 487. Uses of Gutta-percha, 487.
Mixture of Gutta-percha and Caoutchouc, 488. Varnishes, 488. Oil Varnishes,
488. Gold Size, 489. Printing Ink, 489. Oil Varnishes, 489. Spirit Varnish, 489.
Coloured Spirit Varnishes, 490. Turpentine Oil Varnishes, 490. Polishing the
Dried Varnish, 490. Pettenkofer's Process for Restoring Pictures, 490.
CEMENTS, LUTES, AND PUTTY.-Cements, 491. Lime Cements, 491. Oil Cements, 491.
Resin Cements, 492. Iron Cement, 493. Paste, 493.
DIVISION V.
ANIMAL SUBSTANCES AND THEIR INDUSTRIAL APPLICATION.
WOOLLEN INDUSTRY.—Origin and Properties of Wool, 494. Chemical Composition of Wool,
495. Properties of Wool, 497. Colour and Gloss, 497. Preparation of Wool, 497.
Wool Spinning, 498. I. Washing, 498. II. Dyeing, 498. III. Willowing or Devilling,
498. Oiling or Greasing, 498. V. The Carding, 498. VI. Roving, 499. Artificial
Wool, 499. Weaving the Cloth, 499. Washing and Milling the Bough Cloth, 499,
Teasling and Shearing the Cloth, 499. Dressing the Cloth, 499. Other Cloth
Fabrics, 500. Worsted Wool, 500.
SILK.-Silk, 501. Sericiculture-Varieties of Silkworms, 501.
503. The Throwing of Silk, 504. Conditioning or Testing
Boiling the Gum out of Silk, 504. Weaving of Silk, 505.
Silk from Wool and from Vegetable Fibre, 506.
TANNING.-Tanning, 508. Anatomy of Animal Skin, 508.
I. RED OR BARK-TANNING.-Tanning Materials, 509.
Manipulation of the Silk,
of Silk, 504. Scouring or
Means of Distinguishing
Oak Bark, 509.
Sumac, 510.
Dividivi, 511. Nut Galls, 511. Valonia Nuts, 511. Chinese Galls, 511. Cutch, 512.
Kino, 512. Estimation of the Value of the Tanning Materials, 512.
The Skins, 513.
The Several Operations, 513. Cleansing the Hides, 514. Cleansing the Flesh
ziv
CONTENTS.
Side, 514. Cleansing the Hair Side, 514. Stripping off the Hair, 515. Swelling the
Hides, 515. The Tanning, 516. Tanning in the Bark, 516. Tanning in Liquor, 517.
Quick Tanning, 517. Dressing or Currying the Leather, 518. Sole Leather, 518.
Upper Leather, 518. The Paring, 518. The Scraping or Smoothing, 518. Graining
the Leather, 519. Polishing with Pumice-stone, 519. Raising the Grain slightly
with Pommels of Cork, 519. Smoothing with Tawer's Softening Iron, 519. Rolling,
519. Finishing Off, 519. Greasing, 519. Yufts, Russia Leather, 520. Morocco
Leather, 520. Dressing Morocco Leather, 521. Cordwain, Cordovan Leather, 521.
Lacquered Leather, 521.
II. TAWING.-Tawing, Preparation of White Leather, 522. Common Tawing, 522. Hun-
garian Tawing Process, 524. Glove Leather, 524. Knapp's Leather, 525.
III. ŠAMIAN OR OIL-TAWING PROCESS.-Samian Tawing Process, 525. Parchment, 527.
Shagreen, 527.
GLUE BOILING.-General Observations, 528. Leather Glue, 529. Treating with Lime,
529. Boiling the Materials, 530. Fractioned Boiling, 530. Moulding, 531. Drying
the Glue, 531. Glue from Bones, 532. Liquid Glue, 533. Test for the Quality
of Glue 533. Isinglass, 535. Substitutes for Glue, and New Preparations obtained
from Glue, 536.
MANUFACTURE OF PHOSPHORUS.-General Properties, 537. Preparation of Phosphorus,
537. Burning of the Bones to Ash, 538. Decomposition of the Bone-ash by
Sulphuric Acid, 538. Distillation of Phosphorus, 539. Refining and Purifying the
Phosphorus, 540. Moulding the Refined Phosphorus, 541. Other Proposed Methods
of Preparing Phosphorus, 543. Fleck's Process, 543. Gentele, Gerland, Minary,
and Soudry's Methods of Preparing Phosphorus, 544. Properties of Phosphorus, 544.
Amorphous or Red Phosphorus, 545. Properties of Amorphous Phosphorus, 546.
REQUISITES FOR PRODUCING FIRE.-Generalities and History, 546. Manufacture of Lucifer
Matches, 548. The Preparation of the Wood Splints, 548. The Preparation of the
Combustible Composition, 549. Dipping and Drying the Splints, 550. Anti-
Phosphor Matches, 552. Wax or Vesta Matches, 553.
ANIMAL CHARCOAL.-Animal Charcoal, 553. Preparation of Bone-black, 553. Properties
of Bone-black, 554. Testing Bone-black, 554. Revivification (re-burning) of Char-
coal, 555. Substitutes for Bone-black, 555.
MILK.-Milk, 556. Whey, 557. Lactose, Sugar of Milk, 557.
becoming Sour, 557. Testing Milk, 557. Uses of Milk, 558.
Nature of Butter, 559.
MEAT.-Generalities, 562.
Boiling of Meat, 564.
drawal of Water, 565.
Cheese, 559.
Means to Prevent Milk
Butter, 558. Chemical
Constituents of Meat, 562. The Cooking of Meat, 563. The
Preservation of Meat, 564. Preservation of Meat by with-
Salting Meat, 565. Smoking or Curing Meat, 566.
DIVISION VI.
DYEING AND CALICO PRINTING.
ON DYEING AND PRINTING IN GENERAL.-Dyeing and Printing in General, 568. Dyes, 568.
Lake Pigments, 569. Colouring Materials, 569. The Coal-Tar Colours: Coal-Tar,
569. Benzol, 570. Nitro-benzol, 572. Aniline, 573.
I. ANTLINIE COLOURS.-Aniline Colours, 575. Aniline Red, 575.
Anilne Blue, 578. Aniline Green, 578. Aniline Yellow, 579.
Aniline Black, 579. Aniline Brown, 579.
Aniline Violet, 577.
Aniline Orange, 579.
II. CARBOLIC ACID COLOURS.-Carbolic Acid Dyes, 580. Picric Acid, 580. Phenicienne,
581. Grenate Brown, 581. Coralline, 581. Azuline, 581. Pigment Directly from
Nitro-benzol, 581.
III. NAPHTHALINE PIGMENTS.-Naphthaline, 581. Martius Yellow, 582. Magdala Red,
583. Naphthaline Blue and Naphthaline Violet, 583.
IV. ANTHRACEN PIGMENTS. -Anthracen Pigments, 584.
V. PIGMENTS FROM CINCHONINE.-Cinchoine Pigments, 585.
RED PIGMENTS OCCURRING IN PLANTS AND ANIMALS.-Red Dye Materials-Madder, 586.
Madder Lake, 587. Flowers of Madder, 587. Azale, 587. Garancine, 587. Garan-
ceux, 587. Colorine, 588. Brazil or Camwood, 588. Sandal Wood, 588. Safflower,
589. Cochenille or Cochineal, 589. Lac Dye, 590. Orchil and Persio, 590. Less
Important Red Dyes, 591.
BLUE DYE MATERIALS.-Indigo, 591. Properties of Indigo, 592. Testing Indigo, 592.
Berzelius's Indigo Test by Reduction, 593. Penny's Test, 593. Indigo Blue, 594.
Logwood or Campeachy, 594. Litmus, 594.
CONTENTS.
ΣΥ
YELLOW DYES.-Yellow-wood, Fustic, 595. Young Fustic, French Fustet, 595. Annatto
or Arnotto, 595. Yellow Berries or Simply Berries, 596. Turmeric, 596. Weld,
596. Quercitron Bark, 596. Brown, Green, and Black Dyes, 596.
BLEACHING.-Bleaching, 597. Bleaching of Silk, 599.
.
DYEING OF SPUN YARN AND WOVEN TEXTILE FABRICS.-Dyeing, 599. Mordants, 601.
Dyeing Woollen Fabrics, 601. Dyeing Wool Blue, 601. Indigo Blue, 602. Blue
Vats, 602. Saxony Blue, 603. Recovering Indigo from Rags, 604. Berlin or Prussian
Blue on Wool, 604. Dyeing Blue with Logwood and a Copper Salt, 604. Dyeing
Yellow, 604. Dyeing Wool Red, 605. Green Dyes, 605. Mixed Shades, 605. Black
Dyes, 605. White Cloth, 606. Silk Dyeing, 606. Calico Dyeing, 608. Turkey Red,
608. Dyeing Linen, 609.
THE PRINTING OF WOVEN FABRICS.-Printing of Woven Fabrics, 609. Mordants, 609.
Thickenings, 610. Resists, or Reserves, 610. Discharges, 611. Acid Discharges,
611. Oxidising Agents as Discharges, 611. Reducing Agents as Discharges, 611.
Calico Printing, 612. Topical or Surface Colours, 613.
Topical or Surface Colours, 613. Discharge Style, 614.
Aniline Printing, 614. Hotpressing, Finishing, and Dressing, 616. Printing Linen
Goods, 616. Printing Woollen Goods, 616. Printing Silk Goods, 616. Mandarin
Printing, 616. Bandanas. 616.
DIVISION VII.
THE MATERIALS AND APPARATUS FOR PRODUCING ARTIFICIAL LIGHT.
ARTIFICIAL ILLUMINATION IN GENERAL, 617. Flame, 618.
I. ARTIFICIAL LIGHT FROM CANDLES.-Light from Candles, 620. Manufacture of Stearine
Candles, 621. Preparation of Fatty Acids by Means of Lime, 621. Saponification
with Less Lime, 623. Saponification by Means of Sulphuric Acid, 624. Sapo-
nification with Water and High Pressure, 626. Manufacture of Fatty Acids by
Means of Superheated Steam and Subsequent Distillation, 627. Candle Making,
627. Moulding the Candles, 628. Tallow Candles, 629. Paraffin Candles, 630.
Candles from Fatty Acids, 631. Wax Candles, 631. Other Kinds of Wax, 632.
The Making of Wax Candles, 633. Sperm or Spermaceti Candles, 634. Glyce-
rine, 634.
II. ILLUMINATION BY MEANS OF LAMPS.-Illumination with Fluid Substances, 636. Puri-
fying or Refining the Oils, 636. Lamps, 636. Various Kinds of Lamps, 639.
Suction Lamps, 639. The Lamp with Constant Oil Level, 640. Pressure Lamps,
641. Mechanical Lamps, 642. Clockwork Lamp, 642. Moderateur or Moderator
Lamp, 642. Petroleum Oil and Paraffin Oil Lamps, 644.
III. GAS.-General Introduction and Historical Notes, 645. Raw Materials of Gas
Lighting, 646. Coal-Gas, 646. Products of the Distillation, 647. Manufacture of
Coal-Gas, 648. Retorts, 648. Mouth-piece and Lid of Retorts, 649. Retort Fur-
naces, 650. Charging the Retorts and Distillation, 650. The Hydraulic Main, 650.
Cooling or Condensing Apparatus, 652. The Scrubber, 653. Exhauster, 654.
Purifying Gas, 654: Gas Holders, 656. Distribution of Gas, 660. Hydraulic Valve,
661. Pressure Regulator, 661. Testing Illuminating Gas, 661. Methods of
Testing Illuminating Gas, 662. Gas Meters, 664. Burners, 665. Gas Lamps, 665.
By-Products of Coal-Gas Manufacture, 665. Composition of Coal-Gas, 668. Wood
Gas, 668. Method of Wood Gas Manufacture, 669. Wood Gas Burners, 670. Peat
Gas, 670. Water Gas, 671. Gillard's Gas, Platinum Gas, 672. Carburetted Water
Gas, 672. White's Hydrocarbon Process, 673. Leprince's Water Gas, Isoard's
Gas, 674. Baldamus and Grune's Gas, 674. Carburetted Gas, 674. Air Gas, 674.
Oil Gas, Resin Gas, 674. Gas from Suint, 675. Gas from Petroleum Oil, or Oil
from Bituminous Shales, 675. Petroleum Gas, 676. Resin Gas, 678. Lime-Light,
678. Tessie du Motay's Method of Illumination, 679. Magnesium Light, 679.
Chatham Light, 680. Electric Light, 680.
PARAFFIN AND SOLAR OR PETROLEUM OILS.-Paraffin Oils, 683. Manufacture of Paraffin,
683. Preparation of Paraffin from Petroleum, 684. Paraffin from Ozokerite and
Neftgil, 684. Paraffin from Bitumen, 685. Preparation of Paraffin by Dry Distilla-
tion, 685. Preparation of the Tar, 685. Condensation of the Vapours of the Tar,
686. Properties of Tar, 687. Mode of Operating with the Tar, 688. Distillation
of the Tar, 688. Treatment of the Products of Distillation, 689. Rectification of
the Crude Oils, 689. Refining of the Crude Paraffin, 690. Hubner's Method of
Preparing Paraffin, 690. Yield of Paraffin, 691. Brown-coal, 691. Properties of
Paraffin, 692. Paraffin Oil, 693. Preparation of Mineral Oil, 694.
xvi
CONTENTS.
PETROLEUM.—Petroleum Oil and its Occurrences, 695.
leum, 695. Refining of Crude Petroleum, 696.
Technology of Petroleum, 697.
DIVISION VIII.
Origin and Formation of Petro-
Constitution of Petroleum, 696.
FUEL AND HEATING APPARATUS.
Con-
A. FUEL.-Fuel, 698. Combustibility, 698. Inflammability, 698. Calorific Effect, 698.
Determination of Combustive Power, 699. Karmarsch's Evaporation Method, 699.
Berthier's Reduction Method, 700. Elementary Analysis, 700. Stromeyer's Test,
701.__ _Pyrometrical Calorific Test, 701. Mechanical Equivalent of Heat, 702.
WOOD.-Wood, 702. Constituents of Wood, 703. Heating Value of Wood, 704. Wood
Charcoal, 704. Carbonisation of Wood, 705. Carbonisation in Heaps, 705.
struction of the Heap, 705. Charcoal Burning, 706. Carbonisation in Beds, 706.
Carbonisation in Ovens or Kilns, 706. Carbonisation of Wood in Ovens, 708. Pro-
perties of Charcoal, 710. Composition of Wood Charcoal, 711. Combustibility and
Heating Effect, 711. Charbon-Roux; Torrified Charcoal, 711. Roasted Wood;
Bois-Roux, 712.
PEAT -Peat, 712. Drying Peat, 713. Heating Effect of Peat, 715.
Utilising Peat, 715.
CARBONISED PEAT.-Carbonised Peat, 715.
BROWN-COAL.--Brown-coal, 716. Brown-coal as Fuel, 717.
New Method of
PIT COAL, OR COAL.-Coal, 717. Accessory Constituents of Coal, 718. Classification of
Coals, 718. Anthracite, 719. Caking Coal, 719. Calorific Effect, 721. Evaporative
Effect of Coals, 721. Boghead Coal, 722.
PETROLEUM AS FUEL.-Petroleum as Fuel, 722.
COKE.-Coke, 723. Coking in Heaps, 724. Coking in Ovens, 724. Properties of Coke,
729. Composition of Coke and its Value as Fuel, 729.
ARTIFICIAL FUEL.-Artificial Fuel, 729. Peras, 729. Briquettes, 730.
GASEOUS FUEL.-Gaseous Fuel, 730. Gas for Heating Purposes, 731.
HEATING APPARATUS.-Warming, 731.
HEATING DWELLING HOUSES.-Heating Dwelling Houses, 732.
Direct Heating, 732.
Chimney Heating, 733. Stove Heating, 733. Iron Stoves, 734. Fire-clay Stoves,
734. Compound Stoves, 735. Air Heating, 737. Calorifiers, 738. Flue Heating,
739. Hot Water Heating, 739. Heating with Steam, 740. Combination of Steam
and Hot Water Heating, 740. Gas Heating, 740. Heating without Ordinary Fuel,
740.
BOILER HEATING AND CONSUMPTION OF SMOKE.-Boiler Heating, 740. Smoke Consuming
Apparatus, 741. Step Grate, 742. Etage, or Stage Grate, 743. Movable Grate,
743. Chain Grates, 743. Rotating Grate, 744. Improved Fuel Supply, 744. Pult
Fires, 744. Vogl's Grate, 744. Boquillon's Grate, 744. Apparatus of Cutler and
George, 744. Apparatus with Unequal Distribution, 744. Consumption of Smoke
by the Aid of Collateral Air Currents, 745. Gall's Fireplace, 745. Resumé, 745.
INTRODUCTION.
MAN's labour, considered from an economical point of view, is of a threefold kind,
being either productive, improving, or converting. We distinguish likewise between
the productions obtained from the soil taken in its widest sense, and between com-
merce and manufacturing industry.
The department of labour, the object of which is to prepare and render fit for use
the raw materials yielded by nature, is that which, in a more restricted sense, is
called manufacturing industry, and the description and elucidation of the methods
by which this object is attained is called technology, from réxvŋ and λóyos. Taken
in a general sense, this word would apply to all trades, arts, and manufactures,
whatsoever; exclusive, however, of actual artist's work-notwithstanding the
latter exceeds the industries in respect of the money-value of its productions—and
exclusive, also, of such trades as tailoring, dress- and shoe-making, in which only
certain commodities from materials that have been produced by manufacturing
industry are worked up.
Mining and quarrying operations, as well as commerce, do not belong to tech-
nology, because the former deal with the getting to hand of naturally existing '
materials, and the object of the latter is either the carrying and distributing of the
products from various parts of the world to the wholesale consumers, or the pro-
ducts of different kinds of one and the same country to the population thereof. Thẹ
position of some industries is somewhat difficult to define in this sense, for while
metallurgy and the knowledge of tools and machinery are undoubtedly an integral
portion of technology, taken in its widest sense, the construction of railways, roads,
and bridges, as well as shipbuilding, architecture, artillery science, &c., do not come
within the province of technology, but belong either to engineering science or are
specialities to be separately taught and described.
Technology is not a self-contained science which possesses its own peculiar doctrine
and foundation; it simply borrows the principles and experience obtained by
mechanical and natural sciences, always taking into consideration the best mode of
applying these principles to the preparation of raw materials to become objects suit-
able for use.
Technology is accordingly practical natural science, having for its
object the reduction of manufacturing industry to the natural principles upon which
it is based, and teaching the most advantageous methods and processes by which the
raw materials are prepared for use. Raw products, which are either in the con-
dition nature yields them, or which have already been in the hands of the manu-
2
2
CHEMICAL TECHNOLOGY.
facturer, are changed by the labour of men, either in their outward form only, or in
their inner composition, and upon this distinction is based the division of technology
into mechanical and chemical; the former division embraces such industries as have
only for their object the changing, altering, and modifying the form and shape of the
raw material, its inner composition remaining unaltered; as instances we quote the
joiner and carpenter working in wood, the making of iron rails, sheath metal, and
wire, the casting of iron, zinc, and alloys of copper into various objects, the spinning
and weaving of various fibres, flax, cotton, jute, to become materials of greater
value; also the manufacturing of paper from rags, of horn into combs, and bristles
into brushes, belong to this section.
Chemical technology, however, deals with the operations by which a raw material
is not only changed in its form, but especially as regards its nature: such, for instance,
is the case with the extraction of metals from their ores; the conversion of lead into
white-lead and sugar of lead (acetate of lead); the conversion of sulphate of baryta
into chloride of barium and baryta white (permanent or Chinese white); the conver-
sion of cryolite into sulphate of alumina, alum, and soda; the conversion of rock salt
into sulphate and carbonate of soda; the conversion of carnallite and kainite into
chloride and bromide of potassium, sulphate and carbonate of potassa; the conver-
sion of copper into verdigris and sulphate of copper; the manufacture of paraffin and
paraffin or crystal oils from peat, Boghead coal, and lignite; the preparation of kelp
and iodine from seaweeds; the manufacture of stearine candles (stearic acid properly)
and soap from oils and fats; the preparation of sugar and alcohol from starch; the
conversion of alcohol into vinegar; the brewing of beer from barley and hops; the
manufacture of pig-iron into malleable irou (puddling process), and the conversion of
malleable iron into steel; the production of gas, coke, and tar from coals; the extrac-
tion from the tar of such substances as benzol, carbolic acid, aniline, anthracen,
asphalte, naphthaline; the preparation of tar colours, as rosaniline, aniline blue,
Manchester yellow, Magdala red, alizarine, iodine green, picric acid, &c. In very
many cases, however, the preparation which the raw materials have to undergo
before fit for use is simultaneously, or at least consecutively, a mechanical
as well as a chemical process; for instance, in the manufacture of glass, sand,
potash, Glauber salt (sulphate of soda), carbonate of soda, and limestone, are first
fused together to form glass (a true salt, a silicate), and the soft mass is next wrought
in various ways to form window-glass, tumblers, bottles, &c. Another instance is the
manufacture of beet-root sugar, in the extraction of which the sugar itself is, it is
true, not altered or changed in any way (this being as much as possible avoided), but
the process of extraction is a combination of mechanical and chemical operations, the
latter bearing chiefly upon the purification of the sugar, so as to free it from adhering
foreign substances. The same observation applies to the manufacture of starch, to
tanning operations, also to the various processes of dyeing and calico printing.
The ceramic arts (that is to say, the manufacture of earthenware, pottery, china,
&c.), are generally included in chemical technology, although, in the production of
the objects alluded to, the mechanical operations and fine art processes predomi-
nate. Pyrotechny (that is to say, the consideration of fuel and of its most useful
and advantageous application to the production of heat, and the best mode of
constructing furnaces, ovens, chimneys, &c.), is one of the most important parts
of chemical technology.
From the foregoing the reader will readily perceive that it is scarcely possible
INTRODUCTION.
3
to draw a sharp line of demarcation between the two divisions of technology
(mechanical and chemical) alluded to. We therefore define chemical technology
best by designating it as that branch of industrial science which treats of the pro-
cesses and methods by which the nature of raw materials is usually altered.
In mechanical technology, machinery of various description, acting as the motive
agent or for the exertion of great power, for the transference of movement or for the
regulation thereof, and, lastly, as an actual implement, always plays a very prominent
part, whilst in chemical technology its position is altogether subordinate; the great
aim of improvement being chiefly directed towards :-1. Economisation of raw
material, and, if by any possible means, its regeneration. 2. Economy of fuel.
3. Economy of time by improved and shortened methods of the various operations.
The ideal of a chemical manufactory is that there should be no real waste products
at all, but only chief or main, and by-products. The better, therefore, the waste
products are applied to good and advantageous use, the more nearly the manu-
factory will approach the ideal, and the larger will be the profit.
DIVISION I
CHEMICAL METALLURGY, ALLOYS, AND PREPARATIONS MADE AND OBTAINED FROM METALS.
Meaning of the term
Metallurgy.
GENERAL OBSERVATIONS.
Metallurgy, in a more restricted sense, embraces the doctrine of
the various processes and operations, some of which are purely mechanical, others
again purely chemical, by means of which metals and some preparations thereof are
obtained on a large scale. We treat in the following pages almost exclusively of
the chemical operations and processes by the aid of which ores are converted into
metal or into some other product, and we shall therefore investigate the changes
which the ore undergoes when submitted to different processes and operations re-
sulting in the extraction of the metal. The number of the metals which belong to
this category is not very large; the chief are iron, cobalt, nickel, copper, lead,
chromium, tin, bismuth, zinc, antimony, arsenic, mercury, platinum, silver, gold.
Excepting chromium and cobalt,* other metals are brought into the metallic state by
means of smelting furnaces; but preparations of nickel, antimony, and arsenic are
also obtained metallurgically. Magnesium and aluminium are as yet only prepared
in chemical manufactories. Metallurgy, as a part of technology, treats chiefly of
the physical and chemical principles upon which the extraction of metals from their
ores is based; and includes, therefore, the description of the operations as based upon
these principles. Only very few metals are found in the native, that is, metallic
state: most of them occur as chemical compounds in the mineral kingdom, and these
Ores. are termed ores; they are partly chemical combinations of the metal with
metalloids, and partly consist of rock or gangue. Moreover, the term ore applies
only in an industrial sense to those minerals which are worth the miner's working.
Metals are found chiefly in combination with oxygen and sulphur. Metals occur in
the ores in the following conditions:-1. In the native state, embedded in quartz,
granite, gneiss, and other minerais, gold, silver, platinum, mercury, copper, and
bismuth. 2. Combined with sulphur, as, for instance, antimony, arsenic, and lead;
these combinations being-(a) single ores, as, for instance, cinnabar (sulphuret of
mercury), HgS; galena (sulphuret of lead), PbS; speisscobalt (a compound of cobalt
metal and arsenic), CoAs; (b) double ores, as, for instance, sulphuret of iron and
copper (peacock ore), Fe2S3,3Cu₂S; iron and copper pyrites, Fe2S3, Cu₂S; red silver
* Since 1862 M. Fleitmann has prepared chromium and cobalt on the large scale by a
metallurgical process.
PREPARATION OF ORES.
5
10
ore, Sb₂S3,3AgS. 3. Combined with oxygen, ores occur as-(a) basic oxides, as, for
i istance, hematite iron ore, Fe₂03; tinstone, SnO2; red copper ore, Cu₂O; (b) as
hydrated oxides, as, for instance, bog iron ore, Fe2O3,3H2O; (c) as oxysalts, as for
instance, malachite, CuCO3+CuH₂O. 4. Combined with sulphur and oxygen,
as for instance, red antimony ore, 2Sb2S3+Sb2O3. 5. Combined with haloids, as for
instance, the so-called horn silver ore, AgCl. 6. In combination with haloids and
oxygen, as, or instance, horn lead ore, PbCO3+PbCl3.
Dressing of
Ores.
Since the ores are not found in a state anything approaching to purity,
but are mixed in the first place with what is technically termed gangue-rock, stone,
or earth of any kind; and moreover, since very frequently the ores of different
metals occur mixed together, they require, on being brought out of the mine, to be
broken up and to be separated by mechanical means from the gangue and from
other impurities. These operations as a rule are carried out on, or near, the spot
where the ores are raised, and are designated by the name of dressing; the
mechanical preparation of the ore is partly executed by hand, women and children
being frequently engaged in picking out worthless stuff from among the minerals
brought to bank; this sorting, accompanied commonly by the breaking up of the
ore into small lumps, an operation executed by men with suitable hammers, is
usually so carried on as to separate the ore into three kinds. The ore thus selected
is placed in separate heaps, which may be classed as follows:-a heap containing
rich ore of sufficiently good quality to be fit to be directly smelted; another heap
contains ore which, previous to its being fit for the smelter, has to be further
prepared, that is, purified from mechanically adhering impurities; while the third
heap is devoted to such poor ore as would not pay the expense of the extraction of
the comparatively small quantity of metal it contains. The mechanical operations
alluded to are frequently effected by the aid of machinery, stamp and dressing mills,
while very often water is used in completing the operations, its use being chiefly
to remove the clay and earthy matter, sand, and pulverised rock from the specifi-
Preparation of cally heavier mineral. The dressing of the ores having been finished,
they are fit for the smelting operations, but in many instances these cannot be pro-
ceeded with until the ores have undergone a preparation, consisting in some cases
of an exposure to air-weathering; in others, again, in a heating of the ores, without
access of air, designated calcination, or a heating with access of air, termed roasting.
The object of the exposure to air is in some instances to effect the weathering and
subsequent loosening and separation (mechanically) of such minerals as slate, clay,
and marly materials, which frequently adhere to certain kinds of iron and zinc ores;
in other instances, again, the object of the exposure of metallic ores to air is the
oxidation of iron pyrites, which is washed out by rain as sulphate of protoxide of
iron. The object of the calcination of ores is partly to drive off water, carbonic
acid, and bituminous materials; partly, also, to render the ores softer, and thus
better fitted for the metallurgical processes by which the reduction to the metallic
state is effected. The roasting of ores is carried on with the same object, but since
the temperature is far higher, although not carried to the fusion of the ores, a more
energetic chemical action takes place, and is in some cases promoted by the addition
of common salt; moreover, the great object of the roasting of ores is to effect an
oxidation of the same, accompanied in some, if not in all, cases by the volatilisa-
tion of various substances. As instances of the action of this process, we quote
what occurs when magnetic iron ore, (Fe2O3,FeO), is roasted; the protoxide in this
6
CHEMICAL TECHNOLOGY.
case is gradually converted into peroxide. When oxidation is accompanied by
volatilisation three different things may happen.
I. A volatilisation of certain substances attended by oxidation. The ores which are
chiefly submitted to this process are such as are combinations of sulphur, arsenic, and
antimony, either jointly or singly, in which cases sulphurous and arsenious acids and oxide
of antimony are volatilised, with the result that either pure metal is obtained, as is the
case with cinnabar, which yields mercury, or the formation of metallic oxides and sulphates.
The volatilised substances may be collected and utilised, as, for instance, the arsenious
acid, and the sulphurous acid for the production of sulphuric acid, &c.
2. Volatilisation of certain substances by reduction is a less frequently occurring opera-
tion, chiefly carried on with some sulphates and arseniates of metallic oxides by heating
the same with coal or charcoal, the result being the volatilisation of sulphur in the form of
sulphurous acid and of arsenic per se.
3. Volatilisation by conversion into chlorides of metal. When an ore is roasted with the
addition of common salt and free access of air, some partly volatile chlorides may be
formed, as, for instance, in the extraction of silver from its ores by the European amalga-
mation process and M. Augustin's method.
Smelting of the Ores. As soon as the ores are sufficiently prepared by the methods just
described, they are submitted to an operation having for its object the conversion of
the ore into metal, or into some other combination thereof; the process, which is a
true chemical operation, is called the smelting process. It rarely happens that only
one kind of ore is operated upon; the more usual plan is to mingle richer and poorer
ores together in certain quantities, so as to obtain a suitable mixture, attention also
being paid to the various kinds of rock which accompany the ores, so as to obtain by
the smelting process a proper slag; but if, as is more often the case, this end cannot
be attained by the mixing of ores of different quality, it becomes almost always
necessary to add other materials which either chiefly or solely act as fluxes, and
also as reducing or converting agents, by promoting in various ways, to be presently
more fully described, the separation of the metals from their ores. We distinguish
accordingly between such materials as charcoal, coal and coke, lime, and common
salt, which we term roasting materials (Röstzuschläge), and smelting or fluxing
materials, such as quartz and various silicates, among which are hornblende, feld-
spar, augite, greenstone, chlorite-schist, slag; lime-containing minerals, as lime-
stone, fluor-spar, gypsum, heavy-spar; minerals containing alumina, as, for instance,
clay-slate and marl. Saline materials (admixtures) are also used, as potassa, borax,
Glauber salt, and saltpetre; likewise metallic admixtures, as, for instance, iron used
in the decomposition of cinnabar and sulphuret of lead; zinc, for the extraction of
silver from lead; arsenic, in the preparation of certain nickel and cobalt ores; pro-
toxide of iron (anvil dross), hematite iron ore, and manganese, used in the puddling
process; certain saline admixtures, by which we understand, in this instance more
especially, such blast furnace slags as contain a large proportion of protoxide of iron,
and are applied in the process of puddling on account of the oxygen they contain;
or, on the other hand, are used as so-called precipitating agents, on account of the
iron they contain, e.g., for the throwing down of lead from galena. The sub-
stances which act only as fluxes promote the separation of the metal, because the
ore is more readily rendered fluid, thereby causing the particles of metal to unite
more easily. According to their mode of action, fluxes can be brought under three
heads, viz. :—1. Such as exercise no chemical action, but are only substances pro-
moting fluidity, as, for instance, fluor-spar, borax, common salt, and various slags;
2. Such as at the same time exert a reducing action, as, for instance, a mixture of argol
and saltpetre, so-called black flux; 3. Such as act as absorbents, either of acids or of
bases but this class belongs more properly to admixtures already alluded to above.
•
SLAGS.
7
Th- Mixing of the Smelt. That operation, by which the ore and the materials required for
the smelting process are intimately mixed together, often in previously weighed out
quantities, is called the mixing, and the quantity which is to be used within a given
lapse of time (generally 12 or 24 hours) is called the charge.
Products of the
Smelting Operation.
-
The following are the products which, generally speaking, are
obtained by the smelting process:—1. Metals-Educts. The relative degree of the
purity of these substances is indicated when gold or silver is alluded to by the title
of their fineness (purity), fine gold or fine silver being understood as the perfectly
pure metal; but as regards the metals not designated by the term noble, they are
called raw or crude metal, while a higher degree of purity is indicated by refined.
2 Such products as are not present ready formed in the ore, but are the result of
peculiar reactions which take place during the smelting process between the various
ingredients submitted to the operation; these materials are, in most instances,
ready for the market, and comprise the so-called hard lead which contains antimony,
arsenic, and other impurities; arsenical preparations, as, for instance, arsenious
acid, orpiment, realgar; and black sulphuret of antimony. 3. The preparation of
educts is often accompanied by the formation of intermediate or by-products; if
these happen still to contain a sufficient quantity of the metal operated upon to
make it worth while to extract it, they are termed intermediate products; but if
the reverse is the case they are called-4. Dross. Such intermediate products are
often alloys; as, for instance, one consisting of silver, copper, and lead—the so-
called Tellersilber-silver containing lead, consisting chiefly of lead, with a smaller
or larger quantity of copper and some silver; so-called black copper, a mixture of
copper, iron, and lead; sulphurets; arsenic alloys, so-called Speiss, as, for instance,
the cobalt and nickel compounds obtained in smalt works, chiefly consisting of
arsenical nickel; carburetted metals, as, for instance, pig-iron and steel; oxides,
as for instance, litharge (oxide of lead).
Slags.
The material which usually passes by this name exhibits, when cold, an
enamel or glass-like appearance, and is generally made up of various combinations
of silica with earths, such as lime, magnesia, alumina, and metallic oxides, as the
protoxides of iron and manganese. The slags are formed during the smelting process
because the raw materials, and the various substances employed, contain the elements
for their formation. The functions of the slag during the smelting process are rather
important, serving to protect the particles of metal, or of sulphuret of metal, from the
oxidising action of the blast, and promoting the adhesion and union of the particles.
Slags are applied in some smelting processes as a flux; and if they should still contain
a sufficient quantity of metal, they are added to another batch of ore to be operated
upon. As regards their composition and nature, they are classified according to the
quantity of silica they contain as sub-, mono-, bi-, and tri-silicates. The proportion
which the oxygen of the silica bears to that contained in the bases is as follows:
Subsilicate
Monosilicate
Bisilicate
Trisilicate..
3:6
3:3
: 3
3: I
Slags are either vitreous or crystalline. It very frequently happens that from the
latter kind portions of silicates separate, which, as regards their chemical and mineral-
ogical characters, agree with minerals met with in nature, such as augite, olivine,
Wollastonite, mica, idocrase, chrysolite, feldspar, &c. Generally speaking, the
8
CHEMICAL TECHNOLOGY.
·
mixtures of monosilicates produce slags which are very fluid, and apt to consolidate
rapidly while cooling, while the mixtures of bi- and tri-silicates produce slags which
have the opposite properties, being pasty and tough.
The following properties and constitution denote that the slags are suited to the smelting
process-1. The specific gravity of the slag while molten should be less than that of the
product (metal) it is desired to obtain, in order that the slag may cover the surface of the
molten metal. 2. The slag should be homogeneous throughout the duration of the process
of smelting; since the contrary would denote an abnormal working of the operation.
3. The slag should melt readily, and thus admit of the particles of metal readily sinking
downwards as a consequence of their higher specific gravity. 4. The chemical composition
of the slag should be so regulated as to prevent them exerting any decomposing action
upon the metal.
Iron: its occurrence.
IRON.
(Fe=56; Sp. gr. = 7'7.)
Iron is the most important and most useful of all metals. Its
application is most intimately connected with all branches of industry, and almost all
the wants and requirements of common daily life. The reason of this very extended
employment of iron is due, partly to its being plentifully and even superabundantly
met with in nature, but partly, if not chiefly, in consequence of the great ease where-
with this metal, during its reduction from the ore, assumes various modifications and
exhibits different characters, each possessing some special feature of usefulness.
Although the number of minerals which contain iron is very great, comparatively few
are used in practice for the extraction of the metal. Those that are used are all
oxygen compounds of iron, and chiefly what are technically known to ironmasters
and the trade as ironstones.
The following is a list of the minerals termed "iron-tones
>"
1. Magnetic iron ore, (Fe₂O,,FeO=Fe3O4), the richest of all iron ores (it contains
upwards of 72 per cent. of iron), is pretty largely found, especially in Russia, Norway, and
Sweden, in the crystalline schistose rock. The celebrated Dannemora (Sweden) iron is
obtained from this ore. It not unfrequently happens that this mineral is more or less
mixed with iron pyrites, galena, copper pyrites, apatite (chiefly phosphate of lime), and
other minerals, which, by their presence, impair the good qualities of the magnetic iron ore
as a mineral.
2. Hæmatite iron ore, red ironstone, (FeO3), contains about 69 per cent. of iron. This
mineral occurs in seams and veins in the older geological formations, often embedded in
gneiss and granite. It is also met with in the metamorphic rocks, and is frequently called
glassy head, owing to its external lustre; also bloodstone, on account of exhibiting, when
scratched with a file or a knife, a deep red-coloured streak. When this ore is found mixed
with silica, it is called siliceous ironstone; when occurring along and mixed with alumina,
it is called red aluminous iron ore; mixed with lime, the ore is known as minette. The
quantity of iron present in these ores varies, of course, considerably. This ore occurs
in crystalline state, in especially large quantities in the Island of Elba, and ores of the
same kind, but different in quality, are found in England and Ireland, Saxony, and many
parts of Germany. They are, in all cases, especially as regards the first-named country,
largely applied, e.g., Lancashire (Ulverston and Barrow-in-Furness).
3. Spathose iron ore, (FeCO3), with 48.3 per cent. of iron. This ore, which occurs in great
variety, is, indeed, the chief iron-stone, often containing carbonate of protoxide of manganese
in larger or smaller quantity. This ore is often met with in a globular or kidney-like shape,
and hence called kidney iron; in mineralogy, spherosiderite. The ore bears a great many
other names, derived from some peculiarities in its composition; for instance, it is known
and very largely worked in Scotland as black-band, owing to its being mixed with carbon-
aceous and bituminous matters, and alternating with seams of coal. It is known, also, as
clay-ironstone, being then mixed with more or less argillaceous matter, and occurring in
enormous quantities in that condition in Cleveland and Rosedale (Yorkshire), in Wales,
and also on the Continent in various countries.
3
4. When the last-named ore is acted upon by air and water containing carbonic acid, a
secondary ore is formed, known as brown ironstone (partly Fe,O,,H₂O, partly Fe2O3,3H₂Ó).
In mineralogy this ore is named according to its varying physical properties, as follows:
Lepido-crocite, needle-iron ore, pyrosiderite, and stilpnosiderite. As may be expected,
IRON.
9
·
this mineral is often mixed with carbonate of lime, silica, alumina; the yellow ironstone
being a variety of the aluminous kind. Bauxite may in some instances range along with
this kind of ore, when that substance consists of an intimate mixture of alumina and
peroxide of iron.
5. Pea-iron ore, in smaller or larger globular-shaped particles, formed of concentric
layers, containing either an intimate mixture of silica, protoxide of iron, and water, or
brown iron ore and siliceous clay. The origin and mode of formation of this ore are un-
known. It occurs in France and in the South-West of Germany.
6. Marsh iron ore, limonite, met with in parts of Europe, generally those which are
only little elevated above the sea level, and more especially in or near moors and marshes,
peat bogs, &c.; in some parts of the Netherlands, Denmark, Sweden, and North Germany,
and also in the United Kingdom to some extent. This ore owes its origin to the action of
decaying vegetable matter upon water containing carbonate of protoxide of iron in solution.
The ore is met with in irregularly shaped lumps, as hard sometimes as pebbles, but also
in a soft and spongy condition; its colour is brownish, or black, and it consists of prot-
oxide of iron, oxide of manganese, phosphoric acid, organic matter, and sand. According
to M. Hermann, however, the ore contains hydrated peroxide of iron, hydrated oxide of
manganese, phosphate of peroxide of iron, tribasic crenate of peroxide of iron. This
ore is in some instances largely used for the manufacture of cast-iron objects (especially
for domestic and ornamental uses), on account of its yielding an iron of great fluidity,
which fills the moulds very completely, giving sharp-figured castings. This condition is
due to the presence of the phosphorus in such iron; but the presence of this element also
causes the pig-iron made from this ore, if puddled, to yield a wrought-iron which is both
cold- and red-short.
7. Franklinite, (Fe₂0¸[ZnO,MnO]), containing 45 per cent. of iron, 21 per cent. of zinc,
and 9 per cent. of manganese. This ore occurs in New Jersey, U.S., and is there employed
both for the extraction of iron and zinc.
Iron is also obtained from rich slags, which often contain, in the shape of protoxide of
iron, an amount varying from 40 to 75 per cent. of that metal; they are employed in the
puddling process. The scraps of iron resulting from various operations, old iron, and
waste pieces of the metal, are usefully applied, either alone or with the ores, to be re-con-
verted into metal.
Taken from a metallurgical point of view, iron ores are distinguished as reducible easily
or with difficulty (convertible into metal readily, or fusible with difficulty). To the former
class belong all those ores which, while being submitted to a preliminary roasting, become
porous, and hence more readily penetrable by the reducing gases present in the blast-
furnace; and, as a consequence, more rapidly reduced and molten. The spathose iron
ore and brown iron ore belong to this class; the former because on roasting it loses
carbonic acid, while the latter loses water. Magnetic iron ore, and hematite iron ore in all
its varieties, are reducible with difficulty.
from its Ores.
a. PIG OR CRUDE IRON.
Extraction of Iron The extraction of iron from its ores is chiefly based upon the two
following properties:-1. While particles of pure or nearly pure iron are infusible
even by the heat produced in the blast furnace, they are possessed of the property
of agglutination to larger masses; in other words, the property (possessed by iron
and only a few other metals) of welding together at a bright red heat.
2. Iron is capable of uniting, while exposed to a high temperature, and in the
presence of an excess of carbonaceous matter or gases containing carbon, with
that metalloid, forming with it an easily fusible compound, viz., a carburet of iron,
the so-called pig- or cast-iron.
The direct manufacture of malleable iron from iron ores was in former times a
very usual proceeding, and is yet carried on to a small extent in some parts of
Europe (Styria, Andorra, Sardinia, and Sicily), and far more so in Hindostan ; but
this method, known as the Catalan process, is wasteful, and although it yields iron
of excellent quality, it also requires ores of great richness. The process is not
suited to meet the large demands now made for iron; with these trifling exceptions
all iron at the present day is obtained by the production first of pig-iron, which is
afterwards converted into malleable iron by the puddling process.
JO
CHEMICAL TECHNOLOGY.
The operations by which iron is extracted from its ores are:-calcination or roast-
ing, and smelting. The object of the first-named operation is the removal from the
ore of such substances as water, carbonic acid, carbonaceous matter (as present in the
black-band ironstone); also the conversion of any protoxide into peroxide, because
the latter is less apt to become absorbed by the slag, and to promote the porosity of
the ore.
The calcined ores are next broken up to lumps of suitable size by means
either of stamping mills or cylinders, or by machinery specially made for the purpose
on the principle of quartz and stone crushers; after this has been done the ores are
mixed, rich and poor together, in such proportions as have been found in the ex-
perience of the workmen to yield the best quality and largest quantity of iron.
Theory of the Iron Extraction The ores having thus been mingled, constitute a mixture made
up chiefly of an oxide of iron and of gangue (silica) or lime; carbonaceous matter
is added thereto, and the mass is submitted to a strong heat, the result being the
reduction of the iron to the metallic state, according to the following equation:-
Process.
Fe2O+33C=3CO+2Fe;
the action, therefore, of coal is to serve as fuel and at the same time as reducing
agent along with carbonic oxide and carburetted hydrogen; if, however, the opera-
tion were performed by simply mixing the broken up ores and coal or coke, and
submitting this mixture to the smelting process, the iron would be obtained in a
finely divided and spongy condition; and in order to procure the union of the particles
of metal so as to form a molten mass previous to the smelting operation being pro-
ceeded with, certain substances which have the property of forming with the gangue
a readily fusible glassy mass are added. The substance added is technically known
as slag, and it serves not only the purpose just mentioned, but also that of with-
drawing and absorbing from the ore such materials as might injure the quality of
the iron; and, lastly, the slag being by far specifically lighter than molten iron, floats
on the surface and protects the metal from the oxidising action of the air blown into
the furnace. Slag is a mixture of various silicates; in some instances the ore itself
contains, along with the oxide of iron, the constituents necessary to form a good
slag, but in most instances ores require the addition of such materials as will form,
with the constituents (excepting the iron oxides), a proper slag; thus, for instance,
if silica were wanting, quartz or sand would be added; and if bases were wanting,
lime-stone or fluor spar (fluoride of calcium) would be added. The slag should
become fluid at or about the same temperature as the metal. The mixture of iron-
stone and slag-forming material is called a batch, and is so arranged as not to contain
above 50 per cent. of iron. When iron in the molten condition and carbonaceous
matter (coal, coke, or charcoal, although the latter is very rarely used) come in
contact, as is the case during the smelting process just alluded to, the molten
metal dissolves a large proportion of carbon; but when the metal cools a portion of
the carbon separates in the crystalline form; this is termed blast-furnace graphite:
another portion of the carbon remains, however, in chemical combination, and it is
therefore evident that the smelting of iron ores produces an iron-pig or crude iron
—which contains carbon, and is, therefore, not a pure metal.
Blast-furnace Process. At the present day the extraction of iron from its ores (smelting)
is chiefly carried on either in what are termed blast-furnaces or blowing-furnaces.
These contrivances are not essentially different from each other as regards their
action, but their arrangement and construction is so far different that the slag from
blast-furnaces, working as they do with what is termed an open breast-plate, runs
IRON.
II
off continuously, while the slag from the blowing-furnace has to be cleared from
time to time when tapping the metal.
Description of the
Blast-furnace. A blast-furnace is an oven showing on the exterior a heavily made
wall (Fig. 1, a, the outer wall), having a height of from 14 to 35 metres; the inner
lining is made in the shape of two truncated cones placed together at their bases;
the brickwork (fire bricks) which constitute this double cone-like structure, B, is
FIG. I.

།
surrounded by a casing made up of broken scoriæ or refractory sand, which is en-
veloped by the external coating of heavy masonry; the sand is a bad conductor of
heat and admits also of space being allowed for the expansion by heat of the interior
structure. The portion of the internal cone extending from в to c is called the shaft,
or chamber, while the portion which extends from D to E is named the boshes; the
part of B where the diameter is greatest is called the belly or upper part of the
boshes. Below the boshes at F, the space is gradually made narrower, and called
the throat, or tunnel hole, the lower part of which is intended for collecting the
molten metal, and named the crucible or hearth; this portion of the blast-furnace
is the most important, because the smelting process goes on in it; the crucible is
provided with two opening placed opposite to each other, and containing conically-
shaped tubes (see Fig. 2) called the tuyeres, ending in what are termed the nozzles
or nose pipes, or the blast pipes; these tubes serve to convey the air necessary for
the furnace. As shown in the engraving, the admission of air to the nozzles is re-
12
CHEMICAL TECHNOLOGY.
gulated by a valve. The upper open end of the furnace at a is called the mouth or
furnace top; through this opening the fuel and mixture of ore and flux are put into
the furnace, which is (as also shown in Fig. 1) situated on or near the slope of a hill,
so as to have ready access to the mouth by means of the bridge for conveying the
materials to the furnace-top. The lower part of the hearth is prolonged towards the
front, thus forming the breast-pan, which is enclosed by the dam-stone, M; this
stone is somewhat removed at one side from the wall, thereby forming a slit, which
is technically called the tap-hole; this is the discharge aperture; while the smelting
is going on this aperture is closed up with fire-clay, which is removed when it is
required to withdraw the slags or tap the crucible, that is to say, discharge the molten
FIG. 3.

d
C
FIG. 2.
u.
b
d
metal. The dam-stone is protected by an iron plate. Three only of the sides of the
hearth are continued to the stone constituting the bottom of the arrangement; the
fourth is merely brought to within a certain distance of the base, where it is supported
by strong girders of cast-iron firmly fixed into the masonry of the walls, and on
which rests a heavy block of sandstone called the tymp (see Fig. 1), which is
supported by a very heavy and stout piece of iron called the tymp iron.
and Blast
The Blowing Engine In order to provide the necessary quantity of air for the blast-
furnace, a blowing engine is attached; this is now almost exclusively constructed
upon what is termed the cylinder principle, which in one of its most convenient
forms is delineated in Fig. 3. The cast-iron cylinder, A, contains a piston, e, which
by means of the piston rod, a, passing air-tight through the stuffing box, e, can
be moved upwards and downwards; at b and d the cylinder is in communication with
the outer air, and by means of ƒ and g it communicates with the chest, E. The
openings alluded to are provided with self-acting valves for regulating the flow of air,
which is conveyed through into the pipes communicating with the blast-furnace. In
order to regulate the blast, a large sheet-iron vessel, in construction very similar to
the gas-holders of gas-works, and acting on the same principle, is applied. The
application of hot air for the blast is one of the most important improvements in the
IRON.
13
manufacture of iron, since, in this way, a decreased consumption of fuel, to the
extent on an average of 0.366 (from to ), has been obtained; while, moreover,
the absolute gain in the production of iron amounts to about 50 per cent. It is also
stated by many iron-masters that the furnace is more readily and regularly worked;
but this statement is discredited by others, who aver against the hot blast that dis-
turbances arise more frequently in the regular course of working; also, that the very
high temperature in the crucible causes the rapid destruction of the fire-bricks, and
consequently impairs the time of what is technically termed the campaign, that is to
say, the duration of the fabric of the blast-furnace. The air intended for the hot
blast is heated either by the gases given off by the blast-furnace, or by means of
separate fire-places which heat a pipe apparatus, or lastly by means of Siemens's
regenerative furnace system. This system consists in first conducting the gases of
the blast-furnace through a fire-brick built space filled with fire-bricks loosely
piled together, which becoming thoroughly red-hot are in that condition capable of
heating the cold air previous to admitting it, care being taken to shut off the blast-
furnace gases; by this means the air can be heated to a temperature very far ex-
ceeding that which is attainable by passing the air through iron tubes, these not
admitting without serious injury of being heated to so high a temperature in con-
tact with air. The hot blast air is heated to from 200° to 400°C.; blast furnaces fed
with coke as fuel require per minute of time from 2000 to 4000 cubic feet of air.
Smelting Process.
Course of the The blast furnace is worked in the following manner :-The furnace
is first heated by igniting in it a quantity of wood. When this has rendered the
oven thoroughly dry, the fuel intended for use in the course of the continued process
is put in (this fuel used to be in Germany wood charcoal, but at the present time
there, as in England, coke is employed, or sometimes anthracite ; common coals are
rarely used); the furnace is at first entirely filled with fuel, and when quite full the
blast is turned on and a beginning made with the charging of the mixture of ore
and flux, alternating with fresh fuel. By the burning of the fuel, and the fusing of
the ore and flux, the layers sink downwards, the silica fuses, forming, while com-
bining with the earths and some of the oxides present in the ore, a slag which is
commonly coloured by the presence therein of oxide of iron, while the iron reduced
to the metallic state, and semi-fluid at first, combines with carbon to form readily
fusible pig-iron; the molten metal collects in the hearth or crucible; the fused slag
floats on the top of the metal, but is run off over the dam-stone. The molten metal is
tapped off about twice every 24 hours, or as soon as it appears to reach the height of
the dam-stone. The aperture here alluded to, and closed provisionally by means of
fire-clay, is opened by the piercing of the latter, while the molten metal is conveyed
through channels made in the sand to the moulds, also formed in the same material;
during the operation of tapping, the blast is shut off. Crude iron cast in the shape of
cakes is called lump-iron, and when run into bars, pig-iron. The campaign, that
is, the operation of smelting with the same furnace, often lasts many years; it is,
in fact, continued until the oven or blast furnace becomes worn out.
Chemical Process going
on in the Interior of the
Blast Furnace.
The chemical process which is going on in the interior of
the blast furnace when at work (technically, while in blast) differs
considerably in different portions of the vertical section. The annexed Figs 4 and 5
represent the interior of a blast furnace exhibited in perpendicular section, and filled
with alternate layers of fuel and mixed ore and flux, the latter being indicated by the
narrower, the former by the wider layers. Counting from the surface of the fluid slag,
14
CHEMICAL TECHNOLOGY.
ƒƒ, up to the mouth of the furnace the interior may be divided into five zones or
regions, viz. :—
1. The first heating zone, a b.
2. The reduction zone, b c.
3. The carburation zone, c d.
4. The melting zone, d e.
5. The combustion zone, e ƒ.
In the upper part of the furnace, the first heating zone, the materials become
warmed and are rendered thoroughly dry, but they hardly become hotter than a low
red heat. The reduction zone is the largest in extent. In the lower part of the shaft of
the furnace, and especially towards the belly, the oxide of iron is, by the action of the
reducing gases, first converted into protoxide of iron and next into metal. The reduc-
ing agents present in this zone are--carbonic oxide, carburetted hydrogen gas, and
hydrocyanic acid gas (cyanide of hydrogen), or vapours of cyanide of potassium; at
a certain part in this zone the iron is present as malleable iron. Deeper down in the
furnace the carburation zone is met with; here the combination between the iron and
FIG. 5.

FIG. 4.
Z.
6
....
d.
l...
a

b
b
400"
C
d
1000°-1200°
1600°
-1700°:
d
18 00
e
e
-2000
12650º
f
f
carbon takes place, producing a more or less steel-like and somewhat caked iron,
which, when sinking, enters the melting zone and is saturated with carbon and en-
tirely brought to the state of pig-iron. At the portion forming the combustion or oxi-
dation zone, which is, as compared with the other zones, only of very small extent,
the air from the b ast enters the furnace through the nozzles, and meeting with incan-
descent coke at the highest possible white heat, causes the formation of carbonic acid,
but this gas in passing upwards through other layers of incandescent fuel becomes
reduced to carbonic oxide (CO₂+C=2CO); by the combustion of the hydrogen con-
tained in the fuel, water is also formed, which, along with the aqueous vapour con-
IRON.
15
tained in the air of the blast (recently it has been tried to eliminate this aqueous vapour
by passing the air previous to reaching the nozzles through concentrated sulphuric
acid) is decomposed by the enormous heat of the middle portion of the furnace as well
as by the presence of carbon, forming hydrogen and oxygen, the former of which
enters into combination with the carbon, forming carburetted hydrogen, while the
latter combining with the same element produces carbonic oxide. The nitrogen
present in the coke, as well as a portion of the nitrogen present in the air of the blast,
combines with the carbon, forming cyanogen (either as cyanide of some metal or as
cyanide of hydrogen).* The reducing gases meeting with the ores cause the oxides
present to be converted into metal, while the gases remaining (the blast furnace
gases) escape from the mouth of the furnace. The reduced iron combines, while
sinking downwards, with carbon, forming the crude metal, and fuses in so doing;
the union of the particles being promoted by the slag. As soon as the iron reaches
that portion of the furnace where the heat is strongest, the carbon contained in the
metal begins to exercise its reducing action upon such substances as alumina,
lime, silica, &c., which in the reduced, or metallic, state combine with the iron.
Recent researches have proved that the copious production of hydrocyanic acid generated
by the process going on in the blast furnace greatly and very essentially assists the reduc-
tion of the ores; that compound of course combines with the alkalies and alkaline earths
contained in the fuel and other materials. It has been surmised that the crude iron is not
solely a carburet of that metal, as might be produced by the decomposition of cyanide of
iron, but, in addition to a small quantity of that body, contains also nitride (a nitrogen
compound) of that metal. In support of this view the fact is brought forward, that Dr.
Wöhler, of Göttingen, found many years ago that the cubical crystals of what was con-
sidered to be metallic titanium, and found in the blast furnace slag, turned out to be a
compound of nitride of titanium and cyanide of that metal. In order to give some idea
of the large quantity of metallic cyanides generated by the blast furnace process, we
briefly quote from the researches made on this subject by Drs. Bunsen and L. Playfair,
that an English blast furnace, fed with coal as fuel, produced daily a quantity of 225
pounds. M. Eck, who made some researches on this subject at Königshütte, in Upper
Šilesia (Prussia), discovered the formation of both cyanide and sulphocyanide of potassium,
and he found by calculating from the quantity of potassa contained in the ores, flux, and
fuel, a daily production of 35 pounds of cyanide of potassium. The reduction of alumina
and silica to aluminium and silicium also takes place in the melting zone.
Temperature in the Blast-
furnace at Different Points.
each zone.
Fig. 5 exhibits the temperature prevailing at the limits of
The temperature of the combustion zone would be far higher than
happens to be the case were it not that, by the conversion of carbonic acid into
carbonic oxide—that is, the absorption, or more correctly vaporisation of carbon—
a considerable lowering of temperature (in other words, absorption of heat which
becomes latent) is produced. It should be remembered that here the volume of the
carbonic acid is also doubled, while this reaction is taking place, and that process
of course also absorbs heat.
Gases
Taking into due consideration the fact that, under the most favourable conditions,
only 16'55 per cent. of the fuel supplied to a blast furnace is usefully consumed,
while no less than 83'45 per cent. escapes from the mouth in the shape of com-
Bast-furnace bustible gases, it cannot excite any wonder that the idea arose of
utilising these gases; this idea has actually resulted in various useful ways, as,
for instance, for the fusion and puddling of the iron, for the refining and cleansing
by welding of the iron, for the heating of the blast, the roasting of the ore, and
the drying and carbonisation of the wood.
* According to the view of M. Berthelot [1869] there is in this instance first formed
acetylide of potassium, C,K,, which then combines directly with nitrogen to form cyanide
of potassium, 2(CNK).
16
CHEMICAL TECHNOLOGY.
Application of these Gases
to the Manufacture of
Sal-ammoniac.
The application of the gases to the useful purposes just mentioned
does not exhaust the list of such applications. Drs. Bunsen and
Playfair found that the gases emitted by blast-furnaces fed with coal as fuel contain such
a large amount of ammonia that the presence of that gas in the lower parts of the blast-
furnace is even perceptible to the smell. These eminent savants proposed to convey the
gases previous to being used as fuel through a chamber containing hydrochloric acid gas;
the solution of sal-ammoniac thus obtained should be run into the pan of a suitably con-
structed reverberatory furnace; and a small portion of the current of gas, after having
been ignited, being carried over the surface of the liquid, the evaporating process can be
regulated so as to obtain a continuous stream of a concentrated solution of sal-ammoniac
as a metallurgical by-product. Experiments instituted at the Alfreton Iron Works (blast
furnace) proved that in this way about 2:44 cwts. of sal-ammoniac could be produced daily
without any great expense and without any interference with the process of iron manu-
facture. The formation of sal-ammoniac is intimately connected with the formation of
cyanogen just spoken of. When cyanide of potassium comes into contact with aqueous
vapour, it is decomposed into ammonia and formiate of potassa——
(KCN+2H₂0=NH,+CHKO,);
the reverse reaction, that is to say, the withdrawal of all oxygen in the form of water,
from formiate of ammonia would result in the formation of cyanide of hydrogen-
Cast-Iron.
[CH(NH₁)0₂—2H₂0—CHN].
Crude Iron. The iron obtained by the blast-furnace process is impure, and therefore
called crude cast-iron; it contains carbon (in the shape of graphite as well as
in a state of intimate chemical combination with iron as a carburet of that metal),
silicium again as so-called silicium graphite and as a siliciuret of iron, sulphur,
phosphorus, arsenic, and aluminium. The colour and physical properties of the iron
are determined by the quantity of carbon it contains. Formerly the more or less
deep colour of the crude iron was believed to be dependent upon the larger or
smaller quantity of carbon the iron contained, and accordingly, the deepest
coloured metal was supposed to contain the largest, and the least coloured iron, the
smallest quantity of carbon; investigations have, however, satisfactorily proved
that it is not so much the quantity as the manner in which the carbon (likewise
the silicium) is present that determines the quality. The fact is, that with carbon
and silicium a portion only is chemically combined with the iron, while the largest
proportion of these metalloids is only mechanically mixed with the metal, being,
as already stated, present in the form of graphite (graphitic carbon and silicium).
According to the researches of M. Frémy and others, it is probable thst crude iron
frequently contains nitrogen, and that the presence of this element influences the
quality of the metal; but this view is not endorsed by MM. Caron, Gruner, and
Dr. Rammelsberg. There are two chief qualities of crude iron in the trade, viz.,
white and grey coloured.
White Cast-Iron. White cast-iron is distinguished by its silvery white colour, hard-
ness, brittleness, strong lustre, and higher specific gravity, which ranges from 7·58
to 7.68. Sometimes this kind of iron happens to contain prismatic crystals visible
to the naked eye, and such iron is then called spiegeleisen, or crystalline pig (crude
steel iron.) This variety of iron may be viewed as a combination of CFe6, or, more
accurately stated as Fe6C+Fe8C, with 5'93 per cent. of C. If the structure of the
white cast-iron is radiated and fibrous, while the colour is bluish-grey, the metal
is known as white pig-iron with a granular fracture. When the white colour dis-
appears still more, and the fracture becomes jagged, such a metal holds a medium
between white and grey pig, and is therefore called porous white pig.
Grey Cast-Iron Grey cast-iron exhibits a bright grey to deep blackish grey colour.
Its texture is granular or scaly; its specific gravity averages about 7, consequently
less than the white variety, and the grey iron is also less hard. When pigs happen
IRON.
17
to contain both grey and white iron in portions only, or dispersed through their entire
mass, such metal is called half-and-half iron, and is specially applicable to foundry
purposes. The chemical difference between white and grey cast-iron is due to the
fact that the former only contains chemically-combined carbon (from 4 to 5 per cent),
while the latter contains from 0'5 to 2 per cent. of this element in the combined
state, with rather more than that amount mechanically mixed, viz., from 1'3 to 3′7
per cent. As regards the melting-point of cast-iron, the white variety fuses at a
lower temperature and more easily; but the grey cast-iron possesses far greater
fluidity. Crude cast-iron is not malleable, and cannot be welded or forged; when
made red-hot, it becomes very soft-so soft that it can be cut with a saw such as is
used for sawing wood; but when placed on an anvil and hammered, this iron
breaks into fragments even when red-hot. Grey cast-iron is the best, and, in fact,
only suitable kind of crude iron to be used for making iron castings. The perfect
fluidity of this metal when molten causes it to fill the moulds well, and to yield excel-
lently sharp and well-defined forms. White cast-iron, on the contrary, is not used
for iron-foundry purposes, because, while solidifying, it warps, and the surface
becomes concave. Grey cast-iron can be filed, cut with the cold chisel, turned upon
the lathe, and planed. White cast-iron is too hard to admit of any such operations
being performed upon it. Grey cast-iron, molten and then suddenly cooled, is
converted into white cast-iron; on the other hand, white cast-iron, molten at a
very high temperature (heated far above its melting-point), and cooled very slowly,
becomes converted into grey cast-iron.
The quality of the iron produced by the blast-furnace process does not so much depend
upon the ores and other materials used. In this respect the temperature is of far greater
importance. It would appear that after every fresh charge there is at first produced white
cast-iron, which is only converted into grey cast-iron by a very much increased tempera-
ture. If the reduction of the ore to metal-care being of course taken to have a proper
proportion of ore and the other materials-proceeds regularly, the furnace is said to be in
a healthy state of working. Under such conditions, the slag, which contains only very
little protoxide of iron, is never deeply coloured. If fuel were not supplied in proper
proportion and the ore to prevail, the reduction would probably be imperfect and the slag
a deep colour, in consequence of the presence of a large quantity of protoxide of iron
(colour of dark green bottle glass). Such a condition of working is termed irregular.
When, in consequence of an excess of fuel, the heat in the furnace becomes very great,
that condition of working is termed hot, and only grey cast-iron is formed.
The results of the chemical analysis of some varieties of crude metal may elucidate the
general composition of cast-iron: the under-mentioned samples are:-1. Spiegel iron, made
from 14 parts of spathose ironstone and 9 parts brown iron ore (Hammerhütte). 2. White
pig-iron, with a granular fracture, from Styria. 3. White pig. 4. Half-and-half pig.
5. Grey cast-iron (from brown iron ore and charcoal). 6. Grey cast-iron, from brown iron
and spathose iron ore mixed. 7. Grey cast-iron, from ochreous brown iron ore and coke.
The sign-indicates that no search or testing was made for the substance; the sign o in-
dicates that the substance was not found.
I.
2.
3.
4.
5.
6.
7.
Combined carbon
5.14
4'920
2.91
2.78 0.89
1'03
0'58
Graphite
O
о
I'99
3.71
3.62 2:57
Sulphur
O'02
0'017
Ο ΟΙ
O
Phosphorus..
0:08
0.08
1.23
Silicium
Manganese
0*55
4'49
O
8.71
о
I'79
O
The results below are those obtained by M. Buchner, while examining the quantities of
carbon and silicium contained in crude iron: 1, 2, 3, 4, are Spiegel iron, almost or quite
crystalline; 5, 6, porous white pig.
Cy
585
Si
Св
I.
2.
3.
4.
5.
6.
..
..
•
4'14 3.80
4'09
3.75
3.31
3'03
··
•
•
Ο ΟΙ
O'CI
0:26
•
9'27
Spur
0'15
3
18
CHEMICAL TECHNOLOGY.
7, 8, 9. White, very bright, crude iron.
12. Strongly mixed half-and-half.
10. White pig. 11. Half-and-half pig.
7.
8.
9.
IO.
II.
12.
Cy
Св
3'40 2'70
2.13
3.60
3'34
2.72
Si
0'14 O'12
ΟΙΟ
0.66
ΟΙΟ
0'20
cast-iron.
13. Less strongly mixed half-and-half. 14, 15, 16.
18. Over-coaled black-greyish cast-iron.
Grey cast-iron. 17. Coarse-grained
CY
CB
Si
13.
2.17
14.
15.
16.
17.
18.
I'35 1.18
0.71
0.38
0.26
2.II
•
2.47
2.42
2.79
3.28
3.83
0'09 0'70 0.66 1'53
1.62
0'59
Statistics concerning
The present (1870) production of crude iron (pig-iron) amounts to
Crude-Iron. rather more than 200 millions of hundred weights. Of this quantity
the Production of
the under-mentioned countries produced:
United Kingdom of Great Britain and Ireland..
France
North America, U.S.
Prussia
Belgium
Austria
Russia
•
33
•
115,000,000 cwts.
24,500,000
•
20,200,000 ""
16,300,000
""
8,900,000
""
•
•
6,750,000
6,000,000 ""
4,500,000
""
Sweden
Luxemburg
Bavaria
Saxony
Würtemburg
Baden.
Hesse
Brunswick..
Thüringia
Australia
•
•
Italy
Spain
Norway
Denmark
• •
Iron-foundry Work.
•
•
•
1,100,000
732,000
280,000
138,000 ""
16,000
99
250,000
""
90,000
18,000
""
2,000,000
750,000
""
1,200,000
500,000 ""
300,000 ""
209,524,000 cwts.
Having a value of about 97.5 million pounds sterling.
For the manufacture of iron castings a somewhat mixed grey iron
Re-melting Crude Cast-Iron. is employed, because its qualities best suit the purpose. These
qualities are closeness of grain, strength, a capability to well fill the moulds, coupled with
sufficient softness to admit of boring, filing, &c. Although iron castings can be made
directly from the tapping of the blast-furnace, it is found advantageous and preferable in
practice to re-melt the pigs. This operation is carried on in crucibles in a cupola furnace,
or in a reverberatory furnace. Crucibles (made of plumbago or fire-clay) are only used
for making castings of small size. The quantity of iron melted in crucibles does not usually
exceed five or eight pounds.
Shaft or Cupola Furnace. For the purposes of the iron-foundry, the shaft or cupola furnace,
represented in Figs. 6 and 7, is more generally used. The cupola furnace is in form cylin-
drical, and from 25 to 3.5 met. high. The pig-iron, previously broken up to lumps of
suitable size, and the fuel, which may be either coke or wood charcoal, are placed in
alternate layers in the shaft a; the openings c and d are intended for the insertion of the
tuyeres connected with the blast. The opening leading to the spout, B, is closed during
the progress of the melting; as soon as the molten iron reaches the orifice at a, this opening
is closed by means of fire-clay, and the tuyere first placed in a is transferred to the
opening d. The molten metal is either conducted by the aid of channels direct to the
moulds, or tapped into suitable vessels and carried to the moulds. In many instances
cranes are used to transport the molten metal. Here also the application of hot air has
been attended with a great saving of fuel.
•
Reverberatory Furnace. In some cases pig-iron is melted in a reverberatory furnace, the iron
being placed on the smelting-hearth, which is covered with sand; the hearth is slightly
inclined and narrowed towards the tapping-hole. A strong coal fire is made up, and the
flame playing across the fire-bridge is directed over the entire length of the furnace, and
IRON.
19
thence into a high chimney. The molten metal on being tapped is conducted to the
moulds in the same manner as with the cupola furnace. Rather more than 50 cwts. of
pig-iron can be melted at once in a reverberatory furnace; but since the air has free access,
the iron becomes gradually decarbonised, and is thus rendered unfit for castings.
Making the Moulds. The most essential, and also most difficult, part of the iron-founder's
work is the proper construction of the moulds. According to the materials from which the
moulds are constructed, we distinguish-1. Sand moulding or green-sand moulding, the
material being a peculiar kind of sand (foundry-sand).-It is necessary for this sand to be
exceedingly fine, and yet sufficiently coherent that the sharpest angles and corners will
remain standing. This latter property is imparted to the sand by adding as much clay as
will render the mass capable of being squeezed with the hand into balls when moistened
with water. A certain amount of porosity is also requisite to enable the steam which is
formed when the molten iron comes into contact with the mould to readily escape. This
property is communicated by the addition of powdered charcoal. Sand-moulds are not
dried before the molten iron is poured in. Such objects as plates, grates, railings, and
FIG. 6.
FIG. 7.

e
AYAM AWA
AWWWW
་་་་་་ ་་་;
་་་
wheels, which are level on one side, are cast in oper sand-moulds; that is to say, on the
floor of the foundry, previously covered with sand of the requisite quality, the moulds
being obtained by pressing the patterns into the sand. For other branches of the work,
as, for instance, iron-pots, the box mould is used. 2. Dry sand moulding.-The forms are
made in sand and clay, or loam, care being taken to dry the moulds thoroughly before
casting. 3. Loam-casting.-The material used for this purpose is loam, which, previous
to being used, is sifted, moistened, and mixed with horse-dung to prevent the moulds from
cracking during drying. 4. Case-hardening, or casting in iron moulds. This mode of
casting iron only applies to some peculiar descriptions of work, as, for instance, the
cylinders of rolling-mills, some kinds of shot and shells, and railway waggon-wheels.*
By the use of iron moulds, the casting cools and solidifies very rapidly, and, as a con-
sequence, the outer layer becomes converted into white cast-iron, which is very hard.
Thus the cylinders for rolling-mills can be so made, that while the surface is very hard, they
are not brittle, and, therefore, fragile, because the interior consists of grey cast-iron.
Green-sand casting is by far the most general mode of casting: furnace bars, cast-iron
railings, grates, plates, wheels, and a variety of objects, are thus made. Dry-sand
moulding is used for the casting of iron gas- and water-pipes, and also of cast-iron
ordnance. This latter is preferably made from such pig-iron as contains grey and white
iron mixed; a higher degree of toughness and elasticity can thus be obtained. Dry-sand
moulding is also used for the making of small ornamental objects, so-called fer de Berlin,
such as cast-iron ink-stands, candlesticks, and a peculiar kind of cast-iron pins, as well as
brooches, ear-rings, and similar things. Loam-moulding is used for the casting of large-
sized cauldrons, bells, and other large objects for which no wooden pattern is made; also
for the casting of steam-engine cylinders. We distinguish in this kind of moulding three
chief parts, viz. :—
* This may be the case in Germany; but in this country the wheels are made of best
wrought-iron, and forged by means of steam-hammers.-ED.
20
CHEMICAL TECHNOLOGY
a. The core, or kernel, the size and shape of which corresponds to the interior of the
object to be cast.
b. The foundry-pattern.
c. The exterior mould, also termed the case.
The loam mouldings are very rapidly dried; the casting of statues and other monumenta!
work is done by loam moulding, but zinc is beginning to supersede iron for this purpose.
Whenever objects have to be cast, the surface of which is very unequal, i.e., so shaped
that a partial dismounting of the case is impossible, as may happen for instance with
statues and monumental work, the shape is made on the core by means of wax: the
pattern maker constructs a pattern, often consisting of a number of loose pieces; into this
the molten wax is poured, and the mould thus obtained is carefully placed on the core and
properly joined. The wax n:ould is brushed over with a mixture of pulverised graphite and
very finely divided clay, which operation is several times repeated; after this the mould is
covered with a layer of loam mixed with cow hair, and as soon as this layer is dry the wax is
removed by applying a gentle heat, a channel having been left by which the wax can escape.
Annealing. The castings, when sufficiently cool, are cleaned from adhering sand, the seams cut
Tempering off with a cold chisel, and in many cases submitted to a series of mechanical opera-
tions, as, for instance, cast-iron ordnance, which has to be bored, while other objects have to
be worked in the lathe and planed. Frequently cast-iron objects have become as hard and
brittle as if they had been cast from white pig-iron, and consequently are unfit for filing,
&c.; such iron is restored to the requisite softness by annealing or tempering. In this
operation the castings are submitted to a strong red heat and cooled slowly, being at the
same time protected from the oxidising influence of the air; the annealing is effected
either by a physical or chemical process. If the former is used, the castings are simply
covered with a thick layer of clay and made red-hot, the effect being a simple rearrangement
of the molecules of the iron, which is thus rendered soft again; the heating to redness is also
sometimes effected by placing the castings under a layer of dry sand or in suitably con-
structed vessels filled with charcoal or coke powder. If it is desired to impart to the
castings somewhat of the strength and toughness possessed by steel and malleable iron,
the tempering is so arranged, and heat applied for a longer time, while the metal is
surrounded by a mixture of pulverised charcoal, bone-ash, and forge scales, red oxide of
iron, oxide of manganese, or oxide of zine; cast-iron which has been uniformly and
thoroughly decarbonised, is called malleable cast-iron. A great many objects formerly
exclusively made of wrought-iron are now cast and treated in this way, while a number of
others, inclusive even of razors, are made of cast-iron superficially converted into steel by
a method which will be described under the heading of Steel. In order to prevent the
rusting of articles made of cast-iron, they are frequently covered with a varnish made from
coal tar and powdered graphite, or boiled linseed-oil and lamp-black, and when intended
for ornamental or domestic use they are bronzed or burnished.
Enamelling of Among the first cast-iron objects ever enamelled were the pans used in
Cast-Iron. kitchens for culinary purposes, but at the present time, especially in England,
the enamelling of cast-iron is carried on to a large extent, and includes a variety of things
made of cast- and even wrought-iron. The process in use is briefly as follows:-The
surface of the cast-iron to be enamelled is first carefully cleaned by scouring with sand
and dilute sulphuric acid, next a somewhat thickish magma, made of pulverised quartz,
borax, feldspar, kaolin, and water, is brushed over the clean metallic surface as evenly as
possible, and immediately after a finely powdered mixture of feldspar, soda, borax, and
oxide of tin is dusted over, after which the enamel is burnt in by the heat of a muffle.
In France an enamel is applied which consists of a mixture of 130 parts of flint glass,
201 parts of carbonate of soda, and 12 parts of boracic acid fused together and afterwards
ground to a fine powder. Enamelled iron has in some manufactured articles taken the
place of tinned iron or zinc.
Bar Iron.
Refined Iron.
B. MALLEABLE, BAR, OR WROUGHT-IRON.
In comparatively olden times the custom was to produce malleable
iron direct from its ores by a process still in use to some extent in Styria, Illyria, Italy,
Sweden, some parts of Asia, Andorra, and other localities. The process (a modifica-
tion of which is known as the Catalan process) consists in the reduction of the iron
ores, which must be very rich and pure, by means of charcoal, which serves also as fuel
on a hearth, the combustion being aided by a blast, often simply bellows; the lump of
iron thus obtained is immediately submitted to the blows of a heavy forge hainmer.
Excepting in the few instances just mentioned, this process of direct extraction of iron
IRON.
21
from its ores has been altogether abandoned, and has given place to the production of
malleable iron from pig-iron; the process by which this is effected is termed refining.
and consists in the removal of the greater portion of the carbon and other impurities
contained in the crude metal by oxidation. The crude metal chiefly employed for
refining is white pig-iron, preferably that containing the least possible quantity of
carbon, because this kind of iron becomes soft before melting and remains for a long
time very fluid, and therefore presents a larger surface to oxidising agents; the chemi-
cally combined carbon of white pig-iron burns far more readily than the graphite con-
tained in the crude grey cast-iron. The refining process is executed either :—(1) On
hearths (the German process); or (2) In reverberatory furnaces (puddling or English
process); In the preparation of bar-iron (3) by the forcing of air into the molten metal
(Bessemer and other similar processes). This latter process is described under Steel.
German Iron-Refining The hearth on which this process is carried out is represented in
Fig. 8. The crude iron is placed in the cavity a of the hearth, b, and the metal is
brought to fusion in such quantity that the molten mass has a length of from 1 to
13 metre, a width of about 27 centims., and a thickness of from 4 to 9 centims. The
cavity, a, is lined with thick plates of iron, and the tuyere, c, supplies the necessary
air from a blast which is directed against the molten metal. The hearth is first filled
with ignited charcoal; next the blast is turned on, and then the crude metal is placed
on the hearth, b, and becoming gradually melted, flows into the cavity, a. The action
of the blast causes the combustion of the carbonaceous matter of the metal, while the
FIG. 8.
FIG. 9.
Process.

from
sand adhering to the pigs, the silica due to the oxidation of the silicium contained in
the crude iron, and the silica contained in the ash of the fuel also play an important
part in the process, because these substances combine with the protoxide of iron which
is present, forming a slag,* composed of basic silicate of protoxide of iron (in 100 parts,
68.84 protoxide and 31'16 silica). This slag protects the iron during the refining pro-
cess, but is gradually run off, care being taken, however, to leave a sufficient quantity
to cover the metal. Mixed with forge scales (a mixture of proto- and peroxide of iron,)
the slag of the first refining is employed in the further refining process to decarbonise
the iron. When crude cast-iron is heated to redness along with these materials, the
oxygen contained in them is given off, and combining with the carbon contained in
the cast-iron, forms carbonic oxide and leaves malleable iron. The refining process
also causes the more or less complete elimination of such substances as aluminium,
phosphorus, and manganese from the crude metal, by converting them into alumina,
phosphoric acid, and protoxide of manganese, all of which are taken up in the slag.
As soon as all the iron has become fluid the slag is run off and the metal exposed to the
* According to MM. Mitscherlich, Hausmann, Rothe, and others, the slag sometimes
assumes the crystalline form and composition of olivine.
α
22
CHEMICAL TECHNOLOGY.
action of the blast, care being taken to work the metal about so as to render the action
uniform;
the somewhat thickish fluid mass becomes during decarbonisation more and
more fluid; and the stirring up, or raising up, as the operation is termed, is continued
until the iron is refined, which is shown by the fact of the slag becoming very rich in
protoxide of iron. Towards the end of the operation, the rich slag, SiO4,Fe2, is
formed, which along with forge scales, is employed for decarbonising the metal.
This rich slag is never crystalline in structure, but exhibits a dense tough mass of
higher specific gravity than the raw slag. The operation, called the last breaking
up of the lump, consists, first, in the rendering of the entire mass (the contents of
the hearth) semi-fluid by increased heat; and, secondly, in the separation of the
slag from the metal. This end having been attained, the lump, or ball, or bloom,
is removed from the fire, in the red-hot state, and brought under the lift-hammer,
a (Fig. 9) which is set in motion by means of a lifter and beam. By the blows of
the hammer all the particles of slag are squeezed out from the metal; afterwards
the lump is cut into smaller pieces, which are forged into bars; 100 parts of crude
cast-iron yield on an average 70 to 75 parts of malleable iron.
Swedish Refining Process. The Swedish process of iron-refining (also called Walloon-forging)
differs from the German process, inasmuch as only small quantities of crude metal are
operated upon at a time, while no slag is added, the decarbonisation being effected by the
action of the oxygen of the air. This process requires a great deal of fuel (in Sweden
almost exclusively charcoal), while at the same time a not inconsiderable quantity of the
iron is oxidised. The malleable iron obtained is, however, of far better quality, being
denser and tougher, owing to greater purity and freedom from slag.
The Puddling Process. The process designated by this name is carried on in a reverbera-
tory furnace. In countries where charcoal is scarce, and hence too expensive to be
applied to the refining of iron, coal is used, and, indeed, of later years, has be-
come more generally employed on the Continent for this purpose. For, although
the iron thus obtained is of inferior quality to that refined with charcoal, to the use of
coal alone must the increase in the production of iron to the present enormous
extent be attributed. Since coal contains sulphur, direct contact with iron has to
be avoided, and the operation is carried on in a reverberatory furnace, which, in
Puddling Furnace. this instance, is termed a puddling furnace, represented in vertical
section in Fig. 10, and in horizontal section in Fig. 11. F is the fire-place, A the
puddling hearth, and c the flue along which the gases are carried to the chimney.
The puddling-hearth, A, consists of a square iron box, to which air has free access
from the fire-place. A layer of refining (puddling) slag, to which some forge-scales
have been added, is first placed on the hearth, and heated until it begins to soften at
the surface. This point reached, the crude metal (by preference white cast-iron) is
placed on the hearth in quantities of from 300 to 350 lbs. at a time and heated.
When softened, the iron is spread evenly over the surface of the hearth by means
of a rake or stirrer, and continually stirred about (puddled), the heat being greatly
increased. D and E represent openings giving access to the hearth for the tools,
capable of being readily closed.
The soft pasty mass of metal exhibits on its surface blue flames of burning carbonic
oxide, the metal becoming at the same time thicker and thicker: the slag which is
formed runs off at B, and is tapped at intervals at o. When the iron has been
sufficiently puddled, it is scraped together and formed into lumps or balls, which are
submitted to the action either of heavy hammers or squeezers, to free the metal from
slag. Grey cast-iron, when used for puddling, is first converted into white cast-
iron by smelting in a reverberatory furnace, known as the refining process.
IRON.
231
The theory of the puddling process is the following:-The current of air which comes
into contact with the molten iron causes the formation of a not inconsiderable quantity of
protoperoxide of iron, the oxygen of which eliminates the carbon contained in the pig-iron
in the shape of carbonic oxide, which burns off with a bluish flame. The progress of the
decarbonisation renders the mass more and more pasty; while, in the interior, pieces of
malleable iron are gradually formed, which, being gathered together by means of the rake,
become loosely welded, and the iron not fully decarbonised runs together, and being well
stirred up soon undergoes the same change. Although this résumé of the puddling process
FIG. 10.

E
W
TALL
M
AURITIUNILE
is theoretically correct, in practice the process is not so simple, because-1. It is scarcel·
possible to mix all the carbon-containing iron intimately with the protoperoxide, and, as i
consequence, some of that oxide remains mixed with the iron, which is thereby rendere l
incapable of being welded (the iron loses cohesion and becomes of a gritty nature); thi
substance has to be, therefore, removed by the addition of coarse slag, which is thus con
verted into refined slag. The oxidation of the iron causes a loss of some 4 to 5 per cent.
while the loss from the combustion of the carbon amounts to a further 5 per cent.
FIG. II.
2. Th

crude iron always contains more or less blast-furnace slag and adhering sand and dirt con-
taining silica. During the puddling process any free silica present combines with the
blast-furnace slag, and when this slag, rich in silica, comes at the end of the process into
contact with protoxide of iron, while carbon is deficient, a portion of the silica (or silicic
acid) combines with the oxide, forming a slag which adheres to the sides and bottom of the
hearth, while a basic, not easily fusible slag remains mixed up with the metal. In the
puddling process the great drawback is that the complete removal of the slag from the
iron is practically impossible; at least, such has been the case hitherto.
That iron pre-
parel in this way, which may even contain two or more per cent. of such slag, is some-
times brittle and cold-short is not to be wondered at.
24
CHEMICAL TECHNOLOGY.
Heating with Gases. Instead of employing coal or coke as fuel, the reverberatory furnaces
are often heated with combustible gases escaping from the blast-furnaces or with gas made
for the purpose in a generator-an arrangement not unlike a coke-oven, in which such
refuse fuel as cannot be otherwise utilized, viz., waste of timber-yards, refuse charcoal,
peat, and small coal, is submitted to dry distillation. The generator is connected to the
reverberatory furnace in such a manner that the gases evolved in the former reach the
latter very highly heated. For some years Siemens's regenerator-furnace has been applied
to this purpose, and found to surpass all other arrangements of the kind. When crude
ן
P
M N
e
FIG. 12.
pig-iron contains much phosphorus, that element
may be eliminated during the puddling process by
adding to the metal a mixture of manganese,
common salt, and clay, reduced to powder. Sulphur,
when present, may be burnt off by adding litharge;
steam has also been used successfully for this latter
purpose.

Refining of Iron by
Mechanical Means.
The metal obtained by the
puddling process is submitted to heavy hammer-
ing or to squeezers in order to remove as much
mechanically adhering slag as possible; after
this it is ready for the operations carried out
Rolling Mills. in the rolling mill (Fig. 12) which
consists in the main of the following parts:-B B'
and A A' are grooved rollers made of chilled cast-
iron; A A' are destined for shaping flat bars, and
B B', for the shaping of square bars; by means of
the nuts, o o, the position of the rollers towards
each other can be regulated: the tubes, i i, carry
water for keeping cool portions of the machinery.
The contrivance M N serves to connect or dis-
connect the rollers from the steam engine or
water- wheel from which is obtained the motive
power; the cog-wheels F and cimpart motion to
the cog-wheels F' and c' connected with the upper
rollers A' and B', which are thus made to move in
the opposite direction to the under rollers. The
metal to be rolled is first roughly shaped by
means of heavy hammers (steam hammers are
now often used), and then passed gradually
through the variously sized grooves of the rollers.
Fig. 13 exhibits rollers of a peculiar construction,
viz., steel rings or discs wedged to iron shafting
so as to form alternately large and small grooves
for the manufacture of thin bars of iron, such as
nail-rods, &c.
A variety of rolled iron objects are made;
among these, square and flat bars, round bars,
T-pieces, angle-iron, hoop-iron, and nail-rods;
railroad rails constitute an important item.
Boiler Plate Rolling. The rolling of boiler- and armour plate is an isolated branch, since it
requires a metal of good quality, combining softness with toughness, and capable of being
worked far below red heat without becoming too brittle or requiring annealing too often;
for boiler- and armour-plates the metal is formed into slabs of proper size, which, while
nearly white hot, are forced through the rollers. After each succeeding passage of the
slab. the rollers are set tighter, the oxide (forge scale) which is formed on the surface of
IRON.
25
FIG. 13.
the metal is removed by brushing with wet coarsely-made heather brushes. Thin sheet-
iron is rolled out from plate-iron cut into small slabs, which are at first hot, but at a later
stage of the operation the rolling is performed cold, the metal
having been previously annealed in properly constructed
furnaces. Under the headings of Zinc and Tin the galvanising
and the tinning of iron are treated of; corrugated iron is
made by peculiarly shaped and grooved rollers.
Ir. n Wire The drawing of iron into wire requires particu-
Manufacture. larly tough and fibrous metal. In former days iron
wire was made by drawing thin circular bars, by the aid of tongs,
through holes made in steel plates; in the present day iron
wire, if stout, is made with rollers, while the thinner wire is
made with machinery to be presently described. The rolling-
mill for the drawing of iron wire up to a diameter of about 4 of
an inch consists of three rollers provided with grooves which correspond to and catch a bar
of iron when placed between, the bar being thus squeezed in the grooves; these rollers
make 240 revolutions a minute, and since the diameter is 8 inches their circumferential
velocity is 8.37 feet, or in other words 8 feet 4 inches of wire pass through the rollers
in a second of time; thinner wire is obtained by drawing, with the aid of machinery, the
stouter kinds of wire through holes made in hard and unchangeable materials, the size
of these holes gradually decreasing. For this purpose the previously annealed wire, from
toth of an inch diameter, is wound on the reel, A (Fig. 14); the end of the wire shaped
somewhat to a point is put through the hole made in the draw-plate, B; this hole being of a
slightly less diameter than that of the wire, which is next fastened to the hook, e (Fig. 15),
of the conically-shaped drum, c, which acquires a rotatory motion from the main shaft, D,
(Fig. 14), by means of conically-shaped cog-wheels, an arrangement being provided to con-
FIG. 15:


FIG. 14.

D
B
nect or disconnect the apparatus from the steam-engine, so as to stop or set in motion the
wire-drawing machinery without stopping the steam-engine. The shape of the holes in
the draw-plate is of the highest importance for the success of the operation, and to obtain
perfectly round wire the holes ought to be quite true; if, however, the holes were made
perfect cylinders through the entire thickness of the draw-plates the result would be that
the wire, instead of suddenly diminishing in size, would break; on that account the holes
are bored funnel-shaped. The draw-plate is made of steel, but for very thin wire hard gems
properly fastened and pierced are employed. Iron wire has to be repeatedly annealed during
the process, and since by this annealing operation, unless carried on with complete exclu-
sion of air, a layer of oxide of iron is formed, the wire requires treatment in what is
technically termed a scour bath, composed of dilute sulphuric acid and a certain amount
of sulphate of copper; the thin layer of copper deposited on the wire during the immersion
in this bath lessens the friction on the wire in passing through the holes. The thinnest
iron wire met with in the trade has a diameter of only th of an inch, and is known as
piano wire. Iron wire is rendered soft by being heated to redness, and is protected from
rusting by immersion in a bath of molten zinc, so-called galvanising. The uses to which
iron wire is applied are so varied that it is scarcely possible to enumerate them; this is
166
26
CHEMICAL TECHNOLOGY.
the less necessary, as in no country in the world is iron wire so largely used as in the
United Kingdom, especially instead of hemp for rope-making.
Properties of
Bar Iron.
Malleable- or bar iron is made up of an aggregation of fibres which,
according to the researches of Dr. Fuchs, are composed of a series of very small
crystals. Heavy blows, continuous vibration, and sudden cooling of the metal while
red-hot, all cause the particles to lose cohesion and alter the texture from fibrous to
granular: a well-known consequence of this change of structure, which is also
suddenly induced by great cold, is the loss of tenacity in the iron, often attended with
breakage, as happens frequently enough to railway wheel-tyres, axles, &c. The
colour of malleable iron is bright grey, the fracture granular or jagged: its specific
gravity varies from 7·6 to 7·9 (that of chemically pure iron being 7·844); from 0‘24
to 0.84 per cent. of carbon is present in the iron, the greater part in a state of
chemical combination, in fact there is only a trace of graphite.
The chemical constitution of malleable iron is shown in the following analytical
results:-Sample I. being English iron from South Wales; II., soft iron from Magde-
sprung on the Harz (Prussia); III., Dannemora iron from Sweden.
Iron
Carbon
III.
I.
98.904
II.
98.963
98.775
0'4II
0'400
0.843
Silicium
•
0.084
Ο ΟΙ4
0.118
Manganese
Copper
Phosphorus
•
0'043
0'303
0'054
•
nil
0'041
0*320
0.068
nil
nil
;
Malleable iron of good quality does not become brittle when placed red-hot into cold water
it ought not to lose its malleability when thus treated: it is far softer than white and
bright grey cast-iron, and is therefore easily filed, cut with the cold chisel, planed, and
shaped in various ways even cold; it melts with far more difficulty-requiring a much
higher temperature-than cast-iron; but malleable iron is possessed of the valuable property
of becoming, at a bright red heat (orange heat), so soft as to admit of two pieces being firmly
welded together. The malleable-iron of commerce is often more or less mixed with foreign
substances which in some cases impair its quality; if sulphur, arsenic, or copper is present,
the iron is thereby rendered red-short (breaks when hammered in the red-hot state);
silicium renders iron hard and brittle; phosphorus makes it cold-short, i.e. rather readily
breakable when cold, although not so when red-hot; calcium has the effect of greatly
impairing, if not altogether destroying, the welding capability of the metal.
As regards
the choice of the different qualities of malleable iron for various uses, it is not in the scope
of this work to enter into detail, the question being one of applied mechanics and
engineering rather than of chemistry. Swedish bar-iron is for certain purposes in high
repute, owing to the purity and strength of this kind of iron.
Steel.
Y. STEEL.
This substance differs from crude pig-iron and from bar-iron in the amount
of carbon it contains; from crude iron, moreover, by being capable of welding;
and again from bar-iron by being comparatively readily fusible: in reference to the
amount of carbon present, steel holds a position between crude pig-iron and bar-iron.
Recent researches have revealed the fact that steel contains nitrogen; but whether
this element really contributes to the peculiar properties of steel obtained from
different sources is not a definitely settled point. Steel is obtained of various quali-
ties by a number of processes, as will be seen in the following brief reference:
a. Directly from iron ores :—-
1. By the reduction of iron ores directly with the aid of fuel (chiefly charcoal), and a
blast on the hearth, the steel being obtained in the form of lumps (so-called
natural steel).
2. By the heating of certain iron ores along with coal, but without fusion (cementa-
tion steel from ores).
3. By the fusion of the iron ores along with charcoal in crucibles (cast-steel from ores).
IRON.
27
b. By the partial decarbonisation of pig-iron (rough steel, furnace-steel, or German steel):
4. By the refining (partial decarbonisation) of pig-iron by means of charcoal fuel on
the hearth (shear-steel).
5. By treating pig-iron in reverberatory furnaces fed by coal or blast-furnace gases
as fuel (puddled-steel).
6. By forcing air through molten cast-iron (Bessemer-steel).
7. By heating cast-iron to redness along with substances which will effect decarboni-
sation below the fusion point of the metal; if the substances employed for partial
decarbonisation are iron ores, the steel is called iron ore steel.
8. By melting crude cast-iron with such substances as those just mentioned.
9. By treating crude cast-iron with sodium nitrate (Heaton-steel, Hargreave-steel).
c. By imparting carbon to bar or malleable iron :-
10. By ignition with carbonaceous matter, but without fusion (cementation-steel).
11. By fusion with charcoal (cast-steel).
d. By combination of methods b and c, as in fluxed steel :-
12. By melting crude pig-iron and malleable iron together.
In India a kind of steel is still made directly from iron cres, and known as wootz (as to
the composition of this substance, see the "Chemical News," vol. xxii., p. 46); it is possessed
of excellent qualities. The Japanese also understand the art of making steel of most
excellent quality by rather rough and primitive means. According to the modes of
manufacture, we distinguish the following kinds of steel:-
Rough Steel. This material, obtained by the partial decarbonisation of crude pig-
iron, may be either:
1. Rough steel made on a hearth (natural steel), chiefly obtained from the pure
spathic iron ore, from which in Styria, Carinthia, Tyrol, and various other parts,
porous white pig-iron, or white pig-iron, with granular structure, is first obtained by
means of charcoal and coke as fuel; the ordinary grey cast-iron can also be used, but
the resulting steel is not of such good quality. The general arrangement of the
hearths on which rough steel is made is the same as for the operation of iron refining;
the only difference is in the mode of placing the metal in reference to the blast, the
operation being so conducted as to cause only the gradual combustion of the carbon ;
the workmen take care to control the blast and place the metal in a manner which
enables them to stop the further action of the air the moment the proper amount of
decarbonisation has been effected.
2. Steel obtained in a reverberatory furnace, or puddled steel, obtained from various
kinds of cast-iron by a process akin to the puddling of crude cast-iron, the burning off
of the carbon not being carried so far. This mode of manufacturing steel is exten-
sively employed, and yields a material well suited for the making of various kinds
of machinery, railway carriage-wheel tyres, and is also largely used in the manu-
facture of cast-steel.
Styrian and Carinthian cast-steel (charcoal iron-steel) is far more expensive than
puddled steel, but the former is indispensable-at least on the Continent-for the manu-
facture of all kinds of cutting-tools.
3. Bessemer-steel. Mr. Henry Bessemer, in 1855, first applied a process of making
steel directly from cast-iron; the process consists in forcing large quantities of air
through molten crude iron; the consequence is that the conversion of the iron into steel
is effected in a comparatively brief space of time; moreover, the resulting steel remains
fluid; the difference of the action of the air as an oxidising or decarbonising agent in
this instance, as compared with the process of steel-making, mentioned under No. 1
and 2, is that in the case of the Bessemer method, the air thoroughly penetrates and
comes into contact with every particle of iron; whereas, in the other instances, the
action of the air is only at the surface; and since the steel obtained by methods
28
CHEMICAL TECHNOLOGY.
I and 2 is less fusible than the crude iron used, a second refining or smelting becomes
necessary to render the steel uniform and homogeneous.
The Bessemer process is executed either in diminutive shaft-ovens or in egg-shaped
vessels made of boiler-plate converters, and lined with fire-clay; projecting for some inches
through the inside of the bottom, five gth inch wide fire-clay tubes are carried, through
which powerfully compressed air can be forced. The apparatus is placed in close
proximity to a blast furnace, so as to admit of running the molten iron, purposely kept at
a very high degree of heat, readily into the oven or other vessel, while at the bottom of the
converter there is an aperture closed with a fire-clay plug, through which the molten steel
can be discharged. As soon as the blast is turned on and the vessels half filled with
molten iron, a very violent action ensues, the metal apparently begins to boil, flames and
myriads of sparks burst forth from the converter (this phenomenon appears to be due to
the fact that particles of partly decarbonised iron and a mixture of iron and oxide are
driven against each other). According to the duration of the action of the blast (10 to 25
minutes) steel or bar-iron may be made, and of late, even in making steel, the action is
carried to the highest possible pitch, and to the resulting metal a portion of molten white
pig-iron is added. Bessemer steel is largely used for a variety of purposes; but it is not
suitable for the manufacture of such cutting tools and instruments as require a keen and
durable edge; on the other hand, Bessemer metal is an excellent material for the manu-
facture of boiler and armour-plates, ordnance, railroad-rails, and a great variety of heavy
machinery. As might be expected, this method of steel-making has rapidly spread from
England to all parts of Europe and to America; and as a proof of the handsome profit
earned by the inventor, whose royalty amounts to Is. per cwt., we may state that the total
quantity of Bessemer steel produced in Europe in the year 1869 amounted to 5.5 millions
of cwts., 70 per cent. thereof being produced in Great Britain.
M.
4. Uchatius and Martin Steel are also directly prepared from crude cast-iron, by
mixing granulated crude pig-iron, made from native magnetic iron ore, along with
pulverised spathic iron ore, and fusing this mixture in plumbago crucibles.
Martin replaced the use of the crucibles in this process by that of the somewhat
hollow floor of a reverberatory furnace heated by means of a Siemens's regenerative
gas-furnace.
A quantity of crude pig-iron is melted under a layer of slag, and
from time to time bar-iron is added until a sample taken out is found to possess the
texture and good qualities of malleable- iron. When this stage has been reached,
a certain amount of crude cast-iron is added, whereby the entire quantity of metal
is converted into a kind of cast-steel, chiefly suited to the making of railroad-rails,
wheel-tyres, and especially gun-barrels and ordnance. Tunner's steel, which dates
from 1855, also known as malleable cast-iron, is obtained by igniting white pig-
iron to bright redness with substances which give off oxygen (oxides of iron and
zinc and peroxides of manganese) when thus treated.
5. Heaton steel. Prepared by a process devised by Mr. Heaton, in which crude
iron is heated with nitrate of soda (Chili-saltpetre). By this method not only the
carbon is eliminated, but the sulphur and phosphorus being oxidised and converted
into phosphates and sulphates, find their way into the slag. The principle of this
method is the same as in Mr. Hargreaves's plan, and again identical with a proposed
new method of Bessemer steel-making.
Carbon to Wrought-Iron.
Steel Making by Imparting II. The second kind of steel is that known as cementation-
steel-a metal prepared by the ignition of bar-iron in contact with carbonaceous
matter, preferably containing nitrogen. The bar-iron to be employed for this
purpose should be of the very best quality, and since in Great Britain and France,
the best iron produced is not good enough, both these countries draw largely upon
Sweden for a supply of Dannemora iron, made from magnetic and red hæmatite-iron
ores mixed. The Russian iron from the Ural is of the same good quality, but the
transport is at present far too costly. It is almost superfluous to mention that the
chief seat of the steel manufacture in England is Sheffield.
IRON.
29
The process of making cementation-steel is simple enough. The bars of iron are placed
in fire-clay boxes, in layers alternating with the carbonaceous matter (cementation-
powder). Two of such boxes are placed in a furnace which is heated with coal, and the
boxes are kept at a red heat for some six or seven days, and after cooling, the bars, con-
verted into steel, are taken out. Each furnace contains from 300 to 350 cwts. of iron. In
the cementation-powder such substances as will form cyanide of potassium, or ready-
formed cyanides, ought to be present. It appears from recent researches that cyanogen
(CN) is to be viewed as the carrier of the carbon to the metal. The crude steel (blistered-
steel) obtained by this operation is not, as such, fit for use, but has to undergo a process
of purifying.
Refined-Steel. Not only cementation-steel, but also that obtained by the other methods, is
Shear-Steel. too coarse and not sufficiently homogeneous for immediate use, and therefore
a process of refining has to be resorted to. This process consists, firstly, in the hammering
out of the steel bars, previously made red-hot, into thin rods, which are, while red-hot,
quenched with cold water. Next a number of these are placed together in the form of a
bundle, which is again made red-hot, well hammered, and afterwards rolled into bars.
The method of refining here alluded to is more suited to the quality of steel obtained from
crude pig-iron than to cementation-steel. Steel thus refined, on account of being used for
making large pairs of scissors or shears, bears the name of shear-steel.
Cast-Steel. Cast-steel, in modern industry, has assumed a most enormous importance,
as evidenced by such gigantic works as those of M. Krupp, at Essen (Prussia). The
existence of these works notwithstanding, Sheffield takes the foremost rank in the
manufacture of cast-steel. The following is the plan pursued :-The bars of blistered-
steel, cut to a convenient size, are introduced into crucibles made of Stourbridge clay,
which are heated in furnaces similar to glass-melting ovens, fed with coke or coal as
fuel; the molten metal is cast into bar-shaped moulds, and the bars are, after cooling,
again heated to redness and hammered or rolled out in a mill. As to the uses to
which cast-steel is applied, suffice it to say that heavy ordnance, as well as large
bells, excellent cutting-tools and files, best cutlery, and many surgical instruments,
number among them. Cast-steel is homogeneous, and therefore strong and durable.
Steel made from Malleable III. A third kind of steel (varying according to the mode and
materials of production) is that called Glicenti-steel, obtained by melting together a
peculiar white pig-iron (spiegel-iron), and bar or malleable-iron. The toughness,
hardness, and malleability of this metal depend upon the quantity of bar-iron which
has been added to the mixture.
and Crude Cast-Iron.
Surface Steel-Hardening. It frequently happens that for certain purposes soft iron only
requires to be converted into steel superficially, an operation termed surface-harden-
ing or surface-steel hardening, which is done by placing the metal, previously
polished with emery, in a suitable vessel covered in cementation-powder (see
above); the vessel and contents being next heated to redness, malleable iron tools,
spanners, for instance, keys, and small objects, may be readily surface-hardened
by being, while red-hot, dusted over with powdered ferrocyanide of potassium,
yellow prussiate, or with pulverised borax and pipe-clay.
Properties of Steel. The colour of steel is bright greyish-white, its texture is uniformly
granular, the better the quality the smaller the grain. Sound soft (that is not
hardened) steel, never exhibits the coarse texture characteristic of crude cast-iron, nor
the fibrous texture of bar-iron. Hardened-steel exhibits a fracture very similar to
that of the finest silver, so close that the granular texture can hardly be detected with
the naked eye. When red-hot, steel is nearly as readily malleable as bar-iron, and
may be welded, but very careful management is required to prevent its becoming
decarbonised. By immersing a piece of steel in dilute hydrochloric or nitric acid, the
texture of the metal becomes apparent, and this test may be applied to determine the
quality The specific gravity of steel varies from 7.62 to 7·81, and decreases in
30
CHEMICAL TECHNOLOGY.
hardening (for instance, from 7.92 to 7:55); the quantity of carbon contained in steel
varies from o'6 to 19 per cent; the toughness, tenacity, and hardness of steel,
increase with the quantity of carbon it contains, but good steel never contains
graphite; the high degree of elasticity exhibited by good steel decreases with the
hardness. When red-hot steel is suddenly quenched with cold water, the metal
becomes far harder, but also brittle, and will even scratch glass and withstand the
file; when brightly polished, if steel is gradually heated, it assumes peculiar shades
of colour (annealing or tempering colour). This colouration is due to the formation
on the surface of the steel of thin layers of oxide, which exhibit colours like other
very thin surfaces-soap bubbles, for instance, or a drop of oily or tarry matter
extended over water. The operation which causes the formation upon steel of these
colours is called tempering.
Tempering. In judging the proper temperature and the corresponding hardness these
tints serve admirably. Since it is often rather difficult to heat a piece of steel
uniformly, molten metallic mixtures are employed, being chiefly made up of tin and
lead; the bright hardened steel is kept in these molten mixtures until it has assumed
the temperature of the bath. The following tabulated form exhibits the composition
of the metallic baths, which experience has proved to be the best for the tempering of
cutlery :-
Temperature.
Lancets
Razors
Pen-knives
Pairs of scissors
Composition of
metallic mixture.
Melting
point.
Pb.
Sn.
7
4
220°
Hardly pale yellow.
8
4
2280
8/1/1
4
2320
14
4
254°
Brown.
19
4
265°
Pale-yellow to straw-yellow.
Straw-yellow.
Purplish-coloured.
}
48
288~
Bright-blue.
nd } :
50
2
2920
Deep blue.
•
› in boiling
linseed-oil)
3160
Blackish blue.
Clasp-knives, joiners' and
carpenters tools ..
Swords, cutlasses, watch-
springs
Stilettos, boring-tools, and
fine saws
Ordinary saws
other Metals.
Such tools as are required to work iron and other metals and hard stones are
heated to bright-yellow; razors, surgical-instruments, coining dies, engravers'-tools,
and wire-drawing plates follow next to straw-yellow; carpenters'-tools to purplish-
red; while such tools and objects as are required to be elastic are heated to the violet
or deep-blue tint; the less steel is heated the harder it remains, but also the more
brittle. Other substances than carbon (for instance, silicon and boron) may be capable
of imparting to iron properties similar to those we are acquainted with in steel. Some
Steel and other metals mixed with steel in greater or lesser quantity improve the
quality in some respects; for instance, for the last few years steel has been made in
Styria, which, owing to its containing tungsten, is exceedingly tough and hard.
Damascene, or This steel, specially celebrated for making swords, was first made
at Damascus. Its name, Damascene, is applied to the property it possesses of
exhibiting a peculiar appearance when acted upon by an acid; but this appears to be
due rather to some imperfection of the welding of the metal, since, after melting, the
same peculiar shades of colour do not appear. We have already alluded to the recent
researches concerning the true composition of this metal. One of the largest collec-
Wootz- Steel.
IRON.
31
tions of tools, swords, gun-barrels, and bars of this kind of steel to be found in Europe
is in the India Museum, Whitehall. In order to elucidate the composition of some
kinds of steel, the following analyses are appended :-The samples are—1. Refined
steel, from Siegen (Prussia); 2. Cast-steel, from Schmalkalden (Prussia);
3. Puddled-steel; .4. Steel from Russian cast-ordnance; 5. Cementation-steel,
Elberfeld (Prussia); 6. English cementation-steel; 7. Krupp's steel (Essen).
3.
4.
5.
6.
7.
97*91 98*154 98.602 98.75 99*01 99*12 99*351
I.
2.
Iron
Carbon {CB}
I'730
I'69
1*380 I'02 0.41
Ο ΟΙΟ
trace
0'15
0'08
1.87
0'532
Silicium
0'03
0'202
0'006
0'04
ΟΙΟ
0'032
Sulphur
trace
0'003
Ο ΟΟΙ
Phosphorus..
trace
Ο ΟΟΙ
Manganese..
Copper..
I
1
0'012
0'37
100*00 100'000 100'000 100'00 99:50 101'09 99'917
Siderography or Steel The engraving of steel requires plates made of cast-steel, which, in
Engraving. order to be sufficiently soft for the engraver's tools, are first superficially
decarbonised, and after the engraving is made, again hardened. The engraved plate is
not employed direct for printing, but is used as a matrix for the preparation of plates to
be printed from; this process is carried out in the following manner:-A solid cast-steel
cylinder, turned in a lathe, is superficially softened, and the engraved plate is placed
under this cylinder, so that with great pressure and a slow revolution of the cylinder, the
plate moving also very slowly, a relief of the engraving is produced on the cylinder, and
this being again hardened, is employed to reproduce the engraving on other metallic
plates, which may be either copper or soft steel. Instead of engraving the design on
soft steel plates, etching is often resorted to, for which purpose corroding fluids, such as
nitric acid (aquafortis), nitrate of silver, sulphate of copper in solution, or, lastly, a solu-
tion of 2 parts of iodine, 5 of iodide of potassium, and 40 of water, are used.
Statistics of Steel The annual production of steel in Europe may be roughly estimated for
Production. 1870 at 6,285,000 cwts. at 50 kilos. to the cwt.
The imperial English cwt. is equal to 508-023 kilos.; of this total the undermentioned
countries produce:-
Copperas,
Green Vitriol.
United Kingdom of Great Britain and Ireland 2,300,000
France
Belgium..
North German Confederation
Austria
Sweden
Russia
Italy
Spain
• •
•
Total
• •
•
•
•
•
D •
IRON PREPARATIONS.
•
1,350,000
125,000
•
I,120,000
900,000
•
250,000
150,000
75,000
15,000
6,285,000
The substance called copperas and green vitriol, sulphate of protoxide
of iron (FeSO4+7H2O), is met with in the trade in the form of greenish-coloured
crystals possessed of an inky astringent taste; on exposure to dry air the crystals
effloresce, and are gradually converted into a yellowish powder-basic sulphate of
peroxide of iron.
100 parts of the chemically pure crystallised salt consist of:-
26.10 parts of protoxide of iron.
29'90
44'00
""
sulphuric acid.
water.
32
CHEMICAL TECHNOLOGY.
Preparation of Green
in Alum
•
Since the minerals ordinarily used in the manufacture of alum-
Vitriol as a by-product the alum schists—generally contain iron pyrites (FeS2), either as
such or already partly converted into a basic sulphate of the peroxide (which, on
being treated along with the alum shale, becomes by weathering and roasting
converted into protosulphate and peroxide of iron), green vitriol is frequently a by-
product of alum manufacture, and is obtained by evaporating the mother-liquor
containing iron, and leaving it to crystallise. In some localities, as, for instance,
at Goslar (Prussia), on the Hartz mountains, the liquor obtained by the lixiviation
of the iron-containing minerals alluded to is first evaporated for the separation of
the green vitriol, then a potassa or ammonia salt added to the remaining acid liquid
to obtain alum.
Vitriol in Beds.
the residues of
I
Preparation of Green The material sometimes rather largely found in coal pits, and
called brass (iron pyrites), is collected and placed in layers over a somewhat
excavated surface, which has been rendered impervious to water by puddling with
clay, and made to incline slightly in one direction where water-tanks stand,
into which scraps of old iron are placed with the view of saturating any free acid;
the pyrites, placed on these beds to a thickness varying from 1 to 3 or 4 feet, is
slowly oxidised by atmospheric agency, and the falling rain carries into the tanks a
more or less strong solution of copperas, which, when sufficiently concentrated,
is slowly evaporated, some scrap iron being placed in the evaporating-pans. In
Gren Vitriol from Countries where iron pyrites abounds, and fuel and labour are
Pyrites Distillation. Sufficiently cheap to make the distillation of sulphur from pyrites a
profitable business, the residues are utilised in green vitriol making, a salt which
thus made must, of necessity, contain a good deal of impurity. The brown sulphuric
Green Vitriol from acid or chamber acid, also such waste sulphuric acid liquids as are
and Sulphuric Acid. obtained in the oil and petroleum refining, are sometimes used as
solvents for scrap-iron for the preparation of green vitriol, which may also be made
by boiling the finely pulverised puddling and iron refining slags with sulphuric acid.
In localities where spathic iron (carbonate of protoxide of iron, FeCO3)
Iron Ore. occurs in a pure state, that mineral may be usefully applied to the prepara-
tion of green vitriol by treatment with sulphuric acid, and evaporating the solution thus
obtained. The sulphate of iron (protoxide), prepared on the large scale, is often met with
crystallised round a small thin stick of wood, which is hung up in the solution to promote
crystallisation; sometimes, at least abroad, a so-called black vitriol is met with, which is
simply green copperas superficially coloured black by means of some astringent decoction,
such as nut galls.
Metallic Iron
From Spathic
Uses of Green Vitriol. This substance is employed as a disinfectant, as a mordant in dyeing
and calico printing for various black and brown shades, for the preparation of ink, the
deoxidation of indigo-so-called cold vat-in gas purifying, in the precipitation of gold
from its solutions, in the preparation of Prussian blue, in the manufacture of fuming
(Nordhausen) sulphuric acid, and for a host of other purposes.
Iron Minium. During the last 10 or 15 years a large number of substances under this
name have been introduced as paints, especially for iron sea-going vessels and other
ironwork. The late Dr. Bleekrode analysed two samples of this paint, one of which,
made and sold by M. Cartier in Belgium, was found to consist in 100 parts of:-
Moisture
Red peroxide of iron
Clay
Lime..
2.75
68.27
•
27.60
0'40
A sample of Holland's iron minium was found to contain in 100 parts:-
Water
Peroxide of iron
Clay (burnt)
6.00
85:57
8.43
"
IRON.
33
In Dr. G. J. Mulder's work on the "Chemistry of Drying Oils "*-second or applied
part-attention is called to the fact, and supported by results of analyses of different iron
miniums obtained by the author, that some of these paints contain free sulphuric acid,
which is always present in colcothar; this acid may exercise an injurious effect on iron
painted with such materials.
It is hardly necessary to point out that the use of iron minium as paint is less expen-
sive than the use of red-lead, in the proportion of 20 to 30 for coating the same extent
of surface.
of Potassa.
Yellow Prussiate The yellow-coloured salt, generally known as yellow prussiate of
potassa (ferrocyanide of potassium, K4FeCу6 + 3H2O), is, in a technical point of
view, a very important substance. It crystallises in large lemon-coloured prismatic
crystals, which are not affected by exposure to air, are not poisonous, and possess
a sweetish bitter taste. This salt is soluble in 4 parts of cold and 2 of boiling
water, but is insoluble in alcohol; in 100 parts there are:-
37'03 Potassium,
17'04 Carbon,
19.89 Nitrogen,
13*25 Iron,
12'79 Water.
Cyanogen,
At 100° the water is driven off. The salt is prepared on a large scale by igniting
such carbon as contains nitrogen to a red heat with potassa-carbonate in closed
vessels. The quantities of the materials may be varied, the relative proportions
being given by some makers as 100 parts of potassa-carbonate to 75 of the nitro-
genous carbon, or, according to Runge, 100 parts of carbonate of potassa, 400 of
calcined horn, and 10 parts of iron-filings.
The fusion of these ingredients is carried on either in closed iron vessels of a
peculiar shape, or in a reverberatory furnace. The iron-vessel, a, termed a muffle
mr
FIG. 16.
i
FIG. 17.

BEFBE
(Fig. 16) is egg or pear-shaped, having a diameter of 1.2 metres, a width of o'8 metre,
and varying from 12 to 15 centims. in thickness. As shown in the woodcut, the iron
vessel is placed in the furnace in such a manner as to be exposed to the action of the
flame and hot gases on all sides, being supported at the back by a projection about 27
centims. long, and resting at g on the brickwork, leaving space sufficient for the gases
generated in the interior to pass off by c into the chimney-flues; m is an iron cover
which is closed during the operation of melting, g being an opening in the front wall
of the furnace, through which the ingredients are put into the iron vessel, and the
* The original is in Dutch, and the work has not been translated into any other language.
4
34
CHEMICAL TECHNOLOGY.
molten mass taken out. The shallow pan, i, on the top of the furnace, is intended
for the evaporation of the liquor obtained by treating the molten mass with water.
The use of the iron vessel, however, is attended with the serious drawback that the
iron is eaten into holes in a comparatively short space of time; and, though this
action is greatest on the lower part of the vessel, and it may therefore be turned
bottom upwards, and the holes stopped with fire-clay, the vessel has soon to be
replaced by another. It is on this account, and also owing to the fact that a larger
quantity of raw material can be operated upon at once, that instead of the apparatus
described above, there has come into general use a reverberatory furnace, Fig. 17,
arranged with a shallow cast-iron pan, a, from 1 to 1·8 metre in diameter, with a rim
about 1 decim. high; b is the fire-place; g the bridge; c a flue leading to the
chimney, e. Sometimes the hot air is applied to the heating of evaporating-pans,
being carried under them before entering the chimney. The result of the ignition
is the formation of a black mass, technically called the metal, yielding the liquor
from which the crude salt crystallises. The salt is purified by re-crystallisation,
while the black residue is employed as a manure.
The theory of the formation of the ferrocyanide of potassium is as follows:-The
carbonate and sulphate of potassa, the nitrogenous coal and the iron reacting upon each
other, give rise to the formation first of sulphuret of potassium, which in its turn
converts the iron into sulphuret, while the nitrogen contained in the charcoal unites,
under the influence of potassium, with the cyanogen of the carbon, which again in its turn
combines with the potassium, giving rise to the formation of cyanide of potassium. When
the fused mass is treated with water, cyanide of potassium and sulphuret of iron decom-
pose each other, the result being the formation of ferrocyanide and sulphide of potassium,
the last-named salt remaining in the mother-liquor. M. E. Meyer states (1868) that it is
more advantageous to employ, instead of the sulphuret of iron, the carbonate of that
metal, for the purpose of converting cyanogen into ferrocyanogen, because the ferro-
cyanide of potassium crystallises far more completely and freely from solutions not con-
taining any sulphuret of potassium. Professor Dr. von Liebig has since proved that the
fused mass only contains cyanide of potassium and metallic iron, and not any ferrocyanide
of potassium, which is only formed by treating the molten mass with water, or more
slowly by its exposure to moist air. Among the materials frequently added to the fusing
mass are scraps of metal, the refuse of leather, dried blood and other dry animal offal,
because the ammonia evolved by their decomposition in the presence of an alkali aids the
formation of cyanide of potassium. According to M. P. Havrez, the crude suint obtained
from wool is an excellent material for the preparation of ferrocyanide of potassium, since
100 kilos. of the suint contain about 40 kilos. of carbonate of potassa, from 1 to 2 kilos.
of cyanide of potassium, and about 50 kilos. of combustible hydrocarbons, the heating
value of which is at least equal to that of 40 kilos. of coal.
It has been tried to obtain the cyanide of potassium on a large scale, by causing a
current of ammoniacal gas to pass through and over carbonate of potassa heated to
redness; and also to obtain cyanide of potassium from, or by aid of, the nitrogen of the
atmosphere. This process was tried nearly 40 years ago at Mr. Bramwell's works near
Newcastle-on-Tyne, but was found to be a failure commercially. The reader interested in
a detailed account of this process inay find it in the excellently-written chapter on the
manufacture of the prussiates, in Richardson and Watts's "Chemical Technology." As it
has been proved by experiment that baryta, far more readily than potassa, converts carbon
and nitrogen into cyanogen, forming cyanide of barium at a lower temperature, baryta
might perhaps be substituted for potassa, but as yet this plan is not carried out commer-
cially. According to Gélis (1861), the yellow prussiate may be prepared by the mutual
reaction of sulphide of carbon and sulphide of ammonium, the resulting sulphocarbonate
being converted into sulphocyanide of potassium by means of sulphuret of potassium, by
which reaction sulphuret of ammonium and sulphuretted hydrogen are volatilised. The
sulphocyanide of potassium is next converted into ferrocyanide of potassium by being
heated with metallic iron to redness, sulphuret of iron being at the same time formed.
It is evident that this process could not be carried out commercially. Mr. H. Fleck
described, in 1863, a plan for preparing the ferrocyanide by the action of a mixture of
sulphate of ammonia, sulphur, and carbon, upon fusing sulphide of potassium, which
thus becomes sulphocyanide of potassium, one-half of the nitrogen of the sulphate of
IRON.
35
ammonia remaining in the fused metal as cyanogen, while the other half escapes as sul-
phide of ammonium, which is again converted into sulphate of ammonia. The sulpho-
cyanide of potassium produced is treated with metallic iron at a red-heat, and thus
cyanide of potassium and sulphide of iron are produced. This process is also too cumbrous
and expensive on a large scale.
Applications of the This salt is employed in the manufacture of the red-cyanide or prussiate,
Yellow Prussiate. in the preparation of Berlin blue, and of cyanide of potassium (the impure
salt as met with in commerce), in dyeing and calico-printing for the production of blue and
brown-red colours, for the purpose of surface-hardening small iron articles, and lastly as
an ingredient of white gunpowder, and for use in chemical laboratories.
Red Prussiate. The so-called red prussiate of potassa, properly ferricyanide of
potassium, or Gmelin's salt, K3FeCy, is prepared on a large scale and extensively
used in dyeing and calico-printing. This salt crystallises in prismatically-shaped
ruby-red-coloured, anhydrous crystals, which consist in 100 parts of:-
35˚58 Potassium,
21.63 Carbon,
25'54 Nitrogen,
17.29 Iron.
Cyanogen,
It is prepared by submitting either the solution of the yellow prussiate or that
salt in powder to the action of chlorine gas until a sample, when heated, yields
no precipitate with a solution of a per-salt of iron. When the dry and pulverised
yellow prussiate is acted upon by chlorine gas, the salt is frequently placed in casks,
closed so as only to leave a small outlet, while the vessel can be made, by means
of machinery, to turn slowly on its axis, so as to bring all the particles of the
salt into contact with the chlorine. Sometimes, again, the pulverised yellow prus
siate is placed on trays in a chamber, into the top of which chlorine gas is admitted;
when no more chlorine is absorbed the newly-formed salt is, if a solution of the
yellow prussiate has been operated upon, evaporated to dryness, or in the case where
the dry powder of the salt has been taken, the newly-formed salt is dissolved in the
smallest possible quantity of water, and the solution left to crystallise, the mother-
liquor containing chloride of potassium. This reaction is represented by-
K4FeCу6 + Cl = KCl + K3FeCy.
Yellow prussiate.
Red prussiate.
The powdered red prussiate is of an orange-yellow colour.
According to
M. E. Reichardt (1869) bromine may be successfully employed instead of chlorine
for the preparation of this salt, which is chiefly used for dyeing wollen fabrics blue,
and, with solutions of caustic soda or potassa, for the Mercerising process of cotton.
Cyanide of Potassium. This salt is obtained in an impure state-Liebig's or crude cyanide of
potassium-by the fusion of the yellow prussiate of potassa in a porcelain crucible, con-
tinued as long as nitrogen escapes. Carburet of iron sinks to the bottom of the crucible,
while the crude cyanide is poured off in a state of fusion; 10 parts of the yellow prussiate
of potassium yield 7 parts of crude cyanide, (K,FeCy=4KCy+ FeC₂+2N). According
to Liebig's plan, the cyanide of potassium is prepared by fusing 1 molecule of ferrocyanide
of potassium with 1 molecule of carbonate of potassa; by this method 10 parts of the
ferrocyanide, yielding 88 cyanide of potassium, mixed with 2-2 parts cyanite of potassa.
For all technical and industrial purposes it is far cheaper to use cyansalt, a mixture of
the cyanides of potassium and sodium, prepared by fusing together 8 parts of previously
dried (anhydrous) ferrocyanide of potassium and 2 parts of carbonate of soda. As
this mixture fuses readily, the carburet of iron casily separates; moreover, the salt thus
obtained is less liable to decomposition on exposure to air, and its preparation requires
less heat. The industrial applications of the crude cyanide of potassium, or of the cyan-
salt, are the following:-In the process of electro-gilding, for the preparation of Grénat
soluble, isopurpurate of potassa, from picric acid, and in the reduction of metals. It
36
CHEMICAL TECHNOLOGY.
nas been mentioned, while treating of the blast-furnace process, that cyanide of potassium
is formed during the reduction of iron.
Berlin-Blue. This substance, so named when it was accidentally discovered at Berlin,
in 1710, by Diesbach, is chemically a ferrocyanide of iron, more correctly ferrous-
ferric cyanide. A distinct variety of this substance is known as Paris-blue. Three
different kinds of Berlin-blue are known, viz., neutral, basic, and a mixture of the
two, differing in composition and prepared by different processes.
(a). Neutral Berlin-blue, also known as Paris-blue, is obtained by pouring a solution of
yellow prussiate into a solution of chloride of iron, or into a solution of a peroxide salt of
iron the result is the formation of a large quantity of a magnificently blue-coloured pre-
cipitate, very difficult to wash out and always retaining a certain quantity of the yellow
prussiate, which cannot be removed by washing.
:
(b). Basic Berlin-blue is obtained by precipitating a solution of yellow prussiate with a
solution of a salt of protoxide of iron (green copperas), the result being at first the forma-
tion of a white precipitate of protocyanide of iron, which, either by exposure to air, or by
the action of oxidising substances, becomes blue; because a portion of the iron is oxidised
and another portion takes up the cyanogen thus liberated, converting some of the proto-
cyanide into percyanide, which in its turn combines with the unattacked protocyanide to
form Berlin-blue, with which, however, some peroxide of iron remains mixed. It is stated
that basic Berlin-blue is distinguished from neutral Berlin-blue by being soluble in water;
but this solubility is due to the presence of some of the yellow prussiate, and is not a
property inherent in the basic Berlin-blue in a pure state.
(). As the materials employed on a large scale are neither pure protoxide nor pure
peroxide salts of iron, but a peroxide containing protosalt of iron, the precipitate obtained
consists at first of a mixture of neutral Berlin-blue with more or less of the white proto-
cyanide of iron, which afterwards becomes basic Berlin-blue; accordingly the Berlin-blue
of commerce is a variable mixture of neutral and basic Berlin-blues. The iron salt
employed is green copperas (sulphate of protoxide of iron), which of course should not
contain any appreciable amount of copper, the salts of this metal, as is well known,
yielding with yellow prussiate of potassa a chocolate-brown coloured precipitate.
Old Method of Preparing The sulphate of iron and alum are dissolved together in boiling
Prussian-Blue. rain or river-water; the fluid, while yet hot, is decanted from any
sediment and forthwith poured into a hot aqueous solution of yellow prussiate, care being
taken to stir the mixture, and to add the copperas and alum-solution as long as any preci-
pitate is formed. The liquor is run off, and the precipitate washed with fresh water, until
all the sulphate of potassa is removed; after which the precipitate is drained on filters
made of coarse canvas. This having been accomplished the substance is suspended in
water in a boiler, and, while being heated to the boiling-point, nitric acid is added; after
a few minutes' boiling, the contents of the boiler are poured into a large wooden tub or
cask, and strong sulphuric acid is added. The solution is now allowed to stand for some
time, during which the blue colour fully developes. The Berlin-blue is then thoroughly
washed with water, drained on coarse canvas filters, next dried, pressed, and cut into
cakes; finally it is dried in rooms heated to 80°. As Berlin-blue, when once quite dry, is
reduced to powder with great difficulty, and cannot be brought to the state of fine division
as when first precipitated, it is also sent into the market in the state of paste. The
alumina derived from the alum is so intimately mixed with the blue that the bulk of the
mass is thereby increased without any very perceptible decrease in the intensity of the
colour. If the quantity of alumina is very much increased, the colour, of course, becomes
much lighter, and this variety of Berlin-blue is then known as mineral-blue; a name also
given to a preparation of copper obtained either from the native hydrated carbonate of
copper, or artificially prepared by precipitating nitrate or chloride of copper by means of
lime and chalk.
Recent Methods of Among the improvements made more recently, we may briefly notice
Preparing Berlin-Blue. the following:-1. The mixing of the solutions of copperas and alum
with that of yellow prussiate is effected as above described, but great care is taken to
prevent any oxidation of the white precipitate, which is converted into an intense blue by
being treated with nitro-hydrochloric acid, the chlorine evolved serving as an oxidising
agent. The remaining operations, viz., washing, drying, &c., are performed as in the
former methods. 2. Perchloride of iron solution is employed for the purpose of converting
the white precipitate into blue, while the protochloride of iron thus formed serves at a
subsequent operation instead of protosulphate of iron. 3. In some cases perchloride of
manganese (Mn,Cl), is applied; likewise a solution of chromic acid, a mixture of
bichromate of potassa and sulphuric acid; but it is self-evident that the application of
་
COBALT.
37
any of these improvements is dependent as regards success in a commercial point of view,
upon local conditions, and upon the possibility of advantageously obtaining the various
ingredients.
Turnbull's-Blue.
Berlin-Blue as a By-
Product of the
Manufactures of
Coal-Gas and
Animal Charcoal.
By mixing together a solution of red prussiate and of protosulphate of
iron in such proportions as to prevent the entire saturation of the former salt, there is
obtained a blue-coloured precipitate known in commerce as Turnbull's-blue, consisting of
Fe₂Cy3,3FeCy, but also containing some chemically-combined yellow prussiate. MM.
Mallett and Gautier-Bouchard have proved experimentally that Berlin-
blue may
be obtained as a by-product of coal-gas manufacture from the
ammoniacal liquor from the spent lime of the purifiers, and from Laming's
purifying mixture. The spent lime contains, in addition to the cyanides
of calcium and ammonium, a good deal of free ammonia, mechanically absorbed in the
moist lime. Free ammonia is first removed by forcing steam through the lime, and col-
lecting the ammoniacal gas in dilute sulphuric acid.
in dilute sulphuric acid. The lime is next washed with water,
and the liquor obtained, containing the cyanogen compounds, is employed for the manu-
facture of Berlin-blue. According to M. Krafft's experiments, 1000 kilos. of spent gas-
lime yield, when 'treated as described, from 12 to 15 kilos. of Berlin-blue, and from 15 to
20 kilos. of sulphate of ammonia. Mr. Phipson states that I ton of Newcastle gas-coal
yields a quantity of cyanogen which corresponds to from 5 to 8 lbs. of Berlin-blue. The
manufacture of animal-charcoal also yields, if desired, Berlin-blue as a by-product.
Soluble Berlin-Blue. As ordinary Berlin-blue is quite insoluble in water, and the basic
variety only soluble in the presence of ferrocyanide of potassium, these pigments are only
fit for use as paints, and the discovery of the solubility of pure Berlin-blue in oxalic acid
is of some importance, for thereby its application as a water-colour becomes possible.
This soluble blue is obtained by digesting the Berlin-blue of commerce for 1 to 2 days,
with either strong hydrochloric acid or with strong sulphuric acid, which latter, after
having been mixed with the Berlin-blue previously pulverised, is diluted with its own bulk
of water. The acid is next decanted from the sediment of blue, and the latter thoroughly
washed and dried, and then dissolved in oxalic acid, the best proportions being 8 parts of
Berlin-blue, treated as just mentioned, I part of oxalic acid, and 256 of water. According
to other directions, Berlin-blue readily soluble in water can be obtained:-1. By the
precipitation of protoiodide of iron with yellow prussiate of potassa, care being taken to
keep the latter in excess. 2. By mixing a solution of perchloride of iron in alcoholic
ether (tinctura ferrichlorati ætherea, Ph. Russ.) with an aqueous solution of yellow
prussiate.
Pure Berlin-blue is of a very deep blue colour, with a cupreous gloss; it is insoluble in
water and alcohol, is decomposed by alkalies, concentrated acids, and by heat. The
lighter and more spongy it is, the better is its quality; it is employed as a pigment and in
dyeing and calico-printing, but in the two latter instances, pigment-printing excepted, it
is obtained on the tissues by a circuitous process. The Berlin-blue of commerce is fre-
quently adulterated with alumina, pipe-clay, kaolin, magnesia, heavy-spar, and, according
to Pohl, even with starch-paste coloured blue by means of tincture of iodine.
COBALT.
(Co=59; Sp. gr. = 8°7).
Metallic Cobalt. This metal is found native as cobalt-speiss (CoAs2), containing from
to 24 per cent. of cobalt, and from 0 to 35 per cent. of nickel; also as cobalt-glance,
bright white cobalt (CoASS), containing from 30 to 34 per cent. of cobalt. Cobalt is
prepared on a large scale as a metal at Iserlohn, and at Pfannenstiel, near Aue, in
Germany. Metallic cobalt exhibits a steel-grey colour, somewhat verging upon red,
a strong metallic lustre, assumes a brilliant polish, is malleable and ductile, and far
tougher than iron. It requires a very high temperature for fusion, is only slowly
acted upon by dilute acids, but readily dissolved by nitric acid and aqua regia.
Cobalt Colours. The ores intended for the manufacture of the cobalt colours are roasted
for the double purpose of volatilising the sulphur and arsenic they contain, and for
effecting the oxidation of the cobalt. After roasting, the ores are known as Zaffer or
Saphera. According to the degree of purity, the trade distinguishes the ores as
'common," "medium," and "very fine;" they contain essentially a mixture of
38
CHEMICAL TECHNOLOGY
proto-peroxide of cobalt, arsenic, nickel, and traces of the oxides of manganese and
bismuth, and are used in the preparation of cobalt-colours. In Sweden “zaffers”
are prepared by precipitating a solution of sulphate of protoxide of cobalt with a
solution of carbonate of potassa. Zaffer is used for the manufacture of smalt,
cobalt, ultramarine, a misnomer, for evidently ultramarine is contracted from
ultra-mare, because the lapis lazuli was brought across the seas from ludia-Caru-
leum, Rinnman's-green (cobalt-green or Saxony-green), and also cobalt-yellow,
cobalt-violet, and cobalt-bronze.
Smalt. Compounds of cobalt have the property of imparting a blue colour to glassy
substances at a red heat; when, therefore, impure protoxide of cobalt is fused with silica
and carbonate of potassa, the result is the formation of an intensely blue-coloured glass,
which when pulverised is known as smalt. This substance was discovered and first pre-
pared by the Bohemian glass-blower, C. Schürer, who lived in the sixteenth century.
Smalt is now prepared by melting the roasted cobalt ores with quartzose sand and potash,
in crucibles placed in a glass-furnace. The red-hot glass produced is quenched in cold
water to render it brittle. It is next pulverised and scoured with water, by which opera-
tion smalts are obtained of different degrees of fineness, not simply as regards minute state
of division, but also depth of colour, all of which varieties abroad-where to a limited
extent the smalt is still used though it is almost entirely superseded by artificially-made
ultramarine—bear distinctive names. It has been proved experimentally that the colouring-
matter of smalt is potassio-silicate of protoxide of cobalt, in which the proportion of the
oxygen of the acid to that of the base is as 6:1. According to M. Ludwig, 100 parts of
the undermentioned cobalt colours contain :---
German Smalt.
Norwegian Smalt.
Termed
Coarse and
High colour.
high Eschel. pale coloured.
Silica
70.86
65.20
72'11
Protoxide of cobalt
Potassa and soda
Alumina
6.49
6.75
I'95
21.41
16.31
1.80
•
0'43
8.64
20'04
These substances, moreover, contain small quantities of protoxide of iron, lime, prot-
oxide of nickel, arsenic acid, carbonic acid, water, and oxides of lead and iron. Dr. Oude-
mans lately analysed a beautifully ultramarine-coloured sample of smalt, which was
found to contain 5.7 per cent. of protoxide of cobalt. As cobalt-glass obtained with soda
is never of a pure colour, that alkali cannot replace potassa in the manufacture of smalt.
Since the roasting of the cobalt ores is not continued long enough to oxidise the nickel
contained in them, that and some other metals present fuse during the preparation of the
smalt, and, settling to the bottom of the crucible, form an alloy termed Cobalt-speiss.
Cobalt Speiss. This substance is of a reddish-white hue, has a strong metallic lustre, is fine-
grained in structure, and contains on an average from 40 to 56 per cent. nickel, 26 to 44
per cent. arsenic, as well as copper, iron, bismuth, sulphur, &c. Dr. Wagner found that
(1870) a sample of this alloy from a Saxon mine contained in 100 parts :-
Nickel
Cobalt
Bismuth
Iron
·
• ·
•
48.20
1.63
2'44
0.65
1'93
42.08
3:07
Copper
Arsenic
Sulphur
•
•
The material is chiefly used for the preparation of nickel.
100'00
Applications of Smalt is still employed in washing and dressing blue, and for imparting
Smalt. a blue tint to paper. It is not, however, very suitable for this purpose, as,
on account of its hardness, it soon destroys the points of writing pens. Smalt is more
extensively used for blue-enamelling glass, porcelain, and earthenware.
Cobalt Ultramarine. This substance, also known as Thénard's blue, is a pigment consisting
of alumina and protoxide of cobalt. Curiously enough this pigment has been discovered
and prepared at three several periods and localities by different people; first, by Wenzel,
NICKEL.
39
at Freiberg, Saxony; next by Gahn, at Fahlun, Sweden; and lastly, simultaneously at
Paris and Vienna, by Thénard and Von Leithener. The pigment is prepared either by
mixing solutions of alum and a salt of protoxide of cobalt, precipitating the mixture by a
solution of carbonate of soda; or by the decomposition of aluminate of soda by means of
chloride of cobalt. The ensuing precipitate, consisting of an intimate mixture of hydrate
of alumina and hydrate of protoxide of cobalt, is first well washed, then dried and heated
for some time. The pigment thus produced is, when seen in daylight, of course after pul-
verisation, very similar to ultramarine, but by artificial light its colour is a dirty violet. It
is, however, not acted upon by acids, as distinguished from artificial ultramarine; neither
is it affected by alkalies nor heat, as is copper or mineral blue. Cobalt-ultramarine,
chiefly under the denomination of Thénard's blue, is employed as a paint in oil- and water-
colours, and also for staining glass and porcelain.
Cæruleum. Is a pigment prepared in England, exhibiting a bright blue colour, not
changing in artificial light, and consisting of stannate of protoxide of cobalt (SnO,,CoO),
mized with stannic acid and gypsum in the proportions, in 100 parts, of 496 of oxide of
tin, 18.6 protoxide of cobalt, 318 gypsum. This pigment is not affected by heat, or the
action of "dilute acids and alkalies; nitric acid dissolves the proxtoxide of cobalt, leaving
the other ingredients, from which the gypsum may be cleared by water.
Rinmann's or
This substance, also known as cobalt-green, zinc-green, and Saxony-green,
Cobalt-Green. is a compound similar to the cobalt-ultramarine, for the alumina of which
oxide of zinc is substituted. This green is prepared by mixing a solution of white vitriol
with a solution of a salt of protoxide of cobalt, precipitating by carbonate of soda, and
washing, drying, and heating the precipitate. This pigment when pure contains 88 per
cent. of oxide of zinc and 12 per cent. of protoxide of cobalt. It is not affected by strong
heat, tinges the borax-bead blue, dissolves in warm hydrochloric acid, forming a blue
colour, which, upon water being added, becomes a pale red. Treated with caustic potassa,
the oxide of zinc is dissolved, and may be detected, after previous dilution with water, by
the addition of a solution of sulphuret of potassium.
Chemically Pure
Nitrate of Protoxide of
This substance is occasionally employed for the preparation of fine
Protoxide of Cobalt. colours. It may be obtained by heating one part of previously roasted
and finely-pulverised cobalt ore with two parts of sulphate of potassa until no more
sulphuric acid is given off. The fused mass, consisting of sulphate of potassa, sulphate of
protoxide of cobalt, and insoluble arsenical salts, is, when cooled, first treated with water,
and next digested with hydrated protoxide of cobalt to precipitate any iron which may
happen to be present, and in order to eliminate the oxide of that metal the solution is
filtered. It is next precipitated with carbonate of soda, and finally the precipitate is
washed and heated.
This double salt, known by its trade name of cobalt-yellow, is
Cobalt and Potassa. obtained by mixing a solution of protoxide of cobalt with nitrite of
potassa; it is a yellow.crystalline precipitate, perfectly insoluble in water. M. Saint-Evre
first investigated this body, and struck with its beautifully yellow colour, quite like that of
purrhee (euxanthinate of magnesia), and with the fact that cobalt-yellow resists oxidising
and sulphuretting influences, suggested its applicability to artistic purposes. He prepares
this pigment by precipitating with a slight excess of potassa the double salt of protoxide
of cobalt and potassa, obtaining a rose-red-coloured protoxide of cobalt and potassa. Into
this thickish magma deutoxide of nitrogen gas is passed. According to Hayes, this pig-
ment is readily obtained by causing the vapours of hyponitric acid to pass into a solution
of protonitrate of cobalt, to which some potassa has been added; the whole of the cobalt
is then converted into cobalt-yellow. As the nitrite of protoxide of cobalt and potassa
can be obtained even from impure solutions of protoxide of cobalt, so as to be quite free
from any nickel, iron, &c., the use of this preparation of cobalt is preferable for glass and
porcelain staining, when a pure blue is required.
Cobalt-Bronze. This substance, a double salt of phosphate of protoxide of cobalt and
ammonia, prepared at Pfannenstiel, near Aue, in Saxony, has been but lately brought into
commerce. It is a violet-coloured powder, very much like the violet-coloured chloride of
chromium, and exhibits a strong metallic lustre.
Nickel and its Ores.
NICKEL.
(Ni=59; Sp. gr.
8.97 to 9:25).
This metal occurs in the following ores:-Copper nickel or
arsenical nickel, NiAs, containing about 44 per cent. Ni.; antimonial nickel, NiSb,
with about 31'4 per cent. Ni.; white arsenical nickel, NiAs2, with about 28.2 per
40
CHEMICAL TECHNOLOGY.
cent. Ni; in some varieties of cobalt speiss, as, for instance, the capillary pyrites
(sulphuret of nickel) with 64.8 per cent. Ni); and the antimonial nickel-ore,
nese.
NiS₂+Ni(Sb, As2),
with about 26.8 per cent. Ni. There is found at Rewdansk, Oural, Russia, a mineral
known as Rewdanskite, a silicate of hydrated protoxide of nickel (12'6 per cent. Ni),
from which the metal is obtained. Nickel is also extracted from ores which contain
it accidentally, as, for instance, some species of iron and copper pyrites, cobalt-
speiss, and certain copper ores known as Mansfield ores, which yield sulphate of
nickel as a by-product. Several varieties of manganese contain nickel and also
cobalt; and in England the residues arising from the manufacture of chlorine are
in some instances applied in the production of these metals, the process yielding,
according to Gerland, 2.5 kilos. of nickel and 5 kilos. of cobalt for 1 ton of manga-
Some magnetic iron ores yield nickel, a specimen of such ore from Pragaten,
Tyrol, Austria, containing, according to M. T. Petersen, 1.76 per cent. of NiO.
Preparation of Nickel It very rarely happens that the natural ores of nickel are so pure,
that is to say, contain the metal in such a state of combination, as to admit of the
direct extraction of the metal, and therefore, as is the case with copper, a preliminary
operation is required, which aims at the concentration of the metal in combination
either with sulphur, in which case the combined substance is termed regulus, and
sulphuret of iron is applied as a means of concentrating the nickel contained in the
ore as sulphuret: or, if the nickel happens to be combined chiefly with arsenic, the
concentrated mass is termed speiss; while in a few instances an alloy of nickel and
coarse or black copper is obtained. From all these products the metallic nickel, or
sometimes an alloy of nickel and copper, is prepared by the dry or moist process.
Ores.
The method of obtaining nickel embraces two distinct features, viz. :—
I. A smelting process, which aims at rendering the nickel of the ores richer, and con-
centrating the metal-
a. In a regulus.
6. In a speiss, or
7. In alloy with coarse or black copper.
II. In the separation of the nickel, or a definite alloy from the products obtained by
the concentration-smelting; this can be done—
a. By the dry, or
b. By the hydro-metallurgical method.
As it is found that the preparation of an alloy of copper and nickel for the manufac-
ture of so-called German-silver, impairs the most valuable properties of nickel-its
white colour and resistance to chemical action-the obtaining of pure metallic nickel is
preferred.
The Concentration-
Smelting of the
I. This operation is carried on (a) for regulus, when the nickel-ores are
Nickel Ores. mixed with iron pyrites and magnetic pyrites, and consists in smelting the
previously partly roasted ore with quartz or substances rich in silica. During the process
the greater portion of the oxide of iron generated is absorbed by the slag, while the nickel,
also first oxidised, and more readily reduced than the oxide of iron, is converted to the
metallic state and taken up by and concentrated in, the regulus, a mixture of undecom-
posed sulphurets of metals and reduced sulphates. If at the time the ore contains
copper, that metal is even more readily and completely incorporated with the regulus than
the nickel itself. If the roasted mass contains too much protoxide of iron, a portion of
that metal is reduced, and either taken up by the ragulus, or separated as containing nickel.
The separation of the iron from the regulus frequently requires the application of a refining
furnace provided with a blast so as to oxidise the iron. A better result is obtained by
treating the previously roasted ore in a reverberatory furnace with quartz, heavy spar,
and charcoal or coal; sulphuret of barium results, which, becoming converted into baryta,
transfers its sulphur to the oxides of nickel and copper, while the baryta forms with the
quartz and protoxide of iron a readily fusible slag. At Dillenburg an ore which con-
tains the sulphurets of nickel to about 7.5 per cent., and copper, is treated in the fol-
lowing manner :-It is roasted in stacks, built not unlike coke-ovens; next broken up and
NICKEL.
41
smelted in a low-blast furnace heated by means of coke, no other ingredients being added,
as the ore contains silica, alumina, and lime in sufficient quantities, so as to obtain crude
regulus (I.) This crude regulus is next melted with slags, so as to obtain concentrated
regulus (II.) It is lastly submitted to the action of a refining blast-furnace in order
to lessen the quantity of iron, care being taken to leave enough sulphur to keep the
refined regulus (III.) brittle; finally, the regulus is employed in the manufacture of nickel
and alloys of nickel. Composition-
•
Nickel ..
Copper
Iron
Sulphur
I.
II.
III.
19
24
35
13
39
43
•
35
12
2
•
33
25
20
100
100 100
This mode of operation is employed at Klefver (Sweden), and in some other localities.
(8). The smelting of nickel ores for the purpose of concentrating the metal in speiss is
applied when the nickel occurs in combination with either arsenic only or with that
metal and antimony, such compounds being occasionally obtained in the operations of
smelting copper, lead, and silver ores, and as by-products of the smelting of metals not
containing arsenic, as, for instance, in slags from copper-smelting, in which case there
is added arseniuret of iron (arsenical iron pyrites, FeAs + FeS₂, which when heated by
itself splits up into As and 2FeS). When a mixture consisting of nickel, iron, and arsenic
is first submitted to a partial calcination, and next to a simultaneously reducing and
fusing smelting, the iron is taken up by the slag, the nickel-oxide is reduced, and the
arseniates are converted into arseniurets, and as the nickel has a greater affinity for
arsenic than for sulphur, the speiss will also take up that metal.
If the compound
originally operated upon happens to contain copper, that metal is present in the speiss,
from which it may be separated as a sulphuret by the addition of ordinary pyrites to the
arsenical pyrites during the smelting. By frequently roasting and smelting the speis:,
aided occasionally by an oxidising blast and the use of heavy spar and quartz as slag, the
iron is gradually eliminated. At Birmingham, Hungarian and Spanish nickel ores are
smelted for speiss, these minerals containing on an average from 40 to 55 per cent.
of nickel, and from 30 to 40 per cent. of arsenic, as well as sulphur, bismuth, and
copper.
(7). Smelting for the concentration of coarse copper or nickeliferous pig-iron. When
the quantity of nickel contained in the copper ores is very small, the nickel accumulates
in the first portions of the refined copper in such quantities as to repay the trouble of
extraction. M. Wille analysed some refined copper, obtained from the cupriferous slate
of Riechelsdorf, and found it to contain from 7.8 to 13.6 per cent. of nickel; occasionally
the surface-discs of rosette-copper contain crystals of protoxide of nickel.
Preparation of
Metallic Nickel, or of
II. This is effected by submitting the product of the concentra-
Alloys of Nickel and Corper. tion-smelting to either (a) a dry method of treatment, or (b) a
hydro-metallurgical process.
(a). Preparation of nickel by the dry method. It appears that the methods hitherto
employed have not led to very satisfactory results; it is true that when nickel-speiss is, as
suggested by M. von Gersdorf, repeatedly roasted with charcoal-powder and wood-
shavings, oxide of nickel is obtained, and may be reduced by means of coal, coke, or char-
coal; but as this oxide is always mixed with arseniate of oxide of nickel, the metal also
contains arsenic, and any Gernian-silver made with it is brittle and turns brown on
exposure to air; morcover, a small quantity of iron is always present in the nickel thug
prepared. A better result is obtained by the process proposed by the late H. Rose, in
1863, for the preparation of the metal free from arsenic, and which consists in mixing
the pulverised speiss with sulphur, and heating this mixture, thereby forming sulphuret of
nickel and sulphuret of arsenic, the latter being volatilised. This operation is repeated
as often as may be necessary; the sulphuret of nickel is roasted, and sulphate of protoxide
of the metal is formed, which, at a high temperature, as is the case with protosulphate of
iron, loses its sulphuric acid, leaving the oxide of nickel to be reduced to the metallic
state by means of charcoal. At Dillenburg experiments have been made in order to
obtain from what is termed a refined stone-a compound of nickel, copper, iron, and
sulphur-an alloy of nickel and copper, by first completely calcining the sulphurets, and
so driving off the free sulphur; next mixing the remainder of the substance in quantities
of 100 lbs. with 45 lbs. of soda, and submitting this mixture to the heat of a reverberatory
furuace in order to render the sulphur soluble in water as sulphuret of sodium and
42
CHEMICAL TECHNOLOGY.
sulphate of soda, leaving an alloy which, of course, has to be refined in order to eliminate
the last traces of iron.
I.
(b). Obtaining nickel by the wet, or hydro-metallurgical method. A preliminary
roasting of the ores or products of metallurgical operations containing nickel is required
in order to convert the iron into an oxide soluble in acid, and to convert the nickel,
copper, and cobalt, either into sulphates soluble in water or into oxides or basic salts,
both of which are soluble in sulphuric and hydrochloric acids. From any such solution
the nickel is precipitated by a suitable reagent, either as oxide or as sulphuret, and from
these materials metallic nickel or an alloy of that metal with copper is prepared. The
preparation of nickel by the moist method consists of three different operations :-
1. The preparation of the nickel solution. When nickeliferous and metallurgical products
are roasted, either with or without the addition of copperas, the result is the formation of
the sulphates of iron, copper, nickel, and cobalt, and this mixture when roasted becomes
decomposed, the sulphuric acid being driven off first and most readily from the sulphates
of the oxides of iron, and with greater difficulty from the sulphate of protoxide of cobalt.
Accordingly, after roasting, the mass on being treated with water, yields the larger portion
of the nickel and cobalt with some of the copper, while the greater part of the latter,
with very small quantities of cobalt and nickel, and the whole of the iron, remain undis-
solved as oxides; by the use of acids the protoxides of copper and nickel are extracted
from this residue. If the roasted material is immediately treated with hydrochloric acid,
the result is that more of the oxide of copper than of the protoxide of nickel is dissolved;
but by again treating the residue with boiling acid the oxides of iron and nickel are
extracted. Speiss may be used for obtaining a nickel solution by first heating the pre-
viously roasted speiss with a mixture of soda and nitrate of soda, next extracting the
arseniate of soda by means of water, and afterwards treating the residue with sulphuric
acid, roasting the sulphates obtained so as to decompose only that of iron, and finally
treating the mass again with water to obtain the sulphates of nickel and cobalt in solution.
According to Professor Wöhler's plan, the arsenic of the speiss can be removed by fusion
with sulphuret of sodium, and a subsequent treatment with water, in which it, as a sulpho-
salt, is soluble. 2. The nickel may be precipitated from the solution in various
ways. According to M. Stapff's plan (1858), a fractioned precipitation may be obtained
by means of chalk employed at various temperatures, the result being that first iron
and arsenic, and next copper, are separated, so that only the nickel remains in solution,
and can be thrown down by milk of lime. According to M. Louyet (1849), iron and
arsenic are first precipitated by milk of lime mixed with bleaching-powder, and the
liquid containing this precipitate filtered off. From the acid filtrate the bismuth, lead,
and copper that may be present are removed by sulphuretted hydrogen; the filtrate from
these joint sulphides is next boiled with bleaching-powder, the cobalt being separated as
a peroxide, and the nickel remaining in solution. If it is desired to obtain the cobaltic
peroxide in a pure state, the precipitation should be so conducted as to leave a little
cobalt with the nickel, no injury therefrom accruing to that metal. At Joachimsthal,
Bohemia, the nickel is precipitated from. the acid solution after the removal of the
copper by sulphuretted hydrogen, by means of bisulphate of potassa as bisulphates of
protoxide of nickel and potassa, leaving the cobalt in solution free from nickel, which in
its turn is thrown down by carbonate of soda. 3. The conversion of the nickeliferous
precipitate into metal, or into an alloy with copper, may be carried out in the following
manner:-The protoxide of nickel is first separated from the liquid by filtration, then
pressed so as to admit of its being dried by intense heat, and next ground up with water
and washed with very dilute hydrochloric acid, in order to remove the gypsum, of which
some 8 to 12 per cent. is mixed with the oxide. The oxide is then made with beet-root
sugar, molasses, and coarse rye-meal, into a stiff paste, which is shaped into cubes from
15 to 3 centimetres in size; these cubes are next rapidly dried, and after drying are
placed with charcoal powder in crucibles, or in perpendicular fire-clay cylinders, where,
being submitted to a very strong white heat, the metal is reduced, an operation which, in
the case of the alloy of copper and nickel, or of cupriferous nickel, is finished in 1 hour,
the reduction of the pure metal taking fully three hours. The copper soon becomes
molten, but the nickel only sinters together, on account of the very great infusibility of
this metal. The small cubical pieces of nickel as met with in commerce exhibit externally
a strong metallic lustre, produced by putting the cubes with water into casks, which are
made to rotate. In order to ensure uniformity of composition, and hence a good sale for
the alloy of copper and nickel, rosette-nickel, care is taken to procure the mixture of
the two metals in the proportion of 66·67 per cent. copper, and 33.33 per cent. nickel, while
the cubical nickel contains from 94 to 99 per cent. of pure metal. At a nickel-oven at
Dillenburg, the metal is not made into cubes, but treated in the same way as rosette-
copper.
COPPER.
43
Properties of Nickel. Pure nickel has a nearly silver-white colour, with a slight
yellowish hue, is very difficult to melt, rather hard, very ductile, and easily polished;
sp. gr. 8.97 to 9:26. When quite pure this metal may be drawn into wire, rolled
into sheets, hammered, and forged; its tensile strength stands to that of iron as 9 : 7.
Nickel is analogous to iron, but distinguished from it by possessing a greater power
of resisting chemical agents; on this account, and for its not becoming rusty in air
or when in contact with water, nickel is used for obtaining silver-like alloys (see
Copper). In Belgium, Switzerland, the United States, and Jamaica, small coins
have been made of an alloy of nickel with zinc and copper, pure nickel being too
hard to admit of readily coining. An alloy known as tiers-argent, one-third silver,
consists in 100 parts of:-
Silver..
Copper
Zinc...
Nickel
:
•
27'56
59'06
9'57
3°42
99'61
The total annual production of nickel on the Continent of Europe amounts (1870)
to 11,200 cwts., exclusive of what is made in England. Very pure nickel is obtained
at Val Bénoit, near Luik, Belgium, from an Italian nickel ore, the metal containing
less than 1 per cent. impurities.
Copper, where it occurs,
and how.
COPPER.
(Cu 63'4; Sp. gr.
8.9).
Copper is one of the metals met with most abundantly. It has
been known from a very remote antiquity-even before iron-and bears the Latin
name Cuprum, because it was obtained by the Romans and Greeks from the Island
of Cyprus; from the Latin name of this metal the English, German, Dutch, and
French names are derived. Copper is found to some extent in a metallic state
naturally, but it is chiefly obtained from ores, among which the oxides and sulphides
are the chief.
Ores of Copper. Native copper is found in large quantities near Lake Superior, in North
America; and in Chili there is known a peculiar kind of sand called copper-sand, or
copper-barilla, consisting of from 60 to 80 per cent. of metallic copper, and 20 to 40 per
cent. of quartz. This sand is imported into England and smelted, with other copper ores,
at Swansea.
Red copper or (suboxide, or red oxide of copper), Cu,O, containing 88.8 per cent. of
copper, is met with in octahedrical-shaped crystals, disseminated or instratified through
rock in Cornwall. An intimate mixture of suboxide of copper and iron-ochre is known as
tile-ore, or earthy-red oxide of copper. Azurite, or blue copper ore, containing 55 per
cent. of copper, is a compound of carbonate of protoxide of copper and hydrated protoxide
(2CuCO3 + CuН,0). It occurs in beautifully blue-coloured crystals disseminated through
rock and gangue in Cornwall, and was formerly found at Chessy, near Lyons.
Malachite, containing 57 per cent. of copper, consists of basic carbonate of hydrated
oxide of copper (CuCO3 + CuH₂O₂), and occurs in rhombic crystals, also as stalactite and
stalagmite, and in Atlas ore, a veined and earthy ore called copper-green or earthy
malachite, and very frequently with azurite in Australia and Canada.
Copper-glance, copper-glass, sesquisulphuret of copper (Cu,S), contains 80 per cent. of
the metal. Purple copper ore, variegated copper ore, a compound of copper-glance and
sesquisulphuret of iron (3Cu,S+ FeS3), with 55.54 per cent. of copper and copper pyrites
(CuS+Fe$, or CuFeS), with 34.6 per cent. of copper are the chief sulphur ores used in
the extraction of copper. Copper pyrites is often mixed with iron pyrites, and also often
contains silver and nickel. The mineral known as Bournonite, although a lead ore, often
contains as much as 12.76 per cent. of copper.
44
CHEMICAL TECHNOLOGY.
Slaty copper ore is a bituminous marly schist belonging to the Permian formation,
through which sulphuretted copper ores are disseminated; this ore is chiefly found in
Germany.
Grey or black copper ores, so called Fahl ores, are compounds consisting of electro-
positive sulphurets, viz., sulphuret of copper and of silver, with electro-negative
sulphurets, viz., those of arsenic or antimony. As these ores contain silver they are usually
considered as silver ores, the quantity of copper contained in them amounting to about
14 to 14.5 per cent. Atacamite is also a copper ore (3CuH₂O, + CuCl₂), containing 56 per
cent. of copper. This substance is chiefly met with in Chili and other parts of the Western
Coast of South America, in Southern Australia, and in Peru, and in that country it is
ground to powder and used instead of sand or sawdust to strew on the floors of rooms.
It is imported in that state under the name of Arsenillo, and is smelted with the atacamite
in lumps at Swansea.
Mode of treating the Copper
Ores for the Purpose of
Extracting the Metal.
It is quite evident that the treatment of the ores must vary
according to the constitution of the metals. The ores in
which copper is contained as oxide, or ochrey ores, are reduced readily enough by
simple treatment with carbonaceous matter and a flux; but these ores are by no
means abundantly found, and are, therefore, usually mixed with pyritical sulphu-
retted ores.
The smelting of copper from its ores therefore embraces :-
1. The smelting from ores containing oxides.
2. From pyritical ores, and
3. The hydro-metallurgical method.
Pyritical copper ores are smelted either in a shaft, or pit-furnace, or in a reverbera-
tory furnace. In the latter instance the reduction of the metallic regulus of copper
obtained from a previous roasting of the ore, is effected by the aid of sulphur, not by
that of coal. The regulus is gradually rendered richer and richer in metal, until at
last the decomposition of the sulphur is completed by the action of the oxygen of the
air; by this operation suboxide is plentifully formed, and as a consequence the metallic
copper obtained is in the state technically termed "over-refined." When the shaft-
furnace is employed, the first portion of the operation is similar to that alluded to,
but the metal is reduced with coal or charcoal, and hence the copper obtained-
leaving out of the question the presence of the foreign metals-is never over-refired,
but contains carbonaceous matter, so that in order to render the copper, as it is
technically termed, tough-that is to say, malleable when cold as well as when hot,
another operation is required, which it is evident from the foregoing must differ for
the two qualities of crude metal.
Copper Ores in the
Shaft Furnace.
The Working-up of the The ores are first roasted or calcined, and a portion of the
sulphur, arsenic, and the antimony they contain volatilised; sul-
phates of the metals as well as arseniates and antimoniates are at the same time
formed, while a portion of the ore is not acted upon at all. When the smelting
operation is commenced, fluxes are added, and any oxide of copper present is reduced
to the metallic state, while simultaneously the sulphates are again converted into
sulphurets, which jointly with the metallic copper form the rather richer crude
regulus of copper; while if arsenic and antimony prevail speiss is formed. The
more readily oxidised metals present, chiefly iron, form, as protoxides, compounds
with the fluxes. By a repetition of this process with the coarse metal regulus-the
operation being known as a concentration-smelting-there are obtained thin matt,
and what is termed black copper, containing foreign metals, which are got rid of by
a first or coarse refining, a portion of the impurities under the influence of a high
temperature, the oxygen of the air and fluxes, being partly volatilised, partly taken
up in the slag. The copper obtained by this operation, rose- or disc-copper, contains,
COPPER.
45
-
because the calcination is carried rather too far, suboxide of copper, which impairs
the ductility of the metal. This defect is remedied by a rapid smelting under a
layer of charcoal, the suboxide being reduced and tough copper obtained. When a
reverberatory furnace is employed, the coarse and last refinings are usually included
in one process.
According to the Continental methods, the calcined ore is smelted and converted
into coarse regulus in a shaft-furnace, the fuel employed being charcoal or coke, or
a mixture of the two. Fig. 18 exhibits the vertical section of the furnace; Fig. 19
is a front view, the front wall being removed to show the interior construction.
Fig. 20 exhibits the lower part of this furnace; t t are the tuyere-holes for the blast;
the apertures, o o, placed just above the lowest part of the breast of the hearth, com-
municate by means of channels with the smelting-pots, c'c', the object being to
gradually collect the molten contents of the furnace. Since copper ores always contain
more or less iron, it might happen that by simply employing a reducing smelting,
some of that metal would become mixed with the copper; in order to avoid this,
fluxing materials rich in silica are added, with which the protoxide of iron forms a
FIG. IS.
FIG. 19.


FIG. 20.

眼
​readily fusible slag. The oxides of copper present in the calcined materials are
reduced to the metallic state by the sulphuret of iron-
30uO+ FeS SO2 + FeO + 3Cu.
The metal regulus, a mixture of sulphurets of copper and iron and other metals,
containing on an average 32 per cent. of copper, collects in the lower part of the
furnace, and the slag formed is called crude or coarse slag. The roasting of the
regulus aims at its most complete oxidation, while the sulphur is eliminated. The
calcined regulus is next smelted in a shaft furnace with the addition of a flux, a pro-
cess technically known as concentration-smelting.* The refined regulus obtained by
this smelting contains some 50 per cent. of copper, and is next treated to obtain black-
copper, coarse metal. But if the regulus contain a sufficient quantity of silver, that
metal is extracted by methods which will be fully elucidated when silver is treated
of; in some cases this operation is combined with the extraction of lead from the
copper, and effected by what is termed liquidation, of which more presently.
* There are no equivalent terms in English to express the real meaning of the German
words, a fact which is readily accounted for, if we consider that these operations are
essentially German and of very ancient standing.
46
CHEMICAL TECHNOLOGY.
The operation of smelting for a refined regulus is omitted if tolerably pure copper
ores are operated upon, and such ores after calcination are immediately treated in a
low blast-furnace to obtain the black-copper. In addition to black-copper, a thin
matt containing from 93 to 95 per cent. of that metal is obtained. As an instance
of the composition of black-copper, we quote Dr. Fach's analysis of a sample of
that material produced at Mansfeld, in 1866; in 100 parts there are :—
Copper
Lead ..
•
Zinc
Iron
Nickel and cobalt together
Silver
Sulphur
:
93'49
I'49
I'47
1'03
I'25
0'03
o'99
99'75
Refining the Copper.
The black-copper is next submitted to an energetic oxidising
smelting process in order to get rid of the impurities in the slag. This process is
carried on either-
1. In a small refining furnace ;
2. In a large refining furnace; or
3. In a reverberatory furnace.
Refining on the Hearth. 1. This operation is effected in a furnace or hearth, represented
in vertical section in Fig. 21, and in perspective in Fig. 22; a is a semi-globular
FIG. 22
FIG. 21


h
UM TRE
ሃሃሃ
a
ሃገ
excavation, termed the crucible; b is a cast-iron bed-plate; h represents one of the
two tuyeres by means of which a blast is conveyed to the fuel and the surface of the
copper. The black or coarse copper is melted by the heat of charcoal aided by the
blast, the sulphur, arsenic, and antimony being volatilised, while the oxides of iron
and of the other non-volatile metals are taken up with the suboxide of copper by the
slag, which gathers at the surface of the molten metal, and is from time to time
removed. As soon as the refining is complete, the blast is turned off and the sur-
face of the copper, the metal being heated far above its melting-point, covered with
charcoal-dust. When cooled sufficiently, water is poured on, and a portion of the
metal thus suddenly solidified admits of being lifted off from the rest of the molten
mass in cakes or discs, technically known as rose or rosette-copper; this operation
is repeated until the crucible contains no more metal.
large quantities.
Refining Copper in As the refining of copper on the hearth has been found to yield but
poor results, another contrivance, shown in vertical section in Fig. 23, is now more
generally employed. A is the smelting-hearth; B the refining crucible, of which there
COPPER.
47
are two; n, the opening for the tuyere of the blast; 7, the furnace. The mode of
operation is similar to that just given. When the refining is complete the molten
metal is run into the crucibles, and after having cooled sufficiently, water is sprinkled
on and the discs of rose-copper lifted off. For the reason that in this kind of rever-
beratory furnace the copper is not, as is the case on the hearth, in contact with the
fuel, the result is a purer metal.
Liquation Process. When the copper ores contain silver, the black copper is submitted,
before being refined, to a process known as liquation, unless it should be preferred
to extract the silver by the Ziervogel method (see Silver). The liquation process is
based upon the fact that lead and copper may be melted together, but do not remain
alloyed on cooling, so that a compound is formed containing much more copper than
lead, the remainder of the lead separating and, while taking up the silver, settling
down in consequence of its specific gravity. When the molten mass is slowly cooled,
the lead combined with the silver runs off after the solidification of the copper; but
if the molten metals are rapidly cooled, an intimate mixture of the two takes place.
The mode of separating the silver from the lead will be referred to when treating
of the former of these metals.
It has been already mentioned that the refined copper resulting from the above processes
contains suboxide of that metal, which, if amounting to a quantity of II per cent., renders
the copper unfit for use at ordinary temperatures, by impairing its ductility and mallea-
vility while if the quantity of the suboxide amounts to 14 per cent., the metal is unfit for
FIG. 23.

קווה
B
BL — ii
Nutrumo & GR
use both cold and at a red heat-that is, becomes cold- and red-short. This condition of
the metal is, in Germany, termed " over-cooked," and the remedy is simply to melt the
copper and submit it to what is, in England, technically known as poling; that is to say,
a sufficiently long, stout, and green piece of wood, is used for thoroughly stirring up the
molten mass. The rationale is that the carbon and hydrogen contained in the wood
deoxidise the suboxide at the high temperature, rendering the metal very malleable and
ductile, making it, as is technically termed, tough. A sample of Mansfeld refined and
toughened copper was found by Dr. Steinbeck to contain in roo parts:-
94'37
English: Mode
of Copper Smelting.
Copper
Silver
Nickel
Iron..
Lead
•
Oxygen
Sulphur
•
• •
0'02
•
•
.
0.36
0:05
0.60
•
•
0.58
0'02
..
100'00
Owing chiefly to the possession of an enormous wealth of coal, the
fuel most suited for the reverberatory furnaces, a method of copper-smelting peculiar
48
CHEMICAL TECHNOLOGY.
to England is pursued, and a metal obtained of a very superior quality, although
not so good as that extracted from particular ores in Russia and Australia. Swansea
is the chief and most important seat of this industry in the United Kingdom, and
to it copper ores are not only carried from Cornwall, North Wales, Westmoreland,
Anglesea, and other portions of the realm, Ireland included, but are imported from
Chili, Peru, Cuba, Norway, Australia, and other parts of the world. The English
ores are mainly pyritical.
The chief processes of this mode of smelting consist in-1. Calcination of the ore;
2. Smelting for coarse metal; 3. Calcination of coarse metal; 4. Making of white metal,
a concentration process in which calcined coarse metal is smelted with rich ores; 5. Prepara-
tion of the blue metal by smelting together calcined coarse metal and calcined ores of
medium richness; 6. Preparation of a red and white metal by smelting together the slags
of the previous operations; 7. Calcination of the blue metal (5) and preparation of white
extra metal; 8. Calcination of the white extra metal and preparation of the concentration
metal; 9. Calcination of the ordinary white metal of cupriferous residues for the purpose
of obtaining blistered copper. According to M. Gurlt's views, all these operations may be
reduced to, at most, two calcinations and three smelting operations, viz. :—1. Calcination
of the previously pulverised ores with the addition of common salt, or of chloride of
calcium, to form volatile chlorides; 2. The smelting of calcined ores and obtaining a more
liquid slag and a coarse metal; 3. The calcination of coarse metal by the aid of a blast
for the production of blistered copper with or without the addition of chlorides; 4. Re-
fining and toughening the blistered copper.
4
Calcining, or Roasting This operation as carried on at Swansea does not materially differ
the Ores. from that pursued on the Continent. No very appreciable loss of
weight is experienced, as the weight of the oxygen taken up compensates for the loss
occasioned by the more or less complete volatilisation of the sulphur, antimony, arsenic,
&c. The roasted ore is black, this colour being due to the oxides of iron and copper.
During the roasting heavy white fumes are emitted, consisting of sulphurous and arsenious
acids mixed with other substances; more recently, calcining furnaces have been con-
structed on Gerstenhöfer's patent system, so as to admit of the utilisation of the sulphurous
acid for the manufacture of sulphuric acid.
Smelting the Ores. This operation is effected at Swansea in a furnace of which Fig. 24
exhibits a sectional view. K is a funnel intended for the introduction of the roasted ore;
G is an ash-pit filled with cold water. The object in view is to separate the ores from
FIG. 24.

態
​K
mang inventivi empren tirent 313155
purazed inrustry Teeran,
the gangue as well as from oxides other than that of copper, by causing the sulphur of the
sulphurets remaining undecomposed to act upon a portion of the oxides and sulphates in
such a manner that these are either taken up by the slag, as, for instance, the oxide of
iron, or are again reduced to sulphide, as the oxide and sulphate of copper. At a higher
temperature the oxide of copper is reduced to the metallic state by the action of the
sulphurets of iron and copper, oxide of iron forming, and the metallic copper being partly
COPPER.
49
taken up by the regulus, partly converted into suboxide again by the peroxide of iron,
which is converted into protoxide and dissolved by the siliceous matter. The product of
the first stage of the smelting is a coarse metal, regulus.
Ro s'ing or Calcining
The roasting of the coarse metal is performed in the reverberatory
the Coarse Metal. furnace used for the first calcination of the ores. The objects in view
are the oxidation of any metallic iron present, and the partial volatilisation and combus-
tion of the sulphur, partial only, for otherwise the smelting for white metal would be
impeded or not performed without serious loss of copper.
Smelting for White This operation consists in mixing the previously calcined coarse
Metal. metal with rich copper ores containing hardly any sulphuret of iron,
but consisting chiefly of the sulphide and oxide of copper mixed with quartz in such pro-
portion that the pyrites (copper) is oxidised by the oxygen of the oxides present, the result
being that all the copper combines with the coarse metal, while the protoxide of iron
forms with the quartz silicate of protoxide. The white metal, almost entirely consisting
of (Cu,S), is run into cakes in sand-moulds.
Blistered, or Crude The white metal obtained is converted into blistered copper by placing
Copper. it on the hearth of a reverberatory furnace, and causing the fire to act at
first rather gently, but afterwards so as to fuse the mass, the total duration of the
process for each charge being 12 to 14 hours; the result is the volatilisation of the
sulphur in the form of sulphurous acid, and the elimination, partially by volatilisation,
partially by their being taken up in the slag, of such impurities as arsenic, cobalt, nickel,
tin, iron, &c. When the mass becomes fused, suboxide of copper and sulphide of copper
mutually decompose, the result being the formation of sulphurous acid and metallic
copper (2Cu₂0+ Cu₂S=SO₂+6Cu).
The molten coarse metal, impure copper as yet, is run into moulds, and its surface
becoming covered with black-coloured vesiclés, due to the escape of gases and vapours
from the molten metal, it is termed blistered copper. On being broken, after cooling, it
exhibits a honeycombed structure, due to the same cause that produces the blistered
appearance on the surface. Blistered copper, as usually obtained, is comparatively pure.
Refining the The last operation in the English method of copper-smelting is the
Blistered Metal. refining of the blistered metal in a reverberatory furnace, care being again
taken to fire at first gently, so that the metal shall not become molten until after some
six hours. As soon as the entire charge is thoroughly melted down, the slag, rich in sub-
oxide of copper, is tapped off, and the molten metal covered with charcoal-powder. The
operation of poling (see above) is then performed, birch-wood being preferred for the
purpose; this done, the copper having been run into moulds of a rectangular shape, is
known as refined tough cake.
from Oxidised Ores.
Mode of obtaining Copper Copper is readily obtained from oxidised ores by smelting them
in a shaft-furnace with coke or coal, and such fluxes as will produce a slag which
does not absorb copper. The crude metal obtained is refined in a low-blast-furnace.
The smelting of oxidised ores is limited to a few localities, among which the Oural
and Siberian works are the most important. Large quantities of excellent and
very rich oxidised copper ore are found, but not as yet wrought, in the islands of
Timor and Timor-Laout, and the adjacent islands of Polynesia.
of Preparing Copper,
Hydrometallurgical Method This method owes its existence to the application of practical
and analytical chemistry to metallurgy. As copper is very readily obtained, even
from ores too poor to admit of being treated by the dry process, in such a state of
combination as to admit of its being dissolved in water, and thrown down from this
solution by the simple presence of metallic iron, the hydrometallurgical process is
often advantageously applied, One of the oldest of hydrometallurgical methods is
that known as the cementation-process, performed by precipitating copper from a
solution of the sulphate of the metal by means of metallic iron. Solutions of the
sulphate occur naturally in some mines, and are also artificially prepared by treating
poor oxidised copper ores with sulphurous acid, or by exhausting these ores with
hydrochloric or dilute sulphuric acids, or by roasting pyritical ores and exhausting
them with water. The copper obtained by this process is called cementation-copper.
In the island of Anglesea the cementation liquid is conducted first into large basins
in order that the ochrey and other suspended matters may subside, and afterwards
5
50
CHEMICAL TECHNOL) Y.
is run into the cementation tanks containing old scrap-iron intended to serve as a
precipitating agent. This scrap-iron is occasionally stirred up, so as to renew the
metallic surface presented to the solution. The muddy liquid, containing spongy
metallic copper and impurities, is run into reservoirs intended for the deposition of
the spongy mass, which, after the supernatant liquid is run off, is dried in a furnace.
The material contains on an average only 15, but may contain from 50 to 65 per
cent. of copper. The main body is usually composed of basic sulphate of iron,
which is effectually removed by the application of stirring machinery, such as is
used in breweries in the mash-tubs. At Rio Tinto, Spain, and at Schmöllnitz,
Hungary, cementation-copper is prepared on a very large scale. In Norway, copper
solutions are treated, according to Sinding's plan, with sulphuretted hydrogen, and
the precipitate either worked up for metallic copper, or for sulphate of copper.
Instead of sulphur, large quantities of iron pyrites containing more or less copper are
burnt, and the sulphurous acid obtained applied in the manufacture of sulphuric acid.
The spent pyrites is frequently treated hydrometallurgically with a solution of chloride of
iron, the copper being precipitated by means of sulphuret of iron. Poor ochrey copper
ores are often worked up to obtain sulphate of copper, by some method suitable to the
locality; for instance, roasting with iron pyrites or with copperas. It pays in some
instances to roast pyritical copper ores, and after roasting to treat them for obtaining
cementation-copper.
Copper obtined by Copper electrolytically precipitated is, provided pure materials are
Voltaic Electricity. operated upon, and the galvanic current not too strong, the purest
obtainable. This method has been proposed and even tried on a large scale in Italy, in
order to save time and iron, and to throw down the copper of the cementation-tanks.
It is a generally known and daily applied fact that copper, as a coherent mass, can be
separated from sulphate of copper electrolytically.
Properties of Copper. The peculiar and really beautiful red colour of copper, the only metal
so distinguished, is too well known to need mention. It is, although a hard and tough
metal, so ductile and malleable that it inay be drawn out to the very finest wire, and
beaten to extremely thin leaves. Its malleability is increased by increase of temperature,
and at a low red heat it can be hammered, rolled, and beaten into any required shape. Its
fracture is granular. Its sp. gr. is = 89; one cubic metre weighs about 8900 kilos. Its
melting-point, according to Pouillet, 1200°; to Daniell, 1400. The latest and most
careful researches on this topic have been made by Dr. von Riemsdijk at the Utrecht Mint,
and he has found that chemically pure copper fuses in an atmosphere of hydrogen at
1330°; that is to say, at a temperature higher than the melting-point of either gold or
silver, as simultaneously determined by an extensive series of experiments made in
atmospheres of hydrogen. If properly poled, as the term runs, or in other words, free
from suboxide, copper, when molten, flows readily, but when mixed with suboxide the
flow is sluggish. While in the molten state the surface of the metal exhibits a beautiful
sea-green colour. Copper is not suited for the making of castings, and probably this
is due to a peculiar effect of heat upon this metal, as many of its alloys, especially those
with tin, are very suited for casting. Molten copper suffers great expansion on cooling,
and becomes honeycombed and internally crystalline. This defect can only be remedied by
either keeping the metal while molten under a layer of charcoal, or by cooling it to some
extent before casting into moulds, which should be made of a good conducting material, so
as to cause the rapid cooling of the metal. Iron moulds, internally coated with a layer of
bone-ash, are the best. Small quantities, o'i per cent. of zinc, lead, potassium, and other
metals added to the molten copper entirely deprive it of the property of expanding and
becoming honeycombed on cooling; the same effect is observed when copper holds in
solution a small quantity of suboxide, but this fact is not available for any practical use,
as such copper is cold short. Just before cooling the vessel exhibits the phenomenon of
spirting, the flying about of small globules of copper, accompanied, if large quantities of
the metal are treate l, by a distinctly audible report. This phenomenon appears to be
due to a cause similar to that producing it when silver is operated upon, viz., the violent
expulsion of previously absorbed oxygen. At a very high temperature, and with free
access of air, or under the influence of electricity, copper burns, giving a brilliant green
flame. In countries where, as in Sweden, Russia, and Holland, the roofs of churches and
other large buildings are covered with copper--the most expensive at the first outlay, but
the most lasting material for roofing purposes--the phenomenon of the burning of copper
is now and then witnessed on a very large scale when fires accidentally occur. Copper-filings
COPPER.
51
are used in pyrotechny, for producing a green flame. Dry air does not affect copper,
unless sulphuretted hydrogen and other sulphurous emanations are present; but moist
air causes the copper to become covered with carbonate of hydrated suboxide of copper,
verdigris, or rust. Experience has proved, in the case of copper roofs, that this material
protects the subjacent metal, and adheres to it with great tenacity. When solid masses of
copper are heated they at first assume an iridescent rainbow hue, and next become
covered with a brownish-red coloured suboxide, which, if the heating is continued, becomes
black oxide, technically known as copper-ash, or copper-forge scale. In order to remove
this oxide, when the copper is to be rolled into sheets, &c., the metal is dipped into what
is termed a pickle-a solution of ammonia and common salt, and on being taken out is
brushed with a heather-broom. Copper, as usually met with in commerce, is not by any
means pure, but contains variable quantities of other metals, among which are chiefly
iron, antimony, arsenic, lead, tin, zinc, and sulphur; Dr. Reischauer found in perfectly
malleable copper no less than 1.48 per cent. of impurities insoluble in nitric acid. If
this quantity is only slightly increased, the quality of the copper is so impaired that it is
not only unfit for being rolled and hammered, but also for casting statues (always alloyed),
because such copper loses its peculiar colour, and does not withstand atmospheric influ-
ences. Copper is largely used for various purposes, among which we name only a few-
vacuum and other pans in sugar-works; distillery, brewery, and other apparatus; for
covering wooden sea-going vessels, and for a variety of generally well-known purposes.
Dr. Steinbeck found that refined Mansfeld copper, analysed 1868, contained in 100 parts-
Copper
Silver
Nickel
Iron
Lead
99.28
0'02
0'32
0.06
O'12
100'00
The total annual production of copper over the entire globe amounts (1870) to
1,300,000 cwts., of which England alone yields fully 350,000 cwts.
Alloys of Copper. There are several alloys of copper, among which bronze, brass, and
German, or nickel silver, are the chief.
Bronze.
Alloys, consisting of copper and tin, or of copper, tin, and zinc, or of copper
and aluminium, all bear the name of bronze. The addition of any of these metals
to copper renders it more fluid when molten, and hence better suited for castings,
as well as denser, and consequently more easily polished; alloys are harder, more
sonorous, and (the aluminium alloy excepted), far cheaper than copper itself.
The addition of from o'12 to 0'50 per cent. of phosphorus to these alloys renders
them more homogeneous and malleable. The chief varieties of bronze in use are
known as (a) bell-metal, (8) gun-metal), and (7) statuary metal.
(a). Bell-metal consists on an average of 78 parts of copper and 22 parts of tin.
It should be sonorous, hard, and strongly cohesive. Being a brittle alloy it cannot
be worked on the lathe; hence the desired sound or musical note of a bell depends
entirely upon the shape given in the casting, and upon the constituents of the alloy.
In order to save tin, zinc and lead are sometimes added, but too much of these
impairs the goodness of the alloy. It is an error to mix silver with this alloy, in
order to render it highly sonorous; analyses made of bell-metal cast in the middle
ages in various countries, prove the absence of silver from such metal, traces only
being present as an impurity.
(8). Gun-metal consists on an average of 90 parts of copper and 9 of tin. This
alloy should combine mechanical and chemical durability. As regards its mechanical
properties, the metal should be: :-1. Tough, so as to prevent the piece or gun
bursting while the charge is being fired, during which operation the metal is
exposed to a pressure of from 1200 to 1500 atmospheres. 2. Elastic, so that the gun
may be able to yield to some extent to the smart shocks occasioned by the evolution
52
CHEMICAL TECHNOLOGY.
of gas during firing. 3. Hard, so that the motion of the ball should not cause any
damage to the interior of the gun. As regards chemical durability, the alloy must
resist the action of air and of the products of combustion of powder and gun-cotton
at high temperatures. Gun-metal answering these requirements is unfortunately
subject to what is termed liquation; that is to say, while in the molten state it
separates into two qualities of alloy, one more fluid and containing more tin than
the other. This separation makes the casting of guns in this alloy a difficult matter,
because the homogeneity of the mixture is uncertain. It appears, however, that the
addition of from o'12 to 0.5 per cent of phosphorus remedies the defect. Gun-metal,
however, is fast being superseded by steel in the manufacture of ordnance.
MM. Maritz, at the Hague, have for several generations been renowned for the
superiority of their gun-metal manufacture, which is still pursued by them.
According to a statement in the "Handwörterbuch der Chemie" (Art. "Geschütz-
metall," the alloy employed by them consists of o'69 per cent. Fe, 88.61 per cent. Cu,
and 10'70 per cent. Sn; generally the quantity of tin amounts to from 9 to 11 per cent.
(7.) Statuary-bronze for ornamental purposes consists of copper, tin, lead, and
zinc. It is requisite that while molten this alloy should be very fluid, so as to fill
every part of the mould. After cooling, the metal must admit of being chiselled,
and by exposure to air it should assume what is termed patina-a peculiar greenish
black hue. The statue of Louis XIV. at Paris, made 1699, consists of-copper,
91*40; zinc, 5'53; tin, 170; lead, 137. The statue of Henri IV. on the Pont
Neuf at Paris, consists of-copper, 89.62; zinc, 40°20; tin, 5'70; lead, 0°48.
Aluminium-bronze (90 parts copper and 10 aluminium) is used for various orna-
mental purposes, chiefly in imitation of gold.
Brass.
This alloy has been known from a very remote period. Zinc and copper
form various alloys, but brass only is technically applied, and contains on an average
30 per cent. of zinc. The colour of the alloy is inclined to red, when the quantity
of zinc is small, and to yellow or whitish-yellow when the quantity of zinc is
increased. The ductility and malleability of the alloy increase with the quantity
of copper. Brass may be hammered, rolled into sheets, or drawn to wire while cold,
but cannot be worked hot. The so-called yellow metal, Muntz's patent, an alloy
of 40 parts of zinc and 60 of copper, may be wrought while red-hot, rolled into
sheets, and forged into bolts. It is chiefly used for marine purposes, including
the internal lining of air pumps of marine steam-engines. Brass is not so readily
oxidised as copper, being harder, tougher, more easily fusible, and more fluid while
molten. It solidifies without becoming honeycombed, and hence is suited for
making all kinds of castings; while simply by the addition of from 1 to 2 per cent.
of lead, it is capable of being readily worked on the lathe, and may be then filed
without, as it otherwise does, clogging the teeth of the file.
Brass is made by any of the following methods:-1. By melting together a mixture of
calamine stone and black or blistered copper under a layer of charcoal. 2. By simply melting
together zinc and refined copper. The first method is the oldest, and is still carried on
in furnaces arranged so that they may contain from 7 to 9 fire-clay crucibles at the same
time. These crucibles are filled with the necessary materials, viz., previously roasted
zinc ore, or residues from zinc-smelting furnaces, and copper. As by the use of calamine
stone, only some 27 to 28 per cent. of zinc can be imparted to the alloy, it is usual to add,
previously to pouring out the molten alloy, another quantity of calamine stone, rather to
prevent any loss of zinc by ignition than to increase the quantity of that metal. In
former times the manufacture of brass was carried on in two distinct operations, one
being the preparation of an alloy containing only 20 per cent. of zinc, known as arco-
smelting, and the other the conversion of the arco into brass by a second smelting, and the
COPPER.
53
addition of zinc. At the present time the manufacture of brass consists in simply placing
alternate layers of copper and zinc in fire-clay or graphite crucibles, and then smelting
the two metals under a thick layer of charcoal. The alloy is cast in granite moulds
surrounded by a thick coating of clay and cow-dung, or sand-moulds. Occasionally sheet-
copper is converted into brass by exposing the sheets to the fumes of metallic zinc.
Among brass alloys we may notice the following:-Tomback, or red brass, consisting of
85 parts of copper and 15 of zinc. Dutch-gold, a gross misnomer, as none of it is made
in Holland, and as the term really applies to a very pure gold coin, the ducat, still made,
although not current, in Holland, at the Utrecht Mint. The brass alloy thus named con-
sists of II parts of copper and 2 of zinc, and is made chiefly at Nürnberg and Fürth,
Bavaria, for the purpose of being beaten into very thin leaves. The alloy termed Aich-
metal, and consisting of 60 parts of copper, 38.2 parts of zinc, and 18 parts of iron, is in
reality malleable brass. Sterro-metal, though very much harder, is similar to the fore-
going in composition.
1
The well-known yellow, or Muntz, metal, largely used in this country for marine pur-
poses, coating ships, &c., is an alloy of copper and zinc in proportions varying from 50 per
cent. of zinc and 63 of copper, to 39 per cent. of zinc and 50 per cent. of copper. The alloy
in use for coins of small value in this country, France, and Sweden, consists of 95 parts of
copper, 4 parts of tin and I of zinc. The alloy used for this purpose in Denmark consists
of 90 parts of copper, 5 of tin, and 5 of zinc. Bath-metal, or white brass, consists of 55
parts of copper and 45 of zinc. An alloy used for buttons consists of 20 parts of copper
and 80 parts of zinc. The bronze colours (powdered alloys of copper and zinc), now
largely used for bronzing painted surfaces, as well as for lithochromy and various other
purposes, are obtained from scraps of metal rubbed down with oil, tallow, or wax, and
turpentine. The various beautiful colours, violet, copper-red, orange, gold-yellow, green,
are due to partial oxidation. These bronze-colours are not to be confounded with a beau-
tiful substance known as mosaic gold-aurum musicum—bisulphide of tin. Analyses show
the proportions in these alloys to be-
For bright colours
For red or deeper colours
For copper-red colours
Copper
Zinc..
•
83
17
Copper
Zinc..
94-90
6-10
100
Chemical analysis has also proved the quantity of copper to amount to-
a. In French bronzes: Copper-red colour
Orange
Bright yellow
B. In English bronzes: Orange
Deep yellow
Bright yellow
7. In Bavarian bronzes: Copper-red
Violet..
Orange
•
Deep yellow
•
Bright yellow
•
•
97.32 per cent.
94'44 ""
81.29
""
90.82
82.37
•
80.42
""
98.92
98.82
""
•
•
•
95'30
81.55
82.34
""
""
German or Nickel
silver.
German, or nickel silver, also called Argentan, packfong, or white
copper, is an alloy of copper with nickel and zinc, or tin, and may be considered as
a brass to which from one-sixth to one-third of nickel has been added. This alloy
appears to have been known in China from a very remote period; in Europe it has
been more generally in use during the last thirty years. The colour is nearly
silver-white; its fracture small-grained and compact; sp. gr. = 8.4 to 87. It is
harder, but yet quite as ductile as ordinary brass, and takes an excellent polish. It
is prepared by melting together the granulated metals, zinc, copper, and nickel;
these metals are put into a crucible in such a manner that copper is at the bottom
as well as the top, while a layer of charcoal-powder covers the whole. Care is taken
to stir the mass with an iron rod. Nickel-silver of good quality has the appearance
of a silver alloy, containing one-fourth of copper. Nickel-silver is capable of as-
suming an excellent polish, and is not readily acted upon by vinegar and the ordinary
acids in culinary use; hence it is used for spoons and forks.
54
CHEMICAL TECHNOLOGY.
Average German-silver consists of-
Copper
Zinc
Nickel
•
50-66.0
19-31.0
13-18.5
At Sheffield the following varieties of this alloy are made :-
Common
White ..
Electrum
Copper. Nicke
8
Infusible
Tutenac
8
8
oo co co ∞
2 2 463
Zinc.
3.5
3.5
3'5
3.5
6.5
When tried on the touchstone, nickel-silver is hardly distinguishable from the
silver alloy just mentioned, but on applying nitric acid to the streak caused by the
nickel alloy, it is more rapidly dissolved, and by adding a few drops of chloride of
sodium solution no turbidity, or precipitate of chloride of silver, is produced on the
stone. The alloy known as Alfénide, used for making tea-pots, sugar-basins, milk-
ewers, and similar articles, is nickel-silver, thickly electro-plated with pure silver, the
quantity of silver amounting to about 2 percent. The alloy, known astiers-argent (one-
third silver), consists, according to Dr. C. Winkler's analysis (see "Chemical News,"
vol. xxii., p. 225), of—Copper, 59'06; silver, 27.56; zine, 9'57; nickel, 3°42.
Since 1850 the Swiss Confederation has brought into circulation a series of small coins
(monnaie billon) which contain in 1000 parts :-
Pieces of 20 Rappen
""
ΙΟ
5
""
""
Silver.
Copper.
Zinc.
Nickel.
150
500
250
100
100
550
250
100
50
600
250
100
These coins are not turned red by wear, but assume a yellowish hue. In Belgium the
5, 10, and 20 centime pieces are made of an alloy of 25 parts of nickel and 75 parts of
copper; while the United States' cent pieces contain 12 parts of nickel and 88 of copper.
The alloy known on the Continent as Suhler's white copper, consists of 88 parts of copper,
8.75 parts of nickel, and 1.75 parts of antimony.
Amalgam of Copper. By the name of metallic cement is understood an amalgam of 30 parts
of copper and 70 parts of mercury. It is obtained by moistening pulverised copper,
obtained in a spongy state, by reducing its oxide at a low red heat, by means of hydrogen
with nitrate of. suboxide of mercury, care being taken to incorporate this saline solution
thoroughly with the copper, while adding hot water. This cement, at first soft, hardens
in a few hours. It has been successfully applied in stopping decayed teeth.
Blue Vitriol.
Sulphate of Copper.
PREPARATIONS OF COPPER.
This salt is met with naturally in kidney-shaped masses, or as an
outer covering of minerals containing copper, as well as in solution, as referred to
under Cementation-copper. Sulphate of copper, blue- or Cyprus-vitriol, crystallises
in the shape of triclinohedrical blue-coloured crystals, soluble in 2 parts of hot and
4 of cold water, and insoluble in alcohol. 100 parts of the salt contain:
Preparation
of Blue
Vitriol.
Sulphuric acid
Oxide of copper
Water
Formula :-CuSO4 + 5H₂O.
32.14
31.79
36.07
Chemically-pure sulphate of copper is obtained by heating metallic copper
with concentrated sulphuric acid; the metal is oxidised by a portion of the oxygen of
the acid, while sulphurous acid escapes (Cu + 2H2SO4 = CuSO4+2H2O+SO2). If
the metal is previously converted into oxide of copper by exposure to a red heat, only
half the quantity of sulphuric acid is required. Sulphate of copper is manufactured
PREPARATIONS OF COPPER.
55
on a large scale by any of the following processes :-1. By the evaporation of cemen-
tation-water until crystallisation is attained. 2. By heating sheets of copper in a
reverberatory furnace to the boiling-point of sulphur; a quantity of that element
being then thrown in, and the flues and other openings closed, the effect is the forma-
tion of sulphide of copper (Cu₂S), which is converted by a comparatively low heat
and the action of the oxygen of the air into sulphate (Cu₂S+ 50 = CuSO4 + CuO).
The mass is next placed in a suitable vessel, and as much sulphuric acid is added to
it as is sufficient to saturate the oxide of copper. The clear solution, having been
decanted from the insoluble residue, is set aside for crystallisation. 3. By treating
the crude copper obtained by smelting the ores, and containing about 60 per cent. of
metal, with sulphuric acid. The resulting solution is evaporated in leaden vessels,
and the clear liquid left to crystallise in copper pans. From the mother-liquor of the
crystals metallic copper is precipitated by means of iron, because the presence of a
large quantity of sulphate of iron renders this mother-liquor unfit for the further
making of blue-vitriol. This method of obtaining sulphate of copper is the least
expensive, but the salt is not quite pure, containing, according to M. Herter's analysis
of Mansfeld blue-vitriol, about 3 per cent. of sulphate of iron, and 0.083 per cent. of
metallic nickel. Very frequently the scraps and refuse of copper smithies, copper-
scale, and other residues of that metal, are used in preparing sulphate of copper.
4. At Marseilles, malachite is dissolved in sulphuric acid to obtain blue-vitriol.
5. In Norway, iron pyrites containing copper are roasted and treated with water, the
copper contained being precipitated with sulphuretted hydrogen, and the sulphide of
copper, when dry, converted into sulphate by exposure to a gentle heat. 6. Large
quantities of sulphate of copper are obtained as a by-product of silver-refining,
especially when silver is treated for the purpose of extracting the gold it contains, by
fioiling-usually silver coins, chiefly Mexican and Peruvian dollars-with strong
sulphuric acid; sulphate of silver and, as the coins contain some copper, the
sulphate of that metal, are formed, while the gold is left as an insoluble substance.
The silver is reduced to the metallic state (Ag₂SO4 + Cu = CuSO4 + 2Ag) by means of
sheets of copper placed in the acid solution, which is previously diluted, and which,
after having been decanted from the sediment, spongy metallic silver, yields on
evaporation a very pure sulphate of copper. 7. Sulphate of copper is also obtained
as a by-product of the hydrometallurgical process of extracting silver, or Ziervogel's
process. In order to separate the sulphate of iron from the crude blue-vitriol, as
obtained at copper-smelting works from various cupriferous refuse, the crude salt
is roasted so as to bring about a partial decomposition. By this means the sulphate
of iron is decomposed, and the oxide of that metal formed is insoluble in water. The
saline mass is dissolved in water, and the clear solution, decanted from the sediment,
evaporated to crystallisation. According to Bacco's plan, the crude blue-vitriol is
dissolved in water, and carbonate of copper added to the solution, to cause the
pre-
cipitation as oxide of all the iron present, while an equivalent quantity of oxide of
copper is dissolved and converted into sulphate. The purified sulphate of copper
solution having been filtered is evaporated and left to crystallise.
•
Duble-Vitriol. Under the name of double-vitriol, a mixture of the sulphates of copper and
iron crystallised together, and sometimes containing white vitriol, is met with on the
Continent. The Salzburg vitriol, known by the brand of a double eagle, contains about
76 per cent.. the Admont 83 per cent., and the double Admont 80 per cent. of
sulphate of protoxide of iron. Of later years, however, these vitriols have been less in
demand.
56
CHEMICAL TECHNOLOGY.
Applications of
As the base of the pigments obtainable from copper, the sulphate is very
Blue-Vitriol. frequently used, and should be pure, or at least free from the sulphates of
iron and zinc. Blue-vitriol also serves for the manufacture of acetate of copper, for
bronzing iron, for bringing out the colour of alloys of gold. It is used in dyeing and
printing in various ways, for galvano-plastic purposes, and during the last twenty years
large quantities of this salt have been sent to Mexico and Peru to be applied in the
American amalgamation-process of extracting silver.
Copper Pigments. Among the many pigments which owe their blue or green colour
´essentially to copper, we may treat of the following:-1. Brunswick-green. 2.
Bremen-green and Bremen-blue. 3. Casselmann's-green. 4. Mineral-green. 5.
Schweinfurt-green, also known as emerald-green. Many of the pigments men-
tioned here by their German names are known in this country by other denomina-
tions, but are not for that reason any different in composition.
3
Brunswick-Green. Under this name several compounds of copper are applied as oil-paints.
The pigment now chiefly in use bearing this name is basic carbonate of oxide of copper
(CuCO₂+ CuH₂O2), an imitation of mountain- or mineral-green, and obtained from either
finely pulverised malachite or the sediment often met with in cupriferous cementation-
liquids. Brunswick-green is prepared on a large scale by the decomposition of sulphate of
iron by means of either carbonate of soda or carbonate of lime, and in other cases by the
decomposition of chloride of copper by means of a carbonated alkali. The ensuing preci-
pitate is washed with boiling water, and afterwards mixed with a smaller or larger quan-
tity of sulphate of baryta, zinc-white, or gypsum, and frequently with Schweinfurt-green
(aceto-arsenite of copper) in order to obtain the desired hue. Another variety of Bruns-
wick-green, rarely met with in the present day, appears to be a kind of artificially-prepared
atacamite, an oxychloride of copper, the formula of which is, according to Ritthausen,
CuCl2,3 CuO+3Н₂0.
Bremen-Green.
2
Bremen-Blue, or These substances are essentially hydrated oxide of copper, and are
met with as a very bright blue spongy mass with a greenish hue. The value is
greater according to the finer blue colour and loose spongy texture. When used with
water, gum, or glue, this pigment yields a bright blue colour, hence its first name;
but when it is mixed with linseed-oil, the blue colour turns within twenty-four hours
to green, in consequence of the saponification of the oxide of copper, which becomes
oleate, palmitate, and linoxate of that base. Bremen-green occurs in various hues
obtained by mixing the precipitate with well-cleansed gypsum. At the present time
the pigment is generally obtained from oxychloride of copper (CuCl2, 3CuO+4H₂O).
This preparation may be made in various ways, provided care be taken that the
light green paste-technically known as oxide-contains no protochloride of copper
(Cu2Cl2). Gentele's method is as follows :—
I. 112.5 kilos. of common salt, and III kilos. of sulphate of copper, both free from iron,
are ground together with sufficient water to promote reaction. 2. 112.5 kilos. of old
copper sheeting is cut into pieces a square inch in size, and placed with water acidulated
with sulphuric acid in rotating casks so as to remove all rust, oxide and oxychloride, from
this metal, which is next washed with water. 3. The clean metal thus obtained is next
placed in what is known as oxidation-closets, and covered for a thickness of half-an-inch
with the paste mentioned above. A mutual action, aided by that of the atmosphere, is
set up, the result being that the chloride of copper first takes up copper, becoming proto-
chloride; this in its turn takes up oxygen from the atmosphere and water, and thus becomes
converted into the green-coloured insoluble basic hydrated oxide of copper, the action being
greatly aided by the turning over of the mass with a copper spade every two or three
days. As the treatment of protochloride of copper with alkalies or alkaline earths gives
rise to the separation of red or yellow-coloured suboxide, the mass should not, on being
tested and previous to further operations, yield even the faintest indication of the presence
of suboxide, since the slightest trace would spoil the hue of the pigment to be obtained;
consequently in some works the pasty mass is left for years before it is used for further
operations. The action is accelerated by causing the mass to become dry before turning it
over with the spade; the consequence being that the air gets thorough access, and a com-
plete oxidation is obtained in about three to five months time. The mass is then cleansed
with the smallest possible quantity of water, and is thus separated from the non-oxidised
PREPARATIONS OF COPPER.
57
metallic copper. 4. To some 6 gallons of this cleansed material are added 6 kilos. of
hydrochloric acid, and this mixture is allowed to stand for about two days. 5. Into a
tank or tub-the blue tub-are poured some 15 gallons clear colourless potassa-lye. This
having been done, the acid mixture is first diluted with some 6 more gallons of water, and
then, as rapidly and expeditiously as possible, poured into the blue tub, the mixture being
continuously stirred. The result of this last operation is that the previously basic copper
compound, converted by HCl into neutral cupric chloride, is, when brought in contact
with the potassa, converted into blue-coloured oxyhydrate of copper or Bremen-blue,
while chloride of potassium is also formed. 6. After the mass has become pasty, it is left
to stand for a couple of days, and then thoroughly washed by decantation to remove the
chloride of potassium. The cupric oxyhydrate is then put on cloth filters, kept moist, and
exposed to the air for some time. It is next dried at a temperature of from 30° to 35°,
since at a higher temperature the hydrate of the oxide by losing its water becomes
blackish-brown coloured. It is clear that Bremen-blue can be differently obtained, but
these differences of preparation do not bear so much upon the precipitation of the
hydrated oxide as upon the means of obtaining chloride of copper; these means may of
of course be varied in many ways; for instance, by causing a mixture of common salt,
dilute sulphuric, and copper scraps to act upon each other, the mass being afterwards
exposed to the action of the air; by the action of hydrochloric acid upon copper and its
oxide; or by partly decomposing neutral nitrate of copper by means of carbonate of soda.
In this case a precipitate of carbonate of copper is formed, which, while giving off its
carbonic acid, becomes converted into basic nitrate of copper (CuN₂06+ CuH₂02), deposited
as a heavy green powder. A solution of zinc-oxide of potassa (solution of zinc-white in
caustic potassa), is next added, the result being the formation of a deep blue pigment,
very spongy and very covering (a technical term in use by painters); consisting of zincate
of copper, with a small quantity of basic nitrate of copper. A magnesia Bremen-blue is
obtained by the precipitation of a solution of the sulphates of magnesia and copper, to
which some cream of tartar is added, by means of potassa, care being taken to pour the
saline solution into the alkaline, and to keep an excess of the latter.
Casselmann's-Green. In the year 1865 Dr. Casselmann discovered this pigment, a beau-
tiful green free from arsenic. It is prepared by mixing together boiling solutions
of sulphate of copper and an alkaline acetate; the resulting precipitate is a basic
salt of copper (CuSO4 + 3CuH₂O₂+ 4H₂O). After drying, this salt is, next to
Schweinfurt-green, the finest of all colours obtained from copper, and being free
from arsenic, is highly commendable, though yet poisonous, as are most prepara-
tions of, and especially acetates of, copper.
2 2
Mineral-Green This pigment, also known as Scheele's-green, is not so frequently used
and Blue. now as formerly. It is essentially a mixture of hydrated oxide of copper and
arsenite of copper, and does not cover very well. It is prepared by dissolving í kilo. of
pure sulphate of copper in 12 litres of water, to which is added, whilst constantly stirred,
a solution of 350 grms. arsenious acid and 1 kilo. of purified potash (carbonate) in 8 litres
of water. The resulting grass-green coloured precipitate is washed with boiling water and
dried. Another pigment, sometimes known as mineral-green, is obtained from pulverised
malachite, or basic hydrated oxide of copper. By the term mineral-blue is generally
understood a kind of Berlin-blue, rendered less deep coloured by the addition of pipe-clay
or other white-coloured powders, but the term also applies to a pigment formerly obtained
by grinding and washing the purest pieces of lazurite of copper, a mineral
(2CuCO3 + CuH₂O₂)
found in the Tyrol and near Lyons. This pigment is artificially obtained in France,
Holland, and Belgium, by precipitating a solution of nitrate of copper with caustic lime
or caustic potassa, and afterwards mixing the previously washed precipitate with chalk,
gypsum, or heavy spar. The pigment is sent into the trade for use chiefly as a water-
colour. Under the name of lime-blue a similar preparation occurs in quadrangular
lumps, obtained by precipitating a solution of 100 parts of sulphate of copper and
12 parts of sal-ammoniac with a milk of lime containing 30 parts of caustic-lime. The
precipitate is a mixture of hydrated oxide of copper and sulphate of lime, according to
the formula (2CaSO4,2H₂O+3CuH₂O₂). This pigment exhibits a purer tint than
Bremen-blue, but though it covers pretty well as a water-colour, it is almost useless as an
oil-colour.
Oil-Blue. A pigment which, when ground with oils and varnishes, yields a beautiful
violet-blue, and is essentially composed of sulphide of copper (CuS), there being applied
in its manufacture either the native mineral, known as cupreous indigo, or an artificially
58
CHEMICAL TECHNOLOGY.
prepared sulphide, obtained by fusing finely divided metallic copper with hepar-sulphuris,
a mixture of several sulphurets of potassium. The fused mass is treated with water, and
the sulphide of copper remains in small blue-coloured crystals, which, after drying, are
pulverised and mixed with oil.
Emerald-Green.
Schweinfurt-Green, or This pigment is by far the most beautiful, but also the most
poisonous, of all green-coloured copper pigments. In Germany this substance is
known under a number of aliases derived from the peculiar depth of hue as modified
in various manufactories by means of sulphate of baryta, sulphate of lead, and
chrome-yellow. The constitution and mode of preparation of this pigment remained,
at least on the Continent, a trade secret until the researches of MM. Braconnot and
J. von Liebig made the particulars known. According to Dr. Ehrmann, pure
emerald- or Schweinfurt-green is an aceto-arsenite of copper :-
3 2
(C₂H₂O)½ } O₂+3(CuO, As₂O3);
Cu
in 100 parts-Oxide of copper, 31.29; arsenious acid, 58.65; acetic acid, 10'06,
Dr. R. Wagner states that this formula is only empirical, because a portion of the
copper is present as suboxide, and a portion of the arsenic as arsenic acid.
According to Dr. Ehrmann's statement, this pigment is prepared by first separately
dissolving equal parts by weight of arsenious acid and neutral acetate of copper in boiling-
water, and next mixing these solutions while boiling. There is immediately formed a
flocculent olive-green coloured precipitate of arsenite of copper, while the supernatant
liquid contains free acetic acid. After a while the precipitate becomes gradually crystal-
line, at the same time forming a beautifully green pigment, which is separated from the
liquid by filtration, and after washing and carefully drying is ready for use. The mode
of preparing this pigment on a large scale was originally devised by M. Braconnot, as
follows:-15 kilos. of sulphate of copper are dissolved in the smallest possible quantity of
boiling-water and mixed with a boiling and concentrated solution of arsenite of soda or
potassa, so prepared as to contain 20 kilos. of arsenious acid. There is immediately
formed a dirty greenish-coloured precipitate, which is converted into Schweinfurt-green
by the addition of some 15 litres concentrated wood-vinegar. This having been done, the
precipitate is immediately filtered off and washed. It thus appears that the preparation
of this pigment aims first at the least expensive preparation of neutral arsenite of copper,
which is next converted into aceto-arsenite by digesting the precipitate with acetic acid.
The pigment is available as a water- and an oil-colour, but does not cover very well in oil,
although it dries rapidly. The colour cannot be used for mural painting, as the lime
absorbs the acetic acid, leaving a yellowish-green arsenite of copper. The Schweinfurt-
green consists of microscopically small crystals; if these crystals are pulverised, the
colour, previously grass-green, becomes paler. Air and light do not affect this pigment,
which is insoluble in water, but becoming, when boiled with it for a length of time,
brown-coloured, probably in consequence of the loss of some acetic acid. It is a well-
known fact that paper-hangings containing this pigment, and pasted on damp walls,
cause the inmates of the rooms to suffer from headaches, due in all likelihood to volatile
arsenical emanations, among which is arseniuretted hydrogen.
Stannate of Oxide This preparation, also known as Gentele's-green, is obtained by precipi-
of Copper. tating a solution of sulphate of copper with stannate of soda, washing and
drying the precipitate, which forms a beautifully green, innocuous, at least as compared
with the foregoing, copper pigment.
Verdigris. Under this name we meet in commerce with a neutral and a basic
acetate of copper; the one, a crystalline substance is
(C₂H₂O)2O2 + H2O,
Cu
a salt formerly only prepared in Holland, and designated as "distilled verdigris,"
in order to mislead as to its mode of manufacture.
The basic salt, blue verdigris, is chiefly prepared at and near Montpellier, by employing
the marc of the grapes, the skin and stems of the bunches after the juice has been squeezed
out, which readily forms acetic acid by fermentation. Into the marc are placed sheets of
copper previously moistened with a solution of acetate of copper. The metal becomes
coated with a layer of verdigris, which is removed by scraping. It is next kneaded with
LEAD.
59
water, after which the paste is put into leathern bags and pressed, so as to obtain
rectangular cakes. The metal is treated in the same manner until it is entirely converted
into basic verdigris, having a blue colour, and known as French-verdigris. Formula—--
(C,H,O), } 0,CuH_0 +5H,O.
Cu
A green-coloured verdigris is obtained at Grenoble and elsewhere, by submitting sheets of
copper to the action of vapours of vinegar, or by placing the metal between pieces of
coarse flannel soaked with that liquid. The formula of the substance thus produced is—
(CH₂O) 0,2CuH₂O,
Cu
Neutral acetate of copper, first made by the Saracens in Southern Spain, and since the
middle of the fifteenth century by the Hollanders, is now obtained either by---1. Dissolving
the basic salt in acetic acid. 2. Or by the double decomposition of sulphate of copper and
acetate of lead :—
(CHO), } o_= PbSO4 +{ (CHO), } o
CuSO4 + { (C₂H₂O), }
=
Cu
2
2'
By the first method the basic acetate is dissolved in 4 parts of acetum distillatum
(purified vinegar) or in wood-vinegar, the liquid being placed in a copper cauldron and
heat applied. The clear liquid is decanted, and then evaporated in copper pans until a
saline crust makes its appearance, when the fluid is transferred to wooden vessels pro-
vided with thin laths serving as a solid nucleus for the crystals. According to the second
plan, the solutions of the two salts are mixed, the liquid decanted from the sediment of
sulphate of lead, and next evaporated after the addition of some acetic acid, until a crust
of the salt is formed. Instead of acetate of lead, the acetates of lime and baryta are now
used. The neutral acetate of copper is met with in commerce in "bunches (grappes),
consisting of deep green-coloured, non-transparent crystals, soluble in 134 parts of cold,
in 5 parts of hot water, and in 14 parts of boiling alcohol. This salt, like the basic
acetates, is highly poisonous.
Applications of Both basic and neutral are employed as oil-and water-colours. In Russia
Verdigris. verdigris, mixed with white-lead, is frequently used as an oil paint, the
result being the formation of carbonate of copper and basic acetate of lead. The former
of these substances yields with the undecomposed white-lead a bright blue colour, which,
after painting, turns to a peculiarly fine green, the usual colour of the iron roofs of the
houses in Russia, more especially in Moscow and the interior of the country. In Holland
the same mixture is frequently applied as a paint to outdoor woodwork, of which it is an
excellent preservative. Verdigris is sometimes further applied in the preparation of other
copper colours, for instance, Schweinfurt-green; also in dyeing and calico-printing; in
gilding (see Gold). The neutral salt was formerly used in the preparation of acetic acid.
LEAD.
Occurrence of Lead.
(Pb 207; Sp. gr.
1137.)
This metal has been known from a remote antiquity. It is only
rarely found native; its chief ore is galena (PbS). It also occurs as Bournonite,
or antimonial lead ore, consisting of—41'77 parts of lead; 12.76 copper; 26'01
antimony; and 19°46 sulphur; formula (3Cu₂S,Sb2S3 + 2[3PbS,Sb₂S3]). From this
ore copper as well as lead is extracted. The other lead ores of more or less import-
ance are―cerusite or white lead ore (PbCO3); green lead ore (pyromorphite,
phosphate of oxide of lead, 3[P2O5,3PbO]+ PbCl2); mimetesite (arseniate of oxide
of lead, 3[As2O5,3PbO]+PbCl₂); vitriol lead ore or Anglesite, sulphate of lead
(PbSO4); yellow lead ore (molybdanate of lead, PbMo04); and red-lead ore or
krokoite, chromate of lead (PbCrO4).
by Precipitation.
Method of obtaining Lead Galena is the chief lead ore, 98'9 of the metal produced being
extracted from it. It contains 86.57 per cent. of lead, and 13°43 per cent. of sulphur,
with sometimes only mere traces, sometimes an available quantity of silver. Galena
exhibits a lead-grey colour and a strong metallic lustre, crystallises in cubes, is
brittle, and has a sp. gr. 7'75. It is also employed, when finely ground, and known
as Alquifoux, for the purpose of glazing coarse pottery ware; for the manufacture
of Pattinson's white-lead; instead of sawdust for covering the floors of rooms in some
60
CHEMICAL TECHNOLOGY.
of the German mining districts; for ornamental purposes; jewellery; and of late
in a peculiar process of extracting platinum from its ores.
Lead is obtained from galena either by the precipitation method or by roasting.
The former process is based upon the behaviour of metallic iron at a high tempera-
ture towards galena; for if these two substances are heated together the result is
the formation of sulphuret of iron and metallic lead (PbS+Fe=FeS + Pb). Ac-
cordingly, the precipitation method consists in smelting the galena, previously freed
from gangue, with granulated iron obtained by pouring molten cast-iron in a thin
stream into cold water. The operation is carried on in a shaft furnace; the result
is the formation of metallic lead, and of a lead matte consisting essentially of sul-
phuret of iron, undecomposed galena, and sulphuret of copper. Sometimes iron.
ores and slags of ironworks are applied, in which case the oxygen of these substances
aids the desulphuration.
B is the
The furnace in use for the smelting is represented in figures 25, 26, and 27.
shaft; C, D, the hearth and crucible, which, as exhibited by the cut, is partly outside the
furnace. By means of a channel the molten metal can be run off from D into the tap
crucible. The gases and vapours previous to their escape into the chimney, T, are made
to pass through the flues, as indicated by the arrows, in order that any solid particles
containing lead, which the blast at o might carry off, may be arrested. The ore and
iron, previously washed, are placed in alternate layers in the furnace. The products of
FIG. 25.
FIG. 26.


FIG. 27.

D E
the smelting collected in D, are lead, containing silver and lead matte, the latter containing
about 30 lbs. of lead to the cwt., the former sometimes 3 lbs. of silver to the same
quantity, while copper also may be present. This lead matte is, according to its con-
stituents, either worked up for cementation-copper, or added to other slags containing
lead and again smelted.
Obtaining Lead by
Calcination.
This process is based upon the behaviour of oxide of lead and
the sulphate of that oxide towards galena, and is effected on a large scale in a
reverberatory furnace. By the action of the oxygen of the air at a high temperature
upon galena, a portion of this mineral is converted into oxide of lead and sulphurous
acid, while sulphate of lead is simultaneously formed. By the oxygen of the sulphate
and of the oxide the sulphur of any undecomposed galena is oxidised and removed
(3PbO+PbS=4Pb+ SO2+0; PbS04+ PbS= 2Pb+2SO2). If there is present
during the roasting any excess of galena, there is formed a subsulphide of lead
LEAD.
61
(Pb₂S), from which a small quantity of metallic lead is obtained by liquation, while
the residue becomes a higher sulphuret (2Pb₂S=2PbS+2Pb).
The English process of lead smelting by roasting and liquation is based upon the
reaction just described, and is carried on in a furnace exhibited in Fig. 28. The hearth,
constructed of slag and built upon a massive wall, is arranged to slope in all directions
towards the tap-hole, through which the lead runs off into a cast-iron pan set in a niche.
The figures 0, 0, 0, indicate the openings for the doors, three on each side of the building.
T is a funnel through which the ores are placed on the hearth. Every six or seven hours
a charge of 16 cwts. of ore is worked off, while the consumption of fuel amounts to about
half that weight in the same time. Care is taken to spread the ore uniformly over the
hearth; this having been done, the heat is gradually increased, the doors of the furnace
being closed. After a lapse of two hours the doors are opened sufficiently to ventilate
the furnace and dissipate the smoke, and are again closed, and the heat increased until
the mass, from which lead everywhere exudes and runs off to the lowest level, becomes
by stirring and the addition of fluor-spar, almost perfectly fluid. This point having been
reached, the upper layer of slag is run off, at once cooled with water, and thus solidified.
FIG. 28.

זי
..11
1
This slag is termed white slag from its white or light grey colour, and contains about
22 per cent. of sulphate of lead. Some small coal is now cast into the hearth in order to
solidify the tough, pasty slag which covers the lead, after which the tap-hole is opened
and the raw lead run off into the iron pan, previously heated so as to keep the metal in
a molten state.
Raw Lead. The metallic lead obtained as described is by no means pure, usually
containing silver, copper, antimony, arsenic, and other metals according to the purity
of the ore.
The separation of the silver, when in sufficient quantity to repay the
expense of extraction, will be spoken of under Silver; but one of the by-products of
some of the methods of extracting that metal is litharge, oxide of lead, which is
either brought into commerce as such or reduced again to metallic lead by a process
here described.
Revivification of
Litharge.
This process is pursued in a reverberatory furnace by placing on
the hearth a mixture of litharge and small coal. The lead resulting, known as hard
lead, in contradistinction to the soft lead obtained from refined litharge, is usually
not quite pure. In order to give some idea of the composition of the various kinds
of lead as obtained at Freiberg, Germany, we quote the following results of analyses
by Dr. Reich:-
Antimonial lead.
Raw lead. Refined lead. Hard lead.
Müldən.
Halsbrück.
Lead
97'72
99*28
87.60
50'76
87.60
Arsenic
1*36
0'16
7'90
1.28
0.40
Antimony
0.72
traces
2.80
7'31
11.60
Iron
0'07
0'05
traces
O'13
traces
Copper.
O'25
0.25
0'40.
0'35
traces
Silver
0'49
0'53
62
CHEMICAL TECHNOLOGY.
Properties of Lead
1
The colour and general physical properties of this metal are too well
known to require detailed notice. Lead assumes a crystalline form with difficulty, but it
is obtained in that state in a combination of cubes and octahedra by some metallurgical
processes, e. g., Pattinson's method of silver extraction. Lead is, when refined, a very
soft and tractable metal; its absolute cohesive strength is small. When freshly cut it
exhibits a strong metallic lustre, but tarnishes rapidly on exposure to air. If handled it
dirties the skin, and gives, when rubbed on paper, linen, or cotton, a plumbago-coloured
mark. Its sp. gr. is 1137; I cubic foot weighs about 600 lbs. ; I cubic metre, 11,370 kilos.
In addition to the metallic impurities usually present in lead and already alluded to,
some of its oxide is commonly mechanically mixed with it, impairing its malleability and
ductility, but, on the other hand, increasing its resistance to pressure. Lead belongs to
the most readily fusible metals, fusing far below red heat, at 332°; on cooling it contracts
and assumes a concave surface. Lead is volatilised and boils at a strong white heat, air
being excluded. It is not well suited for being worked with files or cold chisels, the former
becoming clogged, and the latter blunt. Sheet lead is cut with knives of well-tempered
steel. This metal does not take up more than about 1.5 per cent. of zinc; 0.07 per cent. of
iron, and rather more copper, but alloys readily with tin, bismuth, and antimony.
Applications of Lead is employed in a variety of ways in building. It is much used for
the leaden chambers of sulphuric acid works, and for this purpose should
be as free as possible from any impurities or foreign metals, all of which impair the
resistance of the sheets of lead to the acid vapours, and cause the metal to become
gradually perforated with holes and cracks. The metal is further employed for leaden
pans and other apparatus in chemical manufactories, for gas- and water-pipes, for rifle
balls, and for many other purposes too numerous to be here specified.
Metallic Lead.
Manufacture of Shot. This manufacture consists of five distinct operations, viz.-(1) the
melting of the lead; (2) the granulation of the molten metal; (3) the sorting of the grain
of various sizes; (4) separation of irregularly-shaped shot; and (5) the polishing of the
shot. Lead intended for this manufacture is never required to be pure, and arsenic is pur-
posely added, because experience has taught that this addition improves the spherical shape
of the shot. The quantity of arsenic depends upon the quality of the lead, but varies from
0.3 to 0.8 per cent.: too much causes an irregular shape, and too little has the same defect.
The arsenic is added either as arsenious acid, in which case the lead is melted under a
layer of powdered charcoal, or metallic arsenic wrapped in a piece of paper is introduced
under the surface of the molten lead by means of a suitable pair of forceps. The
granulation of the lead is obtained by the use of a shallow sieve-like iron vessel,
technically termed a card, provided with holes of regular size. The dross and scrapings
from former smeltings are not removed, as they prevent the lead running too readily
through the holes. The operation of granulation is carried on in shot towers, the card
with the molten lead being at the top, the metal assuming a spherical shape while falling.
The small spheres or drops are collected in water, to every 100 parts of which o'025 parts
of sulphide of sodium is added in order to coat the metal with a small quantity of
sulphide of lead and prevent its oxidation. Shot is also made on an entirely different
plan embodying the application of centrifugal force. The molten metal is forced with
great speed through openings in a centrifugal machine, making 1000 revolutions per
minute, the shot or particles assuming a spherical shape by reason of the great force of
impact with the air near the machine. The sorting of the shot is effected by variously-
sized sieves, and the separation of the imperfectly-shaped grains is obtained by causing
the shot to run over a long slightly sloping table provided with ledges of wood to prevent
the shot falling off sideways. Only the perfectly spherical grains of shot reach the
lower end of the table. Lastly, the shot is polished by placing 100,000 parts by weight
of shot and 6 parts by weight of graphite together in a cylindrical iron vessel made to
rotate slowly on a horizontal axis. In this country some manufacturers prefer to use an
amalgam of tin, or simply mercury, instead of graphite, for polishing. The loss of lead
in the manufacture of shot amounts to about 2 per cent. The sizes and trade names of
the several kinds of shot vary in different countries; in Germany No. o is the largest and
No. 10 the smallest size.
Alloys of Lead. The following alloys of lead in daily use are made on a large scale :—
Soft lead solder as used by tinsmiths, equal parts of lead and tin; the alloy used for
organ pipes, usually 96 parts of lead and 4 of tin, but often more tin is added; white
metal alloy for domestic utensils, as coffee and teapots, consists of lead, antimony,
and tin; alloy for ships' nails, 3 parts tin, 2 parts lead, I part antimony. The lead
used by the Chinese for lining tea-chests consists of 126 parts lead, 17.5 parts tin,
LEAD.
63
1*25 parts copper, with a trace of zinc. Other alloys, such as type metal, will be
spoken of presently.
Oxide of Lead.
PREPARATIONS OF LEAD.
This substance is commercially employed in two different forms, viz.,
as massicot or as litharge.
Massicot. Massicot, or yellow oxide of lead, occurs as a yellow or ruddy-coloured
powder, obtained either by heating carbonate or nitrate of lead, or by calcining
metallic lead on the hearth of a reverberatory furnace. Before chromate of lead
was known, massicot was used as a yellow pigment. At red heat this substance
fuses and becomes glassy. In most instances it is not a pure oxide of lead, but
mixed with silicate of lead, the fact being that oxide of lead at a red heat strongly
attacks any material containing silica, dissolving the silica and combining with it.
Litharge. Litharge is a fused crystalline oxide of lead, and is obtained as a by-
product of the separation of silver from lead in the process to be fully described under
Silver. Litharge always contains a larger or smaller quantity of oxide of copper,
oxide of antimony, traces of oxide of silver, and, according to Dr., Wittstein, metallic
lead, varying in quantity from 1.25 to 3.10 per cent. The oxide of copper can be
removed by digesting the litharge with a solution, cold of course, of carbonate of
ammonia. Litharge absorbs carbonic acid from the atmosphere, combines at a higher
temperature with silica, forming with it a readily fusible glass, is soluble in acetic
and nitric, and also in very dilute hydrochloric acids, and is equally soluble in
boiling solutions of caustic potassa and soda. It is insoluble in carbonate of am-
monia and in the carbonates of potassa and soda. Litharge is largely used, entering
into various compounds for glass, so-called crystal-glass, flint-glass, strass for
imitating jewels, for glazing pottery and earthenware, as a flux in glass and
porcelain staining, for the preparation of boiled linseed and poppy-seed oil, for
the preparations of lead-plaster, putty, minium, red-lead, and acetate of lead. A
solution of oxide of lead in caustic soda lye is applied in the preparation of stannate
of soda; this solution is also used for imparting to combs and other toilet articles
made of horn the appearance of tortoise-shell or of buffalo-horn. A very dilute
solution is used as a hair-dye, and again in metallochromy to produce iridescent
colours on brass and bronze.
Minium. Red-Lead,
Red-lead is a combination of oxide of lead with a superoxide, the
formula being Pb304. Red-lead of excellent quality is largely manufactured near
Newcastle-on-Tyne, by carefully heating oxide of lead in a reverberatory furnace
expressly built for that purpose, the access of air being limited so as to prevent
the fusion of that portion of the oxide which cannot then be converted into
minium. Sometimes metallic lead is oxidised in a reverberatory furnace, the pro-
cess, as, for instance, at Shrewsbury, being so arranged that at the hotter places of
the furnace massicot, and at the cooler red-lead, is produced. The finest coloured
minium, or Paris-red, is obtained from carbonate of lead by the same method.
According to Mr. Burton's plan, sulphate of lead is heated with Chili saltpetre,
and after the mass has been exhausted with water the red-lead is left, while sul-
phate and nitrite of soda are dissolved. Red-lead is used for a variety of purposes,
many similar to the applications of oxide of lead. Besides being applied as a
cement, when mixed with linseed-oil and mastic, for the flanges of steam-pipes, it
chiefly enters the market as a pigment, being for that purpose either mixed with
water or with linseed-oil, in both instances covering extremely well.
64
CHEMICAL TECHNOLOGY.
Superoxide of Lead. When red-lead is treated with moderately strong nitric acid, there are
formed nitrate of protoxide of lead and superoxide of that metal, PbO,, a brown-coloured
powder largely used in the composition of the phosphorus mixture for lucifer matches.
The mixture known in lucifer match works as oxidised minium, is a dried composition,
consisting of nitrate of protoxide of lead, superoxide of lead, and undecomposed red-lead,
and obtained by drying a magma of minium and nitric acid.
Combinations of Oxide Among the salts of lead employed industrially, the following
are the most important :-
of Lead
Acetate of Lead. This salt,
((C2H3O2} } O₂+3H₂O)
Pb
consists in 100 parts of:-Oxide of lead, 58'71; acetic acid, 27.08; water, 14°21.
It crystallises in four-sided columnar figures; is soluble in 166 parts of water and
8 parts of alcohol. When submitted to dry distillation it yields neutral carbonate
of lead and aceton, which volatilisés. When heated with sulphuric acid it yields
acetic acid, sulphate of lead remaining in the retort. Acetate of lead is prepared
by heating litharge or massicot with rectified vinegar, or with wood vinegar, ir
leaden or in tinned copper pans. The clear liquid is decanted and evaporated, and
then left to crystallise in porcelain basins or in wooden tubs: 100 parts of litharge
yield 150 of acetate of lead. This salt is largely used in dyeing and calico
printing, in obtaining red liquor or acetate of alumina; and for the preparation of
varnishes, white-lead, and chrome-yellow. We shall speak of sub-acetate of lead,
tribasic acetate of lead, when considering the manufacture of white-lead.
Chromate of Lead. The basis of chromate of lead, and indeed the substance from which
all chromium preparations are derived, is the chrome-iron ore, consisting mainly of
protoxide of iron and oxide of chromium (FeO,Cr₂O3, or Cr₂FeO4). It is a magnetic
iron ore4
isomeric sesqui-, or per-oxide of chromium having been substituted for the
peroxide of iron, but the mineral varies in composition, often containing consider-
able quantities of aluminia, magnesia, and protoxide of chromium. It is met with
interspersed through very hard metamorphic rocks in some parts of Scotland, ir
colour a steel-grey or pitchy black. Its value for industrial purposes depends upon
the quantity of oxide of chromium it contains; and according to M. Clouet's analysis
(1869) the following chrome-iron ores contained the quoted quantities per cent. of
chromic oxide :-
Chrome-iron from Baltimore
45
""
""
Norway
France
40
37-51
Asia Minor
53
""
Hungary
31
""
Oural (Russia)
49.5
California
""
""
42'5
Neutral, or Yellow Chromate
of Potassa.
This salt,
CrO2 O2, or K2CrO4,
K₂
-2
is prepared by heating chrome-iron ore, previously pulverised and cleansed, with
carbonate and nitrate of potassa on the hearth of a reverberatory furnace. The
oxygen of the saltpetre cause the higher oxidation of the protoxide of iron and
CHROMIUM.
65
sesquioxide of chromium, the latter being converted into chromic acid. The
thoroughly sintered, not molten, mass, is, after cooling, again ground up and
lixiviated with boiling water, and also boiled for a time to extract the neutral
chromate of potassa. Wood vinegar is added to the solution to precipitate the
alumina and silica, after which the clear liquid is evaporated, until a film of saline
material begins to form, when it is left to crystallise. The crystals take a
column-like form, and are of a lemon-yellow colour, readily soluble in water, but
insoluble in alcohol, and having a great tendency to become converted into bichro-
mate or red chromate of potassa. This conversion of the neutral salt into the bi-, or
acid salt, is at once effected by the addition to its solution of sulphuric or nitric acid.
The bichromate of potassa or acid chromate, K2Cr2O7, crystallises in anhydrous,
aurora-red coloured prismatic crystals, soluble in 10 parts of water. This solution
is highly caustic and poisonous. When heated to redness the salt gives off oxygen,
leaving oxide of chromium and neutral chromate of potassa in the retort; the
bichromate is prepared from the neutral salt by the addition to its solution of either
sulphuric or nitric acid, preferably the latter on account of the formation of nitrate
of potassa, which may be either sold or used in the manufacture of the neutral
chromate.
M. Jacquelain proposes that the chrome-iron should be mixed with chalk, and the
mixture heated and frequently stirred, then cooled, pulverised, and put into water, with
the addition of enough sulphuric acid to produce a weak reaction, the result being the
formation, first of chromate of lime, which, by the addition of the acid, becomes the
bichromate of that base. The sulphate of protoxide of iron present in this solution is
precipitated by means of chalk. In order to convert the bichromate of lime into the cor-
responding potassium salt, it is only necessary to add a solution of carbonate of potassa,
the result being of course the precipitation of carbonate of lime, and the exchange of
the chromic acid from the lime to the potassa. According to Tilghmann's process
chrome-iron ore is mixed with 2 parts of lime, 2 of sulphate of potassa, and heated
for eighteen to twenty hours in a reverberatory furnace. The same inventor suggests
the heating of chrome-iron ore with powdered feldspar and lime. Mr. Swindells ignites
chrome ore with equal parts of either chloride of sodium or chloride of potassium to the
highest possible white heat, at the same time exposing the mixture to a constant current of
superheated steam, the formation of sodium or potassium chromate resulting. The most
important improvement in the preparation of chromate of potassa is the substitution of
carbonate of potassa for nitrate of potassa, and the use of a furnace so constructed as to
admit of the proper access of air to the strongly heated mass, the oxygen of the air being
made to oxidise the chromic oxide to chromic acid. Another improvement is, that in using
lime instead of alkali, the oxidation of the chromic oxide is greatly accelerated, by reason
that when lime is employed instead of potassa, the heated materials do not become semi-
fused or pasty, but remaining pulverulent admit of the readier access of air, as well as
preventing the sinking, on account of higher specific gravity, of a portion of the chrome
ore to the bottom of the hearth, and there becoming withdrawn from the action of the
heat.
Applications of the
Before the year 1820, the salts spoken of were only used for the pre-
Chromates of Potassa. paration of chrome-yellow; it was then a very expensive process,
viz., the calcination of the chrome-iron ore with nitrate of potassa only. At this date,
M. Koechlin discovered the applicability of bichromate of potassa to the obtaining of
what is technically termed "discharge" for Turkey-red-a madder colour-a discovery
soon followed by others bearing upon the useful applications of this salt, among which are
the formation of chrome-yellow and chrome-orange in calico-printing, the chrome-black
in dyeing, the oxidation of catechu and Berlin-blue, the discharge of indigo-blue, the
bleaching of palm-oil and other fatty substances, the preparation of mixtures for the heads
of lucifer-matches, the preparation of chromate of protoxide of mercury and chromic
oxide as green-coloured pigments in glass and china painting, and for the preparation of
Vert Guignet, a peculiar hydrated oxide of chromium:-
(Cr₂)2
vi ›0,
H
66
CHEMICAL TECHNOLOGY.
obtained by heating I part of bichromate of potassa and 3 parts of crystallised boric acid,
and used as a pigment in calico-printing. As might be expected, all these discoveries.
gave a strong impulse to the manufacture of the chromates of potassa, which have
recently found still further useful applications in the obtaining of colours from coal-tar, in
the manufacture of chlorine gas, in defuseling brandy and other spirits, and in the purifi-
cation of wood-vinegar made from the crude pyroligneous acid.
According to M. J. Persoz, there exist, America excepted, only six manufactories of the
chromates of potassa, viz., two in Scotland, one in France, one at Trjöndhem, Norway, and
one at Kazan, near the Oural, Russia; the total production of these works amounted in
1869 to 60,000 cwts.
Chromate of Lead."
Chrome. Yellow, or There are in technical use three different compounds of lead and
chromic acid, viz., neutral chromate of lead or chrome-yellow, basic chromate or
chrome-red, and a mixture of these two salts constituting chrome-orange. The first
of these substances is obtained by two methods:-(1) By the precipitation of a
solution of chromate of potassa with a solution of acetate of lead; or (2) by
the use of sulphate or chloride of lead. According to the first plan, the operation
begins with the preparation of a solution of lead, for which purpose granulated lead
is put into wooden tubs placed one above the other, and the taps each tub is provided
with being turned off, vinegar is poured into the upper tub. In about ten minutes
the tap at the bottom of the tub is opened, and the contents let into the second tub.
The operation is repeated with all the tubs, four to eight in number, the object
simply being to moisten the lead thoroughly with the vinegar, so as to cause rapid
oxidation on its subsequent exposure to air. The metal soon becomes coated with
a bluish-white coloured film, and when this is apparent, vinegar is again poured
into the topmost tub and left for about an hour, after which it is run off into the
second tub, and the operation continued until there is obtained a saturated solution
of basic acetate of lead. To prepare chrome-yellow, enough vinegar is added to
obtain a reaction, and the fluid left to deposit any suspended sediment. At the same
time, in another tub, a solution of 25 kilos. of bichromate of potassa in 500 litres of
water is kept in readiness. The clear lead solution is next poured into the bichro-
mate solution as long as any precipitate ensues. This precipitate is well washed,
and usually mixed with gypsum, or sulphate of baryta, to obtain the lighter chrome
colours; finally it is dried. According to Liebig, chrome-yellow is obtained from
sulphate of lead, an almost useless by-product from calico-printing- and dye-works,
by digesting it with a warm solution of neutral chromate of potassa. The depth of
colour of the ensuing yellow pigment depends upon the quantity of sulphate of lead
which is converted into chromate of lead.
4
Dr. Habich states that there exist two binary compounds of chromate and sulphate of
lead, the formula of which are:-PbSO4 + PbCrО and 2PbSO+PbCrO4. The former is
obtained when a solution of bichromate of potassa, previously mixed with enough sul-
phuric acid to cause its dissociation, is precipitated with a solution of lead; while the
second compound is formed if the quantity of sulphuric acid is doubled. According to
M. Anthon a beautiful chrome-yellow is obtained by the digestion of 100 parts of freshly
precipitated chloride of lead with 47 parts of bichromate of potassium.
Chrome-Red. The basic chromate of lead, known as chrome-red and Austrian-cinnabar,
PbCrО+PbH,O,,* is a red-coloured pigment much in demand, and obtained from the
yellow or neutral chromate of lead, either by boiling it with a caustic potassa solution, or
by fusing it with nitrate of potassa, the effect being that half of the chromic acid is with-
drawn from the neutral chromate. Drs. Liebig and Wöhler state that chrome-red is best
obtained by fusing together, at a very low red-heat, equal parts of potassium and sodium
nitrates, gradually pouring into the fused salt small quantities of chemically pure yellow
* According to Dr. Duflos, see "Handbuch der Angewandten Pharmaceutisch-Technisch
Chemische Analyse, &c." Breslau, 1871, p. 293, the formula of this substance is 2PbO,CrO3,
and the dried salt does not contain any water as a component part.
LEAD.
67
chromate of lead. After cooling, the insoluble chrome-red is well washed and dried. It
is then a magnificently-coloured cinnabar-like crystalline powder. Professor Dulong
prepares chrome-red by precipitating a solution of acetate of lead with a solution of
chromate of potassa to which caustic potassa has been added. The various shades and
qualities of chrome-red, from the deepest vermillion to the palest red, are caused by the
difference in size of the constituent crystalline particles. This fact is proved by experiment,
for when several samples are uniformly ground to a fine powder the result is the production
of a uniformly deep-coloured hue. In preparing chrome-red of a deep colour, everything
which Inight interfere with or injure the crystallisation has to be avoided. The pigments
commercially known as the chrome-orange colours are mixtures, in varying proportions, of
the basic and neutral chromates of lead, and are usually made by boiling chrome-yellow
with milk of lime. M. Anthon recommends for the preparation of a good chrome-orange
the treatment of 100 parts of chrome-yellow with 55 parts of chromate of potassa and
12-18 parts of caustic-lime made into milk of lime.
Chrome-Oxide, or This substance, Cr₂O3, is used in glass- and porcelain-staining as a
Chrome-Green. couleur grand feu, that is to say, it stands the most intense heat provided
no reducing materials are allowed to affect it. It is commercially known under the name
of chrome-green as an indelible pigment for printing, being especially employed for bank-
notes. It is prepared in various ways, the finest being obtained by heating chromate of
protoxide of mercury, but this method is far too expensive to admit of any extensive appli-
cation. Dr. Lassaigne heats equal molecules of sulphur and yellow chromate of potassa,
and exhausts the mixture with water, leaving the insoluble green sesquioxide behind.
Professor Wöhler prefers to mix the yellow chromate of potassa with sal-ammoniac, to heat
that mixture, and afterwards treat it with water, leaving the insoluble chrome-green as a
fine powder.
Among other methods of preparing the anhydrous sesquioxide is the heating of an
intimate mixture of bichromate of potassa and charcoal. The hydrated oxide of chro-
mium, according to the formula CrHO,, is met with in the trade under a variety of
names, and often contains boric or phosphoric acids, not, however, as an essential consti-
tuent (See Dr. P. Schützenberger's formula on p. 65 for Guignet's-green), but as a remnant
of imperfect preparation. This hydrated oxide, the preparation of which to ensure a good
colour is rather a difficult matter, requiring very careful manipulation, is known as
Emerald-green, Pannetier-green, Matthieu-Plessy-green, and Arnaudon-green. The pig-
ment is used as an artist's colour and in calico-printing as a substitute for Schweinfurt-
green, but is very expensive.
K₂
2
Chrome-Alum. This salt, Cr₂
} 4SO4+24H2O, is obtained in rather large quantities as a
by-product of the manufacture of aniline-viclet, aniline-green, and anthracene-red. It is
a deep violet-coloured, octahedrically crystallised substance, now used to some extent as a
mordant in dyeing, for rendering gum and glue insoluble, for waterproofing woollen
fabrics, and for the preparation of chromate of potassa.
Chromic Chloride. This compound, Cr,Cl, best prepared by the decomposition of sul-
phuret of chromium by means of chlorine, constitutes a crystalline violet-coloured mica-
like material, employed in the manufacture of coloured paper and paper-hangings.
White-Lead. This very important preparation obtained from lead is the basic car-
bonate of the oxide of that metal, its formula being,
PbOCO₂+x!
2
(РЬОНО)
OC
According to the method employed, white-lead is commercially known as of
Holland or Dutch, French or English manufacture. The Dutch mode of making
white-lead is founded on the fact that when metallic lead comes in contact with
the vapours of acetic acid, carbonic acid, and oxygen, at a sufficiently high tem-
perature, the metal is converted into basic carbonate of the oxide of lead. It is
quite evident from this brief statement that the chief conditions being fulfilled, the
methods of operation may be more or less varied. In Holland, Belgium, and some
parts of Germany, the lead-as pure as possible and free from silver, which, even in
small quantities greatly impairs the good colour of the white-lead-is cast into
thin strips, which are wound in a spiral and placed in coarse earthenware pots.
(Fig. 29.) Common vinegar is poured into the lower part of these pots, some beer-
yeast being added. The lead is then placed on a perforated piece of wood, so as to
68
CHEMICAL TECHNOLOGY.
prevent direct contact with the vinegar. After this the pots are covered with leaden-
plates and buried (see Fig. 30) in a mass of horse-dung or spent-tan and dung. The
fermentation of the dung causes the requisite increase of temperature, and the
vinegar evaporating, aided by the oxygen of the air, converts the lead into basic
acetate, which in its turn is converted into basic carbonate of lead by the carbonic
acid resulting from the fermenting manure. This rather clumsy process has given
place in Germany to the chamber method, consisting essentially in the following
arrangement. Instead of the pots being made the receptacles for the lead, the strips
of that metal are bent and suspended on a series of laths run lengthwise through the
chamber, on the floor of which is placed a layer of spent tan, marc of grapes, or other
fermentable material, saturated with vinegar. An improvement upon this arrange-
ment is to have the chamber constructed with a double flooring, one water-tight, the
other a light planking perforated so as to admit of the vapours of vinegar being
carried into the compartment. The action upon the lead is in each case the same;
it is converted chiefly into white-lead, and this crude product is purified from any
adhering acetate of lead by washing with water before being brought into the market.
There is still in use in this country a modification of the method practised by the
Dutch, who, by-the-bye, are not the inventors of white-lead manufacture, the true
FIG. 30.
FIG. 29.


P
origin being Saracenic, the trade being successfully carried on by these semi-savages
in Southern Spain, whence the Dutch brought over the art in the sixteenth century
to Holland. This modification consists in the following arrangement:-Granulated
lead is first moistened with about 1.5 per cent. of vinegar, the metal being previously
placed on hurdles in a wooden box, the interior of which is heated by means of steam
to 35°, some steam being introduced to keep the lead moist. If care is taken to
supply carbonic acid, after from ten to fourteen days the operation is finished, and
the product having been lixiviated with water and dried, is ready for use.
English Method of
Manufacturing
According to this plan the metal is melted in a large iron cauldron,
White-Lead. and then made to flow on the hearth of a reverberatory furnace so
as to convert the lead, by proper access of air, into litharge, which is obtained in a
very finely divided state by a peculiar arrangement of the furnace. The hearth is
constructed with a gutter, into which the fusing mass flows; and the sides or walls
of the gutter are perforated to admit of the passage of the molten litharge, while the
heavier metal sinks to the bottom. The litharge is next mixed with 1-100th of its
weight of a solution of acetate of lead, and then placed in a series of closed troughs
communicating with each other and admitting of the passage of a current of impure
carbonic acid, obtained by the combustion of coke in a furnace provided with a blast
to give an impulse to the gas. The litharge is continually stirred by machinery to
accelerate the absorption of the carbonic acid gas. White-lead made by this process
LEAD.
69
୫
covers very well, and is preferred to that prepared by the wet method. We may
mention in passing that it is the custom in this country to bring white-lead into the
market ground with linseed oil to a
thick paste, packed in strong oaken
kegs or iron canisters.
French Method of This method, in-

Preparing
White-Lead. vented by MM. Thé-
nard the elder, and Roard, is not
only generally adopted in France
but in all countries where it is
desired to carry out a really sound
and rational plan of white-lead
manufacture. The method is as
follows:-Litharge is dissolved in
acetic acid to obtain a solution of
basic acetate of lead,
(C₂H₂O)² } O₂ + PbH2O2;
Pb J
2
and through the solution a current
of carbonic acid gas is passed. Two
molecules of oxide of lead are con-
verted into white-lead, while neutral
acetate of lead remains. Litharge
is again added to the solution of
this salt, and, by digestion, more
subacetate of lead is obtained, which
is applied as just described.
Apparatus used in The machinery
White-Lead
Clichy.
Manufacture at and contrivances at
Clichy, near Paris, for effecting the
method just explained, are exhi-
bited in Fig. 31. In the tub, A, the
litharge is dissolved in acetic acid.
B C is a stirrer, moved by means of
the shaft shown in the engraving,
bearing at the top a pulley for the
strap. The solution of basic acetate
of lead can be run off through the
tap into the vessel E, made of copper
and tinned inside, the object being
to let the impurities the solution
TH
g
FIG. 31.
might contain subside. From E the fluid is led into the decomposition vessel con-
structed with 800 tubes, which pass from the top to a depth of 32 centims. beneath
the level of the fluid. These tubes are in communication with the main-pipe, gg, which
also communicates with the washing apparatus, P, answering the purpose of purifier
for the carbonic acid gas generated in the small lime-kiln, G, by the ignition of a
mixture of 21 parts by bulk of chalk and 1 part by bulk of coke with sufficient access
of air. The decomposition of the basic acetate of lead being finished in from twelve to
fourteen hours, the supernatant liquor, neutral acetate of lead, is run off into the
70
CHEMICAL TECHNOLOGY.
vessel, i, and the semi-fluid magma of white-lead passes into o. The pump, R, serves
to again convey the neutral acetate to the tank, A, and the operation is re-commenced.
The white-lead in o is well washed--the first wash-water being conveyed rack to the
tank, A-and after drying is ready for use. In order to obtain the carbonic acid
cheaply, it has been proposed to ignite a mixture of chalk or limestone, charcoal, and
peroxide of manganese (CaCO3+C+3MnO2=Mn3O4 + CaO + 2CO2.) Where ad-
missible, the carbonic acid resulting from the fermentation of beer-wort, or of dis-
tillery-wash, may be applied. Natural sources of carbonic acid sometimes occur in
the neighbourhood of active or extinct volcanoes; and near Brohl, close to the
Laacher Sea in Rhenish Prussia, a locality well-known to tourists, a very plentiful
and continuous supply of carbonic acid is naturally obtained and actually applied
for the purpose under consideration.
Among the very various suggestions for improved methods of making white-lead, and
for which an enormous number of patents have been taken out, especially in this courtry
and in the United States, we briefly mention the following:-MM. Button and Dyer first
slightly moisten litharge with water, next mix it with a small quantity of a solution of
acetate of lead, place the mixture in a stone trough, agitating and passing hot carbonic
acid over it. Pallu (1859) causes finely-divided lead to be thrown with great force, by
means of a centrifugal machine, on an inclined plane, care being taken to moisten the lead
with acetic acid. After the lapse of an hour, the finely-divided lead is converted into
acetate and carbonate. A solution of acetate of lead is then poured over the mass, and
the acetate of lead it contains is dissolved, while the white lead is carried into a tank, and
there forms a deposit. M. Grüneberg (1860) prepares white-lead by submitting granu-
lated lead to the simultaneous action of air, acetic, and carbonic acid, aided by the rapid
motion of the metal. From private information obtained from the largest wholesale house
in London, whose connections and trade relations embrace literally the whole world, dealing
in white-lead, we have learned that not 1-1000th part of the lead, as it is technically termed,
of good and saleable quality met with in the trade, is made by these new processes, since
the products of most of them are deficient in some respect or other.
White-Lead from
It is well-known that sulphate of lead (PbSo) is a by-product of
Sulphate of Lead. various chemical operations, especially such as are carried on in connection
with dyeing and calico-printing. The salt of lead thus obtained is a refuse which it has
been sought to utilise in many ways. As it does not possess covering power, it cannot be
used instead of white-lead as a pigment, and the difficulty of reducing it to metallic lead
renders its metallurgical utilisation, if not impossible, at least highly objectionable. It
has been used as a gas-purifier instead of, or in connection with, lime, and for this purpose
it is a very fit material, and by becoming converted into sulphuret of lead it may be
afterwards utilised as a lead ore. It is converted into white-lead by digesting it with a
solution of either carbonate of ammonia or of soda. The best method for converting the
sulphate of lead into metallic lead is to mix the air-dried salt with 67 per cent. of chalk,
12 to 16 per cent. of charcoal, and 37 per cent. of fluor-spar, and to smelt this mixture in a
furnace. The result is the formation of carbonate of lead, which is reduced to the metallic
state by carbon, the sulphate of lead and fluor-spar combining as a slag-
(PbSO4 + CaCO3 + 2C + nFl₂CaPb+3C0+ CaSO4 + F1,Ca).
According to Dr. Bolley, sulphate of lead may be reduced by the moist method by placing
the salt with zinc into water, the result being the formation of chloride of zinc (sic) and
metallic lead.* M. Krafft proposes to convert sulphate of lead into acetate of lead by
boiling the former with a solution of acetate of baryta, sulphate of that base (permanent,
or Chinese-white) being simultaneously formed.
Theory of Preparing Leaving out of the question the preparation of white-lead from sul
White-Lead. phate of lead, the preparation of the pigment as regards all the other
methods is dependent upon :—
1. The formation of basic acetate of lead;
2. The decomposition of that compound into neutral acetate of lead and white-lead.
Viewing white-lead for this purpose simply as a carbonate of lead, although we shall
* It reads in the original exactly as above translated, but whence the chlorine for the
chloride of zinc is to come has been left in nubibus; water, sulphate of lead, and metallic
zinc do not act upon each other unless some acid be present. Should dilute sulphuric be
present there will be formed sulphate of zinc.
LEAD.
71
presently see that the white-lead of commerce is not so simply constituted, the formation
may be illustrated by the following formulæ :—
I.
II.
2
C₁₂H₂O} 0+3PbO= {(C₂HO)) 0,2PbHO₂;
Acetic acid.
2
2
Pb
Basic acetate of lead.
3 2
(C₂H₂0); } 0,2PbH¸¸+200, +2PbCo₂+ { (C₂H₂0); } 0.
Pb
Basic acetate of lead.
Carbonate
of lead.
Pb
Neutral acetate
of lead.
It is therefore evident that a comparatively very small quantity of acetate of lead can
produce a large quantity of white-lead, and the manufacture of that material would be
endless but for the fact that white-lead retains some neutral acetate of lead, and that the
loss of acetic acid cannot be practically avoided.
White-Lead from M. Tourmentin prepares white-lead from basic chloride of lead, obtained
Chloride of Lead. by the action of common salt upon litharge, by mixing that compound
with water, passing through it a current of carbonic acid, and next boiling the fluid in a
leaden-pan with powdered chalk until a test-sample, when filtered, does not become
blackened by the addition of sulphide of ammonium. The white-lead thus formed is freed
from salt by washing with water.
as a Substitute for
White-Lead.
Basic Chloride of Lead Mr. Pattinson, of the Felling Chemical Works, near Newcastle-on-
Tyne, has proposed that, instead of white-lead, a basic chloride (oxy-
chloride) of lead should be used; and he prepares that substance by adding to a hot solution
of chloride of lead (PbCl), containing from 400 to 500 grammes of the salt to the cubic
foot, an equal bulk of saturated lime-water. This addition causes the throwing down
of the compound (PbCl + PbH₂O₂), which after having been collected on a filter and
washed, is dried and used as a pigment. The chloride of lead is obtained directly from
galena, which is decomposed from leaden-vessels with strong hydrochloric acid. The sul-
phuretted hydrogen thus formed is carried by suitable tubing to a burner in the sulphuric
acid chamber, the resulting sulphurous acid from the combustion being used for the pro-
duction of sulphuric acid. Pattinson's white-lead is not so white as ordinary white-lead, its
colour verging to yellow, but this is no objection where white-lead is to be used with other
paints, and the less so as Pattinson's oxychloride of lead covers well.
Properties of When unadulterated and well-made, white-lead is an exquisitely fine white-
White-Lead. coloured powder, void of taste and smell. The white-lead of commerce
exhibits, according to the mode of preparation, different features; one preparation is met
with in flakes, having been obtained by the corrosion of thin strips of lead placed in pots.
The lead known as Krems-lead is pure white-lead made in thin cakes by means of gum-
water.
The variety of white-lead known as pearl-white is blued with either a small quantity of
indigo or Berlin-blue. The white-lead of commerce has frequently been made the object
of chemical analysis, especially by Dr. G. J. Mulder and M. Grüneberg. The results of
the analyses of the under-mentioned samples prove the correctness of the formula given
above. The numbers refer to:-I. Krems white-lead. 2. Precipitated by the Clichy
method and manufactured at Magdeburg. 3. From the Harz. 4. Another sample from
Krems. 5. A sample from a chemical laboratory by imitating the Dutch method on a
limited scale. 6, 7. Samples from Klagenfurt, Carynthia. 8. English lead manufactured
according to the Dutch method.
5.
7.
8.
86.72 86.5 86.51
Oxide of lead
Carbonic acid
Water..
I.
2.
3.
4.
6.
83.77 85.93 86.40 86.25 84.42
15.06 11.89 11'53 11.37 14:45
II.28 113 II.26
2'01 2.13 2.21 1.36 2.00
ΙΟΙ
2.2 2.23
It is certain that the covering properties of white-lead are dependent upon its state of
aggregation, because a loose crystalline white-lead does not cover nearly as well as the
perfectly amorphous lead prepared by the old Dutch method. It appears that the covering
power increases with the amount of hydrated oxide of lead. This is proved by the fact that
those who merely choose white-lead by its covering power are often misled, a fact lately
tested by the translator of this work, by giving to a man, thoroughly acquainted with white-
lead as commercially met with, a mixture of carefully-prepared and dried hydrated oxide
of lead, to which white precipitate, subnitrate of bismuth, and carbonate of bismuth had
been added. The man, after testing a series of samples of purposely-adulterated white-
lead, all of which he detected as adulterated, was unable to speak with certainty of the
above mixture, which he took for pure lead.
72
CHEMICAL TECHNOLOGY.
Adulteration of
It has been, and is still, to some extent, the custom in the manufactories
White-Lead. to add to white-lead a certain quantity of sulphate of baryta, either native
or artificially prepared. Lead is often mixed with sulphate of lead, chalk, carbonate of
baryta, sulphate of baryta, and pipe-clay; but these adulterations are most common in
the retail trade. Not any of these substances ought to be present; they possess no covering
power and needlessly absorb oil. Pure white-lead ought to be perfectly soluble in very
dilute nitric acid, and in the resulting clear solution caustic potassa should not produce a
precipitate, for if it does chalk is present. An insoluble residue in the dilute nitric acid
indicates the presence of gypsum, heavy-spar, or sulphate of lead. The sulphate of lead
may be recognised by reducing the lead with the blowpipe. Sulphate of baryta can be
made evident by ignition with charcoal in the blowpipe flame, treating the residue with
dilute hydrochloric acid, and adding a solution of gypsum, which again yields a precipi-
tate of sulphate of baryta. Gypsum does not yield an insoluble precipitate with dilute
nitric acid, but does so with a solution of oxalate of ammonia. According to Dr. Stein
the most simple method of estimating quantitatively a mixture of white-lead and
sulphate of baryta, is to heat the weighed sample in a piece of combustion-tube, and to
collect the carbonic acid in a Liebig's potassa-bulb, a chloride of calcium-tube being
fastened by a perforated cork to the combustion-tube to absorb the moisture. The
quantity of carbonic acid given off stands in direct proportion to the quantity of carbonate
of lead present. Pure white-lead of good quality gives off about 14.5 per cent. of the
gas, and, according to Dr. Stein's researches, the undermentioned series of mixtures gave
off the quantities of carbonic acid indicated.
33.3 parts of white-lead and 66·6 parts of heavy-spar lost by ignition 4.5-5 per cent.
66.6
""
80.0
""
50'0
""
Applications of
""
"
33°3
20'0
50'0
""
""
""
""
""
""
6.5-7
13.9
10-10'4
""
The extensive applications of this material as a constituent of paints,
White-Lead. "to give body," as the term runs, and as putty, and for various chemical
operations, are well known. It has been experimentally proved by Dr. G. J. Mülder in
his treatise "On the Chemistry of Drying Oils and the Practical Applications to be drawn
therefrom," that the quantity of white-lead used in proportion to linseed-oil for painting
purposes is far too great, being on an average from 250-280 parts of white-lead to 100
parts of oil, while the author found that 52 parts of unadulterated white-lead, or 44 parts
of oxide of lead (PbO) to 100 parts of raw or boiled linseed-oil are amply sufficient
quantities. White-lead, however useful, is very sensitive to the action of sulphuretted
hydrogen, by which it is blackened and discoloured, causing not only all the white paint
to be spoiled, but also all pigments and paints of which white-lead is a constituent, as
may be seen to a very large extent every summer at Amsterdam, where from the stagnant
canals sulphuretted hydrogen is abundantly given off. The action, however, of the sea
air in autumn has the effect of somewhat restoring the blackened and discoloured painted
surfaces to their primitive hue. The late Professor Thénard suggested that pictures which
had become blackened should be cleaned by means of peroxide of hydrogen, the oxygen
of which present as ozone converts the blackened lead colours into white sulphate of
lead.
In this country it has become an almost universal custom to sell white-lead ready
ground with linseed-oil into a thick paste. This practice certainly saves painters a
great deal of trouble, but is also pregnant with the difficulty of detecting adultera-
tion, while there is a chance of an inferior oil, rosin oil, being added. The oil
almost entirely prevents the action of any acid upon the paste; even if very strong
nitric acid be taken, and heat applied, the decomposition and disintegration are
very slow and incomplete, and, besides, owing to the insolubility of nitrate of lead
in nitric acid, the action of strong nitric acid upon oil thus mixed gives rise to a
variety of compounds, which interfere with the usual modes of testing the white-
lead. To remove the oil in order to test white-lead, the best plan is to thoroughly
incorporate some of the sample with a mixture of chloroform and strong alcohol in
equal parts, and to wash the mass by decantation or on a filter with a fluid com-
posed of 2 parts of chloroform and I of strong alcohol. The quantity of the oil
may then be ascertained by the evaporation of this solvent. After washing once
or twice with boiling alcohol and then drying, the white-lead can be readily tested
by any of the known methods.
TIN.
73
Occurrence and
mode of obtaining
the Metal.
(Sn
TIN.
118; Sp. gr. = 7′28.)
Tin does not occur naturally in a metallic state: it is found as
oxide in tinstone, or tin ore, SnO2, containing 79 per cent. of metal,
and as sulphuret of tin in combination with other metallic sulphurets in tin pyrites,
(2Cu₂S + SnS2) + 2(FeS, ZnS), SnS2, with 26 to 29 per cent. of tin. Tin ore occurs
either interspersed in veins, in syenitic and similar rocks, or in secondary formations
deposited from water, and consisting of various detritus, when it is known as seifer.
These ores are not as a rule simply composed of pure oxide of tin, but contain various
other metallic compounds, among which are sulphur, arsenic, zinc, iron, and copper.
In some instances, in Cornwall, Malacca, Banca, and Billiton, tin ore is met with
among the detritus of ancient river-beds in a very pure state, since the mechanical
separation of the ore from impurities has been performed by nature itself, and as a
consequence these ores yield a purer metal than the ore obtained from veins, which
has to undergo dressing, washing with water, and roasting, previously to being
smelted, in order to eliminate the arsenic, sulphur, and antimony. Tinstone occurs
in Saxony in the earlier granitic formation. The ore is accompanied by, and partly
mixed with, wolfram, molybdenum-glance, sulphur, and arsenical pyrites, and bears
the name of Zinnzwitter. Fig 32, I. and II., represent the furnace in use at
Altenberg, Saxony, for smelting the roasted tin ore. It is built of granite upon a
FIG. 32.
I.

W
II.

strong foundation of gneiss, and is about three metres in height. A is the shaft, в the
fore-hearth, and D the bottom-stone, consisting of one single piece of granite scooped
out in the direction of B. B is in communication with the iron cauldron, C; while the
tuyere of the blast is placed at B. The ore, mixed with coke, coal, or charcoal, and
with slag from former smeltings, is placed in a ; the reduced tin collects first on the
fore-hearth, B, and runs thence into c. The metal, however, is not pure, but contains
iron and arsenic. It is separated from these impurities by a process of liquation;
the pure tin fusing more readily, oozes out and leaves behind an alloy of iron and
tin fusible with greater difficulty. The metal thus obtained is very pure, containing
hardly as much as o'i per cent. of foreign metals; it is known in the trade as refined
74
CHEMICAL TECHNOLOGY.
tin. The slags, as well as the alloy remaining, are smelted separately or together
for tin, and the result brought into the market as block-tin. In Bohemia and Saxony,
tin is cast either in ingots or in cakes. Banca and Billiton tin, a very pure metal,
is cast in slabs. If tungsten ores occur with tin ores, there is great difficulty in
obtaining pure metal. Tin ore found in Cornwall—and this county has yielded tin
for at least 2,000 years-has to be smelted according to the ancient Stannary laws.
Properties of Tin. Tin, as regards its colour, approaches the nearest to silver, only
differing by a somewhat bluish hue, and it exhibits a high metallic lustre very
similar to silver. It is, next to lead, the softest metal, yet is somewhat sonorous, for if a
rod of tin be free to swing, and is gently tapped, a sound is produced; this is not the
case under similar conditions with lead, thus proving tin to be considerably harder, also
proved by the fact that it is not easily scratched with the nail. The bending of a rod of
tin causes a creaking noise, which is the stronger the purer the tin. Tin is very malleable,
and admits of being beaten to very thin foil, but it is not a very ductile metal. When
rubbed between the fingers it imparts to them a peculiar odour. The sp. gr. of pure tin
is 7.28, and by hammering may be increased to 7.29; a cubic foot of tin weighs, according
to its purity, from 375 to 400 lbs. Tin fuses at 228°, and becomes very brittle when
heated to nearly that temperature. If the metal is intended for casting-it is, however,
very rarely used in a perfectly pure state for castings, as it does not fill the moulds well-
its metallic lustre and degree of cohesion after cooling entirely depend upon the tempera-
ture of the tin at the time of casting. If too hot and exhibiting rainbow colours, its sur-
face will appear striped and reddish-yellow after cooling, and the metal will be brittle
if again heated to 100° to 140°; if not sufficiently heated, though in a fluid state, it is, after
cooling, dull and brittle. The greatest metallic lustre is obtained, and simultaneously the
greatest cohesive strength, when the surface of the metal while molten exhibits a high degree
of lustre. At a white heat tin boils and volatilises, air of course being excluded; for
if the metal be kept fused in contact with air, it becomes covered with a greyish coating
of protoxide of tin and finely-divided metal, termed tin-ash, which substance when the
heating is continued becomes converted into a yellowish-white stannic oxide, known as
putty powder. Tin by exposure to air gradually loses its metallic lustre, but is by no
means so readily affected by sulphuretted hydrogen and ammoniacal vapours as silver,
and is used to imitate that metal in the construction of lustres for gas lamps, &c.
Applications of Tin... Now that china and earthenware have become cheap, and other alloys
are used for spoons, tin is not so frequently in demand as in former times for domestic
utensils. Tin, though next to silver the dearest of metals, is met with in quantities
measured by the ton, which of tin varies in price from £120 to £180-copper being
from £95 to £105-and is largely used both as an alloy (for those with copper
see under that metal), and in a pure state for various kinds of vessels for pharmaceutical
and chemical operations, for worms of distilling apparatus, for the working parts
for dry and wet gas-meters, and for block-tin pipes for conveying gas and water, &c.
However, for many purposes, an alloy known in this country as pewter, of lead and tin in
varying proportions, is preferred, because this compound is harder and stands wear and
tear better than these metals separately. An alloy of lead and tin is called abroad
two-poundly when the metals are present in equal quantities, and three-poundly when
consisting of 2 pounds of tin and I of lead. Tin, either pure or more or less alloyed with
lead, may be beaten or rolled into thin sheets and foil, and applied in a great many ways;
among which, one of the chief, although gradually being superseded by a process of silvering,
is tinning or amalgamating mirrors. Tin-foil is also used for the packing of chocolate,
soap, cheese, fruit, &c., all of which keep very well under these conditions. Commercial
silver-foil or leaf-silver is an alloy of tin with a little zinc; in combination with other
metals, viz. copper, antimony, and bismuth, in varying but small quantities, it constitutes
a composition metal used for making teaspoons and other similar objects. Britannia metal
consists of 10 parts of tin and I of antimony, its various applications are well known.
As the specific gravity of those metals with which tin is purposely or naturally alloyed
differs, the determination of the sp. gr. is a means of estimating the purity of the metal.
The undermentioned figures illustrate this in the more commonly occurring alloys of tin
and lead :-
Parts Sn Parts Pb
I
I
I
132537
21 21 2
7
Ι
Sp. gr.
8.8640
9.2650
9'5530
9.7700
Parts Sn+ Parts Pb
3
4
2
TIT!
2
9*9387
10.0734
3
Sp. gr.
10.183
8.497
8.226
8.109
7.994
PREPARATIONS OF TIN.
75
The material known as putty-powder and calcined tin-ash is used for polishing glass
and metals, and for producing white enamels.
Tinning. By this term we understand the covering of other metallic surfaces with a thin
and adhesive film of tin. This operation only succeeds well when the surface of the metal
to be tinned is quite free from oxide, and when during the operation the oxidation of the
molten tin is prevented. The former requisite is attained by the action of dilute acids,
rubbing and scouring with sand, pumice-stone, &c.; the latter condition by the use of
either rosin or sal-ammoniac, both of which cause the reduction of any oxide that may be
formed.
Tinning of Copper. Brass, The vessels or other objects intended to be tinned are heated
and Malleable Iron. nearly to the melting-point of tin; some molten tin is then poured
into the vessel, and brushed about with a piece of hemp over which some powdered sal-
ammoniac is strewed. Pins, hooks and eyes, small buttons, and similar objects are tinned
by being boiled in a tinned boiler filled with water, granulated tin, and some cream of
tartar. The tinned objects are dried by being rubbed with sawdust or bran.
Tinned Sheet-Iron. This well-known material, from which so many useful objects are made
by the tinman, is not, as is frequently supposed, rolled out sheet-tin, but tinned sheet-iron.
The iron previously to being covered with tin is thoroughly secured, so as to present a
clean metallic surface, and then immersed in baths of molten tin covered with a layer of
molten tallow to prevent the oxidation of the metal. On being removed from the tin-bath
the sheets are immersed in a bath of molten tallow to remove any excess of tin, wiped
with a brush made of hemp, next cleaned with bran, and packed. In order to obtain iron
covered with an alloy less easily fusible, MM. Budy and Lammatsch add about th of
nickel to the tin.
Moire-Metallique. When tinned sheet-iron, technically termed tin-plate, is washed over
with a mixture consisting of 3 parts of hydrochloric and I part of nitric acid diluted with
3 parts of water, and then cleaned with pure water, there will be observed a peculiar,
somewhat mother-of-pearl-like appearance, due to the crystalline particles of tin, produced
by the rapid cooling, reflecting the light unequally.
Mosaic-Gold.
PREPARATIONS OF TIN.
Aurum Musivum; The substance known under that name is in reality a bisulphide of
tin (SnS2), prepared in the following manner:-4 parts of pure tin, with 2 of mercury,
are amalgamated by the aid of a gentle heat, and introduced with 21 parts of sulphur
and 2 of sal-ammoniac into a flask, and heated on a sand-bath, at first gently and
then gradually increasing to a full red heat. First the sal-ammoniac volatilises, and
next mercury in the shape of cinnabar mixed with a trace of the sulphide of tin; while
there is left the preparation known as mosaic-gold, forming the upper layer of the
remaining contents of the flask, the lower portion being a badly-coloured sulphide.
The rationale of the formation of this peculiar coloured sulphide, that is, peculiar as
regards its physical appearance, is not quite clearly explained; the compound, more-
over, may be prepared without mercury. When properly prepared, it appears as a
golden-coloured metallic substance, greasy to the touch, and soluble in the alkaline
sulphurets. It is chiefly used for imitating gilding on painted surfaces, but its
employment is very much restricted from the fact that the bronze-colours are more
satisfactory in result. Indeed, in the English market, mosaic-gold is almost obsolete.
By the name of tinsalt the trade understands chloride of tin (SnCl2), but
the commercial article, being prepared by dissolving granulated tin in hydrochloric
acid and evaporating the solution, is really (SnCl2 + 2H2O). According to M. Nöllner
hydrochloric acid gas should be caused to act on granulated tin placed in earthenware
receivers, and the concentrated tinsalt solution thus obtained evaporated in block-tin
vessels. The salt occurs in the trade in colourless, transparent, deliquescent
crystals, of course very soluble in water. The aqueous solution, unless acidulated
with more hydrochloric or tartaric acid, soon deposits a basic salt. Tinsalt is used
chiefly in dyeing and calico-printing.
Tinsalt.
76
CHEMICAL TECHNOLOGY.
Nitrate of Tin,
or Physic.
Under this name dyers use a solution of refined block-tin in aqua
regia, and usually this substance is a mixture of perchloride and protochloride of tin.
The material known as pinksalt is a double chloride of tin and ammonium—
(SnCl4 + 2NH4Cl).
A concentrated aqueous solution of this salt is not decomposed by being boiled, but,
when diluted, the oxide of tin is thrown down. Pure chloride of tin is used in France
in the preparation of fuchsine; while as a solution it is used by M. Th. Peter, at
Chemnitz, for dyeing in iodine-green.
Stannate of Soda.
This salt is now very largely used in dyeing as well as in calico
printing, and is prepared in various ways, sometimes by fusing tin-ores with caustic-.
soda and lixiviating the molten mass with water; or, according to Mr. Brown, by
boiling soda-lye with metallic tin and litharge, the effect being the formation of
stannate of soda and metallic lead. Dr. Häffely somewhat modifies this process by
digesting litharge with soda-lye at 22 per cent. in a metallic vessel. Into the solution
of plumbate of soda thus obtained, granulated tin is placed and heat applied. Some-
times a stannite of soda is used and made by dissolving tinsalt in an excess of caustic
soda, but this preparation is unstable, and does not answer well in dyeing and print-
ing; it is only extemporaneously used on a limited scale by small dyers.
Occurrence and Mode
of Obtaining.
BISMUTH.
(Bi=210; Sp. gr.=9'79).
Bismuth is a rather rare metal. It occurs in Peru and Australia,
chiefly native, and with cobalt and silver ores in granite-gneiss and metamorphic
rocks. It is also found as oxide, the ore being known as bismuth-ochre, BiO3, con-
taining 89.9 per cent. metal; as sulphide, or bismuthine, BiS3, with 80·98 per cent.
FIG. 33.

B
M MW.ht/
M AMI Wh V
དོ་། །་་་་་b 'M WW
AÐALGATA AANGAANA: AAMAAVAL. AS
VAGANZO GOGIRON BILA "AVAAWAGA
་་་་་་་་་ ད་་་སྙན་ད་་།་་
དོ་་་་་ད་ད་་་ ་་་་་ ་་ ་་ང་…
GALAMAN JAWAAACwAAAA AAA
AYMAN GYVA JAMU JAUNG (1:9.
་་་་་་ད་་་་་་་་ ་་་་་་་ ་་་་་
ZAMAN-JAMAS ATOPATULA MIEGA
JAAVAAZAN VA-AGO ANGAN PANANAK A
་་་་་་་་་་་་་་་.འ་་་ ་་་་་་ ་་་་
་་ ་ད
t་ M་་་་་་་་་
་ ་་ ་་་་་ ་་་་་་ ་་་་་ ་་་་ .
MAANS
metal; and as bismuth-copper ore, with 47°24 bismuth. As bismuth is chiefly found
in the native metallic state, and is a readily fusible metal, its extraction from gangue
is not a difficult matter, and consists in a process of liquation.
Furnace.
Bismuth Liquation The contrivance in use near Schneeberg, in Saxony, for the smelt-
ing of bismuth is exhibited in Fig. 33. The ore, containing on an average from
4 to 12 per cent. metal, separated as much as possible by mechanical means from the
gangue, is broken up to the size of hazel-nuts and placed in the cast-iron tube, A,
ZINC.
77
heated by means of the furnace. The fluid metal runs out into B, an iron-pot kept
sufficiently hot by means of charcoal to prevent the solidification of the metal, and
partly filled with charcoal-powder to prevent the oxidation of the metal. The
residue in the iron tube is discharged into the water which fills the box, D. By
this method of liquation about two-thirds of the bismuth contained in the ore is
reduced. Bismuth, as has been stated (see Cobalt), is obtained as a by-product,
and from the refuse of the refining of certain silver ores, which are treated with
dilute hydrochloric acid, the basic chloride of bismuth being precipitated by water,
afterwards dried, and reduced by means of soda.
Properties of Bismuth. Bismuth possesses a reddish-white colour, strong metallic lustre,
and crystalline texture. It is hard, but so brittle that is readily pulverised, yet
with careful treatment proves to be somewhat ductile. Its fusion-point is variously
given by different authors, the latest determination of pure metal in an atmosphere of
hydrogen is by Dr. van Riemsdijk, who found bismuth to melt at 268.3°. On cooling
bismuth expands very considerably.
a is Saxony, ẞ Peruvian bismuth; composed in 100 parts:-c. Bismuth, 96.731; anti-
mony, 0625; arsenic, 0'432; copper, 1682; sulphur, 0.530. 8. Bismuth, 93.372;
antimony, 4'570; copper, 2·058.
Applications of Bismuth in the metallic state is chiefly used for certain alloys. Its oxide
Bismuth. enters with boric and silicic acids into the composition of some kinds of
glass, and is used for porcelain- and glass-staining. The basic nitrate, or magisterium
bismuthi, and the carbonate are used in medicine, and the former, under the name of
Blane de fard, is employed by ladies for painting and beautifying their faces. Among the
alloys of bismuth those with lead, tin, and cadmium (see that metal), are the most import-
ant. Newton's fusible alloy is composed of bismuth, 8 parts; tin, 3; lead, 5; and melts
at 94.5°. Rosse's fusible metal consists of 2 parts of bismuth, I of lead, I of tin, and
fuses at 93.75. If a small quantity of cadmium be added to these alloys they are rendered
still more easily fusible. An alloy composed of lead 3 parts. in 2 parts, bismuth 5 parts,
fuses at 91.66, and may be used for stereotyping purposes, but is rather expensive. This
alloy is also used for making the pocket-book metallic-pencil for writing on paper prepared
with bone-ash. Alloys containing bismuth were used as safety-plugs in steam-boilers;
these plugs were screwed into one or more of the plates exposed to the force of the steam,
usually in or near the steam-chest or dome, the idea being that the plugs would melt if the
temperature of the steam rose beyond certain limits. Experience, however, has suffi-
ciently proved that these plugs, although carefully made, did not act as a real preventative
to boiler-explosions.
f
ZINC.
Zn-652; Sp. gr. 7'1 to 7.3)
Occurrence of Zinc. This metal, known only a comparatively short time, is never found
native, but in combination with sulphur (ZnS), with 67 per cent. of metal, under the
name of blende or black-jack, the ore sometimes containing traces of indium. It also
occurs combined with oxygen as noble-calamine, carbonate of zinc, or zinc-spar
(ZnCO3), with 52 per cent. of zinc; as ordinary calamine-stone, or hydrated silicate of
zinc, with 53.8 per cent of metal; as red zinc-ore or red oxide of zinc, frequently
containing manganese; as Gahnite (AIZnO4); and further as an admixture with other
ores.
Method of
Extracting Zinc.
The general plan is to roast the ore and then mix it with the requi-
site quanty of carbonaceous matter and suitable flux, care being taken that the latter
shall not give rise to the formation of any oxidising material; for instance, if the ore
requires lime as flux to take up the gangue, calcined limestone, and not chalk or
limestone is used. The action of the fuel is aided by a blast, best of dry air. The
products of this mode of treatment are:--1. Metallic zinc, the vapours of which
78
CHEMICAL TECHNOLOGY.
condense in properly constructed and cool channels. 2. Hot gases usually applied
for heating steam-boilers or other purposes. 3. The non-volatile materials, gangue
and flux, slag with some metal.
in Muttles.
Distillation of Zinc With the exception of cadmium, zinc is the most volatile of the
readily fusible metals, while its melting-point is nearly twice the number of degrees
of that of tin, the most fusible of the commercially valuable metals; this property
is utilised in extracting the metal from its ores. The mode of distillation varies in
some particulars in the three chief zinc producing countries, Silesia, Belgium, and
England. In Silesia and Germany the apparatus used for the distillation of zinc
consists (see Figs. 33, 34, and 35) of a muffle-shaped fire-clay retort, the front or
mouth of which is provided with two openings, the lower, a, being closed by a door
FIG. 35.
FIG. 34.


which is opened only when the residue of the distillation is taken out. At b, the
other opening, a rectangularly bent tube is inserted, provided with a small hole at c,
closed by a plug when the operation of distilling is proceeding, and by which the ore
is introduced into the retort. At d the molten zinc runs off. The muffles are placed
to the number of from 10 to 20 in a furnace (see Fig. 36) constructed internally
FIG. 36.

somewhat like gas-retort furnaces, and rest on what are technically termed benches.
The arches of the furnaces are so constructed as to concentrate the heat from the
hearths placed longitudinally. The metal is received in crucibles placed in the
recesses, tt. As the first portion of the metal and oxide carried over contains nearly
all the cadmium existing in the ore, that portion is kept separate for the purpose of
extracting cadmium. At the outset of the distillation the condensation room, t, is so
cool that the vapours of the zinc become solid without agglutination, that is, remain
finely divided. This product, though of course containing oxide, frequently yields
98 per cent. of metallic zinc. Afterwards the metal carried over is what is termed
drop-zinc, that is to say, the liquid runs off in a molten state. This crude zinc is
refined by another smelting, and comes in the market in slabs about 2 inches thick
by 10 long and 5 to 6 wide.
ZINC.
79
Distillation in Tubes.
At the celebrated zinc-works of Vieille Montagne, near Liège,
Belgium, zinc ore is distilled in tubes. These tubes are placed in rows in a slanting
position; they are made of fire-clay, 1 metre in length by 18 centims. width and 5
centims. thickness (see Fig. 37), and closed at one end; the open ends are flush
with the front brickwork of the furnace, in order that the charge of ore, flux, and
carbonaceous matter may be introduced. Fig. 38 exhibits a cast-iron conically-
shaped tube, 25 centims. long, and Fig. 39 a sheet-iron tube 20 centims. long, both
FIG. 38.
FIG. 39.
FIG. 37.
of which are fastened to the fire-clay tube to receive the volatilised metal. A vertical
section of the Belgian furnace used for the distillation of zinc is shown in Fig. 40,
with the mode of placing the tubes, the closed ends of which rest on a projection of
the brick-work. The ore is first calcined in a shaft-furnace, and the charging of the
tubes usually takes place every morning at six o'clock, when the fire is rather low.
Distillation of Zinc The zinc-smelting as carried
in Crucibles.
on near Sheffield, Birmingham, and in Wales and
other localities, is performed by downward dis-
tillation. The furnaces represented in Fig. 41
are constructed to contain six or eight fire-clay
crucibles, cc, access to which is obtained through
holes made in the fire-arch of the furnace. The
bottom of each crucible is perforated and fitted
with a tube to carry off the volatilised zinc;
during the time of charging this tube is closed
with a wooden plug, which is of course burnt
during the strong ignition. At first the crucibles
are left open, but as soon as a bluish flame be-
gins to show itself, the covers are put on. The
condensation-tube is then applied over a vessel
containing water to prevent the spirting of the
metal. The zinc is ultimately refined by smelt-
ing in iron crucibles.
Mode of Obtaining Zinc
from Sulphuret of Zinc,
English Miners.
There are two modes of utilis-
In one
FIG. 40.

A1
the Black Jack of the ing this zinc mineral.
plan the sulphuret is first roasted
so as to convert it into oxide, and then treated
as before described; or the ore is directly applied
by adding a quantity of iron ore sufficient to desul-
phurise it, lime being used as flux. The iron ore,
if containing water or carbonic acid, ought to be
calcined previously to being used for this purpose;
but instead of iron ore metallic iron is often used.
Mr. Swindells has proposed to calcine native
sulphuret of zinc with common salt, the result being the formation of sulphate of soda
and chloride of zinc. The mass being lixiviated with water, from which the sulphate of
soda crystallises, the chloride of zinc remains in solution and is precipitated by means of
lime, yielding oxide of zinc. This oxide is treated for metal in the ordinary manner.
The colour of zinc is bluish-white or grey; its crystalline structure
varies according to its purity, and according to the temperature at which it was cast and
the more or less rapid cooling. When zinc is cast and rapidly cooled the specific gravity
Properties of Zinc.
80
CHEMICAL TECHNOLOGY.
is 7.178, but when slowly cooled it is 7.145, and by hammering and laminating may be
increased to 7.2 and even 7.3. A cubic foot of zinc weighs, therefore, from 360 to 390 lbs.
Zinc is slightly harder than silver, but like lead and tin it is not fitted for filing, as it
chokes the teeth of the files. When pure, zinc is sonorous; it is a brittle metal possessed
of a very small absolute tenacity, but offers a great resistance to crushing weight, when
not subjected to sudden blows. Very pure zinc may be hammered out at the ordinary
FIG. 41.
temperature, but the malleability is greatest at tempera-
tures between 100° and 150°. Zinc melts at 412° in the
open air, and perfectly pure zinc melts in an atmosphere of
hydrogen at 420°. According to MM. Troost and Deville
zinc volatilises, air or oxygen being excluded, at 1040°, and
may be distilled; when heated in contact with air to 500°
zinc burns, emitting a very strong greenish blue-coloured
light, and forming oxide of zinc (zinc-white), which is not
volatile. Of all the metals used on a large scale, zinc has
the highest coefficient of expansion by heat, its longitudinal
expansion for temperatures from o° to 100°, being for cast
zinc, for sheet zinc, consequently molten zinc greatly
contracts while cooling. The malleability, tenacity, and
cohesive force of zinc are greatly impaired by temperatures
ranging from 150° to 200°, at which zinc may be pulverised.
Superheated steam oxidises zinc (H₂O+ZnZnO+ H₂),
and this property is made use of in the separation of this
metal from lead. When exposed to a moist atmosphere
zinc is superficially oxidised, but as the oxide adheres
strongly to the metal further corrosion is prevented. Zinc
is so readily oxidised and acted upon by water, weak acids,
and alkalies, that it is not at all a suitable metal for vessels
intended to hold potable liquids or moist solids, as these
substances take up zinc and become poisonous. An addi-
tion of 0.5 per cent. of lead renders zinc far more malleable;
but if the zinc is to be used for the preparation of brass, even 0.25 per cent. of lead is
injurious, and for brass-making zinc containing lead is avoided. Zinc often contains
some 0.3 per cent. of iron, but this does not impair the good quality; the iron is usually
derived from the iron pots used for re-melting the crude metal; if, however, the quantity
of iron increases the zinc becomes brittle and cracks. Zinc obtained from calamine is
usually purer than that obtained from the native sulphuret. The black residue remaining
when zinc is dissolved in acids; and often mistaken for a carburet of zinc, is a mixture in
various proportions of iron, lead, and carbon. The more impure the zinc, the more
readily it is dissolved in acids, but by careful distillation zinc may be almost entirely
freed from any foreign metals. In contact with iron zinc prevents the oxidation of that
metal. Zinc precipitates copper, silver, lead, cadmium, arsenic, antimony, and others
from their solutions.
Applications of Zinc. This metal is very largely used for covering roofs, making water-
spouts, tanks for holding water, and for various architectural purposes. It should be
borne in mind that for roofing purposes zinc is in so far dangerous as to greatly increase
the intensity of fire should buildings covered with zinc become ignited; one instance of
this danger was exhibited in March, 1866, when the huge wooden building then standing
in Lower Kennington-lane, and used as a floor-cloth factory, caught fire, the burning of
the sheets of zinc covering the roof producing a heat so intense as to ignite no less than
sixteen adjacent houses, although these were from 20 to 30 yards from the burning shed.
Zinc is used in galvanic batteries, in various alloys, in chemical laboratories, and for
galvanising iron wires, as well as for the preparation of zinc-white, and for various
ornamental castings, which are made in iron moulds previously thoroughly heated to
prevent a too rapid cooling and contraction of the metal. The Prussians make use of zinc
for cartridges. The total annual production in Europe of this metal amounted (1870) to
2,154,000 cwts., of which England produces 150,000 cwts.; in the metropolis, Vieille
Montagne (Belgium) zinc is almost exclusively used.

PREPARATIONS OF ZINC.
Zinc-White. Under this name there has during the last fourteen years been brought
into the market anhydrous white oxide of zinc, applied instead of white-lead as a
pigment. Zinc-white is prepared for this purpose by oxidising metallic zinc in fire-
PREPARATIONS OF ZINC.
81
clay retorts, placed to the number of 8 to 18, in a reverberatory furnace. As soon
as these retorts are at a bright white-heat, cakes of zinc are placed in them, and the
vapours of the metal on leaving the retort are brought into contact with a current
of air heated to 300°; oxidation results, and the oxide, a very loose, snow-white,
flocculent material, is carried by the current of hot air into condensing chambers,
and gradually deposited. The oxide thus prepared is immediately fit for use; it is
of a pure white colour, and very light. Zinc-white is also prepared by exposing
metallic zinc to the action of superheated steam, hydrogen being at the same time
evolved, and used for illuminating purposes, as at Narbonne, St. Chinian, Céret,
and a few other places, where it is known as platinum-gas, because the flame is
used for imparting a white heat to small coils of platinum wire, thus producing a
very steady and highly pleasant light. As regards the use of zinc-white as a
pigment, it is rather more expensive than white-lead, yet according to some is
a better covering material in the surface proportion of 10 to 13, that is to say, 13
parts by weight of zinc-white cover as much space as 10 of white-lead; moreover,
zinc-white is not affected by sulphuretted hydrogen. Like white-leaf, this com-
pound may be mixed with other pigments. By mixing Rinmann's green with it a
green colour may be obtained; blue with ultramarine; lemon-yellow with cad-
mium orange-yellow (sulphuret of cadmium).
of Zinc.
White Vitriol, Sulphate Zinc-vitriol (SZnO4 +7H₂), sulphate of zinc or white vitriol, is
found as a native mineral, as a product of the oxidation of zinc-
blende; it is also prepared by dissolving zinc in dilute sulphuric acid, and by roasting
native zinc sulphuret. This vitriol occurs in white agglomerated crystals and in small
acicular shaped crystals, as purified sulphate of zinc; it is used as a dryer" in oil paints
and varnishes; as a mordant in dyeing, for disinfecting purposes, and sometimes as a
source of oxygen, since, on being submitted to a red heat, it gives off sulphurous acid and
oxygen, oxide of zinc remaining.
Chromate of Zinc. This preparation, obtained by precipitating a solution of sulphate of
zinc with bichromate of potassa, is a very fine yellow-coloured powder, used now and
then in pigment printing, because it is soluble in ammonia, and thrown down again as a
powder insoluble in water when that menstruum is volatilised. A basic chromate of zinc is
used as a pigment in the paint trade.
Chloride of Zinc. This compound of zinc, ZnCl₂, is obtained either by dissolving zinc in
hydrochloric acid, or more cheaply by causing the hydrochloric acid gas given off in
manufacturing soda to act upon native sulphuret of zinc. By this action sulphuretted
hydrogen is formed, which can be burned to produce sulphurous acid for the sulphuric
acid chambers. The solution of chloride of zinc thus obtained is evaporated to the con-
sistency of a syrup.
Anhydrous chloride of zinc is obtained by heating an intimate mixture of dried
sulphate of zinc and chloride of sodium; chloride of zinc is formed which sublimes, and
sulphate of soda which is left behind (ZnSO4+2NaCl=Na₂SO₁+ZnCl2). This anhydrous
chloride may be sometimes advantageously used instead of strong sulphuric acid, for
instance in rape and colza oil refining, and perhaps, although it would be more expensive
and less manageable, in the manufacture of garancine from madder. This chloride has of
late been applied instead of sulphuric acid in the manufacture of stearic acid, and in the
preparations of ether and parchment paper. Chloride of zinc in a strong and crude solu-
tion is largely and very successfully used for preserving timber; in paper-making for the
decomposition of bleaching powder for bleaching the half-stuff and rags, and also in
sizing the paper. The disinfectants sold as Sir William Burnett's Fluid and Drew's
Disinfectant are solutions of chloride of zinc. The salt used in soldering iron, zinc,
pewter, &c., is a compound of the chlorides of zinc and ammonium (2NH4Cl+ZnCl2); its
solution is obtained by dissolving 3 parts by weight of zinc in strong hydrochloric acid,
and adding, after the solution is complete, an equal weight of sal-ammoniac. Oxychloride
of zinc, obtained by mixing oxide of zinc with a concentrated solution of chloride of zinc,
or with solutions of chlorides of iron or manganese, has been recently proposed by
M. Sorel as a plastic mass suited for stopping hollow teeth.
7
82
CHEMICAL TECHNOLOGY.
CADMIUM.
(Cd112; Sp. gr. 8.6.)
This metal is rather rare, and as yet of very limited use; it is a constant com-
panion of zinc in varying quantities, but is only found in the Silesian zinc ores in
sufficiency to repay the trouble of extraction. It was discovered as a distinct metal
by Dr. Stromeyer, at Hanover, and Dr. Herman, at Schönebeck, in 1817. As
regards its properties, cadmium stands between zinc and tin; the colour and
metallic lustre of cadmium are similar to those of tin; it is ductile and malleable, but
more readily acted upon by atmospheric oxygen and moisture than tin. The specific
gravity of cadmium is 8.6; it melts when quite pure in an atmosphere of dry hydro-
gen at 320°, and boils and volatilises (air and oxygen being absent) at 860° to 746′2°.
The cadmium sold by manufacturing and operative chemists and opticians is in small
round bars, weighing from 60 to 90 grms. Silesian calamine ore contains about 5
per cent. cadmium; the same ore found near Wieslock 2 per cent.; the zinc-blende
found at the Upper Harz contains from 0.35 to 0'79 per cent. cadmium; zinc-blende
from Przibram, Hungary, 178 per cent.; and the zinc ore of Eaton, in North
America, about 3*2 per cent. cadmium. Such ores give off, while being heated in
the zinc furnace, a brownish-coloured smoke, consisting of carbonate of zinc and
metallic cadmium; this smoke, condensed separately, is used as cadmium ore, and
reduced by means of charcoal, the materials being placed in iron retorts and the
metal distilled over, next refined, and cast in the small bars mentioned above.
The annual production of cadmium in Belgium from Spanish zinc ores amounts to
about 5 cwts.; while Silesia produces some 2 cwts. annually.
Mixed with lead, tin, and bismuth, cadmium forms the so-called Wood's alloy or fusible
metal, consisting of cadmium, 3 parts; tin, 4; bismuth 15; and lead 8 parts; this alloy
fuses at 70°, and is used for stopping teeth, and for soldering surgical instruments.
M. Hofer-Grosjean used as stereotype metal an alloy consisting of lead 50, tin 36, and cad-
mium, 22.5 parts. The only preparation of cadmium technically used to any extent is the
cadmium-yellow, jaune brilliant (CAS), sulphuret of cadmium, applied as a pigment in oil
painting, and in pyrotechny for producing blue-coloured flames. This preparation is best
obtained by precipitating a solution of sulphate of cadmium with sulphuret of sodium, and
then thoroughly washing, pressing, and drying the precipitate. Dr. Van Riemsdijk, of
the Utrecht Mint, while experimenting with cadmium and zinc, both pure and kept fused
in an atmosphere of pure dry hydrogen, found that these metals, though perfectly non
volatile at their point of fusion, and while kept fluid at that temperature, became percep-
tibly volatilised at a few degrees above this point.
Antimony.
ANTIMONY.
(Sb 122; Sp. gr.
=
6712.)
This metal, also named stibium, is chiefly found in combination with
sulphur as black antimonial ore, or glass of antimony, containing 71*5 per cent., of
metallic antimony, formula (Sb2S3), in veins interspersed among granite and
metamorphic rocks. Antimony also occurs as oxide (Sb2O3) in the minerals known
as Valentinite (rhombic) and Senarmontite (tesseral), this last variety being found
in large quantities in Constantine, Algeria, and in Borneo. The black sulphuret
of antimony is separated from the gangue which contains it by the application of
heat, as the sulphuret is very fusible.
The operation is carried on at Wolfsberg, near Harzgerode, Germany, by placing the
broken-up ore and gangue in crucibles, (Fig. 42), perforated at the bottom, and placed
on a smaller crucible, c, surrounded with hot sand or ash. The walls are of
ANTIMONY.
83
brickwork, so constructed with openings for causing a draught as to convey most
heat to the upper crucible. Wood is used as fuel. In other localities, especially
in Hungary, the apparatus exhibited in section and plan in Figs. 43 and 44 is used. As
will be seen the principle is the same,
but both the crucibles containing the
FIG. 42.
ore, and the receiving crucibles outside
the furnace, and connected by means
of tubes with the inside crucibles, are
more conveniently placed. The liqua-
tion of the rather fusible antimony
ore is most readily and conveniently
performed in the hearth of a peculiarly
constructed reverberatory furnace, ex-
hibited in Fig. 45; the main point of
the arrangement of the hearth being
that the molten black sulphuret, col-
lected at the lowest level, runs through
the spout, c, to the receiver, f, placed
outside the furnace. At first a mode-
rate heat suffices, but towards the latter
part of the operation a strong heat
is required to eliminate all the sul-
phuret. The opening at f is now
closed with a plug. Not until the gangue becomes semi-fused is the operation finished,
when the heavier sulphuret collected under the slag is run off by the opening of the plug

at f.
FIG. 43.
FIG. 44.


FIG 45.

Metallic antimony is obtained from the black sulphuret, either by roasting or by
smelting it with suitable fluxes. In the former instance the sulphuret is placed on
the hearth of a reverberatory furnace and continuously stirred, while a supply of air
has access to the molten mass; the calcination is continued until the bulk of the ore
is converted into antimoniate of antimony-oxide. This material, also known as
antimonial ash, is reduced to metal in crucibles, and for the reduction heat alone
84
CHEMICAL TECHNOLOGY.
would answer, as the calcined ore always contains undecomposed sulphuret of
antimony (3Sb408+4Sb2S3=20Sb+12SO2); but as some oxide of antimony would
be lost by volatilisation, the crude antimonial ash is mixed with crude argol or
with charcoal-powder and carbonate of soda. A strong red heat is sufficient for the
reduction, and it is customary to allow the metal to cool slowly under the super-
natant slag, in order to obtain the peculiar crystalline appearance desired in
metallic antimony in the trade.
By another mode of operation the sulphur is first removed from the black sulphuret by
means of iron, but which, if used by itself, presents a difficulty arising from the almost
equal specific gravities of the metallic antimony and sulphuret of iron, rendering the sepa-
ration of these substances too imperfect to admit of the use of iron alone; consequently,
either carbonate or sulphate of soda or potassa is added, which tends also to increase the
fluidity of the slag. 100 parts of black sulphuret of antimony, 42 parts of malleable
iron, 10 parts of dry sulphate of soda, and 33 parts of charcoal powder are the pro-
portions. In order to eliminate the arsenic from the metallic antimony thus obtained, 16
parts are taken, and there are added 2 parts of protosulphuret of iron, I of sulphuret of
antimony, and 2 of dry soda; this mixture is kept fused for fully one hour's time,
the resulting metal is next fused with 1 parts of soda, and a third time with I part
of soda, until the supernatant slag attains a bright yellow colour.
I
Properties of Antimony. The metallic antimony of commerce is never quite free fror:
arsenic, iron, copper, and sulphur; the influence of these impurities on the physical
properties of antimony is not well ascertained, as those of chemically pure antimony,
are not well known.
Antimony may be purified by fusing it with oxide of antimony; the sulphur
and iron are oxidized and some of the oxide of antimony reduced to metal. For
pharmaceutical purposes antimony is purified by the addition to the molten metal of
pure saltpetre, but this process is attended with a loss of antimony. Antimony pos-
sesses a nearly silver-white but slightly yellowish colour, strong metallic lustre, and
a foliated crystalline structure; it crystallises like arsenic and bismuth in rhomboidic
crystals. The specific gravity of antimony is 6712; it melts at 430°, the pure
metal fuses at 450°, and, according to Dr. Duflos, does not expand on cooling.
Antimony is volatilised, air and oxygen being excluded, only at a bright white heat.
It is a very brittle metal, neither ductile nor malleable, but harder than copper.
Antimony forms alloys readily, imparting to them some of its own brittleness and
hardness; it is, therefore, added to tin, lead, and pewter, in small quantities,
to render these soft metals hard. As antimony is not readily acted upon by air, it
has been suggested to electrotype copper with a thin layer of this metal. The
powder sold as ironblack, and used to give to papier maché and plaster of Paris
figures the appearance of polished steel, is finely divided antimony, obtained by preci-
pitating that metal from its solution in an acid by means of metallic zinc; this
powder is also used to impart a lustre to cast zinc ornaments. The chief use made
of antimony is as an alloy for printing type, which usually consists of 4 parts of
lead and 1 of antimony with a small quantity of copper. Antimony also enters into
the hard so-called anti-friction alloys used for the bearings of machinery.
I
ANTIMONIAL PREPARATIONS IN TECHNICAL USE.
Oxide of Antimony. This substance (Sb2O3), obtained by calcining sulphuret of antimony,
or by the precipitation of a solution of chloride of antimony with a solution of carbonate
of soda, finally washing and drying the precipitate, has of late been used as a substitute
for white-lead, but does not cover so well and is more expensive, though it is not affected
by sulphuretted hydrogen. As this oxide takes up oxygen in the presence of alkalies, and
is converted into antimonic acid (Sb,O,), it has been lately proposed for use in the prepa-
ARSENIC.
85
ration of aniline red and for the conversion of nitrobenzol into aniline; also for the
preparation of iodide of calcium by keeping antimonic oxide suspended in milk of lime,
and adding iodine as long as the latter is taken up.
Black Sulphuret of This compound (Sb,S,), obtained by liquation, occurs in commerce in
Antimony. the conical shape it has assumed while cooling; its colour is like that
of graphite, but it has a stronger metallic lustre, is of a deeper black colour, fibrous,
crystalline structure, and very brittle; it usually contains iron, lead, copper, and arsenic,
and is employed for separating gold from silver, in veterinary surgery, pyrotechny, and in
the preparation of the percussion pellets used in the cartridges of the now celebrated
Prussian needle-gun.
Neapolitan Yeilow. This pigment, used as an oil paint and in glass and porcelain staining,
is of an orange-yellow colour, and very permanent. It is antimoniate of oxide of lead,
and is prepared as follows:-1 part of antimonio-tartrate of potassa (tartar emetic),
2 parts of nitrate of lead, and 4 parts of common salt, are fused at a moderate red heat,
and kept at that temperature for 2 hours. The molten mass is put after cooling into
water and becomes disintegrated, the salt dissolved and the pigment precipitated. When
required for staining glass or porcelain it is mixed with a lead-glass, and has recently
been prepared by roasting a mixture of antimonious acid and litharge.
Antimony Cinnabar. Oxysulphuret of antimony (Sb¿SO), is a compound in colour similar
to vermillion, and is obtained by causing dithionite of sodium or calcium to act upon proto-
chloride of antimony in water, and boiling this mixture, a precipitate being readily
deposited; it is a soft, velvety powder, unaltered by the action of air and light, and suited
for either oil- or water-colour. This substance may be prepared on a large scale by the
following process:-(1.) Black sulphuret of antimony is calcined in a current of air and
steam, antimonic oxide being formed as well as sulphurous acid, which may be employed
for the preparation of calcium-dithionite from soda waste; the antimonic oxide is
next dissolved in crude hydrochloric acid. (2.) Large wooden tubs which admit of being
internally heated by steam, are for ths of their capacity filled with the solution of
calcium dithionite, and the solution of protochloride of antimony is gradually added, the
liquid being stirred and heated to about 60°; the reaction soon ensues, and the precipitate
having subsided, is thoroughly washed and dried at a temperature not exceeding 50°.
There are prepared on a large scale, by operative pharmaceutical and manufacturing
chemists, numerous varieties of antimonial preparations, among which are several
sulphurets and one oxysulphuret, different from the preparation here mentioned.
ARSENIC.
(As=75; Sp. gr.
5'6.)
Arsenic. Arsenic occurs in the mineral kingdom either native or in combination
with sulphur. Although a few minerals are found containing arsenic in a state
of oxidation, the quantity is so small that their technical utilization for the obtaining
of arsenical compounds is altogether out of the question. Metallic arsenic is a
solid, cystalline, steel-grey coloured substance. It is prepared either by the subli-
mation of the native metal, or by the ignition of arsenical iron pyrites (FeS2+FeAs₂)
and of arsenical pyrites (Fе4As6), or by the reduction of arsenious acid
(As2O3+3C=3CO+As2). Metallic arsenic is met with in the trade in an impure
state, often containing no less than 10 per cent. of sulphuret of arsenic, in the form of
greyish-black coloured crusts and lumps, known as fly poison. Pure metallic arsenic
is rarely employed; a small quantity is used in the manufacture of shot, and in pyro-
techny for white Bengal fire, which gives a very brilliant light, but should only be
ignited in the open air. Lastly, arsenic burnt in oxygen gas is used as signal lights
in the Trignometrical Survey Service.
Arsenious Acid.
The substance known as white arsenic is really arsenious acid, As2O3,
and obtained as a by-product of a great many metallurgical operations, for instance,
the roasting of cobalt ores for smalt, of tin and silver ores; the volatilised acid is
condensed by conducting it through channels into wooden chambers. In some
localities, as in Silesia, where fuel and labour are cheap, arsenical pyrites is
purposely calcined, and the crude arsenious acid obtained is refined by another
86
CHEMICAL TECHNOLOGY.
sublimation process. For this purpose the cast-iron vessels, a, Fig. 46, are used, upon
which are placed iron rings or collars, b, c, d, and a hood e, communicating by means
of tubes with a series of chambers, of which the first only is shown in i. The
flanges of the cast-iron collars and all other joints having been thoroughly luted, the
fire is lighted and the heat so increased as to
cause the semi-fusion of the arsenious acid,
which after cooling exhibits a peculiarly
porcelain-like appearance, at first being as
transparent as glass and very similar to fused
anhydrous phosphoric acid.
i
a
ManAZA
FIG. 46.

α
MOJB2
This compound, like all arsenical prepara-
tions is very poisonous; but it is a remarkable
fact, proved by direct experiment, that pure
metallic arsenic introduced into the stomach
of rabbits and other small animals in a finely
divided state, by the aid of pure water freed
from air, does not act on them as a poison,
being found in their fæces unaltered. The
commercial article is sometimes more or less
mixed with oxide of antimony and sulphuret
of arsenic. Arsenious acid is used in dyeing
and calico-printing, in glass-making, for the
purpose of clearing the molten glass, for the
preparation of other arsenical compounds and
pigments, and further in arsenical soap for
the preservation of stuffed animals. The air
in museums is sometimes poisoned by ar-
seniuretted hydrogen being evolved if the
arsenical compound has not been properly
prepared ; and in places where there are large
collections of stuffed animals there should always be a good ventilation and a dry
atmosphere. Arsenious acid is also employed in the manufacture of aniline.
Arsenic Acid. This acid (H3AsO4) has become an article of large consumption.
it is obtained by boiling 400 kilos. of arsenious acid in 300 kilos. of nitric or nitro-
hydrochloric acid, and evaporating the solution to dryness. Recently it has
been prepared more cheaply by passing chlorine gas into water wherein arsenious
acid is suspended, and evaporating this solution. Arsenic acid is sometimes
employed in calico-printing instead of tartaric-acid, and is very largely used in the
preparation of rosaniline or fuchsine, some manufacturers of these dyes annually
consuming 2000 cwts.
The acid arseniate of soda, so-called dungsalt, now used instead of cows'-dung in
certain calico-printing operations, and consisting of 25 parts of soda and 75 of
arsenious acid, is prepared by heating for a length of time, either 36 parts of
arsenious acid, and 30 parts of nitrate of soda, or a mixture of arsenite of soda and
nitrate of soda. This salt is obtained as a by-product of the preparation of aniline
from nitrobenzol.
Sulphurets of Arsenic.
There are two sulphurets of arsenic employed industrially, viz.,
realgar and orpiment.
QUICKSILVER, OR MERCURY.
87
Reaigar. Red arsenic or realgar (As,S,) is found native in a crystalline state and among
other ores.
It is artificially prepared by fusing together sulphur and excess of either
metallic arsenic or arsenious acid, or on a large scale by distilling arsenical pyrites and
ores containing sulphur. Realgar is a ruby-red coloured substance, exhibiting a conchoidal
fracture. Its use in pyrotechny is based upon its property of yielding, when mixed with
saltpetre and ignited, a brilliant white light. This mixture is known as Bengal white
light, and is best prepared with 24 parts of nitrate of potassa, 7 parts of sulphur, and 2
parts of realgar.
Orpiment. Auri pigmentum, yellow sulphuret of arsenic (As,S3), is likewise found native,
but is generally artificially prepared by fusing together either sulphur and arsenious acid
or realgar and arsenious acid. This sulphuret is of a bright orange-colour, somewhat
transparent; it contains, if prepared by the dry method, free arsenious acid, and may
therefore be considered as arsenoxysulphuret. It is also prepared by precipitating a
hydrochloric acid solution of arsenious acid by means of sulphuretted hydrogen, or by
decomposing a solution of the double sulphuret of arsenic and sulphuret of sodium with
Rusma. dilute sulphuric acid. Orpiment is used in dyeing to reduce indigo, and to
prepare what is termed rusma, a paste applied in dressing skins in order to remove the
hair, and which consists of 9 parts of lime and I of orpiment mixed with water. This
paste is also employed in the toilet to remove superfluous hair; but instead of this very
poisonous compound, either the spent lime from the purifiers of gasworks, or the sulphuret
of lime solution obtained by passing a current of sulphuretted hydrogen through milk of
lime, may be advantageously used.
Occurrence and
Mode of Obtaining
QUICKSILVER, OR MERCURY.
(Hg=200; Sp. gr. 13'5.)
This metal is not met with so generally dispersed as silver and gold.
Mercury It occurs in the following forms:-1. Sparingly in the metallic state
interspersed in globules through the gangue, and in small quantities in mercury
mines, sometimes containing silver. 2. As a sulphuret, known as cinnabar, HgS, con-
taining 86*29 of metallic mercury and 13.71 of sulphur. This ore is met with among
primitive as well as metamorphic and sedimentary rocks, and is often accompanied
by sulphuret of iron, while the gangue or matrix is generally quartz, calcareous
spar, or spathic iron ore. The richest mercury mines are those of Almaden and
Almadenejas in Spain, which were worked at a remote period of antiquity, and next
are those of Idria, Carynthia. Cinnabar is found also in the Rhenish Palatinate,
at Olpe in Westphalia, Horzowitz in Bohemia, in various parts of Hungary, at
Vall'alta in Venetia, in the Oural, in China and Japan, in Borneo, Mexico, at
Huancavelica, in Peru, and in considerable quantities in California, where mercury
is largely produced.
Among the less important mercury ores is found the so-called liver-coloured ore, a clay
mixed with cinnabar, bitumen, paraffine, and coal-slate. This ore is only met with in
Carynthia. There is also the fawn-coloured mercury ore, containing 2 to 15 per cent. of
mercury, with sulphur, copper, and other impurities. The annual production of mercury
throughout the globe amounted in 1870, to 84,500 cwts., of which California yields 56,000
against 22,000 from Spain.
Mercury is extracted from its chief ore, cinnabar, by :
1. Calcination in shaft furnaces, the mercurial vapours being condensed in chambers con-
structed either of brickwork or boiler-plate, or in earthenware vessels (Aludels) joined
together by flanges similar to earthenware drain-pipes.
2. By decomposing cinnabar in closed vessels, the ore being mixed with either lime or
forge scales. This method is usual in Bohemia and the Bavarian Palatinate.
Method of Extracting
Mercury pursued
in Idria.
The contrivances in use in Idria for the extraction of mercury
from its ores are illustrated in Figures 47, 48, and 49. A is a cal-
ciantion furnace, which is flanked on cach side by a series of condensation chambers,
C CD, communicating with the furnace. The ore is placed in lumps on the perforated
arches, n n', of the furnace, and the space v completely filled. On the arch, p p', the
88
CHEMICAL TECHNOLOGY.
smaller lumps of ore are placed, and on r r, the dust, pulverulent ore, and residues
of former operations. This having been done, the fuel, commonly dry beechwood, is
ignited on the furnace-bars. The heat is gradually raised to and kept at a dark red
heat for 10 to 12 hours. The draught created carries into the furnace sufficient air
FIG. 47.

C
FIG. 48.

FIG. 49.
O CEO DEL D
L

to convert the sulphur of the volatilised ore into sulphurous acid and set the
mercury free (HgS+20=SO2+ Hg). The products of the combustion are carried
into the chambers, c. The bottom of each chamber is made of strongly pressed clay,
shaped so as to form two planes inclined towards each other, and connected with
gutters leading to a reservoir cut out of a solid block of porphyry in which the
mercury is collected. A jet of water is made to play constantly in the last conden-
sation-chamber, in order to keep it and the adjoining smoke-chambers, D D, quite
cool, the last traces of mercury being condensed in D D.
Very recently experiments have been made at Idria to distil he mercury continuously
from its ore by the use of a reverberatory furnace, whereby both time and fuel are saved.
QUICKSILVER, OR MERCURY.
89
Spanish Method of
The arrangement for condensing the mercurial vapours in use at
Extracting Mercury. Almaden is exhibited in Fig. 50. It consists of a string of pearl-
shaped vessels open at both ends. These vessels, locally known by the Arabian term,
Aludels, are made of earthenware, and so constructed that the narrow end of one fits
into the wider end of the other, care being taken to lute the joints with clay. The
mode of arranging these rows or strings of aludels is delineated in Fig. 52, which
represents the plan of the furnace shown in Fig. 51. This furnace consists of a
FIG. 50.
ď
FIG. 51..

b
FIG. 52.

I
cylindrical shaft oven, which by means of a perforated arch is divided into two
parts. The fire is lighted in the lower part of the shaft, while on the perforated
arch is first placed a layer of sandstone containing cinnabar, in quantities too small
to admit of being otherwise advantageously treated. The rich ore is then placed on
this layer of stone, and the openings in the arch of the furnace covered with tiles
and tightly luted. The mercurial vapours are first conducted into the space c c,
and thence through the twelve rows of aludels, each row having a length of from
20 to 22 metres, and containing 44 aludels. The aludels are placed on a somewhat
inclined plane as shown in the woodcut. At f the condensed mercury is run off by
90
CHEMICAL TECHNOLOGY.
the gutter, g, into the stone cisterns, hh; the vapours not condensed being carried
on to the chamber, B, where they are completely liquefied. The smoke escapes
through a chimney at b. As the mercury thus obtained is mixed with scot it has
to be purified and cleansed; this is effected by causing the metal to flow down an
inclined plane, to which the soot adheres. The sooty mass and the impurities
collected in the room B, are submitted to distillation for the purpose of extracting
the last traces of mercury. The quantity of ore operated upon at each calcination
amounts to 250 to 300 cwts. Spanish mercury is met with in the trade packed in
wrought-iron canisters or in sheepskin bags. The apparatus above described for
separating mercury from its ores was invented by the Moors, who for several centu-
ries were the only civilised inhabitants of the greater portion of southern Spain.
Method of mercury distillation pursued at Horzowitz in Bohemia.
The sulphuret of mercury is mixed with from to of its weight of
forge-scale, and the mixture placed on the iron plates, bb, Fig. 53. These plates are fixed to an
FIG. 53.
Method of Decomposing
the Ore by the aid of
other Substances.


TURBARTA GLANZO
B
! นเนย 1
iron rod, and covered by the iron cupola, e e, which rests in a tank filled with water. The
cupola is removable from the furnace by means of the frame g. The metal is collected
in the water at d. Each cupola covers about cwt. of ore and cwt. of forge-scale, and
there are generally six cupolas in one furnace. The operation lasts for 30 to 36 hours.
In the Rhenish Palatinate mercury has been extracted from its ores since 1410. It is
there usual to mix the mercury ore with other metallic ores, that mainly worked being
cinnabar interspersed in sandstone. The decomposition of the ore, which is a rather
poor material, can be made to pay only by skilful management. The ore is mixed with
Îime and placed in iron retorts, very similar to those used in gas-works, and heat having
been applied the cinnabar is decomposed, the result being the formation of metallic
mercury, which volatilises and is condensed in suitably-constructed receivers, while there
remains in the retorts a mixture of sulphuret of calcium and hyposulphite of lime. The
operation lasts ten hours, after which the contents of the receivers are poured into
PREPARATIONS OF MERCURY.
91
earthenware tanks filled with water; the mercury sinks to the bottom and the water is
allowed to run off, carrying with it a blackish powder, consisting of finely-divided mercury
mixed with a volatilised black sulphide, which is again submitted with lime to another
distillation.
Properties of Mercury. Mercury is the only metal remaining fluid at ordinary temperatures.
It freezes at-32·5°, and is in that state a malleable and ductile metal. At 360" it boils,
and at a slightly higher temperature distils over, but is volatilised to some extent at all
temperatures above its freezing-point, as may be proved by suspending a piece of gold-leaf
in the neck of a bottle containing a small quantity of mercury. Mercury readily combines
at ordinary temperatures with various metals, forming what are termed amalgams. The
amalgams most readily formed are those of lead, bismuth, zinc, tin, silver, gold; next is
that with copper, while with iron, nickel, cobalt, and platinum, mercury will only amalga-
mate with difficulty. The application of mercury in metallurgy in the extraction of gold
and silver from their ores is based upon the property mercury possesses of readily combining
with these metals. Amalgams of various kinds are industrially employed, as, for instance,
with tin for covering mirrors and looking-glasses, with gold for the so-called process of
fire-gilding. An amalgam of 4 parts mercury with 2 parts zinc and 1 part tin is used for
the cushions of electrical machines.
Applications of Mercury. By far the most extensive application of mercury is in the con-
struction of various physical instruments, for filling the mercurial gauges of steam-boilers,
and on the Continent these gauges are attached to all boilers, locomotive engine-boilers
alone excepted. Mercury is employed in the preparation of a variety of compounds,
among which is the fulminate of mercury; and, further, for various purposes in chemical
and physical laboratories. More recently, an amalgam of mercury and sodium has been
very successfully used by Mr. Crookes in the metallurgical extraction of silver and gold;
and a solidified amalgam of the same metals is recommended to facilitate the transport of
mercury, the amalgam admitting of being very readily decomposed by treating with dilute
sulphuric acid.
PREPARATIONS OF MERCURY.
Mercurial Compounds. The more important mercurial compounds which are manufac-
tured on the large scale are the following:
Mercuric Chloride. The substance commonly known as corrosive-sublimate is the per-
chloride of mercury, HgCl, equivalent=135, consisting, in 100 parts, of 73.8 parts of
mercury and 26.2 parts of chlorine. It is prepared either by sublimation from a
mixture of sulphate of peroxide (red oxide) of mercury and common salt, or by dis-
solving the same oxide in hydrochloric acid, and also by boiling a solution of
chloride of magnesium with the peroxide (MgCl2+HgO=HC1+MGO). When
sublimed, this salt forms a white crystalline mass, which fuses at 260º, boils at 290º,
is soluble in 13.5 parts of water at 20°, and in 1.85 parts of the same liquid at 100º.
It is more readily dissolved by alcohol, 1 part of the salt requiring only 2'3 parts of
cold and 118 parts of boiling alcohol. Mercuric-chloride has been industrially
employed as a preservative for timber by Mr. Kyan, and is used in the manufacture of
aniline-red, in dyeing, and calico-printing, in etching on steel-plates, and for the
preparation of other mercurial salts. Lately, the use of the double salt, HgCl2,2KC1,
obtained by boiling chloride of potassium with peroxide of mercury, has been sug-
gested as a preservative for timber. It should be borne in mind that this prepara-
tion of mercury is extremely poisonous, and easily absorbed by the skin of the hands.
Cinnabar. Under this name is designated the mercuric-sulphide, HgS, which occurs
native in crystalline or compact red-coloured masses, and was known in Pliny's
time by the term minium.* The cinnabar, or vermillion of commerce, used as a
pigment, is always artificially prepared either by the dry or wet way. By the former
process 540 parts of mercury and 75 of sulphur are very intimately mixed. The
* Red-lead, afterwards called minium, was, as far as it appears, unknown to the ancients,
being first prepared by the Arabs and Saracens.
92
CHEMICAL TECHNOLOGY.
ensuing black-coloured powder is introduced into iron vessels, and exposed to a
moderate heat so as to cause the fusion of the mass, which, after cooling, is broken
up and then introduced into earthenware and loosely closed vessels, heated on a
sand-bath. The sublimed mass is of a cochineal-red colour, exhibits a fibrous
fracture, and yields when pulverised a scarlet powder, which is the more beautiful
the purer the materials used in its preparation and the greater the care taken to avoid
an excess of sulphur. Some chemists allege that a greatly improved vermillion is
obtained if I part of sulphuret of antimony is added to the mixture of sulphur and
mercury previously to the sublimation, and the sublimed and pulverised mass placed
in a dark room for several months and treated with either dilute nitric acid or caustic
potassa. According to Dr. J. von Liebig, vermillion is obtained in the wet process
by treating the white precipitate of the Pharmacopoeia, or hydrargyrum amidato
NHH bichloratum, according to the formula, HgCl, Hg NH2, which corresponds to the term
used, but in Dr. A. W. Hofmann's opinion, does not express the true composition of
the compound. He considers white precipitate to be a chloride of ammonium, in the
ammonium of which 2 equivalents of mercury have taken the place of 2 equivalents of
hydrogen; formula Nge Other chemists, again, hold different views as to the
constitution of this body, which has been used in medicine since, if not before, the
time of Paracelsus. Vermillion is generally obtained by precipitating a solution of
corrosive-sublimate in ammonia with a solution of sulphur in sulphide of ammonium;
or, according to Dr. von Martius, by agitating, in a suitable vessel, I part of
sulphur, 7 of mercury, and 2 to 3 of a concentrated solution of liver of sulphur.
According to M. Brunner's method, by which decidedly the finest vermillion is
obtained, 114 parts by weight of sulphur and 300 parts by weight of mercury are
mixed, with the addition of a small quantity of caustic potassa solution, and incorpo-
rated by being shaken by machinery. The resulting black compound is next treated
with a solution of 75 parts caustic potassa in 400 parts of water, and heated on a
water-bath to 45°. The mixture assumes a scarlet colour after a few hours, and as
soon as this is apparent the semi-liquid mass is poured into cold water, next collected
on filters, washed, and dried. The vermillion of commerce is often adulterated with
red-lead, peroxide of iron, chrome-lead, and more frequently with from 15 to 20 per
cent. of gypsum. These adulterations are, however, readily detected, as they are left
behind when the vermillion is sublimed. Red-lead, one of the most usual adultera-
tions of vermillion, can be readily detected either by treating a small quantity of the
suspected sample with nitric acid, when in consequence of the formation of
puce-coloured peroxide of lead, the mass assumes a brown colour, or by the addition
of hydrochloric acid, when chlorine is given off. Pure cinnabar is completely and
readily soluble in hydrosulphuret of sulphide of sodium (NaSH).
2'
Hg 2
},CN.
Fulminating Mercury. The compound known as fulminating mercury is a combination of
fulminic acid, an acid unknown in a free state, and of oxide of mercury; its formula may
be written C₂Hg,NO In 100 parts it consists of 77.06 of peroxide of mercury and
23.94 of fulminic acid. According to the late Dr. Gerhardt's view, this body is a nitro-
compound which may be regarded as cyan-methyl, the hydrogen of the methyl of which
has been replaced by hyponitric acid and mercury; the formula is then: C{ CN. This
substance was first discovered by Mr. Howard, and was known, until Dr. von Liebig gave
the clue to its nature, as Howard's detonating powder. It is prepared on a large scale in
the following manner. First, 2 lbs. of mercury are dissolved, by the aid of a gentle heat,
in 10 lbs. of nitric acid (sp. gr. 1°33), and 10 lbs. more of nitric acid are then added. The
resulting fluid is poured into six tubulated retorts, and to the contents of each retort is
NO
2
PREPARATIONS OF MERCURY.
93
added 10 litres of alcohol (sp. gr. 0.833). If the ingredients are mixed by measure instead
of weight, for every volume of mercury, there is taken 7 volumes of nitric acid, and
10 volumes of alcohol. After a few minutes a strong evolution of gas takes place, and at
the same time a white precipitate, the fulminate of mercury, is formed. The retorts are
fitted with tubulated receivers, from which glass tubes carry off the very poisonous gas
and fumes, either to a flue or directly to the outside of the shed in which the operation is
performed. The precipitate is collected on filters, and washed with cold water to
eliminate the free acid. The fulminate is next dried, filtered, and all being placed on
plates of copper or earthenware, heated by steam to less than 100°. 100 parts of mercury
yield in practice from 118 to 128 parts of fulminate, while, according to theory,
142 should be obtained. The dried fulminate is, with cautious manipulation, divided into
small portions, kept separately in a paper bag. The fulminate thus prepared is a crystal-
line white-coloured substance, which, by being heated to 186°, or by a smart blow, explodes
with a loud report. When placed on iron and struck with an iron instrument, the
detonation is much increased. This substance also explodes by contact with concentrated
sulphuric acid. When mixed with 30 per cent. of its weight of water, the crystalline
fulminate may be rubbed to powder with a wooden pestle on a marble slab. The manu-
facture of this substance on a large scale requires peculiar arrangements, into the particu-
lars of which we cannot here enter.
Percussion-Caps. The fulminate of mercury is chiefly used for filling percussion-caps.
For this purpose 100 parts of the fulminate are rubbed to powder with 30 parts of water,
50 to 625 parts of saltpetre, and 29 of sulphur. This mixture is dried sufficiently to
admit of being granulated, after which it is forced, by means of machinery, into the
copper caps, and simultaneously covered with either a layer of varnish or tin-foil, to
protect it from damp. Tin-foil being more expensive is not used for military gun-caps.
The best varnish for the purpose is a solution of mastic in oil of turpentine. The caps
are finally dried by a gentle heat, and packed in boxes. One kilogramme of mercury
converted into fulminate suffices for the filling of 40,000 gun-caps of the larger or military
size, and for 57,600 caps of the size used by sportsmen.
PLATINUM.
(Pt=197'4; sp. gr.210 to 23*0.)
Occurrence of Platinum. This metal is only found native, and then not very abundantly,
in platinum ore, more especially met with in the alluvial deposits of South America
and the Oural, in grains of a steel-grey colour and metallic lustre. More recently,
granules of metallic platinum have been found among the gold-washings in Califor-
nia, the Brazils, Haiti, Australia, and Borneo. A very short time ago this metal was
discovered in Europe, interspersed in rocks situated in the parish of Roeraas, in
Norway, and it is reported to have been found in the lead-mines near Ibbinbüren, in
Westphalia. Dr. Pettenkofer states that a proof of the far greater dispersion of
platinum than is generally supposed lies in the fact that all silver contains a
small quantity of platinum. The metal has also been found to accompany some of
copper and antimony ores of Timor and New Guinea. Platinum was discovered
in South America by the Spaniards, who, believing it to be an inferior silver, gave it
the diminutive platina of the Spanish name for silver, plata. It was brought from
Jamaica and made known in Europe by a Mr. Wood in 1740, and somewhat investi-
gated in 1767 by Dr. R. Watson, then Professor of Chemistry at Cambridge.
Dr. Scheffer, Director of the Mint at Stockholm, was the first who thoroughly inves-
tigated the various physical and chemical properties of this metal in 1752; but as his
researches were published in the Swedish language, they remained comparatively
unknown in this country.
the
Platinum Ores. The substance met with in commerce under the name of platinum ore,
or crude platinum, is a mixture of a variety of metals, among which the following
predominate:-Platinum, palladium, rhodium, iridium, osmium, ruthenium, iron,
copper, lead, and frequently granules of osm-iridium, gold, chrome-iron ore,
94
CHEMICAL TECHNOLOGY.
titanium-iron ore, spinel, zircon, and quartz. The reason why this ore is found in
alluvial soil is, that the rocks originally containing the ore having been disintegrated
by water, it is carried off by the streams and water-courses. Boussingault found,
when travelling in South America, a seam of somewhat weathered syenite containing
the platinum ore yet in situ; while, as regards the Oural, it has been proved by
Pallas that the ore was originally imbedded in serpentine-rock which has been
washed away by water, the water, however, leaving such minerals as chrome-iron
ore, zircon, titanium-iron ore, &c. In the Island of Borneo, platinum ore is mixed
with sesqui-sulphuret of ruthenium, a mineral which has been named by Dr. Wöhler
(1866) Laurite.
The composition of some platinum ores is exhibited in the following table :-Analysed
by Dr. Berzelius, a, ore from the Oural; Dr. Svanberg, b and c, from Columbia and
Choco;
Dr. Bleekrode, d, from Borneo; Dr. Weil, e, from California.
a.
ს.
C.
d.
e.
Platinum
Rhodium
86.50
84.39
86.16 71.87
57.75
1'15
3:46
2.16
2:45
Iridium
I'46
I'09
7.92
3.10
+
Palladium
I'IO
1'06
0'35
1.28
O'25
Osmium
1'03
0'97
0.48
0.81
Osm-iridium
I'14
I'91
8.43
27.65
Copper
0'45
0.74
0'40
0'43
O'20
Iron
8.32
5°31
8.03
Lime
Quartz
O'12
8.40
7.70
•
0.60
According to Dr. H. Deville, the average quantity of platinum contained in the fol-
lowing ores is:—
Columbia..
California.
Oregon
Australia
Siberia
Borneo
··
• •
·
..
•
..
..
76.80-86.20 per cent.
76·50—85·50
•
•
50'45
59.80-61.40
•
•
73'50-78.90
•
57.75-70*21
""
The annual production of metallic platinum amounts to from 35 to 50 cwts., of which
quantity the Oural yields 28 to 49 cwts., Columbia and the Brazils, 6 to 8 cwts.
Extracting Platinum
from its Ores.
Wollaston's Method of The method originally devised by the late Dr. Wollaston, and still
employed by the Parisian platinum-makers, Chapuis, Desmoutis,
and Quennessen, is as follows:-The ore is first treated with cold aqua regia to
dissolve any gold, and the liquid separated from the ore by filtration. The mineral
is again treated with aqua regia in a retort, and heat applied; the distillate contains
osmic acid, and the insoluble residue in the retort osm-iridium, ruthenium,
chrome-iron ore, and titanium-iron ore. The acid liquid contains palladium,
platinum, rhodium, and some iridium, in solution, and the acid having been neutral-
ised with carbonate of soda, the fluid is mixed with cyanide of mercury, whereby
palladium is separated as cyanide of palladium. That precipitate having been
removed by filtration, the liquid, diluted with water, is next concentrated by evapo-
ration, and then mixed with a concentrated solution of chloride of ammonium, the
mixture resulting in a precipitate (PtC14,2NH4Cl), of the double chloride of platinum
and ammonium, containing only a trace of iridium, which, as it imparts greater
hardness to platinum, is not injurious. The platinum sal-ammoniac, as the precipi-
tate is industrially named, is first dried and afterwards ignited, leaving spongy
platinum, which is forced by means of properly fitting pistons into steel tubes heated
to redness, the operation being repeated as often as is required to obtain the metal
in a compact coherent state. According to MM. Descotil and Hess, platinum ores
PREPARATIONS OF MERCURY.
95
should be first fused with from 2 to 4 times their weight of zinc, the cooled brittle
mass pulverised, and treated with dilute sulphuric acid to eliminate some of the
iron and zinc; the remaining substance is then treated with nitric acid, which
dissolves the rest of the iron, copper, and lead. The ore is afterwards treated with
aqua regia, which acts more readily on account of the fine state of division of the
mineral. M. Jeannetty (Paris) found that platinum becomes readily fusible by
the addition of metallic arsenic, which is afterwards volatilised.
and Debray.
Method of Deville The excellent method introduced by MM. Deville and Debray, in
1859, is based upon the fact that metallic lead, while fusing with platinum ore,
dissolves all the foreign metals, osm-iridium alone excepted. The platinum ore is
consequently placed on the hearth of a reverberatory furnace, and having been
mixed with its own weight of galena, a regulus is obtained, under which the osm-
iridium is left, while a lead slag floats on the top, the iron decomposing a portion of
the galena and producing metallic lead. The regulus is heated in a cupel furnace,
whereby all foreign metals are volatilised or absorbed as oxides, leaving the metallic
platinum, which is refined by being again melted in crucibles made of lime, which
absorbs and eliminates all impurities, such as silicium, iron, copper, &c. The fuel
used for this purpose is coal-gas, the combustion being kept up by means of oxygen.
The smelting of 1 kilo. of platinum requires 100 litres of oxygen gas and 300 litres
of coal-gas. The firm of Messrs. Johnson, Matthey, and Co., the most eminent and
extensive platinum smiths in the world, exhibited at the International Exhibition
of 1862 an ingot of pure platinum weighing no less than 2 cwts., valued at £4,000,
smelted by the method of MM. Deville and Debray. The molten platinum is after-
wards submitted to the action of a steam-hammer to render it dense, solid, and
fully malleable.
I
Properties of Platinum. This metal is nearly as white as silver, but with a steel-grey shade.
It exhibits considerable lustre; is very malleable and ductile, and so soft that it readily
admits of being cut with a pair of scissors. It may be drawn in wire thinner than a
spider's web, an operation conducted by coating an already thin platinum wire with
silver. The wire thus prepared is drawn out and the silver afterwards removed by nitric
acid, which dissolves that metal but leaves the platinum. The specific gravity of platinum
varies from 210 to 23.0. This metal admits of being welded at a white heat, and may be
melted by the oxyhydrogen flame, its melting-point, according to Dr. Deville, being
between 1460° to 1480°. Platinum occurs in commerce as spongy platinum, black platinum,
forged or hammered and cast platinum.
Black Platinum.
Black and spongy platinum possess the property of absorbing and con-
Spongy Platinum, densing large quantity of gases, more especially oxygen. If a jet of hydro-
gen is directed upon the spongy metal, black platinum being only an exceedingly finely
divided spongy platinum, the gas combines with the oxygen absorbed by the metal, forming
water; and this combination is attended with so great a development of heat that the
platinum becomes red-hot and causes the ignition of the hydrogen. It is upon this property
that the well-known Döbereiner lamp is based. Black platinum is prepared either by
boiling sulphate of platinum with carbonate of soda and sugar, when the black platinum is
precipitated as a very fine powder, or by melting platinum and zinc together, and treating
the alloy with dilute sulphuric acid. Black platinum is industrially employed in the
manufacture of vinegar directly from alcohol.
Hammered or Cast
Platinum and its
Platinum may be worked by hammering or by casting. The following
Applications. firms are platinum workers:-Heraeus, at Hanau; Frères Chapuis; Des-
moutis and Quennessen, Godart and Labordenave, at Paris; and Messrs. Johnson, Matthey,
and Co., London. The chief use of platinum is for various apparatus in chemical
laboratories. Although this metal withstands a very high temperature, and is proof
against a large number of chemicals which attack or destroy other materials, it requires
great care in its use, as it is readily acted upon by caustic alkalies, fusing nitrate of potassa,
free chlorine, alkaline sulphurets, phosphorus, molten metals, and readily reducible metallic
oxides. Crucibles, spoons, blowpipe points, the points of lightning conductors, tongs and
forceps, and boilers for concentrating sulphuric acid are made of this metal. A boiler
96
CHEMICAL TECHNOLOGY.
capable of concentrating daily 8 tons of sulphuric acid costs about £2500, while a smaller
but similar vessel for concentrating daily 5 tons of acid costs £1640, the value of the
metallic platinum for this size exceeding £1000. Platinum is also used for galvanic
apparatus, mustard. spoons, and now and then for ornamental work in watchcases, chains,
&c. More recently platinum has been used in porcelain-staining to produce a greyish hue.
In the year 1828, the Russian Government commenced coining platinum, 3, 6, and 12
rouble pieces; but by a ukase of 22nd June, 1845, this coinage was discontinued, and the
money made, 14,250 kilos. in weight, called in. In France platinum is used for making
medals, especially prize medals for exhibitions. The first platinum coin ever made was
struck at the Paris Mint in 1799, the dies having been engraved by M. Duvivier with
the effigy of the first Consul, afterwards Napoleon I. In the year 1788 there was presented
to Louis XVI. a watch, some of the works of which were made of platinum. Small
caps or cylinders woven in platinum wire, are used to emit light when rendered highly
incandescent by the flame of burning hydrogen, the arrangement being termed a platinum
gas lamp. According to M. Kraut, platinum frequently contains barium, or a combination
of that metal.
Platinum, Alloys. As before observed platinum readily alloys with other metals. Among these
alloys, that first made by Deville, consisting of 78.7 platinum and 213 iridium, especially
deserves notice, as it is not acted upon by nitro-muriatic acid, and is hard and malleable.
An alloy of platinum containing 10 to 15 per cent. of iridium withstands fire and reagents
far better than platinum alone and is harder; hence the vessels made with it are not so
liable to be bent out of shape as those of platinum. According to M. Chapuis, an alloy of
92 parts of platinum, with 5 parts of iridium, and 3 parts of rhodium, resists various
reagents better than platinum alone. The alloy of 3 parts of platinum with 13 parts of
copper is, according to M. Bolzani, equal in all respects to gold. Dr. Percy states that an
alloy of platinum and gold for crucibles and other small vessels applied in chemical opera-
tions, is best proof against alkalies. An alloy of equal parts by weight of steel and
platinum is the best white speculum-alloy known; its sp. gr. 9.862.
Elayl Platino-Chloride. This compound (PtCH,Cl) is obtained by repeatedly dissolving
chloride of platinum in alcohol, and evaporating the solution to dryness. A very dilute
solution when heated on a sheet of glass or a porcelain slate, yields a lustrous coating of
platinum
SILVER.
(Ag=108; Sp. gr. 10°5 to 10'7.)
Silver and its Occurrence. Silver is a tolerably abundant metal, and is found partly in the
native metallic state, almost always containing gold; partly in combination with
other metals, as arsenic, antimony, tellurium, mercury, or combined with sulphur
and other sulphurets. Silver rarely occurs as oxide or combined with acids. The
chief ores are :---The sulphuret, silver-glance (Ag₂S), containing from 84 to 86 per
cent. of silver; the dark-coloured ruby ore (3Ag₂S + Sb2S3), with 58 to 59 per cent.
of silver; the light-coloured ruby ore (3Ag₂S+ As₂S3), with 64 to 64.5 per cent. of
silver; miargyrite (Ag₂S+ Sb,S3); and the brittle antimonial silver ore (6Ag,Sb,S),
with about 67 to 68 per cent. of silver; polybasite [(Ag₂S, Cu,S),,Sb,S3], with 64 to
72.6 per cent. of silver; and the white ore [(FeS, ZnS, Cu₂S)4, Sb₂S3+(PbS,AgS)4,Sb₂S3],
with 30 to 32.69 per cent. of silver. Galena frequently contains silver, usually
between o'or and 0.03 per cent., and sometimes as much as o'5 to 10 per cent.
This lead ore is the chief source of the silver produced in the United Kingdom.
Some copper ores contain silver to an amount varying from o‘o20 to 1'101 per cent.
With regard to zinc ore the reader is referred to the statements under that head.
The metallurgical process employed in the extraction of silver may be
any of the following:
Extraction of Silver
from its Ores.
I. By the wet way.
1. By the aid of mercury.
a. European method of amalgamation.
b. American method of amalgamation.
2. By means of solution followed by precipitation.
a. Augustine's method.
b. Ziervogel's method.
c. Sundry methods.
SILVER.
97
II. By the dry way.
1. By concentrating lead ores rich in silver.
2. Separation of the silver from the lead.
a. Separation on the hearth.
b. Concentrating the silver in the lead by Pattinson's method.
c. Eliminating the silver from the lead by means of ziuc.
d. Refining the silver-glance.
Smeiting for Silver Directly.
1. It only rarely happens that silver ores are rich enough
to admit of the metal being obtained by a direct smelting process.
Amalgamation.
Extraction of Silver by 2. The method of obtaining silver by the aid of mercury, or the
amalgamation process, is chiefly applied to very poor ores, and to such metallur-
gical products as contain only 100 to 120 grms. of silver to the metrical cwt.
Process.
European Amalgamation This process-now obsolete—was conducted in four principal
operations—viz., 1. The roasting; 2. Amalgamation; 3. Separation of excess of
mercury from the amalgam by mechanical means; 4. Volatilisation of the mercury.
There was first added to the ores about 10 per cent. of common salt, and the mix-
ture roasted to volatilise the antimony, arsenic, and other volatile minerals, the
fumes being condensed in properly arranged rooms. By the reaction of the com-
mon salt upon the pyrites, converted by the roasting into sulphate of iron, there is
formed sulphate of soda, chloride of iron, and sulphurous acid, which escapes. The
chloride of iron exchanges its chlorine with the silver, the result being the forma-
tion of peroxide of iron. There are also formed sulphate of copper and persulphate
of iron, which, while oxidising any sulphuret of silver to sulphate, become reduced
to protosulphates. By the further action of the common salt, chloride of silver and
sulphate of soda are formed, and the other metals converted into chlorides. The
brown-coloured mass is next transferred to the amalgamation tuns; and after the
addition of water, mercury, and iron, these tuns are made to rotate on their longi-
tudinal axes for a period of 16 to 18 hours, the velocity being regulated to 20 to 22
revolutions per minute.
minute. The iron while combining with the chlorine, causes the
reduction of all the other metals to the metallic state, and as far as capable these
then form an amalgam with mercury.
In order to elucidate the amalgamation process we will, for example, take a silver ore to
consist of-
(Cu₂S,AgS,FeS) + (As₂S3,Sb₂,S3)
from which the silver is to be separated, according to the method just described.* After
the roasting with common salt (CINa), there being taken up in this instance 30 mols.
of oxygen, the following substances are formed:
[(CuCl¸‚AgCl‚FeCl₂) + 3Na₂SO₁]+[As¿O3 + Sb₂O3+6SO₂],
Non-volatile substances.
Volatilised substances.
The changes which are effected by the action of the iron, mercury, and water in the amal-
gamation tuns are exhibited by:-
[(Cu¸ClAgCl‚FeCl¸) + 3Na₂SO4+ 3Fe+nHg=3Na₂SO4+ (Cu,Ag,nHg) + 4FeCl2].
Amalgam.
At the end of the period destined for the rotation of the tuns, the amalgam is run
off. The excess of mercury is strained through a coarse canvas bag, and collected
in a stone trough or tank. The real amalgam, a thick pasty mass, remains in the
* No attention is paid in this case to the volatile chlorides of sulphur, arsenic, and
antimony which are simultaneously formed. The reader who desires more extensive
information on the subject here briefly outlined, is referred to Mr. Crookes's "Metallurgy,"
vol. i.
8
98
CHEMICAL TECHNOLOGY.
J
bag, which is next strongly pressed between planks to squeeze out any further
excess of non-argentised Mercury. The solid amalgam* is then transferred to the
iron plates, bb, (Fig. 54), arranged as shown in the woodcut, and as already described
under the article Mercury. By the action of the fire the mercury is separated from
the amalgam, and being volatilised, is collected under the water contained in d,
while the metallic silver and other metals mixed with it are left on the iron plates.t
FIG. 54.

T

At the present time, instead of the above contrivance, there is used an iron dis-
tilling apparatus, not unlike cylindrical iron gas retorts, one end being fitted with a
movable lid for the introduction of the amalgam, and the other end connected with
an iron tube which dips into a trough filled with water to condense the volatilised
mercury. Superheated steam is also advantageously used to separate the mercury
from the amalgam. The crude silver left after the separation of the mercury is
submitted to a first refining smelting, by being put into graphite crucibles, and the
surface covered with charcoal powder. But even after this smelting the silver
always contains a certain quantity of copper, from which it can only be separated
by refining in a cupel furnace.
Process.
American Amalgamation The American process is chiefly used in Mexico, Peru, Chili, and
California. The ores to which it is generally applied are the ruby-
silver ores and fahl ores. These are first pulverised in stamping mills, and are next
* According to Dr. Karsten, the composition of the solid amalgam is:-Silver, 110;
mercury, 84.2; copper, 3'5; lead, o'1; zinc, o‘2.
†The silver left on the plates at the Freiberg mines consists, according to Professor
Lampadius, of :-Silver, 750; mercury, o'7; copper, 21.2; lead, 15. The refined silver
of the same place contains, according to Professor Plattner :-Silver, 71.55; copper, 28.01.

SILVER.
99
ground with water under granite or porphyry millstones, to a thoroughly impalpable paste.
This material is placed in a yard paved with flags, which are laid with a slight inclination
sufficient to cause the rain-water to run off. After having been kept there for some days,
there is added from to 3 per cent. of what the miners locally designate as magistral,
that is to say, roasted iron and copper pyrites (FeCuS), which is thoroughly mixed with
the finely-divided ore. Mercury is then added in quantity equivalent to about six times
the amount of silver contained in the ore; this operation is termed incorporation. The
kneading of the mercury is continued on alternate days for two to five months, and after
that time the mass is washed with water in stone cisterns in order to separate the heavy
amalgam from the light gangue. The amalgam thus obtained is separated from any
excess of mercury by being pressed in canvas bags; the remainder of the mercury being
separated by distillation. The rationale of this amalgamation process is:-The roasted
copper-iron pyrites is essentially made up of mixed sulphates of copper and iron, which
when reacting upon the common salt, are converted into chlorides of the metals and sulphate
of soda. The chlorides acting upon the silver convert it into chloride, and this becoming
dissolved by the excess of salt, is converted by the mercury to the metallic state. Some of
the mercury is converted into calomel, and the excess dissolves the silver, becoming amal-
gamated with it. This American process requires a great length of time, and, moreover,
occasions an enormous loss of mercury, as for every mol. of silver reduced from the chloride
of that metal there is formed I mol. of calomel (Hg₂Cl₂). On the other hand, this method
admits of the extraction of silver from ores too poor to be treated in any other way,
while a great saving of fuel is obtained.
Silver Extraction.
Augustin's Method of This hydrometallurgical method, invented by M. Augustin, is
based upon the formation of a soluble double chloride of silver and sodium when
chloride of silver is treated with an excess of a warm solution of common salt, and
also upon the fact that copper is capable of precipitating all the silver from this
solution. The ore is first reduced to a finely-divided powder, which essentially con-
tains sulphurets of copper, silver, and iron. This powder is roasted, first without
the addition of common salt, with the result that sulphates of the metals are formed,
and excepting that of silver, again decomposed by a higher temperature. The mass
is next roasted with common salt, whereby the sulphate of silver is converted into
chloride. The mass is then treated with a concentrated hot solution of common
salt, which dissolves the chloride of silver, and from this solution the silver is pre-
cipitated by metallic copper, which becomes chloride of copper, and is, in its turn,
precipitated by metallic iron.
Ziervogel's Method. This method is to some extent similar to that just described, but
no roasting with common salt takes place. The roasted ore, chiefly containing as
essential ingredients sulphate of copper and sulphate of silver, is treated with boiling
water to dissolve these sulphates, and yield a solution from which metallic silver is
precipitated by means of copper, the sulphate of that metal being obtained as a
by-product. When the ores happen to contain arsenic and antimony, this method is
not applicable, as, by the roasting, arseniate and antimoniate of silver are formed,
which are insoluble in water. If lead is present, the ore becomes fluxed and the
roasting a far more difficult matter.
Methods of Extracting
Silver.
Sundry Hydrometallurgical Dr. Carl Ritter von Hauer suggests the treatment of the ores
as in the European amalgamation process, and the extraction of
the chloride of silver by means of a hyposulphite of soda solution, the metallic silver being
next precipitated by the aid of copper or tin. Dr. Patera suggests the substitution in
Augustin's method of a hyposulphite of soda solution for that of common salt, the former
being more manageable and applicable cold. Similar suggestions have been made by
Dr. Percy, who also advocates the applicability of hypochlorite of lime, and of chlorine gas
for converting the silver into chloride. MM. Rivero and Gmelin were the first to suggest
the use of ammonia for the purpose of extracting and dissolving the chloride of silver after
the ores had been roasted with common salt; the precipitation of the chloride from the
ammoniacal solution by means of sulphuric acid, and the smelting of the chloride with a
suitable flux to obtain metallic silver. We must not omit to mention the method of
extracting silver from copper regulus and mattes by means of hot dilute sulphuric
100
CHEMICAL TECHNOLOGY.
acid, whereby the copper is dissolved and a residue left containing the silver, which is
further extracted in the dry way by means of lead.
Extraction of Silver The method of extracting silver from its ores by means of lead is based
by the Dry Way. upon:-
1. The property of lead to decompose sulphuret of silver, with the formation of sulphuret
Ag₂ Pbn
PbS.
Ag,S
nPb
of lead and metallic silver; yield 3.
}
As lead hardly acts at all upon the other metallic sulphides, and least of all upon those of
copper and iron, the products of the smelting are lead combined with silver, and a regulus
consisting of the sulphurets of lead, copper, and iron. This method of extraction succeeds
best with ores containing as small a quantity of copper as possible.
2. Upon the decomposing reaction exerted by oxide of lead and sulphate of lead upon
the sulphuret of silver, in consequence of which there are formed metallic lead containing
silver and sulphurous acid :-
Ag₂S
2Pb0} yield (Pb.Ag.
SO₂
2
and
Ag₂S
PUSO yield
PbAg₂
2SO
4
3. Upon the reducing action of lead upon oxide of silver or upon sulphate of silver:-
and
2Pb
Ag₂0} yield
3Pb
(PbO
Ag,Pb
Åg280} yield
PbAg
2PbO
2SO₂
4. Upon the greater affinity of the silver for lead than for copper. If copper that
contains silver is melted with lead, the result is the formation of a readily fusible alloy of
lead and a difficultly fusible alloy of copper and lead, the former metal being separable by
liquation.
Lead-containing
Mode of preparing the Only genuine silver ores are submitted to the operation of
smelting with lead, but these ores usually contain variable pro-
portions of copper, lead, cobalt, sulphur, and other substances. The result of the
Silver.
F
FIG. 55.

D
B
smelting with lead is the production of a metal containing silver, to be separated by
any of the following operations:-
1. On the refining-furnace;
2. By Pattinson's process;
3. By means of zinc.
Refining Process. This operation is as frequently carried on at lead-ore smelting-works
as where only silver is smelted. The rationale of the operation is that lead is
readily separated from such metals as are at a high temperature either oxidisable
with very great difficulty or not at all; whereas lead oxidises readily, its oxide
SILVER.
ΙΟΙ
becoming fluid. But it is requisite that the oxide of lead should be removed or ab-
sorbed by a suitable medium, generally the porous substance composing the cupel or
bottom of the hearth of the refining furnace. The operation is carried on as long as
any oxide and metallic lead remain, so that only the silver is left. This operation is
the exact counterpart on the large scale of the well-known lead-silver assay carried
on in a muffle with bone-ash cupels. The refining furnace, see Fig. 55, is a circular
reverberatory blast-furnace. The hearth, A, is covered with a dome of stout sheet-
iron, lined inside with fire-clay, and removable by means of a crane, D.
That por-
tion of the hearth upon which the smelting is carried on is constructed of a porous
substance, generally lixiviated wood-ash or marl of good quality. The cavity, c, is
intended for collecting the silver; B is the space for the flame. In the circular wall
which surrounds the hearth there are:-(1). The door, not exhibited in the cut, which
represents a vertical section intended for the discharge of the molten litharge. At
the outset of the smelting this door is only partly closed with fire-clay to admit of
the litharge being run off. The furnace is charged with lead to a little above the
level of the lower sill of this door, and the fire-clay gradually removed as the level
of the fused litharge sinks. (2). The door, P, opposite to the fire-place, and intended
for the charging and construction of the hearth. (3). The openings, a a', admit-
ting the tuyeres of the blast.
The refining operation is carried on at a gradually increased temperature until only a very
thin layer of oxide of lead covers the surface of the silver. This is known by the peculiar
display of colours, technically known as the brightening, more aptly expressed in German by
a word which means lightening, for that is really the appearance. This being observed, the
fire is slackened, and the silver having been cooled with water, is removed from the
hearth. The litharge which runs off is, on cooling, a yellow or reddish-yellow crystalline
mass (see Lead, p. 63).
Pattinson's Method. The refining process just described is not suited, that is to say,
does not pay, when the lead contains only o 12 per cent. of silver. Now it so happens
that the various kinds of galena met with in England yield a lead which contains
only o'03 to 0.05 per cent. of silver. In 1833, Mr. H. L. Pattinson, of the Felling
Chemical Works, near Gateshead-on-Tyne, instituted a series of experiments relative
to a new method, applicable on the large scale, for separating lead from silver when
the latter is present in small quantities. His efforts were successful, and have
greatly benefited his own and other countries where his process is worked.
Pattinson's method essentially consists in a concentration process, based upon the pheno-
menon that when a certain quantity of lead that contains silver is melted in iron cauldrons,
and the fluid mass allowed to cool uniformly, there ensues a formation of small
octahedral crystals which do not contain any silver at all, or, at any rate, are a great
deal poorer in silver than the metal originally taken, while the portion of the metal
remaining fluid is found to contain an increased quantity of silver. It is clear, there-
fore, that if the crystals first obtained are again melted and cooled uniformly, another
concentration will be obtained, and that the operation can be repeated until a lead is
obtained rich enough in silver to admit of undergoing a refining process. Practically,
Mr. Pattinson's method admits of concentrating 2.5 per cent. of silver. In the execution
of this process, the and systems are employed. If the first, at every operation two-
thirds of the contents of the cauldron are removed with perforated ladles, while in the
other case, seven-eighths is the quantity of crystals ladled out, leaving respectively one-
third and one-eighth of the contents of the cauldron in the shape of fluid lead. The
system is better suited for the richer lead, the system for very poor lead. M. Boudchen
has recently modified Pattinson's process. Instead of ladling out the crystals, he
diffuses them in the lead, and stirs them about to prevent them enclosing any lead
likely to contain silver. The lead is withdrawn from the cauldron by means of a tap at the
bottom. In all cases, however, the quantity of lead operated on at one time is always
large, generally 200 cwts., to cause the cooling to proceed slowly. At the Freidrich Lead
Silver Works, near Tarnowitz, the enriched lead contains 1.28 per cent. of silver.
102
CHEMICAL TECHNOLOGY.
Reduction by Means
of Zinc.
This process, suggested by Mr. Parker, in 1850, has only recently
been practically carried out by M. Cordurié, at Toulouse. This method, as far as
we are now capable of judging, will probably supersede even Pattinson's excellent
method. The rationale of the process is based upon the facts:-1. That lead and
zinc do not alloy together. 2. That the affinity of silver for zinc is much greater
than for lead.
The following is the manner of execution:-20 cwts. of lead, which may contain (per
ton) only 0-25 kilo. of silver, is melted, and when properly liquefied there is added I cwt.
of molten zinc. The zinc having been thoroughly mixed with the lead, the molten mass
is left to stand until the zinc, which has risen to the surface, forms a cake that is easily
removed. The zinc is then separated from the silver by distillation. The residue of the
distillation is melted with lead, and the alloy thus obtained refined as above described.
The zinc obtained by the distillation is used for another operation. According to a more
recent improvement, the zinc is separated from the silver by oxidation by passing super-
heated steam over the red-hot zinc (Zn+ H₂0=ZnO+H₂). The lead, which of course
after this operation contains traces of zinc, is purified by being melted with either chloride
of lead, or a mixture of sulphate of lead and chloride of sodium, or with chloride of potas-
sium from Stassfurt, the result being the formation of chloride of zinc, which collects at
the surface or may be volatilised at a low red heat.
The Ultimate Refining In whatever manner silver may have been metallurgically obtained,
of Silver. the metal is a crude material, very far from being cent-per-cent
silver. The impurities, foreign metals, or, more correctly, base metals, often amount to
7 and even 8 per cent.; and in order to remove these, the silver is submitted to a process
of ignition in, or rather on the surface of, vessels made of an absorbent material. This
material is, for this ultimate refining, generally bone-ash, which is pressed into iron rings
of convenient size, care being taken to fuse some lead with the silver, if there is not already
sufficient. As regards this ultimate refining, there can be distinguished three different
methods. The first has just been described. The second is carried on in muffles, the
base metals burning off slowly. The third, and most advantageous method, is carried on
in a reverberatory furnace. 100 parts of crude silver yield 96-8 parts of refined silver at
99.9 per cent. pure fine metal, which is cast in large-sized bars. The value of the annual
production of fine silver amounts to £9,000,000. Of this, Mexico's share is the largest,
being half of the entire production. The bulk of this silver contains some gold and
platinum.
Chemically Pure Silver. When for certain purposes metallic silver is required chemically
pure, it may be obtained by dissolving any ordinary silver coin in nitric acid, and precipi-
tating the solution with an aqueous solution of common salt or hydrochloric acid. The
chloride of silver thus obtained should be reduced by ignition in a crucible with dry car-
bonate of potassa, to which a little resin may be added. But chloride of silver is now
commonly reduced by the wet way, by causing it to be acted upon by metallic zinc and a
dilute solution of either sulphuric or hydrochloric acid.
(2AgCl + Zn+ClH = ZnCl₂+Ag₂+CIH).
Properties of Silver. Silver obtained by smelting exhibits a pure white colour and a strong
metallic lustre, which is greatly increased by polishing. Its fracture is compact rather
than fibrous. It is softer than copper, but harder than pure gold; when chemically pure
its softness is greatest. It is not a sonorous metal, bearing a resemblance in this respect
to tin and lead. Gold only excepted, silver is the most ductile of the metals, a property
impaired by the presence of foreign metals other than copper and gold, by the latter of
which the ductility is slightly increased. Lead and antimony render silver brittle. When
silver contains an excess of carburet, produced by smelting the metal with an excess of
carbon, the metal is rendered less ductile; but a small quantity of the carburet, as much
as is found in coins of a high percentage of silver, is rather advantageous, increasing the
hardness of the metal, and causing it to wear well. Smelting in plumbago crucibles does
injure silver. Its specific gravity varies from 10.5 to 107. The absolute strength is far
less than that of copper. Its expansion by heat in o° to 100°C. is th. According to
M. Deville, the melting-point is 916°; but Dr. van Riemsdijk states that the results of a
series of experiments made at the Utrecht Mint in 1868, showed the melting-point to be
1040°, the metal being kept in a slow current of pure hydrogen. At a very high tempera-
ture, such as can be produced only by the oxyhydrogen flame or by electricity, silver is
volatilised. When alloyed to other metals, especially to copper, the volatility is increased,
and even at a lower temperature than the melting-point of copper, viz., 1330°, Dr. van
Riemsdijk found such silver to be perceptibly volatile. M. Stas, of the Brussels Mint, in
1869, distilled some 50 grms. of silver by means of the oxyhydrogen flame, in order to
SILVER.
103
obtain the metal perfectly pure. Molten silver absorbs oxygen, which is again expelled
from the metal on solidification, and gives rise to the phenomenon known by silver-assayers
as spirting, the escape of the gas causing the metal to be forced asunder in small drops.
However, when the molten silver contains even I per cent. of either lead or copper, it
solidifies without spirting. Silver is not acted upon by dilute acids, but is readily dissolved
in the cold by nitric acid. Silver is very sensitive to the action of sulphuretted hydrogen,
by which it is readily tarnished.
900
Alloys of Silver, Silver alloys readily with lead, zinc, bismuth, tin, copper, and gold ;
but the most important alloy, in an industrial point of view, is that with copper,
pure silver being too soft for general application. All silver, therefore, whether used
for plate, coin, or for ornamental purposes, invariably contains a certain amount
of copper. In most civilized countries there exist laws regulating the alloy of silver
to be used for coin or plate. Pure silver, or fine silver, is now generally indicated
by 1008. The alloy for the silver coins of Germany is indicated by ; meaning
that 1000 parts by weight of the coin contain 900 parts of pure silver, the remainder
being copper. Twenty-seven Union thalers weigh 1 half kilo., therefore a single
thaler weighs 18'518 grms., and contains 16.666 grms. of pure silver. By an inter-
national treaty with France, Italy, Belgium, Portugal, Switzerland, and Spain, 1 kilo.
of silver is to yield 200 franc pieces, i.e., 2223 franc pieces to 1 kilo. of fine silver.
The same alloy is employed for pieces of 2 and 5 francs, there being 200 of the
latter to the kilo. In the Netherlands, where, by-the-bye, gold coin is no longer
current, and silver is the standard, the alloy used is. The silver coins of the
United Kingdom are made of an alloy; 1 lb. Troy, or 373 228 grms., of this
alloy is coined into 66 shilling pieces. A pound Troy of fine silver would yield
71 shillings.
TOUG
Plate, &c.
Silver Alloy for In nearly all European countries the laws have fixed the composition
of the alloy of silver which, duly marked and stamped, shall be offered for sale as
plate by gold- and silver-smiths, who, in Holland, Belgium, France, and Sweden, are
not allowed to have in their workshops any electro-plated articles, or any alloys
other than those fixed by law. The composition of these alloys varies; expressed in
millièmes of fine metal, it is for Austria and Bavaria, 812; for Prussia and Saxony,
750; for England, 925. For France, Belgium, and the Netherlands, a double alloy
is fixed, the higher being 950, the lower 800. The alloy lately brought into use
under the name of tiers-argent, one-third silver, really consists of 27:56 per cent.
silver, 59 per cent. copper, 9'57 per cent. zinc, and 3'42 per cent. nickel, though in
the trade this alloy is alleged to consist of nickel and silver. Tiers-argent sells
at £3 128. per kilo. This alloy is harder than silver; its colour and polish are as
good. It is extremely well adapted for all kinds of plate.
Silver Assay. If it be desired to know the quantity of fine silver contained in an alloy of
silver-which for our present purpose we will assume to contain only silver and copper-
there are three different methods by which this proposition can be solved, viz.:-1. The
assay by the dry way, termed cupellation. 2. The assay by the wet way, or titration pro-
cess. 3. The hydrostatic assay.
Dry Assay. Usually this assay is conducted by first testing the alloy by comparing the
streak it makes upon touchstone-a piece of polished basalt or siliceous schist-with the
streak produced upon the same stone by test-needles; that is to say, small bars of silver
of known composition. It should, however, be borne in mind that the surface of silver
articles, as well as of coins, may have been blanched, as the term runs; that is to say, acted
upon by hot, dilute sulphuric acid, to dissolve a portion of the copper of the alloy, and
leave a film of alloy richer in silver. The alloy to be further assayed is next melted down
with a piece of pure soft lead, or lead containing a known quantity of silver, in a capsule,
technically called cupel, made of bone-ash. The cupel is previously well heated in a muffle,
and the lead is placed in it. As soon as the lead has become quite liquid, the sample of
104
CHEMICAL TECHNOLOGY.
silver to be assayed is added; the copper and lead are oxidised, and in that state absorbed
by the porous substances of the cupel. As soon as the surface of the silver button appears
quite bright, the operation is finished, and the cupel slowly cooled. The button of silver
is then weighed. It is usual to make two assays of the same sample; these assays should
agree in their results to within and to be of any value.
Wet Assay. This method of assaying silver was devised some sixty years ago by the late
Professor Gay-Lussac, at the request of the French Government, in consequence of the
great irregularity of the results obtained by the dry method. The wet assay, having been
very greatly improved in detail by Dr. G. J. Mulder, M. A. W. H. van Riemsdijk, Dr. Stas,
and M. J. Dumas, is now generally adopted, and will remain to all time a masterpiece
worthy of the ingenuity of its original inventor, who, by introducing this method, laid the
foundation of volumetric analysis, now so usefully and completely applied. Gay-Lussac's.
wet method of silver assay is more easily executed than the dry assay, while it is far more
correct, admitting an accuracy of judgment withinth per cent. The method is based
upon the property possessed by common salt of precipitating silver as chloride of silver
from its nitric acid solution. As 5'4274 grms. of pure common salt exactly convert i grm.
of pure silver, previously dissolved in nitric acid, into chloride of silver, it is evident
that, from these data, and with the application of suitably constructed apparatus for the
volumetric analysis, the fineness of any alloy of silver may be ascertained readily, rapidly,
and with great accuracy.
1000
Hydrostatical Assay. This method is of course by no means so correct as either of the
foregoing, and, moreover, is impaired by the fact that, although alloys of copper and
silver expand under pressure, they become denser, so that the hydrostatic weighing, that is
to say, the estimation of the specific gravity of the alloy, is only admitted as a test of its
relative value. With such alloys as have, like coins, to be rolled, pressed, or drawn,
the hydrostatical results rarely differ more than 104 from the results obtained by cupella-
tion. The empirical rule for the estimation of the value of silver assayed by this method
is the following:-The number 8.814 is subtracted from the specific gravity of the alloy,
two cyphers are added to the difference, and the figure thus formed, considered as a whole
number, is divided by 579; the quotient is the fineness of the silver alloy expressed in
grains. For instance, let the specific gravity of the alloy be 10'065, then the fineness
is 216 grains, or 750 since-
2000,
10.065-8.814=1'251
and
125,100
=216
579
Silvering. The coating of metals with a film of silver can be effected by :—1, plating;
2, the igneous process; 3, in the cold; 4, the wet way; 5, galvanically, or electro-plating.
Silver-Plating. In order to coat metallic copper with a layer of silver, the sheet copper is
first thoroughly cleansed, then treated with a moderately strong solution of nitrate of
silver, and next covered with a sheet of silver. After having been made red-hot, the two
metals are rolled out together. The silver then adheres so strongly to the copper as to admit
of the metals being beaten or stamped into various shapes. Copper-wire is readily silvered
by being covered with thin strips of silver, and passed through rollers. But this method
of plating is almost entirely superseded by electro-plating.
Silvering.
Igneous, or Fire- This method of silvering is effected by the aid either of a silver-amalgam,
or by applying to the well-cleansed surface of the metal intended to be
silvered a mixture of 1 part of spongy precipitated metallic silver, 4 parts sal-ammoniac,
4 parts common salt, and part corrosive sublimate. The metal to be silvered is rubbed
with this mixture, and then heated in a muffle. Buttons intended to be silvered are covered
with a paste consisting of 48 parts of common salt, 48 parts sulphate of zinc, I part of
mercuric chloride, and 2 parts of chloride of silver.
Silvering in the Cold. The metallic surface intended to be silvered, having been well cleaned,
is rubbed by means of a smooth cork, with a mixture of equal parts of chloride of silver,
common salt, & of chalk, and 2 of carbonate of potash, made with water into a creamy
paste. Professor Hein recommends that I part of nitrate of silver and 3 of cyanide of
potassium should be rubbed together in a mortar, with the addition of sufficient water to
form a thick paste. The paste is rubbed on the metal to be silvered with a piece of flannel.
MM. Roseleur and Lavaux recommended a mixture of 100 parts of sulphite of soda and
15 parts of any salt of silver. For silvering the dial-plates of watches, &c., M. Thiede
recommends a mixture of spongy silver with equal parts of common salt and cream of
tartar. In order to silver iron it is first covered with a layer of copper.
GOLD.
105
Silvering by the
This is effected by immersing the metal intended to be silvered in a
Wet Way boiling aqueous solution of equal parts of cream of tartar and common
salt, with part of chloride of silver. The description of the methods of electro-plating
will be given at the end of the chapter on Metals.
Oxidised Silver. The small ornaments met with under the name of oxidised silver are pre-
pared with either sulphur or chlorine; in the former case a bluish-black colour is imparted,
in the latter a brown. The sulphur is applied simply by dipping the object into a solution
of sulphuret of potassium, while for the chlorine colour a mixture of sulphate of copper
and sal-ammoniac is used.
Nitrate of Silver. This salt (AgNO3) is now prepared on the large scale by dissolving silver
containing copper in nitric acid, evaporating the solution to dryness, and igniting the
residue until all the nitrate of copper is decomposed. The residue is next exhausted with
pure water, the solution filtered and left to crystallise. For medical purposes the crystals
are fused, and while liquid poured into moulds to form small round sticks. The most
extensive use of nitrate of silver obtains in photography, a re-crystallised neutral and pure
salt being preferred. Under the name of Sel Clément, there is now in use in photography
a mixture of fused nitrates of silver, sodium, and magnesium, recommended as preferable
to nitrate of silver alone. It is stated that the consumption of this salt for photographic
purposes amounted, in 1870, to 1400 cwts. for Germany, France, England, and the United
States; the money value of this quantity being estimated at £630,000.
Marking Ink. A large quantity of nitrate of silver is also used for the purpose of making
indelible ink for marking linen. This ink often consists of two different fluids, one a solu-
tion of pyrogallic acid in a mixture of water and alcohol, being intended to moisten the
linen previous to writing; the other, or writing fluid, consisting of a solution of ammo-
niacal nitrate of silver thickened with gum. More recently aniline black has been applied
in the marking of linen.
Occurrence and Mode of
Extracting Gold.
(Au
GOLD.
197; Sp. gr. 19.5 to 19‘6.)
Gold is found only in the native metallic state, sometimes in
veins interspersed in rocks, and accompanied by quartz, iron pyrites, and iron ore.
More frequently gold is found finely divided in sand, mixed with larger or smaller
nuggets, and imbedded in quartz, with various other minerals, such as mica, syenite,
chlorite slate, chrome-iron ore, and spinel. Native gold commonly contains some
silver and other metals, among which are palladium and platinum. According to
recent analyses, the composition of samples of gold obtained from several countries
is:-
I.
Hungary. S. America. Siberia. California.
Gold
Silver
64.77
35°23
Iron and other metals
II.
Australia.
88.04
11'96
86*50
89.60
99'2
95'7
13'20
10'06
0'43
3'9
0'30
0'34
0.28
0'2
Gold is found native with tellurium and telluride of silver, and among antimony,
zinc, arsenic, and other ores. It is also found in galena and various kinds of clay;
indeed, gold is, next to iron, the most widely dispersed metal. The chief gold-
yielding countries are:-Africa, Hungary, the Oural, Australia, and America, espe-
cially Mexico, Peru, the Brazils, California, Columbia, and Victoria.
The total value of the gold produced in the year 1869 is computed at £60,000,000,
one-fourth of this representing the value of the production of California. The
value of the joint production of the Australian Colonies is a little above another
one-fourth.
Mode of Extracting Gold.
The mode of extracting gold is determined by the circum-
stances of its occurrence. By far the largest portion of the gold in circulation is
obtained by the washing process; that is to say, the elimination by means of water
of the lighter minerals, the finely-divided gold being left behind. This process may
be carried on in remote districts in a very primitive manner, by simply putting the
sand into wooden bowls, and washing it gradually away with water. The gold
106
CHEMICAL TECHNOLOGY.
so obtained is not pure, but contains titanic iron and other minerals. Wherever
gold washing is a regularly established business, as in some parts of the Oural,
properly constructed contrivances are applied.
Extraction by means of
Mercury.
The application of mercury to the extraction of gold is based
upon the fact that mercury amalgamates with gold readily and very effectively. The
operation is carried on with the gold-containing sand in peculiarly constructed
mills. Mr. Crookes has shown that the addition of sodium to the mercury
facilitates the extraction of the gold. The excess of mercury having been removed
from the amalgam by pressure in leathern or stout linen bags, the remainder
in amalgamation with the gold is volatilised by ignition in suitably constructed
furnaces.
Smelting for Gold. By a far more perfect process than washing, gold is extracted from
the gold sand by smelting with a suitable flux in a blast furnace. The object in
view is to produce a rough or crude iron from which the gold is separated by means
of sulphuric acid. This process yields from 25 to 30 times more gold than merely
washing the sand.
Treating with Alkali.
Mr. Hardings proposed to obtain the gold by treating the quartz
or sand with caustic alkalies under a high pressure of steam, thereby forming a
soluble silicate and leaving the gold.
other Metallic Ores.
Extraction of Gold from If gold happens to be interspersed through copper or lead ores,
they are roasted and then washed. When the quantity of gold is sufficient such
ores are treated with mercury, while sometimes they are treated for coarse metal;
and this, containing all the gold, is smelted with litharge, which absorbs the gold,
and is next separated from it on a refining hearth.
Extraction of Gold from
Poor Minerals.
Some minerals and metallurgical refuse containing only a very
small quantity of gold have been treated at Reichenstein, in Silesia, by means of
chlorine water, or an acidulated solution of bleaching powder. The gold is con-
verted into chloride of gold (AuCl¸), and is precipitated from the solution by sul-
phate of iron or sulphuretted hydrogen. This method has been severely tested by
MM. Plattner, Th. Richter, Georgi, and Dr. Duflos, and has been found to answer
exceedingly well, even with very poor ores. This plan is of course generally
applicable to gold sand and gold quartz. According to M. Allain, pyritical ores,
having been roasted and treated with sulphuric acid to eliminate the iron, zinc,
and copper, can be then treated with chlorine water so as to extract the gold present,
to an amount only of 1 part of gold in 10,000 of mineral.
Refining Gold. In order to separate any foreign metals from the gold obtained by
the above process, the following methods have been employed, but only the last (5.)
is now in general use. For that reason the other methods will only be briefly
described:
I Refining by means of sulphuret of antimony (Sb₂S3).
2. By means of sulphur and litharge.
3. By cementation.
4. By quartation.
5. By means of sulphuric acid.
By means of Sulphuret This process is effected by first smelting the alloy, which ought to
of Antimony. contain at least 60 per cent. of gold, in a graphite crucible. Pulverised
black sulphuret of antimony is added in the proportion of 2 parts to 1 of alloy, and the
molten mass is then poured into an iron mould, which is rubbed with oil. The mass on
cooling will be found to consist of two separate layers-the upper, technically termed
GOLD.
107
plagma, consisting of the sulphurets of silver, copper, and antimony; the lower, an alloy
of antimony and gold, which is separated in a muffle or a wind furnace. The remaining
gold is fused with borax, saltpetre, and some powdered glass.
By the aid of Sulphur. This process does not aim at the entire separation of the gold from
the other metals, but rather at its concentration in a smaller quantity of silver than was
originally present in the alloy, so as to render it suited for quartation. The alloy,
previously granulated, is mixed with part of powdered sulphur, put into a red-hot
graphite crucible, and covered with charcoal powder. The crucible is kept at a low red
heat for 2 hours, and then raised to the point of fusion. If the alloy contained gold in
any considerable quantity, a layer of silver separates, which will be rich in gold, but if the
original alloy was rather poor in gold, litharge is added to the molten mass, the oxygen of
the litharge causing the combustion of the sulphur of a portion of the sulphuret of
silver, the metallic silver combining with nearly all the gold." The reduced lead is taken
up by the sulphurets of the other metals present.
Cementation Process. The alloy containing gold having been either granulated or rolled
into thin sheets suitably cut up, is placed in a crucible, in this instance technically termed
a cementation box, and mixed with 4 parts of pulverised bricks, and 1 part each of
common salt and dried copperas. The crucible is then gradually raised to a cherry-red
heat. Chlorine is evolved in this operation by the action of the sulphate of iron upon the
common salt; there is consequently formed chloride of silver, which is absorbed by the
pulverised bricks, while the gold is left unattacked. After cooling, the mass is boiled in
water in order to obtain the gold. Here must be mentioned Mr. F. B. Miller's process of
passing chlorine into molten gold in order to eliminate the base metals which render
it brittle, while the silver, converted into chloride, floats to the surface.
Quartation. This process has obtained its name from an opinion that, to ensure success,
there should be three times more silver in the alloy than gold, i.e., the gold should amount
to a quarter of the entire alloy. But Dr. M. von Pettenkofer has proved that if the
amount of silver be double that of the gold, the separation of the two metals will
be complete, provided sufficiently strong nitric acid be employed, and the boiling con-
tinued for a length of time. Practically this method is as follows:-There is added
to the gold a sufficient quantity of silver, and the two metals are smelted together. The
alloy is next granulated, placed in a platinum vessel, and boiled with nitric acid of 1.320
sp. gr., care being taken that the acid is free from any chlorine. The silver being dis-
solved, the gold is left behind, and further refined by fusion with borax and saltpetre in a
crucible.
of Sulphuric Acid.
Refining Gold by the Aid This method of refining, which has been briefly alluded to
under Copper, is preferable to any of the foregoing on account of its perfection,
cheapness, and simplicity. By this method almost any alloy containing gold in
addition to copper and silver can be treated, but the quantity of gold should not
exceed 20 per cent., nor that of the copper 10 per cent., while the best proportions,
according to Dr. Pettenkofer's researches are, that in 16 parts of the alloy, the gold
should not exceed 4 or be much less than 3 parts, and the rest copper and silver.
Usually the alloy intended for this mode of operation is first granulated, or if it
happens to be in the shape of silver coins-Mexican dollars, for instance—they are
cut to pieces. Formerly, platinum vessels were employed in the boiling of the
alloy with thoroughly concentrated sulphuric acid (sp. gr. 1·848), but cast-iron
vessels, or sometimes hard porcelain vessels, are now employed, the proportion
being 2 molecules of acid to 1 molecule of the alloy. The heating is continued
some twelve hours, until the copper and silver are completely dissolved. The sul-
phurous acid evolved is employed in the manufacture of sulphuric acid, or is
absorbed by a soda or lime solution to form sulphite or bisulphite of soda or bisul-
phite of lime. The solution of mixed sulphates of silver and copper is poured into
leaden pans, and becoming solidified on cooling, the pasty mass is dug out with
iron spades, and put into leaden tanks filled with boiling water, in 88 parts of
which I part of sulphate of silver is soluble. The silver is precipitated from this
solution by strips of copper, and the solution of sulphate of copper obtained, having
been deprived of its excess of free acid by the addition of oxide of copper, is further
108
CHEMICAL TECHNOLOGY.
treated for blue vitriol. The gold which has remained as a dark, insoluble, spongy
mass, is first boiled with a solution of carbonate of soda, next with nitric acid, to
free it from any adhering oxide of iron, sulphuret of copper, sulphate of lead, and
other impurities; and after having been dried, is melted with the addition of salt-
petre. By this process it has become possible to extract the 1-10th to 1-12th per
cent. of gold contained in old silver coins; therefore this method of refining has come
largely into use, as within the last thirty years nearly all European States have
recoined the silver money in circulation. Still Dr. von Pettenkofer has observed,
that nearly all the gold obtained by this process contains silver and platinum,
in the proportion of 97'0 gold, 2.8 silver, and 0'2 platinum. These metals are
eliminated by fusion with saltpetre and bi-sulphate of soda.
3
At Paris, Frankfort, London, and Amsterdam, this method of refining is carried on to a
large extent by private firms. According to the Paris custom, the refiners return to their
clients all the silver and gold, retaining only the copper, and being paid at the rate of
from 5 to 5 francs per kilo. of refined metal; but if the alloy contains less than 1-10th
of gold, the refiners retain 1-2000th of that metal, paying a premium of franc per
kilo. of refined metal to their client. If the client desires all the gold and silver to be
returned to him, the refiner charges 2 francs and 10 to 68 centimes per kilo., according to
the market price of silver, and retains all the copper. Usually, however, a charge of
5 francs per kilo. is paid to the refiner. The value of the silver annually refined for gold,
at and near Paris, amounts to about £5,500,000.
Chemically Pure Gold. In order to obtain perfectly pure gold, that of commerce is dissolved
in nitro-hydrochloric acid, the solution evaporated to dryness, the residue, chloride of gold,
dissolved in water, and that solution precipitated by a solution of sulphate of iron :-
Chloride of gold, 2(AuCl3)
Sulphate of iron, 6FeSO4
yield
Gold, 2Au.
Persulphate of iron, 2Fe₂3SO4.
Chloride of iron, Fe,C16.
According to Mr. Jackson, gold may be readily obtained in a yellow spongy mass, by
adding carbonate of potassa and an excess of oxalic acid, to a concentrated solution
of chloride of gold, and rapidly heating this solution to the boiling-point :-
Chloride of gold, 2(AuCl3)
Oxalic acid, 3C₂H₂04
yield
Gold, 2Au.
Hydrochloric acid, 6CIH.
Carbonic acid, 6CO,.
According to Mr. Reynolds, peroxide of hydrogen precipitates gold from its acid solution
in beautifully lustrous metallic spangles:
Chloride of gold, 2(AuCl₂)
Peroxide of hydrogen, 3H₂O₂
Gold, 2Au.
yield
Hydrochloric acid, 6C1H.
Oxygen, 60.
Sometimes gold is precipitated by chloride of antimony or chloride of arsenic. The
metallic gold obtained or precipitated by any of the above processes is next fused with
borax in a graphite crucible.
Properties of Gold. The peculiar colour of gold is too well known to require description.
The richness of that colour is very much impaired by even small quantities of other
metals. Many of the Australian sovereigns, for instance, are of a pale greenish
yellow, due to the presence of a small quantity of silver. A small quantity of copper
gives a red colour to the gold. Gold assumes a very high polish; is, when un-
alloyed, but slightly harder than lead, and yet is the most malleable and ductile of
all metals. Its absolute strength is equal to that of silver. The specific gravity of
gold varies from 19°25 to 19°55, and even 19'6, according to the mode of mechanical
treatment. Its co-efficient of expansion by heat=682 per 100º C., and its melting-
point, according to Dr. Deville, is 1037°. Dr. Van Riemsdijk, however, fixes the
melting-point at 1240º, the metal being molten in quantities of several kilos. in an
atmosphere of pure dry hydrogen. Molten gold exhibits a sea-green colour. The
great value of gold is in a considerable measure due to its not being acted upon by
air, water, ordinary acids, and alkalies; but, on the other hand, even very small
GOLD.
109
quantities of lead, antimony, and bismuth impair its malleability to such an extent
as to render it unfit for use either as coin or for ornamental purposes. The fol-
lowing metals have the same effect, but to a less extent: arsenic, zinc, nickel, tin,
platinum, copper, and silver; the two latter being the only metals suitable to alloy
with gold to make it sufficiently hard to resist wear and tear. Gold, of all the
metals, is most readily affected by mercury, even to such an extent that the mer-
cury present in the imperceptible perspiration of such individuals as have been
treated medicinally with calomel for some length of time, is sufficient to act very
perceptibly upon their jewellery, while gold coins kept for some days in their
pockets become blanched. Gold-leaf imparts to transmitted light a blue-green hue.
Alloys of Gold. Pure gold is used only for certain chemical processes, and beaten
into leaf for gilding; the Staffordshire potteries consuming for this purpose alone
£60,000 worth annually. All other gold, be it used for jewellery or for coinage, is
always alloyed with copper or silver to produce the degree of hardness requisite for
hammering, stamping, &c. Generally such alloys are considered as consisting of so
many carats to the unit, the pound or half-pound being divided into 24 carats, each
of which contains 12 grains. What is termed 18 carat gold is a unit of 24 carats of
alloy, containing 18 carats gold and 6 of silver or copper. If the latter, the alloy is
termed red; while if silver is used, it is termed white; and if both metals are alloyed
with the gold, the caratation is termed mixed. In most countries there are legally
fixed certain standards for gold jewellery. In this country, 16, 18, and 22 carat gold
is stamped, or, as it is termed, Hall marked; in France, 18, 20, and 22 carat; in
Germany, 8, 14, and 18 carat, and also under the term of Joujou gold, a 6 carat gold,
used for jewellery, to be electro-gilt. Among the coined gold of European States
the term carat is almost everywhere replaced by the expression of so many parts fine
per mille.
Exceptionally fine gold coins are the Austrian ducats, 23 carats 9 grains,
98611 of gold; the Dutch, or more correctly Holland, ducats, or 23 carats 6 to
6'9 grains gold. Neither of these coins are at present a legal tender in Austria
or Holland, but they are continually made at the Utrecht Mint, having been for many
years the circulating medium in the North Baltic and White Sea ports, as well as in
the Black Sea, Levant, and Egypt. Originally they were coins of the Holy Roman
Empire (Germany). The English sovereigns and half-sovereigns are coined from
or 22 carat gold; or in thousands — 96; the Prussian Friedrich d'Or 902
Wilhelm d'Or 21} carat; the 20-franc pieces of France, Belgium, Switzerland,
and Italy 21 carat 7 grain, or 0. According to the Vienna Treaty of 1857, the
current gold coins of Germany are made in 1000 parts of 900 of gold and 100 of
copper, the relative value of silver to gold being taken as 1 : 15'3, or 1: 15.5.
11
1000
900
T000
1000
1000;
Colour of Gold. As all gold alloys, commercially or industrially used, exhibit colours
different from that of pure gold, it is customary to produce superficially on such
alloys the deep yellow of fine metal by boiling in a solution of common salt, salt-
petre, and hydrochloric acid; the effect is the evolution of some chlorine, which
dissolving a small quantity of the gold, again deposits it as a film of very pure gold.
Electro-gilding is, however, frequently substituted for this colouring process.
Jewellers and goldsmiths generally use touch-needles made from
varying gold alloys. The resistance of the streak made upon the touchstone to the
action of the dilute nitro-muriatic acid is the test of the fineness of the gold; but
it is clear that this method is only approximative, and it cannot be relied on, as
jewellery is often superficially coated with a film of pure gold. The most reliable
Testing the Fineness
of Gold.
110
CHEMICAL TECHNOLOGY.
test is afforded by cupellation, for which purpose the gold alloy to be tested is,
according to its colour, fused with twice or three times, or an equal weight of silver,
and about ten times its weight of lead. This compound alloy is submitted to cupel-
lation in a muffle. The button which remains on the cupel is first flattened on an
anvil, next annealed, and rolled into a thin strip, and then boiled with strong nitric
acid to dissolve the silver, the remaining gold being washed with boiling water,
dried, re-ignited in the muffle, and finally, when cold, weighed.
18
Applications of Gold. It is not necessary to speak of the well-known uses of gold, the
most extensive being its application to coinage, and next that to gilding and
jewellery. Gold in sheets ¦ inch thick has been used to cover the large dome of
Isaac's Church, at St. Petersburg, while three, at least, of the countless crosses on
the domes of the Moscow churches are made of solid gold; a portion of one of the
domes of a church in the Kremlin is likewise plated with gold.
Gilding. This is done either with gold-leaf, or by means of the cold process, the
wet process, fire-gilding, or electro-gilding.
Gilding with Gold-leaf. Gold-leaf, applied in gilding on wood and stone, is prepared
in the following manner:-Fine gold is molten and cast into ingots, which are
hammered and rolled into thin sheets about an inch in width, technically termed
ribbon. The ribbon is cut into small pieces an inch in length, which are placed
between pieces of parchment, and beaten out to a moderate thinness. Goldbeaters'
skin- the exterior membrane of the intestina crassa of oxen-is then substituted for
the parchment, and the hammering continued until the metal is of extreme tenuity,
The refuse gold of this operation is used for the preparation of bronze-gold for
painters. The articles to be gilded with gold-leaf are first painted over with a
suitable varnish or size, and the gold-leaves pressed on gently with a piece of soft
cotton-wool. Iron and steel, as, for instance, swords, gun-barrels, &c., are first
bitten, as it is termed, with nitric acid, next heated to about 300°, and then covered
with gold-leaf.
Gilding by the Cold
Process.
For this purpose fine gold is dissolved in aqua regia; clean linen rags are
soaked in this solution, and then burnt to tinder, consisting of carbon and
very finely divided gold. This tinder is rubbed on the article to be gilded with a cork
moistened in brine; the metallic surface to be gilded should be well polished.
Gilding by the This process is carried out by placing the article to be gilded in either a
Wet Way. dilute solution of chloride of gold in ether, which rapidly evaporates, or in
a boiling dilute aqueous solution of the same salt, and adding to it carbonate of soda or
potassa solution. Iron or steel should be first superficially coated with a film of copper
by immersion in a dilute sulphate of copper solution; or these metals, after being bitten
with nitric acid, are painted over with a solution of chloride of gold in ether. A solution
of chloride of gold in solution of pyrophosphate of soda has lately been suggested as a
suitable bath.
Fire-gilding. Articles of bronze, brass, copper, silver, especially buttons and ornaments of
military uniforms, are gilt with an amalgam of gold and mercury, 2 parts of the former
and I of the latter being applied by means of a solution of nitrate of mercury. The
articles being next heated in a muffle, the volatile metal escapes, leaving an adhering film
of gold, which may either remain dull or be polished, the colour being preserved in the
former case by a momentary immersion in a fused mixture of nitre, alum, and common
salt, and immediately after in cold water. If it be desired to leave only some portions
of the gilding dull, the portions to be afterwards polished are covered with a mixture
of chalk, sugar, gum, and sufficient water to form a paste. The rationale of the action
of the fusing mixture is that chlorine gas is evolved, which, as the term runs, bites the
gold. If it is desired to impart a red-gold colour, a paste of wax, bolus, basic acetate
of copper, and alum is spread on the gilding, and the article held over a clear fire, the
result being the reduction of the copper, which combines with the gold. As the use
of the so-called quicksilver-water (nitrate of mercury) is very injurious to the opera
tives, M. Masselotte, of Paris, coats the articles with mercury, afterwards with gold,
MANGANESE AND ITS PREPARATIONS.
III
and again with mercury, by means of galvanism. Finally, the mercury is volatilised by
ignition in a muffle, so arranged that the vapours escape only in the flue. According to
M. H. Struve, so-called fire-gilt articles are not really covered with a simple film of gold,
but with an amalgam of gold and 13.3 to 16.9 per cent. of mercury. Electro-gilding will
be treated in a separate section.
Cassius's Purple. The preparation which bears this name was discovered by Dr. Cassius, at
Leyden, in the year 1683. It is prepared by adding to a solution of chloride of gold a
certain quantity of sesquichloride of tin. Dr. Bolley prescribes the following process:-
First, 107 parts of the double chloride of tin and ammonium are digested with pure
metallic tin until the metal is quite dissolved, 18 parts of water are then added, and the
liquid mixed with the gold solution previously diluted with 36 parts of water. The result
is the throwing down of a purple or black-coloured precipitate, about the chemical
constitution of which nothing is certainly known. Well-prepared Cassius's purple should
contain 39.68 per cent. of gold.
Salts of Gold. The double salts of chloride of gold and sodium (AuCl,,NaCl + 2HO), and
the corresponding potassium salt (2AuCl3,KCI+5HO), are employed in photography and
medicine.
Manganese.
MANGANESE AND ITS PREPARATIONS.
Of all the ores of manganese met with in various degrees of oxidation,
only the peroxide, mineralogically known as pyrolusite, polianite, and technically as
glass-makers' soap, is industrially of much importance. When perfectly pure this
mineral consists of 63.64 per cent. of manganese, and 36.36 per cent. of oxygen, its
formula being MnO2; but the ore, as met with in commerce, frequently contains
baryta, silica, water, and sometimes oxides of iron, nickel, cobalt, and lower oxides
of manganese, viz., Braunite, Mn2O3; Manganite, Mn2O,,H₂O; Hausmannite,
Mn,04; and various other minerals, as potassa compounds, lime, &c. In Ger-
many, the ore is purified by most ingeniously contrived machinery, which might be
very advantageously applied to a great many other metallic ores and phosphatic
minerals. Manganese is industrially employed in making oxygen, the preparation of
bromine and iodine, glass-making, colouring enamels, for producing mottled soaps, in
puddling iron, and in dyeing and calico-printing, for preparing permanganate of
potassa; but the largest consumers are the manufacturers of chlorine. The bulk of
the manganese of commerce is derived from Germany, which supplies about 700,000
cwts. to Europe annually. It is found also very largely and of excellent quality in
Spain, as well as in Italy, Greece, Turkey, Sweden, and British India.
of Manganese.
Testing the quality The value of manganese for technical purposes depends-1. On
the quantity of oxygen it is capable of yielding, or the quantity of chlorine it will
evolve, not taking into account the O of the MnO. 2. On the nature and quantity
of the substances soluble in acids, such as the carbonates of lime and baryta, prot-
oxide of iron, which, not yielding chlorine, saturate a certain quantity of hydro-
chloric acid. But even if these impurities are absent, it may happen that, of two
samples of manganese, one requires more acid than the other to evolve the same
bulk of chlorine gas, as, for instance, when one of the samples contains in addition
to peroxide of manganese (MnO2) also the sesquioxide (Mn2O3), especially if the
latter is present as hydrate. 3. On the quantity of water, which may amount even
to 15 per cent.
According to the experiments of Dr. Fresenius, the most suitable temperature for drying
a weighed sample of manganese, in order to estimate the water it contains, is 120°, no
water of hydratation being expelled at that heat; but for commercial analysis the drying of
a sample at 100° is quite sufficient, provided it be kept at that heat for some hours con-
secutively. Among the many methods proposed for testing manganese, that originally
invented by Drs. Thompson and Berthier, and improved upon by Drs. Will and Fresenius,
is based on the fact that a molecule of peroxide of manganese treated with sulphuric
acid is capable of converting, by the O given off, I molecule of oxalic acid into 2 molecules
of CO₂
II2
CHEMICAL TECHNOLOGY.
1 mol. Oxalic acid, C,H,O4
I mol. Peroxide of manganese, MnO,
I mol. Sulphuric acid, H₂SO4
2
give
FIG. 56.
2
I mol. of Sulphate of protoxide of man-
ganese, MnSo.
2 mols. of Carbonic acid, 2CO,.
2 mols. of Water, 2H₂O.
From the weight of CO, evolved is determined the quantity of peroxide of manganese con-
tained in the sample. The operation is performed in the apparatus shown in Fig. 56. The
flasks A and B are fitted with perfectly tight-fitting corks, perforated for admitting the glass-
tubes, as seen in the woodcut. In the flask A is placed the mixture of previously dried
manganese and oxalic acid, with enough water to fill about one-third of
the flask. The flask B is about half-filled with strong sulphuric acid;
the end of the tube c is plugged with a piece of wax and the apparatus
weighed. Next some air is sucked out of в, by means of the tube d,
so as to cause a small quantity of acid to run over into A; thereupon the
evolution of CO₂ sets in, and the escaping gas passing through the acid
in B is dried. The suction having been repeated, the wax plug at c, as
soon as the evolution of CO, ceases, is for a moment removed, and the
suction again repeated to remove all the CO, from the apparatus. The
plug of wax is now replaced and the apparatus again weighed; the
loss of weight gives by calculation the quantity of peroxide of man-
ganese contained in the sample, if one holds in view that 2 molecules
CO₂.(CO₂= 88) stand to I molecule MnO, as the quantity of carbonic
acid found to x. If 298 grms. of dried manganese are taken, and the
quantity of CO, divided by 3, the centigrammes of CO, lost express the
proportion per cent. of pure peroxide of manganese contained in the sample; to 1 part of
manganese 1 parts of neutral oxalate of potassa should be taken for the experiment. If
the sample of manganese happens to contain carbonates, it has, previously to being tested,
to be treated with very dilute nitric acid, and of course well washed with distilled water
and afterwards dried. For other methods of testing manganese, the reader is referred to
Mr. Crookes's work on "Select Methods in Chemical Analysis."

A
B
2
PERMANGANATE OF POTASsa.
Permanganate of Potassa. This salt (KMnO4), used for disinfecting, bleaching, and
other oxidising purposes, and constantly employed in chemical laboratories, owes its
efficiency to the fact that, in contact with dilute sulphuric acid, it yields protoxide of
manganese and oxygen (Mn20,=2MnO+50). The permanganate of potassa is for
technical purposes prepared in the following manner :-500 kilos. of caustic potassa
solution at 45° B. (= 1'44 sp. gr.) are added to 105 kilos. of chlorate of potassa and
the mixture evaporated to dryness, there being gradually added 180 kilos. of pow-
dered manganese, and the heating continued to the fusion of the mass, which is
stirred until cold. The powder thus obtained is heated in small iron crucibles to a
red heat, and when semi-fluid is cooled; the mass is next broken up and put into a
large cauldron filled with hot water, and left stauding for about an hour. The clear
liquid having been decanted from the sediment, hydrated peroxide of manganese, is
evaporated to crystallisation; 180 kilos. of manganese yield 98 to 100 kilos. of crys-
tallised permanganate. Approximately the process may be elucidated as follows:-
a. By the fusion of the potassium manganate and chloride of potassium
6MnO2+2KCIO3 + 12KOH= (3K₂MnO4)+ KCl + 6H₂O;
B. During the solution of the fused mass in water, the manganate of potassium is
converted into hydrate of potassa, hydrate of peroxide of manganese, and perman-
ganate of potassa :—3K₂MnO4+6H20=4KOH+2KMnO4+MnO2+4H₂O. Con-
sequently one-third of the manganic acid is lost by the formation of peroxide of
manganese. This also occurs when, according to M. Tessié du Motay's plan, the
conversion of manganate of potassa into permanganic acid is effected by sulphate of
magnesia :—3K2MnO4 + 2MgSO4 = 2KMnO4 + MnO2 + 2K2SO4 + 2MgO. Dr.
Staedeler therefore suggests that the manganate of potassa should be converted into
ALUMINIUM.
113
permanganate by chlorine, according to the formula:-K2MnO4+Cl=KCl+KMnO4•
For disinfecting purposes a mixed permanganate of potassa and soda, or even the
latter alone, is usual; the well-known Condy's fluid is a solution of this salt in
water containing per-sulphate, not proto-sulphate of iron. Permanganate of potassa
is used to some extent in dyeing, and for staining wood.
ALUMINIUM.
(Al=274; Sp. gr. 25).
Preparation of Alumi ium. Aluminium, discovered at Göttingen, in 1827, by Dr. Wöhler,
belongs in the shape of its oxide to the most widely dispersed as well as the most
commonly occurring materials on our globe. The properties of this metal were more
particularly studied in 1853 by Dr. Deville, who found that aluminium is far less
readily acted upon in the molten state by oxygen, in the cold by dilute acids and
by boiling water, than was at first thought to be the case, and this eminent author's
researches gave rise to the production of this metal for industrial purposes, two
manufactories existing in France, viz., at Salyndres and Amfreville, and one in
England, at Washington, county Durham.
Aluminium is obtained from the double chloride of aluminium and sodium by the aid
of the latter alkali-metal, which is prepared for this and other purposes by the ignition of
a mixture of 100 parts of calcined soda, 15 parts of chalk, and 45 parts of small coal.
Chloride of aluminium is best prepared from bauxite, native hydrate of alumina, which,
having been previously mixed with common salt and coal-tar, is next heated in an iron
retort with chlorine gas, the result being the formation of carbonic oxide and the double
chloride of aluminium and sodium, which volatilises, and is condensed in a reservoir lined
with glazed tiles. The salt so obtained contains iron, and consequently the aluminium
derived from it is alloyed with that metal. The double chloride of aluminium and sodium
is converted into metallic aluminium by being heated in a reverberatory furnace with
sodium; while the aluminium is set free, a slag is formed consisting of the double salt with
excess of chloride of sodium. Professor H. Rose, at Berlin, first used cryolite for his
experiments on aluminium, the mineral bearing that name being a compound of the double
fluorides of aluminium and sodium (Al,Fl,+6NaFl). This mineral being treated at a high
temperature with sodium yields aluminium and fluoride of sodium, and the latter treated
with quick-lime yields caustic soda and fluoride of calcium.
Properties of Aluminium.
The colour of this metal is intermediate to those of zinc and
tin; its hardness exceeds that of tin, but is less than that of zinc and copper, and
about the same as that of fine silver; it is a very sonorous metal, rather brittle,
malleable to some extent, readily rolled into thin sheets, and may be beaten into
leaf; on the other hand, it is not ductile. Aluminium does not rust by exposure to
air, and it may be even heated to redness without suffering much oxidation. When
fused, however-it melts at 700°-it oxidises so much as to necessitate the use of a
flux-best chloride of potassium-to absorb the alumina which is formed. It is very
readily and rapidly dissolved by hydrochloric acid and solutions of caustic potassa
and soda, hydrogen being copiously evolved; but the metal is not in the least acted
upon by nitric acid. It does not amalgamate with mercury. With tin it yields an
alloy of considerable hardness, yet to some extent malleable; with copper in the
proportion of go to 95 per cent. of copper and 10 to 5 per cent. of aluminium, it
forms aluminium-bronze. This alloy, in colour similar to gold, is used for artificial
jewellery and small ornaments. Aluminium does not alloy with lead. The aluminium
of commerce is never quite pure, always containing silicium, found by Dr. Ram-
melsberg even to 10'46 per cent., and frequently present to 07 to 3.7 per cent.;
while the quantity of iron varies from 16 to 7.5 per cent.
9
114
CHEMICAL TECHNOLOGY.
Applications. Aluminium is now not so much in use: when first introduced aluminium
jewellery was the order of the day. The metal is at present more usefully employed for
small weights, light tubes for optical instruments, and to some extent for surgical instru-
ments. The price, however, of this metal, £5 128. per kilo., is too high to admit of its
extended use; while great lightness combined with comparative strength are its only
prominent qualities.
MAGNESIUM,
(Mg=24; Sp. gr. 1'743).
Magnesium. As an oxide, and in combination with chlorine and bromine, as well as
with other metalloids, magnesium is found in very large quantities, for instance, in
sea-water and carnallite, as sulphate of magnesium, as kieserite, schoenite, kainite,
in rocks as a pure carbonate, and as magnesian limestone; further as a silicate in
meerschaum. Metallic magnesium has but limited commercial applications. It is
silvery white in colour, somewhat affected by the oxygen of the air, but not more
so than zinc; fuses at about the same temperature as that metal, and when heated
a little above this point, burns with an intensely brilliant white light, and in oxygen
gas the combustion is attended with a lignt almost equal to bright sunlight. Mag-
nesium may be readily drawn into wire; it is at the ordinary temperature of the
air as malleable as zinc, and boils and distils over at about the same temperature as
that metal. Magnesium is at present only applied to yield an intense light in
photography, and for signals; for this latter purpose it was extensively used in the
Abyssinian campaign (1868). It has been suggested to alloy magnesium instead of
zinc with copper.
Magnesium is prepared by a process very similar to that of aluminium manufacture :—
Sodium is ignited with either chloride of magnesium-Bunsen, Deville, and Carron
methods—or the double fluoride of magnesium and sodium-Tissier's plan-or the double
chloride of magnesium and sodium-Sonstadt's method. Dr. H. Schwarz employs the
double chloride of calcium and magnesium, and M. Reichardt carnallite, double chloride
of magnesium and potassium. Several other suggestions have been made as to the mode
of preparing this metal, but it does not appear that they are available in practice. Mag-
nesium is manufactured on the large scale by the Magnesium Metal Company at Man-
chester, and the American Magnesium Company at Boston, the English firm producing
about 20 cwts. annually.
ELECTRO-METALLURGY.
Application of Galvanism, It is one of the most prominent properties of the continuous
electric current, that it is capable of decomposing compound substances in such a-
manner as to cause the constituents to be deposited on or near the place where the
current leaves the body to be decomposed; this property is termed electrolysis, the
body decomposed being termed electrolyte, and the places where the electric current
enters and leaves electrodes; the positive pole of the battery being named anode, and
the negative cathode. The constituents of the body decomposed by electricity are
termed ions (from wv, participle of eμ, to go); that deposited or separated at the
anode (+pole) being distinguished as the anion, and that making its appearance at
the cathode the cation. An electric current strong enough to decompose a molecule
of water is also capable of decomposing a molecule of a binary compound; accordingly
the quantities by weight of a body decomposed by the electric current are propor-
Electrolytic Law. tional to the chemical equivalents. The main laws of electrolysis
were discovered by Faraday, who was the first to show that the constituents
attracted by the anode (+ pole) are electro-negative, and those by the cathode
ELECTRO METALLURGY.
115
(pole) electro-positive. As water is a common solvent, it frequently occurs that
during electrolysis its elements are secondarily decomposed. For instance, sulphate
of copper gives, at the anode oxygen gas, and at the cathode metallic copper, because
the oxide of copper appearing at this pole is at once de-oxidised by the simultaneous
appearance of hydrogen: the oxygen set free at the positive plate combines with the
zinc, forming an oxide, converted by the acid into sulphate of zinc; so that for every
equivalent (634) of copper deposited, one equivalent (652) of zinc is dissolved. If,
instead of sulphate of copper, suitable solutions of gold, silver, &c., are employed,
the electro-deposition of these metals can be effected.
Electrotyping. The following are the chief technical applications of electrolysis:-
Electrotyping. It has just been said that the copper separated electrolytically from
the sulphate of that metal is deposited in a coherent state, and if the operation is
continued for some time the layer of metal may become sufficiently thick to admit of
being detached from the form upon which it was deposited. This principle of electro-
typing was discovered in 1839, simultaneously at St. Petersburg by Dr. Jacobi, and
at Liverpool by Mr. Spencer; among those who have laboured to improve this art,
are Messrs. Becquerel, Elsner, Smee, Ruolz, Elkington, and many others. The
metallic solution applied for the preparation of casts to be electrotyped is always a
saturated solution of sulphate of copper, and the form, technically termed the pattern
or matrix, upon which it is desired to deposit the copper, should not consist of any
metal, such as zinc, tin, or iron, acted upon by a solution of sulphate of copper.
The matrix is usually, if it be a metal, made of copper; but more frequently it
consists of gypsum or gutta-percha. In order to render the electric current uni-
form, the zinc plate of the battery is amalgamated by dipping it in hydrochloric or
dilute sulphuric acid, and then rubbing mercury over the surface with a brush or
piece of soft rag.
Reproduction of Copper- The engraved copper-plate to be reproduced is placed at the
Plate Engravings. bottom of a wooden trough lined with resin or ashphalte. Above the
plate is fixed a wooden frame, on which is strained a sheet of bladder or parchment, to
serve as a diaphragm; and on the top of the frame a plate of zinc is placed, and con-
nected with the copper-plate by a strip of lead. A saturated solution of sulphate of
copper is poured into the bottom of the trough, and in order to maintain the saturation a
few crystals are added. Above the porous diaphragm a concentrated solution of sulphate of
zinc is placed. This plan is also pursued in electrotyping woodcuts, stereotype-plates, &c.
Deposition of Metals. To reproduce medals and other small objects a weak current only is
required. The plate or object on which it is desired to cause the deposition to take place
is suspended vertically from the cathode, and a plate of the metal to be deposited from
the anode; in proportion as the metal is precipitated at the cathode, it is dissolved at the
anode, leaving the concentration of the fluid unchanged. Such substances as are
non-conductors, wax, paraffine, and gypsum, are first superficially coated with some
conducting material, as graphite, silver, or gold-bronze. Gutta-percha is an excellent
material for casts, owing to its becoming plastic in boiling water. According to M. von
Kobell, a tough malleable copper is obtained by adding to the copper solution some
sulphate of soda and sulphate of zinc. Unless a rather weak current is applied, the
copper is separated from its solution in a spongy state; on no account should the
current be strong enough to decompose water.
Gold and Silver.
Electro-Plating with In order to apply a coating of gold or silver to copper, brass,
bronze, or other metallic alloy, the surface should be first very thoroughly cleaned
by boiling in a caustic soda solution. Smee's battery-a platinised silver plate, and
a plate of amalgamated zinc-is now generally used, the elements being placed in
leaden vessels lined with asphalte. The solution of gold or silver in cyanide of
potassium is employed as the decomposition liquid, in which the objects to be silvered
or gilded are suspended by a wire connected with the negative pole of the battery;
116
CHEMICAL TECHNOLOGY.
and to another wire, connected to the positive pole of the battery, is fastened a piece
of platinum, which is also immersed in the liquid of the decomposition-cell. The
whole process only lasts a few minutes, the cathode during the time being moved
backwards and forwards by hand to render the deposit uniform. Plates of gold or
silver are generally used instead of platinum at the anode, and become gradually
dissolved by, and maintain, the cyanide solution at a constant strength.
Gold Solution. 100 grms. of cyanide of potassium are dissolved in 1 litre of distilled
water, and 7 grms. of very fine gold in nitro-hydrochloric acid, this solution being
evaporated to dryness on a water-bath, the residue dissolved in distilled water,
and to the solution some cyanide of potassium added; or the gold salt obtained on
evaporation may be dissolved in distilled water, and the solution carefully precipi-
tated with sulphate of iron, the finely-divided gold being collected on a filter, next
washed with distilled water, and finally dissolved in cyanide of potassium.
Silver Solution. This solution is prepared by dissolving well-washed chloride of silver
in the above solution of cyanide of potassium, so as to obtain a saturated solution
of cyanide of silver, afterwards to be diluted with an equal bulk of water.
Copper, bronze, brass, iron, and steel can be electro-plated directly; but polished steel,
tin, and zinc have to be first coated with a film of copper. German or nickel-silver is now
generally electro-plated. The thickness of the film of silver may vary from 1-42nd to
1-450th, or even to 1-9400th of a millimetre, corresponding to 1240 grms. of silver
on I square metre of surface. Frequently the best electro-plated ware made in this
country is afterwards coated with a very thin film of palladium to prevent the silver being
affected by sulphuretted fumes.
Copper Solution.
For the purpose of electro-coppering, a solution of oxide of copper
in cyanide of potassium is the most suitable fluid; this solution is prepared by first
decomposing a solution of sulphate of copper in water, with the aid of caustic
potassa and grape sugar, so as to obtain a precipitate of sub-oxide (red oxide) of
copper, which, having been collected on a filter, and well washed, is next dissolved
in a solution of cyanide of potassium. For the purpose of electro-coppering iron and
steel, M. Weil, of Paris, prepares a fluid-350 grms. of cupric sulphate, 1500 grms. of
potassio-tartrate of soda (sal seignette), and 400 to 500 grms. of caustic soda dissolved
in 10 litres of water.
M. Oudry's method of depositing copper on iron candelabras, gas lamps, fountain
ornaments, &c., is in some particulars quite different, the copper not being immediately
deposited on the iron, which is first coated with an impermeable layer of a kind of red-
lead paint, graphite being afterwards rubbed in for the purpose of rendering the surface of
the object a conductor. To obtain a coating of copper i millim. in thickness, such articles
as candelabra are left in the solution for 4 days; the ornamental fountains of the Place
la Concorde, Paris, have been for a period of two months in the solution.
Zinc and Tin Solution. To coat iron with zinc, a solution of the sulphate of the latter
metal may be used, but the so-called galvanised iron of commerce is made by a
different process, viz., by placing the iron to be coated in a bath of molten zinc,
covered, for the purpose of preventing oxidation, with a layer of molten tallow or
paraffin. For the purpose of electro-tinning, a solution of tin in caustic soda is
employed, the anode being of tin.
A so-called electro-steeling, really a deposit of iron on the copper plates used for engrav-
ing, is effected by M. Meidinger in the following manner :--The bath is a solution of sul-
phate of iron and chloride of ammonium: to the copper pole of the battery a plate of
iron, and to the zinc pole the engraved copper plate, are connected. These steeled plates
serve for as many as 5000 to 15,000 impressions. This method has been applied to
stereotyping with great success, and indeed the deposition of iron electrolytically is
a valuable addition to technology.
ELECTRO METALLURGY.
117
Etching by Galvanism. This process is based upon the fact that, under certain conditions, the
substances separated at, combine with the electrodes, the consequence being that the
electrode is gradually corroded and destroyed. The copper-plate intended to be etched is
uniformly covered with a mixture of 4 parts of wax, 4 of asphalte, and I of black pitch;
the design is then drawn or rather scratched with proper tools through this non-con-
ducting layer, and the plate attached to the anode of a galvanic battery, and placed in
a solution of sulphate of copper, containing also a copper-plate connected to the negative
electrode of the battery. On this plate is deposited the copper of the solution, while the
oxygen of the decomposed water, with the sulphuric acid, act upon the portions of metal
not covered with the protective layer and produce the etching.
Metallochromy, Or galvanic painting, consists in depositing thin films of oxide of lead in
a coherent state on metal plates, thus producing Nobili's colours. The oxide of lead is, for
this purpose, best dissolved in caustic potassa or soda solutions. In England, this method
of ornamenting is not much applied; but at Nuremburg, where toys are largely manufac-
tured, this process is very simply carried out by placing the metallic object, previously
connected with the cathode of a battery, in a concentrated solution of oxide of lead in
caustic potassa, while to the anode is affixed a piece of platinum foil.
Electro-Stereotyping. For the purpose of reproducing printing-types by galvanic means,
a wax impression of the type is placed in the deposition-cell. This operation is also
employed for the reproduction of woodcuts, gutta-percha being used as a mould.
Glyphography. By this name is understood a process for reproducing woodcuts, but it is
now altogether obsolete, having been superseded by electro-typing. A further disadvantage
was, that the glyphographic plates could not be printed from the same matrix as type.
Galvanography. At the suggestion of Dr. von Kobell, the reproduction of some kinds of
drawings and pictures has been tried, in order to enable exact copies to be printed from
plates electrolytically obtained from the original drawings; but this method, of very difficult
and costly execution, is superseded by photography.

DIVISION II.
CRUDE MATERIALS AND PRODUCTS OF CHEMICAL INDUSTRY.
CARBONATE OF POTASSA.
(K2CO3=138*2; in 100 parts, 68.2 potassa and 31.8 parts carbonic acid.)
is derived.
Sources whence Potassa The substance known in chemistry as carbonate of potassa is
generally termed potash, because it was formerly obtained from wood-ash, which,
after lixiviation with water, was evaporated to dryness in cast-iron pots. Potassa
occurs native in considerable quantities, but never free, being combined with silica in
many minerals, also in combination as chloride of potassium, sulphate of potassa,
and in various plants with organic acids. The following are the sources whence
potassa is industrially obtained:-
A. Inorganic sources
of Potasssa.
B. Organic sources
of Potassa.
Potassa Salts from the
Stassfurt Salt Minerals.
I. The salt minerals of Stassfurt and Kalucz; products-
carnallite, sylvin, kainite, and schoenite.
II. Feldspar and similar minerals.
III. Sea-water and the mother-liquor of salt-works.
IV. Native saltpetre.
V. The ashes of several plants.
VI. The residue of the molasses of beet-root sugar after
distillation.
VII. Sea-weeds, as a by-product of the manufacture of iodine.
VIII. The suint of the crude wool of sheep.
I. The very abundant salt-rocks near Stassfurt, in Prussia, and
Kalucz, in Hungary, chiefly yield carnallite, sylvin (CIK), and kainate, a compound
of sulphate of potassa and magnesia with chloride of magnesium. Carnallite, so
named in honour of Carnall, a Prussian mining engineer, consists, in 100 parts,
leaving the bromine out of the question, of—
Chloride of potassium
Chloride of magnesium
Water..
:
27
34
39
Formula-KCL, Mg {012
ΙΟΟ
Cl₂
Br₂
+6H20. This salt is applied in the manufacture of—
a.
Chloride of potassium.
B. Sulphate of potassa.
y. Potash (carbonate).
CARBONATE OF POTASSA,
119
a. Preparation of Chloride of Potassium.-According to the process originally
patented (1861) by Mr. A. Frank, the abraum salts are ignited in a reverberatory
furnace, with or without the aid of a current of steam, and next lixiviated with
water, the resulting liquor yielding chloride of potassium. The rationale of this
process is:-1. That the carnallite of the abraum salts is separated by the action of
the water into chloride of potassium and chloride of magnesium. 2. The latter salt,
on being ignited in a current of steam, is decomposed into hydrochloric acid, which
escapes, and magnesia, which is practically insoluble in water, and which conse-
quently remains. This process is not found to answer well on the large scale,
because the abraum salts contain other chlorides, the chloride of sodium and tachy-
drite, by the presence of which the decomposition of the carnallite is hindered.
Dr. Grüneberg, therefore, suggested that the abraum salts should be first mechani-
cally purified, that is to say, the different components of the abraum salts should be
separated from each other according to their varying specific gravity, which for—
Carnallite
is 1.618
Chloride of sodium is = 2.200
Kieserite
is 2.517
The abraum salt having been ground to a coarse powder is passed through sieves,
and treated as minerals are in metallurgical processes, with the difference that, instead
of water, which of course would dissolve the salts, a thoroughly concentrated solution
of chloride of magnesium is applied, this solution not acting upon the salts, and being,
moreover, obtained as a by-product in enormously large quantities. The above-
mentioned salts settle in layers according to their densities, the carnallite forming
the upper, and the kieserite the lowest layer. The carnallite is at once applied to
the preparation of chloride of potassium; the middle layer of common salt is so free
from other foreign salts as to be fit for domestic use; the kieserite, after having been
washed with cold water to remove any adhering chloride of sodium, is applied to the
FIG. 57.
FIG. 58.


187
о
о
取
​T
manufacture of sulphate of potassa, to be presently described. However, the greater
number of manufacturers at Stassfurt prefer another plan, applying the five following
operations to the abraum salts as delivered from the salt quarries:-1. Lixiviation
of the carnallite with a limited quantity of hot water, sufficient to dissolve the
chlorides of potassium and magnesium, leaving the bulk of the common salt and
magnesian sulphate. 2. Crystallising the chloride of potassium by artificially
120
CHEMICAL TECHNOLOGY.
freezing. 3. Evaporating and cooling the mother-liquor to produce a second yield
of crystallised chloride of potassium. 4. Again evaporating and cooling the mother-
liquor, which yields the double salt of the chlorides of potassium and magnesium,
or artificial carnallite, which is next treated in the same manner as the native salt.
5. Washing, drying, and packing the chloride of potassium.
1. The carnallite is put into cast-iron lixiviation vessels and mixed with three-fourths of
its weight of water, previously employed for the washing of crude chloride of potassium,
and, therefore, containing a large quantity of common salt and some chloride of
potassium; steam, at 120°, and at a pressure of 30 lbs. to the square inch, is forced
through the perforated circularly bent tube, T (Fig. 59) at the bottom of the vessel.
=
Fig. 59.
In
Mr. Douglas's works the lixiviation vessels, Figs. 57,
58, and 59, have a cubical capacity of 20 tons. They
are closed with a tightly-fitting lid, an opening being
cut for the escape of surplus steam. The stirrer, c, is
kept in motion by steam-power. When the admission
of steam and the stirring has been continued about
three hours, the contents of the vessels are left at rest
for two days, after which the saturated solution has a
density of 32° B. — 1·286 sp. gr., and is forced by steam
pressure into crystallising vessels; the residue in the
lixiviation vessels, amounting to about one-third of the
weight of the carnallite, is again treated as described.
2. The crystallisation vessels are of wood or sheet-
iron, 120 metres diameter, by 1.5 to 19 metres height.
The chloride of potassium crystallises in combination
with common salt, and is strongly impregnated with the
very soluble and highly deliquescent chloride of mag-
nesium; the salt deposited at the sides of the vessel
contains upwards of 70 per cent. of chloride of potassium, while that collected at the
bottom contains only 55 per cent. If shallow vessels are employed, the saline solution
cools more rapidly, and a finer grained salt is obtained, mixed, however, with impurities,
and requiring more washings, an operation which, with the coarse salt, has only to be
performed once to yield 80 per cent. chloride of potassium. Most of the chloride of
potassium sold by the manufacturers contains 80, and in some cases 85 and 90, per cent.
of the pure salt.
3. The evaporation of the first mother-liquor is carried on in iron pans of various
sizes. As by the evaporation common salt is largely deposited, which has a tendency to
FIG. 60,


T
T
FIG. 61.
K T

T
T
ས་ལམ་ གས་ ས་
cake at the bottom of the pans, and check the conduction of heat, the pans are set so as
to receive the action of the flame only on the sides (Fig. 61), and the liquid kept constantly
CARBONATE OF POTASSA.
121
stirred. When the liquor has been reduced to about two-thirds of its bulk, with a density
of 33° B. 1298 sp. gr., it is run into the crystallising vessels. The mass remaining in
the evaporating pan, consisting of 60 to 65 per cent. common salt, 6 per cent. chloride of
potassium, and 30 percent. double sulphates of magnesium and potassium, is used as manure.
Steam-heated evaporating pans, represented in Fig. 60, are employed by some manu-
facturers; the four steam-tubes, T, are placed parallel to the sides of the vessel, and open in
u, the waste steam being carried off by the tube r'. As might be expected, the concen-
tration of the liquor is more rapidly performed by means of steam, but the crystallisation
of the second crop of salt is poorer, yielding only 50 to 60 per cent. chloride of potassium,
and requiring two to three washings to accumulate 80 per cent. pure potassium salt.
4 and 5. The second mother-liquor is again concentrated by evaporation to 35° B.
=sp. gr. 1'299, yielding a saline mass similar to the residue of the first evaporation, and
to which it is added and used as a manure. On being submitted to crystallisation, this
last liquor yields artificial carnallite, treated as the salt obtained from the native deposit,
giving, however, with less labour 80 to 90 per cent. chloride of potassium. The chloride
of potassium, after washing with pure water, is dried either in rooms heated by steam, or
in a moderately-heated reverberatory furnace. The dry salt is then packed in casks,
each containing about 500 kilos.
B. The preparation of sulphate of potassa may be effected :—
ɑ. From chloride of potassium and sulphuric acid.
b. By Longmaid's (see Soda Manufacture) roasting process, viz., the calcina-
tion of chloride of potassium and sulphuret of iron, and in metallurgical
processes where chloride of potassium is used instead of chloride of sodium.
From chloride of potassium and kieserite.
C.
d. From kainite.
The conversion of chloride of potassium into the sulphate of potassa by double
decomposition with sulphate of soda is not practicable on the large scale, as the two salts
have a tendency to form double salts; therefore, the methods a and b are practically
available only under certain peculiar conditions. A small quantity of chloride of potassium,
obtained in Scotland as a by-product of the preparation of kelp, is converted into sulphate
of potassa by the means in use for the manufacture of soda (quod vide). The leading
points in the manufacture of sulphate of potassa by the aid of the sulphuric acid contained
in kieserite are the following:-First schoenite and carnallite are prepared by dissolving
chloride of potassium and kieserite in boiling water, and crystallising the solution thus
obtained :-
4 mols. Kieserite
2 mols. Schoenite.
I mol. Carnallite.
3 mols. Chloride of potassium
} = {
The schoenite and artificial carnallite are separated by crystallisation, and the former
decomposed by chloride of potassium :--
4 mols. Schoenite
3 mols. Chloride of potassium
4 mols. of Sulphate of potassa.
2 mols. of Schoenite.
I mol. of Carnallite.
The sulphate of potassa crystallises first, and is simply purified by washing with water.
As kainite is found in very large quantities among the saline deposits near Stassfurt, it is
also used for the preparation of sulphate of potassa; by a simple washing with water,
the chloride of magnesium contained in the kainite is removed, and the salt thus converted
into schoenite :-
Kainite
Chloride of magnesium} = Schoenite.
The schoenite is then employed in the manufacture of sulphate of potassa by being
treated with chloride of potassium; the sulphate of potassa thus obtained is used either
in alum or potassa manufacture, or as a potassa manure.
y. Preparation of Carbonate of Potassa or Mineral Potash.-Very many sug-
gestions have been made for converting by simple means chloride of potassium and
sulphate of potassa into carbonate of potassa, industrially known as potash; but
most of the plans proposed are unfit for use on the large scale, and even the method
adopted by Leblanc for soda manufacture has not been in every case successful
when applied to the production of chloride of potassium. At Kalk, on the opposite
I 22
CHEMICAL TECHNOLOGY.
bank of the Rhine to Cologne, a process, said to be based upon Leblanc's method,
is successfully in operation, but the real arrangements are carefully kept secret, no
one being allowed to visit the works; however, it is stated that sulphate of potassa
containing schoenite is mixed with chalk and small coals, and calcined, the cal-
cined mass being lixiviated when cool, and yielding carbonate of potassa in
solution, and a residue of sulphide of calcium.
from Feldspar.
Mode of Obtaining Potassa II. Potassa-salts from feldspar. It has been found by the
analysis of minerals entering largely into the constitution of rocks, that potassa is
present in considerable quantities. The following may be taken as instances:
Orthoclase, or potash feldspar, contains from 10 to 16 per cent.; potash mica, 8 to
10 per cent.; trachyte, glaukonite, phonolithe, 7 to 8 per cent.; porphyry, granu-
lite, and mica schist, 6 to 7 per cent.; granite, syenite, gneiss, 5 to 6 per cent. ;
dolerite, basalt, kaolin, and clay, 1 to 2 per cent.
Before the discovery of the potassa-salt deposits at Stassfurt, Kalucz, and elsewhere,
there were many suggestions made as to the obtaining of the potassa on the large scale ;
but at present this branch of industry lies dormant, notwithstanding the theoretical value
of Mr. Ward's (1857) suggestion that feldspar should be mixed with fluor-spar, both finely
pulverised the fluorine being equal in quantity to the potassa contained in the fluor-spar
-a mixture of chalk and hydrate of lime added, the mass ignited in kilns or gas-retorts,
and finally treated with water to yield caustic potassa and a residue, which, after another
calcination, yields excellent hydraulic lime.
Sea-Water.
Potassa-Salts from III. Dr. Usiglio found that the water of the Mediterranean contains
in 10,000 parts by weight 5'05 parts of potassa; and after the removal of the more
readily crystallisable salts left by the spontaneous evaporation of the water by the
sun's heat, this natural mother-liquor is applied to the preparation of potassa-
salts, according to the following method:-
The process now in use near Aigues Mortes, and other localities in proximity to the
Mediterranean, was invented by Professor Balard, the discoverer of bromine, and yields
from I cub. met. of mother-liquor, equal to about 75 cub. mets. of sea-water, at 28° B.
=1′226 sp. gr. 40 kilos. of sulphate of soda, 120 kilos. of refined common salt, and
10 kilos. of chloride of potassium. It has been found, however, that this method is rather
costly, and the mother-liquor is generally left to spontaneous evaporation, yielding the
three following kinds of salt:-a. The first salt separated from a liquor of 32° B.
=1′266 sp. gr., only impure common salt. b. The second salt separated from a liquor,
32° to 35° B. = 1.266 to 1.299 sp. gr., consisting of equal parts of common salt and Epsom-
salt, and termed mixed salt. c. The third salt, 35° and 37° B. 1.299 to 1.321 sp. gr.,
termed summersalt. The second salt having been dissolved in fresh cold water, the
solution is placed in Carré's ice-making machine, and yields sulphate of soda by an
exchange of its constituents. The third salt is dissolved in boiling water, yielding on
cooling half its potassa as kainite. The mother-liquor, containing carnallite, common
salt, and bitter, or Epsom-salt, yields sulphate of soda, and, when treated with chloride
of magnesium, all its potassa as carnallite, which, by being washed with water, yields
chloride of potassium. In this way it has become possible to obtain 45 per cent. of the
potassa of the mother-liquor as chloride of potassium, and 55 per cent. of schoenite, which
is converted into sulphate of potassa.
Ashes of Plants.
Potash from the IV. The residue left from the ignition of the organic matter, or wood,
as it is usually termed, of plants, contains those mineral substances which the plant
has taken from the soil, chiefly potassa, soda, lime, magnesia, small quantities of the
protoxides of iron and manganese, combined with phosphoric, sulphuric, silicic, and
carbonic acids, and also with the haloids. These combinations are not, however, the
same as those existing in the living plant, because the high temperature of the
ignition has the effect of changing the affinities. Plants growing near the sea gene-
rally contain large quantities of soda, while those inland contain generally more
potassa. The quantity of ash varies not only for different kinds of plants, but for
various parts of the same plant, very succulent plants and the most succulent parts
CARBONATE OF POTASSA.
123
generally yield the largest quantity of ash; herbs yield more ash than shrubs,
shrubs more than trees, and the leaves and bark of these more than the wood. It
is evident that the inorganic matter, chiefly alkaline salts, being contained in the
juice of plants in a soluble state, the quantity must of necessity be greatest in the
Juicy and succulent parts.
Dr. Böttger found the ash of beech-wood to contain-
21.27 per cent. of soluble salts,
78.73. "
of insoluble salts.
""
The soluble salts were found to be-
Carbonate of potassa
Sulphate of potassa
Carbonate of soda
Chloride of sodium..
15'40 per cent.
•
2.27 ""
""
3:40 "
""
O'20 ""
""
21.27 per cent.
The value of an ash for the manufacture of potash is chiefly dependent, in the first
place, upon the quantity of potassic carbonate it will yield, upon the abundance of the
wood or other vegetable product, and the cost of labour. The undermentioned woods
yield, on an average, for 1000 parts, the following quantities of potash :—
Pine
Poplar
•
Beech-bark..
Dried ferns
6:00
Beech
•
0'45
0*75
•
6.26
•
I'45
1'53
Stems of maize (Indian corn)
Bean-straw.
• •
•
•
17.50
20'00
·
•
2:26
•
2.85
Sunflower-stems.
Nettles ..
20'00
25.03
•
3'90
Vetch-straw
·
27.50
3'90
Thistles
35.37
4.20
Dried wheat-plant previous
to
blooming..
47.00
5'08
Wormwood..
73.00
5'50
Fumitory
79'00
5.80
Oak
Box-wood
Willow..
Elm
Wheat-straw
Bark from oak-knots..
Cotton-grass (Eriophorum vaginatum) 5·00
Rushes..
Vine-wood
•
Barley-straw
According to M. Höss, 1000 parts of the following kinds of wood yield
Pine
•
Beech
Ash
Oak
Elm
Ash.
Potash.
Ash.
Potash.
3'40
0'45
Willow
28.0
2.85
5.80
I'27
Vine..
•
34'0
5.50
12.20
0'74
Dried ferns
36.4
4:25
..
13.50
I'50
Wormwood
97'4
73.00
25.50
3'90
Fumitory..
219'0
79.90
The preparation of potash from vegetable matter is effected in three operations, viz.:-
a. The lixiviation of the ash.
b. The boiling down of the crude liquor.
c. The calcination of the crude potash.
The combustion of the vegetable matter should be so conducted as to prevent its
becoming too violent, and giving rise to the combustion of some of the reduced potassa-
salt; nor should too strong a current of air be admitted for fear of the ash being mechani-
cally carried off. A distinction is made abroad-no potash from wood or other vegetable
matter being produced in the United kingdom, nor wood used as fuel in sufficient quantities
to yield ash for the preparation of potash-between the ash obtained by the combustion of
the refuse wood of forests and the ash from wood used as fuel, the former being termed
forest- and the latter fuel-ash. As ash from other fuel than wood may be mixed with fuel-
ash, a sample may be roughly tested by lixiviation, and the density of the liquor taken by
the areometer, the higher the specific gravity the larger the quantity of soluble salts. For-
merly the forest ash was purposely prepared, and sold to potash-boilers. There is still
known in Eastern Prussia and Sweden a material termed okras or ochras, holding a position
intermediate to crude ash and potash.
a. The lixiviation of the ash effects the separation of the soluble from the insoluble saline
matter, the former amounting to about 25 to 30 per cent. of the entire weight of the ash.
The operation is carried on in wooden vessels shaped like an inverted truncated cone, and
provided with a perforated false bottom, which is covered with straw; in the real bottom
a tap is fixed for removing the liquor. If the lixiviation is systematically carried on,
124
CHEMICAL TECHNOLOGY.
several of these vessels are placed together, forming what is termed a battery, and under
each a tank to receive the liquor. The ash to be lixiviated is first separated from the coarse
particles of charcoal, next put into a small square water-tight wooden box, and thoroughly
saturated with water for at least twenty-four hours. By this proceeding the lixiviation is
greatly assisted, and the silicate of potassa to some extent decomposed by the action of
the carbonic acid of the atmosphere. The next step is to transfer the wet ash to the
lixiviation vessel, care being taken to press it tightly down on to the false bottom; cold
water is then poured in, until the liquor begins to run off at the taps left open for that
purpose. The liquor which runs off, after the water has remained some little time in
contact with the ash, is found to contain about 30 per cent. of soluble salts, afterwards
decreasing to about 10 per cent., when hot water is employed to complete the lixiviation.
The insoluble residue left in the lixiviation-tub is of value as a manure, on account of the
phosphate of lime it contains, and is also used in making green bottle-glass, and for
building up saltpetre-beds.
b. Boiling down the liquor. The liquor obtained by lixiviation is of a brown colour,
owing to organic matter, humin or ulmine, which the carbonate of potassa has dissolved
from the small chips of imperfectly burnt charcoal. The evaporation is carried on in large
shallow iron pans, fresh liquor being from time to time added, and the operation continued
until a sample of the hot concentrated liquor exhibits on cooling a crystalline solid mass.
When this point is reached the fire is gradually extinguished, and as soon as the contents
of the pan are sufficiently cold to handle, the solid salt mass is broken up; its colour is a deep
brown. This crude product, containing about 6 per cent. of water, is known in the trade as
crude, or lump-potash. It is evident that this method of boiling down may cause consider-
able damage to the iron pans, therefore in many instances the operation is conducted in a
somewhat different manner. The liquid is kept stirred with iron rakes, and the salt, instead
of forming a hard solid mass, is obtained as a granular powder, containing upwards of 12
per cent. water. Some manufacturers first separate the sulphate of potash, which, being
less soluble, crystallises before the carbonate, a deliquescent salt, is separated from the
liquor; in most cases, however, this operation is only carried on where the sulphate of
potash is required for alum-making. The pearl-ash or potash of commerce almost invari-
ably contains a large quantity of sulphate of potash.
c. In order to expel all the water and to destroy the organic matter, the saline mass is
calcined, and as this operation was formerly performed in cast-iron pots, the salt has
obtained the name of potash. A calcining furnace, Fig. 62, is now used, distinguished
from ordinary reverberatory furnaces by being provided with a double fire-place. These
FIG. 62.

ARBAREND PROGRAM AN
ВІНЦЕВИМ ПЕРЦЕН
hearths, one of which is exhibited in section at A, FIG. 62, are placed at right angles to
each other, and the flame and smoke meeting in the centre of the furnace, pass off at o,
the work-hole, into the chimney, K. Wood is used as fuel, and as the heating of the
furnaces requires a very large quantity, they are only in use when a sufficient supply of
crude potash is ready for being operated upon. The furnace is thoroughly heated in about
five to six hours, care being taken to fire gradually, and to bring the interior of the furnace
to nearly red heat, so that the vapour due to the combustion of the wood may not condense
inside the furnace, but be carried off by the flue. The crude potash, broken up to egg-size
lumps, is next placed in such quantities at a time as may suit the size of the calcining
hearth; for instance, if the hearth is roomed to contain 3 cwts., that quantity is divided
into three portions and put in at intervals of a few minutes. The first effect of the heat
is to expel the water from the potash, the escape of the steam being promoted by stirring
CARBONATE OF POTASSA.
125
the mass with iron rakes. In about an hour all the water is driven off, and the mass
takes fire in consequence of the burning of the organic matter, the salt at first being
blackened, but gradually becoming white as the carbon burns off. As soon as this stage
is reached, the potash is removed to the cooling-hearth, and when cold, packed in well-
made wooden-casks, which, as this salt is very hygroscopic, are rendered as air-tight as
possible. The heat of the furnace has to be well regulated to prevent the potash
becoming semi-fused, in which case it would attack the siliceous matter of the fire-
bricks; the workmen from time to time take a small sample to test how far the calcination
is complete.
We, in Europe, obtain a considerable quantity of potash from the United States and
Canada, known as American potash, of which there are three different kinds, viz.:—
1. Potash prepared as described. 2. Pearl-ash, or potash, purified by lixiviation, decan-
tation from sediment, boiling down, and the calcination of the salt thus obtained.
3. Stone-ash, a mixture of uncalcined potash (potassic carbonate), and caustic potash
obtained by treating the crude potash liquor with caustic lime, and boiling down the mass
to dryness; this article has the appearance of the crude caustic soda of this country, but
is usually coloured red by oxide of iron; the lumps, stone-hard, are from 6 to 10 centims.
in thickness, and contain upwards of 50 per cent. caustic potash. The under-mentioned
analyses exhibit the varying composition of the potash of commerce:-Sample I is
from Kasan (Russia); analyst, M. Hermann. 2. Tuscany. 3 and 4-the latter of a
reddish colour-from North America. 5. Russia. 6. Vosges (France); analyst of 2, 3, 4,
5, and 6, M. Pesier. 7. Helmstedt, in Brunswick; analyst, M. Limpricht. 8. Russia;
analyst, M. Bastelaer.
I.
2.
3.
4.
Carbonate of potash
78.0
Carbonate of soda
74'I
3.0
Sulphate of potash
17'0
13'5
5.
71'4 68.0 69.9 38.6
2.3. 5.8 3.1
14'4 15'3 14'I 38.8
6.
7.
8.
49'0
50.84
4.2
12.14
40'5
17.44
Chloride of potassium.. 30
0'9
Water
•
7.2
3.6 8.1
4'5
2'I
9.I
Insoluble residue..
O'2
O'I 2.7 2.3 2.3
8.8 5.3
3.8
1 300
IO'O
5.80
10.18
3.60
The calcined potash varies in colour, being either white, pearl-grey, or tinged with
yellow, red, or blue. The red colour is due to oxide of iron, the blue to the manganates of
potash, a hard, light porous, non-crystalline mass, never entirely soluble in water. For-
merly, a large quantity of potash was obtained from the residues of wine-making, and
called vinasse, the semi-liquid left after the alcohol has been distilled from the wine, and
containing, among other substances, argol, or crude bitartrate of potash; it was boiled
down, and next calcined, yielding a kilo. of very good potash for every hectolitre of vinasse.
The large quantity of potash thus formerly produced may be judged from the fact that 19
of the wine-producing departments of France, those only where large quantities of wine
are converted into alcohol, technically termed trois six and cinq huit, yield annually about
9 to 10 million hectolitres of vinasse, at the present time employed for the preparation on
the large scale of cream of tartar, glycerine, and tartaric acid.
Potash from Molasses. V. Of late years, the manufacture of potash salts from the
vinasse left after the distillation of fermented beet-root molasses has been added
as a new branch of industry by M. Dubrunfaut, and introduced into Germany by
M. Varnhagen, in the year 1840, at Mucrena, Prussian Saxony.
Beet-root, on being subjected to ignition, yields an ash containing a large percentage of
potash, a fact first observed in the early part of this century by M. Mathieu de Dombasle,
a celebrated French agriculturist, who discovered that 100 kilos. of dried beet-root leaves
yield 105 kilos. of ash, containing 51 kilos of potash; but this author's idea that the
leaves might be cut off and gathered for the purpose of potash manufacture, proved
erroneous, in so far that the growth of the roots was greatly impeded. After the publica-
tion of M. Dubrunfaut's researches on this subject, in 1838, the vinasse of the beet-root
molasses distillation was evaporated to dryness, next calcined, and the calcined mass refined
for the production of potash and other salts of that base, an industry which has obtained
a great development, as may be judged from the fact that the quantity of these materials
produced on the European continent in 1865 amounted to 240,000 cwts.
The reader who desires details on this subject is referred to the work, "On the Manu-
facture of Beet-Root Sugar in England and Ireland," by Wm. Crookes, F.R.S., &c., p. 250
et seq.
126
CHEMICAL TECHNOLOGY.
The molasses from beet-root sugar consists, previous to the fermentation and
distillation, of the undermentioned substances, as recorded by the several analysts
whose names are subjoined :-
Water
Sugar
Salts and organic substances
30'5
The following analyses by M. Heidenpriern exhibit the average composition of the
Brunner. Fricke. Lunge.
Heidenpriern.
15'2
18'0 18.5
19'0
19'7
49'0 48.0
35.8 34'0
50'7
45.9
49.8
30.8
34'I
ashes of molasses :-
Potassa
Soda
Lime
Magnesia
Carbonic acid
I.
2.
3.
51'72
47.67
50*38
8:00
.II°43
8.29
5'04
3.60
3°12
0.18
ΟΙΟ
0'18
•
28.90
28.70
27'94
The remainder of the 100 parts consists of phosphoric and silicic acids, chlorine,
oxide of iron, &c. The quantity of ash amounts to 10 or 12 per cent. According to
Dubrunfaut the alkalimetrical degree of the ash of beet-root sugar molasses is a
constant, as the ash obtained from 100 grms. of molasses neutralises on an average
7 grms. of sulphuric acid (H2SO4).
The molasses is generally treated in the following manner:-It is first diluted with
either water or vinasse to 8° or 11° B=1056 or 1*078 sp. gr., and mixed with 0.5 to
1'5 per cent. of a pure mineral acid, the object of this addition being not simply the
neutralisation of the alkali, but also the conversion of dextrine and such unferment-
able sugar into fermentable sugar. Formerly, sulphuric acid was used, but upon the
recommendation of M. Wurtz, hydrochloric acid is now generally employed, the
advantage being the formation of readily soluble chlorides, instead of comparative
insoluble alkaline sulphurets, the action of the organic matter present in the molasses.
The diluted molasses is next mixed with yeast, left to ferment, and the alcohol
distilled off; the residue is a liquid of about 4º B. density [=1'027 sp. gr.] containing
undecomposed yeast, ammoniacal salts, various organic substances, and all the
inorganic salts of the beet-root juice. The potassa is present in this liquid as nitrate
chiefly, although by the addition of hydrochloric acid a portion of this salt is decom-
posed, red nitrous fumes sometimes being seen in the fermentation room. Evrard
suggests that the saltpetre should be separated from the beet-root molasses by evapo-
ration, and further purified by the aid of the centrifugal machine. The acidity of the
vinasse is neutralised by chalk, and afterwards it is evaporated to dryness in an iron
vessel, the total length of which is 2013 metres, by an average width of 1.6 metre,
extended at the top to 2 metres, the depth being 0.34 metre. The vessel is made of
stout boiler plate, strengthened by stays and angle irons, and is divided into two
divisions, the larger of which has a length of 14.3 metres, and is the real evaporating
pan, while the other is used as a calcining furnace, and covered with an arch of fire-
bricks o‘6 metre high. The fire-place is 13 metre wide, and the fire-box has a
surface of 3.3 square metres. The evaporation is effected by surface heating, that
is to say, the flame and hot gases from the burning fuel, after passing across the fire-
bridge are conducted over the surface of the vinasse, the calcining pan being nearest
to the fire, while the evaporating pan is at its other extremity in contact with the
CARBONATE OF POTASSA.
127
fiue or chimney. The vinasse, having been run off from the still, is kept in cisterns,
from which it is forced by means of a pump into a reservoir so placed as to admit of
the liquid running in a constant stream into the evaporating pan. At a first operation
both the evaporating and the calcining pan are filled with vinasse, but afterwards
the latter is filled regularly with concentrated thick liquor, which is simply carbon-
ised, the organic matter being only destroyed.
The daily average of carbonised vinasse is about 5 to 5 cwts. The composition
of that substance may be gleaned from the following approximate analysis:-
Insoluble matter
Sulphate of potassa
=23 per cent
= 1107
= 11.61
>>
Chloride of potassium
Carbonate of potassa
=3140
""
Carbonate of soda
=23°26
Silicic acid and hyposulphite of potassa
= traces
""
99.34
In Germany, the calcined vinasse is generally sold to saltpetre manufacturers, but
in Belgium and France this material is calcined, lixiviated, and the salts it contains
separately obtained. For this purpose the vinasse is first evaporated to 38° or 40° B.
(1·33 to 1·35 sp. gr.), and next carbonised and calcined in a furnace constructed
as exhibited in Fig. 63. V is a reservoir containing the concentrated vinasse, which
by means of a tube is gradually run into the furnace, of which G is the fire-place; M
the calcination space, destined to contain the concentrated or carbonised vinasse,
FIG. 63.

M
ILUOLEELAN
NELLIENTE.
which is evaporated to dryness and calcined in M'; a door is fitted to each com-
partment, and at P, the end of the furnace opposite to the fire-place. The air required
for the calcination is admitted partly through the ash-pit, partly through the
openings, B, in the brickwork. The thickish liquid vinasse admitted into M' is
constantly stirred, and, as soon as it is quite dry, it is shovelled across the brickwork
ridge, A', into the calcining space, M, care being taken to again fill a' with concen-
trated vinasse. The organic matter of the saline mass soon takes fire, emitting
noxious fumes. The calcination is greatly aided by the access of air at B, and also
to some extent by the nitrate of potassa present. The temperature has to be regulated
to prevent the salts becoming fused and forming a hard compact mass, in which case
the sulphate of potassa would be reduced to sulphuret of potassium, a salt which
128
CHEMICAL TECHNOLOGY.
·
could not be removed. The calcined vinasse, technically termed salin, contains,
when removed from the furnace, 10 to 25 per cent. of insoluble substances, viz.,
carbonate and phosphate of lime, more or less charcoal, and in addition 3 to 4 per
cent. moisture; the remainder consists of carbonates of potash and soda, sulphate of
potassa, chloride of potassium, and sometimes cyanide of potassium in considerable
quantity. The relative quantities of potassa and soda are, of course, not at all
constant, but vary according to the soil on which the beets have grown; it has been
observed in France that the molasses obtained from beets grown in the Département
du Nord are less rich in potassa than those grown in the Départements de l'Oise et
de la Somme. The average composition of the salin is:-
7 to 12 per cent. of sulphate of potassa.
18 to 20
of carbonate of soda.
""
17 to 22
30 to 35
of chloride of potassium.
""
of carbonate of potassa.
""
The complete composition of the salin may be gathered from the following
tabulated results:
a.
b.
C.
d.
Water and insoluble matter..
26'22
19.82
17'47
13°36
Sulphate of potassa
12.95
9.88
2'55
3°22
Chloride of potassium
Chloride of rubidium
Carbonate of soda ..
..
*.. 15.87
20*59
18.45
16.62
0'13
O'15
0.18
O'21
•
•
25°52
19'66
19*22
16.54
Carbonate of potassa
23'40
29'90 42'13
50'05
100'00
100'00
100'00
100'00
The method of separating the soluble salts from each other, invented by M. Kuhl-
mann, is generally executed as follows:-The saline mass is first broken up and
granulated by the aid of grooved iron rollers, after which it is placed in lixiviation-
tanks, each containing 26'4 cwts., and arranged precisely in the same manner as
those in use in soda works. The liquor tapped from the tanks has a sp. gr. of 1*229
(= 27° B.); the insoluble residue is used as manure. The liquor having been col-
lected in a large reservoir, capable of containing some 210 hectolitres, is concentrated
by waste heat (abgängiger wärme) to a density of 1:26 (= 30° B.); on cooling, the
greater part of the sulphate of potassa crystallises, and is removed, care being taken
to wash off the adhering mother-liquor. The sulphate thus obtained contains 80 per
cent. pure potassic sulphate, the rest being carbonate of potassa and organic matter:
this material is converted into potash by Leblanc's process. The liquor at 30° B. is
next poured into evaporating-pans, each capable of containing 90 hectolitres, and
concentrated by means of heat and a steam pressure of 3 atmospheres (=45 lbs. to
the square inch) to a density of 42° B. (=1*408). By this operation a mixture of
carbonate of soda and sulphate of potassa is separated, which frequently exhibits
30 alkalimetrical degrees; the liquor is transferred from the evaporating-pans to
crystallising vessels, in which it is cooled down to not less than 30°. If, by careless-
ness, the temperature should fall below 30°, the chloride of potassium crystals
become mixed with a layer of carbonate of soda. The liquor at a temperature of
30°, and having a density of 42° B., is again transferred to evaporating-pans, each
capable of containing 20 hectolitres, and evaporated
In winter to a sp. gr. of 1°494 (=48° B.), and
In summer to a sp. gr. of 1°51 (= 49° B.)
CARBONATE OF POTASSA.
129
By this operation sodic carbonate separates, the first and purer portions of which
are of 82 alkalimetrical degrees, and the last of 50° only. After the separation of
the salt, the remaining liquor is poured into small crystallising vessels, each capable
of holding 2 hectolitres, and having been left standing for some time, yields in´
each vessel about 130 kilos. of a crystalline salt, mainly composed according to the
formula (K,CO₂+Na₂CO₂+12H,O). The remaining mother-liquor, when evapo-
rated to dryness and calcined, yields a semi-refined potash, tinged with red by oxide
of iron. This product is again lixiviated with water, and the liquor having been
concentrated to 1.51 to 1*525 sp. gr. (= 49° to 50° B.), deposits a large quantity of
sulphate of potassa and carbonate of soda. The mother-liquor having been again
evaporated and calcined, yields a potash consisting in 100 parts of—
Carbonate of potassa
Carbonate of soda
Chloride of potassium and sulphate of potassa
91'5
5'5
3'0
ΙΟΟ Ο
The carbonate of soda possessing a strength of 80 to 85 alkalimetrical degrees is
refined by being washed with a very concentrated aqueous solution of sodic carbonate,
and thus brought to a strength of fully 90 alkalimetrical degrees.
The sulphate of potassa, chloride of potassium, and the double salt of the two
carbonates, are purified and re-crystallised. The following analyses exhibit the
composition of refined potash obtained from beet-root sugar molasses:
α.
b.
C.
Carbonate of potassa
88.73
94'39
89*3
Carbonate of soda
6'44
traces
5.6
Sulphate of potassa..
2°27
0'28
2*2
Chloride of potassium
I'00
2.40
I'5
Iodide of potassium
0'02
O'II
Water
I'39
1'76
Insoluble substances
O'12
a and b are from Waghäusel in Baden; c is doubly refined French potash. The
crude potash from beet-root sugar works, a product not to be confused with salin,
is composed as follows:
a.
b.
C.
d.
e.
Carbonate of potassa
53'9
79°0
76'0
43'0
32.9
Carbonate of soda
23'I
14'3
16.3
17'0
18.5
Sulphate of potassa
Chloride of potassium..
2.9
19'6
3'9
I'19
4.7
14 '0
2.8
4*16
18.0
16.0
a is French product; b, from Valenciennes; c, from Paris; d, Belgian; e, from
Magdeburg, Prussia.
Potassa Salts from
Sea-weeds.
VI. Potassa salts are obtained in large quantities from various
sea-weeds, as a by-product of the manufacture of bromine and iodine. The three
following methods are employed for this purpose :
a. The old calcination method, consisting in a complete reduction of the weeds to
ash, and the methodical lixiviation of that product, so as to obtain various salts by
crystallisation.
b. The carbonisation, or Stanford's method, consisting in the dry distillation of
the weeds to convert them into a carbonaceous mass, afterwards lixiviated, while
10
130
CHEMICAL TECHNOLOGY.
products are simultaneously obtained, the sale of which considerably lessens the cost
of the preparation of the potassa salts.
c. A third mode of treatment, that of Kemp and Wallace, consisting in boiling the
weeds with water, evaporating the solution, and carefully incinerating the residue.
The oldest method is still the most generally employed in France, on the coasts
of Brittany and Lower Normandy, especially in the neighbourhood of Brest and
Cherbourg, and in Scotland and Ireland.
The process is mainly conducted as follows:-After drying in the air, the plants are
incinerated, the result of which is the formation of a black semi-fused mass, which
in France is termed Varech or Fraie, and in England and Scotland is known as kelp.
A distinction is made between the kelp obtained by the incineration of the weeds,
Fucus serratus and Fucus nodosus, found on rocks near the sea coast, and the kelp
obtained from the plant botanically known as Laminaria digitata, thrown upon the
coast during the storms. The latter is richer in potassa salts, but contains much
less iodine; it is found plentifully on the western coast of Scotland and Ireland,
while on the eastern coast of the British Isles the other weed is the chief source of
kelp, having an average composition of:-
Insoluble matters ..
Sulphate of soda
Chloride of potassium
Chloride of sodium
Iodine
Other salts
•
:
:
•
57'000
10'203
13'476
16.018
0.600
•
2.703
100'000
The best kelp met with in commerce is that from the island of Rathlin, the value
at Glasgow amounting to £7 10s. to £10 10s. per ton of 223 cwts.; while Galway kelp
is valued at only £2 or £3 per ton, owing to the large quantity of salt it contains.
22 tons of moist sea-weed yield :—
Medium kelp..
Chloride of potassium..
Sulphate of potassa
•
I ton.
5 to 6 cwts.
3 cwts.
The Scotch mode of treating kelp is briefly the following:-The material is
first broken into small lumps, and put in large iron cauldrons, hot water being
added to exhaust all the soluble matter. This operation follows the method of
the manufacture of soda from common salt, to be presently considered. The water is
first made to act upon nearly exhausted kelp, and at last with quite fresh kelp,
until a liquid is produced marking 36° to 40° Twaddle=1*18 to 1'20 sp. gr. The
insoluble residue contains chiefly silica, sand, carbonate of lime, carbonate of
magnesia, its sulphates and phosphates, and particles of charcoal, and is used for
bottle-glass manufacture. The liquor from the kelp is evaporated in large cast-iron
semi-globular cauldrons by the direct action of a coal fire, and contains chiefly
chloride of potassium, a comparatively small quantity of chloride of sodium, sulphate
and carbonate of potassa, carbonate of soda, some iodide of potassium, sulphuret of
potassium, and dithionite of potassium and sodium. The mode of separating these
salts from each other is based upon their varying solubility in water, and is therefore
conducted by alternate evaporation and cooling. As the sulphate of potassa is
·
CARBONATE. OF POTASSA.
131
the least soluble, it falls to the bottom of the cauldron during the first evaporation,
and is collected by the workmen by means of perforated ladles, and brought into the
trade as plate sulphate. After this salt has been collected the liquid is run
into coolers, in which the greater bulk of the chloride of potassium crystallises; the
mother-liquor from these crystals is again transferred to the evaporator, and by
the continued application of heat, and consequent concentration of the liquid, the
common salt is separated. It should be borne in mind that common salt is scarcely
more soluble in hot than in cold water, while the solubility of most other salts
is greatly increased by a higher temperature; it is therefore possible to push
the evaporation and concentration to the point of incipient precipitation of the
chloride of potassium, the common salt being then ladled out of the cauldron,
and the liquid again run into the coolers in order to obtain another deposit of
chloride of potassium, always more or less contaminated with common salt. This
operation is repeated four times; the first crop of chloride of potassium contains
from 86 to 90 per cent. of this salt, the remainder is chiefly sulphate of potassa; the
second and third crop yield a very pure salt, 96 to 98 per cent. of chloride of
potassium; the fourth crop contains some sulphate of soda mixed with the chloride
of potassium. The liquor left after the fourth crystallisation having a sp. gr.
1*38 = 66° to 76º Twad., and containing among other compounds sulphate of soda,
sulphurets and hyposulphites of the alkalies, alkaline carbonates, and iodide of
potassium, is not submitted to further evaporation, but having been poured into
shallow vessels placed in the open air is mixed with dilute sulphuric acid, sulphu-
retted hydrogen and carbonic acid gases being largely evolved, while in consequence
of the decomposition of the polysulphurets and hyposulphites, a thick foam of pure
sulphur appears on the surface of the liquid. This sulphur is ladled off, and after
having been washed on filters and dried, is sold. Almost as soon as the evolution of
gas ceases, there is added to the liquid more sulphuric acid and some manganese,
and the mixture treated for the preparation of iodine (quod vide). In order to guard
against loss of valuable substances by volatilisation during the crude and imperfect
mode of incineration, it has been tried to simply carbonise the weeds (Stanford's
method). The weeds are first dried and strongly pressed into the shape of peat
blocks; these are submitted to dry distillation in retorts arranged similarly to those
in gas-works. The products of the dry distillation collected in the usual manner
contain in 100 parts of fresh weed:-
68.5 to 72°5 parts of Ammoniacal liquor,
4'0
7.0 to 7:5
2.0 to 2.5
>>
""
""
Tar,
Carbonised weed, or coke-weed,
Illuminating gas.
I'33 to
The coke contains 33 per cent. carbon, the remainder consisting of alkaline and
earthy salts; the volatile products of the distillation are treated for paraffin,
photogen, acetic acid, and ammoniacal salts, the gas being used for lighting
purposes. Although Mr. Stanford's mode of treatment is undoubtedly rational,
there are difficulties in its practical execution which have prevented its adoption in
Scotland as well as in France. The quantity of potash salts obtained from sea-
weeds in the year 1865 amounted, according to M. Joulin, to a total of 2,700,000
kilos., of which the United Kingdom produced 1,200,000 kilos., the remainder
being produced by France.
Since the production of chloride of potassium at Stassfurt and Kalucz has
132
CHEMICAL TECHNOLOGY.
become so extensive, the production of potassa salts from sea-weeds is of little
consequence.
Potassa Salts from Suint. VII. The fact is well known that sheep while browsing
abstract a considerable amount of potassa, which, after having passed into the blood
and tissues, is sweated through the skin, and deposited on the wool as suint.
Professor Chevreul's researches have proved that suint constitutes nearly the third
part of the weight of crude merino wool, while the soluble portion of the suint
consists of the potassa salts of a fatty acid, potassic sudorate (suintate de potasse).
According to Messrs. Reich and Ulbricht, the fatty acids of suint are compounds of
oleic, stearic, and probably palmitinic acids. The better wool contains more suint
than the coarser kinds; on an average the quantity of suint amounts to 15 per cent
of the weight of the fleece.
Since the year 1860, and based upon the researches of MM. Mauméne and
Rogelet, the manufacture of potash salts from the wash-water of the crude wool has
become, in the centres of the French woollen manufacture (Rheims, Elbœuf, Four-
mies) an industrial branch. The wash-water is valued according to its degree of
concentration; 1000 kilos. of wool yielding a liquid which, according to M. Chan-
delon, has a sp. gr. of 1·03, is paid for at the rate of 5 francs 48 cents.; at a sp. gr.
of 1'05, at the rate of 10 francs 45 cents. ; sp. gr. 1·25, 18 francs 47 cents. The
liquid is evaporated to dryness, the carbonaceous residue put into gas retorts, and
heated to redness, the result being the formation of carburetted hydrogen gas and
ammonia, which having been eliminated, the gas is used for illuminating purposes.
The coke left in the retorts is lixiviated with water to obtain the soluble salts,
chloride of potassium, carbonate and sulphate of potassa, which are separated
from each other by methods already described.
The residue left after the lixiviation with water contains earthy matter mixed with
charcoal so very finely divided that it can be used as black paint. According to
MM. Maumené and Rogelet, a fieece weighing 4 kilos. contains 600 grms. of suint,
capable of yielding 198 grms. of pure carbonate of potassa; according to M. Fuchs,
however, the quantity of suint only amounts to 300 grms., containing—
Sulphate of potassa
Carbonate of potassa..
Chloride of potassium
Organic matter
· •
7'5 grms. =
133'5
""
2.5 per cent.
44'5"
""
•
9'0
150'0
""
""
3.0 ??
50'0"
""
""
300'0
100.0
""
It appears that the woollen industry of Rheims, Elbœuf, and Fourmies consumes
annually 27 million kilos. of wool, the produce of 6,750,000 sheep. According to
MM. Maumené and Rogelet this quantity of wool will yield 1,167,750 kilos. of
potash, representing a money value of £80,000 to £90,000. According to M. P. Havrez,
at Verviers, Belgium, suint is more advantageously worked up for the manufacture of
carbonate of potassa and yellow prussiate of potassa than for carbonate of potassa
alone. Suint has been recently (1869) chemically investigated by MM. Märker and
Schulze (see Journ. für Prakt. Chemie, vol. 103, pp. 193-208). It is clear that
the production of potash from the wash-water of sheep's wool can only be carried out
in the centres of woollen industry; the sheep-farmers will always do better to return
the wash-water and potash compounds it contains to the soil from which the animals
have taken it. In an industrial point of view the extensive importation of foreign
CARBONATE OF POTASSA.
133
wool, especially from Australia and the Cape, is of great importance. In 1868 there
were imported into the United Kingdom from those countries 63 million kilos. of
wool, containing one-third of its weight of suint, from which between 7 and 8 kilos.
pure potash could have been obtained, representing a money value of about £260,000.
Preparation of Purified Potash.—The potash formerly obtained by the lixiviation
of wood-ash was mainly a mixture of carbonate, sulphate of potassa, and chloride
of potassium, the value of each of these salts being of course very different. At the
present time, in consequence of the production of pure carbonate of potassa from
vinasse, it has become necessary to treat the crude liquor obtained by the
lixiviation of wood-ash methodically, so as to obtain the salts separately in as pure
a state as possible.
The carbonate of potassa used in chemical and pharmaceutical laboratories was
formerly, obtained by the ignition of cream of tartar or a mixture of that salt with
nitre, as well as by the ignition of acetate of potassa; at the present time it is pre-
pared by the careful ignition of nitrate of potassa with an excess of charcoal, or by
the ignition of bi-carbonate of potassa. In England carbonate of potassa is manu-
factured on the large scale, the pure salt being used in the manufacture of flint-
glass, this glass owing its great superiority and perfect want of colour to the
application of very pure materials in its manufacture. The preparation is pure
crystallised carbonate of potassa, containing from 16 to 18 per cent. water, equal to
somewhat less than 2 molecules, the second molecule being partly expelled by the
heat applied in the manufacture. This salt is met with in the trade in small
cubical crystals; the raw material used in its preparation is American pearl-ash,
which, after having been mixed with sawdust for the purpose of converting the
caustic alkali and sulphuret of potassium into carbonate of potassa, is ignited and
fused in a reverberatory furnace, constructed like those used in the manufacture of
soda. When cold the fused mass is treated with water, and the clear liquor having
been decanted from the sediment, is evaporated to dryness in a reverberatory furnace;
the greyish-black mass thus obtained is again lixiviated with water, and the opera-
tion repeated. The white saline mass from the third ignition is again dissolved in
water, and gently evaporated until the sulphate of potassa crystallises out; the
mother-liquor left is next evaporated until a sample yields on cooling a salt of the
composition mentioned above. If this salt is further ignited all the water is
expelled, and a dry white granular mass left. The specific gravity of carbonate of
potassa solutions at 150 is, according to Dr. Gerlach—
Percentage.
Sp. gr
Percentage.
Sp. gr.
I
I'009
30'000
I'3010
2
1'018
35'000
1*3580
4
I'036
40'000
1'4180
5
I'045
45'000
I 4800
ΙΟ
I'092
50'000
I'5440
15
I'141
51'000
I'5570
20
I'192
52'000
I'5704
25
I 245
52'024
I'5707
Caustic Potassa.
Preparation of Caustic Potassa.-Caustic potassa, hydroxide of
potassium, KHO, consists in 100 parts of 83'97 of potassa or dry oxide of potassium,
and 16'03 of water. Caustic potassa is prepared on the large scale in England.
134
CHEMICAL TECHNOLOGY.
The raw material for this preparation is always a crude carbonate of potassa
obtained from chloride of potassium, carnallite from Stassfurt, vinasse, or any
other source. The crude carbonate is lixiviated with water, and the liquor rendered
caustic with quick-lime. A more advantageous method of preparing caustic
potassa is to mix sulphate of potassa with limestone and small coal, in sufficiently
large quantities, and to ignite this mixture in a furnace. The crude material is,
after cooling, lixiviated with water at 500, yielding at once raw caustic potassa
liquor, which does not require any further addition of lime. The liquor is put into
a steam-boiler and evaporated to a sp. gr. = 125; it is next evaporated to dryness
in open pans, the foreign salts which separate being removed. Caustic potassa is
employed for the conversion of soda-saltpetre into potassa-saltpetre, and with
caustic soda for the manufacture of oxalic acid from sawdust. The following
reactions, yielding caustic potassa, deserve a brief notice:-1. Decomposition of sul-
phate of potassa by means of caustic baryta. 2. Conversion of chloride of
potassium into silico-fluoride of potassium, and decomposition of that salt by means
of caustic lime. 3. Ignition of potassic nitrate with thin sheet-copper. The fol-
lowing table exhibits the quantity of potassa contained in solutions of that
substance of varying specific gravity :-
Sp. gr.
I'06
Degrees Baumé.
Percentage of potassa.
9
4'7
I'II
15
9'5
I'15
19
13.0
I'19
24
16:2
I'23
28
19'5
1.28
32
23'4
1*39
4I
32'4
1'52
50
42'9
I'60
53
46.7
1'68
57
51°2
SALTPETRE, NITRATE OF Potassa.
(KNO3 = 101°2. In 100 parts, 46′5 parts potassa, and 53'5 parts nitric acid.)
Saltpetre. This salt is to some extent a native as well as a chemical product. The
well-known flocculent substance often observable on walls, especially those of
stables, is composed in a great measure of nitrates; a similar phenomenon is seen
in subterranean excavations, and even in many localities the surface of the soil is
covered with an efflorescent saline deposit, consisting largely of nitrate of potassa.
These deposits are most common in Spain, Hungary, Egypt, Hindostan, on the
banks of the Ganges, in Ceylon, and in some parts of South America, as at Tacunga
in the State of Ecuador; while in Chili and Peru nitrate of soda, so-called Chili
saltpetre, is found in very large quantities under a layer of clay, the deposit
extending over a tract of land some 150 miles in length.
Occurrence of Native Although native saltpetre is met with under a variety of conditions,
Saltpetre. they all agree in this particular, that the salt is formed under the
influence of organic matter. As already stated, the salt covers the soil, forming an
efflorescence, which increases in abundance, and which if removed has its place supplied
in a short time. In this manner saltpetre, or nitre as it is sometimes called, is obtained
from the slimy mud deposited by the inundations of the Ganges, and in Spain from the
lixiviation of the soil, which can be afterwards devoted to the raising of corn, or arranged
SALTPETRE, NITRATE OF POTASSA.
135
in saltpetre beds for the regular production of the salt. The chief and main condition
of the formation of saltpetre, which succeeds equally in open fields exposed to strong
sunlight, under the shade of trees in forests, or in caverns, is the presence of organic
matter, viz., Humus, inducing the nitre formation by its slow combustion; the collateral
conditions are dry air, little or no rain, and the presence in the soil of a weathered
crystalline rock containing feldspar, the potassa of which favours the formation of the
nitrate of that base. All the known localities where the formation of nitre takes place
naturally, including the soil of Tacunga, formed by the weathering of trachyte and
tufstone, are provided with feldspar. The nitric acid is due to the slow combustion of
nitrogenous organic matter present in the humus, it having been proved that the nitric
acid constantly formed in the air in enormously large quantities by the action of
electricity and ozone, as evidenced by the investigations of MM. Boussingault, Millon,
Zabelin, Schönbein, Froehde, Böttger, and Meissner, has nothing whatever to do with
the formation of nitre in the soil, a fact also supported by Dr. Goppelsröder's discovery
of the presence of a small quantity of nitrous acid in native saltpetres.
Mode of obtaining
Saltpetre. The mode of obtaining saltpetre in the countries where it is naturally
formed is very simple, consisting in a process of lixiviation with water, to which
frequently some potash is added for the purpose of decomposing the nitrate of lime
occurring among the salts of the soil, the solution being evaporated to crystallisation.
Soils yielding saltpetre are termed Gay earth or Gay saltpetre. The process by
which nitrate of potassa is naturally formed is imitated in the artificial heaps
known as saltpetre plantations, formerly far more general than at the present
time, it having been found that the importation of Indian saltpetre, and the
manufacture of nitrate of potassa by conversion from nitrate of soda, are cheaper
sources. Thus, saltpetre beds are to be met with only under peculiar conditions, as,
for instance, in Sweden, where all landed proprietors are required to pay a portion
of their taxes in saltpetre.
The mode of making these plantations may be briefly described as follows:-Materials
containing much carbonate of lime-for instance, marl, old building rubbish, ashes, road
scrapings, stable refuse, or mud from canals-is mixed with nitrogenous animal matter,
all kinds of refuse, and frequently with such vegetable substances as naturally contain
nitrate of potassa, such as the leaves and stems of the potato, the leaves of the beet,
sunflower plants, nettles, &c. These materials are arranged in heaps of a pyramidal
shape to a height of 2 to 2 metres, care being taken to make the bottom impervious to
water by a well puddled layer of clay, the heap being in all directions exposed to the
action of the atmosphere, the circulation of which is promoted through the heap by
layers of straw. The heap is protected from rain by a roof, and at least once a week
watered with lant (stale urine). The formation of saltpetre of course requires a considerable
length of time, but, when taught by experience, the workmen suppose a heap ripe, the
watering is discontinued, the salt containing saltpetre soon after efflorescing over the
surface of the heap to 6 to 10 centims. in thickness; this layer is scraped off, and the
operation repeated from time to time until the heap becomes decayed and has to be
entirely removed. In Switzerland saltpetre is artificially made by many of the farmers,
simply by causing the urine of the cattle, while in stable in the winter time, to be
absorbed by a a calcareous soil purposely placed under the loose flooring of the stables,
which are chiefly built on the slope of the mountains, so that only the door is level
with the earth outside, the rest of the building hanging over the slope, and being supported
by stout wooden poles; thus a space is obtained, which, freely admitting air, is filled
with marl or other suitable material. After two or three years this material is removed,
lixiviated with water, mixed with caustic lime and wood ash, and boiled down. The liquor
having been sufficiently evaporated, is decanted from the sediment and left for crystalli-
sation; the quantity of saltpetre varying from 50 to 200 lbs. for each stable.
Treatment of the Ripe
Saltpetre Earth.
The crude salt from the heaps is converted into potassic nitrate
by the following processes :-a. The earth is lixiviated with water, this operation
being known as the preparation of raw lye. b. The raw lye is broken, that is to
say, it is mixed with a solution of a potash salt in order to convert the nitrates of
magnesia and lime present into nitrate of potassa. c. Evaporation of this liquor
to obtain crude crystallised saltpetre. d. Refining the crude saltpetre.
•
136
CHEMICAL TECHNOLOGY.
Raw Lye.
Preparation of The ripe earth is lixiviated to obtain all the valuable soluble matter,
it being expedient to use as little water as possible in order to save fuel in the
subsequent evaporation, for which the liquor is ready when it contains from 12 to
13 per cent. of soluble salts.
Raw Lye.
Breaking up the The raw lye, sometimes known as soil water, contains the nitrates
of lime, magnesia, potassa, soda, the chlorides of calcium, magnesium, and
potassium; also ammoniacal salts and organic matter of vegetable as well as of
animal origin. In order to convert the nitrates of lime and magnesia into nitrate
of potassa, the raw lye is broken up as it is termed, that is to say, there is added to
it a solution of 1 part potassic carbonate in 2 parts water:-
Nitrate of lime, Ca(NO3)2
|
Nitrate of magnesia, Mg(NO3)2 yield
Carbonate of potassa, 2K2CO3
Nitrate of potassa, 4KNO3.
Carbonate of lime, CaCO3.
Carbonate of magnesia, MgCO3.
The chlorides of calcium and magnesium are also decomposed, being converted
into carbonates, while chloride of potassium is formed. The addition of the solution
of potassa to the raw lye is continued as long as a precipitate is formed; in order,
however, to have some approximative idea of the quantity of carbonate of potash
which may be required, a test experiment is made with litre of the raw lye.
Sometimes sulphate of potassa is used instead of the carbonate, but in that case
the magnesia salts of the raw lye have first to be decomposed by milk of lime, an
operation which has to be followed by the evaporation of the fluid. If, after this,
sulphate of potassa is added, sulphate of lime is precipitated—
[Ca(NO3)2+K2SO4 = 2KNO3+CaSO4].
When chloride of potassium is used for the decomposition of raw lye, the salts of
magnesia are first removed by the addition of milk of lime; and the clear super-
natant fluid having been decanted from the sediment, there is added a mixture of
equal molecules of chloride of potassium and sulphate of soda, the result being the
formation of gypsum, while the sodic nitrate generated exchanges with the chloride
of potassium, carrying over to the latter the nitric acid, and taking up the chlorine
to form common salt.
Raw Lye.
Boiling down the The clarified raw lye decanted frem the precipitate of the earthy
carbonates consists of a solution in
FIG. 64.
D
C
TA PAKEITHIN, PIEZIUA RAPEDA MARITES ABET
B
AMURES, TENTA
VECHBAU, TALA
PARER VEHITTLE BEA
which there are present the chlorides of
potassium and sodium, nitrate of potassa,
carbonate of ammonia, excess of potassic
carbonate, and colouring matter. The boiling
down of this liquid is effected in copper
cauldrons, Fig. 64, so set in the furnace as
to admit of the circulation of the hot air and
smoke from the fire-place, passing by c c
below the heating pan, and thence by g into
the chimney. In some works this waste
heat is utilised in drying the saltpetre flour.
As the bulk of the fluid in the cauldron
decreases by evaporation, fresh lye enters by
means of a pipe and tap from the pan, D.
About the third day the alkaline chlorides begin to be deposited, and the workmen
have then to take great care to prevent these salts from becoming what is technically

SALTPETRE, NITRATE OF POTASSA.
137
termed burnt, which might give rise to serious explosions, and for this purpose the
liquid is stirred with stout wooden poles. After each stirring the loose saline matter
is removed from the boiling liquid by means of perforated copper ladles. However,
as a hard deposit is always formed, a peculiar arrangement exhibited in Fig. 64,
consisting of a shallow vessel, m, suspended by a chain, k, and weighted with a piece
of stone, is lowered into the middle of the cauldron to about 6 centims. from the
bottom, the object being to catch the solid particles, which would, when aggregating,
form an incrustation, previously to their reaching the bottom of the vessel; and as
no ebullition takes place at m, the particles once deposited remain there, and can be
readily removed by raising the dish out of the cauldron, and emptying it into a box
placed over the cauldron, the bottom of the box being perforated to admit of any
liquor which may have been raised with the solid salt to return again to the
cauldron. The deposit thus removed consists chiefly of gypsum and carbonate of
lime.
When a portion of the impurities contained in the boiling liquid have been
removed, the raw lye still frequently contains some chloride of sodium, as this salt is
not, as is the case with nitre, more soluble in boiling than in cold water. The
abundant crystallisation of the saltpetre is a sign that the lye has been sufficiently
evaporated; in order, however, to prove this, a small sample is taken, and if on
cooling the nitre crystallises so that the greater part of the sample becomes a solid
mass, the liquid is run into tanks and left for 5 or 6 hours, during which time
impurities are deposited, and the liquid rendered quite clear. As soon as the
temperature of the liquid has fallen to 60°, it is poured into copper crystallisation
vessels; after a lapse of 24 hours the crystallisation is complete, and the mother-
liquor being separated from the salt is employed in a subsequent operation.
Refining the
Crude Saltpetre.
The crude saltpetre is yellow-coloured, and contains on an average
some 20 per cent. of impurities, consisting of deliquescent chlorides, earthy salts, and
water. The object to be attained by the refining is the removal of these substances.
At the present day a large portion of the refined saltpetre met with in commerce is
obtained by the refining of the crude saltpetre imported from India. It may be noted
that this importation is steadily increasing, there being, in 1860, 16,460,300 kilos.,
and in 1868, 33,062,000 kilos. of the salt brought to England; and, indeed, the
production of saltpetre from natural sources in Europe is now limited to very few
and unimportant localities.
The method of refining saltpetre is based upon the fact that nitrate of potassa is
far more soluble in hot water than are the chlorides of sodium and potassium.
600 litres of water are poured into a large cauldron, and 24 cwts. of the crude saltpetre
are added at a gradually increasing temperature; as soon as the solution boils,
36 cwts. more crude saltpetre are added. Supposing the crude nitre to contain
20 per cent. of alkaline chlorides, the whole of the nitre will be dissolved in this
quantity of water, while a portion of the chlorides will remain undissolved even at
the boiling-point. The non-dissolved salt is removed by a perforated ladle, and the
scum rising to the surface of the boiling liquid by the aid of a flat strainer. The
organic matter present in the solution is removed by the aid of a solution of glue—
from 20 to 50 grms. of glue dissolved in 2 litres of water are taken for each hundred-
weight of saltpetre. In order that the saltpetre may crystallise, the quantity of
water is increased to 1000 litres, and as soon as this water is added the organic
matter entangled in the glue rises as a scum to the surface and is removed. The
138
CHEMICAL TECHNOLOGY.
operation having progressed so far, and the liquid being rendered quite clear, it is
kept at a temperature of 88° for about twelve hours, and then carefully ladled into
copper crystallising vessels, constructed with the bottom a little higher at one end
than at the other. The solution would yield on cooling large crystals of saltpetre,
but this is purposely prevented by keeping the liquid in motion by means of stirrers,
as as to produce the so-called flour of saltpetre, which is really the salt in a finely-
divided state. This is next transferred to wooden boxes termed wash-vessels, 10 feet
long by 4 feet wide, provided with a double bottom, the inner one being perforated;
between the two bottoms holes are bored through the sides of the vessel and when
not required plugged with wooden pegs. Over the flour of saltpetre contained in
these wooden troughs, 60 lbs. of a very concentrated solution of pure nitrate of
potassa are poured, and allowed to remain for two to three hours, the plugs being
left in the holes. The plugs are then removed, the liquor run off, the holes again
plugged, and the operation twice repeated, first with a fresh 60 lbs., and next with
24 lbs. of the solution of nitrate of potassa, followed in each case by an equal quan-
tity of cold water. The liquors which are run off in these operations are of course
collected, the first being added to the crude saltpetre solution, while the latter, being
solutions of nearly pure nitre, are again employed. The saltpetre is next dried at
a gentle heat in a shallow vessel, sifted, and packed in casks.
of Potas-a from
Chili-saltpetre.
Preparation of Nitrate During the last twenty years the preparation of nitrate of
potassa from Chili-saltpetre has become an important branch of
manufacturing industry. The product obtained by any of the following processes is
called "converted-saltpetre," to distinguish it from the preceding preparation. The
method of procedure may be one of the following :—
1. The nitrate of soda is decomposed by means of chloride of potassium-
100 kilos. of sodic nitrate
1191 kilos. potassa nitrate.
68.8 kilos. common salt.
87·9 kilos. of potassium chloride yield
MM. Longchamp, Anthon, and Kuhlmann first suggested this mode of prepara-
tion, which is now generally used on the large scale, as the decomposition of both
salts is very complete, and as the common salt as well as the saltpetre can be utilised.
The chloride of potassium is obtained by the decomposition of carnallite, or by means
already mentioned.
Equivalent quantities of nitrate of soda and of chloride of potassium are dissolved
in water contained in a cauldron of some 4000 litres cubic capacity. As the nitrate
of soda of commerce (Chili-saltpetre) does not, as regards purity, vary very much
from 96 per cent., some 7 cwts. are usually taken, while of the chloride of potassium,
which varies in purity from 60 to 90 per cent., a quantity is taken corresponding, as
regards the amount of pure chloride, to the quantity of nitrate of soda. The chloride
of potassium is first dissolved, the hot solution being brought to a sp. gr. = 1*2 to 1*21,
next the nitrate of soda is added, and the liquid brought, while constantly heated,
to a sp. gr.=1'5. The chloride of sodium continuously deposited is removed by
perforated ladles, and placed on a sloping plank so that the mother-liquor may flow
back into the cauldron, care being taken to wash this salt afterwards, so as to
remove all nitrate of potassa, the washings being poured back into the cauldron.
When the liquid in the cauldron has been brought to 1.5 sp. gr. —an aqueous solu-
tion of nitrate of potassa at 15°, with a sp. gr.=1*144, contains 21°074 per cent..of that
salt—the fire is extinguished, the liquid left to clear, the common salt still present
carrying down all impurities, and when clear it is ladled into crystallising vessels,
SALTPETRE, NITRATE OF POTASSA.
139
which being very shallow, the crystallisation is finished in twenty-four hours. The
mother-liquor having been run off, the crystals are thoroughly drained and covered
with water, which is left in contact with the salt for some seven to eight hours, and
then run off; this operation is repeated during the next day; the mother-liquor and
washings are poured back into the cauldron at a subsequent operation.
2. Nitrate of soda is first converted into chloride of sodium by means of chloride
of barium, nitrate of baryta being formed, and in its turn converted into nitrate of
potassa by the aid of sulphate of potassa :-
a. 85 kilos. of nitrate of soda
122 kilos. of chloride of barium yield (1305 kilos. nitrate of baryta.
B. 1305 kilos. of nitrate of baryta
require for conversion into
nitrate of potassa
58.5 kilos. of common salt.
87.2 kilos. of potassic sulphate,
or
69.2 kilos. of potassic carbonate.
When sulphate of potassa is used, permanent-white, baryta-white, or sulphate of
baryta is obtained as a by-product, while if carbonate of potassa is used, carbonate
of baryta remains, and of course may be readily re-converted into chloride of barium.
In order to estimate the advantages of either process, the following points must be
kept in view :-a. Taking into consideration that it is profitable to convert native
carbonate of baryta into chloride of barium-for instance, by exposing witherite to
the hydrochloric acid fumes produced in alkali works by the decomposition of salt-
and to precipitate an aqueous solution with dilute sulphuric acid to obtain permanent-
white, it may be inferred that it will also pay to obtain it as a by-product. b. Not-
withstanding the complication of this process, it is advantageous as producing a far
purer nitrate of potassa.
3. Nitrate of soda is converted by means of potash into the nitrate of that base,
pure soda being obtained as a by-product :-
85 kilos. Chili-saltpetre
(1012 kilos. of potassic nitrate.
53 kilos. of soda (calcined).
69'2 kilos. carbonate of potassa} yield
This mode of manufacturing saltpetre was first introduded into Germany during the
Crimean War (1854-55) by M. Wöllner, of Cologne, who established large works to
prepare saltpetre in this way, and very soon after, during the continuance of the war,
five other manufactories of potash-saltpetre had been established on this method.
In 1862 the production amounted to 7,500,000 lbs. of potash-saltpetre, the carbonate
of potassa required being obtained from beet-root molasses, the soda resulting as a
by-product being even superior to that produced by Leblanc's process.
4. Nitrate of soda being decomposed by caustic potassa yields potassic nitrate and
caustic soda.
According to M. Lunge's description, this process, first suggested by MM. Land-
mann and Gentele, afterwards modified by M. Schnitzer, and practically applied by
M. Nöllner, is carried on in Lancashire in the following manner:-There is added to
a caustic potash lye of 1.5 sp. gr., containing about 50 per cent. of dry caustic potassa,
an equivalent quantity of nitrate of soda, and the whole, after a short time, crystal-
lised. The nitrate of potassa having been separated from the mother liquor, that
fluid, the density of which has been greatly decreased by the reaction, is by evapo-
ration again brought to its former density, and yields on cooling another crop of
crystals of potash-saltpetre. Usually there then only remains a solution containing
caustic soda with saline impurities; sometimes, however, a third crop of crystals is
obtained. The deposit during the evaporation is chiefly carbonate of soda derived
140
CHEMICAL TECHNOLOGY.
库
​from the chloride of sodium contained in the potassium chloride from which the
caustic potassa is made, this chloride being also converted into carbonate. The
small quantities of undecomposed chlorides of potassium and sodium and sulphate of
lime are retained in the mother-liquor, which is evaporated to dryness and ignited,
yielding a dry caustic soda of a bluish-colour. The crystallised nitrate of potassa
is now carefully refined to remove all impurities to about o'i per cent. of chloride of
sodium, converted into saltpetre-flour, and treated as already described. Notwith-
standing that the various operations have been carried on in iron vessels, the salt
does not contain any of this metal, nor is the colour in any way affected. The flour
is dried in a room 2 metres wide by 5 metres in length, built of brick-work, similarly
to the chloride of lime rooms, and having a pointed arched roof 2 metres in height.
The saltpetre-flour is spread on a wooden floor, under which extends a series of hot-
air pipes, keeping the temperature at 70°, and very rapidly effecting the drying.
30
30
Testing the Saltpetre. If, when perfectly pure, saltpetre is carefully fused, and allowed
to cool, it becomes a white mass, exhibiting a coarsely radiated fracture; even so
small a quantity as th of chloride of sodium causes the fracture to appear somewhat
granular; with th the centre is not at all radiated, and is less transparent; and
with th the radiation is only slightly perceptible at the edges of the fracture.
Nitrate of soda has the same effect. This method of testing the purity of nitre, due
to M. Schwartz, is employed in Sweden, where every landowner pays a portion of
his taxes in saltpetre of a specified degree of purity. A great number of methods of
testing saltpetre have been suggested by various authors for the purposes of the
manufacture of gunpowder, not, however, in sufficiently general use to interest the
reader. Werther's test for chlorine and sulphuric acid is by solutions of the nitrates
of baryta and silver; the silver solution is such that each division of the burette
corresponds to o·004 grm. of chlorine, and with the baryta solution to o‘002 grm. of
sulphuric acid. According to Reich's plan, o'5 grm. of dried and pulverised saltpetre
is ignited to a dull red heat, with from 4 to 6 times its weight of pulverised quartz;
the nitric acid is expelled, the loss of weight consequently indicating the quantity,
the sulphates and chlorides not being decomposed at a dull red heat. If the loss
=d, we have 1.874 d nitrate of potassa, or 1.574 d nitrate of soda.
Quantitative Estimation This method, due to Dr. A. Wagner, is based upon the fact
that when saltpetre, or any other nitrate, is ignited, access of air
being excluded, with an excess of oxide of chromium and carbonate of soda, the nitric
acid oxidises the chromic oxide according to the formula Cr₂O3+NO5=2CrO3+NO2.
76'4 parts, by weight, of oxide of chromium are oxidised to chromic acid by 54 parts
of nitric acid, or of 1 of chromic oxide by 0·7068 of nitric acid. The operation is
performed by taking from 0.3 to 0'4 grm. of the nitrate, mixing it intimately with
3 grms. of chromic oxide and 1 grm. of carbonate of soda, introducing this mixture
into a hard German glass combustion-tube, one end of which is drawn out, and a
vulcanised india-rubber tube attached to it, which is made to dip for about a quarter
of an inch into water, while to the other open end, by means of a cork and glass tube
bent at right angles, an apparatus is fitted for the evolution of carbonic acid gas,
which is made to pass through the tube before igniting it, and kept passing through
all the time until the tube is quite cool again after ignition. The contents of the
tube are placed in warm water, and after filtration the chromic acid is estimated by
Rose's method. This process of estimating nitric acid has been found to yield very
of the Nitric Acid in
Saltpetre.
accurate results.
SALTPETRE, NITRATE OF POTASSA.
141
Uses of Saltpetre. This salt is employed for many purposes, the most important
being:-1. The manufacture of gunpowder. 2 The manufacture of sulphuric and
nitric acids. 3. Glass-making, to refine the metal as it is termed. 4. As oxidant,
and flux in many metallurgical operations. By the ignition of 1 part of nitre and
2 of argol, in some cases refined argol (cream of tartar), black flux is formed consist-
ing of an intimate mixture of carbonate of potassa and finely divided charcoal. The
ignition of equal parts of saltpetre and cream of tartar gives white flux, consisting
of a mixture of carbonate of potassa and undecomposed saltpetre; both these
mixtures are often used. Black flux may also be made by intimately mixing
carbonate of potassa with lamp-black and white flux. 5. When mixed with
common salt and some sugar in the salting and curing of meat. 6. For preparing
fluxing and detonating powders. Baumé's fluxing powder is a mixture of 3 parts
of nitre, 1 of pulverised sulphur, and 1 of sawdust from resinous wood; if some
of this mixture be placed with a small copper or silver coin in a nutshell and
ignited, the coin is melted in consequence of the formation of a readily fusible
metallic sulphuret, while the nutshell is not injured. Detonating powder is a mix-
ture of 3 parts saltpetre, 2 carbonate potassa, and 1 pulverised sulphur; this powder
when placed on a piece of sheet-iron, and heated over a lamp, will explode with a
loud report, yielding a large volume of gas:
Saltpetre, 6KNO3,
Potassic carbonate, 2K2CO3,
Sulphur, 5S.
Nitrogen, 6N.
Carbonic acid, 2CO2.
Sulphate of potassa, 5K₂SO4.
7. For manure in agriculture. 8. In many pharmaceutical preparations. 9. For
the preparation of Heaton steel.
Sodic Nitrate. This salt, also known as cubical saltpetre, Chili-saltpetre, nitrate
of soda, NaNO3, containing in 100 parts 36'47 soda, and 63*53 parts nitric acid,
is found native in the district of Atacama and Tarapaca, near the port of Uquique,
in Peru, in layers termed caleche or terra salitrosa, 0°3 to 1'0 metre in thickness, and
extending over more than 150 miles, nearly to Copiapo, in the north of Chili. The
deposit chiefly consists of the pure, dry, hard salt, and is close to the surface of the
soil. It is also found in other parts of Peru mixed with sand, in some places close
to the surface of the soil, in others at a depth of 2.6 metres. Valparaiso being the
great exportation dépôt for Peru, Bolivia, and Chili, both surface and deep soil salts
are met with in tthe rade of that important port. The unrefined Chili-saltpetre is
crystalline, brown or yellow, and somewhat moist; but the salt sent to the Euro-
pean markets is commonly semi-refined by being dissolved in water and evaporated
to dryness. The composition of a sample in 100 parts is :-
Nitrate of soda..
Nitrate of soda
Chloride of sodium ..
Chloride of potassium
Sulphate of soda
Iodide of soda ..
Chloride of magnesium
Boric acid..
Water
•
:
:
•
94'03
0.31
1.52
0'54
O'92
0'29
o'96
traces
I'96
100'00
142
CHEMICAL TECHNOLOGY.
in the
Being deliquescent the salt is not employed in the manufacture of gunpowder,
but may be used for blasting powder. It is largely used for the preparation of
sulphuric and nitric acids; for purifying caustic soda; for making chlorine in the
manufacture of bleaching powders; for the preparation of arseniate of soda ;
curing of meat; glass-making; in the preparation of red-lead; in large quantities
in the conversion of crude pig-iron into steel, by Hargreaves's and by Heaton's
processes; for preparing nitrate of potassa; and for the preparation of artificial
manures and composts, it being used unmixed as a manure for grain crops.
It may be seen from the analysis of nitrate of soda quoted above that that
salt contains a small quantity of iodine, which at Tarapaca is extracted from the
mother-liquor remaining from the re-crystallisation. According to M. L. Krafft
the iodine amounts to o°59 grm. in 1 kilo. of crude nitrate; 40 kilos. of iodine being
prepared per day. M. Nöllner thinks that the formation of the nitre deposits in
Chili and other parts of South America has taken place under the influence of
marine plants containing iodine. In order to give some idea of the large and
increasing exportation of Chili-saltpetre, we quote from the published statistics,
that in 1830, 18,700 cwts., and in 1869, 2,965,000 cwts., were shipped.
Methods of Manufacturing
Nitric Acid.
NITRIC ACID.
This acid (NHO3) is generally manufactured by decomposing
nitrate of soda by sulphuric acid, and condensing the vapours set free. It is
obtained on the large scale by placing in a cast-iron vessel, A, Fig. 65, the nitrate to
be operated upon, to which is added by means of a funnel strong sulphuric acid.
The lid is replaced, and the vessel connected by means of the clay-lined tube B,
with the glass tube, c, dipping into the large stoneware flask, D, which serves the
FIG. 65.

T
B
A
a
D
D"
purpose of a receiver. This flask is connected by means of a tube, a, to a similar
vessel, D', and that to a third vessel, D", and so on, in order to completely condense
the vapours which might have escaped through the first, second, and third vessels.
The iron vessel, A, is heated by means of the fire placed in the hearth, F, the smoke
and hot gases being carried off by G H. At the outset of the operation the damper,
d, is so regulated as to shut off the lower channel, and cause the smoke and hot
gases to pass through E, heating the vessels D, D', and D", this precaution being
NITRIC ACID.
143
required to prevent their cracking by the hot acid vapours entering from A. As
soon, however, as the distillation has fairly commenced, the damper is altered to
shut off E, and pass the hot air and gases through G. The nitric acid condensed in
the first receiver is sufficiently strong for immediate use, but to facilitate the con-
densation some water has been poured through the openings b′ b″, into the other
receivers, the acid from which is weaker and known in the trade as aquafortis.
Very frequently the distillation of nitric acid is conducted in a series of glass
retorts placed on a sand-bath; there are generally two rows of retorts, the heating
apparatus being a galley oven. If the acid is to be pure, the first condensations
are collected in separate receivers, as the acid first condensed contains hydrochloric
acid due to the chlorides contained in the nitrates under operation.
The proportion of materials employed is :—
30 kilos. of Nitrate of potassa to 29 kilos. of strong sulphuric acid; or,
""
Nitrate of soda
to 14°5
""
17
The bisulphate of soda which remains may either be used for the preparation of
fuming sulphuric acid, or may be mixed with common salt, and ignited, to pro-
duce hydrochloric acid and neutral sulphate of soda, available in the preparation
of sodic carbonate.
-
The nitric acid (NHO3) resulting from the above operation is a colourless, trans-
parent fluid, having a sp. gr. of 1'55, and boiling at 80°. When diluted with water
the boiling-point is higher. An acid containing 100 parts (NHO) and 50 parts of
water boils at 129°, but if the dilution with water is carried further the boiling-point
is again lowered; consequently, when such an acid is heated above 100º the result
is that at first water with only a trace of acid distils over, and if the process be con-
tinued the boiling-point gradually increases until it reaches 130°, when there distils
over what is termed double aquafortis, sp. gr. 135 to 1'45, ordinary or single
aquafortis having a sp. gr. =1*19 to 1.25. Nitric acid, when in contact with air,
emits fumes, owing to the absorption of water from the atmosphere.
Bleaching Nitric
Acid.
The stronger acid manufactured as described is usually of a yellow
colour, due to the presence of hyponitric acid. If a colourless acid is desired, the
crude acid must be submitted to a bleaching operation, consisting of the follow-
ing:-The coloured acid is poured into large glass vessels placed (Fig. 66) in a water-
bath, heated to 80° to 90º, and left in these vessels as long as any coloured vapours
FIG. 66.

are given off. The escaping hyponitric acid is carried by means of glass or glazed
earthenware tubes either into a sulphuric acid chamber and there utilised, or into
the flue of a chimney, and thus into the air. Any hydrochloric acid present in the
nitric acid is also carried off as chlorine. In order to remove any sulphuric acid it
144
CHEMICAL TECHNOLOGY.
Acid.
is necessary to distil the nitric acid over pure nitrate of baryta, while the last traces
of hydrochloric acid can be removed by distillation over pure nitrate of silver.
Condensation of the Nitric More recently improvements have been made in the manu-
facture of nitric acid, bearing especially upon the possibility of omitting the bleach-
ing process, and a better mode of condensing the vapours of the acid. The first
point is supplied by an arrangement introduced in the manufactory of M. Chevé,
in Paris. Every practical chemist knows that the red vapours appear only at the
outset and towards the end of the distillation of the nitric acid, and it is therefore
only required to distil fractionally to obtain on the one hand a red-coloured acid,
the acidum nitroso-nitricum or acidum nitricum fumans fortissime of the pharma-
ceutists, and on the other a colourless acid, which can be forthwith delivered to the
consumer. In order to practically effect the fractional distillation, a tap of porce-
lain or hard-fired stoneware, constructed as exhibited in Fig. 67, is fixed by means
of A, in communication with the iron distilling vessel, while the tubes B and B are
connected with two different receivers. The tap is bored in such a manner, that
FIG. 67.
B
B
A
at pleasure either the communication
between A and B', or the communica-
tion between A and B, can be esta-
blished. By proper management,
therefore, it is possible to separate the
red-coloured acid entirely, and with-
out any additional expense, from the
colourless acid.


A second improvement, contrived by MM. Plisson and Devers, Paris, bears upon
the condensation apparatus, which consists in their works of a battery of ten pecu-
FIG. 68.

M
Ra
A
G
G'
B
BY H
R
FIG. 69.
L
FIG. 70.
E

liarly constructed bottles, six of which are open at the bottom and funnel-shaped,
so as to fit in the necks of large carboys, &, Fig. 68. From a cylinder not shown
in the engraving, being hidden by the wall, M, a stoneware tube is connected with
NITRIC ACID.
145
the bent glass tube, a, which communicates with one of the three tubulatures of
the first carboy, A, which serves to collect the acid, that, by the boiling over of the
mixture in the iron vessel, has been rendered more or less foul. The carboy a is pro-
vided with a small tube, T, arranged to act as a hydraulic valve in such a manner
that, when the fluid in the carboy has risen to a height of some centimetres, any
additional fluid entering A is carried off into the well-stoppered carboy A'. The
second tubulature of the carboy A is fitted with a funnel through which water flows
from the bottle F into A, thereby aiding the condensation. The acid vapours pass
through the curved glass tube F, into the carboy B, from which, as likewise from the
carboys B' and B", the condensed fluid is carried by the tube T into the carboy A".
Any vapours which escape condensation in B are carried off to c, and thence to D, a
portion of the acid being condensed in each of the vessels, and flowing back first to
B and then to A'. Any vapour not condensed in C and D is conducted by the glass
tube G, first to D', next to c", and finally to B, where condensation takes place. Any
vapours not now condensed are carried to B',C'', D'', and finally to the chimney stalk.
Thẻ Mariotte botttles F' and F' contain water, which flows into the condensing
vessels and dilutes the acid to 36" B. (=1'31 sp. gr. 42°2 per cent. N2O5). In order
to reduce any pressure arising in the vessels a' and A', a tube H, and a similar one
not represented in the cut, are connected with T and T', for the purpose of carrying
any non-condensed vapour into B', where these vapours collect.
Although this apparatus appears complicated, the working is very readily managed.
The acid vapours issuing from the distiliatory apparatus are partly condensed in the
vessel A, and thence carried to a', the vapours still uncondensed continuing their
course to B, B′, B'', the fluid there collected flowing back to the general receiver a”.
This apparatus when once well put together, has rarely to be repaired, saves much
labour, and produces a larger quantity of acid than the ordinary apparatus, this
being due to the more complete condensation; while by the ordinary method only
125 to 128 kilos. of nitric acid are obtained from 100 kilos. of nitrate, the quantity
obtained by this apparatus amounts to 132 to 134 kilos. The following brief descrip-
tion, illustrated by Figs. 69 and 70, will explain the internal construction of the
bottles and of the syphon funnel. In each of the carboys of the lowest row is
inserted a bent stoneware tube, T, Fig. 69, the opening, o, of which is outside
the bottle; a narrow space, L, admits the fluid to the interior of the tube, and it
is clear that the acid can only attain a certain height in the carboy. The syphon
funnel consists of a stoneware tube about 3 centims. in diameter, the side of which,
Fig. 70, is perforated in a longitudinal direction; any fluid therefore flowing into
this tube from E can only reach to the opening o.
Manufacture.
Other Methods of Nitric Acid The following methods, differing from that above described,
must here be mentioned; but the reader should not infer that they
are actually in practice:-1. Action of chloride of manganese (chlorine preparation
residues) upon nitrate of soda. When a mixture of these salts is heated to about 230°,
nitrous vapours (NO₂+0) are evolved, and there remains oxide of manganese, which can
be again employed in the manufacture of chlorine.
2
5MnCl₂
and
IoNaNO3
yield
{
(2MnO+3MnO),
IoNaCl,
IONO₂+0,
By causing the mixture of hyponitric acid and oxygen to come into contact with water
in the condensing apparatus nitric acid results. the excess of hyponitric acid being decom-
posed into nitric acid and deutoxide of nitrogen. If the quantity of air in the apparatus
is sufficiently large to oxidise the entire bulk of the nitrogen deutoxide into nitric acid
this process is continuous, but if there is not enough air, the deutoxide of nitrogen is
11
1.46
CHEMICAL TECHNOLOGY.
dissolved in the nitric acid, any excess of that gas escaping. From the experiments on this
process by Dr. Kuhlmann, who used clay retorts, it appears that 100 parts of nitrate of
soda yield from 125 to 126 parts of nitric acid at 35° B.; this result almost agrees with
that obtained by the ordinary process. Dr. Kuhlmann also instituted experiments with
other chlorides, viz., those of calcium, magnesium, and zinc, the result being the formation
of nitric acid and chloride of sodium with lime, magnesia, and oxide of zinc.
2. Action of certain sulphates upon alkaline nitrates. Dr. Kuhlmann has proved by a
series of experiments that the sulphates, including only those having no acid properties,
decompose the alkaline nitrates. Sulphate of manganese decomposes nitrate of soda, the
result being the formation of products similar to those when chloride of manganese is
employed; similar reactions take place when sulphate of zinc, sulphate of magnesia, and
gypsum are used for this purpose.
3. From nitrate of soda and carbon, yielding soda and nitric acid.
4. From nitrate of soda and silica or alumina, yielding nitric acid, silicate of soda and
soda.
5. From nitrate of baryta and sulphuric acid, without distillation; the nitric acid
(= 10° to 11° B.) decanted from the sulphate of baryta (permanent white) can be concen-
trated by boiling to 25° B.
Density of Nitric Acid. According to Kolb, the specific gravity of nitric acid bears to the
quantity of concentrated acid contained the following relation:
Density.
100 parts contain
Density.
100 parts contain
NHO3.
N₂05.
at 0°. at 15°C.
NHO3. N2O5.
at 0° at 15°C.
100'00
85.71
I'559 I'530
55'00 47.14
1*365 I'346
97'00
83*14
I 548
I'520
50'99
43'70
1*341
I'323
94'00
80'57
I'537 1'509
45'00
38.57
I'300
I.284
92'00
78.85
I'529
I'503
40'00
34°28
1267
I'251
91'00 78'00
1*526 I'499
33.86
29'02
I'226
I'211
90'00 77'15
I'522
I'495
30'00
25'71
I'200 1*185
85'00 72.86
I'503
1*478
25'71 22'04 I'171
I'157
80'00 68.57
I*484
I'460.
23'00 19'71
I'153
I'138
75'00
64.28
1*465
I'442
20'00
17.14
1°132
I'120
69*96 60'00
I'444
1'423
15'00
12.85
I'099
I'089
65'07 55'77 I'420
I'400
II'41
9'77
I'075
I'067
60'00 51'43 I'393
T'374
4'00
3°42
I'026
I'022
2'00
to Baumé :-
100 parts contain at
Degrees according
0°
Density.
to Baumé.
I'7I I'013 Ι'ΟΙΟ
The following table exhibits comparative data of density and degrees according
100 parts contain at
15° C.
NHO3.
N205.
NHO3.
N205.
6
I'044
6'7
5'7
7.6
6.5
7
I'052
8.0
6.9
9°0
7'7
9
1'067
IO'2
8.7
11:4
9.8
ΙΟ
I'075
II.4
9.8
12'7
10'9
15
1.116
17.6
15'1
19'4
16.6
20
I'161
24°2.
20'7
26'3
22:5
25
I'210
31°4
26'9
33.8
28.9
30
1.261
39'I
33°5
41'5
35'6
35
I'321
48'0
41'1
50'7
43'5
40
1.384
58.4
50'0
61'7
52'9
45
I'454
72°2
61'9
78.4
72°2
46
I'470
76'1
65°2
83'0
71'1
47
1*485
80°2
68.7
87'1
747
NITRIC ACID.
147
47° B. correspond to 96º Twaddle.
460
920
""
45°
880
""
43°,
84°
420
80°
>>
380
>>
>>
70°
34°,,
""
60°
29°,,
""
50⁰
""
25°,,
""
400
""
1
20⁰
200,,
""
30⁰
14º "
70,
""
200
""
100
">
Nitric acid of 1'52 sp. gr. boils at 86º
I'50
""
99º
I'45
>>
1150
""
I'42
"
1230
I'40
""
119°
135
""
1170
>>
1°30
"
113°
1'20
1080
>>
I'15
104°
Fuming Nitric Acid.
I
When in the preparation of nitric acid there is taken for 1 mole-
cule of nitrate of potassa 1 molecule of sulphuric acid, there is obtained by distilla-
tion a reddish-yellow fluid, consisting of a mixture of nitric and hyponitric acids,
known as red fuming nitric acid. When equal molecules of nitrate of potassa and
sulphuric acid are taken, only one-half of the quantity of nitric acid is expelled,
while the other half is decomposed into hyponitric acid and oxygen, the former
combining with the nitric acid, and forming the fuming nitric acid. When in the
preparation of nitric acid by the decomposition of the potassium or sodium nitrate,
two molecules of sulphuric acid are employed, all the nitric acid in these salts is
obtained, and there remains in the retort bisulphate of either base. When nitrate
of soda is employed, it is, owing to the easier decomposition of this salt by sulphuric
acid, not necessary to use exactly 2 molecules of sulphuric acid; 1.25 to 1'50 mole-
cules of that acid have been found to be practically sufficient. 100 parts of Chili-
saltpetre yield 120 to 130 parts of nitric acid at 36° B.
The red fuming nitric acid is now generally prepared by adding to the ordinary
concentrated nitric acid a substance which effects its decomposition. Sulphur
has been employed for this purpose, but starch is generally used, and, according to
M. C. Brunner's recipe, in the following manner:-To 100 parts of saltpetre,
3 parts of starch are added, and placed in a capacious retort, into which is poured
100 parts of strong sulphuric acid, sp. gr. 1.85. The distillation usually sets in with-
out the aid of heat, but towards the end of the operation the application of a gentle
heat is required. 100 parts of nitrate of potassa yield by this method about 60 parts
of fuming nitric acid. The retort in this operation should not be filled to more than
one-third of its capacity, owing to the very strong evolution of gas which takes place.
Uses of Nitric Acid. The technical application of nitric acid is based on its property of
oxidation when in contact with certain substances, the acid splitting up into deut-
148
CHEMICAL TECHNOLOGY.
oxide of nitrogen, hyponitric acid, and ozone, the latter forming with the body
which caused the decomposition of the acid either an oxide or a peculiar compound,
while the hyponitric acid, when organic substances are present capable of combining
with it, forms the nitro-compounds, nitrobenzole, nitronapthaline, nitroglycerine,
nitromannite, nitrocellulose, or gun-cotton, &c. A large number of metals are
soluble in moderately concentrated nitric acid, but the strongest acid fails to
act upon iron and lead. Proteine compounds, albumen, the skin of the hands, silk,
horn, feathers, &c., are stained yellow by nitric acid, hence the use of this acid
in dyeing silk. If the acid is in contact with these substances for any length of time,
they are completely decomposed, and partly converted into picric acid. Starch,
cellulose, and sugar are converted by the action of nitric acid into oxalic acid;
but very dilute nitric acid converts starch into dextrine, and concentrated acid
into xyloidine. Owing to the property nitric acid possesses of destroying certain
pigments—for instance, indigo-it is sometimes employed in calico printing to produce
a yellow pattern on an indigo ground. This acid is also used in dyeing woollen
materials; in hat-making, to prepare a mercurial solution used in dressing felt hats;
in the manufacture of sulphuric acid; in the preparation of lacquers; in the prepa-
ration of nitrate of iron, a mordant used in dyeing silk black; for preparing picric
acid from carbolic acid, and naphthaline-yellow from naphthaline; in the manufacture
of nitrobenzol, nitrotoluol, and phthalic acid; and for the preparation of nitrate of
silver, arsenic acid, fulminate of mercury, nitroglycerine, dynamite, &c.
TECHNOLOGY OF THE EXPLOSIVE COMPOUNDS.
a. Gunpowder, and the Chemistry of Fireworks, or Pyrotechny.
On Gunpowder in General. The substance known as gunpowder, or simply as powder, is
a more or less finely granulated mechanical mixture of saltpetre, sulphur, and char-
coal, the quantities of these materials being properly defined. It ignites at 300°,
also when touched with a red-hot or burning body, or under certain conditions by
friction or a sudden blow. Powder under these conditions burns off rapidly but not
instantaneously, yielding as the products of its combustion nitrogen, carbonic acid,
or carbonic oxide, while there remains a solid substance consisting of a mixture of
sulphate and carbonate of potassa. When the powder is ignited in a closed vessel,
the sudden evolution of the large volume of gases causes a pressure impossible to be
withstood; and even in guns and large ordnance, in which one side of the vessel is
formed by the yielding shot, the metal forming the other sides must possess great
elasticity. In guns and artillery the pressure only lasts as long as the ball is inside
the gun, therefore the slower the combustion of the powder through its entire mass,
the lower is the velocity of the projectile.
Manufacture of Gunpowder. It is essential that the materials employed in the manufacture
of powder should be very pure; the saltpetre should not contain any chlorides; the
sulphur should be free from sulphurous acid, hence not flowers of sulphur but
refined roll sulphur is used; and lastly the charcoal requires very great attention.
The wood from which it is intended to prepare a charcoal for gunpowder should be
such as yields the least possible quantity of ash, while the charcoal should be soft
like that used in pharmacy. The stems of the hemp and flax plants, especially the
former, yield excellent charcoal, but in consequence of the limited supply, the wood
of the wild plum tree (Prunus padus) is largely used in Germany, France, and
EXPLOSIVE COMPOUNDS.
149
Belgium; and in England the lime, willow, poplar, horse-chestnut, vine, hazel,
cherry, alder, and other light white woods are employed for this purpose. All these
varieties yield on being carbonised-effected in various ways, in retorts similar to
those used in gas-works, in pits dug in the earth, by the aid of superheated steam,
the wood being placed in boilers, &c.—from 35 to 40 per cent. charcoal. The tem-
perature during the progress of carbonisation being kept as low as possible, there is
obtained a very soft reddish-brown charcoal, known as charbon roux. The charcoal
prepared in cylindrically-shaped retorts is very inappropriately designated distilled
charcoal.
Mechanical Operations
of Powder Manufacture.
These operations include:—
1. The pulverising of the ingredients. 2. The intimate mixing of these sub-
stances. 3. The moistening of the mixture. 4. The caking or pressing. 5. The
granulation and sorting of the grain, as it is termed. 6. Surfacing the powder.
7. Drying. 8. Sifting from the dust.
Pulverising the Ingredients. This operation can be performed in three different ways:--
a. By means of revolving drums.
b. By mill-stones; or
c. In stamping-mills.
a. The pulverisation by means of revolving drums is an invention due to the French
revolution, and has the advantages of being very effective, rapid in execution, and of pre-
venting the flying about of the ingredients in a fine dust. The drums are made of wood,
lined with stout leather, and provided with a series of projections. The substance to be
pulverised is put into the drum with a number of bronze balls of about inch diameter,
their action aided by that of the projections, when the drum is turned on its horizontal
axis at a moderate speed, soon effecting a reduction to a fine powder. The charcoal
and sulphur are separately pulverised; the saltpetre being obtained as a flour. (See
Saltpetre.).
b. Grinding by the aid of mill-stones. Two heavy vertical stones, similar to those in
use for crushing linseed, revolve on a fixed horizontal stone. This contrivance is the most
frequently used.
c. Stampers are now employed only in small powder-mills. Frequently 10 to 12 stamps
made of hard wood are placed in a row, each stamp being fitted with a bronze shoe, the
entire weight being about I cwt. The stamps are moved by machinery, and make from
40 to 60 beats a minute. The materials to be pulverised are placed in mortar-shaped
cavities in a solid block of oak wood, each cavity containing 16 to 20 lbs. In Switzerland
hammers instead of the stampers are employed.
Mixing the Ingredients. The mixing is performed by the aid of drums similar in size
and shape to those used in the pulverisation, but made of stout leather instead of
wood. The mixing of 100 kilos. of the ingredients, aided by the action of 150 bronze
balls, takes fully three hours, the drum making ten revolutions a minute. It is
usual to moisten the materials with 1 to 2 per cent. of water, supplied by fine jets
regulated by taps.
When stampers and mill-work are employed, the sulphur and charcoal are first
separately pulverised by 1000 blows, and saltpetre having been mixed with these
ingredients in the proper proportion, the machinery is again set in motion, and at
first, after every 2000 blows, and then after every 4000 blows, the contents of the
stamp-holes are removed from the one to the other, this operation being repeated
some six or eight times. Where drums are used for the mixing operation, the
moistening takes place after the mixture has been removed to a wooden trough,
where 8 to 10 per cent. of its weight of water is added, care being taken to stir with
a wooden spatula.
150
CHEMICAL TECHNOLOGY.
Caking or Pressing
the Powder.
This operation, which in stamping-mills is the last of a continuous
series, is separately performed where other machinery is employed. In the French
and German powder-mills, the compression is effected in a rolling-mill, the rollers
having a diameter of o'6 metre. The lower roller is made of wood, the upper of
bronze; between the two an endless piece of stout linen is arranged, and upon this
the moist powder is placed. The cakes are 1 to 2 centims. in thickness, with the
hardness and very much the appearance of clay-slate.
The operation of pressing is of great importance; the stronger the pressure the greater
the quantity of active material present in a given bulk, and hence the larger the volume
of gas given off by the ignition of the powder. In many English powder-mills the
pressing is effected by very powerful hydraulic machines, because, within certain limits,
the more the materials are pressed, the more slowly the powder burns, when finished,
while the temperature of ignition being lower, the expansion of the gases is less. If the
powder were finished either without having undergone any pressure at all, or with only a
slight pressure, it would act as a detonating-powder, the decomposition being instan-
taneous throughout its entire mass.
Granulation of the Cake, The conversion of the cake into granules is effected-
and Sorting the Powder.
1. By means of sieves.
2. By means of peculiarly-constructed rollers, Congreve's method; or
3. According to Champy's method.
The granulation of gunpowder by the aid of sieves is carried on in the following
manner :--The sieves consist of a circular wooden frame, across which a piece of parch-
ment is stretched perforated with holes; the sieves are distinguished according to their
uses, and by the size of these holes; that employed for breaking up the cake having larger
holes, and bearing a name different from the sieves used to produce the granules; this
sieve again being distinguished from that employed for sorting the powder into the
variously sized grain as commercially known. The sieves are provided with a so-called
rummer, a lens-shaped disc made of hard wood, guaiac, box, or oak-wood, motion being
imparted to the sieves by hand if they are small, or by suitably arranged machinery if
they are large, in which case Lefebvre's granulating-machine fitted with eight sieves in an
octagonal wooden frame is generally employed.
Congreve's granulating-machine consists of three pairs of brass rollers, o'65 metre in
diameter, provided with diamond-shaped projections 2 millimetres high, the projections
of the upper rollers being coarser than those of the others. The broken-up cake is
conveyed to the upper rollers by means of an endless canvas sheet. The mode of feeding
this sheet is somewhat peculiar and ingenious: the loose bottom of a square box filled
with coarsely-pounded cake is made to rise slowly upwards, and discharge the cake uni-
formly upon the sheet through an opening in the side of the box. The cake while passing
through the rollers is granulated, and then showered upon two sets of wire-gauze sieves to
which a to-and-fro motion is imparted. Below these sieves again is a frame containing
wire-gauze, the meshes of which are too small to admit of the passage of ordnance powder,
while the dust and cartridge-powder readily fall through upon another wire-gauze, the
meshes of which retain the rifle-powder but let the dust pass. The quantity of dust
made by the Congreve machine is very small, owing to the fact that the rollers do not
crush but break the cake. Champy's method, by which a very round-grained powder is
obtained, is performed in the following manner :--Through the hollow axis of a wooden
drum a copper tube, perforated with very small holes, is carried, and from these holes
water spouts in a fine spray upon the broken-up powder-cake placed in the drum, to
which a comparatively rapid motion is imparted. Each drop of water forms the nucleus
of a grain of powder, which is constantly increasing in size by being turned round in the
midst of a mass of damp powder-cake; the rotation of the drum is discontinued as soon
as the grain has attained a sufficient size. The powder thus obtained is almost perfectly
globular, but not of the same size; the sorting is effected by means of sieves, the over-
sized grains being returned to the drum, as well as the undersized grains, which become
the nuclei of proper-sized grain. According to the Berne method, round-grained powder
is prepared by causing the angular-shaped powder to be rotated in stout linen-bags; but
by this plan much dust is formed.
Granulated Powder.
Polishing the The aim of this operation is to impart symmetry to the grain, and
to separate all the dust. It is performed in drums similar to those described above;
5 cwts. of the powder is polished at a time, the drums rotating slowly for a few hours.
EXPLOSIVE COMPOUNDS.
151
▼
In some countries the polishing is effected by placing the powder in casks internally
provided with quadrangular rods. In Holland, Dr. Wagner states that some black-lead
is added to the powder during this operation to prevent ignition, but this is not generally
done. Highly-polished powder does not readily attract moisture, and is to be preferred in
a very damp climate.
Drying the Powder.
It is clear that this operation requires very great care in more
than one respect. In small powder-works the powder is sometimes dried by
exposure to the heat of the sun, being spread out on canvas sheets stretched in
wooden frames; or the drying-room is heated by a stove. In large powder-mills
other methods of drying the powder are general.
The quality of the powder very much depends on the care bestowed upon the drying.
A tuo rapid drying entails the following disadvantages:-a. The powder may be very wet
and not polished; coarse ordnance and ordinary military powder is never polished, and
hence blackens the hands; while, although the water is driven off, the nitre is carried to
the surface of the grain, which thereby cakes together. b. By the too rapid evaporation of
the water, channels and cracks are made in the grain, impairing its density, increasing
its bulk, and rendering it more hygroscopic. c. Lastly, rapid drying entails a large
amount of dust. For these reasons gunpowder, before being placed in the drying-rooms,
is exposed for some time to a gentle heat in a well-ventilated room, the heat from a waste
steam-pipe being sufficient.
Sifting the Dust from
the Powder.
Having been dried, the powder is sometimes glazed, as it is
termed; that is to say, again polished in the manner above described; but generally
this second polishing is dispensed with, and the dry powder cleansed from the dust
which adheres to it, by being placed in bags, made of a peculiar kind of woollen
fabric, and arranged in frame-work to which a to-and-fro motion is given by
machinery, the fine dust passing between the threads of the fabric into a box. The
loss thus occasioned amounts on an average to 0.143 per cent., the dust consisting
chiefly of charcoal.
Properties of Gunpowder. Good powder is recognised by the following properties:-
1. Its colour should be slate-black; when blue-black it indicates that the powder
contains too much charcoal, while a deep black colour shows the powder to be damp.
If the charcoal employed was the so-called charbon roux, the colour of the powder
will be a brown-black. 2. It should not be too much polished so as to shine like
burnished black-lead. Small shining specks indicate that the saltpetre has crystal-
lised on the surface. 3. The grains should be uniform in size, unless, of course,
two differently-sized powders have been mixed. 4. The grain should crack uniformly
when strongly pressed, should withstand pressure between the fingers, and should
not be readily crushed to powder when pressed between the hands. 5. When pul-
verised the mass should feel soft; hard sharp specks show that the sulphur has not
been well pulverised. 6. Powder should not blacken the back of the hands or a
sheet of white paper when gently rubbed. If it does so, there is either powder-dust
or too much moisture. 7. When a small heap of powder is ignited on paper the
combustion should be rapid, completely consuming the powder, and not setting fire
to the paper. If black specks remain, the powder either contains too much charcoal,
or it is an indication that that substance has been badly incorporated with the rest
of the materials. Yellow streaks left after the ignition show the same defects for
the sulphur. If no grains of powder remain, it is a proof that the powder was not
well mixed; when any remaining grains of powder cannot be separately ignited, the
saltpetre used was impure. If the powder on being ignited sets fire to the paper, it
is a proof that it is either damp or of very inferior quality.
152
CHEMICAL TECHNOLOGY.
The fact that different kinds of powder, although of the same weight to the cubic
foot, do not have the same specific gravity, is shown by the following table:
I cubic foot
in pounds weight.
Neisse's ordnance powder
""
"
..
(new mill)
Berlin ordnance powder
Russian ordnance powder
Berne ordnance powder (No. 6)
Berlin rifle powder (new mill)
Berne rifle powder (No. 4)..
Hounslow rifle powder
60
60
60
60%
•
•
599
calco
60
60
10100
Sp. gr
I'77
1.67
1.63
1.56
1.67
*1*63
1.67
Berlin sporting powder (old mill)
Le Bouchet's sporting powder..
Very coarse-grained ordinary Dutch powder..
Very coarse-grained ordinary Austrian powder
59
I'72
62
I'77
591
1.87
60
1.87
64
1'72
Gunpowder can absorb more than 14 per cent. of moisture from the air; if the
quantity of water thus taken up is not above 5 per cent., the powder, on being gently
dried, reassumes its former activity; but if the quantity of water absorbed exceeds
that amount, the gunpowder will not burn off rapidly, and when dried the single
grains become covered with an efflorescence of saltpetre, of course impairing the
composition and active qualities of the powder. Even what is termed dry powder
contains at least 2 per cent. of hygroscopic moisture. Powder can be exploded by a
heavy blow as well as by an increase of temperature, and as regards its explosion
by a blow, very much depends upon the material upon which it is placed and with
which the blow is imparted. The following list exhibits in decreasing order the
materials between which a blow most readily ignites powder:—Iron and iron, iron
and brass, brass and brass, lead and lead, lead and wood, copper and copper, copper
and bronze. For this reason gunpowder magazines are provided with doors turning
upon bronze and copper hinges, the locks also being of copper. When dry powder
is rapidly heated to above 300° it explodes. Even if only a very small portion of the
powder is thus rapidly elevated in temperature, the entire quantity, be it large or
small, is exploded; hence, a very small quantity touched by a red-hot or burning
body is sufficient to effect an explosion. It is generally held that the charcoal is
first ignited, and that it spreads the ignition to the other materials. Although
Mr. Hearder found by experiment that powder does not ignite when touched with
a red-hot platinum wire while under the receiver of an air-pump, Professors v.
Schrötter and Abel proved that gunpowder so placed ignited rapidly when heated
by a spirit-lamp.
*
Composition of Gunpowder. Gunpowder consists very nearly of 2 molecules of saltpetre, 1 mole-
cule of sulphur, and 3 of charcoal. Accordingly 100 parts of powder contain-
Saltpetre
Sulphur
Charcoal (No. I.)
74.84
II.84
13'32
The above figures approximately express the composition of the best kinds of sporting
and rifle-powder. Ordinary powders, such as blasting-powder, consist of nearly equal
molecules of nitrate of potassa and sulphur, with 6 molecules of charcoal. Accordingly
100 parts contain—
Saltpetre
Sulphur
Charcoal (No. II.)
66.03
10'45
23°52
!
EXPLOSIVE COMPOUNDS
153
Products of the
Drs. Bunsen and Schischkoff found the composition of a sporting and
Combustion of Powder. rifle-powder to le, in 100 parts, as follows :—
Charcoal consisting of
Saltpetre
Sulphur
Carbon..
Hydrogen
Oxygen
Ash.
•
•
Sulphate of potassa
The residue of this powder after combustion was found to consist of—
56.62
Carbonate of potassa
Hyposulphite of potassa
Sulphuret of potassium
Hydrated oxide of potassa (caustic potassa)
Sulphocyanide of potassium
Saltpetre
•
Carbon
Carbonate of ammonia..
Sulphur
•
27'02
7:57
1'06
I'26
0.86
5'19
0'97
} traces
100.55
78.99
9.84
7.69
0'41
3:07
traces
It appears from this analysis that the residue left after ignition of the gunpowder
consists essentially of sulphate and carbonate of potassa, and not, as has been formerly
stated, of sulphuret of potassium. Thé composition of the smoke of the powder was
ascertained to be-
Sulphate of potassa
65.29
Carbonate of potassa
23.48
Hyposulphite of potassa
4'90
Sulphuret of potassium
Caustic potassa
1'33
Sulphocyanide of potassium
0'55
Saltpetre..
3:48
Carbon (charcoal)
1.86
·
Sesquicarbonate of ammonia
O'II
Sulphur
100'00
From these figures it is clear that the smoke of gunpowder consists essentially of the
same substances as the residue from the combustion, the only difference being that the
sulphur and nitrate of potassa of the powder have been more completely converted into
sulphate of potassa, while instead of the sulphuret of potassium, carbonate of ammonia
makes its appearance. 100 parts by volume of the gaseous products of the combustion
were found to consist of—
Carbonic acid..
•
•
•
Hydrogen
Oxygen
Protoxide of nitrogen
Nitrogen
Oxide of carbon
Sulphuretted hydrogen
52.67
41'12
3·88
I'21
0.60
0'52
100'00
The solid residues of combustion formed during the generation of the gases were found
to be-
Sulphate of potassa
Carbonate of potassa
Hyposulphite of potassa
62.IC
18.58
4.80
Sulphuret of potassium
Sulphocyanide of potassium
Nitrate of potassa..
Charcoal
3'13
0'45
5'47
1'07
Sulphur
•
0'20
Sesquicarbonate of ammonia
•
4'20
:
100'00
£54
CHEMICAL TECHNOLOGY.
The decomposition of powder by its ignition may be represented by the following
forinulæ :-
Grm.
K₂SO
0'422
K₂CO3
0.126
22
K₂S₂03
0.032
K'S
0.021
Residue
KCNS
0.680
0'003
KNO3
0037
I grm. of powder
Saltpetre
Sulphur 0'098
C 0·076
Charcoal Ho⚫004
100·030
0.789
C
0'007
S
Ο ΟΟΙ
yields after
combustion
(NH,),CO3
0.028
Grm.
C.c.
N
0*0990 =
79'40
Gases
CO₂ 0·2010 = 101*71
0'314
CO 0·0090 =
H
0'0002
O'994
7'49
2'34
1.16
0'0014 =
I'00
193.10
SH₂ 0·0018
According to the recent researches of Mr. Craig, and later investigations of M. Fedorow
(1869), the products of the combustion of powder vary according to the pressure this
substance is subjected to while being ignited. There has not hitherto been found any
really effective substitute for gunpowder; fulminates and mixtures containing chlorate
of potassa ignite too quickly and cause the bursting of the gun, while gun-cotton yields
among its products of ignition water and nitrous acid, which act destructively on the
metal, and also interfere with continued firing.
Powder.
New kinds of Blasting Under the name of pyronene there is sold a new kind of blasting-
powder, consisting of nitrate of soda 52.5 parts, sulphur 20, and
spent tan 27.5 parts. It is, of course, far cheaper than ordinary powder, but presumably
not very useful nor active. Captain Wynands, of Belgium, has successfully introduced
a substance, to which he has given the name saxifragine, consisting of nitrate of baryta
76, charcoal 22, and nitrate of potassa 2 parts. Schultze's (1864) wood-gunpowder consists
of granulated wood treated with a mixture of nitric and sulphuric acids, and next
impregnated with a solution of nitrate of potassa; this material is manufactured at
Edgeworth Lodge, Hants. M. Bändisch has invented a process by which this wood-
gunpowder may be compressed into a solid substance exerting great power, and free
from danger by transport. Lithofracteur, a white blasting-powder used in Belgium,
is a substance similar to gun-cotton. The haloxylin of MM. Neumeyer and Fehleisen is
a mixture of charcoal, nitre, and yellow prussiate of potassa. Callou's blasting powder
is a mixture of chlorate of potassa and orpiment. Nitroleum is, in fact, nitroglycerine,
which, with dynamite and dualin, will be spoken of presently. Picrate of potassa is used
in France and in England for filling shells intended for the destruction of armour-plated
ships, and for the manufacture of picrate gunpowder.
Testing the Strength In order to determine the strength or projectile force of gunpowder,
of Gunpowder. and which for equality of composition is dependent on the mechanical
treatment the powder has undergone, the following apparatus are used:-Test mortar,
rod testing machine, lever testing machine, ballistic pendulum, and chronoscope. The
first of these contrivances is a piece of heavy ordnance, charged with 92 grms. of powder,
and a ball weighing 29′4 kilos., the mortar being placed at an angle of 45°. The bore of
the mortar is 191 millemetres in diameter by 239 in depth. Powder of good quality should
propel the ball a distance of 225 metres, and frequently the ball is carried a distance of
250 to 260 metres. The rod gunpowder testing apparatus consists of a mortar placed
vertically, and which, when charged with 22 to 25 grms. of powder, lifts a weight of 8 lbs.,
made to move between toothed rods; by the height this weight is raised, springs attached
to the weight fastening in the notches of the rods and holding it, the quality of the powder
is judged.
White Gunpowder. In the year 1849 M. Augendre brought out a new kind of gunpowder,
which, under the names of German white and American white gunpowder, has been
occasionally employed. This powder consists of yellow prussiate of potassa, chlorate of
potassa, and cane sugar. These materials, having been thoroughly mixed in a dry state,
can be used in powder or in grains, igniting in contact with red-hot and flaming substances,
but not by friction nor percussion. This white gunpowder may be preferred to the
EXPLOSIVE COMPOUNDS.
155
ordinary powder for the following reasons:-Being composed of unvarying substances,
this powder can always, by weighing out the proper quantities of each ingredient, be
obtained of uniform strength and quality. The ingredients are not hygroscopic to any
extent, and are not acted upon by exposure to the air. The manufacture requires but a
very short time, the projectile force is far greater, and the powder need not be granulated.
On the other hand, this powder acts, during its ignition, so very strongly upon iron and
steel that it can only be used in bronze ordnance, and in the filling of shells, &c. It
is more readily fired than ordinary gunpowder, although less so than other mixtures
containing chlorate of potassa. Finally, its manufacture is very expensive. According
to the experiments of J. J. Pohl (1861) on this subject, the following is the best recipe
for this powder :-
Yellow prussiate of potassa
Loaf Sugar
Chlorate of potassa..
This mixture is approximatively equal to-
••
•
•
28 parts
23
49 ""
""
I molecule of Prussiate of potassa,
I
""
Sugar,
3 molecules of Chlorate of potassa ;
corresponding in 100 parts to 28 17 of prussiate of potassa, 22.78 of sugar, and 49'05 of
chlorate of potassa. As no accurate and reliable analyses of the products of the com-
bustion of this powder have been made, and as these products will vary with respect to
the conditions under which the ignition takes place, whether in open air or in a close
vessel, it can be merely calculated, that assuming complete combustion to take place,
100 parts of this powder will yield:
•
Nitrogen.
Carbonic oxide
Carbonic acid
Water
Total gaseous products
The solid residue will consist of-
•
1.865 parts
•
II 192
•
""
17.587 "
16.788"
47'442"
Cyanide of potassium.. 17.385 parts
Chloride of potassium.. 29.840
Carburet of iron (FeC₂)
Total non-volatile products
5'333"
52.558
The bulk of gaseous matter evolved by the ignition of 100 grms. of this powder, taken
at o° and 760 m.m. Bar., is as follows:
Nitrogen..
1927'0 cubic centims.
Carbonic oxide
Carbonic acid
8942.9
""
8942.9
""
Aqueous vapour 20867.9
40680'4
""
As the temperature of combustion is estimated at 2604·5° the quantity of the gases is
431162 c.c.
Chemical Principles of
Pyrotechny.
Under the name of fireworks we include certain mixtures of
combustible substances employed as signals, as destructive agents (for instance,
Congreve rockets), and for purposes of display.
The various forms are, according to the end in view, so contrived as to burn
off either rapidly or slowly, and with more or less emission of gaseous matter, heat,
and light. These mixtures are mainly distinguished as heat-producing, ignition
communicators (technically termed a match), and light-producing. The principle
of the rational manufacture of fireworks, applying the word in its extended sense, is
that neither any excess of the combustible nor of the combustion promoting and
supporting agents should be employed, and that unavoidable accessory materials,
viz., such as are intended only to keep the essential ingredients in a certain required
shape, the paper casings, &c., be in precisely the quantity required. The best
156
CHEMICAL TECHNOLOGY.
proportions of the combustible and combustion-supporting substances can be readily
ascertained by theoretical calculations; for instance, it will be evident that a
mixture of 2 equivalents of saltpetre and 1 equivalent of sulphur (1), or a mixture
of 2 equivalents of saltpetre and 3 equivalents of sulphur (2), is in each instance
wrong; in the latter, too much of the combustible body is used; and in the former
case, too much of the supporter of combustion is employed :-
(1). S can take up from 2KNO, at most 30, consequently 30 remain inactive.
(2). 3S and 2KNO, yield either K₂S and 2SO3, or a mixture of K₂SO4, K2S,
and SO2; in each case some sulphur remaining unburnt.
We have to bear in mind, however, that it is not always possible to elucidate
theoretically the decomposition of firework mixtures, as the affinity of the substances
which react upon each other is not well known, and depends on accessory con-
ditions and comparatively unknown influences. It will require a more advanced
knowledge of the products of the decomposition of the different substances and
their specific heat before we can predict with some degree of certainty the best
mixtures. As regards the existing mixtures, they are the result of a lengthy series
of experiments, really made by rule of thumb, though with a certain correspondence
with the best composition theory can give, that is to say, many of these mixtures
have been somewhat modified and improved by modern science.
The more commonly used These mixtures consist mainly of saltpetre, sulphur, and charcoal,
Firework Mixtures either in the same proportions as those in use for gunpowder, or
with an excess of sulphur and charcoal. Some mixtures contain instead of saltpetre
chlorate of potassa and other salts, not always essential to the combustion, but intended
either to intensify the light evolved or impart to it a distinctive colour, as in signals
and Bengal lights.
Gunpowder Is used in fireworks when it is desired that there should be projectile force.
A slower combustion of the powder is obtained partly by the use of the so-called flour of
powder, that is pulverised, not granulated powder, partly by compressing the mixture. If,
however, it is intended to produce loud reports, granulated powder is used.
Saltpetre and Sulphur Mixture. This consists of 2 molecules (75 parts by weight) of saltpetre,
and I molecule (25 parts, by weight) of sulphur, and is used as the chief constituent of
such firework mixtures as are intended to burn off slowly and evolve a strong light.
However, this mixture is not used by itself for two reasons, viz., it does not develope
a sufficient degree of heat to support its continued combustion, and does not possess a
sufficient projectile force, being capable of producing in the best possible condition of
complete ignition only 1 molecule of sulphurous acid-
2KNO₂+S=K₂SO, + SO₂+N;
4
that is to say, I part by bulk of this mixture only yields 7.28 volumes of gas. For these
reasons the saltpetre-sulphur mixture is employed with charcoal or floury gunpowder.
Grey-coloured Mixture. Such a mixture, sanctioned by long use, is that known as grey-
coloured mixture, consisting of 93:46 per cent. of saltpetre-sulphur, and 6.54 of floury
gunpowder. This mixture is the chief constituent of other compounds intended to burn
slowly, emitting at the same time a brilliant light, owing to the fact that the sulphate of
potassa formed by the combustion acts similarly to a solid brought to an incandescent
state. All mixtures intended to emit light, including coloured lights, are prepared upon
the same principle, that the salt which is to give colour shall be non-volatile at the tem-
perature of combustion.
Chlorate of Potassa Mixtures. This salt, KClO3, when in presence of combustible sub-
stances, gives off its oxygen to the latter more readily, rapidly, and completely than salt-
petre; accordingly this salt is used in all mixtures in which it is desired to combine rapid
ignition with combustion. Formerly a mixture of 80 parts by weight of chlorate of
potassa and 20 parts of sulphur, was added to intensify and quicken the combus-
tion of mixtures consisting of more slowly burning salts. A mixture of sulphur, char-
coal, and chlorate of potassa constitutes an active percussion
Percussion Powders. powder. A mixture of equal parts by weight of black sulphuret of
antimony and chlorate of potassa is used for the purpose of discharging ordnance by
means of a percussion tube placed into the touchhole of the gun. Sir William Armstrong
uses for this purpose a mixture of amorphous phosphorus and chlorate of potassa.
Friction Mixtures.
EXPLOSIVE COMPOUNDS.
157
?
Mixture for Igniting the
This mixture consists either of chlorate of potassa and black sul-
Cartridges of Needle-guns. phuret of antimony, or a compound containing fulminate of mercury.
The following is a good preparation:-16 parts of chlorate of potassa, 8 parts of black
sulphuret of antimony, 4 of flour of sulphur, I of charcoal powder, are moistened with
either gum or sugar water, and about 5 drops of nitric acid added. A small quantity,
technically known as the pill, is placed in the cartridge, and ignited by the friction pro-
duced by the sudden passage of the steel needle through it. In this country either the
above or a mixture of amorphous phosphorus and chlorate of potassa is used. Leaving
the fulminates of silver and mercury out of the question, the explosive bodies and
their applicability to warlike purposes and war pyrotechny have not been sufficiently
investigated. Nitromannite or fulminating mannite, the picrates of the alkalies,
and nitroglycerine, of which we shall presently treat more fully, especially deserve notice.
M. Dessignolles, who suggests that instead of saltpetre, picrate of potassa should be used
in the manufacture of gunpowder, states that quite different products are formed by the
ignition of picrate of potassa, when effected in the open air (a), or under pressure (8):-
a. 2C¿H¸K(NO2)30=K₂C03+5C+2N+NO+ NO₂ + 4CO₂+ CHN.
Picrate of potassa.
ß. 2C¿H¸K(ÑO̟₂)30=K,CO3+6C + 3N+ 5CO₂+2H₂+0.
Picrate of potassa.
Fulminating aniline, chromate of diazobenzol, obtained by the action of nitrous acid
upon aniline, and the precipitation of the product by the aid of a hydrochloric acid solu-
tion of bichromate of potassa, is, according to MM. Caro and Griess, an efficient substituto
for fulminating mercury.
These consist chiefly of floury gunpowder and grey mixture,
Heat-producing Mixtures.
to which are added those organic substances, as pitch, resin, tar, igniting readily, but
The heat generated by the combustion of
consumed more slowly than any firework.
fireworks is much higher than is required to ignite wood, but not of sufficient duration tò
cause the thorough burning of the wood, hence the addition of tar, &c.
Coloured Fires. The salts employed to produce coloured flames are-the nitrates of
baryta, strontia, and soda, and the ammoniacal sulphate of copper. The so-called cold
fused mixture, composed of grey mixture, floury gunpowder, and sulphuret of antimony,
moistened with brandy and then mixed, produces a white flame. The mixtures for
coloured fires used in artillery laboratories are the undermentioned, calculated for 100
parts of each mixture:-
d.
Red. Yellow. Blue.
1. Chlorate of potassa
2. Sulphur..
3. Charcoal
4. Nitrate of baryta..
e.
White
a.
b.
Ꮹ.
Green.
32.7
29.7
54'5
9.8
•
5'2
17.2 23.6
I'7 3.8
20
18:1
52'3
45.7
•
111
9.8
111
27.4
62.8
8111
5.7
5
15
5. Nitrate of strontia
6. Nitrate of soda
7. Ammoniacal sulphate of copper
8. Saltpetre
9. Black sulphuret of antimony
10. Floury gunpowder
•
It is hardly necessary to mention that great care is required in mixing these mate-
rials, and that each ingredient ought to be pulverised separately.
According to M. Uhden a beautiful white flame edged with blue is obtained by
the ignition of the following mixture:-20 parts of saltpetre, 5 of sulphur, 4 of sulphuret
of cadmium, and I part of charcoal. Chloride of thallium with other ingredients yields a
beautiful green flame. Magnesium was used during the Abyssinian war in various ways
when a brilliant light was required. The chlorates of the alkaline earth bases and the
chlorate of soda would be preferable, were it not for the expense, and for the facts
that these salts are rather hygroscopic and liable to spontaneous combustion. The car-
bonates of baryta and of strontia are sometimes used instead of the nitrate. According to
MM. Dessignolles and Castelhaz, most brilliant coloured flames are obtained with picrate
of ammonia in the following proportions:-
Picrate of ammonia
50
Picrate of protoxide of iron 50
(Picrate of ammonia
Yellow{
Green
Nitrate of baryta
Picrate of ammonia
•
Red
Nitrate of strontia
:::
48
52
54
46
158
CHEMICAL TECHNOLOGY.
b. Nitroglycerine.
Nitroglycerine. This substance, also known as fulminating oil, nitroleum, trinitrine,
glyceryl-nitrate, glonoine, was discovered in 1847 by Dr. A. Sobrero, while a student
in the laboratory of Professor Pelouze, at Paris. Since the year 1862, M. Alfred
Nobel, a Swede, has manufactured this liquid on the large scale. The formula of
nitroglycerine is C₂H,N₂O, or O3; consequently it consists of glycerine,
C3H5
CHO,, in which 3 atoms of H have been replaced by 3 atoms of NO2. 100
parts of nitroglycerine yield on combustion-
3
Water
C3H5
9
Carbonic acid
Oxygen
Nitrogen
20 parts.
58
3'5 ""
18.5
""
100'0 parts.
As the sp. gr. of nitroglycerine is 16, 1 part by bulk will yield on combustion-
Aqueous vapour
Carbonic acid ..
Oxygen
Nitrogen
554 volumes.
469
""
39
>>
236
>>
1298
According to experiments made in Belgium, the combustion of nitroglycerine
does not yield free oxygen, but a large quantity of protoxide of nitrogen; accord-
ingly, the following equation will give some idea of the mode of explosion:-
2 molecules of
Nitroglycerine, C3H5N3O9
=
Carbonic acid, 6CO2.
Water, 5H2O.
Protoxide of Nitrogen, N₂O.
Nitrogen, 4N.
M. Nobel states that the heat set free by explosion causes the gases to expand to
eight times their bulk; accordingly, I volume of nitroglycerine will yield 10'384
volumes of gas, while I part by bulk of powder only yields 800 volumes of gas; the
explosive force of nitro-glycerine is, therefore, to that of powder—
By volume as 13: 1,
By weight as 8: 1.
In order to prepare nitroglycerine, very strong nitric acid, density 49° to 50° B.
=1'476 to 1'49 sp. gr., is mixed with twice its weight of concentrated sulphuric acid.
3300 grms. of this mixture, thoroughly cooled, are poured either into a glass flask
or into a glazed earthenware jar, placed in a pan of cold water, and there is next
gradually added 500 grms. of concentrated and purified glycerine, having a density
at least of 30° to 31° B = sp. gr. 1°246 to 1*256, care being taken to stir constantly.
According to Dr. E. Kopp's recipe (1868) the acid mixture should consist of 3 parts
of sulphuric acid at 66° B. = 1767 sp. gr., and 1 part of fuming nitric acid. To 350
grms. of glycerine 2800 grms. of the acid mixture are added; and in performing this
operation care should be taken to avoid any perceptible heating for fear of con-
verting by a violent reaction the glycerine into oxalic acid. The mixture is now left
to stand for five or ten minutes, and afterwards poured into five or six times its bulk
EXPLOSIVE COMPOUNDS.
159
of very cold water, to which a rotatory motion has been imparted. The newly-
formed nitroglycerine sinks to the bottom of the vessel as a heavy oily liquid, which
is washed by decantation; but if not intended for transport-and experience has
proved the transport of nitroglycerine to be highly dangerous-the washing may be
dispensed with, as neither any adhering acid nor water impairs the explosive
properties. Nitroglycerine is now generally made on the spot in America and else-
where by those whom experience in mining, quarrying, and engineering matters
has taught the real value of this very powerful agent.
Nitroglycerine is an oily fluid of a yellow or brown colour, heavier than and
insoluble in water, soluble in alcohol, ether, and other fluids; when exposed to
continuous cold, not of great intensity, it becomes solidified, forming long needle-
shaped crystals. The best means of exploding nitroglycerine is a well-directed
blow, neither a spark nor a lighted body will cause the ignition, which even with a
thin layer takes place with difficulty, only part being consumed. A glass bottle filled
with nitroglycerine may be smashed to pieces without causing the contents to explode.
Nitroglycerine may even be gently heated and volatilised without decomposition or
combustion, provided violent boiling is carefully prevented. When a drop of nitro-
glycerine is caused to fall on a moderately hot piece of cast-iron the liquid is quietly
volatilised; if the iron is red-hot the liquid burns off instantaneously, just as a grain
of powder would do under the same conditions; if, however, the iron is at that heat
which will cause the immediate boiling of the nitroglycerine, it explodes with great
force. Nitroglycerine, especially if sour and impure, is liable to spontaneous decom-
position, which, accompanied by the formation of gas and of oxalic acid, may have
been the proximate cause of some of the dreadful explosions of this substance, it
being surmised that the pressure exerted by the generated gases upon the fluid in
hermetically closed vessels had something to do with the occurrences. On this
account M. K. List advises that vessels containing nitroglycerine should be only
loosely stoppered, or if being transported provided with safety-valves. Nobel
secures nitroglycerine from explosion by dissolving it in pure wood-spirit, from
which it may be again separated by the addition of a large quantity of water. Mr.
Seeley on this score observes that:-1. The wood-spirit is expensive, and lost in the
large quantity of water required for precipitating the nitroglycerine; 2. Wood-spirit,
being volatile, may evaporate, and leave the nitroglycerine unprotected; 3. There
is a change of chemical action between these bodies; 4. The vapour of wood-spirit
is very volatile, and forms with air an explosive mixture. Many suggestions have
been made as to rendering nitroglycerine safe to warehouse; among them may be
noted the mixing with pulverised glass in a manner similar to Gale's process for
gunpowder. Wurtz recommends the mixture of nitroglycerine with equally dense
solutions of either of the nitrates of zinc, lime, or magnesia, so as to form an
emulsion, the nitroglycerine being recovered simply by the addition of water. The
taste of nitroglycerine is sweet, but at the same time burning and aromatic; it is a
violent poison even in small doses, and its vapour is of course equally virulen, hence
great care is required in working with this substance in localities where, as in mines
and pits, the supply of fresh air is limited. Instead of manufacturing nitroglycerine
in works specially arranged for that purpose, and transporting this dangerous
compound, it is better, as advised by and executed under the direction of Dr. E.
Kopp, at the Saverne quarries, to have the quantity required for daily use prepared
on the spot by intelligent workmen. Notwithstanding the very serious accidents
160
CHEMICAL TECHNOLOGY.
which have been caused by the explosions of nitroglycerine in this country as well
as abroad, and the consequent prohibition of its use, there is no reason why this
powerful agent should not be employed according to Kopp's suggestion. Instead of
the acid mixture used in the preparation of nitroglycerine, M. Nobel suggests the
following:—In 33 parts of strong sulphuric acid of 1.83 sp. gr. is dissolved 1 part
of saltpetre, and the fluid cooled down; the result is the separation of a salt consisting
of 1 molecule of potassa, 4 molecules of sulphuric acid, and 6 molecules of water,
and which at 320 F. is altogether eliminated from the fluid, leaving an acid which,
by the gradual addition of glycerine, is converted into glonoine, afterwards separated
by water, as already described.
Nobel's Dynamite. Under the name of dynamite, Nobel, in 1867, brought out a new
explosive compound, consisting of 75 parts of nitroglycerine absorbed by 25 parts
of any porous inert matter, as finely-divided charcoal, silica. As evidenced by the
experiments of Bolley and Kundt, dynamite has the advantage over nitroglycerine
of not being exploded even by the most violent percussion, therefore requiring a
peculiarly-arranged cartridge. The explosion is attended with such force that
large blocks of ice are shattered to atoms. Dynamite burns off quietly in open
air, or even when loosely packed, the combustion being accompanied by an evolution
of some nitrous acid; but when dynamite is exploded there are generated only
carbonic acid, nitrogen, and aqueous vapour, no smoke being formed, and only a
white ash left. Dynamite is not affected by damp, and undoubtedly offers great
advantages as regards its use in mining, quarrying, and similar operations, for
although the price exceeds four times that of powder, dynamite performs eight times
as much work with less danger, and less labour in boring blast holes. The dynamite
is placed in cartridges of thick paper, and ignited by means of a fusee, which passes
through the sand serving the purpose of a wad. Dynamite can be transported
without danger of explosion. Dittmar's dualin is a mixture of nitroglycerine with
saw-dust or wood-pulp as used in paper mills, both previously treated with nitric and
sulphuric acids.
c. Gun-Cotton.
Gun-Cotton. This substance, also known as pyroxylin and fulmicotton, was discovered
in 1846, simultaneously by the late Professor Schönbein, at Balse, and by Dr. R.
Böttger, at Frankfort-on-Main. The mode of preparing this substance is as follows:-
Equal parts of strong concentrated sulphuric acid, sp. gr. 1.84, and fuming nitric
acid are poured into a porcelain basin; as much cotton-wool is steeped in the fluid as
the acid is capable of thoroughly moistening, and the vessel covered with a glass
plate, and left for a few minutes. The cotton-wool is then removed from the acid,
immediately transferred to a vessel containing a large quantity of water, and washed
with care, the water being renewed until no more acid adheres to the gun-cotton,
which is next dried in a current of warm air, and finally combed to remove all the
lumps. The cotton should not be left too long in the acid, as it might become
entirely dissolved. According to experiments instituted at Paris, in one of the
powder mills—for in France no one is allowed to manufacture powder or gun-cotton
except the Government—the following are the conditions under which the best results
are obtained:—1. Equal parts of sulphuric and nitric acids and well-cleansed
cotton. 2. Time of immersion in acid mixture from 10 to 15 minutes. 3. The same
acid may be used once again, but then the time of immersion of the cotton
GUN COTTON.
161
should be longer. 4. The gun-cotton having been thoroughly washed should be driod
slowly at a gentle heat. 5. Impregnating with nitre increases the strength of the
gun-cotton.
Properties of Gun-Cotton.
In its outward appearance gun-cotton does not differ from ordinary
cotton, neither is any difference perceptible by microscopic investigation. It is insoluble
in water, alcohol, and acetic acid, difficultly soluble in pure ether, but readily soluble in
ether which contains alcohol, and in acetic ether. Gun-cotton is liable to spontaneous
decomposition, which may even induce its spontaneous combustion; this decomposition is
attended with the evolution of aqueous vapour and of nitrous acid fumes, the remaining
substance containing formic acid. As regards the temperature at which gun-cotton
ignites statements differ; it has in some instances been dried at 90° to 100° without
any dangerous consequences, while it has been found to ignite at 43°. Instances are
on record of serious explosions of gun-cotton having taken place under conditions
which leave no doubt that the greatest care is required in handling and warehousing
this substance; for instance, a small magazine, filled with gun-cotton, situated in the
Bois de Vincennes, Paris, was exploded by the sun's rays; and at Faversham the Le Bouchet
drying-rooms, which could not possibly be heated above 45° to 50°, exploded with great
violence. Gun-cotton explodes by percussion, leaving no residue after its ignition. Good
gun-cotton may be burned off when placed on dry gunpowder without igniting the latter.
It is very hygroscopic, but may be kept for a length of time under water without affecting
its explosive properties.
According to the best chemical analysis, gun-cotton is trinitro-cellulose,
C6H7(NO2)305,
consequently it is cotton considered in a pure state as cellulose, C6H10O5, 3 atoms of
the hydrogen of which have been replaced by 3 atoms of hyponitric acid.
of gun-cotton contain—
100 parts
Carbon
Hydrogen
Oxygen
Nitrogen
• •
:
24°24
2:36
•
59'26
•
14'14
100'00
The conversion of cotton into gun-cotton may therefore be expressed by the following
formula:-
C6H1005+3HNO3= C6H5(NO2)3O5 +3H2O;
Cotton.
Gun-Cotton.
the sulphuric acid being employed only for the purpose of absorbing water.
Assuming that the cellulose is entirely converted into trinitro-cellulose, 100 parts of
cotton ought to yield 185 parts of gun-cotton, and when the conversion forms binitro-
cellulose, 100 parts of cotton ought to yield 155 parts of gun-cotton. The under-
mentioned are the results of direct investigation. For 100 parts of cotton—
Pelouse (in ten experiments, 1849)
found 168 to 170 parts of gun-cotton.
Schmidt and Hecker (1848)
169
Van Kerckhoff and Reuter (1849)
,, 176.2
W. Crum (1850)
", 178
Redtenbacher, Schrotter, and Schneider (1854),, 178
V. Lenk (1862)
Blondeau (1865)
,, 155
›› 165°25
""
""
""
در
ر,
""
""
""'
By the explosion of gun-cotton in vacuo, carbonic oxide, aqueous vapour, and
nitrogen are evolved. The same products, with the addition of nitrous acid and
cyanogen, are generated by the explosion of gun-cotton in closed vessels.
I grm. of
12
162
CHEMICAL TECHNOLOGY.
gun-cotton yields, according to Schmidt, 588 c.c. gases, these gases consisting in
100 parts by volume of—
Carbonic oxide
Carbonic acid
Marsh gas.
Deutoxide of nitrogen
Nitrogen
Aqueous vapour
:
•
30
20
IO
9
8
23
100
I part by weight of gun-cotton is equal in projectile power to 4'5 to 5 parts of gun-
powder.
for Gunpowder.
Gun-Cotton as a Substitute Gun-cotton has not yet been adopted in practice as a good
substitute for gunpowder; its large bulk, coupled with the fact that the explosion is
attended with the evolution of much water and nitrous acid, render it inconvenient
as a substitute for powder.
Other uses of Gun-Cotton. Gun-cotton is advantageously employed in blasting, and has been
used as a substitute for fulminating mercury in gun-caps when mixed with chlorate of
potassa. The experiments of Professor Abel, of Woolwich, have led to great improve-
ments in the manufacture of gun-cotton, carried into practice by Messrs. Prentice, of
Stowmarket, and consisting chiefly in mechanical operations. The cotton, either by
spinning and weaving, by pulping, or the aid of suitable solvents, is brought into a con-
dition in which it has been found an excellent and cleanly substitute for gunpowder,
having the advantages of not giving off smoke, exploding with less noise, and not fouling
the guns. The detailed description of the method of these operations is not necessary
here. Gun-cotton in many cases may serve the purpose of asbestos for filtering strong
acids and other concentrated fluids which cannot be filtered through paper.
| Collodion. Maynard employs a solution of gun-cotton in ether as a kind of glue or
varnish, and gives it the name of collodion. This solution has the appearance of a
syrup, and a thin film poured on the skin, leaves, by the evaporation of the ether, a
strongly adhesive compact layer; hence collodion is applied in surgery, photography,
and as a waterproof coating instead of varnish, especially to protect the composition
of lucifer-matches from the effects of damp. The film of pyroxylin, deposited after
the evaporation of ether, is insoluble in water and alcohol, becomes highly negatively
electric when rubbed with the dry hand, and may be obtained so thin as to exhibit
the colours of the Newton rings. Legray prepares in the following manner a gun-
cotton quite soluble in ether :-80 grms. of dried and pulverised nitrate of potassa
are mixed with 120 grms. of concentrated sulphuric acid, and in the pulpy acid mass
are thoroughly immersed by the aid of a glass rod or porcelain spatula 4 grms. of
cotton, which is stirred about for a few minutes; next the vessel containing acid and
cotton is placed in a large quantity of water, and the converted cotton washed until
all the acid is eliminated, when it is dried. Soluble cotton may be made with
nitrate of soda, 17 parts; sulphuric acid, sp. gr. = 1.80, 33 parts; cotton, part.
The converted cotton is soluble in acetic ether, acetate of oxide of methyl, wood-
spirit, and aceton; the usual solvent is a mixture of 18 parts of ether and 3 parts
of alcohol.
COMMON SALT.
163
COMMON SALT.
Occurrence.
Common salt, or chloride of sodium, consists of—
Chlorine, Cl
35'5
60'41
Sodium, Na
23'0
39'59
58.5
100'00
and is found on our globe in the solid, as rock-salt, as well as dissolved in sea-water
in enormously large quantities. It occurs as rock-salt in extensive layers alternating
with those of clay and gypsum at an average depth of 100 metres. The following are
a few of the localities where rock-salt is met with in the tertiary formation :
Wieliczka, Poland; the northern slopes of the Carpathian mountains, and in several
districts of Hungary; in the chalk formation of Cardona, Spain; in the Eastern
Alps, Bavaria, Salzburg, Styria, and the Tyrol. Among the trias formation are the
salt deposits of the Teutoburg-wood, Germany, and a great many others, among them
the celebrated Stassfurt deposits. In England rock-salt is found in Cheshire, this
county being also plentifully supplied with saline springs, the water of which yields
on evaporation an abundance of salt. Petroleum wells are found with salt in many
parts of Asiatic Russia, in Syria, Persia, and the slopes of the Himalaya. Salt
occurs plentifully in several districts of Africa, America, and other parts of the
world, and mixed with clay and marl, forming salt-clay. Salt occurs secondarily by
having been dissolved, at a depth varying in Germany from 91 to 555 metres, by
water, which carries it again to the surface, there forming salt springs and salt lakes,
from which the salt is obtained by evaporation. Among the salt lakes may be
noticed the lake near Eisleben, Germany, the Elton Lake, near the Wolga, Russia,
the Dead Sea, and the Salt Lake of Utah, United States.
There can be no doubt that the common salt met with in salt springs owes its
origin to the solvent action of water upon rock-salt, and as rock-salt is largely met
with in sedimentary geological formations, the prevalence of this formation in
Germany has there given rise to a large number of salt springs. Common salt is
also found in sea-water, and if obtained by its evaporation is often termed sea-salt;
or if deposited, as is the case in the Polar regions, by intense cold on the surface of
ice-fields, it is known as rassol. Common salt is largely obtained as a by-product
of some chemical operations, as in the conversion of sodium-nitrate into potassium-
nitrate by the aid of chloride of potassium.
Salt from Sea-Water.
Method of Preparing Common The constituent salts of sea-water do not differ in any part
of the world: even the difference in quantity is very small, and is generally due to
local causes, as the dilution of the sea-water by river-water, melting icebergs, &c.
The sp. gr. of sea-water at 17º, varies from 1'0269 to 1*0289, the sp. gr. of the water
of the Red Sea being as high as 1'0306. One hundred parts of sea-water contain-
Pacific
Atlantic
German
Red
Ocean.
Ocean.
Ocean.
Sea.
Chloride of sodium
2.5877
27558
2'5513
3'030
Bromide of sodium
0'0401
0*0326
0'0373
0'064
Sulphate of potassa
-
O'1359
0*1715
0'1529
O'295
Sulphate of lime
0.1622
0*2046
0'1622
0*179
Sulphate of magnesia
O'1104
0'0614
0'0706
0'274
Chloride of magnesium
0'4345
0*3260
0'4641
0'404
Chloride of potassium
0.288
3°4708
3'5519
3'4384
4'534
164
CHEMICAL TECHNOLOGY.
The composition of the salt contained in the water of the several seas is shown
by the following table:-
Caspian Sea.
Black Sea.
Baltic.*
English Channel.
Average of
7 localities.
Mediterranean.
Average of
2 localities.
Atlantic Ocean.
Average of
3 localities.
Dead Sea.
Average of
5 localities.
• •
Average quantity of salt and water—
Solid salt
Water
The dissolved solid matter consists in 100 parts of—
0'63
99'37 98.23 98.23
I'77
I'77
3'31
3.37 3.63 22.30
96.69
96.63
96.37 77'70
Chloride of sodium
58.25 79'39 84'70
78.04
77.07
77'03 36'55
Chloride of potassium.
I'27
I'07
2'09
2*48
3.89 4'57
Chloride of calcium
O'20
•
11.38
Chloride of magnesium 10'00
7.38
9'73
8.81
8.76
7.86 45'20
Bromides of sodium and
magnesium
0'03
0.28
0°49
1'30
0'85
Sulphate of lime
•
7°78
o'60 0'13
3·82
276 463
0'45
Sulphate of magnesia.. 19.68
8.32
4'96
6'58
8.34
5'29
Carbonates of lime and
magnesia
3'02
3°21
0*48
0'18
ΟΙΟ
Nitrogenous and bitu-
minous matter
1'00
• •
One cubic metre (35.3165 cubic feet) of sea-water contains consequently about
28 to 31 kilos. of chloride of sodium, and 5 to 6 kilos. of chloride of potassium.
Chloride of sodium (common salt) is obtained from sea-water:-
a. By the evaporation of the water by the aid of the sun's heat.
b. In winter by freezing.
c. By artificial evaporation.
Method of Obtaining Common
Salt in Salines.
This method of obtaining common salt from sea-water is
limited to certain of the coast-lines of Southern Europe, and is never effected
beyond 48° N. latitude. The countries best situated for this industry are France,
Portugal, Spain, and the coasts of the Mediterranean. The arrangement of the
salines, or salt-gardens, is the following:-On a level sea-shore is constructed a
large reservoir, which, by a short canal, communicates with the sea, care being
taken to afford protection against the inroads of high tides. The depth of water in
these reservoirs varies from 0.3 metres to 2 metres. The sea-water is kept in the
reservoir until the suspended matter has been deposited, and is then conveyed by a
wooden channel into smaller reservoirs, from which it is conducted by underground
pipes to ditches surrounding the salines, where the salt is separated from the water.
The salt is collected, placed in heaps on the narrow strips of land which separate the
ditches from each other, and sheltered from rain by a covering of straw. As these
heaps are left for some time, the deliquescent chlorides of magnesium and calcium
* According to the experiments of Baron Sass, the water of the Baltic from the Great
Sound between the Islands of Oesel and Moon only contains o·666 per cent. of solid matter,
and is of a sp. gr. 1'00474.
COMMON SALT.
165
are absorbed in the soil, consequently the salt is comparatively pure. The mother-
liquor is used in the production of chloride of potassium (see ante, p. 119), sulphate
of soda, and magnesia salts, the process employed being that originally suggested by
Professor Balard, and afterwards improved by Merle.
By Freezing.
This process is based upon the fact that when a solution of common
salt is cooled to several degrees below the freezing-point, it is split up into pure
water, which freezes, and a strong solution of salt. The solution becomes more
concentrated by repeated freezing and removal of the ice, until at last a solution is
obtained which by a slight evaporation yields a crop of salt. In order to render the
product purer, some lime is added to the solution before evaporation to decompose
the magnesia salts.
By Artificial Evaporatiɔn. Common salt evaporated from sea-water by the aid of fuel,
or sel ignifère, is chiefly prepared in Normandy, in the following manner:-The
sand impregnated with salt is employed to saturate the sea-water, which is next
evaporated. Very frequently an embankment of sand is thrown up on the shore, so
as to be covered at high tides only; in the interval between two tides a portion of the
salt dries with the sand, which in hot summer weather is collected twice or three
times daily. The sand is lixiviated in wooden boxes, the bottoms of which are con-
structed of loose planks covered with layers of straw; the sand having been
put in the boxes sea-water is allowed to percolate through them till the specific
gravity of the water increases to 1*14 or to 1*17, the density being observed by means
of three wax balls weighted with lead. The salt boilers at Avrauchin consider that a
solution or brine of 1.16 sp. gr. is the most suitable for evaporation. The evapora-
tion is carried on in leaden pans, and during the process the scum is removed and
fresh brine added until the salt begins to crystallise out, when again a small quantity
of brine is added to produce more scum, which is at once removed, and the evapo-
ration continued to dryness. The salt thus obtained, a finely divided but very
impure material, is put into a conical basket suspended over the evaporating pan,
the object being to remove by the action of the steam the deliquescent chlorides of
calcium and magnesium. The salt is next transferred to a warehouse, the floor
of which is constructed of dry, well-rammed, exhausted sand, and here it is
gradually purified by the loss of deliquescent salts, the consequent decrease in weight
amounting to 20 to 28 per cent. 700 to 890 litres of brine yield, according to the
quantity of salt contained in the sand, 150 to 250 kilos. of salt. A very similar
method is in use at Ulverstone, Lancashire.
At Lymington and the Isle of Wight, sea-water is concentrated by spontaneous
evaporation to one-sixth of its original bulk, the brine being then evaporated by the aid
of artificial heat. In the neighbourhood of Liverpool salt is obtained by employing
sea-water in refining crude rock-salt; in this way at least 2.3 per cent. of common
salt results as a by-product. During a continuation of hot summer weather, salt is
deposited from the water of many of the salt lakes in immense quantities, amounting,
for instance, at the Elton Lake, Russia, to 20 millions of kilos.
Rock-salt. This mineral is frequently accompanied by anhydrite, clay, and marl,
and is sometimes found in what are termed pockets of irregular shape, interspersed
with clay. Again, in some cases saline deposits are separated by layers of marl.
With rock-salt other minerals sometimes occur, as, for instance, brongniartine
(Na2SO4 + CaSO4), near Villarubia, in Spain, and the remarkable minerals of the
salt deposit near Stassfurt. Above the latter deposit is a layer 65 metres thick,
of bitter, many-coloured, deliquescent salts, consisting of 55 per cent. of carnallite,
166
CHEMICAL TECHNOLOGY.
sylvin, and kainite; 25 per cent. of common salt; 16 per cent. of kieserite; and 4 per
cent. of chloride of magnesium. As this saline layer contains 12 per cent. of
potassa it is an important deposit in an industrial sense.
The composition of rock-salt is as follows:-
I. White rock-salt from Wieliczka; II. White, and III. Yellow rock-salt from
Berchtesgaden; IV. From Hall in the Tyrol; V. Detonating salt from Hallstadt;
VI. From Schwäbischhall.
I.
II.
III.
IV.
V.
VI.
Chloride of sodium
100'00
99'85
99'92
99'43
98.14
99.63
Chloride of potassium
traces
0'09
Chloride of calcium
traces
0*25
0'28
Chloride of magnesium traces
0*15
0'07
0.12
Sulphate of lime
O'20
1.86
100'00
100'00
100'00
100'00
100'00
100'00
The so-called detonating salt, found at Wieliczka in crystalline granular masses,
has the property when being dissolved in water of giving rise to slight detonations
accompanied by an evolution of hydrocarbon gas from microscopically small cells,
the walls of which becoming thin when the salt is dissolved in water, give way, and
cause the report. If the solution of the salt takes place naturally in the mine, the
gas partly escapes, partly becomes condensed, forming petroleum, often met with in
beds of rock-salt. The minerals of the salt deposit of Stassfurt are, according
to MM. Bischof, Reichardt, Zincke, and others, the following:—
Chemical
Formula.
In 100 parts are
contained:
Sp. gr. of the
compound.
100 of Sulphate of lime 2.968
100 parts of
water dis-
solve at
182°C.
0*20
Synonyms
and Obser-
vations.
Karstenite.
Anhydrite.. CaSO4
Boracite
26.82 Magnesia
B16030Cl2 65:57 Boric acid
Mg7 10.61 Magnesium chlo-
2·9 {
Almost
insoluble
} Stassfurtite.
ride
26 76 Chloride of potas-
sium
Carnallite..
KMgCl
+6й20 34'50 Magnesium chlo- 1.618
64'5
Contains
Bromine.
ride
38.74 Water
Red oxide of
iron
Fe2O3 100 of Oxide of iron
3*35
Insoluble.
Kieserite
..
(MgSO4 +
87.10 Sulphate of mag-
nesia
H₂0*
2.517
40'9
Martinsite ?
12.90 Water
45 18 Sulphate of lime
2CaSO4
1993 Sulphate of mag-
nesia
Polyhalite.. MgSO4
K₂SO 28'90 Sulphate of po-2720
4
2H2O
tassa
5'99 Water
Is decom-
posed while
being dis-
solved.
* According to Rammelsberg it is probable that kieserite is originally an anhydrous
mineral, a conclusion which seems justified by the variable quantity of water found in
different analyses.
COMMON SALT.
167
Chemical
formula.
In 100 parts are
contained:
Sp. gr. of the
compound.
182° C.
100 parts of
water dis-
solve at
Synonyms
and Obser-
vations.
Rock-salt...
NaCl
100 Chloride of sodium 2*200
36.2
Sylvin
...{
.{ KCL
tassium
100 Chloride of po-} 2*025
34'5
21.50 Chloride of cal-
CaCl2
cium
Tachhydrite
2MgCl2
36′98 Chloride of mag-> 1671
160°3
12H₂O
nesium
41'52 Water
36.34 Sulphate of po-
K₂SO4
tassa
MgSO4 25 24 Sulphate of mag-
nesia
Contains
Kainite
M&Cl₂
Bromine.
6H20
18.95 Magnesium chlo-
ride
Schönite or
Pikromerite
19.47 Water
43°18 Sulphate of po-
tassa
MgSO4 29.85 Sulphate of mag-
K₂SO4
6й₂0
nesia
26'97 Water.
Sylvin is also found in large quantities in the salt deposit near Kalucz, Galicia.
Mode of Working Rock-Salt. Rock-salt, like other minerals and according to its mode of
occurrence, is either quarried or mined. If it happens, however, that the rock-salt
is mixed with other minerals, clay, gypsum, dolomite, &c., a solution in water is
effected, which is pumped up from the mine as a concentrated brine. In many
instances rock-salt is wrought in extensive and deep mines, as in the celebrated
rock-salt mines of Wieliczka.
Mode of Working Salt-springs, Natural salt-springs sometimes occur which have been
imitated artificially by boring to a great depth into layers of earth containing saline
deposits. In this manner a brine may be obtained sufficiently concentrated to
be at once boiled down. The method of working the natural salt-springs is to form
a convenient reservoir from which the saline solution is immediately pumped up for
the purpose of being gradated (see p. 168). The solution previous to being boiled
down is left to allow the suspended matter to settle. The salt-springs obtained
by boring either yield a native brine, or the borings are carried into solid rock-salt
and water caused to descend into the salt deposit. This artificial brine is then pumped
up, unless there is naturally an artesian formation. The brine previous to further
operations is left for some time in reservoirs to deposit suspended insoluble matter.
These saline solutions are not always free from impurities; in considering their admixture
brine may be divided into two classes; the first containing sulphate of magnesia or soda,
with chloride of magnesium; the other class embraces brine containing the chlorides
of calcium and magnesium. If the brine happens to pass through peaty soil or layers of
lignite, there often accrues organic matter, humic, crenic, and apocrenic acids.
168
CHEMICAL TECHNOLOGY.
Preparation of Common
Salt from Brine.
This operation is duplex and consists in--
a. Concentrating the brine.
a. By increasing the quantity of salt.
B. By decreasing the quantity of water.
b. The boiling down of the concentrated brine.
Concentrating the Brine. Native brines or salt-springs seldom contain enough common
salt to make it profitable to boil them down at once; it is consequently necessary to
enrich the brine, and this may be done either (a) by dissolving in it rock-salt
or crude sea-salt, neither being suited for culinary and many other purposes unless
refined, or (B) by decreasing the quantity of water without the use of fuel.
Enriching by Gradation. The enriching or concentration of a brine by decreasing the
quantity of water it contains is called a gradation process, and may be proceeded
with by freezing off the water in winter time, or more generally by evaporating the
water by a true gradation process; either-a. Gradation by the effect of the sun's
rays. b. Table gradation. c. Roof gradation. d. Drop gradation.
Gradation by means of the sun's rays is obviously the same method of procedure as
that described under the treatment of sea-salt. Table gradation has been only experi-
mentally tried at Reichenhall, and consists simply in causing the brine to flow slowly
from a reservoir down a series of steps, constructed so as to give as much surface as pos-
sible, and thus hasten the evaporation. Roof gradation is effected by utilising the roofs
of the large tanks containing the brine as evaporation surfaces, by causing the contents of
the tanks to flow in a thin but constant stream over the roofs, which, of course, are
exposed to the open air.
Faggot Gradation.
This operation, also known as drop gradation, is carried on by
means of the following apparatus, termed gradation house, and consisting of a frame-
work of timber, fitted with faggots of the wood of 'runus spinosa, which being
thorny, presents a large surface. The entire construction is built over a water-tight
wooden tank, which receives the concentrated brine, and frequently the top of
the gradation house is provided with a roof. Under the roof and above the faggots
a water-tight tank is placed containing the brine to be gradated; this tank is
provided with a number of taps, from which the brine trickles into channels provided
with holes to admit of the brine falling on the faggots. These taps are placed
on both sides of the gradation house, and are generally connected with levers to
admit of being readily turned on and off from below. The gradation process is con-
tinued until the brine is sufficiently concentrated to admit of being further evapo-
rated by the aid of fuel; the brine may be gradated to contain 26 per cent. of salt,
but the operation is rarely carried so far.
The gradation process not only serves the purpose of concentration, but also that
of purifying the brine, as some of the foreign salts are deposited on the faggots, this
deposit of course varying in composition according to the constituents of the brine,
but chiefly consisting of carbonate of lime, with the sulphates of potassa, soda, and
magnesia. The deposit has in some instances been used as manure. In the tanks
where the gradated brine is collected another slimy deposit is gradually formed,
consisting of gypsum and hydrated oxide of iron. As in the present day the brine
obtained from bored wells is generally sufficiently concentrated to be at once boiled
down, gradation is less frequent, being a very slow process and involving a loss of
the salt carried off by the wind.
Boiling down the Brine. The object is to obtain with the least possible expenditure of
fuel the largest quantity of pure dry salt. Formerly the evaporation was carried on
COMMON SALT.
169
in large cauldrons, but at the present time evaporating vessels are constructed of
well rivetted boiler-plate, the shape being rectangular, the length 10 metres, depth
o'6 metre, and width from 4 to 6 metres. These pans are supported by masonry,
which also serves to separate the flues. Over the pans a hood is fixed and con-
nected with a tube carried to the outside of the building to afford egress to the
steam. The brine, concentrated to contain from 18 to 26 per cent. of salt, is poured
into the pans to a depth of o‘3 metre.
The boiling down process is in many salt works conducted in two different opera-
tions:-
a. The evaporation of water to produce a brine saturated at the boiling-point.
b. The boiling down of the saturated brine until the salt crystallises out.
The boiling down is generally carried on for several weeks, the scum being
removed, and also the gypsum and sulphate of soda deposited at the bottom of the
pan, with perforated ladles. As soon as a crust of salt is formed on the surface of
the liquid, a temperature of 50° is maintained. At this stage the salt is gradually
deposited at the bottom of the pan in small crystals, and being removed, is put into
conical willow baskets, which are hung on a wooden support over the pan to admit of
the mother-liquor being returned to it. Finally, the salt is dried and packed in casks.
The quantity of mother-liquor collected after boiling for some two or three weeks is,
compared with the quantity of brine evaporated, very small; it was formerly thrown away
or used for baths, but is now employed for the preparation of chloride of potassium, the
sulphates of soda and magnesia, artificial bitter water, and in some instances for pre-
paring bromine. It is evident that by the boiling down all the salt contained in the brine
is not reduced as dry refined salt, a portion being retained among the early deposit formed
at the bottom of the pan, another portion remaining in the mother-liquor, and finally
some loss accrues from the nature of the operations, amounting generally from 4 to 9:25
per cent. As in some countries salt is an article upon which an excise duty is levied,
in order that it may be employed duty free for certain industrial purposes, it is mixed in
various proportions with substances rendering it unfit for culinary use.
Properties of Common
Salt.
Chloride of sodium crystallises in cubes, the size of the crystals
determining the varieties known in the trade as coarse, medium, and fine grained
salt, and depending upon the rate of evaporation of the brine, a slow evaporation
producing very coarse salt. Perfectly pure common salt is not hygroscopic, but the
ordinary salt of commerce contains small quantities of the chloride of magnesium
and sodium. Usually salt contains from 2.5 to 5.5 per cent. water, not as a constituent,
but as an intermixture; hence the phenomenon called decrepitation, due to the
breaking up of the crystals by the action of the steam when salt is heated. Ignited
to a strong red heat chloride of sodium fuses, forming an oily liquid, and at
a strong white heat is volatilised without decomposition. Common salt is readily
soluble in water, and is one of the few salts almost equally soluble in cold and in
hot water; 100 parts of water at 12° dissolve 35'91 parts of common salt.
In order to express the quantity of salt contained in a brine, it is usual to say the
brine is of a particular fineness, strength, or percentage; for instance, a brine at
15 per cent. contains in 100 parts by weight 15 parts of salt and 85 parts of water.
The Grädigkeit or degree of a brine means the quantity of water which holds in solu-
tion 1 part by weight of salt; a brine of 15'6 Grädigkeit contains, therefore, I part
by weight of common salt in 15.6 parts of water. The poundage (Pfündigkeit) of a
brine indicates in pounds the quantity of salt contained in a cubic foot of brine.
The following table shows the percentage of salt contained in brines of the several
specific gravities:-
170
CHEMICAL TECHNOLOGY.
Salt per cent.
Sp. gr.
Salt per cent.
Sp. gr.
Salt per cent.
Sp. gr.
I
I'0075
7'5
10565
16
I'1206
1'5
1'0113
8
1'0603
17
I'1282
2
I'0151
8.5
I'0641
18
I'1357
2.5
1'0188
9
1*0679
19
I'1433
3
I'0226
9'5
1*0716
19'5
I'1510
3'5
I'0264
ΙΟ
I'0754
20
I'1593
+45
1.0302
10'5
I'0792
21
1*1675
4'5
I'0339
II
1'0829
22
1*1758
I'0377
11:5
1*0867
23
1*1840
5'5
I0415
12
I'0905
24
I'1922
6
I'0452
13
1'0980
25
I'2009
6'5
I'0490
14
I'1055
26°39
I'2043
7
I'0526
15
I'1131
Uses of Common
It is not necessary to enter into particulars on this subject. Salt is used
Salt. as a necessary condiment to food; a man weighing 75 kilos. contains in his
body 0·5 kilo. of common salt, and requires annually 7.75 kilos. to maintain this supply.
Common salt is used in agriculture, and is as necessary for cattle and horses as for man.
It serves industrially in the preparation of soda, chlorine, sal-ammoniac, in tanning, in
many metallurgical processes, the manufacture of aluminium and sodium. Further, it is
employed in the glazing of the coarser kinds of pottery and earthenware, from the fact that
when common salt is fused with a clay containing iron, the sodium is oxidised at the
expense of the iron, and forms soda, which, combining with the alumina and silica, sup-
plies a glaze, while the iron combining with the chlorine is volatilised. The uses of common
salt for the preservation of wood, for curing meat, preserving butter, cheese, &c., are toc
well known to require explanation. Among the salt-producing countries of Europe, Eng-
land takes the lead, producing annually 32,400,000 cwts., while Germany only produces
and Russia 20 million cwts.
10,
MANUFACTURE OF SODA.
(Soda or Sodium carbonate, Na2CO3 = 106. In 100 parts, 58'5 parts soda and
41.5 parts carbonic acid.)
Soda.
sources :-
All the soda commonly used is derived from the three undermentioned
Soda.
a. Natural or native soda
B. From plants;
7. Chemical production.
a. Native Soda.
Occurrence of Native Soda is found in many mineral waters, as at Karlsbad, where the
waters yield annually 133,700 cwts. of carbonate of soda, and at Burtscheid, Aix-
la-Chapelle, Vichy, and the Geyser, in Iceland. Soda occurs as an efflorescence on
some kinds of rocks, chiefly of volcanic origin, as trass and gneiss. Sesquicarbonate
of soda, C3O8Na4+ 3H2O, is met with in large quantities in the water of the so-called
soda lakes of Egypt, Central Africa, the borders of the Caspian Sea and Black Sea,
in California, Mexico, and elsewhere. During the hot summer season a portion of
the level country of Hungary is covered with an efflorescence of carbonate of soda,
locally known as Székso, which is collected and brought to market. The Egyptian
name for soda is Tro-Na, hence the German term Natron. The soda locally known
in Columbia as Urao is obtained from a lake, La Lagunilla, distant 48 miles from
the town of Merida. During the hot season the urao crystallises from the water,
SODA.
171
and is gathered from the bottom of the lake at a depth of 3 metres by divers, with
great risk of their lives; the annual quantity collected amounts to 1600 cwts. When
the Spaniards were in possession of this territory the urao was a government
monoply, and was brought to Venezuela for the preparation of Mo or inspissated
tobacco juice. Very recently an inexhaustible supply of native soda has been
found in Virginia.'
Various theories have been proposed to explain the origin of native soda, but here
as in other instances it is best to bear in mind that a posse ad esse non valet conclusiv.
Native soda is rarely exported from the countries where it is found and collected,
excepting the Egyptian Tro-Na, which is brought to Venetia for glass-making
purposes and met with in the trade in the shape of bricks made up with sand.
Soda from Soda Plants,
and from Beet-root.
B. Soda from Plants, or Soda-ash.
When treating in a former chapter of potassa we saw that the
ash of plants, especially of those grown at a considerable distance from the sea,
contains carbonate of potassa; likewise that plants grown near the sea-shore and in
the localities known as salt steppes yield an ash which contains more or less soda
in the living plant combined with sulphuric and organic acids, and which under the
influence of the carbonate of lime is during the ignition of the plant converted into
carbonate of soda. In addition to the species of Fucus growing in the sea itself,
the genera known as Salsola, Atriplex, Salicornia, &c., are employed for the pre-
paration of soda, and until lately were largely cultivated for this purpose. The
process of obtaining soda from these plants simply consists in burning them in pits
dug in the sand near the sea-shore, the heat of the combustion becoming so intense
as to cause the ash to flux, so that after cooling the material forms a hard slag-like
mass, termed in the trade crude soda or soda-ash, the quantity of carbonate of soda
it contains varying from 3 to 30 per cent. This new material is refined by exhausting
with water and evaporating the liquor. From the different plants and modes of
preparation employed we obtain the following distinctions in kind:
a. Barilla, from Alicante, Malaga, Carthagena, the Canary Islands, and the Barilla soda
(Salsola soda) produced on the Spanish coast; contains on an average from 25 to 30 per
cent. of carbonate of soda.
b. Salicor, or soda from Narbonne, obtained by the ignition of the Salicornia annua,
planted purposely, and gathered when the seed is ripe; contains about 14 parts of carbonate
of soda.
c. Blanquette, or soda from Aigues-Mortes, prepared from the plants growing wild on
the tract of comparatively barren land lying between Aigues-Mortes and Frontignan, viz.,
the Salicornia Europea, Salsola tragus, Salsola kali, Statice limonium, Atriplex portulacoides.
This soda only contains from 3 to 8 per cent of sodic carbonate.
d. Araxes soda, of about the same value as the preceding, is largely used in Southern
Russia, and is obtained from plants of the mountain plateau of the Araxes in Armenia,
where the soda is prepared.
e. Of less value even than the preceding is the Parec soda, obtained on the coasts of
Normandy and Brittany from the goëmon, Fucus vesiculosus.
f. Kelp is obtained in Scotland and the Orkneys by the combustion of various sea-weeds,
the Fucus serratus, F. nodosus, Laminaria digitata, and Zostera marina. Notwithstanding that
480 ewts. of dried plants only yield 20 cwts. of kelp, containing no more than from 50 to
100 lbs. of sodic carbonate, 20,000 people are occupied in the Orkneys alone in the prepara-
tion of kelp.
g. Among the varieties of soda derived from plants may be mentioned that obtained in
considerable quantity from the vinasse of beet-root, but this soda, according to Tissandier's
analysis, always contains carbonate of potassa.
*See "Chemical News," vol. xxi., p. 129.
172
CHEMICAL TECHNOLOGY.
Soda from Chemical
Processes.
y. Soda prepared by Chemical Processes.
M. Leblanc, the inventor of the successful method of converting
common salt into carbonate of soda, may indeed be considered as an immediate
benefactor to his countrymen, who, until the latter half of the last century, annually
paid 20 to 30 millions of francs to Spain for barilla. The war which broke out in
1792 terminated the importation of soda, potash, and saltpetre into France, and
hence the Comité du Salut Public decreed in 1793, amongst other measures, that
all soda manufacturers should give the fullest particulars of their mode of working,
and the processes they imagined might be used on the large scale to obtain soda
equally good and cheap as that from barilla without the use of that or any similar
material. The manufacturer Leblanc was the first who sent in full particulars on
this subject, and his process was declared by the committee to be the best and most
suitable, the verdict standing unshaken to the present day, which witnesses the
improvement of the recovery of the sulphur from the soda waste.
Leblanc's Process. This now consists in the following stages :—
a. The preparation of sulphate of soda from salt by the aid either of sulphuric
acid or sulphates, or by the roasting of common salt with iron pyrites or
other native metallic sulphurets.
b. Conversion of the sulphate into crude soda by roasting with a mixture of
chalk and small coal.
c. Conversion of the crude soda into refined soda or caustic soda by lixiviation
and evaporation.
d. Recovery of the sulphur from the soda waste.
Sulphate, or
Decomposing Furnace.
a. The most usual mode of converting common salt into sul-
phate of soda is by the action of sulphuric acid. The condensation of the hydro-
chloric acid gas is generally effected by a method introduced in 1836 by Mr. Gossage,
and consisting in the use of a contrivance known as coke- or condensing-towers.
These are square buildings from 12 to 14 metres in height, by an interior width of
1.3 to 1.6 metres, constructed of stone not acted upon by hydrochloric acid, the
joints being cemented with a mortar made of coal-tar and fire-clay. To nearly the
top these buildings are divided by a wall, each compartment thus formed being
filled with pieces of coke resting on a perforated stone floor. Water is caused to
flow constantly from the top of the tower on to the coke. The hydrochloric acid gas
resulting from the decomposition of the salt by sulphuric acid is conducted by means
of stoneware tubes to the bottom of the first compartment of the condensing-tower,
and there meeting with the moist coke is condensed to within 95 per cent. of the
entire quantity, the other compartment of the condensing-tower being usually in
direct connection with the chimney-shaft of the alkali-works. The decomposition-
furnaces at first in use were reverberatory furnaces so constructed that the smoke
and gases from the combustion of the coals and the hydrochloric acid gas passed off
together, and as a consequence the hot gases were not in the best condition
for condensation. The furnace now in general use is that invented in 1836 by
Gossage, and improved in 1839 by Gamble, who was the first to arrange the two
phases or stadia of the decomposition in the separate compartments, & and E, of the
furnace exhibited in Fig. 71. This arrangement has been used for a very long
period, the alkali manufacturers employing a reverberatory furnace which could be
put into communication at pleasure with a kind of muffle, the bottom consisting of a
stout cast-iron plate, the flame from the furnace-grate being made to play against
SODA.
173
this muffle previously to entering the chimney. The muffle communicated with a
condensing apparatus, M M'. According to this plan of working, the common salt
was placed in G, and well warmed sulphuric acid made to flow over it; a very strong
and violent reaction took place, and half or nearly two-thirds of the hydrochloric
acid formed was readily condensed, as it was not mixed with the hot gases of the
combustion. The product resulting from this mode of operation was a mixture of
bisulphate of soda and common salt, 2NaCl + H2SO4 = NaHSO4 + NaCl + HCl.
This mixture was next shovelled into the reverberatory furnace, E, the muffle being
again charged with salt and acid. By the intense heat of the reverberatory furnace
the mixture of bisulphate of soda and common salt was converted into neutral
sulphate, NaHSO4+ NaCl = Na2SO4 + HCl; the hydrochloric gas evolved in
this operation was, however, condensed with difficulty, in consequence of being
mixed with nitrogen, carbonic acid, and carbonic oxide; and besides the con-
FIG. 71.

Y!'
M.
+t
densing towers other and complicated apparatus were required to prevent the escape
of acid fumes into the air. These defects have been remedied in the construction
of an improved decomposition-furnace.
I
New Decomposition-Furnace. This furnace consists of two muffles, one of cast-iron, the
other of fire-bricks; the interior of the former is a segment of a hollow sphere of
9 feet or 2.74 metres diameter, and 1 foot 9 inches or o'52 metre deep, resting on
brick-work. A cast-iron lid is provided, in shape also a segment of a sphere, having
a depth in the centre of 1 foot or 0.30 metre; in this lid are arranged two openings
with suitable doors, through one of which the common salt is introduced, while the
other communicates with the second muffle. The hearth is placed obliquely, the
flames first playing on the lid, and then passing under the muffle; accordingly the
hydrochloric acid gas is unmixed with other gases, and its temperature being com-
paratively low, condensation is more readily effected. The second or brickwork
muffle encloses a space of 30 feet or 9.14 metres in length, by 9 feet or 2'74 metres
in width; under the floor of this room a series of flues or channels are built, while
the top is formed of a double vault to admit the circulation of the flames, which
are next conducted through the channels under the floor.
174
CHEMICAL TECHNOLOGY.
I
The mode of operation is as follows:-Into the iron muffle, previously well heated,
half a ton of common salt is introduced, to which is added sulphuric acid of 17 sp. gr.,
the quantity of the acid being regulated so as to leave 1 to 3 per cent. of salt unde-
composed in order to obtain a perfectly neutral sulphate. 100 parts of salt require
for their complete decomposition 95 parts of an acid at 60° B. — 1'7 sp. gr., or
104 parts of an acid at 55° B. =1.62 sp. gr. The mixture of acid and salt is occasion-
ally well stirred, and after the lapse of 1 hour has become sufficiently dry to be
raked over into the brickwork compartment of the oven, which is kept at a bright
red heat to assist the expulsion of the hydrochloric acid gas. If it is desired to
obtain a concentrated hydrochloric acid solution, the escaping gas must be cooled
down before entering the condensing-towers. There is generally a valve or damper,
by which the communication between the two muffles may be closed, in order that
the hydrochloric acid gas evolved in each may be separately collected and condensed.
With these contrivances, and well constructed condensers supplied plentifully with
water, the preparation of sulphate of soda may be carried on without any inconveni-
ence to the neighbourhood in which the works are situated. For more than twenty
years Messrs. Tennant, of Glasgow, have employed this kind of furnace, decomposing
500 tons of common salt per week without receiving any complaints. On the Conti-
nent, alkali-works are legally compelled to have the decomposition-furnaces con-
structed according to a plan first brought out in Belgium, and which is very similar
to the furnace already described. The assertion of Dr. Wagner, in his original text,
concerning the many complaints now arising in England in reference to the escape
of hydrochloric acid fumes from alkali-works, is altogether unfounded, the fact being
that according to the published reports of the inspector, Dr. Angus Smith, under
the Alkali Act, nearly all the manufacturers condense, instead of 95 per cent. of the
hydrochloric acid, as required by the Act, from 97 to 98.5 per cent.
into Crude Soda.
Conversion of the Sulphate b. In order to convert the sulphate of soda into crude or
raw sodic carbonate, the former salt is mixed with chalk, or sometimes with
slaked lime and small coal, and this mixture, fused in a reverberatory furnace.
According to Leblanc's directions, the proportions are—
Sulphate
Chalk..
100 parts
ΙΟΟ
""
50
Slaked lime
but the quantities as employed in ten different works vary for 100 parts of sulphate
from 90 to 121 parts of chalk, and the quantity of small coal from 40 to 75 parts.
FIG. 72.

GET MAS MALICI
In some alkali-works for a portion of the chalk is substituted the desulphurised and
lixiviated soda waste. The reverberatory furnace generally used in English alkali-
works, and technically known as a balling furnace, is shown in Fig. 72, and that
SODA.
175
employed in Germany in Fig. 73. In England, the materials having been first
heated on the upper stage of the furnace by the waste heat, only remain in the
working furnace (see Fig. 72) for about half-an-hour; in German works the mixture
of sulphate, chalk, and small coal is strongly heated in M (see Fig. 73), until the
mass becomes fluxed and pasty, and lambent flames of burning carbonic oxide are
ejected from the surface. When this is seen the semi-fluid mass is removed from
the furnace through the openings P P, and transferred to an iron car, C, where it is
left to cool.
It is difficult to say whether the English or Continental method is the more
preferable; viewed from a theoretical point of view, it would appear that the English
method is the better of the two. As in English works, a smaller quantity of
FIG. 73.

materials, only about 7 cwts., while in Continental works from 30 to 70 cwts., is
operated upon at a time, the labour is lighter; the materials, too, are not exposed to
an intense heat for a long period; thus a loss of soda by the volatilisation of the
sodium is less likely to occur. According to Wright's investigations (1867), the loss
of soda by the conversion of the sulphate amounts to 20 per cent. of the sodium
contained in the sulphate, as shown by the following figures :-
Undecomposed sulphate ..
Insoluble sodium compounds..
Volatilisation of the sodium
•
3'49
5'44
I'14
Sodium retained in the waste
3.61
Loss occasioned by the evaporation of the liquors
6'56
Soda Furnace with
Rotatory Hearth.
20*24
In 1853 Elliot and Russell suggested a contrivance which dis-
pensed with the stirring of the materials by manual labour, and consisted of a cylin-
drical vessel made to rotate on a horizontal axis. Stevenson and Williamson im-
proved upon this idea, and according to their plan of working (see Fig. 74) the
mixture of sulphate, chalk, and small coal is placed in the iron cylinder, A, lined
with fire-clay. Ribs or rails, B, cast on the cylinder, run on the wheels, C, receiving
motion from machinery with which they gear, and causing the cylinder to rotate.
The heated air of the hearth, D, flows through the opening E into the cylinder, and
passing through F, reaches the vaulted compartment, G, and is carried off by the flue,
K, to the chimney. The interior of the cylinder having been heated to redness, the
materials are allowed to fall into it from the waggon, J, through the funnel, H.
After the lapse of ten minutes the cylinder is caused to make a half revolution, and
is then left for five minutes, the operation being continued until the mass inside the
176
CHEMICAL TECHNOLOGY.
cylinder fuses, which takes place in about half-an-hour. The cylinder is then set
continuously in motion so as to make one revolution every three minutes. The
progress from time to time is watched through a door-way constructed in the
cylinder, and as soon as the operation is complete the molten mass is run off through
the opening B'. There can be no doubt that the rotatory furnace is a great improve-
ment, and one which, besides saving labour, prevents a loss of soda by volatilisa-
tion. A cylinder 11 feet long and 7.5 feet in diameter converts in two hours 14
cwts. or 700 kilos. of sulphate at an expenditure of only 2s. 1d.
FIG. 74.

B
H
The composition of the crude or ball soda is approximately :
Carbonate of Soda
Sulphuret of calcium
45
30
Caustic lime
IO
Carbonate of lime
Foreign substances
5
ΙΟ
100
In this country large quantities of soda ash are used in glass-making, soap-boiling,
bleaching, and other operations.
Crude Soda.
Lixiviation of the c. Conversion of crude into refined soda by lixiviation and
evaporation. a. Lixiviation of the crude soda. When the crude soda is acted upon
by water there results a solution containing chiefly carbonate of soda, and a mass
remaining undissolved known as soda waste.
Soluble matter
Soda waste
100 parts of raw soda yield :-
45'0 parts
58.7
103'7
""
As a rule English ball soda has a deeper colour, and contains more carbon than
the soda of Continental manufacture. Ball soda, previously to being lixiviated, is
usually exposed for at least two and sometimes for ten days to the action of the air,
to gain in porosity, and hence be more readily acted upon by the water.
Of the several methods of lixiviation proposed, and in more or less successful use
on the large scale, may be mentioned the following:-The method of lixiviation by
simple filtration is not to be recommended on account of the great labour it requires,
but the process consists in putting the crude soda, previously broken up into lumps
of suitable size, into tanks provided with a perforated false bottom, upon which the
SODA.
177
FIG 75.
F'
K
T
crude soda is placed, water being poured on. This arrangement is repres nted in
Fig. 75, A, B, C, D. The perforated false bottom is about 25 centims. from the bottom
of the tanks. The wooden channel, K, suspended from the ceiling of the shed by
the iron bands, F F', conveys water,
which by means of the plugs, t, ť, and
t', can be let into the tanks, these
being provided with taps, r, r', and
r", by which the liquid can be run off
into the channel, K'. To illustrate the
modus operandi three tanks, A, B, C,
are sufficient; A is filled with fresh
ball soda, B with ball soda once,
and c with ball soda twice lixiviated.
We then begin by filling each tank
with the liquor which has been used
for washing the soda waste the last

K
time before throwing it aside; this liquid remains in each tank for a period of eight
hours, and the alkaline ley, which then marks 30° B., is run off from A, and the
operation repeated with weaker liquors in B and c, the leys being all conveyed to a
large reservoir, the contents of which mark 25° B. Fresh liquor is poured into a
and B, and into D, which is filled with ball soda. By this arrangement a constant
supply of ley at 25° B. is kept up.
Desormes's lixiviation apparatus, Fig. 76, consists of a series of twelve to fourteen
tanks, of which only five, A, B, C, D, E, are exhibited in the woodcut. By means of
the bent tubes, fitted about 15 centims. from the bottom of each tank, the liquor
flows into the next lower tank of the series, and so to the tanks, F F', called the
clearing or settling tanks, of which there are six connected together by tubes. The
ball soda to be lixiviated is ground to powder, and placed in the perforated sheet-
iron vessels, e e, a d, and so on. At the commencement the tanks are filled with
FIG. 76.

晨
​B
D
E
T
F
warm water, and two perforated vessels placed in E filled with 50 kilos. of ball soda;
after twenty-five minutes these vessels are removed to D, and others filled with fresh
soda placed in E. In this manner the operation proceeds, so that after eight hours,
when fourteen lixiviation tanks are worked, there are found in A perforated vessels
which have been gradually removed from the lowest to the highest tank, a, two
13
178
CHEMICAL TECHNOLOGY.
vessels, ƒƒ, having been removed from that tank and placed upon the shelf, k, to
drain, where having remained for about half-an-hour they are removed, the contents
emptied, and other vessels placed to drain. Each time that two of the perforated
vessels filled with ball soda are placed in the lowest tank, there is poured into the
uppermost as much water as corresponds with the bulk of the fresh soda; this water
displaces the heavy ley which runs through the tube from A to B, and so on, until at
last the concentrated and nearly saturated liquor runs from E into F F,
where any
suspended matter is deposited. The temperature of the liquor in these tanks should
be from 45° to 50°; but not higher, in order to prevent any decomposition of the
sulphide of calcium. The lixiviation tanks, as well as the clearing tanks, are
provided with steam pipes for the purpose of keeping the liquor sufficiently heated,
and to prevent any soda crystallising out by cooling. It is almost evident that this
method of lixiviation is the best which can be adopted, as the concentrated liquo
cannot adhere to the solid substance which it is intended to dissolve, because in
consequence of its high sp. gr. the liquor sinks to the bottom of the tank. Fig. 77
represents two lixiviation tanks drawn to a larger scale, and of a somewhat different
arrangement. Each tank is divided into three compartments by means of a double
partition wall, communication between the two compartments being provided by the
FIG. 77.

g
A
h
g
12
A
12
12
12
A
holes a and b and the space between the partition plates receiving the steam pipes,
hh. gg are the tubes for conveying the liquor, and n n the perforated vessels, to
which are rivetted iron bars serving the purpose of handles. Mr. James Shanks, of
St. Helen's, was the first to found a rational and economical plan of lixiviation, on
what is termed methodical filtration, based upon the fact that a solution becomes more
dense the more saline matter it has in solution, and that a column or weak ley of a
certain height equilibrates a shorter column of a stronger ley. In accordance with
this principle, the tanks, four or eight in number, are placed as shown in Fig. 78,
and through them water is caused to flow, exhausting the crude soda in its passage,
and becoming consequently denser in each consecutive tank of the series; hence,
the level of the liquid is lowered in each tank from the first, which contains pure
water, to the last, from which a saturated ley runs off. The length of the tanks is
2.6 metres by 2 metres in depth; F is a perforated false sheet-iron bottom supported
by iron bars. From the bottom of each tank an open tube, T, the lower opening
being cut diagonally, and at the top a smaller tube, t, soldered on, connect the tanks.
The water pipes, r r r r, fitted with taps are placed to admit of water being
supplied to each tank; by means of the taps, R R', the ley can be run off into the
channel, c'. Four lixiviations as a rule suffice. The working is as follows :-The
SODA.
179
first tank contains ball soda already three times lixiviated; the liquor added to it is a
very weak soda solution from a former operation, which percolates into the second tank.
The liquid there meets with soda which has been twice submitted to the lixiviation
process, and next flows over into the third tank, the solid contents of which have
been only once previously lixiviated. Finally, the lye arrives in the fourth tank, in
FIG. 78.

R
which fresh ball soda has been placed, and from this tank flows into a large reservoir.
The first tank having been cleared of soda waste is now filled with fresh ball soda,
and the succession of the operation reversed by the aid of taps fitted to the tubes
connecting the tanks. The larger the number of tanks the more rapidly within
certain limits a given weight of crude soda can be exhausted. The density of the
ley ought to be from 1°27 to 1*286, a cubic foot, or o'028 cubic metre, containing
from 4'5 to 4'95 kilos. of solid matter. The advantages of this mode of lixiviation
are-1. That the carriage of the crude soda from one tank to another is dispensed
with, and consequently much labour saved. 2. The soda being always covered with
liquid cannot cake. 3. As the current is always downwards the most concentrated
portion of the fluid is conveyed forward, and consequently less water is required.
4. By the continuity of the operation any reaction between the alkali and the
insoluble calcium sulphuret is prevented, or, in other words, the formation of soluble
alkaline and other sulphurets, entailing a loss of soda, is reduced to a minimum.
5. The high degree of concentration of the ley effects a considerable saving in the
expense of the evaporation.
The nature of the ley after the suspended matter has been deposited, greatly
depends upon the condition of the ball soda employed, the duration of the process,
and the temperature of the water; it is, therefore, difficult to make any general
observation. Kynaston, Scheurer-Kestner, and Kolb have proved that ball soda
does not contain caustic soda, and that consequently the presence of this substance
in the ley is due to the action under water of the lime upon the sodic carbonate.
Sulphuret of calcium can only be present in the dry ball soda in very small quantities,
but sulphuret of sodium may exist in the ley to a greater extent than caustic soda,
the quantity varying with the mode of lixiviation. Commonly, only monosulphuret
of sodium is present in the ley; even if a polysulphuret were temporarily formed it
would be immediately converted into monosulphuret by the presence of the caustic
soda. The dry ball soda contains peroxide of iron, converted into sulphuret of iron
by the action of the water; this sulphuret dissolving in the sulphuret of sodium
causes the green- or yellow-brown colour of the ley. The quantity of water employed
180
CHEMICAL TECHNOLOGY.
in the lixiviation has no effect upon the causticity of the ley, but the quantity
of sulphuret of sodium increases with the quantity of water, the duration of
the lixiviation, the temperature, and the concentration; this is owing to the
increased solubility of the sulphuret of calcium, which, when in contact with water,
is converted into hydrosulphuret of calcium and hydrate of lime, the former yielding
with caustic soda the more sulphuret of sodium the higher the concentration of the
ley. The same reasoning holds good for carbonate of soda, which is also converted
into sulphuret, but only in very dilute solutions, at a higher temperature after a
lengthened contact.
According to Kolb's researches, ball soda should be lixiviated rapidly, with but a
small quantity of water, and at a low temperature. If it were possible it would be
a great improvement to contrive an apparatus in which ball soda could be lixiviated
ir. a few hours with only so much cold water as would yield a very concentrated ley;
the liquors obtained under such conditions would be free from sulphuret of sodium.
The following analysis will give some idea of the composition of the crude ley.
The sample was obtained from the alkali-works of Matthes and Weber, at Duisburg,
the sp. gr. = 125, 1 litre containing 313'9 grms. of solid saline matter, consisting
in 100 parts of—
Carbonate of soda..
Caustic soda
Common salt
Sulphite of soda
Hyposulphite of soda
Sulphuret of sodium
Cyanide of sodium
Argillaceous earthy matter
•
Silica
Iron..
:
:
•
71'250
24'500
I 850
O'102
0*369
O'235
0*087
I'510
0.186
traces
100*089
Another crude ley from some works near Aix-la-Chapelle was of a sp. gr. 1'252,
and contained 311 grms. of solid matter per litre.
Evaporation of the Ley. B. The clarified liquor contains essentially carbonate of soda
and caustic soda, with common salt and other soda salts in smaller quantities. Owing
to the presence of the double sulphuret of iron and sodium, the ley is coloured
during the evaporation, if it be performed with the liquor immediately from the
lixiviation tanks; to prevent this result it is necessary that the leys should stand for
a considerable time in the clearing reservoirs to effect a slow oxidation of the com-
pound salt, more rapidly attained by forcing a current of air through the ley, as
suggested by Gossage. Bleaching-powder and nitrate of soda are used as oxidising
agents; a lead-salt, oxide of copper, and spathose iron ore have been employed. As
Kolb's researches have proved that monosulphuret of iron is insoluble in caustic and
in carbonate of soda solutions, an addition of sulphate of iron will have the effect of
converting the double sulphuret of iron and sodium into monosulphuret of iron and
sulphate of soda, the former salt settling rapidly and yielding a clear colourless -
liquid, and on evaporation a colourless salt.
The ley is treated in either of the two following ways:—
a. Evaporated to dryness, the result being a homogeneous product which contains
unaltered all the constituents of the ley, including the caustic soda.
SODA.
181
B. The ley is evaporated to a certain degree of concentration, the supersaturated
solution depositing on cooling carbonate of soda as a crystalline powder, containing
I molecule of water, Na2CO3 + H₂O; the salt is gradually removed from the liquor
by perforated ladles. During the evaporation fresh ley is run into the pan from a
reservoir at a higher level, and in this way the operation is continued for several
months. It is clear that by conducting the evaporation in this manner, the carbonate
of soda collected becomes gradually less and less pure, being mixed with chloride of
sodium and sulphate of soda; at last a mother-ley is left, containing chiefly caustic
soda and sulphuret of sodium, and in a concentrated solution of these substances the
other salts are insoluble. The crystalline carbonate of soda is first drained, an opera-
tion sometimes performed in centrifugal turbines, and then calcined in a reverbera-
tory furnace to oxidise any sulphuret of sodium that might be present; after this
calcination the salt constitutes the calcined soda of commerce. The quality of the
commercial article varies considerably, the difference being partly due to the care
taken in the evaporation. The first crop of salt is always the best, that is to say,
contains the largest percentage of sodic carbonate, sometimes amounting to 90 per
FIG. 79.

cent. When the ley is to be evaporated to dryness, the operation is carried on in a
reverberatory furnace, Fig. 79. The hearth is floored with fire-bricks, on to which a
thick coating of carbonate of soda is well rammed. The fuel burning in a'is coke;
as soon as the furnace has become thoroughly red-hot, ley previously evaporated to
33° B. in the pans D and E, is run into the furnace, effecting a very rapid evapo-
ration to dryness, care being taken to stir the saline mass to keep the salt in a
pulverulent state. By means of the dampers, F, G, and the flues, cc', the hot air and
flame of the burning fuel may be conducted under the pans D and E or into the
chimney. The composition of soda thus evaporated to dryness is, according to the
analysis of two samples by Mr. J. Brown, as follows:-
Carbonate of soda
Caustic soda
Sulphite of soda
Hyposulphite of soda
Sulphuret of sodium
Chloride of sodium
Aluminate of soda
Silicate of soda
Insoluble matter
•
:
:
:
:
1.
II.
68.907
65'513
14'433
16.072
7:018
7.812
2*231
2 134
I'314
I'542
3'972
3.862
1'016
1*232
I'030
0.800
0.814
0'974
100*735
99'941
182
CHEMICAL TECHNOLOGY.
The salt is next calcined, and the sulphuret of sodium converted into sulphite of soda,
a portion of the caustic soda being converted into carbonate of soda. The calcined salt
is now ready for the market; but in some of the large alkali-works near Newcastle-on-
Tyne it is re-dissolved in water, treated with carbonic acid, and again evaporated. A
better product results from another method, namely, evaporating the ley to a known
degree of concentration, and obtaining small crystals of soda-salt (NaCO3 + H₂O). In
this case, as regards the methods of evaporation employed, the two following are most
general:-Heat is brought to bear on the surface of the liquid contained in shallow
rectangular iron pans fitted to the hearth of a reverberatory furnace; the liquid rapidly
boils at the surface, and a saline crust is formed, which is constantly broken up and
collected with iron rakes by the workmen. Now and then the salt deposited at the bottom
is removed and placed on a sloping ledge to drain. This method of evaporation is econo-
mical, but attended with the disadvantage that the ley is constantly in contact with the
carbonic and sulphurous acid gases arising from the combustion of the fuel, the conse-
quence being that a portion of the caustic soda is converted into carbonate and sulphite
of soda, the latter by the subsequent calcining operation being converted into sulphate.
By the second plan of evaporation the heat is conveyed to the bottom of the pans, but
then many precautions are required to prevent the bottom being burned in consequence of
the settling down of a saline mass not conducting heat. Mr. Gamble, at St. Helens,
employs a pan of a peculiar form, the section being like that of a boot; it is heated by the
waste heat of the soda furnace, and the inclination of the sides of the pan greatly assists
the removal of the salt, which, having been drained, is calcined, yielding a grey-coloured
salt, afterwards purified by solution with the aid of steam in a small quantity of water,
decanting the clear solution, and again evaporating it. Ralston obtains a purer product
by washing the impure carbonate with a cold saturated solution of pure carbonate of soda,
the chloride and sulphuret of sodium and the sulphate being thus removed. As already
stated, the evaporation is not always continued to dryness, but to a degree of concentra-
tion determined by experience. By varying the relative bulk of the liquid a more or less
pure product may be obtained; when, for instance, the ley of the lixiviation tanks
(=1·286 sp. gr.) is evaporated to 7ths of its bulk, and the salt separated removed, this
salt corresponds to a purified soda salt of 57 per cent.; by evaporating the remaining
liquid to ths of its bulk, a salt of 50 per cent. is obtained. When the mother-liquor is
evaporated to dryness, a very caustic and impure salt is obtained. Kuhlmann, at Lille,
employs pans which are graduated so that the bulk of the liquid may be readily ascer-
tained for the purpose of fractioned evaporation. The purification of the crude ley,
containing sulphuret of iron dissolved by sulphuret of sodium, may be effected, as
suggested by Gossage, in 1853, by filtering the liquid through a coke-tower (one of the
towers used for condensing hydrochloric acid), a current of air being forced upwards to
assist in oxidising the sulphuret of sodium.
The composition of refined soda, according to Tissandier's analyses, is :-
I.
2.
3.
4.
5.
Moisture
2.22
3.11
1'15
I'00
0'40
Insoluble matter..
Chloride of sodium
O'12
O'22
0'08
0.06
•
•
12:48
6.41
3.28
2.II
O'99
Sulphate of soda
Carbonate of soda
8.51
3.25
2'15
I'50
0'35
76·67
87.01 92.34
95.39
98:20
100'00
100'00
100'00
100'00
100'00
The composition of soda, containing caustic soda, is:-
I.
2.
3.
4.
Moisture
2'10
1.50
2:48
1.38
Insoluble matter
O'12
O'II
0'21
0'09
Chloride of sodium
4.32
2:43
3.50
4'II
Sulphate of soda
8.80
1.62
2.15
2.50
Carbonate of soda
Caustic soda
82:47
88.09
84.54
81.67
2.II
6.25
7.12
10'25
100'00
100'00
100'00
100'00
In order to obtain crystallised soda, Na2CO3 + 10H20, with 63 per cent. of water,
a saturated solution of calcined soda in hot water is poured into large iron vessels,
and yields crystals on cooling. The calcined soda is generally dissolved in conical
vessels (Fig. 80), made of boiler-plate. c is a steam-pipe, в a water-pipe, D a per-
SODA.
183
forated vessel to contain the calcined soda to be dissolved. The boiler is three-
fourths filled with water, the perforated vessel filled with soda is then lowered into
the liquid, and the steam turned on. The soda is rapidly dissolved, and when the
solution marks 30° to 32º B. it is run into the crystallising vessels; the crystallisa-
tion is complete in five to six days in moderately cool weather. The crystals are
broken up, and again dissolved in water in the vessel A (Fig. 81), heated by the fire
at C. DD are flues carrying flame and heated air round the vessel; B is a water-pipe.
The vessel having been filled with crystals, a small quantity of water is added, and
as soon as the salt is completely dissolved, the fire is extinguished, the liquid being
left to settle. The clear liquid is next syphoned into a reservoir, and from this poured
B
FIG. 80.

FIG. 81.

into cast-iron crystallising vessels. After seven or eight days the mother-liquor is
removed, and the crystals are detached from the surface of the iron by placing
the crystallising vessels for a few moments in hot water, the result being that by the
incipient fusion of the crystals in their water of crystallisation, they are loosened
from the metal to which they adhere. After, draining the salt is dried in rooms
heated to 15° to 18°, and then packed in casks. Although a crystalline salt is gene-
rally purer than a non-crystallised mass, yet the large quantity of water contained
in crystallised carbonate of soda is an impediment to its extensive use, both on
account of expense of carriage and the weakness of the alkali. In this country,
however, owing to the great facility of water carriage, crystallised carbonate of soda
is very largely used.
Theory of Leblanc's Process. The process of M. Leblanc has been best elucidated by the
more recent researches of Gossage and Scheurer-Kestne. Formerly it was
assumed that when a mixture of sulphate of soda, carbonate of lime, and carbon
were calcined, the carbon while yielding carbonic oxide converted the sulphate of
soda into sulphuret of sodium, in its turn decomposed by the carbonate of lime, the
result being the formation of carbonate of soda, oxysulphuret of calcium, and the
evolution of a portion of the carbonic acid; (a) Na2SO4 2C=Na2S+2CQ2;
184
CHEMICAL TECHNOLOGY.
(B) 2Na2S+3CaCO3 = 2Na2CO3 + CaO, 2CaS+ CO2. According to Unger the car-
bonate of lime loses its carbonic acid as soon as sulphuret of sodium is formed,
there remaining a mixture of caustic lime, sulphuret of sodium, and carbon, which
becomes converted into oxysulphuret of calcium, and caustic soda, the latter by
taking up the carbonic oxide resulting from the combustion of the carbon becoming
sodium-carbonate; this view appears to be nearest the truth, but as proved by
Scheurer-Kestner, Dubrunfaut, J. Kolb, and Th. Petersen, it is not necessary to
assume the existence of oxysulphuret of calcium for the purpose of explaining the
fact that the sulphuret of calcium does not act upon the sodium-carbonate, because
sulphuret of calcium is almost insoluble in water, 12.5 parts of water dissolving at
12.6° only 1 part of sulphuret of calcium. This view is also confirmed by the
results of experiments made by Pelouze. During the formation of soda in the cal-
cining furnace the carbon is only converted into carbonic acid, viz. :-
a. 5Na2SO4+10C5Na2S+IOCO₂.
B. 5Na2S+7CaCO3=5Na2CO3 + 5CaS+ 2CaO+ 2CO₂.
However, as there is formed during the calcination process, especially towards the
end of this operation, a not inconsiderable quantity of carbonic oxide which burns
off with a bluish flame, this substance, although a secondary product, has to be taken
into account in the formula; moreover, the formation of this gas is important, for
as soon as it makes it appearance the chief reaction is being completed, proving
the heat to be at its proper degree.
•
The researches of Unger have undoubtedly proved that when the sulphat›
is reduced by carbon there is only carbonic acid and not a trace of carbonic oxide
formed, so that carbonic oxide is the result of the action of the excess of carbon
upon the carbonate of lime; this reduction of the carbonate of lime by carbon takes
place at a much higher temperature than that at which the sulphate is reduced,
therefore the formation of carbonic oxide takes place after that of the carbonate
of soda. Consequently there must be distinguished three phases in the formation of
soda, viz. :-
a. The reduction of the sulphate, with evolution of carbonic acid gas-
(Na2SO4 + 2C = Na2S+ 2CO2)..
B. Double decomposition of the newly formed sulphuret of sodium and carbonate
of lime (Na2S+ CaCO3 Na2CO3 + CaS).
y. The reduction of the excess of carbonate of lime by the carbon-
(2CaCO3+2C=2CaO+4CO).
During the lixiviation the presence of caustic lime aids the formation of caustic
soda. According to theory, 100 parts of sulphate only require 20 of carbon, but it
is the practice to employ an excess of carbon, as much as 40 to 75 per cent., to pro-
vide against incomplete mixture, the combustion of carbon without effect, and
because of the necessity of obtaining the reaction of the carbonic oxide in order
that the progress of the operation may be observed, as experience has proved that the
mass should not be removed from the furnace until this combustion is nearly over.
Utilisation of Soda Waste. The greater part of the soda now employed is obtained by
Leblanc's process, which, while it admits of lixiviating the soda readily and com-
pletely, is defective, inasmuch as the residue, or waste as it is technically called,
contains nearly all the sulphur used in the manufacture; and that this is not a slight
loss may be inferred from Oppenheim's statement, that in the alkali works at Dieuze,
SODA.
185
Lorraine, the accumulated waste contains an amount of sulphur valued at £150,000.
For every ton of alkali made there is accumulated 1 tons of waste, containing
80 per cent. of the sulphur used in the manufacture; and this waste, until lately
thrown on a refuse heap in some fields adjacent to the works, often proved a nuisance
in hot weather, giving rise to fumes of sulphuretted hydrogen. For the last forty
years much time and money have been spent in trying to recover the sulphur,
but not until 1863 was any attempt successful. Three different processes are now
resorted to, viz.-Guckelberger's, modified and practised by Mond; Schaffner's plan;
and the process invented by M. P. W. Hofmann, at Dieuze. Since the first suc-
cessful experiment the methods have been so rapidly improved that, at the Paris
Exhibition of 1867, no fewer than nine samples of recovered sulphur were sent in.
All the methods mentioned above are based upon the same principle-the conversion
of the insoluble sulphurets of calcium contained in the waste into soluble compounds
by the aid of the oxygen of the atmosphere; the lixiviation of the oxidised mass,
and precipitation of the sulphur contained in the leys by a strong acid, practically
hydrochloric acid.
neration Process.
Schaffner's Sulphur Rege- M. Schaffner's plan for the regeneration of sulphur from soda
waste involves the following operations:-
a. Preparation of the liquor containing sulphur
B. Decomposition of the liquor.
y. Preparation of the sulphur.
a. The soda waste is submitted to a process of oxidation by the action of the air,
and for this purpose is placed in large heaps, where heating takes place, together
with the formation of polysulphurets and subsequently hyposulphites. After a few
weeks the interior of the heap assumes a yellow-green colour, when the material
is ripe for lixiviation; the heap is then broken up into large lumps, which remain for
another twenty-four hours' oxidation. These lumps are next submitted to lixiviation
with cold water, and a concentrated liquor obtained. After this process follows
another oxidation, effected by placing the lixiviated residues in a pit dug in the soil
to a depth of 1 metre, and situated close to the lixiviation tanks; by this burying the
heat generated by the oxidation suffers less dissipation than when the material is ex-
posed on all sides to currents of air. The second oxidation proceeds more rapidly than
the first in consequence of the greater porosity of the mass, so that besides poly-
sulphurets more hyposulphites are formed. Instead of effecting the second oxida-
tion by burying, the waste may be left in the lixiviation tanks, and the oxidation
accelerated by forcing the hot gases from a chimney under the perforated bottom of
the tank; by these means both time and labour may be saved, the oxidation being
complete in 8 to 10 hours. According to the quality of the alkali waste, this process
of oxidation may be repeated three to four times; the gases accompanying the smoke
of burning fuel are exceedingly well suited for effecting the decomposition of
the sulphuret of calcium in such a manner as to cause the formation of poly-
sulphurets and hyposulphites. The liquors resulting from the first lixiviation con-
tain chiefly polysulphurets and hyposulphites; but the liquors obtained after the
second and third oxidation contain essentially hyposulphites; all the liquors are col-
lected in one reservoir.
B. The decomposition of the lixiviation liquor by means of hydrochloric acid is
carried on in a closed apparatus of cast-iron or stone, and is based upon the fact that,
186
CHEMICAL TECHNOLOGY.
hyposulphites when treated with hydrochloric acid, evolve sulphurous acid gas,
sulphur being precipitated (Ca₂O3+2HCl yields CaCl2 + SO₂+S+H₂O), and
upon the reaction exerted by sulphurous acid upon the polysulphuret, which, while
sulphur is deposited, is again converted into hyposulphite of lime-
(2CaSx+3SO₂2=2CaS2O3 + Sx).
The liquor is tested by titration to determine the quantity of polysulphuret and of
hyposulphites contained, and according to the result the residue is more or less
oxidised.
The apparatus generally employed in the decomposition is shown in Fig. 82; A and B
are the vessels to contain the liquor; is the pipe by which the liquor is conveyed to
A or B, regulated by a piece of elastic tubing entering at q into a, or q' into B. T and T'
are earthenware tubes by which the hydrochloric acid is introduced. c and d are glass
FIG. 82.

R
h
A
B
I'
-
As soon
tubes, c is fitted to the top of A, and has a longer leg dipping into the fluid at B; the reverse
is the case for d, the short leg of which is fitted to B, while the longer leg dips into the
fluid in A. The tap, a, is closed when the gases should enter through c into the fluid
contained in B, but the tap, b, is shut, and a opened, when the gases passsing through d are
to enter the fluid contained in a. The excess of gas is carried off by the tube R.
as the decomposition by the action of the hydrochloric acid is effected, steam is injected
through the valves, vv, to expel the last traces of sulphurous acid from the liquor.
The liquor and finely divided sulphur are run off at o and o', care being taken to let the
chloride of calcium solution run off by removing the wooden plug, p. In order to ascertain
whether all the sulphurous acid is expelled, the wooden taps, h h', are opened, the smell
of the gas being a sufficient indication of its presence. The taps, ƒ and f', are employed
as test cocks to ascertain the progress of the operation, and also to see whether the
vessels are properly filled with liquor.
The sulphur obtained by this process is fine-grained, and mixed with some gypsum,
chiefly due to the sulphuric acid contained in the hydrochloric acid. The sulphur and
chloride of calcium liquor are conducted by the spout, g, to a vessel with a false bottom,
perforated and covered with a flannel cloth, through which the liquor passes, the sulphur
being retained.
7. The sulphur is prepared for the market by a very simple process. It is mixed
with sufficient water to constitute a paste, which is put into a cast-iron vessel, and
steam at a pressure of 12 atmospheres admitted to melt the sulphur, the water
taking up any adhering chloride of calcium solution, and also the gypsum. The
molten sulphur collects in the bottom of the vessel, and is tapped off into moulds ;
the supernatant liquor does not mix with the sulphur owing to the greater specific
weight of the latter. In order to perfectly saturate any free acid which might still be
SODA.
187
present some milk of lime is added; by this addition another end is gained, viz.,
the removal of any arsenic, in the following manner:-If during the melting process
an excess of lime be present, sulphuret of calcium is formed, and this sulphuret
dissolves any sulphuret of arsenic which is thus removed to the supernatant liquor.
The advantages of melting and purifying the sulphur by the above process are —
the sulphur need not first be carefully washed and dried, fuel is saved, the sulphur
freed from arsenic, and brought to the best state for pouring into moulds. Figs. 83
and 84 represent the melting vessel; the cast-iron cylinder, B, is surrounded by a
wrought-iron cylinder, A, and the whole inclined to admit of the molten sulphur
FIG. 83.

A
R
FIG. 84.

(0)
A
え
​α
10 10
collecting at the lower part of B. The sulphur paste is being stirred by an apparatus
in gearing at R with some motive power. The paste is poured into B at m; at
a steam is introduced, passing at o into the inner cylinder, and let off, when the
melting is finished, through d and the valve, v; the molten sulphur is run off at z;
s is a safety valve. By this process 50 to 60 per cent. of the sulphur contained in
the soda waste is recovered, for every cwt. recovered 2 to 24 cwts. of hydrochloric
acid being employed. If this acid were too expensive, the residues of chlorine
manufacture might be used, these residues consisting mainly of chloride of manganese,
free hydrochloric acid, and chloride of iron; the first step would then be to free
these residues from the chloride of iron by means of the lixiviated soda waste added
in small quantities at a time; sulphuretted hydrogen would be given off, and
Fe₂Cl reduced to FeCl2, the changed colour indicating the end of the reaction.
The dirty grey-coloured sulphur from this reaction should be burnt in the pyrites
or sulphur-burning furnace. The prepared residue would now be fit for employment
as a substitute for hydrochloric acid. Should, however, some monosulphuret of
calcium be present in the soda waste liquor-not a very likely occurrence—some
hydrochloric acid must be added before using the residues.
Sundry Methods of
Preparing Soda from
Sulphate of Soda.
Among the many methods which have been proposed for the
preparation of soda the following especially deserve notice. Ac-
cording to Kopp's methods of soda manufacture sulphate of soda, oxide of iron,
and carbon are smelted together in an ordinary soda furnace :-
188
CHEMICAL TECHNOLOGY.
2Fe20
3 Na2SO4
yield by
calcination
Fе Na6S3.
14ČO.
160
2CO2.
The crude soda absorbs from the air water, oxygen, and carbonic acid, becoming
converted into carbonate of soda and an insoluble residue of sulphuret of iron
containing sodium, Fe,Na6S3 :— .
Fе4Nа6S3
20
2CO2
yield
2Na2CO3.
Fe Na2S3.
The lixiviation is effected with warm water at 30° to 40°; the liquors yield after
twenty-four to twenty-eight hours, without any previous concentration, a large
crop of beautifully crystallised soda. The insoluble residue of the lixiviation is dried
and roasted to produce sulphurous acid, employed in the manufacture of sulphuric
acid, used in its turn for the conversion of common salt into sulphate of soda. Thus
the cycle of changes in the sulphur is complete :-
Fez Na2S 3
140
Field
2Fe2O3
Na2SO4
2SO2
The sulphate of soda present in the calcined residue is removed by lixiviation.
It cannot be denied that this process presents certain advantages.
Direct Conversion of
Common Salt
into Soda.
A plan for the direct conversion of common salt into soda has long
been sought, but hitherto not successfully carried into practice. When
a concentrated solution of bicarbonate of ammonia is mixed with
strong brine, or, better still, the pulverised bicarbonate stirred through a concentrated
solution of salt, and this mixture left to stand, the result will be that after some hours
bicarbonate of soda will be deposited in crystalline state, the supernatant liquid being a
solution of sal-ammoniac. As bicarbonate of soda on being gradually heated to redness
loses a portion of its carbonic acid, and is converted into monocarbonate of soda, this
process has been suggested as suited for the manufacture of soda, and has been
tried by Dyar and Hemming in England. Schlosing and Rolland in 1855 took out a
patent for some improvements on this method of soda manufacture, of which the following
is an outline:-The first operation consists in the action of ammonia and carbonic
acid upon a concentrated salt solution; to 100 parts of water 30 to 33 parts of common
salt, 8 to 10 of ammonia, and carbonic acid in excess are taken. The next step is the
separation of the bicarbonate of soda, which is effected by a centrifugal machine.
The third stage is the calcination of the bicarbonate of soda in cylindrical iron vessels,
the carbonic acid gas given off being collected. The fourth and fifth operations aim at
the recovery of the carbonic acid and ammonia from the liquid drained from the bicar-
bonate of soda while in the centrifugal machine. The liquid is heated in a boiler, the
result being the escape of the ammonia and carbonic acid, which are conducted to a
cylinder filled with coke, through which a cold aqueous solution of carbonate of amı-
monia trickles, causing the condensation of the ammonia, the carbonic acid escaping
into a gasholder. Next, milk of lime is added to the liquid, and the heating being con-
tinued, all the ammonia is expelled. Lastly, the clear supernatant liquid is evaporated to
recover the common salt. According to Heeren's researches on this subject, this process is
more suited for the preparation of bicarbonate of soda; it is stated, however, that the
researches of Marguerite and Sourdival have resulted in improvements on this method
which may in future lead to its being advantageously adopted in some localities for the
manufacture of soda.
Soda from Cryolite. Cryolite (Al2F16,6NaFl) is largely employed for the manufacture
of soda by decomposing the mineral by ignition with lime :-
1 mol. of Cryolite
}
6 mols. of Lime yield {
´6 mols. of Fluoride of calcium.
I mol, of Aluminate of soda.
This last compound being soluble in water is decomposed by carbonic acid, and
alumina precipitated, soda remaining in solution. 100 kilos. of cryolite yield-
SODA.
189
Dry caustic soda
Calcined soda
44 kilos.
...
Crystallised carbonate of soda
Bicarbonate of soda
•
75
203
119'5 ""
Bauxite (see under Alumina), on ignition with sulphate of soda and carbonaceous
matter, yields in a similar manner soda and alumina.
Soda from Nitrate
of Soda.
By the conversion of nitrate of soda into nitrate of potassa by the aid
of carbonate of potassa (see under Saltpetre) not inconsiderable quantities
of a strong solution of soda are obtained; the sodium of the sodium nitrate may be
converted by any of the following means into soda or caustic soda :-
a. By igniting nitrate of soda with carbonaceous matter.
b. By igniting nitrate of soda with silica, and decomposing the silicate of sodium by
carbonic acid.
c. By igniting nitrate of soda with manganese.
d. By the decomposition of nitrate of soda.
a. By means of carbonate of potassa; or,
B. By means of caustic potassa.
In the latter case, besides nitrate of potassa, caustic soda is formed.
Caustic Soda, This substance, sodium hydroxide (NaHO), is met with in commerce
as a highly concentrated solution, or more frequently as a solid mass, fused hydrate
of soda, consisting in 100 parts of 77.5 parts of soda and 225 parts water. For
many years a moderately strong solution of caustic soda was prepared by treating
a carbonate of soda solution with caustic lime, but Dale was the first to use this
solution instead of water in his boilers, and thus concentrate the lye to a sp. gr. of
1*24 to 1*25, after which the ley was further evaporated in cast-iron cauldrons to a
sp. gr. of 1'9, at which point it solidifies on cooling.
Instead of using caustic lime, caustic soda is now directly produced by simply
increasing the quantity of small coal added to the mixture of sulphate and chalk,
the crude soda being at once lixiviated with water at 50°. After the liquor has
cleared, it is rapidly concentrated to 15 sp. gr., when carbonate, sulphate, and
chloride of sodium are deposited, the liquor assuming a brick-red colour, due to a
peculiar compound of double sulphuret of sodium and sulphuret of iron.
The ley
is next strongly heated in large cast-iron cauldrons, and there is added 3 to 4 kilos.
of Chili-saltpetre for every 100 kilos. of caustic soda required; by this operation the
nitrate of soda reacts upon the sulphuret of sodium and cyanide of sodium present,
causing an abundant evolution of ammonia and nitrogen. This somewhat com-
plicated process may be elucidated by either of the two following formulæ :—
a. 2Na2S+2NaNO3 + 4H2O=2Na2SO4 + 2NaHO+2NH3.
B. 5Na2S+8NaNO3 + 4H20=5Na2SO4+8NaHO+8N.
According to Pauli, the kind of reaction depends chiefly on the temperature of the
heated ley; at 155° ammonia is largely evolved; above 155° and with greater con-
centration of the ley nitrogen is given off. As for every ton of caustic soda produced
this process absorbs 0·75 to 1 cwt. of nitrate of soda, the ley is in some works oxidised
by filtering it through a column of coke, or by forcing air through it in minute jets.
Among these is the decomposition of sulphate of soda by means of
Soda Manufacture. caustic baryta, a rather expensive process, baryta white or permanent
white being a by-product. Unger uses caustic strontia instead of caustic baryta. Caustic
soda may be prepared by treating cryolite for sulphate of alumina (see Ålum), or by
igniting nitrate of soda with manganese; or by decomposing silico-fluoride of sodium
or fluoride of sodium with caustic lime. In England very pure caustic soda is prepared
from sodium by carefully oxidising the metal with pure water in bright iron or silver
vessels.
New Methods of Caustic
190
CHEMICAL TECHNOLOGY.
According to Dalton's researches :
A caustic soda liquor of the
undermentioned sp. gr.
2'00
1.85
Contains percentage of caustic
soda (NaHO.)
77.8
63.6
I'72
53'
1.63
46.6
1'56
41'2
I'50
36.8
I'47
34'0
1'44
31'0
I'40
29'0
I'36
26'0
I'32
23°0
I'29
19'0
I'23
16'0
1.18
13.0
I'12
9'0
I'06
4'7
Caustic soda is largely used in soap-making, paraffin and petroleum refining, and the
preparation of silicate of soda and artificial stone by Ransome and Sims's method.
Bicarbonate of Soda. This substance, NaHCO3, called erroneously carbonate of soda
in many of the London shops, consists in 100 parts of 36'9 soda, 10'73 water, and
52.37 carbonic acid, and is prepared by passing a current of washed carbonic acid
gas through a solution of carbonate of soda. If the solution is concentrated the
bicarbonate is deposited as a powder, but from a dilute solution large crystals are
obtained. It is, however, more advantageous to cause the carbonic acid to act upon
crystallised and effloresced carbonate of soda; a suitable mixture consists of 1 part
of crystallised and 4 parts of effloresced carbonate of soda. The sources of carbonic
acid may differ, bnt in this country the gas is generally prepared by the action of
weak hydrochloric acid upon chalk or limestone; of course the carbonic acid evolved
during the fermentation of wort, or must, may be applied.
When carbonic acts upon crystallised carbonate of soda there is first formed
sesquicarbonate of soda; the 9 equivalents of water which are displaced from each
equivalent of crystallised carbonate of soda are collected in a reservoir, and this
liquid having of course dissolved a portion of the bicarbonate is employed at a
future operation for moistening the crystallised soda carbonate. The bicarbonate
is dried at 40° in a current of carbonic acid gas. The preparation of the bicarbonate
by withdrawing from the monocarbonate by the aid of an acid one-half of the soda
it contains has been suggested; for this purpose 28 parts of crystallised sodic
carbonate are dissolved in twice their weight of warm water, and 4 parts of
sulphuric acid added, care being taken not to move the vessel. Being left to stand
for several days the bicarbonate is deposited in crystals. It has been seen
that when a solution of common salt is treated with bicarbonate of ammonia, the
result is the formation of bicarbonate of soda and sal-ammoniac, which remains in
solution. Bicarbonate of soda crystallises in monoclinical, tabular crystals; has a
weak alkaline reaction; loses its carbonic acid at 70°, and becomes monocarbonate
of soda; and by exposure to dry air is gradually converted into sesquicarbonate.
The bicarbonate is employed generally in the preparation of effervescing drinks, and
IODINE AND BROMINE.
191
with hydrochloric or phosphoric acid in making bread without fermentation. The
further uses of this salt are the precipitation of the alumina from sodium-aluminate
solutions, for the preparation of baths, for gilding and platinising, and for purifying
and cleansing silk and wool. I grm. of the bicarbonate yields, when completely
decomposed by an acid, about 270 c.c. of carbonic acid gaso˚52 grm. by weight.
The total production of soda in Europe amounted in 1870 to 11,850,000 cwts., of
which Great Britain produced 6,250,000 cwts.
PREPARATION OF IODINE AND BROMINE.
Preparation of Iodine. This element occurs in sea-water, from which it is taken up by
various sea-weeds; from these sea-weeds iodine is derived industrially. Chili-salt-
petre and some saline springs (for instance, the Sulza, Sadiem Weimar) contain
iodine in considerable quantity. Although iodine is found in the mineral kingdom
(for instance, in the iodide of lead and phosphorites of Amberg, Bavaria, and Diez
on the Lahn), it is not in this case industrially important. The chief seat of iodine
manufacture is at Glasgow, where there are twelve factories; there are two iodine
factories in Ireland, and two at Brest, in France.
Preparation from Kelp. In order to obtain iodine from sea-weeds, the latter are first con-
verted into kelp, that is to say, they are incinerated, the product broken to pieces
and lixiviated with water, leaving an insoluble residue of 30 to 40 per cent., and
yielding to the liquid 60 to 70 per cent. This solution, having a sp. gr. of
118 to 120, contains chlorides, sulphates, and carbonates of alkalies, sulphuret
of potassium, iodide of potassium, and hyposulphites of alkalies; by evaporating
and cooling the liquor, the sulphate of potassa and chlorides of potassium and
sodium are removed. To the remaining mother-liquor, previously poured into
shallow open vessels, dilute sulphuric acid is added, the result being, that while
a strong evolution of gases, sulphuretted hydrogen, and carbonic acid takes place,
there is formed a thick scum and a deposit of sulphur at the bottom of the vessel;
the sulphur when washed and dried is sold. When the evolution of gas has
completely ceased, more sulphuric acid is added, and, according to Wollaston's
method, the required quantity of manganese; this mixture is poured into a large
leaden distilling apparatus, c, Fig. 85. By this means the iodine is set free, carried
FIG. 85.

P" B
I' B
over in the state of vapour to the receivers, B, B', B″, and condensed as a solid
crystalline mass. In Paterson's large iodine works at Glasgow this operation is
carried on in a cast-iron hemispherical vessel of 13 metres diameter, the cover
192
CHEMICAL TECHNOLOGY.
being a leaden dome, to which are fitted two earthenware stillheads, connected
by means of porcelain tubing with two earthenware receivers, Fig. 85, each con-
sisting of 4 to 5 parts. At Cherbourg, iodine is obtained, according to Barruel's
plan, by passing chlorine gas into the mother-liquor; by this plan the iodine is
separated from the iodide of magnesium, the latter taking up chlorine instead—
(MgL+Cl, MgCl,+I).
A more recent method, by which all the iodine present in the mother-liquor is
obtained, consists in distilling the liquor with chloride of iron-
(2NaI + FeCl21+ 2NaCl + 2FeCl2).
As iodine is only very slightly soluble in water, 1 part of iodine requiring 5524 parts
of water at 10° to 12° for its solution, that is, 1 grain of iodine to 12 ounces of water,
it is carried over with the steam and deposited at the bottom of the receiver in the
form of a black powder. When iodine is prepared by the aid of chlorine, the
quantity of gas should be exactly sufficient to decompose the iodide of magnesium,
for if the quantity of chlorine be too small no iodine is separated, and if too large
chloride of iodine is formed and free bromine, both of which being volatile escape.
The iodine when removed from the receivers is drained on porous bricks or tiles,
and dried between folds of blotting-paper. It need hardly be said that the iodine
FIG. 86.
a
B
α
should not come in contact with a
metallic surface. The iodine thus
obtained has to be purified by sub-
limation, an operation carried on in
the apparatus represented in Fig. 86,
consisting of stoneware retorts, c c,
placed in the sand-bath, B, heated
as shown in the woodcut. Each of
these retorts is filled with upwards
of 40 lbs. of crude iodine, and en-
tirely surrounded by sand, in order
to prevent the sublimation of any
iodine in the necks of the retorts.
These are then connected with the

I ton of kelp
receiver or condenser, R R, in which the crystalline iodine is deposited, the tubes,
a b, a b, being for the purpose of carrying off the watery vapour.
yields on an average 4·07 kilos. of iodine.
Method of Preparing Iodine
Stanford and Moride's In 1862, Mr. Stanford suggested that the sea-weeds should not
from Cabonised ea-weed. be calcined, but simply distilled with superheated steam, so as to
prevent volatilisation of the iodine, while the tarry and gaseous products should be sepa-
rately utilised. This carbonised sea-weed, when quite cold, is lixiviated with water, and
the solution treated for iodine and chloride of potassium (see p. 130). The volatile pro-
ducts of the distillation are illuminating gas, acetic acid, ammonia, mineral oil, and
paraffin. M. Moride, of Nantes, has modified this process: he prepares by evaporating
the liquor from the lixiviation of the carbonised sea-weed, sulphate and chloride of
potassium. &c. The mother-liquor is treated with chlorine or hyponitric acid, and then
with benzine, in an apparatus so arranged that the benzine directly gives up the iodine it
has dissolved to soda or potassa, the benzine thus acting as a continuous solvent. The
liquor containing iodine is treated for the separation of iodine in the usual manner.
Crude Chili-saltpetre contains on an average 0059 to 0.175
Preparation of Iodine frum
Chili-Saltpetre. per cent. of iodine. According to Nöllner, the iodine occurs from
the formation of the Chili-saltpetre in the presence of decaying sea-weeds from shallow,
stagnant, inland seas, which have dried up. The mother-liquors, left after the refining
of the salt, or from its use for the conversion of chloride of potassium into nitrate of
potassa, and containing 0.28 to 0.36 per cent. of iodine, are treated with sulphurous
IODINE AND BROMINE.
193
acid until the iodine separated begins to re-dissolve. More recently nitrous acid has
been used instead of sulphurous acid. The iodine thus obtained is refined by sublima-
tion, while that remaining in the residual saline matter is removed by a further treat-
ment with chlorine.
Properties and Uses of Jodine. Iodine (I=127; Sp. gr. =4′94) is a black-grey coloured
crystalline substance, with a metallic appearance not unlike graphite. On being
heated iodine is converted into vapours, which, according to Stas, when concentrated
exhibit a blue colour, and a violet in a more dilute state. Iodine fuses at 115°,
and boils above 200°. It is somewhat soluble in water, readily so in alcohol,
ether, hydriodic acid, iodide of potassium solution, sulphide of carbon, chloroform,
benzol, aqueous solution of sulphurous acid, and solution of hyposulphite of soda.
A solution of iodine imparts a violet colour to starch. Adulteration of iodine
with either pulverised charcoal or graphite may be at once detected by treating a
sample with alcohol or a solution of hyposulphite of soda, in each of which the
iodine, if pure, ought to dissolve completely, leaving no residue on sublimation.
Sometimes the weight of iodine is fraudulently increased by the addition of water.
Iodine is largely used in photography combined as iodide of potassium; for the
preparation of other iodine compounds, for instance, iodide of mercury; also in the
preparation of some of the tar colours, iodine violet, iodine green, and cyanine blue,
the latter a compound from iodine and lepidin, a volatile base. The total produc-
tion of iodine in Europe and Chili amounted in 1869 to 3453 cwts., more than half,
or 1829 cwts., being produced in Scotland and Ireland.
Preparation of Bromine. The element known as bromine occurs to a small extent in sea-
water, a litre containing o'oб1 grms. bromine. The mother-liquors, however, of
many salt works (for instance, those at Schönebeck, near Magdeburg, and the
liquors left from many of the Stassfurt salts) are so rich in bromine, that its pre-
paration is worth the cost and trouble. In order to avoid as much as possible the
admixture of chlorine, there is added to the mother-liquor dilute sulphuric acid;
this mixture is heated to 120°, and the hydrochloric acid set free by the sulphuric
acid evolved, while the less volatile hydrobromic acid is left in the liquor, from
which, on cooling, sulphates are deposited. The decanted liquor is distilled after the
addition of more sulphuric acid and some manganese. Two Woulfe's bottles serve
as receivers; in the first are condensed water, bromine, bromoform, and bromide of
carbon, while any bromine vapours which pass over to the second bottle are absorbed
in the caustic soda it contains. The ley contained in this vessel is evaporated to
dryness, the residue ignited in order to convert bromate of soda into bromide of
sodium; the saline mass being then mixed with sulphuric acid and manganese and
distilled, yields pure bromine. best preserved under strong sulphuric acid.
According to Leisler's patent (1866) bromine is separated from the mother-liquor left by
operations with kainite, or carnallite, or from the water of the Dead Sea (containing,
according to Lartet's analysis. in 1 litre. taken from a depth of 300 metres. 7093
grms.07 per cent. of bromine) by adding bichromate of potassa and an acid; heat
being applied, the bromine is volatilised and collected in a condenser filled with metallic
iron. From the bromide of iron thus formed, either the element itself or any of its com-
pounds may be obtained. The apparatus employed by this patentee is a distilling ap-
paratus; the acid is hydrochloric diluted with four times its bulk of water; to 100 parts
by bulk of the bromine fluid, I part by bulk of acid is added. The bichromate is added
in a saturated aqueous solution. The bromide of iron formed becomes dissolved by the
aqueous vapour, and condensed in the receiver. Bromine is the only metalloid fluid at
ordinary temperature. Seen in thick layers its colour is a deep brown-red, but in thin
layers a hyacinth-red; its odour is strong and similar to that of chlorine gas. The
aqueous solution of bromine 1 part requiring 30 parts of water for its solution-is of a
yellow-red colour when freshly made, but like chlorine-water does not keep well, and is
14
194
CHEMICAL TECHNOLOGY.
soon converted, especially if exposed to light, into a colourless solution of weak hydro-
bromic acid. 100 parts of bromine water contain at 15°, 3:226 parts of bromine; bromine
forms with water a solid hydrate at o°. It is readily soluble in ether, alcohol, chloroform,
and hydrobromic acid. It yields with an aqueous solution of sulphurous acid hydro-
bromic acid—
(SO₂+ H2O+ 2Br = SO3 + 2BrH).
Bromine boils at 63°, giving off deep red vapours; at -7.3° it becomes a lead-grey
coloured, foliated, graphite like mass. Bromine acts upon colouring matters, dyes, and
the colours of flowers as does chlorine, while organic matters, especially those of animal
origin, are coloured brown. It is used in combination as bromides of potassium, ammo-
nium, cadmium, and hypobromite of potassa, for photographic purposes and in medicine;
and further as bromides of ethyl, amyl, and methyl, for the preparation of some of the tar
colours, Hofmann's blue, and the preparation of alizarine from anthracen. Bromine is
also used as a disinfectant, and, according to Reichardt, may with advantage be sub-
stituted for chlorine in the preparation of ferricyanide of potassium. Since the year
1866 bromine has been manufactured at Stassfurt, now the chief bromine-producing
locality. The total annual production of bromine in Europe and America amounts
to 1150 cwts., of which 400 cwts. are obtained at Stassfurt, and 300 cwts. in Scot-
land.
SULPHUR.
Sulphur. In combination with coals, rock-salt, and iron, sulphur is the mainstay of
present industrial chemistry. It is often found native between gypsum, clay, and
marl in tertiary deposits, more rarely in veins between crystalline rocks of the
schistose and metamorphic varieties, and not unfrequently in coal and lignite
deposits. Sulphur is an almost constant product of active volcanoes, being sublimed
and deposited on surrounding objects. The largest sulphur deposits in Europe are
met with in Sicily. It is also found in Egypt on the banks of the Red Sea, espe-
cially near Suez; at Corfu, one of the Ionian Islands; near the Clear or Borax Lake
in California; on the slopes of the Popocatepetl, in the province of Puebla, Mexico,
where yearly 2000 cwts. of sulphur are collected. Frequently, sulphur is deposited
from the sulphuretted waters of mineral springs; for instance, the waters of Aix-
la-Chapelle. Sulphur occurs in combination with metals, as in iron pyrites, FeS2,
with 53.3 per cent. of sulphur; this mineral often contains thallium. The quantity
of sulphur contained in the following minerals is, from 100 parts:-Iron pyrites
(FeS2), 53'3; copper pyrites (Fe, Cu,S), 34'9; magnetic iron pyrites, mundic
(Fe,S。, or, according to Th. Petersen, FeS), 39′5; galena (PbS), 13'45; black-jack
(ZnS), 33'0; kieserite (MgSO4 + H₂O), 23'5; anhydrite (CaSO4), 23'5; gypsum
(CaSO4+2H₂O), 18.6; gas coal, 10. According to Dr. Wagner, the quantity of
sulphur present in the coals used in the London gasworks annually, amounts to
200,000 cwts., equal to 612,500 cwts. of sulphuric acid.
Although sulphur occurs native as sulphuretted hydrogen and sulphurous acid,
especially near active volcanoes, this is not of much industrial use. The regenera-
tion of sulphur from soda-waste is decidedly one of the most important items in the
sulphur industry.
Smelting and Refining
Sulphur.
According to the comparative richness of the raw material, the
sulphur is separated from its concomitant impurities by melting or by distillation.
When the raw material is rather rich it is simply submitted to a process of melting
in a cast-iron cauldron, B (Fig. 87), heated by a gentle coal or charcoal fire placed
in A. During the melting the mass is stirred with an iron rod, and as soon as the
sulphur has become quite fluid, the gangue and small stones are removed by means
of the ladle, c. This done, the sulphur is poured into a wooden or sheet-iron vessel
D, thoroughly wetted with water to prevent the adhesion of the sulphur to the
SULPHUR.
195
sides. The sulphur when cold and solid is broken into large lumps and packed in
casks ready for the market. The stones and gangue are placed in heaps, or more
commonly introduced into a shaft furnace (Fig. 88), and, a portion of the sulphur
being sacrificed to serve as fuel, the greater part of the element is eliminated by the
following plan:-A small portion of the crude sulphur is ignited in the lower part of
the furnace, and the shaft, E, filled with large lumps of the earthy sulphur ore, from
FIG. 88.

FIG. 87.

D
|000730)
E
h
The
which, rapidly ignited superficially, the molten sulphur trickles down.
openings, ƒƒƒ, give access to the air required for the combustion of a portion of the
sulphur. The sulphur collects in the lower part of the furnace and is tapped off
by the channel g into wooden or sheet-iron vessels. A far better method of pre-
paring sulphur from the ore is by distillation, the apparatus being that exhibited in
Fig. 89. A is a cast-iron cauldron, which is filled with raw material, and covered
FIG. 89.

P
with a tightly-fitting iron lid. The flues are so constructed as to heat the vessel D
gently. The vapours of sulphur are carried by the tube m into the condenser, B,
whence the molten sulphur runs off into the vessel k. The previously warmed oṛe is
readily admitted to A by lifting the damper, p. From a suggestion made by E. and
P. Thomas, sulphur is obtained from its ores by the application of superheated
steam at 130°, this mode of working being the same as that employed by M. Schaffner
for purifying the sulphur recovered from soda-waste. In passing, it may be men-
tioned that very recently the extraction of sulphur from its ores has been attempted
195
CHEMICAL TECHNOLOGY.
by the aid of solvents, viz., sulphide of carbon and a light coal-tar oil of sp. gr.=0·88.
M. Mène's analyses of several samples of crude Sicilian sulphur obtained by smelting
are-
Sulphur (soluble in CS₂)
Carbonaceous matter
• ·
I.
2.
3.
4.
5.
•
90'1
96.2
91.3
COO
88.7
ΙΟ
0'5
0.7
I'I
ΙΟ
Sulphur (insoluble in CS₂)
2.0
1'5
2'I
I'7
Siliceous sand
2.3
1.5
3'3
2.8
5.5
Limestone (sometimes cœlestin)
Loss
4'I
1.8
2.5
3°0
2.8
0.5
0'7
I'O
0.3
The bottom portion of the blocks of crude sulphur often contains 25 per cent. of
foreign substances. The crude sulphur is refined in order to eliminate all traces
of earthy matter; and after this process it is brought into commerce in sticks or
rolls or in powder.
Lamy's Refining Apparatus.
The apparatus for refining sulphur, invented by Michel and
improved by Lamy, at Marseilles, consists mainly of two cast-iron cylinders, B
(Fig. 90), used as retorts, and a large brick-work condensing-room, G. The cylinder B
FIG. 90.

F
VEGNIS
肉​燒
​SEONDO
JH
M
N
L
is directly heated by the fire, the smoke of which is carried off by the chimney, E.
The flues, c, however, surround D, where the crude sulphur undergoes a partial
refining, and whence it flows by the tube F into the cylinder B. The cylinder B is
SULPHUR.
197
in communication with the vaulted room G. At the bottom of this room is placed
a cast-iron plate in which a hole is bored, and fitted with a conical plug, J, con-
nected with a rod, H, so as to admit of being shut and opened for the purpose of
tapping sulphur into the cauldron, L, whence it is ladled over into the moulds
placed in M. N is a box for the roll sulphur when it has become cold.
Roll Sulphur.
If it is intended to prepare roll-sulphur, the mode of proceeding is the
following:-Each of the cylinders is filled with crude sulphur, the lids firmly
fastened, and the joints luted. Heat is at first applied to only one of the cylinders,
and not until half of its contents are distilled off is the second cylinder heated.
Gradually the heat at D increases to such an extent as to melt the crude sulphur; by
this fusion the heavier earthy impurities settle down, while any moisture present is
driven off. When the distillation of the contents of the cylinder first heated is
finished, that cylinder is filled with liquid sulphur from D by means of the tube F.
The quantity of sulphur treated in twenty-four hours yields 1800 kilos. pure material
collected in G. The temperature of this room being 112°, the sulphur is there kept
in a molten state, and as soon as a sufficient quantity has collected at the bottom, it
is tapped off into L, and cast in the moulds. When it is desired to prepare flowers
Flowers of Sulphur. Of sulphur, the mode of operation is the same, but the temperature of
G should be kept at or rather below 110°. This is effected by making the distillation
interrupted instead of continuous, so that in twenty-four hours there are only two
distillations of 150 kilos. each. As soon as a sufficient quantity of flowers of sulphur
has been condensed in the room G, the door of the room is opened and the sulphur
removed.
Dujardin improved upon this apparatus in 1854. By this process of distillation
of sulphur a loss of 11 to 20 per cent. is incurred, partly due to combustion of a
portion of the sulphur. The residue left in the cylinders and vessel D is known as
sulphur-slag. The ordinary flowers of sulphur of commerce always contain some
sulphuric and sulphurous acids, which can be removed by carefully washing with
water. Sulphur so treated and gently dried is known in pharmacy as washed flowers
of sulphur, Flores sulphuris loti.
from Pyrites."
Preparation of Sulphur Where fuel and labour are cheap, and a good quality of iron or
other pyrites is found in abundance, sulphur may be prepared by the following
process:-
1. From iron pyrites, FeS2. As this mineral consists in 100 parts of 46'7 of iron
and 53.3 of sulphur, it is clear that if half of the latter be removed by distillation,
there will be left a compound of iron and sulphur yielding green copperas after
oxidation. Accordingly iron pyrites might by distillation lose 26·65 parts of sulphur,
and the residue still be fit for making green copperas; but if this quantity were to be
driven off in practice, the temperature would require to be raised so high as to melt
the remaining monosulphuret and lead to the destruction of the fire-clay cylinders.
The quantity of sulphur actually distilled off on the large scale is only 13 to 14 per
cent., leaving a pulverulent residue which does not attack the fire-clay cylinders.
The process thus briefly outlined is carried on in the following manner :-
-The pyrites
is put into conical fire-clay vessels, a A, Fig. 91, placed in a somewhat slanting position in
the furnace; the lower and narrower portion of these vessels is fitted with a perforated
diaphragm preventing any pyrites falling down b, while the volatilised or fluid sulphur
can pass readily through the holes into a receiver, c, filled with water. After the vessels
A A have been filled with pyrites, the fire is kindled and the distillation set in progress.
The sulphur collected in the receiver has a grey-green colour, and is purified by being
re-melted, after which it is sent into the market in coarsely broken up lumps. In order to
198
CHEMICAL TECHNOLOGY.
free this kind of sulphur from sulphuret of arsenic, it is submitted to distillation, the
residue being used in veterinary practice. The dark colour of the sulphur obtained
from pyrites is due to an admixture of thallium far more than to the presence of
A
FIG. 91.
arsenic. Mr. W. Crookes found in the
sulphur obtained from Spanish pyrites as
much as 0.29 per cent. of thallium.
Preparation of Sulphur by 2. Sulphur may be
Roasting Copper Pyrites. obtained by the roast-
ing of copper pyrites, and in this way
becomes a by-product of smelting copper
ores. Formerly this operation was carried
on in peculiarly constructed furnaces in
the copper-smelting works of the Lower
Hartz, Germany; at the present time
sulphur from this source is only obtained
at Agordo in Italy, Wicklow in Ireland,
and at Mühlbach, Salzburg, Austria.

Manulacture.
Sulphur obtained as a 3. Since Laming's
By-Product of Gas mixture has been em-
ployed in purifying coal-gas, sulphur has
to some extent been obtained as a by-
product. Laming's mixture is hydrated,
or any soft porous peroxide of iron mixed
with sawdust; and in this mixture sulphur
may accumulate to upwards of 40 per cent.
(Fe₂O3+H₂S=2FeO+H₂0+S). Ac-
cording to Hill's patent the sulphuret of
iron is calcined to obtain sulphurous acid,
which is employed in the preparation of
sulphuric acid.
Sulphur from Soda Waste. 4. We have already
seen, while treating of the manufacture of
soda (vide p. 185) that several processes
due to MM. Schaffner, Guckelberger, Mond,
P. W. Hofmann, and others, are in use for the regeneration of sulphur from soda waste;
and that the quantities recovered are not small may be inferred from the fact that the
Austrian Association for chemical and metallurgical products, under the management of
M. Schaffner, at Aussig, produces annually 450,000 kilos. of sulphur in this manner.
Production of Sulphur by
the Reaction of Sulphuretted
5. Dumas first made the observation that when one-third of
Hydrogen upon Sulphurous Acid. sulphuretted hydrogen is burned off, and the sulphurous acid
produced conveyed with another one-third of sulphuretted hydrogen into a leaden or brick
chamber, where moisture abounds, nearly all the sulphur is regenerated :-
Sulphurous acid, SO₂
Sulphuretted hydrogen, 2H,S) yield (Sulphur, 38.
Water, 2H₂O.
By this reaction, by which, however, nearly half the sulphur is lost in the formation of
pentathionic acid, it has been frequently attempted to obtain sulphur from gypsum,
heavy spar, and soda waste. The process is briefly as follows:-For instance, heavy spar,
native sulphate of baryta, is reduced to sulphuret of barium, which is treated with hydro-
chloric acid, sulphuretted hydrogen and chloride of barium of course being formed.
Either a portion of the gas is burnt and to the products of the combustion, sulphurous acid
and water, the rest of the gas added, or the sulphuretted hydrogen is conveyed into water
to which sulphurous acid is simultaneously conveyed from the combustion or roasting of
iron pyrites. Mr. Gossage long since proved that, by conveying sulphuretted hydrogen into
cride of iron, the sulphur of the gas is deposited. Sulphur may be obtained by
a similar reaction as a by-product of the manufacture of iodine and potassa salts from
kelp. At Paterson's iodine factory at Glasgow, 2000 cwts. of this sulphur are obtained
annually. According to E. Kopp the incomplete combustion of sulphuretted hydrogen
yields sulphur economically (H₂S+0=H₂OS).
Acid on Charcoal.
2
Sulphur obtained by the 6. When sulphurous acid gas is conveyed over red-hot charcoal,
Reaction of Sulphurous the latter is converted into carbonic acid, while sulphur is set free.
By this reaction the sulphurous acid from the roasting of zinc ores (black-jack) is con-
verted into sulphur in large quantities at Borbeck, near Essen, Prussia.
By Heating of Sulphuretted 7. When sulphuretted hydrogen is passed through red-hot tubes
Hydrogen. it is decomposed; but this reaction is not industrially applicable tc
the preparation of sulphur.
SULPHUR.
199
Properties and Uses
of Sulphur.
The yellow colour of sulphur is generally known; at 100° this colour
deepens and nearly disappears. At -50°, sulphur is very brittle and
readily pulverised, becoming by the friction, especially in warm and dry weather, so highly
electric as to cause the particles to adhere strongly to each other. The sp. gr. of this
element varies from 198 to 2:06. It melts at 115°, forming a thin yellow liquid, which, at
160°, becomes thick and assumes an orange-yellow colour; when heated to 220°, sulphur
is a tough, red, semi-solid; between 240° and 260° the colour becomes red-brown, but
being heated above 340° the sulphur is again somewhat fluid, and at last boils at 420° without
having lost its deep colour, which also characterises the vapours. When sulphur heated
to 230° is suddenly poured into cold water, it remains soft and so plastic that it may be
advantageously employed for obtaining impressions of medals, woodcuts, and engraved
plates, these impressions, as the sulphur again hardens after a few days, serving as
moulds. On being heated in contact with air, sulphur burns, forming sulphurous acid.
It is insoluble in water, very slightly soluble in absolute alcohol and ether, and rather
more soluble in warm fixed and volatile oils, forming the so-called sulphur balsam. The
best solvents for sulphur are-sulphide of carbon, coal-tar oil, benzol, and chloride of
sulphur.* It also dissolves in boiling solutions of caustic soda or potassa, in hot solutions
of sulphurets of calcium and potassium, in the solutions of certain sulpho-salts; for
instance, the compound Sb,S,,Na,S, which is converted into Sb,S,,Na,S, and in solutions
of alkaline sulphites, converted thereby into hyposulphites.
Sulphur is used in the manufacture of sulphuric acid, gunpowder, fireworks, for sulphuring
hops and vines as a preservative against some diseases of these plants; the quantity of sulphur
used for the purpose of sulphuring vines in France, Spain, and Italy, amounted, in 1863,
to 850,000 cwts. of Sicilian sulphur, being about from 20 to 25 per cent. of the entire
production. It is further employed in the manufacture of sulphurous acid, sulphites, and
hyposulphites, sulphide of carbon, cinnabar, mosaic gold or bisulphide of tin, and other
metallic sulphurets, ultramarine, various cements, and for vulcanising and ebonising
india-rubber and gutta-percha.
The greater part of the total sulphur production of Europe comes from Sicily, whence,
in 1868, 4,052,000 cwts., in value about £1,500,000, were exported. The total sulphur
production in Europe in 1870 amounted to 7,012,500 cwts., but in this quantity the
sulphur recovered from soda waste is not included.
Sulphurous Acid.
SULPHUROUS AND HYPOSULPHUROUS ACIDS.
This acid (SO2, or hydrated H₂SO3) may be obtained—
a. By oxidation of sulphur;
b. By reduction of sulphuric acid;
c. By a combination of the processes a and b.
The preparation of sulphurous acid by the oxidation of sulphur may be-a. By
burning brimstone in the air; ß. By roasting or calcining iron and copper pyrites, or
the product of Laming's mixture from the purifiers of gas-works; y By igniting a
mixture of manganese and sulphur. The preparation of sulphurous acid by roasting sul-
phurets when coupled with metallurgical operations, is, especially since Gerstenhöfer's
furnace has been more generally introduced, the most advantageous plan of obtaining
this acid, and also where the acid is required for the manufacture of sulphuric acid.
When, however, sulphurous acid is required for the purpose of preserving food,
and as a raw material in the preparation of wines, hops, &c., it should not be
* According to Cossa (1868)—
100 parts of sulphide of carbon dissolve at
100
""
""
""
100
100
""
""
benzol
""
""
100
19
99
100
ether
99
100
""
100
chloroform
aniline
""
""
""
According to Pelouze-
15'0°
31·15 parts of sulphur. /
38.0°
94'57
""
""
48.5° 146.21
""
26.0°
0.96
""
""
71.0°
4.37
""
""
23.5°
0'97
"
22.0°
I'20
"
1300°
85°27
""
**
100 parts of coal-tar oil, sp. gr. 0·88, dissolve, at 130·0°,
43'0 parts of sulphur.
200
CHEMICAL TECHNOLOGY.
made from pyrites, but from sulphur, as, when obtained from pyrites, it is always
mixed with arsenious acid. The Laming's mixture saturated with sulphur from
gas-works is largely used in the preparation of sulphurous acid in sulphuric acid
works in and around London. The ignition in close vessels of metallic oxides and
sulphur can only be advantageously used for the preparation of sulphurous acid
under certain conditions. The oxides chiefly used for this purpose are those of
manganese and copper; the former yields, according to the weight of the materials
employed, either only half the weight of the sulphur in the shape of sulphurous
acid, or the whole of the sulphur may be converted into acid. Sulphurous acid is
sometimes prepared by heating a mixture of sulphate of iron and sulphur—
FeSO4+2S=FeS + 2SO2).
When sulphate of zinc is calcined it yields sulphurous acid and oxygen-
(ZnSO4 = SO₂+0+ZnO).
Kieserite (MgSO4 + H2O), mixed with charcoal yields all its sulphuric acid as
sulphurous acid.
The preparation of sulphurous acid by the reduction of sulphuric acid is very frequent;
sulphuric acid is reduced by being strongly heated in contact with certain metals; for
instance, copper, mercury, and silver :-
Sulphuric acid, 2H,SO4 yield
Copper, Cu
A small quantity of sulphuret of copper is
acid with carbonic acid and carbonic oxide
Sulphuric acid is decomposed and reduced by
wood-shavings, &c.
Sulphuric acid, 2 H₂SO 4 yield
Charcoal, C
Sulphate of copper, CuSO4,
Sulphurous acid, SO,
Water, 2H₂O.
also formed. The dilution of sulphurous
does not interfere with its intended use.
being boiled with charcoal-dust, sawdust,
Sulphurous acid, 2SO₂,
Carbonic acid, CO,,
Water, 2H₂O.
This mode of operation may be made continuous by keeping up a supply of sulphuric
acid and sawdust in the glass retort, as the decomposition of both these substances is
complete, yielding sulphurous acid, water, and carbonic acid. When the vapours of
sulphuric acid are passed through red-hot glass or porcelain tubes, the result is the
formation of sulphurous acid, oxygen, and water (H₂SO4 = SO₂+0+H₂0). The reduction
and decomposition of sulphuric acid by the aid of sulphur may be viewed as a combined
process of preparing sulphurous acid by oxidation and reduction:
2
Sulphuric acid, 2H,SO4 yield Was acid, 3SO
} Sulphurous acid, 3SO,
Sulphur, S
Water, 2H₂O.
In practice, however, this operation is very difficult, owing to the fact that, long before
the reaction begins to take place, the sulphur is molten, while as soon as the reaction sets
in it becomes very tumultuous, and with the sulphurous acid gas vapours of sulphur are
carried over, which solidify and obstruct the passage. At the ordinary temperature and
pressure of the atmosphere, sulphurous acid is a gas having a pungent odour, and a
sp. gr. 2.21.
This gas dissolves readily and in large quantity in water, 1 volume
absorbing at 18°, 44 volumes of gas. It is even more soluble in alcohol. When water is
present all the higher oxides of nitrogen give up some of their oxygen to the sulphurous
acid, converting it into sulphuric acid, the oxides forming deutoxide of nitrogen.
Chlorine also converts moist sulphurous acid gas into sulphuric acid, and similar
results obtain with iodine. The mixture of sulphurous acid and sulphuretted hydrogen
causes their mutual decomposition, water being formed, and sulphur deposited. Sulphu-
rous acid is chiefly employed in preparing sulphuric acid, in the manufacture of paper, as
so-called antichlorine, in the preparation of madder by E. Kopp's process, the preparation
of hyposulphite of soda, and the manufacture of sulphate of ammonia from lant (stale
urine). Sulphurous acid is employed according to Laminne's patent for the purpose of
decomposing alum-shale in the manufacture of alum.
It is further employed in some metallurgical processes, for preserving food, bleaching
syrups, silk, wool, sponges, feathers, glue, isinglass, and other animal substances, which
do not admit of being treated with chlorine, and for bleaching straw hats, willow
and wicker baskets, gum arabic, &c. The bleaching property of sulphurous acid may be
considered as due to two entirely different causes: in some instances the pigment is only
SULPHUR.
201
masked, not destroyed, as sulphurous acid enters with some pigments into a colourless
combination; in other instances, however, a real decomposition of the pigment takes
place. The former condition obtains with most of the blue and red flowers and fruits; a
red rose bleached by sulphurous acid has its colour restored by immersion in very dilute
sulphuric acid. The pigments of yellow flowers are not affected by sulphurous acid;
it also does not at first act upon indigo and carmine and the yellow colour of raw silk, but
by the combined and continued action of this acid and direct sunlight, the oxygen of the
acid acts as ozone and determines the bleaching. The avidity of sulphurous acid for
oxygen may be utilised in extinguishing fires, especially in the case of the soot of
chimneys catching fire, which may be very readily subdued by throwing a few ounces
of flowers of sulphur into the fireplace or stove.
3
Sulphite of Lime. Neutral sulphite of lime (SCa¸¤¸+H₂O), containing in 100 parts
41 parts of sulphurous acid, deserves attention as a cheap, commodious, and very efficient
substance for the development of sulphurous acid, the gas being readily set free by the
action of hydrochloric or sulphuric acid. Bisulphites of lime and soda, the former
in solution, the latter as a solid dry powder, are largely produced in some of the beet-root
sugar manufacturing countries.
Hyposulphite of Soda.
This salt (S₂Na2O3 + 5H2O) is largely used in photography, in
metallurgy, as a mordant in calico-printing, and as antichlor in paper-making.
Hyposulphite of soda may be prepared by several methods. According to Anthon, 4
parts of calcined sulphate of soda are mixed with 1 to 14 parts of charcoal powder,
the mixture is moistened and placed in an iron crucible, and calcined at red heat for
6 to 10 hours; the cooled mass broken into small lumps is again moistened with
water and then exposed to the action of sulphurous acid; the resulting product is
dissolved in water, filtered, concentrated by evaporation, and left to crystallise.
According to E. Kopp's method, carried out industrially by Max Schaffner at Aussig,
hyposulphite of lime is first prepared by causing sulphurous acid to act upon.
sulphuret of calcium (soda waste). The lixiviated mass is treated with sulphate of
soda, the result being the formation of soluble hyposulphite of soda and practically
insoluble sulphate of lime. Very recently the pentathionic acid (S5O5,H₂O),
obtained in large quantity as a by-product of the reaction between sulphuretted
hydrogen and sulphurous acid in preparing sulphur, has been converted into hypo-
sulphite of soda by boiling with soda lye (2S5O5,H2O+ 3H2O=5S202,H2O).
As hyposulphite of soda possesses the property of readily forming with oxide of silver
a soluble double salt, hence dissolving easily such insoluble compounds as chloride and
iodide of silver, it is employed in photography and in the hydrometallurgical extraction of
silver. Being a solvent for iodine it is used in chemistry for purposes of volumetrical
analyses. A mixed solution of sulphite and hyposulphite of soda dissolves malachite and
blue copper ore, forming hyposulphite of protoxide of copper and sodium. Stromeyer
has applied this reaction to the hydrometallurgical extraction of copper. Hyposulphite
of soda is also used for preparing antimonial cinnabar and aniline green; the hyposul-
phites of lead and copper have been proposed as a paste for lucifer matches. The
property possessed by hyposulphite of soda of fusing at a comparatively low temperature
in its water of crystallisation, and of readily solidifying on cooling, has been utilised by
Fleck, in the sealing of glass tubes containing explosive compounds to be used under
water in torpedoes. The enormous consumption of hyposulphite of soda may be readily
inferred from the fact that the chemical factory near Aix-la-Chapelle produces 2000 cwts.,
and the factory at Aussig, Austria, 6000 cwts. of this salt annually.
MANUFACTURE OF SULPHURIC ACID.
Sulphuric acid. H2SO4, consists in 100 parts of 81 parts of anhydrous sulphuric
acid and 18.5 parts of water.
Sulphuric Acid.
There are in the trade two distinct varieties of this acid :—
a. Fuming, or Nordhausen sulphuric acid (oil of vitriol), obtained by distillation
from sulphate of iron, bisulphate of soda, sulphate of peroxide of iron, or by the
decomposition of sulphate of soda by means of boric acid in the preparation of
borax.
202
CHEMICAL TECHNOLOGY.
b. Ordinary sulphuric acid, known abroad as English sulphuric acid, prepared by
the oxidation of sulphurous acid by means of nitrous acid, or, very rarely, separated
from native sulphates.
Fuming Sulphuric Acid. At a red heat all sulphates, except those of the alkalies and
alkaline earths, are decomposed, and therefore may be employed in the preparation
of fuming sulphuric acid; but on account of its cheapness sulphate of iron is pre-
ferred. This salt, on exposure to red heat, is decomposed into anhydrous sulphuric
acid and sulphurous acid :-
Peroxide of iron, Fe2O3,
Sulphate of iron, 2FeSO4, yields Sulphuric acid, SO3,
Sulphurous acid, SO2.
Anhydrous sulphuric acid would indeed be obtained from sulphate of iron if it
were possible to procure the salt perfectly anhydrous, but as this cannot be done
without decomposition, some water is always retained, the result being the compound
known as fuming sulphuric acid, that is to say, a mixture of anhydrous and ordinary
acid (H2SO4), the former in very variable quantities.
Fuming sulphuric acid is prepared on the large scale in the following manner :-The
solution of sulphate of iron is first evaporated to dryness, and dried in open vessels
as much as possible. The dry saline mass, vitriol-stone it is termed in Germany, is next
transferred to fire clay flasks, A, Fig. 92, placed in a galley-furnace, the necks passing
through the wall of the furnace, and being properly secured to the necks of the receivers,
B B. Into each of the flasks 2.5 lbs. of vitriol-stone are put: on the first application of
heat only sulphurous acid and weak hydrated sulphuric acid come over, and are usually
FIG. 92.

B
allowed to escape, the receivers not being securely luted until white vapours of anhydrous
sulphuric acid are seen. Into each of the receiving flasks 30 grms. of water are poured, and
the distillation continued for 24 to 36 hours. The retort flasks are then again filled with
SULPHUR.
203
raw material, and the operation repeated four times before the oil of vitriol is deemed
sufficiently strong. The residue in the retorts is red oxide (peroxide) of iron, still
retaining some sulphuric acid. The quantity of fuming acid obtained amounts to
45 to 50 per cent. of the weight of the dehydrated sulphate of iron employed; at
Davidsthal, in Bohemia, 14 cwts. of vitriol-stone yield in thirty-six hours, 5 cwts. of
fuming sulphuric acid.
It is preferable, however, to use sulphate of peroxide of iron instead of the dried
protosulphate: the sulphate of the peroxide can be readily prepared by means of the
peroxide and ordinary sulphuric acid. Frequently the fuming acid is prepared by passing
anhydrous sulphuric acid, obtained by calcining perfectly dehydrated protosulphate of
iron, or, better still, the persulphate of iron, into ordinary oil of vitriol. Fuming
sulphuric acid is now and then prepared from the bisulphate of soda left after the
preparation of nitric acid from Chili-saltpetre. In France calcined sulphate of soda and
boracic acid are intimately mixed and calcined, and the vapours of anhydrous sulphuric
acid disengaged are absorbed by strong ordinary sulphuric acid. Fuming sulphuric acid
is an oily liquid of a brown yellow or deep brown colour; it emits the pungent smell of
sulphurous acid, fumes on being exposed to air, and yields on being heated vapours of
anhydric sulphuric acid: the sp. gr. varies from 186 to 192. It is industrially hardly
used for any other purpose than dissolving indigo, I part of the latter requiring for its
solution 4 parts of fuming and 8 parts of ordinary sulphuric acid.
Ordinary or English
Sulphuric Acid.
The concentrated sulphuric acid (H2SO4), oil of vitriol of
commerce, consists in 100 parts of 81.5 parts of anhydrous acid and 18.5 of water.
The preparation of this acid on the large scale in leaden chambers dates from the
year 1746, when Dr. Roebuck, of Birmingham, erected the first leaden chamber at
Prestonpans, near Edinburgh.
The rationale of the manufacture of sulphuric acid by the chamber process, in which
sulphurous acid, nitric or nitrous acid, and water are employed, is, according to the latest
researches of R. Weber (1866) and Winkler (1867), the following:-The oxidation of the
sulphurous acid to sulphuric acid takes place in the leaden chambers under the influence
of the vapour of water at the expense of the oxygen of the nitrous acid, which is con-
verted into deutoxide of nitrogen. It is necessary, however, that the nitrous acid be first
absorbed in plenty of water, which takes up the free nitrous acid, and decomposes the
hyponitric acid, a process greatly promoted by the presence in the chamber of sulphurous
acid purposely introduced. The water, usually in the form of steam, because practical
experience proves that a certain elevation of temperature is required, acts in this process
as in others wherein sulphurous acid effects reduction. By the presence of atmospheric
air in the chamber the deutoxide of nitrogen is oxidised into hyponitric or nitrous acid,
and this acid again decomposed by sulphurous acid; if the conditions are favourable
the process is continuous. It occasionally happens that the nitrous acid in contact with
sulphurous acid and excess of water forms protoxide of nitrogen, of course causing a loss
of the efficient oxides of the nitrogen. The formation of the so-called chamber crystals,
consisting according to R. Weber of (H₂SO4 + N₂O3,SO3) only takes place when the
process is not well managed, and is chiefly due to want of water.
Sulphuric Acid.
Present Manufacture of Although the use of leaden chambers is due to an Englishman,
the present mode of manufacturing sulphuric acid was invented (1774) by a calico
printer at Rouen, and improved by the celebrated Chaptal. The apparatus
consists essentially of four parts, viz.-1. A furnace, F, Fig. 93, where, by the com-
bustion of sulphur or pyrites, sulphurous acid is formed; the sulphurous acid,
carrying with it the nitrous vapours prepared in the sulphur burner by means of a
2. An apparatus
peculiar contrivance, escapes from the furnace through the tube, T.
filled with coke through which mixed sulphuric and nitric acids percolate. 3. A
number of leaden chambers, A, A', and A”, wherein, under the influence of high
pressure steam, the sulphuric acid is formed. 4. A large apparatus, K, known as
* In order to convert I kilo. of sulphur into sulphuric acid, the following quantities of
air are required:
When the sulphur is present in free state, 5275 litres of air, containing 4220 litres
of nitrogen.
When the sulphur is present as pyrites, 6595 litres of air, containing 5276 litres of
nitrogen.
204
CHEMICAL TECHNOLOGY.
Gay-Lussac's condenser, filled with coke, through which sulphuric acid of 66° B.
(=1°84 sp. gr.) percolates, the aim being to take up the nitric and hyponitric acids, not
the deutoxide of nitrogen as was believed before Winkler elucidated this point,
C
FIG. 93.

M'
T
from the gases which flow into the last chamber previously to being discharged.
The furnace or burner, as it is technically called (see Fig. 94), is built of bricks; at a
height of 80 centims. from the floor a stout cast-iron plate is placed so as to have
*
FIG. 94.
In
a slight inclination towards the
front. The walls are also covered
with heavy cast-iron plates.
front of the burner are three or six
large openings, P, F', P', which can
be closed by iron doors fitted with
wooden handles. On the bed or
bottom plate three iron rails or
ledges, each 10 centims. high, are
placed to divide the bottom of the
furnace into three or six compart-
ments. At H, H', and H" are the
holes for the necessary supply of
air. On the top plate is firmly
fixed the tube, T, which conveys

the gases generated in the burner to the leaden chamber of each section or com-
partment. The burner is charged with about 50 kilos. of sulphur; this is kindled
at the top, the draught of air through н, Í', and " being so regulated as to cause
SULPHUR.
205
the sulphur to be burnt off without becoming sublimed, for if any sulphur were
volatilised it would cause the sulphuric acid to be turbid and milky.
Not only
does the burner supply sulphurous acid, but also the nitric acid or nitrous
vapours required in the leaden chamber; these are generated from a mixture of
nitrate of soda and sulphuric acid at 52º B. (= 1*56 sp. gr.) placed in the cast-iron
pot, N, which when filled is placed on the burning sulphur.
H
FIG. 95.
T
K
N
T
The construction and arrangement of the denitrificateur is shown in Fig. 95. At &
is placed an iron grating covered with thick perforated sheet lead; the vapours and
gases generated in the burner pass through м into the
space immediately below G, upon which a column of
coke is placed, and kept saturated with sulphuric
acid strongly charged with nitric acid, obtained by the
condensation of the gases from the last chamber. This
acid is forced by means of compressed air from the
vessel y into the Mariotte bottle, v, and passes thence
through T into H, thence by T' to the coke, over which
it is delivered in fine jets by means of a perforated
plate fitted to the lower part of the cover A. The acid
coming in contact with the warm gases from the
chamber yields to them, in the state of vapour, all the
nitrous compounds dissolved in the sulphuric acid, and
charged with these vapours the gases pass through
m, Fig. 93, into the leaden chambers. The denitrified
sulphuric acid runs off through the tube t into a reservoir.

M
G
&
The formation of sulphuric acid takes place in the leaden chambers or chamber. In many
cases, especially abroad, only one large chamber is worked, which is then, as shown in Fig. 93,
divided by the leaden plates R R', technically termed curtains, into three or more compart-
ments, these curtains reaching to the bottom into the acid collected there. If several
chambers are worked, communication is maintained by means of leaden tubes. The
tubes v v'v", convey steam to the chambers. The chambers are not usually all of the
same size, one being considerably larger than the others; in the largest most of the acid is
generated. The gases and vapours contained in the last chamber being almost free from
sulphurous acid, and consisting mainly of atmospheric air and nitrous vapours, are
conveyed through r' to the leaden reservoir, D, where the last traces of sulphuric acid are
deposited. The action of Gay-Lussac's condenser, K, is based upon the fact that concen-
trated sulphuric acid absorbs and combines with nitrous acid. The apparatus consists
essentially of a column of coke 8 to 10 metres in height, through which strong sul-
phuric acid, 62° or 64° B., percolates, the flow being regulated by the apparatus shown in
Fig. 95.
The acid saturated with nitrous acid is conveyed by the tubes h h into a
reservoir, G, from which it is again forced by means of the monte-acid to the Mariotte
flask, M. By the tube T"", the gases are conveyed to the chimney stalk of the works.
regards the cubic capacity of the leaden chambers, each 20 kilos. of sulphur consumed in
twenty-fours hours requires 30 cubic metres (about 100 cubic feet) capacity; as this
=
As
* According to theory, I molecule of sulphur requires only 3 molecules of oxygen, viz.,
2 to form sulphurous acid, and I to convert the latter into sulphuric acid; that is to
say, I kilo. of sulphur requires 1500 grms. 1055 litres of oxygen 5275 litres of air,
in which 4220 litres of nitrogen are contained. In order to regulate this supply of air
many contrivances have been adopted, among them the anemometer invented by Combes;
this is fitted to the sulphur burner by means of a tube, through which the air supplied
has to pass.
In England reliance is placed upon the skill of the workmen who regulate
the draught, as it is termed, simply by the slides in the doors of the burners.
The air discharged from the chambers should not contain more than 2 to 3 per cent. of
oxygen. By careful management and with good apparatus the maker may succeed in
obtaining from 100 kilos. of sulphur 306 kilos. of strong acid at 1.84 sp. gr.; but the
usual quantity from 100 kilos. of sulphur is seldom more than 280 to 290 kilos.
206
CHEMICAL TECHNOLOGY.
quantity of sulphur corresponds to 60 kilos. of hydrated sulphuric acid, a chamber of
the capacity mentioned yields 2.5 kilos. of sulphuric acid per hour. One hundred parts
of sulphur require from 6 to 8 parts of nitrate of soda, but if pyrites is employed this
quantity is often increased. Also when pyrites is burnt larger chambers are used. Lately
Gay-Lussac's condenser has, in many cases, fallen into disuse, on account of the low price
of Chili-saltpetre, and the expense of keeping the apparatus in working order.
of Sulphurous Acid.
Use of Pyrites for the Preparation Instead of sulphur native minerals containing that
element are frequently employed for the preparation of sulphurous acid. Among
these minerals, iron pyrites, bisulphuret of iron, FeS2, containing 53'5 per cent.
d
α
FIG. 96.
u.
of sulphur, is the most largely used. The pyrites are calcined
in peculiarly constructed kilns, built with fire-bars, the
spaces between which may be adjusted by means of a key,
and the admission of the air required for combustion regu-
lated with great nicety. The best pyrites oven known on
the Continent is Gerstenhöfer's, invented in 1864; the prin-
ciple of this oven, Fig. 96, is that the pyrites is made to
fall through and meet the column of heated air sup-
porting the combustion. In order to prolong the fall of
the powdered pyrites, terraces or banks are built at intervals
in the shafts. The broken up pyrites falls through the
funnels a, provided with grooved rollers to pulverise it, on to
the banks c, from one terrace, as they are termed, to
another. As the furnace has been previously made red-hot,
the sulphur ore ignites and burns off, aided by a moderate
blast at c. The sulphurous acid formed is discharged by the channels d into the
sulphuric acid chambers, sometimes being first conveyed to an ante-room, where
the dust of the pyrites mechanically mixed with the gases is deposited.

C
I
The nitrous acid vapours are generated in a manner similar to that used for
sulphur. It will be seen that when pyrites is burnt, a far larger quantity of air is
required for the same quantity by weight of sulphur, amounting for 1 kilo. of pyrites
to 6595 litres of air. This excess is due to the oxidation of the iron of the pyrites,
and the large bulk of nitrogen accompanying the excess of oxygen
(2FeS2+110=4SO₂+Fe2O3).
According to Fortman, the gases from the pyrites burners also contain vapours of
anhydrous sulphuric acid. Among the substances found in the flue dust of the
pyrites burners are selenium and thallium. Carstanjen found thallium to the amount
of 3.5 per cent. in the flue dust of a sulphuric acid works near Berlin, where a
pyrites from Mezzen was used.
Chamber Acid. As soon as the acid formed in the leaden chambers has acquired a sp. gr. of
1*5=50° B. = 104° Twaddle, it is run off into a reservoir, and is frequently used in that state
of concentration for the purpose of preparing artificial manures or superphosphates in
alkali works, for the preparation of nitric acid, and for other purposes. This acid may be
freed from arsenic by treating with sulphuretted hydrogen.
Sulphuric Acid.
Concentration of This operation is effected in two different stages, the first being car-
ried on in leaden pans, the latter in platinum or glass retorts. Weak and cold sul-
phuric acid does not act powerfully on lead, but as soon as the acid becomes concen-
trated, and especially when hot, the lead is dissolved, sulphurous acid given off, and
sulphate of lead formed. Many sulphuric acid makers concentrate their acid to
60° B.=1'71 sp. gr., in leaden pans; others, however, concentrate in leaden pans to
55° B.=1*59 sp. gr. only.
SULPHUR.
207
Concentration in Leaden Pans. The pans employed for this purpose are rectangular in
shape, rather shallow, but long and wide, and supported by iron plates, so that the
fire shall not strike the bottom directly. The modes of placing and construction are
shown in Fig. 97; the acid is more strongly heated in the pan, m, while in n it is only
FIG. 97.

น
m
566
affected by the hot air. The depth of the acid in the pans varies from 24 to 36
centims. As soon as the acid is of about 1'71 sp. gr., it is further deprived of its
excess of water, in glass, porcelain, or platinum vessels.
Platinum Retorts. Platinum retorts are now very frequently employed, although it is
clear that these vessels, considering the high price of platinum, are expensive,
FIG. 98.

n
C
B
the price depending upon the weight, size, and workmanship. Messrs. Johnson,
Matthey, and Co, Hatton Garden, London, are among the best makers of these
and other platinum apparatus.
Fig. 98 is an enlarged view of the platinum retort, represented together with the
leaden pans in Fig. 97. The hearth communicates with a. By means of the
208
CHEMICAL TECHNOLOGY.
syphon, x, the acid from n can be transferred to B; the longer leg of x dipping into a
leaden vessel, which admits of being lowered to d by the aid of the pulley. The acid
then runs from the spout c into the channel d, and thence, through the funnel-tube,
into the retort, B. The head, C, communicates by means of tubing, not shown in the
cut, with a worm, where the water and very weak acid mechanically carried over
with the steam are condensed. When the temperature of the acid in the platinum
still attains to 310° to 320°, strong acid comes over, and is condensed in the worm.
C
α
Glass Retorts.
FIG. 99.
a e
In order to withdraw the acid from
the still, when concentrated to 1.78 to
1*80(=63° to 66° B.), the Breant syphon,
Fig. 99, is used. It is made of platinum;
the outer leg has a length of about
5 metres, and is surrounded by a copper
tube 15 centims. wide by 36 centims. long,
which can be filled at a from the tank M
(see Fig. 97) with cold water, the outlet
for the hot water being at b. In order
to increase the surface the main syphon
tube is divided into four narrower tubes.
The syphon is filled with sulphuric
acid by d and e after closing the tap c.
The very hot acid cools while flowing

through the platinum tubes, and is collected in jars, a, a', a″,
Concentration in When glass retorts of good quality and sufficiently large size can be
obtained at a cheap rate, they are very frequently employed, being placed to the
number of ten or more (Fig. 100) in sand-baths. The retorts are connected to
FIG. 100.

سالنتي
earthenware balloons, in which the acid fumes are condensed. 70 per cent. of the
strong sulphuric acid sold in this country is concentrated in glass retorts. Very
recently cast-iron vessels have been used for concentrating sulphuric acid.
Other Methods of Sulphuric Many methods of preparing sulphuric acid have been suggested,
Acid Manufacture. but hitherto none have anywhere superseded the process generally
adopted. For this reason it is necessary to mention a few only of the reactions upon
which these methods are based. Hahner oxidises sulphurous acid with chlorine, care being
taken that steam is present at the time :—
Sulphurous acid, SO,
}
Aqueous vapour, 2H2O yield Hydrochloric acid, 2CIH.
Sulphuric acid, H₂SO3,
Chlorine, 201
SULPHUR.
209
Persoz's method is based upon the following reactions:-1. Oxidation of sulphurous
acid by means of nitric acid, the latter being heated to 100° and diluted with four to six
times its bulk of water. 2. The vapours of hyponitric acid are again converted to nitric
acid by the oxygen of the air and steam. In this process the leaden chambers are replaced
by a series of large stone-ware Woulfe's bottles. Although enormous quantities of gypsum
are found native, all attempts to prepare sulphuric acid from this mineral on an industrial
scale have failed. Gypsum is decomposed, by superheated steam and at red heat, into sul-
phuric acid, oxygen, and sulphurous acid, leaving caustic lime in the retort. Shanks
mixes gypsum with chloride of lead and water at about 60°.
Gypsum, CaSO4+2H¸0
Chloride of lead, PbCl
}
Chloride of calcium, CaCl2,
yield Sulphate of lead, PbSO4,
Water, 2H₂O.
The chloride of calcium solution having been withdrawn from the precipitate of
sulphate of lead, the latter is heated with hydrochloric acid :—
Sulphate of lead, PbSO
Chloride of lead, PbCl₂,
Hydrochloric acid, 2011} yield (Sulphuric acid, H, SO
H.SO
4
Properties of Sulphuric Acid. The most highly concentrated sulphuric acid contains 18:46 per
cent. of water; its formula is H₂SO; sp. gr. 1848. In a perfectly pure state it is a
colourless liquid, but commonly is more or less yellow or brown, owing to the presence of
organic matter. It destroys many organic substances, leaving a carbonaceous residue.
This sulphuric acid does not fume on exposure to air; it is very hygroscopic, and when
left exposed to air, gradually absorbs fifteen times its bulk of water. When mixed with
water great heat is evolved. The boiling-point of the most highly concentrated acid is 338°.
The following table gives the quantity of anhydrous sulphuric acid contained in sul-
phuric acid at 15.5° C. :-
Hydrated
Sulphuric acid. Sp. gr.
Anhydrous
acid.
100
1.8485
81.54
Hydrated
Sulphuric acid.
76
Sp. gr.
Anhydrous
acid.
1·6630
61.97
99
1.8475
80.72
75
1.6520
61.15
98
1.8460
79'90
74
1.6415
60'34
97
1.8439
79'09
73
1·6321
59'55
96
1.8410
78·28
72
1.6204
58.71
95
1.8376
77.40
71
1*6090
57.89
94
1·8336
76·65
70
I'5975
57:08
93
1.8290
75.83
69
1.5868
57:26
92
1·8233
75'02
68
I'5760
55'45
91
1.8179
74'20
67
1*5648
54.63
90
1.8115
73.39
66
I'5503
53.82
89
1.8043
72.57
65
I'5390
53'00
88
I'7962
71.75
64
1.5280
52.18
87
1·7870
70'94
63
1'5170
5137
86
I'7774
70'12
62
I'5066
50'55
85
1.7673
69.31
6I
1*4960
49'74
84
I'7570
68.49
60
1°4860
48.92
83
1'7465
67.68
59
I'4760
48.11
82
1*7360
66.86
58
I'4660
47.29
81
I'7245
66.05
57
I'4560
46.58
80
I'7120
65·23
56
I'4460
45.68
79
I'6993
64.42
55
1'4360
44.85
78
1.6870
63.60
54
1*4265
45'03
77
1'6750
62.78
53
I'4170
43'22
Comparative degrees of Baumé and Twaddle, with the corresponding sp. gr. :-
Degrees Baumé.
Degrees Twaddle.
Sp. gr.
45
a8bhg。8
66
168
1.84
63
154
I'77
60
140
1.70
57
130
.1.65
50
104
* 1'52
88
40
76
I'44
1.38
35
62
1.31
30
52
1.26
25
42
I'21
15
210
CHEMICAL TECHNOLOGY.
The reader desirous of more information as to the specific gravities indicated by
Baumé's hydrometers is referred to the "Chemical News," vol. xxiv., p. 28, et seq.
The uses of sulphuric acid are so numerous that it would be impossible to mention all
of them, sulphuric acid being to chemical industry what iron is to the mechanical.
Sulphuric acid is employed in preparing a great many other acids, among them nitric,
hydrochloric, sulphurous, carbonic, tartaric, citric, phosphoric, stearic, oleic, and palmitic.
Further, sulphuric acid is used in making superphosphates, soda, sulphate of ammonia,
alum, sulphates of copper and iron, in paraffin and petroleum refining, silver refining,
manufacture of garancine, garanceux, and other madder preparations, manufacture of
glucose from starch, to dissolve indigo, &c.
SULPHIDE OF CARBON.
Sulphide of Carbon. This compound, consisting in 100 parts of 15'8 parts of carbon
and 84°2 of sulphur, formula CS2, was discovered in 1796 by Lampadius, at Frei-
burg. It is obtained by causing the vapour of sulphur to pass over red-hot coals,
or by distilling an intimate mixture of native metallic sulphurets with charcoal or
coke. The largest quantity of sulphide of carbon is obtained, according to Sidot
and W. Stein, at not too high a red heat, that is to say, at what is termed in
gas-works orange-red heat.
Sulphide of carbon is best manufactured by means of Peroucel's apparatus
(Fig. 101). A is a fire-clay gas-retort, supported on the fire-clay block B; E and E
FIG. IOI.

I P
Ꭲ .
D
Ꮮ
are openings, one being that of a porcelain tube firmly cemented into the cover of a,
serving for the introduction of sulphur; the other opening is for the introduction
of pieces of coke, with which, before the operation commences, the retort is filled.
The vapours of the sulphide of carbon pass through the tubes H and I into the
vessel J, wherein part of the sulphide is condensed and flows through K into the flask,
L, filled with water, thence through м into o, finally being run off by the tap, N. Any
vapours not condensed in J pass through P P into the worm, T, the condensed sulphide
being collected in s. The crude sulphide of carbon is rectified by re-distillation
over zinc or over bichloride of mercury by means of steam or a water-bath. If the
bichloride is employed, the crude sulphide should remain in contact with the salt for
at least twenty-four hours before re-distillation. With the apparatus described, the
retort being 2.1 metres in height and 0.3 inetre in diameter, 2 cwts. of crude sulphide
GLAUBER'S SALT.
211
of carbon may be prepared in twelve hours. The quantity of sulphide resulting
from a given weight of materials is always much less than the quantity theoretically
obtainable; this is, of course, partly due to an unavoidable loss of liquid, and probably
to the formation of monosulphide of carbon (CS), a compound corresponding to
carbonic oxide. Crude sulphide of carbon contains usually 10 to 12 per cent. of
sulphur in solution, and also sulphuretted hydrogen. To purify the crude sulphide,
bleaching-powder solution is added to the liquid in the retort, into which steam at
15 lbs. pressure is forced to effect the reaction between the chloride of lime and the
impurities present in the sulphide of carbon. Sulphide of carbon is usually kept
under water. When pure, sulphide of carbon is a colourless liquid, strongly
refractive, exhibiting extremely bright colours when in the sunlight. Its odour
somewhat resembles that of chloroform; the taste is aromatic. Its sp. gr.=1'2684;
the boiling-point is 46.5°, consequently the liquid is very volatile at the ordinary
temperature of the air.
Carbon. Sulphide of carbon does not combine with water or spirits of wine. It is not
soluble in every proportion in water (see “Chemical News," vol. xxiv., p. 34); in ether
and chloroform, however, it is freely soluble. Sulphide of carbon is an excellent
solvent for resins, essential and fixed oils, caoutchouc, gutta-percha, camphor,
sulphur, phosphorus, and iodine. It is highly inflammable, burning with a red-blue
flame; the products of complete combustion are sulphurous and carbonic acids. The
vapour of sulphide of carbon with oxygen or air constitutes an explosive mixture;
the light given by a mixture of deutoxide of nitrogen and sulphide of carbon is
very intense, and has been employed in photography. To Mr. Fisher, of Birmingham,
is due the honour of having first prepared sulphide of carbon for industrial
purposes. At the present day these purposes are very varied, but consist chiefly of
the vulcanisation of caoutchouc, the extraction of fat from bones, and oils from oil
seeds and olives, the extraction of sulphur from its concomitant rocks, and of fat
from crude wool. Sulphide of carbon is also used in electro-plating to obtain by its
addition to the silver-bath a bright and polished surface. It is highly valued for
killing vermin in corn.
Chloride of Sulphur. Chloride of sulphur (Cl₂S2), important only in its technical use
for the vulcanising of caoutchouc, is an oily fluid, sp. gr. 1'60, of a brown colour,
fuming on exposure to air. It boils at 144°. On being mixed with water it is
decomposed, yielding sulphurous and hydrochloric acids, a very small quantity of
sulphuric acid, and sulphur. Chloride of sulphur converts rape-seed oil into a mass
resembling caoutchouc, and linseed oil into a varnish. Chloride of sulphur is
prepared by passing chlorine gas over sulphur heated to 125° to 130°; the product
is rectified by distillation.
HYDROCHLORIC ACID AND GLAUBER'S SALT, OR SULPHATE OF SODA.
Hydrochloric Acid.
The commercial article known as hydrochloric or muriatic acid,
or spirits of salt, is, as has been explained in the manufacture of soda, a solution
of the gas given off during the decomposition of common salt by sulphuric acid.
In order to effect this condensation, the gas is conveyed to the coke columns, or in
many instances is prepared and condensed by the aid of the apparatus shown in
section in Figs. 102 and 103, and in plan in Fig. 104. The apparatus consists of
several cast-iron cylinders, 17 metres long by o'7 metre diameter, closed similarly
212
CHEMICAL TECHNOLOGY.
to gas retorts by lids luted with clay. One of the lids is provided with an opening,
o, into which is fitted the stoneware or leaden pipe, a, conveying the hydrochloric
acid to the condensing apparatus. The other, or posterior lid, is also provided with
an opening, d, through which is passed the tube of a leaden funnel, so that after
the retort is filled with salt, sulphuric acid may be poured in. The construction of
FIG. 102.

B
SASSINSEEEEEEEEEEE
NNNNNNAPOS
the furnace, in which two retorts are usually placed, allows the flame of the fire at
o to play round the cylinders before reaching the flue leading to the chimney, F.
B is an arch covering the furnace. The first stage of the operation is to fill each
cylinder with 150 kilos. of salt or chloride of potassium, in localities where the latter
is abundant. The lids or covers are next luted on, and the fire kindled. The
FIG. 103.

FEFFFREEEEEEE
required quantity of strong sulphuric acid is now poured into the retort, and the
funnel having been withdrawn from d, the hole is closed by a clay plug. As soon
as the reaction is over, the 180 kilos. of sulphate of soda produced are removed, and
the operation repeated. The condensation apparatus, Figs. 102 and 104, consists of
GLAUBER'S SALT.
213
rows of Woulfe's bottles partly filled with water, care being taken to place the first
pair of these bottles in a tank of cold water. The condensation of the last portions
FIG. 104.

T
10
of the hydrochloric acid gas is effected either by the aid of coke columns, or in
leaden chambers, into which fine jets of cold water are injected on all sides.
Acid.
Properties of Hydrochloric Crude commercial hydrochloric acid is commonly a yellow
liquid, this colour being due to chloride of iron. It has a caustic sour taste, and
fumes on exposure to air. At 20° water is capable of absorbing 475 times its own
bulk of hydrochloric acid gas; a saturated solution contains 42.85 per cent. of
gas, the sp. gr. being=1°21. The following table shows the sp. gr. of hydrochloric
acid at various degrees of concentration, and the quantity of pure acid (real gas)
contained at 70° :—
Specific Degrees Degrees Percentage
Baumé. Twaddle. of acid.
Specific Degrees Degrees Percentage
gravity. Baumé. Twaddle. of acid.
gravity.
I'21
26
42
42.85
ΙΙΟ
14'5
20
20°20
1'20
25
40
40*80
I'09
12
18
18.18
I'19
24
38
38.88
I'08
II
16
16.16
1.18
23
36
36°36
I'07
ΙΟ
14
14'14
I'17
22
34
34°34
1'06
9
12
12'12
1'16
21
32
32°32
1'05
I'15
20
30
30°30
I'04
a co
8
ΙΟ
IO IO
6
8
8.08
I'14
19
28
28.28
I'03
I'13
18
26
26.26
I'02
I'12
17
24
24°24
ΙΟΙ
53 2
6
6.06
4
4'04
2'02
I'II
15'5 22
22*22
Acid,
Uses of Hydrochloric Hydrochloric acid is very largely employed in the manufacture
of chlorine, sal-ammoniac, chloride of antimony, glue, phosphorus, in the prepara-
tion of carbonic acid for the manufacture of artificial mineral waters, in beet-root
sugar works, bleach works, hydro-metallurgy, and alone or mixed with nitric acid
for dissolving various metals.
Glauber's Salt.
Sulphate of soda, or Glauber's salt, consists in 100 parts of 19°3 soda,
24°7 sulphuric acid, and 56 water; formula, Na,SQ4+10H₂O; anhydrous, Na₂SO4)
in 100 parts-soda, 43'6; sulphuric acid, 56.4. It is prepared as described under
hydrochloric acid by decomposing common salt with sulphuric acid. It is also
found native as Thenardite (NaSO4), Brogniartine or Glauberite (NaSO4 + CaSO4),
and it occurs in sea-water and some mineral waters, as in those of Püllna and
Carlsbad.
214
CHEMICAL TECHNOLOGY.
Sulphate of soda is indirectly obtained by various processes, among which are-
1. The double decomposition of common salt and sulphate of magnesia or kieserite from
the mother-liquor of sea-water, or of salines when exposed to a low temperature either
naturally in water or artificially by the assistance of Carré's ice-making machine.
2. Longmaid's process of roasting sulphuret of iron or copper with common salt. 3. Cal-
cination of kieserite or magnesian sulphate with common salt. 4. Kuhlmann's process,
the calcination of sulphate of magnesia and nitrate of soda, hyponitric acid and sulphate
of soda being formed. 5. As a by-product of paraffin and petroleum refining. The
sulphate of soda of the alkali works contains on an average 93 to 97 per cent. of the pure
salt, the remainder being chiefly chloride of sodium.
Uses of Sulphate This salt is extensively employed in the manufactures of soda, ultra-
of Soda. marine, and glass. In the last case the sulphate is mixed with coal and
silica, and calcined, its sulphuric acid being reduced to sulphurous acid, which is volatilised,
while a silicate of soda is formed. Sulphate of soda when thus employed should be
purified from all traces of iron by being dissolved in water, some lime added to the
solution, and the clear liquid evaporated to dryness. Sulphate of soda is used in
metallurgy in the treatment of some kinds of antimonial ores, the sulphuret of antimony
found near Bouc and Septèmes, France, &c. It is also employed in certain processes of
wool-dyeing.
Ι
Bisulphate of Soda. This salt (NaHSO4) is obtained in large crystals when I molecule
of sulphate of soda and 1 molecule of sulphuric acid are dissolved in water and the
solution left to evaporate slowly. One of the chief uses of the bisulphate is in a
mixture with abraum salt containing chloride of magnesium, employed for re-
moving zinc from lead. As a by-product sulphate of soda is obtained in the manu-
facture of nitric acid from nitrate of soda and sulphuric acid, and by heating cryolite
with sulphuric acid.
BLEACHING-POWDER AND HYPOCHLORITES.
Chlorine. It is one of the most valuable properties of chlorine that it destroys
organic pigments and miasmata, and is hence useful as a bleaching agent, and as a
disinfectant. It is also employed as an oxidising agent in the extraction of gold
from pyritical ores.
At the ordinary temperature and pressure of the atmosphere chlorine is a
greenish-yellow gas, its sp. gr. = 1.33; it possesses a peculiarly disagreeable,
irritating odour, and is very soluble in water, 1 volume absorbing 2'5 volumes of
gas, forming the well-known aqua chlorii, or acidum muriaticum oxygenatum aqua
solutum of the pharmaceutists, and the chlorine water of the scientific chemist.
The bleaching property of chlorine gas, possessed also by its solution, is due to the
great affinity of chlorine for hydrogen, so that the chlorine while seizing upon the
hydrogen of the organic body in most instances causes the simultaneous decomposi-
tion of water, and by the formation of ozone destroys the organic colouring matter,
hydrochloric acid being at the same time formed, a fact requiring attention in the
use of chlorine as a bleaching agent. When linen, or rather flax, raw cotton, and
paper pulp are bleached by chlorine, the fibre, really cellulose, is not acted upon,
but only the colouring matter is oxidised by the ozone formed. Chlorine cannot be
used to bleach animal matters, or such as contain nitrogen, these becoming yellow
by its action. Chlorine is not suited for transport either as gas or in aqueous solu-
tion, therefore one of its combinations with oxygen and a base, viz., a hypochlorite,
is used. Hydrated oxide of calcium or slaked lime is the chief constituent of
bleaching-powder. Usually the alkali manufacturers prepare bleaching-powder.
Preparation of Bleaching- Bleaching-powder is prepared on the large scale in the fol-
lowing manner :-In works where soda and chloride of lime are to be manu-
factured simultaneously, the chlorine is obtained by mixing the common salt to be
BLEACHING-POWDER.
215
converted into sulphate of soda by the action of sulphuric acid with peroxide of
manganese, heat being applied.
The process is as follows:
Common salt, 2NaCl,
Glauber's salt, Na2SO4,
Peroxide of manganese, MnO2,
yield
Sulphuric acid, 2H2SO4
Sulphate of manganese, MnSO4,
Chlorine, 2C1, and 2H2O.
In some works chlorine is prepared by the reaction of hydrochloric acid and
manganese, and sometimes with the addition of sulphuric acid. In the first instance
only half the chlorine contained in the hydrochloric acid is given up, because the
other half forms chloride of manganese; for—
Manganese, MnO2,
Hydrochloric acid, 4CIH, yield
Chlorine, Cl2,
Manganic chloride, MnCl2,
Water, 2H2O.
In the second instance all the chlorine contained in the hydrochloric acid is
obtained -
Manganese, MnO2,
Hydrochloric acid, 2CIH,
yield
Sulphuric acid, H2SO4,
I
Sulphate of manganese, MnSO4
Chlorine, Cl₂,
Water, 2H2O.
As proposed by Clemm, a chloride of magnesium solution, as largely obtained at
Stassfurt, may be employed by concentrating the solution to 44° B (= 1*435 sp. gr.,)
and adding manganese, so that to 1 mol. of MnO2, 2 mols. of MgCl₂ are taken. The
cooled, solid mass, when exposed to the action of superheated steam at 200° to 300°,
yields chlorine gas.
Preparation of Chlorine
without Manganese.
and interesting:
The following methods are selected as being the most scientific
1. Mac Dougal, Rawson, and Shanks's process, consisting in the decomposition of
chromate of lime by hydrochloric acid, the result being the formation of chloride of
chromium, chloride of calcium, and the evolution of free chlorine-
(2CaCrO4 + 16HCl = Cr₂Cl6 + 2CaCl2 + 3H2O+ 6C1).
158 parts of chromic acid yields 106 parts of chlorine. The chloride of chromium is
again precipitated with carbonate of lime, and by ignition converted into chromate
of lime. Only three-eighths of the chlorine contained in the hydrochloric acid is
given up, while manganese yields one-half.
2. Schlösing's method consists in acting upon manganese with a mixture of hydro-
chloric and nitric acids, the degree of concentartion of the acids being so regulated by
the addition of water that the mixture yields only chlorine, while nitrate of protoxide
of manganese is formed; this salt being calcined yields manganese, peroxide, and
nitric acid. The nitric acid aids the oxygen of the air in decomposing the hydro-
chloric acid. The nitrate of manganese begins to decompose at 150°, and the decom-
position is completed at 175° to 180°, yielding much peroxide, in some cases even
93 per cent.
3. Vogel's method of decomposing chloride of copper by heat. 3 mols. of chloride
yield 1 mol. of chlorine; according to Laurens the process is :—
2CuCl₂ = Cl₂+ Cu₂Cl₂.
The chloride in crystalline state is mixed with half its weight of sand, and heated in
earthenware retorts to 200° to 300°, yielding chlorine gas, while the remaining proto-
chloride of copper is re-converted into perchloride by the action of hydrochloric
acid. Mallet has constructed a peculiar rotating apparatus for the decomposition of
216
CHEMICAL TECHNOLOGY.
this salt, the same apparatus serving to prepare oxygen. 100 kilos of cupric
chloride yield 6 to 7 cubic metres of chlorine gas.
4. Péligot's method. When 3 parts of bichromate of potassa and 4 parts of con-
centrated hydrochloric acid are gently heated, the fluid yields on cooling crystals of
bichromate of chloride of potassium, KCl,CrO3; at 100° this salt yields chlorino.
Ι
5. Dunlop's process is followed at Mr. Tennant's works, Glasgow. Sulphuric acid
is made to act upon a mixture of 3 mols. of common salt, and I mol. of nitrate of
soda, the result being the formation of chlorine and hyponitric acid. The latter is
absorbed by passing the mixed gases through strong sulphuric acid.
6. Mr. Walter Weldon's process is performed by means of an apparatus comprising
five vessels arranged at successive elevations, so that after having been pumped up to the
highest of them, the liquor operated upon can afterwards descend to all the others by its
own gravity. The lowest of these vessels is a well, which is furnished with a mechanical
agitator. The slightly acid chloride of manganese liquor with which the process com-
mences runs from the stills in which it is produced into this well, and is there treated with
finely divided carbonate of lime, the action of which is facilitated by the energetic
agitation. When the neutralisation of the free acid which is at first contained in this
liquor and the decomposition of the sesquichloride of iron and sesquichloride of aluminium,
which are also at first contained in it, are completed, the liquor is pumped up into
settling tanks, placed nearly at the top of the apparatus, and known as the "chloride of
manganese settlers.
It now consists of a quite neutral mixed solution of chloride of
manganese and chloride of calcium, containing in suspension considerable quantities of
sulphate of lime, and small quantities of oxide of iron and alumina. These solid
matters rapidly deposit in the chloride of manganese settlers, leaving the bulk of the
liquor perfectly bright and clear, and of a faint rose-colour. The next step is to run off
the clear portion of the contents of the settlers into a vessel immediately below, called
the oxidiser. This is usually a cylindrical iron vessel about 12 feet in diameter, and about
22 feet deep. Two pipes go down nearly to the bottom of the oxidiser, a large one for
conveying a blast of air from a blowing engine, and a smaller one for the injection of
steam. The latter is for the purpose of raising the temperature of the contents of the
oxidiser when necessary; for sometimes the chloride of manganese liquor reaches
the oxidiser sufficiently hot-between 130° and 160° or 170° F. Immediately above the
oxidiser is a reservoir containing milk of lime. The oxidiser having received a charge of
clear liquor from the settlers, and this liquor having been heated up to the proper point, if
it was not already hot enough, blowing is begun, and milk of lime is then run into
the oxidiser as rapidly as possible, until the filtrate from a sample taken at a tap placed
nearly at the bottom of the oxidiser, ceases to give a manganese reaction with solution of
bleaching-powder. A certain quantity of milk of lime is then added, and the blowing
continued until peroxidation ceases to advance. That point is usually attained when
from about 80 to 85 per cent. of the manganese present has become converted into
peroxide. The contents of the oxidiser are now a thin black mud, consisting of solution
of chloride of calcium containing in suspension about 2 lbs. of peroxide of manganese
per cubic foot, these 2 lbs. of peroxide of manganese being combined with varying quan-
tities of protoxide of manganese and lime. This thin mud is now run off from the oxidiser
into one or other of a range of settling tanks or "mud settlers," placed below it, and is
there left at rest until it has settled as far as it will, usually until about one-half of its
volume has become clear. The clear part is then decanted, and the remainder, containing
about 4 lbs. of peroxide of manganese per cubic foot, is then ready to be used in the stills.
There it reacts upon hydrochloric acid, liberating chlorine, with reproduction of exactly such
a residual solution as was commenced with. With that solution the round of operations is
bein again; and so on, time after time, indefinitely.
Chlorine.
Apparatus for Preparing When hydrochloric acid and manganese are used, the apparatus
is that delineated in Fig. 105. It consists of a large stoneware jar, A, provided with
an opening, a, over which an air-tight cap is fitted when the apparatus is at work,
and by which the jar is filled with manganese. and acid; b is another opening fitted
with a leaden or earthenware gas tube; c is a tube serving to run off the spent
manganese liquor. B is a wooden box into which steam is admitted for the purpose
of heating A and its contents sufficiently to promote the reaction between the hydro-
chloric acid and the manganese.
BLEACHING-POWDER.
217
When chlorine is prepared from a mixture of common salt, sulphuric acid, and man-
ganese, the apparatus is required to withstand more heat, and is therefore constructed
entirely of metal. a a, Fig. 106, is a shallow iron pan, fitted with the tube b for the purpose
of emptying the contents of the leaden cylinder, d d. This iron vessel serves as the lower
part of the leaden cylinder, dd, the top of which is provided with an opening for a funnel
syphon-tube for the introduction of the acid, and another opening, f, for the manganese.
The entire apparatus stands on a flue leading from a furnace.
FIG. 105.
โค
FIG. 106.


d
B
a
Condensing Apparatus. The chlorine passes from the generator through the tube, M, Fig. 107,
into a room constructed of large blocks and slabs of sandstone joined by means of asphalt
cement, or a mixture of coal-tar and fire-clay. Sometimes the room is built of bricks laid
in a similar cement, the interior being lined with asphalt; leaden chambers also are use 1
for this purpose. The room is fitted with several shelves upon which slaked lime is placed
in layers of three to four inches and more in thickness. The chlorine gas is readily absorbed
UNCHIUD
BIZENAM
DEDRIAN
FIG. 107.

M
heat being evolved. Care is to be taken that the temperature does not exceed 25º, because
then chlorate of lime is formed; this is prevented by admitting the gas slowly. As soon as
the absorption ceases, the bleaching-powder is removed with rakes from the shelves, and
fresh lime introduced. Frequently the chloride of lime is somewhat diluted by an admixture
of slaked lime.
When it is desired to prepare a solution of chloride of lime, the apparatus shown in
Fig. 108 is employed. Two or four earthenware vessels, A, about 2 hectolitres capacity, are
placed in the leaden trough, B, the bottom of which is protected by a cast-iron plate and a
stoneware slab, F, from the direct action of the fire at D. B represents a concentrated solu-
218
CHEMICAL TECHNOLOGY.
tion of chloride of calcium serving the purpose of a bath, such a solution boiling at 179.5°.
By the syphon funnel, K, the hydrochloric acid is poured into a. I is a perforated cistern
filled with manganese.
s is the leaden gas tube. The chlorine being first washed in R,
passes through into T, filled with pieces of manganese, to decompose any vapours of
hydrochloric acid carried over, and lastly, the chlorine passing through m reaches the
absorption vessel, s. This vessel is a lead-lined wooden cask, fitted with an axle bearing
spokes to which are fastened gutta-percha floats. The bearing and plummer-blocks of the
axle are made of guaiacum wood and ebonite. The axle, o, gears with a suitable motive
power, the purpose being to keep the milk of lime in continuous motion while the gas is
being admitted.
W
VIR
VA
FIG. 108.

m
च
T
Z
The chlorine gas enters above the level of the fluid, which is kept constantly stirred, to
assist in the absorption. From the vessel wherein the absorption takes place a small tube
leads into another vessel filled with water to a depth of 18 to 24 centims.; a tube fitted to
this vessel leads into the open air to convey away any unabsorbed chlorine. As in the
preparation of solid chloride of lime, it is here necessary to guard against an increase in
temperature and also saturation; Schlieper has proved that too concentrated solutions
evolve oxygen, while too dilute solutions yield chlorate of lime.
Production Residues.
Utilisation of the Chlorine As the chlorine required for the preparation of chloride of
lime is generally obtained by the aid of manganese and hydrochloric acid, the resi-
dues consist chiefly of free acid and protochloride of manganese. The principal
suggestions as to the utilisation of these substances are :—
a. Those aiming at the regeneration of peroxide of manganese; and
B. Those not proceeding with this view. The former are of course the more
important.
Dunlop's Process. This process is one of the oldest and the best, excepting perhaps,
Balmain's, in which the chloride of manganese is neutralised with the ammoniacal water
of gas-works, the supernatant liquor being employed for preparing sal-ammoniac, while
the precipitate is ignited in a reverberatory furnace and converted into peroxide of
manganese. Dunlop's process, as practised at Tennant's works at Glasgow, is based upon
the fact, first observed by Forchhammer, that carbonate of manganese, when heateď to
260°, is converted into peroxide of manganese; that is, the carbonic acid is driven off,
and the compound, 2MnO₂+MnO, obtained. The process consists in the following
operations:-
1. Conversion of the chloride of manganese into carbonate of manganese.
2. Conversion of the carbonate into peroxide of manganese.
To the chlorine preparation residues, when they have become clear, either chalk or milk
of lime is added to neutralise the excess of acid and precipitate the oxide of iron. This
precipitate having settled, the clear liquid, a rather pure solution of protochloride of man-
ganese, is poured into shallow troughs and intimately mixed with finely powdered chalk.
The magma thus formed is transferred for further decomposition to a large cast-iron.
trough, 27 metres long by 3 metres wide. Parallel to the length of this vessel, a stout
wrought-iron axle is carried, to which are fitted cast-iron branches serving as stirrers.
BLEACHING-POWDER.
219
The axle passing through stuffing boxes at each end of the trough, gears with a motive
power, whereby the stirrers are caused to keep the chalk constantly suspended in the
manganese solution. High-pressure steam is conveyed into the trough and aids decom-
position. The carbonate of manganese obtained is freed by washing from chloride of
calcium, and having been well drained, is calcined in a peculiarly constructed furnace, in
which the carbonate is first dried on a higher stage, and then is transferred to a lower and
hotter stage, where oxidation is commenced. The oxidation is completed at the lowest
stage of the furnace, to which plenty of air is admitted. The fire-place is constructed to
admit of the regulation of the heat with great nicety, because too high a temperature would
cause the formation of protosesquioxide, and too low a temperature would leave the car-
bonate undecomposed.
In this process the residues are converted into nitrate of manganese,
which is next decomposed by heat. The residues are evaporated to the consistency of a
syrup, and mixed with nitrate of soda :----
Gatty's Process.
To 76 kilos. of protochloride of manganese
and to 95 kilos. of sulphate of manganese
}
106 kilos. of nitrate of soda are taken.
The mixture is dried, and then heated to a dull red heat in an iron retort, the fumes of
nitric acid given off being used in the manufacture of sulphuric acid. The residue in the
retort consists, according to the salt of manganese employed, of peroxide of manganese
and chloride of sodium or sulphate of soda; it may be lixiviated with water to obtain the
peroxide of manganese in a pure state if sulphate of soda is present.
Hofmann's Process. The processes of regenerating manganese by the application of soda
waste are more important than the preceding. In Hofmann's process the protochloride
of manganese is, by the addition of the yellow ley obtained from the lixiviation of soda
waste converted into sulphuret of manganese. The precipitate, consisting of—
Sulphuret of manganese
Sulphur
Protoxide of manganese
55.00
40'00
5'00
100'00
is dried and calcined, the sulphurous acid given off being led into the sulphuric acid
chambers. The remaining residue, consisting of—
Sulphate of manganese
Peroxide of manganese
Protoxide of manganese..
44.5
18.9
36.6
ΙΟΟ Ο
is next mixed with nitrate of soda and heated to 300°, yielding sulphate of soda and
nitrate of manganese, the latter, however, being at once decomposed into peroxide of
manganese and hyponitric acid :-
Mn(NO3)2 + Nú₂SO4 ;
a. MnSO4+2NaNO3
B. Mn(NO3) + MnO2 + 2NÒ₂.
After the mass has cooled, the sulphate of soda is removed by lixiviation, the residue
yielding a material free from iron, and according to the inventor, equal to native manganese.
Weldon's Process. To the residue, consisting of protochloride of manganese, are first added
for every molecule of that salt 2 molecules of hydrate of lime. Into this magma, consist-
ing of hydrate of protoxide of manganese, hydrate of lime, and chloride of calcium, air
is forced, the effect being that the manganese is rapidly higher oxidised, and forms cal-
cium-manganite (CaMnO3, or MnO,,CaO), which, having subsided, and the supernatant
chloride of calcium solution being run off, is ready for chlorine making by the addition of
hydrochloric acid. The same process is repeated, and even a change of vessels is not
required. (See p. 216.)
the Residues.
Other Methods of Utilising B. Utilisation of the residues without regeneration of the
peroxide of manganese. M. Schaffner, at Aussig, precipitates the
protochloride of manganese with lime, dries the precipitate, and calcines it in a rever-
beratory furnace, obtaining protosesquioxide of manganese, employed with iron ore in the
blast furnace. The solution of chloride of calcium simultaneously obtained is precipi-
tated by sulphuric acid, yielding the material known as annaline; that is to say, the
gypsum used in paper manufacture. In the process of soda-making from sulphuret of
sodium and iron, as suggested by Malcherbe and improved upon by Kopp, for the oxides,
and carbonate of iron, the corresponding manganese compounds may be substituted.
Carbonate of manganese may be used to convert sulphuret of sodium into soda, and may
also serve for the preparation of permanganates. A. Leykauf suggests that the residues
2 20
CHEMICAL TECHNOLOGY
of chlorine manufacture should be employed to form a violet-coloured paint, known as
Nüremberg-violet, a compound of ammonia, oxide of manganese, and phosphoric acid.
In England the residues are frequently employed in the purification of coal-gas and as
disinfectants.
of Bleaching-Powder.
Theory of the Formation When chlorine gas and slaked lime (hydrated oxide of calcium,
CaH₂O₂) are brought in contact, a portion of the oxygen of the lime combines with
the chlorine, forming hypochlorous acid, which, combining with the undecomposed
lime, forms hypochlorite of lime, while another equivalent of chlorine combines
with the deoxidised lime (calcium) forming chloride of calcium :—
Hydrate of lime, 2CaH2O2,
Chlorine, 2Cl2,
Hypochlorite of lime, Ca (Clo)2,
yield Chloride of calcium, CaCl2,
Water, 2H₂O.
This bleaching-powder consists in 100 parts of:-
Hypochlorite of lime
Chloride of calcium
Water
49°31
38.28
or of-
12'41
100'00
Chlorine
Lime ..
Water
:
:
:
:
:
48.90
38.69
12'41
100'00
A bleaching-powder of this theoretical composition does not and cannot occur in
the trade; a good sample, containing 26.52 per cent. of active chlorine was composed
as follows:-
Hypochlorite of lime
26'72
Chloride of calcium
25°51
Lime ..
23.05
Water of composition and moisture
24°72
100'00
This analysis may be more intelligible by the following arrangement:-
Powder.
Hypochlorite of lime
Active chloride of calcium
Excess of chloride of calcium
Hydrate of lime ..
•
Water of composition and moisture
:
26'72
20'72
4'79
30°45
17.31
100'00
According to Dr. Fresenius (1861), bleaching-powder is a mixture of 1 molecule
of Ca(CIO), and 2 molecules of basic chloride of calcium, CaCl2,2CaĦ₂O₂+2H₂O.
Properties of Bleaching Bleaching-powder is a white, rather moist powder, consisting
of hypochlorite of lime, chloride of calcium, and excess of slaked lime. 10 parts of
water dissolve the bleaching material, leaving the excess of lime; the chlorine con-
tained in the chloride of calcium also acts as a bleaching agent, as on adding an
acid to the bleaching-powder the hypochlorous acid set free reacts upon the hydro-
chloric acid evolved from the chloride of calcium, forming water and chlorine:—
C1
H
H
H
0+
(}+{}=}o+a})
BLEACHING-POWDER.
221
The bleaching power of chloride of lime does not come immediately into play
unless an acid is added; this property is turned to account in the producing of white
patterns upon fabrics dyed turkey-red, by printing the pattern in a thin paste of tar-
taric acid, the fabric being afterwards immersed for a few minutes in a solution of
hypochlorite of lime. Instead of employing acids for setting the chlorine free from
chloride of lime, sulphate or chloride of zinc may be substituted, the result being
that gypsum and oxide of zinc are precipitated, while hypochlorous acid remains in
solution.* The various industrial uses of bleaching-powder have already been men-
tioned. Chloride of lime, as bleaching powder is generally termed in this country,
is sometimes used for the preparation of oxygen, 1 kilo. (of the formula Ca(ClO)2),
yielding 132.2 grms. 92'4 litres of oxygen.
Chlorimetry. As the value of a sample of chloride of lime depends upon the quantity of
of the really active chlorine and hypochlorous acid it contains, methods have been
devised for ascertaining with a greater or less degree of accuracy the quantity of
these active agents. Formerly the test was the discolouration of a certain quantity
of indigo solution by a certain quantity of bleaching-powder solution, as compared
with the action of chlorine upon indigo, but it is clear that this method could
not yield accurate results.
Gay-Lussac's Chlorometric
Method.
This eminent savant makes use of the oxidising action of
chloride of lime upon arsenious acid, a volume of dry chlorine gas dissolved in
water being employed. The solution of chlorine is poured into a graduated tube
divided into 100 parts, each of these divisions corresponding to one-hundredth of
chlorine. A solution of arsenious acid in dilute hydrochloric acid is also prepared,
the strength of the solution being such that equal bulks of the two liquids suffer
mutual decomposition :--
Arsenious acid, As2O3,
Water, 2H2O,
Chlorine, 2Cl2,
yield
Arsenic Acid, As2O5.
Hydrochloric acid, 4CIH
Water is decomposed; its oxygen combines with the arsenious acid, forming arsenic
acid, while the hydrogen combines with the chlorine. Usually 1 litre of dry chlorine
gas is dissolved in 1 litre of distilled water. The normal solution of arsenious acid
is so prepared that it is entirely decomposed by the chlorine water to arsenic acid.
The test is carried out as follows:-Take 10 grms. of the sample, and triturate with
distilled water, adding sufficient of the latter to make up a litre. Next take, by
means of a graduated pipette, 10 c.c. of the arsenious acid solution, and pour it
into a beaker, adding a drop of indigo solution to impart a faint colour; next add,
by means of a burette, sufficient of the bleaching powder solution to cause the
colour nearly to disappear, then add more of the indigo solution, and again bleaching-
powder solution, until the fluid becomes quite colourless. The normal arsenious,
acid solution is prepared by dissolving 4'4 grms. of this acid in 32 grms. of hydro-
chloric acid, the liquid to be diluted to 1 litre. If 10 grms. of bleaching-powder
contain 1 litre of chlorine gas, it is of 100 degrees strength.
I
Penot's Test.
Penot has modified Gay-Lussac's method in the following particulars:—
For the arsenious acid solution he substitutes arsenite of soda, and for the indigo
* Explosions have occurred from bleaching-powder being kept in too tightly closed
vessels, due to spontaneous decomposition, (Ca(CIO), + CaCl₂ = 2CaCl, +0₂). As a pre-
vention it is suggested that the powder should be ground, packed in casks, and strongly
pressed into a hard mass.
222
CHEMICAL TECHNOLOGY.
solution a colourless iodised paper, which is turned blue by the smallest quantity of
free acid. The paper is prepared in the following manner:-1 grm. of iodine,
7 grms. of carbonate of soda, 3 grms. of starch, and litre of water are mixed. When
the solution becomes colourless, it is diluted to a litre; in this fluid white paper is
soaked. The arsenical fluid is prepared by dissolving 4'44 grms. of arsenious acid,
and 13 grms. of crystallised carbonate of soda in 1 litre of water. This solution is
poured by means of a burette into the solution of the chloride of lime intended to
be tested (10 grms. of the sample to 1 litre), the completion of the reaction being
known by the paper remaining uncoloured. Mohr, again, has modified this process,
in not however very essential particulars.
Dr. Wagner's Method. This test, discovered in 1859, is the so-called iodometrical
method, and is based upon the fact that a solution of chloride of lime separates the
iodine from a weak (1 to 10) and slightly acidified iodide of potassium solution, the
iodine being quantitatively estimated by means of hyposulphite of soda :—
Iodine, 21,
Iodide of sodium, 2NaI,
Hyposulphite of soda, 2Na₂S₂O3+5H₂O, yield Tetrathionate of sodium, Na2S406,
Water, 5H2O.
The test is thus executed :-100 c.c.1 grm. of bleaching-powder solution,
obtained by dissolving 1 grms. of chloride of lime in 1 litre of water, are mixed
with 25 c.c. of solution of iodide of potassium acidified with dilute hydrochloric
acid. The ensuing clear, deep brown coloured solution is treated with hypo-
sulphite of soda solution until quite colourless. The hyposulphite of soda solution
is composed of 24'8 grms. of that salt to 1 litre of water; 1 c.c. of this solution
neutralises o‘0127 grms. of iodine and 0.00355 grms. of chlorine.
Chlorometrical Degrees. The strength of bleaching-powder is indicated in England,
Russia, America, and Germany by degrees corresponding to the percentage of active
chlorine; but in France the degrees denote the number of litres of chlorine gas at o°
and 760 millimetre Bar., which 1 kilo. of bleaching-powder can evolve. The
following table compares the chlorometrical degrees of France and England:-
English.
French.
63
20'02
65
70
75
80
20.65
22°24
23.83
25'42
85
27'01
90
28.60
ΙΟΟ
31.80
105
33°36
IIO
34'95
115
36'54
120
38.13
125
39°72
126
40'04
The percentage is calculated by multiplying the French degrees by the coefficient
0*318, a litre of chlorine gas = 35'5 criths, weighing 3·18 grms.
CHLORATE OF POTASSA.
223
Alkaline Hypochlorites.
A solution of hypochlorite of potassa is known in commerce
under the name of Eau de Javelle, while the corresponding soda solution is known as
Eau de Labarraque; these solutions are prepared by passing chlorine gas into a
solution of either caustic (1), or carbonated (2) alkali :—
(1). 2NaOH+Cl₂ = NaOCl + NaCl + H₂O;
(2). 2Na2CO3 + Cl2 + H2O = NaOCl + NaCl +2NaHCO3;
or by exhausting bleaching-powder with water, and precipitating the solution with
sulphate or carbonate of soda solution, sulphate or carbonate of lime being thrown
down, while the hypochlorite and chloride of the alkali remain in solution.
Hypochlorite of aluminium, or Wilson's bleaching powder, is obtained by mixing chloride
of lime solution with sulphate of alumina; its action is by evolving oxygen, leaving
chloride of aluminium in solution. Hypochlorite of magnesia (Ramsay's or Grouville's
bleaching liquor) is obtained by adding sulphate of magnesia to a solution of bleaching-
powder; the result is the formation of a very energetic bleaching compound, which, espe-
cially for the purpose of bleaching finely-woven-fabrics, as muslins, &c., is preferable to
chloride of lime on account of the absence of caustic lime. Varrentrapp's bleaching salt,
or hypochlorite of zinc, is another energetic bleaching compound obtained by treating a
solution of chloride of lime with sulphate of zinc, the result being the precipitation
of sulphate of lime, while hypochlorite of zinc remains in solution; chloride of zinc may
be employed, but, of course, the solution then retains chloride of calcium. Hypochlorite
of baryta is sometimes used, hypochlorous acid being obtained by the addition of
very dilute sulphuric acid.
Chlorate of Potassa. This salt (KC103) consists in 100 parts of 38.5 of potassa and
61*5 of chloric acid; its crystals are rhombic and tabular in form. It formerly was
prepared by passing chlorine gas into a concentrated solution of carbonate of
potassa, the result being the formation of chlorate of potassa and chloride of
potassium. As the chlorate is the least soluble it crystallises first, while by evapo-
ration the mother-liquor yields chloride of potassium. The chlorate is then washed
with cold water, and purified by re-crystallisation. 100 kilos. of carbonate of
potassa yield in this manner 9 to 10 kilos. of the chlorate. At the present day,
however, chlorate of potassa is prepared by a method, the suggestion of the late
Dr. Graham. Chlorine is caused to act at a high temperature upon milk of lime, with
the result of the formation of chlorate of lime and chloride of calcium, the chlorate
of lime being afterwards decomposed by chloride of potassium. The method by
which chlorate of potassa is prepared on the large scale according to this plan is the
following:-1 mol. of chloride of potassium and 6 mols. of hydrate of lime, having
been mixed with water, are submitted to the action of chlorine gas; the solution yields
on evaporation crystallised chlorate of potassa, while chloride of calcium remains.
This operation is carried on by the aid of the apparatus illustrated in Fig. 109. BB are
earthenware jars, placed in a chloride of calcium bath, and filled with a mixture for
evolving chlorine gas.
This gas
is conveyed through the leaden tube, F F, to the vessel, c,
which is placed in cold water for the purpose of condensing any aqueous vapours. From
o the gas passes through the leaden tube g into the absorption vessel, a, in which the
mixture of lime and water has been placed. E is an iron stirrer covered with lead, h, a
portion of the tube for carrying off the non-absorbed chlorine; d, a tube closed with
a plug during the operation, and intended for tapping off the contents of the vessel. The
milk of lime is poured into the vessel at 50° to 60° C., while sometimes steam is injected
for the purpose of keeping up the temperature, which rises as soon as the reaction com-
mences nearly to the boiling-point. A small quantity of hypochlorite of lime is always
formed. As soon as no more chlorine is absorbed the fluid is tapped off into a lead-lined
tank, and after the suspended matter has been deposited, is syphoned over into a leaden
evaporating pan and concentrated to 25° to 30° B., any hypochlorite of lime being thus
converted into chlorate. To the evaporated and concentrated solution there is added
a hot solution of chloride of potassium, after which the evaporation is continued to crys-
tallisation. According to theory, 24 parts of lime require I part of chloride of potassium;
224
CHEMICAL TECHNOLOGY.
in practice, however, to every 3 parts of lime I part of chloride of potassium is taken.
Old chloride of lime which has become unfit for bleaching purposes may be utilised
by first preparing chlorate of lime, and boiling a solution of this chlorate, adding to the
concentrated fluid chlorate of potassium to obtain chlorate of potassa. Chlorate of
potassa is not altered by exposure to air, is soluble in 16 parts of water at 15.8°, in 8 parts
of water at 35°. and in 1·6 parts of water at 100°. On being heated to fusion, this salt
yields oxygen; if incautiously rubbed in a mortar with combustible substances, as
sulphur or phosphorus, violent explosions will ensue. I kilo. of the chlorate yields, when
FIG. 109.

F
F
J
h
heated with either o 5 kilo. of manganese or I kilo. of oxide of iron, or, better still, with
a small quantity of oxide of copper (see "Chemical News," vol. xxiv., p. 85), 3912 grms. =
273.5 litres of oxygen. Chlorate of potassa is chiefly employed in pyrotechny for the pre-
paration of white powder, as an ingredient in the explosive mixture for the cartridge
of needle-guns, as an oxidising agent in calico-printing, and in the preparation of aniline
black. Perchlorate of potassa (KClO4) is now more frequently used in pyrotechny,
being less dangerous to manipulate, and owing to the large quantity of oxygen, emitting
more intense light.
Alkalimetry.
ALKALIMETRY.
The potash met with in commerce, no matter from what source it
is obtained, is always a mixture of carbonate of potassa with other salts of potassa
and soda; and again the carbonate of soda of commerce is a mixture of the car-
bonate with other soda salts, chiefly sulphate and chloride. The value of either of
the salts of course depends chiefly upon the quantity of pure carbonate present in a
given sample. The quantitative determination may be effected by either of two
rapid, yet sufficiently accurate, methods:-
a. The estimation of the quantity of acid required to neutralise the alkaline
carbonate;
b. The determination of the quantity of carbonic acid evolved by the addition of
a strong acid.
It is clear that these methods can be applied only when no other than the
alkaline carbonate is present.
Volumetrical Method. This method, invented by Descroizilles and improved by Gay-
Lussac, is based upon the measurement of the quantity of sulphuric acid required to
ALKALIMETRY.
225
expel the carbonic acid from a certain quantity of carbonate of potassa, this measure-
ment giving the quantity of pure salt. The best sulphuric acid is prepared by
mixing 100 grms. of pure sulphuric acid, sp. gr. = 1.842, with 1000 grms. = 1000 c c.
= 1 litre of distilled water; or, instead of weighing the acid, 54′268 c.c. may be
mixed with a litre of water. 50 c.c. of this normal acid solution suffice for converting
4.807 grms. of potassa into sulphate of potassa. The burette of 50 c.c. capacity and
graduated to half a c.c., is filled with test-acid; next 4807 grms. of potassa are
weighed out and dissolved in boiling water. Some litmus tincture is now added,
and the test-acid poured from the burette into the potash solution until the colour is
a wine-red. Supposing 60 demi-c.c. to have been used in saturating the potash,
and deducting c.c. for possible excess, the sample contains potash of 59°. The
quantity of potassa per cent. is calculated by multiplying the quantity found by
1'47. Potash of 50° contains 50 X 1'47=75°5 per cent. carbonate of potassa.
Mohr substitutes for the sulphuric acid crystallised oxalic acid—-
(C₂H₂04,2H₂O—126; mol.=63),
Mohr's Method.
because :--1. It is as strong as, and similar to, sulphuric acid in its action upon
litmus; 2. Being neither deliquescent nor efflorescent, it can be readily weighed off
in a dry state with accuracy; 3. Its aqueous solution is not liable to become mouldy
by keeping, as are the solutions of citric and tartaric acids; 4. It is not volatile
when in hot water. To prepare the normal acid liquor, 63 grms. of oxalic acid are
dissolved in a litre of water; on the other hand, there is prepared a corresponding
solution of caustic potassa so titrated that, on being mixed with an equal bulk of
the acid solution, the last drop of the alkaline solution restores the blue colour of
the previously reddened litmus, provided the liquor does not contain carbonic acid in
solution. For alkalimetric purposes 6'911 grms. of potash or 532 grms. of soda are
weighed out, these quantities being equal to molecule, and as the test-acid contains
in 1000 c.c. molecule of oxalic acid, 100 c. c. will exactly neutralise the quantity of
alkali. Some litmus tincture is mixed with the alkaline solution, to which the
oxalic acid solution is added in a slight excess (5 to 6 c.c.), the solution being
boiled to expel all the carbonic acid. There is now added by means of a pipette
divided into tenths-c.c., just sufficient caustic alkali to turn the litmus blue;
the number of c.c. of alkali solution employed is deducted from the number of c.c.
of acid solution employed, the difference giving the percentage of pure carbonate of
potassa contained in the sample. For instance, if 3'45 grms. of the potash = mole-
cule, require 36 c.c. of the acid and 3 c.c. of the alkaline liquor, there will be 33 c.c.
test-acid ½
66 per cent. carbonate of potassa, as, instead of mol., mol. having
been employed, the number of c.c. of test-acid must be doubled.
20
These instances of alkalimetric processes will suffice for the purposes of elucidation,
but the reader will find fuller explanations in works on volumetric analysis. However, it
is still to be observed that as potash is a very hygroscopic substance, it is necessary to
estimate the water it contains, or at least to dry the sample. As 629 grms. of commercial
potash and 4.84 grms. of soda contain when pure exactly 2 grms. of carbonic acid, every
2 centigrms. loss equals 1 per cent. of carbonate. Supposing the loss of weight to amount
to 164 centigrms. the sample will contain 16482 per cent: of carbonate of potassa; for
scientific purposes it would answer to say that such a sample consists in 100 parts of:-
Carbonate of potassa..
Foreign salts
Water
82
8
IO
:
16
100
226
CHEMICAL TECHNOLOGY.
109
60
100
For commercial purposes, however, at least abroad, the value (titre) of a sample
of potash expresses the percentage of anhydrous salt; for instance, by potash at T009
is meant potash containing 60 per cent. of real carbonate when in a dry state. But
if, by having taken up moisture, 100 lbs. have increased in weight to 105 or 109 lbs., the
60 60
expression or is equivalent to saying that the amount of money that would buy of
103
dry material will also buy and of the moist salt; the purchaser, therefore, does not
pay for water, and all that he has to do is to ascertain the quantity of water present in the
sample. In France the quantity of soda contained in a sample is usually expressed in
degrees indicating the percentage of carbonate of soda, and in England the percentage of
caustic soda; thus, as 100 parts of carbonate of soda contain 58-6 of soda and 41.4 of car-
bonic acid, it follows that—
Estimating the Value
of Potash.
105
T09
80° French are equal to 46.9° English.
86°
96°
>>
""
""
""
50.5°
52.8°
Gruneberg's Method of In the preceding methods of testing potash no notice is taken of the
soda contained in the samples, nor is the quality of the potassa salts
considered. It is clear that these determinations require a full analysis, which, by
Grüneberg's method, is executed in the following manner :-The carbonate of potassa
is estimated by Gay-Lussac's method, the chlorine by the aid of nitrate of silver, the
sulphuric acid by nitrate of lead, and the quantity of any free caustic potassa is determined
by means of tartaric acid. All the chlorine is calculated as chloride of potassium, all the
sulphuric acid as sulphate of potassa, and the rest of the potassa as carbonate; the quantity
thus found is deducted from that found alkalimetrically, and the remainder is calculated to
be carbonate of soda in the proportion of 69.1 to 53'0.
Ammonia.
AMMONIA AND AMMONIACal Salts.
Ammonia occurs in the atmosphere. Ammoniacal salts are met with in
a few minerals and in volcanic districts. But the bulk of the ammonia and
ammoniacal salts industrially used, is obtained from the dry distillation of coals,
bones, and animal substances, also by the distillation of lant (stale urine), by the
action of steam on some cyanogen compounds, and as a product of the blast-furnace
process.
The following sources of ammonia are technically available:
a. Inorganic
sources.
B. Organic
1. Native carbonate of ammonia,
2. Preparation of ammoniacal salts with boracic acid,
3. Volcanic sal-ammoniac,
4. Ammonia from nitric acid in the purifying of caustic soda,
5.
""
""
6.
""
7.
""
deutoxide of nitrogen and nitrous acid,
the nitrogen of the air,
certain cyanogen compounds.
8. Coals yield ammonia :-
a. By the dry distillation for the purpose of gas manufacture,
b. By the coking of coals,
c. By the use of coals as fuel;
9. Ammonia from lant,
sources.
IO.
II.
""
""
the dry distillation of bones,
beet-root juice.
Ammonia, NH3, consists of 1 volume of nitrogen and 3 volumes of hydrogen, con-
densing to 2 volumes of ammonia gas, a colourless gas of a peculiar and well-known
odour and sharp biting taste. At 15° water absorbs 727, and at 0° 1050 times its
own bulk of this gas, the solution being known as liquid ammonia, or spirit of sal-
ammoniac, the sp. gr. of which is o·824 (=31′3 per cent. NH3). Usually, however, a
weaker and more stable liquid ammonia is prepared for pharmaceutical and technical
purposes, having a sp. gr. — 0′960 (= 9'75 per cent. NH3). The following table
shows the specific gravity of liquid ammonia, and the percentage of ammonia
contained :-
AMMONIA.
227
}
Sp. gr.
0.875
NH3 per cent.
Sp. gr.
32'50
O'959
NH3 per cent.
ΙΟ Ο
0.824
31°30
0.961
9'5
o'goo
26'00
0°963
9'0
0'905
25*39
0*965
8.5
o'925
19.54
0*968
8.0
0'932
17.52
0'970
7'5
0'947
13'46
0*972
7°0
O'951
12.00
O'974
6'5
O'953
II.50
0*976
6'0
o'955
o'957
II 00
10'50
0'978
5'5
Ammonia gas is very soluble in alcohol. The spiritus ammoniaci caustici Dzondii of
the Prussian Pharmacopoeia is a solution of ammonia gas in alcohol of o·820 sp. gr.; the
ammoniacal solution containing 10 per cent. of real NH3, and having a sp. gr. of o·808 to
0810. The liquor ammonii vinosus is a mixture of I part of liquid ammonia (at 10 per
cent. NH3) and 2 parts of strong alcohol. Liquid ammonia is industrially employed for
the extraction of the lichen (orchil) pigments, in the preparation of carmine, the manu-
facture of snuff, the purifying of coal-gas, for the removal of carbonic acid and sulphuretted
hydrogen, for the saponification of fats, the preparation of ferrocyanide of potassium
according to Gelis's plan with the aid of sulphide of carbon, for the extraction of chloride
of silver from its ores, as antichlor in bleach-works, and in the manufacture of pigments
and dyes. As regards the use of liquid ammonia for the extraction of copper from
pyritical ores, Barruel stated (1852) that the copper might be dissolved by simply impreg-
nating finely pulverised ore with liquid ammonia, and forcing air through the mixture,
the metal being obtained as black oxide of copper after the ammonia is distilled off.
This process, however, has not been found to answer on the large scale. The researches
of von Hauer, Schönbein, Tuttle, and others, have proved that the oxidation of the
ammonia is simultaneous with the oxidation of the copper, and that the nitrous acid thus
formed is the active agent. Moreover, the experiments of Liebig and Way have proved
that even if the operation were carried on in air-tight vessels, the ammonia could not be
entirely recovered, owing to the fact that the ores absorb ammonia, and render it
insoluble, thereby preventing its action on the copper. But if the copper ore be tolerably
pure malachite or lazulite, only containing lime or carbonate of that base, liquid ammonia
may be successfully employed. Liquid ammonia is used in Carré's ice-making machine.
The rationale of this machine is that ammoniacal gas being expelled by heat from its
aqueous solution, is again condensed and liquefied by pressure and cooling; the retort in
which the ammonia is heated being next cooled by water, a vacuum is created, and as a
consequence the ammonia contained in the condenser volatilised, returned to the retort, and
again taken up by the water present. On again resuming the gaseous state, the ammonia
absorbs a great amount of heat, causing a diminution in temperature sufficient to freeze
water. Carré's ice-machine yields 10 kilos. of ice for every kilo. of coal consumed as fuel.
Although Fournier has suggested that ammoniacal gas might be usefully employed in
testing the joints of gas-fittings in houses, this is more readily effected by the use of a
hand air-pump. The application of ammonia as a source of motive power has been tried,
but it is not at present likely that it will supersede steam.
Ammonia.
Preparation of Liquid By decomposing with caustic lime either chloride of ammonium
or sulphate of ammonia, ammoniacal gas is set free, and can be absorbed by water,
care being taken that the lime is in excess. When carbonate of ammonia is prepared
on the large scale by sublimation of a mixture of chalk and sal-ammoniac, a
large quantity of ammoniacal gas, 14 parts for each 100 parts of carbonate of
ammonia, is obtained and may be utilised. Wagner has been the first to observe
that the technical preparation of liquid ammonia might be combined with the
preparation of baryta-white by precipitating a solution of sulphate of ammonia
with caustic baryta-water; the clear supernatant liquor will be a solution of
caustic ammonia.
223
CHEMICAL TECHNOLOGY.
The preparation of liquid ammonia on the large scale is effected by means of the
apparatus shown in Fig. 110. A is a cast-iron distilling vessel placed in a brickwork
furnace. To the neck of the vessel is fitted a lid secured to the flange by means of
bolts and nuts, and luted with red-lead. The lid carries an iron tube, m, leading to the
wash vessel, B, of wrought-iron. This vessel is surrounded by cold water contained in a
wooden tank, and is provided with a wide tube, o, through which m passes. The wash
vessel is filled with only so much water as will close the tubes and o hydraulically,
as during the operation a large quantity of water is distilled over from a. 100 parts of
slaked lime are mixed with a sufficient quantity of water to form a thin milk of lime,
which is poured into a; the lime solution having become quite cold, there is added 100
parts of pulverised sal-ammoniac or sulphate of ammonia, being thoroughly mixed by
stirring with an iron rod. The lid being screwed on A, the fire is lighted in c; the
FIG. IIO.

ID=
m
B
"
mercurial gauge, b, shows the course of the operation. The ammoniacal gas proceeds
from the wash vessel, B, through the tube t into the condensing apparatus, D, invented
by Brunnquell, and highly useful for this and for similar purposes where it is desired to
work under a low pressure. This apparatus consists of a large tank or box in which
four shallow boxes, d', a", a", a"", are placed bottom upwards, the sides of the boxes being
perforated with small slits. The outer tank is filled with water. When ammoniacal
gas enters through t into a""", it forms a large bubble, similar to an air bubble under
ice, and reaching one of the small slits rises into a"", and so on, the bubble becoming
smaller and smaller as the water gradually absorbs the gas. The box or tank, D, is
placed in a large tank, not represented in the cut, filled with cold water constantly
renewed. The still, a, is of sufficient capacity to contain 20 kilos. of sulphate of ammonia
and 80 litres of water. The operation is continued until the bottom of the still becomes
red-hot. The water contained in в is used at a subsequent operation for mixing with
the lime. The preparation of liquid ammonia directly from gas liquor, the ammoniacal
water of gas works, will be mentioned presently. The application of the property of
chloride of calcium to absorb ammonia and deliver it up on the application of heat
has been attempted industrially by Knab for the storing up of ammonia. Strong liquid
ammonia only contains 25 per cent. NH3, and Knab's preparation 50 per cent.; as
regards transport this may not be an uninteresting fact, but chloride of calcium is a very
deliquescent salt.
Ammonia.
Inorganic Sources of Before proceeding to describe the preparation of ammoniacal
salts from bones, coals, lant, &c., we must first enumerate the inorganic sources of
ammonia of industrial importance.
1. Native carbonate of ammonia, met with in large quantities in the guano deposits of
South America, was imported into Germany as a commercial article in 1848. On being
analysed this substance was found to consist of Ammonia, 20:44; carbonic acid, 54:35:
AMMONIA.
229
water, 21:54; and insoluble matter, 21:54 parts. It is, therefore, a bicarbonate of aınmonia
(NH4) HCO3.
2. The preparation in Tuscany of native sulphate of ammonia as a by-product of the
preparation of boracic acid has recently become important. The suffioni contain, in
addition to boracic acid, sulphates of potassa, soda, ammonia, rubidium, &c.; and that
the quantity of these substances is by no means small may be inferred from Travale's
researches, from which it appears that four suffioni yielded within twenty-four hours
5000 kilos. of saline matter, consisting of 150 kilos. of boracic acid, 1500 kilos. of sulphate
of ammonia, 1750 kilos. of sulphate of magnesia, 750 kilos. of the protosulphates of
iron and manganese, &c. The ammonia is probably due to the decomposition of
nitrogenous organic matter, occurring largely in the Tuscan mountains, the soil near the
lagoons being impregnated with sulphate of ammonia. In combination with the sulphates
of soda, magnesia, and iron, sulphate of ammonia forms the mineral Boussingaultite,
discovered by Bechi.
3. The ammoniacal salts due to volcanic action are of no or of little value to industry.
Mascagnin, sulphate of ammonia, is met with on Vesuvius and Etna; sal-ammoniac is
sometimes also found on Etna, as in the years 1635 and 1669, in such large quantities as
to become temporarily an article of commerce at Catania and Messina.
4. Ammonia is formed during many inorganic chemical operations, but rarely in
quantities rendering its preparation or recovery commercially available. Ammonia is,
for instance, set free in the preparation of caustic soda (see page 189), and the purifi-
cation of caustic soda by means of nitrate of soda; the quantity of ammonia set free in
this case is so large that it would be commercially worth trying to condense the gas in a
coke scrubber or condenser. When arseniate of soda is prepared by dissolving arsenious
acid in a caustic soda solution, evaporating this liquid to dryness, and igniting the residue
with nitrate of soda, ammonia is disengaged in large quantity.
5. Under the heading "Ammonia as a by-product of the manufacture of sulphuric
acid," there is in the original German text a description of a mere suggestion, embodied in
a provisional specification of an English patent, for the utilisation of the waste nitrous
vapours of sulphuric acid manufacture in the preparation of ammonia, by passing these
vapours, with steam, through red-hot tubes or retorts filled with charcoal, the ammonia
thus formed being absorbed by sulphuric acid. This process could never be available but
in badly arranged sulphuric acid works, because in well managed works the escape of
nitrous fumes is so very small that it certainly would not pay to convert them into
ammonia.
6. Of the many unsuccessful attempts made to directly convert the nitrogen of the
atmosphere into ammonia, it will only be necessary to mention Fleck's suggestion, to
pass a mixture of nitrogen, oxide of carbon, and steam over red-hot hydrate of lime,
whereby ammonia and carbonic acid are formed:-
Nitrogen, 2N
}
Oxide of carbon, 3CO yield Carbonic acid, 3CO2.
Ammonia, 2NH3, and
Water, 3H₂O
7. Perhaps the indirect application of atmospheric nitrogen for the preparation of
ammonia is of more importance. Margueritte suggests that cyanide of barium should be
prepared, and its nitrogen converted into ammonia by the aid of a current of superheated
steam at 300°. According to the description of this process in an English patent, not
however in practice, native carbonate of baryta is calcined with some 30 per cent. of coal-
tar, for the purpose of rendering the mass porous as well as more readily converted into
caustic baryta at a lower temperature. The carbonaceous mass is, after cooling,
placed in a retort, and kept at a temperature of 300°, while air and aqueous vapour
are forced in, the result being the formation of ammonia in considerable quantity, and
carbonate of baryta, which is again used. Ammonia is evolved from ball soda while
cooling, during the formation of cyanogen and cyanide of potassium in blast furnaces,
and the formation of sal-ammoniac in the process of iron smelting.
Ammonia.
Organic Sources of Industrially speaking, the organic sources of ammonia are far
more important than the inorganic. Among the ammonia-yielding organic sub-
stances coal (8) takes the first place; the average quantity of nitrogen-o'75 per
cent.-contained in coal is converted into ammonia during three different processes
employing this valuable mineral, viz. :—
a. By the dry distillation of coals for the manufacture of illuminating gas, ammonia is
obtained in the so-called gas-, or ammoniacal gas-water, the liquid mainly consisting of
an aqueous solution of sesquicarbonate of ammonia. The importance of this source
230
CHEMICAL TECHNOLOGY.
of ammonia production may be inferred from the fact that the one million tons of coals
yearly carbonized by the London gas-works will yield, supposing all the nitrogen to be
converted into sal-ammoniac, 9723 tons of that salt.
6. Ammonia is also formed when coal is converted into coke in coke ovens. Very
recently the utilisation of this source of ammonia has been successfully carried on at the
large coking establishment at Alais, Département du Gard, France, and also at the coke
ovens belonging to the Société de Carbonisation de la Loire, near St. Etienne, where, in
ovens constructed according to Knab's method, large quantities of ammoniacal salts are
produced.
y. Ammonia is produced during the combustion of coal as fuel, a portion of the nitrogen
contained in the coals being eliminated as ammonia; but this, it should be borne in mind,
is a consequence of imperfect combustion, and consequently of loss of fuel; and although
a series of experiments have been made, and apparatus devised for collecting and con-
densing the ammonia evolved with the smoke, the industrial production from this source
has hitherto been very limited.
Gas-Water.
Ammonia from This is the most important source of ammonia production. By
the dry distillation of coals for the purpose of gas manufacture there are formed, in
addition to permanent gases, various vapours, some of which on cooling yield tar
and ammoniacal liquor, consisting chiefly, as before stated, of a solution of sesqui-
carbonate of ammonia, but containing sulphuret and cyanide of ammonium, sulpho-
cyanide of ammonium, and sal-ammoniac, and being coloured by tarry matter.
Ι
It is obvious that the quantity of ammonia contained in this liquor is not always
constant, but depends upon several conditions; for instance, the quantity of nitrogen
contained in the gas coals, the hygroscopic moisture of the coals, and the degree of
heat applied to the retorts. The nearer the retorts are kept to a bright orange-red
heat, and the longer the distillation is continued, the larger the quantity of ammonia
formed; for at a lower temperature, of course always above red heat, there may be
formed aniline, chinoline, lepidine, and cyanogen compounds. Taking the average
quantity of the hygroscopic moisture of coals at 5 per cent., and the nitrogen at an
average of 0*75 per cent., 100 kilos. of coal would yield, under the most favourable
conditions, oʻ91 kilo. of ammonia. According to Dr. A. W. Hofmann's report (1863),
coal yields, when distilled, only one-third of its nitrogen, two-thirds being retained in
the coke; but no accurate experiments have been made on this subject. It has been
practically ascertained on the large scale, that I cubic metre (=220*096 gallons) of
gas-water yields at least 50 kilos. of dry sulphate of ammonia. The ammonia of the
gas-water may be utilised in various ways. Where fuel is cheap, and crude sulphate
of ammonia or crude sal-ammoniac marketable article, the gas-water may be at once
neutralised by an acid, and the liquid thus obtained evaporated. This is done in a
sal-ammoniac factory at Liverpool, where, during the colder season of the year,
300 cwts. weekly of this salt are prepared. Generally, however, the gas-water
is submitted to a process of distillation, and the ammonia evolved converted into
sulphate, as in Mallet's apparatus, or into sal-ammoniac, as in Rose's apparatus.
Mallet's Apparatus. This apparatus, in use in many of the large gas-works, is shown in
vertical section in Fig. 111. The plan of action is to force steam into large vessels
filled with gas-water, the effect being the volatilisation of the carbonate of ammonia.
Sometimes lime is added. The volatilised ammonia-of course if lime is added
caustic ammonia is evolved-is next conveyed into an acid liquor, and thus
converted into sulphate of ammonia. The apparatus consists of two cylindrical
boiler-plate vessels, A and B. A is heated directly by the fire, and is provided with
a leaden tube, c, dipping into the liquid contained in B, this vessel being placed
to catch the waste heat from the fire. b and e are man-holes; a and a' stirrers. By
means of the tube d the fluid from B can be run off into A. Gas-water is poured
AMMONIA.
231
into both vessels and lime added; ammonia is set free, while carbonate of lime and
sulphuret of calcium are formed, and of course remain in the vessels after the vola-
tilisation of the ammonia. The vessel D is also filled with ammoniacal water, and
when the operation is in progress this water, already warmed, is run by the aid of
the tube h from D into B. E is a gas-water tank, from which D is filled by means of g.
The ammonia set free in a is, with the steam, conveyed by the pipe c into B,

C
h
H
FIG. III
E
thence through c', into the wash-vessel, C, and thence again through c", into the first
condenser, D. The partially condensed vapour now passes into the condensing
vessel, F, the worm of which is surrounded by cold water. The dilute ammonia is
collected in G, and forced by means of the pump R into C, whence it is occasionally
syphoned into either A or B. The non-condensed ammoniacal gas is carried from G,
through a series of Woulfe's bottles, the first bottle, H, containing olive oil for the
K
232
CHEMICAL TECHNOLOGY.
•
purpose of absorbing any hydrocarbons mixed with the gas; the bottle I contains
caustic soda ley, in order to purify the ammonia and retain impurities; the bottle K
is half-filled with distilled water. The ammoniacal gas having passed through K,
is conveyed to the large lead-lined wooden tank, L, filled with dilute sulphuric acid
if it is intended to prepare sulphate of ammonia, or with water for making liquid
ammonia. The vessel L is placed in a tank of water; i is a small pipe for intro-
ducing acid; while the tube leading to M serves to carry off any unabsorbed ammonia,
м being also filled with acid.
Rose's Apparatus. In the manufacture of liquid ammonia the apparatus devised by Mr.
Rose, and shown in Fig. 112, may be advantageously employed. It consists of:-A, a
boiler; B and C, two vessels in which the gas-water is warmed by the aid of the tubes,
e and f, through which and g the steam and ammonia gas evolved in a pass to the
absorption vessels, D, E, and F, the connection between E and F being formed by the gas-
filters, G and H. The ammoniacal water can be run into a by means of the tubes, 7 and m,
FIG. 112.

A
K
m
Ꮹ
H
n
F
9
each of which is fitted with a tap or stopcock. A is filled two-thirds with gas-water and
e-third with slaked lime. The cylindrical sheet-iron gas-filters, G and H, are filled with
freshly burnt charcoal to retain any empyreumatical matter which might be carried over
by the gas. The absorption vessel, D, is filled with hydrochloric acid, while pure water
is poured into E and F. When A is filled, and the rest of the apparatus put in working
order, the fire is kindled, the ammoniacal gas evolved in a passes with the steam to в and
c, where a portion of the steam is condensed and retained as water in e and f. Into the
boiler, A, is fitted a tube, b, containing a thermometer, surrounded by brass fittings for the
better conduction of the heat; when this thermometer indicates 92° to 94°, the tap h is
opened, and the tap, i, open up to this time, shut in order to cause the gas to pass into the
hydrochloric acid contained in D, until the vessels G and H have been filled with fresh
charcoal, an operation which is required at the beginning of the working as well as when
the temperature in a has risen to 96º, 98°, and 100. This having been done, the tap h is
again opened. When the temperature has reached 103°, taking the boiling-point of
the liquid at 100°, all the ammonia is expelled, and the liquid is then run off by opening
the stopcock, a. Fresh lime having been put into the boiler, the operation is repeated.
When the temperature in a reaches 103°, the liquid in в becomes heated to 90°, and that
in c to from 25° to 30°. The vessel F contains from 120 to 150 litres of water, which is con-
verted into liquid ammonia of a sp. gr.=0.910 to 0.920. c and n are glass safety tubes.
Lunge's Apparatus. This apparatus, also intended for the utilisation of gas-water, is shown
in Fig. 113; a is the boiler; h the gas tube connected with the worm, c, which is placed in
a tank, d, filled with gas-liquor, run into a by means of the tube e. The tube f is so fitted
AMMONIA.
233
to a as to admit of discharging the waste liquor readily. b represents a stirrer fitted to
the boiler by a stuffing box, and being intended to rake up the lime and prevent it getting
caked to the bottom of a; h1, a tube intended for running gas liquor into d, from a tank
placed at a higher level; , a tube provided with a tap and fitted to the cover of d, to

FIG. 113.
J21
convey any gas or vapours from into the worm. k represents a wash vessel, some-
times filled simply with water, at others with milk of lime. The gas and vapours having
passed through k, are conveyed to the absorption vessel, 7. The tube, m, through which
the gas passes, is funnel-shaped, and opposite to the mouth of the funnel, at the bottom of
the tank, a thick disc of lead is fixed, because at this spot the action of the gas would soon
wear away the leaden lining of the vessel. o is a smaller wooden tank, also lead-lined,
into which sulphuric acid is poured, and whence it runs into through the stoneware
syphon, p. Any vapours given off are caught by the hood, r, and thence conveyed by a
tube into the chimney. The saline matter deposited in 7 is removed by a leaden pail, as
shown in the cut; when this pail is filled it is drawn up by means of the chain and
pulley aided by the counter weight, t. The salt (sulphate of ammonia) is placed in the
234
CHEMICAL TECHNOLOGY.
basket, u, from which the mother-liquor adhering to the salt drains again into the tank, 7.
Evaporation is therefore unnecessary with this apparatus.
Ammonia from Lant.
9. Lant, or stale urine, is a very important source of ammonia.
Whenever nitrogenous organic bodies are decaying, ammonia is always formed ;
when the organic substance is a proteine compound, there is formed carbonate of
ammonia as well as sulphuret of ammonium; but when the organic substance con-
tains no sulphur, only carbonate of ammonia is formed, as is the case with the urea,
CH4N2O, contained in urine, the urea by taking up the elements of the water being
converted into carbonate of ammonia. Lant is frequently employed without further
preparation for various purposes, on account of the carbonate of ammonia it con-
tains, as, for instance, in washing wool and removing the fat from flannel and other
woollen fabrics.
The apparatus exhibited in Fig. 114, contrived by Figuera, and until lately in operation
at a large establishment for the utilisation of the contents of the latrines and cloacæ of
Paris, consists of a steam-boiler, w, the steam generated in which is conveyed to two large
iron cylinders filled with lant. The carbonate of ammonia expelled is, with the steam,
condensed in a leaden worm; the cooled liquid is conveyed to a tank filled with acid, and
FIG. 114.

ل النملة المتعال المال
T
T mi
n
W
thus converted into carbonate of ammonia.
The arrangement of the apparatus is as
follows:-The wooden vessel, A, contains some 250 hectolitres of lant, and is filled by
means of the tube h. c and c' are two cylindrical sheet-iron vessels of 100 hectolitres
capacity; P and P' are similar vessels, the use of which will be presently explained. At
the commencement of the operation the boiler, w, is filled with about 130 hectolitres of
exhausted lant, taken from the vessels c and c'. The lant in A, warm in consequence of
having served for condensation, is conveyed to c by a tube, and thence by the tube h" to
c', cold lant being poured into a. The boiler, w, is fitted with three tubes, viz., T,
the steam pipe, m, a safety tube, brought to within a few centimetres from the bottom of
the boiler, and carried above the roof of the shed, and » a smaller safety tube; v is a tube
fitted with a stopcock. The steam evolved in w is carried by T into c', evolving from the
liquid therein the carbonate of ammonia it holds in solution. The carbonate, with the steam
passes through t into the vessel, P, which serves to retain any liquid carried over from c'.
The carbonate of ammonia vapour now passes from P through the tube r' to c, and
taking up in that vessel more carbonate of ammonia, is conveyed through the tube T into
P' (which again serves the purpose of P), and thence through T" into the leaden worm of
the condensing apparatus. The condensed liquor, a more or less concentrated solution of
carbonate of ammonia, is run through t" into s, a wooden vessel, lead lined, and filled
with a sufficient quantity of sulphuric acid to saturate the carbonate of ammonia. The
whole operation lasts about twelve hours; after this time the waste liquid in the boiler is
run off by opening the stopcock, v, and the operation again repeated. On an average the
lant operated upon at Bondy, near Paris, yields per cubic metre from 9 to 12 kilos. of
AMMONIA.
235
sulphate of ammonia, and at each operation 200 kilos. of that salt are obtained by the
working of one of the apparatus just described. It is stated that from the 800,000 cubic
metres of urine yearly run waste in Paris alone, there could be obtained, by proper treat-
ment, 7 to 800,000 kilos. of sulphate of ammonia.
Ammonia from Bone. 10. By the destructive distillation of animal substances, such as
bones, hoofs of horses, refuse horn, skins, hides, decayed meat, &c., there is obtained
a series of products, among which carbonate of ammonia prevails, with cyanogen
compounds, sulphuret of ammonium, and tarry matter-a very complex liquid con-
taining pyrrol, bases of the ethylamin series, pyridin, C,H,N, picolin, C6H-N,
lutidin, CH,N, and collidin, CзHIN. The organic matter of these substances
contains from 12 to 18 per cent. nitrogen; the organic matter of bones contains 18
per cent. of nitrogen, and, as the organic matter amounts to about one-third of the
weight of the bones, these contain about 6 per cent of nitrogen. Buffalo horn con-
tains 17, waste woollen fabrics 10, and old leather 67 per cent. of nitrogen.
II
It is evident that the quantity of ammonia in the products of the dry distillation
of animal substances depends upon the kind and condition of these materials, and
upon the temperature at which the operation takes place. The carbonate of am-
monia is obtained in the condensers as a solid saline mass, the crude sal cornu cervi,
or in aqueous solution (so called spiritus cornu cervi), floating on the surface of the
tar. At the present time the manufacture of ammonia and its salts from the products
of the dry distillation of animal substances is a matter of but limited industrial
importance, owing to the extended coal-gas manufacture. Indeed, dry distillation
is now only carried on for the purpose of obtaining animal charcoal, and the occur-
rence of ammoniacal products is rather considered as a necessary but unavoidable
evil. A large quantity of animal matter is used for the manufacture of phosphorus
and of prussiates, and in these operations the manufacture of ammoniacal salts is
either altogether out of the question or effected only on a limited scale.
The apparatus used for the destructive distillation of animal matter is in some respects
similar to a coal-gas oven. Fig. 115 exhibits the construction in general use for what is
termed animal charcoal burning. The retorts intended to contain the bones are set in
NATI OAMMUNTAI
FIG. 115

ין
furnaces and fitted at the end farthest from the mouth with tubes, c c, communicating
with leaden chambers, B, C, &c. In these chambers the vapours are condensed, forming
a solid saline mass, which is purified by sublimation in the iron vessels, D D, fitted with
leaden covers. If, instead of bones, other animal matters, for instance, horn, woollen
rags, hair, and leather-cuttings, are operated upon, the result is that, instead of solid
•
236
CHEMICAL TECHNOLOGY.
carbonate of ammonia, an ammoniacal fluid of 13° to 15° B. is obtained, which may be
utilised in various ways. Where the mother-liquors of salt-works are readily obtainable,
they may, especially if rich in chloride of magnesium, be employed for the preparation of
sal-ammoniac by using the hartshorn spirit (crude carbonate of ammonia solution) for the
precipitation of the chloride of magnesium solution.
Ammonia as a By-Product
of Beet-Rcot Sugar
Manufacture.
When the beet-root juice is boiled, ammonia is evolved in
large quantities, and may be utilised in the preparation o
sulphate of ammonia. The ammonia yielded by the juice is the product of the
decomposition of the aspartic acid and betain present in the roots. According to
Renard, a beet-root sugar manufactory which yearly consumes 200,000 cwts. of
beets might thus obtain 887 cwts. of sulphate of ammonia.
Technically Important Sal-ammoniac, chloride of ammonium, NH4Cl, consists in 100
parts of--
Ammoniacal Salts.
Ammonia,
31.83
or
Hydrochloric acid, 68.22
Ammonium, 33'75
Chlorine, 66°25
From the thirteenth to the middle of the eighteenth century this salt was imported
into Europe exclusively from Egypt, where it was obtained by the combustion of
camel's dung. The camel feeds almost exclusively upon plants containing salts, and
the sal-ammoniac is sometimes found ready formed in the animal's stomach. The
sal-ammoniac having sublimed with the soot from the combustion of the dung, was
collected and refined by a second sublimation.
In localities where dung is used as fuel, it has been tried to obtain sal-ammoniac
by combustion with common salt. The first sal-ammoniac manufactory in Germany
was established by Gravenhorst Brothers, at Brunswick, in 1759. We have already
seen how crude sal-ammoniac may be prepared from gas-water or by other means.
The salt, no matter whence derived, is purified by sublimation in cast-iron caul-
drons, w, Fig. 116, lined with fire-clay. As soon as the crude sal-ammoniac is put into
EA
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UDKIHIVEPAURDIZ
FIG. 116.

these vessels and tightly rammed, heat is applied, at first gently, so as to drive off
any moisture. This effected, iron lids, F, G, H, are luted to the cauldrons; the lids
can be readily moved by means of the pulleys and chains provided with counter-
weights, B, C, D. Instead of iron covers lead hoods sometimes are employed, the
opening of which is temporarily closed with an iron disc. The hoods or covers are
always securely fastened to the cauldrons, to prevent them being forced off by the
pressure of the vapours. The temperature has to be regulated during the process
with great nicety, for too low a degree of heat yields a loose salt, and with too high
AMMONIA.
237
a degree of heat the organic matter present in the crude sal-ammoniac is liable to
give off empyreumatic matter, spoiling the appearance of the sublimed salt and
interfering with its good quality. Experience has proved that it is expedient to
have the sublimation vessels of rather large size, 24 to 3 metres interior diameter.
When the sublimed sal-ammoniac cake has attained a thickness of 6 to 12 centims.
the operation is discontinued, and the cake removed. The furnace is provided with
an oven for drying the sal-ammoniac, this oven being shut with a door, E, movable
by means of a chain running over a pulley, and aided by a counterpoise. At the
present day sal-ammoniac is often sublimed in earthenware vessels or large glass
flasks, the crude salt being first mixed with 20 to 30 per cent. of its weight of
powdered animal charcoal, then dried over a good fire, and next put into the stone-
ware sublimation vessels, B and M, Fig. 117, placed in two rows over the fire-place, G.
Fig. 117.

Each of these vessels is 50 centims. in height; the openings are surrounded by an
iron plate properly fitted to the neck and provided with a flange upon which rest the
earthenware vessels wherein the sublimed sal-ammoniac is condensed. When glass
flasks are used, the height of these vessels is 60 centims. by 30 centims. diameter.
Sixteen of these flasks, each charged with 9 kilos. of the mixture of sal-ammoniac and
charcoal, are placed upon a furnace in cast-iron pots, which are filled with sand.
The cover is in this case a leaden plate. The sublimation is carefully conducted,
and goes on slowly, lasting about 12 to 16 hours. After this time, the leaden plates
are removed, bungs or plugs of cotton-wool inserted, and the flasks allowed to cool
very gradually, for as the salt expands on cooling the glass vessels may be broken.
The cake of sal-ammoniac when quite cool is scraped clean with a knife, and after-
wards presents a perfectly crystalline appearance. When it is desired to obtain the
salt free from iron, the crude salt should be mixed, before the sublimation, with
about 5 per cent. of superphosphate of lime, or with 3 per cent. of phosphate of
ammonia; by this addition any chloride of iron is decomposed and left in the retort
as phosphate. The sal-ammoniac of commerce is met with either in crystalline state
or as a compact fibrous sublimed material; in the latter case the cakes or discs have
a meniscus shape, weigh abroad from 5 to 10, but in England usually about 50 kilos.,
and exhibit the appearance of having been formed in layers. Crystalline sal-
ammoniac is obtained by adding to previously re-cystallised sal-ammoniac a boiling
hot and saturated solution of the same salt, so as to form a thickish magma, which
is next placed in moulds similar in shape to those in use for making loaf-sugar; after
draining, the loaf of sal-ammoniac is removed, dried, and packed in paper ready for
sale. Besides the use made of sal-ammoniac in chemical laboratories, by pharma-
238
CHEMICAL TECHNOLOGY.
ceutists and veterinary surgeons, it is industrially in demand for tinning, zincing, and
soldering, in calico-printing and dyeing, in the manufacture of paints and pigments,
in the preparation of platinum, snuff, and very largely in the preparation of a
mastic-1 part of sal-ammoniac, 2 of sulphur, and 50 of iron-filings-used in joining
steam-pipes, the sockets and spigots of iron gas- and water-pipes, &c. Sal-ammoniac
is also employed in the preparation of pure ammonia liquida and ammoniacal salts.
Sulphate of Ammonia. It has been already mentioned that sulphate of ammonia-
(NH4)2SO49
is met with native in small quantities in the mineral known as mascagnin, in larger
quantities in the boracic acid of Tuscany, while it is also found in Boussingaultite.
The modes of preparing this salt from the ammoniacal water of gas-works, lant, the
products of the dry distillation of bones, by the aid of sulphuric acid, or by double decom-
position by means of gypsum or sulphate of iron, have been already given. The concen-
tration of the weak solution by evaporation yields the crystalline salt, which, however,
when obtained from liquors containing tarry matters is usually of a deep brown colour,
and has therefore to be purified by being dissolved in hot water, filtered through animal
charcoal, and then re-crystallised, the best plan being to evaporate the solution rapidly,
and remove the salt gradually by means of perforated ladles. The salt is then drained by
being placed in baskets, and next quickly dried on heated fire-clay slabs, in which opera-
tion any particles of tar are decomposed. Sulphite of ammonia obtained by saturating
carbonate of ammonia solution with sulphurous acid gas is, when exposed to air, gradually
converted into sulphate. Sulphate of ammonia is, industrially speaking, far the most
important of the ammonia salts, because besides being very largely used in artificial
manure mixtures, and by itself for the same purpose, it is extensively employed in alum-
making, and is the starting-point of the preparation of chloride of ammonium, carbonate
of ammonia, liquid ammonia, and other similar products.
Carbonate of Ammonia. The salt used in pharmacy and industry under this name is in
reality sesquicarbonate of ammonia, and composed according to the formula
(NH4)4C308, or 2 ([NH₁]2CO3) + CO2.
It is obtained either directly from the products of the distillation of bones, or by
subliming a mixture of chalk and sal-ammoniac.
Among the products of the dry distillation of bones is found a solid sublimate, essen-
tially impure carbonate of ammonia, purified by sublimation. For pharmaceutical use
carbonate of ammonia is prepared by submitting a mixture of either chloride of ammo-
nium or sulphate of ammonia with chalk-4 parts of the ammonia salt, 4 of chalk, and I
of charcoal powder-to a low red heat. The product is a perfectly pure white salt; during
the operation a large quantity of ammoniacal gas is evolved, which is either absorbed by
water or by coke moistened with sulphuric acid. Kunheim decomposes the sal-ammoniac
by subliming it with carbonate of baryta, chloride of barium being obtained as a by-
product. When freshly prepared, carbonate of ammonia is a transparent crystalline
mass, which, while absorbing water from the atmosphere, and evolving ammonia, is
superficially converted into bicarbonate of ammonia (hydrocarbonate of ammonia,
NH4 CO3). Owing to the penetrating odour emitted by this salt, it is known as smell-
H
ing salts. Impure carbonate of ammonia is also used for cleaning woollen and other
fabrics, for the removal of grease from cloth, and further, for the extraction of the orchil
pigments. Pure carbonate of ammonia, besides its use in pharmacy, is an ingredient of
baking and yeast powders.
Nitrate of Ammonia. This salt, (NH4)NO3, is prepared by the double decomposition
of solutions of sulphate of ammonia and nitrate of potassa. The sulphate of potassa
is first separated, and the solution of ammonia nitrate having been concentrated by
evaporation is left to crystallise, its crystalline form being similar to that of salt-
petre. When dissolved in water this salt produces cold, and is therefore used in
freezing mixtures; while the fact that when strongly heated it is converted into
protoxide of nitrogen and steam (N₂O + 2H₂O) might perhaps render it of use in
the preparation of a blasting powder.
SOAP.
239
SOAP-MAKING.
Soad.
By soap we understand the product of the action of caustic alkalies upon
neutral fats, and consequently soap may to all purposes be considered to consist of
stearate, palmitate, and oleate of potassium or sodium. Although soap has been
manufactured from a very remote antiquity, this industry did not attain its present
development upon scientific and rational principles until Chevreul published the
results of his researches on the fats, and before the discovery of Leblanc called the
soda industry into existence.
Raw Materials of Soap-boiling. The raw materials used in soap-boiling, as soap manufac-
ture is usually termed in this country, are of two kinds, viz., fatty substances and
solutions of caustic alkalies. Among the more important fatty substances are the
following:-Palm-oil, of vegetable origin, met with in the fruit of a palm tree,
Avoira elais or Elais guianensis; according to others, however, this oil is derived
from the Cocos butyracea, C. nucifera, and Areca oleracea, trees growing wild, and
also cultivated in Guinea and Guiana. The colour of this oil is a red-yellow, its
consistency that of butter, while it possesses a strong but by no means disagreeable
odour, similiar somewhat to that of orris root. When fresh, this oil melts at 27°, but
by becoming rancid as it is termed—that is, by its decomposition into glycerine
and free fatty acids-its melting point rises to 31° and even to 36°. It is chiefly
composed of palmitine mixed with a small quantity of oleine. Palmitine, formerly
confused with margarin, is saponified by the alkalies and converted into palmitate
of potassa or soda, while glycerine is set free:
C₂H, 03
Palmitine (tripalmitine), (C6H310)3
Hydroxide of potassa, 3KOK
(caustic potassa)
Glycerine, C303,
Palmitate of potassa, 3 { C16H100.
-3
K
Palmitic acid is very similar to, and has often been confused with, stearic acid;
the former is in a pure state a solid white crystalline mass, which fuses at 62º.
Palm-oil often contains one-third of its weight of this acid in free state, and the
quantity increases with the age of the oil. The red-yellow pigment of the palm-oil
not being destroyed by its saponification, the soap made from this oil is of yellow
colour, but if, previous to saponification, the oil is submitted to a bleaching process,
that is to say, the pigment destroyed by chemical agents, such as the joint action
of bichromate of potassa and sulphuric acid, the oil becomes nearly white, and
yields, on being saponified, a white soap.
The illipe, or bassia-oil, very similar to palm-oil, is obtained by pressure from the
seeds of the Bassia latifolia, a tree growing on the slopes of the Himalaya. At first
the colour of this oil is yellow, but by exposure to sunlight it becomes white. Its
odour is not very strong, but rather pleasant. At the ordinary temperature of the air
this oil has the consistency of butter; its sp. gr. is=0·958; its melting-point 27°
to 30º. It is somewhat soluble in alcohol, readily in ether, and easily saponified by
potassa and soda. In its saponification, oleic acid and two solid acids with a variable
melting-point are formed. The galam butter produced by the Bassia butyracea,
a tree met with in the interior of Africa, is sometimes confounded with palm-oil, to
which it is very similar, but of a deeper red colour. Galam butter fuses at 20° to 21º,
and is in its properties very much like palm-oil. Carapa oil and vateria tallow
belong to the same class of fatty substances; the first, the product of the kernel of a
species of Persoonia, a palm tree met with in Bengal and Coromandel, is a bright
240
CHEMICAL TECHNOLOGY.
yellow coloured material, which at 18º separates into an oil and a solid fat; known
as pine-tallow, Malabar tallow, and obtained from the fruits of the Vateria indica,
is a white-yellow waxlike-tallow, melting at 35°. Mafurra tallow is obtained by
boiling in water the seeds or kernels of the mafurra tree found at Mozambique ;
this seed, very rarely seen in Europe, is of the size of small cacao beans. Mafurra
seed also occurs in the Islands of Madagascar and Isle de Réunion. The fat obtained
from this seed has a yellow colour, the smell of cacao butter, and melts more readily
than tallow. The fat of the seeds of the Brindonia indica, employed at Goa, instead
of butter, also for medicinal purposes, and for use in lamps, is nearly white; melts
at 40º, and is insoluble in cold, but somewhat soluble in boiling alcohol. Cocoa-nut
oil, obtained from the kernels of the cocoa-nut (Cocos nucifera, C. butyracea), is
largely used in the tropics, where the tree abounds. This oil is imported into
Europe, and is also obtained here by pressing and by treating the kernels of
the imported nuts with sulphide of carbon. It is white, has the consistency of
lard, but possesses a disagreeable odour and a somewhat foliated texture; its
melting-point is 22°. Chemically considered this fat consists of a peculiar substance
termed cocinin, with small quantities of oleine; by saponification the former yields
glycerine and cocinic acid (cocoa-stearic acid), C13H26O2. W. Wicke obtained in
1860, 61'57 per cent. of fat from the kernels. During the last twenty years cocoa-
nut oil has been largely used for soap-boiling, because it is an excellent material for
the preparation of so-called fulling soaps. Tallow is obtained by melting the fatty
matter deposited in the cellular tissue of the abdominal cavity of cattle and sheep.
The hardness of the tallow depends partly upon the animals from which it is
derived, partly upon the food they eat; if the food be fodder, the hardest tallow is
produced, while if it consists of the refuse from breweries and distilleries the tallow
is soft. Russian tallow owes its hardness to the fact that the cattle in that country
are for fully eight months in the year kept on dry fodder. Generally tallow melts at
37°, and contains 75 per cent. of its weight of solid fatty matter, stearin (tristearin)
and palmitin (tripalmitin), the remainder being olein. If previous to being melted-
that is, separated by the application of heat from the cellular tissue and membranes
in which it is enclosed-tallow is preserved for too long a time, it obtains a
bad odour, removed with difficulty. The operation known as tallow-melting can
be performed in two ways, either by simply applying heat, which causes the
cellular tissue to shrink and become dry, the fat being expelled; or the membranes
and cellular tissue are destroyed by chemical agents, viz., the use of either
sulphuric or nitric acid, or caustic ley. Among these methods, that of D'Arcet, in
which sulphuric acid is used, and the operation carried on in closed vessels, is one
of the best; the sulphuric acid decomposes the vapours which are given off and
destroys their fœtidity, while more tallow and of a better quality is obtained. The
vapours are carried either into the furnace or into condensing apparatus. D'Arcet
recommends that to 100 parts of cut-up tallow, I part of sulphuric acid and 50
parts of water should be used. While the loss by the ordinary method of tallow-
melting amounts to 15 per cent., it is only 5 to 8 per cent. when this method is
employed.
Lard, owing to its high price, is rarely used in Europe for making soap, but is
largely employed in the United States, where, especially at Cincinnati, enormous
quantities of lard are converted into a solid fat (42 to 44 per cent.), and into a fluid
oil (lard oil, 56 to 58 per cent.)
SOAP.
241
Olive-oil is obtained from the fruit of the olive tree, Olea Europea, belonging
to the natural order of the Jasmineæ, and largely cultivated in the whole of Southern
Europe and the coastlands of North Africa.
In order to obtain an oil of good quality it is essential that the olives should
be gathered when they are fully ripe, which happens in the months of November and
December. Unripe olives yield an oil having a harsh bitter taste, while, again, over-
ripe fruit yields a thick oil, readily becoming rancid. The method of oil extraction
from olives as carried on in Southern France is the following:-The ripe olives are
first reduced to pulp in a mill; this pulp is put into sacks made of strong canvas,
or, better, of horsehair, and submitted to pressure. The first portion of oil thus
obtained is the best, and is known as virgin oil, or huile vierge. In order to eliminate
all the oil as much as possible, the cake, after the first pressing, is treated with
boiling water and again pressed. The oil thus obtained possesses a fine yellow
colour, but is more liable to become rancid than the virgin oil. Notwithstanding the
second pressure the cake retains enough oil to make it worth while to submit it to
further operation. Some kinds of olive-oil obtained by the second pressing are
employed, under the name of Gallipoli oil, in dyeing Turkey-red. This oil has an
acid reaction, consequent upon its containing free fatty acids, is turbid, rancid, and
possessed of the property of forming with carbonates of alkalies a kind of emulsion,
which in dyeing is known as the white-bath. The olive-oil used for the purpose of
greasing wool in spinning is known as lampant-oil. Under the name of Huile d'enfer
is understood the olive-oil deposited in the tanks, where the water used for adding
to the olives about to be pressed is kept; it is used in the manufacture of soap.
During the last few years it has become the custom to exhaust the olives with
sulphide of carbon instead of pressing them.
Fish-oil, seal-oil, obtained from the thick skin of several varieties of mammalia
inhabiting the seas, especially of the colder regions of the globe, and belonging to the
cetacea and phocena, varies somewhat in its properties, according to the mode
of preparation and the animal from which it has been derived. The sp. gr. of this oil
is 0·927 at 20°; when cooled to o° it deposits solid fat; it is readily soluble in
alcohol, and consists of oleine, stearine, and small quantities of the glycerides
of valerianic and similar fatty acids. Fish-oil, besides being an important material
in soap-making, is also used in tanning, tawing, and leather-dressing operations.
Hemp-oil, obtained from the hemp-seed (Cannabis sativa) containing about 25 per
cent. of oil, is chiefly used for making black, green, or soft soap. When fresh
pressed, hemp-oil possesses a bright green colour, which in time becomes a brown-
yellow. Linseed-oil, like the former a so-called drying oil, is obtained from the well-
known linseed (Linum usitatissimum) containing about 22 per cent. of this oil,
the sp. gr. of which is at 12°=0*9395. This oil consists chiefly of a peculiar
glyceride which on being saponified yields a fatty acid different from oleic acid;
moreover, linseed-oil contains some palmitin. Castor-oil, from Ricinus communis,
behaves when saponified very much like cocoa-nut oil. As yet, however, this oil is
not used in soap-making. Rapeseed-oil, as it occurs naturally, does not yield so
good a soap when saponified as when the oil is first converted into rapselaidin,
which, according to A. Müller, is done in the following manner :-To 1 cwt. of the oil
is added 1 lb. of nitric acid diluted with 1 to 2 lbs. of water; next some iron nails
are added, and the acid fluid is well stirred through the oil with a wooden spatula.
By the action of the nitrous acid set free, the oil is gradually converted into a yellow
I
17
242
CHEMICAL TECHNOLOGY.
fatty mass, which after having been left standing for some weeks in order to solidify,
may be directly saponified with soda. The oleic acid largely obtained in the manu-
facture of stearine candles is a very important material in soap-making. This acid
is a solution of impure stearic and palmitic acids in oleic acid.
Colophonium, the residue of the distillation of oil of turpentine, a yellow or
black-brown coloured material, is largely imported from the United States for the
purpose of preparing resin soaps, for sizing paper, and for the preparation of yellow
soaps, which are resin and tallow saponified together in certain proportions.
Ley.
The other important material required for soap-making is the ley; that is to
say, an aqueous solution of caustic potassa or caustic soda. Ley is not so much a
constituent of soap as the material by which the chemical process termed saponi-
fication is brought about. Usually the soap-boiler prepares the caustic ley, and
formerly wood-ash or potash was used for this purpose, but at present soda is more
extensively employed. The conversion of the alkaline carbonates into caustic
alkalies is effected by means of quick-lime; but abroad chemical manufacturers
produce caustic soda, and sell it to the soap-boilers under the name of soap-stone.
The preparation of soap-boilers' ley from wood-ash is carried on in the following
manner:―The sifted ash is placed on a paved floor, and moistened with enough water to
render it somewhat pasty. This paste is then formed into heaps, constructed with an in-
dentation, into which the caustic lime in quantities of one-tenth to one-twelfth of the weight
of the ash is placed. Over the lime is next poured sufficient water to cause it to slake,
care being taken to cover the lime up with ash. The ash and lime having been thoroughly
mixed, are placed in a tank, shaped like a cone from which one-fourth of the narrow
part is cut off, and fitted near the bottom with a tap. At a distance of some five inches
from the bottom a false and perforated bottom is fixed, so that the ley can collect between
the two bottoms. Under the tap a large iron tank is placed to receive the ley. The mixture
of ash and lime having been placed upon a layer of straw upon the perforated bottom,
and care having been taken to squeeze the mass together, water is poured over it for
the purpose of lixiviating the material until completely exhausted. Usually three different
kinds of ley are prepared and kept, viz.-I. Strong ley, 18 to 20 per cent. of alkali;
2. Middling strong ley, 8 to 10 per cent. of alkali; and 3. Weak ley, containing only 1 to 4
per cent. of alkali. This weak liquor is commonly used instead of water for lixiviating
a new ash and lime mixture. The sodium-aluminate obtained by the decomposition of
cryolite is used in the United States under the name of "Natrona refined saponifier," for
soap manufacturing purposes. Sulphuret of sodium may also be used instead of caustic
alkali.
Theory of Saponification.
Before Chevreul published his researches, it was supposed
that fats and oils possessed the property of combining with alkalies. Chevreul
found, however, that fats separated from their state of combination as soaps
possessed properties differing from those existing before they were saponified, the
fact being that the substances we are acquainted with as oil or fats are compounds
of peculiar acids, stearic, palmitic, margaric, oleic, all non-volatile substances;
while certain fats which give off a peculiar odour contain in addition to these acids
volatile fatty acids, as butyric, capric, capronic, valerianic, &c. The volatile acids
in the ordinary oils and fats are combined with a sweet material, discovered by
Scheele, and known under the name of glycerine.
According to Berthelot's researches it is held that all the oils and fats which are
used in soap-making are ethers of glycerine, C3H8O3, that substance being viewed as a
C3H5
trivalent alcohol, C3} 03. Palmitin, for instance, the main constituent of palm-
-3
oil, is glycerlyl-tripalmitate, or tripalmitin, that is to say, glycerine in which three
C₂H₁
atoms of hydrogen are replaced by the radical of palmitic acid, 316,10} 03.
3C16H31
SOAP.
243
Stearine (tristearine) and oleine (trioleine) have an analogous constitution. When
the fats, take palm-oil for instance, are saponified with caustic alkalies, say caustic
soda, the fat—that is, in chemical parlance, the ether-is decomposed into alcohol, i.e.,
glycerine, and sodium palmitate, i.e., soap, according to the following equation:-
Tripalmitin {C3H5
3 C 16 H 310
} 03
and Caustic soda, 3NaOH,
yield
Glycerine, C3H50
}
03
and Soap, or sodium palmitate, 3163100.
The glycerine formed during the process of saponification remains, after the
separation of the soap, dissolved in the mother-liquor from which it is prepared.
It is clear that such fats as palm- and cocoa-nut oil, which in their ordinary state
contain fatty acids, are more readily saponified than the perfectly neutral fats, viz.,
olive-oil and tallow; while the oleic acid derived from the stearine candle manu-
factories is readily saponified by carbonated alkalies. This observation applies to
colophonium (resin), which consists essentially of a peculiar acid, pinic acid, but
in these instances no real saponification takes place, inasmuch as no glycerine is
formed. The decomposition of a fat by an alkali does not take place suddenly and
throughout the whole of the fat at once, in the manner of inorganic salts, but passes
through several stages, the first being the formation of an emulsion of ley and fat ;
next fat acids and fat acid salts are formed, retaining the rest of the fatty matter in
suspension; gradually the free fatty matter is saponified, and the fat acid salts are
converted into neutral salts, or in other words, soap.
When caustic potassa is used, soft soaps are produced, while the hard soaps
result from the use of caustic soda. We distinguish soaps :—
a. As hard soaps or soda soaps.
B. As soft soaps or potassa soaps.
According to the fatty substances used in soap-boiling, soaps are distinguished as
tallow, oil, palm-oil, oleic acid, cocoa-nut, fish-oil, and resin soaps, &c. Technically, hard
soaps may be divided into :-
1. Nucleus soaps.
2. Smooth soaps.
3. Fulling soaps.
The term nucleus soap designates the soap that after having been made and separated
from the ley by the aid of common salt is boiled down to a uniform mass, free from air
bubbles, and exhibiting after solidification small crystalline particles. The portion of the
soap which does not separate in that state assumes, by becoming mixed with a large or
smaller quantity of the impurities of the ley, a mottled appearance. The soap directly
separating by the addition of salt into globules or nuclei is pure soap, free from any
adhering ley, water, or glycerine. Smooth soap is obtained by boiling for some time with
either water or weak ley, the soap taking up a portion of the water, and losing the crys-
talline and mottled appearance. In the preparation of this soap it is first separated by
means of salt from the mother-liquor (in saline solutions soap is insoluble), but after that
separation the soap is boiled with weak ley. The only difference existing between the
two kinds is, that the latter contains more water than the former. The fulling soap, at
the present that chiefly met with in commerce, is essentially the worst kind of soap, as an
insufficient quantity of salt is used, the result being that the entire contents of the boiling-
pan are kept together. The process of boiling is continued until on cooling the mass
solidifies. The soap is removed, cut into bars, and sold. Soap made from cocoa-nut oil
possesses especially the property of being hard and dry, notwithstanding that it contains
a large amount of water; consequently the use of cocoa-nut oil, both alone and with other
fats to which it imparts its property, is greatly on the increase. Soaps of this kind will
produce 250 to 300 parts of soap from 100 of oil.
Chief Varieties The German tallow soap or curd soap is essentially a mixture of stearate
of Soap. of soda and palmitate of soda, and is commonly prepared indirectly by first
saponifying tallow with caustic potassa, and next converting, by means of common salt, the
stearate and palmitate of potassa into the corresponding soda compound.
244
CHEMICAL TECHNOLOGY.
The soap-boiling pan employed is somewhat conical in shape. It is made of cast-iron, and
provided at the top with a high lintel or bulwark to prevent any fluid boiling over. Supposing
it to be intended to convert to cwts. of tallow into soap:-Into the cauldron is first poured
about 500 litres of strong lye at 20 per cent. (−1·226 sp. gr.); next the tallow is added,
and a wooden or iron lid having been fitted to the cauldron, the fire is kindled. When
ebullition sets in, it is kept up, with occassional stirring of the contents of the cauldron, for
five consecutive hours. The materials in the cauldron are converted into soap-glue, as it
is termed, a gelatinous mass, which, if the operation has been well conducted, ought not,
upon the addition of fresh ley, to become thin, while it also should not flow in drops, but
similarly to treacle from a spatula. The production of this substance is promoted by adding
oil of tallow to the ley gradually and in small portions at a time.
Mège-Mouriès recommends either yolks of eggs, bile, or albuminous compounds. Asproved
by the researches of F. Knapp, it is always advantageous to first convert the fat, with the
requisite quantity of ley, into an emulsion, and to leave the ley either not heated at all, or
only to 50° in contact with the fat, so as to saponify first slowly in the cold and to finish
off with ebullition. When caustic soda ley is used it is of a density 10° to 12° B.
(=1°072 to 1·088 sp. gr.) When the saponification is complete the operation of fitting or
parting is proceeded with, and consists in adding 12 to 16 lbs. of salt to 100 of tallow.
The soap is kept boiling until the soap-glue has become a greyish mass, from which
the mother-liquor or under-ley readily separates, the latter being let off by a tap; or, if
no tap is fitted to the cauldron, the soap is gradually ladled over into the cooling-tank.
The addition of salt not only aims at the separation of the soap from the ley, but also at
the partial conversion of the potassa into soda-soap. If the soap-glue has been removed,
it is again put into the cauldron, and there is added a moderately strong ley and heat again
applied. The soap again becomes quite fluid, but consists chiefly of soda-soap glue. The
ebullition is kept up, and during its continuance fresh ley and salt are added alternately.
By continued boiling the soapy mass becomes more and more concentrated; as soon as
the foaming ceases, and the whole mass is in a steady ebullition, it is again ladled over into
the cooling-tank, or the mother-liquor is tapped off. The object to be gained by this
second boiling is the conversion of the material into a uniform mass free from air-bubbles;
another is promoted by beating with iron-rods. The hot soap is next placed in a wooden
box, so constructed that it can be taken to pieces; upon the bottom of this box, which
is perforated, a piece of cloth is stretched, so as to allow of any adhering ley running
off. When the soap is cool the box is taken to pieces, the soap cut into bars, and these
placed in a cool, dry room. The cutting of the soap into bars is now effected by machinery;
formerly it was performed by hand with a peculiar tool, a copper-wire with suitable
handles, such as cheesemongers sometimes use. 10 cwts. of tallow yield on an average 163
cwts. of soap, which by drying loses some 10 per cent. As it is impossible, even with re-
peated applications of salt, to convert potassa-soap completely into soda-soap, the German
nucleus, or Kernseife, is always mixed with a considerable quantity of potassa-soap, to
which it owes its peculiar softness. According to the researches of Dr. A. C. Oudemans
(1869) only half the potassa is converted into soda-soap.
Olive-Oil Soap. This kind of soap, also known as Marseille, Venetian, or Castilian soap, is
chiefly prepared in the southern parts of Europe. The olive-oil is frequently mixed with
other kinds of oil, such as linseed, poppy-seed, cotton-seed oil, &c. Two kinds of ley are
employed in the prepapation of this soap: the first ley is only a caustic soda solution,
and used for fitting or preparatory boiling; the other ley is mixed with common salt,
and intended to effect the separation of the soap. The preparatory boiling aims at the
formation of an emulsion or the production of an état globulaire, whereby the contact of
oil and alkali is greatly promoted, and a real soap-glue ultimately results. In order to
remove the water from this material as much as possible, a ley containing common salt is
employed, and lastly by a third boiling the saponification is rendered complete. By the
use of the ley containing common salt it is possible to keep the soap-glue in such a con-
dition that it can take up alkali without combining with the water. The preparatory boiling,
or fitting, is carried on in large copper vessels, capable of containing 250 cwts., the
caustic soda employed for this purpose having a strength of 6° to 9° B. (= 1041 to 1'064
sp. gr.) The ley is brought to ebullition first, and the oil to be saponified is next
added, care being taken to stir the mixture in order to promote the reaction. Gradually
the mass becomes thick, and as soon as black vapours arise, due to the decomposition of
a small quantity of the soap-glue by coming in contact with the very hot copper, there is
added the stronger ley of 20° B. (1157 sp. gr.) If it is intended to produce a blue-
white soap, some sulphate of iron is added. As soon as the mass has become sufficiently
thick, the soda-ley mixed with salt is added. After some hours the soap entirely separates
from the mother-liquor, which is then run off, and fresh ley added also containing common
salt. The final boiling is then proceeded with, the ley having a strength of 20° to 28° B.
The ebullition is continued gently until the alkali is exhausted, when the mother-liquor
SOAP.
215
is again run off, and fresh ley mixed with common salt again added; this operation is
repeated some four or six times, when the soap is at last quite ready. This stage is indi-
cated by the absence of all smell of oil and the peculiar grain of the mass, which is left
to cool; but if sulphate of iron has been added, it is necessary to stir the soap continuously
until nearly cold, in order to produce the mottled appearance due to the formation of sul-
phuret of iron from the sulphate by the action of the sulphuret of sodium of the soda-ley.
Mottled-soap is produced in England by adding a concentrated solution of crude caustic
soda containing sulphuret of sodium to the liquid soap, previously impregnated with
sulphate of iron. When nearly cold the soap is placed in wooden boxes and left to com-
pletely solidify. After ten to twelve days it is ready for being cut into bars. 64 litres of
oil, 58 to 60 kilos., yield 90 to 95 kilos. of soap. White-oil soap is prepared in a similar
manner, but purer materials are employed. A good sample of Marseilles mottled soap
should contain:
Fat acids
Alkali
Water
I.
II.
63
62
13
II
24
27
100
100
Oleic Acid Soap. Is obtained from crude oleic acid, a by-product of stearine candle
manufacture. The oleic acid produced by the distillation process is less suitable for soap-
making purposes. Oleic acid is saponified simply by being mixed with a strong solution
of carbonate of soda, or by the application of caustic soda. In the use of the carbonate
of soda, however, there is the disadvantage of the effervescence due to the evolution of
carbonic acid, and consequent boiling over or spilling of the materials. Pitman uses the
carbonate of soda in a dry state. Heat is best applied by Morfit's arrangement, in which
steam is passed through a system of pipes moved by machinery and acting as stirrers.
Resin is sometimes added. As soon as the mass has acquired sufficient consistency, and the
effervescence ceases, the soap is put into moulds to cool and solidify. When caustic soda
is used, half the ley (sp. gr. 115 to 120=20° to 25° B.) is first poured into the cauldron
and brought to ebullition, next the oleic acid is added, and as soon as the soap-glue is
formed, the other half of the ley is put in, and the ebullition continued until the soap is
formed. The separation from the mother-liquor is greatly promoted by the addition of
some salt. The soap is poured into moulds to cool and solidify. In order to impart greater
hardness to the soap, some 5 to 8 per cent. of tallow is added to the oleic acid.
kilos. of oleic acid yield from 150 to 160 kilos. of soap, which, when well made, consists in
100 parts of:
Fat acids..
Soda..
Water
66
13
21
100
100
Resin-Tallow Soaps. Colophonium and ordinary fir-tree resin combine at boiling heat more
readily with alkalies than fats and oils; but the compounds obtained by treating resins
alone with alkalies are not soaps in a chemical sense, nor have they the appearance or
properties of soap. When tallow is saponified with a portion of resin, a true soap is
obtained. In England resin-tallow soap is manufactured very largely by first preparing a
tallow-soap, and when this is ready adding to it about 50 to 60 per cent. of the best resin
previously broken into small lumps. The mass is thoroughly stirred, and after the resin
has become incorporated with the tallow, the mother-liquor or under-ley is run off, and
the soap-making finished by boiling with a quantity of fresh ley at 7° to 8° B. The inso-
luble alumina and iron soaps having been removed as scum from the top of the liquid, the
hot soap is poured into moulds made of wood or sheet-iron; sometimes palm-oil is added
in order to improve the colour of the soap. Usually, palm-oil is not saponified alone, but
is added to tallow; by treating a mixture of 2 parts of tallow and 3 parts of palm-oil with
potassa or soda-ley in the ordinary manner, and by mixing this soap with a resin soap
prepared from I part of resin and a proper quantity of potassa-ley, the German palm-oil
soap is obtained.
Fulling-Soaps. As it is possible to incorporate soda-soaps with a certain quantity of water
without impairing the appearance, the soap-boilers at the present day only prepare so-
called fulling-soaps, that is, such as are not completely separated from the under-ley by
the aid of salt. These soaps contain, in addition to water, glycerine and the salts existing
in the under-ley. It is owing to the large amount of water contained that the soap-boiler
is enabled to sell cheap soaps notwithstanding the very greatly increased price of fatty
246
CHEMICAL TECHNOLOGY.
substances. Soap of this kind (in Germany known as Eschweger soap) appears when
freshly made quite hard and dry, though containing such a large quantity of water.
possible to make from 100 kilos. of fatty matter 300 kilos. of good, bright, hard soap.
It is
The manufacture of cocoa-nut oil soap resembles that of the other kinds of soap.
With a weak ley cocoa -nut oil does not form the emulsion common to other soaps,
but swims on the surface as a clear fat; when, by boiling, the ley has reached a
proper consistence, the oil suddenly saponifies. A strong soda-ley is used in the
preparation of this kind of soap. Cocoa-nut oil in saponifying does not separate
from the under-ley, therefore potash-ley is never employed. To prevent the separa-
tion of the soap from the mixing, the quantity of caustic-ley used must be accurately
measured. Pure cocoa-nut oil soap hardens quickly. It is white, like alabaster,
shiny, soft, and easily lathered; it has, however, a peculiarly unpleasant smell,
which cannot be entirely masked by any perfume. Cocoa-nut oil is seldom used
alone, but usually as an addition to palm-oil and tallow. This kind of soap can be
made without boiling, by merely heating to 80° C., by means of steam, to melt the
fats, a strong soda-ley being added, and the mixture quickly stirred. This is known
as the “cold method," and soap can be thus prepared in large quantities in a short
time, and is generally hard and dry. When exposed to the air for a month or so,
the soap loses considerably in weight, and becomes effloresced superficially. B. Unger
(1869) prepares a soap in the following manner :--He saponifies palm-oil with soda-
ley and salt as usual. The product is palmitate of soda. At the same time cocoa-
nut oil is saponified by means of carbonated and caustic soda-ley; this is added to
the palm-oil soap, and they are boiled. As a rule there are taken 2 parts of palm-oil
to I part of cocoa-nut oil; and to 100 parts of the latter there are added 14°3 parts of
caustic soda (Na₂0) and 12.8 parts of carbonate of soda. According to Unger's
experiments, this soap contains 5 mols. palmitate of soda, I mol. carbonate of soda,
and x mol. water. The "marbling or mottling" is effected in the following
manner :-Colouring matters, oxide of ircn, brown-red, Frankfort-black, are mixed
with a small portion of soap; this is poured into the rest of the soap, with which
it forms layers of unequal thickness. The entire mass is now stirred, and by
this means a marbled or grained appearance imparted.
r
Soft-Soap. As before mentioned, potash forms with fats and oils only a soft-soap,
which does not dry when exposed to the air, but on the contrary absorbs water,
remaining constantly like a jelly. As a rule, these so-called soaps are impure
solutions of oleate of potash in an excess of potash-ley, mixed with the glycerine
separated in the saponification. Soft-soaps can be prepared only with potash-
leys, although in practice I part of soda-ley is substituted for a part of the potash
to assist in somewhat hardening the soap. There is no separation of the soap
from the under-ley, which contains all the impurities; consequently these are disse-
minated in the soap.
In consequence of the solubility and cleansing properties of soft-soap, its use is
preferred to that of soda-soap in the manufacture of cloth and woollen articles. It
will have been seen that the difference in manufacturing hard- and soft-soaps
consists in employing potash-ley for the latter, and soda for the former. Wood-ash
is not used in preparing the potash-ley, but always pure potash; the preparation
follows the usual method with caustic lime. The fats used are mixtures of the
vegetable and animal oils, as the fish-oil known as "Southern," with rape, hemp, and
linseed oils. The particular oil used varies according to the time of the year and
SOAP.
247
market price: in winter the soit ons are employed; in summer the firmer oils.
Soft-soap is generally used for fulling and scouring; but abroad it is sometimes
used for washing linen, to which it imparts a most disagreeable fishy odour, hardly
concealed by any amount of perfume. The best soft-soap is made from hempes ed
oil, this oil imparting a green tinge, which, however, can be imitated by adding
indigo to inferior soaps. Summer soap, as it is termed, contains, owing to the fat
employed, more palmitate of potash in proportion to oleate than the winter soap.
Sometimes saponification is effected with a mixture of hemp- and palm-oil or
tallow, of train-oil and tallow, &c.
The boiling of the soft-soap commences with a strong ley containing 8 to 10 per
cent. potash, by which an emulsion is formed. The scum is dashed about with a
stick, the beating-stick, and by this means all the alkali is caused to be taken up.
A fresh ley is then added, and the boiling continued, until the soap upon cooling
stiffens into a clear tough mass. When the soap contains too much caustic alkali,
which can be ascertained by the taste, more oil is added. The clear-boiling now
commences, during which the excess of water is removed. To avoid lengthy
evaporation a concentrated ley is employed, and the soap, instead of bubbling up,
has its surface covered with blisters as large as the hand; these blisters are termed
leaves. When the boiling is finished-ascertained by placing some of the soap to
cool on a glass plate, from which, if firm, it can be separated—the soap is cooled,
and stored in barrels.
Soft-soap will take up a considerable quantity of water-glass solution without
alteration. Recently, for fulling, there has been added to the soft-soap a solution of
sulphate of potash, or a mixture of alum and common salt and also potato-starch.
Various other Soaps. Another soap is prepared from hog's-lard, and when scented with oil
of almonds or essence of mirbane (nitrobenzol) is sold as almond-soap, and as a cosmetic.
A soap is made from the grease of sheep's-wool. The so-called bone-soap is nothing more
than a mixture of the usual hard or cocoa-nut oil soap with the jelly from bones. The bones
are first treated with muriatic acid to separate the phosphate of calcium. A variety of
bone-soap is the Liverpool common soap. Flint-soap is an oil- or tallow-soap with which
siliceous earth is mixed. When powdered pumice-stone is substituted for the siliceous
earth, the soap is called pumice-soap. In America as well as in England a water-glass
solution is substituted for the siliceous earth, although according to Seeber the result is
not so efficacious. Cocoa-nut oil soap, however, containing 24 per cent. silicate of soda
and 50 per cent. water, is very firm. In the United States water-glass is added to the soap
when, still hot from the boiling-pan, it is poured into the moulds. The water-glass solu-
tion is of a density= 35° B. (= 1.31 sp. gr.); the proportion of soap is 60 per cent.
cent. This
kind of water-glass soap generally sets hard. Recently cryolite and aluminate of soda
have been employed.
Toilet Soaps.
On account of the reduction in the duty toilet soaps are now very
largely in demand. They are generally made by re-melting and perfuming
common soap. English toilet soap is considered the best, as that of France and
Germany being perfumed while cold is not so equable a product.
There are three modes of preparing toilet soap, viz. :—
1. By re-melting raw soap;
2. By the cold perfuming of odourless soap;
3. By direct preparation.
1. In the method of re-melting, good raw soap is scraped into a boiling pan, and
after melting and skimming the perfume is added. The soap is then cast in moulds
of the required form. 2. In the method of perfuming in the cold, odourless soap is
cut into fine shreds by a machine; the perfume is then added, and the soap is
248
CHEMICAL TECHNOLOGY.
passed between rollers, the sheets or bars thus formed being cut into tablets.
Struve, of Leipsic, has invented a machine by means of which soap is stamped into
the shape required. 3. The direct preparation of toilet-soap consists in colouring
and scenting pure white common soap without an intervening cooling. The colour-
ing materials are—for red, cinnabar, coralline, and fuchsine; the violet tar colour
for violet; for blue, ultramarine; for brown, a solution of raw sugar or caramel.
Windsor soap is prepared in the following manner :-40 pounds of mutton tallow
and 15 to 20 pounds of olive oil are mixed with soda-ley marking 19°, making a
soap of 15°; finally, with ley marking 20°, when the soap is of the consistency of
marrow. The excess of ley is then neutralised. When the soap is set it is allowed
to stand six to eight hours, and during this time most of the under-ley separates.
It is then placed in a flat form, and pressed until no fluid exudes. It is scented
with cumin oil, bergamot, oil of lavender, oil of thyme, &c. Moist sugar is used
to impart the brown colour. Rose soap, savon à la rose, is manufactured by melt-
ing the ingredients of three parts of oil-soap with two parts of tallow soap, and
sometimes water; the perfume is attar of roses, oil of roses, or gilliflower-water,
the colouring matter being generally cinnabar. Shaving-soap must not contain
free alkalies. It is sometimes prepared by boiling fat acids with a mixture of the
carbonates of soda and potash. Lather-soaps have in equal volume only half the
substance of the other soaps. Palm- or olive-oil soap is melted with an addition
of one-third to one-eighth the volume of water, and the mass stirred until it has
increased to double the volume. It is then placed in a mould. It should be
remarked that the oil-soaps, and not tallow-soaps, are the true formatives of the
lather-soaps.
Transparent Soap.
Ordinary dry tallow-soap is cut into splinters and heated with an
equal weight of alcohol, in which the soap dissolves. The mixture is allowed to
cool; therewith all impurities are thrown down, and the clear fluid is placed in the
moulds, where it has to remain three to four weeks to harden. Tincture of cochi-
neal and aniline red are employed for colouring transparent soaps, and also
Martin's yellow. The perfume is chiefly oil of cinnamon, sometimes oil of thyme,
oil of marjoram, and sassafras-oil. Glycerine-soap is prepared from an alcoholic
solution of ordinary soap, to which glycerine is added. Or 5 cwts. of soap with an
equal quantity of glycerine are heated by steam in a copper vessel. The mixture
is placed in moulds, and allowed to set in the usual manner. A solution of soap
in an excess of glycerine (35: 30) forms fluid glycerine-soap, which is of a clear
honey consistency. Both varieties are perfumed with essential oils.
Uses of Soap. Soap is used for cleansing purposes in washing, in bleaching cloth and
woollen materials; for the preparation of lithographic tints, &c. The cleansing proper-
ties of soap are due to the alkalies it contains. The alkali, although combined with the
fat acids, loses none of these properties, which are in fact included in the combination of
the alkali with the fatty substances of the dirt to be removed. The explanation of the
action chemically, according to Chevreul, is the following.—The neutral salts formed by
the alkalies and the fat acids, stearates, palmitates, and oleates are decomposed by the
water, whereby insoluble double fat acid salts are separated, while the alkali is set free. By
means of the free alkali the impurities clinging to the materials are removed, and taken
up by the fat acid salts, the suspended dirt being thus contained in the lather.
Soap Tests.
The greater the quantity of fat acids combined in the soap, the higher is its
value. A normal soap, besides alkaline fat acids, should only contain free water, the
quantity of which gives a means of estimating the value of the soap.
It is in the power
of the soap-maker to manufacture 300 parts of a good hard soap out of 100 parts of fat.
When too small a quantity of water is contained the soap becomes too hard, and
BORACIC ACID.
2.49
much labour is lost in obtaining a lather. If, on the other hand, water is held in too large
a quantity there is a great loss of material. The degree of hardness of the soap forms,
therefore, another means of estimating its value. Many soaps contain 2 to 3 per cent.
glycerine. But the proportion of water and the hardness of a soap are not the only
means of estimation, there still remains the estimation of the neutral fat acid alkalies,
the free alkali, common salt, or unsaponified fat in the residue left after the drying of the
soap. According to W. Stein, the presence of free alkali may be ascertained by means
of calomel, or according to Naschold, by nitrate of protoxide of mercury. Uncombined fat
retards the formation of a lather, and after a time imparts to the soap a rancid odour.
But the worth of a soap can only be accurately ascertained by means of chemical
analysis.
Insoluble Soap. All soaps that have not potash or soda for a base are insoluble in water.
Many of the insoluble soaps are of technical importance.
Calcium-soap plays an important part in stearine-wax manufacture. It is made either
directly by saponifying fat with hydrate of lime, or by treating soluble soap with a solu-
tion of a salt of lime; this soap is formed to some extent when ordinary soap is dissolved
in hard water. Barium- and strontium-soap are similar to calcium-soap. Magnesium-
soap is made directly with difficulty; it may be obtained indirectly by dissolving ordinary
soap in sea-water. Aluminium-soap is without doubt an insoluble soap; argillaceous
earths will not saponify fat unless aluminate of soda or potash is present. Aluminium
soap is used in waterproofing. According to Jarry, wood impregnated with oleate or
stearate of aluminium is impervious to moisture. Lately many materials have been ren-
dered waterproof by being dipped into a solution of acetate of aluminium, and then into
a soap solution, aluminium soap being thus formed.
Manganese-soap is prepared by the addition of sulphate of manganese to ordinary soap,
or by boiling carbonate of manganese with oleic acid. It is usually applied as a siccative.
Zinc-soap is prepared by the double decomposition of sulphate of zinc and soap, or by the
saponification of zinc-white with olive-oil or fat, forming a yellow-white mass. Zinc-soap
is used as an oil-colour, and also as zinc-plaster. Lead-soap or lead-plaster is made by
adding white-lead to olive-oil, or acetate of lead to soap solution. Tin-soap is prepared
by the double decomposition of chloride of tin with soap. Copper-soap, formed by the
addition of sulphate of copper solution to soap, is soluble in ether and oil, less so in alcohol;
it is used in preparing water-colours. It may be made by boiling oleic acid with
carbonate of copper. Mercury or quicksilver-soap is prepared from chloride of mercury
and soap; it is difficult to dry; is white, but when exposed to air and light turns grey.
Mercury-soap was formerly known as quicksilver-soap and quicksilver-plaster. Silver,
gold, and platinum-soaps, are severally prepared by double decomposition; but they are
not much used. Gold-soap is employed in gilding porcelain; and silver-soap for dark-
ening the hair.
BORIC OR BORACIC ACID, AND BORAX.
Boracic acid occurs native as sassolin, HBO3; in 100 parts:-
Anhydrous boracic acid, B₂03
Water..
56'45
43'55
100'00
and further in the following minerals :—
Boracite, or borate of magnesium with
chloride of magnesium
Rhodicite, or borate of calcium
Hayescine, Tiza, or borate of lime
Hydroboracite..
Tincal or borax, borate of soda
Datholite, or boro-silicate
Botryolite..
Axinite
Tourmaline
:
•
:
:
:
} with 62.5 per cent. Boracic acid.
""
30 to 45
30 to 44
47
""
""
""
""
36.53
""
18
""
>"
""
20*35
""
""
2 to 6.6
2 to 11.8
250
CHEMICAL TECHNOLOGY.
Boracic acid is found also in small quantities in many mineral waters and in sea-
water. Larderellite, or borate of ammonia, and lagonite, or borate of iron, are both
found in very small quantities in Tuscany, but are interesting to mineralogists only.
Boracic acid is found as sassolin in many volcanic regions mixed with sulphur,
and in the hot springs of Sasso, in Tuscany, and also between Volterra and Massa
Maritima in the clefts and rents of the volcanic formation of rock. Höffer and
Mascagni (1776), first mentioned the occurrence of boracic acid in the waters sub-
jected, in the clefts of the rock, to the sulphurous exhalations. The little pools
formed in these clefts are variously known as fumacchi, fumaroles, soffioni, and
mofetti. The boracic acid deposits in some cases cover an extent of six miles.
Since 1818 artificial soffioni have been constructed, and the benefit derived by the
country from the introduction of the industry is immense. The first artificial lake
was situated near Monte Cerboli, and the product was for some time known as
Larderellite, from the owner's name, Larderel. The production from these works
alone amounted in 1839 to 717,333 kilos., and in 1867 to 2,350,000 kilos. The
increase has been greatest since 1854, owing to the energy with which Gazzeri and
Durval entered upon the construction of the artificial soffioni.
The soil of the natural lakes, or beds of the natural soffioni, are of a slimy
formation, and have a peculiar seething movement due to the escape of the
sulphurous vapours from the fumaroles or vents. According to Payen, this vapour
or steam may be considered as condensed and as non-condensed, the former con-
taining besides water, sulphate of lime, sulphate of magnesia, sulphate of ammonia,
chloride of iron, hydrochloric acid, organic substances, a fishy-smelling oil, clay,
sand, and a small quantity of boracic acid. The non-condensed vapour consisted of—
Carbonic acid
Nitrogen
Oxygen
•
0'5730
0*3480
0'0657
0'0133
Sulphuretted hydrogen
Payen is of opinion that the vapours contain no boracic acid, while C. Schmidt
thinks otherwise, as the vapours, when condensed without contact with the water
of the soffioni, yield boracic acid. The condensed vapours contain o'r per cent.
boracic acid.
Theory of the Formation
of the
Native Boracic Acid.
Dumas and Payen found an explanation of the formation of
volcanic boracic acid upon the hypothesis that there exists in
the interior of the volcano or beneath the under-crust of the earth a layer of sulphide
of boron (B₂S3), which under the action of the mineral waters becomes converted
into boracic acid and sulphuretted hydrogen. P. Bolley gives the action as similar
to that occurring in the formation of sal-ammoniac, a very common mineral in
volcanic regions. Professor Becchi, of Florence, found nitride of boron (BN) in
one of the under-strata, from which he prepared artificially by means of steam
ammonia and boracic acid. Also Warrington (1854) and Popp (1870) attributed the
appearance of boracic acid and ammonia in volcanoes to the decomposition of nitride
of boron by evaporation. Recently (1862) Becchi has obtained boracic acid by the
decomposition of borate of calcium in a stream of superheated steam.
Boracic Acid.
The Production of The most general method of obtaining boracic acid is by the evapora-
tion of the water of the natural or artificial soffioni. The water is either naturally or
BORACIC ACID.
251
artificially introduced into the natural fumaroles, as these sometimes do not re-
supply themselves with sufficient rapidity. As soon as the water has absorbed a
considerable quantity of the vapours it is removed and placed in a large mason-
work cistern; this cistern is imbedded in the soil near the fumaroles, and the
natural heat is sufficient to cause evaporation. The vapours are condensed in a
wooden chimney. The separated impurities, gypsum, &c., remain in the cistern. As
soon as the solution is of a sp. gr.—1'07—1'08 at 80º, it is poured into leaden
crystallising vessels where the boracic acid crystallises out. The mother-liquor is
evaporated to dryness. It should be remembered that the entire operation is con-
ducted with the assistance of the natural heat of the fumaroles only. Occasionally
the boracic acid is only present in the natural waters to o·002 of a part; and in
these cases fuel must be used in the evaporation, which therefore entails the expense
of carriage, as fuel is very scarce near the soffioni. Charcoal is generally used.
But by this means an acid is obtained, containing about 70 to 80 per cent. hydrated
boracic acid, with 10 per cent. impurities. Clouet removes the impurities by treat-
ment with 5 per cent. of ordinary hydrochloric acid. Boracic acid for pharma-
ceutical purposes may be prepared by dissolving I part of borax in 4 parts of
boiling water, and decomposing the solution with one-third part of sulphuric, or
better with half part of hydrochloric acid of 12 sp. gr. The acid separates on
cooling, and can be purified by crystallisation.
In 100 parts of commercial boracic acid from Tuscany, H. Vohl (1866) found:—
5.
I.
2.
3.
4.
Boracic acid
45*1996
47.6320
48.2357
45*2487
48 1314
Water of crystallisation.. 34'8916
35'6983
37°2127
34'9010
38.0610
Water
4'5019
2*5860
I'0237
4'4990
I'5240
Sulphuric acid..
9.6135
7'9096
8.4423
9*5833
7.8161
Silicic acid
0.8121
1*2840
0.6000
0*2134
0'0861
Sand..
0.2991
0'5000
Ο ΙΟΟΟ
0°7722
0'4154
Oxide of iron
O'1266
0*1631
0'0920
0'1030
0'0431
Protoxide of manganese..
0'0031
traces
traces
traces
traces
Alumina
0'5786
0'0802
0'0504
O'1359
0*1736
Lime..
Ο ΟΙΟ9
0'3055
0'5178 traces
traces
Magnesia.
0.6080
traces
traces
traces
traces
•
Potash
0*1801
•
O'2551
0'5178
0.6140
0'4134
Ammonia..
•
2'9891
3'5165
3'5169
3*7659
3'0890
Soda ..
0'0029
traces
traces
traces
traces
Chloride of sodium..
0*1012
0'0595
0'0401
0*1671
0'0321
Organic substances and loss o‘0918
Ο ΟΙΟΙ
Ο ΟΙΟΙ
0'0449
100'0000
100'0000
100'0000
100'0000 100'0000
Properties and Uses
of Boracic Acid.
Pure boracic acid crystallises in mother-of-pearl-like leaves
which at 100º C. lose half their water of crystallisation without melting, the other
half being driven off at a red-heat. After cooling the anhydrous acid appears as a
hard, transparent, brittle glass of 1.83 sp. gr. 1 part boracic acid dissolves in 25.6
parts water at 15º C., and in 2'9 parts at 100° C. At 8° a saturated solution has a
sp. gr. of 1014. It imparts a green colour to the flame of the spirit-lamp. In a
252
CHEMICAL TECHNOLOGY.
chemical point of view it is similar to silicic acid. Boracic acid is largely used in
the preparation of borax, for glazing porcelain, and mixed in a weak aqueous solu-
tion with sulphuric acid in the preparation of the wicks of stearine and paraffin
candles. It is also used for colouring gold, for decorating iron and steel, in the
preparation of flint-glass, and artificial precious stones. In 1859 boracic acid was
used in the preparation of hydrated oxide of chromium, known under the name of
Pannetier's - green, Vert-Guignet, &c.
Borax.
Borax, or bi-borate of soda, when anhydrous according to the formula
Na2B4O7, contains in 100 parts:-
Anhydrous boracic acid (B₂O3)
Soda (Na2O)
:
69'05
30'95
100'00
I
It is found native in Alpine lakes, on the snow-capped mountains of India, China,
Persia, in Ceylon, and Great Thibet. It is found in large quantity at Potosi in
Bolivia, where the Borax Luke, according to Moore's analysis (1870) contains in 1 litre
of its water (sp. g.=1'027), 3′96 grammes of borax. Pyramid Lake, Humboldt Co.,
Nevada, yields also large quantities. By the heat of the sun the water of the borax
lakes is evaporated and the borax crystallises out, and is gathered and brought into
commerce under the name of Tincal. It appears in small six-sided crystals, more or
less smooth. The Clear Lake in California, to the north of San Francisco, yields
daily 2000 kilos. of borax.
Formerly tincal was purified by washing in water containing soda to free the
borax from adhering fatty substances which combine with the soda to form an
almost insoluble soap. After the borax has been well washed it is dissolved in
boiling water; for each 100 parts of refined salts there are 12 parts of carbonate of
soda. The solution is next filtered, and then evaporated to 18° to 20° B. It is now
placed in wooden crystallising vessels lined with lead, where it is necessary to allow
the fluid to cool gradually. Another method is to place the tincal in cold water, and
to stir in 1 per cent. of caustic lime. The fatty substances are thus removed, com-
bining with the lime to form an insoluble calcium soap. 2 per cent. of chloride of
calcium is added to the fluid, which is next evaporated, and set to crystallise.
Clouet recommends the powdering of the tincal, which is next mixed with 10 per
cent. nitrate of soda, and calcined in a cast-iron pan, the fatty substances being thus
destroyed. The calcined mass is dissolved in water, and the solution evaporated to
crystallisation.
Borax from Boracic Acid.
:
In 1818 the manufacture of borax from boracic acid was com-
menced, and since that time borax has sunk to three-fourths its former price. Both
according to the proportion of water and the crystalline form, there may be consi-
dered two varieties of borax. 1. The ordinary or prismatic borax; 2. Octahedral
borax. The prismatic borax (Na2B4O7+ 10H20) contains in 100 parts :—
Boracic acid
Soda
Water of crystallisation
•
•
36.6
16'2
47°2
ΙΟΟ Ο
BORACIC ACID.
253
69'36
30'64
The octahedral borax (Na2B4O7+5H2O) contains in 100 parts :-
Boracic acid
Suda
Water
•
100 00
Prismatic borax is manufactured in the following manner :-There are dissolved in a
lead-lined vessel, a, Fig. 118, 26 cwts. of crystallised carbonate of soda in about 1500 litres
of water, heated by means of steam, to the boiling-point. The boiler, c, is for the
purpose only of generating steam, which is passed by the pipe, c, and the rose, m, into a.

K
K
น
A
P
FIG. 118.
By means of the large taps, b and r, the fluid may be removed from A. Through the
tube a the substances thrown down from the solution can be removed. Boracic acid is
added in quantities of 8 to 10 lbs. after the solution has been heated to the boiling-point.
Besides carbonic acid a small quantity of carbonate of ammonia is developed, and passes
by o into the vessel D, containing dilute sulphuric acid, by which it is absorbed. To
saturate the solution of 26 cwts. of soda, 24 cwts. of crude boracic acid are necessary.
The boiling saturated solution marks 21° to 22° B., and has a temperature of 104°. If
254
CHEMICAL TECHNOLOGY.
the solution is too strong, water is added; if too weak, a small quantity of crude borax, to
bring it to 21° B. The solution is allowed to stand in a until all insoluble substances are
deposited. The clear ley is conducted by means of the tap, r, into the crystallising
vessels, P P, the mud or deposit being received into K. The crystallising vessels are of wood
lined with lead. The crystallisation is complete in two to three days, and the mother-
liquor is drawn off into the vessel H. The crystals are placed to drain on the inclined
plane, M. The mother-liquor is retained for the dilution of a fresh quantity of soda.
After three or four operations, the mother-liquor contains sufficient sulphate of soda to
admit of profitable crystallisation; and the ley is allowed to cool at 30°. As the solubility
of sulphate of soda has reached the maximum at a temperature of 33°, it is clear that the
crystallisation of the sulphate commences at the completion of that of the borax.
After the crystallisation of the sulphate of soda, the mother-liquor is evaporated to dry-
ness, and the saline residue is sold to the glass-manufacturer.
Purifying the Borax. The crude borax to be purified is placed in a lead-lined wooden
cistern, A, Fig. 119, heated by steam. The borax is suspended in a wire sieve
immediately under the surface of the water with which a is filled. To 100 parts
of borax, 5 parts of crystallised carbonate of soda are added, and the liquid
K
Fig. 119.

XI
B
is strengthened from time to time till it marks 22° B. When the solution is settled
it is removed by the tap to the cooler, B. To prevent loss of ley, the floor under B
is stippled with waterproof cement, and sloped towards a gutter. The crystallising
vessel is of thick timbers, H F H, lined stoutly with lead; this vessel is filled with
ley to within an inch of the edge, the cover being then placed on. The steam con-
denses on the cover, which when removed is found covered with small crystals, the
larger crystals falling to the bottom of the vessel. To hasten the cooling, spaces
are left in timbers, F; but the crystallisation is not effected under 16 to 28 days.
After this time the ley still has a temperature of 27° to 28° C. When quite cool the
foreign substances separate from the borax. The vessel, B, contains the large
borax crystals from which the adhering mother-liquor is separated by a sponge.
If the crystals are not thus carefully treated, they split into thin leaves; for this
reason also the cooling, should be gradual. The crystals are dried on a wooden
table, finally sorted, and packed.
In England borax is prepared from boracic acid in the following manner: -The
crude boracic acid is mixed with half its weight of calcined soda and submitted to
the action of heat in a muffle-oven. The ammonia, which as sulphate is an im-
portant constituent of crude boracic acid, is, with carbonic acid, given off during
the process, and passes through a tube to a condensing chamber. The melted
mass is removed, and lixiviated in an iron pan; the suspended matter is allowed to
BORACIC ACID.
255
settle, and the clear liquor is put into smaller vessels to cool, in which beautiful
crystals form. It has already been mentioned that this manufacture had its origin
in France, where sulphuric vapours were employed. A mixture of calcined
Glauber salts and boracic acid were placed in a retort and subjected to distillation,
the residue on lixiviation and crystallisation yielding borax. Köhnke substitutes
caustic soda for the carbonate of soda, the borax crystallising from a very alkaline
solution.
Recently borax has been obtained from native borate of calcium, tiza or borocalcite,
(formula, according to Wöhler, Na2B4O7+2CaB40, + 18H₂0), which occurs in large
quantities at Tarapaca in Peru, and in Western Africa. Treatment with sulphuric acid
gives only unsatisfactory results, and hydrochloric acid is therefore employed. The acid
is poured upon the mineral to two-thirds of its weight with twice the quantity of water,
and the whole heated to the boiling-point, and allowed to digest. The heat must be main-
tained to the completion of the digestion, and the water lost by evaporation re-supplied.
The clear liquor is then decanted, and on cooling the boracic acid crystallises out, the
mother-liquor retaining chloride of sodium, chloride of calcium, with a slight excess of
hydrochloric acid. Stassfurt boracite or Stassfurtite, is also becoming largely used in the
preparation of borax.
The prismatic borax is colourless and forms transparent crystals of 175 sp. gr., dis-
solved in 12 parts cold and 2 parts boiling water, the solution having a weak alkaline
reaction upon test-paper, although borax is an acid salt. By exposure to the air it loses
water. At a moderate heat it separates into a spongy mass known as calcined borax, and
at a red-heat assumes a glassy appearance; in this condition it is used as a blowpipe
flux.
Octahedral Brax. Octahedral borax (Na2B4O7+5H2O), is prepared in the following
manner :—Prismatic borax is dissolved in boiling water till the solution marks
30° B. =1'260 sp. gr. This solution is then allowed to cool very slowly. When the
temperature has fallen to 79° C., the octahedral crystals begin to form, the forma-
tion continuing till the temperature reaches 56°. After this the mother-ley yields
only prismatic crystals. Unless great care be taken, a mixed crystallisation results.
Buran recommends the preparation of octahedral borax by evaporating a borax
solution to 32° B. — 1.282 sp. gr., when it is removed to a crystallising vessel. When
10 cwts. of borax are operated upon, the process will take six days to complete. The
prismatic and octahedral salt crystallises in distinct layers that can be separated
mechanically. Indian borax and Chinese half-refined borax sometimes contain
octahedral crystals. Octahedral borax is known in French commerce under the
names of calcined borax, jeweller's borax, surface borax, &c. It is distinguished
from prismatic borax by its crystalline form and the proportion of water contained,
by its sp. gr. 181, and its greater hardness. While the prismatic borax remains
unaffected in transparency by exposure to air, the octahedral borax rapidly becomes
opaque, and absorbing five equivalents of water is converted into the prismatic salt.
Uses of Borax. The uses of borax are very numerous. Molten borax has the property, at
high temperatures, of fluxing metallic oxides, vitrifying with them into coloured trans-
parent glasses; for instance, with protoxide of cobalt a blue glass is formed, and with oxide
of chromium a green glass. This property is of great utility in chemical analysis, as the
various metallic oxides may be thus distinguished in the blowpipe flame. It is also used
for soldering metals; and is a constituent of Strass, used in glass-manufacture and
enamelling. It is used extensively in glazing the finer kinds of earthenware, and for
separating metals from their ores. Borax forms with shellac in proportion of 1 part to 5
parts of a peculiar varnish, soluble in water, and used when mixed with aniline black to
stiffen felt hats. With casein its gives a fluid resembling a solution of gum-arabic, for
which it is often substituted. Borax is made into a soap for washing purposes, into a
solution for cleansing the hair, and it is also used in various cosmetics, &c. It is largely
employed to fix mineral mordants. According to Clouet, a mixture of horacic acid and
nitrate of potash or soda is in many cases a better flux than borax. He recommends 100
parts boracic acid and 100 parts of the nitrate to be placed in an enamelled iron kettle
256
CHEMICAL TECHNOLOGY.
with 10 per cent. water and heated till fluid. When cooled, flat white crystals are formed;
those made with nitrate of potash can be used for crystal-glass manufacture, and those
with nitrate of soda for enamelling. Borate of chromium is known in commerce as Vert-
Guignet or Pannetier's green.
Diamond-Boron, or
Wöhler and H. Deville in 1857 were the first to notice that boron forms
Adamantine. similarly to carbon in two allotropic conditions, namely, crystalline *
and amorphous. Diamond boron is prepared in two ways, either by the reduction of
calcined borax with aluminium :-
Alumina, Al¸03,
Boracic acid, B03, yields {Boron, 2B;
Aluminium, 2A,
or by converting amorphous boron into crystalline. The latter method gives the better
result. 100 grms. of anhydrous boracic acid are mixed with 60 grms. of sodium in a small
iron crucible heated to a red-heat. To this mixture 40 to 50 grms. of common salt are
added, and the crucible is luted down. As soon as the reaction is finished, the mass, con-
sisting of amorphous boron with boracic acid, borax, and common salt intermingled, is
stirred into water acidified with hydrochloric acid. The boron is filtered out, washed with
a weak solution of hydrochloric acid, and placed upon a porous stone to dry at the ordinary
temperature. Molton iron, it is well known, converts amorphous carbon into crystalline
graphitic carbon, and aluminium exercises a similar action upon boron. The crystalline
boron is prepared in the following manner:-A small crucible is filled with amorphous
boron, in the centre of which a small bar of aluminium weighing 4 to 6 grms. is placed.
The crucible is submitted to a temperature sufficient to melt nickel for 1 to 2 hours.
After cooling the aluminium will be found covered with beautiful crystals of boron. The
diamond boron is easily separated from the graphitoid. The form is a transparent tetra-
gonal crystal, of a garnet-red or honey-yellow colour, or, if perfectly pure, colourless. It
is very brittle, hard, and lustrous; it will scratch rubies easily. This discovery may in
time be of great technical importance.
Alum.
PRODUCTION OF ALUM, SULPHATES OF ALUMINA, AND ALUMINATES.
Alum is a saline substance, consisting of sulphate of alumina, sulphate of
potash or ammonia, and water of crystallisation. It occurs native as potash-alum
and as ammonia-alum, being, in fact, a double salt, consisting of either sulphate of
alumina and sulphate of potash, or sulphate of alumina and sulphate of ammonia.
Al₂
The alum known as potash-alum, 4S04+24HO, is found in alum-shale. But
K
all natural alums are of more mineralogical than technical interest, the alums
of commerce being always artificially prepared. We shall, therefore, pass on to the
consideration of the latter.
Material of Alum
Manufacture.
The manufacture of alum grounds itself on the formation of sulphate
of alumina and aluminate of soda from the various alum-ores. These ores or
earths necessitating different methods of treatment, may be divided into four
groups, viz. :—
I. Those which contain alumina, potassa, and sulphuric acid in such proportions that
the addition of an alkaline salt is not requisite. To this group belongs alum-stone, and
several varieties of alum-shale.
2. Those in which the sulphate of aluminia is alone present, necessitating the addition
of alkali salts in large quantities. To this group belong the alum-shale and alum-earths
found in the brown-coal formation.
3. Those in which alumina only is contained, and to which both sulphuric acid and
alkali salts must be added. To this group belong-a. Clay; B. Cryolite; y. Bauxite;
d. Refuse slack.
4. To the fourth group belong those materials, such as felspar, containing alumina and
potash in sufficient quantity, but needing the addition of sulphuric acid.
* Graphitic_boron is by a later discovery of Wöhler's (1867) resolved into boracic-
aluminium; formula, AlB,.
ALUM.
257
Preparation of Alum
from Alum-stone.
1st Group.-Alum-stone or alunite occurs only in volcanic
regions, and is the product of the action of the sulphurous vapours upon sub-
stances rich in felspar. It is found at Talfa, near Civita-Vecchia, and in large
quantities at Muszag, in Hungary. The crystallised alum-stone consists of sulphates
of potash and alumina with hydroxide of aluminium, according to Al. Mitscherlich---
K₂SO4+Al2(SO4)3+2(Al2O3,3H2O).
Alum-stone loses its water at a red-heat, the product of the calcination being influenced
by water, while unburnt alum-stone is not. At a strong red-heat the sulphate of alumina
separates into alumina, sulphurous acid, and oxygen, and the sulphate of potash is also
decomposed. The mineral is calcined in lime-kilns in the ordinary manner. The calcined
alum-stone is lixiviated with boiling water, the supernatant liquor decanted, and the alum
crystallised out. Roman rock, or roche alum is prepared in a similar manner, the red
colour being due to peroxide of iron.
Preparation of Alum from
Alum-shale
and Alum-eaths.
2nd Group.-This mode of preparation yields the greatest
amount of alum with as much facility as from alum-stone.
Alum-shale or schist is a sulphurous iron pyrites, found under beds of
clay in Upper Bavaria, in Prussia, near Dusseldorf, Saxony, Bohemia, Belgium, &c.
Only very inferior kinds require an addition of alkali salts.
Alum-shale.
Alum Earths. Alum-earth is more or less a mixture of sulphurous iron pyrites with
various bitumnious matters. The sulphur is present partly in free state, partly as
iron and vitriol pyrites; the iron is present partly as sulphuret, partly as iron
humate.
Preparation of Alum. The preparation of the alum may be considered in the following
six operations:-
Roasting the Alum-Earth.
1. The roasting of the alum earths is the easiest of the opera-
tions. The greater part of the alum manufactured is produced by precipitating sulphate
of alumina with a solution of alkali salts. It is not always necessary the schist should
be burnt to concentrate the sulphate of alumina, a lengthy weathering being sufficient.
The action may be explained as follows:-By the weathering the bisulphide of iron ab-
sorbs oxygen, to form sulphate of iron, which separates into protoxide of iron and sulphuric
acid, the latter acting upon the alumina forming an equivalent quantity of sulphate of
alumina. Or by roasting, the bisulphide is decomposed to monosulphide and sulphur,
which, with the sulphur of the alum-earth, gives rise to sulphurous acid, and this acting
upon the alumina produces sulphite of alumina and also the sulphate. The roasting or
calcination, however, should not take place with earths that have been subjected to less
than a year's weathering, as there is found to be in practice a loss of one-sixth of the sul-
phate of alumina.
Lixiviation. 2. The lixiviation of the calcined alum earths is effected in a lixiviation
cistern in which the earth is placed. These tanks stand in rows of five, the best arrange-
ment being to build them on a slope near the calcination heaps. Each vessel has a length
of 6 to 7 metres, is 5 metres broad, and about 13 metres in height. They are three-parts
filled with the burnt earth, and completely with water; the lixivium flows from the highest
tank to the lowest. If the ley is not of 1'16 sp. gr. fresh shale is added.
Evaporation of the Ley. 3. The concentration of the raw ley by evaporation is accomplished in
leaden pans. These, however, deteriorate, crack, are easily melted, and their place is now
generally supplied by cisterns of masonry. But most to be preferred is Bleibtreu's method
of heating with gas, introduced in the alum-works on the banks of the Rhine. The treat-
ment of the raw ley while being concentrated depends upon its condition and upon the
sulphate of iron it contains. As sulphate of iron is commonly present in large quantities
in the raw ley or liquor, many of the German alum-works are also vitriol-works. When,
however, the quantity of sulphate of iron is too small to admit of being advantageously
treated for the preparation of sulphate of iron, the liquor is at once evaporated until it has
attained a sp. gr. of 140. During the ebullition basic sulphate of iron is deposited, the
liquor becomes of yellow-red colour, assumes a somewhat slimy condition, and has to be
rendered clear before alum is obtained from it. This clearing is effected by pouring the
liquor into large wooden water-tight tanks; the liquor having deposited, the suspended
matter is tapped or sy plicned off from the sediment, and transferred to the precipitation
tanks.
}
18
258
CHEMICAL TECHNOLOGY.
Alum-Flour. 4. The precipitation of flour of alum is effected in case it is desired to
make potash-alum by the addition to the liquor of a potash salt, or of an ammonia salt
if it is desired to make ammonia-alum. The solution of the alkaline salt is called the
precipitant; by the combination of the sulphate of alumina contained in the liquor with
the precipitant alum is formed, and deposited as a solid salt, care being taken to prevent
the formation of large crystals by keeping the liquid stirred. By this means the alum is
deposited as a crystalline powder or so-called flour of alum, which by being washed with
cold water can be freed from any adhering mother-liquor. The precipitation was formerly
effected by the addition of wood-ash ley or lant; at the present day chloride of potassium
obtained either from kelp, carnallite, or beet-root molasses, and sulphate of potassa derived
from the decomposition of kainite, are employed for this purpose. Chloride of potassium
is useful only when the solution contains large quantities of sulphate of iron, which being
converted into chloride of iron forms sulphate of potassa. Potash can only be used when
the ley contains enough free sulphuric acid to combine with the salt, for otherwise a
portion of the sulphate of alumina would become precipitated as insoluble alumina. The
ammonia salt made use of is generally sulphate of ammonia; 100 parts of sulphate of
alumina require for precipitation-
Chloride of potassium
Sulphate of potassa
Sulphate of ammonia
43'5 parts
50.9
47.8"
The liquor covering the alum-flour is somewhat of a green colour, and contains little
alum, but chiefly proto-perchloride of iron, sulphates of iron, sulphate of magnesia, or
chloride of magnesium, dependent upon whether the precipitation was effected by sulphates
or by chlorides. This liquor is used for making impure alum, sulphate of iron, or is em-
ployed in the preparation of sulphate of ammonia.
from Clay.
Washing and 5. The floury alum is generally washed in the hydro-extractor or cen-
Re-crystallisation. trifugal machine and the liquor obtained again used for preparing alum.
The washed floury alum is (6) converted into large crystals by re-crystallisation, the alum
at the same time being purified. For this purpose the alum flour is dissolved in 40 per cent.
of its weight of boiling water, the operation being carried on in wooden lead-lined tanks.
The hot solution is run into crystallising vessels, where the_crystallisation is finished
according to the temperature of the air in eight to ten days. From this operation hardly
any mother-liquor remains, the vessel being almost entirely filled with alum crystals.
Preparation of Alum 3rd Group.-The manufacture of alum and of sulphate of alumina
from such materials as contain only alumina, to which consequently sulphuric acid
and alkaline salts have to be added, has come largely into practice in England. The
materials employed are:-a. Clay; B. Cryolite; y. Bauxite; d. Blast-furnace slag.
a. Preparation of Alum from Clay.-The clay to be employed for this purpose should
be as free as possible from carbonates of lime and iron. It is first gently heated in
contact with air, partly with the view of dehydratation, partly for the purpose of converting
any iron into oxide, and lastly to render the clay more readily soluble in acids. By
dehyadratation the clay becomes porous and fit to take up sulphuric acid by capil-
larity. The gently ignited and powdered clay is gradually put into sulphuric acid of 50° B.
(=1.52 sp. gr.) contained in a leaden pan, and heated nearly to the boiling-point. The
mass effervesces and becomes thick, and is next transferred to iron tanks, where it
solidifies. It is afterwards lixiviated with water, or better, with the liquor obtained by
washing the alum-flour. The lixivium having become clear by standing is syphoned off
from the sediment, and boiled with a sufficient quantity of bisulphate of potash or
sulphate of ammonia from gas-liquor. The hot solution is transferred to a shallow
leaden pan, and kept stirred for the purpose of converting the alum on solidifying into
flour. The flour is washed, dried, and is then converted into large crystals as described
above. The product known in the trade as alum-cake is the result of the action of
sulphuric acid upon clay; it is met with in a pulverised state, is used more especially
in the manufacture of inferior kinds of paper, and contains from 13 to 17 per cent. of
alumina.
Preparation of Alum
from Cryolite.
B. Since the year 1857 alum and sulphate of alumina have been
prepared along with soda, from the mineral known as cryolite or Greenland spar,
Al₂Fl6+6NaFl, and consisting in 100 parts of—
Fluorine
Aluminium.
Sodium
:
54'5
13'0
•
32'5
ALUM.
259
The following are the methods employed for this purpose:-
a. Decomposition of Cryolite by Ignition with Carbonate of Lime according to Thomsen's
Method. -I molecule of cryolite is ignited with 6 molecules of carbonate of lime, carbonic
acid escapes, and soluble aluminate of soda, and insoluble fluoride of calcium are formed
(A1F1,6ÑaFl)+6CaCo¸=AI¸03,3Na₂O+6CaFl+6CO₂- From the ignited mass the
aluminate of soda is obtained by lixiviation with water, and into the solution carbonic
acid gas is passed. The result is the precipitation of hydrated gelatinous alumina
and carbonate of soda, which remains in solution. If it be desired to obtain the alumina
as an earthy compact precipitate, bicarbonate of soda is used as a precipitant instead of
carbonic acid. While the clear liquor is boiled down for the purpose of obtaining car-
bonate of soda, the precipitated alumina is dissolved in dilute sulphuric acid; this solution
is evaporated for the purpose of obtaining sulphate of alumina (so-called concentrated
alum), or the solution after having been treated with a potassa or ammonia salt is converted
into alum. 100 lbs. of cryolite yield 33 lbs. of alumina, which require 90 lbs. of sulphuric
acid to yield a neutral solution; 100 lbs. of cryolite will therefore yield 305 lbs. of alum,
and may give in addition :-
Calcined soda
75.0 lbs., or
Crystallised carbonate of soda
Caustic soda
•
Bicarbonate of soda..
203'0
440
119'5"
or
""
or
""
b. Decomposition of Cryolite with Caustic Lime by the Wet Way (Sauerwein's Methodj.
Very finely ground cryolite is boiled with water and lime, the purer the better, and as free
from iron as possible, in a leaden pan. The result is the formation of a solution of alumi-
nate of soda and insoluble fluoride of calcium.
(A1F16,6NaFl)+6CaO=A1¸03,3Na¸0+6CaFl¸.
When the fluoride of calcium has been deposited, the clear liquid is decanted, and the
sediment washed, the first wash-water being added to the decanted liquor, and the second
and third wash-waters being used instead of pure water at a subsequent operation. In
order to separate the alumina from the solution of aluminate of soda, there is added to the
liquid while being continuously stirred, very finely pulverised cryolite in excess, the result
of the decomposition being exhibited by the following formula :—
(Al¸03,3Na₂0)+(AÏFl¸,6NaFl)=2A103+12NaFl.
When no more caustic soda can be detected in the liquid-a small quantity of which
should, after filtration, yield, upon the addition of a solution of sal-ammoniac and applica-
tion of heat, a precipitate of alumina—it is left to stand for the purpose of becoming clear.
The clarified solution of fluoride of sodium is then drawn off, and the alumina treated as
above described. The solution of fluoride of sodium having been boiled with caustic lime
yields a caustic soda solution which, having been decanted from the sediment of fluoride
of calcium, is evaporated to dryness. Recently the fluoride of calcium obtained as a by-
product of the cryolite industry is used in glass-making.
c. The decomposition of cryolite by sulphuric acid yields sulphate of soda, convertible
into carbonate by Leblanc's process, and sulphate of alumina free from iron. 238 parts of
cryolite require for decomposition 240 parts of anhydrous or 321 parts of ordinary sulphuric
acid. The resulting compounds are sulphate of alumina, sulphate of soda, and hydrofluoric
acid :-
A1F16NaFl,
6H SO
Al2(SO4)3.
yield 3Na,SO4.
12HFl.
This method of decomposing cryolite is, however, by no means to be recommended, as
owing to the liberation of hydrofluoric acid, peculiarly constructed apparatus are required;
while the sulphate of soda has to be converted into carbonate of soda. Persoz suggests that
cryolite should be treated in platinum vessels with three times its weight of strong sulphu-
ric acid, to be recovered with the hydrofluoric acid by distillation. The solid residue
should be treated with cold water in order to dissolve the larger part of the bisulphate of
soda contained in the saline mass, from which the anhydrous sulphate of alumina is ex-
tracted with boiling water, and converted by the addition of sulphate of potassa or ammonia
into alum free from iron. The solution of bisulphate of soda having been evaporated to
dryness, is employed for the preparation of fuming sulphuric acid, Glauber's salt remain-
ing as a residue.
Preparation of Alum
from Bauxite.
Y.
In some parts of Southern France, in Calabria, near Belfast, Ire-
land, and other parts of Europe, a mineral occurs, consisting essentially (60 per cent.)
of hydrated alumina of greater or less purity, termed bauxite, from the fact of
260
CHEMICAL TECHNOLOGY.
having been first found in the commune of Baux, in France. In order to prepare
alum and sulphate of alumina from this mineral it is first disintegrated by being
ignited with carbonate of soda, or with a mixture of sulphate of soda and charcoal;
in each instance the lixiviation of the ignited mass yields aluminate of soda, from
which, by processes already described under Cryolite, alum, or sulphate of alumina,
and soda are prepared.
Preparation of Alum
from Blast-Furnace Slag.
d. J. Lürmann recommends that the slag be decomposed by
means of hydrochloric acid. From the resulting solution of chloride of aluminium
the alumina is precipitated by carbonate of lime, any dissolved silica being preci-
pitated at the same time. The alumina is dissolved in sulphuric acid, leaving the
silica. 100 kilos. of slag containing 25 per cent. of alumina yield 180 kilos. of alum
and 31 kilos. of silica.
Alum from Felspar. 4th Group.-The manufacture of alum from minerals, (for instance,
felspar) containing alumina and potassa, is not of any industrial importance; we
therefore refer the reader to what has been said (see page 122) on the Preparation of
Potassa Salts from Felspar.
Al½
Properties of Alum. Potash-alum, 24S04+24H2O, or K₂SO4+Al2(SO4)3 +24H₂O,
consists in 100 parts of:-
Potassa
• 9'95
Alumina
Sulphuric acid
Water
•
•
•
10.83
33'71
• 45°51
100'00
crystallises readily in regular octhahedra, loses at 60° 18 mols. of water, and fuses
at 92° in its water of crystallisation, yielding a colourless fluid which retains its state
of aggregation for some time after cooling before solidifying into a crystalline mass.
At a temperature a little below red heat alum loses all its water, becoming converted
into burnt-alum, alumen ustum, a white, porous, readily friable mass. When ignited
with carbonaceous matter, air being excluded, potash-alum forms a pyrophoric
compound :-
100 parts of water at o° dissolve 3'9 parts of potash-alum.
""
""
200
""
15.8
400
""
31'2
1000
""
360'0
""
""
""
""
""
""
The solution of alum in water (the salt is insoluble in alcohol) has an astringent sweet
taste, and possesses an acid reaction so strong that when alum is heated with common salt
hydrochloric acid is evolved; while a concentrated solution of alum destroys the blue colour
of many-not of all-artificial ultramarines.
24S04+24H0, or (NH),SO+Al(SO4)3 + 24HO,
Ammonia-Alum.
This salt,
Al₂
(NH,),)
consists in 100 parts of:-
Ammonia
Alumina ..
Sulphuric acid
Water
3.89
11'90
35'10
48.11
100'00
Ammonia-alum is now far more extensively manufactured than potash-alum. When
ammonia-alum is strongly heated, sulphate of ammonia, water, and sulphuric acid are
driven off, and alumina remains.
ALUM.
261
100 parts of water at o° dissolve 5.22 parts of ammonia-alum.
""
""
""
20°
40°
100°
""
99
13.66
27.27
421'90
>>
""
99
"9
""
Soda-Alum.
""
The formula of this salt is-
Al½ } 4804 + 24H₂O, or Na2SO4+ Al2(SO4)3 + 24H₂O
Na2
containing in 100 parts:-
Soda
Alumina
Sulphuric acid
Water ..
6.8
II.2
34'9
47'I
100'0
It is as readily prepared from sulphate of alumina and sulphate of soda as the alums
already mentioned, but its solubility prevents the separation from the mother-liquor,
while its solution when boiled loses the property of crystallising. As iron cannot be
removed from this salt by re-crystallisation, the materials it is obtained from should be free
from that metal. The solutions should be mixed cold, and gently evaporated at a
temperature not exceeding 60º.
Neutral or cubical alum (K₂SO4 + Al2O3,2SO3) is obtained either by adding to an alum
solution so much carbonate of potassa or soda as will begin to separate the alumina, or ə
solution of alum is treated with gelatinous alumina. By boiling 12 parts of alum and i part
of slaked lime in water, the same salt is obtained. This neutral salt is often preferred
in dyeing and calico printing, as it does not affect certain colours. When ammonia-alum
is similarly treated, it also yields a neutral alum.. Blesser (a) and Schmidt () found the
following to be the composition of cubical alum in 100 parts:-
Sulphuric acid
Alumina..
Potassa
Water
b.
α.
•
34:52
33.95
11.86
II.48
9'44
9.04
45'27
45.61
101'09
100'08
Al₂
2
}
K
Insoluble, or basic alum, 280, is obtained by boiling a solution of alum with
hydrate of alumina; it is a white, insoluble powder, and as regards its composition
similar to alum-stone. Basic alum is soluble in acetic acid.
Sulphate of Alumina, The active principle of alum is evidently the sulphate of
alumina, not the sulphates of potassa and ammonia, the object of the preparation of
the double salt being simply the obtaining of a definite compound, which, while it
readily crystallises, can be obtained in a pure state, especially free from iron, a very
injurious ingredent in alum used in dyeing and calico-printing. However, at the
present day, with improved methods of manufacture, sulphate of alumina is largely
prepared, and of excellent quality. It is often sold under the name of concentrated
alum; and occurs in the trade as square cakes. It is white, somewhat transparent,
and may be cut with a knife; is readily soluble in water, contains always free
sulphuric acid, and also to some extent potassa, and soda-alum.
In the pure state this salt has the formula, Al2(SO4)3 + 18H2O, and contains in
100 parts-alumina, 18'78; sulphuric acid, 38'27; water, 42'95; total, 100. That
the composition of this salt as met with in commerce varies greatly may be inferred
from the following results of Varrentrapp's analyses of different samples of this
salt :-
I.
2.
3.
4.
Alumina
Sulphuric acid ..
15'3
12'5
15'1
13.0
38.0
30.6
38°0
34'0
262
CHEMICAL TECHNOLOGY.
According to the formula, the quantity of sulphuric acid in these samples should
have been-
I.
35.8
2.
29.2
3.
43'3
4.
30'5
The quantity of water even varies between 56 and 48 per cent. for different
parts of the same cake. Weygand found a sample of this salt prepared at Schwemsal
to contain-alumina, 15˚57; sulphuric acid, 38'13; oxide of iron, 115; potassa,
o'62; water, 45'79 parts. The sulphate of alumina prepared from cryolite at
Harburg contains about 5 per cent. of sulphate of soda. The results obtained in
the analyses by H. Fleck of various samples of sulphate of alumina are :—
Sulphate of alumina
47°35
50.80
51.63
Sulphate of soda
4'35
I'24
0'77
Free sulphuric acid
0'73
0'27
Water
47.37
47'47
46.94
99.80
99'78
99'34
Sulphate of alumina is prepared either from clay, cryolite, or bauxite by methods
already described. When clay is employed, the iron has to be removed from the dilute
solution of the sulphate of alumina by precipitation as Berlin blue by means of ferro-
cyanide of potassium. When cryolite is used, the alumina, separated from the solution
of aluminate of soda by carbonic acid, or powdered cryolite, is put into sulphuric acid,
contained in a wooden lead-lined tank, and heated to 80° to 90°, the addition of the alumina
to the acid being continued until solution ceases to take place. The solution having been
clarified by standing for some time is next evaporated in a copper vessel until the salt
fuses; it is then cast into moulds. With due care sulphate of alumina may be used in
dyeing and calico-printing, but it cannot be altogether substituted for alum, owing to its
variable composition.
Aluminate of Soda. Aluminate of soda is now prepared on the large scale, as it has
been found to be a useful form of soluble alumina, especially in dyeing and calico-
printing. The preparation of this compound is based upon the solubility of hy-
drate of alumina in caustic potassa or soda-ley, and the ready decomposition of
the solution by carbonic and acetic acids, bicarbonate and acetate of soda, sal-
ammoniac, &c.
Aluminate of soda was first brought under the notice of dyers by Macquer and
Haussmann in 1819, but owing to the preparation being too expensive it did not come
into industrial application until comparatively recently. We have already described
the mode of manufacturing aluminate of soda from cryolite; but in Germany—the
chief seat of cryolite industry-this salt is not made on the large scale; in France
it is manufactured by Merle and Co., at Alais, and in England at the Washington
Chemical Works. In France bauxite, containing 60 to 75 per cent. of alumina, and
from 12 to 20 per cent. of oxide of iron, is the raw material, and is treated with
caustic or carbonate of soda. If caustic soda is used the pulverised mineral is
boiled with a solution of the alkali; while if the carbonate is employed the mixture
is ignited in a reverberatory furnace. In either case aluminate of soda is produced,
dissolved—in the case of ignition the semi-fused mass is lixiviated with water-and
evaporated to dryness. The salt met with in commerce is a white powder with a
green-yellow hue, dry to the touch, and consisting of-
Alumina
48
Soda
44
Chloride of sodium and Glauber's salt
8
100
•
ALUM.
263
The formula, Nas}
Ala} 06 would require :—
Alumina
Soda
•
52°79
47°21
100'00
Aluminate of soda is equally soluble in cold and hot water. Exposed to air it absorbs
moisture and carbonic acid, and consequently on being dissolved in water the salt so
changed yields a turbid solution, owing to alumina being suspended. The aqueous solution
of this salt is not stronger than 10 to 12° B., 107 to 1'09 sp. gr. According to Le
Chatellier, Deville, and Jacquemart, sulphate of alumina is the starting-point of the
preparation of the aluminate of soda by precipitating from the sulphate the alumina,
and re-dissolving the latter in caustic soda ley. Aluminate of soda is used in dyeing
and calico-printing; further, for the preparation of lake colours, induration of stone,
and the manufacture of artificial stone, and for the saponification of fats in stearine
candle manufacture, an alumina soap being first formed, which is decomposed by
acetic acid into acetate of alumina and free fatty acid. Aluminate of soda is largely
used in the preparation of an opaque, milky-looking glass, or semi-porcelain. Aluminate of
soda is a by-product of Balard's method of soda manufacture from bauxite, Glauber's
salt, and coal; this by-product, or rather product of the second stage of the process, is
decomposed by carbonic acid into carbonate of soda and alumina, which is thrown down.
The Pennsylvania Salt Manufacturing Company at Natrona, near Pittsburg, manufacture
large quantities of aluminate of soda, which is used in soap-boiling under the name of
natrona refined saponifier.
Uses of Alum and of Owing to the great affinity of the alumina contained in alum for
Sulphate of Alumina. textile fibres, especially wool and cotton, alum is largely used as a
mordant in dyeing, except when the tar colours are employed. Again, owing to the
affinity of alumina for many pigments, alum is employed in the preparation of the lake
colours, combinations of active colouring principles with alumina. It is also used in the
melting of tallow; for hardening gypsum; is found in the preparation used for sizing
hand-made paper, the alum in this case forming with the glue or size an insoluble com-
pound. Alum with resin is employed for the same purpose in machine-made paper, an
alumina-pinate being formed. It is very largely used for the preparation of acetate of
alumina, and with common salt in the tawing of leather. Alum is employed in clarifying
turbid fluids, more especially water; in this case the alum takes up the alumina suspended
in the water, and forming an insoluble (basic) alum carries down organic and other
suspended impurities. A boiling solution of alum, common salt, and nitrate of potassa
is used by jewellers for the purpose of colouring gold, that is to say, to produce a film of
pure gold on the alloy, the copper of which is dissolved by the boiling solution.
Acetate of Alumina. This salt is prepared by double decomposition; generally sulphate of
alumina and acetate of lead are used, and occasionally the acetates of baryta and lime.
The liquor, separated by filtration from sulphate of lead, is gently evaporated to dryness;
the dry salt is gelatinous, and does not crystallise, is very hygroscopic, and possesses a
strongly astringent taste. When a solution of acetate of alumina is evaporated in con-
tact with air, acetic acid is driven off, and a basic acetate, insoluble in water, formed.
Commercially pure acetate of alumina is rarely used, as the so-called red-liquor, mordant
rouge, consists of a mixture of alum, acetate of potassa, and sulphate of potassa. When
it is desired to prepare neutral acetate of alumina from alum, to 100 parts of acetate of
lead 62.6 parts of alum are required for complete mutual decomposition; but it is more
advantageous to convert a solution of alum into insoluble alumina by means of
carbonate of soda, and to treat with acetic acid. Acetate of alumina is not an ordinary
Besides being
article of commerce, as the salt is usually prepared by the consumers.
largely used in dyeing and calico-printing, acetate of alumina is employed for water-
proofing woollen fabrics. Among the salts of alumina employed industrially are-hypo-
sulphite of alumina, suggested by E. Kopp as a mordant for cotton; hypochlorite of
alumina, known as Wilson's bleaching-liquor, and used in bleaching-works; sulphite of
alumina, for the purpose of purifying beet-root juice; oxalate of alumina, suggested by
Dent and Brown for the preservation of stone. marble, dolomite, &c.
264
CHEMICAL TECHNOLOGY.
ULTRAMARINE.
Ultramarine. Under this name is now understood an artificial blue pigment,
formerly and still obtained in small quantities from the lapis lazuli. The quantity
of artificial ultramarine manufactured in Europe amounts to 180,000 cwts. annually.
Lapis lazuli is a scarce mineral, possessing a beautiful blue colour. The sp. gr.
varies from 2.75 to 2'95. The coarser pieces of this mineral are pulverised, heated
to redness, and immediately dipped into water, then very finely ground, and the
Native Ultramarine, powder treated with dilute acetic acid to eliminate carbonate of
lime. The powder is next well incorporated with a mixture of equal parts of resin,
wax, linseed-oil, and Burgundy-pitch; this paste is kneaded under water until no
more blue pigment remains suspended. The quantity of ultramarine obtained
amounts to 2 to 3 per cent. This natural ultramarine is highly prized for its extreme
beauty, softness of colour, and durability, not being affected by light, oil, and lime.
Chemical analysis of the lapis lazuli first gave the clue to the true composition of
this material, and led, after many unsuccessful attempts, to the preparation of artificial
ultramarine, not, however, by any means equal to the native pigment, although it
has driven smalt and other blue pigments nearly out of the market. Lapis lazuli
consists in 100 parts of silica, 45°40; alumina, 31′67; soda, 9'09; sulphuric acid,
5.89; sulphur, o'95; lime, 3'52; iron, o86; chlorine, o°42; and water, o'12.
Artificial Ultramarine. Gmelin first made artificial ultramarine on a very small scale in
1822; but not before 1828 was ultramarine industrially obtained by Guimet, at
Lyons. In Germany the first manufactories of ultramarine were established at
Wermelskirchen, in 1836, by Dr. Leverkuss, and at Nuremberg, in 1838, by MM.
Zeltner and Leykauf: the manufacture of artificial ultramarine in England is of
very recent date, and is still on a very limited scale. France and Germany are the
countries where this industry is most developed. Of late years the process of
manufacture has been improved by R. Hoffmann, the manager of a factory at
Marienberg, in Hessen; Wilkins, at Kaiserslautern; Fürstenau, at Coburg; and
Gentele, at Stockholm.
Raw Materials. These are—1. Silicate of alumina as free as possible from iron, a
good china clay, the kaolin of Cornwall being esteemed the best; 2. Calcined sul-
phate of soda; 3. Calined soda; 4. Sulphuret of sodium, as a by-product of the
manufacture; 5. Sulphur; 6. Pulverised charcoal, or pit-coal.
Porcelain, or china-clay, is generally used, or a white clay, the composition of
which is nearly the same. Small quantities of lime and magnesia have no injurious
effect, but the oxide of iron should not exceed 1 per cent. The composition of the
clay should approach as nearly as possible to the formula Si207Al2; the silica may
be combined or partly free. The clay is washed with water and treated in the same
manner as for the making of porcelain; it is next dried, ignited, and ground to a
very fine powder. The sulphate of soda should not contain any free acid, lead, or
iron. If the sulphate does not possess the requisite qualities it is dissolved in
water, milk of lime being added to neutralise the acid and to precipitate oxide of
iron. The clear solution is left to crystallise; and the crystals are ignited in a
reverberatory furnace and then pulverised by millwork. The clear solution is in
some cases evaporated to dryness and ignited in iron vessels. Barium, but not
potassium salts, form ultramarine (see "Chemical News," vol. xxiii., pp. 119, 142, 204).
The calcined soda is obtained from the alkali works, and should contain at least yo per
ULTRAMARINE.
265
cent. of carbonate of soda; it is also finely pulverised. Very recently caustic soda
has been substituted in some ultramarine works. Sulphuret of sodium (Na2S) is
usually a by-product of the process of making ultramarine, and is obtained either
in solution or as a dry powder. The sulphur is used very finely pulverised. The
carbonaceous matter employed is also in a very fine powder. Its use was introduced
by Laykauf for the purpose of deoxidation. In order to have the carbon in as
finely divided state as possible it is ground to a pulp with water under granite stones;
the pulp is lixiviated, and the fine powder obtained dried and passed through a sieve:
in some cases resin and pitch is employed. For those ultramarines not to have their
colour discharged by alum, pure silica, either as fine glass, sand, or pulverised
quartz is used. Several substances are used to reduce the depth of colour of
ultramarine, viz.-gypsum, sulphate of baryta, baryta-white, and flour; the last is
employed in making up washing-blue.
Manufacture of Ultramarine. The methods of ultramarine preparation may be classified,
according to the crude materials employed, as the three following:-
a. Preparation of Sulphate, or Glauber's salt ultramarine.
B.
Y.
""
,,
Soda-ultramarine.
Silica-ultramarine.
a. Preparation of Sulphate-Ultramarine.—This ultramarine is prepared according
to the Nuremberg process from kaolin, sulphate of soda, and charcoal; the pre-
paration consisting in two distinct stages, viz. :—
a. Preparation of green ultramarine.
b. Conversion of green into blue ultramarine.
a. Preparation of Green Ultramarine.-In order to obtain a most intimate mixture of
the dry and finely pulverised materials, small quantities are weighed off, mixed in wooden
troughs by means of shovels, and several times passed through sieves. If solutions of
Glauber's salt, soda, and sulphide of sodium are used instead of powders, the kaolin is
mixed with these solutions, and the whole evaporated to dryness, gently ignited in a
reverberatory furnace, and then pulverised and sifted. The quantities of the crude
materials vary, but the following conditions have to be complied with:-1. Soda, whether
sulphate or caustic, must be present in such quantity that it can saturate half of the silica
of the clay (kaolin). 2. There must be sufficient soda remaining to form with the sulphur
a certain quantity of polysulphuret of sodium. 3. There ought to remain enough sulphur
and sodium to form another sodium sulphuret (Na,S), after deducting from the whole
mixture as much green ultramarine as, according to its composition as proved by recent
analysis, the silica and alumina present are capable of forming. The following figures will
give an idea of the proportions:
Kaolin (dried)
I.
II.
100
100
Calcined Glauber's salt
Calcined soda
83-100
41
41
17
17
13
Carbon (char- or pit-coal).
Sulphur
For 100 parts of calcined soda 80 parts of calcined Glauber's salt, and for 100 parts of
the latter 60 of dry sulphuret of sodium are taken.
It is usual to have a large quantity of this mixture prepared for use. If this mixture is
ignited without access of air, a white mass is obtained, which, having been treated with
water, is a light, somewhat flocculent, white substance, to which Ritter has given the
name of white ultramarine. It becomes green by exposure to air, and blue by being cal-
cined in contact with air. The mixture is well rammed into fire-clay crucibles, placed
in furnaces similar in construction to those used for burning porcelain, being raised and
maintained at a high temperature with a very limited supply of air. This operation lasts
seven to ten hours, and is completed at a bright white heat. The furnace is closed and
slowly cooled; on removing the crucibles, the contents appear as a semi-fused grey- or
yellow-green mass, which is repeatedly treated with water. The ultramarine thus obtained
266
CHEMICAL TECHNOLOGY.
is in porous lumps, which are pulverised to an impalpable powder; this is washed, dried,
and again ground, then sifted, and finally packed in boxes or casks, and sent into the
market as green ultramarine, consisting, acccording to Stölzel's analysis (1855), in 100
parts, of—
Alumina
Iron
Calcium
Sodium
•
•
30.II
049 (peroxide of iron, o'7)
0'45
•
19.09 (soda, 25'73)
Silica
..
37:46
Sulphuric acid
0.76
Sulphur
6.08
Chlorine
0'37
Magnesia, potassa, phosphoric acid
traces
94.81
Oxygen
5.19
100'00
Green ultramarine is a pigment of comparatively inferior value, owing to its being less
brilliant than the green copper pigments.
b. Conversion of Green into Blue Ultramarine.—This operation may be variously effected,
generally by roasting the green ultramarine and sulphur at a low temperature with access
of air, so as to form sulphurous acid, while a portion of the sodium is oxidised into
soluble sulphate and afterwards washed out; but the sulphur originally present in the
green ultramarine remains combined with a smaller quantity of sodium. The roasting
may be variously carried out, but very frequently the apparatus consists of a fixed iron
cylinder similar to a gas-retort, provided with a stirring apparatus, by means of which
the mixture of green ultramarine and sulphur (25 to 30 lbs. of the former to 1 lb. of
sulphur) is submitted equally to the source of heat. The addition of sulphur is repeated
until the desired blue colour is produced; but in some works this calcination is interrupted
by repeated lixiviation, the object being to produce a superior article. Muffle-ovens
and a kind of reverberatory oven are also used for this operation. The sulphurous acid,
which is evolved in large quantities, is now generally employed in making sulphuric
acid, sometimes a co-product of ultramarine manufacture, and used for the preparation
of the sulphate of soda required. The ultramarine, when quite blue, is pulverised, lixi-
viated, dried, and finally separated into various qualities known in the trade as No. 00, I,
2, 3, &c.
Ultramarine.
Preparation of Soda- B. As manufactured in France, Belgium, and some parts of
Germany, this ultramarine is either pure soda-ultramarine or a mixture of soda-
and sulphate-ultramarine. The materials and proportions are—
I.
II.
III.
Kaolin
Sulphate
•
100
ΙΟΟ
ΙΟΟ
41
Soda ..
100
41
90
Carbon (charcoal or pit-coal)
I2
17
6
Sulphur
Rosin
бо
13
100
6
The ignition takes place either in crucibles, or, better, in a reverberatory furnace;
the result is the formation of a brittle and porous green substance, which absorbs
oxygen very rapidly, so that during the cooling of the mass in the oven, the greater
part is converted into blue ultramarine. The complete conversion, after the addition
of sulphur, is obtained by heating in a large muffle to redness, the product being
distinguished from the foregoing by a greater depth and beauty of colour. By
increasing, within certain limits, the quantities of soda and sulphur, the formation
of blue ultramarine may be at once obtained, the product containing 10 to 12 per
cent. of sulphur.
į
ULTRAMARINE.
267
Preparation of Silica-
Ultramarine.
Silica-ultramarine is really soda-ultramarine in the prepara-
tion of which silica to the amount of 5 to 10 per cent. of the weight of the kaolin is
added. The calcination at once yields blue ultramarine, and further treatment with
sulphur is therefore unnecessary.
This ultramarine is not acted upon by a solution of alum, and may be recognised
by its peculiar red hue, the intensity of which is increased by an increase of silica.
Notwithstanding the superiority of the ultramarine obtained by this process, its
preparation is disadvantageous owing to the tendency of the mixture of crude
materials to fuse during ignition.
Constitution of Ultramarine. Since 1758 the chemical constitution of ultramarine has
been the object of a series of researches. The latest experiments are those of
W. Stein, who comes to the conclusion that ultramarine consists chiefly of a white
mass, with which black sulphide of aluminium is most intimately and molecularly
incorporated, the blue colour being due, not to chemical composition, but to the
optical relation of its component substance. Green ultramarine contains less soda
than the blue pigment, and that again less than the white (so-called) ultramarine.
The quantity of sulphur contained in blue ultramarine is less than that in green.
Properties of Ultramarine. Artificial ultramarine is an impalpable powder of a fine blue
colour, entirely insoluble in water, and when washed with distilled water leaving no
residue on evaporation of the filtrate. It is not acted upon by alkalies, but is highly
sensitive to the action of even very dilute acids and acid salts, sulphuretted hydrogen being
evolved and the colour discharged. Native ultramarine obtained from lapis lazuli is not
thus decomposed by weak acid solution. There sometimes accidentally occurs in soda
furnaces a more or less blue ultramarine which exhibits the same resistance to acids. That
kind of ultramarine commercially termed acid proof is manufactured with the addition
of silica, as described, but it really only resists the action of alum-salts. Ultramarine is
now largely used for the purposes to which smalt, litmus, and Berlin-blue were applied;
that is to say, ultramarine is employed as a paint, as a pigment in stereochromy, for
paper-hangings, calico-printing with albumen as fixing material, for colouring printing-
ink, for the bluing of linen and cotton fabrics, paper, stearine, and paraffine-candles, and
lump-sugar. For 1000 cwts. of sugar 21 lbs. of the pigment are employed, a quantity so
small as to be perfectly innocuous; further, ultramarine does not contain anything
injurious to health. Green ultramarine is a dull-coloured powder used by wall-paper
stainers, and is sometimes mixed with indigo-carmine and a yellow pigment to improve the
colour.
Adulterations of ultramarine with Berlin-blue, smalt, and other blue pigments do not
now occur, as ultramarine is a cheaper material; but to obtain lighter tints ultramarine
is sometimes mixed with chalk, kaolin, alabaster, and chiefly with sulphate of baryta.
DIVISION III.
TECHNOLOGY OF GLASS, CERAMIC WARE, GYPSUM, LIME, AND MORTAR.
Definition and General
Properties of Glass.
GLASS MANUFACTURE.
Glass is an amorphous composition of various silicates obtained
by a process of smelting, alkaline and calcium silicates being the chief constituents.
That which is termed glass-water-viz., a silicate of potassa or soda-of course con-
tains no other silicates; but real glass contains other bases in addition to soda
and potassa, either alkaline earths, as lime, baryta, strontia, or other more or less
basic bodies, as magnesia, alumina, or metallic oxides,—those of lead, bismuth, zinc,
thallium, protoxides of iron and manganese, while in the case of optical or fine
crystal glass boracic acid or borax is substituted for a portion of the silica.
Glass is generally transparent; when opaque it is either white or coloured. Glass
is not acted upon, in the common acceptance of the term, by either water, acids, or
alkalies. It is, as has been said, amorphous, for as scon as it becomes crystalline it
ceases to be glass. The amorphism of glass is due to its composition; simple sili-
cates have a tendency to crystallise, and are hence unfit for glass manufacture.
Owing to its amorphism glass exhibits a conchoidal fracture. When blown to very
thin laminæ or drawn into thread, glass possesses a remakable degree of elasticity.
As regards the chemical and physical qualities of glass, much depends upon the
constituent silicates; the alkaline silicates render glass soft and contribute to its
ready fusibility. Silicate of potassa glass is less bright and glossy than glass in
which silicate of soda prevails, but the latter silicate imparts a blue-green colour.
Silicate of calcium renders glass harder, brighter, but less readily fusible. Silicates
of lead and bismuth render glass very fusible, impart to it a high degree of lustre,
and greatly increase the refrangibility; they are therefore used in making glass for
optical purposes. Silicates of zinc and baryta impart similar properties; the former
has the property of reducing the blue-green colour due to silicate of soda. Silicates
of iron and manganese render glass readily fusible, and impart colour to it. Silicates
of other metallic oxides are only of secondary importance in imparting colour to
glass.
Classification of the Various
Kinds of Glass.
as follows:
According to its chemical composition glass may be classified
I. Potassium-calcium glass, or Bohemian crystal glass, is quite colourless, very
difficultly fusible, hard, and very difficultly acted upon by chemicals. Abroad,
mirrors are often made of this glass, mixed with any of the following kinds.
II. Sodium-calcium glass, French glass, window glass, somewhat harder than the
GLASS.
269
preceding but more readily fusible, exhibiting, as does all soda-containing glass,
a peculiar blue-green hue. Crown-glass is of similar composition.
III. Potassium-lead glass, crystal glass, very readily fusible, soft to cut, has a
higher sp gr. than other glass, and is more refractive. Among the varieties of this
glass are:-1. Flint-glass, optical glass, in addition to lead often containing bis-
muth and boracic acid. 2. Strass used for preparing imitation gems.
IV. Aluminium-calcium-alkali glass, or bottle-glass, always contains oxides of
iron and manganese; and sometimes magnesium instead of calcium. The colour
varies from a red-yellow to a deep black-green.
The sp. gr. of glass depends upon its composition. The alkali-calcium glass is
the lightest, next follows aluminium-calcium-alkali glass, while thallium glass is
the heaviest, as may be seen in the following table :-
Bohemian crystal glass
Crown-glass
Mirror-glass
Window-glass
Bottle-glass..
Lead glass
Flint-glass (Frauenhofer's recipe).
""
(Faraday's
Thallium glass
•
""
)..
2'396 Sp. gr.
2.487
2*488
""
•
•
2.642
29732
•
•
2'9 to 3.255
3'77
5'44
""
5'62
""
Slowly cooled glass possesses single, rapidly cooled doubly refractive powers; the
refractive index of glass differs considerably, but is never so high as that of the diamond.
Taking the index of refraction of the vacuum of Torricelli as unity, that of quartz is
=1547; diamond, 2:506; optical glass (2:52 sp. gr.)=1'534 to 1'544; flint-glass of
3.7 sp. gr., 1.639; thallium glass 171 to 1965.
Raw Materials used in These are:-I. Silica, viz. quartz, for very pure glass, for other
Glass-making. kinds sand of varying quality or pulverised flint stones.
For very
pure glass the silica ought to be free, or very nearly so, from iron; in some cases the
peroxide of iron adhering to the quartz or mixed with the sand is removed by hydro-
chloric acid, while the sand is always first ignited and in some instances previously
washed to remove clay, marl, humus, &c. Ordinary glass is made with coarser materials,
the sand is not required to be so pure, as when it contains lime, chalk, or clay, it renders
the mass more fusible.
2. Boracic acid is sometimes used as a substitute for a portion of the silica. It
increases the fusibility of the glass, imparts to it a high polish, and prevents devitrifica-
tion. It is employed as borax or as a boro-calcite, a native boracic acid.
3. Potassa and soda are used in a variety of forms, the former chiefly as potash
(carbonate of potassa), or partly lixiviated wood-ash.
Not so large a quantity of soda is required as of potash; 10 parts of carbonate of soda
correspond to 13 parts of carbonate of potash. Recently the soda has been used in the form
of Glauber's salt; in this case, so much carbon is added to the siliceous earth and Glauber's
salt as will reduce the sulphuric acid of the sulphate of soda to sulphurous acid, and the
carbon to carbonic oxide. The silicic acid then easily decomposes the sulphurous acid of the
sulphite. To 100 parts of Glauber's salt (anhydrous) 8 to 9 parts of coal are measured.
An excess of carbon is detrimental, as a large quantity of sulphide of sodium is formed,
which imparts a brown tint to the glass.
4. The lime used in glass-manufacture must be free from iron. It is generally
employed as marble or chalk, either raw or burnt. To 100 parts by weight of sand, 20
parts by weight of lime are added. In the Bohemian manufacture the lime is employed
as neutral silicate of calcium, Wollastonite, SiO,Ca. Instead of lime, strontia, and
baryta can be used, the former as strontianite (SrCO3), the latter as witherite (BaCO3).
Fluor-spar (CaFl₂), and aluminate of soda were at one time used in making milky or
semi-opaque glass.
5. Oxide of lead is employed in most cases in the form of minium or peroxide, giving
up some of its oxygen to form a lower oxide, and purifying the glass. The lead gives the
glass a higher specific gravity, greater brittleness, transparency, and polish. It must be
270
CHEMICAL TECHNOLOGY.
free from oxide of copper and tin, the former imparting a green colour, and the latter an
opacity to the glass. White-lead is as efficacious as red-lead, provided no heavy spar be
present.
6. Oxide of zinc is always added as zinc-white. When the colour is not of importance,
zinc-blende with sand and Glauber's salts may be used.
7. Oxide of bismuth is only added in small quantities in the preparation of glass for
optical instruments. Bismuth may be employed either as oxide or nitrate of the oxide.
The natural silicates are only employed alone in the manufacture of bottle-glass; some
of the preceding additions are requisite in clear glass manufacture.
Bleaching. Coloured glass as it occurs in the first process of manufacture may have the
colour disguised by mechanical mixture with white glass, or the colour may be discharged
by chemical agents. Such agents are usually-braunite, arsenious acid, saltpetre, and
minium or red-lead.
1. Braunite, MnO,, has long been used as a material for glass-clearing. This oxide of
manganese is, however, used only in small quantities; too much imparts a violet cr
amethyst-red colour to the glass; while an excessive amount renders the glass dark
coloured and opaque. The violet-coloured glass is generally prepared with silicate of
manganese by the addition of braunite to colourless glass. The action of braunite
in clearing glass or rendering it colourless has been variously explained. It may be con-
sidered that there arises in the molten glass the colours complementary to white, that is,
the green from silicate of iron and the violet from silicate of oxide of manganese; this view
is supported by the experiments of Korner, who obtained a colourless glass from a mix-
ture of red and violet glasses; and further by those of Luckow who obtained a colourless
glass by the melting together of a glass strongly tinted red by protoxide of manganese
with oxide of copper. The glass-blowers of the Bavarian Waldenses assert that a rose-red
quartz there found is equalled by no other quartz in the production of the best crystal or
clear glass. Von Fuchs says that this quartz contains I to 15 per cent. of oxide of
titanium, which similarly to braunite, effects the chromatic neutralisation. Kohn
employs for this purpose protoxide of nickel or oxide of antimony. Oxide of zinc has
lately been employed to remove or mask the green colour of Glauber's salt glass, also
imparting a higher polish. 2. Arsenious acid effects the removal of colour by chemical
means only from glass containing carbon or silicate of iron: in glass containing carbon—
Arsenious acid, As₂03
3} give {Carbonic oxide, 3C0;
Carbon, 3C
in glass containing protoxide of iron :-
Protoxide of iron, 6Fe,
Arsenious acid, As₂O3,
give
Arsenic, As.
Oxide of iron, 3Fe₂03,
The arsenious acid is reduced by the carbon and protoxide of iron at a dull red heat,
while the arsenic is volatilised.
3. Saltpetre is added chiefly as Chili-saltpetre or nitrate of soda. In the manufacture
of lead-glass (flint-glass) nitrate of lead is substituted for the nitrate of soda. Nitrate
of barium has recently been employed to discharge the colour of glass; its action is similar
to that of arsenious acid.
4. That minium serves to render glass colourless has already been noted. Chambland
states that glass may be whitened by forcing through it while molten a stream of air.
Utilisation of Refuse The materials of glass manufacture are never melted alone, but
Glass. always with nearly the third part of prepared or finished glass. For
this purpose, pieces of broken glass, flaw glass, the hearth droppings, and the glass
remaining adherent to the blowers' pipes may be utilised, serving a purpose in the
manufacture of glass similar to the rags in paper-making. Thus there is only a very
small loss of materials. At each re-melting, however, a portion of the alkali of the frag-
mentary glass is volatilised, and must be replaced by the addition of an alkaline salt.
The Melting Vessel. The vessels in which the glass is melted are placed immediately
upon the hearth, and are made of difficulty-fusible clay and powdered chamotte-
stone. They are usually o'6 metre in height, the walls being 9 to 12 centimetres
thick. They are dried in a temperature of 12° to 15°, and then placed in a chamber
heated to 30° to 40°. After remaining about a month, the vessel is put into the
tempering or annealing oven, heated to 50°; it is next removed to the ordinary
melting-oven, and gradually heated to the melting-point of glass, at which it remains.
for three to four hours. When a new pot is first used for glass-melting, the alkaline
constituents of the glass act upon the clay, forming a rich clay glaze or glass, which,
if allowed to mix with the ordinary glass, would be highly detrimental. Conse-
GLASS.
271
quently broken glass and refuse are first melted in the vessel, and the glaze
imparted, termed technically the lining, is a sufficient protection to the glass in
after practice. The shape of the melting vessels varies. For melting with wood or
gas the conical form, Fig. 120, is employed. When coal is used as fuel, the vessel
takes the covered form, Fig. 121. Fig. 122 represents a rather peculiar form; the
FIG. 120.
FIG. 122.
FIG. 121.



FIG. 123.

B
glass constituents are melted in A, the clear molten glass passing by the aperture in
the central wall into B. The glass in B is thus always free from glass-gall or impu-
rities, which remain behind in A. In the manufacture of looking-glasses, large
quadrangular vessels, Fig. 123, are employed for refining purposes.
The Glass-Oven. The glass-ovens are respectively-1. The melting-oven; 2. The
tempering- or annealing-ovens, used in the after-manufacture. The melting-oven
can only be made of fire-proof clay. It is built of a mixture of white clay and burnt
clay of the same kind. Ordinary mortar and cements are useless for this purpose
on account of their fusibility, therefore the same clay as is used for building is also
used for binding. The oven must be built on dry ground; if built on damp ground
it is difficult to maintain the lower parts at a constant heat, requiring a larger supply
of fuel. The arch is closed with a single piece of fire-proof clay weighing 800 to
1000 cwts. After building the oven is dried for four to six months at a temperature
of 12° to 15º; a low fire is then lighted, and the temperature gradually increased for
about a month until the oven is fit for actual work. The arch is further covered
with massive backstones, and these again are covered to a thickness of 5 to 6 inches
with a lime-mortar. When much in use, and if not built of very good clay, an oven will
not remain in working order for longer than 1 to 12 years; but if fire-clay is used, and
only easily-fusible lead-glass is manufactured, the oven may last for four to five years.
The oven contains six or eight to ten melting-pots, which must all be raised to the
272
CHEMICAL TECHNOLOGY.
same temperature. Further, the melting-oven is placed over half the fire-room.
The annexed woodcut, Fig. 124, is a ground plan of a complete oven. Fig. 125 is a
section showing the melting-oven and work-holes; Fig. 126 a vertical section
FIG. 124.

f
f
7
through the length of the oven; Fig. 127 a vertical section of the breadth. In the
ground plan, Fig. 124, 00 is the flue; ccc are the melting-pots; nn, pots containing
glass in another stage of preparation; d d d, the work-holes; bb, the banks; ii, warm-
ing and cooling ovens; h h, tempering ovens; e e, the breast walls; ƒ ƒ, the splint
walls; 7 are small hearths to increase the heat in the tempering oven when
FIG. 125:

| |
hummailuinua
required. In Fig. 125 7 is the flue; y y are blocks of stone, bearing the wooden
frame-work, z z, on which the wood used as fuel is placed to dry. Fig. 126 shows
the bank, ƒ ƒ, on which the melting-pots, h h h, stand; over these pots are the work-
holes; n n are the side chambers. In Fig. 127, b b is the key-stone; c d are the
banks; g the flue, although in most glass-ovens there are no flues. The flame from
GLASS.
273
the fuel burning in both grates, m m, Fig. 126, after heating the melting oven,
passes by the tempering rooms, and finally to the chimney-stalk.
At the Paris International
Siemen's gas-oven has lately found extensive use.
Exhibition of 1867 this oven obtained the gold medal. It consists of two parts, the
FIG. 126.

generator, Fig. 128, and the melting oven, Fig. 129. These parts are separate, and
can be 30 or more metres from each other, being connected by a large gas-pipe. The
fuel, brown coal, turf, stone coal, or wood, is placed in the generator at A, Fig. 128,
FIG. 127.
I

and falls on the sloping grid, o. The gas, a mixture of carbonic oxide and nitrogen,
ascends at a temperature of 150° to 200°, and flows out of the generator by a large
pipe, v, 4 to 5 metres in height, and is conveyed thence by a horizontal pipe to the
19
274
CHEMICAL TECHNOLOGY.
melting oven. The upper chambers of the melting oven are similar to those of the
usual ovens. P P are the melting-pots. The gas first passes into the first system of
regenerators, the stones of which are raised to a red-heat, and passes thence to the
melting room, where it meets with air heated in like manner. The products of com-
bustion then pass to the second regenerating system, the stones of which are cold
until heated by the passing gases. The waste gas is finally conducted to the
chimney-stalk. When stone-coal is used in the generator, lead-glass may be melted
in the oven in open vessels without reduction. The saving of fuel in comparison
with the old system is about 30 to 50 per cent.
Preparation of the Material, Formerly manufactured glass was only an imitation of crystalline
and Melting. siliceous earths, the chemical action being but little known. The
alkaline constituents were added as fluxes, and to this day retain that name. However,
most of the results attending the variations
of temperature were known, and, in fact, the
chief practical detail.
U
FIG. 128.

Ꮴ
AMUUTEN INGURUL PERENT SUTTOMINATRIUM
區
​Of especial importance in glass manufacture
is the knowledge of the behaviour of glass
in the fire. At the maximum temperature of
glass-melting ovens, 1200° to 1250° C., the
glass forms a thin fluid of the consistency of
syrup.
This condition is essential to the
refining of the glass, as the thinness of the
fluid admits of the settlement of foreign
substances to the bottom, or of their floating
to the surface of the glass contained in the
melting-pot. In this condition also the clear
molten glass can be run off. At a red-heat
glass is exceedingly ductile and flexible; upon
this quality depends its application in manu-
facture. Two pieces of glass raised to a red
heat can be welded into one piece by mere
pressure. Glass as a fine thread is generally
flexible, and may be spun. Undoubtedly glass
will be used as a spinning-fibre at some
future time; even now, in the International
Exhibition of 1871, there are several articles
of habiliment made of spun glass, exhibited by
an Austrian firm. Brunfaut, of Vienna, in 1869,
prepared glass-wadding, feathers, bows, favours,
nets, &c. Glass fibre, according to the mea-
surement of Fr. Kick, of Prague, can be spun to
a diameter of o'006 and oor2 millimetres.
When glass is allowed to cool extremely slowly it loses its transparency, and is transformed
into an opaque mass known as Réaumur's porcelain. The chemical action taking place when
glass is rendered opaque is, in spite of numerous researches, still unexplained. On the other
hand, glass cooled too suddenly acquires peculiar properties. Detonating bulbs are small
glass flasks which have been cooled immediately after being made. If a sharp grain of
sand be dropped into the interior of one of these flasks it will fly to pieces with excessive
violence, while the exterior will bear hard usage without result. Another peculiarity of
glass manufacture are glass-tears, or Prince Rupert's drops, long pear-shaped drops
of glass, tapering to a very slender tail, which are formed by dropping molten glass
into cold water. The bulb of these drops may be struck with a hammer; but if
only a small portion of the tail be snapped off, the entire drop will break up with a loud
report. This brittleness is more or less the characteristic of all unannealed glass,
and is probably due to unequally cooled layers, which are consequently at different degrees
of tension.
Drying the Materials. Before the materials are placed in the melting oven, they are first
subjected to a tolerably strong heat, not sufficient, however, to effect fusion in the
drying oven. The benefit of this operation is the removal of the carbonic acid and
water which would otherwise be disseminated in the melting oven. Some manufac-
GLASS.
*275
turers dispense with this portion of the process, running a risk of turning out
imperfect glass that can be avoided at a very small expense.
Melting the Glass Material. When the temperature of the melting oven has reached the
required degree, the material first frits together and is then melted. The oven
must be heated equably throughout. At the melting-point the siliceous earth
combines with the potash, soda, lime, alumina, oxide of lead, &c., to form
FIG. 129.

P
P
P
GROTTAD
冰​M
DURANDEZ ANON
HADE
VIENU
glass. The substances not taken up form a scum, known as glass-gall, upon
the molten glass, which is removed by the aid of iron shovels. This scum is
generally composed of sulphate of soda and chlorides of the alkalies. The progress
of the melting process is from time to time ascertained by removing a sample of the
glass by the help of an iron rod terminating in a flat disc, in fact a large flat spoon.
Clear-melting. When the mass is well molten it is "cleared," that is, maintained for
some time at such a temperature that the glass remains in a thinly fluid condition.
During this period the uncombined substances settle to the bottom of the melting
vessel, the air-bubbles disappear, and the glass-gall still remaining is volatilised or
separated. At the commencement of the melting the disengagement of the gases
from the molten mass causes an advantageous agitation, by which the several con-
stituents of unequal specific weight and different composition become well mixed.
After the disengagement of the gases the lower part of the melting vessel is at a
lower temperature than the upper part, consequently the molten glass is well stirred
with the iron ladles or 'poles." Lastly, a piece of either arsenious acid, damp
wood, raw turnip, or any other water-containing substance, is introduced to the
bottom of the vessel on an iron rod, the end in view being the violent agitation of
the molten glass by the steam evolved.
<<
Cold-stoking. After the completion of the clearing follows the cold-stoking, that is,
the lowering the temperature of the oven till the glass attains a tough fluid consis-
tency requisite before it can be blown. The glass remains at this temperature,
700° to 800° C., during the rest of the manufacture.
:
276
CHEMICAL TECHNOLOGY.
The length of the several processes is as follows:
Melting
Clearing
Blowing
10 to 12 hours.
""
4 to 6
10 to 12 ""
so that five to six meltings can be effected in a week.
Defects in Glass. It is extremely difficult to prepare glass perfectly free from blemish.
The principal defects are-streaking, threading, running unequally, or dropping, stoning,
blistering, and knotting. Streaking follows from heating the glass unequally, another
consequence of which is the threading or the formation of the striæ, by glazing, into
coloured threads, generally green. By dropping is understood the lumps or globules
formed in the glass by the glazing of the clay cover of the melting vessel, and its combi-
nation with the volatilized alkalies, the crude glass thus formed on the cover dropping
into the molten glass contained in the vessel. Blistering is a common result of the imper-
fect clearing of the glass from air bubbles. Lastly, knotting, another common defect,
results from uncombined grains of sand taken up in the glass; the small particles of the
oven and melting vessel detached during the melting similarly giving rise to stoning.
Other defects, such as the imperfect combination of the materials, arising from careless-
ness or inability of the workman, need not here be noticed.
Various Kinds of Glass. Glass is separated according to its composition or method of
manufacture into :—
I. Glass free from Lead.
A. Plate-glass. a. Window-glass :-
a. Rolled glass.
B. Crown glass.
b. Plate-glass :—
B. Bottle glass :—
a. Blown plate-glass.
B. Cast plate-glass.
a. Ordinary bottle glass.
b. Medicine and perfumery glass.
c. Glass for goblets, drinking glasses, &c.
d. Water pipes and gas tubes.
e. Retort glass.
C. Pressed or stamped glass.
D. Water glass.
II. Glass containing Lead (Flint-Glass).
A. Crystal glass.
B. Glass for optical purposes.
C. Enamel.
D. Strass.
Plate or Window-Glass.
III. Coloured Glass and Glass Staining.
IV. Glass Decorations.
4
The glass melted in muffles or vessels is manufactured as plate-
glass or as crown-glass. Plate-glass, as its name implies, is formed in large or small
plates; window glass is generally either ordinary bottle glass, or a finer glass of
a whiter colour. Recently, thick has taken the place of thin glass for windows, but
the colour is hereby considerably increased. That window glass should be prepared
cheaply is an essential point, consequently crude materials are employed-crude
potash and soda, wood-ash, Glauber's salt, ordinary sand, and broken glass from the
GLASS.
277
warehouses, &c. Plate- or window-glass is generally composed of 100 parts sand,
30 to 40 parts of crude calcined soda, 30 to 40 parts of carbonate of calcium.
Instead of the soda may be substituted an equivalent quantity of Glauber's salt.
Benrath (1869) found in several kinds of plate-glass the following constituents :-
Silicic acid
70'71
71'56
73'II
Soda
13'35
12'97.
13.00
Lime
13°58
13°27
13'24
Alumina and oxide of iron..
I'92
I'29
0.83
99'46
99'09
100*18
Tools. The tools ordinarily used by the glassblower in the preparation of plate- and
crown-glass are the following:-
a. The pipe or blow-tube, Fig. 130, is an iron pipe 15 to 18 metres in length, 3 to 4
centimetres thick, and I centimetre interior diameter. a is the mouthpiece, made so as
FIG. 130.

b
to turn easily between the lips. c is a hollow handle from 0.3 to 0.5 metre in length. bis
the part attached to the glass.
b. The handle or hand irons are rods 1 to 13 metres in length, used to transport the
hot vessels, &c. c. The marbel, Figs. 131 and 132, is a piece of wood with semi-globular
indentations, which serve as matrices for the glass to be taken up on the blower's pipe.
d. The whip, a block of wood, hollowed so as to form a long neck to the soft semi-molten
FIG. 131.
FIG. 132.
FIG. 133.


FIG. 134

B
D
bod
glass; it is also used to remove the glass from the pipe. e. Fig. 134 are the shears used
for trimming the molten glass, and to cut openings during the blowing of various
articles.
Plate-glass is manufactured as crown-glass or as rolled glass.
Crown-glass. Crown-glass is the oldest kind of window glass. It is formed in the manufac-
ture as a disc of glass, generally of about six inches in radius from the periphery to the
centre knot left by the glassblower's pipe, technically termed the bull's-eye. The
largest discs are scarcely 64 to 66 inches, from which a square plate of 22 inches only can be
cut, the bull's-eye interfering with the cutting of a larger size. In the preparation of this
glass three workmen are employed; the first takes so much molten glass on the end of a
pipe as will serve for a single disc, and passes pipe and glass to the second workman, the
blower. He blows the glass into a large globe or ball, which, when finished, he hands tɔ a
third workman, the finisher, who opens the globe and forms the sheet or pane. The
labour is divided in detail in the following manner:--The first workman receives the
warın pipe, thrusts it into the vessel of molten glass, and turns it steadily round until he
has collected upon the end a knob of glass of sufficient size. The weight of this knob is
generally 10 to 14 lbs. The first workman imparts somewhat of a spherical form by
means of the marbel to the solid glass ball, which is now taken in hand by the blower,
278
CHEMICAL TECHNOLOGY.
who by turning and shifting the glass about, at the same time blowing throngh the tube,
perfects the hollow spheroid. The glass has by this time cooled considerably, and with
the pipe is therefore returned to the oven, the tube of the pipe being fastened in a fork or
hook in the ceiling of the oven. As the globe of glass is gradually heated the weight of
the rod causes it to flatten out, and it is removed by the finisher as a disc of nearly
molten glass. He places the tube in the cavity of the whip, and by a series of dexterous
movements perfects the shape, enlarges the disc if required, or in some cases makes
a larger disc by removing the partially flattened sphere from the oven, opening the bottom
with a maul or iron rod, and causing the glass to take the form of a disc by means of the
centrifugal force resulting from a rapid rotary motion of the rod. Finally the discs are
separated from the pipe by the help of a drop of cold water, and are next placed in an
▼
FIG. 135.






h
¿
annealing oven to the number of 150 to 200 to cool. The finished plates are cut to the
required size; the centres or bull's eyes serve for the making of strass and for other pur-
poses.
Cylinder Glass.
Sheet Glass, or Rolled or sheet glass is made by cutting a glass cylinder or roll
throughout its length, and beating or rolling it out flat on a table. It is for this
reason termed sheet glass. Usually this sheet glass is used for ground glass, and is
further separated into ordinary sheet or roll-glass and fine sheet glass, the latter
having larger dimensions.
GLASS.
279
The preparation of sheet glass is one of the most difficult processes of glass manu-
facture; it may be considered as consisting of two operations—
1. The blowing of the roll, or cylinder; and
2. The flattening.
After the molten glass has cleared, and attained the barely fluid consistency
before mentioned, the workman inserts his pipe into. the mass, and by turning
manages to accumulate on it a globe of glass, during the time blowing into the tube
to keep it clear of the molten glass. The glass now takes the form a, Fig. 135. By
continued manipulation in the marbel, and by blowing, the enlarged forms, b and c,
and finally d, are obtained. The glass has by this time cooled, and is taken to the
oven to be re-heated. When this is effected, the workman by means of his tools, by
a continued rotation of glass, and by blowing, brings the globe to the shape repre-
sented by f. He then opens out the bottom of this form with a maul-stick, and
obtains the cylinder e, which is separated from the pipe by dropping a little cold
FIG. 136.

FIG. 137.

water upon the neck, o, joining the two. The removal of this neck is next effected
by means of a red-hot iron rod, which also serves to open the cylinder throughout
its length as shown by h.
After a great number of these cylinders have been blown, the operation being generally
continued for three days, the opening into plates is commenced. The cylinders are placed
in an oven termed the plate-oven, shown in ground plan in Fig. 136, consisting of two
chambers, one the heating room, c, and the other the tempering or annealing room, D. In
the passage B, the heated glass rolls or cylinders, a a a, are suspended upon two iron rods,
where they are maintained at a certain heat. The most important part of the plate-oven
is the platten, c, made of a well-rammed fire-clay. A similar plate, D, is placed in the
annealing room. When sufficiently heated, the cylinders are brought to the flattening
table, c, Fig. 137, where they are speedily opened out in the manner shown in the woodcut.
A workman stationed at d, Fig. 136, receives the flat panes of glass, and leans them
against the iron bars, s s, in the annealing room, whence, having gradually cooled during
four to five days, they are removed to be sorted and packed.
Plate-Glass.
very
Plate-glass is either blown or cast. The manufacture is similar
to that of table-glass just described. The materials are in great part the same as
those employed in the manufacture of fine white glass. This branch of glass manu-
facture is most strikingly illustrative of the rapid growth of the industry during the
last ten or twenty years. Formerly plate-glass was esteemed an article of luxury,
whereas now it is that most generally used for workshop windows, carriages, show-
rooms, &c., and for windows of private residences. It far surpasses in transparency
280
CHEMICAL TECHNOLOGY.
and elegance the small panes formerly used. By the Glass Jury of the Interna-
tional Exhibition of Paris of 1867, it was surmised that before ten years had elapsed
plate-glass would be that most generally in the market. The blowing of plate-glass
is effected with the same tools as the blowing of table-glass; and the cylinder is
obtained in a similar manner. The lump of glass taken by the blower on his pipe
from the melting vessel weighs about 45 lbs., from which a plate of 1.5 metres in
length and I to II metres breath by I to II centimetres thickness is obtained.
But the chief method of making plate-glass is by casting. Cast plate-glass is
always made from pure materials, and may be considered as a soda-calcium glass
free from lead. Potash-calcium glass is far more expensive, being almost a colour-
less glass. In England, Belgium, and Germany the raw materials used in manfac-
turing cast plate-glass are-sand, limestone, and soda, or Glauber's salts.
Benrath (1869) found in English (a) and in German (3) plate-glass :—
Silica
Soda
Lime
Alumina and oxide of iron
•
α.
թ.
76*300
78.750
16.550
13'000
6'500
6'500
0'650
I'750
100'000
100'000
2 448
Sp. gr.
2'456
The following description of casting the plates is mainly founded upon the method
pursued at St. Gobin and Ravenhead. The manufacture is included in-
1. The melting and clearing,
2. The casting and cooling,
3. The polishing: including
a. The rough-polishing,
B. The fine-polishing,
7. Finishing.
The Melting and Clearing.
The melting and clearing vessels are of very different form and
size. The first is a conical vessel surmounted by a cupola having three apertures, making
Fig. 138.

an angle of 120° with each other. The clearing pans are small, wide, and low vessels.
These vessels are never in the same oven. After the materials are melted, which is
effected in sixteen to eighteen hours, the molten mass is poured into the clearing vessels.
GLASS.
281
The impurities are then removed with a. large copper ladle, this process occupying about
six hours. During the clearing the excess of soda is volatilised. When the glass is
Casting and Cooling. sufficiently cleared the casting commences. The vessel containing the
molten glass is taken up by a crane and swung to the casting table, this table or mould
being on a level with the cooling or annealing oven. The casting table consists of a
large polished metal plate, Fig. 138, in the French work of copper or bronze, 4 metres
long, 2.25 metres wide, and 12 to 18 centimetres thick. The plate at St. Gobin weighs
55,000 lbs., and cost 100,000 francs (£4000). In England the plates are of cast-iron, 25
centims. thick, 5 metres in length, and 2.8 metres wide. In order that the glass plate shall
be of equal thickness, a bronze or cast-iron roller passes over the surface on guides of the
thickness required. The metal plate is first warmed to prevent the sudden cooling of the
glass. The operation of casting includes-
a. The conveyance of the pan to the table;
b. The cleansing of the plate and the pan;
c. The casting and conveyance of the plate to the annealing room.
The cooling room has two fire-places and three glass tables. The temperature is at first
that of the glass plate introduced. So soon as three plates are placed in the oven, all the
openings are closed, and the glass left for a day to cool. The cooled glass plate is taken
out of the annealing oven to the cutting room, laid on a cloth-covered table, and cut to
size with a diamond.
Polishing. The glass plate is cut into tablets. The under side of the plate, where it has
been in contact with the table, is smooth, while the upper surface is wavy, and requires to
be polished. This is effected by fastening the plate or tablet to a bench with plaster-of-
Paris, and grinding the upper surface smooth with some sharp powder; or another plate
is caused by machinery to move above the former in such a manner that the surfaces of
both are ground smooth. The ground plates are then removed to the polishing table,
where a similar process is gone through, but with a finer powder. Finally, when placed
upon the finishing table only the finest powder and leathern pads are employed. By grind-
ing and polishing the glass sometimes loses half its weight and thickness. Suppose a plate-
glass manufactory to produce 400,000 square feet of glass annually, there will be with this
amount of glass weighing about 16,000 cwts., a loss of 8000 cwts., corresponding to 2700
cwts. of calcined soda, and a money value of more than £1000.
Silvering. After polishing, each glass tablet intended to make a looking-glass is silvered,
or more correctly coated on one side with an amalgam of tin. In the preparation of this
amalgam tin-foil is used, but it must be beaten from the finest tin, and possess a surface
similar to that of polished silver. The art of silvering is simple, and merely requires
dexterity. The glass plate having been thoroughly cleansed from all grease and dirt with
putty-powder and wood-ash, the workman proceeds to lay a sheet of tinfoil smoothly
upon the table, carefully pressing out with a cloth dabber all wrinkles and places likely to
form air bubbles. He spreads over it a quantity of mercury, taking care that all parts are
equally covered, and then the glass plate is pushed gently on to the surface, commencing
at one edge. A glass plate of 30 to 40 square feet requires 150 to 200 pounds of mercury,
although the amalgam is not so thick as a sheet of the finest paper. The glass is allowed
to remain for twenty-four hours. It is then removed to a wooden incline similar to a
reading desk, to allow of the excess of mercury draining off. As the amalgam gradually
sets, the incline is increased till finally the plate reaches the perpendicular, when the pro-
cess is finished, and the mirror removed to the store-room.
Silvering by The former method of coating the glass with tin-amalgam obtains its
Precipitation. name of silvering by analogy only: the true process of silvering is the fol-
lowing, patented in 1844 by Mr. Drayton :-32 grms. of nitrate of silver are dissolved in
64 grms. of water and 16 grms. of liquid ammonia, adding to the filtered solution 108
grms. of spirits of wine of o 842 sp. gr., and 20 to 30 drops of oil of cassia. Call this fluid
No. I.
Another fluid (No. 2) is prepared by mixing I volume of oil of cloves with 3
volumes of spirits of wine. The workman places the glass plate upon a table, carefully
levels it, and floods it to a depth of 0.5 to 1 centimetre with fluid No. 1.
He then preci-
pitates the silver by adding 6 to 12 drops at a time of fluid No. 2 until the whole of the
surface is covered. For every square foot of glass 9 decigrammes of nitrate of silver are
required. Liebig recommends an ammoniacal solution of fused nitrate of silver, to which
450 c.c. of soda-ley of 1035 sp. gr. are added. The precipitate thrown down is dissolved
by means of ammonia, the volume being increased to 1450 c.c., and by water to 1500 c. c.
This fluid is mixed shortly before application with one-sixth to one-eighth of its volume of
solution of sugar of milk, containing 10 parts by weight to 1 of sugar of milk. The glass
is flooded with this fluid to about half-an-inch in depth; reduction soon sets in, and the
glass becomes thickly coated. I square metre of glass plate requires 2:210 grms. of silver.
282
CHEMICAL TECHNOLOGY.
The plate is then dried, cleaned, and polished. Lowe employs nitrate of silver, starch-
sugar, and potash; A. Martin, nitrate of silver, ammonia, and tartaric acid.
The
Platinising. According to the researches of Dodé, platinum may be used for coating plate-
glass. In France, Creswell and Tavernier have already brought platinised mirrors before
the public. Hitherto platinum has been used in ornamenting porcelain, and the glass
plates are prepared in a similar manner, the metal being burnt in, as it is termed.
platinum is precipitated from its chloride by oil of lavender, the chloride being spread
equally over the glass with a fine-haired paint-brush. The plate is then placed in a
muffle. Cheapness is a prominent feature of this process; while all faulty glasses can be
very easily repaired, these by the old methods being thrown aside as useless. In Paris the
lids of boxes and fancy articles are largely manufactured from platinised glass.
Bottle Glass. Bottle glass includes all kinds of glass made into vessels for holding
fluids. It is made from common green glass, from fine white glass, and from crystal
glass. Medicine bottles, &c., are made from common green glass; tumblers, or
drinking glasses, from fine white glass; and crystal glass is employed for the same
articles, but selling at a higher price.
The materials for ordinary bottle glass are sand, potash or soda, basalt, &c. For
medicine glass the materials must be free from iron, and still purer for the articles
of white glass. In the manufacture of bottle glass no considerable amount of care
is required, the desiderata being strength and sufficient resistance to the action of
ordinary acids. The processes of melting and annealing are conducted in the
ordinary manner. The analyses of several glasses gave the following results :-
Silicic acid
• •
74'71
74.66
75'94
74°37
74°26
Potash
•
4'32
12:48
Soda
15'74
ΙΙΟΙ
15'15
3°42
14'06
Lime
8.77
9'13
8.01
9'02
8.60
Alumina
0'43
2°52
Oxide of iron
0'14
0.88
o'90
0'71
0'38
Oxide of manganese
O'21
0*18
100'00
100'00
Sp. gr.
2.47
2:48
100'00
2.47
100'00
2'30
100'00
2.40
The details of the several processes of bottle glass manufacture are, after the making
of the rough shape out of tough fluid glass, so various that only single examples can be
b
a
Fig. 139.
d
given. We will select the ordinary wine-bottle.
The glassblower, taking some molten glass on
his pipe, turns and moulds it into the shape
of a, Fig. 139. By continued blowing the
enlarged form, b, is obtained; this form still
more enlarged, as at c, is placed in the mould,
d. The workman now blows sharply into the
incipient bottle, the glass filling out the
mould and producing the sharp curve of the
shoulder of the wine-bottle. The rod or pun-
til, e, is now introduced, and a firm footing
given by pressing in the bottom of the bottle.
While the blower prepares a new bottle, the
assistant places that already formed in the
annealing oven. In the making of flasks
and retorts the flask-tongs, Fig. 140, are em-
ployed, the neck being allowed to remain
straight, as at a, Fig. 141, to form a flask, or
bent, as at b, to make a retort. The manu-
facture of a beaker will be readily understood
from Figs. 142 and 143, A, B, C, being the
method of producing a globular body, and
a, b, c, a beaker with nearly perpendicular sides. Glass-tubing is drawn out as shown at
Fig. 144. Glass rods are similarly made, but without blowing.

GLASS.
283
Pressed and Cast Glass.
Pressed or cast glass comprises the many cheap glass orna-
ments, and, indeed, ornamental glass work of all kinds, now so general. The tall,
narrow-mouthed chimney ornaments are thus made by being blown into engraved
brass moulds, instead of into plain moulds as in the case of the bottle. Cup-shaped
articles are made with molten glass pressed between a concave and convex surface,
the surplus glass escaping at some point purposely arranged. As a rule the objects
taken from the moulds require but little polishing.
FIG. 140.
FIG. 141.

Y
a
Water-Glass.
By water-glass is understood a soluble alkaline silicate. Its prepara-
tion is effected by melting sand with much alkali, the result being a fluid substance,
first observed by Von Helmont, in 1640.
FIG. 142.
A
B
FIG. 144.
FIG. 143.





C
It was made by Glauber in 1648 from potash and silica, and by him termed fluid
silica. Von Fuchs, in 1825, obtained what is now known as water-glass by treating
silicic acid with an alkali, the result being soluble in water, but not affected by
atmospheric changes.
The various kinds of water-glass are known as—
Potash water-glass.
Soda
Double
Fixing
Potash water-glass is obtained by the melting together of pulverised quartz or
purified quartz sand 45 parts, potash 30 parts, powdered wood charcoal 3 parts, the
molten mass being dissolved by means of boiling in water. The solution contains
284
CHEMICAL TECHNOLOGY.
much sulphuret of potassium, which is removed by boiling with oxide of copper.
The addition of carbon assists in reducing part of the carbonic acid to carbonic
oxide, which disappears during the melting. Soda water-glass is prepared with pul-
verised quartz 45 parts, calcined soda 23 parts, carbon 3 parts; or, according to
Buchner, with pulverised quartz 100 parts, calcined Glauber's salt 60 parts, and
carbon 15 to 20 parts. Double water-glass (potash and soda water-glass), is
prepared, according to Dobereiner, by melting together quartz powder 152 parts, cal-
cined soda 54 parts, potash 70 parts; according to Von Fuchs, from pulverised
quartz 100 parts, purified potash 28 parts, calcined soda 22 parts, powdered wood
charcoal 6 parts. It is further obtained by melting tartrate of potash and soda,
Na} C4H4O6+4H2O, with quartz; from equal molecules of nitrate of potash and
soda and quartz; from purified tartar and nitrate of soda and quartz. It is more
fusible than the foregoing. For technical purposes a mixture of—
K
3 volumes of concentrated potash water-glass solution.
2
""
soda
is employed. By the name of fixing water-glass, Von Fuchs designates a mixture
of silica well saturated with potash water-glass and a silicate of soda, obtained by
melting together 3 parts of calcined soda with 2 parts of pulverised quartz. It is
used to fix or render the colours permanent in stereochromy.
That known commercially as prepared water-glass is obtained by boiling the pow-
dered water-glass with water; and the solution, as found in the market, is known
as of 33° and 66°, the difference being that the first 100 parts by weight contain 33
parts by weight of solid water-glass and 67 parts by weight of water. It therefore
follows that in solutions of 40° and 66°, the water is proportioned as 60 and 34 parts
respectively. Acids, with the exception of carbonic acid, decompose water-glass
solutions, separating the silica as a gelatinous substance; it should, therefore, be
kept in vessels well set apart from volatile acids.
Water-glass is an important product in industry. It is used to render wood, linen,
and paper non-inflammable. The water-glass of 33° is first mixed with double its
amount by weight of rain-water, and is then treated with some fire-proof colouring
matter, as clay, chalk, fluor-spar, felspar, &c. The material to be rendered unin-
flammable is painted with the solution, and again with another coat after the first
has remained twenty-four hours to dry. Wood is thus preserved from being worm-
eaten, from encrustation of fungi, &c. Another industrial application of water-
glass is as a cement; in this it is equal to lime, and, indeed, is known as mineral
lime." Chalk mixed with water-glass forms a very compact mass, drying as hard as
marble; no chemical change is hereby effected; there is no conversion to silicate of
calcium or carbonate of potash; the hardening is entirely the result of adhesion.
Phosphate of calcium treated with water-glass acts similarly. Zinc-white and
magnesia lose none of their useful properties when mixed with water-glass.
Another important application of water-glass is in the painting of stone and concrete
walls, and in the preparation of artificial stone. The latter, first made by Ransome,
is daily meeting with more extended application in England, India, and America. It
is prepared by mixing sand with silicate of soda to a plastic mass, which is pressed
into the required shape, and then placed in a solution of chloride of calcium. By
this means siliciate of calcium is formed, and cements the grains of sand together,
while the chloride of sodium is removed by repeated washings. As cement for stone,
GLASS.
285
glass, and porcelain, water-glass is especially useful. It is also employed in the
preparation of xyloplastic casts, made of wood rendered pulpy by treatment with
hydrochloric acid, and aftewards impregnated with water-glass.
Stereochromy. An interesting and important application of water-glass is in the new
art of mural and monumental painting, termed by von Fuchs Stereochromy (σtepeos,
solid, and xpwµa, colour). In this method of painting the water-glass forms the
foundation or binding material of the colour. There is first to be considered the
mortar or cement ground upon which the painting is to be executed. This groun1
has to receive an under- and an over-ground. It is essential, of course, that the
fundamental groundwork should be of a stone or cement possessing every requisite
for durability. The next, or under-ground, is made with lime-water, and is allowed
to remain for some time to harden. When well dried the water-glass solution is
applied, and allowed to soak well into the interstices of the mortar. After the under-
ground has been thus prepared, the over-ground, or that to receive the painting, is
laid on. This consists of similar constituents to the under-ground, with the exception
that a good sharp sand is used, and the mixture treated with a thin ley of carbonate
of lime. This over-ground of fine cement being nicely levelled, and having dried, it
is thoroughly impregnated with water-glass. When this is dry, the painting is
executed in water-colours. Nothing further is necessary than to fix these colours,
which is effected by a treatment with a fixing water-glass. The colours employed
are:-zinc-white, chrome-green, chrome-oxide, cobalt-green, chrome-red (basic
chromate of lead), zinc yellow, oxide of iron, sulphuret of cadmium, ultramarine,
ochre, &c. Vermillion is not employed, as it changes colour in fixing, turning to
a brown. Cobalt-ultramarine, on the contrary, brightens on the application of the
fixing solution, and is, therefore, a very effective colour. As a decorative art
stereochromy will doubtless attain great importance, the paintings being unaffected
by rain, smoke, or change of temperature.
Orystal Glass. Crystal glass includes all lead-containing potash glass. Crystal glass
was first prepared in England. There are a few difficulties in manufacturing this
glass. The smoke from an anthracite coal fire is injurious to the pure colour of
the glass, so that the melting-pot is provided with a cover; but this addition has the
disadvantage that the temperature necessary to melt the glass cannot easily be
obtained. A larger proportion of alkali must therefore be added, which deteriorates
from the quality of the glass, rendering it liable to after-change. To prevent this
as much as possible oxide of lead is used to make the glass more easily fusible,
and by this means a beautifully clear, transparent glass results. The following
table will give some idea of the proportions of the materials :—
Sand
Potash
•
Broken glass
Minium
300
100
•
300
200
0'45
•
0'60
Sesquioxide of manganese
Arsenious acid
The following mixture is used in the glass houses of Edinburgh and Leith:-
Sand
Potash
• •
Minium..
Lead-glaze..
300
100
150
50
And a small quantity of sesquioxide of manganese (braunite) or arsenious acid.
ต
286
CHEMICAL TECHNOLOGY.
To render the glass fluid, saltpetre is sometimes added, but in moderate quantities.
Dumas recommends sand 300, minium 200, dry potash 95 to 100. On the suppo-
sition that there is no loss during melting, the mixtures contain :-
Silica
57'4
Oxide of lead..
Potash
36°3
57
36
6'3
7
100'0
ΙΟΟ
The whole melting process is included in 12 to 16 hours. The glass is treated in
a manner similar to that already described, but is more easily worked. Benrath (a)
and Faraday (B), found crystal glass by analysis to consist of:
Silicic acid
Oxide of lead.
Potash
Alumina, &c.
:
a.
3.
50*18
51'93
38.11
33°28
11.61
13.67
0'04
99'95
98.88
According to Benrath normal crystal glass has the formula KoPbySi36084 (i.e.,
5K20,7PbO,36SiO2).
Polishing. Crystal glass is either cast in brass moulds or is ground.
Its hardness
admits of its taking a better polish than other glasses. The grinding wheel is of cast-
iron; above the periphery is fixed a vessel containing water and fine washed sand, which
constantly drops upon the wheel, assisting in the cutting. The polishing wheel is of wood,
well served with pumice-powder and water.
Optical Glass.
The preparation of good optical glass, especially in large dimensions,
is a matter of much difficulty. Transparency, hardness, a high refractive power
with perfect achromatism are all required, and must be obtained at the outlay of any
amount of labour. The glass must also be entirely homogeneous, else the light
is not refracted regularly; threads and streaks (stria) are the results of inequality,
and it naturally follows that if these appear to the unassisted eye, they will
seriously affect delicate observations when high magnifying powers are used, as
in telescopes and microscopes. It is an error, however, to suppose that these irre-
gularities arise from impurities; they are rather due to interruptions in heating
and cooling, or to unequally heating and cooling during manufacture. This must
especially be evident in the case of waviness or an undulating structure of the glass.
Crown-glass, free from lead, is not so liable to faults as flint-glass; both these
are employed for optical purposes.
The Rev. Mr. Harcourt's experimental researches as to the best optical glass, communi-
cated to the British Association at the recent meeting at Edinburgh, by Professor Stokes,
show fully what has been accomplished in preparing glass of this order. Mr. Harcourt's
researches were chiefly carried on with phosphates, combined in many cases with fluorides,
and sometimes with tungstates, molybdates, and titanates, owing to the difficult fusibility
and pasty consistency of silicate glasses. The experiments included glasses containing
potassium, sodium, lithium, barium, strontium, calcium, aluminium, manganese, magne-
sium, zinc, cadmium, lead, tin, nickel, chromium, lead, thallium, bismuth, antimony,
tungsten, molybdenum, titanium, vanadium, phosphorus, fluorine, boron, and sulphur.
The molybdic glasses first prepared were of a somewhat deep colour, deteriorating with
age; but at length molybdic glass was obtained free from colour and permanent.
Titanic acid gave results much superior to those obtained with molybdic. Glass made
with terborate of lead agreed in dispersive power with flint-glass; while a prism of this
glass extends the red and blue ends of the spectrum equally with a prism of one part by
GLASS.
287
volume of flint-glass with two of crown-glass. Notwithstanding the great difficulties
arising from striae, Mr. Harcourt finally succeeded in preparing discs of terborate of lead
and of a titanic glass, 3 inches in diameter, almost homogeneous.
It is well known that flint- and crown-glass form an achromatic combination. Flint-
glass is very easily rendered fluid, conducing to the formation of striæ. A variation of
the proportions of the constituent materials, though not producing effects visible to the
eye alone, will strongly striate the glass, rendering it unfit for optical purposes. The con-
stituents must be equally distributed throughout, and this is a great difficulty. The
oxide of lead being of so much greater weight sinks to the bottom, while the lighter con-
stituents float at the upper part of the melting vessel. Usually this is so much the case
that glasses of different specific gravities are obtained from the upper and lower parts of
the melting-pot. Lamy has lately employed thallium flint-glass in the preparation of
optical glass, thallium taking the place of potash. Cl. Winkler substitutes bismuth for the
lead.
Bontemps manufactures flint glass in the following manner :-A glass mass is
prepared of-
White sand
Minium
Carbonate of potassa
100 kilos.
106 ""
43
and placed over an anthracite or stone-coal fire in a small melting oven, shown in
Fig. 145 in vertical, and in Fig. 146 in horizontal section. The oven contains only
one covered melting vessel, B, standing on the bank, A. a a are the grate bars; c
an iron rake, enclosed in a fire-clay cylinder, d, and resting upon the roller, ƒ.
After about fourteen hours the mass becomes equally fluid; and a red-hot rake is
introduced into the vessel by which the several layers of material are intimately
FIG. 146.
FIG. 145.


B
mixed In about five minutes the mass is sufficiently stirred; the iron rod is then
removed, the clay cylinder remaining. This stirring is effected several times with-
out removing the clay cylinder; and the glass is then ready for blowing or casting.
But for optical purposes it is, after the removal of the clay cylinder, allowed to cool
gradually during eight days in an annealing oven. The most perfect pieces of glass
288
CHEMICAL TECHNOLOGY.
are then cut from the interior of the mass. According to Dumas's analysis of a
sample obtained from Guinand, flint-glass consists of—
Silica
Oxide of lead
Lime
•
42'5
43'5
0'5
Potash..
11'7
Alumina, oxide of iron, and
protoxide of manganese
1.8
100'0
The second kind of optical glass, crown-glass free from lead, contains, according
to Bontemps :-Sand, 120; potash, 35; soda, 20; chalk, 15; and arsenious acid,
I part.
Strass. The imitation of precious stones is an interesting feature of glass manu-
facture, and in Egypt and Greece it is an art that has attained to great perfection.
All precious stones, with the solitary exception of the opal, can be imitated arti-
ficially. The chief constituent of these artificial gems is strass, or as it is termed
by Fontanier, Mayence base; and in France artificial gems are mostly known as
Pierres de Strass. This base, then, is colourless, and may be considered as a boro-
silicate of the alkalies containing oxide of lead, this being in larger proportion than
in flint-glass.
Donault-Wieland found colourless strass by analysis to consist of:-
Silica
Alumina
38'1
ΙΟ
Oxide of lead
53'0
Potash..
7'9
Borax
Arsenious acid
}
traces
100°0
This analysis gives the formula-
(3K20,6SiO2)+3(3PbO,6SiO2).
The various gems are imitated by the addition of colouring oxides, the whole of
the materials being ground to a fine powder, intimately mixed, and melted at a
strong heat. The imitation of the topaz is obtained by taking-strass, 1000; anti-
mony, 40; and Cassius's purple, 1 part. The topaz can also be imitated with-
strass, 1000; oxide of iron, I part. The imitation ruby is obtained with 1 part of
the topaz paste, and 8 parts of strass, the whole being melted together for thirty
hours. A ruby of less beauty is obtained with-strass, 1000; peroxide of man-
ganese, 5 parts. A good emerald can be prepared from-strass, 1000; oxide of
copper, 8; oxide of chromium, o 2 parts. The sapphire is obtained from strass,
1000; pure oxide of cobalt, 15 parts. The amethyst from-strass, 1000; peroxide
of manganese, 8; oxide of cobalt, 5; Cassius's purple, oʻ2. The beryl or aqua
marina is imitated by—strass, 1000; glass of antimony, 7; oxide of cobalt, 0*4.
The carbuncle by-strass, 1000; glass of antimony, 500; purple of Cassius, 4;
peroxide of manganese, 4 parts. Much attention has not been paid to the mode
in which the colouring is effected by the metallic oxides; nor have experi-
GLASS.
289
ments been tried with any definite result as to the application of tungstic acid,
molybdic acid, titanic acid, chromic acid, and protoxide of chromium, &c.
Coloured Glass and
Glass-Staining.
Coloured glass may be considered in two classes-that coloured as
a whole, and that only partially coloured. The latter is prepared with such
metallic oxides as will impart to the glass very intense colour; for instance, prot-
oxide of copper, protoxide of cobalt, oxide of gold, and oxide of manganese. This
kind of glass is termed superfine, and is prepared in the following manner :-Two
melting vessels are placed in the oven; one contains a lead-glass, the other the
coloured glass. We will take as an example glass coloured red with protoxide of
copper, which if further oxidised imparts a green colour to the glass. The glass-
blower dips his pipe first into the red glass, and collects a sufficient quantity to blow;
then he dips this into the white glass, and proceeds to form a cylinder or roll, as in
the making of table glass. Superfine glass is known as “outside” and “double,”
or "double layer." In the first case the workman takes a lump of white glass upon
his pipe and covers it with the coloured glass; or, in the second case, he takes up
only a small quantity of white glass, then sufficient of the coloured glass, and again
more white glass. Red glass may be obtained with either Cassius's purple, protoxide
of copper, or oxide of iron as the colouring ingredient. Cassius's purple is used
chiefly for ruby-red glass. It was long thought that ruby-coloured glass could not
be obtained with any other preparation than Cassius's purple, but twenty-five years
ago Fuss showed that chloride of gold was effectual. If glass containing salts of
gold or protoxide of copper is cooled suddenly, the colour disappears; then if again
gently warmed, not quite to softness, the colour suddenly reappears in full splendour.
This phenomenon occurs equally in atmospheres of oxygen, hydrogen, and carbonic
acid. In the preparation of protoxide of copper glass, lead-glass is taken as a basis,
to which 3 per cent. of the protoxide is proportioned. The drawback to the employ-
ment of the protoxide is the readiness with which it becomes oxide, this imparting
a green colour to the glass. To prevent this change iron filings, rust, or tartar is
added, or the glass is stirred with green wood. Copper-glass, as has just been said,
is colourless on cooling, regaining its colour during the process of annealing. Oxide
of iron, known commercially as blood-stone, ochre, or red chalk, is also used to
impart a red colour. Yellow and topaz-yellow are obtained by means of antimoniate
of potash or glass of antimony, chloride of silver, borate of oxide of silver, and by
sulphuret of silver. Oxide of uranium imparts a green-yellow. Blue is obtained
from oxide of cobalt, more seldom by means of oxide of copper. Green results
from the addition of chrome-oxide, oxide of copper, and protoxide of iron. Violet
is obtained from oxide of manganese (braunite) and saltpetre; black, from a mixture
of protoxide of iron, oxide of copper, braunite, and protoxide of cobalt. A beautiful
black results from sesquioxide of iridium.
Glass Painting.
The delineation of figures and scriptural events in coloured glass
dates from, a very remote period. At first the work was merely mosaic, pieces of
coloured glass being inserted in leaden framework. Glass painting was known in
Germany in the middle ages, and soon extended throughout Europe. In the 13th
century, when Gothic architecture became prevalent, glass painting also became
more general, as until then the heavy, round-arched windows were too small to
admit of ornament. But it was not until the 15th century that the heavy outlined
figures were discarded for the more mingled colours of heraldic device, as seen in、
20
290
CHEMICAL TECHNOLOGY.
the churches of Sebaldus and Lorenz, of Nuremburg, in the productions of the
celebrated Hirschvogel family. This style lasted till the 16th century, when the
glass-maker tried the effect of pigments upon glass. Since that time the art has
gradually improved, the improvement at first being most manifest in France and
the Netherlands.
The nature of glass-painting or staining is in principle the following:-When
coloured glass, rendered easily fusible by the metallic oxide it contains, is finely pul-
verised, and laid upon a plain glass surface and heated, it forms a skin, or flash,"
as it is termed, this skin or layer of glass being said to be "flashed on." It is evident
that very brilliant effects may thus be attained. The near surface of the glass
receives the strong shades and colours, the other or distant surface the lighter tints.
White was not employed in the older glass paintings, but is now used in the flesh-
tints, pure white effects, &c. Oxide of tin and antimoniate of potash yield a good
white. For yellow, Naples-yellow, or antimony-yellow, or a mixture of the oxides
of iron, tin, and antimony, or of antimonic acid and oxide of iron, of sulphuret of
silver and sulphuret of antimony, or chloride of silver is used; for red, oxide of iron,
purple of Cassius, and a mixture of oxide of gold, oxide of tin, and chloride of
silver; for brown, oxide of manganese, yellow ochre, umber, and chromate of iron;
for black, oxide of iridium, oxide of platinum, oxide of cobalt, and oxide of man-
ganese; for blue, oxide of cobalt, or potassium-cobalt nitrate; for green, the oxides
of chromium and copper. Two kinds of colours are distinguished, the hard and the
soft. The soft are called varnish colours, are not very easily fluid, forming a kind of
glaze upon the glass. These colours are placed upon the outer surface. The hard or
decided tints are semi-opaque, and are placed upon the inner surface of the glass.
The binding fluid or vehicle is a mixture of silica, minium, and borax, with which
the colour, being previously ground to a fine powder, is intimately mixed. This
mixture is painted on the glass with a pencil, and the glass plate is afterwards fired
in a muffle. Recently volatile oils have been employed as a vehicle, viz., oil of
turpentine, lavender, bergamot, and cloves. The burning-in, or firing, the colours
was formerly effected by placing the glass tablet with dried and pulverised lime in
an iron pan raised to a red heat. But recently the muffle oven has been employed.
The bottom of the muffle is covered to a depth of one inch with dry powdered lime,
upon which the plate of glass is laid, and again a layer of lime. The oven is then
raised equally to a dark red heat. After six to seven hours the fire is gradually
withdrawn, and the oven allowed to cool. The glass is taken out, cleansed with
warm water, and dried.
Enamel. Bone Glass.
Alabaster Glass.
By enamel is understood in glass manufacture a coloured or
colourless glass mass rendered opaque by the addition of oxide of tin. It formerly was
prepared in the following manner :—An alloy of 15 to 18 parts tin and 100 parts lead
was oxidised by heat in a stream of air, the oxide pulverised and washed. The
mixture of the oxides was then fritted with the glass. An enamel-like appearance
is imparted to glass by arsenious acid, chloride of silver, phosphate of calcium,
cryolite, fluor-spar, aluminate of soda, and precipitated sulphate of barium. Bone
glass, so-called, is a milk-white, semi-opaque glass, containing phosphate of calcium
in the shape of white bone-ash, sombrerite, or phosphorite. It is employed for lamp-
globes and shades, thermometer scales, &c. It is made by adding to white glass
about 10 to 20 per cent. of white bone-ash, or a corresponding quantity of mineral
phosphate. After melting the glass is generally clear and transparent, becoming
GLASS.
291
milk-white and opaque during the process of blowing. The colour is finally
developed during annealing. A similar glass to the preceding is alabaster glass, but
the latter is more opaque. It is also termed opal glass, rice glass, or rice-stone
glass, and Réaumur's porcelain. The materials are the same as in the preparation of
crystal glass, of which it may be considered the scum or underlayer of impurities,
though it is really imperfectly prepared crystal glass.
Cryolite Glass. Cryolite glass, or hot-cast porcelain, has recently been manufactured
in Pittsburg. It is a milk-white glass, obtained by melting together
Silica..
Cryolite
67.19 per cent.
23·84
Oxide of zinc .
8.97
""
Fluor-spar or aluminate of sodium may be substituted for cryolite. Benrath
found (1869) in such a milk glass-
Silica
Alumina ..
Soda
•
:
70'01 per cent.
10'78
""
•
19'21
""
100'00
Ice Glass.
Ice glass is made by plunging the mass of glass attached to the end of the
blower's pipe, still at a glowing red-heat, into hot water, in which the glass is opened
and blown out. It then resembles a mass of thawed ice, with a beautifully pellucid
appearance. It is also known as crackle-glass; in France, as verre craquette. Agate glass
is obtained by melting together the waste pieces of coloured glass.
Hæmatinon. Astralite. This is a glass resembling that found in the Pompeiian excavations,
and mentioned by Pliny. It possesses a beautiful red colour, between that of vermillion
and of minium, is opaque, harder than ordinary glass, bears a high polish, and has a
sp. gr. 35. The colour is lost by melting, and by no addition can be recovered. The
glass contains no tin or protoxide of copper as a colouring matter. Von Pettenkofer
assimilated to this glass by melting together silica, lime, burnt magnesia, litharge,
soda, copper hammerings, and smithy scales. A part of the silica in the mixture is decom-
posed by means of boracic acid, and a mass is obtained which, when ground and polished,
exhibits a dark red colour of great beauty. Pettenkofer gave to this glass the term
astralite, from the beautiful shotte-colour of blue or dichromatic tint shimmering through-
out the mass.
Aventurin Glass.
Aventurin or avanturin glass was formerly made only in the Island of
Murano, near Venice, but is now prepared throughout Germany, Italy, Austria, and
France. It is a brown glass mass in which crystalline spangles of metallic copper
according to Wöhler (of protoxide of copper according to von Pettenkofer) appear
dispersed. Fremy and Clemandot have produced a glass similar to aventurin glass, and
which consisted of 300 parts glass, 40 parts protoxide of copper, and 80 parts copper-scale.
The Bavarian and Bohemian glass-houses produce an aventurin glass rivalling the
original. Von Pettenkofer has prepared aventurin glass direct from hæmatinon by mixing
sufficient iron-filings with the molten mass to reduce about half the copper contained.
Pettenkofer surmises, and with good reason, that aventurin glass is a mixture of green
protoxide of copper glass with red crystals of silicate of protoxide of copper, these comple-
mentary colours giving the brown tint. This glass is also well imitated by melting a
mixture of equal parts of the protoxides of iron and copper with a glass mass. The protoxide
of copper appears after a long annealing as a separate, crystalline, red combination,
while the protoxide of iron is lost in the green colour it imparts to the glass. Pelouze
found that by freely adding chromate of potash to the glass materials spangles of oxide of
chromium were separated. He termed this glass chrome-aventurin; it has been
employed by A. Wächter in the glazing of porcelain.
Glass Relief. Glass relief is obtained by enclosing a body of well-burnt unglazed white
clay, moulded to the required form between layers of lead-glass, the result being similar
in appearance to an article in matted silver. Gold matte is imitated by employing a yellow
glass. This branch of their art has been known to the Bohemian glass manufacturers for
upwards of eighty years.
292
CHEMICAL TECHNOLOGY.
Glass.
Filigree, or Reticulated By fibre or filagree glass is understood that kind of glass work
formed of variously coloured or white opaque glass threads, these
threads being sometimes as fine as a single hair. They are generally drawn out from
tubes or sticks of glass of various colours, heated to redness, and formed into sticks, tubes,
or spirals. Two of these tubes are taken, placed together, and blown out into a vessel of
the required form, which is characterised by the conformation of the glass threads in the
stick. From the spiral network thus formed this kind of glass is sometimes termed
reticulated.
Milifiore Work. Millifiore work is a peculiar form of mosaic glass work, in preparation
similar to that of Petinet glass. Small filagree canes of different coloured glass are placed
side by side to form a thick cord or column, the cross section of which appears of a parti-
coloured grain. These cords or columns can be twisted to almost any required form, or
when heated and drawn out the glass threads of various colours of which it is composed
form a single thread of very varied hue and great beauty. These threads again can be
worked into ornaments, or formed into lumps or balls. The best kind of millifiore work
are the paper-weights, often sold at fancy bazaars as Bohemian glass weights-these are
merely lumps or rolls of the many-coloured glass thread placed together, heated, and
finally coated with a film of clear white glass by being for a few moments held in the
white glass melting-pot.
Glass Pearls. There are two kinds of artificial or glass pearls, namely, solid or massive
pearls and blown pearls. The first are known as Venetian pearls, and those made in
Venice are preferred, the export from this city in 1868 representing a money value of
7,755,000 francs. The manufacture is chiefly carried on in the Island of Murano. The
pearls are made from small glass tubes, either white or coloured. Oxide of tin is employed
in the preparation as well as the various metallic oxides for imparting the desired colours.
Solid Pearls. The glass tubes are cut into small pieces or cylinders. The sharp edges of
these cylinders are removed by placing them in an iron vessel brought to a red heat,
the beads being constantly stirred with an iron spoon. Previous to this operation the
interior or hollows of the beads are filled with powdered charcoal. They are then
well washed, dried, and packed. By another mode of preparation the pieces of glass
tubing are placed in a revolving vessel similar to a coffee-roaster. The finished pearls
are generally strung, the charcoal being placed in the interior or tube of the bead to
prevent its closing.
Blown Pearls. The preparation of blown pearls is quite a distinct manufacture. They
resemble the real pearl in form, colour, and surface. Jaquin, a French paternoster or
rosary maker, in the year 1656, remarked that when whitings (Cyprinus alburnus, ablettes)
were washed with water, a residue remained consisting of a beautiful pearly substance.
This was the foundation of the manufacture of the artificial pearl. Jaquin scaled the
fish, mixed the scales with water, and obtained the celebrated "Oriental pearl-essence," or
"Essence d'Orient," a substance identical with Guanin. A small bead of gypsum or
other hardening paste is coated with this mixture, dried, and dipped into molten glass, a
thin film of which adheres.
The pearl is sometimes round, sometimes pear-shaped, or flat. Another method of
preparing the pearls is by means of beads blown from glass tubes of various thicknesses.
These beads or small bulbs are then filled with pearl-essence. To prepare this essence,
say a quantity of 120 grms., 4000 fish are necessary; thus a pound of pearl-essence
requires 18,000 to 20,000 fish for its preparation. The scales are allowed to stand about
an hour in water to permit the slimy matter adhering to them to settle; they are rubbed
down in a mortar with fresh water, and strained through a linen cloth. Thus prepared
the paste is ready for insertion in the glass beads, a little ammonia being added to prevent
decay.
Hyalography. Hyalography, or the art of etching on glass, is due to one Heinrich
Schwankhardt or Schwandard, an artist living at Nuremburg in 1670. It consists of the
following operations :-Powdered fluor-spar is treated with concentrated sulphuric acid in
a leaden vessel; gentle heat is applied, the vessel being covered with the glass plate to be
etched coated with wax, through which the design is traced with a steel etching-needle.
Vapours of hydrofluoric acid (FIH) are evolved, which combine with the silica of the
glass, forming fluoride of silicon, SiFl, and volatilising. The plate is afterwards washed
with warm oil of turpentine. The first practical application is due to Hann, of Warsaw,
in 1829. More recently, Böttger and Brömeis, with Auer, of Vienna, have improved the
processes. The etching-ground used for engraving on metallic surfaces would not in this
case give favourable results. Pül recommends a molten mixture of 1 part asphalt and
I part colophonium, with so much oil of turpentine as will bring the mass to the con-
sistency of a syrup. Etched glass plates have been used by Böttger and Brömeis to print
from instead of steel and copper. In the press the glass plate is backed by a cast-iron
EARTHENWARE.
293
plate. The process, however, has not been practically successful; it is better suited to
the production of bank notes, &c., than engravings, the resulting etchings being hard in
tone. But for purposes of decoration, etched glass is largely used. By the method of
Tessié du Motay and Maréchal of Metz, a bath is made of 250 grms. of hydrofluoride or
fluoride of potassium, I litre of water, and 250 grms. of ordinary hydrochloric acid. Kessler
employs a solution of fluoride of ammonium.
CERAMIC OR EARTHENWARE MANUFACTURE.
Clays and their Application.
Felspar.
3 Si
To the most important alumina combinations found native
belongs felspar. This mineral is one of the chief members of the class containing
gneiss, granite, and porpyhry. Potash-felspar, Os, with 6:54 parts of silica,
18 alumina, and 16.6 potash, is also known as orthoclase or adularia; when sodium
takes the place of potassium, the felspar albite is formed. According to Mitscher-
lich some felspars contain o'4 to 2.25 per cent. of barium. When felspar is under
the influence of water and carbonic acid with changes of temperature, it loses its
silicate of potash, which being washed out, the potash is taken up by plants, and will
perhaps account for some portion of the potash always present in their ash; some
of the silicate is acted upon by carbonic acid, by which the silicic acid is separated
and soluble carbonate of potash formed. In following this decomposition to a con-
clusion, we may surmise that the silicic acid thus set free becomes a constituent of
the opal and chalcedony spar. All clays are essentially silicate of alumina; and in
many instances, as in Devonshire and Cornwall, the change from felspar of the fine
white granite to clay by disintegration is very perceptible. By washing this clay
to free it from quartz and mica a fine white clay is obtained, known as kaolin or
Kaolin, or Porcelain Clay. porcelain clay. Again, by washing with potash ley, whereby the
free silica is taken up, there is obtained, in most cases, a fine plastic mass, consisting
of 1 molecule of alumina, 1 molecule of silica, and 2 molecules of water. The
quantity of free silicic acid varies between 1 to 14 per cent.
The weathering of the felspar may be formulated thus-
or 3Si
I mol. felspar, Si¸O¿KAI, or
gives, under the influence of water,
AIK
} Os
I mol. porcelain clay, SiO HAl, and
I acid silicate of potash,
the latter forming a soluble combination similar to water-glass. Porclain clay occurs in
the following localities:-1. Bavaria: Aschaffenburg, Stollberg, Diendorf, Oberedsdorf.
2. Prussia: Morl and Trotha, near Halle (material for Berlin porcelain manufacture—-
decomposed or disintegrated porphyry). 3. Saxony: near Schneeberg and Mionia.
The first is a weathered granite; the latter, porphyry. 4. Eastern Hungary:
Brenditz in Moravia; near Carlsbad, Bohemia; Prinzdorf in Hungary. 5. France:
St. Yrieux, near Limoges. 6. England: St. Austell, in Cornwall. Weathered granite ;
a mixture of orthoclase and quartz. It is found chiefly on Tregoning Hill, near Helstone.
7. China. It naturally follows that the clay should contain foreign substances; and it is
from the quality and quantity of these substances that the several varieties of clay are
obtained, of course with due reference to the chief constituents-silicic acid and alumina.
The purer clays contain generally the following foreign substances:-Sand, partly as
quartz sand, as silicate of potash, and partly as particles or fragments of undecomposed
minerals; baryta combinations; carbonate of magnesium; carbonate of calcium; oxide of
iron; sulphur pyrites; and organic matter.
Qualities of the Clays.
The Technically Important •For the technical application of the clays the important
qualities are colour, plasticity, and well hardening under heat.
294
CHEMICAL TECHNOLOGY.
Colour.
Naturally clays are white, yellow, blue, or green. Pure clay is white;
coloured clays are the result of several admixtures. White clay contains but a small
quantity of protoxide of iron, and becomes after burning yellow or red; these colours
originating from the organic substances disappear on their being volatilised after many
firings. The coloured clays change their colour during firing, becoming red or red-
yellow. Fine clays are prepared only from those becoming white by continued
burning.
Plasticity. The clay should absorb water readily, forming a tenacious mass, capable
of taking sharp and clear impressions. It is clear that the plasticity of the clays
depends in a great measure on their composition. Sand is the constituent most
prejudicial to plasticity, lime less so, and oxide of iron least of all. Clay pos-
sessing a high degree of plasticity is said to be fat or long, and when in the opposite
condition lean, thin, or short. All shrunk clays, that is, all clays decreased in volume
by burning, are said to be either drawn or burst. The amount of shrinkage depends
of course upon the quantity of water the clay contains; the same kind of clay does
not always exhibit the same shrinkage. Fat clays shrink more than short clays.
The diminution in surface by shrinkage varies between 14 and 31 per cent., the
capacity or solid contents between 20 and 43 per cent. Clay may be burnt so hard
as to give sparks when struck with steel; but its property to form a plastic mass
with water is then wholly lost. Pure clay (silicate of alumina) is by itself infusible,
but by mixture with lime, oxide of iron, and other bases becomes more or less easily
fusible. According to the experiments of E. Richters (1868) the refractory qualities
of clay are least influenced by magnesia, more so by lime, still more by oxide of iron,
and most by potash. Fusible clay obviously is not adapted to the manufacture of
porcelain or such ware as is likely to be exposed to a high temperature. A. fusible
and a refractory clay, when heated together, enter into a mass that does not cleave
to the tongue. By the manufacture of clay ware, then is understood the binding of
certain clays together by means of a suitable flux.
Kinds of Clay.
The clays employed in ceramic manufacture are—
1. Refractory clays: as porcelain and plastic clays.
2. Fusible clays; as potter's clay.
3. Limey clays; as marl, loam.
4. Ochre clays; as ruddle, ochre.
Of these porcelain clay is the most important; it is of various colours, very
tenacious, plastic to a high degree, burns white, and is not fusible in a porcelain-
oven fire. It is ordinarily found in the tertiary formation, almost always accom-
panied by other kinds of clay, by quartz-sand, and by brown coal. For practical
purposes it is important to know that clays of the same strata and of the same pit
often differ largely in their refractory property. This is not only the result of
experience, but of a lengthy series of experiments made by C. Bischof, Otto, and
Th. Richters. The strata near Klingenberg-on-the-Maine, at Coblenz, Cologne,
Lautersheim, and Vallendar-on-the-Rhine, Weisboch in Baden, Bunzlau in Silesia,
Schwarzenfeld near Schwandorf, and Kemnath in Bavaria, in the province of
Hessen, in Saxony, in Belgium, near Dreux in France, and Devonshire and Stour-
bridge in this country, are all celebrated for this clay. The following analyses
give the composition of various refractory clays:-
EARTHENWARE.
295
I.
2.
3.
4.
5.
Silica
47'50
45'79
53'00
63°30
55.50
Alumina
34°37
28.10
27'00
23°30
27'75
Lime
0'50
2'00
I'25
0'73
0'67
Magnesia
I'00
0'75
Oxide of iron
I'24
6'55
I'75
1'80
2'01
Water
I'00
16.50
10'30
10'53
1. Almerode in Kurhessen (crucible). 2. Schildorf near Passau (graphite crucible).
3. Einberg near Coburg (porcelain capsule). 4. Stourbridge. 5. Newcastle (fire-brick).
The composition of the Stourbridge fire-clay will be seen from the following
analyses by Professor F. A. Abel, F.R.S., Chemist to the War Department :--
Alkalies, Waste, &c.
Sample.
Silica.
Alumina.
Peroxide of Iron.
I
66.47
26.26
6'63
0'64
2
65.65
26'59
5'71
2'05
3 4 5 6
65°50
27.35
5'40
1.75
67'00
25.80
4'90
2.30
63°42
31°20
4'70
0.68
65'08
27'39
3.98
3'55
7
65'21
27.82
3'41
3'56
8
58.48
35'78
3'02
2972
9
63°40
31'70
3'00
I'90
The sample No. 9, containing only such a small quantity of iron, is much
superior to No. 1, whose refractory properties may be doubted. The clay is dug
from pits varying from 120 to 570 feet in depth. It is generally found below three
workable coal measures, between marl or rock and an inferior clay. The seam
averages 3 feet in thickness, never exceeding 5 feet, and the middle of the seam
contains the clay selected for crucibles, &c. Pot-clay or crucible-clay only occurs
in small quantities, and costs at the pit-mouth 55s. a ton, ordinary fire-clay only
realising ros. a ton,
Potter's Clay. Ordinary potter's clay also possesses most of the properties of plastic
clay; many varieties form with water a similarly tenacious mass. But potter's clay
is highly coloured, retaining the colour after burning. It effervesces on the applica-
tion of hydrochloric acid, and changes to marl. It follows from its containing large
proportions of lime and oxide of iron that it is fusible, and melts according to
the quantity of these constituents at a higher or lower temperature into a dark
coloured, slag-like mass. It is found in the last formation, or entirely on the
surface of the earth, and sometimes in the tertiary formation. It contains among
other foreign substances organic matter, iron and other pyrites, gypsum, &c.
Walkerite. Walkerite, or Walker's clay, is a soft, friable mass, occurring from the
weathering of Diorite and Diorite slate. In water it separates to a powder, not
forming a plastic pulp. In its powdered condition it is of use as an absorbent of
fat, &c., whence its application to the removal of grease spots in books, &c. It is
found at Reigate in Surrey, Maidstone in Kent, further at Aix-la-Chapelle, in
Saxony, Bohemia, Silesia, and Moravia. It is employed in paper-making, and as
an addition to ultramarine.
Marl.
Marl is a mechanical mixture of clay and carbonate of calcium, containing
sand (sand-marl), and other constituents; that containing lime is called lime-marl;
296
CHEMICAL TECHNOLOGY.
mass.
that clay, clay-marl. In water it falls to powder, and forms a non-adhesive, pasty
With acids it effervesces, whereby more than half the weight is lost. It melts
easily. It is found in the lias and chalk formation. Its chief application is to the
improvement of land.
Loam. Loam may be considered as the result of the mixture of clay with sand. It
is a clay more or less mixed with quartz-sand and iron-ochre, also with lime, when
it assumes a yellow or brown colour, changing on burning to a red. It forms with
water a slightly plastic mass, and is not very refractory. It is found always on the
surface of the earth, and known as common clay, employed in the manufacture of
bricks, coarse pottery, &c.
There is sometimes, but very seldom, used in earthenware manufacture, a mixture
of clay and iron-ochre or hydrated oxide of iron (2Fe2O3,3HO).
Composition of Kaolin. Kaolin in pure condition, and only by means of washing, freed
from coarse substances, quartz, sand, &c., is a mixture of porcelain clay with rocky
residue. Porcelain clay, i.e. the plastic part of kaolin, is always of equal composi-
tion. The composition of kaolin is given in the following analyses:-
་
Silica.
From.
Rocky residue.
Free.
Combined
with Alumina.
Alumina.
Water.
St. Yrieux
9'7
10°9
31'0
34.6
12*2
Cornwall
19.6
I'2
45'3
24.0
8.7
Devonshire
4'3
ΙΟΙ
34°0
36.8
12'7
Passau
4'5
9'7
36'7
37'0
12.8
Aue
18.0
1'7
34°2
34°I
ΙΙΟ
Morl, near Halle.
43°8
4'4
21.6
22.5
7'5
Kinds of Clay Ware.
The
Clay ware is generally separated into dense and porous ware.
dense ware is so strongly heated that half its mass is lost; its fracture is glazed and
conchoidal; it is translucent and compact, being impenetrable to water; and it gives
a spark when struck with steel. Porous clay ware is, in the mass, not glazed, its
fracture open and earthy; and, when not superficially glazed, water freely per-
colates through it. It also clings to the tongue. The burnt mass, whether dense or
porous ware, either remains rough or is glazed.
The following are the essential varieties of clay ware :-
I. Dense Clay Ware. A. Hard porcelain. The mass equal throughout; not indented
with a knife; fine-grained, translucent, sonorous, and white. Fracture, fine-grained, and
conchoidal. Sp. gr. 207 to 2:49. It may be considered as composed of two substances-
namely, as a natural clay or true kaolin, infusible, and preserving its whiteness under a
strong heat; and as a flux consisting of silica and lime, or felspar, with or without
gypsum, chalk, and quartz. The glazing is essentially due to this flux, and not to oxide of
lead or tin. It is characteristic of the manufacture of hard porcelain that the burnings
are included in one operation.
B. Soft or tender porcelain. The mass more easily fluid than hard porcelain. Two kinds
are known :—
a. French porcelain, a glass-like mass, essentially a potash-alumina silicate, prepared
with the addition of clay, therefore erroneously termed a clay ware, and containing lead
similarly to crystal glass.
8. English soft porcelain. The mass similar to kaolin, plastic, remaining white when
burnt (pipe-clay). It is made with a vitreous grit, consisting of gypsum, Cornish stone
(weathered pegmatite), bone-ash (essentially phosphate of calcium), in very varied pro-
portions. The glaze is obtained by pulverised Cornish stone, chalk, powdered fire-clay,
and borax, mostly with, seldom without, the addition of oxide of lead. The glazing is a
second process.
EARTHENWARE.
297
C. Statue porcelain, or biscuit ware:-
a. Genuine and unglazed porcelain.
B. Parisian porcelain, or parian. Unglazed statue porcelain is similar to English
porcelain.
y. Carrard, less translucent than parian, and sometimes of a whiter colour.
D. Stoneware. Dense, sonorous, fine-grained, homogeneous, only in the least, if at all,
translucent, white or coloured.
a. Glazed porcelain stoneware. Plastic, remaining white after burning, slightly refrac-
tory with the addition of kaolin and fire-clay; a felspar as flux; the glaze contains borax
and oxide of lead.
B. White or coloured unglazed stoneware. Wedgwood ware.
7. Common stone-ware (salt-glazed). No fluxing material is employed, but the firing
is increased. Glazed with siliceous soda-alum.
II. Porous Clay Ware. A. Fine Fayence with transparent glaze. The body earthy,
clinging to the tongue, non-transparent, sometimes sonorous; the glaze containing lead,
borax, felspar, &c.
B. Fayence, with non-transparent glaze. The body of a yellow burnt potter's clay or
clay-marl, with non-transparent white or coloured glaze or enamel, containing tin. To this
class belongs majolica, delf ware, &c.
C. Ordinary potter's ware. The body of ordinary potter's clay or clay-marl, red-
coloured, soft, and porous. Mostly glazed with lead, the glaze being always non-trans-
parent. According to the colour of the glaze, the ware is distinguished as white and
brown.
D. Plate, terra-cotta, fire-clay ware, tubes, ornaments, vases, &c. The body earthy;
mostly more or less unequal; always coloured, porous, easily fluid, and slightly sonorous.
Is not usually glazed.
Grinding and Mixing
the Material.
I. HARD PORCELAIN.
Hard porcelain is composed of a mixture of colourless porcelain
clays with felspars as a flux, which sometimes is composed of quartz, chalk, or
gypsum. The porcelain clay, in itself infusible, and becoming in the fire only an
earthy, opaque mass, when intimately mixed with the flux material, melts easily at
a higher temperature than that of the glass oven. The materials of porcelain
manufacture are not found native in such a condition that they may at once be
employed; they must be ground to a fine powder, and this washed to separate the
foreign substances. Pure kaolin, however, is not utilisable in porcelain manufacture,
as it becomes much decreased in volume on the application of heat. It is therefore
mixed with fine washed quartz sand, although this addition somewhat impairs the
plasticity. This mass on treatment with fire would be porous, and it is for the
closing of the pores and to form a binding glass that felspar is added. The propor-
tions in Berlin porcelain, according to G. Kolbe (1863), are 666 parts silica, 28′0
parts clay, 0'70 part protoxide of iron, o'6 part magnesia, and 0 3 part lime.
Proportions of the materials as employed at-a.
a. Nymphenburg; ß. Vienna; y. Meissen:-
a. Kaolin from Passau
Sand therewith
Quartz
Gypsum
··
Broken biscuit ware
B. Kaolin from Zedlitz
Kaolin from Passau
Kaolin from Unghvar
Quartz
Felspar
Broken ware
7. Kaolin from Aue
Kaolin from Sosa
Kaolin from Seilitz
Felspar
Broken ware
..
•
65
4
21
5
5
34
25
56
•
14
6
3
18
18
..
•
36
26
2
298
CHEMICAL TECHNOLOGY.
The mixture of the materials in the required proportion takes place in large vats,
whence the thin pulp is pumped and forced through sieves into another vessel.
Drying the Mass.
After the water is removed from the sediment at the bottom of the
vat or tank, the clay appears as a slime, which has to be dried to the required con-
sistency. The drying or evaporation of the water is effected in wide wooden tanks
exposed to a strong current of air. This is a very general method of drying the
mass, but can only be employed during the summer months on account of the
dampness of our climate. It is not, therefore, sufficiently extensive for large
manufacturers, and consequently other means of drying are resorted to-usually
by means of absorption, the mass being laid on a porous layer of burnt lime,
gypsum, &c. Drying by means of gypsum is expensive, as it soon becomes
hardened, and has to be removed. The mass can also be dried by means of air-
pressure, being in this case placed in flat porous boxes, under which a vacuum
chamber is situated. Talbot's apparatus is formed on this principle. In
Grouvelle and Honoré's system of drying, the water is first partially removed,
by means of draining over gypsum, and the mass is then put into firm
hempen sacks, which are subjected to pressure in a screw or lever press. Pressed
clay has greater plasticity than that dried by artificial heat; but the method is
expensive, as the sacks soon require replenishing, being speedily worn out by the
constant pressure. When the mass is dried by pressure or by absorption, the water
Kneading the Dried in all cases is not equally expelled, and there are also air-bubles,
which must be removed. This is done by kneading and treading the mass with the
feet and hands, and by this means also the plasticity of the mass is improved.
Another method of improving the plasticity is by allowing the moist clay to stand
till it becomes putrid. Stagnant water is often employed. Brongniart explained
the action of this rotting, as it is termed, to be that gases were formed in the body
of the clay, and that by the continuous movement caused in their endeavour to
escape, the finest particles of the material were intimately mixed. Salvétat gives
the following hypothesis:-By the rotting there is formed in the mass a large
quantity of sulphuretted hydrogen gas. This gas effects the reduction of the
alkaline sulphurets to sulphuret of calcium under the influence of the organic sub-
stances, the sulphuret of calcium being set free, a similar action taking place with
the carbonic acid in contact with the air. The bleaching of the mass on exposure to
the air is due to the oxidation of the black sulphuret of iron to sulphate of iron,
which is removed by washing. The decomposition of the felspar constituents may
also ensue from the long-continued action of the water. According to E. von
Sommaruga, of Vienna, the existing sulphates are decomposed by the air into
sulphuretted hydrogen and carbonated salts, and these being removed with the
water, the refractory nature of the clay is improved.
Mass.
The Moulding. The kneading and rotting accomplished, the porcelain mass is taken
to another room to be moulded. This is effected either on a potter's wheel or in a
mould.
The Potter's Wheel. The potter's wheel consists of a vertical iron axis, on which a
horizontal solid wheel is fixed, and caused to revolve by the feet or by steam-power,
the motion in the latter case being regulated by the feet. A lump of clay is placed
upon the wheel, the thumb being placed in the centre of the lump and pressed down-
wards; a hollow is thus formed, which is widened, or the walls continued vertically
according to the shape of the vessel to be made. The constant revolution of the
wheel easily allows of the moulder obtaining a perfectly cylindrical form. By thus
EARTHENWARE.
299
humouring the clay, elongating the vessel, again depressing it, widening it, and by
continued manipulation in this manner, the most exquisite shapes are produced.
To form the ridges or sharp edges of the vessel a small piece of iron, a strip of horn
or wood, termed a bridge, is used. The perfectly formed vessel is cut away from
the wheel by a piece of brass wire.
Paris Forms.
Moulding in Pla-ter of A mould is first taken from the pattern or original object, which
may be of clay, wax, gypsum, or metal. The moulding is performed with dry
material, with clay of the consistency of dough, or with fluid clay. The moulds
must possess a certain amount of elasticity, and be porous in order to absorb the
moisture expressed. For these reasons plaster-of-Paris is generally used. The
mould is taken from the original article in parts, which are trimmed to fit together
accurately; into each part is then pressed sufficient clay to fill the indentations of
the pattern, more clay being added till a proper thickness is obtained. The parts are
then fitted together, and the moulds left for some time. This method of moulding
is sometimes called presswork, and is adapted to all kinds of pottery not of circular
form. Plates, cups, and dishes are also made in a similar manner. A leaf of clay
is rolled out and pressed between flat moulds. Sometimes, instead of rolling, the
clay is beaten out with a wooden hammer covered with leather.
Casting.
Moulding porcelain articles out of thin pulpy clay is one of the most
ingenious arts of the potter. The fluid clay is poured into porous moulds, which
absorb a portion of the water, thereby reducing the pulp to a certain consistency.
The interior pulp remaining fluid is now poured out, and the cast or coating of clay
adhering to the mould allowed to harden. When sufficiently hard the vessel is
taken to the lathe to be finished, or if not of circular form, to the finishing room,
where with sharp tools any required pattern is cut, or handles, spouts, &c., which
have been made in separate moulds, attached.
Preparation of Porcelain
Articles without Moulds.
The finest porcelain is finished by hand, as machinery or
moulds could not give sufficient sharpness to the beautiful flowers and figures sculp-
tured on vases, &c. The flowers, &c., are first prepared in moulds, are then
attached to the body of the article, and finally are finished off with edged tools.
The stalks of the flowers are sometimes formed on wire; and the leaf is first roughly
constructed in the palm of the hand, the furrowing and veining being done after-
wards. The texture of drapery is imitated by means of a piece of tulle, which is
laid on the clay, and allowed to dry. During the burning the tulle is consumed,
leaving the pattern on the porcelain.
Drying the Porcelain.
After the porcelain ware is formed, it is dried for some time at
the ordinary temperature. This is continued till the clay contains no moisture,
that is, until its weight is tolerably constant. During this drying the clay is said
to be in the green state, and possesses a greater tenacity than it has in any of the
former processes.
Glazing. Only very few articles of porcelain ware, generally statues or figures, remain
unglazed; these are termed biscuit ware. All other articles are glazed. The glazings
employed are of four kinds:-1. Earth or clay glazings are transparent, and formed by
melted silica, alumina, and alkalies; they easily become fluid, and melt about the
temperature at which the vessels are baked. This kind of glazing is used for hard
porcelain. 2. Lead glazes are transparent glazes containing lead; most of these melt
at the temperature at which the articles are burnt. 3. Enamel glazes are partly white,
partly coloured opaque glasses containing oxide of tin besides oxide of lead. This kind
of glaze is easily melted, and serves to cover the unequal colour of the under mass.
Lustres are mostly earth and alkali glazes. This class includes the ordinary salt-glazed
ware, as well as glazes containing metallic oxides used to imitate gold and silver surfaces
for ornament merely.
4.
300
CHEMICAL TECHNOLOGY.
Porcelain Glaze.
We will here, however, concern ourselves only with porcelain
glaze. It is necessary that this glaze should melt readily at the temperature at
which the article is fired; that it should be colourless and opaque; that it should
fire sufficiently hard to withstand pressure, grinding, and ordinary cutting. The
glaze is added to the porcelain mass with a flux, so that the melting may be readily
effected. At Meissen the glaze used contains:
Quartz
Kaolin from Seilitz
Lime from Pirna
Broken porcelain
37'0
37'0
•
17:5
8.5
100'0
In the Berlin porcelain manufacture the following glaze is employed :-
Kaolin, from Morle, near Halle
Quartz-sand
Gypsum
Broken porcelain
:
31
·
43
14
12
100
Applying the Glaze.
The glaze can be put on in four ways:—1. By immersion. 2. By
dusting. 3. By watering. 4. By volatilisation. The glaze is either mixed with
the ingredients, or applied superficially by one of the preceding methods. Glazing
Immersion. by immersion is employed in the case of porcelain, the finer Fayence ware,
and sometimes for stoneware. It requires some degree of porosity in order that the
glazing pap may be absorbed. The glazing materials are mixed with water to form
a thin pulp. The articles previous to their immersion are slightly baked to prevent
the clay being softened and running fluid in contact with the water of the glaze.
The articles are dipped into the glaze, which they readily absorb, a coating or thin
layer of glaze remaining on their surface when they are removed from the bath.
The glaze is removed from the bottom of the article immediately in contact with
the substance on which it stands to prevent its sticking. Glazing by dusting is a
Dusting. surface method, and only used for costly ware. The freshly formed and
still damp ware is dusted with lead glaze or minium, a layer being left on the
surface. The powders employed chiefly contain oxide of lead, which combines with
the silica and alumina of the clay mass during the firing to form a glaze. Re-
Watering. cently finely-pulverised zinc blende and Glauber salt have been em-
ployed. Watering is a method of glazing employed for non-porous articles,
such as English porcelain, ordinary pottery ware, and some kinds of Fayence
ware. Glaze of the proper consistence is poured over the articles, the in-
terior sometimes being left coated with a white glaze, while the outside is
again coated with a coloured glaze, as is seen in common brown-ware.
By Volatilisation or Smearing. Glazing by volatilisation is effected by conveying into
the oven a salt or metallic vapour which shall form with the silica of the mass an
efficient glaze. The most general method is applied to ware not requiring to be
baked in fire-clay vessels. Common salt is placed in the oven with green wood for
fuel to form an irriguous smoke. This, the salt, heated to redness, receives, and is
decomposed into hydrochloric acid and soda, the vapours of which fill the oven.
The inside and the outside of the vessel submitted to this process are thus simulta-
neously glazed. Fine stoneware baked in fire-clay vessels may be glazed by the
ignition of a mixture of potash, plumbago, and common salt. During the baking
EARTHENWARE.
301
or firing chloride of lead is formed, which combines with the silica of the clay to
form a thin glass. This method of glazing is in England termed smearing, boracic
acid being employed.
Lustres and Flowing
Colours,
A method of glazing by volatilisation, known as glazing with
flowing colours, is employed for porcelain. It essentially consists in the ignition
of a mixture of chloride of calcium, chloride of lead, and clay, placed in a small
vessel in the firing capsule or firing chamber, and to which some metallic oxide is
added, as cobalt oxide. The oxide is converted into chloride, and combines with
the constituents of the article.
The Capsule, or Sagger. Porcelain ware and superfine earthenware are not exposed,
when burnt, to the free action of the flame, as various impurities, such as ashes
and smoke, would deteriorate the beauty. They are therefore enclosed in fire-clay
vessels, termed in France gazettes, in Germany kapseln, and in England saggers.
These saggers are manufactured of the best fire-clay, with which is mixed a
cement made from broken saggers. First, into each sagger is put a perfectly true
disc of the same material, and upon this the porcelain ware is placed, three knobs
FIG. 148.
FIG. 147.


V
1
or small props projecting from the disc, and keeping the article from contact with
a large surface to which the glaze would cause it to adhere.
The Porcelain Oven. Fig. 147 is a vertical section of the porcelain oven, and Fig. 148
the elevation. The oven is essentially a reverberatory furnace with three stages
302
CHEMICAL TECHNOLOGY.
and five fire-rooms supplied with wood fires. The oven may be considered as a tall
cylinder, surmounted by a cone, in the apex of which is the chimney opening, the
flat vaults by which it is divided being pierced to allow of communication. Both
the stages, L and L', serve for the " strong firing" of the porcelain. The upper
stage, L", termed variously the howell, crown, or cowl, serves for the raw burn-
ing." At the bottom of both the lower stages are built the fire-places, ƒ, leading
by g into the oven. & is the ash-pit, T the opening to the ash-pit closed during the
burning; o is an opening through which fuel is introduced; c c are the openings
admitting of the circulation of the hot gases. P is the door by which the oven is
entered. The ovens are gradually heated first to glowing heat and then to a strong
red heat. At this stage the openings are closed and the oven raised to a stronger
heat, at which it is allowed to remain for a short time. This intense burning lasts
about seventeen to eighteen hours; the oven is then opened, and allowed to cool
gradually for three to four days.
Emptying the Oven and After the oven is cooled, the saggers containing the ware are re-
Sorting the Ware. moved, and the ware taken out. It is then separated into four kinds :-
a. Superfine, containing no blemished ware. b. Medium, the ware slightly inferior in
glaze, &c. c. The chipped and imperfectly glazed ware. d. Waste, or ware so dis-
torted or cracked as to be useless.
Faulty Ware. The chief faults are:-Cracking, from the porcelain not being sufficiently
plastic, from drying unequally, and from unequal heating. Part fusing from a too strong
heat. Air-bubbles causing lumps to appear on the surface of the ware through the
expansion of the air by heat. Spotting, from fragments of the sagger fusing and falling
in upon the ware. Yellow-colouring, from smoke having entered the sagger. The chief
faults in the glaze are:-Blowing, the result of the development of gas by the reaction of
the constituents of the glaze upon each other; also resulting from too strong a firing.
Shelling, or the exfoliating of the glaze.
Porcelain Painting. Porcelain painting is really a branch of glass painting, the colours
being glass-colours, which when burnt in become durable and bright. The
colours employed, technically termed mufile colours, are:-
Oxide of iron, for red, brown, violet, yellow, and sepia.
chromium, for green.
""
"
>>
cobalt and potassium-cobalt-nitre, for blue and black.
uranium, for orange and black.
""
manganese, for violet, brown, and black.
iridium, for black.
""
titanium, for yellow.
""
""
antimony, for yellow.
copper (and protoxide), for green and red.
Chromate of iron, for brown.
""
""
lead, for yellow.
barium, for yellow.
Chloride of silver, for red.
Chloride of platinum, for platinising.
Purple of Cassius, for purple and rose-red.
These colours are mixed with a fluxing material, so that by the melting a silicate
or borate may be formed, yielding a good glaze. Therefore the oxide of cobalt and
the oxide of copper must first be mixed with silicic acid and boracic acid, oxide of
antimony with oxide of lead, &c., to form a blue, green, or yellow colour, because
there are few metallic oxides yielding these colours that are not affected injuriously
by heat, or are by themselves sufficiently easily fluid. The burning-in of the
EARTHENWARE.
303
colours is effected in a muffle, Fig. 149, the opening o, serving as a communication
with the interior, by which the degree of heat may be ascertained; the opening, m,
serves for the escape of the vapours of the essential oils (oil of turpentine, oil of
lavender, &c.), with which the enamel colours are sometimes ground up. Fig. 150
FIG. 150.

FIG. 149.

m
shows the method of heating the muffle. The heating is commenced at a low tem-
perature and is gradually increased to a red heat. From time to time the muffle is
opened till the colours begin to disappear; then the muffle is carefully closed, raised
to a bright red heat, and finally allowed to cool as slowly as possible.
Ornamenting the Porcelain. The gold employed for decorating the porcelain is dissolved in
aqua regia, and precipitated with either sulphate of iron, nitrate of protoxide of mercury,
or by means of oxalic acid. In its application the gold must be intimately mixed with a
flux, generally nitrate of oxide of bismuth. Shell gold is employed, also gold-beaters'
refuse. The article to be gilt must be thoroughly freed from grease, else the gold will not
adhere. The gold powder, finely ground up with sugar or honey, or some such soluble
substance, is applied with a pencil brush. The burning-in is effected in a muffle. The
gold is not melted during the burning, but becomes firmly set upon the article by means
of the flux. After burning the gold does not at once appear bright, but requires
burnishing with an agate tool.
Bright Gilding. Bright gilding differs from the foregoing in requiring no after polishing
or burnishing. It is effected by burning-in a solution of sulphuret of gold or fulminating
gold in balsam of sulphur. When an article is gilded with precipitated metallic gold or a
bright gold preparation, the gilding is secure from injury by handling or scratching with
the finger-nail, &c.
Silvering and Platinising.
Silvering and platinising are usually only in slight requisition.
Metallic silver is thrown down from its solution by means of copper or zinc; the
platinum is precipitated from its neutral chloride by means of boiling with potash
and sugar. The tarnishing of silver on porcelain by sulphuretted hydrogen may,
according to Rousseau, be prevented by placing, before burning, a thin layer of gold upon
the part silvered; the result then is a white layer of gold-silver. Much care is not neces-
sary in this process. The silver and platinum are mixed with basic nitrate of oxide of
bismuth, painted on and burnt in, and afterwards burnished.
Lithophanie. Transparent porcelain is used in the art of lithophanie, or making transpa-
rencies. A thin and unglazed porcelain plate is pressed into a flat gypsum mould
bearing the pattern in high relief. The figures by transmitted light appear in delicately
rounded tones of light and shade. The applications of this art to the manufacture of
lamp-shades, window ornaments, &c., are too well known to need remark here.
¡
304
CHEMICAL TECHNOLOGY.
French Fritte Porcelain.
II. TENDER PORCELAIN.
Tender or fritte porcelain, is distinguished in commerce as of
two manufactures-French and English. The French manufacture, in 1695, was
first carried on at St. Cloud, near Paris, by Morin, who employed a glassy mass
without the addition of kaolin, but containing lead, somewhat similar to crystal
glass. It can, therefore, hardly be considered a porcelain, strictly so called, until
melted with lime and alumina. Thus fritte porcelain is composed of:-1. A glass
mass or fritte, obtained from silica and alkalies. 2. Marl, as a clay constituent.
Chalk, as a lime constituent. The proportions of these constituents are:-
Fritte
Marl..
Chalk
•
75
75
17
8
8
17
The fritte is mixed with the chalk and marl to form a thin pulp, which is allowed
to remain for a month to dry, and then again pulverised. When required quickly
plasticity is obtained by adding soap- or lime-water. Fritte porcelain is burnt
in saggers, generally before glazing. During the burning this kind of porcelain
softens more than the hard, and requires supporting on every side. It is for this
reason generally baked in fire-clay moulds. The ordinary oven is employed. The
glaze for tender porcelain is a kind of crystal glass containing lead. This glaze
is poured over the articles, as they are non-absorbent on immersion. French porce-
lain is similar to cryolite glass or hot-cast porcelain. (See p. 291.)
English Fritte Porcelain. English tender porcelain consists of a plastic clay, so-called
China clay or Cornish stone, a weathered pegmatite, with fire-clay and bone-ash. The
addition of the latter is due to Mr. Spade, in 1802; recently phosphate of calcium,
as apatite, phosphorite, staffelite, or sombrerite, has been substituted. The glaze is
composed of Cornish stone, chalk, fire-brick, borax, and oxide of lead. The article
must be baked before glazing, as the glaze is so much more easily meltible than the
body of the article; and in this second firing lies the difference between the manu-
facture of tender and of hard porcelain. In hard porcelain the melting-point of the
glaze and the body are the same. English porcelain is far less solid and more liable
to crack than the hard; upon the other hand, English porcelain is the more plastic,
and can be produced at a lower temperature in saggers of inferior fire-resisting
qualities, consequently at a less expense. The burning takes place in a stage oven
with anthracite coals, the articles being placed in saggers. The glaze is applied by
immersion. Recently boracic acid has been largely employed in glazing English
porcelain.
Parian and Carrara. Parian is an unglazed statue-porcelain, similar to English porcelain,
but more difficultly fusible, containing less flux and more silica. The colour is a very
slight yellow, the surface is wax-like. Parian was first prepared by Copeland, in 1848,
although the idea was not new, as before this time Kühn, of Meissen, had prepared
statues and medallions of porcelain in imitation of marble. The composition of parian
is very variable; some on being tested yield phosphate of calcium, others silicate of barium,
and again some contain only kaolin and felspar.
Carrara, so named in its imitation of the marble produced from Carrara in Tuscany, is
intermediate to parian and stoneware, is less transparent than parian, and sometimes
whiter in colour.
"
EARTHENWARE.
305
III. STONEWARE.
Stoneware. Stoneware differs entirely from porcelain; it is dense, sonorous, fine-
grained; does not cling to the tongue. It is semi-fused and opaque. Even fine
white stoneware is different from porcelain in transparency, being entirely opaque,
although in some other respects similar. Stoneware is distinguished—
1. As porcelain glazed.
2. As white or coloured unglazed.
3. As common stoneware, salt-glazed.
The fine white stoneware is made from a plastic clay, burning white, and not very
refractory. To the clay is added kaolin and fire-clay with a felspar mineral,
generally Cornish stone, as a flux. The glaze contains oxide of lead and borax, and
FIG. 151.

E
Ε
a
b
O
n
i
a
h
C
d
f
a
FIG. 152.

i
K
Ъ
i
M
~. N.
h
B
h
g
h
C
is transparent. The flux is used in the making of stoneware much more freely than
in porcelain, in the proportion of more than half the weight of the mass. It follows
that stoneware can be burnt at a lower temperature than porcelain. The articles
21
306
CHEMICAL TECHNOLOGY.
are fashioned out of the plastic clay in the same manner as porcelain. Fine stone-
ware is used as a cheap substitute for porcelain, it being much more easily burnt.
White or coloured unglazed stoneware, or Wedgewood ware, is made from a
plastic, slightly refractory clay, kaolin, fire-clay, and Cornish stone, the latter in
the proportion of half the weight of the whole. It is more easily fusible than porce-
lain, requiring a lower temperature in burning. The coloured stoneware is of the
same composition as the white, the colouring being only superficial. Frequently
other coloured clays are used for ornaments in relief. Coloured Wedgewood-ware
is known as Egyptian, bamboo, fine salt ware, fine biscuit, &c.
Common stoneware differs from the preceding in containing no flux, the clay
being semi-fused by the continued action of the fire. To the clay is added fine
sand, or pulverised fragments of stoneware. Chemical and pharmaceutical utensils,
acid tanks, &c., are made of this ware, it being strong and durable. The colour is
generally grey.
Stoneware Ovens.
The ovens for burning stoneware are so constructed that the articles
can either lie down or be placed vertically. Fig. 151 is the vertical section of such
an oven through the line A B in Fig. 152. Fig. 153 is a section through the line
CD, seen from B. Fig. 154 is a section through CD, seen from A. Fig. 152 is the
plan on the line EF, Fig. 151. aa is the arch or vault of the oven, built of clay ;
b, the vessel chamber; c, the fire-room; d, the fire-bars; e, the stok ›-hole;. ƒ, the
ash-pit; g. an air-draught; ii, a pierced wall; k, a pierced back-wall, through
which the flame and hot gases escape into o, serving as a flue. Stone-coal is used as
fuel. Another form of oven in which mineral water bottles are burnt is shown in
FIG. 153.
FIG. 154.


a
α
α
a
Fig. 155. It is constructed on an easy slope; at the lowest part is the fire-room, a.
In the middle of the burning-room is the pierced wall, c, technically terined the
window, through which the hot gases and flame escape into D. The vault and walls,
Band E, are of broken earthenware bound with mortar. A chimney is unnecessary,
the gases escaping through the pierced wall, E, into the air. The burning usually takes
about eight days. The high temperature at which common stoneware is burnt, and
the nature of its components, render glazing unnecessary; but generally a glaze is
obtained with the help of common salt placed in the oven during burning. After the
EARTHENWARE.
307
placing of the salt the openings of the oven are closed for some time, and then a
second quantity of salt is introduced. The silica, with the assistance of the steam,
decomposes the salt into hydrochloric acid and soda, with which it combines. Thus
there is formed on the surface of the ware a glaze of silicate of soda and alumina.
The salt will take up more than 50 per cent. silica, according to Leykauf's experi-
ments; therefore, the more silica the better glaze. An oven of moderate size will
FIG. 155.

E
D
C
B
F
G
require 80 to 100 pounds of salt; the purity of the salt is not a subject of much
consideration. The glaze is colourless, and the vesse lappears the colour of the clay.
Stoneware that is unequally coloured, one part brown, the other grey, has been
brought to that state by the escape of hydrocarbons into the burning-room.
Lacquered Ware. Lacquered ware, known as Terralite and Siderolite ware in northern
Bohemia, and manufactured by the firms of Villeroy and Boch, of Dresden, is an inter-
mediate ware to fine and common stoneware; it has no glaze, but a strong surface colour
of varnish or lacquer. Candlesticks, bowls, flower-vases, jugs, flower-pots, baskets,
butter-dishes, fruit-dishes, &c., are formed from this ware, and baked in saggers in the
usual manner. Great care and attention are required in burning the ware. The colour
or bronze is mixed with varnish thinned with turpentine or linseed-oil, and applied with
a pencil. The ware is then placed in a slow oven; the etherial oils volatilise, and the
bronze colour becomes fixed to the surface of the ware.
IV. FAYENCE WARE.
Fayence Ware. Fayence ware (English fine stoneware) derives its name from the
town of Faënza, in the Italian States, where the ware was skilfully made. In the
9th century the Spanish Moors manufactured fayence in the Island of Majorca,
whence the present Majolica, the slight alteration in the manner of spelling being
accounted for by Dante in his "Tra isola di Capri e Majolica," on the ground that
the older Tuscan writers spell the name of the Island "Majolica." The industry
developed from the 13th to the 15th century; from that to the 17th it culminated,
and then commenced to decline. In the middle of the 16th century Bernard Palissy
introduced the ware known as Palissy-fayence into France. Palissy's celebrated
Pièces rustiques consist of ware ornamented with fish, fruit, vegetables, &c.,
naturally coloured in enamel. The body of porous fayence ware is earthy, and
clings to the tongue. It is opaque, with more or less plasticity, and little or no
sonorosity. It consists generally of plastic clay, or a mixture of this with common
potter's clay. It differs from clay ware in the employment of finer materials, mani-
pulated with greater care. Fine white fayence is distinct from common enamelled
fayence. Fine fayence (semi-porcelain) consists of a plastic clay with pulverised
quartz or fire-bricks, with kaolin or pegmatite and felspar minerals. It remains
white after burning, and is coated with a transparent glaze. The fayence
ware of different countries differ greatly; some are easily fusible, others again are
308
CHEMICAL TECHNOLOGY.
burnt to a high temperature. The composition of the glaze is therefore very varied.
Common lime fayence is a mixture of potter's or plastic clay, marl (clay with
carbonate of lime), or quartz and quartz-sand. It is characterized by containing
15 to 25 per cent. of lime, that, at the low temperature at which common fayence is
burnt, only loses a portion of its carbonic acid. The common fayence ware is thus
easily distinguished from other wares by its property of effervescing when an acid
is poured into a vessel made of this ware. Its fracture is earthy; the colour, con-
sequent upon its containing 2 to 4 per cent. of oxide of iron, a decided yellow, so that
an opaque glaze is employed. The glaze or enamel contains usually oxide of tin,
oxide of lead, alkalies, and quartz. The more oxide of iron and lime contained in the
mass, the lower the temperature required for burning. Fayence, like porcelain, is
twice burnt, first without, and finally with, the glaze. It is burnt in saggers; the
ware is placed in the saggers, and these are piled one upon the other in the furnace,
with a layer of fat clay between each pair. The articles stand in the saggers upon
small tripods in order to expose as small a contact surface as possible. The hard-
burnt ware has next to be glazed. A thin pulp with water is made of the materials
of the glaze placed in a cistern into which the articles are dipped. The glaze usually
consists of felspar (Cornish stone), 'fire-clay, heavy spar, sand, borax, and boracic
acid, crystal-glass, soda and nitrate of soda, white-lead, minium, and smalt. The
composition of this glaze is ordinarily very complicated, but the essential consti-
tuents are silica, boracic acid, alumina, oxide of lead, and alkali. Recently the
Peruvian mineral, so-called tiza (borate of soda and lime), has been employed. The
addition of lead serves to render the glaze easily fusible, while the felspar imparts
the softness characteristic of a lead-alkali glaze.
Fayence.
Ornamenting Fayence is ornamented by-1. Painting; 2. Casting; 3. Printing;
4. Lustring. Painting is usually done with the brush, partly under, and partly
upon the glaze. The glazing oven not attaining so high a temperature as the porce-
lain oven, the colours are not affected by the heat. The colours used are oxide of
chromium, oxide of cobalt, oxide of iron, oxide of antimony, &c. The rose- and
purple-red colours are obtained from gold preparations. The pink colour, carna-
tion pink, was discovered in this country, and is essentially a protoxide of chro-
mium. To make this colour-
Stannic acid
Chalk
ΙΟΟ
34
Chromate of potash
Silica
Alumina
•
3-4
5
I
·
The mass
are well mixed and allowed to stand for some hours in a strong heat.
appears as a dirty rose-red colour, attaining its full brilliancy when washed with
water acidulated with hydrochloric acid. The casting consists in the fayence vessel
receiving a surface layer of coloured clay in any required part, independently of the
colours of the mass. These coloured clays or clay-washes are made of the ordi-
nary fat clays and metallic oxides. The printing is accomplished with the aid of a
thin tissue paper, upon which the pattern is first printed from a copper plate, and
afterwards transferred to the ware. For black, a mixture of forge-scale, manga-
nese, oxide of cobalt, or chrome-black is employed; for blue, oxide of cobalt mixed
with, for bright blue, fire-brick, and for less intense colours, heavy-spar, both of
course being pulverised. This mixture is burnt, the frit ground, and mixed with a
EARTHENWARE.
309
flux of equal parts of flint-glass and fire-clay. Copper plates, in which the pattern
is deeply cut, are charged with colour mixed with linseed-oil; a transfer is then
taken on the fine "pottery tissue" paper, and laid on the ware. By means of a
rubber the colour is caused to leave the paper, which has been previously moistened
with water, and adhere to the ware. The paper is then washed off, and the article
taken to the kiln.
Flowing Colours.
Flowing colours are much employed in ornamenting fayence. The
common fayence or delf ware is coloured blue in this manner by means of prot-
oxide of cobalt mixed with the glaze. When the vessels are taken to the burning-
kiln, a mixture of chloride of calcium, chloride of lead, and clay is also introduced
on a small plate. The protoxide of cobalt is converted into a chloride by combin-
ing with the volatilised materials, and in turn combines with components of the
material of the vessel. By this means the articles obtain an apparent transparency
somewhat similar to the characteristic of porcelain.
Lustres. Some kinds of ware have a second coating-a metallic lustre or glaze—given
to them after burning. Gold Lustre : The different kinds of gold lustre are very similar
and need not be detailed. They are essentially composed of fulminating gold and balsam
of sulphur, the latter prepared by heating linseed oil and sulphur together. Platinum
Lustre: This is obtained by mixing anhydrous chloride of platinum with lavender oil or
balsam of sulphur; also by the well-known precipitation of platinum by sal-ammoniac.
Silver Lustre is either a yellow lustre or a cantharidine lustre, so-called from its simi-
larity in appearance to the wing-case of the Spanish fly (Cantharis vesicatoria). Salvétat
believes that chloride of silver may be employed as a yellow lustre, similarly to gold
preparations. The cantharidine lustre is generally a yellow lustre, the difference being
that it is only used for white grounds, while the former is employed for blue grounds, on
which it appears slightly tinged with green. Copper Lustre is both red and yellow; it is
used for Spanish fayence and Majolica wares. It is chiefly formed by a silicate of copper.
Oxide of lead, or lead-lustre, is merely a lead-glaze. Chloride of silver mixed with lead-
lustre is reduced, the result being a deposit of a gold-yellow or a silver-white colour accord-
ing to the proportion of silver.
Etruscan Vases. The vases of the old Romans were a kind of fayence ware, containing
iron, and formed of a clay decomposed by quartz, only slightly burnt, sometimes unglazed,
sometimes coated with an easily fusible glaze. These vases and articles are celebrated
more for their beauty of form than for any peculiarity in composition, which is very
analogous to the well-known delf-ware of which our table services are made.
Clay Pipes. In the manufacture of clay pipes there is employed the beautifully white
pipe-clay, containing neither iron, sand, nor carbonate of lime. The clay, if pure,
always burns white; but occasionally, when a yellow colour appears, the clay is burned
for a longer time, whereby the oxide of iron colouring the clay is removed. The pipes
are formed in a mould similar in shape to the pipe. A roll of clay is taken, and care-
fully spread out to the length of the pipe. The mould is constructed in two halves,
hinged together like a meerschaum pipe-case, and is generally of iron. The roll of clay
is placed on the lower half of the mould, and the other half is then pressed or screwed
down. A wire is then pushed up the entire length of the stem. The pipe is then taken
out of the mould, and set aside to dry. It is afterwards taken to the oven, where about
a gross of pipes are introduced into cach sagger. The saggers are long clay tubes.
Sometimes the pipes are burnt without saggers. To prevent the pipe adhering to the lips
on account of the porosity of the clay, the end put to the mouth is rubbed with a mixture
of soap, wax, and lime-water.
Water Coolers. The Spanish water-cooling vessels, or alcarrazas, are made of a porous,
unglazed earthenware. The constant evaporation of the water exuding to the outer
surface of the vessel causes the water to be kept cool in the hottest climates. The vessels
are only slightly burnt. According to Sallior, water can be cooled 15° in an alcarraza,
while Sèvres ware only permits of the cooling of its contents in a similar manner some
2° or 3°. These vessels are known in France as hydrccérames. In this country Egyptian
wine- and butter-coolers are very common, while in Egypt, Spain, Turkey, the Indies, and
Americas, they are really necessaries. In Bengal these coolers are made from the mud of
the Ganges. In the Levant they are termed baldaques; in Syria and Egypt collies or
gives, while in many places they are also known as gargoulettes.
310
CHEMICAL TECHNOLOGY.
Common Pottery.
V. COMMON POTTERY.
To distinguish between the different kinds of this ware is extremely
difficult. The manufacture is entirely distinct from the preceding. For the so-
called white pottery, used for culinary purposes, ordinary potter's clay is employed,
and for brown-ware a moderately refractory clay. The natural clays are, as a rule,
too fat to be used without the addition of some other material, generally sand;
besides sand, fire-brick, chalk, charmotte, and anthracite coal-ash. The vessels
are formed upon a potter's wheel, air dried, and then glazed. The employment of
a lead-glaze was but a short time ago unknown in the glazing of this kind of ware.
Ordinarily the mass is white or yellow, sometimes brown-red; the glaze being
transparent, the colour of the body or mass is always apparent. Partly because
the ware is very easily fusible, and partly because a low heat is used in the burn-
ing, the glaze must also be very easily fusible. For this reason a lead-glaze, forming
an aluminium and lead glass is very applicable, and is employed mixed with loam
(clay and sand). The materials are ground and very intimately mixed in a hand-
mill. The lead used is generally a lead-glance. During the burning the lead-
glance is roasted, and the sulphur is driven off as sulphurous acid. The oxide of
lead combines with the silica and alumina of the loam, or mixture of sand and
clay, to form aluminium lead and silicate.
The glazing of the air-dried ware can be performed in three ways; either by immersion,
by sprinkling, or by dusting. By immersion the workman's hands come into contact
with the lead-containing glaze, with detriment both to his health and the adhering of the
glaze if his hands should be greasy. This method is not therefore often employed.
Sprinkling is generally adopted. In dusting, the ware is first immersed in a pulp of fat clay,
and then, while still damp, dusted with the finely pulverised glaze. The danger of this
process is the inhaling of the fine particles of glaze floating in the air of the workroom.
When the oxide of lead is properly proportioned to the silica of the clay or loam, the
resulting lead-glass is not affected by ordinary organic acids. But if the oxide of lead is
not well combined with the silica, it will be dissolved by boiling vinegar. The experiments
of Buchner, A. Vogel, Erlenmeyer, and others, have shown that the insolubility of lead-
glaze is not so great as has been suppose 1, very dilute vinegar in some cases being suffi-
cient to effect a solution. The use of vessels thus glazed may therefore have no little
influence upon the health of a family, and it becomes necessary to consider if there is not
some substitute. All injury likely to accrue from the use of this glaze would be removed
if the potter would but re-burn imperfect ware, or employ ovens of the best construction;
but this is not always the case. Recently the preparation of a glaze free from lead has
been attempted, by employing water-glass, or a mixture therewith of borate of lime.
Burning. The glazed vessels are next taken to the oven. This is generally a reverbera-
tory furnace, 2 to 2 metres in height, and 7 to 10 metres in length. At one end is the
fire-grate, and at the other the chimney. The vessels are burnt without saggers, and are
exposed to the full influence of the flame. The fire is at first kept low for eleven to twelve
hours, and then maintained strongly for four to five hours. The vessels can be removed
from the oven about eighteen to twenty-four hours after being burnt.
VI. BRICK- AND TILE-MAKING, &c.
Bricks. This manufacture may be said to include brick-making, tile-making, and
the manufacture of terra-cotta goods, and must not be confounded with the ancient
Egyptian method of making air-dried bricks, still pursued for some minor purposes.
In order to the better comprehension of the methods of brick-making, we will first
consider the preparation of the material. This may be divided into—
The preparation of the clays;
The moulding of the brick;
a. By hand.
B. By machinery ;
The burning of the dried brick.
EARTHENWARE.
311
Terra-Cotta. The term terra-cotta ware generally includes the burnt, unglazed
yellow or red clay ware, and also tiles, employed in building and architectural
ornamentation. The preparation of this ware is almost entirely mechanical, and
does not call for any further elucidation in this work than will be found in the
following pages descriptive of the class of manufacture to which it belongs.
Brick Material.
Various clays are used in brick-making. Usually those only are
selected that will form a brick capable of bearing a considerable strain. In the
burning a test-brick is employed, which is removed from time to time to see the
progress of the fire, to prevent the over-burning of the bricks, or the lowering of the
fire till the bricks are sufficiently burnt; but this brick must not be confounded
with another test-brick for the following purpose. A brick is made of any new clay
to be tested, and is set apart in an active kiln, being burnt at the same temperature
as the bricks of this kiln afterwards sent into the trade. By the qualities of this
test-brick the nature and worth of the new clay is judged. A batch of bricks should
be composed of clays that may all be burnt at the same temperature, else very
unequal results will follow; some bricks will be under-burnt and some over-burnt,
while only those bricks to the clay of which the temperature is adapted will be of use
commercially. A brick-clay containing much carbonate of lime can be burnt at a
very low temperature, and indeed bricks so composed are very solid, and have great
durability. Brick-clays often contain felspar, mica, hydrate of oxide of iron, phos-
phate of iron, besides organic matter. When these are not in large quantities their
presence is not detrimental. Mica and felspar with oxide of iron act as fluxes, and
in known quantities are useful rather than pernicious. Flint stones, large pieces of
carbonate of lime and gypsum interfere with the easy applicability of brick-clays.
Sulphur pyrites render clays unsuited to the manufacture of bricks, as the sulphuret
of iron remaining in the brick after burning oxidises in the air to sulphate, which in
a short time weathers out and renders the brick brittle. In the Netherlands, in the
Thames near London, on the banks of the Ganges and Níle, in the mouths of rivers,
and in nearly all clays exposed to the ebb and flow of water, is found an admirable
material for brick-making. Since 1852 a mixture of lime, river sand, and water has
been extensively used as a brick material, and for other building purposes.
Preparation of the Clays. The excavating of the clay for making bricks is carried on in the
summer or spring. The clay is placed in not too high a layer, and allowed to weather.
It is very advantageous if, during the weathering, a frost sets in. The clay is allowed to
remain thus exposed to atmospheric influence until it becomes boggy or marshy. In this
condition it is brought to a tank dug in the ground, 4 metres long, 2 metres broad,
and 13 metres in depth, where it is mixed with about as much water as will stand to a
height of 6 centimetres in the tank. So soon as the clay is thoroughly saturated it is
treadled, that is, the brick-maker fastens boards or wooden shoes to his feet, and care-
fully treads over the clay, picking out all the flints, &c., which resist the passage of his
foot to the bottom of the layer. This process is repeated two or three times. Sand is
then added to the clay. If the clay is fat the mixture is proceeded with; but if it is a
poor clay it is advantageous to wash out a portion of the sand. This may be affected in
two ways. The ground-tank just described may be inundated with water, and the sand
allowed to settle to the bottom; or the mixed sand and clay is placed in a large wooden
tub with a hole in the side near the bottom stopped with a plug. When the water has
thoroughly impregnated the clay it is let off, carrying part of the sand with it. Or the clay
is stirred with the water to a thin pulp, and allowed to run out of the wooden cistern
into a ground tank, where, with the water, the sand settles to the bottom. London clay,
being mostly alluvial, has to be very carefully treated to free it from flint stones, &c.;
it is afterwards mixed with ash or sand.
pug"
The "treading" of the clay is at the present time performed in mills, termed “
mills and “washers." At the late International Exhibition (1871) several machines were
312
CHEMICAL TECHNOLOGY.
exhibited for performing the whole process of brick-making continuously. Among these
was the three-process brick-making machine of Messrs. Clayton, Son, and Howlett, of
the Atlas Works, and combining at one operation crushing, pugging, and brick-making.
The rough clay is thrown into the hopper of the machine; in this hopper revolves a
shaft, upon which are keyed several small knives to cut up the clay previously to its
being crushed. It next passes through a pair of crushing rollers, and these effectually
reduce any stones or hard lumps of clay which may enter. The clay, thus partially
prepared, next passes into a horizontal pugging or mixing cylinder situated beneath,
where it is mixed by the pug-knives fixed upon the central shaft. The knives force the clay
towards the further end of the cylinder, where it is received by rollers and forced through
the dies, forming a smooth bar of clay of the width and depth of a brick. This bar is
cut into the required lengths by wires. The machine is capable of producing 20,000 to
30,000 bricks per diem, and is, perhaps, the best of its class. Mr. Bawden has constructed
a machine in which no rollers or crushers are employed, the clay being turned out as
wet and as soft as in hand-moulding. One horse will pug the clay and mould from 12,000 to
15,000 bricks per day. It consists of a square pug-mill, through which runs a vertical shaft
bearing pug-knives. On the top of this shaft, above its bearing, is attached the horse-pole,
which gives motion to the whole machine. Upon the lower end of the shaft, which
passes through the bottom of the pug-mill, is a wheel having two cams, on which two
rocking arms work. One arm presses the soft clay through a grating into a six-brick
sanded mould, and the other arm is connected to a slide for pushing the empty sanded
moulds under the grate, the empty mould at the same time pushing the full one out.
Among the best Continental machines are those of Henschel of Cassel, and of Karrens.
Moulding the Brick. The moulding of the brick by hand is a very simple matter. A
mould of wood or cast-iron sufficiently large to allow for the shrinkage of the
material during burning is usually employed. Fig. 156 shows the plan (B), and the
section (A), of the mould. Sometimes it is made so that two bricks can be
moulded at the same time, Fig. 157. The moulder takes a ball of clay and places it
in a sand-strewn mould, pressing it well in. Then with the striker, A, Fig. 158,
he removes the superfluous clay. The mould is then emptied, and the brick placed
FIG. 157.
FIG. 158.
FIG. 156.
A D
B
B
A
by a child on a barrow, to be taken to some other part of the brick-field, to be sun-
and air-dried. The air-dried bricks are then taken to a kiln to be burnt. In many
cases the bricks are dried by artificial heat in sheds, the floors of which are heated
by fires. A gang of labourers, numbering five to ten persons, can at the maximum
produce only 1000 bricks per day.
Brick Moulding by Machinery. The moulding of bricks by machinery is daily becoming
more general. A moulder, no matter how experienced, has never been known to pro-
duce more than 6000 bricks in a day, and a continuity of this labour would be most
improbable. Where there is a large demand, it becomes necessary to produce
30,000 bricks per day regularly, and this can be done by machinery, without
employing a large number of hands. Further, the consumption of fuel in the
machine can at once be stopped, or regulated to meet the demand, while a large
number of workpeople cannot always be dealt with so satisfactorily to the well-
meaning employer. But the machine engrosses a large capital that is not always to
be invested, whereas a number of hands may be paid from the result of their labour,
if the demand is good. It therefore does not always happen that machinery can
compete with hand labour in this particular, as there are, in this trade especially,
EARTHENWARE.
313
many makers who pay as they receive, sending out the bricks as soon as they
are burnt. The machines constructed may be classed as follows:-
1. Those in which the brick is moulded or finished as by hand.
2. The machines in which the moulding proceeds uninterruptedly.
3. Those in which the brick is cut out of a cake of clay.
4. Those in which a band or stream of clay of the length and breadth of the
brick is cut by means of knives or wires to the requisite depth.
I. The machines of the first class, imitating the motion of the moulder's hands,
are constructed of an iron mould, with machinery or arms having a to-and-fro
motion, somewhat similar to a shuttle in a loom. Such a machine is that of Carville
of Issy, near Paris (Fig. 159). The brick material flows from the pug-mill, A, under
the press roller, B, which is supplied with water from the reservoir, c, to prevent the
clay adhering. Sand is next spread over the clay from D. The clay now arrives
FIG. 159.

F
D
H
J
M
N
B
A
K
I
under the pressing apparatus worked by the arm, F, and counterpoise, G. The bricks
then pass away on the endless band of moulds, 1, to which motion is imparted by
means of the revolving arms, JJ. The bricks in the passage of the moulds over
these arms are shot out, the chain of moulds passing through the tank of water, N,
and thus being cleansed. M is a box to receive the waste clay, which is taken to the
M
FIG. 160.

M
M
pug-mill. Fig. 160 is an enlarged view of the chain of moulds; M M being the plan,
and the lower figure the side view.
II. The second class of machines are very similar to the foregoing. Instead
of the pressing apparatus, a roller is substituted, which presses the clay into the
314
CHEMICAL TECHNOLOGY.
moulds as they pass under it. The moulds sometimes form the periphery of a large
circle in the horizontal plane, as by this means the operation can be going on under
several rollers at the same time.
III. The machines of the third class differ from the preceding in that the mould
descends upon a cake of clay of the required thickness. This kind of machine
is generally used in the manufacture of ornamental bricks, as by substituting other
moulds any desired pattern may be produced.
IV. The machines of the fourth class, in which a band of clay is divided in cross
section, may be best considered under two subdivisions, the one containing those
machines in which the clay is forced through an opening of the proper size, the other
those in which the clay is pressed by rollers into a band of the required dimensions.
The separation is effected either by a knife or by cutting wires. By a method similar
to the first process, drain pipes are manufactured. The machine of Terrasson-
Fougères is a very fair example of the older system of rolling the clay. An endless
band, B, conveys the clay under the press-roller, A, Fig. 161, the motion being
FIG. 161.

D
C
B
A
continued by the rollers, D, and the clay kept to the required breadth by the guides,
c. Fig. 162 shows the cutting apparatus mounted on a strong timber framework, G,
and also on wheels for the removal to any part of the shed or field. It will be
readily seen from the woodcut how the copper or iron wires kept taut by the weight,
F, sever the band of clay.
Fig. 162.

F
O
Bricks from Dried Clay.
Pressed bricks are bricks pressed from dried clay in which the
natural moisture of the clay is all that is employed to render the brick coherent. The
pressure must, therefore, be considerably more than that used in the making of moist
clay into bricks; but pressed bricks are much more solid and firm than moist clay bricks,
a smaller number making a more secure wall. One of the most general machines
for making this kind of brick is that of Nasmyth and Minton, in which a peculiar form of
EARTHENWARE.
315
eccentric sets the moulds in action. The same movement of the primary axis pul-
verises the clay, and causes it to be forcibly compressed into the mould. With this
machine and with that of Julienne, who has recently made some improvements, 4000
bricks can be made daily with the labour of a man and boy.
The Burning of the Bricks.
The burning of the air-dried bricks or tiles is carried on in
ovens or in kilns. The ovens are either open ovens, similar to a blast furnace,
or vaulted, or ovens in which the burning is continuous. The fuel is partly wood,
FIG. 163.
FIG. 164.

N
7
J
K
C
INN
F
D
N

M
REIS
J.1
C
B
H G
HB
H
A
A
partly turf, brown coal, and anthracite or stone-coal. From the many forms of
brick-kilns and ovens, the following are selected as best conveying a clear idea of the
process. Fig. 163 is a stage-oven, fuelled with wood, and consisting of three
FIG. 165.
I
H
B
B
FIG. 166.

A
KROKETFERTIL.
ANNETIKDIELKA PIUBETTI
P
0
0
BELIU
chambers lying one above the other, A, B, and c. These floors can be heated in rota-
tion. The furnace D, fed through the door, F, gives a great length of flame, which
passes through the pierced wall, I, into the chamber, A, and thence through the
B
316
CHEMICAL TECHNOLOGY.
furnace, H, fed through the door, G. The flame from this hearth passes to the upper
chamber, c, passing through J and the pierced wall, K, and eventually by L to the
chimney, N. Fig. 164 is another section of this furnace. Fig. 165 is a plan of the
middle stage. This kind of oven effects a considerable saving in fuel, as bricks can be
burnt in all the stages. One of the most economical ovens burning wood fuel is shown
in section in Fig. 166, and in plan in Fig. 167. There are three fire-places, of which P
FIG. 167.

Manabaininfarinadashoðana
B
is the middle one. The fire-place has no grating, but is vaulted in by a series of iron
bars, ooo, through the interstices of which the flame passes into the chamber, B B,
open at the top. The bricks to be burnt are placed upon the bars o o o transversely,
spaces being left for the passage of the flame and hot gases. It will be seen that this
method of burning is much more expensive than the foregoing, owing to the
amount of heat wasted; while wood as a fuel is naturally more expensive than
FIG. 168.
FIG. 169.
B

с

G
A
ستا
F
AA
stone-coal, to produce the same amount of heat. With the form of oven designed by
Carville, and shown in Figs. 168 and 169, 80,000 bricks can be burnt with 160 hecto-
litres of stone-coal. Thus, as I hectolitre of stone-coal weighs 80 kilos., and
as 100 kilos. of coal cost 3 francs 12 cents., the burning of the 80,000 bricks can be
effected at a cost of 400 francs (£16). Stone-coal may be burnt in the oven shown
in Fig. 170. The capacity of this oven is limited only by the enclosing walls, B B, of
thick masonry. The bricks to be burnt are placed upon the sole of the oven, c,
EARTHENWARE.
317
which is constructed to admit of the free circulation of the products of combustion.
Fig. 171 shows the method of placing the bricks in the oven; and Fig. 172, a plan,
the two hearths, D D.
.D
FIG. 170.
A
FIG. 171.
A
A
FIG. 172.



Many experiments have been made with the view of combining the burning of
lime with the burning or baking of the bricks. Figs. 173 and 174 show an oven
built for this purpose. The sole of the chamber, A, is covered with limestone, which
is burnt equally with the bricks placed above it. The draught is regulated by
the dampers in the chimney, B, and by the openings, c. The six fire-rooms are sepa-
rated from each other by the blocks of strong masonry, D and G.
in the furnace, E, under which is the ash-pit, F.
FIG. 173.
B
The fuel is placed
FIG. 174.

F
效
​A
A
ES
F
F
F
Annular Kilns. The circular or annular kilns of Hoffmann and Licht, are much used.
These ovens are in plan in the form of a ring, capped by a chimney. In each oven
there are a number of chambers in which the bricks are stacked. One of these
chambers is filled with what are termed green bricks, that is bricks fresh from the
field. The fire being applied, the steam passes off to the chimney. The second
chamber is then filled with bricks; and when the steam has passed off from the first
chamber, the products of combustion there are admitted to the second chamber
through fiues in the partition wall. This process is repeated with each chamber in
succession. As soon as the bricks are burnt the door and flues of the chamber are
opened to admit the cold air; when cold the bricks are removed, and green ones
supplied in their place. It is clear that by this means there need be no interruption
in the burning; and also that—
318
CHEMICAL TECHNOLOGY.
a. As the doors and flues are opened in the chamber in which the bricks have
been finally burnt, the air entering is highly heated.
b. The effect being to augment the heat of the next chamber; while
c. This heat can be so proportioned out to the unburnt bricks as to render only
a very short actual firing necessary.
The saving of fuel by the use of these kilns must be evident. Also from the con-
tinuity of the firing, which in practice is never allowed to go out, the ovens or
chambers never get perfectly cold, and are consequently soon re-heated.
Field Burning.
In contrast to the permanent kiln is the field-kiln, in which bricks or
tiles are burnt at the same place that building is going on, or where a sufficiency of
brick-clay is likely to yield a good return. Bricks burnt in these temporary kilns
are termed field-bricks. The fuel employed is either turf, wood, or stone-coal. When
turf or wood is used, the bricks are stacked similarly to the method employed in
ovens in which these fuels are the firing materials. Flues are constructed in these
kilns of the bricks themselves set in a thin layer of lime; while the wind-side of the
stack is covered with hurdles thatched with straw. 50,000 bricks can thus be burnt
at one firing. The flames and hot gases find their way hither and thither in the
stack, and finally escape at the top. By the time that the outer bricks are hot, the
interior of the stack or kiln has reached a very high temperature. When coal is
employed the bricks are laid alternately with a layer of coal, a layer of lime serving
as an outside cover, in which draught holes are made to regulate the burning.
When the kiln is built the firing is commenced, and gradually extends to the
several layers of coal until all is burnt. The kiln, consequently upon the con-
sumption of the coal, falls or sinks together, a matter of no importance.
Dutch Clinkers.
Hollanders, or Dutch clinkers, are a very hard, semi-glazed brick, of a
green or dark brown colour, and possessing the property of not absorbing water.
Roofing and Dutch Tiles. For the manufacture of tiles a better and more carefully selected
clay than that for ordinary bricks is employed. While "treading" is much used
in the making of bricks, a mill is always considered necessary for tiles. As a rule they
are burnt at the same time as bricks; the upper part of the oven being sufficiently heated
for the purpose, owing to their thinness. When it is desired that the tiles should be of a
grey colour, there is added to the fire, while the tiles are at a red heat, a quantity of leaves
and damp twigs. By this means large volumes of smoke are disengaged, and pass into
the interior of the kiln, where the pores of the tiles absorb the carbon, which imparts the
grey colour remaining on cooling. Similarly the dark green colour results from the
reduction of the peroxide of iron to black oxide and protoxide. Flat tiles are mostly used
for paving purposes. Roofing tiles are made in many shapes; some with a nose or pro-
jecting piece, with a hole through which a nail passes to fasten the tile to the rafters;
others without this protection, and with a couple of holes simply. Ridge tiles form the
capping of pointed roofs and dormer windows, &c.
Drain and Gutter Tiles. The use of hollow tiles and bricks dates from a very remote
period. Vaulting tiles are no more than hollow bricks or tiles, employed to reduce the
weight of upper parts of large arches or masses of brickwork; they are 21 to 24 centi-
metres in height, and 9 to 13 centimetres in diameter, with the middle hollow and hard-
burnt. A similar form of pipe is used for draining land, &c. For some purposes, bricks
are constructed hollow through their width and not through the length. The advan-
Lages of hollow bricks where they are applicable are:-1. That 60 to 70 per cent. of
materials are saved. 2. That they materially reduce the pressure by decreasing the
weight of superincumbent masonry. 3. They dry more equally, and admit of good ven-
tilation. 4. They can be baked at a lower temperature, with a saving of 20 to 30 per
cent. of fuel. 5. The cost of transport is less consequent upon the reduced weight.
Figs. 175 and 176 show two kinds of hollow tiling.
Floating Bricks. Floating bricks, or bricks sufficiently light to float upon water, are of
very ancient date. Posidonius, and after him Strabo, state that a peculiarly argillaceous
earth was brought from Spain, which was used to polish silver, and from which bricks
could be made that would float upon water. Further, that these bricks were made in
several parts of Asia, and on an island of the Tyrian Sea. Vitruvius Pollio thought
EARTHENWARE.
319
these bricks to be made of a very light unknown stone; and Pliny likens it to pumice
stone. But the secret remained hidden for a thousand years, until Giovanne Fabroni, in
1791, after many experiments, succeeded in producing a brick that would remain on the
surface of water. The material employed was fossil meal, found near Santafiora in Tus-
cany. It was capable of combining with lime mortar, resisted water, and was unaltered
by variation in temperature. The strength of these bricks was scarcely inferior to that
of ordinary bricks, and greatly more in the proportion of their weight. Fabroni, as an
experiment, constructed the powder magazine of a wooden ship of these bricks; and the
vessel, being set on fire, sank before the explosion of the powder. About the same time,
FIG. 176.
FIG. 175.


Faujes, of Coiron, France, found a fossil meal possessing the properties of that found in
Tuscany; and in 1832, the labours of the Count de Nantes, and of Fournet, a mining
engineer of Lyons, found an application for these bricks. The powder magazines,
the cooking-galleys, the hearth of the steam-engine, the flues, the spirit-room on board
ship can all be made of these bricks, and the chances of fire reduced. This kind
of brick is also useful for the vaults of ovens, &c., in which a high temperature is main-
tained, as they are infusible. Kützing found that these bricks contained immense
numbers of the microscopic siliceous shells of infusoria. While an ordinary brick
weighs 2.70 kilos., the weight of an equal bulk of this infusoria clay is only 0·45 kilos.
Coated with wax it swam like a cork. The strongest porcelain-oven-fire was without
effect upon it. By the addition of clay or lime the firmness and tenacity of an ordinary
brick was obtained.
Ordinary porous bricks are made by adding to the clay, coal-dust, saw-dust, turf, tan,
&c. Light bricks were used for building purposes in Nuremburg in the 14th and 15th
centuries. Chimneys were built of them. In Southern Bavaria, a light brick made from
a mixture of turf and sand lime has been in use for many years.
Fire-Bricks. Fire-bricks, or bricks made with fire-clay, are employed instead of
ordinary bricks in the construction of furnaces, and all places exposed to an
exceedingly high temperature, which would melt the common brick. These bricks
contain silica and alumina, but little or no lime, protoxide of iron, or alkalies;
while the clay, to prevent contraction in burning, is mixed with already burnt
clay, sand, carbon (coal, coke), &c.
The process of manufacturing fire bricks at Stourbridge is so admirably described
in Lieutenant Grover's "Report on Fire-clay Goods" in the International Exhibi-
tion of 1871, that the particulars may be quoted in extenso.
"The clay," he says,
"is firstly exposed in spoil heaps over as large an area as can be secured, for from
3 to 18 months, according to the state of the weather. The action of frost, as with
ordinary brick earth, is of great service in disintegrating the compact tough lumps of
clay, and in dry weather the clay is frequently watered. In very wet weather, a
3 months' exposure will suffice for its proper mellowing' or 'ripening,' and it ulti-
mately slacks and falls to pieces. When new, it is termed, in the local phraseology,
'short and rough;' after due exposure it becomes 'mild and tough.' On some of
the works the spoil heaps of clay contain over 10,000 tons, and it is estimated that
7 tons measure about 6 cubic yards. After sufficient weathering, the clay is ground
320
CHEMICAL TECHNOLOGY.
6
in a circular pan by two rollers or cylindrical stones, shod with iron rims 24 inches.
thick, and weighing from 2 to 3 tons a-piece. After being ground, the clay is car-
ried on an endless band to a 'riddle' of about 4 or 6 mesh to the inch for fire-bricks,
6 or 10 for fine cement clay, and 12 or 14 mesh to the inch for glass-house pot-clay,
the larger sized mesh being used for the sifting of the clay in wet weather. The
large particles which will not pass through the 'riddle' are carried back on an end-
less band to the pan, and there re-ground. As a general rule, it is only for very
large fire-brick lumps, that re-ground pots, crucibles, or bricks-locally termed
grogg'
are added to the clay before grinding; and fire-cement clay is always
ground pure. After passing through the riddle' the clay is tempered, or brought to
a proper degree of plasticity by the addition of water. It is then thoroughly stirred
and kneaded in a circular cast-iron pug-mill, by revolving knives projecting from a
vertical shaft driven by steam-power. The clay is forced down by the obliquity of
the rotating knives, and streams slowly from a hole near the bottom, whence after
being cut by wires into the proper forms, it travels on in an endless band to the
moulding sheds. The bricks are then moulded by hand in the usual manner,
and dried at a temperature of 60 or 70 degrees, in sheds about 120 feet long and 30
feet wide, beneath whose floors run longitudinally two flues. In fine weather, how-
ever, the sun's heat is made to economise fuel. The bricks are burnt in circular-
domed kilns or cupolas, locally termed ' ovens,' where they remain for from eight to
fourteen days, being fired with the real intensity of flame or white heat, for about
four days and three nights. They usually require seven days to cool down. The fire
s slowly increased and gradually lowered, the time of burning being regulated
by the kilnman in charge, who inspects the baking bricks from time to time through
holes in the domed roof of the 'oven.' The chimney stack is on the outside of the
kiln, and the flame burns with a down draught, descending through holes in
the floor, the fire-holes being merely openings left in the thickness of the wall of the
kiln, and protected from the wind by buttresses long enough to allow room for
the firemen to attend the fires. The coal is of course obtained from the pits which
provide the clay. Most of the kilns hold each 12,000 bricks, but some are large
enough to contain each 30,000 or 35,000 bricks, the capacity of a kiln being roughly
calculated upon the assumption that ten bricks require one cubic foot of space in
the kiln."
6
Some analyses of fire-clay were given when treating of the different kinds of clay.
Several analyses of fire-bricks are as follows:-
I.
2.
3.
4.
5.
Silica
63'09
88.1
88.43
69'3
77.6
Alumina
29'09
4'5
6.90
29'5
19'0
Lime
0°42
I'2
3°40
Magnesia
0.66
2.8
1
Oxide of iron
2.88
6.1
1'50
2°0
0'3
Potash ..
I'92
I
Soda
0'31
Titanic acid..
2.21
100'00
ΙΟΟ Ο
100'00
ΙΟΟ Ο
100'0
1. Clay from Dowlais. 2. Brick from copper-smelting furnace in Wales. 3. In Pem-
broke. 4. Brick from a blast-furnace. 5. Brick from a reverberatory furnace.
EARTHENWARE.
321
Dinas bricks are made from material obtained from the Vale of Neath, in Glamorgan-
shire; but they have been imitated in Germany by a mixture of pure quartz-sand with
I per cent lime. Dr. Siemens, F.R.S., says of these bricks-"Welsh Dinas brick, con-
sisting of nearly pure silica, is the only material of those practically available on a large
scale that I have found to resist the intense heat (4000° F.) at which steel-smelting furnaces
are worked." Messrs. Martin Brothers, of Lee Moor, Plympton, have made some bricks
from the refuse of kaolin, or china-clay, mixed with quartz-sand, carefully selected and
washed. The kaolin is found in Cornwall and Devonshire, and is produced by the disin-
tegration of pegmatite or felspathic granite, under the action of the atmosphere; it then
becomes a basic silicate of alumina. The following are some analyses of these kaolinitic
bricks; they possess remarkably high refractory power from the small quantity of iron
contained:
75.89
21.61
76.70
Silica
+
Alumina
75:36
21.47
73.50
22.70
20'10
Peroxide of iron
Alkalies, waste, &c.
1.96
I'79
1.70
1'70
0.50
1.38
2.10
I'50
100'00
100'00
100'00
100'00
Sanitary Ware. Sanitary ware is one of the largest branches of stoneware manufacture.
Stoneware is admirably adapted for employment where an impermeable and water-tight.
body is desired, as in drains, sewers, subways, &c. Formerly, when about thirty years ago
the manufacture of stoneware drains was commenced, the processes were all manual, and
consisted in building up the large pipes or tubes section by section on a strong potter's
wheel. But machinery now effects the formation of this ware with a great economy of time
and labour. The clay is placed in a strong cylinder of iron, in the bottom of which is a
circular opening corresponding with the solid section of the pipe; an iron piston, driven
by steam, descends, forcing the clay through this opening. By this means the pipe is
formed: the socket or joint is generally added on a wheel. Bends, for the turning of the
corners of streets, &c., are made by simply bending the pipe by hand as it is squeezed out
of the machine. Messrs. Clayton, Williams, Whitehead, and Ainslie are among the most
celebrated manufacturers of these machines. Messrs. Clayton recently exhibited, at the
International Exhibition, a small machine working on the principle just described, that
can be manipulated by a man and a boy.
Crucibles. For crucibles it is necessary that materials shall be used that will with-
stand the highest temperature. Good crucibles do not crack on being rapidly cooled,
and they must also withstand the action of the fluxes that may result from the
smelting of metals. The most common crucibles are the Hessian, the graphite or
plumbago, and the English. The Hessian crucible is made of 1 part clay (of 71 parts
silica, 25 parts alumina, and 4 oxide of iron) and one-half to one-third the weight of
quartz-sand. They are refractory, remain unaltered by variations in temperature,
but are unsuited to some chemical operations on account of coarseness of grain and
porosity. If containing too large a proportion of silica, they become perforated by
oxide of lead, alkalies, &c. Graphite or plumbago crucibles are made from I part
of refractory clay and 3 to 4 parts graphite. The Patent Plumbago Crucible Company
of Battersea, as well as the Nuremberg manufacturers, employ Ceylon graphite and
fire-clay. Graphite crucibles will bear the highest temperature, and they can be
made to almost any required size. English crucibles are made from 2 parts of
Stourbridge clay and I part of coke. Crucibles containing coal become reduced
when heated in contact with metallic oxides, and are therefore unfitted to the
smelting of metals. Recently lime and chalk crucibles have been employed for this
purpose. Caron has used magnesia crucibles in the smelting of iron and steel.
Gaudin employs an equal mixture of bauxite or cryolite and magnesia. Very
similar are the bauxite crucibles of Audouin.
22
322
CHEMICAL TECHNOLOGY.
Lime.
LIME AND LIME-BURNING.
Lime, protoxide of calcium (CaO=56), in its combination with carbonic acid
as carbonate of lime (CaCO3) is a substance of the most frequent occurrence. It is
a constituent of bone, of the shells of the mollusca, and is found most extensively
in the minerable kingdom as marble, lime-stone, coral, Iceland spar, arragonite,
chalk, &c. Its technical applications are as marble in building, in the manufacture
of artificial mineral waters, as Iceland spar for optical purposes, as chalk in colours
and drawing materials, in the manufacture of soda, in the preparation of hydraulic
mortars, building and plastering materials, &c. Limestone, Alpen lime, lias lime,
Jura lime, &c., is, when mixed with clay, iron, and other metallic oxides, used as a
colour. Lithographic stone is a yellow-white limestone, employed as its name im-
plies, in lithography. Chalk or earthy carbonate of lime occurs in strata in North
Germany, Denmark, France, and England. To this class belongs marl-limestone,
distinguished by containing clay. With carbonate of soda, carbonate of lime
forms Gay-Lussite (CaCO3 + Na2CO3); with carbonate of baryta, baryto-calcite
(CaCO3 BaCO3); and with carbonate of magnesia, bitter-spar or dolomite
(CaCO3+ MgCO3), the latter occurring with 3 molecules of carbonate of magnesia
to I molecule of carbonate of lime.
Ι
Properties. Carbonate of lime is not soluble in pure water; but if the water should
hold carbonic acid in solution, bicarbonate of lime is formed. When this solution
by means of evaporation loses half its carbonic acid, an insoluble carbonate is formed.
In this manner are naturally formed stalactites and stalagmites. The deposit of calc-
sinter upon objects deposited in caverns, in limestone-rock, &c., is thus explained.
When carbonate of lime is ignited to whiteness in a porcelain crucible, the car-
bonic acid is disengaged, and there remains protoxide of calcium (CaO) or caustic
lime. 100 parts of carbonate of lime yield 56 parts of burnt lime. The volume
of the lime undergoes no diminution by burning. Burnt lime is the form under
which lime most commonly appears in the market. Carbonate of lime, heated in
a closed porcelain tube, melts, and forms a crystalline mass, a carbonate, afterwards
unalterable.
Lime-Burning.
The burning of the lime is effected—
In kilns,
In field-ovens, and
In lime-ovens.
Lime-burning in kilns is accomplished in the following manner :-The limestone,
unless it has previously been broken into small pieces, is heaped up into cairns similar
to the heaps of wood to be converted into charcoal. The kiln is then covered with
earth or turf, and the fire so placed that the larger pieces of lime in the interior of
the heap are burnt. The regulating of the draught, the kindling, the covering, and
the cooling, are on the same principle as that followed by the charcoal burner in the
conversion of wood into charcoal by combustion. According to P. Löss, a kiln of
this kind, 4'5 metres in height, contains 35.5 cubic metres of lime as well as 2·6 cubic
metres of lime-dust. In the field-ovens the burning is similarly conducted, but
sometimes on a larger scale, the kilns being always temporary. It is easy to see
that the burning in this manner is only of slight technical importance; besides the
LIME.
323
A
great waste, only a small quantity could be produced at an operation. Therefore
permanently constructed ovens are employed. These are divided into
a. Those kilns in which the burning is interrupted, or occasionally employed
(the periodical kiln).
b. Those kilns in which the burning is continuous (the continuous kiln).
In the occasional kiln, after the burning is finished, the kiln is cooled, and the lime
then removed. In the continual kiln, on the contrary, the calcination is continuous,
the kiln never being allowed to cool. It is so constructed that the burnt lime can be
removed and fresh limestone introduced, without in the least interrupting the process.
The continual kiln has many recommendations-among them that of effecting a
saving in fuel, as use can be made of the refuse lime for this purpose. In a small
way, where, as a rule, burning cannot be constantly carried on, the small occasional
kiln is, of course, to be preferred.
Periodic Kilns.
Occasional, or The occasional or periodic kiln with interrupted burnings have, or
sometimes have not, a grated furnace. Figs. 177 and 178 show two lime-kilns of the
ordinary construction without grated furnaces. They are built either on the slope of
a hill or on the slope of the limestone quarry itself. As a rule the kilns are built
near one another, so that one wall serves for two kilns. The height of the vault
varies from 13 to 1.6 metres, and it is generally built of the largest limestones, while
FIG. 178.

FIG. 177.

the smaller stones and lime-dust are placed in the interior of the kiln. Through the
furnace doors, easily combustible fuel, such as brushwood, light timber, shavings, &c.,
is introduced. The mass becomes gradually heated, the larger stones crack and break
up, and the whole mass sinks together. As the firing is increased the lime becomes of
a brighter colour and the flames free from smoke. As soon as the lime immediately
under the stones on the top of the kiln is at a white heat the burning is complete.
The mass by this time will have sunken one-sixth. A burning generally occupies
thirty-six to forty-eight hours. An occasional kiln with a grated furnace effects a
quicker and more complete combustion of the fuel; but they are open to the objec-
tion that the consumption is greater. On the other hand, the kilns without a grated
furnace are less perfectly heated. A kiln much used in Hanover is shown in
Fig. 179, and in plan in Fig. 180; Fig. 181 shows the under part of the kiln in
vertical section. The lower room serves for the calcination of the lime; over this is
a vaulted chamber 3.12 metres in diameter and 11 feet in height. e e e e, Figs. 180
324
CHEMICAL TECHNOLOGY.
and 181, are four stoke-holes for the introduction of fuel, stone-coal, brown-coal,
breeze, &c. B is the approach by which the limestone is introduced into the furnace;
d the door by which entrance is obtained to remove the burnt lime. Both these
openings are closed during the actual burning. a is an approach to the " upper
jacket," as the upper chamber is termed. This opening is necessary as a draught to
assist the flame and hot gases in their escape from the top of the kiln; it also causes a
more intense flame in other parts of the kiln. Figs. 180 and 181 show how the lime-
FIG. 179.

B.
.....
d
stone is kept clear of the hearths. A piece of wood is placed vertically in the centre
of the oven to direct the flames upwards when the fire is lighted. During the first
six hours the fire is weak; then a stronger fire is obtained until the yellow lime-
flames spring from the openings in the vault, and the oven is in a clear glow.
The construction of the kilns for continuous burning is somewhat
different to that of the preceding. They are of two kinds. In one the fuel and the
limestone are placed in alternate layers; in the other kind, the fuel and the limestone
The Continuous Kilns.
FIG. 180.
FIG.

D

.
wight fo
ע
are not in contact, there being furnaces for the former and separate chambers for
the latter. In either, fresh limestone is added in proportion as the burnt stone is
removed from the bottom of the kiln.
LIME.
325
FIG. 182.
At Rüdersdorf, near Berlin, a very efficient kiln is employed, shown in section in
Fig. 182. The lining wall of the shaft, d, is built of fire-brick, the counter wall,
e, is separated from the lining wall by a chamber filled with ashes, building refuse,
&c. The outer wall, B B, is not an essential portion of the kiln; it serves merely
as a jacket for the retention of the heat, while the galleries, H and F, can be used
as drying rooms for wood, fuel, &c. During the process, the under part, B, of the
shaft is filled with prepared lime,
which is removed by the draught
hole, a, in the sole of the shaft.
For the purpose of hastening the
descent of the burnt lime, the
sides of the lower part of the shaft
are sloped towards the draught-
holes. The shaft is usually 14°123
metres in height. About 4 metres
above the sole of the shaft is situated
the fire-room, h. Three to five fire
rooms are in action in a single shaft.
The fuel is wood or turf. is the
ash-pit, whence the asbes fall into
E. The flame enters the shaft
through the opening, 3, at the end
of the fire room. The freshly-burnt
lime is received in F. KK is a draught
gallery communicating with H.

B
جم
The kilns are locally known as three-, four-, or five-fired kilns according to the
number of fire rooms. Should the kiln not have been in use for some time, the
firing is commenced by adding fuel, such as wood, turf, &c., to the limestone in
the shaft. When the shaft is thoroughly warmed and a good draught obtained,
lime only is introduced into the shaft. The shaft is entirely filled with limestone,
and sometimes the limestone accumulates upon the mouth or top of the kiln to a
height of 13 metres.
Kilns for Burning
When the locality is favourable the kilns are arranged to burn both lime
Lime and Bricks and bricks at the same time. The annular kiln of Hoffmann and Licht,
described under Brick-making, is the most suitable for this double purpose.
Properties of Lime. The quality of the burnt lime is greatly influenced by the consti-
tution of the limestone burnt. When the limestone consists chiefly of pure car-
bonate of lime, the resulting lime is what is termed a "fat" lime. On the other
hand, if the limestone is of similar composition to dolomite (CaCO3 + MgCO3),
containing magnesia, the resulting lime forms a short, thin pulp with water, and is
termed "poor." With 10 per cent. of magnesia the lime is noticeably poor, and
with 25 to 30 per cent. almost useless. The lime on being taken from the kiln is
by no means found to be burnt equally. Some pieces that have almost escaped
the fire are merely superficially burnt, and contain a kernel of unburnt limestone.
Other pieces exposed to the full heat of the kiln are "over-burnt.” The "
burning" of the lime is either due to the forming of "half-burnt" lime
(CaCO3 + CaH₂O₂) by a strong and sudden ignition; or by means of the high tem-
perature the small quantity of silica and alumina contained in the limestone
over-
+
326
CHEMICAL TECHNOLOGY.
become sintered over the surface, and the lime is thus prevented by a coating of
silicate from combining with the water to form a pulp.
Slking Lime.
I
Burnt lime moistened with water slakes with great violence, 100
parts by weight of lime requiring only 32 parts water, or 3 vols. of lime to 1 vol.
water, to obtain by the combination a temperature of 150°. The result of the
slaking is a soft, white powder, lime-meal or powdered lime, hydrate of protoxide
of calcium (CaH2O2), which in volume exceeds three times that of the lime slaked.
If less water is added than is requisite for the formation of the hydrate, a sandy
powder is obtained of little value technically. It is therefore very disadvantageous
to place lime in baskets in damp situations. For technical application to building
purposes, after the lime has been slaked with one-third of its weight of water, an
equal quantity of water is added to the mass to form a thin pulp. Slaked lime retains
its water of formation with such obstinacy that at a temperature of 250° to 300° no
loss of weight occurs. The hydrate forms a thin pulp with water, and from this
pulp by further dilution lime-water or milk of lime is obtained. If the lime-water
be filtered, there results a saturated solution of hydrate of lime, containing 1 part
hydrate to 778 parts water. When exposed to the atmosphere, lime-water rapidly
absorbs carbonic acid, and is soon covered with a thin film of carbonate. Lime-
water has a strong alkaline reaction, due partly to the lime itself, and partly to the
fact that most limestones contain common salt and alkaline silicates, which, under
the influence of the caustic lime, are converted into caustic alkali.
Uses of Lime. The technical applications of lime are very many. Its great affinity for
carbonic acid fits it especially for the preparation of the caustic alkalies. Slaked lime is
employed in the preparation of ammonia from sal-ammoniac, of hypochlorite of calcium
(chloride of lime), in the precipitation of magnesia from the mother-ley of salines; in the
purification of illuminating gas from carbonic acid and partly from sulphuretted
hydrogen; in the refining of sugar and the separation of the sugar from beet-root juice;
in the manufacture of soda; in tanning, to remove the hair and prepare the hide; in
bleaching; in the manufacture of stearine candles; in the preparation of alum and sul-
phate of alumina from cryolite; for neutralising the sulphuric acid in the preparation of
starch-sugar, &c. One of the latest applications of lime is to the oxy-hydroger or
oxy-calcium light, which is of so much importance in signalling, and such a valuable aid
to the lecturer. The most important application of lime is doubtless in the making of
mortar.
MORTAR.
Mortar. Mortar is a mixture of sand with cream of lime, used in building as a
binding material. The ordinary mortar sets or hardens only in the air; hydraulic
mortar sets under water.
a. Common or Air-setting Mortar.
When slaked lime is exposed to the atmosphere it absorbs carbonic acid, and the
mass becomes much shrunken and cracked. The hydrate of lime thus formed on
becoming perfectly dry attains the hardness of marble. Such a material, with
certain modifications, is consequently admirably adapted as a cement to bind
together bricks, blocks of stone, &c., in building. But as the contraction or
shrinkage would give rise to great unevenness in the construction of walls, it
becomes necessary to add sand or some similar substance to the lime-cream. This
addition gives a body to the mortar, which with the bricks combines into one
coherent mass. Common mortar is ordinarily made with slaked lime, an intimate
mixture with sand and water being formed. Angular or sharp sand is preferred to
smooth, round sand, as making a more tenacious mortar. Round-grained sand
yields a very brittle mortar. The proportion of sand to the lime is a matter imme-
LIME.
327
diately affecting the quality and hardness of the mortar. In practice, 1 cubic
metre of stiff lime-cream requires 3 to 4 cubic metres of sand; but poor, magnesia-
containing lime will only admit of 1 to 2 cubic metres of sand. When mortar is
employed in brick-laying, the surface of the brick is moistened, the mortar laid
between each brick, and left to dry. When dry it is often harder than the brick
itself.
Hardening the Mortar. Mortar sets or hardens very quickly; after a day it will attain a
firmness that will last for centuries. The drying out of the water from the mortar is not
the sole cause of its hardening, as may be very easily ascertained by drying the mortar in
a water-bath or over the spirit-lamp; the result is not a stone-like, but a friable, non-
coherent mass. Fuchs accounts for the hardening of mortar by supposing the formation
of the so-called neutral carbonate of lime (CaCO3 + Caн₂O₂), a combination which has not
been known to suffer conversion into ordinary carbonate of lime (CaCO3). Recent
researches have shown this supposition to be erroneous, as it does not agree with the
results of analyses, which have yielded a quantity of carbonic acid incompatible with the
existence of a neutral carbonate; 20 and even 70 per cent. of carbonic acid have been found.
The experiments of Alexander Petzholdt, A. Von Schrötter, and others, have proved there
to be an increase of soluble silica. The conversion of quartz-sand into soluble silica under
the influence of hydrate of lime, is not, however, a reaction at all explanatory of the
hardening of mortar, as washed chalk instead of silica forms an equally hard mass.
W. Wolters gives the formation of silicate of lime as accounting for the hardening of
mortar. It is not seldom in the analysis of old mortar from the interior of walls that
caustic alkalies are found.
b. Hydraulic Mortar.
Hydraulic Mortar. Limestone containing more than 10 per cent. silica possesses, when
burnt and made into a mortar, the peculiar property of hardening under water.
Lime burnt from such limestone is termed hydraulic lime, and the mortar hydraulic
mortar.
When unburnt, hydraulic lime is a mixture of carbonate of lime with silica or a
silicate, generally silicate of alumina, the latter being insoluble in hydrochloric
acid. During the burning, the hydraulic lime suffers a change similar to that
taking place when a silicate insoluble in acid is precipitated, during the application
of heat, with an alkaline carbonate. After burning, the lime is to a great extent
soluble in hydrochloric acid, and has lost some of its carbonic acid. Von Fuchs,
Feichtinger, Harms, Heldt, W. Michaëlis, and A. von Kripp's experiments have
proved that the silica of hydraulic lime is precipitated in a gelatinous condition,
and that constituents such as alumina and oxide of iron are of influence only when,
under ignition, they have formed a chemical combination with the silica.
Hydraulic mortars are made:-
1. With a thin cream of lime and water to which sand is added; or with
2. A mixture of ordinary air-mortar with water and cement.
During the slaking of the hydraulic lime water is absorbed, but without any con-
siderable evolution of heat or increase in volume. Hydraulic mortar is applied in
the same manner as ordinary mortar-the lime-cream must be freshly made, and
the brick or masonry work moistened. The mortar should be placed thickly
between each layer of bricks, in order to afford a good firm bed, and allow for
shrinkage.
Cements. It follows from what has been said that an artificial hydraulic mortar
can be prepared from ordinary lime by the addition of silica. Such a preparation
is termed a cement. A few natural cements are found, and may be considered as
chiefly of volcanic formation. To this class belong tuff-stone, tarras, or trass, a
tertiary earth, the basis of which appears to be pumice-stone with small quantities
of basalt and calcined slate, the pozzolano of Italy, and santorin.
328
CHEMICAL TECHNOLOGY.
Tarras, or trass, also contains magnetic iron in small quantities, as well as titanic iron.
The following are the constituents according to analysis:
Silica
Lime..
Magnesia..
Potash
•
Soda..
Alumina
•
·
Oxide of iron
Water
· •
•
Soluble in
hydrochloric acid.
11.50
Insoluble in
hydrochloric acid.
37.44
3.16
2:25
2.15
O'27
0.29
0.08
2.44
I'12
17.70
1.25
11'17
0'75
7.65
56.86
42.98
This cement has been employed for 300 years as a hydraulic mortar, and is one of the
most important of its class.
Pozzolano is another tertiary earth, occurring chiefly at Puzzuoli, near Naples, as a
loose, grey, or yellow-brown mass, of partly a fine-grained and partly an earthy
fracture. It contains in 100 parts :-
Silicic acid
Alumina
Lime
Magnesia
Oxide of iron
Potash
Soda
Water
•
•
•
•
44'5
•
15'0
8.8
4'7
12'0
5.5
·
9.2
100'0
The oxide of iron contains small quantities of titanium. More lime must be added to
form a hydraulic mortar. The masonry of the light-room of the Eddystone Lighthouse
is cemented with a hydraulic mortar formed from equal parts of pulverised pozzolano and
slaked lime.
Santorin derives its name from the Greek Island of Santorin, where it was first found.
It is, similarly to trass, a volcanic formation, and, according to G. Feichtinger (1870) con-
sists of a mixture of cement and sand, the latter containing large quantities of pumice-
stone. It is not largely employed as a cement, on account of the difficulty of separating
the true cement from the accompanying sand.
Artificial Cements. The high price of natural cements consequent upon the smallness
of the quantity found, and the difficulty of working them, has given much en-
couragement to the manufacture of artificial cements. Indeed, the use of natural
cements is the exception and not the rule. Parker, Wyatt, and Co., were the first
artificial cement manufacturers, and took out their English patent in 1796; they
may therefore be considered as the founders of the extensive industry of the pre-
sent day. The cement prepared by them, and now in use, is known as English
or Roman cement. It is manufactured by burning a peculiar clay-shale found
above the chalk formation in the Isle of Sheppey and the Isle of Wight. The burn-
ing is effected in an ordinary lime kiln, and the burnt shale is afterwards pul-
verised. The resulting red-brown powder eagerly absorbs carbonic acid and water
from the air. It is packed in casks and stored ready for use. When prepared as a
mortar, it hardens or sets in fifteen to twenty minutes.
Michaëlis found by the analysis of various Roman cements:-
I.
2.
3.
4.
Lime
58.38
55'50
47.83
58.88
Magnesia
5'00
I'73
24°26
2.25
Silicic acid
28.83
25'00
5.80
23'66
Alumina
6'40
6.96
I'50
7'24
Oxide of iron..
4'80
9'63
20.80
7'97
LIME.
329
The analyses are from cements free from water and carbonic acid. No. 1 is
Roman cement from Rüdersdorf limestone; 2. From limestone from the Isle of
Sheppey, yellow-brown in colour, coarse and hard; 3. From limestone forming
the under bed of the lead ores at Tarnowitz, of a blue-grey colour, firm, and of a
crystalline appearance; 4. From Hausbergen limestone.
Portland cement, so named from the resemblance it bears when set to Portland
stone, is a scaly crystalline powder of grey colour, and was first prepared by Mr.
Joseph Aspdin of Leeds, in 1824. According to his Letters Patent, he prepared
the cement in the following manner:-A large quantity of limestone was taken
and pulverised; or the dust or pulverised limestone used to mend the roads was
employed. This material was dried and burnt in a lime-kiln. An equal quantity
by weight of clay was added to the burnt lime, and thoroughly kneaded with water
to a plastic mass. This was afterwards dried, broken in pieces, and burnt in a
lime-kiln to remove all the carbonic acid. The mass, thus transformed to a fine
powder, is ready for the market. It is known in commerce as a grey, or green-
grey, sandy, palpable powder. But Pasley must be considered the true founder of
artificial cement manufacture in England; he, in 1826, obtained a cement by the burn-
ing of river-mud from the Medway, impregnated with the salts from the sea-water,
with limestone or chalk. The mud from the Medway is probably best adapted for the
manufacture of Portland cement on account of the sodium salts it contains, and
from this supposition there seems good ground for Pettenkofer's recommendation
that various marls, burnt after lixiviation with a solution of common salt, should
be tried. At the present time the mud from the mouths and delta formations of
several large rivers is employed in the preparation of this cement.
The manufacture of Portland cements usually follows this mode. The raw mate-
rials, limestone and clay or mud in equal quantities, are intimately mixed, the
mixture dried in the air, and then burnt in a shaft-oven. The shaft-oven is gene-
rally 14 to 30 metres in height, with a width of 2.3 to 4 metres. At a height
of 1 to 13 metres from the ground is a strong grating, through which the lumps of
limestone mostly fall, those remaining being afterwards broken by the heat. The
oven is so arranged that a layer of fuel and a layer of cement stone alternate.
Coke is generally chosen as fuel, being found by experience best adapted for the
purpose. After the mass has been submitted to a red heat for one hour, it assumes
a yellow-brown colour, and at a higher temperature becomes a dark brown. Gra-
dually the lime becomes causticised, and enters more and more into chemical com-
bination with the silicates. At a white heat the mass becomes grey in colour, with
a streak here and there of green. If during the operation these colours are shown
at the several stages, the resulting cement will be good and set hard. If the heat-
ing is continued, the cement will assume a blue-grey colour and become quite use-
less. If removed at the first stage the mass yields a yellow-brown, light powder;
at the second, a grey, sharp powder tinged with green. Beyond this stage the
powder is blue-grey, or grey-white, clear and sharp, and very similar to glass-
powder. The more lime the mixture contains, or, it might be said, the more basic
the mixture, the more durable is the cement, and the less it falls to pieces in burn-
ing. A mixture in which clay predominates is always more or less a weaker
cement, falling to pieces readily, or, technically, not binding well. According to
Michaëlis, the addition of lime or alkalies prevents the cement separating, and
renders it more binding; but in practice this addition would not be sufficiently
330
CHEMICAL TECHNOLOGY.
economical. The more intimately the clay and lime are mixed, the larger the
amount of lime that may be incorporated. From the moment of stiffening till the
final hardening, the cement, if set in the air, experiences no change; but if in water,
there is at first a small loss of the more soluble constituents-the alkalies.
Portland cement mixed with water to a pulp stiffens in a few minutes, and after
the elapse of a day sets tolerably hard. After a month the cement sets into a sub-
stance so hard and firm that it emits a sound when struck by a hard body. It is
admirably adapted, when mixed with sand or gypsum, for being cast into the
various architectural ornaments, and, indeed, has from this property been termed
artificial stone. Lately Grüneberg has made crystallizing-vessels of this cement,
and Posch employs it in constructing reservoirs for hot fluids.
Manufacture of Artificial The process of manufacturing true Portland cement being confined
Cement in Germany. to England by letters patent, the cements of this kind made in Ger-
many may be considered as artificial cements. They result but from a slight variation in
method only, chalk and clay or mud being mixed, and the mixture formed into bricks or
tiles, then burnt and ground to powder. This cement answers in every respect the
purposes of the original cement. In the preparation of hydraulic mortar a mixture
of chalk and lime is also used, together with marl, the ashes of pit-coal and turf, the
alum-shale and alum-earth resulting from alum manufacture, burnt potter's earth, broken
porcelain, pulverised flint, &c. Chalcedony cement is a mixture, invented by H. Frühling
(1870), of I volume of burnt chalcedony with I volume of lime and 2 volumes of white
sand. This cement has a glaze much resembling polished marble. Although the prin-
ciples of the hydraulic nature of various cements and mortars are known, not many
experiments have been made in verification. The elements of success seem to lie in
a due regulation of the heat during burning, in the intimate mixing of the ingredients;
the chief principle, the chemical combination of the several substances, is but very little
known. Of the various uses of hydraulic mortars, we have nothing to do; the conditions
of applicability are:-1. That the proportion of 25 per cent. of clay be preserved; 2. That
the clay be of the requisite quality, rich in silica, finely divided, and form an intimate
mixture with carbonate of lime. These conditions are very seldom entirely fulfilled.
Portland cement was first introduced into Germany in 1850, by M. Gierow, of Stettin;
and in 1852 M. H. Bleibtreu, of Stettin, erected a building at Bonn in which this cement
was largely employed. Since that time there has hardly been a building in the erection
of which Portland cement was not used.
M. W. Michaëlis gives the following analyses of Portland cements, the samples being
free from water and carbonic acid:-
I.
2.
Lime
Silicic acid
•
•
Alumina
Oxide of iron
Magnesia
3.
59:06 62.81 61.91 60'33
24.07 23'22 24'19 25.98
6.92
5:27
7.66 7.04
6.17
3.4I 2.00 2'54 2:46 2.13
0.82 I'14 115 0'23
4.
5.
61.64
6.
7.
8.
9.
23.00
61.74 55:06 57.83
25.63 22.92
55.28
23.81
22.86
6.17 8:00 9:38
9.03
0'45 5'46 5:22
6.14
2.24
0.77 1.35 1.64
Potash..
0.73
Soda
0.87)
1.27
077
10:46
O'94
0.60
0.30
Sulphate of lime 2.85
Clay
Sand
}
I'30
I'47 2:54 I'32
I'52 I'53
1'04 1.28
1'13 0.59 0.77
0.40 1'70 0'71
1.64 I'75 I'II 3.20
1'13 2.27
1.08
No. I is Portland cement from White and Brothers, analysed by Michaëlis. No. 2 is
Stettin cement, analysed by Michaëlis. Nos. 3 and 4 are Wildauer cements. No. 5, known
as Star cement; and No. 6, another Stettin cement, by the same analyst. No. 7 is
English cement. No. 8 cement from works near Bonn, both analysed by Hopfgartner.
No. 9 is a strong and porous cement, analysed by Feichtinger.
An analytic comparison of German and English cements will be interesting. German
Portland cement has the same colour as English cement, and similarly hardens under
water to the same degree of durability. Under the microscope both possess the same
foliated and slaty appearance. The specific weight is in both cases the same. A peculiar
marl, Kufstein marl, is found in the Tyrol, near Kufstein, yielding an excellent cement, of
which Feichtinger gives the following notice :-"Kufstein Portland cement is a natural
LIME.
331
hydraulic lime, unlike English Portland cement, which is an artificial hydraulic lime. It
is the product of burning a marl found largely in most Alpine districts, and in every
applicable condition similar to English Portland cement. The following is an analysis
of this marl:-
Constituents
soluble in
Carbonate of lime
Carbonate of magnesia
Oxide of iron
hydrochloric
Alumina
acid
Gypsum
Water and organic substances
Total constituents soluble in hydrochloric acid
Constituents
Silica
Alumina
•
insoluble in
Oxide of iron
hydrochloric
acid
Potash..
Soda
•
•
•
•
70.64
I'02
2.58
2.86
0'34
0.79
..
78·23
15.92
3.08
I'40
0'55
•
0.82
21.77
Total constituents insoluble in hydrochloric acid
The quantity of the insoluble constituents amounts only to 21.77 per cent., while most
marls contain much more clay; in practice, however, the clay is increased to 25 to 30 per
cent. The Kufstein marl, differs, too, in the chemical composition of the clay, and as
is known, the constitution of the clay greatly affects the qualities of the cements.
comparison of the two clays will therefore possess interest. În 100 parts of silica :-
Clay from
Clay from
Medway mud.
A
Alumina
Oxide of iron
Potash
Soda
• •
•
•
Kufstein marl.
•
•
19'34
•
· •
8.79
3'45
5:15
36.73
17'0
21.6
2.8
3:0
44'4
These analyses show, that with the clay of the Kufstein marl, a large quantity of
important bases enter into combination, more than possessed by the clay of the Medway
mud. Therefore the clay of this marl may be more readily smelted in a small fire. The
small quantity of magnesia contained in the Kufstein Portland cement probably is
productive of good effect; all good hydraulic cements contain but little magnesia.'
The mention of concrete, so largely used in England where a good weathering mortar is
required, must be included in that of cements. Concrete is a mixture of ordinary mortar
with stones, grit, broken brick, tiles, &c. To the concrete is generally added lime, and
then the whole mixed with two to three times the quantity of fine sand. Pasley tells us that
a better product may be obtained with I part of freshly burnt lime, in pieces not larger than
the fist, 3 parts of sharp river-sand, and 15 parts of water, the whole being well
mixed. The bricklayer prefers to mix the dry materials and then add water, the concrete
in this manner taking a longer time to harden, and admitting of greater care being taken
to fill all interstices. The several uses of concrete are too well known to need mention.
The employment of unslaked lime in the preparation of concrete was first introduced by
Mr. Smirke, of London, to whom also its employment as a foundation to brickwork is
mainly due.
Hydraulic Moriars.
The Hardening of The hardening of hydraulic mortars has often been the subject of
investigation. Two views may be taken: first, the mere setting, the congealing of
the mass from a fluid state to a moderate degree of hardness; and then the harden-
ing to a stony state. The knowledge we possess of the setting of these mortars is
chiefly due to the experiments of Von Fuchs, Von Pettenkofer, Winkler, Feich-
tinger, Heldt, Lieven, Schulat-Schenko, Ad. Remete, Heereen, W. Michaëlis, and
Von Schonaich-Carolath. The cements when thus considered are best divided in
two classes :—The first class, of which Roman cement is the type, embraces the
mixture of caustic lime with pozzuolane, pulverised tile, and brick, and such
hydraulic mortar as is obtained by burning hydraulic lime and marl. All the
cements contain caustic lime unacted upon. The second class comprehends Port-
332
CHEMICAL TECHNOLOGY.
land cements, containing no fresh caustic lime. M. Von Fuchs has explained the
chemical actions taking place during the hardening of Roman cements as being
principally the combination of the lime with silicic acid, the combination giving
rise to the peculiar property of hydraulic mortars. He draws this conclusion partly
from the fact that from all hydraulic mortars the silica can be thrown down as an
insoluble gelatinous mass by the action of carbonic acid.
A similar gelatinous mass results from the combination of silicic acid and lime.
Silicates do not yield when treated with hydrochloric acid alone, gelatinous silica,
but attain this property when subjected for a length of time to the influence of
lime under water; the water also dissolves out the alkalies. Kuhlmann, who has.
long been employed in the study of the chemistry of hydraulic cements and arti-
ficial stones, states that lime can be rendered hydraulic by the intimate mixture of
10 to 12 per cent. of an alkaline silicate, or by treating with a water-glass solution.
Collecting the results of these experiments, the setting of Roman cement appears
due to the combination of acid silicates or silica with burnt lime, forming a hydrated
silicate of lime intermixed with the alumina and oxide of iron.
The hardening of Portland cements has been investigated by Winkler and
Feichtinger. According to the former, the chemical action, which is effected under
the co-operation of the water, consists of the separation of the silicates into free
lime and combinations between the silica and the calcium, the alumina and the
calcium. The separated lime combines with the carbonic acid in the air to form
carbonate of lime. The hardened Portland cement contains the same combinations
as hardened Roman cement; these combinations are formed, however, under the
influence of water on opposed conditions. From the results of Winkler's experi-
ments it would appear that the silicic acid in the Portland cements can be repre-
sented by alumina and oxide of iron. Alumina does not affect the hardness, but
may lessen the capability of the cement to withstand the action of carbonic acid.
During the hardening the influence of the water separates the lime, till finally the
combinations Ca3Si3O, and CaAl204 remain, the latter being gradually decomposed
by carbonic acid, remaining, however, so long as there is any hydrate of lime in
the cement. G. Feichtinger maintains a theory differing from that of Winkler.
His experiments lead him to the opinion that in all hydraulic mortars the harden-
ing depends upon the chemical combination between lime and the silica, and
between lime and the silicates contained in the cement. In all hydraulic cements
free lime is contained; and upon this fact we may base the following experi-
ments. When Portland cement is brought to a pulp with a concentrated solution
of carbonate of ammonia, and stirred for a long time, no hardening is traced, the
greater part of the lime forming carbonate of lime. Then let the excess of car-
bonate of ammonia be washed away, the cement dried, and made into a mortar
with pure water. This mortar will not harden unless some hydroxide of lime be
added, when it hardens similarly to fresh mortar. The same result may be obtained
by substituting a stream of carbonic acid gas for the carbonate of ammonia; by
this means 27 per cent. of carbonate of lime may be obtained. Consequently the
views of Winkler must be regarded as the most correct. These experiments also
show that in Portland cements silicates or free silica are contained; that, further,
free lime does and must exist. Portland cement will not take a glaze, and can
only be so far affected by burning as to cause the sintering of the clay contained in
the cement.
GYPSUM.
333
GYPSUM AND ITS PREPARATION
Occurrence. Gypsum is a hydrated sulphate of calcium according to the formula
CaSO4+2H2O.
4+2H₂O. 100 parts contain :
Sulphur
Oxygen
Lime
32'56
27'91
18.60 Sulphuric acid
..
46°51
Water..
20'93
100'00
It belongs to the commonly occurring class of minerals, and is found alone or with
anhydrite (karstenite, CaSO4) in strata chiefly of the tertiary formation. The
following kinds are distinguished:-1. Gypsum spar, foliated gypsum, glass-stone,
isinglass-stone, or selenite, possessing a very perfect cleavage, and allowing fine
laminæ to be separated. 2. Fibrous gypsum, or satin spar. 3. Froth-stone, a scaly
crystalline gypsum. 4. Granular gypsum, or alabaster, of coarse or fine-grained
texture. 5. Gypsum stone, plaster stone, or heavy stone, a laminated gypsum.
6. Earthy gypsum, or plaster earth.
Nature of Gypsum. Gypsum is soluble in 445 parts of water at 14° C., and in 420 parts
at 20:5° C.; the solubility is increased by the addition of sal-ammoniac. Its
behaviour under the influence of heat is important. Graham states that gypsum
placed in a vacuum over sulphuric acid and heated to 100° C., loses half its water,
forming the combination CaSO4 + H2O, with 12.8 per cent. water. According to
Zeidler, the statement that this combination does not harden with water is incorrect.
By heating to 90° for some time 15 per cent. of the water may be expelled; at 170°,
according to the experiments of Zeidler, all the water will be given off. But of
more importance are the experiments not carried on in vacuo.
In the air gypsum
begins to lose its water at 100º, and the loss is not complete under 132°. Gypsum
from which all the water has been removed is termed burnt gypsum, or spar-lime;
it has the property of re-forming with water the same hydrate, then becoming
hardened. Advantage is taken of this property in the application of gypsum as a
mortar. According to Zeidler, gypsum as technically employed in stucco-work, &c.,
is not anhydrous, but ccntains 5*27 per cent. water. If gypsum is "over-burnt,” that
is, heated above 204°, it loses the property of hardening with water, probably owing
to the fact of its being converted into anhydrite, which does not re-form with water.
The water of crystallisation of the gypsum is saline, and consequently can be
removed by the addition of salts; this probably accounts for the hardening of unburnt
gypsum when treated with a dilute solution of sulphate or carbonate of potash, &c.
The hardening in this follows more quickly than with burnt gypsum and pure
water. With sulphate of potash a double salt is formed according to the formula
K2SO4 + CaSO4+ H2O); gypsum and bitartrate of potash gives rise to tartar and
crystalline gypsum. Chlorate and nitrate of potash, as well as sodium salts, do not
effect the hardening of powdered gypsum. Gypsum thus hardened, if re-powdered
and again treated with sulphate or carbonate of potash solution, hardens once more.
Technical use is made of this property in re-hardening old or in hardening gypsum
not sufficiently burnt, by employing instead of water a solution of carbonate of potash.
The Burning of Gypsum. Gypsum is burnt to effect the removal of the water. Lately
many improvements have been made in the methods of burning, it having been found
334
CHEMICAL TECHNOLOGY.
that the good qualities of the gypsum mainly depend upon the preparation. There
is, however, a choice in the stone to be burnt, the heavier and denser varieties of
gypsum yielding the best commercial article.
Payen, by experimenting with large quantities of gypsum, obtained the following
results:-(a.) The lowest temperature at which the gypsum can be burnt with
advantage is 80° C., a long time even then being required. (b.) A temperature of
110°—120° yields the best technical preparation. (c.) In order that the burning may
take place equally, the gypsum should be first reduced to powder or small pieces.
The aim, of course, is in all cases to obtain a small homogeneous product rather than
a large quantity unequally burnt. Small quantities of gypsum may be burnt in an
iron vessel over a coal fire: the operation should be continued till no aqueous vapour
is condensed on a cold glass plate.
Kilns, or Burning Ovens. In large quantities gypsum is burnt in an oven or kiln, the one
necessary precaution being to avoid arranging the layers of gypsum with such fuel
as will reduce the gypsum to sulphuret of lime (CaSO4 + 4C = CaS+4CO).
FIG. 183.
FIG. 184
A very simple and very general
construction of kiln is shown in
Fig. 183. It consists of walls of
strong masonry, A, spanned by a flat
arch, ventilated at a a a. In this
room is placed the gypsum only, the
fire being lighted in a series of small
chambers in the lower part of the
room brushwood is the best fuel.
b is a door through which the ma-
terial is introduced. The oven
(Fig. 184) used by M. Scanegatty is
very similar. The inner room is
divided unequally by an arch, P,


P
GYPSUM.
335
I
about 1 foot from the floor; into the upper part the gypsum is introduced through the
door G.
The under part or fire-room is in connection with a flue, E, of a furnace,
A A, the flames from which, driven by the draught from the gallery C, are carried
through x to play upon the arch P, the hot air and gases passing through c c c into
the upper room. The aqueous vapour escapes through H.
Lately Dumesnil's oven, shown in
plan at Fig. 185, and in section
Fig. 186, has been much employed.
It somewhat resembles Scanegatty's
oven in construction, and consists of
an under fire-room and an upper
room or oven in which the gypsum
is burnt. The fire-room contains an
ash-pit, A, with a door, B, a grate or
grid, c, and the hearth, D. A draught, x-..
H, assists the combustion. The hot
air and gases pass by the flues, E, to
the chamber, F. The walls of the
oven, J, K, L, are of solid masonry.
I is a depth, furnished with a stair-
case, gh, to facilitate access to the
furnace. P, the chimney, is of iron
plate, with a clack, o, which can be
regulated by the chain u u. o o are
ventilating pipes. In the wall of the
burning-room are two openings; one,
M, through which admittance to the
interior is gained to place the lower
layers of gypsum: the other, N, for
the upper layers of gypsum: both are
closed by doors of iron plate. An
equal heat is necessary in the burning-
room, and is maintained by the pe-
culiar arrangement of the chamber F.
This chamber, closed at the top by the
cap, G, is provided with twelve open-
ings, each 07 metre high, the chamber
itself being i metre in diameter. The
channels thus commenced by the
openings in F are continued to the
walls of the room by the arrangement
of large blocks of gypsum. The layers
of gypsum, R, S, T, are placed cross-
wise alternately with intermediate
layers, so as to facilitate the draught
in every possible way. The firing is
ģ
店​の
​FIG. 185.
W

FIG. 186.
P
U
T
P
回
​MIETT RISK
-X

continued gently for four hours, then strengthened for eight hours, when all the openings
are closed, and five to six cubic metres of coarse gypsum powder spread equally over the
top of the burning gypsum. By this means the quantity of burnt gypsum is increased
without a further expenditure of fuel. After standing twelve hours in the oven to cool
the whole contents are removed.
Grinding the Gypsuni. After the burning the gypsum is to a certain extent in powder,
but if not sufficiently even it has to be ground. The usual modes of grinding are in
a stamp or roller mill. After grinding the gypsum is sifted, and placed in some
position where damp cannot affect it. Sometimes the grinding and sifting are con-
ducted in one apparatus; generally the mill and sieves are separate.
Uses of Gypsum. Gypsum is employed industrially in very many ways. It is some-
times used unburnt in building; it is then difficult to manipulate with water, but
becomes soluble by continued moistening. The heavy and fast fine-grained gypsum,
especially the white powdered gypsum, is used in building for architectural purposes.
336
CHEMICAL TECHNOLOGY.
From the alabaster of Voltena, Florence vases were fabricated of great beauty: the
same material is used for making Roman pearls. The clear varieties of g psum are
used in the manufacture of cheap jewellery, being ground and polished. The fibrous
gypsum is sometimes used for writing sand, as a substitute for pounce, &c. Fine
gypsum powder is an ingredient of porcelain manufacture. Unburnt gypsum finds
further application in the conversion of carbonate of ammonia into sulphate.
Gypsum contains 46.5 per cent. sulphuric acid and 18.6 per cent. sulphur. It is
largely employed in agriculture as a manure, both burnt and unburnt. It is
generally received that the favourable action of the gypsum upon vegetation is due
to the absorbed ammonia which is again yielded up.
Putridity gives rise to the formation of carbonic acid, which combines with the
lime of the gypsum, leaving carbonate of lime and sulphate of ammonia. This
explanation of the efficacy of gypsum-dunging, as it is termed, is, however, insufficient.
The investigations of Mayer have shown that in clayey soils the oxide of iron, &c., affords
larger and better combinations with ammonia than the gypsum. The quantity of gypsum
used is generally about 5 cwts. to the acre, containing and realising at the most 2 cwts.
of carbonate of ammonia. Mayer's researches, however, show that in an acre of
Field land
Chalky soil
227 cwts.,
158 cwts.,
of ammonia were contained. According to Liebig's late researches (1863) it appears that
the gypsum gives up to the earth a portion of its lime in exchange for magnesia and
potash. But it must be borne in mind that pulverised gypsum, as well as unburnt gypsum,
when brought into contact with a solution of potash, sets into a difficultly soluble mass.
We must, then, wait for an adequate theory until the several reactions have been more
closely studied.
Gypsum Casts.
The employment of gypsum in casting, and in all cases where im-
pressions are required, is very extensive. A thin pulp of 1 part gypsum and 22 parts
water is made: this pulp hardens by standing, forming (CaSO4+2H2O). The
hardening of good, well-burnt gypsum is effected in one to two minutes, and more
quickly in a moderate heat. Models are made in this substance for galvano-plastic
purposes, for metallic castings, and for ground works in porcelain manufacture. The
object from which the cast is to be taken is first well oiled, to prevent the adhesion
of the gypsum. Where greater hardness is required a small quantity of lime is
added: this addition gives a very marble-like appearance, and the mixture is much
employed in architecture, being then known as gypsum-marble or stucco. The gyp-
sum is generally mixed with lime water, to which sometimes a solution of sulphate
of zinc is added. After drying, the surface is rubbed down with pumice-stone,
coloured to represent marble, and polished with Tripoli and olive-oil. Artificial
scaliogla work is largely composed of gypsum. Gypsum is also largely employed
in the manufacture of paper.
Hardening of G psum. There are several methods of hardening gypsum. One of the
oldest consists in mixing the burnt gypsum with lime-water or a solution of gum-
arabic. Another, yielding very good results, is to mix the gypsum with a solution
of 20 ounces of alum in 6 pounds of water: this plaster hardens completely in 15 to
30 minutes, and is largely used under the name of marble cement. Parian cement
is gypsum hardened by means of borax, 1 part of borax being dissolved in 9 parts
of water, and the gypsum treated with the solution. Still better results are ob-
tained by the addition to this solution of 1 part of cream of tartar.
The hardening of gypsum with a water-glass solution is found difficult, and no
better results are obtained than with ordinary gypsum. Fissot obtains artificial
stone from gypsum by burning and immersions in water, first for half a minute, after
GYPSUM.
337
which it is exposed to the air, and again for two to three minutes, when the block
appears as a hardened stone. It would seem from this method that the augmenta-
tion in hardness is due to a new crystallisation. Hardened gypsum, treated with
stearic acid or with paraffine, and polished, much resembles meerschaum: the re-
semblance may, be increased by a colouring solution of gamboge and dragon's blood,
to impart a faint red-yellow tint. The cheap artificial meerschaum pipes are
manufactured by this method.
23
DIVISION IV.
VEGETABLE FIBRES AND THEIR TECHNICAL APPLICATION.
THE TECHNOLOGY OF VEGETABLE FIBRE.
5:
Vegetable fibre or cellulose, CН1005, is the fundamental constituent of the struc-
ture of plants, forming a large proportion of the solid of every vegetable. The
fibres of the hemp-plant, the nettle, and the cotton-plant are long and fluffy, and
are technically termed spinning fibres. These and similar fibres are employed in
fabricating woven tissues, paper, &c. Treated with sulphuric acid, cellulose is
converted into dextrose or glucose. The pure cellulose constituents of wood,
cotton, flax, and paper are nearly equal, as shown by the following analyses :—
Material of Cells.
Wood. Cotton. Flax.
Paper.
Carbon ..
Hydrogen
Oxygen..
43.87
43'30
43'63
43.87
6.23
6'40
6'21
6.12
49'90
50*30
50'16
50'01
100'00
100'00
100'00
100'00
The vegetable fibre for use in spinning must be firm, pliable, easily divided, and
capable of withstanding bleaching operations, if required.
FLAX.
Flax. The flax used in spinning is the fibre of the flax-plant, Linum usitatissimum,
a plant of the class Pentandriæ, order Pentagyniæ, in the system of Linnæus, and
the type of the order Linacea in the natural system of Botany. The flax is gathered,
tied in bunches, and dried in the fields. After drying the plant is combed with an
iron or flax comb, to separate the seeds, and is then bound in thick bunches. The
flax fibre used in linen fabrication lies under the bark of the plant, and is surrounded
by a gummy substance, or pectose according to J. Kolb, which must be removed by
mechanical means to fit the fibre for industrial purposes. This is done by "softening"
or "rottening,” by which, according to Kolb, pectin-fermentation is set up, and the
pectin converted into pectic acid. The flax is kept under water until the impurities
float on the surface, leaving the fibre intact; this is the soaking method. Another
method, dew-softening, as it is termed, consists in spreading out the flax in layers
to the influence of the atmosphere, water being occasionally thrown over the flax.
Both these methods are unsound, as the flax is liable to become rotten, while the
impurities are not thoroughly removed.
VEGETABLE FIBRE.
339
Hot water Cleansing.
After many experiments with different chemical substances, an
alkaline bath and dilute sulphuric acid have been found the best agents to effect the
separation. The flax is placed in large vessels of water heated to 25°—30° by steam:
after standing 60 or 90 hours the operation is complete. This mode of treatment,
aided by an alkaline or acid solution, yields the best results, the value of the process
being-1. That the construction of the fibre is equally affected, rendering the article
better suited for manufacture. 2. That the fibre does not lose weight as in the other
methods, where 10 per cent. is sometimes lost. 3. That there is a considerable saving
in expense.
The retted flax, as it is techni-
cally termed, consists of cellulose
and pectic acid. The next process
is termed scutching, and includes
the separating of the fibre from the
woody structure of the stem. The
machine for this purpose is shown
in Fig. 187. It consists of two
parts; the upper, B, is of wood, in
the form of two splints, working on
hinges. Wooden knives are placed
FIG. 187.

B
A
Ꮯ
under the splints, and are arranged to act upon the fibre placed in A by pressure
upon the handle c.
Beating or Batting the Flax.
Fig. 188.
Scutching consists in two operations bruising
the flax and beating away the woody part from the fibre. For the
latter operation the Belgian batting-hammer, Figs. 188 and 189, is
generally used. It is a deeply grooved wooden block, furnished with a
long curved handle. The sheaf of flax is laid on the ground, untied,
and spread out, and is beaten with the hammer by the workman. If the flax is not suffi-
ciently loosened by batting, it is submitted to the swinging block, Fig. 190, having a cut
FIG. 189.
FIG. 191.
FIG. 192.
FIG. 190.




0
at three-fourths of its height serving to hold about a handful of flax. This flax is then
beaten with the scutch-blade, Fig. 191, a piece of hard, tough wood, generally walnut-
wood. Instead of the swinging-block a grinding knife, Fig. 192, is sometimes used on an
340
CHEMICAL TECHNOLOGY.
iron block. This knife is formed of a thin blade, o, and a heavy wooden handle, p. A
bunch of flax is held in the left hand, at an angle for the easy use of knife with which
the flax is beaten. Notwithstanding these clarifying processes the bark still adheres to
the flax, which has to undergo a further operation, that of combing.
Combing the Flax. The combing or hackling of the flax removes all the material detrimental
to the ultimate spinning of the fibres, and also equalises their length, rendering them
smooth and parallel. The combs are made of zinc or steel, and are of varying degrees
of fineness, the process commencing with a coarse comb and finishing with a fine one.
Tow, or Tangled Fibre. However carefully the operation of scutching may be performed,
there is always a certain amount of waste resulting from the entanglement of the fibre,
and this waste is termed scutching-tow or codilla. It is used in the manufacture of ropes,
and for similar inferior purposes. The flax fibre, before it is fitted for spinning, has to
be boiled in an alkaline ley, to remove the dirt and grease.
100 kilos. of cleansed flax weigh after
Bruising
Scutching
Combing
•
45-48 kilos.
15-25
10
""
Flax Spinning. The spinning of the combed flax into yarn is effected by hand and
by machinery. The combed flax is first placed in bands of equal thickness, and
then stretched. The hand-spinning wheel is universally known. The mechanical
spinning consists in-1. Placing the fibres in a parallel series of equal thickness
and length throughout. 2. These bands are stretched, the finer the fabric to be
woven the greater being the stretching required. 3. By further stretching and
twisting cord is spun. 4. The fine cord is still further stretched and twisted. Tow,
or codilla, is spun similarly to the flax, being previously combed and placed in bands
of equal length. Flax yarn is either used unbleached or is bleached before
spinning. Linen thread is obtained by twisting several cords together.
Weaving the Linen Threads, By weaving the cords parallel to one another, chain cords
are spun. Webbing, wrappers, and thick fabrics are made in this way.
Linen. Linen is produced by weaving the twisted cord. The selvage is made by
the return of the shuttle on each side of the fabric. For coloured fabrics
coloured threads are used instead of white, only more shuttles are required, one
shuttle to each colour. Linen damask is woven in various patterns, as well as drill,
the difference being that the woof forms the pattern on drill, while chain-cord is
used for that of damask. Batiste is a fine linen cloth, slightly thinner than
cambric.
HEMP.
Hemp. Hemp (Cannabis sativa), is chiefly cultivated for the fibre of its inner bark.
This fibre, although rough, is very hard and firm, and better adapted for the manufacture
of sail cloth, canvas, rigging, &c., than any other. Its uses for inferior domestic pur-
poses are manifold.
The working of the hemp stalk accords essentially with that of
flax, being steeped in water, dried and crushed in a hemp mill. By the old method
the husk is crushed under a large stone cone, Fig. 193, moving in a circular course around
a vertical axis. The construction of the new hemp mill, Fig. 194, is more advantageous.
The hemp is purified by winnowing and afterwards combing. It is difficult to spin
on account of its length, and is woven in two or three parts. Of late various foreign fibres
have been used as substitutes, principally the following:
Its Substitutes. a. Stalk Fibre.
1. Chinese grass (Chinagras Tschuma), a fibre from Urtica s. Boehmeria nivea and hetero-
phylla, which is cultivated in China and the East Indies, Mexico, the Valley of the Mis-
sissippi, Cuba, the Waldenses in Russia, the South of France, and in Algiers. The
Chinese method of treating the fibre is remarkable. The fibre is not spun, but cut into
appropriately small pieces, these being placed end to end, and rolled by the hand until joined
together. The fibre is thus rolled quite smooth and does not require pressing. It forms
VEGETABLE FIBRE.
341
a beautiful texture of singular brightness, called grass linen, or China grass cloth. The
raw material is of a green or brown colour, but when bleached can, be dyed any colour.
2. The Great Nettle, Urtica s. dioica. The interior fibrous pith supplies the material
for nettle cloth and muslin.
3. Ramie hemp, from Urtica s. Boehmeria utilis, is of the nettle species, and a native
of Borneo, Java, Sumatra, and other islands of the Indian Archipelago. Of late various
experiments as to its mode of manufacture have been tried in Germany. It is from
one to two metres in length, of a delicate golden white, and not so bright and stiff as
flax.
4. Rhea Grass, Urtica s. Rhea tenacissima, is a native of the East Indies, of little
value for manufacture.
FIG. 193.
FIG. 194.


MAKARAAAAAKARAR
5. Jute (paut hemp), is obtained from a lime tree, a native of the East Indies and
China, Corchorus capsularis, C. textilis, C. olitorius, C. siliquous. The fibre for spinning is
brown, and in England is used for sackcloth and coarse packing thread. It is not a
material adapted for purposes of nautical application, as it has not sufficient firmness to
withstand water.
6. Bombay Hemp, from Hibiscus cannabinus. The woody fibre of this plant is roasted
and separated by means of beating. In England it is used for cordage, rigging, &c.
7. Sun Hemp, Japan, or East Indian Hemp, from Crotolaria juncea, resembles other
hemp in the length and firmness of its fibres.
B. Leaf Fibre.
8. New Zealand Flaxes (Phormium tenax) are used in their native country for articles
of domestic use. The leaf is straight, the fibre tough, and of a shining white. The pre-
pared material is similar to ordinary hemp in roughness and stiffness.
9. Aloe Hemp is a native of Peru, the East and West Indies, and Mexico. 4.
Americana, A. Vivipara, A. Foetida, &c., where the leaf is cultivated for its fibre, which is
generally a yellow-white, and used for rope-making.
10. Manilla Hemp (Feather Fibre) comes from Musa textilis, M. troglodytarum, and
M. paradisiaca, a native of the East Indies and many islands of the Indian Archipelago.
It is commercially known as a yellow-white or brown-yellow fibre, from 13 to 2.2 metres
long. The inside bark is stripped off from the bottom upwards, refined, and combed. The
white kind is silky and bright, and is used in the manufacture of damask furniture and
various fancy articles.
II. Ananas Hemp comes from the West Indies, Central and South America, where the
common Ananas is cultivated, Ananassa sativa s. Bromelia ananas, as well as other species.
It is rather inferior to some for spinning.
12. Pikaba Hemp is from the leaf of the Attalia funifera, a Brazilian palm. It is
used in rope-making.
13. Cocoa-nut Fibre is a reddish-brown fibrous material, in which the cocoa-nut shell
(Cocos nucifera) is enveloped. It is very strong and elastic, and is used for matting, ropes,
hurdles, &c
342
CHEMICAL TECHNOLOGY.
Cotton.
COTTON.
Cotton is the fruit of a shrubby plant of the species Gossypium, cultivated
in the tropics and the Southern States of America for manufacturing purposes. The
fruit consists of a cup-shaped calyx, enclosed in a three-cleft exterior calyx, bearing
a soft white down. Another species, Gossypium religiosum, bears a yellow down,
used by the Chinese in manufacture. The down is kept separate from the seed when
packed for travelling, to prevent its becoming oily and unfit for use. While in a raw
state, it is subjected to an operation termed ginning in a saw-gin, to separate the
wool from the seed. Whitney's saw-gin consists of 18 to 20 circular saw-blades,
revolving on a horizontal axis about 100 times a minute. The teeth of these saws
project through a grating, seize the wool and pull it through, the bars of the grating
being too narrow to admit the seed. Twenty saw-blades will clean 400 lbs., and 80
saw-blades. worked by 2-horse power, 500 lbs., raw cotton per day. Of late the
carding cylinder is sometimes used instead of the saw-gin. In America oil is largely
extracted from the seed, 30 lbs. yielding about one pound of oil. The seed is also
used for manure.
Species of Cotton. The quality of cotton is decided by its smoothness, and distinguished by
the country from which it is imported. The various kinds are:-North American: Sea
Island, or Long Georgia, Orleans, Upland, Louisiana, Alabama, Tennessee, Georgia,
Virginia. South American: Fernambac, Bahia. Columbian and Peruvia. West Indian:
Domingo, Bahama, Barthelemy. East Indian: Dhollerah, Surate, Manilla, Madras,
Bengal. Levant: Macedonian, Smyrna. Egyptian: Mako or Jümel. Australian:
Queensland. European: Spanish and Sicilian.
Cotton Spinning. Before being spun into yarn, the cotton has to be subjected to the
following processes :-
I. The loosening and purifying of the raw cotton from the various impurities, such as
sand, grit, &c., is accomplished by beating with the hand, or by the Wolf machine, by
means of a cylinder, the surface of which is covered with sharp iron teeth. The Willow is
similar to the Wolf, but it is not furnished with such sharp teeth. The fulling or rolling
machine (batteur étaleur), and the beating machine (batteur éplucheur), are both employed.
The beating machine loosens the cotton that was not quite opened, and allows it to fall
through a grid beneath.
The Fulling or Rolling Machine (batteur étaleur).-The mechanism of this machine is
smoother, and pulls in the cotton more quickly, working it into fibres of the consistence
of flax, which are drawn over the roller and afterwards carded. A new machine has been
constructed under the name of l'Epurateur, a step between the beating and cleaning
machine, which supplies advantages not met with before. The Epurateur is preferable
for the manufacture of wadding.
2. The Combing or Carding.—Before the cotton is placed in the carding machine, it is
passed under a wooden roller to remove the surface thread and other small impurities
which fall off. After the rolling the fibre appears like a delicate flax. The next operation
is the true carding, in which two machines are used, the coarse comb, a revolving wooden
drum covered with steel teeth, and the fine comb, which finishes the separation of the
filaments of the fleece. The combed fleece, when it leaves the carding machine, is in the
form of a loose ribbon band. It is now submitted to the doubling or lapping machine,
to equalise the length of the bands, the carding process making the fleece loose and of
unequal substance. Of late the fibres are separated before carding, the chief distinction
being between the long fibre of Georgia (Sea Island), and the finer or silky fibres of
Florett silk.
3. The Streching or Drawing.-The machine effecting this consists of sometimes two to
six rollers, but usually two pairs of small rollers, over which the ribbons are drawn until
they are of equal substance.
4. Roving, or unwinding the ribbon into yarn, which may be considered as the first
process of spinning. The fleece is stretched 100 times finer than it was before drawing,
and the more it is stretched the finer becomes the yarn for spinning. The yarn is strained
loosely at first, in proportion to its length, and drawn more tightly as required. By this
process yarns of various degree of fineness are easily obtained. The first drawing yields
VEGETABLE FIBRE.
343
coarse yarn, the subsequent drawings furnish the finest and most delicate yarn for spinning.
If the yarn be too fine for the purpose required, as in the manufacture of coarse fabrics,
several card ends, as they are technically termed, are placed together from the first drawing
and formed into one ribbon; this process can be continued until the required texture is
obtained.
Fine Spinning. The yarn (twist) is now rendered firmer by means of the throstle and the
self-acting mule machine, which has quite superseded the Jenny. To the mule machine
Yam. we owe the yarn termed water twist, which is very strong and indispensable in the
manufacture of corded materials.
Cotton Fabrics. Of the different textures in which cotton is employed, we have those
with parallel cords:-
a. Linen, glazed:-1. Calico, cotton and linen prints. 2. Nankeen. 3. Shirting.
4. Towelling cambric. 5. Scotch cambric. 6. Jaconet, 7. Printed
calicoes. 8. Coloured textures, such as gingham, cotton barége. 9. Various
transparent muslins, such as Zephyr, organdi, vapour, corded mull muslin,
tulle, and gauze.
b. Cotton materials with cross cords:-1. Huckaback. 2. Cotton merino.
3. Drill. 4. Bast. 5. Satin. 6. Fustian.
c. A rough woollen stuff called beaverteen, resembling fustian, a finer moleskin.
d. Other cotton fabrics are:-1. Dimity. 2. Drill and fustian. 3. Cotton
damask. 4. Pique.
e. From the same manufacture we get cotton velvet (Manchester).
Substitutes for Cotton. Substitutes for cotton are found in the black poplar (Populus nigra)
and the aspen (P. tremula); the fibres of the latter are not so elastic as some of the sub-
stitutes discovered. The rush (Juncus effusus), the German tamarisk, and the thistle
(Agrostis), the Salix pentandra, the Zostera marina, and the flax tree, supply material for
manufacture. Some twenty years ago Chevalier Claussen endeavoured to open the filaments
of flax by chemical action by steeping the fibres in a bath of 1 part sulphuric acid to 200
parts water, and then dipping it into a weak solution of carbonate of soda. By this pro-
cess the flax is changed into a downy mass resembling cotton in lightness; but the method
was not successful, as the firmness of the fibre was injured, and its value deteriorated in
other ways.
Detecting Cotton in
Linen Fabrics.
There is a great difficulty in detecting cotton in linen fabrics when
the fibres are closely interwoven. The old method of testing the presence of cotton in
linen was by placing it under a powerful microscope, but chemical analysis presents
more reliable methods. The following tests, recommended by Kindt and Lehnert,
proves the existence of cotton in linen by absorption. The linen containing cotton
fibre is placed in a bath of sulphuric acid of 1·83 sp. gr. for 1 to 1 minutes. The
cotton fibre is immediately absorbed, the sulphuric acid acting upon it more quickly
than upon the linen; the fabric upon being dried has a curled or shrivelled
appearance. Other fibres, sheep's wool, silk, and flax, are now treated chemically,
and their smoothness and glossiness are attributable to chemical agency, which is
found to be the greatest preservative against decay. The colour test of Elsner is
useful, but not always successful, on account of the transition of the delicate colours
being so instantaneous as to make it difficult to form a decision. As a colour-test
there may be taken half an ounce of the root rubia tinctorum, macerated in 6 ounces
of alcohol at 94 per cent. for twenty-four hours. When filtered, the tincture appears
a clear brown-yellow. Pure linen fabrics immersed in it become a dull orange-red,
and pure cotton yellow; the flax fibre will assume a yellow-red, and the cotton a
bright yellow, the fabric appearing not uniform in colour, but streaky. When the
fabric becomes so unequally streaked as to make it difficult to discern whether it be
linen or cotton, the following test will prove decisive:-Place the streaky fabric in a
solution of spirits of wine, and then in a weak solution of aniline red, by which it
344
CHEMICAL TECHNOLOGY.
becomes coloured, and finally let it remain one to three minutes in a weak solution
of sal-ammoniac; the colour of the cotton fibre will be dissipated and the linen will
become a beautiful rose-red. From Elsner's first test for change of colour the
method of previously colouring the linen fabric was established. Cochineal was
selected for this purpose, and the linen placed in a weak solution, chloride of lime
being used to prevent the colour in the linen running, while the cotton contained in
the fabric changes colour immediately. Frankenstein's oil test for uncoloured fabrics
can be recommended for its simplicity and excellence. The fabric is dipped in olive
or rape-seed oil; it quickly becomes soaked through, and the surplus oil is removed
by blotting-paper, the linen fibre becoming transparent, leaving the cotton opaque.
When an unbleached fabric is tested in this manner it appears shining at first, but
becomes dimmer in the parts where the cotton is present. A truer method of testing,
however, is given by the magnifying glass. Böttger gives a test with potash. The
linen fabric is immersed in a concentrated solution of potash; in about two minutes
it becomes a deep yellow, the cotton fibre assuming a light yellow.
Stöckhardt gives a spirit test. Linen fabrics are placed in layers with lighted
brandy; the linen fibre extinguishes the flame, while the cotton acts as a wick,
absorbing the spirit. This experiment can be successfully used with coloured
materials, with the exception of those coloured with chrome-yellow, chromate of
oxide of lead. The singeing test requires the most delicate treatment. The fibre is
placed in a glass vessel over the flame of the spirit-lamp until it becomes a light
yellow; then by microscopic examination the cotton fibres will be found curled up,
while the flax fibres are distended and clearly separated from each other. Hemp and
flax act in the same manner, but do not separate so much. Nitric acid can be so
FIG. 196.

FIG. 195.
FIG. 197.


applied as to leave the flax fibre unchanged in colour, while the hemp immediately
becomes a pale yellow, and the New Zealand flaxes, Phormium tenax, a blood-red.
The admixture of cotton in linen fabrics became known through O. Zimmermann,
who tried the following test:-Place the fabric in a mixture of 2 parts saltpetre and
3 parts sulphuric acid for eight to ten minutes, then wash, dry, and treat with alcohol
containing ether. The cotton so treated is soluble as collodion, the linen fibre is not.
Separation of Animal and Vegetable Fibres by Means of Singeing. The mixture
is placed near a bright flame to singe until the hair is consumed, leaving a black
ashy mass in the same proportion as the fibre, if it be mixed with sheep's wool.
PAPER.
345
Animal and flaxen fibres are separated by boiling in potash, which loosens the
filaments of wool or silk, leaving the cotton and linen fibres unaltered. Pohl gives
us the following test :-Place the fibres in a solution of picric acid for one minute;
then carefully wash; the wool or silk filaments will have turned yellow, the cotton
or flax fibre remaining white. This can be applied to mixed fabrics; but the most
certain method is under the microscope, where the linen fibre appears in a cylindrical
form, Fig. 195, and never flat. It is not stiff nor twisted, and is chiefly characterised
by the narrowness of its inner tube. Hemp is similar to flax fibre, being easily
broken; its ends branch out stiffly, and its tube is open. The fibres in cotton fabrics
are long, of a close, thin texture, like a twisted band, as in Fig. 196. Sheep's wool
under the microscope appears thicker than the other filaments, having a perfectly
circular stalk with tile-shaped scales, as seen in Fig. 197. The silken fibre, Fig. 198,
FIG. 199.

FIG. 198.
FIG. 200.


is a slender column, smooth on the exterior and easily distinguishable from wool,
Fig. 200, representing a mixed silken and woollen fabric, as it appears under a low
power. Wool and cotton, Fig. 199, are also easily distinguished from one another.
History of Paper,
PAPER MAKING.
Paper is in reality a thin felt of vegetable fibres mechanically and
chemically clarified, crushed and torn into a pulp suspended in water. This pulp is
spread equally in thin layers, drained, pressed, and dried into the compact substance
we call paper.
Of the history of paper we have the following:-In very ancient times men engraved
signs upon stone, iron, lead, ivory, wood, &c., and by this means handed down their
thoughts to posterity. Later, palm and other leaves were used for this purpose, also
various barks of trees, especially the smooth inner bark. The old Germans wrote upon
birch bark, and there is still an old Pagan poem in existence written on this bark. Other
nations painted with a brush on cotton or taffeta. Indeed, about 600 years before
Christ the Egyptians prepared the Cyprus grass, Cyperus Papyrus or Papyrus antiquorum,
for writing purposes. This grass grew from 2 to 3 metres high; specimens are very rare.
In the time of the Roman Empire it was the customary means of conveying intelligence,
and was considered a luxury until 1100 or 1200, when its use was discontinued. A cotton
cloth was then substituted under the name of parchment, and was held in great favour on
account of its strength. Spanish paper was much esteemed until 1200. About that time
an attempt was made to mix cotton with linen rage. This was accomplished in 1318. It
was not well known in Germany until 1400, although the first account of its manufacture
346
CHEMICAL TECHNOLOGY.
is in 1390, when Murr opened a large paper mill in Nuremburg. Later still we have
mention of a paper mill by Shakspeare in the Second Part of Henry VI., the plot of the
play being laid about a century before the time it was written. History records that
Sir John Spielman owned a paper mill near Dartford in 1588, for the erection of which he
was knighted by Queen Elizabeth. Since this time the manufacture has steadily
progressed.
Paper Manufacture.
Materials of The chief materials of paper manufacture are the waste rags from
flax, hemp, silk, wool, and cotton. The linen rags are mostly in request for making
the best and most durable white writing and printing paper. Silk and woollen rags
are unfit for this purpose, as the bleaching material will not act upon animal sub-
stances. Cotton in a raw state requires less preparation than hemp. Rags are
classed under different denominations,-fines, seconds, and thirds, the latter com-
prising fustians, corduroys, stamps, or prints as they are technically termed. The
waste refuse from the wadding machine used in cotton spinning is employed for
scribbling paper. Bibulous papers, such as blotting and filter papers, are made from
woollen rags, on account of their open texture; cotton rags, also, make a spongier,
looser paper when unmixed with linen.
Substitute for Rags. The consumption of paper in Europe has more than doubled within the
last fifty years, and, owing to the inefficient supply of rags, substitutes had to be found
in straw and wood. The Chinese first used vegetable pulp for paper manufacture. The
inner bark of the bamboo is particularly celebrated as affording a paper yielding the most
delicate impressions from copper-plate, and this paper was originally called India-proof.
The Chinese also use the bark of the mulberry and elm trees, hemp, rice-straw, and wheat.
Among the straw species appears the maize (Indian corn), from the fibre of which a paper is
made that for purity and whiteness cannot be equalled. Also the Andropogon glycichylum,
or Sorghum saccharatum, a native of North America, is used; in fact nearly every species
of tough fibrous vegetable, and even animal, substance has been tried, but of these straw
has been most successfully applied, in combination with linen and cotton rags, when the
silica contained in the straw is destroyed by means of a strong alkali. If the straw is
The use of straw is
not properly prepared the paper will be brittle, and unfit for use.
not very extensive, owing to the extra expense of preparation, and its waste under the
process. It is used for making common brown paper, but it is chiefly used for giving a
stiffness to cheap newspapers. All soft woods are fit for paper-making, such as the
trembling poplar, linden, aspen, fir, &c.; the pine is of too resinous a nature to be of
much value. The preparation from wood is made in the following manner:-The bark is
sawn and split into suitably-sized pieces, and the fibres separated by pressure between
horizontal rollers copiously supplied with a stream of water. The water, which forms
two-thirds of the mass, is then removed by further pressure, generally hydraulic.
1867, Bashet and Machard treated the woody material with hydrochloric acid. Later,
waste wood has been treated chemically, in the large manufactory of Manayunk, of
Philadelphia. The finest wood is set apart into lots. No. I is used for making writing
and printing paper; No. 2, wall paper, packing paper, and inferior kinds of printing
paper; Nos. 3 and 4 for label and pasting paper. Spanish woods are largely used, on
account of their smoothness.
to the Rags.
In
Mineral Additions We find minerals used in the present manufacture. A moderate addition
of a mineral body to the paper material whitens the whole, and for inferior
or ordinary paper is successfully employed. It is unfit for very thin paper, making it
shiny and brittle. A profitable addition of mineral matter is from 5 to 10 per cent. of the
weight of paper, a greater addition making the paper dull, brittle, and hairy to write upon.
The usual mineral mixtures in frequent use at the present day are-clay free from sand,
China clay, and kaolin. Aniline pearl-hardening, dissolved into a pulp resembling clay,
is most preferred, being not so expensive. In 1850 it was favourably received, under the
names of fixed white, raw white, patent white, or permanent white. With 100 kilos. of
paper pulp 15 kilos. of the paste is generally employed.
by Hand.
Manufacture of Paper The old method of making paper by hand was from the pulp of
waste paper placed in a mould of the required size; but this method, although still
used for writing paper, was found to restrict the size of the sheets, and different
methods were tried with varied success, until a machine was invented which, without
the aid of moulds, manufactured the paper in any length.
PAPER.
347
the Rags.
Cutting and Cleaning The Cutting and Sorting of the Rags. The first operation is per-
formed by two machines, called the half-hollander and the whole-hollander. The
rags are next treated chemically with potash to rot them. By the old method, rags
were cut into pieces about 4 inches square, by being drawn across a sharp knife fixed
upon a table. Machinery has superseded this arrangement, and various cutting
machines have been invented, among which we may mention that of Mr. Davey, in
which a horizontal knife revolves around a fixed cylinder cutting the rags into strips.
Bennet's cutting machine consists of two knives radiating from a wheel, and bearing
against another knife. Some machines are constructed with a quantity of circular
sharp-edged steel plates, like the machine of Uffenheimer, of Vienna. After cutting,
the rags are cleansed from dust and other impurities by the Willow machine. The
best kind of sifting machine is in the form of a drum with the upper part covered
with a wire grating. The rags are put in by a side door, which acts, as the drum
revolves, as a refuse door, casting off the sand and impurities, leaving the rags win-
nowed. They are next boiled in an alkaline ley, or solution of 4 to 10 pounds of
carbonate of soda, with one-third of quick-lime to 100 of the material. The rags
are placed in large cylinders slowly revolving, and causing them to be constantly
turned over. Into these cylinders a jet of chlorine water, with a pressure of 30 lbs.
to the square inch, is directed. H. Volter patented in 1859 a horizontal steam
cylinder, which receives the steam from a tubular guide-cock provided to the boiler,
an inner cylinder revolving to move the rags. The distant end of the boiler and the
tubular cylinder draws up, and the mass is easily poured into the washing machine
when in a fluid state (Silberman's Washing Hollander). Although partly cleansed
by the above method the rags still require further boiling.
The Separation of the Rags
for Half-stuff and the Whole-stuff.
are:-
The machine used in separating and rending the rags
1. The German stamping machine.
2. The rag mill (rolling hullander).
a. The half-hollander.
B. The whole-hollander.
Formerly the rags were rotted before crushing, being placed in a stone trough, where in
two or three days they became heated, and developed a strong ammoniacal odour.
When the surface was covered with a mould, the rags were sufficiently decayed for the
purpose of manufacture. They were then taken out in a brown mass, those remaining
behind as sediment being used for coarse paper. The present method of boiling the rags
with alkalies is preferable, giving the paper greater firmness.
Stamp Machine.
The German stamp machine is at the present time only to be found in
smaller manufactories. It is of the nature of a hammer. Six or eight stamp rods are
fixed into a strong oak beam, and work intermittently with a set below. Through an
opening provided with a fine sieve the water is conveyed away. As the hammers rise
and fall, the stamp holes serve for a water conduit. Three to five hammers work in each
hole. The rags are mixed with sufficient water to form a pulp, and remain in the
machine 12 to 20 hours and more.
The Hollander. The hollander mill is fast becoming a universal favourite. It is somewhat
similar in principle to the stamping machine, but in strength and speed greatly excels
every other machine. Fig. 201 is a half-hollander; Fig. 202 the vertical section
through the line a B.
The chief characteristics of the hollander are:-1. Speed of
2. The box of knife edges under the revolving
revolution of the trimming knife.
cylinder. 3. The trough and revolving cylinder. 4. The cap or partition above the
trough to prevent the mass being cast out when in motion. The trough, c C, is a long
oblong cistern of cast-iron, stone, or wood lined with lead. The cover rests upon a
348
CHEMICAL TECHNOLOGY.
partition, xx, of equal height with the outside wall. The machine is divided into two
parts, the working side in which the rags are torn or shredded between the knife-·
edges on the cylinder and those in the box, and the running side into which the
shredded rags are thrown by the revolving cylinder. Under the cylinder is a
massive oak block, t, the craw, its concave surface comprising the fourth part of the
circumference of the cylinder. The side y is a little, and z much inclined. Half-
FIG. 201.

h
X
In
ל!
፮
VD
---B
I'm
h
way between h i are two strong beams, l, m, supporting the metal bearings, in which
works the axle, o o, of the cylinder. From the roller, Q, a numbers of cutters run
parallel to the axis. The knives are of soft steel, and in the whole-hollander some-
times bronze. Beneath these a series of knives is placed, against which the rags are
drawn by the cylinder. In order that by the movement of the cylinder none of the
material should be thrown out, a cover is provided, the dirty water thrown up
"l
FIG. 202.

Ꭱ
k
W
u
falling through the sieves, v v, and flowing through the opening, gg. Clean water
flows in from the top of the hollander. The washing finished, the water pipe is shut
by means of a sliding partition, each partition having an inner one to prevent the
pulp passing away. The rags are poured into the top of the hollander with
the requisite quantity of water. The roller revolves 100 to 150 times a minute, the
PAPER.
349
knives cutting more readily in the fluid. Having passed the cylinders and the lower
set of knives, the mass flows over the steep slope of the craw, z, while the roller
continues its work. This mode has this advantage, that the rags have an uninter-
rupted flow, and that all parts have the same resistance under the roller. The work
of the half-hollander is of two hours duration for soft and clean rags, a longer
time being requisite for coarse and dirty materials.
Bleaching the Pulp. After this the mass is placed in another machine, the whole-
hollander, and bleached by a solution of chloride of lime, chlorine water, chlorine
gas, or other bleaching agents. The lime is retained in the machine until the
rags are sufficiently bleached; the pulp is then let down into long slate cisterns to
steep before placing in the beating machine.
FIG. 203.
A
An arrangement for bleaching by means of chlorine gas is exhibited in Fig. 203.
The gas passes from the generator, a a, into a wooden chamber, A, in which the
damp pulp is arranged on shelves. These shelves have openings admitting the
chlorine gas as shown by the
arrows. The surplus gas escapes
through opening, c, to a reservoir,
which is also used for bleaching
the pulp. The pulp is then re-
moved, washed by a solution of
soda, potash, or urine, and after
standing, worked with antichlore, a
term given by bleachers to any salt
that neutralises the pernicious
after effects of chlorine upon the
pulp. By this means, in each 100
kilos. of half-stuff, 2.5 to 5 kilos. of
common salt is developed by the
action of the chlorine gas upon the
soda. When bleached by chloride
of lime, 1 to 2 kilos. are applied to
100 kilos. of pulp. When greater
smoothness is required, a little hydrochloric or sulphuric acid is added, although care
must be taken in its use, for applied too largely it destroys the fibre. Orioli employs
hypochlorite of aluminium, known by the name of Wilson's bleaching preparation,
chloride of aluminium being obtained on the one hand, while, on the other, all the
bleaching effects arise from the delivery of ozonised oxygen (Al₂C1603=30+ A₁₂C16).
Varrentrapp's hypochlorite of zinc, under the name of Varrentrapp's bleaching-
powder, is worthy of notice as being extensively used. In this powder, chloride
of lime, decomposed with zinc vitriol, or, better, with chloride of zinc, is employed.
When bleached by chloride of zinc, the mineral acid decomposes the chloride of
lime, therefore no risk is incurred by the fibre.

Antichlore.
When the bleach retains chlorine, it is washed in soda, potash, or anti-
chlore, to neutralise the adhering hydrochloric acid, which merely washing in water
would not effect. The chief constituents of antichlore are sulphite of soda, chloride of
tin, and hyposulphite of soda. A molecule of sulphite of soda (Na,SO, +7H¸0)
removes i molecule of chlorine (Cl2), whilst hydrochloric acid and sulphate of soda
are formed. A mixture of sulphite with carbonate of soda is employed to neutra-
350
CHEMICAL TECHNOLOGY.
lise the hydrochloric acid. The sulphate of soda and chloride of sodium are re-
moved by washing. Sulphite of calcium is greatly approved, and is considered
to be as effective as antichlore, when applied as the corresponding sodium salt. A
molecule of tin-salt (SnCl₂+2H2O), is taken up by a molecule of chlorine (Cl₂), by
which chloride of tin (SnCl4) arises. After the working is completed, so much
carbonate of soda is added as is required to saturate the hydrochloric acid. A
molecule of hyposulphite of soda (Na2S2O3+5H₂O), absorbs 4 molecules of chlorine,
whilst sulphate of soda, hydrochloric, and sulphuric acids are formed. Some salts
of lime are also commercially known as antichlore.
Blueing. Notwithstanding the careful chemical bleaching, the pulp has still a
yellow tinge, and requires a colouring matter which is generally introduced in the
process of beating. The blues generally used are ultramarine, Paris blue, indigo,
aniline blue, oxide of cobalt. With 100 kilos. of the dry paper stuff, o'5 to 1'5
kilos.
of ultramarine are mixed, according to the strength of the colour required.
Sizing.
The pulp requires sizing to preserve the colour. It is guided, as it issues
from the hollander, through a tub of size, and afterwards carried over skeleton
drums, containing revolving fans to dry it as it passes; heated cylinders are also
used for drying. Starch is used to give a thicker consistence to the size, which is
generally made from the best glue, resin being added in quantities, never exceed-
ing 3 kilos. per 100 kilos. of pulp, to impart the desired amount of stiffness.
a. Hand Paper.
Straining the Paper Sheets. There are three ways of straining or filtering the pulp:—
First, by straining through a brass sieve with fine slits to allow the pulp to pass,
and retaining all lumps and knots. Secondly, by pressure; and thirdly, by evapora-
tion. In the first operation the sheet is formed by a mould of the size required,
being dipped into a tub of pulp previously strained. The pulp becomes distended to
a thin layer and the water filters off. The tub is either round or of a quadrangular
shape made of wood, lined with lead. A broad board running across the tub is
called the bridge, and a smaller one under the larger one, the little bridge. The
large bridge has a pointed support, technically termed the donkey, for the form or
frame to lean against.
The sifting machine, technically termed the knotter, used in the manufacture
of hand-paper, consists of an upright cylindrical sieve, in which an inner cylinder
revolves. As the whole-stuff is taken from the tub, the remainder becomes massed
together, and steam or other pressure is employed to force the pulp through the sieve
and cylinder, the latter retaining the lumps and knots. The paper forms, upon which
the whole-stuff is placed, are constructed with brass wires to allow the water to drain
off, retaining the pulp. There are two kinds of forms :—
1. The Ribbed form.-A square or oblong frame of oak or mahogany with parallel
brass wires and cross wires at intervals to steady them. Lined paper is made on this
form, and is not much glazed on account of the time and expense, being reckoned an
inferior paper.
2. The Vellum Form.-A frame of finer brass wire-work. Vellum paper is made on
this form, and has a delicate even surface; it can be made to present any degree of glossi-
ness by pressing and satining. When held to the light it appears uniform, not possessing
bright and opaque lines as in the former paper.
A ribbed form similar to the vellum form is employed in the manufacture of paper
distinguished by trade marks, coats of arms, &c., the impress of the wire forming what is
termed the water-mark; bank-notes are made separately in a mould in this way. The
edge of the form makes the edge of the paper, forms being used according to the size
PAPER.
351
required; also the quantity of the whole-stuff varies in accordance with the required
thickness of the sheets. Felt is extensively used in the manufacture of paper; it is un-
like the ordinary felt for hats, being a coarser, looser, white woollen fabric, more suitable
for rolling.
The work of the pulp-tub is divided into two parts, the squaring and the scooping; the
latter is the placing of the pulp in the mould, the former the placing of the sheets between
felt. The tub is stirred occasionally with a pointed stick, technically termed the scoop
stick. The pulp is taken out on the form in a sloping position, shaken a little to aid
cohesion, and finally placed on the small bridge. The next sheet is placed on the large
bridge. The form is laid in a sloping position against the donkey-rest to drain, and the
paper finally placed on the felt to dry a little, the empty form returning to the tub. The
first paper sheet is covered with felt, on which the next is placed; the average number of
sheets manufactured exceeding 5000 a day.
Pressing the Paper. As soon as there is a sufficient number of sheets, they are made
into a thick bale and placed under the press, the number of sheets comprising a bale
being generally 181. Three bales, 181 × 3 = 543 sheets; twenty quires 480 sheets
sized, and 500 unsized. Pressing gives firmness and glossiness, and by continued
pressing exceeding smoothness is obtained.
Drying the Paper. The process of pressing has not quite removed the water from the
paper, which has to be dried in an airy chamber, the sheets being placed separately,
or two to five together as required. An expert workman can place 800 to 900 layers
of two to five sheets each in a day, as well as hanging and drying the sheets and
taking them off the cord.
Sizing the Paper. The paper is not durable unless it is sized, and is only used for filter-
ing, packing, printing, or scribbling papers. Sizing gives the paper substance by
filling the pores, and making it firmer, stiffer, and harder. Ordinary size dissolved
in water will not always prove effective, and it is necessary to add a solution of an
aluminium salt, such as that of alum, sulphate of alumina, or chloride of aluminium,
to prevent decay. Without chemical preparation the sheets are rendered sticky and
have to be sized separately, but with the above addition 80 to 100 sheets can be
successfully sized by hand; a good workman can size 40,000 to 50,000 sheets in
twelve hours. The sheets must not be dried too quickly after sizing.
Preparing the Paper.
After the sized paper is pressed and dried, it requires further pre-
paration to make it fit for use. The first process consists in the finishing or trim-
ming to remove all the little specks and blemishes, and to smooth the sheets. The
finished sheets are counted and placed together, the workman by continued practice
counting 8000 to 15,000 sheets as he places them, and separating them into whole and
half quires, twenty-four sheets of sized and twenty-five sheets of unsized paper
making a quire; the upper and under quire of each ream being placed on an extra
sheet, known as outsides. The even and glazed surface is mostly obtained by hot-
pressing, when every sized sheet is interposed between two unsized sheets; this is
called interchanging. The preparation of the various kinds of paper is now accom-
plished, with the exception of the finest letter paper, which requires an extra pro-
cess to give it a final gloss, by pressing between the rollers of the satining machine.
The different varieties of paper are classed under three denominations:
The Different Kinds
A. Writing and drawing paper, the smaller kinds of copy paper, deed
of Paper. paper, the finer post and letter paper, and vellum letter paper.
B. Printing paper for books, as distinguished from copy printing, deed printing, post
and vellum printing, note and copper-plate printing paper. Silk papers for valentines,
ornamented with gold or silver, and printed from engraved copper plates.
C. The looser textured papers, such as unsized parcel paper; the better kinds are
filter- and blotting-papers. Packing paper is half-sized, and appears as a yellow straw
paper, blue sugar paper, and pin and needle papers.
i
352
CHEMICAL TECHNOLOGY.
Manufacture of Machine Paper.
B. Machine Paper.
Manufacturing paper by hand requires much time and
labour, and machinery is found to be quite as efficient. Endless paper of any breadth
can be made by machinery with the same amount of strength and firmness as hand
paper.
The straight form and the vibrating machine are used for finer paper.
1. It is requisite that the machine should make the pulp of a suitable consistence by
diluting it with water.
2. Purify the whole-stuff from knots.
3. When free from knots work the material by means of regulators, delivering the
stuff from the form, and producing by the uniform flow of the pulp a smooth paper leaf
of the breadth required.
4. Be so regulated that the stream of whole-stuff may form a sharply turned leaf.
5. Free the paper leaf from water, so that it only requires drying in an airy chamber
and pressing.
6. For removing the water, steam cylinders are principally used.
7. The finished paper is cut into sheets by the paper cutting machine.
After the whole-stuff is thinned to a consistence easily moved by water, it flows
to the knotter, placed in a perforated cylinder of sheet brass, which is supplied with
an interior mechanism revolving with greater velocity. One of the best knotting
machines is Mannhardt and Steiner's, of Munich. After the whole-stuff is
purified by the knotting machine it passes out, and the whole-stuff reservoir is sup-
plied anew. In course of time the consistence becomes altered, sometimes producing
a thicker sheet than required; this variation is obviated by the regulator, an
essential in the paper manufactory. A complete paper machine is shown in Figs. 204
and 205. The drawing is divided into two parts; Fig. 205 is seen as the continua-
tion of Fig. 204. After the whole-stuff has passed from the knotting machine, a, it
flows into the small trough, a', and is forwarded by the regulators to the form. The
form, a"a", is an endless wire sieve, similar to the vellum form, the upper part
extending horizontally over a number of copper rollers. The forms are from 3 to
4 metres long, and 1 to 16 metres broad, and are moved by means of a band
passing over pulleys Next to the regulators, a', the rollers lie closer together.
The form of course has a double motion, advancing in the direction of the paper
sheet, which is carried to a vacant part of the wire and deposited, the form completing
its circuit underneath. Periodically the form receives a shaking or vibratory move-
ment breadthways. The paper has sometimes an uneven margin, and to equalise the
substance of the layer, two fine brass wires are placed near the under edge of the form,
while leather bands, mm, kept in place by the pulley, t, are placed on both sides of
the form to keep the sheet straight, the bands passing through a vessel of water, n,
to cleanse them of the adhering pulp. The water in the cistern, c, cleanses the wire-
work forms. It is now necessary to commence the drying of the pulp; this is
effected by an air-pump, or preferably by suction apparatus placed in the box, dd,
over which the whole breadth of the paper sheet passes. After the paper leaf passes
the box, it is pressed under a wirework cylinder, e', under which is a corresponding
cylinder; these perforated rollers are called dandy rollers. The paper sheet is now
somewhat pressed and dried; the empty form returns, and the leaf passes free from
the form over an endless felt to the wet press, hh, which consists of two iron rollers;
one glazing the paper, the other passing the leaf to another pair of rollers, h'h',
Fig. 205, which press and dry the leaf. The paper leaf is finally submitted to the
dry press, which consists of a larger cast-iron cylinder, u, v, w, interiorly heated to
nearly 130° C. by steam. These cylinders and the corresponding rollers, u', v', w', are
PAPER.
353
FIG. 204.
n
b
"
M
In
W
covered with felt. By the double
pressing, the paper becomes dry
and requires damping before the
final pressing. The press w w is
not so effective as v v, as it dries the
surface unevenly, causing one side
to be more glazed than the other.
The finished paper passes under
the roller, y, to the windlass, j, and
is transferred by means of the arm,
k, to the windlass, j', where it arrives
at its journey's end. It is then cut
into sheets of the size required, by
the paper-cutting machine.

Paper-Cutting Machine.
When finished
At-
by the machine, the paper is cut off
into long lengths and rolled by hand
for the manufacturers of drawing and
wall paper, scene-painters, &c.
tached to a large wheel is a knife,
whose regular strokes cut the paper
into the size required. The clipping
machine is used for cutting the edges
of books.
y. Pasteboard and other Paper.
Making Pasteboard. Pasteboard is made
in three ways:—
1. By placing the pulp in a form
-form-board.
2. By pressing several
several damp
sheets to form a thick card-elastic
pasteboard.
3. By pasting together the finished
paper sheets-sized pasteboard.
1. Form-board is an inferior kind
employed for ordinary purposes of
packing, bookbinding, &c. It is made
from waste paper, refuse rags, and the
coarser parts of the pulp. Clay or
chalk is sometimes present to 25 per
cent. of the weight of this pasteboard.
It is made in a coarse ribbed form,
goes through the same process of
knotting as the paper sheet, and is
dried and pressed under a roller.
2. Elastic pasteboard is of better
material, and presents a smoother
surface; six to twelve sheets of paper
previously damped are placed together,
and pressed into one compact sheet.
A separate and harder kind of paste-
board is the thick elastic board used
for binding books. The inner layer is
made of coarser stuff, sawdust, &c.
24
354
CHEMICAL TECHNOLOGY.
3. Sized pasteboard, or cardboard, is made of two to fifteen sheets of sized paper,
pressed, and satined. There are varieties of this cardboard, such as Bristol-board,
FIG. 205.

H
'n'
A
London-board, the former being extensively used for water-colour drawings, mounting-
board, ornamental-board, &c.
STARCH.
355
Papier maché is used for fancy articles, such as the covers for albums, inkstands,
blotting-books, paper-knives, &c., as well as for the cells of galvanic batteries. It is
obtained from old paper made into a pulp with a solution of lime, and gum or starch,
pressed into the form required, coated with linseed-oil, baked at a high temperature, and
finally varnished. The pulp is sometimes mixed with clay, sand, chalk, &c., and other
kinds are made of a paste of pulp and lime, and used for ornamenting wood, inlaying, &c.
The papers made from coloured rags are the brown packing paper
and coarse coloured papers, such as sugar and pin paper.
Coloured pin paper
requires to 50 kilos. of dry pulp the several undermentioned substances:
(2:05 kilos. Acetate of lead,
Coloured Paper.
Bichromate of potash;
Sulphate of iron,
Ferrocyanide of potash;
Blue,
Yellow;
Yellow
10:45
""
Blue
ર
Green
...
Violet
Rose
11.05
(3.00
I'05
I'05
6.00
{2:05
""
""
>>
""
Buff
༥ 3,༠༠
""
Extract of Brazil wood;
Oil of Vitriol,
Extract of logwood;
Chloride of lime.
Ultramarine and aniline blue are also used in colouring the paper. In variegated
papers, chemical, mineral, and vegetable colourings are used according to the
required colours. Body colours are rendered fluid by a solution of gum arabic or
alum in the size, which can be applied by a brush or sponge when only one side is
to be coloured. Variegated and tapestry papers are an important part of the
manufacture.
Parchment Paper.
Parchment, although made of animal membranes, is often con-
founded with vegetable parchment (phytopergamet). The latter is made of
unsized paper treated with sulphuric acid or a solution of chloride of zinc :—1 kilo.
of concentrated sulphuric acid and 125 grms. of water, in which the paper is immersed
so as to equally affect both sides. The length of time differs according to the quality
of the paper, the thicker or firmer paper taking a longer time to saturate; soft paper
will take five to ten seconds. It is then placed in a weak solution of sal-ammoniac,
rinsed in water until no trace of the acid remains, and then dried. When these
operations are effected mechanically, a steam machine first pulls the endless paper
through a vat of sulphuric acid, then through water, sal-ammoniac, and again
water, the paper passing on over cloth rollers to dry, and finally over polished
rollers to press and glaze the surface.
Parchment paper, as a rule, is of one colour; when dipped into water it is
rendered soft and limp. It is used for documents, deeds, records, &c., also for
drawing plans, charts, bookbinding, printing, and cards.
STARCH.
Starch granules, one of the vegetable substances most extensive in nature, always
appearing organically, are the foundation which, chemically treated, yield starch as
commercially known. Starch is found in most organic combinations considered in
chemistry and morphology, and in which cellulose is necessarily a component,
being closely allied to, if not really isomeric with, this vegetable substance; its
formula is C6H1005. In following its connections it becomes the starch that,
by means of chemical and physical agents, in the preparation of starch gum
(soluble starch-dextrine) and sugar forms one of the most important substances
356
CHEMICAL TECHNOLOGY.
presented to the consideration of the technologist. It seldom appears in a large
granular form, but presents itself as a white glistening powder, which upon micro-
scopic examination seems to be made up of various rounded bodies with rings con-
centric to a central spot; these lines are more plainly indented and cover a greater
extent in some than in others, whilst the interior of the grain appears hollowed.
The granules from different plants vary in size and form; those from wheat being
smaller, whilst those from tropical products are thicker and more lenticular. Payen
gives the largest dimension of the granules as o'001 millimetre'; from his researches
we gain also the following examples :-
Starch granules from close Potatoes
""
""
""
""
""
ordinary Potatoes
Maranta indica
Beans
Sago Palm
•
•
• •
Iceland Moss
Pea
""
Wheat
""
""
""
""
""
""
Indian corn
• •
•
•
185
140
140
·
74
70
67
엉엉엉
​50
50
50
Fig. 206 shows, according to Schleiden, granules of potato starch, and Fig. 207 of
wheat starch. The potato has a larger granule, and sometimes gives a finer powder
than wheat.
Nature of Starch.
The usual starch contains in its dry state nearly 18 per cent. water,
and in this state has a tendency to form itself into globules; it has been proved that
exposed to a damp atmosphere it absorbs 33.5 per cent. water. Starch is insoluble in
FIG. 206.
FIG. 207.


80
O
с
со
со
80
оо
cold water, alcohol, ether, and oil. At a temperature of 160° starch yields dextrine.
Starch mixed with twelve to fifteen times the quantity of warm water at a temperature
of 55° varies little in substance; at a temperature of 55° to 58° it begins to change,
the higher temperature making the fluid thicker. Lippmann says that potato starch
is affected at 62.5°, wheat starch at 67.5°. When boiled the granules burst and form a
gelatinous mass, which, largely diluted with water, can be made of a consistence to be
filtered through paper, and, when allowed to cool, sets in a jelly. A stiffer paste,
according to J. Weisner (1868) is made from Indian corn than from the potato or
STARCH.
357
wheat. The longer the starch is boiled the stiffer the paste becomes, I part of starch
separating in 50 parts water, and upon cooling setting into paste of a blue or violet
hue. Dry starch possesses a specific weight of 153. Alkalies and dilute acids,
with lime, tend to re-form the granules; when boiled with 2 per mille of oxalic acid,
the starch loses its consistence, becoming thin, and changing into a soluble substance
called dextrine. Starch treated with almost any dilute acid, or with diastase
obtained from an infusion of malt, at the proper temperature is converted into
dextrine, forming a liquid which after a few hours' standing can be made into
sugar. Starch is soluble in the cold in concentrated nitric acid; water dropped
into this solution precipitates the granules as an explosive combination. Under
the name of xylodine, or white gunpowder, this combination has lately been
employed for pyrotechnical experiments. By boiling starch with concentrated nitric
acid, a formation of oxalic acid is obtained, evolving nitrous vapours. Starch paste
upon exposure to the atmosphere becomes sour, forming lactic acid.
Sources of Starch. But few vegetables yield starch in large quantities: the potato
yields 20 per cent.; wheat 55 to 65 per cent. ; rice 70 to 73 per cent. ; and the roots of
Jatropha Manihot and Maranta arundinacea, palm pith, and the Canna coccinea,
similar quantities. In Germany starch is prepared only from potatoes, rice, and
wheat, the latter yielding a greater quantity of gum, and potato starch being thinner
and not so gelatinous.
Starch from Potatoes. Potatoes form an important material in the manufacture of starch;
their constitution is as follows:-
Water
Albumen
Fatty matter
Cellulose
Salts
Starch..
•
•
Newly dug
Potatoes.
Potatoes
dried at 100°.
75'1
•
2.3
9.6
O'2
0.8
0'4
I'7
I'O
4'I
21'0
83.8
100'0
ΙΟΟ Ο
They contain 28 per cent. dry substance, or 23 per cent. insoluble substance, and
77 per cent. sap. The starch found in potatoes is of cellular construction; the cell
walls require breaking up to fit it for manufacture. Fig. 208 shows, according to
Schleiden, a fine specimen of a healthy potato under the microscope. On the outside
of the potato a layer of flat, pressed, brown cells are found, sometimes appearing
in a patch, a, forming the outer skin of the potato, and covering the cells, b, which
sometimes contain a finer grain, but mostly a clear fluid. These cells become
wider as they near the interior of the potato. The series of cells, c, enclose the
inner cells, d, the pith of the potato. When the potato is dried, the cells separate
from each other, as in Fig. 209, a specimen of a mealy potato. The starch granules
swell in each cell, the cells uniting in reticulated streaks. The process of manu-
facturing starch consists in :-
1. Triturating the fresh potato.
2. Washing the starch granules from the pulp.
3. Purifying and drying the starch.
The potatoes are placed in a grinding cylinder, which formerly consisted of wood, with
iron plate rollers placed half way in water to cleanse the pulverised potato pulp. Of late
grinding cylinders with saw-teeth are used (Thierry's machine). The saw-blades have
short teeth, lacerating the cells to obtain the starch granules, which mere gentle
washing and grinding would not effect; the cylinder revolves 600 to 700 times a minute.
358
CHEMICAL TECHNOLOGY.
One cylinder with knives o'50 metre in length and saw-blades of 0.40 metre, can grind
fourteen to fifteen batches in an hour to a pulp, which is afterwards submitted to the
process of washing. A cylindrical metal sieve is generally used for separating the
starch granules from the potato pulp; it contains a pair of brushes slowly rotating,
whilst water is supplied to the sieve to wash the pulp, which is ground to a consistence
that will admit of its readily flowing off, in order that fresh pulp may be received on the
sieve. The starch granules are suspended in the water strained off, and finally settle to the
bottom as a soft white powder. Laine's uninterrupted cleansing sieve is now generally
used; it consists of a series of wire-work frames placed over a trough. The potato pulp
flows from the grinding cylinder to a space under the cleansing sieve, from thence over
two gratings, where the pulp is cleansed by a stream of water playing all over it, the
granules settling down at the bottom of the trough. The granules are then crushed
between steel rollers to separate the starch from the fibre. 80 to 100 cwts. potatoes can
be thus prepared in a day. From the above method of preparing starch from the potato
we gain the general principles of such operations. The structure of the potato is shown
to be partly chemical, partly mechanical, and by destroying the latter we gain starch, which
is separated after the potato pulp has been standing eight days, when it becomes a white
FIG. 208.

b
C
ď
FIG. 209.

e
pasty mass containing starch. This is placed in a coarse sieve, which retains a greater
part of the fibre, another finer hair sieve being used to receive the starch and finer
fibre, separated from each other by means of a cleansing apparatus, which washes the
fibre away, leaving the starch granules and sugar behind.
Drying the Potato Starch. The result of the washing is a milk-like fluid, which settles at
the bottom of the trough as starch; it is then mixed with fresh water and allowed to
solidify into a hard substance, which is cut into pieces, poured upon a linen cloth placed
on a hurdle, with a plaster-of-Paris vessel, or a vessel containing gypsum, underneath, to
dry the starch. After being watered and left to stand for twenty-four hours, the
starch dries to the thickness of 2 decimetres upon the gypsum. Of late the water has
been removed by a centrifugal machine. The moist starch contains 33 per cent. water,
and is called fresh starch. The average temperature of the drying rooms is not over 60º.
When the starch is dried it is broken into pieces by iron rollers. The stalk or whole
starch is made by boiling to a thick paste, which is forced by machinery through a small
opening into a trough, where it dries in a kind of mould.
According to M. O. Dempwolf, 1869, the unprepared wheat
Preparation of Wheat Starch.
contains:
Water
Ash
Gum
Starch
•
.
•
Fatty and woody fibre
:::
:
•
•
::
::
::
•
10'51
I'50
14:35
65.40
8.24
100'00
STARCH.
359
From the constituent parts of wheat it is seen that:-
Starch
Gum
Husk
}
are insoluble in water.
Salts
Albumen
Dextrine
are soluble.
The first three are insoluble, the gum, however, being gradually dissolved by the
lactic acid developed from the seed, while the starch and husk remain unattacked.
The different modes of preparing wheat starch are, namely:-
A. By fermentation (old method) of the-
Unground Wheat.
B. Ground
B. New mode of treatment without fermentation.
The old method consists of the following operations:-
1. Fermenting the wheat.
2. Washing the starch from the mass.
3. Washing and cleansing the starch.
4. Drying the starch.
The whole wheat is soaked in water until soft. The seed is separated from
the husk either by treading in sacks in a flat tub of water, or by being placed under
rollers, and the pulp thinned with water to a milky.fluid, in which a greater part of
the starch and gum are found. After standing a day this fluid turns acid; a part
of the gum becomes diluted by the action of the lactic and acetic acids, and is taken
away and replaced by fresh water, the same process being gone through until
the fermentation ceases, when the starch is washed with water and dried. In the
fermentating tub it forms with the water a thin, sour pulp. The time varies
according to the temperature; all the gum is not separated until about twelve to
thirty days. The sour water contains acetic acid, lactic acid, butyric acid, succinic acid,
ammoniacal salts, and the mineral constituents of the wheat. The mass is then placed
in a sack and trodden, the milky fluid being allowed to escape, leaving the husk and
refuse gum behind. The milky fluid containing starch is strained through a fine
hair sieve and washed with water. Another method is that of placing the milky
fluid in a tub and allowing it to settle. The first layer of the sediment is fine
starch, next a mixture of starch, husk, and gum, the last layer containing but little
starch. In the preparation a little ultramarine blue is added during the cleansing
process. Of late the centrifugal machine has been used for the purpose of drying
the starch.
Preparing wheat starch without fermenting :—
According to E. Martin's treatment, wheat flour is mixed with water to a paste,
100 parts flour to 40 parts water; the paste remains to 2 hours to affect the gum,
and is then washed in a fine wire sieve placed over a tub. The starch is found at the
bottom of the tub mixed with water, and is placed in a warm spot to ferment
slightly. It is dried in a mass, and goes through similar processes to the other
starch, being made into stalk and powder starch, and sold in packets.
100 parts of wheat flour yield 25 per cent. of gum (gluten, gluten granulé), with
33 per cent. of water; the fresh gluten is mixed with a double weight of flour, the paste
360
CHEMICAL TECHNOLOGY.
rolled into long strips, and ground into granules, which become dry at 30° to 40°, and
are afterwards sifted. The consumption of this granular gum is extensive, it being
employed for food (with ordinary flour as macaroni), art purposes, and manu-
facture.
Constituents and Uses of
Commercial Starch.
are as follows:
According to M. J. Wolff, the constituents of commercial starch
I.
2.
3.
4.
5.
6.
Water
17.83
15:38
14'52
17'44
14'20
17:49
Gum
ΟΙΟ
traces
1.84
4'96
Fibre
0*48
0'50
I'44
I'20
3'77
2.47
Ash
0'21
0'53
0'03
0'40
0'55
I'29
Starch
•
•
81.48
83.59
83.91
81.32
79.63
73.79
100'00
100'00
100'00
100'00
100'00
100'00
1. The finest white patent starch in stalks, of a bright and crystalline appearance,
made from pure potato starch. 2. The finest blue patent starch, potato starch
coloured with ultramarine. 3. Pure wheat powder. 4. Fine wheat starch in pieces.
5. Medium fine wheat starch in yellowish-white pieces. 6. Ordinary wheat starch
in greyish yellow coarse pieces, that upon microscopic examination appear as a mix-
ture of potato and wheat starch. Starch is used for stiffening domestic articles in
washing, for stiffening paper, and extensively in linen and cotton manufacture,
in gum, syrups, sago, vermicelii, &c. It is also a basis from which we can obtain
sugar. Potato starch is preferred for domestic washing, but where great stiffness is
requisite, wheat starch is used, as in bookbinding, &c. In wheat starch, the paste is
formed of closely united gelatinous particles, which are more widely disseminated in
potato starch, the latter being transparent and more suitable for stiffening fine linen,
ironing smoother, and not sticking. Wheat starch will keep fresh upon exposure to
the atmosphere longer than potato starch, the latter turning sour after a day's
standing.
According to C. Wiesner, 1868, maize starch possesses the highest, wheat the next,
and potato starch the most inferior stiffening qualities. Maize and wheat are consi-
dered the best for forming a smooth equal paste. Sugar can be prepared from
starch by means of the active principle of malt-diastase. From this sugar, again,
brandy and spirits can be distilled. According to the researches of Lüdersdorff:
100 pounds of potato starch need 25'5 pounds of dry malt, and
100 pounds of wheat starch
90'5
>>
to effect the full conversion of the starch into sugar.
Starch. Cassava Starch.
Rice Starch. Chestnut Rich starch is largely manufactured in England, France, and Bel-
Arrow-Root. gium. To extract the gum, rice is placed in a bath of weak soda
solution-287 grms. of caustic soda to the hectolitre. After standing twenty-four hours,
the rice grain becomes softened, and is then washed, ground between rollers or mill-stones,
and placed on a sieve with brushes to retain the husk or bran. The water strained off
contains the starch, which is washed, dried, and manufactured into the form required.
The gum-containing alkaline ley being neutralised with sulphuric acid is fit for inferior
uses. J. and J. Colman's rice starch manufacture employs 1000 workpeople, and the
result of their manipulation is used as the customary washing starch, the stiffer and
brighter starch for ball dresses, window hangings, and for the size in paper manufacture.
In France the chestnut is used for the manufacture of starch. Chestnuts produce a starch
possessing the evenness of potato starch with the stiffness of wheat starch. 100 parts of
the fresh bitter chestnut give 19 to 20 per cent. dry starch.
Arrow-root is obtained from the Maranta arundinacea, and M. indica, cultivated in the
West Indies; it is very like potato starch, and is prepared in a similar manner. Cassava
starch is made from the root of Jatropha Manihot, or Manihot utilissima, and M. Aipin,
largely cultivated in South America, the West Indies, and the Brazils.
STARCH.
361
Cassava is used as an article of consumption both in Europe and the tropics. The
root of the manioc is thoroughly purified from its poisonous juice, being coarsely
ground to allow the sap to escape, and roasted in an earthenware vessel,
the cassava forming into granules on the sides of the vessel (Cassava sago, or
Manioka), the prussic acid contained in the root becoming volatilised. From arrow-
root and the analogous roots containing a poisonous juice, arrow-root derives its
name, having been used by the Indians as a poison for the tips of their arrows. Its
components, according to Benzon, in 100 parts, are-Volatile oil, o'07 parts; starch,
26 parts; 89 per cent. of the starch being obtained in a powder, while the remainder
is extracted from the parenchyma by boiling water; albumen, 1.58 parts ; gum, o‘6
part; chloride of calcium, o‘25; insoluble fibrin, 6 parts; and water, 65'5 parts.
It is known in commerce in several varieties, viz. :-Portland arrow-root, Arum
vulgare; East India arrow-root, Curcuma augustifolia; Brazilian arrow-root,
Jatropha Manihot; English arrow-root, from the starch of the potato; Tahiti arrow-
root, Tacca oceanica.
Sago. Sago is made from the soft central portion of the stem of the palm, Sagus
Rumphii. According to J. Weisner, the Guadeloupe sago is prepared from Raphia
farinifera, and an East Indian variety from Caryota urens. The stem is torn to fila-
ments and elutriated on a sieve with water. The starch obtained is then washed,
dried, and sifted into a copper plate, where it remains a hard granular substance. A
greater part of the common sago is manufactured from potato starch, coloured with
oxide of iron or burnt sugar.
Dextrine. Dextrine, gommeline, moist gum, starch gum, or Alsace gum, isomeric
with gum arabic, and expressed by the formula, C6H1005, is formed by boiling
starch with a small quantity of almost any dilute acid, which thins its consistence,
and converts it into a soluble substance similar to gum arabic. It is soluble in cold
water, insoluble in absolute alcohol, but slightly soluble in weak spirits of wine.
Dextrine derives its name from dexter, the right, from the action of this substance on
polarised light, twisting the plane of polarisation towards the right hand. Dextrine
in grape sugar is converted into dextrose by the action of dilute acids. Dextrine
solution does not ferment with yeast; but a little yeast mixed with a large quantity
of gelatinous starch, at a temperature of 160°, quickly liquefies it, dextrine being
produced, the greater part of which, if allowed to stand, becomes converted into
grape sugar. From this decomposed dextrine a cheap and largely employed sub-
stitute for gum arabic is obtained. The components of this decomposed dextrine,
according to the analyses of R. Forster (1868) are:---
6.
I.
Dextrine.
2.
3.
Dextrine
Sugar..
Insoluble substances
Water
Opaque Dark
Starch. Dextrine.
72.45 70'43 63.60 59*71
8.77
I'92
7.67
13'14 19'97 14'50
5'64
7.68
14°23
4.
Gommeline.
5.
Old Bright
Dextrine. Starch.
49'78
5'34
5-76
20'64
13.89 18.00
1'42
0*24
30.80
86'47
7'95
100'00
100'00
100'00
100'00
100'00
100'00
Potato starch is preferable to wheat starch for the manufacture of this material,
not only on account of its cheapness, but for its greater purity at an equivalent
price.
362
CHEMICAL TECHNOLOGY.
***
Dextrine is prepared by :-
a. Gently roasting.
b. Carefully treating with nitric acid.
c. Boiling with dilute sulphuric acid.
d. Treating with malt extract (diastase).
Preparing dextrine by means of gentle heat is an easy operation. The starch
is roasted until it becomes brown-yellow in colour, in a large copper or iron
plate cylinder, similar to a coffee drum, situated on one side of the oven. Dextrine
is formed at a temperature of 225° to 260°. According to Heuzé, the following is a
better method: -2 kilos. of nitric acid, of 14 specific weight, with 300 litres of water,
are mixed with 1000 kilos. (= 20 cwts.) of starch, and boiled to form a mass, which,
when exposed to the air, becomes dry. It is sometimes affected at 80°, but it
becomes a paste at 100° to 110°. The starch changes into dextrine in an hour or an
hour and a half at the most; it is white and soluble in water. Sulphuric, hydro-
chloric, and lactic acids will produce dextrine; and by the addition of water to dex-
trine, dextrine syrup, or gum syrup, is obtained.
Dr. Vogel gives a simple experiment to illustrate the action of dilute sulphuric acid
upon starch. Nearly all kinds of writing paper are so very largely sized with starch, that
if figures or letters are traced on the paper with very dilute sulphuric acid, and then dried,
the application of iodine in a dilute solution will impart a blue tinge to that portion of
the paper not affected by the acid, the characters remaining white.
Dextrine is extensively used instead of gum arabic in printing wall papers, for
stiffening and glazing cards and paper, for lip glue, surgical purposes, wines, and
in the fine arts it is applied in many ways.
SUGAR MANUFACTURE.
History of Sugar. Sugar has been known in the East Indies and China since a very
remote period. In Europe honey was used for sweetening purposes in the olden
time, and although sugar was known to the inhabitants of Greece and Italy, the
commercial intercourse with India being limited, it was but little used until the time
of Alexander the Great. After the conquest of Arabia sugar-canes were propagated
in Western Asia, Africa, and Southern Europe. The Crusaders became acquainted
with this useful product, and the Venetians began to cultivate it about that time in
Europe and Northern Africa. Malta, Cyprus, Candia, and Egypt, yielded the first
sugar-cane, which was next cultivated in Sicily, Spain, Portugal, and the Canary
Islands, about 1420. In 1506, sugar was cultivated in the West Indies, Brazil,
Haiti, and in many islands of the Indian Ocean. Cane sugar, a substance found in
the juice of various grasses, was first discovered in South America. Ritter mentions
it as a plant capable of great cultivation, to be found in different parts of the globe-
eastwards from Bengal to China; westwards, the Indies, North Africa, Southern
Europe to America. Slaves were imported to cultivate the sugar-canes in North
America in 1800, when the first cultivation commenced, and sugar, which until now
had been a curiosity and a luxury, being chiefly used for medicinal purposes, became
cne of the daily necessaries of life. The art of extracting sugar from the canes and
refining the raw product soon became known, and this useful article of food was
extensively manufactured.
Nature of Sager, Sugar is known as cane sugar and grape sugar, dextrose, glucose
crumbling sugar, starch sugar, potato sugar, and coarse law sugar or fruit sugar
SUGAR.
363
8
12
Cane sugar is prepared from the sugar-cane, maize, the Andropogon glycichylum,
the sap of the sugar maple, the birch, the sweet turnip, and carrot. According to
W. Stein, & per cent. of sugar is found in the root of the madder. The pumpkin,
melon, banana, and most of the species of palms yield sugar. Cane sugar has the
formula C₁₂H22. The crystallised sugar, known as sugar-candy, is hard and has
a spr. gr. of 16; it is unaffected by exposure to the air, and when heated at a
temperature of 180° it dissolves into a sticky colourless fluid, which upon rapid
boiling resolves itself into a pliant uncrystallised mass, commonly known as
barley-sugar. At a very high temperature it becomes black and decomposed. At
210' to 220° cane sugar becomes a dark brown substance termed caramel, used in
colouring spirits, and for other purposes. Sugar has a pure sweet taste, is soluble
in one-third of its weight of cold water; by continued boiling it loses its power of
crystallising. It is insoluble in absolute alcohol and ether, but soluble in dilute
alcohol, especially when warmed. Gerlach, 1864, gives in the following table
the specific weight of sugar solutions with the corresponding percentage of cane
sugar at 17.5° C. :-
Percentage Specific
Cane Sugar. weight Sol.
Percentage Specific
Cane Sugar. weight Sol.
Percentage Specific
Cane Sugar. weight Sol.
75
1*383342
49
1*227241
24
I'101377
74
1'376822
48
1*221771
23
1.096792
73
I'370345
47
1*216339
22
I'092240
72
1*363910
46
I'210945
21
1'087721
71
1*357518
45
1*205589
70
1351168
44
I*200269
69
1*344860
43
1*194986
68
I*338594
42
1*189740
67
I'332370
4I
1*184531
2 HH HH
20
1.083234
19
1*078779
18
1'074356
17
1059965
16
1065606
66
1'326188
40
1*179358
15
1061278
65
I'320046
39
I'174221
14
1*056982
64
1*313946
38
1'169121
13
1*052716
63
1*307887
37
1*164056
12
1*048482
62
1 301868
36
I'159026
II
I 044278
61
I'295890
35
1*154032
ΙΟ
60
1*289952
34
59
1*284054
33
58
1*278197
32
57
I'272379
31
I 149073
I'144150
I*139261
1134406
56
I'266600
30
I'129586
55
I'260861
29
I'124800
54
1*255161
28
I*120048
3
53
I*249500
27
I'115330
52
1*243877
26
1'110646
98 76 4m & H
1*040104
1'035961
1031848
1*027764
5
I'023710
1*019686
I'015691
2
1*011725
1'007788
I
1*003880
51
1*238293
25
I*105995
1'000000
50
1*232748
A watery solution turns the rays of polarised light to the right hand. Dilute
sulphuric and muriatic acids, with most of the organic and mineral acids, tend to
convert cane sugar solutions into a mixture of dextrose and levulose according to
the equation :-
C₁₂H22O11 +H₂O= C6H12O6+C6H12O6.
II
Cane sugar or
sucrose.
Dextrose
(glucose).
Levulose.
From the above it may be deduced that cane sugar is found only in the neutral
juices of plants, while juices like that of the grape containing free acid, tartaric,
#
364
CHEMICAL TECHNOLOGY.
22
12 *22 II)
malic, and citric acids, can yield only levulose and glucose. By treating with
yeast the sugar separates and produces the usual alcoholic fermentation products,
alcohol, carbonic acid, glycerine, &c. Cane sugar enters into combination with
the hydroxides of calcium and barium, forming saccharates, which in the prepara-
tion of sugar on the large scale are of great interest. The sugar solution contain-
ing hydroxide of calcium becomes especially interesting as being the origin of the
application of lime to the refining of cane and beet-root sugars, the hydroxide of
calcium forming a clear fluid with a raw sugar solution containing C₁₂H₂O₁, be-
coming dull upon standing, the sediment containing C₁₂H₂O,,.CaO. Carbonic acid
gas has of late been applied to the sugar lime solution, the lime thrown down as
carbonate and the sugar separating and becoming colourless in the solution.
Preparing cane sugars with hydroxides of barium gives rise to sugar barytes,
C₁₂H₂OBаO, worthy of notice as being insoluble in water and originating the
method of extracting sugar from the juice of beet-root and molasses with caustic
baryta. Sugar barytes is decomposed by means of carbonic acid. An explosive
mixture is formed with nitric and concentrated sulphuric acids and sugar, and
known as nitro-sugar. Cane sugar when mixed with a solution of sulphate of
copper with an excess of caustic potash, is at first but slightly affected; a small
quantity of red powder is thrown down after a time; but the liquid long retains
its blue tinge, while with grape sugar the effects are much increased.
'12 *22 II
Cane Sugar.
Sugar from the
Sugar-cane.
The sugar-cane, Saccharum officinarum, is a plant of the grass species;
its stalk is round, knotted, and hollow, and the exterior of a greenish-yellow or blue,
with sometimes violet streaks. It grows from 2.6 to 6·6 metres high, and from 4 to 6
centimetres in thickness; the interior is cellular. The leaves grow to a length of
1*6 to 2 metres, and are ribbed. The plant is grown from seed, and also cultivated
from cuttings.
A hectare of land yields raw sugar:—
By 15 Months' Cultivation.
""
From Martinique
Guadeloupe
Mauritius
..
""
Brazil
""
Components of the
Sugar-Cane.
2500 kilos.
..
3000
5000
""
7500
In 1 Year.
2000 kilos.
2400
""
4000
6000
The sugar-cane yields the largest amount of sugar, generally 90 per
cent. juice, containing, according to Péligot, 18 to 20 parts crystallised
sugar. The components of sugar-cane, according to the analyses of Péligot, Dupuy, and
Icery, are as follows:-Martinique (a); Guadeloupe (b); Mauritius (e).
Sugar
Water
Cellulose
(a).
Péligot.
(b).
Dupuy.
(c).
Icery.
18.0
17.8
20'0
72.1
72.0
69.0
9'9
9.8
IO'O
0'4
Salts
0'7—1'2
From 18 per cent. sugar found in the sugar-cane, as a rule not more than 8 per cent•
crystallised sugar can be realised. The loss may be accounted for thus:-90 per cent.
juice is expressed from the cane, from which only about 50 to 60 per cent. can be clarified
from the straw, &c.; a fifth part is exhausted by refining; and finally two-thirds of the
sugar is obtained by boiling, while the rest goes to the molasses. The 18 per cent. sugar
may be realised in the following manner :-
SUGAR.
365
Preparing the Raw Sugar
from the Sugar-Cane.
In the refuse sometimes remains
By skimming..
In the molasses
As raw sugar..
6 per cent.
2.5 ""
3
99
6.5
""
18
""
The preparation of raw sugar from the sugar-cane consists in
first expressing and then cleansing and boiling the juice.
1. Expressing the Juice.-The sugar-canes are crushed in a press consisting of
three hollow cast-iron rollers, a b c, Fig. 210, placed horizontally in a cast-iron
frame. By means of the screws, i i, the approximate distance of the rollers is
adjusted. One roller is half as large as the others, and is moved by three cogged
FIG. 210.

粉
​n
wheels fitted on to the axis of the rollers. The sugar-canes are transferred from the
slate gutter, d d, to the rollers, a c, which press them a little, and from thence they
are carried over the arched plate, n, to the rollers, c b. The pressed sugar-canes
fall over the gutter, f, the expressed juice collecting in g g, and running off through
h. The middle roller is termed the king roller; the side cylinders are individually
the side roller and macasse.
2. Refining and Boiling the Juice.-The expressed juice is removed to the boil-
ing-house, which is fitted with five iron or copper vessels. To 15,000 litres of ex-
pressed juice 5 to 9 litres of milk of lime are added. The lime neutralises the
ınalic and other vegetable acids, and upon boiling forms with the albumen and the
other constituents of the juice a thick green scum, which being removed the juice
is allowed to remain in two of the pans to evaporate. A fresh scum is formed on
the first pan, which returns after a second or third time of removal. The juice as
it issues from the press is received into the first pan, in which by slow boiling it
becomes a thick froth, changing by rapid boiling to a clear colourless fluid; in the
third and fourth pans the liquid becomes gradually purer, until in the fifth it crys-
tallises. The finger is dipped into the boiled juice to test its consistence, and by
the length of the pendant drop, which ought to be about 3 centimetres, the thick-
ness is ascertained. The boiled juice is placed in a large open wooden vessel of
about 16 centimetres capacity, and termed the cooler, where after standing twenty-
four hours the sugar crystallises, the cooler being provided with a double per-
366
CHEMICAL TECHNOLOGY.
forated bottom to allow the molasses to escape, leaving the crystals behind. After
standing five or six weeks, the molasses dries into a mass commonly known as moist,
raw, or Muscovado sugar. The molasses passes into a cistern placed underneath
the cooler, capable of containing 15,000 to 20,000 litres of juice, and after standing
fourteen days is ready for the market. In the French and English colonies sugar
is exported in chests covered with fire-clay under the name of chest or tub sugar.
Varieties of Sugar. European commerce deals with the following kinds of raw sugar:-
1. West Indian-Cuba, San Domingo or Haiti, Jamaica, Porto-Rico, Martinique,
Guadeloupe, Saint Croix, St. Thomas, Havana.
2. American-Rio Janeiro, Bahia, Surinam, Pernambuco.
3. East Indian-Java, Manilla, Bengal, Mauritius, Bourbon, Cochin China, Siam,
Canton.
Of late there has been a distinction between sugar cultivated by slave and that by free
labour; the latter comes from Jamaica, Barbadoes, Demerara, Antigua, Trinidad, Dominica;
the former from Cuba, Havana, Brazil, St. Croix, and Porto Rico.
The mode of manufacture varies according to the nature of the foreign sub-
stances that always form part of the constituents of sugar, such as water, fibre,
gluten, sand or earth, soluble mineral salts, acetic and other acids, all of which
must be destroyed before the sugar can be refined. According to Renner we have
in the following sugars from :--
Havana.
97'0-87'3
In Sugar- In Balm.
Raw Sugar
Java.
98.6—83'1
Surinam.
Candy.
92.3-85'4
99.6
99'7
Slime Sugar
5'5-0'3
Water
6'1— 0'3
3'7— 0.9
3'50'9
44— 1'6
ΟΙ
O'2
6'3— 3.6
0'2
O'I
Ash ..
2'10'2
I'4 0'0
20 1'2
O'I
45- 0'4
2′I— I'I
Caramel, gum, vege-35-05
table acids, &c.
Molasses.
The production of molasses is due to the long-continued heating of the
cane juice, but the quality varies according to the nature and culture of the sugar-
canes, the heat of the season, &c. By chemical treatment molasses appears as a
concentrated watery solution of crystallised sugar, slime sugar, with a small admix-
ture of caramel and mineral salts. It is a dull red-brown sweet fluid used princi-
pally in the colonies for the manufacture of rum; it is soon converted to spirit,
and then quickly becomes acetated. Renner gives the constituents of molasses as:
Raw Sugar
Slime sugar
Water
Ash
Caramel, gum, &c.
Refining the Sugar. Sugar refining consists in :-
32.97
40°36
4'30
7'38
13'71
16.25
3°35
378
45'65
32°22
1. Dissolving and refining. The raw sugar is dissolved in water, and during
the process cf evaporation the apparatus is connected by a gutter to a reservoir,
into which the sugar flows. It is then submitted to a straining apparatus, which
retains the several impurities. The refined fluid is then heated in a copper pan,
termed the melting-pan, the water adding 30 per cent. to the weight of the sugar,
and is afterwards placed in the refining pan, a vessel constructed with a double
bottom. For the purpose of clearing, a mixture of albumen is added in the shape
of serum of blood, or white of egg, with lime-water and sulphuric acid, an addition
afterwards being made of 3 to 4 per cent. animal charcoal and to 2 per cent.
*
SUGAR.
367
blood, and the whole heated to the boiling-point. The albumen coagulates and
forms a fibrous scum, containing all the impurities.
2. Taylor's filtering apparatus is now much used for filtering the sugar, charcoal
being employed as the purifying agent.
3. The boiling of the clear sugar in pans placed over a vacuum apparatus, re-
sembles the previous boiling, with the exception that the fluid is rendered purer,
10 to 12 per cent. water remaining.
4. Cooling and crystallising. When the sugar begins to crystallise on the sur-
face of the vaccum pan, generally at 80°, the temperature is lowered to about 50°,
as too great heat at this stage of the process exercises an injurious effect upon the
sugar, which now forms an amorphous mass, and is drained, washed with clean
syrup, and prepared for ordinary loaf-sugar. Sugar-candy is the result of slow
crystallisation, the crystals by this means acquiring a larger size and more regular
form.
5. The shaping of the crystallised mass into the form of a sugar-loaf is accom-
plished by evaporating the sugar and placing it in earthen conical moulds to soli-
dify at a temperature of 25° to 30°. After standing ten minutes the sugar sets into
form.
6. Drying the sugar. After standing twelve hours a green-coloured syrup is
obtained from the crystalline mass, which is removed, and the crystals submitted
to a centrifugal process of drying, then placed in a drying-stove at a temperature
of 25°, which is gradually increased to 50°. By thus refining the raw sugar, the
ordinary loaf sugar is obtained.
Production of Raw Sugar. The estimated production of raw sugar in 1870 was 55,000,000
cwts., the largest instalment being from Cuba.
Beet-Root Sugar.
Its Nature. In the year 1747 Marggraf, a chemist of one of the Berlin academies,
discovered crystals of sugar in the red beet, Beta cicla, which he deemed capable of
manufacturing into the commercial article. He found that, treated with alcohol, the
white beet yielded 6.2, and the red variety 4.6 per cent. of sugar. But the prepara-
tion of beet-root sugar was not developed until the close of the year 1800. Achard
and Hermbstädt, of Berlin, tried many experiments with this new product with
equal success, always finding that beet-root contained crystallised sugar to the
amount of 6 per cent., with 4 per cent. of molasses, and sometimes a larger quantity
of sugar. About the time of the Continental war native products were in request
on account of the difficulty and expense of obtaining foreign articles. The first
Napoleon supported the new product in the pursuance of his "Continental system'
of excluding cane sugar from the French markets, and a trial of the German
method was made, but it was not crowned with the success it has now achieved
until ten years after his overthrow. The annual production of sugar in 1811 did
not exceed 13,000,000 lbs. ; the present yearly consumption of beet-root sugar ex-
ceeds 15,000,000,000 lbs., this enormous amount being supplied by more than
eighty manufacturers.
""
Species of Beet. The vegetable known as beet-root is a large fleshy root of the beet, a
plant of the species Beta maritima, largely cultivated in France, Belgium, and
Portugal for the production of sugar. There are several varieties of the two species,
the white beet being preferred on account of its yielding more sugar, and also for
368
CHEMICAL TECHNOLOGY.
its purity of colour, the red beet being chiefly cultivated for culinary purposes.
There is also the field beet, commonly known as the mangold wurzel, which was
first used as provender for cattle about the end of the last century. The sugar beet
has, in course of cultivation, been improved by many new methods of manuring,
&c., until it yields 13 and sometimes 14 per cent. of sugar. In Germany the follow-
ing varieties of beets are principally cultivated :—
1. Quendlinburg beet, a slender rose-coloured root, and very sweet; it is matured
fourteen days before any other kind. 2. Silesian beet is pear-shaped, with bright
green ribbed leaves; it is known as the green-ribbed beet, and does not produce so
much sugar as the former. 3. Siberian beet is pear-shaped, with white-green
ribbed leaves, and is known as the white-ribbed beet. It does not yield so well as
the Silesian beet, although of a greater weight. 4. The French, or Belgian beet,
has small leaves and a slender and spiral root, yielding sugar. 5. The Imperial
beet is slender and pear-shaped, yielding much sugar. The king beet is a bien-
nial; in the first year the root is merely developed, in the second it bears seed.
The following is a list of the countries where the beet is cultivated for sugar:—
Austria
Austria
Bohemia
•
Prussia
Prussia
Baden
In
•
•
France :-
Northern Departments
Other
France
""
Beets
According to gathered
The manufacture
of suitable Beets
in cwts.
88-123
143-164
95-123
in cwts.
Krause
104-145
Burger
169-193
Neumann
112-145
Lüdersdorff
146
I24
Thaer
180
Stölzel
120-160
153
102-136
Dumas
Boussingault
{193
168
124
105
149
127
Into Sugar
in pounds.
770-1084
1256-1560
836-1160
1088
1336
896-1196
1476
924
1116
In general 140 to 160 cwts. are cultivated, cut, and cleaned, per acre, there being four
Magdeburg acres to one hectare, which usually yields sufficient roots for three days' work.
The flesh of the beet consists of a quantity of small cells con-
Chemical Constituents
of the Beet.
taining a clear, colourless fluid. The constituents of the sugar-beet, according to
chemical analyses, are:-
Water
Sugar
Cellulose..
Albumen, caseine, and other bodies
Fatty matter..
:
Organic sub-tances, citric acid, pectin and pectic acid,
asparagin, aspartic acid, and betain, a substance having,
according to M. Scheibler, the formula C15H33N306
Organic salts, oxalate and pectate of calcium, oxalate and
pectate of potash and sodium ..
Inorganic salts, nitrate and sulphate of potash, phosphate
of lime and magnesia
8297
II.3
0.8
I'5
ΟΙ
3'7
Near Magdeburg, where the beet is extensively cultivated, the general results
give:-
The greatest sugar production, as 13.3 per cent.
That from inferior beets, as
The average beet yielding.
9°2 ""
II'2
SUGAR.
369
The components of the beet vary according to the time of the year, it at some
periods containing more water than at others, from 82 to 84 per cent. being the
average. In the autumn it does not contain slime sugar; in February and March
the components intermingle and some decrease nearly 2 per cent., as shown by the
following analyses :-
Woody fibre and pectin
October.
February.
252 per cent.
3'49 per cent.
Water
Sugar
Slime sugar
..
82.06
84.36
""
12'40
10.60
""
""
Ο '00
""
0'65
Mineral salts
0'75
""
0'63
""
Organic acid and extractives
1'30
""
I'24
100'00
100'00
124 cwts. of beet yield on an average 1 cwt. of raw sugar.
Saccharimetry. The measure of the amount of saccharine matter contained in the
various crude sugar productions can be estimated either by the—
1. Mechanical,
2. Chemical, or
3. Physical method.
Mechanical Method. The middle part of the beet is cut in thin slices to the weight of 25
to 30 grms. each, and dried. From the difference in weight before and after drying, the
quantity of water contained in the root is ascertained. The dry residue is pulverised, and
then treated with boiling dilute alcohol of a specific gravity of 0.83. By this means the
sugar
is dissolved, and the weight ascertained. The insoluble residue gives after drying
the weight of the cellulose, protein bodies, and mineral constituents. If the alcoholic
solution be placed in a vacuum over caustic lime, it gradually becomes more and more
concentrated, until after standing about a day, the sugar, owing to its insolubility in abso-
lute alcohol, may be collected in small colourless crystals, only absolute alcohol remaining.
Good sugar beets give 20 per cent. dry residue, the water amounting to 80 per cent. Of
the 20 per cent., 13 per cent. is usually sugar, and the remaining 7 per cent. pectin, cellu-
lose, protein, and mineral substances. The higher the specific weight of the juice of the
beet, the more sugar it contains. The juice of a good beet properly cultivated marks 8°
and sometimes 9° B.
Chemical Method. The chemical method is based upon the following facts:-
a. The known proportional solubility of hydrate of lime in cane sugar.
b. The capability of a cane sugar solution to reduce the hydroxides of copper to
protoxides, the quantity reduced affording an estimate; and the conversion
by acids of cane sugar into inverted sugar (a mixture of levulose with
dextrose or glucose).
c. The fermentation of sugar, giving rise to the formation of alcohol and
carbonic acid, the amount of which can be ascertained, 4CO2 corresponding
to I mol. of cane sugar, C₁₂H22O11.
Ι
The first of these methods is that of determining the solubility of hydrate of
lime in a cane sugar solution. The fluid containing sugar is stirred with
hydrate of lime, the quantity of which dissolved, estimated by titration with
sulphuric acid, determines the quantity of sugar. The second method is
grounded on the researches of M. Trommer, who found (1.) That cane sugar
in an alkaline fluid does not reduce oxide of copper; but it becomes reduced
if the sugar has previously been boiled with sulphuric or hydrochloric acid,
the acid converting the cane into inverted sugar. 2. The quantity of the reduced
protoxide is proportional to the quantity of sugar.
Barreswil and Fehling give a
25
370
CHEMICAL TECHNOLOGY.
test based on this law:-An alkaline solution of oxide of copper is made by
dissolving 40 grms. of sulphate of copper in 160 grms. of water, and adding
a solution of 160 grms. of neutral tartrate of potash in a little water, with
600 to 700 grms. of caustic soda ley of a specific gravity=1'12. The mixture
should be next diluted to 1154°4 c.c. at 15°. A litre of this copper solution contains
34'65 grms. of sulphate of copper, and requires for its reduction 5 grms. of
dextrose or levulose; or 10 atoms sulphate of copper (1247′5) are reduced, by
means of 1 atom of dextrose or levulose (180), to protoxide (34 65:5=1274*5:180,
or=6′93:1), 10 c.c. of the copper solution corresponding also to o‘050 grms. of dry
dextrose or levulose. Mulder prefers a solution in which 1 part of oxide of copper
corresponds to o‘552 part of dextrose or levulose of the formula C6H12O6+H2O; by
the use of this test-liquor, the amount of sugar may be ascertained with great
accuracy. By another method 10 c.c. of this copper solution are heated with 40 c.c.
of water, and placed in a sugar solution till all the oxide of copper is reduced. When
this point is nearly reached, the precipitate becomes redder, and forms more rapidly.
Testing the filtrate with ferrocyanide of potassium will throw down a yellow pre-
cipitate if there be sugar in excess. The copper salts are instantaneously reduced
by the sugar in corresponding quantities; long boiling is not necessary. 100 parts
dextrose or levulose correspond to 95 parts cane sugar.
Ferment Test.
The third method, the ferment test as it is generally termed, is
grounded on the fact that a solution of sugar may be preserved for an indefinite
period in an open or close vessel; but that if decomposing azotized matter be acci-
dentally or intentionally added, the sugar is converted first into dextrose or levulose,
which suffering vinous fermentation is converted into alcohol with the evolution
of carbonic acid.
I mol. of cane sugar,
yields by 4 mols. of carbonic acid=176,
fermentation 1 4 mols. of alcohol = 188.
} a
CHO=342,
The estimation of the quantity of carbonic acid is easily performed by means of
the alkalimetric apparatus of Fresenius and Will. The fermentation being com-
plete, the air is sucked out of the apparatus, and the amount of carbonic acid
estimated from its loss, which
Multiplied by 1=1′9432, gives the quantity of cane sugar.
Physical Method.
""
180=2*04545, gives the quantity of dextrose.
88
The raw sugar containing dextrose or dextrine rotates the plane
of polarised light to the right hand in proportion to the quantity present. A
sugar solution of 100 c.c. containing 15 grms. of sugar turns the ray of polarised
light of 200 millimetres length, 20° to the right. Proportionally a solution of
100 c.c. containing 30 grms. of sugar, turns the ray 40°. The forms of polarimeters
are very various, and this method of estimation has received attention from many
eminent physicists.
Preparation of Sugar
From the Beet.
operations:-
The preparation of sugar from the beet consists in the following
1. Washing and cleansing the beet.
2. Obtaining the juice from the root.
a. The root is ground to a pulp and subjected to hydraulic pressure.
B. The juice is extracted from the pulp by means of a centrifugal machine.
y. According to Schützenbach, after the maceration juice is separated from the
pulp by water.
8. The root is cut into thin slices and placed in a vessel (diffusion apparatus) with
water at a certain temperature.
SUGAR.
371
3. Refining the juice with lime, and removing the lime with carbonic acid.
4. Filtering the juice through charcoal.
5. Boiling the refined juice for crystallisation.
6. The manufacture of raw and refined sugar.
a. Raw or moist sugar.
8. Refined or loaf sugar.
1. Washing and Cleansing the Beet.-The beet when newly dug requires washing
and cleansing, which takes 10 and sometimes 20 per cent. from the weight of the
root. Champonnois's washing machine, is, perhaps, the most successful; it
consists of revolving drums of open iron- or wood-work placed in a trough supplied
with water, the drums making from 8 to 40 revolutions in a minute. The beets
cleansed from all impurities, washed, are cut and submitted to elutriation on a sieve.
From 1000 to 1200 cwts. beets can be prepared per day of twenty-hour hours with
2-horse power; the length of the washing drum being from 3.1 to 4 metres with a
diameter of 1 metre, the drum making from 30 to 40 revolutions per minute.
2. Separating the Juice from the Root.—There are two methods of effecting this;
the first by grinding the root to a pulp, and then removing the juice by :—
a. Pressing.
B. Centrifugal force.
y. Maceration.
The sugar in the beet-root is contained in the cells, which are easily opened, but
require a moderate pressure to extract the juice containing the sugar. A hand-
grinding machine is sometimes found suficient for this purpose, but Thierry's
crushing machine, shown in the following illustration, Fig. 211, is generally used.
The grinding cylinder, Fig. 212, is o̟:5 to 0-6 metre in length, and 0·8 to 1'o metre
FIG. 211.

in diameter, the periphery being set with 250 saw-blades. t (Fig. 211) is a funnel
to admit water; i the trough into which the roots are placed; m the cistern to
receive the pulp. The motive power gears with a and s; and the motion of the
axis of a is by means of the pinion, b, communicated to the eccentric, d, and friction
roller, e, thence by the arm, g, and connecting-rod, h, to the plunger, f, which presses
372
CHEMICAL TECHNOLOGY.
甲
​the roots against the edges of the saw-blades concealed by the case, u, the pressure
being regulated by the weight, k. The cylinder revolves 1000 to 1200 times a
minute, reducing from 800 to 1000 cwts. of beets to pulp in twenty-four hours.
The water from t is necessary, that
212
the pulp may be ground to a finer
consistence.
a. The juice is obtained by
pressing the pulp by means of a
stone or iron roller through a series
of linen cloths. But in the French
manufactories the hydraulic or
Bramah press is most generally
adopted. The pulp is placed in
sacks or bags between iron plates,
and subjected to a pressure of 500

to 600 lbs. The expressed juice flows from the bed-plate into a pipe, which conducts
it to a receptacle. 100 cwts. of beet, with a pressed residue of 18 per cent., yield
82 per cent. good juice.
The Residue. According to the researches of M. Wolff, the residue of the crushers
used at Hohenheim contains-
When the beets are pressed with:-
Water
Fresh Roots.
81.56
0.89
20 per cent.
Water.
68.01
5'47
14 per cent.
Water.
67.92
5'74
Without
Water.
65'94
5:28
6.68
6.72
ETITI
Ash..
Cellulose
Sugar
Protein substances.
Other nutritious
1'33
11.88
0.87
3'47
6:25
7.86
1:05
11.36
6.04
7:58
1.67
10.05
II'02
14'31
100 parts of beet leave 23.2 parts residue and 76.8 parts juice of the following compo-
sition:-
Water
Ash
Cellulose
Sugar
Carbon hydrate
Protein substances
Residue.
Juice.
•
•
15.61
65.95
1.27
(?)
1'47
I'72
10'17
2.84
0.63
0.28
0.58
1
23.20
76.80
B. The juice is now generally obtained from the pulp by means of the centrifugal
machine to the extent of 50 to 60 per cent., water being applied to the residue to
obtain a thin pulp also used in sugar manufacture. A centrifugal machine 1 metre
in diameter will express 100 cwts. per day. The power to which the first juice is due
is 5.1 atmospheres, 60 per cent. juice being expressed. The remainder of the juice,
after the addition of water to the contents of the machine, is expressed at a pressure
of 1.8 atmospheres, the quantity of water amounting to 50 to 60 per cent. of the
quantity of beets. Of the roots 50 per cent. remain, 20 per cent. in the residue,
and 30 per cent. in the clarifying vessel.
7. Treating the beet-pulp according to Schützenbach's method of immersion and
maceration in order to obtain the juice. The roots are cleaned and then cut in
slices by a cutting machine. They are then passed to a drying chamber heated to
50°, and subsequently ground to a meal. Four parts of this meal are allowed to
SUGAR.
373
macerate in 9 parts water, to which sometimes sulphuric acid is added. Another
method is to moisten the dried beet-meal with milk of lime, and afterwards continue
the operation in a bath of water heated to 80°. These methods are largely used in
Germany, where in general practice it is found that 4'75 cwts. of green roots yield
I cwt. of dry beet-meal. The juice is afterwards treated with lime-water for the
purposes of purification.
d. Before any juice can be obtained it is necessary to open the cells in which it is
confined. This, as it has been seen, may be effected by pressure or by maceration in
water, by which the cells are broken and to which they yield their sugar. The
action with each cell is very similar to that of the dialyser used in dialysis; the
sugar becomes gradually diffused in the water, the insoluble substances remaining
with the cell. By this means a very pure sugar solution may be obtained and
afterwards concentrated. The diffusion residues are always very watery, containing
93 per cent. water and 7 per cent. dry substances.
Components of the Juice. The juice after being expressed from the pulp, if allowed to
remain exposed to the action of the air, throws down a dark flaky precipitate.
The more free acids the juice contains the lighter will be the colour of the
precipitate, and the juice will appear of a brown-red. The juice is not only
a solution of sugar, but contains the soluble constituents of the beet, in
which nitrogenous and mineral substances are very prominent. Sugar under
fermentation forms lactic acid and other products; but is is separated from all im-
purities and refined into crystals. The usual method of refining is to boil the
The
juice rapidly in copper refining-vessels constructed with double bottoms.
rapid boiling separates the coagulated juice, whilst the free acid is neutralised
by the introduction of dilute milk of lime. The lime also serves to separate
the nitrogenous substances of the juice, and enters into a combination with a
small portion of the sugar, forming sugar-lime or calcium saccharate. Lime, too,
throws down from their salts protoxide of iron and magnesia, while potash and
soda are set free. The quantity of lime added depends upon the condition of the
root. As a rule, to 100 pounds of juice, 1 to 2 pounds of lime are added, or to 2 cwts.
of roots 1 pound of lime. The insoluble combinations of lime are separated from
the juice as a slime by filtering in a filtering press.
3. De-Liming, or Saturating the Juice with Carbonic Acid.-The clear juice is by no
means a pure sugar solution, but contains besides free sugar, sugar-lime, free potash,
and soda, sometimes ammonia, and a small quantity of nitrogenous organic substances.
decomposed by the free alkalies, ammonia being largely developed by their evaporation.
The juice also contains various organic acids (as aspartic acid) and alkaline salts (as
sulphate and nitrate of potash). The decomposition of the sugar-lime effects the
removal of the extraneous substances from the juice. The physical method of puri-
fying the juice is by filtering it through animal charcoal, while the chemical method
is effected by means of carbonic acid. The use of carbonic acid was first recom-
mended by Barruel, of Paris, in 1811, and later by Kuhlmann, Schatten, and
Michaelis. The latter obtained the gas from the action of sulphuric acid upon
chalk, or better upon magnesite; the former employed the gas resulting from the
combustion of charcoal or coke. Lately, Ozouf has prepared carbonic acid gas by
heating bicarbonate of soda. In the German manufactories the decomposition of the
sugar-lime is effected in a Kleeberger's pan, Fig. 213. This apparatus consists of a
cast-iron cistern, B, to contain the juice. The carbonic acid, having been washed in
374
CHEMICAL TECHNOLOGY.
pure water, is admitted by the pipe, m, which dips nearly to the bottom of the
vessel, B, and is divided internally by a partition for the better dissemination of the
gas. The unabsorbed gas collects in B over the juice, whence it passes through the
opening, p, into the upper chamber, A. When the juice sinks through p into B, the
gas there collected passes through A into n, and is thence re-conducted to the
reservoir. When the juice is sufficiently cleared, the carbonic acid cock, o, is turned
off, and the juice allowed to flow into a reservoir through 7, where the carbonate
of lime settles. The clear juice is then fit for crystallisation. The man-hole, e,
is
FIG. 213.

the Juice.
provided for the cleansing of the apparatus from separated carbonate of lime. The.
juice to be de-limed is supplied to the cistern, B, by means of the pipe, s, and the
gutter, t.
Other Methods of De-Liming Instead of employing carbonic acid or animal charcoal, the lime
of the sugar-lime. may be removed by the addition of a substance
or an acid which forms with it an insoluble body, but does not affect the sugar. Oxalic
acid is suitable for this purpose, oxalate of lime being insoluble in the sugar solution,
but the acid is very expensive, and, besides, the precipitate is too fine, passing through the
filter. Phosphoric acid is used for the purpose, phosphate of lime separating into flakes
which can be easily removed by filtering through a thin layer of charcoal. Any free
phosphoric acid is converted into phosphate of ammonia, neutralising the alkali, while the
excess of ammonia is volatilised on the application of heat to the juice. Oleic, stearic, and
hydrated silicic acids, and casein, similarly throw down precipitates. Acar uses pectic acid,
which forms with the lime an insoluble pectate. Morgenstern has found sulphate of mag-
nesia prepared from the Stassfurt kieserite successful in removing part of the impurities as
well as a portion of the colouring matter. Frickenhaus tried hydrofluoric acid. In 1811
Proust recommended sulphite of lime; and in 1829 Dubrunfaut took out a patent for the
employment of sulphurous acid. Melsens, of Brussels, in 1849, employed hyposulphurous
acid, which at 100° separates the lime and most of the protein substances, and disguises
for a time the colouring matter, the colour, however, returning on exposure to air, and
remaining permanent.
12 22 II
Purifying with Baryta. About fifteen years ago Dubrunfaut and De Massy patented a
method of purifying the juice by means of caustic baryta, which forms with cane sugar
at the boiling-point the insoluble saccharate, C₁₂HO,,.BaO; in practice sufficient caustic
baryta is added to throw down all the sugar. The sugar-baryta is thus separated
from the supernatant fluid in which all the foreign substances remain suspended; and is
next treated with carbonic acid to form carbonate of baryta and set the sugar free. The
solution is then filtered and some gypsum added, which gives rise to the double decom-
position of the carbonate of baryta into sulphate, and of the gypsum into carbonate of
lime.
4. The Filtration of the Juice through Animal Charcoal, and the Evaporation of
the Juice.—The various apparatus here play the most important part.
SUGAR.
375
The Filter.
Besides acting as a filter, charcoal possesses the property of removing
the colour from the liquid allowed to percolate through it. Wood charcoal was
first used for the purposes of sugar-refining in 1798, but lately has given place to
the employment of animal charcoal (bone charcoal), which, according to Schatten,
has a tendency to remove the lime and salts in the juice. At first it was used in
powder, but now it is employed in the form of lumps. The old method consisted
in boiling the powdered charcoal with the juice, blood being afterwards added, as
in the usual methods of sugar-refining.
Fig. 214 exhibits a section of Taylor's filter, which has been in use since 1825.
The juice is admitted to the upper cistern, A, by means of the pipe, o, and gra-
dually percolates through the long linen bags suspended from the bottom of a in
B, and containing charcoal, a layer of charcoal being also placed in A. The mouth
FIG. 214.

B
A
P
of each bag is kept open by a funnel-piece shown at P. The filtered juice is received
into the lower cistern, whence it passes by the pipe, a, into the reservoir.
Dumont's Filter. Pajot des Charmes employed animal charcoal in 1822, but Dumont
was perhaps the first to make its use successful by means of a filter still bearing
his name, shown in vertical section in Fig. 215, and in plan in Fig. 216. The juice
is supplied to the filter, A, from the cistern, D, the supply being regulated by the
ball-cock. de. The pieces of charcoal in a rest upon the sieve, b b, the percolating
juice being received into the cistern, and removed by the tap, o. c is a man-hole
for the cleansing of the apparatus.
Evaporation Pans. The pans generally in use for evaporating the juice to crystallisa-
tion are made sufficiently strong to withstand high steam and atmospheric pressure.
The processes of evaporation are :-
I. Under the usual air-pressure:
a. In pans suspended over an open fire;
b. With high steam pressure;
c. By hot air.
376
CHEMICAL TECHNOLOGY.
II. By diminished air-pressure or vacuum pans, the vacuum being produced:
a. By the air-pump;
b. On the principle of the Torricelli vacuum;
c. By means of steam and condensation ;
d. By combining the methods a and b.
The pans are constructed to prevent the boiling over of the juice. One of the
ill effects of an open fire is the danger of over-heating, or burning as it is called,
FIG. 215.

SENENÉJENENENEN:
which deteriorates the quality of the sugar solution in various ways, forming
caramel. Fig. 217 is a vertical section, and Fig. 218 the plan of an open pan
arrangement. D is the evaporating pan, A the fire-place, c the ash-pit, E and G
the flue. The fuel is placed on the sloping grid, b, through the furnace-door, a.
FIG. 216.

D
The use of
When the
The fire-room is arched, the flame and hot gases passing through the openings, e e,
into contact with the evaporating pan; 77 admit air to the fire-place.
a suspended pan, as shown in Fig. 219, is preferable for many reasons.
juice is sufficiently concentrated, the workman has only to pull the rope, m, to
empty the pan.
The Pecquer evaporating-pan is heated by steam, the pipes, Figs. 220 and 221,
being placed horizontally under the pan. The steam enters by a into b, passes
through the pipes, and is conveyed away by d and e. The heating by steam.
SUGAR.
377
besides the advantage of cleanliness, is more equable and easily managed. When
the juice is sufficiently heated, the pan, by means of the lever, m, is tilted up, and
the juice run off by opening J.
The evaporation by hot air is best exemplified in the pans of Brame-Chevallier
and Péclet. That of the latter is shown in Fig. 222. The evaporating-pan, A, is
1353
FIG. 217.

FIG. 218.

E.
directly over the fire, the products of the combustion passing by the pipes, B, to the
chimney, g. The steam from the evaporating-pan passes away through e. By
means of the axis, a, and sieves, c d, set in motion by steam-power gearing with b,
the juice is thoroughly exposed to the blast of hot air generated in c, and passes by
FIG. 219
FIG. 220.


m
FIG. 221.

PLO
772
the hot pipes, B, into the pan, A. By this constant stirring the juice is prevented
from adhering to the pans, and becoming burnt.
Vacuum Pans. An improved evaporation apparatus was invented by Howard, in
1812, in which the juice was placed in chambers of rarified air, or vacuum pans.
378
CHEMICAL TECHNOLOGY.
The lowest boiling-point of the clear juice in the vacuum pans is 46′1º C. ; the
usual temperature at which the sugar is boiled 65.5° to 71'1º C.; at a higher tem-
FIG. 222.

G
B
FIG. 223.

7
m
perature the juice loses its power of crystallisation, and forms caramel. The vacuum
may be considered as two distinct apparatus:-1. The boiling-pan; 2. The appa-
ratus for exhausting the air and condensing the steam from the juice.
SUGAR.
379
In France, Derosne's apparatus is extensively used; but that which we shall
describe meets with general approval in Germany, and has the advantages of being
simpler in construction and less costly to work. Fig. 223 is a perspective view,
and Fig. 224 a section of this form of evaporating pan. The boiling-pan, B, con-
sists of two air-tight hemispheres, surmounted by a funnel connected by the tube,
7, with the condenser, A. The apparatus is supplied with steam by rs, the steam
circulating in the boiling-pan by means of the pipes, g, Fig. 224. By opening the
lever valves, ƒ, the juice can be run by means of the pipe, o, into the pan, p.
When the pan, after continued boiling, requires to be re-filled, the pipes and w
are connected to an air-pump. The manometer, h, shows the state of the air-pres-
sure, which can be regulated by opening the pipes connected to the vacuum-
FIG. 224.

RE
AL
chamber. By means of the gauge-cylinder, G, the quantity of syrup in the boiling-
pan can be ascertained, the gauge-cylinder being connected to the boiling-pan by
the pipes a and i, and the height read off from the gauge-tube, n. The syrup can
be removed, for the purpose of ascertaining its consistency, from the gauge-cylinder
by means of either of the three pipes, bed. By u steam can be admitted to the boil-
ing-pan and condenser. e is generally of stout glass, through which the state of
the juice can be observed. g is the grease-cock, butter or Sostman's paraffin being
generally used to prevent the adhesion of the scum to the working parts of the pan,
the taps, &c., ƒ is the man-hole. The condenser consists of the jacket, B, arranged
to prevent the mixing of the juice with the water used for condensation. x is the
gauge. The pipe m, conveying water to the condenser, terminates in a rose.
z is a
thermometer, showing the interior temperature of the boiling-pan.
The air-pump being set in operation, the tube c is opened, and the gauge-cylinder
filled by the juice rising from q. By closing m and opening z the juice is admitted
to the boiling-pan. When this is half full the steam-pipe, s, is opened, the steam
quickly heating the contents of the pan to the boiling-point. The condenser is then
380
CHEMICAL TECHNOLOGY.
placed in working; by opening the pipe, 7, the steam of the juice passes into the
condenser, where it is speedily condensed, passing with the water through ß.
Trappe's arrangement is sometimes found useful in working the Torricelli vacuum.
The condenser is 10'6 to 11 metres above the pan; from it reaches a pipe to a water
reservoir beneath, the height of the water in this pipe indicating the degree of rare-
faction in the pan.
Juice.
Evaporating the Notwithstanding the first purifying, many substances still remain
in the juice, the carbonic acid treatment not completely removing the lime, free
potassa or soda, ammonia, and nitrogenous organic substances. According to
Leplay and Cuisinier, 1000 hectolitres of juice yield 300 kilos. of sulphate of am-
monia. Among the former decomposition products are also found nitrate and sul-
phate of potassa, chloride of sodium, &c., besides levulose, and humus substances,
which impart a brown colour to the juice. The clear juice is, therefore, again
evaporated to density of 24° to 25° B., and afterwards filtered through animal char-
coal. During this second evaporation the ammonia is got rid of, as well as the
organic substances, while the filtration removes the alkaline salts and the lime, and
also lightens the colour.
5. Boiling the Evaporated and Filtered Juice to Crystallisation. After the second
filtering and evaporation the juice is technically termed "thin juice," and is con-
centrated to "thick juice" by boiling to the point of crystallisation. As a rule,
the juice speedily begins to seethe and rise in the usual manner of boiling fluids ;
but if the throbs in this "dry boiling," as it is termed, sound heavy or dull,
'fat” as it is called, it indicates that some quantity of free alkali still is contained
in the juice, and a remedy is found in the cautious addition of sulphuric acid. The
estimation of the specific gravity of the boiled juice is not practically available as a
means of ascertaining the degree of concentration. This is best arrived at by
noting the boiling-point of the juice, which varies for pure juice from 112° to 120°;
but generally an empirical test is employed, a small quantity of the juice being
removed from the pan on a stick of wood, and rubbed between the fingers, a little
practice soon enabling the workman to estimate pretty accurately the consistence
of the syrup. In some cases the juice is removed in a ladle, and the consistency
judged from the tenacity with which the juice clings to the side of the ladle when
sharply blown with the breath. The juice when sufficiently concentrated is re-
moved to the cooler to crystallise.
6. Preparation of Moist or Raw Sugar, and of Loaf Sugar.-When the juice has
been brought to such a degree of concentration that it crystallises on cooling, the
final processes commence. The crystallisation proceeds gradually, the crystals form-
ing more quickly the purer the juice. The further the purification has been carried,
the easier is the separation of the sugar into molasses, and loaf or crystallised
sugar. The loaf sugar is again warmed in a pan and allowed to crystallise in a
form to which the general name of sugar-loaf is given, variously distinguished
according to their size into-
Loaf form, containing 30 to 34 pounds sugar.
Coarse lump form
Inferior form
وو
60 to 70
120 to 150
""
The forms are generally made of clay, Fig. 225, encircled by a band of wood to
preserve the shape. Sometimes the forms are of polished plate iron; papier maché
has been used with tolerable success for this purpose. By the old method of boil-
SUGAR.
381
ing the sugar in an open pan, the crystals formed unequally in the mould, and had
to be removed in several ways. The vacuum pan, however, does away with this
process, the sugar crystallising evenly in very large quantities. To heighten the
whiteness of the loaf sugar, the manufacturer sometimes adds últramarine in
quantities of 2 pounds to 1000 cwts. sugar.
After standing twenty-four hours the sugar is sufficiently set
to be removed from the mould. In working on the large scale,
the moulds are generally arranged as shown in Fig. 226, the
overflowing syrup falling into m, whence it is conveyed by o.
This syrup is known in the trade as green treacle or golden
syrup.
Draining the Crystals.
FIG. 225.

It is very necessary that all sugars before being
moulded should be thoroughly drained from all non-crystallised juice,
which would, if allowed to remain, injuriously affect the colour,
firmness, and dryness of the sugar loaf. The method of effecting
this drying is by first passing a small quantity of water through the
sugar; the water combines with a small portion of the sugar to
form a very pure syrup, which supplants the molasses or non-
crystallised juice in the interstices of the loaf. Practically this
filtering takes place in linen cloths, or the form is filled with a layer of pure juice to a
thickness of 2 to 3 inches, water being added till a syrup of the consistency of honey
is obtained, when the crystallised sugar is forced in, and the form set aside to drain.
Lately, a suction apparatus, the invention of M. Kranschütz, has been employed. This
apparatus consists of the usual series of
forms, to the bottom of each of which is
attached a tube proceeding to a vacuum
chamber, serving also as a reservoir for the
extracted molasses. The vacuum chamber
is attached to an air-pump in the ordinary
manner.
The Centrifugal Drier. The labour and uncer-
tainty attending the above methods of drying
have given rise to the invention of a ma-
chine by which the non-crystallised juice
may be extracted before the sugar is moulded.
FIG. 226.

717
Schützenbach's machine for this purpose merely consists of a cistern, the bottom of
which is formed by fine metal sieves, admitting the percolation of the juice, the
damp sugar crystals being removed from the cistern and placed in forms. But the most
effective is the centrifugal drier, shown in Fig. 227, the invention of M. Fesca, con-
sisting of an open drum, a, of fine meshed wire-work, caused to revolve in the cast-
iron case, bb, by means of the bevel-wheels, cd, gearing with a motive power, the
drum making 1000 to 1500 revolutions per minute. The motion of the drum can be
stopped by means of the break, e, and regulated by the weights placed at o.
The sugar
containing non-crystallised juice is poured into the drum, which being set in revolution,
the molasses is, by centrifugal force, driven through the sieve, the dry sugar remaining
in masses of 60 to 100 pounds weight. The action of the machine is aided by the cone, g.
By means of this apparatus, a hundredweight of sugar can be dried in ten to fifteen
minutes.
Removing the Sugar from
the Form.
When all the syrup has been removed, the bottom of the loaf in
the form becomes quite dry and hard; the loaf is now loosened in
the mould by means of a long knife, so that when the mould is inverted, the sugar-loaf
may stand by itself on the "unloading block," as the bench is termed where this operation
takes place. From the unloading block the loaf is removed to the drying room, where,
first at a temperature of 25° and finally at 50°, it is dried. The loaf is now ready for the
market or warehouse. When the pure juice is evaporated to the crystallising point, the
small granular crystals formed upon cooling are commercially known as the first product;
the syrup removed still contains a quantity of crystallisable sugar, and is further evaporated,
the result being known as the second product, and of course considered inferior to the first.
In the same way a third and a fourth product, known as after-products, may be obtained.
On an average 100 kilos. of beet-root yield :-
382
CHEMICAL TECHNOLOGY.
First product at 97 per cent.
Second
92
Third
""
87
""
Fourth product, molasses, &c.
Total ..
5.80 kilos.
""
2.25
0.80
""
8.85 kilos.
3.65"
12.50
And again, the sugars of each refining is distinguished according to its quality, viz., as
refined sugar, lump or boiled sugar, crystallised sugar, raw or moist sugar, and molasses.
Beet Molasses. The molasses so largely formed during the manufacture of beet-root
sugar contains most of the foreign substances-caramel, salts, aspartic acid-
common to the cane-sugar molasses. Beet molasses is used extensively for sweeten-
ing purposes, for the preparation of a coarse spirit, and in many parts of France
and Germany as fodder for cattle. The quality depends on the mode of preparing
the beet. 100 parts of molasses contain :—
1
Sugar
Non-saccharine matter
Water
50'1
49'0
48.0
50'7
33'3
35.8
34'0
30.8
16.6
15°2
18.0
18'5
100'0
100'0
100'0
FIG. 227.
Sugar Candy.
ΙΟΟ Ο
The large, hard crystals

formed during the various stages of
sugar manufacture, are known as sugar-
candy. The commercial article is gene-
rally obtained from cane sugar, the
crystals of beet-root sugar being too long
and flat. The amount of sugar-candy
made from beet sugar does not exceed
20 per cent. of the entire production. The
sugar selected for candy is mixed with
3 to 4 per cent. of animal charcoal,
then cleared with white of egg, and
filtered. It is next boiled in a copper
or an enamelled iron pan over an open
fire; whence it is conveyed to a crystal-
lising vessel, the sides of which are
perforated with a series of holes, in eight or
ten concentric rings, the distance between
each hole laterally being less than that
between each ring. Through these holes
the candy crystallises, the size of the
holes being adjusted to the consistency of
the boiled sugar by means of a paste
made of fine clay, ashes, and ox-blood.
The temperature of the drying room
is maintained at 75° for six days, when it
is reduced to 45° or 50°, and in 8 to 10
days the crystallisation is complete. During the crystallisation the candy must not be moved
or shaken, or the air allowed to affect it. Upon the completion of the crystallisation, the
candy is found covered with a mixture of syrup and small crystals; these are removed by
filling the crystallising vessel with weak lime-water. The rinsing water must be lukewarm,
as cold water cracks the crystals, and hot water makes them, as it is technically termed,
blind. The crystallising vessel, when emptied of the rinsing water, is soaked to remove
all saccharine matter, and if this be not effected with hot water, a smooth stone is used to
knock away the adhering crystals. After standing a day to dry, the sugar candy is ready
for the market. It is commercially known as of three kinds: the finest, refined white,
has a large colourless crystal; yellow candy, a straw-coloured crystal; and brown candy
is similar in colour to ordinary moist sugar. In some parts of France a dark candy
is manufactured under the name of Sucre de Boerhave. Inferior cane sugar is employed
SUGAR.
383
for the brown, boiled sugar for the yellow, and refined sugar for the white candy. Sugar-
candy is extensively used, the white principally in preparing "Liqueur," a solution of
candy in wine or cognac, also in champagne manufacture, and in all cases where a clear
sweetening solution is required in large quantities. The yellow candy is used for sweetening
tea and coffee in restaurants, and enters largely into the recipes of the pharmaceutist for
affections of the throat and chest, as well as for making syrups intended as vehicles for
nauseous medicines.
The total annual production of beet-root sugar amounted in 1870 to 16,000,000 cwts., of
which 6,000,000 cwts. are due to France.
Grape Sugar.
Grape Sugar.
Grape sugar, potato sugar, starch sugar, glucose, or dextrose, is a
sugar crystallisable with difficulty, occurring in a non-crystallised state as levulose
or chylariose (yuλapıov, syrup) in many sweet fruits, in the vegetable kingdom, and
it forms the solid crystalline portion of honey. It may be obtained by any of the
following processes:—
a. By the conversion of starch, dextrine, cane sugar, or some gums by means
of dilute acids or diastase.
b. By treating cellulose and similar vegetable matters with dilute acids.
c. By decomposing organic substances, such as amygdalin, salicin, phloridzin,
populin, quercitrin, gallo-tannic acid, &c., that by treatment with dilute
acids or synaptase (emulsin) are separated into grape sugar and other
substances.
Grape sugar is found in the various fruits in the following quantities :-
Peach
Apricot
Plum
Raspberry
Blackberry
Strawberry
•
Bilberry
Currant
Per cent.
I'57
1.80
•
2.12
4'00
•
4:44
5'73
5.78
6.10
•
6.26
Plum
Gooseberry
Cranberry
Pear
Apple
""
Sour cherry
Mulberry
Sweet cherry
Grape
•
•
•
•
•
7'45 (according to Fresenius).
7:15
8.02 to 10-8 (E. Wolff).
8.37 (Fresenius).
7.28 to 8'04 (E. Wolff).
8.77
9'19
•
10'79
14'93
Grape sugar, C6H12O6,H₂O, crystallises from its aqueous solution in granular,
hemispherical, warty masses. It is less easily soluble in water than cane sugar,
and requires 1 of its own weight of cold water, while in boiling water it is
soluble in all proportions, forming a syrup possessing but poor sweetening qualities.
There are required 23 times more grape sugar than cane sugar to sweeten the same
volume of water. At 120° grape sugar loses its water, and has the formula C6H12O6•
At 140° it is converted into caramel. Heated with caustic alkalies melassic acid is
formed, together with humus-like substances. Treated with sulphuric acid, grape
sugar forms sulpho-saccharic acid, and with common salt a soluble compound of
sweetish saline taste. With caustic potash in excess a grape sugar solution, when
heated to the boiling-point, reduces the hydrate of oxide of copper to suboxide,
oxide of silver to metallic silver, and chloride of gold to metallic gold. A mixture of
384
CHEMICAL TECHNOLOGY.
$
ferridcyanide of potassium and potash with the aid of heat decomposes grape sugar,
and discharges the original yellow colour of the fluid. Under the influence of a
ferment grape sugar suffers many changes, the product varying with the ferment
and method of treatment employed. Beer yeast decomposes grape sugar into alcohol
and carbonic acid.
100 kilos. of grape sugar give :-
Alcohol
Carbonic acid
• •
•
51 II
48.89
There are also found under certain conditions of temperature and concentration
the homologues of alcohol, viz., propylic alcohol, butylic alcohol, and amylic alcohol,
and under all conditions glycerine and small quantities of succinic and lactic acids.
When fermentation is effected in the presence of alkaline reagents, lactic acid is formed
without any disengagement of gas. Ordinarily the formation of lactic acid is merely
a stage in the process of conversion, the lactic acid decomposing into butyric and
acetic acids with development of hydrogen. Under certain conditions mannite
may be prepared from grape sugar; several other gum-like substances may also be
obtained. If to a grape sugar solution a small quantity of caseine and of carbonate
of lime be added, and the mixture submitted to a temperature of 90°, butyrate of
lime will be thrown down after fermentation, carbonic and hydrogen gases being
continuously evolved.
Preparation of Grape Sugar.
Grape sugar may be prepared from :-
a. Grapes.
b. Starch.
c. Wood and similar vegetable substances.
When grape sugar is prepared from the grape, the juice of the white grape is
preferred, and set aside to clear. The cleared must is heated to the boiling-point with
pieces of marble, chalk (not with burnt lime), or witherite (carbonate of baryta) to
neutralise a portion of the tartaric acid. It is then allowed to stand for twenty-four
hours, and during this time the insoluble salts of lime are deposited. The must is
now cleared with ox blood in the proportion of 2 to 3 litres of blood to 100 litres of
must, and next evaporated to 26º B. After remaining a short time in a tub to clear,
the impurities are removed, and the must again evaporated-this time to 34° B.
By these means a syrup is produced, from which the grape sugar can be imme-
diately obtained. The syrup is concentrated by boiling and run into crystallising
vessels, where after three to four weeks the sugar crystallises out; it is separated
from the non-crystallised chylariose in a centrifugal machine. For experimental
purposes the crystals may be separated by placing the concentrated syrup on a
heated porcelain or glass plate.
1000 parts by weight of grapes give:-
Must
Syrup
•
Raw grape sugar
• 800
Pure grape sugar
200
140
6.0-70
The preparation of grape sugar from starch is an important branch of the sugar-
boiler's art. Dilute sulphuric acid and the fecula of potato starch are the active
agents. The principal processes are the following:
a. The boiling of the starch-meal with dilute sulphuric acid is effected on a small
scale in leaden pans, but in an extensive preparation iron pans are employed. The
SUGAR.
385
requisite quantity of water is first heated to the boiling-point, and to this is added
the sulphuric acid diluted with 3 parts by weight of water. The starch is also
previously brought by the addition of water to a milky consistency. The liquids so
prepared are mixed, and the boiling continued until all the starch is converted into
sugar. An intermediate stage, not usually noticed by the manufacturer, is the
conversion of the starch into dextrine, which in its turn suffers conversion into
grape sugar. The entire conversion of the dextrine into grape sugar cannot be
ascertained with certainty by the iodine test, as sometimes a purple-red tint is
produced, while in others there is no change. The most reliable test is that with
alcohol, founded on the known insolubility of dextrine in an alcoholic menstruum. To
I part of the solution to be tested there are added 6 parts of absolute alcohol; if no
precipitate is thrown down there is no dextrine remaining, and the conversion has
been entire. The proportions of the materials are generally to 100 kilos. of starch
meal-2 kilos. of ordinary sulphuric acid of 60° B. and 300 to 400 litres of water.
The conversion of the starch into grape sugar is hastened by the addition of a
small quantity of nitric acid.
b. The separation of the sulphuric acid from the sugar solution is a most important
operation, for the colour, purity, and flavour all depend upon success in this stage
of the process. The acid is neutralised by baryta or by lime, with either of which
it forms an insoluble salt, deposited at the bottom of the neutralisation vessels, and
leaving a clear supernatant syrup. The baryta can be employed as carbonate
(witherite), and is without doubt the better neutralising agent, sulphate of baryta
being very insoluble. Lime, although ordinarily used, forms with the sulphuric acid
a sulphate (gypsum) that is not perfectly insoluble in water. It can be employed
either as marble, chalk, or caustic lime. The neutralisation is completed in the
boiling-pan while the sugar solution is still hot. For every kilo. of sulphuric acid
(technical atomic weight=100 to 106) so much pulverised marble (chemical atomic
weight=100) is required as the varying strength of the acid may demand. After
the addition of the marble powder, and when the effervescence has subsided, the
liquid must be tested with litmus paper, or, better, with tincture of litmus; if
the sugar solution be neutralised when at 26º B. density, the following evaporation
will concentrate even the smallest quantity of sulphuric acid which may have
remained, and render another neutralisation necessary. To ensure perfect neutral-
isation it is useful to add an excess of carbonate of baryta in the proportion of 250
to 500 grms. to every 10 kilos of sulphuric acid.
c. Evaporating and Purifying the Sugar Solution.—This part of the process is ac-
complished first in a copper pan over a slow fire, or better, by heating with steam.
The impurities separate and are absorbed in the scum, which is removed by means
of ladles. The evaporation is continued until the syrup marks 15° to 16° B., when it
is passed through a filter, generally of animal charcoal. It is then removed to a
large reservoir, and, if a granular sugar be desired, evaporated to 40° to 41° B., in flat
pans, from which it is taken to be placed in the crystallising vessels. These vessels
are provided at the bottom with twelve to twenty-four holes, into which wooden plugs
are fitted, by removing which, when the sugar has crystallised, the molasses are
removed. The crystals are dried, sifted, and either pressed into sugar-loaf forms
or packed in casks. The crystallisation is effected in eight to ten days.
The manufacture of grape sugar from wood and similar vegetable substances is
26
386
CHEMICAL TECHNOLOGY.
only of value iu relation to the production of spirits, and recently as a by-process
of the manufacture of paper from wood.
Composition of Starch Sugar. The composition of starch sugar as it occurs in commerce is
very varied. During inferior seasons the marketable starch sugar may contain 50
per cent. sugar, 32'5 per cent. foreign substances, and 175 per cent. water.
G. Schwaendler found by the analysis of various samples of last year's (1870) sugar
the following percentages:
I.
2.
3.
4.
5.
Grape sugar
67'5
64°0
67.2
75.8
62.2
Dextrine..
9'0
17'4
9'I
9'0
8.8
Water
19'5
11.5
20'0
13'1
24'6
Foreign substances
4'0
7'1
3'7
2'I
4'4
100'0
ΙΟΟ Ο
ΙΟΟ Ο
100'0
100'0
Uses of Grape Sugar.
The sugar prepared from starch, in addition to the sugar yielded
really by the grape, is largely employed in wine-making and in the brewing of beer. In
the latter case the grape sugar is prepared by means of diastase; that its use is extensive
may be gathered from the fact that to 3 cwts. of malt I cwt. of potato sugar is
employed. It is also employed instead of honey in confectionery, for colouring liquors
and vinegars brown, in rum and cognac, beer and wines. In the latter cases it is known
as sucre couleur, being then a grape sugar that has been re-melted, sometimes with the
addition of carbonate of soda or caustic soda to deepen the colour.
FERMENTATION.
Fermentation. Fermentation is a term applied to the peculiar changes of complex
organic substances of the amylaceous and saccharine type under the influence of
certain putrescible nitrogenous substances or ferments. The decomposition of
fermentable organic bodies by a ferment effects the separation of their constituents
into two or more combinations, as when by a yeast-ferment dextrose and levulose
are converted into alcohol, its homologues, and carbonic and succinic acids; or the
molecules of the original substances are re-grouped, as in the conversion of sugar of
milk into lactic acid during lactic acid fermentation; finally, the elements of the
organic substance may enter into combination with the oxygen of the atmosphere
either to form new organic combinations, or to separate into its inorganic constituents
carbonic acid, carburetted hydrogen, &c. This latter decomposition is termed
mouldeirng when a residue rich in carbon (humus) remains, but when only the
mineral constituents remain, decay is said to have been reached. These terms are
thus defined more by custom or usage than by direct etymology--dictionaries hardly
distinguish between them, but the difference is known to all. If large quantities of
water be present both these processes are resolved into putrefaction, in which chiefly
gases carbonic acid, ammoniacal, sulphuretted hydrogen—and water are disengaged.
But fermentation always results in the remaining or the formation of other organic
compounds, and the variety of fermentation set up mostly depends on the state of
decomposition of the azotised matter employed as a ferment. The most important
ferment is undoubtedly yeast, but the ferment may be either an organic substance
(yeast) or a protein body in a putrescent state-it is always a nitrogenised body. In
a technological work the varieties of fermentation may be classed as—
1. Vinous or alcoholic fermentation, including the changes observed during
the processes of wine-making, beer-brewing, and the production of alco-
holic liquors or spirits.
FERMENTATION.
387
2. Lactic acid fermentation, taking place during the souring of milk; and at a
higher temperature changing to
3. Butyric acid fermentation.
To these fermentations may be added-
4. Putrescence, noticeable only in technological chemistry as a stage to be
most carefully avoided.
Vinous Fermentation. Vinous or alcoholic fermentation is the result of the decomposi-
tion of saccharine matter, dextrose or glucose, levulose or chylariose, and lactose
into several products; principally alcohol and carbonic acid. According to the
recent researches of Lermer and Von Liebig (1870) dextrine in the presence of
sugar is converted into equal parts of alcohol and carbonic acid. This will be seen
from the following table, which gives the result for 100 parts by weight:
Crystallised dextrose, C6H1407,
Anhydrous dextrose, C6H12O6,
Cane-sugar,
Starch-meal,
Alcohol.
Carbonic Acid.
C12H22O11,
46.40 + 44'40 = 90.86.
51'10 + 48'90 = 100'00.
53.80 + 51'46 105.26.
C6H1005,
56.78 +54°32 = 111*1Ö.
mols. alcohol, 2C2H6O
1 mol. dextrose, C6H12O6 = 180, gives {2 mols. carbonic acid, 2002
2CO2.
=92
=88
180
Recently Pasteur has shown that lactic acid does not result from alcoholic fermen-
tation, but that succinic acid is a constant product of this fermentation in quantities
never less than o'6 to o'7 per cent. of the weight of the sugar employed. Glycerine
is another constant production to the extent of 3 per cent. of the sugar; this
substance occurs in all wines. The 5 to 6 per cent. of substances remaining may
therefore be thus divided:
Succinic acid
Glycerine ..
0'6 to 0'7
3°2 to 3.6
Carbonic acid
0'6 to 0.7
Cellulose, fatty substances, &c.
1'2 to 1'5
5'6 to 6'5
Yeast. The nature of alcoholic fermentation was first investigated by Cagniard-
Latour, while our present knowledge is due chiefly to the researches of A. de Bary,
J. Wiesner, Hoffman, Bail, Berkley, Pasteur, Hallier, Béchamp, Lermer. Yeast
on being introduced into a fermentable fluid rapidly throws out fermenting arms, as
it were, until the fluid is covered with a superficial ferment, termed in German
the Oberhefe, while at the bottom of the vessel a viscid sediment is deposited, known
in German as the Unterhefe. The oberhefe or superficial ferment, is employed as
barm by the baker, for the purpose of leavening his bread; while the unterhefe or
sedimentary ferment is that employed in the fermentation of wines and of Bavarian
beers;
these beers differ from the general beers of England, France, and Germany,
in not souring by exposure to air, this quality being due to the peculiarity in the
process of fermentation, Untergahrung, or fermenting from below, during which the
gluten, the substance absorbing the oxygen of the air, is removed. In the distilla-
tion of brandy, the yeast employed is a mixture of barm and bottom yeast, as the
358
CHEMICAL TECHNOLOGY.
terms run in this country. Fresh yeast appears as a grey-yellow or red froth of
strong odour, and with an acid reaction. Under the microscope the two kinds of
yeast are easily distinguished. The superficial yeast or barm consists of globular or
ellipsoidal cells of equal size, and about o'oi millimetre diameter. They float partly
alone, partly in groups in the fluid. The walls of the cells are so transparent that
the inner cells can be seen through the upper. In the centre of each cell appears a
dark speck or grain, the protoplasma, sometimes consisting of more than one grain.
The bottom yeast or sedimentary ferment also consists of cells, but these do not
cling together so tenaciously as the cells of the barm, and are generally isolated,
while the adhesion is merely mechanical between those that do cling together, a
slight concussion being sufficient to effect their separation. Sometimes a large cell of
the bottom yeast contains two, three, or even four smaller cells, the dimensions of these
cells varying greatly, and not being nearly so constant as in the cells of the barm.
I found," says Dr. Wagner," from the researches of Mitscherlich, communicated
to the Philosophical Faculty of the University of Leipsig, that the sprouting or trans-
planting of the cells had been actually witnessed under the microscope—that a parent
cell had been observed to put forth little cells, which gradually grew in size. These
observations had been made with barm or superficial yeast, and I wished to
ascertain if the cells of the bottom yeast or sedimentary ferment were propagated in
the same manner. For this purpose I placed a sedimentary yeast-cell, containing a
germ, under the microscope in a bath of concentrated beer-worts. The temperature
varied between 7° to 10°. The cell remained unaltered for some time, but finally
there appeared 30 to 40 small cells. These cells were either separated from the
mother-cell by the bursting of the cell walls, or had been introduced as spawn into
the field of the microscope in the beer-worts; which was the true case the microscope
could not reveal, for no separated spawn were visible. An analysis of the two
yeasts gave:—
Carbon
Hydrogen
Nitrogen
Oxygen, sulphur, and ash
:
Barm.
Sedimentary Yeast.
44°37
49.76
6'04
6.80
9'20
9°17
40.38 ·
34.26
"The barm contained 2.5 per cent., the sedimentary yeast 5:29 per cent. of ash.
The amount of sulphur was o‘5 to 0.8 per cent. The ash consisted essentially of
potash, phosphoric acid, silica, and magnesia."
According to the recent researches of Liebig, Pasteur, Lemaire, and others,
alcoholic fermentation is essentially due to the formation of yeast-cells, and to the
development of organic substances. There are two cases to be considered. Yeast,
with its botanical names, Saccharomyces cerevisiae, or Hormiscium cerevisiæ, a
descendant of the fungi, Penicillium glaucum, Ascophora Mucedo, A. elegans, and
Periconia hyalina, the spawn of which is always occurring in the atmosphere, ferments
either with a pure sugar solution, without the existence of protein substances, or
in the presence of albuminous substances. The latter case occurs also when
a solution of sugar containing an albuminous body is so situated as to be partially or
wholly open to atmospheric influence. The local ferment floating in the air in the
shape of yeast-spawn finds in this solution a ready agent for its extension. But in the
first case, where the sugar solution is mixed with the yeast, without the necessary
FERMENTATION.
389
protein substance as food or nourishment for the cells, the fermentation is after
a time exhausted, and is not again set up. It is for a similar purpose that during
the process of brewing the yeast cells are fed with a substance formed in the germi-
nation of barley. During this germination the gluten of the seed passes over into
diastase, of all nutriment that upon which the yeast cells flourish best.
The nature of the yeast cell is a most interesting question. Is it more nearly allied to
the animal or to the vegetable kingdom? The line of demarcation is not always defi-
nite, yet there would appear some interesting analogies that should not be overlooked.
"Plants," says Professor Williamson, "build up complex substances from simple.
All the most complex substances that we can get are made in the organisms of
plants. They may have been taken over by animals from plants, but they are
formed in the main by plants. And the chief chemical activity of animals is
precisely opposite; they take those complex substances and break them down,
by means of their vital functions, to the simple products which are exhaled and
given off in the processes of animal life. Therefore, the question whether the
process which the yeast carries on is a synthetical process-a building up-or whether
it is in the main an analytical process, is certainly one of the most important which
can guide us. From what we know best regarding the nature of the yeast cells, the
food which we know they take in large quantities, and upon which they thrive,
is certainly exceedingly complex, and the products which they give off are exceed-
ingly simple in comparison. Their functions are in the main (those which we know
best at any rate) analogous to those which take place in animal organisms, and
are most remote from those which take place in vegetable organisms.'
""
Among the most remarkable decompositions effected with the aid of yeast cells are
those described by Liebig in a recent paper, in which it is stated that yeast cells will
assimilate tartaric acid, malic acid, and nitric acid; the latter it deprives of a portion
of its oxygen, converting it to nitrous acid.
Conditions of Alcoholic or
The conditions of alcoholic fermentation are the general conditions
Vinous Fermentation. of the vegetation of the yeast plant, with the distinction that by vinous
fermentation the largest amount of alcohol is obtained. The following conditions must
be fulfilled when alcoholic fermentation is the desideratum:-
1. An aqueous solution of sugar, in the proportion of 1 part of sugar to 4 to 10 parts of
water. The sugar can be employed as grape sugar, dextrose, or levulose, which is always
capable of fermentation, or an unfermentable sugar, cane sugar, or sugar of milk, may be
converted by means of an acid or suitable agent into fermentable sugar. However
gradual the process may seem, cane sugar is always converted into grape sugar before fer-
mentation sets in.
2. The presence of yeast, or spawn. In the first case, I part of yeast to 5 parts of sugar
is sufficient to effect a strong fermentation. If spawn only is present, there must also
be present substances upon which the spawn may feed or develope-protein substances,
phosphoric acid, humus, and alkalies. If no ferment exists, the only other condition
under which fermentation is effected is by exposure to-
3. The atmosphere, which introduces the before-mentioned ferment and furnishes life.
4. A known temperature, the limits of which are 5° and 30° C. As a rule vinous fermen-
tation is effected between 9° and 25°. The lower the temperature the longer the time
required for the fermentation to subside, and conversely. At 30° and at higher tempera-
tures, the vinous fermentation easily goes over into butyric acid fermentation. The
making of wines is based on a practical acquaintance with alcoholic fermentation; but
in this case only a portion of the sugar of the must goes over into alcohol and carbonic
acid. The alcohol remains, while the greater part of the carbonic acid escapes.
In beer-brewing the substance forming alcohol is mostly starch, part of which goes over
into unfermentable dextrine, but the greater into easily fermentable dextrose. It is
arranged that the beer shall hold a small portion of the dextrose unchanged until the after-
fermentation at a lower temperature, during which much of the carbonic acid is expelled,
the alcohol remaining in the beer.
390
CHEMICAL TECHNOLOGY.
In the brewing of beer, only a part of the raw material or starch employed goes over
into dextrose, and finally into alcohol and carbonic acid; but in the manufacture of
spirituous liquors the given material-starch or sugar-is converted into the greatest
possible quantity of alcohol in the shortest time, and afterwards separated by distillation.
The aim of the wine maker is, of course, to produce the greatest quantity of wine; of the
brewer, the maximum amount of beer and of the distiller, the largest yield of spirit.
The residue from the distillation of spirits is often employed in making concentrated food
for animals.
In the baking of bread and confectionery the lightening or leavening of the dough is
effected by alcoholic fermentation, but only the carbonic acid, and not the alcohol, is
of use.
In the foregoing illustrations of the application of fermentation, it will have
been perceived that the object is the generation of alcohol or of carbonic acid, or of both,
according to the requirements of the case. The particulars we will consider under
separate divisions.
WINE-MAKING.
Wine. By the name of wine is generally distinguished an alcoholic fluid prepared
without distillation by the fermentation of grape-juice. In the widest meaning
of the term is included the result of the vinous fermentation of all natural juices.
The Vine and its Cultivation. The vine, Vitis vinifera, is generally cultivated in Europe at
a temperature of 50°, while the best and ripest drinking wines are obtained from
grapes grown at a temperature of 51° to 52º. It requires an average temperature of
10° to 11º, and an average summer temperature of 18° to 20°; but it is the summer's
sun that forms the sugar. A climate with severe winters and hot summers is therefore
as favourable to the cultivation of the grape as a temperate climate. England, with a
mean average annual temperature of 11º, is consequently very unsuited to the growth
of the vine. The weather has the greatest influence upon the vine: during the
growth rain is required, but during the ripening only the sun's rays should reach the
grape. The soil is not so much a matter of consequence if a quantity of potash be
present; but a warm, loose soil is the best. Clay shale, clay marl, gypsum, lime,
and chalk formations are very suitable to the vine. The uses of the grape are
numerous in the highest degree; it serves chiefly in the preparation of must for
wine, the preparation of grape sugar, French brandies or cognacs, wine-vinegars, &c.
Oil is prepared from the seeds, and the lees are burnt for their potash.
Vintage. The sugar is found at an early stage of the growth of the grape. When
unripe the grape contains malic, citric, and tartaric acids, bitartrate of potash and
lime, organic salts in smaller proportions, and a little colouring and extractive
matters. Successive analyses have been made of the grape during its period of
growth by C. Neubauer, from samples obtained from the Neroberg, near Wiesbaden
(1868), and have given the following results:-
0'6 per cent. Sugar and 2.7 per cent. free acid.
""
July 27th
August 9th..
17th..
28th
0'9
وو
""
2.9 "
2.3
2.8
""
8.2
""
I'9
"
""
September 7th
119
I'2
""
>>
"
""
17th 18*4
""
0'95
""
""
28th 17°5
0.8
,,
وو
""
October 5th.. 16'9
12th.. 18.6
0.8
""
""
""
0°9
""
وو
22nd
""
17'9
""
""
o'g
WINE.
391
It appears that the riper the grape the more sugar it contains, and it produces a
wine richer in alcohol, so that the grapes are never gathered until perfectly ripe. The
grapes of the white vine are of a brown-yellow when ready for gathering for wine,
and the red and blue grape must be extremely dark before the seed will separate
from the fleshy part of the grape sufficiently for wine-making purposes.
The grapes are sometimes plucked, and sometimes left on the stalk. The separation
of the grape from the stalk is effected either by hand or by the aid of a hurdle, the
openings between the bars of which are only sufficiently wide to admit of the passage of
the grape, or by a wooden or brass trellis-work, or finally with a large wooden fork o'5 to
06 metres in length. The stalk contains much tannic acid, and it is therefore necessary
that all the grapes should be thoroughly separated before pressure; but in some cases
when the grape contains too little of this acid, a few stalks are purposely allowed to
remain.
Grapes.
The Pressing of the After the grapes are stripped from the stalks, they are placed in a
vat and stamped with a wooden maul or pestle to express the juice. They are
generally allowed to remain for some time, and afterwards submitted to a second
bruising, the maceration being for the purpose of softening the skins and fleshy part
of the grape. The whole of the juice and grape-skins, or marc, is then put into a
butt with perforated sides, through which the must trickles into the fermentation vat
beneath. If a white wine is being operated upon, to prevent it becoming stringy, as
the term runs, from an insufficient supply of tannic acid, small quantities of stalks
are added from time to time. This addition renders the wine more easily clarified
by the addition of white of egg or isinglass in a subsequent stage of the process. While
the wine is in the vat, the fermentation is allowed to proceed, and the slight acidity
generated reacts upon the colouring matter and aromatic constituents of the grape,
these being taken up in the alcohol set free.
The wine-presses are of very various construction. The most general is the beam-press,
roughly constructed with a pole 12 to 16 metres in length, and four to six oaken cross beams.
These presses have considerable power, but they are tedious to work, and soon get dirty.
The lever-press is more efficacious, and is made in many forms, the pressure being mostly
from below. The hurdle- or sledge-press is of the rudest kind, consisting merely of
hurdles and rough heavy stones. The best presses are the screw-presses made of wood
or cast iron. 100 parts of grapes yield 60 to 70 parts of must. The ripest grapes yield
the first juice in the press; the results of stronger pressure are more acid. The result of
the first pressure is termed the wine or the first wine; then comes the press wines; and
finally the after wines. The residue or marc is sometimes treated with water to obtain
an inferior wine.
The Centrifugal Machine. In 1862 Steinbeis, of Stuttgart, with the co-operation of
Reihlen, endeavoured to express the juice of the grape with the aid of the
centrifugal machine instead of the press. They were enabled in ten minutes to
express the juice perfectly from 100 to 120 pounds of grapes, including the time
required to fill and empty the machine. In 1869, Ballard and Alcan obtained
equally successful results, some of which were made comparative with those ob-
tained by a good press :-
Must..
Residue
Luss
:
Centrifugal Machine.
79°141
20*214
0:645
100'000
Press.
77'086
18.601
4'3-3
100'000
Chemical Constituents
of the Must.
Besides the stalk of the grape, there are the outside skin, the
hull. the seeds, and the juice. Of the composition of all these substances, with the
exception of the grape juice, our knowledge is very deficient. Besides cellulose,
392
CHEMICAL TECHNOLOGY.
the stalks contain much tannic acid, and an acid very sour to the taste. The hull of
the
grape contains the colouring matter and a small quantity of tannic acid. The
seed contains a peculiar acid, oenanthic acid, and an ether, bearing the same name,
to which the bouquet of the wine is due.
Grape.
The Sugar of the The wine grape contains more sugar than any other kind of grape.
The quantity of sugar-a mixture of dextrose and levulose-is seldom than
12 per cent., while it is scmetimes as much as 26 to 30 per cent. The proportion of
acid to sugar is in good years and in a good grape, according to Fresenius, 1: 29;
in average years and cases, 1 : 16; nd when the proportion is only as 1 : 10, the
grapes are useless for the production of wine. The proportion between the acid and
sugar in wine-must from the same kind of grape for different years is, according to
this eminent chemist:-
In a very inferior year, 1847, as 1 : 12
In a better year,
In a good year,
1854, I: 16
""
1848, I: 24
""
During the fermentation of the must, bitartrate of potash is deposited, and from
this source most of the tartar of commerce is obtained. This salt is insoluble in
dilute alcohol; consequently as the sugar changes into alcohol it is thrown down.
It is from the fact of containing tartaric acid, which, by combining to form an
insoluble salt, is thus prevented exerting an unfavourable influence on the wine, that
grapes possess so much the property in proportion to other fruits of making a good
wine. The malic and citric acids contained in currants and gooseberries cannot be
withdrawn in this manner: hence the addition of sugar to wines made from these
fruits to veil the acidity; the addition, however, giving rise to the danger of a second
fermentation, and consequent acidity. According to Al. Classen, 1 kilo. of ripe grapes
gave (in 1868) 577 to 688 grms. of juice; and 1 litre of juice contained:
Water
I
Sugar (dextrose and levulose)..
Pectin, gums, extractive matter,
Protein substances, organic acids,
and mineral matters
860 to 830 grms.
150, 300 >>
30, 20 >>
1040 to 1150
""
1000 parts of juice of ripe (Rhine, 1868) grapes contained :-
I.
2.
3.
Solid matter
164'4
189'7
204'6
Sugar
149'9
162'4
174'0
Free acid..
:
7.2
6.8
4.8
Ash ..
2'7
3'0
4'0
In 100 parts of the ash were contained :—
I.
2.
3.
Phosphoric acid
16.6
16.1
14'0
Potash
64°2
66'3
71°4
Magnesia
4'7
2.8
2.6
WINE.
393
C. Neubauer (1868) analysed two kinds of grapes, and found―
Sugar
Neroberger
(large grapes). (selected grapes).
Steinberger
18.06
24°24
Free acid..
•
0°42
0'43
Albuminous substances
O'22
0'18
Mineral constituents (potash,
phosphoric acid, &c.)..
0'47
0'45
Combined organic acids and
extractive matter
4'11
3'92
Total of soluble constituents
23*28
29°22
Water
76.72
70-78
100'00
100'00
The Fermentation of the
Grape Juice.
The fermentation of the grape juice is spontaneous; that is, it
is consequent upon the exposure of the grape juice to the atmosphere, without the
addition of yeast. The albuminous matter of the must forms, under the influence
of the atmospheric spawn or yeast germ, the well-known fungus Penicilium glaucum,
or yeast cells. The fermentation begins at a temperature of 10° to 15°, and is effected
more or less rapidly according to the temperature. Too low a temperature will
retard the progress of fermentation, as also will the addition of sulphurous acid;
the same effect is obtained by the addition of other sulphur compounds, as, for
instance, the essential oil of mustard, which contains sulphocyanide of allyl. The
must is left in open vats; bubbles of carbonic acid soon appear, scum collects upon the
surface of the juice, and an alcoholic odour pervades the wine at this stage. About
the seventh day the fermentation commences to decrease, and about the tenth or
fourteenth day the fluid begins to clear, no more carbonic acid or scum appearing.
The yeast cells formed are carefully removed from the bottom of the vessel, and the
wine run into casks, where it undergoes a slight after-fermentation. If there be
much sugar contained in the grape, and a small quantity of azotised matter, the
resulting wine will be sweet; but if the proportion of sugar be small and albumen
large, a dry wine is the result.
CC
the Wine.
Drawing off and Casking After the principal fermentation the greater part of the sugar
of the must is found to be separated into alcohol and carbonic acid. There is still
likely to arise, unless the temperature be considerably decreased, a fresh fermenta-
tion, known as the after-fermentation. Should this after-fermentation continue too
long, vinegar is formed, and to prevent this, the wine, after the disappearance of the
bubbles of carbonic acid upon the conclusion of the principal fermentation, is at
once spigotted off" from the lees into casks, the object being to cut off communica-
tion with the atmosphere as much as possible. The casks are nearly filled, and are
bunged loosely, being filled completely a day or two after. Wines casked in Decem-
ber will often continue fermenting till February or March. Strong wines rich in
alcohol can be kept in cask until they have become quite clear; but weak wines
must be soon bottled, as the oxygen of the air is liable to convert the hydrate of the
oxide of ethyl or alcohol into trioxide of acetyl or vinegar.
Constituents of Wine. Constituents that were not found in the must are characteristic of
the wine-the chief of these is alcohol. Succinic acid and glycerine, the constant
products with alcohol and carbonic acid of vinous fermentation, are also to be found.
A "dry" wine, such as the French and Rhenish wines, is one in which all the sugar
has been decomposed; a sweet" wine, on the other hand, is one in which some
sugar has remained undecomposed either from an insufficiency of albuminous matter
394
CHEMICAL TECHNOLOGY.
to nourish the yeast cells, or from the checking of the fermentation by exposure to a
low temperature. A very sweet and thickly fluid wine is termed a "liqueur." The
difference in colour is due to three substances-a blue colouring matter, a brown
colouring matter, and tartaric acid. The brown colouring matter is present in all
light or white wines, while the blue colouring matter, found in the skins of purple or
black grapes, is in the wine a red colour, the change arising from the contact with
the tartaric acid. Wines of the first year after growth are termed new or
wines. The average composition of wines, in 1000 parts, is the following :-
Water
Alcohol*
Homologues of alcohol (propylic, butylic alcohol) *
Ethers (acetic, œnanthic)*
Essential oils
Grape sugar (dextrose and levulose)
•
*
•
900-891
80-70
green
""
Glycerine*
•
Gums
•
Pectin
Colouring and fatty substances
•
•
Protein bodies
Carbonic acid*
Tartaric and racemic acids
Malic acid
Tannic acid
Acetic acid*
Lactic acid (?)
Succinic acid*
Inorganic salts
•
•
•
•
·
•
•
•
•
·
•
•
•
•
•
•
20-30
Of
Those substances marked (*) are formed during the principal fermentation.
The quantity of alcohol contained in a wine is due partly to the quantity of sugar and
partly to the quantity of albuminous matter contained in the must. It is chiefly ethylic
or ordinary alcohol. The specific weight of the wine gives only approximately the
alcoholic contents; a better method of estimation is by means of an alcoholometer.
these instruments, Geissler's Vaporimeter is, perhaps, one of the best, in which the
pressure exerted by the vapour of the wine upon a column of mercury gives a measure
of the alcohol contained. The vapour of absolute alcohol at a temperature of 78.3°
exerts a tension equal to that exerted by aqueous vapour at 100°. It is therefore only
necessary to ascertain the height of the column of mercury and the temperature to
arrive at the quantity of alcohol. The apparatus is shown in Fig. 228, and consists
essentially of four parts, viz.-I. A brass vessel, A, half-filled with water, heated by
means of the lamp to the boiling point. 2. A bent glass tube, B, to which a wooden scale
is fixed. 3. A cylindrical glass vessel, o, filled with mercury and the wine to be tested.
4. A cylinder of sheet brass, in the upper part of which a thermometer, T, is fixed. The
glass vessel, o, is filled with mercury to the mark, a, and then completely filled with the
liquid to be tested. The boiling-vessel is now affixed, the brass cylinder drawn over the
mercury tube, and the thermometer inserted. Heat is applied, and the water raised to
the boiling-point; the steam ascends into the brass cylinder, and heats the wine and
mercury to the boiling-point of water. The wine expands, and is partly vaporised,
forcing the mercury up the arm, B, which has been previously graduated by experiments
with fluids of known alcoholic contents; the mercury of course rises the higher the more
alcohol there is contained in the wine. The variable constituents of the wine, the
extractive matter, &c., do not influence the result. The carbonic acid must have been
removed previously by filtering the wine through freshly-burnt lime. Equally good, if
not better, results are, however, to be obtained by the distillation test, effected by
distilling 10 c.c. of the wine, and adding to the distillate sufficient water to make a total
of 10 c.c., the specific weight of the fluid giving the alcoholic contents of the wine. The
alcoholometer most generally employed is the Ebullioscope of Tabarié, Fig. 229.
With
the barometer at 760 m.m. water boils at +100°, and alcohol at + 78-3° C. The nearer
therefore the boiling-point of the fluid tested approaches 78.3°, the greater the alcoholic
contents. The wine is poured into the vessel, c, and the cover, E H, replaced. The fluid is
heated by means of the lamp, L, and the steam ascends round the thermometer, t t',
height of the mercury of which when the fluid boils varies inversely as the alcoholic contents
of the wines tested. The vessel, м м', is filled with cold water to hasten the condensation
the
WINE.
* 395
of the vapours. If the boiling point of pure water be taken at 99'4° C., the following
boiling points show the quantity of alcohol contained:
96.4° C. 3 per cent. alcohol.
91.1° C. 9 per cent. alcohol.
95'3" 4
""
""
90'2"
IO
""
""
94'3", 5
""
""
93'5"" 6
""
""
""
""
89.7"
89.3 "
88.8
88.4, 14
II
""
12
""
""
,, 13
""
92.7" 7
91'9 " 8
99
""
Red French wines contain 9 to 14 percentage by volume of alcohol; Burgundy, 9, 10,
and 11 per cent.; Bordeaux, 10, 11, and 12 per cent. Other French wines contain 8 to 10
per cent.; the wines of the Palatinate, 7 to 9.5 per cent.; Hungarian wines, 9 to 11 per
cent. Champagne contains 9 to 12 per cent.; Xeres, 17 per cent.; Madeira, 17 to 237
per cent.
Acids exist in all wines, and are generally carbonic, succinic, tartaric, malic,
and acetic acids; these acids are found partly free, partly combined as salts; tartaric
FIG. 228.

T
O
M
C
FIG. 229.

H
M
M
:
acid, for instance, as cremor tartari, bitartrate of potash, and other acid tartrates. Fauré
found an essential gum, which he termed oenanthin, and which with glycerine-first
shown by Pasteur in 1859 to be a normal constituent of wine-helps to give a certain con-
sistency to the wine. Pohl found (1863) in Austrian wines 2.6 per cent. glycerine. As
wine ages the glycerine disappears. The colouring matter of wine is of interest in the
396
CHEMICAL TECHNOLOGY.
case of red wines only, as the yellow-brown colour of some wines is undoubtedly due to
oxidised extractive matter. The colouring matter of red wines has received from Mulder
and Maumené the name of œnocyan, while it is commonly termed wine-blue; it is a blue
substance similar to litmus, possessing the property of turning red in the presence of
acids. It is insoluble in water, alcohol, ether, olive oil, and oil of turpentine; but soluble
in alcohol containing small quantities of tartaric or acetic acid. With a trace of acetic
acid the solution is practically blue, turning red upon the addition of more acid;
neutralised with alkalies the solution remains blue. On the evaporation of a wine to
dryness the extractive matter remains, consisting of a mixture of non-volatile acids, the
salts of organic and inorganic acids, with oenanthin, colouring matter, sugar, protein
substances, and extractive matter, the nature of which is unknown. The quantity of
extractive matter differs greatly, varying with the kind of wine and the degree of fermen-
tation of the sugar. Fresenius found in Rhine wines a maximum of 106, and a minimum
of 42 per cent. of extractives; Fischern, in the wines of the Palatinate, 107 to 19 per
cent.; in Bohemian wines, 2·26; in Austrian, 2'64; in Hungarian, 2·62 per cent. The
mineral constituents of wines exist in but small quantities-as an average in old
Madeira to 0.25 per cent.; in old Rhine wines, o 12 per cent.; and in old ports, 0.235 per
cent. Van Gockom, Veltmann, and Mösmann found in 1000 parts of wine:-
Madeira
Teneriffe
Rhine wine
Port
•
•
+
•
""
2:55 parts of ash.
2.91
I'93 ""
2.35
""
Pohl estimated the following number of parts of ash in 100 parts of wine :—
Slavonian
Bohemian
Croatian
Craniola
Lower Austrian
1'97 parts.
1.68
1.81
""
""
2'00
""
Styrian..
Tyrol
Hungarian..
•
•
•
1'91 parts.
1.63
•
1.84
""
1.80
""
The ash contains potash, lime, magnesia, soda, sulphuric acid, and phosphoric acid.
The "Handwörterbuch der Reinen und Angewandten Chemie" (B. ix., Seite 676), gives
the following analyses of wine-ash, the first four being by Crasso, and the fifth by
Boussingault
I.
2.
3.
4.
5.
Ash (per cent)
0.26
0.34
0'41
O'29
0'18
Potash
65.5
63.9
71.3
62.0
45'0
Soda
Lime
Magnesia
•
•
0'3
0'4
I'2
2.6
•
•
5*2
3'4
3'4
5'1
4'9
• •
3'3
Oxide of iron
Oxide of manganese
•
0.7
0.8
378
4'7
4.0
4.0
9°2
0.4
O'I
0'4
0'7
O'I
0'3
Phosphoric acid
•
15'4
16.6
14'I
17.0
22'I
Sulphuric acid..
5'2
5'5
3.6
4.9
5'1
Silica ..
2'0
2.I
I'2
2'2
•
0'3
Chloride of potassium
1'5
2.I
ΙΟ
1°5
Carbonic acid
13'3
100'0
ΙΟΟ Ο
100'0
ΙΟΟ Ο
100'0
The bouquet of wines or their peculiar odour is due to oenanthic ether mixed with
the alcohol. According to C. Neubauer ("Chemie des Weines; " Wiesbaden, 1870, Seite 97),
this œnanthic ether is a combination of various substances, of which caprylic and caproic
acid ethers are the most important, and is a product of the fermentation of the must.
During the fermentation of the sugar there are formed, besides ordinary alcohol, propylic
and butylic alcohols, and succinic acid as a constant product, while in the juice of the
grape there occur tartaric, malic, and racemic acids; these with acetic, propionic, and
butyric acids, and the aldehydes of these acids, together with the oil of the seed of the
grape (oleic and palmitic acids), cannot but greatly influence the bouquet of the wine,
which of course will vary according to the proportion of these constituents.
Maladies of Wines.
Wines are subject to various causes of deterioration, termed
maladies, distempers, or diseases. That most commonly occurring is ropiness or
viscidity, the cause of which was for a long time unknown. Francois showed that
it was due to the decomposition of the glucose into azotised matter and mannite,
WINE.
397
and at the same time indicated the proper remedy, the addition of tannic acid. He
employs 15 grms. of tannin to 230 litres of wine. This is well mixed with the wine,
which is allowed to stand for a few days. At the end of this time the tannin will
have separated the azotised matter, and the wine may be bottled off.
The souring of wine is due to the conversion of the alcohol into acetic acid, caused,
according to Pasteur, by the formation of the vinegar plant or Mycoderma aceti,
which he found in all sour wines. This disease is very common, and may result
from too small a proportion of alcohol, too high a temperature of the cellars, or
exposure to the atmosphere. The wine, if too far soured, is fit only for making
vinegar; but slight cases can be remedied by an addition of sugar. The formation
of vinegar may be somewhat delayed by impregnating the wine with sulphurous
acid. In some cases the acetic acid may, by the addition of tartaric acid, be removed
as acetic ether; but the acetic acid can never be neutralised with alkalies, as the
salts formed are very easily soluble.
The bitering of wine, or its acquirement of a bitter flavour, is due to another
cause, the formation of a bitter substance, which developes as the wine ages, or at
too high a temperature. Maumené suggests as a remedy the addition of slaked
lime in the proportion of 0.25 to 0'50 grm. per litre. Bittering is due also to the
formation of brown aldehyde resin. Mould in wines appears as a white vegetable
(fungus) film covering the surface, and arises from an insufficiency of alcohol;
consequently weak wines are more subject to this malady. The film of mould
should be removed and the wine used as soon as possible, for wine affected with
this disease soon turns sour. The decaying of a wine is due to the dissipation of
the alcohol and the decomposition of the acids of the wine; the wine obtains an
astringent taste, and a dim, thick colour, finally turning sour. The bitartrate of
potash is converted into carbonate of potash, affecting the colouring matter and
tannic acid, which pass over into humus substances. At the commencement of
this decomposition a remedy may be found in the addition of a small quantity of
sulphuric ether. Caskiness, or the taste of the cask, due to an essential oil formed
in casks that have long stood empty, is best removed by the addition to the wine of
a small quantity of olive oil and agitation; the olive oil absorbs the essential oil,
and brings it to the surface of the wine, whence the oily matter may be skimmed, or
the wine may be filtered through freshly burnt charcoal. All casks and vessels that
have stood long empty should be well steamed before use.
Ageing and Conservation
of Wines.
The Pasteuring, a term which usage has substituted for
pasteurisation, or the conservation and artificial ageing of wines, according to
Pasteur's method, is a great improvement in the general treatment of wines to
ensure their keeping. It consists essentially in heating the wine to 60° C., and for
this purpose the apparatus designed by Rossignol is best suited. A metal cask, T,
Fig. 230, contains at the bottom a copper vessel, C, with a trumpet-shaped cover
extending in the open tube, c, above the top of the vessel, T. t is a thermometer.
Water is poured into the vessel, c, until the tube, c, is three parts full. The wine
is placed in the metal cask, T, and by means of the tap, r, and the tube, ƒ, run off
into the cask, F, when sufficiently heated. The water in the copper vessel, c, is em-
ployed to prevent the direct heating by the flame of the vessel containing the wine,
and the consequent burning of any insoluble matter settling to the bottom of the
vessel. Fig. 231 shows in detail the manner of fastening the vessels together. A
copper ring, a, encircles the vessel, T, and beds with the walls of this vessel into the
398
CHEMICAL TECHNOLOGY.
india-rubber band, d, into which it is pressed by the tightening of the bolts, e,
binding the ring of angle-iron and lower iron ring, b, together,. The joint is thus
rendered water-tight. The vessel, T, is not quite filled with wine to allow for
expansion under heat; by this means the wine is exposed to a known quantity of
air. Wine should not be artificially aged in contact with air, as Pasteur has proved
FIG. 230.

G
E
F
f
7°
FIG. 231.

T
e
that such processes deteriorate the colour and the flavour of the wine; and in
ordinary cases, where part of the process of ageing consists in heating the wines
for a short time in an open vessel with a full exposure to air, the wine acquires a
peculiar boiled flavour, goût de cuit, easily recognisable by the connoisseur. By
Pasteur's method, however, neither the flavour nor colour of the wine is deteriorated;
indeed, the latter is improved by the expulsion of the carbonic acid.
Pasteur has shown that most of the diseases of wine, acetification, ropiness,
bitterness, and decay or decomposition, are due to the growth of different fer-
ments, consisting of minute vegetable cells always existing in wines, and becoming
active and destructive under certain conditions, such as a change of temperature
and oxidation. He recommends ("Comptes Rendus," May 1st, 29th; August 14th,
1865), that these plants of fungi should be killed, as the best means of ensuring the
keeping of the wine, and the particular modus operandi selected is essentially the
following, differing considerably from the foregoing method. The bottles are quite
filled, the wine touching the cork, which is inserted with such a degree of firmness
that the wine in expanding may force the cork out a little, but not so much as
to admit air into the bottle. The bottles are then placed in a chamber heated to
45° to 100°, where they remain for an hour or two, after which they are removed, set
aside to cool, and the cork driven in. By this means the life or active principle of
the fungi is destroyed, while the wine acquires an increased bouquet, is of a more
beautiful colour, and, in fact, is to a considerable extent aged. Both new and old
wines can be thus treated.
WINE.
Clearing or Fining the
Wine.
399
Most wines are self-clearing, the ferment settling to the bottom.
of the cask, and leaving the wine clear and pure. This applies chiefly to dry wines
which have less sugar than sweet wines. The sweet wines are generally more
thickly fluid on account of the quantity of sugar they contain, and consequently
more frequently need clearing. Fining, as it is sometimes called, or clearing,
consists in adding to the muddy wine some albuminous or similar substance that will
mix with the suspended matter and carry it to the bottom or bring it to the sur-
face of the wine. The substances most generally employed are white of egg, ox-
blood, and milk, or mixtures of these substances. Liming, or the addition of
gypsum, is for the purpose of heightening the colour, chiefly of red wines; further,
it converts the soluble potash salts of the wine into insoluble lime-salts and sulphate
of potash.
The Residue or Waste The waste of wine-making consists of the stems, husks, and seeds of
of Wine-making. the grapes, as well as of the fermentary sediment and tartar. Both
descriptions of waste find numerous applications. The lees left from the pressing of the
wine contain a not unimportant quantity of must, which (1) is employed in preparing an
inferior wine. 2. In the making of an inferior brandy. 3. In the preparation of ver-
digris (see p. 58). 4. In vinegar making, and for promoting the formation of
vinegar from saccharine or alcoholic fluids. 5. In wine-making countries the lees are
much employed as fodder for horses, mules, and sheep. While (6) the residue of the
after-pressing or final pressing is used as manure. 7. The grape seed yields an oil
in quantities of 10 to 11 per cent.; or (8) tannic acid in large quantities. The oil can be
extracted by pressure or by treatment with benzole, or with sulphide of carbon. The
tannin obtained can be employed for the preservation of hides, &c. 9. Potash is prepared
from the calcined lees. 10. The stalks and seeds when calcined are employed in
the preparation of a black colouring material (vine black). 11. The ferment and stalks
are in some wine-producing countries, besides being employed in the preparation of tartar
and potash, also used in the distillation of a peculiarly rich brandy, in which an oil
is found possessing highly the flavour of cognac, and known in commerce as wine oil,
cognac oil, huile de març. 12. Crude tartar is found with tartrate of lime, colouring
matter, and yeast, forming a more or less thick crust on the walls of the wine cask or in
the crust deposited in the wine, but not firmly attached to the vessel, and is the chief
source of the pharmaceutical bitartrate of potash (CH-KO), and tartaric acid.
Effervescing Wines. Effervescing wines have been known for many centuries. Some of
Rembrandt's paintings exhibit among the accessories, a champagne glass with
effervescing wine. And from Virgil-
"Ille impiger hausit,
Spumantem pateram-"
it would appear that this description of wine was known to the Romans. In 1870,
there were in Germany fifty producers of effervescing wines, with a production
of 2 to 3 millions of bottles, 1 millions of which were exported. In France the
production amounts yearly to 16 to 18 millions of bottles.
All wines are capable of being produced as effervescing wines if bottled before the
fermentation is over. By bottling at this period the carbonic acid is retained in the
wine, and when the bottle is opened the disengagement of this gas causes the appear-
ance of effervescence. In this country the effervescing wine most generally known
is champagne; but Hocks, Moselles, and even red wines are very admirable when
thus treated. If the wines contain much sugar, the fermentation is arrested in the
bottle before all the sugar is consumed, producing a sweet effervescing wine. On
the other hand, if the sugar is all exhausted in producing the carbonic acid,
the result is a dry effervescing wine. These wines are very agreeable to the
palate, and may be supposed to assist the digestion of the food with which they
are taken; but when new, they are dangerous as being likely to communicate their
state of change to the contents of the stomach, interfering seriously with digestion,
400
CHEMICAL TECHNOLOGY.
and producing what is well known as acidity." Dry effervescing wines are less
likely to disagree than sweet wines of this class containing much sugar and
fermentable matter. The connoisseur places great reliance in his judgment of a
champagne upon the loudness, or rather sharpness, of the report when the cork
is drawn, and upon the "bead" or bubble formed on the side of the glass by the car-
bonic acid gas. These effects are not proportionate, for while a loud report results
from an extended fermentation, a good bead may be obtained with a very weak fer-
mentation. The gas in a bottle of champagne exerts a pressure of some five
atmospheres, and it will at once be evident that if the bottle be made a little
smaller, reducing the space between the cork and the wine only one-twentieth,
a considerable increase in loudness of the report will ensue.
The process of manufacturing effervescing wines is in general the following:-The
best grapes are used for this purpose; for champagne, the black grape, called by the
French noirien, is employed. The juice is expressed from the grape as soon
after gathering as possible, in order to prevent the colouring matter of the skin
affecting the wine; while the fruit is pressed as quickly and as lightly as possible.
The juice from the second and third pressings is reserved for inferior, or red-tinted
effervescing wines. The expressed juice is immediately poured into tuns or vats,
where it is left to stand for twenty-four to thirty-six hours. In this time any earthy
matter or vegetable impurities will have settled, and the juice is ready to be trans-
ferred to the fermenting vats, where it remains for about fifteen days. It is then put
into casks, which are securely bunged; sometimes brandy is added in the proportion
of one bottle to one hundred bottles of juice or must. Towards the end of December,
the wine is fined with isinglass, and a second time in the ensuing February. About
the beginning of April the clear wine is fit for bottling. It now contains, if a good
wine, 16 to 18 grms. of sugar, 11 to 12 per cent. of the volume of alcohol per bottle,
and an equivalent to 3 to 5 grms. of sulphuric acid in free acids.
Great care is necessary in the manufacture of champagne bottles; they must be
free from flaws, and made of pure materials. Generally each bottle is from 850 to
900 grms. in weight, and equal in thickness throughout. Formerly the flawed bottles
amounted to 15 to 25 per cent., but recent improvements in manufacture have reduced
the percentage to 10. Before the wine is introduced, the bottle is rinsed with a
liqueur of white sugar-candy 150 kilos., wine 125 litres, cognac 10 litres, the liqueur
being allowed to remain in the bottle: according to F. Mohr the cane sugar of the
liqueur becomes converted into grape sugar in the champagne. It is doubtful
whether glycerine might not be advantageously substituted for a portion of the sugar
of the liqueur. The liqueur employed varies with the flavour of the wine: port,
Madeira, essence of muscatels, cherry water, &c., are used, but rarely unmixed with
some other favourite solution of the manufacturer, as, for instance, water 60 litres,
saturated solution of alum 20 litres, tartaric acid solution 40 litres, tannin solution
80 litres. About 2 litres of this mixture would in practice be added to a butt of
wine. The bottles are filled by women, the proportion of liqueur introduced being
about 15 to 16 per cent. of the wine. A space of about 2 to 3 inches is left between
the wine and the cork, which, after being thoroughly moistened, is next inserted by a
machine. The bottle is then passed to a man, termed in the French establishments
the maillocher, who drives the cork home with a mallet. Another process, now gene-
rally effected by the aid of a machine, is the " wiring," or securing the cork with
wire or string. The bottles are now conveyed to the cellar, where they are laid in
horizontal racks against the wall. In about eight or ten days a deposit, termed
WINE.
4CI
"griffe," is formed, and shows that the time has arrived for the wine to be transferred
to the cellar, where it is to remain until sold to the merchant. The deposit is allowed
to form during the summer, and in the ensuing winter means are taken for its
removal. The bottles are well shaken, and placed with their mouths downwards, to
cause the deposit to settle on the cork. The cork being removed, the sediment falls
out, when more liqueur is added, and the bottle re-corked and again wired. The
bottle is now laid upon its side at an angle of about 20°, and in about eight to ten
days the inclination is gradually increased until the vertical position is attained,
when, by a dexterous movement of the cork, the gas is permitted to force out the
remaining sediment. This process is repeated as many times as may be necessary,
until the wine is perfectly clear. Wine thus prepared, generally known as sparkling
wine, vin mousseux, is ready for the consumer at the end of 18 to 30 months, the time
varying with the temperature of the season. One of the greatest causes of loss is
the bursting of the bottles, sometimes as much as 30 per cent. of the wine being
wasted. This in some measure accounts for the dearness of these wines.
By the analysis of several sparkling wines (1867 and 1870) the following results
were obtained:-
I.
2.
3.
4.
5.
6.
Per mille. Per mille. Per mille. Per mille. Per mille. Per mille.
Free acid
5'300
Per cent. Per cent.
5'900
7.600
7.800
6'200
Per cent.
Per cent. Per cent.
5'600
Per cent.
Alcohol
8*400
9'500
8.700
8.400
9.800
8.400
Sugar
8.200
4'300
7'900
9'100
7'500
5'400
Extractive matter
II.600
7'500 10'300
12'000
II.600 15'200
Specific gravity.
1'036
I'029 I'039 I'046 I'039 1'041
I. From Chalons. 3 and 4. From Wirtzburg. 2. From the same place, but intended
for export to India; 3 being the manufacture of J. Oppman, and 4 of Silligmüller, both
well-known German firms. 5. From Sutaine and Co., of Rheims. 6. From a well-known
Rhenish firm, glycerine being substituted for a portion of the sugar.
Wine Must.
The Improving of the The worth or character of a wine is determined by its aroma
and the amount of alcohol and free acid contained-decreasing with an increase of the
latter, and increasing with increase of the former. The proportion between the
chief constituents of the grape-juice, sugar, acid, and water, is nearly equal in all
good wines, and this proportion is never accidental, but always belongs to a good
wine. The grapes not fitted for making good wines are treated in two ways: either
the expressed juice is allowed to ferment as it is, in which case an inferior wine is
obtained; or, by the study of chemical analyses of good wines, the incomplete con-
stituents are supplied, and others injurious to the wine removed, to make the must
of that quality which will yield a good wine. The following are the best methods
of improving the must:
1. The addition of sugar to wine poor in this constituent, and the neutralisation of an
excess of acid by means of pulverised marble (Chaptal's method).
2. The addition of sugar and water to must poor in sugar and rich in acid (Gall's
method.)
3. Repeatedly fermenting the husks with sugar-water (Petiot's method.)
4. Removing the water by means of freezing, or by treatment with gypsum.
5. Removing the acid by means of a chemical reaction.
6. Addition of alcohol to poor wines.
7. Treating the prepared wine with glycerine (Scheele's method).
The addition of sugar to must poor in this constituent is the oldest method of improve-
ment, and appears to have been known to the Greeks and Romans. At that time cane
27
402
CHEMICAL TECHNOLOGY.
sugar was unknown, honey being used for sweetening purposes, and which, being added
to the wine, gave it a peculiar flavour, and rendering it thick. In years when honey
was scarce, we are informed that the wine was inferior. Chaptal, in 1800, wrote a work
on the cultivation of the grape, in which he gives a recipe for adding sugar to an inferior
must, to render the wine equal to that of better years, the acid being neutralized with pieces
of marble. In Burgundys, Chaptal's method is not much required to be used, as these
wines rarely contain more than 6 parts per 1000 of free acid. The amount of pulverised
marble (carbonate of lime) required to neutralise 60 parts of free acid is, as a rule, 50
parts; and the amount of sugar to be added, when the acid is in excess, is 100 parts for
each 50 parts of alcohol required after fermentation, it being found that 15 per cent. of
sugar in the must produces 7.5 per cent. of alcohol in the prepared wine. Thus should it
be desired to heighten the alcoholic contents from 7.5 to 10 per cent., to every 1000 kilos.
of must are added 50 kilos. of sugar.
The cause generally of the poorness of the must in sugar is a wet or cloudy season, during
which there has been but little warmth from the sun to ripen the grapes. Most German
wines show, besides a lack of sugar, a superabundance of acid, malic and tartaric acids;
and while the addition of a sugar solution increases the alcoholic contents, it does not
remove these acids, which impart a flavour to the wine and lessen its worth. The addition
of a saccharine solution does not, as might be expected, enfeeble the bouquet of the wine,
if pure starch sugar, containing no dextrine, be employed. The use of impure starch sugar
causes a quantity of unfermented matter to remain in the wine, imparting to it a tendency
to decay. Gall's method is found to be economical, as a flavouring material can be added
to very inferior must. According to Gall a normal must should consist of---
Sugar
Free acid
Water
•
24'0 per cent.
0.6
•
99
75'4
""
ΙΟΟ Ο
""
1000 kilos. of such a must contain, therefore 240 kilos. of sugar, 6 kilos. of free acid, and
75.4 litres of water. If, by analysis, the must to be improved yields only 16·7 per cent.
sugar and 0.8 per cent. acid, there are to be added-
153 kilos. of sugar, and
180
""
or litres of water,
by which addition 1333 kilos. of normal must are obtained, corresponding to an increase
in quantity of 33 per cent; while in some years, when the acid contents are as much as
12 to 14 per cent., the increase in quantity rises to 100 to 115 per cent., but seldom more.
Petiot based his method on the fact that, according to the usual process of preparing
the must, the colouring and bouquet constituents remaining in the maic are sufficient to
give the flavour and odour of wine to a lixivium of sugar-water. This method may,
therefore, very justly be considered as yielding a wine without the aid of grape-juice. To
the marc left after the expressure of the grape-juice cold water is added, equal in quan-
tity to the must removed: in this water the marc is allowed to macerate for 2 to 3 days.
The water takes up the various soluble constituents of the marc; after the time speci-
fied the liquor is removed, and the amount of sugar and acid it contains ascertained.
There is usually only 2 to 3 per cent. of sugar, consequently an addition of 17 to 18 per
cent. must be made; and if there should be too little acid, tartaric acid must be added to
approximate the acid contents of a normal must. The artificial must. as it may be con-
sidered, is then put into the fermenting vat, while the marc is again treated in a similar
manner, a longer immersion being this time required. The resulting wines are darker
in colour than wines prepared from the natural must, in consequence of a larger propor-
tion of tannin. The flavouring of these wines is a matter of experience, and does not fall
under any chemical consideration.
Freezing is employed in the improvement of wine, for the purpose of reducing the
aqueous contents. According to the experiments of Vergnette-Lamotte and Boussin-
gault, the effect of cold upon wine is of a very complicated nature. By cooling the wine
at a temperature of 0.6° there first occurs the precipitation of those substances that are
insoluble at this temperature. These consist of cream of tartar; colouring matter, and
nitrogenous substances, and a fluid possessing the property of becoming solid at 6º.
When these substances are removed the wine becomes more ardent, richer in alcohol, aud
its peculiar merit is that it is not liable to after-fermentation, and can be kept in vats and
half-empty casks. The removal of the acid from wine is effected best by means of car-
bonate of lime (pulverised marble, chalk), sugar of lime, or neutral tartrate of potash.
An addition of carbonate of lime to the must, or to the wine, is not detrimental, in so far
that the wine retains none, or a very small quantity, of the lime-salt. Carbonate of lime
will not be of service in the case of so-called acid fermentation, as acetate of lime will
BEER.
403
then be formed, and the wine is no longer worthy the name. Liebig recommends the use
of neutral tartrate of potash for this purpose, as bitartrate of potash is formed, which
settles as an insoluble salt to the sides of the vessel or bottle. The use of this neutral-
ising agent has the merit, moreover, of not injuring the flavour and odour of the wine.
Sugar of lime can be employed in the case of win s not containing acetic acid. To pre-
pare the sugar of lime, slaked lime is diluted with ten times the quantity of water, to
form a thin cream. This cream is thinned with sufficient water to obtain a milk of lime,
in which sugar-candy is dissolved. The solution is left to stand, and the clear supernatant
liquor-a solution of sugar of lime-decanted to mix with the wine as required. When
the wine is treated with the sugar of lime solution, the lime forms with the acid of the
wine an insoluble salt, which is precipitated, while the sugar remains in the wine.
Another addition to wine, hardly bearing upon its improvement, but effected as a means
for its preservation during removal or exportation, is that known in France as the vinage,
a certain quantity of brandy being mixed with the prepared wine. When the wine is to be
exported from France, the law permits the addition of 5 litres of brandy to each hecto-
litre of wine, provided the alcoholic contents after the addition do not exceed 21 per cent.
But experiments have proved that the wine delivered to private consumers does not on the
average contain more than 10 to II per cent. of alcohol, while the wine delivered to retail
firms averages 16 to 17, and to wholesale firms 22 to 24 per cent. To prevent this fraudu-
lent proceeding, the operation of vinage is permitted only in the Departments of the
Pyrénées Orientales, Aude, Hérault, Garde Bouches du Rhone, and Var, immediately under
the inspection of the Commissioners appointed to this duty. In 1865, Scheele introduced
his method of improving wine by the addition of glycerine, the addition being made after the
first fermentation has subsided. The limits of the addition lie between 1 to 3 litres of
glycerine to I hectolitre of wine. But the expense will not permit of extended operations.
Beer.
BEER BREWING.
Beer is a well-known liquor obtained from germinated grain-chiefly barley
and wheat, sometimes from rice, maize, potatoes, and starch sugar-and hops, by
means of a yeast fermentation, but without distillation of any kind. It contains the
constituents of the grain employed, which constituents by decomposition form
dextrose, dextrine, and albuminous substances, alcohol, carbonic acid, small quan-
tities of succinic acid and glycerine, organic matter, with phosphates of the alkalies
and alkaline earths, besides the constituents of the hops.
In Bavaria, the Schenk, or pot beer, is brewed in the winter, and the Lager, or store
beer, in the summer. The winter beer is brewed during October to April, when the
highest range of the thermometer is 12° to 13°. A part of the beer by a short storing is
set aside for winter consumption, while the remainder is used during the summer months.
I volume of malt gives on an average 2.5 to 2.6 volumes of winter beer.
2.0 to 2.1
summer beer.
I
""
""
""
In some of the North German States, potato-sugar and syrup are much employed in brew-
ing, sometimes supplying a third part of the malt. But generally I cwt. of the malt gives—
300 quarts light heer.
200
180
""
""
double beer.
Bavarian or bock beer.
Materials of Beer Br、wing. The materials of beer brewing are:-1. Grain, or amylaceous
substances. 2. Hops. 3. A ferment. 4. Water.
The Grain.-The grain selected for this purpose is generally barley, as containing
the proportion of sugar and starch best adapted to form alcohol. Many substitutes
have been suggested, but with inferior success. In Bavaria, the large double barley
(Hordeum distichon), is preferred. According to Lermer, 100 parts of dried barley
contain:-
Starch
68.43
Protein subst inces
Dextrine
16.25
6.63
Fat..
3'08
Cellulose
7.10
Ash and other constituents
3°51
404
CHEMICAL TECHNOLOGY.
The ash of barley contains in 100 parts:-
Potash
Phosphoric acid
Silicic acid
Magnesia
Lime
17
30
33
7
3
with other constituents. Potatoes, rice, maize, glycerine, and potato- or starch-
sugar, are employed in some modern breweries.
Hops. The hop (Humulus lupulus), is a diacious plant of the natural order of
Urticaceae, the female flowers of which, or catkins, are used for flavouring beer.
The catkins, or strobils, are composed of a number of bracts or scales, which are
green, afterwards changing to a pale yellow. At the base of each flower is seated
the pistil containing the seed, while surrounding the pistil are a number of little
grains, embedded in a yellow powder, the farina, containing the active property of
the hop, essentially lupuline, the grains being termed lupulinic grain. This yellow
pulverulent substance contains an essential oil, tannic acid, and mineral con-
stituents. The essential oil, the flavouring principle of the hops, is found in air-
dried hops, to the amount of o.8 per cent.; it is yellow-coloured, with an acrid taste,
without narcotic effect, of a sp. gr. =0‘908, turning litmus paper red. It requires
more than 600 times its weight of water to effect a solution. It is free from sulphur,
and belongs to the group of essential oils characterised by the formula, CH8, and
can become oxidised under contact with the air into valerianic acid (C5H10O2), this
oxidation being the cause of the peculiar cheesy odour of old hops; it is a mixture
of a hydrocarbon, CH8, isomeric with the oils of turpentine and rosemary, with
an oil containing oxygen, C10H180, having the property of oxidation alluded to
Tannic acid is found in the several kinds of hops, in quantities varying from 2 to 5
per cent., and is an important constituent, as it precipitates the albuminous matter of
the barley, and serves to clear the liquor. It gives with the per-salts of iron a green
precipitate; treated with acids and synaptase, does not separate into gallic acid and
sugar; and by dry distillation does not give any pyrogallic acid. The hop resin is
the important constituent of the hops, and contains the bitter principle or lupuline.
It is difficultly soluble in water, especially in pure water, and when the lupuline or
essential oil is absent. But water containing tannic acid, gums, and sugar
dissolves a considerable quantity of the resin, especially when the essential oil is
present. It is intensely bitter in taste, and becomes foliated when exposed to the
atmosphere. Hop resin and the essential oil are not identical; the former is soluble
in ether, the latter is not. In the course of long exposure it becomes insoluble. The
The mineral constituents of
gum and extractive colouring matter are of little use.
hops dried at 100º are :—in ash, 9 to 10 per cent.; 15 per cent. of phosphoric acid;
17 per cent. potash, &c.
IO
Quality of the Hops. The quality of the beer is almost proportionate to the quality of
the hops. A rich soil is required for the growth of the hop-plant, well exposed to
the influence of the sun's rays, and protected from easterly winds, which are highly
detrimental. The hops must on no account be gathered until the seed is perfectly
ripe, as it is only then that the bitter quality is fully developed. The ripeness of
the hops can be ascertained by rubbing them between the fingers; if an oily matter
remains, with a strong odour, they are fit for gathering. When gathered, the next
most important operation is the drying, which is effected in kilns or stoves, at a
BEER.
405
temperature of 40°, with a good ventilation. When sufficiently dried, the small stem
attached to the flower snaps readily. The temperature must be carefully regulated;
not permitted to range so high as to run the risk of burning the hops, nor allowed to
fall so low that the hops may afterwards become mouldy from under-drying. When
dried the hops are carefully packed, the finer kinds being put into cauvas pockets,
and the inferior into hop-bags of a coarser texture. The bags are then subjected to
slight pressure in a hydraulic or screw press, to render them more impervious to air.
· To preserve the hops they are sometimes sulphured, that is, subjected to the action
of vapours of burning sulphur, 1 to 2 lbs. of sulphur being employed to 1 cwt. of
hops. Old hops are sometimes treated in this manner, to impart the colour and
appearance of freshly-dried hops, but the fraud can be detected by the odour. The
best method of testing for sulphur in hops is as follows:-A sample of the hops is
placed in a sulphuretted hydrogen apparatus, with some zinc and hydrochloric acid;
the disengaged gas is passed through a solution of acetate of lead. If the hops
contain sulphurous acid, sulphuretted hydrogen will be disengaged-
(SO2+ 2H2=SH₂+ 2H₂O),
I
and black sulphide of lead thrown down from the lead solution. Better still is to
receive the disengaged gas in a solution of nitroprusside of sodium, to which a few
drops of potash-ley have been added; the slightest trace of sulphuretted hydrogen
imparts a beautiful purple-red colour to the solution.
Substitutes for Hops. Other substances have been used as substitutes for hops, as the bark of
some species of the pine, quassia, walnut leaf, wormwood, bitter clover, extract of aloes,
&c.; recently picric acid has been employed. Although all these substances impart a bitter
taste to beer, they are inferior to hops. They contain the same constituents, namely,
tannic acid, a resin, a bitter extractive, and an essential oil.
Wa er. Water is employed for steeping the barley for the purpese of inducing ger-
mination. Brewers are careful as to the usual distinction of hard and soft waters. Soft
water contains fewer mineral constituents. Rain, like distilled water, is a very soft water,
containing traces only of organic matter, nitrates and carbonate of ammonia. Spring and
well water are in most cases hard waters, while river water is often soft. Soft water, or
nearly so, is best adapted for brewing. River water is preferred for malting. According
to Mulder, in water containing lime an insoluble phosphate is deposited, while in the
course of time lactic acid is formed. The water employed is usually purified by filtra-
tion through sand, gravel, and charcoal.
The Ferment. The yeast of former operations is generally employed in fermenting the
beer-worts. The preparation of the yeast, and the rationale of the process of fermenta-
tion, given in a previous section of this work, should be consulted.
The Processes of The brewing of beer may be considered to consist of the following
Beer Brewing.
operations:-
1. The malting.
2. The raashing.
3. The fermentation of the beer-worts.
4. The fining, ripening, and preservation of the beer.
The Malting. 1. Malting is the process during which the grain-barley-is germi-
nated, by means of steeping in water until it swells and becomes soft. The non-
germinated grain possesses only in a very small degree the property of changing its
starch into sugar (dextrose): this property is very fully developed during the germi-
nation, so much so that it would be an easy matter to distinguish between the
germinated and non-germinated seed by the degree of this property alone. As has
been already stated, barley is the grain preferred, on account of its forming sugar in
larger quantities than any other kind of grain. The germination of the seed takes
place in three well-marked periods. In the first, the seed is enveloped in an outer
406
CHEMICAL TECHNOLOGY.
organ, which becomes exhausted and withered. In the second, the growth of the
germ is shown by the swelling at the end by which it was attached to the stalk; and
in the third period, the little plumule or acrospire, which would form the stem of the
new plant, is put forth. The germinating seed is similar to an egg, with its white,
yolk, and embyro; the shell corresponds with the outer or hard coating of the seed ;
the white and yoke of the egg appear as the albumen, or meal of the grain; while
the embyro of the egg has its analogue in the germ of the grain. A remarkable
change takes place during germination; the glutinous constituent has passed from
the body of the grain to the radicula, or rootlet, which has grown to nearly the length
of the grain, while about one-half of the starch has been converted into sugar.
This conversion is the aim of the malting, as by its means the sugar can be readily
dissolved. The grain is supposed to have been sufficiently treated when the plumula,
or acrospire, has attained a length equal to two-thirds of the entire length of the
grain. The operation of germination is the same with all kinds of grain employed
in brewing. The conditions of success are the saturation of the grain with mois-
ture, and a temperature of not higher than 40° nor lower than 4º, with access of air
and exclusion of light.
a. The softening or soaking of the grain is accomplished in large cisterns of wood,
sandstone, or cement, half-filled with water. The grain is poured into the water,
and after the lapse of an hour or so, sinks to the bottom of the tank, only the infe-
rior and diseased seed remaining on the surface, to be removed with wooden shovels,
and thrown aside for use as fodder for horses, cattle, &c. The steep water receives
the soluble constituents of the husk of the seed, and becomes of a brown colour and
peculiar flavour, with a decided inclination to lactic, butyric, and succinic acid fer-
mentation. The duration of the softening varies according to the age of the grain,
the temperature of the water, &c. A young fresh grain requires 48 to 72 hours'
soaking, while an older grain, containing more gluten, is not thoroughly softened
under 6 to 7 days. Grains of equal age and constitution must be soaked together, to
obtain an equally softened product. After sufficient soaking the grain is allowed to
drain for 8 to 10 hours, then taken out and thrown into heaps on the floor of the malt-
house. The sufficiency of the soaking is ascertained-1. By pressing the grain
between the finger and thumb-nail, when, if sufficiently moistened, the germ or
embyro will be projected. 2. The husk is easily destroyed by pressure between the
fingers. 3. When crushed with a piece of wood the grain yields a floury mass.
The grain when softened has a peculiar aroma, resembling that of apples. The
quantity of water usually absorbed by the barley amounts to 40 to 50 per cent. of its
weight, while the grain correspondingly increases in volume 18 to 24 per cent.
During this absorption the grain loses 1'04 to 2 per cent. of its own weight in solid
matter. Lermer states, that in fresh steep water he has found succinic acid in the
proportion of 30 grms. to 1 bushel of grain soaked.
I
b. The Germination of the Softened Grain.—As soon as the grain is thoroughly
saturated with moisture, the conversion of the starch into sugar commences. When
germination has proceeded far enough it must be stopped, as about this time the
formation of sugar has reached a maximum. The softened barley is, as before
stated, transferred to the floor of the malting-room, where it is "couched," or placed
in a layer 4 to 5 inches in thickness. Here the germination proceeds till the plumules
have attained the desired length. The temperature rises some 6° to 10°, on account of
the heat developed during germination, and consequently much of the moisture is
BEER.
407
dissipated. The chief art of the maltster consists in stopping the germination at
that point when the plumules and roots commence to draw upon the constituents of
the grain. The duration of the germination varies, during the warmer months of
the year, from 7 to 10 days, while towards autumn the process will not be completed
under 10 to 16 days, but the average duration is 8 days. The grain during the ger-
mination loses about 2 per cent. of its weight, probably by the oxidation of the
carbon to carbonic acid by the oxygen of the air.
c. The Drying of the Germinated Grain.-The grain is now removed to the drying
floor (welkboden), where it is exposed to the air in layers 3 to 5 centims. in depth, and
turned about with rakes 6 to 7 times daily. When the malt becomes dry it is
cleared from the rootlets, some of which drop off by themselves, while others have
to be removed by winnowing. Malt must be dried for the making of most kinds of
beer, and has to undergo a roasting process before quite fitted for use.
This drying
or roasting is effected in a malt kiln or cylinder heated by flues to the boiling-point
of water. During the roasting the malt acquires a darker colour, due to the con-
version of the remainder of the starch into sugar. The equality of the temperature
is of the utmost importance, so that one part of the malt may not be more strongly
heated than another. Before the malt is submitted to this operation, however, it is
first heated to 30° or 40°. By this means some of the starch is converted into gluten,
and forms a coating to the grain impervious to water, the malt being in this stage
known as "bright
bright" malt from its smooth glossy appearance.
The malt kilns consist essentially of the drying plates upon which the malt is
laid, and the heating flues. The plates used to be of stone or sheet-iron, but
modern brewers employ wire-wove frames, placed one above the other, so that the
hot air from the flues beneath may ascend through the interstices. The flues are
generally of sheet-iron for the better conduction of heat to the surrounding
atmosphere. Coke is used as fuel on account of the absence of smoke; as with coal
or wood in the event of a leakage in the flues considerable damage would be done
to the malt.
The malt is not all dried at the same degree (50° to 100° C.), but is distinguished
as pale, amber, brown, or black malt, according to the degree of heat to which it has
been exposed. Pale malt results from heating to 33° to 38°; amber, from a tempera-
ture of 49° to 52°; and brown from the rather high temperature of 65.5° to 76′5°.
Black malt, commonly called patent malt, is prepared by roasting in cylinders, like
coffee cylinders, at a temperature of 163° to 220°. These darker malts are used in
England for colouring porters and stouts.
100 parts of barley give 92 parts of air-dried malt. The loss of 8 parts may be
thus accounted for :-
In the steep-water
During malting ..
During germination
Other losses
Total loss
:
I'5
3'0
3°0
0'5
8.c
The moisture in air-dried malt amounts to 12 to 15.2 per cent., which is expelled
during the kiln drying. According to C. John (1869) 100 parts of dried barley
give-
408
CHEMICAL TECHNOLOGY.
I.
II.
Malt
83'09
85.88
Plumules
3.56
3'09
Radicules (rootlets)
4'99
4.65
Fermentary products
8.36
6.38
100'00
100'00
The change undergone during the drying or roasting of the malt is shown in the
following table, the result of Oudeman's analyses :—
Air-dried Malt. Kiln-dried Malt. Strongly dried Malt.
Products of roasting
Ο Ο
7.8
14'0
Dextrine..
8.0
6.6
10'2
Starch
58.1
58.6
47.6
Sugar
0'5
0'7
0'9
Cellulose..
14'4
10.8
115
Albuminous matter
13'6
10'4
10'5
Fat..
2.2
2.4
2'6
Ash
3°2
2.7
2.7
The amount of sugar is undoubtedly increased during the process; and the
dextrine appears to increase with decrease of starch, and vice versa. The conversion
of starch into dextrine and sugar is effected, as far as is known, by the agency of
diastase. Dubrunfaut has only lately (1868) shown that malt presents another
substance similar in its effect to diastase, and which he termed maltin. This principle
is found to be much more active than diastase, so that with the same quantity
of maltin which a known quantity of malt contains, ten times as much beer can be
obtained as when diastase only is employed. Dubrunfaut has also found a second
but less active substance. Its behaviour with respect to the decomposition of starch
is similar to that of diastase; malt contains 1 per cent., while only 1 per cent. of
maltin is found. The treatment with alcohol necessary to obtain diastase destroys
tho maltin. Dubrunfaut believes diastase to be only a less active modification of
these new substances.
Preparation of the
Wort.
2. Under this head is included the preparation from malt of the
wort—a saccharine fluid containing dextrine- and the flavouring with hops. The
general method of preparation is in three operations:--
Malt.
a. The bruising of the malt.
b. The mashing.
c. The boiling and flavouring of the wort with hops.
The Bruising of the a. Beer-wort, or the wort, as it is generally termed, is obtained
by means of the extraction of the bruised malt with water. To the end that all the
active principles may be extracted from the malt, it must be bruised or ground to a
fine meal. The obtaining of a clear liquor after the extraction is effected by
means of filtration. The grinding is ordinarily performed in a malt mill, a machine
with rollers being preferred as affording a more equable product.
Mashing. b. The mashing is a most important operation, on success in which
depends many of the good qualities of the beer. It
It is during this operation that
not only the sugar and dextrine already existing in the malt are set free, but
also the unconverted starch, by the aid of diastase, the water, and a favourable
BEER.
409
temperature, suffer conversion into sugar and dextrine. Lermer found in the best
cases of mashing that only half the starch was converted into a corresponding
quantity of sugar. The operation is very variously performed, but generally may be
considered as effected by either of two methods:-
a. The Infusion Method, according to which the mash is prepared at a certain degree
of heat, but never attains the boiling-point. The crushed malt is thrown into hot
water (first cast) in the mash tun, and when the mash has reached a certain
saccharine condition, a further addition of water is made (second and third cast).
The infusion method is much employed in North Germany, France, England,
Austria, and Bavaria.
b. The Decoction Method:-After the infusion has been made the mash is brought to the
boiling-point, and
a. A portion of the water evaporated to form a thick mass (thick mash
boiling). At a subsequent stage, only a portion of the mash having been
thus treated, the remainder of the mash is added, and
B. The whole of the mash is heated to the boiling-point (clear mash boiling).
During the clear mash boiling the hops are added.
The mashing vessels are either round tubs or wooden cisterns with a double
bottom, the upper being perforated, and about an inch above the true bottom. Between
the bottoms is a tap through which the wort is drawn off. In large breweries these
bottoms are of metal instead of wood. The hot water is supplied from the bottom
and not from the top of the vessel. Under the mashing vessel is situated a large
reservoir, either of stone, cement, wood, or masonry, and destined to receive the
fluid run off from the mash. The continuous stirring of the contents of the mash-
tun or tub is effected either by hand or machinery driven by water or steam power.
Decoction Method. The general description of the mashing process having been given,
we now pass on to the particular method of preparing the wort by decoction. The
infusion takes place in the mash-tun, in which the required quantity of water is
placed, and the malt to be mashed shaken in. The quantity of water employed in
making the infusion is generally in the proportion of 202 volumes of water to 100
volumes of malt, both at the ordinary temperature. After the bruised malt has
been well stirred in the water, the whole is allowed to stand for 6 to 8 hours.
During this time the necessary quantity of water is heated to the boiling-point in
the copper. The quantity of water used to prepare an estimated quantity of beer is
termed the "cast," and the quantity of malt the "yield." In Bavaria the quantity
of beer prepared from a defined quantity of malt is as follows:
{ 173'4
100 volumes of malt yield (2023 volumes of Schenk beer.
,, Lager beer.
In order to produce this quantity of beer an equivalent quantity of water must of
course be employed, so that in a Bavarian brewery to 100 volumes of malt there are
taken of water-
For infusion
For mashing
Schenk beer.
202.3 vols.
•
170'0
Lager beer.
202'3 vols.
130'0
""
372.3 vols.
332*3 vols.
These proportions vary according to the quality of the grain, the state of the
weather, the length of time of keeping, &c.
The various modifications of the decoction method are:--1. The Bavarian or Munich
method. 2. The Augsberg-Nuremberg, or Swabian method, sometimes termed " sediment
brewing" (satz brauen).
Thick Mash Boiling. According to the Munich method (thick mash boiling) the cast of water
is divided into three portions, two of which are poured into the mash-tun to form a
410
CHEMICAL TECHNOLOGY.
paste with the bruised malt. After this mash has stood for two to four hours, the re-
maining third of the water, which during this time has been heated to the boiling-point in
the copper, is added, the whole of the mash attaining thereby a temperature of 30° to 40°.
Then follows the first thick mash boiling; for this purpose the brewer draws the mashed
grain to one side of the tun, and removes a portion to the copper, where for _schenk beer
it is boiled for thirty minutes, and for summer beer for seventy-five minutes. The quantity
of mash boiled at each operation is generally about half the cast. The boiling mass is
returned to the mash tun. Then follows the second thick mash boiling, which for schenck
beer last seventy-five minutes, and for summer beer an hour. By means of the first
boiled mash the contents of the mash tun are raised to a temperature of 48° to 50°, and
by the second addition to 60° to 62°. After the finishing of the second mashing the clear
mashing begins, that is, the thinly fluid part of the mash is placed in the copper and boiled for
about fifteen minutes, and is then returned to the mash tun. The temperature of the mash
is now 72° to 75°, and is most suited for the formation of sugar. The mash remains in
the covered tun 1 to 2 hours. During this time, and as soon as the clear mash has been
removed from the copper, the latter is re-filled with a sufficient quantity of water for the
purposes of brewing small beer. When the sugar has been properly formed and dis-
solved in the wort the latter is removed from the mash tun to the fermenting vessels. The
remaining mash is then treated with hot water to yield small beer, I bushel of malt yielding
35 to 50 quarts of this beer. The residue of the small beer is again treated with water,
the resulting infusion being employed in vinegar-making. The residue from this process
is used as fodder for cattle.
The thick mash boiling is by no means a rational method, as the separation of the mash
and the several removals are unnecessary labour, and do not contribute so much to the
complete extraction of the malt as is generally supposed; the high temperature renders
a portion of the diastase ineffective, while much of the starch remains unconverted into
dextrine and dextrose.
All who have tried to reduce the brewing process to simple methods based upon sound
chemical and physical principles declaim against the process of thick mash boiling,
stating-and with good sound reason proved by experiments-that the advantages of
this method are absurdly overrated; and that in order to lessen the bad effects of this
method as much as possible it should be replaced by a method of hot mashing, viz.,
at a temperature of from 60° to 65°.
Augsburg Method. Distinct from the foregoing mash methods is the so-called "sediment
brewing" used in many Swabian and Franconian breweries. It essentially consists in
treating the bruised malt with cold, and then with hot water to obtain a saccharine
wort. The bruised malt is mixed with cold water in the mash tun in the proportion of
7 Bavarian bushels to 30 to 35 eimers (each 68 41 litres of water. After standing for
four hours, two-thirds of the fluid is drawn off. During this time a quantity of water
(48 eimers to 7 bushels of bruised malt) is brought to the boiling-point in the copper; a
portion of this water is now added to the contents of the mash tun, which thus attains a
temperature of 50° to 52°, while the liquor or weak wort drawn off from the mash
tun is poured along with the rest of the water in the copper. The liquor that has
been drawn off contains albumen, diastase, dextrine, and dextrose. The mash is allowed
to stand for a quarter of an hour in the tun, when the fluid is entirely drawn off,
transferred to the copper, and hated to the boiling-point. This is termed the "first
mash." While this is going on enough fluid will have drained from the malt in the mash
tun to fill the space between the double bottoms of the tun; this fluid is at once removed
to the cooling vessels. The fluid heated in the copper is now returned to the mash tun,
the entire contents of which attain a temperature of 72° to 75°. This "second mash" is
after an hour's interval followed by a third mash." The wort is then run into the
cooling vessels.
Infusion Method. The infusion method is distinguished from the decoction method by
a slight difference in the procedure, the bruised malt being treated with water at a
temperature of 70° to 75°, but without any portion of the mash being boiled. The
method is that usually employed in this country, North America, France, Belgium,
and North Germany.
The quantity of water intended to be used for the mashing process is, according
to the initial temperature of the water the brewer has at hand, heated either wholly
or only a portion in the copper, the temperature of this fluid being raised in winter
to 75°, in summer to from 50° to 60°. The necessary quantity is first poured into the
mash tun, the bruised malt being next added, and the mixture made up so as to
BEER.
411
form a moderately thin paste. Water is heated to the boiling-point in the copper in
order to proceed further with the mashing process. As soon as a sufficient quantity
of water boils it is usually by means of properly constructed pipes-allowed to
run into the mash tun, wherein it is considerably cooled owing to the colder water
(liquor) present in that vessel; the increase of temperature of the contents of
the tun to 75° (the most suitable for saccharification) is generally made in order to
prevent the formation of starch paste, whereby the formation of diastase would be
interfered with. Since the conversion of amylum (starch) into dextrine and dextrose
proceeds gradually only, it is clear that the contents of the mash tun should be kept
at the temperature suitable for that process; while, however, on the other hand, care
has to be taken to prevent the mash becoming sour by the formation of lactic
(probably also propionic) acid.
The progress of the formation of dextrine and dextrose is best ascertained by the
help of an aqueous solution of iodine, or preferably of iodine dissolved in iodide of
potassium, in the proportion of o‘1 grm. of iodine and 1'o of iodide of potassium to
100 c.c. of water; this solution will at first. give with a sample of the mash a dark
blue colouration, next a wine red, and finally, when only dextrine and dextrose are
present, no colouration at all. The addition of two to three drops of the clear
wort to a small quantity of this iodine solution is sufficient for testing. When
the mash has been kept for about one hour's time at the temperature most suitable
for the saccharification, the wort is run either into a large reservoir, or into a
vessel kept expressly for this purpose, or lastly, at once into the copper; and a
fresh quantity of water is then poured into the tun, and the contents of the tun
are allowed to remain for half to one hour at a temperature of 75°. It is as a
matter of course quite evident that the infusion method may be varied as regards
the quantity of water and repeated number of infusions; but in order to brew
a beer of a certain and fixed brand it is requisite that the degree of concentration
of the wort be always the same. For the purpose of ascertaining the degree of
concentration, Balling's saccharometer is generally employed, which instrument when
put into sugar solutions indicates the percentage of sugar they contain. Balling
has shown that solutions of dry extract of malt have the same specific weight as
cane sugar solutions of equal percentage. For use in a brewery the saccharometer
need only be graduated for solutions varying between 20 to 30 per cent.
Extractivcs of the Wort. The quantity of extract which a wort should contain depends,
of course, upon the quality of the beer which the brewer desires to make, and differs
according to the nature of the beer, whether it shall be thick, heavy (rich in
extract), or strong (of great alcoholic strength). The quantity of malt extract varies
in different beers from 4 to 15 per cent., that of the alcohol from 2 to 8 per cent.
I per cent. of sugar in the wort yields after fermentation o 5 per cent. of alcohol. To
produce a beer containing 5 per cent. of alcohol and 7 per cent. of malt extract, the
wort should, before fermentation, mark the degree on the saccharometer corre-
sponding to 17 per cent. A beer of 3.5 per cent. of alcohol and 5'5 per cent. of malt
extract will have resulted from a wort containing 12.5 per cent. of sugar.
Boiling the Wort. c. The prepared but not yet boiled wort contains dextrose, dextrine,
some unconverted starch, protein substances, extractive matter, and organic salts.
The colour of the wort is a brown or yellow-brown, according to the variation of
colour of the malt from which it has been obtained. The odour is agreeable and the
taste sweet. The wort exhibits an acid reaction to test-paper, owing to the presc nce
412
CHEMICAL TECHNOLOGY.
in that fluid of small quantities of free phosphoric, lactic, and probably other acids;
but in case the wort has by accident become sour, or if wort is made purposely
from already exhausted grain which has become sour, this reaction is far stronger,
and may be ascertained by the odour, owing to the formation of volatile acids,
among which butyric, and in the latter case, lactic and propionic acids are present
in large quantity. The boiling of the wort aims at its concentration, and also
at the extraction of the bitter principle of the hops; further also for the purpose
of coagulating and precipitating a portion of the albuminous substances, by the aid
of the tannic acid contained in the hops. This latter reaction renders the wort
clear. In many breweries gypsum is added to the boiling wort to reduce the whole
of the nitrogenous substances. The boiling is generally effected in copper cauldrons
(technically, also simply, "the copper”), set in masonry over a fire-grate. The fire
is very carefully disposed to prevent the burning of the wort, as the pans are
exposed to the direct action of the flame. The manner of hopping (as it is termed),
that is to say, the mode of adding the hops to thewort, varies in different breweries,
and depends as regards quantity also upon the quality (strength) of the hops, the
larger or smaller amount of extract contained or desired to be retained in the beer,
and last, but not least, the mode of preservation and length of time it is intended to
keep the beer.
Adding the Hops. To winter beer, which in Germany, as a rule, is consumed in four to
six weeks after brewing, the old hops (viz. one year old), are added in the proportion
of 2 to 3 pounds to a Bavarian bushel of malt (2·22 hectolitres). For summer beer, to
be consumed in May and June, 4 to 5 lbs. of new hops are added to the bushel of
dried malt; while for the beer for September and October consumption, 6 to 7 pounds
of new hops are employed with each bushel of malt. Among the constituents of
hops which are active in the process of brewing, we mention in the first place the
bitter ingredient it contains (not correctly known, notwithstanding recent research)
and which as well imparts to beer its bitter taste as its narcotic property; further, the
tannic acid which combines during the boiling of the wort with a portion of such
of its protein compounds as are not rendered insoluble by the boiling alone, and
form together a precipitate, rendering the wort-previously turbid-quite clear,
and also regulating the first and second (so called after) fermentation. The essential
oil and resin met with in hops act to a certain extent as retarding the fermentation,
and thus as preventatives of converting the wort into a sour liquid; as regards the
inorganic constituents of hops they do not appear—at least cannot be directly
proved to be of much consequence. As regards the degree of concentration to
be given to the wort by the process of boiling, it should be observed that the degree
of concentration as ascertainable by the saccharometer should remain from 0·5 to 1
saccharometrical percentage under the degree of concentration which the wort
should indicate at the beginning of the fermentation, because while cooling, the
wort gains in concentration just the percentage alluded to. The separation of the
coagulated albumen does not take place until the temperature of the wort has
reached 90°; and the quantity separated is greater from wort prepared by the
infusion method than from that prepared by the decoction method. As soon as it
appears that in a sample of the boiling wort taken from the pan and poured into a
large test-glass the suspended flocculent matter settles rapidly to the bottom of
the glass, the boiling can be discontinued, the wort being then ready; but in the
case of the infusion method, the boiling is continued for the purpose of further
BEER.
413
concentrating the liquor, and the boiling for this purpose may even last for from
5 to 8 hours. If the boiling only aims at the coagulation of the albuminous
compounds, one hour's boiling in winter, and three-quarters of an hour in summer,
is quite sufficient. As regards the hops, it is best to add them in a somewhat cut
up state, and not before, by a good boiling of the wort, the greater part of the albu-
minous compounds have been, as far as possible, precipitated. In order to extract the
hops, the wort is either passed through a basket filled with hops or through any
suitably constructed perforated vessel retaining the hops, this vessel being placed in
communication with the coolers; or the hops are boiled along with the wort; or
again, several portions of the wort are boiled successively along with the same quantity
of wort; and lastly, even with the weakest wort or after-run.
Cooling the Wort. The cooling of the wort to the degree necessary for the commence-
ment of the fermentation is effected in large wooden, stone, or iron cisterns. As
at a temperature of 25° to 30° C. the wort has a great tendency to set up lactic acid
fermentation, the cooling has to be very rapid in order that the temperature of the
liquid may be soon much below 25° to 30°, and thus any danger of souring
prevented.
The cooling of the wort is an operation which is performed in well constructed
and in all directions well ventilated buildings, protected from rain, in which
buildings the coolers are placed. Owing to improvements in the modes of cooling,
it is now possible even to brew beer in localities (as for instance Montpellier and
Marseilles, Barcelona, and Naples) where formerly, on account of the prevailing
high temperature during the greater portion of the year, brewing could not take
place at all; while also for the same reason in various countries (America,
United States especially), excellent lager beer is brewed. The cooling vessels
are generally only 6 to 8 inches deep, of wood, iron, or copper, and are placed in
an airy situation near or immediately under the roof of the brewery. Metallic
vessels are of course more effectual in cooling the wort in a short time than wooden
ones; they are also more cleanly, and less liable to get out of order. In some
breweries, where a constant stream of cold water is available, the coolers are placed
therein; but this is of course a matter entirely depending on the locality of the
brewery. Without doubt the surest means of cooling the wort rapidly is by
employing ice, either in blocks in the wort or in pans placed in the cooling tuns.
But for economic reasons this plan is not generally available. The temperature
to which the wort is to be cooled is that best suited to fermentation, the next process
to which the wort is subjected. The following are the temperatures at which fer-
mentation most readily sets in, depending upon the temperature of the locality and
upon the kind of fermentation:-
Temperature of the locality
where the fermentation
takes place.
6° to 70
70 to 80
8⁰ to 9º
9° to 10º
Temperature of the wort.
In sedimentary
fermentation.
120
110
100
9⁰
7° to 80
In superficial
fermentation.
15°
14º
13c
120
10° to 12º
12° to 11°
The concentration of the boiled and hopped wort is expressed in degrees per cent.
of the saccharometer.
414
CHEMICAL TECHNOLOGY.
According to J. Gschwändler's researches (1868), the undermentioned Bavarian
beer worts had the following composition:
Sugar
Dextrine
:
Nitrogenous substances
Other constituents
Specific weight
Extract (direct estimation)..
Decoction. Bock.
Method.
Sedimentary Infusion.
4.850
7.100
4'370
5'260
•
6'240
8.600
7.610
6.680
•
0'790
I'350
0'410
0·630
0'950
0'700
I'050
I'073
1'052
I'051
11.870
17'050
11.980
II'940
12.290
17.680
12'930
12'640
"
(according to Balling)
While the wort remains in the cooler a yellow-grey or brown sediment is
deposited, consisting of a compound of coagulated albumen with the tannic acid of
the hops, and some starch similarly combined. This sediment during the first
cooling is formed in quantities varying between 3 to 4 per cent. of the quantity of
the cooled wort; the sediment when washed and dried amounts to o'5 per cent. of
the quantity of malt employed.
The Fermentation. III. The Fermentation of the Beer Wort.-The wort when cool is run
into the fermenting tanks, where fermentation sets in either spontaneously, or is
induced by the addition of yeast. The first kind-spontaneous fermentation-sets in
as soon as the wort, having been cooled down to the temperature most suitable for
fermentation, is left to itself, and this fermentation is induced by the sporules of
yeast (ferment cells) always present in all fermenting localities, which meeting with
the wort, find in that liquid the proper conditions suited for their growth. This kind
of spontaneous fermentation is applied usefully in the brewing of the Belgian beers
known as Faro and Lambick, which are rich in lactic acid. Usually, however,
yeast is added to the wort, and there is avoided the dangerous first stage of
spontaneous fermentation, for by the addition of the yeast a regular and rapid
fermentation is set up, but yet so regulated that the yeast only gradually converts
the dextrose into alcohol and carbonic acid.
*
The higher the temperature of the wort and of the locality the smaller the quantity
of yeast required. A yeast formed by a violent fermentation and at a high tempera-
ture, has more active qualities than yeast formed at a lower temperature and by a
longer fermentation. The first spreads itself rapidly over the surface of the fluid,
and is termed superficial yeast (oberhefe): while the second sinks to the bottom of the
vessel, and there continues its action; this is termed―sedimentary, or bottom yeast
(unterhefe). The fermentations resulting from these two yeasts are respectively
termed superficial fermentation (obergährung), and sedimentary fermentation (unter-
gährung). The latter fermentation is induced in worts that are intended to yield
beers of great durability, such as the Bavarian beers. The superficial fermentation
is induced in such beers as are intended to be soon drunk. Where fermentation
is induced in a wort at a low temperature and with deposit only (bottom-yeast) the
so-called surface fermentation- that is to say, a vinous fermentation whereby yeast
* The results of the researches made by Von Lermer and Liebig (1870), are of great
importance for a rational basis of the brewer's business. According to these savants, an
addition of sugar to a solution of dextrine, to which previously beer-yeast has been added,
causes a large quantity of the dextrine to be converted into alcohol and carbonic acid, just
as if the dextrine were sugar.
BEER.
415
is carried to the surface of the fermenting fluid-is employed chiefly for such
kinds of worts as are intended to produce a beer which is not required to be
kept for any length of time, but rapidly consumed after having been brewed. The
wort is in this instance generally rich in sugar (glucose); and while only a portion
of this sugar is converted into alcohol (sweet beer being formed), the formation
of a small quantity of alcohol (the wort being only lightly hopped), contributes
largely to the preservation of this kind of beer. Surface fermentation is also
induced in such kinds of worts as are either very concentrated or contain sub-
stances which to some extent retard, or might even altogether impede, ferimentation;
as, for instance, the empyreumatic substances present in a very highly roasted malt
or a large quantity of hops, these conditions obtaining in the brewing of porter,
stout, and, as regards hops, the bitter ale. Worts of this description come com-
paratively very difficultly into .fermentation. Fermentation, no matter whether
surface or sedimentary (the yeast is in this case slowly deposited as a sediment on
the bottom of the vessel), exhibits the three following phases, viz. :—
1. The chief fermentation, beginning soon after the addition of the yeast,
characterised by the decomposition of glucose, by the formation of new yeast, and
by an increase of temperature.
2. The after-fermentation, during which decomposition of glucose continues
slowly, while the formation of new yeast cells does not ensue so energetically as
in the first phase, the suspended particles of yeast settling down, and the beer
becoming clear.
3. The quiet or imperceptible fermentation taking place when the after-fermenta-
tion is finished is characterised by a further decomposition of glucose, while the
formation of yeast is not perceptible to any extent.
Sedimentary Fermentation. Sedimentary fermentation is employed in the brewing of the
Bavarian schenk and lager beers, taking place in large fermentation vats con-
taining 1000 to 2000 litres of wort. Recently, upon the suggestion of G. Sedlmayer,
these vessels have been constructed of glass. The addition of yeast may be effected
in two different ways: yeast may be either added to the wort, or a small portion of
the wort is first separately brought into a state of fermentation, and next added to
the bulk of the liquid. In the first case, dry yeasting, as it is termed, the yeast is
placed in a small tub and wort poured over it, and these substances having been well
mixed, the whole of the contents of the vessel are thrown into the fermentation vats,
and there worked about by the aid of a stirring pole. According to the second
method, wet yeasting or yeast carrying, to 1000 maas* of wort, 6 to 8 maas of yeast
are added and well mixed with about 3 eimers of wort, the mixture being allowed
to stand for four to five hours. After fermentation has set in, the fermenting liquid
is mixed with the wort in the fermentation tank. The yeast intended to be used
for this purpose should be obtained from a former and normal fermentation; it should
not be too old, and should possess a pure odour (not be foul), thick consistency, and
be frothy.
After the wort has been mixed with the yeast the following phenomena are exhibited :-
After ten to twelve hours the decomposition of the dextrose becomes apparent by the
evolution of bubbles of carbonic acid gas, which forms a wreath of white froth at the
edge of the vessel. In another twelve hours larger quantities of a more consistent froth
are formed, causing the surface of the liquid to exhibit a very peculiar appearance, which
* The Bavarian maas is equivalent to 125 English quarts.
416
CHEMICAL TECHNOLOGY
might be compared to that of irregular masses of broken up rocks; at the same time a
more vivid evolution of carbonic acid takes place and becomes perceptible by the smell.
The German term for this phase of the fermentation, Das Bier Steht im Krüusen, can
hardly be expressed in English, but the meaning is the fermentation is in full force; these
phenomena to continue with a regularly proceeding fermentation in full activity for from
two to four days, and then gradually subside, there remaining on the surface of the liquid
a somewhat brown-coloured film of froth, much contracted, and chiefly consisting of the
resinous and oily constituents of hops.
in the Casks.
The yeast formed is only to a very small extent present on the surface of the liquid,
as in the case of sedimentary fermentation the carbonic acid evolved cannot carry the
isolated yeast cells to the surface. The temperature of the fermenting liquid increases
at the beginning of the fermentation, so that the liquid becomes several degrees
warmer than the air of the locality where the fermenting vats are placed. By the
fermentation the wort loses the greater portion of its dextrose, about half of which is
evolved in the shape of carbonic acid, while the remainder is converted into alcohol;
further, a portion of the albuminous substances dissolved in the wort is rendered
insoluble and deposited in the shape of yeast. On being tested with the saccharometer
the liquid-for reasons just explained-exhibits after fermentation a less degree of
strength than before. The difference in percentage shown by the saccharometer before
and after fermentation is in direct proportion to the quantity of dextrose decomposed,
and provides a means of ascertaining the course of the progress of the fermentation.
If this difference be made the numerator of a fraction, the denominator of which is the
percentage indicated by the saccharometer before fermentation, the value of the fraction
will increase proportionately with the completeness or efficacy of the fermentation; if,
for instance, a wort before fermentation marks a saccharometrical percentage of 115,
and afterwards gives 5 per cent.; the difference 6.5 divided by 11.5 gives the coefficient
0.565, that is, of 100 parts of malt extract 56.5 per cent. are decomposed during fermentation.
After-Fermentation After the chief fermentation is completed, which for summer or lager
beer requires nine to ten days, and for winter or schenk beer seven to eight days, the
young or green beer is put into barrels, after having become quite clear by the sepa-
ration of the yeast. Before the beer is vatted the scum present on its surface is
removed. The yeast, settling to the bottom of the vat in which the fermentation took
place consists of three layers, the middle being the best yeast; the lowest, decomposed
yeast and foreign matter, is mixed with the yeast of the upper layer, and if not other-
wise saleable is sometimes employed in the distilleries of malt spirits. The middle
layer serves for further fermenting operations. In breweries where pure water (the
reader should bear in mind that Bavaria is alluded to) is not to be had, this yeast is
occasionally obtained fresh from other breweries. It is usual to fill casks or vats
with winter beer at once quite full; but as regards summer beer several brewings
are mixed in smaller vats in order to obtain an uniformly coloured mixture. The
barrels are usually coated with pitch on the inside, the aim being to prevent the beer
soaking into the wood, and thus giving rise when the cask is emptied to the forma-
tion of acetic acid. For the after-fermentation the beer is placed in stone cellars,
which should be as cold as possible, so as to cause the after-fermentation to proceed
as slowly as possible, and thus admit of the beer being kept until the brewing season
opens.
In all parts of Germany, but mostly so in Bavaria, great attention is paid to the
construction of the cellars: often these cellars are excavated in rocks, and some-
times ice-pits are placed in the cellars to keep them very cool. The after-fermenta-
tion of the beer sets in when it is vatted, the moment of the beginning of this
process partly depending upon the condition of the beer when vatted and partly upon
the temperature of cellar. The after-fermentation, which becomes apparent by the
appearance of a bright white-coloured foam at the bung-hole, may set in imme-
diately after the vatting of the beer, or may only become apparent some eight days
after. Should the beer happen not to exhibit any sign of incipient after-fermen-
BEER.
417
tation, green, young, or new beer is added for the purpose of inducing this process.
When the after-fermentation is finished, the bungs of the casks or tuns are not
tightly fastened, and the beer is left in this condition (in the cellars of course)
during the summer months. About a fortnight before the beer in the casks is
intended to be tapped, the bungs are tightly closed in order to cause as much car-
bonic acid to accumulate in the fluid as will occasion the beer to foam on being
tapped; but if beer happens to be vatted in very green condition, the bung-hole
should not remain closed for so long a period, because then so violent a fermenta-
tion may set in that, on tapping the cask, its contents become too much agitated,
and thereby a very turbid (full of yeast) beer is served to the customers. Some-
times the addition of liqueur (a solution of white sugar) is resorted to for the
purpose of setting up a strong fermentation in very old beer.
According to
J. Gschwändler (1868) beer obtained by the processes alluded to has the following
composition:-
Decoction.
Bock.
Sedimentary
Method.
Infusion.
Alcohol
Sugar..
2.810
3*380
2'940
3°130
1*580
2°320
I'460
I'339
Dextrine
4'610
6'910
4'770
4'800
Nitrogenous substances
0°380
0'740
Other constituents
0'380
0.890
0'550
Sp. gr. of solution of extract..
1'022
I'042
I'028
1'026
Extract (direct estimation)
6'570
9'980
6'230
6.130
6'950
10'380
7.120
6.680
(according to Balling)
Surface Fermentation. Surface fermentation is that induced in the worts intended for
the brewing of the bottled beers of North Germany, Bohemia, Alsace, England, and
Belgium. Beer obtained by this process of fermentation is not so lasting as that
prepared by the sedimentary fermentation process. This difference is due to the
fact that the surface fermentation goes on at a higher temperature, proceeds more
rapidly, while the elimination of the nitrogenous compounds is also less complete.
The reason why this process is preferred to the sedimentary fermentation process is
that brewing, by the application of the last process, is so greatly dependent upon a
low temperature that this mode of brewing cannot be continued throughout the
whole year; while as regards the other process it may be continuously carried on,
and the stock of beer kept ready for use can thus be considerably decreased. Sur-
face fermentation, however, is the only plan for preparing briskly foaming and
strong beers. Porter, stout, and ale could be brewed as well by the sedimentary
method—although in the English climate this process would be more difficult to
conduct successfully-but the main reason why the surface fermentation is em-
ployed for English malt liquors is that this method-by a great saving of time-is
cheaper. The phenomena of the surface fermentation are similar to those of the
sedimentary, with the exception that the process is by far more violent, the froth
surging more to the surface of the wort. The yeast is employed in the same
manner. An ingenious contrivance is adopted in the London breweries for the
purpose of carrying off the yeast from the beer after it has undergone the process of
fermentation. The wort is placed in large hogsheads, or rounds, the tops of which
are fitted with wooden troughs. Into these troughs the yeast runs as it rises, and
is carried away. The beer now becomes clear, and is pumped into the stone vats.
28
418
CHEMICAL TECHNOLOGY.
Steam Brewing. The extensive application of steam to the manufacture of beet-root sugar
and alcoholic spirits has given rise to many suggestions for the substitution of heating by
steam for direct firing in brewing. The heating is effected by a system of tubes similar
to that described in the preparation of beet-root sugar (see p. 377). In brewing, how-
over, though much would be gained by uniformly heating the worts, and by reducing the
chances of burning, there would not ensue any great economising of fuel; Lut much
labour might be saved. Steam could not be employed directly without a series of tubes,
as the condensation would cause a great dilution of the mash.
Constituents of Beer. The constituents of a normal beer prepared from malt and hops
(not from substitutes) are:-Alcohol, carbonic acid, undecomposed dextrose, dex-
trine, constituents of the hops (oil and bitter substance, no tannic acid), protein
substances, a small quantity of fat, some glycerine, and the inorganic matter of
the barley and hops. The acid reaction which a normal beer exhibits after the
carbonic acid has been expelled from it by boiling is due to succinic and lactic acids,
with traces of acetic acid, and perhaps propionic acid. The sum of all the consti-
tuents of a beer after the abstraction of the water is termed the total contents; the
sum of the non-volatile constituents, the extractive contents. Beer rich in malt
extract is termed rich, fat, or full-bodied beer; and that which is poor in extract,
but contains much alcohol, the wort having been rich in sugar which has all been
converted, is termed a dry beer.
The proportion of alcohol in beer can be estimated by distillation and the testing
of the distillate with an alcoholometer, or by means of an ebullioscope, or with
the help of a vaporimeter (see Wine-testing, p. 394). The following table shows
the average weight per cent. of the alcoholic contents of several beers:
Wirtzburg lager beer (1870)
""
schenk beer..
Stuttgardt lager beer (1865)..
Culmbach lager beer (1865) ..
Coburg lager beer
Munich lager beer.
:
:
:
:
Per cent.
40-4'3
3°3—4°2
4'I
4'5
4'4
4'3-5'1
schenk beer
""
3.8-4.0
Bock (Munich, 1870)
4.3-4.8
Porter (Barclay, Perkins, and Co., London, 1862)
5'5-7'0
Strasburg beer (1870)
4'2I
Vienna beer (1870)..
4'I
:
Rice beer of the "Rhenish Brewery" in Mentz
3.6
The quantity of carbonic acid in beer varies between o'r to o'2 per cent.
According to C. Prandtl (1868) dextrose is found in beer in quantities varying from
02 to 1'9 per cent. The quantity of dextrine, according to Gschwändler's analyses,
varies from 4'6 to 48 per cent. The proportion of sugar to dextrine is never
constant. The occurrence of protein substances in beer has not been sufficiently
investigated to warrant an exact conclusion. It may be said that on an average
malt extract contains 7 per cent. protein substances, from which Mulder deduces that
1 litre of beer should contain 5'6 per cent. albuminous substances. A. Vogel (1859)
found that I Bavarian maas (=1069 litres) of beer on an average contained
I to 12 grms. nitrogen; and Feichtinger (1864) obtained from 1 Bavarian maas
of several Munich beers between 0°467 and 1*248 grms. nitrogen. Succinic acid,
acetic acid, and lactic acid occur in Belgian and Saxony beers in large quantities.
Tannic acid occurs in Bavarian beers only in small quantity.
The inorganic
BEER.
419
constituents of beer have received great attention. Martius obtained from 1000 parts
of Bavarian lager beer 2.8 to 3'16 parts ash, containing one-third potash, one-third
phosphoric acid, and one-third magnesia, lime, and silica. J. Gschwändler and
C. Prandtl (1868) found an average extractive contents in 100 parts of—
Schenk beer (Munich)
•
Lager beer (Munich)
Schenk beer (Wirtzburg
Lager beer (Wirtzburg)..
Bock (Munich)
Salvator (Munich)..
Rhenish rice beer
:
:
:
Porter (Barclay, Perkins, and Co., London)
Scotch (Edinburgh)
Burton ale
Parts.
5'5-6'0
6'1
4'6
4'4
8.6-9.8
9'0-9'4
7°3
5'6-6'9
10'0-II'O
14'0-19'29
100 parts of extractive matter contain, according to A. Vogel (1865) 3·2 to 3'5 parts
of ash; 100 parts of ash contain 28 to 30 parts phosphoric acid. 1 litre of beer
contains o‘57 to 0.93 grm. of phosphoric acid.
Lermer (1866) subjected several Munich beers to analysis with the following
results:
.I.
2.
Sp. gr.
1*02467
1'0141
per ct.
per ct.
3.
1*01288
per ct.
4.
5.
6.
7.
1*0200 102678 1'03327 1'0170
per ct.
per ct.
per ct.
per ct.
Extractive matter
7'73
4'93
4'37
4'55
8.50
9.63
5'92
Alcohol
5'08
3.88
3'51
4'41
5°23
4'49
3'00
Inorganic constituents o⚫28
0'23
0'15
0'18
1
Nitrogen:
In 100 parts extract 11'15
8.71
12'19
8.85
100
>>
beer 0.87
0'43
0'53
0.39
6'99.
0.67
1. Bock beer. 2. Summer beer. 3. White beer.
4. White Bock beer (superficially
fermented, obtained by surface fermentation from malted wheat). 5. Another sample of
Bock beer. 6. Salvator beer. 7. Winter beer.
The analysis of the ash of five of these beers gave:-
I.
24.
3.
4.
5.
Potash
Soda
Chloride of sodium
Lime
Magnesia
Oxide of iron
29°31
33°25 24.88
34'68
29°32
I'97
0'45 20'23
4'19
Ο'ΙΙ
•
4'61
6'00
6'56
5'06
6'00
2934
2'98
2:58
3°14
6.21
:
11.87
8.43
0'34
7'77
7'75
ΙΟΙ
O'II
0'47
0*52
0.84
Phosphoric acid
Sulphuric acid
34'18
32'05
26.57
29.85
29.28
I'29
2'71
6'05
5'16
4.84
Silicic acid
12'43
14*12
7°70
2.86
8.01
Sand
0.83 0'67
2'30
5'20 6.27
Carbon ..
0'49
0.81
0'40
0'65
0'28
100'33
101'47 98.03
99'08
98'91
420
CHEMICAL TECHNOLOGY.
The high importance of beer, both as regards its value as nutriment as well as regards
the enormous trade done in this article, has given rise to attempts to find proper and
suitable means for testing that liquid in respect of its quality and purity.
Beer-Testing. The experiments proposed for ascertaining the strength as well as
freedom from adulteration of beer, is termed beer-testing; it is desirable that these
operations should be easily executed and yield sufficiently reliable results. The
strength of a beer is judged according to the quantity of alcohol, extract, and car-
bonic acid it contains; it is evident, however, that an intimate knowledge of the
real constituents of the extract, viz., the therein contained quantities of dextrine,
hop constituents, the by-products of alcoholic fermentation, such as, for instance,
succinic acid and glycerine, not to mention such substances as, for instance,
glucose and glycerine purposely added to the wort, as substitutes for malt, largely
influence the quality of any kind of beer, and therefore ought to be determined
when any rigorously exact analysis of that liquid is wanted.
Beer-testing is effected partly by ascertaining certain physical qualities of the
beer, partly by chemical means. To the former belong its flavour, odour, colour,*
consistency, transparency, specific gravity, refractive power to light, &c. By
chemical analysis we ascertain and determine the immediate constituents, viz.,
carbonic acid, alcohol, extractives, and water. The carbonic acid contained in the
beer is first eliminated either by repeatedly pouring a quantity of beer from one
tumbler or beaker-glass into another, care being taken to let the beer fall from
some height, or the carbonic acid is removed by shaking the liquid up in a bottle and
pouring it out of the same and into it again. The gas having been driven off, the
specific gravity of the beer is taken by means of the hydrometer or saccharometer;
the beer is next boiled down to half its original bulk; next there is added to it
it as much water (best distilled) as is required to restore the liquid to its original
bulk, and of this liquid the specific gravity is again determined; this will be found
greater than that previously obtained. The difference between the two determina-
tions gives the amount of alcohol contained in the beer.
Beer-Test.
Balling's Saccharometrical Since by fermentation 100 parts of malt extract yield 50 parts
alcohol, twice the quantity of alcohol found will indicate the quantity of malt ex-
tract necessary for its formation. This quantity of malt extract added to that still
existing in the beer indicates the whole of the malt extract existing in the wort
before fermentation.
The specific gravity of the beer-wort becomes lower by fermentation, partly
because the specifically lighter alcohol is formed, partly by the loss of some of the
extractive matter, and partly also by the loss of the substances taken up in the yeast.
This decrease of the specific gravity, or attenuation, as it is termed, can be estimated
either directly by weighing, or by means of the saccharometer. The degree marked
by the saccharometer in a beer freed from carbonic acid we will call m; the malt-
extract of the wort, p. Subtracting in from p, the difference (p-m) gives the
apparent attenuation, which is the greater the mcre thorough the fermentation.
The quantity of alcohol in a beer varies in direct proportion with the apparent
attenuation. The empirical alcohol factor, a, by which the apparent attenuation
must be multiplied to obtain the alcoholic contents of the beer A in weight per
* Very recently, C. Leyser has invented a colorimeter with which, by means of a
normal solution of iodine (12.7 grms. iodine to a litre) after having brought the peers to
an equal colouration with water, he estimates the relative degree of the original colour.
The invention is fully described in the "Jahresberichte der Chem. Technologie" for 1869.
P. 467
BEER.
421
Am).
cent. [(x — m) a =A] becomes the greater, the higher the original degree of concen-
tration of the wort. For worts between 6 to 30 per cent. of extractive matter, this
factor varies from 0.4079 to 0'4588. The alcohol factor can be found by the follow-
ing equation, when the apparent attenuation (p-m) and the alcoholic contents of
the prepared wort (A) are known; then a =
With the help of the
Ρ
alcohol factor, a, the alcoholic contents in weight per cent. can be calculated. A
quantity of beer being boiled to volatilise the alcohol, and the residue having been
diluted with water to the original bulk or weight, if a weighed quantity were
operated with, the specific gravity gives the quantity of extractive matter contained
in the beer, which Balling terms n. The difference between the extractive matter
contained in the wort (p) and that of the beer (n), or (p—n), gives the actual
attenuation, which, multiplied by the alcohol factor for the actual attenuation (b),
likewise gives the quantity of alcohol contained in the beer expressed in percentage
A
by weight. The alcohol factor for the actual attenuation is b
Sub-
p n
tracting from the apparent attenuation (p — m) the actual (p --- n), the difference (d)
in the attenuations is obtained :—
d = (p— m) — (p—n); or d=m—n.
d is known, when the extractive matter contained in the beer (n) and the saccharo-
metrical percentage (m) of the beer free from carbonic acid are known; d is the greater
the more alcohol the beer contains. The alcohol factor multiplied by the difference
in attenuation gives the percentage (A) of alcohol, from which the alcohol factor for
the difference in attenuation can be obtained by the following equation :-
p N
C
A
(p—m)
It averages 2:24. Finally, with the help of c the difference in attenuation of the
alcoholic contents of a beer can be calculated approximatively, even when the quantity
of extractive matter of malt contained in the wort is not known. The apparent
divided by the actual attenuation gives a quotient (d), which is the ratio of the
attenuations, d—P—m, and can be calculated with the help of the alcohol factor
for the apparent attenuation (a), and of the original extractive contents of the wort
(p). First—(a) is obtained by the division of the alcohol factor for the actual
attenuation by the corresponding attenuation quotient or ratio. Assuming the
alcohol factor for the difference in attenuation to be 2*24, and next doubling the
approximative alcoholic contents thus obtained, we arrive at the quantity of the
extractive matter of the wort from which the alcohol was formed. Adding to this
the extract yet met with in the beer, the sum thus found expresses the approximate
percentage of the extractive contents of the wort. When (p) has thus been approxi-
mately obtained, Balling's tables give the corresponding attenuation quotient 9,
reckoning all decimals above o‘5 as units, and neglecting those under o5. If only
the original concentration of the wort (p) is to be calculated, the percentage of the
alcohol of the beer may be obtained from the equation to the actual attenuation
A=(p-n) b. If the degree after fermentation is 9'75 (or 16 29-6'54), the
saccharometrical percentage (see p. 363)
9'75
=0'542.
16.29
422
CHEMICAL TECHNOLOGY.
Fuchs's Beer Test. Hallimetrical Beer Test.-Fuchs's test, based upon the presumption
that the beer has been brewed from malt and hops only, starts from the fact
that 100 parts of water, independently of temperature, dissolve 36 parts of pure
common salt (=2'778:1), and that a fluid dissolves the less salt the greater the
FIG. 232.
ta
15
quantity of alcohol and extractive matter it contains.
It is therefore possible to estimate by this means the
quantity of water in a beer by determining the quantity
of common salt which remains undissolved; this is done
by means of the hallimeter, Fig. 232, an instrument con-
sisting of two glass tubes, one very wide and cup-shaped,
the other narrower and attached to the bottom of the
former. The smaller tube is so graduated that the
larger divisions correspond to a quantity of 5 grains of
common salt, while the smaller divisions correspond to
I grain of salt. In all hallimetrical experiments it is
very essential that the pulverised common salt be
always as much as possible of the same degree of
fineness, while care has also to be taken that this sub-
stance be reduced to its smallest bulk when put into
the tube by gentle taps, so as to expel air, and thus
cause the salt to occupy exactly the space intended
for it. It is therefore required to pass the pulverised
salt through a wire-gauze sieve, after which the pre-
pared salt is kept for use in a glass-stoppered bottle.
The testing requires two experiments. By the first is estimated the amount of
water together with the entire quantity of carbonic acid, alcohol, and extractive
matter contained in the sample; while the second experiment gives the quantity
of extractive matter, which when the carbonic acid is deducted from the total
contents, yields the amount of alcohol contained in the beer. The alcohol is
not anhydrous, but is mixed with a certain quantity of water. 1000 grains (62.5 grms.)
of the beer to be tested are poured into a flask with 330 grains (20:46 grms.) of the
common salt. The flask, lightly closed with a stopper or cork, is frequently
agitated, and having been placed on a water-bath is heated to 38°. After six to ten
minutes the flask is removed from the water-bath, the carbonic acid being
expelled by gently blowing into the flask, which is next weighed; the loss of weight
indicates the quantity of carbonic acid, which in good beer averages 15 grains.
The mouth of the flask having been closed with the thumb is turned upside
down in order thereby to collect any non-dissolved salt in the neck of the flask,
and the salt along with the fluid transferred to the hallimeter, the non-dis-
solved salt settling down in the graduated tube, this movement being promoted
by gently shaking the instrument. As soon as the volume of the undissolved salt
ceases to increase, the number of grains is read off and deducted from 330, the
difference being the number of grains dissolved from which the quantity of water
present is calculated.
Example: 1000 grains (62.5 grms.) of beer dissolve 330

18=312 grains common
salt; therefore these 1000 grains of beer contain 866-6 grains of water; for
36: 100 312: x,
x=866.6
1000 — 866·6 — 133'4 grains indicate the total quantity of carbonic acid, extractive matter,
=
BEER.
423
and alcohol present in the beer. If the contents of the flask by heating have lost 15
grains in weight, the extractive matter and alcohol together amount to 1319 grains.
The second experiment is now made to estimate the amount of extractive matter. For
this purpose 1000 grains (62.5 grms.) of beer are weighed off and poured into a flask, and
boiled down to half the quantity, that is, 500 grains. Both the carbonic acid and the
alcohol are driven off. 180 grains of common salt are now added, and the experiment
proceeded with as before. Supposing 180· 20160 grains of common salt to be dis-
solved, there will have remained 444'4 grains of water; for
18: 50 160: x
=
x=444'4,
which shows the quantity of the extractive matter to be 55.6 grains. If the preliminary
estimation of the carbonic acid has been correct, the quantity of alcohol contained in the
beer will be 76.3 grains, for 1334 — 55.6 — 1·5=76.3. This corresponds, according to a
table published with each instrument, to 42°27 grains of absolute alcohol. The beer
would, therefore, contain in 1000 parts:-
Carbonic acid
Free water
Combined water
Extractives
Alcohol
1.50
866.60
..
34'03
55.60
42.27
1000'00
The hallimetrical assay of beer is entirely worthless when beer is made with the addition
of glucose or glycerine.
By-products of the Among the by-products of brewing the residue of the mash tuns is
Brewing Process. perhaps the most important. 100 parts of kiln-dried malt leave on an
average 133 parts of residue, which being dried at the temperature to which the malt
was subjected give 33 parts. It is used as fodder for cattle under the name of brewers'
grains. This material yet contains, in addition to the husks and cellulose of the grain,
undecomposed fatty matter and protein substances, upon which its value depends.
Exhausted mashed grain from a Munich brewery used to prepare summer beer (by the
thick mash method) had the following composition:—
Water..
Ash
Wet Grains.
74'71
Air-dried.
Dried at 100°.
7.28
I'06
3.87
Cellulose
3'06
II*22
4.18
12'10
Fat
1'70
6.23
6.72
Nitrogenous nutritive matter..
6.26
22.89
24'71
Non-nitrogenous nutritive matter
13.21
48.51
52.29
100'00
100'00
100'00
The rootlets and plumules of the germinated malt present in the proportion of about
3 per cent. of the weight of the dried malt, form a very concentrated and rich fodder.
According to the analyses of Scheven, Way, and Lermer (Hungarian barley), the
following is the composition of that substance :--
Water
Ash..
Cellulose..
Protein substances
Non-nitrogenous nutritive matter
Scheven.
Way.
Lermer.
7.2
3.7
10.72
6.8
5'I
6.91
17.0
18.5
45'3
48.9
32'40
23.6
23.8
49'77
The sediment of the cooling tuna (see p. 414), part of which is used as fodder and part
in the preparation of brandy, amounts to about 3 per cent. of the wort. The after-
washes are also used in malt spirit making, as well as in the preparation of vinegar. The
thick mash processes yield an after wash containing from 4 to 8 per cent. extract,
while by the infusion methods this amounts only to 2 to 3 per cent. Much of the yeast
formed during brewing is employed in bread-making, as well as in the manufacture of
vinegar and brandy
424
CHEMICAL TECHNOLOGY.
*
THE PREPARATION OR DISTILLATION OF SPIRITS
Alcohol. Since alcohol happens to be in almost all countries an article which in a
nearly pure state (that is to say more or less diluted with water) is a fluid used as an
article of consumption, and therefore very properly submitted to a more or less
heavy duty or impost, the mode of manufacturing alcohol on the large scale, and
the raw materials from which it is obtained, vary in different countries, and conse-
quently these conditions very greatly influence the industry of alcohol production.
When a fluid containing alcohol is distilled, alcohol and water are collected in the
receiver, while the non-volatile constituents remain in the retort in a concentrated
condition. The act of distillation of an alcoholic fluid is termed the brennen,* while
the product of the operation is designated as brandy, a fluid which contains on an
average from 40 to 50 per cent. of alcohol. A distillate which contains more alcohol
than the quantity just alluded to is designated as spirits of wine, or simply
spirit. Originally, that is to say when spirits (now some two and a half
centuries ago) were first commenced to be made industrially on the large scale,
it was only made for the purpose of being drunk, and the liquor prepared in
the comparatively dilute state in which it is offered for sale for consumption.
More recently (within the last forty or fifty years), the use of alcohol in various
branches of industry (varnish-making, ether preparation, perfumery, preparation of
cordials, liqueurs, &c.) is so great, that as a rule distillers at once prepare strong
alcohol, which, if required for consumption as a beverage, is suitably diluted and
sweetened if desired. Since the distillation of alcohol has been carried on on the
large scale the apparatus have been very greatly improved; and those now in
use in the best arranged distilleries are constructed upon scientific principles, while
care is also taken that the surveillance on the part of the excise officers is rendered
an easy task, and fraud almost impossible. The whole art of the production of
alcohol-its ready preparation from grain (partly malted), from beet-roots, potatoes,
refuse of saccharine liquors from sugar works, the proper utilisation of the residues
of the distillation, either as food for cattle or otherwise-is now brought to a degree
of perfection almost unequalled in any other branch of industry.
Important Properties.
Alcohol and its Technically The formula of alcohol (as a chemically pure substance) is
C₂HO, or C2H5O. It is a colourless, thin, very mobile fluid of 0.792 sp. gr.,
H
boiling at 78.3°, while water boils under the same atmospheric pressure at 100°; thus
there is afforded a means of ascertaining by the boiling-point of an alcoholic fluid, the
quantity of alcohol contained. Between o° and 78.3° (its boiling-point), alcohol
expands o‘0936 of its volume, while the coefficient of expansion of water between
the same degrees is 0.0278. The expansion of alcohol is thus 33 times greater than
that of water; and this fact is made available in alcoholometry. The tension of the
vapour of alcohol at 78.3° is equal to an atmosphere, while water must be raised to a
temperature of 100° to obtain the same pressure. Thus, the variation in height of a
column of mercury subjected to the pressure of these vapours may be made a mea-
sure of the quantity of alcohol contained in a fluid. On this principle the vapori-
meter (see p. 395) is constructed. Alcohol is readily inflammable, and burns with a
pale blue flame without giving off soot. Its heat of combustion corresponds to 7183
* There is no equivalent term for this word in English neither also in the French lan-
guage; the real meaning is "the firing,'
"the firing," in Dutch (branden); the term Brennerei
(German), and brandery (Ďutch), meaning a distillery."
(6
SPIRITS.
425
units of heat. It eagerly absorbs water, and upon this property is based its use for
the preservation of articles of food, cherries, and other fruit, and also anatomica,
preparations. It mixes with water in all proportions, whereby a decrease of bulk
of the mixture and increase of specific gravity is observed—
53'9 volumes of alcohol, with
49.8
دو
water, form a mixture not of
103.7, but of 100 volumes.
Alcohol is a solvent for resins (upon which property is based its application to the
manufacture of varnishes, cements, and pharmaceutical preparations), and also a
solvent of many essential oils. These solutions are employed either as perfumes, such
as eau de Cologne, or as liqueurs, cordials, and aqua vitæ, or as spirits for burning
in lamps, as, for instance, the mixture of oil of turpentine and alcohol, so-called fluid
gas; alcohol also dissolves carbonic acid gas, a property made available in the
making of effervescing wines.
By the influence of certain oxidising agents alcohol is converted first into aldehyde
and next into acetic acid, as illustrated in the so-called quick vinegar-making
process. Alcohol does not dissolve common salt, and upon this property Fuch's test
(see p. 422) is based.
By the action of most of the stronger acids aided by heat alcohol is converted
into what are termed ethers; as regards the action of sulphuric acid upon alcohol,
it depends upon the relative quantities and degree of concentration of these liquids,
whether sulphovinic acid, ether, or bicarburetted hydrogen gas, be formed.
Hydrochloric acid forms with alcohol chlorine of ethyl or hydrochloric ether.
Butyric and oxalic acids form ethers directly when heated along with alcohol; but
most of the other organic acids require the addition and the aid of sulphuric or
hydrochloric acid for this purpose. Alcohol is the intoxicating principle of all
spirituous liquors.
Raw Materials of Spirit
Manufacture.
Alcohol is always the product of vinous fermentation. The
manufacture of spirits therefore includes three principal operations :—
1. The preparation of a saccharine fluid.
2. The fermentation of this fluid.
3. Separation of the alcohol by distillation
All saccharine fluids, therefore, or those substances which yield alcohol by fermen-
tation, can be employed in the manufacture of spirit; and all materials so employed
contain already either completely formed alcohol, or cane sugar and dextrose, or
finally substances which by the influence of diastase or dilute acids are converted
into dextrose. Such substances are starch, inuline, lichenine, pectin compounds, and
cellulose. The raw materials of spirit manufacture may be generally classed in the
three following groups:
1st Group.-Fluids in which the alcohol is already present, requiring only distil-
lation to effect its separation. Such fluids are wine, beer, and cider.
2nd Group.—Substances either solid or liquid which contain sugar, which may be
either cane sugar, or dextrose and levulose, or sugar of milk. In this group are
included the beet-root, carrot, sugar-cane, maize stalk, the Chinese sugar-cane
(sorghum), some kinds of fruit-viz., apples, cherries, figs, some berries (grapes,
mountain ash berries, &c.), the melon and gourd, some fruits of the cactus tribe, the
426
CHEMICAL TECHNOLOGY.
molasses of cane and of beet-root sugar manufacture, the marc of grapes and refuse
grain of beer-making, honey, and milk.
3rd Group.—All substances which originally contain neither alcohol nor sugar, but
the constituents of which may be converted into sugar and dextrose. Such are
starch, inuline, lichenine, pectin compounds, and cellulose, chiefly found in-
a. Roots and bulbs: Potatoes, dahlia roots, &c.
b. Cereals: Rye, wheat, barley, oats, maize, and rice.
c. Leguminous and other seeds: Buck-wheat, millet, black or negro millet, peas,
lentils, beans, vetch, chestnut, horse-chestnut, oak leaves, &c.
d. Substances containing cellulose: Sawdust, paper, straw, hay, leaves, osier,
moss.
In the future a—
4th Group may perhaps be added, which will embrace all substances as probably
may enter into the synthetic preparation of alcohol, and thus form what might be
called a mineral spirit. Berthelot in 1855 proved that alcohol can be formed from
olefiant gas and water (C₂H4 + H₂O=C₂H₂O). Olefiant gas, when agitated for a
length of time with concentrated sulphuric acid, gives rise to the formation of
sulphovinic acid; and from this liquid after having been diluted with water
a dilute alcohol can be distilled. This experiment has as yet only a scientific
interest; the process has been tried on the large scale in France, but failed to be
commercially available.
Vinous Mash from Cereals.
a. Preparation of a Vinous Mash.
Grain brandy (corn brandy) may be prepared from either
wheat, rye, or barley. Generally more than one kind of grain is used, because
experience has proved that a larger quantity of alcohol is obtained when two kinds
of grain-for instance, wheat and barley, rye and barley--are mixed. A mixture of
rye with wheat or barley malt, or wheat with barley malt, is very generally used, at
least abroad. To 1 part of malt from 2 to 3 parts of non-malted grain are usually
taken. Either, as is done in England, wort is made, the grain being first malted,
next mashed, and the wort drawn off, or the nixture of malted and unmalted grain is
allowed to ferment together. The latter method is more usual in Germany, and will
be that described in this work. In Russia and Sweden brandy is prepared without
malting; by properly mashing rye meal a reaction ensues between its constituents,
the effect of which is the same as if it had been acted upon by diastase of malt-
The preparation of a mash from grain may be considered as consisting of the following
four operations:-
1. The Bruising.-The materials, malted as well as unmalted grain, are first bruised.
As it is not essential in the manufacture of spirits that a clear wort should be prepared,
the grain may be broken up very small, whereby the formation of sugar is rendered more
complete. Green malt is now generally considered preferable by many distillers.
2. The Mixing with Water.-Making of Mash.-This operation is almost identical with
that of the mashing of the brewer; the only distinction being that the distiller aims at the
entire conversion of the starch into glucose, while the brewer does not require this as he
also wants some dextrine. The complete saccharification, and next the complete conversion
of the glucose into alcohol during fermentation, are possible only with a certain degree
of dilution of the mash. The quantity of water to be mixed with the grain cannot be
reduced too much, because that would involve a loss of spirits.
3. The Cooling of the Mash.-When the saccharification is complete, the mash should
be rapidly brought to the temperature suitable for fermentation by being placed in
cooling vessels, just as is done with the wort in brewing, by being placed in an apparatus
termed a refrigerator, or by the application of ice or cold water. The temperature
to which the mash has to be cooled varies according to the locality and the duration of
SPIRITS.
427
the fermentation, but it averages 23° C. When sufficiently cooled the liquid is placed in
the fermenting vats.
4. The Fermentation of the Mash.-The fermentation vat is generally made of wood and
sometimes of stone. The first possesses the property of retaining the heat for a longer
time, and for the same reason large vessels are preferred. The capacity seldom exceeds
4000 litres.
Either beer yeast in its fluid condition or dry yeast is used to set up
fermentation. The latter is mixed with warm water before being added to the contents of
the fermentation tanks. Of the fluid beer-yeast, there is usually taken to 1000 litres of
mash 8 to 10 litres; while for 3000 litres of mash 15 to 20 litres of yeast are a sufficient
quantity. Of the dry yeast, a kilo. is employed to 1000 litres of mash, or 1 kilo. of
yeast to 3000 litres of mash. In large distilleries artificial yeast is sometimes employed,
as beer yeast of the requisite quality cannot always be procured at a remunerative price.
The mode of adding the yeast is the same as that employed in breweries. After
standing 3 to 5 hours the temperature of the mash will have increased to 30° to 32°.
Carbonic acid is then given off, and the heavier substances settle to the bottom of the
tank. This continues for about four days, when the clear fluid may be considered ready
for further operations.
Mash from Potatoes. Potatoes consist of about 28 per cent. of dry substances, 21 per
cent. of which is starch, with 2.3 per cent. of albuminous matter, and 72 per cent.
of water. The active principle under the influence of which the starch is converted
into dextrose is diastase, but this substance is not found even in the germinated
potato. It therefore becomes necessary, in order to convert the starch of the pota-
toes into dextrose, to add malt, or to treat the potatoes first with dilute sulphuric
acid. Accordingly, the preparation of a mash from potatoes may be performed by
either of these two operations. The former is that most generally employed. The
preparation ordinarily includes the following operations:-1. The washing and boil-
ing of the potatoes.-Before the potatoes can be boiled or steamed, they must be
cleansed from the adhering earth. After the washing the potatoes are boiled with-
out previous paring. Finally, they are steamed. 2. The chopping of the boiled
potatoes.—As soon as the potatoes are boiled they are placed in a chopping machine,
and cut into small pieces, care being taken to keep them hot by the aid of steam,
so that the cut up mass admits of being readily mixed with hot water into a uniform
mass, which is the best condition for the potato starch to be most readily converted
into dextrose. In some cases the boiled potatoes are passed between two hollow
cast-iron cylinders, the axles of which are so arranged and fitted in a frame-work
as to admit of the cylinders being moved in an opposite direction, and thus capable
of converting the boiled potatoes into a uniform mash. 3. The mashing.—After
the addition of the grain or diastase-containing material, the mashing proceeds as in
the case of malt. The grain or malt added is sometimes rye malt, sometimes barley
malt, and generally a mixture of the two. Green malt has greater power of con-
version than air-dried malt, ultimately producing a larger quantity of alcohol. The
proportion of bruised malt to be employed varies in many instances; while in some
cases only 2 to 3 per cent. of barley as malt is added to 100 parts of potatoes; in
others as much as 10 per cent. is used. A medium quantity between these two ex-
tremes, or about 5 per cent., is perhaps that most in use. 100 parts of potatoes con-
taining about 20 per cent. of starch yield on an average 17.3 parts of dry extractive
matter in the mash wort, 5 parts of barley malt yielding 3 parts of dry malt ex-
tract; the yield of spirits has therefore to be calculated from these two substances.
When a thick mash of potatoes is made a different proportion of the dry substances
to the water to be added is obtained from that which obtains when malt or raw
(unmalted) grain is made into a mash; these proportions are in the case of potatoes
as 1 : 4'5, 1:4, even 1 : 3. It is clear that the large quantity of water contained in
potatoes (viz., 72 to 75 per cent.) has to be taken into account.
428
CHEMICAL TECHNOLOGY.
The operation of cooling is performed as already described. While the mash is
placed in the cooling vessels it undergoes changes which are partly favourab.3 and
partly unfavourable to the yield of alcohol. The increase of sugar is f course
favourable; this increase can only be accounted for by the action of the protein
compounds contained in the malt, whereby the dextrine is converted into dextrose.
All albuminous substances possess the property of converting starch into dextrose;
and this the more so if the albuminous substances are themselves already in a
state of decomposition. Blood, brain, albumen of malted barley, saliva, meat in a
state of incipient decay, are all capable of converting starch into dextrose. When
Mulder suggests that the word diastase should be banished from science, and for it
substituted that of starch converter, he is right in a scientific sense, because
diastase does not exist as a chemical body by itself; but the word diastase may be
conveniently used in technology for the purpose of indicating an albuminous body,
which being itself in a state of decomposition, is capable of converting starch into
dextrose. Another change of the mash consists in the formation of lactic acid,
always readily formed from sugar under the influence of a peculiar ferment. The
quantity of this acid is increased by slowly cooling to the suitable temperature for
fermentation; it is therefore best to cool the mash as rapidly as possible. Recently,
an aqueous solution of sulphurous acid is employed, some of this being added to the
mash mixture, the effect being the prevention of the formation of lactic acid, and
thus increased yield of alcohol.
Acid.
Mash with Sulphuric The Preparation of a Mash by means of Sulphuric Acid.-We
have already seen that some dilute acids are as capable of converting starch into
dextrose as the so-called diastase of malt: dilute sulphuric acid is usually applied
for this purpose. Leplay first recommended this mode of preparing mash. The
raw potatoes are first converted into a pulp, which is thrown into a large vessel
containing water. The starch cells separate, some settling to the bottom of the
vessel, others becoming mixed with the cellular tissue of the pulped potatoes. The
brown-coloured supernatant fluid (wherein is also contained the albumen of the
potatoes, which would, if left, interfere with the action of the sulphuric acid upon
the starch) is first syphoned off. This liquid is given as drink to cattle, or is used
for the purpose of moistening dry fodder. While this operation is in progress there
is heated to the boiling-point in another vessel the required quantity of dilute sul-
phuric acid, the heating apparatus consisting generally of steam pipes. To every
hectolitre of potatoes from 15 to 2 kilos. of strong sulphuric acid diluted with
3 to 4 litres of water is usually taken. The previously more or less washed green
potato starch is gradually and by small quantities at a time added to this boiling
fluid. The boiling is continued until the whole of the starch as well as all the
dextrine are converted into glucose, the course of the progress of the conversion
being ascertained by means of iodine water, while the insolubility of dextrine in
alcohol affords a means of ascertaining whether the conversion of this substance is
complete. A sample of the fluid when agitated with alcohol should exhibitno milky
appearance. After about five hours' boiling the formation of sugar will be complete.
The fluid is then first run into a vessel with double bottoms, one of which is
perforated with small holes so as to admit of acting as a strainer to retain cellular
tissue, &c., after which the fluid is run into another vessel, and while therein is
neutralised by the addition of chalk. The gypsum having settled down, the fluid
is again transferred to another vessel. The wash water of the sediment having
been added, the liquids are ready to undergo fermentation.
SPIRITS.
429
4. The Fermentation of the Potato Mash.-The addition of yeast to the cooled
mash in the fermenting vat takes place in the same manner as with malt. To 100
kilos. of mash are added 1 to 2 litres of beer yeast, or to 1 kilo. of dry yeast. The
potato mash contains besides the husk of malt and grain some finely divided cellular
tissue; these substances during fermentation are carried to the surface of the mash
and form a scum, the appearance and behaviour of which gives an opportunity of
judging the progress of the fermentation. The fermentation is said to be regular or
irregular; the former begins some four to six hours after the yeast has been added,
and proceeds in a regular manner, the end depending upon the quantity of yeast
added and upon the temperature. The progress is quiet, not violent, the scum which
appears on the surface sinking or being drawn down at one side of the vat and thrown
up at the opposite side, while bubbles of air or gas appear and burst on the surface,
much as bakers' dough heaves under the influence of the ferment. Irregular fermen-
tation is so far opposed to the former that the surface of the mash is only partly
covered with froth, which remains in one position, and does not move of itself. The
result of such a fermentation is generally defective, the reason being the incomplete
saccharification of the mash, the addition of too small a quantity of yeast, or finally
working at too low a temperature. After about 60 to 70 hours with a regular fer-
mentation, the mash is ready for distillation. Recently large quantities of spirits
have been prepared from maize and also from rice.
Mash from Roots. By the use of those vegetables which contain alcohol-forming bodies,
either in the shape of cane sugar or as dextrose, the mashing process is avoided, and
the prepared fluid is immediately ready for fermentation as soon as the saccharine
fluid has been completely squeezed out of the cells wherein it is contained in the
vegetable. The great advantage of the preparation of spirits with the avoiding of
the mashing process is too important to be overlooked, and it is therefore clear that
effort should be made to substitute for the starch-containing vegetable products
those which contain sugar, the more so as it has been recently proved in England
perfectly possible to arrange this industry in every way to the satisfaction of the
excise authorities.
every
One of the most important of such roots is the sugar-beet so largely employed
in the manufacture of beet-root sugar. Although it would appear to be a
simple matter to extract the juice from the previously pulped juice, this is yet—
notwithstanding even the large quantity of juice, viz., 96 per cent. of the
weight—a difficult matter, because the remaining 4 per cent. of substance have
all the properties of a sponge and tenaciously retain the juice; it is this spongy
nature of the solid constituents of the root which prevents the conversion of
the whole root into a sufficiently concentrated mash. If it were possible to set up
fermentation in the thick pulp obtained from the roots 100 kilos. of the pulp would
yield 6 litres of alcohol, a quantity sufficiently large to be remunerative even with
a very low market price of spirits. Indeed it is maintained by the advocates
of beet-root distilleries, that the distillation of spirit is a more profitable business
than the manufacture of beet-root sugar. In Belgium and Germany, distilleries
are frequently to be found attached to the beet-root sugar manufactories; and
the combination of the industries possesses the advantage that, in a season when the
proportion of sugar in the roots is too poor to yield much profit to the manufacturer
as sugar, he may ferment the sugar-containing juice and obtain a fair yield of
spirit. Beets to be available to the distiller may contain only 5 to 6 per cent. of
430
CHEMICAL TECHNOLOGY.
sugar; but for the purposes of the manufacturer of sugar they must contain at
least 8 to 9 per cent. The products of the first distillation of the fermented beet-
roots contain, in addition to water, oils known as fusel oils, of very unpleasant
taste and smell and of poisonous quality. These oils, however, disappear during
rectification. The methods of obtaining the juice are the following:-
a. By pulping and
a. Pressure, or
b. By treatment in a centrifugal machine.
By maceration, or by the dialytical method.
a. The sliced roots being treated with cold or with hot water (Siemens' and
Dubrunfaut s methods).
b. The sliced roots being treated with hot wash from former distillations.
y. According to Leplay's method, somewhat modified by Pluchart, the sliced roots are
submitted to fermentation without previous extraction of the juice, and also without
addition of yeast, the alcohol being afterwards distilled from the sliced roots with the aid
of steam.
Spirits from the By-Products
of Sugar Manufacture.
In the East Indies the scum from the boiled sugar, the molasses,
&c., are brought to fermentation and the fermented fluid distilled.
The product is in the English colonies known as Rum, in Madagascar and the Isle of
France as Guildine. The peculiar aroma of rum is contained in the portion which first
distils over. By the fermentation and distillation of the scum from the boiling of the
sugar-cane juice, a coarse, sour, dark brown or black-coloured acrid tasting brandy is
obtained; it is known as Negro rum. In England and Germany rum is frequently made
from the diluted molasses of the sugar refineries fermented with yeast, the fermented
fluid being distilled after about 3 to 4 days' fermentation. The aroma peculiar to rum
is obtained by the addition of some pelargonic ether or essence of pine-apple. Beet-root
molasses are also largely used for the purpose of obtaining spirits. By itself the beet-root
sugar molasses are difficult to ferment, but if the alkalinity of this material is first
neutralised by the addition of some sulphuric acid, and the material next boiled with a
further addition of acid for the purpose of converting the cane sugar it yet may happen
to contain into inverted sugar, the fermentation may be readily set up and regularly pro-
ceed. 100 kilos. of molasses yield on an average 40 litres of spirit. The very objectionable
odour of this spirit is due to fusel oil, which contains small quantities of propylic, butylic,
and amylic alcohol, pelargonic acid, and caprylic acid, while later researches have added
to this list œnanthic, caproic, and valerianic acids. The residue left in the retort is used
for the preparation of potassa (see page 118). The addition of sulphuric acid has not only
the effect of converting the cane sugar into an easily fermentable sugar, but also prevents
the setting up of lactic acid fermentation.
Spirits from Wine and Marc. The distillation of spirits from wine is chiefly carried on in
France, Spain, and Portugal. The yearly production of spirits from wine or
French brandy (alcool de vin) in France alone, amounts to 450,000 hectolitres of
85 per cent., and 400,000 hectolitres of 60 per cent. The quality of the spirit is
indirectly affected by the degree of ripeness of the grapes, and directly by the care
bestowed upon the fermentation and distillation, the more or less intimate mixture of
the volatile principles of the wine with the alcohol, and by the age of the wine. Old
wine yields a spirit of better quality than new wine. The freshly distilled brandy is
colourless, and remains so even when bottled; but since the spirit is kept in oaken
casks it extracts therefrom some colouring and extractive matter. The best kinds of
brandy are distilled in the Département de Charente, and the brand known in
commerce as Cognac (name of a town) is the most valued. From the marc and
wine-lees spirit is also distilled. By the distillation of spirits from wine a residue
is left in the retort (the vinasse) which contains a large quantity of glycerine which
may thus be obtained as a by-product.
SPIRITS.
431
b. Distillation of the Vinous Mash.
Distillation of the Mash. The fermented mash (as obtained from potatoes is a mixture or
non-volatile and volatile substances. To the first belongs the fibre, malt, husks,
inorganic salts, protein substances, undecomposed and decomposed yeast, succinic
acid, lactic acid, glycerine, &c.; to the volatile, the alcohol, fusel oil, water, and
small quantities of acetic acid. The volatile constituents of the mash, the products
of the fermentation, are separated from the non-volatile by distillation, during
which the volatile constituents are converted into vapour afterwards cooled and con-
densed in another vessel. When a vinous mash is heated to the boiling-point,
vapours are generated which consist essentially of alcohol and water; by condensing
these vapours there is obtained a mixture of alcohol and water.
Water boils at +100° C., barometer 760 mm.
Alcohol ,,+78.30 C.,
""
""
Thus it might be thought that while the boiling-point of water is 21'70° C. higher
than that of alcohol, it would follow that when a vinous mash is heated to 80° C.,
only the alcohol would be converted into vapour, the water remaining behind. But
this is not the case, for under all circumstances the boiling-point of a mixture of
alcohol and water is higher than that of pure alcohol alone, and the vapour formed
consists of both alcohol and water. The reason is partly due to the affinity of alcohol
for water, partly also to the fact that water evaporates at a lower temperature than
its boiling-point; the former (affinity) retains alcohol and prevents it to escape at
proper boiling-point (78.3°) in the shape of vapour. If the mixture of alcohol and
water be heated to its boiling-point (suppose 90° C.) much more alcohol will be con-
verted into vapour, because its boiling-point is lower, while of water only just so much
is evaporated as would be the case were it when pure to be heated to this temperature,
while simultaneously a current of air is passed through it, because the vapours of
alcohol evolved from the mixture act exactly in the same manner as would a current
of air carried through the mixture of alcohol and water, the former substance taking
up just as much water as will be volatilised at the boiling-point of the mixed liquids.
As the quantity of vapour evolved from a liquid bears a direct relation to the
temperature of that liquid, the quantity of aqueous vapours in the mixture of
vapours will increase according to the increase of temperature, until at last, as soon
as the boiling-point rises to that of water (= 100°) no more alcohol will be present in
the vapours which are given off. At the commencement of the distillation the vapour
given off contains much alcohol and very little water; presently more water comes
over, and finally only water. It is therefore quite evident that we cannot by distil-
lation separate alcohol at once from the rest of the volatile constituents of a vinous
mash liquor. By interrupting the distillation at the proper time, there is obtained
in the distillate all the alcohol contained in the mash along with a certain quantity
of water, while the residue of the distillation will not contain any trace even of
alcohol. The liquor obtained by the first distillation is generally very weak alcohol,
and requires further rectification, as it is termed, to increase the proportion of
alcohol. This rectification (another process of distillation) may be continued till the
alcohol contains only a small quantity of water, which can only be eliminated by the
aid of such substances as have a greater affinity for water than the alcohol, which
retains that liquid very tenaciously. Anhydrous, or absolute alcohol, can only be
432
CHEMICAL TECHNOLOGY.
obtained by treating highly rectified alcohol with some substances which have a
great affinity for water, such as caustic lime, fused chloride of calcium, &c.; but
really absolute alcohol is never used on the large scale in industry. The first
portions of liquid obtained by the distillation of vinous mash are rich in alcohol, and
termed fore-run or first-run, while the last portions of the fluid yet containing alcohol
are termed after-run. A doubly-rectified alcohol contains 50 per cent. pure spirit;
but by means of rectification alone a stronger alcohol than of 95 per cent. cannot be
obtained. The residue of the distillation is called fluid-wash.
The Distilling Apparatus. A distilling apparatus as usually employed consists in its
simplest form of four parts, namely, the still or retort, the head or cap of the still,
the cooling apparatus, and the receiver.
I
The still or retort is generally constructed of sheet copper-more rarely of iron boiler-
plates. The shape of the vessel varies, but is generally a somewhat flattened cylinder, pro-
vided with a round opening of 12 to 14 inches in diameter, fitted with a collar about 1 inch
in height forming the neck, on which the cap or head is placed. The bottom of the still
is either somewhat bulged inwards at the centre or is quite flat. The residue of the
distillation is removed through a waste-pipe fitted with a stop-cock attached to the
bottom of the vessel. From the cap or head a pipe conveys the volatilised alcohol to the
receiver, while jutting obliquely from the top of the still is a pipe for the introduction of
the mash. The head carries the vapours from the still into the cooling or condensing
apparatus; although a simple tube might answer this purpose, it is preferred to make
the head of the stills large and wide, not only for the purpose of separating any particles
of mash which might happen to be carried off with the vapours of the boiling liquid, but
also to obtain a distillate richer in alcohol, because an increased surface is favourable to
the cooling of the vapours, whereby thus the aqueous vapour is first condensed; more-
over, large heads are advantageous in case, by a rapid evolution of vapours, the mash
might boil up (priming); roomy space in the head prevents then the liquid passing over
into the worm. Since the volume of the vapours decreases during the condensation, a
somewhat conically-shaped head would be the best form for this portion of the apparatus.
The cooling apparatus is not simply destined to convert the vapours carried into it from
the head into liquid, but it is also required that this liquid be so far cooled down as to
prevent at least as much as possible the evaporation of the distillate; the condensing
apparatus should not be too roomy; that is to say, there should not be too much
space for the vapours, because this would cause air to enter the cooling apparatus,
and this air, while mixing with the vapours of alcohol, carries off along with it some of
this fluid, thereby causing a loss of the fluid. It is also requisite that the cooling
apparatus be strongly made, yet at the same time so constructed as to admit of being
readily taken down for cleansing purposes and easily fitted up again; usually the cooling
apparatus-technically termed worm-consists of a series of spirally bent tubes made of
either block-tin or copper, seldom of lead; this apparatus is placed in a large wooden
or metal vat containing cold water, or as in the more recently constructed distilling
apparatus, cold vinous mash, which is thus made warm previous to being transferred into
the still, whereby of course a saving of fuel is effected.
Apparatus.
Improved Distilling However much the shape and details of construction of the apparatus,
with the aid of which strong alcohol can at once be obtained by one distillation, may
vary, these apparatus all agree in this respect, that the mixture of vapours of alcohol
on their way from the still to the condenser become continuously richer in alcohol, so
that on reaching the cooling apparatus strong alcohol is the result of the operation.
This result can be attained in two different ways, viz. :-
1. By causing the mixture of vapours to pass repeatedly through alcoholic liquids
formed by the condensation of the vapours first given off; when afterwards the
temperature increases in consequence of the continued rush of vapours into the
liquid, a new process of distillation begins, the vapours generated by it being far
richer in alcohol than when the first distillation took place (principle of rectification).
2. By so cooling the mixed vapour that the water only is condensed, the alcohol
passing on as vapour (principle of dephlegmation).
SPIRIT.
433
When, in former days (sixty to sixty-five years ago), it was desired to prepare
strong alcohol, a repeated process of distillation was adopted; this of course was a
costly affair both as regards consumption of materials, fuel, &c., and loss of time.
At the present day distillation apparatus are generally so arranged that by a kind
f dissociation of the mixture of vapours, alcohol of any desired strength can be at
Once prepared.
Most of the recent distillation apparatus may be considered to consist of the
following parts :—
1. The still or vessel in which the fermented mash is placed.
2. Two condensing apparatus, one of which serves as rectifier, while the other
completes the condensation of the products.
3. A dephlegmator in which the mixed vapour separates, a portion of the water
becoming condensed and a vapour richer in the alcohol being carried on; this latter
is carried into the cooling apparatus, while the former flows back into the still.
Among the many distilling apparatus employed in Germany for distilling fermented
potato mash, we propose to describe those of Dorn, Pistorius, Gall, Schwarz, and
Siemens.
Dorn's Apparatus. Dorn's apparatus, Fig. 233, consists of the still, A, the helm, B, which
acts as dephlegmator, the condensing apparatus, D, and between the still and con-
densing apparatus, a copper vessel divided by a partition into two compartments,
FIG. 233.

c and F, the upper of which, c, is termed the fore-warmer, the under, F, the recti-
ficator. Connected with the helm is a small condenser, n, for the purpose of taking
an occasional sample of the distillate which passes over. The fore-warmer is filled
with mash to a level with the tube, o, and usually contains as much mash as is
necessary to fill the still. With the help of the revolving arms, xx, the mash is
from time to time kept stirred, and thus equally heated throughout to about 85° by the
vapour passing through the pipe, i i, from the still. When the distillation is finished
the wash (waste residue) is run off by opening the tap a, the still being re-filled with
mash from the fore-warmer. As soon as the distillation commences the vapour is
condensed in the worm, i i, the condensed fluid flowing into F. When the steam is
no longer condensed in i, which occurs as soon as the mash has reached a certain
temperature, the vapours pass over into the low wine, which thus becomes rapidly
29
434
CHEMICAL TECHNOLOGY.
FIG. 234.
πν
small cooling apparatus, K, to test the quality of the mash, and in order to
ascertain whether it contains any more alcohol. When the distillate collected at n
is found to be only water the operation is finished. The wash is run off from the
still, and it is then re-filled with fresh mash from the fore-warmer through 1, and
S
10
heated to the boiling-point. By this means a second distillation is effected, really a
rectification, the vapour or steam from which passing by the tube, y, is carried to the
worm, z z, placed in the condenser, D, and having been converted into a fluid flows
off at p. The distillation is continued until the fluid which comes over (the distil-
late) contains only 35 to 40 per cent of alcohol; a sample is then taken at the

SPIRIT.
435
the distillation again proceeded with. The low wine contained in the vessel F flows
through the tube j or q back into the still. As may be seen in the cut, Dorn's appa-
ratus has not a separate dephlegmator and only one still or retort. This apparatus
is now rarely used for distilling mash, but frequently for rectifying spirits.
Pistorius's Apparatus. Pistorius first introduced in Germany a distilling apparatus
fitted with two stills ingeniously connected with rectificators and dephlegmators.
When a distilling apparatus is required which not only extracts all the alcohol from
the mash, but also produces the alcohol in a very pure and concentrated state,
performing this work with the least possible expenditure of fuel and labour,
Pistorius's apparatus answers the purpose admirably. A and B, Fig. 234, represent
the two stills. A is the main still, which is either placed on a furnace and heated
directly by fire or by means of steam. Heating by steam-pipes instead of direct
firing possesses many advantages. The second still, в, is placed at a somewhat
higher level than the first, and when not heated by steam-pipes is situated
on the flue of the furnace fire of the first still. The main still, A, is fitted with a
large helm, D, fastened on the still with bolts and nuts. p is a tube projecting from
the helm and provided with a safety valve which opens inwards, in order to give
access to air as soon as towards the end of the distillation a vacuum might ensue in
the interior of the apparatus in consequence of the condensation of the vapours.
There is also connected with this tube, p, a small condenser, q, as in Dorn's
apparatus, from which samples showing the progress of the distillation may be taken.
In both stills stirring apparatus, m and n, are fitted to prevent the mash burning.
By the tube x the vapour of the "low wine" is admitted to the second still, the
mash-still. From the helm, F, of the mash-still a curved pipe, s, conveys the vapour
to the mash fore-warmer, which, as in Dorn's apparatus, is divided into two parts, the
upper, E, containing the mash, the lower, g (the "low wine" cistern); the vapour
ascending along the narrow passage, v, to the rectification apparatus, H. Frequently
the vapour is conveyed to a third still before entering g; this still is not shown in the
drawing. The rectification apparatus, H, consists of two or three conically-shaped
vessels, made of sheet-copper and connected together, and is provided with a cistern
filled with water, w; it is connected with the condenser, R, by the tube c. The
tube x conveys cold water to the rectification apparatus, and the short tube, y, does
so to the fore-warmer. The pump, r, is employed to pump the mash from the
cistern, L, to the fore-warmer; thence it is carried to the second still, and thence
again to the first still. When both stills and the fore-warmer are filled with mash,
the fire is lighted under the first still. The steam or vapour from the mash in a
passes to the mash in B, which is thereby heated to the boiling-point. The still B
serves, therefore, the purpose of a rectificator. When the distillation has begun, the
vessel, w, on the rectificator is filled with cold water, which is re-supplied when it
has become warmed by the passing vapours. As soon as the steam reaches the upper
rectificator, the real distillation commences. The condensed fluid drops into a
cistern in which a hydrometer is placed.
Gall's Apparatus. In most apparatus for distilling from a vinous mash the distillate
becomes gradually weaker and is not throughout of the same strength. Gall and
Marienbad have endeavoured to avoid this defect in their apparatus, Figs. 235 and
236, so as to obtain a more uniform product during each distillation. Two stills are
placed in a suitable manner in a steam-boiler and the stills are connected with the
separator (low wine cistern). BB are the stills; c is a boiler with flues, i i.
436
CHEMICAL TECHNOLOGY.
the stills, in order to prevent them cooling, are fixed into the boiler; D is a third
still placed on, not in, the boiler; E is the low wine cistern; F and G two dephleg-
mators or separators; a is a condenser with a worm, H. The mash is put first into
the still ▷ by means of the tube a a, this still serving as a fore-warmer and recti-
ficator. From this still both the stills в в are filled. From the boiler a current of
steam is conveyed through the bent tube, b, into the three-way-cock, c, whence the
steam is either passed into one or both the stills B B or is conveyed upwards by the
tube d to the vessel destined to steam the potatoes. The vapour from one or both of
the stills B B proceeds to the still D, and thence into the low wine cistern, E, and
passing through the dephlegmators, F and G, finally enter into the condenser. The
FIG. 235.

peculiarity of Gall's apparatus consists in that by the peculiar arrangement of
tubes and stop-cocks, each of the two stills may at will be brought into action, it
being possible to turn the steam at pleasure into the right-hand still, and next
into the left-hand still, or vice versa. Each still may be also disconnected, the
wash therefrom discharged and re-filled without in the least interrupting the
working of the other portions of the apparatus; the distillation can therefore
proceed uninterruptedly, one part of the apparatus being filled while the other is
at work.
Schwarz's Apparatus. Schwarz's apparatus is in very general use in the south-west of
Germany. It consists, Fig. 237, of the steam boiler, D; two mash stills, A and B; the
SPIRIT.
437
fore-warmer, c; the "low wine" cistern, or receiver, E; the rectificators, H and F; and
the condenser, G. M is a reservoir for cold. N one for hot water. The steam generated
in the boiler, D, passes through the pipe, g, into the under compartment, a, of the
double still, through the mash contained there; becoming mixed with vapours of
alcohol, it arrives in the helm, z, and further makes its way by means of the tube u
into the upper part of the double still; thence after a double rectification it is
conveyed by means of the tube t to the fore warmer, c; the upper part of this
vessel provided with the tubes aaa acts as a dephlegmator or separator, the con
densed fluid flowing into E.
The steam which arrives from the upper part of the
still passes through E, and thence by way of the tubes aa into the helm, and
the tube n, which latter is surrounded with the vessel н kept cold by means of cold
FIG. 236.

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water; the dephlegmation continues here. From н the steam passes through v to r,
an apparatus corresponding to the fore-warmer, c, but of smaller dimensions;
because here the quantity of vapour has become greatly reduced while it has become
richer in alcohol. The dephlegmator tubes are here surrounded by cold water, not
ly cold mash, the former liquid being constantly renewed so as to keep cold. The
steam or vapour collected in the helm, b, is sufficiently laden with alcohol to
admit of being at once conveyed to the condenser, G, the condensed distillate flowing
out at i. The vinous mash is first poured into the fore-warmer, c, wherein it is
438
CHEMICAL TECHNOLOGY.
occasionally stirred by the arms, dd, and crank, d, so as to keep it uniformly mixed
and heated. When the mash has become warm it is conveyed into the upper com-
partment of the double still by the pipe, e, and into the lower compartment through
the open valve; this compartment also serves as cistern for the phlegma from all
other parts of the apparatus; the fluid flows backwards from the compartments h and l

FIG. 237.
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of the rectificators, H and F, by way of the tubes m' and n, into the low wine cistern, E,
thence into the upper compartment of the double still, where it mixes with the mash.
As soon as the mash has given up all its alcohol, which can be ascertained by testing
the inflammability of the vapour issuing from the test stop cock, o, the residue is
SPIRIT.
439
removed by opening the tap, p. By means of the tubes qqq the rectificators and
condensing apparatus are supplied with cold water. The warm water from the con-
denser is conveyed by the tuber into the boiler. By means of R, the steam can be
admitted to the potato vessels, and by s into the reservoir N, when it is desired to
heat the water it contains to the boiling-point. Schwarz's apparatus possesses the
advantage of being easily taken to pieces and cleansed. But, on the contrary,
among its disadvantages are the following:-the construction of the mash-warmers is
not quite suited for the purpose, while also the condensed liquid in E is not brought
sufficiently into contact with the hot steam to affect a thorough distillation or rectifi-
cation. The steam passes so quickly through the liquid that it is only very
FIG. 238.

CLEVERDA
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A
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AVAMIWANAWAY
MAWAKAWAYANWAMY
AWW
imperfectly deprived of its water (dephlegmated) when it reaches the dephlegmation
apparatus, where it will consequently be but imperfectly rectified, while the vertical
steam-pipes offer too few points of contact, and allow much steam to pass off with-
out being fully condensed; while even the partly condensed vesicular steam is
carried off along with the condensation escaping steam. The condenser itself is
imperfect, being constructed of a number of vertical pipes, through which the con-
densed liquid rapidly falls without becoming quite cold, and in order to obtain a
sufficient condensation an immense quantity of cold water has to be used.
440
CHEMICAL TECHNOLOGY.
Siemens's Apparatus. Among the apparatus capable of producing a large quantity of
spirits at a small cost is that of Siemens. This apparatus is much used in the dis-
tillation of brandy. It consists, Fig. 238, of two mash-stills set in a boiler, and
capable of being alternately used (by means of the three cocks, a, b, and c), in the
same manner as in Gall's apparatus, while the fore-warmer and dephlegmator is
constructed according to Siemens's plan. L is the boiler; P one of the mash-retorts;
K is the low wine receiver; R the fore-warmer; A, a reservoir in which the condensed
water intended as feed water of the boiler is collected; c is the dephlegmator; в a
reservoir for the vapours condensed in c. From the dephlegmator the vapour
passes to a condenser not shown in the engraving. This apparatus is constructed of
such dimensions that it can perform the work about to be mentioned. The
boiler has to steam about 5000 kilos. of potatoes in four lots, during from 40 to
45 minutes each, and should thus be capable to yield in three hours the fifth
part of the weight of the potatoes = 1000 kilos., or in one hour 333 kilos. of
steam, which renders necessary a steam-generating surface of about 11 square metres.
But since the distillation requires steam also, this generating surface has to be
increased by about 20 per cent, and should consequently be 13.5 to 14 square metres.
The size of the mash stills should be sufficiently large to contain with ease 500 litres
when properly filled; because, as already stated, the fluid from a is not returned to
the still but to the steam-boiler, the stills being set into the last-named vessel not
becoming externally cooled, whereby the quantity of water carried along with the
vapours of spirit is compensated for.
The mash warmer consists of a cylindrical portion, i i, the lower part of which
has an indentation, c. In the cylinder is placed a narrower portion, o o, of the real
mash-containing vessel fitted with the heating tube, ƒ n. The upper part of the
fore-warmer is fitted to the lower part by means of the flange, hh. r is a stirring
apparatus, which is frequently set in operation during the process of distillation.
The vapours from the second still are carried into the depression, c, under the fore-
warmer, which in order that the vapours may come into contact with the phlegma is
covered with a sieve. The vapours surround the under part of the mash reservoir
and enter into the tube, f, through which they pass to the lower cylinder of the
dephlegmator. The condensed water of the dephlegmator is conducted into the
reservoir, A. The upper and under part of the fore-warmer are made of cast-iron,
but the interior bottom and heating surfaces are made of copper. This kind of
fore-warmer has the advantage of uniformly distributing the heat, while it can be
easily cleansed. The dephlegmator, c, is so contrived that the rectified vapour can
be conveyed to the condenser by two separate pipes placed in an opposite direction
to each other, and are joined again in close proximity to the condenser. The
remainder of the details will be seen on studying the drawing.
Apparatus.
Continuous Distilling Among the distilling apparatus intended for the distillation of
wine (not of mash), and so constructed as to be fit for continuous working, we
must not neglect to mention the apparatus of Cellier-Blumenthal, as improved
by Derosne, and represented in Fig. 239. This apparatus consists of two stills,
A and a'; the first rectificator, B; the second rectificator, c; the wine warmer and
dephlegmator, D; the condenser, F; the regulator, E;
a contrivance for regu-
lating the flow of the fluid wine from the cistern, G. The
well as the still A is filled with wine, acts as a steam boiler.
still A', which as
The low wine
SPIRIT.
441
vapours evolved come, when they have arrived in the rectificators, in contact
with an uninterrupted stream of wine, whereby dephlegmation is effected; the
vapour thus enriched in alcohol becomes still stronger in the vessel D, and thence
FIG. 239.

K
2
F
B
ESTELA DEMASSVIK KAN DIBUNUH
ISTULAR KITALET LINTISI SLEDITII
arrives at the cooling apparatus, F. In order that a real rectification should take
place in the rectificators, the stream of wine should be heated to a certain
temperature, which is imparted to it by the heating of the condenser water.
442
CHEMICAL TECHNOLOGY.
The steam from the still A' is carried by means of the pipe z to the bottom of
the still A. Both stills are heated by the fire of the same furnace. By means
of the tube B' the liquid contained in the still a can be run into the still A'. The
first rectificator, в, contains a number of semi-circular discs of unequal size, placed
one above the other, and which are so fastened to a vertical centre rod that they can
be easily removed and cleansed. The larger discs, perforated in the manner of
sieves, are placed with their concave surfaces upwards. In consequence of this
arrangement the vapours ascending from the stills meet with large surfaces moistened
with wine, which, moreover, trickles downwards in the manner of a cascade from
the discs, and comes, therefore, into very intimate contact with the vapours. The
second rectificator, c, is fitted with six compartments; in the centre of each of the
partition walls (iron or copper plates) a hole is cut, and over this hole by means of a
vertical bar, is fastened an inverted cup, which nearly reaches to the bottom of
the compartment wherein it is placed. As a portion of the vapours are condensed
in these compartments the vapours are necessarily forced through a layer of low
wine, and have to overcome a pressure of a column of liquid 2 centimetres high.
The fore-warmer and dephlegmator, D, is a horizontal cylinder made of copper
fitted with a worm, the convolutions of which are placed vertically. The tube м
communicates with this worm, the other end of which passes to o. A phlegma
collects in the convolutions of this tube, which is richer in alcohol in the foremost
windings and weaker in those more remote: this fluid collecting in the lower part
of the spirals may be drawn off by means of small tubes, thence to be transferred at
the operator's pleasure, either all or in part, by the aid of another tube and stop-
cocks to the tube o, or into the rectificator. By means of the tube L the previously-
warmed wine of the dephlegmator can be run into the rectificator. The condenser, F,
is a cylindrical vessel closed on all sides, and containing a worm communicating
with the tube o. The other end of the condensing tube carries the distillate away.
On the top of this portion of the apparatus the tube K is placed, by means of
which wine is run into the dephlegmator. The cold wine flows into the cooling
vessel by the tube 1. When it is desired to work with this apparatus, the first
thing to be done is the filling of the vessels A and A' with wine. The stop-cock, E.
is then opened, whereby the tube J, the condenser, F, and the dephlegmator are filled
with wine. The wine in the still a' is next heated to the boiling-point; the steam
enters the tube z and is condensed in A until the wine here is heated to the boiling-
- point by the combined effect of the steam and the hot gases circulating in the flue.
The low wine vapour then passes to the rectificator, B, and thence into the worm of
the dephlegmator, D, where the greater portion of it is condensed, the phlegma flowing
backwards into the rectificator As soon as the fore-warmer is so far heated that the
hand cannot be kept in the hot wine, the stop-cock of the vessel E is opened, and
the distillation commences. The wine which is conveyed by the tube 3 into the
cooling vessel, F, soon begins to become hot, and is then conveyed to the fore-
warmer, where its temperature becomes nearly as high as the boiling-point; by
means of the tube L this fluid is conveyed into the rectificator, B, and thence into
the still A.
As soon as the wine in the still a' contains no more alcohol, the stop-cock, fitted to
the lower part of the vessel is opened, and the vinasse run off at R, the still being
re-supplied by opening the stop-cock, B'. The vapour proceeds in the same
way, but in a reversed direction; when the vapour has been condensed in F it is
SPIRIT.
443
first collected, as alcohol, in the small vessel, N, provided with an areometer, and
thence conveyed to the cistern, H. The strength of the alcohol obtained by means
of this apparatus increases with an increase of the number of the windings of the
condenser placed in the dephlegmator and connected with the rectificator. Practical
experience decides, according to the alcoholic strength of the wines to be distilled,
and the quantity of pure alcohol desired in the distillate, the opening or shutting
of the various stop-cocks of this apparatus. Derosne's apparatus may be readily
made continuous; for this purpose it is only necessary to fill the reservoir, conden-
sing apparatus, and rectificator with cold water, while the lower portion of the tu be L
is closed.
Laugier's Apparatus.
Laugier's apparatus, shown in section in Fig. 240, is also of great
interest. Notwithstanding the fact that Derosne's apparatus is exceedingly com-
mendable for great economy of fuel, rapidity of distillation, and excellence of product,
FIG. 240.

་
B
m
500úinn
the apparatus is rather of a complicated construction, because it is arranged to
distil all kinds of wine, be they weak or strong, while at the same time alcohol of
any desired strength may be obtained. Apparatus of the construction of Laugier's,
arranged for the distillation of one kind of fluid, wine or mash, and for the pro-
duction of a distillate which is always of the same strength of alcohol, may be
far more simply constructed. The fluid to be distilled flows from the tube, s,
into the funnel, p, thence into the vessel A, entering its lower part and serving to
444
CHEMICAL TECHNOLOGY.
14
condense the alcoholic vapour. From this vessel the warmed fluid passes
by means of the tuber into the lower part of the second vessel, B, where
dephlegmation takes place by means of a condensing tube. Thence the fluid
flows by way of the tube c into the second still, c, which is heated by the hot
gases evolved from the fire kept burning under the first still, D; in the still c the
fluid undergoes a rectification, and the vinasse flows by the tube e into the
still D.
M is the pipe conveying the hot vapour from D into c; the tube b conveys
the alcoholic vapours into the dephlegmator. By means of the tube d the phlegma
is conveyed into the still c; ƒ serves as a means of emptying the still D; g and h
are glass-gauging tubes for indicating the height of the fluid in the interior of the
still; the tube / conveys the non-condensed vapours from the dephlegmator into the
condensing apparatus; while i conveys the vapours formed in the vessel B into the
condensing apparatus. The alcohol condensed in the cooling apparatus flows, as is
exhibited in the cut, into a vessel, o, provided with an areometer to indicate the
strength of the fluid. The cooling apparatus of the vessel в consists of seven
compartments or divisions formed by wide spirals, each of which is at its lower
level fitted with a narrow tube, all of which are connected to the tube d, by way
C
B
E
FIG. 241.
F
G
M
D
L
K
of which the condensed fluids are
made to flow back into the still. By
properly regulating the boiling of
the liquid in the first still and by
adjusting the flow of wine, the
condensation of the vapours in the
dephlegmator can be arranged at
will, so that either brandy of 50
per cent or alcohol of above 80 per
cent be obtained.
Sometimes an apparatus of even
more simple construction is em-
ployed, in which the fluid to be
distilled is heated by a spiral tube,
through which high pressure steam
is made to circulate. Such an
apparatus is exhibited in Fig. 241.
A is a cast-iron or copper cylinder,
in which the fluid to be distilled
is heated by a spiral tube made
of copper; the inlet of this tube is at
b, and the outlet at a; by means of e
the vinasse, devoid of alcohol, is run
B is the dephlegmator, through
which the fluid to be distilled con-

off.
tinually flows in a downward direction, while the vapour of the low wine evolved in A
ascends uninterruptedly. In order to increase the surface and points of contact the
arrangement in the deplegmator is very different. The vapour ascends to the reservoir,
E, and by way of the tube F enters the rectificator, c, which is arranged as usual; the
condensed portion returning through н to the dephlegmator, while the uncondensed
vapour passes on to the condenser of the vessel D there to become condensed
1
SPIRIT.
445
Removing the Fusel Oils.
Defuseling.
and carried off through M. The fluid to be distilled is kept in a tank (not represented
in the cut) placed higher than the apparatus, being conveyed to the latter by way of
the tube L I fitted with the stop-cock к, so that the liquid arrives first in D, is next
conveyed to c, thence through & into the dephlegmator, and lastly into the cylinder.
It has been already mentioned (see p. 431) that in addition to
ethylic alcohol there are formed during vinous fermentation-under conditions not at
all clearly understood nor scientifically elucidated-larger or smaller quantities of
alcohols homologous with ethylic alcohol; such, as, for instance, propylic, butylic,
amylic alcohols, which, when mixed with larger or smaller quantities of complex
ethers, bear the name of fusel oil, a fluid which imparts to the ethylic alcohol (in
the shape of brandy, gin, whiskey, &c.) a very unpleasant flavour, also rendering
these spirits when crude very injurious to the human system. Fusel oil differs
according to the nature of the mash, potatoes, grain, and beet-roots being used
in its preparation. Fusel oil is formed in large quantity only when fermentation
takes place at a high temperature in a concentrated saccharine fluid, while no
tartaric acid is simultaneously present. A fluid which ferments at a low temperature
and is very dilute does not yield fusel oil, at least no amylic alcohol, which also is
never formed in such wines as have been fermented when tartaric acid has been
present in the fermenting fluid.
As it is a property of all fusel oils that they are less volatile than water and
alcohol, they are only condensed when brandy, gin, whiskey, &c., are distilled towards
the end of the distillation; while as regards the distillation of the alcohol these oils
are chiefly met with in the products of the condensation of the dephlegmators. A
portion, however, of the fusel oils comes over along with the alcohol, and being
Potato
very intimately mixed therewith is not readily removed from these fluids.
fusel oil is essentially amylic alcohol (C5H12O), a colourless, very mobile fluid
of o·818 sp. gr., of penetrating odour, provoking coughing, and of a burning taste;
it boils at 133°. By means of oxidising agents, such as manganate and per-
manganate of potash, a mixture of sulphuric acid and bichromate of potash, or
manganese as well as platinum black, amylic alcohol is converted into valerianic
acid (C5H1002). By the action of acids this amylic alcohol is converted into peculiar
kinds of ethers in the same manner as this effect is produced by acids upon ordinary
(ethylic) alcohol. Some of the ethers thus formed exhibit a highly agreeable
odour, and are therefore used in perfumery, and for the flavouring of sweetmeats,
bon-bons, &c.
As for many of the applications of potato-spirit the fusel oil is a disadvantage,
the spirit has therefore to be submitted to an operation of rectification whereby the
fusel oil is got rid of. The suggestions which have been made for this purpose refer
either to the destruction of the fusel oil by oxidation or the action of chlorine, or the
masking of the oil and its conversion into less disagreeable compounds; partly
also to a real removal of the fusel oil from the spirit. When the fusel oil con-
taining spirit is rectified over chloride of lime (bleaching-powder), permanganate of
potassa, &c., valerianate of fusel-ether is formed; but since the action of these
reagents is not limited to the amylic alcohol but extends to the ethylic, it is
very difficult to adjust the quantity of these reagents so that only the amylic
alcohol be acted upon.
If the spirits from which the fusel oil is to be re-
moved are treated with a mixture of sulphuric acid and vinegar, there is formed,
44б³°
CHEMICAL TECHNOLOGY.
-3
CHOO, of a pleasant fruity flavour.
besides some acetic ether, acetate of amyl, II
Hydrochloric and nitric acids, also used to remove fusel oil, act in a somewhat
similar manner. The most approved method of removing the fusel oil is by means
of well-burnt charcoal (vegetable charcoal, charred peat, bone-black), which, when
brought into contact with the crude spirit, absorbs the fusel oil mechanically. By
the aid of charcoal, spirits and brandy (not when obtained from wine), are purified
either in the state of vapour, or by digestion with the charcoal, and filtration at the
ordinary temperature of the air; rectification at boiling temperature over charcoal
is altogether unsuitable, owing to the fact that the fusel oil absorbed by the
charcoal is again readily dissolved at that temperature. The charcoal to be
employed is granulated and passed through a sieve in order to remove adhe-
ring dust. The granulated charcoal is placed in a copper cylinder, fitted at top
and bottom with a perforated plate or disc; this cylinder is connected with the
distilling apparatus between the dephlegmator and rectificator in such a manner that
the vapours pass through the charcoal. To roo litres of brandy to be purified 3 to 5
litres of granulated charcoal are generally required; this can be again employed after
f
f
A
FIG. 242.
Ꭺ.
having been re-burnt at a bright red heat. Falkman's
apparatus consists of a helm-shaped vessel, a, Fig. 242,
in which the perforated diaphragms, bbb, are placed;
upon each diaphragm a layer of charcoal, surmounted
with a cover, c, is placed. The apparatus is closed
with a hollow cover containing a layer of charcoal,
e dd. The vessel A is surrounded by a cooling appa-
ratus, which in the cut is represented by the cold water
tubes, fff, and the hot water (which becomes hot by the
passage of alcoholic vapours through A) tubes, eeee;
these serve the purpose of regulating the temperature
of the layers of charcoal.
Yield of Alcohol. The quantity of alcohol obtainable from
any given substance does not only depend on the rela-
tive quantity of the alcohol-forming constituents
(starch, dextrose, or cane sugar) of the raw material applied for the purpose
of distillation, but depends very largely also on the more or less suitable mode
of conducting all the operations of the spirit distillation (mashing, fermentation), in .
properly constructed apparatus. Leaving out of the question the small quantities
of glycerine and succinic acid formed by vinous fermentation, chemistry teaches
that:-

100 parts of starch
100
""
100
""
cane sugar
dextrose
yield 56.78 of alcohol.
53.80
5ΙΟΙ
""
""
Experience teaches that the yield of alcohol is in practice less than it should be,
premising that every 1 mol. of starch or sugar yields 2 mols. of alcohol; 100 parts of
cane sugar do not yield in practice the quantity of alcohol above indicated-viz. 53'8
parts, but only 51'L
SPIRIT.
100 kilos. of barley
give 44 64 litres of corn brandy at 50° Tralles.
100
100
barley-malt
wheat
""
54'96
49°22
99
100
""
100
rye
potatoes
45.80
18:32
""
99
potato spirit
447
6 litres (quart or maas) of brandy, from the metrical hundredweight (hectolitre, &c.),
is reckoned to yield 6 × 50=300 per cent alcohol; 7 litres, consequently, 350;
8 litres, 400. 8 litres at 48 per cent Tralles = 384 per cent alcohol. The number of
litres of brandy or spirit multiplied by the alcohol in percentage according to
Tralles therefore yield:-
I metrical cwt. of barley
44'64 X 50=2232 per cent alcohol.
54'96 X 50=2748
""
I
,,
""
I
barley-malt
wheat
""
""
I
""
I
rye
potatoes
49°22 X 50=2461
45.80 X 50
2290
18:32 X 50 = 916
""
"
""
Usually I Bavarian maas is taken as equal to 1069 litres, 1 Prussian quart = 1*145
litres.
In quoting the prices in the following foreign markets, it is usual to take as
a unit-
In Breslau
In Berlin
4,800 (60 quarts at 80°).
10,800 (200
In Magdeburg 14,400 (180
54°).
80°).
Recently it has become general to adopt as a unit 8000 (100 quarts at 80°).
Alcoholometry. For the purpose of ascertaining the quantity of alcohol contained in a
fluid which consists only of alcohol and water, the areometer, or alcoholometer, is
Areometer. generally employed. The vaporimeter and the ebullioscope (see p. 395)
are seldom used. The application of the areometer is based upon the principle that a
body immersed in a fluid (for instance, water) always displaces a quantity of water
equal to its own volume, and loses in weight proportionately to the quantity of water
displaced. It therefore follows, that by the depth to which the areometer sinks, as
noted by the degrees on the spindle, we can determine the quantity of absolute
alcohol contained in the fluid under examination. The areometer of Tralles and that
of Richter are most generally used in Germany. Stoppani's is similar to that of
Richter. Both are centesimal alcoholometers and show by the number of the degree
to which they sink the percentage of pure alcohol. The difference between these
two instruments consists in that the areometer of Tralles indicates percentage by
volume, and Richter's percentage by weight. Tralles's alcoholometer is much used
in the Zollverein (German Custom's Association, viz. of the various States constitu-
ting, with the exception of Luxemburg, the German Empire) for the purpose of
ascertaining the alcohol contained in spirituous liquors (at 14°44°R.); in Austria the
same instrument is used, with a difference, however, in the temperature at which
the observation is made, the degree of the thermometer being usually taken at
12' R. (= 15° C.)
The following table exhibits a comparison of both scales, and with the true
weight per cent, along with the corresponding specific gravity at a temperature of
15° C. :—
448
CHEMICAL TECHNOLOGY.
Sp. gr..
per cent.
0'990
4'99
0.981
II'II
ΙΟ
0'972
18.12
15
True weight
Approximate weight
per cent according
to Richter.
5
Percentage of
volume according
to Tralles.
6.23
13.73
22'20
o'964
24.83
20
30'16
o'956
29.82
25
36.50
0'947
35°29
30
42.12
o'937
40'66
35
48'00
o'926
46.00
40
53.66
0'915
51°02
45
58.82
0:906
54-85
50
62.65
0*899
60*34
55
67.96
0'883
64 79
бо
72.12
0872
69'79
65
76.66
0.862
74'66
70
80'36
0.850
78.81
75
84.43
0·838
83.72
80
88.34
0'827
88.36
85
91-85
0.815
92'54
90
95'05
0*805
96'77
95
97'55
0'795
99'60
100
99'75
The most usual alcoholometer is that which indicates the percentage of volume, or how
many volumes of absolute alcohol there are contained in 1oo volumes of the alcoholic
fluid. Brandy of 50° Tralles is therefore understood to be a spirit, 100 litres of which
contain 50 litres of alcohol; and from which by distillation these 50 litres of alcohol can
be extracted. Considering that when alcohol and water are mixed a considerable contrac-
tion and decrease of bulk is the result, it is clear that 50 litres of alcohol (absolute is here
meant) and 50 litres of water will only yield a mixture measuring 96 377 litres; and
accordingly 100 litres of such a fluid contain instead of 50 litres of alcohol, 51.88 litres of
that liquid.
Relation of Brandy The relation of the distillation industry to agriculture, and more
Distilling to Agriculture. especially as a means of providing fodder for cattle, is very interesting
and important. The distillation of spirits leaves a residue which may be usefully employed
as fodder for cattle; the distillatory process extracts from the starch-containing materials
which are employed only the alcohol which is formed in the mash by fermentation, but it
leaves behind in a concentrated state all the nutritive substances (especially albumen
compounds), which not being acted upon by the fermentation, are left in the residues in
almost the same state as they were originally present in the potatoes and grain made use
of by the distiller. It is evident that when the expenses of the production of the spirits
are paid to the distiller, the residues of the operation become a valuable material obtained
cost free, the production of which is an important item in this industry.
Viewed in the light of agricultural industry the preparation of spirits from potatoes
becomes in reality a chemical decomposition of the substances of which potatoes are com-
posed, and a product of a relatively far greater value, and more readily transportable
and preservable--viz., spirits and wash, and fodder material.
The Residue or Wash. The wash is a fluid in which starch, dextrine, pectin substances, pro-
tein compounds, fat, small quantities of sugar, husks of grain, succinic acid, glycerine,
salts, and some of the constituents of yeast are met with, partly in solution, partly sus
pended, while some of these materials are more or less decomposed and altered. The
quantity of dry substance only amounts to from 4 to 10 per cent; this is due to the
varying nature of the raw material, to the quantity of water used in mashing, and to
the unequal quantity of water absorbed by the fermented mash during the process of dis-
tillation.
SPIRIT.
449
Ritthausen analysed several varieties of wash with the following results, the proportion
of dry substance to the water being in (I.) as 1:73; in (II.) as 1:6; in (III.) as 1:4·08;
in (IV.) as 1:4; in (V.) as 1:3:-
I.
II.
III.
IV.
V.
Non-nitrogenous substances
2.78
3.23
3'08
4'14
5'31
Protein compounds
0.82
I'04
1.26
I'39
1'78
Cellulose
Ο 0'46
0'43
0'94
0.78
I'00
Ash
0'52
0'59
0'72
0'79
ΙΟΙ
Water
95'40
94.71
94'00
92'90
90'go
When in a distillery potatoes and malt are always used in equal quantities and of the
same quality, and the mash made at the same degree of concentration, the wash will
always be of nearly as possible the same composition. It may be assumed that, on an
average, three-fourths of the solid matter met with in the wash is nutritive; the
proportion of nitrogenous to non-nitrogenous matter is on the average as 1:3, while
in the potato it is only as 1:8. When the potatoes are converted into wash they lose
the greater part of their non-nitrogenous inatter, and thus become a fodder rich in
protein compounds. In practice, 150 to 250 kilos. of potato mash are considered
equivalent to 50 kilos. of hay.
Dry Yeast. By the fermentation of the beer-wort containing hops, yeast is pro-
duced in large quantities, and this is used in most cases when it is desired to induct
a vinous fermentation; but for some purposes, such as bread-making for instance,
this yeast is not applicable owing to its containing much of the bitter principle of
the hop, and therefore possessing a very disagreeable flavour. This bitter principle
may be removed by thoroughly washing with cold water, or, as recommended by
Trommer, by first dissolving the yeast in a solution of caustic alkali, and then pre-
cipitating it therefrom by means of dilute sulphuric acid; such proceedings, how-
ever, always impair the efficacy of the yeast as a ferment, and the additional amount
of time and labour required necessarily enhances the price of the yeast. The pro-
duction of yeast in breweries is, moreover, only a subordinate affair, the main
point being the preparation of beer of good quality. The production of yeast,
although it can only be obtained by vinous fermentation, is best combined with the
distillation of spirit, whereby, if desired, the preparation of dry yeast may be made
a principal, and the production of spirit to a certain extent a subordinate,
affair.
We have in a former portion of this work, while treating on fermentation in general,
explained the mode of formation and the nature of the yeast, and that this yeast has
been proved by experience to be best fed and most rapidly propagated by the gluter
and other protein compounds of the cereals in solution. Yeast may be made in various
ways. At Schiedam (Holland) it is made of excellent quality by a mode which is to
a certain extent a trade secret-and differs materially from the following process:-
A mash is made in the ordinary manner of 1 part of bruised barley malt with
3 parts of bruised rye, the mash being cooled with the fluid portion of the wash.
To 100 kilos. of the bruised grain is added o'5 kilo. of carbonate of soda and 0′35
kilo. of sulphuric acid diluted with water; these ingredients having been added to
the mash it is brought to fermentation by the aid of yeast. The newly-formed
yeast is removed from the strongly-fermenting fluid by the aid of perforated ladles
it is then strained through a linen cloth or fine sieve, and poured into cold water,
wherein it is allowed to form a sediment. The sediment thus produced is col-
lected after the supernatant water has been run off, is placed in a stout canvas
bag under a press, and formed into a stiff clayey dough, to which usually 4 to IC
30
450
CHEMICAL TECHNOLOGY.
(sometimes as much as 24) per cent of dry potato starch is added. Sometimes the
water is removed from the yeast by placing that substance upon slabs made of
gypsum or other absorbent materials, care being taken to keep the yeast in a
cool place; by the use of the hydro-extractor-expressly arranged as regards its
construction for this purpose-yeast may be very rapidly rendered dry. As regards
the use of the carbonate of soda, it appears to assist in the separation of the glu-
tinous constituents of the cereals; the action of the sulphuric acid is partly
similar, and it also prevents the formation of lactic acid, which, if formed, causes
a loss of bath starch and spirit; the sulphuric acid also accelerates the separation of
the yeast. According to communications by some of the most eminent distillers at
Schiedam to Dr. G. J. Mulder, neither soda nor sulphuric acid are used at
Schiedam in the preparation of what the trade terms dry or German yeast, some of
which is imported into this country from Hamburg. Assuming the researches of
Pasteur and others on fermentation to be correct, these observations are of great value
in reference to the manufacture of yeast. It is found that the yeast sporulæ become
properly developed when they are placed in a fluid which, instead of containing
protein compounds, consists of aqueous saline solutions mixed with a sugar
solution, such as, for instance-tartrate of ammonia, phosphate of potash, gypsum,
phosphate of magnesia. It would hence appear that under such conditions yeast
cells take up the material for the propagation of new cells, partly from inorganic
substances, partly from organic, viz., the decomposing sugar which yields
carbonic acid: in this respect the yeast cells agree, then, with higher organised
plants. As regards the quantity of yeast obtainable from a given weight of
materials, it may be stated that from 100 kilos. of rye, including the bruised malt,
about 15 to 16 kilos. of dry yeast can be obtained. As the quantity of real yeast
or of the nitrogenous matter for sale present in the ready prepared dry yeast amounts
at the most to 20 per cent, the nutritive value of the wash obtained after the dis
tilling off of the spirits from the fermented liquid is but little impaired.
So-called Artificial Yeast. We have yet to refer to what is termed artificial yeast, in reality
a substance only intended for transferring the fermentation of the wort or mash in
activity to-day to a fresh batch to-morrow, so that it bears the same relation to the
spirit preparation as leaven does to bread-baking. There are a great number of
recipes for the preparation of artificial yeast and of artificial fermentation-inducing
substances; as far as these are known they may be brought to the following cate-
gories:- 1. A small quantity of fully and strongly fermenting mash is mixed with
fresh mash. 2. A small quantity of the fluid portion of the fermenting mash
is cautiously drawn off by the aid of a syphon, and this portion having been set
into fermentation, is added to the freshly made mash of the next day. 3. As soon
as in the last-made mash the fermentation is strongest and most active, a small
quantity of the ferment (yeast) separated from the fluid, and floating on its surface, is
mixed with freshly made mash, the temperature of which has been purposely made
sufficiently high to start the fermentation. The mash thus prepared may be used after
a few hours to induce fermentation in a freshly made mash. A really artificial yeast,
that is, yeast only prepared for the purpose of obtaining that substance by itself and
independent of either brewing or distilling, is made in various ways, but always by a real
process of fermentation. As an excellent instance of this mode of preparation, we quote
the mode of preparing Vienna yeast :-
Vienna Yeast. This yeast is prepared in the following manner :-Previously-malted
barley, maïs, and rye are ground up and mixed, next put into water at a temperature of
65° to 75°; after a few hours, the saccharine liquid is decanted from the dregs, and
the clear liquid brought into a state of fermentation by the aid of some yeast. The
fermentation becomes very strong, and, by the force of the carbonic acid which is evolved,
the yeast globules (the size of which averages from 10 to 12 m.m.) are carried to the
BREAD.
451
surface of the liquid, and, forming a thick scum, are removed by a skimmer, then placed
on cloth filters, drained, washed with a little distilled water, and next pressed into
any desired shape by means of hydraulic pressure, and covered with a strong and well
woven canvas. This kind of yeast keeps for eight to fourteen days according to the season,
and is, both for bakers and brewers, very superior to that ordinarily used; the extra good
qualities of Vienna beer and bread are partly due to the use of this yeast in preparing
these articles.
Duty on Spirits.
In the original work a couple of pages are devoted to an uninteresting
discussion on this subject, which, as might be expected, has been treated not from a
general point of view but from one bearing upon conditions which are altogether
different from those existing in this country. There can be no doubt that a duty
on spirits is a very excellent thing; indeed, in this country this tax brings in such an
enormous sum as to lead to the inference that spirits are consumed in larger quantities
than is consistent with healthy conditions of body and social comfort.
BREAD BAKING.
Modes of Bread Making. The preparation of bread aims at the production in the flour
obtained by grinding up the cereals of such a chemical and physical condition as
will tend to render it most readily masticated by the teeth, and after having
been duly mixed with saliva in the mouth, digested by the juices of the stomach.
When flour is mixed with water so as to form a dough, and this mixture dried at the
ordinary temperature of the atmosphere, a kind of cake is obtained which contains the
starch unaltered and in an insoluble state, so that this kind of cake is very difficult
to digest, while, moreover, its taste is so unpleasant as to create no appetite.
Again, if the cake is dried at the boiling-point of water, it becomes like a dried
starch paste, which is also very difficult to digest. When this temperature only acts
upon the surface of such dough, and does not penetrate into the interior, the resulting
cake will be a mixture somewhat similar to ship's biscuit, which may always be
considered as a strongly-dried dough, and although it may be preserved for almost
any length of time, it is far less digestible than bread. The object of the baking
process is to impart to the dough so high a degree of heat as to render the starch
soluble, while it is further desired to form a light spongy mass, instead of a
brittle or watery paste; the heat should be strong enough to torrify and roast the
outer surface of the bread mass to such an extent as to form a deeply coloured
crust, whereby not only the taste of the bread is greatly improved, but it can
also be kept in good condition for some time. The usual means of rendering
dough spongy is by vinous fermentation set up by the addition of a ferment, this
being either leaven or yeast; a small portion of the starch of the flour is thus
converted into glucose, which is then decomposed, yielding alcohol and carbonic acid
gas; the latter, while trying to escape, is prevented from doing so by the toughness
of the dough, which is thereby rendered spongy.
The alcohol is of no consequence whatever. White bread is prepared with
wheaten flour and yeast; rye meal or a mixture of rye meal and wheaten flour with
leaven, yields "black" or rye bread. Heeren found that flour in the state in
which it is usually applied for bread baking contains an average of 13 per cent
moisture.
The Details of Bread Baking. The raw materials employed in the preparation of bread are
flour, water, and a ferment, salt, spices, &c., are also used. The composition of the
most important kinds of flour and meals is as follows:-
452
CHEMICAL TECHNOLOGY.
a.
b.
C.
d.
Water
Albumen
Vegetable glue
Casein
Fibrin
Gluten
Sugar
Gum
...
...
...
15'54
14.60
14'00
11.70
:
I'34
1'56
I'20
1'24
1'76
2.92
3.60
3.25
0'37
o'90
I'34
O'15
:
...
5 19
7.36
8:24
14.84
Fat
Starch
Sand
...
:
:
:
:
:
:
3'50
2.33
3:46
3'04
2.19
...
6:25
4'10
6°33
2.81
1'07
63.64
1.80
2.23
567
64.28
53 15
58.13
6·85
a. Wheat flour. b. Rye meal. c. Barley meal. d. Oatmeal.
In addition to these kinds of meal, those derived from zea-maïs (Indian corn)
beans, peas, &c., are occasionally employed for making bread.
The principal phases of the preparation are :—
and the Kneading.
The Mixing of the Dough 1. The mixing of the flour with water is the first manipulation
of the baking process. The object of this operation is first to render dextrin and
sugar (owing to the action of the gluten upon the starch, the quantity of sugar
becomes increased while the mixing process is going on) and some albuminous
substances soluble, and next to mix the solution thus formed thoroughly with
the starch and gluten of the flour, and to soak and somewhat dissociate these
substances; dry yeast or leaven are at the same time added to the bread mass, the
former ferment being used when it is intended to make white; the latter when
black bread is desired to be made.
•
By sour dough or leaven is understood that portion of the already fermenting
dough which is set apart and kept for the next baking operation; it consists of a
mixture of flour and water, in which a portion of the starch is converted—
partly into sugar, which is again changed by vinous fermentation, and acetic
acid-but chiefly into lactic acid, by a process of fermentation set up by the
peculiar conversion into active ferments of the protein compounds of the flour
itself. Leaven therefore acts as a fermentation-producing substance in a fresh
batch of dough, its action being similar to that of yeast, or of already fermenting
wort when added to a freshly made wort. After a length of time the leaven
becomes putrid and unfit for use as a ferment. As regards the quantity of leaven
to be used with the dough nothing definite can be said, since it depends as
much on the degree of sourness of the leaven as on the quality of the bread in-
tended to be made; usually 4 parts of leaven are added to 100 parts of flour, or to
80 parts of bread 3 parts of leaven. In the case of white bread, 100 parts of flour
require 2 parts of dry yeast. The mixing of the flour is effected with lukewarm
water, at a temperature of from 21° to 37°.
Kneading The thin dough obtained from flour, water, and ferment, is dredged over
with dry flour, and placed in a warm situation for a time, generally during the
night. Fermentation is thus set up by the action of the ferment upon the dextrose
of the dough, the carbonic acid developed rendering the dough spongy. The
BREAD.
453
sponge thus prepared, is next mixed with more flour to bring it to the consistency
required for the baking, this operation being known as the kneading of the
sponge. The method usually employed in these operations is that one-third of
the total quantity of flour required for a batch is mixed first with water and
ferment, and when this mass has come into full fermentation, the two other thirds
of flour are kneaded up along with the sponge, sufficient water being added to
form a normal dough. After the kneading operation the dough is again dredged
over with some dry flour, and left in a warm situation for the purpose of becoming
thoroughly spongy for this continued fermentation only about half the time is
required as for the first-mentioned fermentation. In most bakeries, however, this
second fermentation is not proceeded with, but the dough is, immediately after
having been kneaded, cut up and shaped into loaves.
By means of the kneading the dough becomes squeezed together, and has, there-
fore, again to be left in a warm situation for further fermentation, during which
it heaves up and increases to double its size. The dough is generally put either into
a basket or tied in a stout cloth, which is previously dusted over with bran to
prevent the pasty mass adhering to the cloth. The bulk of the dough increases
twofold. When rye bread is made, the dough is frequently moistened on its
external surface with lukewarm water, applied by the aid of a brush, in
order to prevent cracks in the outer coating of the dough by the evaporation
of the water; just before putting the loaves into the oven this brushing over
with water is repeated. The water softens the outer surface of the dough,
and dissolves some of the dextrine it contains, which substance, after the evapo-
ration of the water from the surface, remains as a glaze upon the crust of this
kind of bread. When the loaves have risen sufficiently and exhale a vinous
peculiar odour, it is time to commence the baking process. Since the bread loses
considerably in weight during the baking, the baker must proportion so much dough
to each loaf before baking as will yield the legal weight of the baked bread. The
weight of dough to be proportioned to a loaf of a certain fixed weight varies
according to the size of the loaf, but increases comparatively with decrease in the
size of the loaf. The dough generally loses in baking about 25 per cent of its
weight. The smaller the loaf, the more crust in proportion to crumb; and since the
crust contains less moisture, and, consequently, weighs less than the crumb,
the loss of weight is greater in a small than in a large loaf.
Kneading Machines. The kneading of the dough by hand is not only very heavy
work, but is unhealthy and objectionable on account of being unclean; the
uniform quality of the dough is, moreover, by no means to be depended upon.
Although it is impossible to perform by machinery any labour which absolutely
requires the touch of the human hand, bread-kneading machines have been
introduced wherever the making of only one and the same kind of bread is
required. Among the numerous kinds of machines invented for this purpose we
select for description that of Clayton (see fig. 243.) The constituents of the dough
are placed in the cylinder, a, mounted in the framework, b b, and provided with
hollow axles, c and d, turning in their bearings at e. The interior of the cylinder is
fitted with the framework, f, which may be made to revolve by aid of the axles g and h.
The two halves of this framework are connected together by the diagonal knives, ii,
which, when the machinery revolves, work up the dough; the trough or outer
cylinder revolves in the opposite direction to the revolution of the framework. The
454
CHEMICAL TECHNOLOGY.
P,
crank, o, is connected with the axle of the trough or outer cylinder; the crank,
with that of the inner framework. As the two cranks are turned in opposite
directions they impart opposite movements to trough and framework. The revolving
FIG. 243.

m
ད་་་་
of the machinery may be performed by one man by the aid of one crank, since the
axle, h, of the crank, o, which is fitted to the inner frame by means of the hollow
axle-tree, and revolves along with it, carries a conically-shaped wheel, m, fitted to
the wheel k, which being connected with 7 causes the trough also to revolve; when,
therefore, the wheel m turns towards the right, the wheel t will revolve towards
the left.
The Oven.
The conversion of the prepared dough into bread by baking is effected
in an oven, ordinarily a circular or oval hearth or furnace, spanned by a vault,
constructed with an opening at one end termed the mouth, serving alike for the
introduction both of bread and of the fuel. The oven is built of bricks cemented
together with fire-clay, the sole of the hearth being laid with tiles or lined with
fire-clay. The vault is usually elliptical, in order to reflect the heat as much as
possible. The mouth is closed with a door made of boiler-plate or of cast-iron;
and as the mouth also serves as an exit for the smoke, a flue is constructed at some
short distance above it, and made to communicate with the chimney. Two small
openings in close proximity to the mouth of the oven serve to burn therein small
pieces of wood to afford light, while the bread is being placed in the oven. The air
necessary for the combustion of the fuel enters the oven from the lower part of the
mouth, while from the upper the gases of combustion and the smoke escape.
It is preferable, however, to construct these ovens with a separate flue and
chimney communicating with another part of the vault, and to fit the flue with a
damper to regulate the draught of the fire. Fig. 244 exhibits the vertical sec-
tion, and Fig. 245 the plan of the sole of a baking oven. The sole, A, which
is made so as to slope upwards towards the back of the oven, has a breadth
of 3.1 metres, and a depth of 4 metres; it is spanned by a vault o˚5 metre
high. The mouth is o'8 metre wide. eee are the flues through which the gases
of combustion pass into the chimney, D, the draught being regulated by means of
the damper, u. The trench, x, affords standing-room for the baker. Under the oven
is a chamber serving as a store-room for the coal. The space E serves as a hot
room wherein the bread is placed previous to being put into the oven in order that
the dough may rise. Thoroughly dried wood is used as fuel; it is placed cross-
wise upon the hearth. Coals are used in England as fuel for this purpose. The
BREAD.
455
oven has reached the required temperature, when a piece of wood rubbed on the
hearth gives off sparks. The glowing charcoal is removed through the mouth of
the oven, and extinguished in the lower chamber. Before the bread is put into the
oven the sole is carefully cleaned with a wet swabber fastened to a pole, and ash and
FIG. 244.

B
76.
FIG. 245.
cinders having been removed the bread is put into the oven with the aid of an
oven-shovel, fixed to a very long handle. The proper temperature of the oven for
baking is between 200° and 225° C. Before the loaves are put into the oven they
are brushed over with water wherein a small quantity of flour has been mixed, in order
to prevent the crust of the bread formed by the first action of the heat flying off
and cracking by the rapid expansion
of the vapours formed by the heat
to which the bread is exposed. The
steam, which after some time fills
the oven, materially assists the
baking process, and very greatly
aids the chemical changes which
are especially apparent in the crust,
which owes its glazed appear-
ance thereto. The time necessary
for the baking varies according to
the size of the loaves, the form,
and the kind of bread. The nearer
the bread approaches to a globular
form, and its surface therefore
relatively smallest in relation to its contents, so much the longer time is
necessary for the baking. Black bread takes a longer time to bake than white
bread. These ovens are, however, not of the best construction: it is evident
that they cannot be uniformly heated throughout, while they cool unequally also, and
of course most so at the front part by the rushing in of cold air. After every batch
of bread baked it therefore becomes necessary to fire the oven again for a short time

456
CHEMICAL TECHNOLOGY.
before a fresh batch of bread is put into it; of course less fuel is required to bring
up the requisite temperature again than will be required when firing is commenced.
When the baking of bread is carried on continuously and on a manufacturing
scale, ovens are employed in which the baking- and the fire-rooms are separate and
distinct.
Substitutes for the Ferments. Substitutes for the Ferments in the "Raising" of Bread.-We
have seen from the preceding details that the preparation of bread is essentially
based upon the fact that by the act of fermentation the gluten of the flour forms a
kind of cellular tissue by which the escape of the carbonic acid is prevented, and thus
the bread rendered porous and spongy, whereby its digestibility is increased.
This
quality of the bread is obtained at the cost of a portion of the starch of the flour,
which is first converted into starch-sugar, and then by means of fermentation into
alcohol and carbonic acid gas; to the expansion of the latter the bread owes its
spongy texture.
Many attempts have been made for the purpose of effecting
the "raising" of the bread, as it is termed, without the use of a ferment, by
introducing into the dough some gas or vapour-producing substance, which
would have the same mechanical effect at least as the carbonic acid derived from
the fermentation. Although the problem of preparing bread of good quality without
the aid of fermentation cannot be said to be quite settled, many proposals have
been made in this direction, and some of these deserve notice; we therefore quote
the most important. When sesquicarbonate of ammonia (the so-called sal cornu
cervi of pharmacy) is added in small quantity to the dough, it will cause the raising
of the same, partly because some acid is always present in the dough, whereby
the salt is decomposed and carbonic acid set free, partly because by the heat of
the oven the salt is volatilised, and by assuming the state of vapour causes the
expansion and consequent sponginess of the dough. Liebig recommends the
addition of bicarbonate of soda and hydrochloric acid to the dough, the carbonic
acid being evolved according to the formula (NaHCO3+HCl=NaCl+H2O+CO₂)
with the formation of common salt which remains in the dough. The proportions
are as follows:-To 100 kilos. of meal for making black bread 1 kilo. of bicarbonate
of soda is taken, and 4'25 kilos. of hydrochloric acid of 1063 sp. gr. (=9°5° B.= 13
per cent CIH), yielding 175 to 2 kilos. of common salt; the quantity of water to be
added amounts to from 79 to 80 litres. From this mixture is obtained 150 kilos. of
bread. The proportion of the bicarbonate of soda to the hydrochloric acid is so
arranged that 5 grms. of the former are fully saturated by 33 c.c. of the latter, leaving in
the bread a faintly acid reaction. The substance known and sold as Horsford's yeast
powder, also recommended by Liebig, is preferable and more readily applied. This
powder consists of two separate preparations, viz., the acid powder (acid phosphate
of lime with acid phosphate of magnesia), the other the alkali powder (a mixture of
500 grms. of bicarbonate of soda and 443 grms. of chloride of potassium). To
100 kilos. of flour, 2.6 kilos. of the acid powder, and 16 kilos. of the alkali powder
are added. During the kneading the following changes occur: the bicarbonate of
soda and chloride of potassium are first converted into chloride of sodium and
bicarbonate of potash, the latter salt being in its turn decomposed by the acid
phosphate, whereby carbonic acid is set free. By the use of this baking powder it
is possible to make flour into bread within two hour's time, while, moreover, 100
pounds of flour yield 10 to 12 per cent more bread than with the best method of
baking in the usual way. The plan of incorporating pure carbonic acid gas with
BREAD.
457
the dough has been frequently taken up and abandoned again; many trials have
been made in this direction, and the process has its opponents as well as its
defenders. Of later years the late Dr. Dauglish and Mr. Bousfield have taken this
subject up, and after having obtained a patent have started the Aërated Bread
Company. This process as carried out in practice is best described by an extract
from Dr. Dauglish's pamphlet, using his own words:—
เ
manner.
I first prepare the water which is to be used in forming the dough by placing it
in a strong vessel capable of bearing a high pressure, and forcing carbonic acid into
it to the extent of ten or twelve atmospheres, taking advantage of the well-known
capacity of water for absorbing carbonic acid, whatever its density, in quantities
equal to its own bulk. The water so prepared will of course retain the carbonic acid
in solution so long as it is retained in a close vessel under the same pressure. I there-
fore place the flour and salt of which the dough is to be formed also in a close
vessel capable of bearing a high pressure. Within this vessel, which is of a
spheroidal form, a simply constructed kneading apparatus is fixed, working from
without through a closely packed stuffing box. Into this vessel I force an equal
pressure to that which is maintained on the aërated water vessel; and then, by
means of a pipe connecting the two vessels, I draw the water into the flour and set
the kneading apparatus to work at the same time. By this arrangement the water
acts simply as limpid water among the flour, the flour and water are mixed and
kneaded together into paste, and to such an extent as shall give it the necessary
tenacity. After this is accomplished the pressure is released, the gas escapes from
the water, and in doing so raises the dough in the most beautiful and expeditious
It will be quite unnecessary for me to point out how perfect must be the
mechanical structure that results from this method of raising dough. In the first
place, the mixing and kneading of the flour and water together, before any vesicular
property is imparted to the mass, render the most complete incorporation of the flour
and water a matter of very easy accomplishment; and this being secured, it is evident
that the gas which forms the vesicle, or sponge, when it is released, must be
dispersed through the mass in a manner which no other method-fermentation not
excepted—could accomplish. But besides the advantages of kneading the dough
before the vesicle is formed, in the manner above-mentioned, there is another and
perhaps a more important one from what it is likely to effect by giving scope to the
introduction of new materials into bread making; and that is, I find that powerful
machine kneading continued for several minutes has the effect of imparting to the
dough tenacity or toughness. In Messrs. Carr and Co.'s machine, at Carlisle, we
have kneaded some wheaten dough for half-an-hour, and the result has been that
the dough has been so tough that it resembled bird-lime, and it was with difficulty
pulled to pieces with the hand. Other materials, such as rye, barley, &c., are
affected in the same manner; so that by thus kneading I am able to impart to
dough, made from materials which otherwise would not have made light bread, from
their wanting that quality in their gluten which is capable of holding or retaining,
the same degree of lightness which no other method is capable of effecting. And I
am sanguine of being able to make from rye, barley, oatmeal, and other wholesome
and nutritious substances, bread as light and sweet as the finest wheaten bread.
One reason why my process makes a bread so different from all other processes
where fermentation is not followed is, that I am enabled to knead the bread to any
extent without spoiling its vesicular property, whilst all other unfermented breads
458
CHEMICAL TECHNOLOGY.
are merely mixed, not kneaded. The property thus imparted to my bread by
kneading renders it less dependent on being placed immediately in the oven.
It certainly cannot gain by being allowed to stand after the dough is formed; but it
bears well the necessary standing and waiting required for preparing the loaves for
baking.
"There is one point which requires care in my process, and that is the baking: as
the dough is excessively cold, first, because cold water is used in the process, and
next because of its sudden expansion on rising. It is thus placed in the oven some
40° F. in temperature lower than the ordinary fermented bread. This, together with
its slow springing until it reaches the boiling-point, renders it essential that the top
crust shall not be formed until the very last moment. Thus, I have been obliged to
have ovens constructed which are heated through the bottom, and are furnished
with means of regulating the heat of the top, so that the bread is cooked through
the bottom; and, just at the last, the top heat is put on and the top crust formed.
"With regard to the gain effected by saving the loss of fermentation, I may state
what must be evident, that the weight of the dough is always exactly the sum of the
weight of flour, water, and salt put into the mixing vessel, and that in all our
experiments at Carlisle we invariably made 118 loaves from the same weight of
flour which by fermentation made only 105 and 106. Our advantage in gain over
fermentation can only be equal to the loss of fermentation. As there has been
considerable difference of opinion among men of science with respect to the amount of
this loss—some stating it to be as high as 17 per cent and others so low as I per
cent-I will here say a few words on the subject. Those who have stated the loss to
be as high as 17 per cent have, in support of their position, pointed to the extra
yield from the same flour of bread when made by non-fermentation compared with
that made by fermentation. Whilst those who have opposed this assertion, and
stated the loss to be but I per cent or little more, have declared the gain in weight to
be simply a gain of extra water, and have based their calculations of loss on the
destruction of material caused by the generation of the necessary quantity of carbonic
acid to render the bread light. Starting, then, with the assumption that light bread
contains in bulk half solid matter and half aëriform, they have calculated that this
quantity of aëriform matter is obtained by a destruction of but 1 per cent of solid
material. In this calculation the loss of carbonic acid, by its escape through the
mass of dough during the process of fermentation and manufacture, does not appear
to have been taken into account, that our calculations may be correct.
"One of the strongest proofs that the escape of gas through ordinary soft bread
dough is very large arises from the fact, that when biscuit dough, in which there is a
mixture of fatty matter, is prepared by my process, about half the quantity of gas only
is needed to obtain an equal amount of lightness with dough that is made of flour
and water only, the fatty matter acting to prevent the escape of gas from the dough.
Other matters will operate in a similar manner-boiled flour, for instance, added in
small quantities. But the assumption that light bread is only half aëriform matter
is altogether erroneous. Never before has there been so complete a method of
testing what proportion the aëriform bears to the solid in light bread as that which
my process affords. The mixing vessel at Messrs. Carr and Co's. Works, Carlisle,
has an internal capacity of 10 bushels. When 3 bushels of flour are put into this
vessel, and formed into spongy bread dough, by my process it is quite full. And
when flour is mixed with water into paste, the paste measures rather less than half
BREAD.
459
I
the bulk of the original dry flour. This will, therefore, represent about 1 bushels of
solid matter expanded into 10 bushels of spongy dough, showing in the dough
nearly 5 parts aëriform to 1 solid and in all instances, if the baking of this dough
has not been accomplished so as to secure the loaves to spring to at least double their
size in the oven, they have always come out heavy bread when compared with the
ordinary fermented loaves. This gives the relative proportion of aëriform to solid in
light bread at least as 10 to 1, and at once raises the loss by fermentation from 1 to 10
per cent, without taking into account the loss of gas by its passage through the mass
of dough.
"I may be allowed here to state, what will be evident to all, that the absence
of everything but flour, water, and salt, must render it absolutely pure; that its
sweetness cannot be equalled except by bread to which sweet materials are super-
added; that, unlike all other unfermented bread, it makes excellent toast; and, on
account of its high absorbent power, it makes the most delicious sop, puddings, &c.,
and also excellent poultices. Sop, pudding, and poultice made from this bread, how-
ever, differ somewhat from those made from fermented bread, in being somewhat
richer or more glutinous. This arises from the fact of the gluten not having been
changed or rendered soluble in the manner caused by fermentation; but that this is a
good quality rather than a bad one is evident from the fact, that the richer and purer
fermented bread is, the more glutinous are the sops, &c., made from it; and the
poorer and more adulterated with alum it is, the freer the sops, &c., are of
this quality."
It should be observed that the alcohol formed during the fermentation of the
bread and volatilised by the heat of the oven, acts along with the carbonic acid
in rendering the dough spongy; upon this action of the alcohol is based the applica-
tion of rum or brandy, which in small quantities are added to pastry and puddings
made with flour, suet, eggs, sugar, butter, &c.
Yield of Bread. As regards the quantity of bread obtained from a given quantity
of flour, it varies according to the quality of the latter; 100 kilos. of flour usually
yield from 125 to 135 kilos. of bread.
Composition of Bread. The flour from various kinds of grain contain in its ordinary
air dry condition from 12 to 16 per cent of water; by its conversion into bread the
flour takes up much more water. 100 pounds of fine wheaten flour combine with 50
pounds of water, and give 150 pounds of bread. The composition of the flour and
of the bread is, therefore, as follows:-
Dry flour
...
Water originally contained in the flour
Water added for making the dough
Wheaten Flour. Wheaten Bread.
!
84
16
84
16
50
100
150.
According to Heeren, 100 pounds of wheaten flour yield at least 125 to 126 pounds
of bread; 100 pounds of rye meal, 131 pounds of bread. Fresh wheaten bread con-
tains 9 per cent of soluble starch and dextrin, 40 per cent of unchanged starch, 6·5
per cent of protein compounds, and from 40 to 45 per cent of water. As is generally
known newly baked bread possesses a peculiar softness, and is at the same time
tough; does not yield crumbs readily after one or more days' keeping, the bread
loses this softness, becomes dry, crumbles readily, and is then called stale or old
460
CHEMICAL TECHNOLOGY.
bread; it is usually supposed that this change is due to a loss of water; but,
according to the researches of Boussingault, stale bread contains just as much water
as fresh bread; the alteration is solely due to a different molecular condition of the
bread.
Impurities and Adulteration
of Bread,
When the flour intended for the preparation of bread is more
or less decayed, the gluten it contains is thereby altered; the carbonic acid evolved
during the fermentation of the bread does not render the dough spongy, but it
becomes, owing to the altered state of the gluten, a more or less slimy mass, which
yields a tough and far less white-coloured bread; in order to counteract this defect,
and to impart a good appearance to the bread made from flour which has been damaged
by damp, or by having been too closely confined in casks and thereby heated,
the bakers in Belgium and Northern France (and may we not say of England too),
add to the dough a small quantity of sulphate of copper, É to sʊʊʊ; the base of
this salt combines with the gluten, forming therewith an insoluble compound, thus
rendering the dough tough and white, and capable of taking a large quantity of
water. In order to detect the sulphate of copper in the bread, a portion of the bread
to be operated upon is first dried, then ignited, and the copper separated from
the ash by gently washing away the lighter particles, leaving the metallic copper
in the shape of small shining spangles. In England alum is very generally added
to bread. In Germany the addition of sulphate of copper and alum (0.5 per
cent) to bread is prohibited by law, but in some parts of that country leaven is
kept in copper vessels, whereby verdigris is formed, the appearance of which is by no
means disliked by the bakers.
Vinegar, and its Origin.
THE MANUFACTURE OF VINEGAR.
The fluid known in common life as vinegar is essentially a mix-
ture of acetic acid and water. Acetic acid, C2H4O2. or C₂H₂O, consists, in its
highest degree of concentration, in 100 parts, of—
Carbonic acid
Hydrogen
Oxygen
...
3
24
40'0
4
6'7
32
53°3
60
ΙΟΟ Ο
and is formed by the oxidation of alcohol as well as by the dry distillation of cellu-
lose.
As regards the first mode of formation, the process of the conversion of alcohol
into acetic acid may be represented by the following formula :—
I mol. alcohol C2H6O = 46
2
""
oxygen
20 =
=32
} yield {
1 mol. acetic acid C2H4O2:
60
I
water
H20=18
""
78.
78
Accordingly 100 parts of alcohol should give 129˚5 parts of acetic acid of the highest
degree of concentration. The process of conversion is, however, by no means
so simple as just mentioned, because the alcohol is not at once converted into acetic
acid, but first converted into a body which contains less oxygen than the acetic acid,
viz., aldehyde, C₂H4O. The conversion of the alcohol into acetic acid may be eluci-
dated in the following manner:—
VINEGAR.
461
Alcohol C2H60 =46
Subtract
Remainder
H2
= 2
{
Aldehyde C2H40=44
|
Add
Result-
Acetic acid
H₂ becomes, by the aid of O taken up
from the air, oxidised to H₂0.
0 = 16 from the air.
C2H4O2=60
100 kilos. of alcohol therefore need 300 kilos. (=2322 hectolitres) of air, con-
taining 69 kilos. of oxygen, for the conversion of the alcohol into acetic acid. It is,
however, evident, that in practice this quantity of air is insufficient, and only that
portion of the oxygen which is in the state of ozone is capable of performing
the duty of acetification. Alcoholic liquids, in order to become converted into
vinegar, require the presence of a peculiar fungus (cryptogamic plant), known as
Mycoderma aceti, which appears to act as the carrier of the oxygen of the air,
which is also by it rendered active and given up to the alcohol.
The origin of vinegar or acetic acid as a product of the dry distillation of cellu-
lose cannot be elucidated by a simple formula, because there are formed in
addition to acetic acid a large number of other compounds, among which are gaseous
and fluid hydrocarbons, wood spirit, aceton, creosote, oxyphenic acid, tar, &c.,
the relative quantity of which depends not only upon the temperature at
which the distillation took place, but also upon the shape of the retorts used,
the quantity of hygroscopic water contained in the wood, &c.
a. Preparation of Vinegar from Alcoholic Fluids.
Vinegar from Alcohol. When alcohol is left exposed to air or to pure oxygen it is not
converted into acetic acid. Nevertheless the conversion is due to the alcohol
becoming oxidised; therefore it is evident the alcohol must be placed under such con-
ditions as are most favourable to the formation of vinegar. In this, as in many other
chemico-technical processes, practical experience is the best teacher. The most
important points are, of course, the preparation of vinegar in the shortest time with
the least expenditure of alcohol. The conditions most favourable to the formation of
vinegar on the large scale are the following:-
1. The alcoholic fluid-prepared from grape wine or fruit wine, fermented malt
infusion, beer, and brandy—should be sufficiently diluted; it should contain not more
than 10 per cent of alcohol. Experience has proved that fluids prepared by
the direct application of alcoholic fermentation, viz. wine, beer, &c., are more
readily converted into vinegar than mixtures of brandy or alcohol and water. But
too great a dilution should be avoided; for although a liquid containing 3 per cent or
less alcohol can be converted into vinegar, the acetification proceeds very slowly in
so dilute liquids.
2. A suitable temperature-not above 36° C., not below 10° to 12° C. At a tempe-
rature of 7° C. and less the formation of vinegar no longer takes place, a fact
usually overlooked when the advantages, of keeping beer and other fermented
liquids in ice pits or very cool cellars are enumerated. Above 40 to 60° the acetifi-
cation proceeds very rapidly, but there is a loss of alcohol and vinegar by evapo-
ration.
3. A plentiful supply of air or oxygen to the alcoholic fluid and an intimate con-
tact between the two. Small quantities of alcoholic fluid with an extended surface
462
CHEMICAL TECHNOLOGY.
are more readily converted into vinegar than large bulks of fluid, because the former
present a larger number of points of contact.
4. The presence of substances which conduce to the formation of vinegar; they
are as regards their action similar to the ferments, and are therefore called acetic acid
or sour producing ferments; but the acetification is not a physiological process, as is
vinous fermentation, but simply one of oxidation. The best ferment is vinegar, and
all substances impregnated with it, such as for instance the so-called vinegar plant,
the Mycoderma aceti; it was formerly thought that the vinegar mycoderms stood to
alcohol and vinegar in the same relation as yeast stands to sugar and alcohol, but this
opinion is correct only so far as the addition of Mycoderma aceti to an alcoholic
fluid, as proved by Pasteur's experiments (1862), is alike in the action of small quan-
tities of vinegar and other acetification-inducing substances upon wooden vats and
chips of wood thoroughly impregnated with vinegar; many of these substances con-
tain particles which are undergoing a process of oxidation (molécule en mouvement),
and by coming into contact with alcohol they draw that fluid into a course of oxidation
also. Pure acetic acid is therefore incapable of inducing acetification, but vinegar, on
the contrary, is capable of doing so because it always contains smaller or larger quan-
tities of the protein compounds alluded to; but unless these are in a peculiar
state of activity they are useless; this is shown by platinum black and spongy
platinum, both of which are capable of converting alcohol immediately into acetic
acid. We may therefore conclude that, by the presence of Mycoderma aceti as well
as of spongy platinum, the oxygen of the air is rendered active-ozonised—and that
only ozonised oxygen is capable of converting alcohol into vinegar. Acetic acid is,
therefore, an oxidation product, not one of the Mycoderma. A more accurate inves-
tigation of the behaviour of peroxide of hydrogen and other ozone-containing or
producing materials with mixtures of alcohol and water, will no doubt lead to a
better knowledge of the theory of acetification, and may lead also to a more rational
and improved mode of vinegar making.
Phenomena of Vinegar Formation. Acetification exhibits phenomena which are important
for observation because they indicate the progress of the conversion of the alcohol
into acetic acid; these phenomena are partly of a chemical, partly of a physical
kind. In proportion as the formation of vinegar advances, the alcoholic fluid loses
its peculiar flavour and odour, and acquires the refreshing sour taste of vinegar. To
the physical phenomena belong:-1. An increase in the specific gravity of the fluid;
and (2) an increase of the temperature. The increase of temperature is due to the
conversion of the oxygen from a gas to a fluid. The more active the absorption of
oxygen the higher the temperature.
Vinegar Making.
The Older Method of According to the substance from which vinegar is prepared the
following kinds are distinguished:-1. Wine vinegar, prepared from wine, and
containing in addition to acetic acid many of the other constituents of wine, namely,
tartaric acid, succinic acid, and certain kinds of ethers, the latter imparting to wine
vinegar its peculiarly agreeable flavour and odour. 2. Brandy vinegar, spirit
vinegar, or artificial wine vinegar, generally only a mixture of acetic acid and water
with a small quantity of acetic ether. 3. Fruit vinegar, prepared from cider and
perry and containing acetic and malic acids. 4. Beer, malt, or grain vinegar,
prepared from non-hopped beer wort, and containing, besides acetic acid, also
extractive matters, such as, for instance, dextrin, nitrogenous constituents and
phosphates. 5. Vinegar from the sugar beet-root. The roots are converted into
VINEGAR.
463
a pulp and then pressed; the juice is next diluted with water and afterwards boiled.
When sufficiently cooled, yeast is added and alcoholic fermentation set up; this
having been finished the alcohol contained in the liquid is converted into vinegar.
The vessel in which the acetification takes place is connected with a blowing fan; by
the aid of a plentiful supply of air and the keeping up of a uniform temperature the
alcoholic liquid to which some vinegar has been added is rapidly converted into
acetic acid. 6. Vinegar prepared from the so-called wood vinegar or acetic acid
obtained by the dry distillation of wood.
As regards the so-called old method of vinegar making it is without doubt an
imitation of the spontaneous souring of beer, wine, and fermented liquors generally
and on conditions which are conducive to the improvement of the product;
such conditions are-a suitable temperature, intimate contact of the souring
liquor with air, and a so-called acetification-inducing ferment. This method is
very generally employed for making wine vinegar, French vinegar as it is termed in
England, but may of course be used for malt or fruit vinegar making as well.
Generally a “souring" vessel or "mother" vessel made of oak wood is employed;
this vat is first, when newly made, thoroughly scalded with boiling hot water, and
when thereby the extractive matter of the wood is exhausted the vessel is filled with
boiling hot vinegar; when the wood is soaked with vinegar there is poured into the
vessel 1 hectolitre of wine, and after eight days again 10 litres of wine are added,
and this operation continued weekly until the vessel is filled for two-thirds of its
cubic capacity. About fourteen days after the last addition of the wine the whole of
the contents will have become converted into vinegar. Half this quantity is with-
drawn from the souring vessel and carried to the store: to the remainder more wine
is added, and the preparation of vinegar proceeded with uninterruptedly by the opera-
tion described. A souring vessel may continue to serve its purpose for six years,
and often longer, but generally at the end of this time there is collected in the vessel
so large a quantity of yeast sediment, argol, stone, and other matter as to
render the thorough cleansing of the vessel necessary; after this operation it is
again fit for further use. Although it might appear that in this process of
acetification there is no great contact of air, and the fluid is apparently quite at rest,
there is a constant change of the particles of the surface of the fluid, owing to the
fact that every drop of vinegar formed sinks to the bottom of the vessel, or at least
below the surface, owing to its increased specific gravity; while as regards the air,
that portion of it from which the oxygen has been absorbed by becoming specifically
lighter (09 sp. gr.) has a tendency to rise upwards, and to be replaced by heavier
air (1′0 sp. gr.); thus a constant circulation of air is provided.
Quick Vinegar Making. The so-called quick vinegar process, founded on an older
method of vinegar preparation suggested by Boerhaave in 1720, was first introduced
by Schützenbach in 1823. The chief principle of this method consists in bringing
the fluid, generally brandy, to be converted into vinegar into ultimate contact with
the atmosphere at the requisite temperature, or, in other words, the oxidation of the
alcohol to acetic acid is effected in the shortest time and with the least possible loss.
The intimate contact of the fluid with the air is effected by:-1. Increasing the
quantity of air admitted by means of a continual current of air being made to meet
the drops of the fluid intended to be converted into vinegar in opposite direction to
that in which these drops fall downwards. 2. By causing the liquid to be operated
upon to trickle down drop by drop. A peculiarly constructed vessel is required for
464
CHEMICAL TECHNOLOGY.
this operation; according to the strength of vinegar desired to be made two to four
of these vessels are employed, these constituting a group or battery as it is termed.
A sectional view of such a vessel is exhibited in Fig. 246; it is made of stout oaken
FIG. 246.
staves, the vat being from 2 to 4
metres in height, and from 1 to 13 in
width; at a height of from 20 to 30
centimetres from the bottom of the
vessel are bored at equal distance
from each other six holes-air
holes-of about 3 centimetres in
diameter, so cut that the inner
mouth of the hole is situated a little
deeper than the outer, that is to
say, the holes are bored towards
the bottom in a slightly sloping
direction. About one-third of a
metre above the real lower bottom
a false bottom is placed, similar in
construction to a sieve, and at a
height of a centimetre above the
air-holes; upon the false bottom is
a layer of beech-wood shavings
extending upwards to about from 15

to 20 centimetres below the upper edge of the vat. The false bottom is sometimes
constructed of laths of wood, forming a kind of gridiron-like network. Before their
application the wood shavings are thoroughly washed with hot water and next
dried. The tub is then nearly filled with the dry wood shavings, which are next
"soured." For this purpose warm vinegar is poured over them, and allowed to
remain in contact with the wood for twenty-four hours so as to cause the acetic
acid to soak into the wood. At from 18 to 24 centimetres below the upper edge
of the vat is fixed a perforated wooden disc, the holes of which are as large
as a goose-quill, and are bored from 3 to 5 centimetres apart from each other.
In order that the liquid intended to be converted into acetic acid may trickle slowly,
and in fine spray, as it were, over the wood shavings, or thin chips of wood,
through the holes, strings of twine or loosely spun cotton yarn are passed so
as to penetrate downwards for a length of 3 centimetres, while at the top a knot
is tied which prevents the strings slipping through the holes; by the action of
the liquid, dilute spirits of wine usually, which is poured into the vessel, the
twine becomes more or less swollen, and thereby obstructs the passage of the
fluid so as to divide it into constantly trickling drops. The sieve bottom is fitted
with from five to eight larger holes, each about 3 to 6 centimetres wide, which by
means of glass tubes, each of from 10 to 15 centimetres in length, inserted and
firmly fastened therein act as draught tubes, so placed that no liquid can pass
through them The vat is covered at the top with a tightly-fitting wooden lid,
in the centre of which a circular hole is cut, which serves as well for the
purpose of pouring the liquid into the vessel as for the outlet of the air which
enters the vessel from below. In consequence of the absorption of the oxygen so
VINEGAR.
465
much heat is generated in the interior of the vessel that the air streams strongly
upwards, causing fresh air to enter by the lower air-holes.
After the vinegar tub has been soured the fluid to be converted into vinegar-
generally brandy, more rarely malt liquors or wine-is poured in; the fluid flowing
off from the first vessel is poured into the second, and if the original liquid did
not contain more than from 3 to 4 per cent of alcohol the fluid which runs off from
the second vessel will be completely converted into good vinegar. The vinegar
collects between the true and false bottoms. As will be seen from the woodcut the
vinegar cannot flow out until its level is equal to that of the mouth of the glass
tube. In consequence of this arrangement a layer of about 16 to 20 centimetres
in depth of warm vinegar assists in the acetification by the evolution of acid
vapours which ascend into the fluid above. The tube must dip into the lower part
of the fluid in the interior of the tub, as it is there that the specifically heavier
vinegar collects.
The arrangement will be readily understood from Fig. 247;
cp is the perforated bottom, just below which is situated the wooden tap, h, fastened
to the bent glass tube, m m, the free open end of which touches the bottom of
the tub.
Recently (1868) Singer's vinegar generator has been introduced. It consists of a
number of vessels, one placed above the other, and so connected together by wooden
FIG. 247.

tubes that the liquid intended to be converted into vinegar trickles drop by drop
from the one vessel into the other; in each tube is cut a longitudinal slit, through
which air freely circulates; the apparatus is placed in a suitably constructed shed,
wherein a convenient temperature is kept up and from which draught is excluded.
By the use of this apparatus the loss of alcohol experienced in the use of the
vats above mentioned is prevented. Singer's apparatus is fully described in the
"Jahresbericht der Chem. Technologie," 1868, p. 580.
The composition of the fluid to be acetified varies very much; one of the mixtures
very generally used is made up of 20 litres of brandy of 50 per cent Tralles, 40
litres of vinegar, and 120 litres of water, to which is first added a liquid, made by
soaking a mixture of bran and rye meal in water in order to promote the formation
of the vinegar fungus (Mycoderma aceti). The room in which the vats are placed
should be heated to 20° to 24°; the temperature in the vats rises to 36° and more,
consequently the alcohol, aldehyde, and acetic acid are volatilised, and this loss
may amount to about one-tenth; taking this loss into account we may assume
31
466
CHEMICAL TECHNOLOGY.
that 1 hectolitre of brandy at 50 per cent Tralles (= 42 per cent according to weight)
yields by weight—
130 hectolitres of vinegar of 3 per cent acetic acid contents.
9'9
"
7'9
6.6
4
""
""
">
5
6
""
""
""
5'6
4'9
44
""
3'9
""
99
་
""
7
8
9
ΙΟ
""
"
"
""
,,
When required for transport it is, of course, most advantageous to prepare very
strong vinegar, which at the place where it is to be consumed can be diluted with
the requisite quantity of water.
Vinegar from the Sugar-Beet. Vinegar from the sugar-beet is prepared from the expressed
juice, having a sp. gr. of 1035 to 1045, diluted with water to 1025 sp. gr., fermented
with yeast, the fluid being next mixed with an equal volume of prepared vinegar. This
mixture being well exposed to the influence of the oxygen of the atmosphere, acetification
soon sets in.
Vinegar with the Help of the
Mycoderma Aceti.
Pasteur, who refers acetification, as Dr. Wagner thinks
erroneously, to a physiological process, has in 1862 described a new method of pre-
paring vinegar with the help of the vinegar fungus, the Mycoderma aceti. This
fungus is first propagated in a fluid, consisting of water and 2 per cent of alcohol
with 1 per cent of vinegar and a small quantity of phosphate of potash lime and
magnesia. The small plant soon spreads itself over the entire surface of the fluid,
without leaving the smallest space uncovered. At the same time the alcohol is aceti-
fied. As soon as half of the alcohol is converted into vinegar, small quantities of
wine or alcohol mixed with beer are added daily. When the acetification becomes
weaker, the complete conversion of the free alcohol still present in the fluid is allowed
to take place. The vinegar is then drawn off and the plant again employed in
the same apparatus. Vinegar prepared by this method possesses much of the aroma
characteristic of wine vinegar. An essential condition to the rapid formation of
vinegar by this method is a strong development of the plant. A vessel with 1 square
metre of surface, and capable of containing 50 to 100 litres of fluid, yields daily
5 to 6 litres of vinegar. The vessels are circular or rectangular wooden tanks,
with but a slight depth, and covered with lids. At the ends are bored two
small openings for the entrance of the air. Two tubes of gutta-percha, pierced
laterally with small holes, are carried down to the bottom of the tank and used
to pour alcohol into the tank without opening the lid. The tank which
Pasteur employed had a surface of 1 square metre and a depth of 20 centims.
He found phosphates and ammonia necessary for the growth of the plant: When
wine or malt liquor, &c., is employed, these substances are present therein in suffi-
cient quantity; but when only alcohol is used, sulphate of ammonia, phosphate of
potash and magnesia are added in such quantity that the fluid contains 100th
of this saline mixture, to which also some vinegar is added. It has been long
known that the addition of bread, flour, malt, and raisins to alcoholic fluids about to'
be acetified greatly promotes the formation of vinegar, as these substances contain
the requisite organic and inorganic food suited for the propagation of the vinegar
fungus.
VINEGAR.
467
Vinegar with the help
of Platinum Black.
FIG. 248.
Dobereiner was the first who pointed out that, with the aid of
platinum black, alcoholic vapours could be acetified in a very short time; and to this
process the following apparatus is especially adapted. Fig. 248 shows a small glass
house, in the interior of which are seen a number of compartments. The shelves
forming these compartments support a number of porcelain capsules. The alcohol to
be acetified is poured into these capsules, in each of which is placed a tripod, also of
porcelain, supporting a watch-glass containing platinum black or spongy platinum.
In the roof and at the bottom of the apparatus are ventilators, so constructed as to
admit of regulating access of air.
By means of a small steam pipe
the interior of the house is heated
to 33°. By this means the alcohol
is gently evaporated, and coming
into contact with the platinum black
or sponge, is acetified. So long as
the ventilation is maintained, the
platinum black retains its property
of oxidising the alcohol. With an
apparatus of 40 cubic metres capa-
city and with 17 kilos. of platinum
black, 150 litres of alcohol can daily
be converted into pure vinegar.
If it be desired to prepare the
vinegar without any loss of alcohol,
it becomes necessary to pass the
outgoing air through a condenser in
order to collect the vapours of alcohol and acetic acid which otherwise would be
carried off.

Testing Vinegar.
The value of a vinegar is dependent upon its flavour and upon
its strength, or upon the quantity of acetic acid it contains. According to its con-
taining more or less acetic acid the vinegar tastes more or less sour. The colour
varies with the fluid from which the vinegar has been prepared; wine vinegar is
of a yellow or red-yellow colour, fruit vinegar exhibits a golden colour, brandy
vinegar is colourless; but as a rule the latter is coloured with caramel in imitation
of wine vinegar. Freshly made vinegar contains besides small quantities of uncon-
verted alcohol, some aldehyde, which always occurs largely in vinegar not properly
prepared. Recently it has become customary to add a small quantity of glycerine
to the prepared vinegar.
The quantity of acetic acid contained in a vinegar depends upon the alcoholic con-
tents of the fluid to be acetified, and also upon the more or less perfect conversion of
the alcohol into acetic acid. Malt vinegar contains from 2 to 5 per cent, brandy
vinegar from 3 to 6 per cent, wine vinegar from 6 to 8 per cent, of acetic acid. The
specific gravity of various kinds of vinegars differs from 1'oro to 1030; the more
alcohol a vinegar contains the lighter is it, the more extractive matter the
heavier. The densities of mixtures of acetic acid (C2H4O2) and water are, at
15° C., according to Oudemans, the following:-
468
CHEMICAL TECHNOLOGY.
Per-
Per-
Per-
Per-
centage. Dens. Diff. centage. Dens.
Diff. centage. Dens. Diff. centage. Dens. Diff.
OHNM+no 7∞
o'9992
26
10363
52 10631
78
1*0748
Ι
1'0007
+15
15
I2
27
I'0375
53
10638
7
2.
1'0022
3
I'0037
4
I'0052
5
1'0067
6
10083
1'0098
8
1'0113
9
1'0127
IO
1'0142
10 10 10 INLO IN IN & IN IN
HHH
HHHHHH
13
8
79
1'0748
O
28
1'0388
54
1'0646
80
I'0748
15
12
7
I
29
I'0400
55
1'0653
81
I 0747
15
I2
30
1'0412
56
10660
7
82
15
12
6
1'0746
31
I'0424
57
10666
83
I'0744
16
12
7
32
1'0436
58
10673
84
15
ΙΙ
6
I'0742
33
I'0447
59
1'0679
85
1'0739
15
12
34
1'0459
60
1'0685
86
3
10'736
14
II
6
35
I'0470
61
1'0691
15
II
6
87
1'0731
36
1'0481
62
1'0697
15
II
5
II
I'0157
37
I'0492
63
∞ ∞
88
10726
1'0702
89
1'0720
14
ΙΟ
12
I'0171
38
1'0502
64
1'0707
90
1'0713
14
II
13
1'0185
39
1'0513
65
1'0712
91
I'0705
15
ΙΟ
1 2 2 3 min 1∞ o
I
5
5
7
8
9
14
I'0200
40
I'0523
66
10717
92
1'0696
14
ΙΟ
4
ΙΟ
15
1'0214
4I
I 0533
67
1'0721
93
I'0686
14
ΙΟ
KH H
16
10228
42
1'0543
68
4
I2
1'0725
94
10674
14
9
14
17
1'0242
43
I'0552
69
I'0729
95
1*0660
14
ΙΟ
16
18
I'0256
44
1'0562
70
1'0733
96
1'0644
14
9
19
19
1'0270
45
I'0571
71
1*0737
97
1*0625
14
9
20
1'0284
46
I'0580
72
I'0740
14
21
1'0298
47
1'0589
73
I'0742
13
9
22
1'0311
48
I'0598
13
23
I'0324
49
1*0607
13
24
I'0337
50
10615
13
25 I'0350
5I 1'0623
∞∞∞∞
8
8
7777
74
I'0744
75
1'0746
32 2 2 1
21
98
1'0604
24
99
1'0580
27
100
I'0553
I
76
77
8
10747
10748
I
13
Acetometry. Commercial vinegar varies greatly as regards the quantity of acetic acid
it contains. The specific gravity of a commercial vinegar is no certain indication of
the quantity of acetic acid, owing to the fact that the vinegar nearly always con-
tains foreign matters. The testing of the strength can therefore only be accurately
effected by means of saturating it with an alkali. According to the ordinary method
first introduced for this purpose by Otto, ammonia is added to the vinegar to be
tested until the previously added tincture of litmus becomes again blue; although
this method is not absolutely correct-owing to the fact that the neutral alkaline
acetates exhibit an alkaline reaction-this does not much impair the correctness
of this process. Otto's acetometer is a glass tube sealed at one end, 36 centims.
long by 15 wide, whereon is engraved a double scale of divisions, one of these
towards the bottom of the tube serving for measuring the vinegar coloured by
litmus, while the other upper scale is intended for measuring the test liquor. When
it is intended to apply the test with this measuring tube, a certain quantity (indicated
by the divided scale) of litmus tincture is first poured into the tube, next vinegar is
added in sufficient quantity to fill the tube up to the second division; afterwards so
much of the test-liquor is added as to restore again the blue colour of the litmus.
The quantity of test-liquor employed indicates the percentage of acetic acid con-
tained in the vinegar. The test-fluid should contain 1369 per cent of ammonia.
According to Mohr's method there are taken of the vinegar to be tested
( 2C₂H40₂ - H₂O =
102
2
and usually having a sp. gr. varying between 1'010 and 1'011, 5°04 C.C.,
(for 51
Ι'ΟΙΙ
=5'04
51);
:)
VINEGAR.
469
or simply 5 c.c., to which is added tincture of litmus, the whole being titrated with a
normal alkali blue (a titrated caustic potassa solution rendered blue with litmus). It
is better to take 10 c.c. of the vinegar and halve the number of c.c. of potassa
employed.
Examples:-1. 10'o c.c. of a Würtzburg table vinegar required
Wood Vinegar.
11.8 c.c. of potash solution, and the vinegar therefore contained
5'9 per cent of so-called anhydrous acid, or 6.7 per cent of acetic
acid (C2H4O2).
2. 100 c.c. of a vinegar prepared from wood vinegar required
125 c.c. of potash solution, corresponding to
6.25 per cent of anhydrous acid, or 7.3 per cent (C2H4O2).
B. Preparation of Vinegar from Wood Vinegar.
From the dry distillation of wood a portion of the carbonised matter
remains in the retorts as charcoal, while the remainder of the constituents of the
wood are eliminated partly in the state of gases and vapours, such as carbonic oxide,
carbonic acid, hydrogen, light and heavy carburetted hydrogens-partly in the shape
of a condensed matter, consisting of a thick, brown, oily fluid floating upon a stratum
of a watery liquor. The latter, wood vinegar, consists essentially of impure acetic
acid, some propionic and butyric acids, small quantities of oxyphenic acid, creosote,
FIG. 249.

DJEMBUTTER ON
and an alcoholic wood spirit, a mixture of methylic alcohol, aceton, and acetate of
methyl, the brown, thickish fluid substance known as wood tar, consisting of a
number of both fluid and solid bodies, paraffin, naphthalin, creosote, benzol, toluol, &c.
A well-conducted distillation will yield as much as from 7 to 8 per cent of the weight
of the wood acetic acid. According to the researches of H. Vohl, peat can be employed
in the preparation of wood vinegar and of wood spirit. 10 cwts. of peat yield 3 kilos.
of acetic acid and 1°45 kilos. of wood spirit. The Table on the next page shows the
principal products of the destructive distillation of wood.
Raw wood vinegar contains in solution a not inconsiderable quantity of resin, and
also small quantities of phenol and guaiacol; all these bodies impart a more or
less brown colour and empyreumatic odour and flavour, but they also render it a
470
CHEMICAL TECHNOLOGY.
a. Wood
Wood b. Hygroscopic
Water
a. Illuminating
Gas
Acetylen, C₂H₂
Elay1, C2H4
Trityl, C3H6
Ditretyl, C4H8
Benzol, C6H6
Toluol, C-H8
Xylol, C8H10
Naphthalin, C10H8
Carbonic oxide, CO
Carbonic acid, CO2
Hydride of Methyl, CH4
Hydrogen, H₂
(Benzol, C6H6
Toluol, C-H8
Styrolen, CsH8
B. Tar
Naphthalin, C10H8
Retene, C18H18
Paraffin, C20H42, or C22H46
Carbolic acid, C6H6O
Phenol Cresylic acid, C-H8O
Phlorylic acid, C8H100
Guaicol (Oxyphenic acid, C6H6O2
(C-H8O2
Creosote C8H1002
Resin
C6H12O2
Combinations of
oxyphenic
acid
and homologous
acids with methyl*
Acetic acid, C₂H₁02
Propionic acid, C3H6O2
Butyric acid, C4H8O2.
y. Wood Vine-
gar
Valerianic acid, C9H1002
Caproic acid, C10H12O2
Aceton, C3H60
Acetate of methyl, C3H6O2
Wood spirit, CH40
Phenol, Guaicol, and Resin
Carbon
85 per cent.
Hygroscopic water 12
d. Charcoal
Ash
3
valuable antiseptic. Where the principal aim is to obtain wood vinegar, an
iron retort, somewhat similar to a gas retort, is employed for the distillation
of the wood; but in France, a vertical retort of boiler plate, exhibited at a,
Fig. 249, is employed, fitted at the upper part with a tube, o, to which is fastened
the projecting part, B. When the iron cylinder is filled with wood, a lid is tightly
screwed on to it, it being next lifted up and placed into the cylindrical furnace, B,
by means of the crane, D, after which the furnace is closed at the top with
the firebrick lid, E. The products eliminated from the wood contained in the
retort pass into the tube b, Fig. 250, and thence into the condensing apparatus, c,
placed in a framework, d, which condensing apparatus is kept continually supplied
with cold water by the tube f, while the warm water flows off at k. Vinegar, tar,
and wood spirit are condensed and flow into the vessel g, in which the tar separates,
the lighter fluids flowing into h through the tube m. The non-condensed gases
pass through the tube i into the fireplace, where they assist in heating the retort,
so that but very little fuel is required. In large factories, instead of the wooden
receivers, large stone or brickwork cisterns are employed, generally several of such
tanks being used, the largest quantity of tar being condensed in the first cistern,
while the wood vinegar, mechanically freed from the tar and floating on its surface,
* According to S. Marasse (1868), Rhenish beech-wood tar creosote is a mixture of equal
parts of-
Cresylic acid, C,H8O, boiling at 203°,
and Guaiacol C-H8O2
The latter is methylic ether with oxyphenic acid,
C6H502
CH3
200°.
VINEGAR.
471
finds its way into a second cistern. Pettenkofer's patent wood-gas generators
produce a not inconsiderable quantity of wood vinegar.
Purifying Wood Vinegar. Raw wood vinegar is a clear dark brown fluid, having a tarry
It is employed in small quantities in the preservation
taste and smoky odour.
of meat, also for the preservation
of wood, ropes, &c.; but by far
the largest quantity is employed in
the preparation of the various
acetates used in dyeing and calico
printing, chiefly as crude acetate of
iron and crude acetate of alumina.
It is also used in the preparation of
concentrated acetic acid for indus-
trial purposes, that is, for the pre-
paration of aniline from nitro-ben-
zol, and of sugar (acetate) of lead.
Lastly, it is largely used in the
preparation of table vinegar, an
operation economical only where,
as in England, there is a high
duty on alcoholic fluids.
Among the means of purifying
crude wood vinegar, the most
FIG. 250.

d
b
m
simple-leaving out of the question the filtration of the crude liquor over
coarsely granulated wood charcoal as recommended by E. Assmus-is distillation,
an operation usually carried on in a still made of copper fitted with a copper
condensing apparatus. At first a yellow fluid comes over-raw wood spirit from
which the wood spirit of commerce is prepared-and next the distillate becomes
richer in acetic acid.
The principal methods at present employed for the purification of wood vinegar
may be considered as falling under either of two classes :—
a. The first includes the purifying of wood vinegar without saturation with a
base; while
B. The second includes those methods in which the wood vinegar is purified by
conversion into an acetate, the acetic acid being next separated by distillation
with an acid possessing greater affinity for the base.
To the first class belongs Stoltze's method, consisting in first obtaining by dis-
tillation 10 per cent of a liquid which is employed for the preparation of wood
spirit; 80 per cent of the liquid is next distilled off and the empyreumatic
substances contained are destroyed by the action of either ozone or chlorine.
The purification of the crude wood vinegar by the second method is more
generally in use among manufacturers, the inventor of the system being Mollerat.
The crude wood vinegar is first saturated with lime and the solution next
precipitated with Glauber's salt to obtain acetate of soda; this salt is purified by
crystallisation, and when in a dry state is so far heated that the empyreumatic
matter it is mixed with becomes carbonised and is thus rendered insoluble; the
acetate of soda is then extracted with water, and the acetic acid separated from it
by distilling the previously crystallised and dried salt with sulphuric acid. Instead
472
CHEMICAL TECHNOLOGY.
of acetate of soda the acetate of lime is frequently employed in the preparation of
acetic acid from crude wood vinegar, the latter being saturated with lime, and the
salt formed evaporated to dryness. The dry salt is roasted and treated similarly to
the acetate of soda to calcine any empyreumatic products. The acid employed in
the distillation is, according to the method invented by C. Völckel, hydrochloric
acid. The distillation can be effected in a retort with a helm of copper and a
condenser of lead, tin, or silver. Upon 100 parts of acetate of lime 90 to 95 parts of
hydrochloric acid at 1´16 sp. gr. are used. When hydrochloric acid is used in this
preparation instead of sulphuric acid, any contamination of the crude acetate of lime
with empyreumatic or tarry matter does not affect the purity of the acetic acid
which is obtained, provided the crude acetate be first so well dried as to be free
from all other volatile substances; when sulphuric acid is used for this purpose
the result is that an acetic acid is obtained, which contains not only a large quantity
of sulphurous acid, but also other offensive volatile compounds due to the decompo-
sition (by the sulphuric acid) of empyreumatic resins and tarry matter present in
the crude acetate of lime.
Wood Spirit. When the acid liquid obtained by the dry distillation of wood is
distilled on the large scale, there comes over at first a certain quantity of a
yellow fluid, lighter than water, and exhibiting an ethereo-empyreumatic odour.
This fluid (wood spirit) consists chiefly of methylic alcohol, CHO, or CH3O,
aceton, acetate of methyl, and other substances to which no reference need be
made. Wood spirit was first discovered by Taylor in 1812, and was for a long
time only employed for burning in spirit-lamps; it was not until 1822 that Taylor found
this body was a new substance. Wood spirit is in a pure state a colourless fluid of
0814 sp. gr., boiling at 66° C. It is in all respects very similar to alcohol, and can
be employed as a source of heat in spirit-lamps; it evaporates, however, more
rapidly and gives a less intense heat, for whereas 1 part by weight of alcohol yields
by its complete combustion to carbonic acid and water 7189 units of heat, an equal
quantity of wood spirit only yields 5307 units of heat. It is employed in the
preparation of furniture polish and in varnish making; for these purposes, how-
ever, it requires to be well purified, and its rapid evaporation is a drawback to its
extensive use; confirmed spirit drinkers have now and then used it instead of
whiskey and the like, and, it appears, without bad effects. Its most recent use is in
the preparation of iodide and bromide of methyl, which substances are employed
in the manufacture of violet and blue coal-tar colours.
On the Durabilty of
Wood in general.
THE PRESERVATION OF WOOD.
The durability of wood, viz., its power of resisting the destructive
influences of wind and weather, varies greatly, and depends as much upon the
particular kind of wood and the influences to which it is exposed as upon the origin
of the wood (timber), its age at the time of felling, and other conditions. Beech-
wood and oak placed permanently under water may last for centuries. Alder wood
lasts only a short time when in a dry situation, but when kept under water it is a
very lasting and substantial wood. Taking into consideration the different kinds
and varying properties of wood and the different uses to which it is applied, we have
to consider as regards its durability the following particulars:-
WOOD.
473
1. Whether it is more liable to decay by exposure to open air or when placed in
damp situations;
2. Whether it is when left dry more or less attacked by the ravages of insects which,
while in a state of larvæ, live and thrive in and on wood.
Pure woody fibre by itself is only very slightly affected by the destructive
influences of wind and weather. When we observe that wood decays, that decay
arises from the presence of substances in the wood which are foreign to the woody
fibre, but are present in the juices of the wood while growing, and consist chiefly
of albuminous matter, which, when beginning to decay, also causes the destruction
of the other constituents of the wood; but these changes occur in various kinds
of wood only after a shorter or longer lapse of time; indeed, wood may in some
instances last for several centuries and remain thoroughly sound; thus the roof of
Westminster Hall was built about 1090. Since resinous woods resist the action of
damp and moisture for a long time, they generally last a considerable time; next
in respect of durability follow such kinds of wood as are very hard and com-
pact, and contain at the same time some substance which-like tannic acid-to
some extent counteracts decay. The behaviour of the several woods under water
differs greatly. Some woods are after a time converted into a pulpy mass. Other
kinds of wood, again, undergo no change at all while under water, as, for instance,
oak, alder, and fir.
Insects chiefly attack dry wood only. Splint wood is more liable to such attack than
hard wood; while splint of oak wood is rather readily attacked by insects, the hard
wood (inner or fully developed wood) is seldom so affected. Elm, aspen, and all
resinous woods are very seldom attacked by insects. Young wood, which is full of
sap and left with the bark on, soon becomes quite worm-eaten, especially so the alder,
birch, willow, and beech. The longer or shorter duration of wood depends more or
less upon the following conditions:-
a. The conditions of growth. Wood from cold climates is generally more durable
than that grown in warm climes. A poor soil produces as a rule a more durable
and compact wood than does a soil rich in humus, and therefore containing also
much moisture.
b. The conditions in which the wood is placed greatly influence its duration. The
warmer and moister the climate the more rapidly decomposition sets in; while a dry,
cold climate materially aids the preservation of wood.
c. The time of felling is of importance: wood cut down in winter is considered
more durable than that felled in summer. In many countries the forest laws enjoin
the felling of trees only between November 15 and February 15.
Wood employed for building purposes in the country, and not exposed to either
heat or moisture, is only likely to suffer from the ravages of insects; but if it is placed
so that no draught of fresh air can reach it to prevent accumulation of products of
decomposition, decay soon sets in, and the decaying albuminous substances acting upon
the fibre cause it to lose its tenacity and become a friable mass. Under the
influence of moisture fungi are developed upon the surface of the wood. These fungi
are severally known as the "house fungi" (Thetephora domestica and Boletus
destructor), the clinging fungus (Cerulius vastator). They spread over the wood in a
manner very similar to the growth of common fungi on soil. Their growth is greatly
aided by moisture and by exclusion of light and fresh air. A chemical means of
preventing such growths is found in the application to the wood of acetate of oxide of
474
CHEMICAL TECHNOLOGY.
iron, the acetate being prepared from wood vinegar. Wood is often more
injuriously affected when exposed to sea water, when it is attacked by a peculiar
kind of insect known as the bore-worm, Teredo navalis. This insect is armed with
a horned beak capable of piercing the hardest wood to a depth of 36 centimetres.
These insects originally belonged to and abound in great number in the seas
under the tropical clime: but the Teredo navalis is met with on the coasts of
Holland and England.
Preservation of Wood
in Particular.
The means usually adopted to prevent the destruction of wood by
decay are the following:-
1. The elimination, as much as possible, of the water from the wood previously
to its being employed;
2. The elimination of the constituents of the sap;
3. By keeping up a good circulation of air near the wood so as to prevent its
suffocation, as it is termed;
4. By chemical alteration of the constituents of the sap;
5. By the gradual mineralisation of the wood and thus the elimination of the organic
matter.
Drying Wood.
1. Thoroughly dried wood remains for a long time unaltered while in
a dry situation, more especially so when dried by so strong a heat that it
becomes browned. When timber has to be put into a damp situation, it should,
after having been well dried, be first coated with a suitable substance to prevent
the moisture penetrating into the wood. This purpose is attained by coating
the wood with linseed oil, so-called Stockholm tar, coal tar, creosote, and other
hydrocarbons. Hutin and Boutigny adopt the following method to prevent the
absorption of moisture by wood that is put into the ground. The portion of
the post or wood to be buried is first immersed in a vessel containing benzol,
petroleum, photogen, &c., and when taken out is ignited and thus charred.
When extinguished the wood is put to a depth of from 3 to 6 centimetres into a
mixture of pitch, tar, and asphalte, and next the entire piece of wood is thoroughly
painted over with tar.
Elimination of the Constituents
of the Sap.
2. The constituents of the sap are the chief cause of the
decomposition of wood, and they should consequently be removed: many plans are
adopted. In order that the wood may contain the smallest quantity of sap, it should
be felled during the winter months. The constituents of the sap can be eliminated
from the felled tree by three methods:-
a. By treatment with cold water, with which the wood must be thoroughly saturated
to dissolve the constituents of the sap, which are removed when the wood is exposed to a
stream of water. It is evident that with large timber a long time is necessary to ensure
perfect saturation.
b. By employing boiling water the sap is removed much more quickly and efficiently.
The pieces of wood are placed in an iron vessel with water and boiled. Large pieces of
timber cannot be treated in this manner, but are immersed in a cistern in which the fluid
is heated by means of steam. According to the thickness of the wood, the boiling
occupies some 6 to 12 hours.
c. By treatment with steam (steaming of wood)—the most effectual method of removing
the constituents of the sap, the hygroscopicity of the wood thus treated being rendered
much less, while the wood is far more fitted to resist the effects of weather. The
apparatus employed in carrying out the method consists of a boiler for the generation of
steam, and a cistern or steam chamber, for the reception of the wood, this chamber being
constructed of masonry and cement, of boiler plate, or being simply a large and very
wide iron pipe. In most cases a jet of steam is conveyed from the boiler to the steam-
chamber, where it penetrates the wood, and dissolves out the constituents of the sap,
which on being condensed is allowed to run off. In the case of oak, this fluid is of a
WOOD.
475
black-brown colour; with mahogany, a brown-red; with linden wood, a red-yellow; and
with cherry tree wood, a red, &c. The operation is finished when the outflowing water is
no more coloured. The steamed wood is dried in the air or in a drying room; it loses
5 to 10 per cent in weight by the process, and becomes of a much darker colour.
The steam is sometimes worked at a temperature of above 100°, but generally the con-
tents of the steam chamber are maintained at 60° to 70°. Towards the end of the
operation some oil of coal-tar is introduced into the boiler, and is consequently carried
over with the steam, impregnating the wood.
The removal of the sap can also be effected to some extent by means of mechanical
pressure between a pair of iron rollers, which are gradually brought more closely
together. Another method is by means of air pressure. Barlow employs for this
purpose a metal case in which the wood is enclosed, and to one end of which an air
pump is attached. Air being forced into the tube or case, the sap flows away at the end
opposite to which the pump is attached. But both these methods are costly and not in
all cases applicable.
Air Drains. 3. The construction of air drains or passages around woodwork to be
preserved is, where the method is applicable, a great aid to the preservation of the wood.
The consideration of the best means of effecting ventilation in this respect, is not a
matter with which we can deal in this work. It is sufficient to say, that in many
instances, the air channels are connected on the one hand with the open air, and on the
other with the chimney.
Chemical Alteration of the
Constituents of the Sap.
4. One of the most usual and most effective means of pre-
venting the decomposition of wood is by effecting a chemical change in the
constituents of the sap, so that fermentation can no longer be set up. To this class
belongs the well-known plan of protecting woodwork that is to be exposed to
the action of the moisture of the earth by charring the wood, either by fire or
by treatment with concentrated sulphuric acid, so that the wood is coated to a certain
depth with a layer of charcoal, the charcoal acting as an antiseptic. The charring
or carbonisation of the wood can be effected either with the help of a gas flame or
the flame from a coal fire. The apparatus of De Lapparent, invented for this purpose,
became very generally employed in 1866 at the dockyards of Cherbourg, Pola, and
Dantzic. According to another method the wood is impregnated throughout its
whole mass with some substance that either enters into combination with the con-
stituents of the sap, or so alters their properties as to prevent the setting up of
decomposition. To this class belong the four following methods, these being the
only ones that have met with any more extensive use.
1. Kyan's preserving fluid is a solution of bichloride of mercury of variable
degree of concentration. In England a solution of 1 kilo. of corrosive sublimate in
80 to 100 litres of water is generally employed for railway sleepers. The timber is
laid in a watertight wooden trough, containing the solution, where, according to its
size, it remains a longer or shorter time. In Baden the wood remains in the
kyanising solution, when it is to be impregnated to a depth of—
82 m.m. for 4 days.
85 to 150
150 to 180
7
""
ΙΟ
""
180 to 240
240 to 300
""
14
18
""
the solution consisting of 1 kilo. of sublimate to 200 litres of water. The prepared
wood is washed with water, rubbed dry, and then placed in sheds free from exposure
to rain and strong sunlight. The principal action of the bichloride of mercury is to
convert the albumen of the sap into an insoluble combination, capable of with-
standing decomposition, while the bichloride becomes gradually reduced to proto-
chloride of mercury (calomel). A great objection to this method is the danger to
476
CHEMICAL TECHNOLOGY.
which the carpenter or joiner who may afterwards shape the wood is exposed, the
free chemicals acting upon his system through his hands, nostrils, and mouth. In
England wood to be varnished is seldom kyanised.
Erdmann remarks upon this plan of preserving wood that the interior of the log is
still left in its original condition. To answer the objection the kyanising has been
made more effective by placing the wood into a water-tight trough, with the solution
of sublimate, and by a great pressure of air thoroughly impregnating the wood.
Kyanising by this method becomes, however, as expensive as any other impregnation
method. Recently there has been substituted for the pure bichloride of mercury a
double salt of the formula HgCl₂+KCl, obtained by decomposing a solution of
carnallite with oxide of mercury.
2. Burnett's patent (1840) fluid consists of 1 kilo. of chloride of zinc dissolved in
90 litres of water. Wood treated with Burnett's fluid has been buried in earth for
five years without undergoing any change, while unprepared wood buried for the
same length of time has been totally destroyed. Chloride of zinc has been much
used in Germany as an impregnating material. Besides this salt sulphate of copper
and acetate of oxide of zinc-pyrolignite of zinc (Scheden's method), have been
employed. The action of the copper and zinc salts may be explained by considering
that the metallic oxides of the basic salt formed during seasoning, separates and
combines with the colouring matter, tannic acid, resin, &c. of the wood, to form an
insoluble compound.
3. Bethell's (1838) patented method consists in treatment under strong pressure
with a mixture of tar, oil of tar, and carbolic acid, this mixture being known com-
mercially by the name of gallotin. In and near London wood thus treated has
remained eleven years in the earth without undergoing change; other pieces of
timber so treated were subjected to the action of the sea for four years and still were
in good condition. Vohl employs for preservation peat and brown coal creosote;
Leuchs uses paraffin. Such agents, however, render wood treated with them highly
inflammable.
4. Payne's method. This includes two patents, the first having been taken out in
1841. Both are based on the impregnation of the wood-first with one salt, and
next with another salt, which is capable of forming a precipitate insoluble in water
and sap of the wood with the first. The first solution is usually one of sulphate of
iron or of alum, then follows a solution of chloride of calcium or of soda. The wood
to be impregnated is placed in a vessel from which the air is exhausted, the
first solution being then admitted, and subsequently pressure is applied. The first
solution being removed, the second is admitted, and pressure again applied. It is
necessary to dry the wood partially between the two impregnations. Payne's
method, much used in England, possesses, moreover, the advantage of rendering the
wood somewhat uninflammable. The same effect results with the methods of Buchner
and Von Eichthal, who impregnate the wood with a solution of sulphate of iron,
and then with a water-glass solution, whereby the pores of the wood are filled with
ferro-silicate. Ransome attains the same end by an impregnation with a water-glass
solution and subsequent treatment with an acid. It is found that the treatment of wood
according to the above methods is generally attended with good results. A method
of impregnation with materials forming an insoluble soap, oleate of alumina, oleate of
copper, &c., patented in 1862, has given some moderate results on the small scale.
Mineralising Wood. 5. When the terms mineralised, petrified, metallised, or incrusted
are applied to wood, they include the meaning that the wood has undergone impreg-
TOBACCO.
477
nation with an inorganic substance, which has so filled the pores of the wood that it
may be said to partake of the characteristics of a mineral substance. Suppose that
the wood has become impregnated with sulphate of iron, when exposed to the rain
the sulphate will be gradually dissolved out, in time leaving only a basic sulphate.
By the researches of Strützki (1834), of Apelt in Jena, and of Kuhlmann (1859), the
influence of oxide of iron upon wood fibre has been rendered very clear. Wood
impregnated with basic sulphate of iron ceases to be wood after some time.
Impregnation.
Boucherie's Method of 6. This method consists in the impregnation of the wood with
the necessary substance, in a manner similar to the natural filling of the pores with
sap; that is to say, the solution is introduced into the tree from its roots, and is thus
made to take the place of the sap in all parts of the timber. When the tree is felled
the root end is placed in a solution of the salt (sulphate of copper, acetate of iron),
and allowed to remain for some days; at the end of the required time the wood will
have become completely impregnated with the salt. Occasionally this method is
employed in colouring woods, colouring matter being used instead of, or as well
as, the salt.
The linden, beech, willow, elm, alder, and pear tree can be treated in
this manner. The fir, oak, ash, poplar, and cherry tree do not, however, absorb the
impregnating fluid sufficiently.
TOBACCO.
Tobacco, Tobacco, as employed for snuff and for smoking and chewing, is the
product of various kinds of annual plants belonging to the genus Nicotiana, of the
family of Solanea, generally cultivated in warmer parts of the globe, but capable of
growing in countries situated under 52° N. lat. The best tobaccos are grown in
America, and are chiefly exported from the southern states of North America, viz.,
Maryland, Virginia, &c., from Orinoko, Havanna, and Cuba, &c. The European
tobaccos are those of Holland, Hungary, Turkey, and France. In Europe three
separate botanic varieties are cultivated. They are:-
1. Common or Virginian tobacco (Nicotiana tabacum), with a large lancet-shaped
ribbed leaf.
2. Maryland tobacco (Nicotiana macrophylla), with broad and not so strongly pointed
leaves as those of the common tobacco plant.
3. The farm or violet skin tobacco (Nicotiana rustica), with an oval leaf and long stalk.
The quality of the tobacco is dependent upon the climate, upon the soil, and upon
the seed it is obtained from. Next to the vine, the tobacco plant is that requiring the
most care in its cultivation. The influence of careful culture is so great, that plants
grown in some parts of Germany yield tobacco unequalled by some of the richest
tropical produce.
According to the most recent researches, tobacco contains the following sub-
stances:-
Mineral bases
Potash
Lime
Magnesia
Oxides of iron and manganese
Organic
base{ Nicotine
Ammonia
Nitric acid
Malic acid (Tobacco acid?)
Citric acid
Mineral aids
Hydrochloric acid
Organic Acetic acid
Sulphuric acid
acids
Oxalic acid
Phosphoric acid
Pectic acid
\Ulmic acid
478
CHEMICAL TECHNOLOGY.
Other mineral Silica
substances Sand
Nicotianin
substances
Other organic Wax or fat
Green and yellow resin
Nitrogenous substances
Cellulose
Chemical Composition of the
Tobacco Leaf.
The chief characteristic constituents of the tobacco leaf are
the three following:-namely, nicotianin, nicotine, and malic acid. Nicotianin, or
tobacco camphor, is a fatty substance, possessing strongly the odour of tobacco, and
a bitter, aromatic flavour. Experience has shown that the varieties of tobacco con-
taining the most nicotianin are those most preferred. It is generally considered that
nicotianin is identical with cumarin (C9H8O2), found in the tonka bean (Dipterix
odorata), in the Asperula odorata, in the Melilotus officinalis, and Anthroxanthum
odoratum, as well as in the leaves of the Angraecum fragrans, and the Liastris odora-
tissima. Nicotine (C10H14N2) is an organic base, and exists in a pure condition as a
colourless oil, possessing the odour of tobacco and a caustic flavour; it is soluble in
water, alcohol, ether, and some oils. It is even in very small doses a deadly poison;
and in the very smallest quantities it will cause convulsions and paralysis. The pro-
portion of nicotine met with in the various kinds of tobacco leaves varies greatly.
From the experiments of Schlæsing, made with many kinds of French and American
tobaccos, the following quantity per cent of nicotine is found in the dry leaves of
tobacco from :-
Departement Lot
...
...
Lot-et-Garonne
...
Nord
:
""
Ille-et-Villaine
...
""
Pas de Calais
Alsace
Virginia
Kentucky...
Maryland
:
:
:
:
...
Nicotine.
7.96
7.34
:
:
:
6:58
6.29
4'94
3'21
6.87
6.09
2:29
less than
2'00
Havanna
Dried snuff-tobacco contains about 2 per cent of nicotine, and contains on an
average in its undried (usual) condition 33 per cent of water, the nicotine then
amounting to 1.36 per cent. The nicotine is contained in the tobacco in the form of
a salt. The characteristic acid is nicotic or tobacco acid, C3H404, which recent
numerous researches have proved to be identical with malic acid. The tobacco leaf
also contains albumen, woody fibre, gums, and resin. The leaves are also very rich
in mineral constituents, these amounting to 19 to 27 per cent of the weight of the
dried leaf. Merz obtained about 23.33 per cent ash with several varieties of
tobacco leaf. 100 parts of this ash contained potash, 26′96; soda, 2.76; lime, 39′53;
magnesia, 9*61; chloride of sodium, 965; sulphuric acid, 278; silica, 4′51; and
phosphate of iron, 4'20 parts. There is found, also, nitrate of potash, the quantity of
which does not, however, influence the combustibility of the tobacco.
Manufacture of Tobacco. Good smoking tobacco should give off an agreeable odour,
should not deflagrate while burning, and not bite the tongue. Taste differs consider-
ably in the respect of strength in this country from abroad; nowhere but in the
TOBACCO.
479
United Kingdom are such strong smoking tobaccos met with. The freshly dried
tobacco leaves are not suited for smoking, because they contain a very considerable
amount of albuminous matter, and on burning give off an odour of burnt horn, while
they contain too large a quantity of nicotine. The preparation or manufacture of
tobacco aims at the more or less complete destruction of the albuminous matters, the
partial elimination of the nicotine, and the development of a peculiar aroma, while
the leaves are formed by mechanical means into a suitable shape for smoking and
snuffing. The leaves are moistened with water and placed together in heaps so as to
cause a kind of fermentation, the temperature increasing to about 35°, the effect of
which is that the albuminous matter of the tobacco is destroyed, while aromatic
substances are developed. This process is assisted by the addition of what the trade
terms “sauce,” but nothing is known of the reactions and changes which take place.
When the tobacco leaves are gathered from the plants they are laid one upon the other to
the number of ten or twelve and placed in heaps in a dry shed, care being taken to cover
the heaps with canvas. As soon as the sweating sets in, the leaves are suspended
one by one on ropes stretched through the shed, and dried by exposure to a current
of air; when dry the leaves are packed together to the number of thirty, so as to
form a bundle, several hundreds of which are put together into casks. The weight
of the casks filled with tobacco averages from 19 to 26 cwts. In some, but by no
means in all instances, the cultivators of tobacco prepare the leaves to some extent by
first moistening them with brine and causing them to undergo a partial fermentation.
The leaves are then dried and packed in casks. By this means the tobacco may be
preserved for a great many years, improving with age.
Smoking Tobacco. The tobacco leaves are first sorted; that is, those of the same colour
and thickness are put together. They are next stripped, the thicker parts (stem or
nerve) being cut out, because as these consist chiefly of woody fibre they would on
burning impart an unpleasant odour to the tobacco. The leaves are next sauced or
moistened with a liquor containing chiefly salts (common salt, saltpetre, sal-ammo-
niac, nitrate of ammonia), saccharine matter, spirits, and some organic acids, such as
tartaric and oxalic acid; the salts assist in the preservation as well as in the
retardation of the combustion of the tobacco. The other substances impart, under
the influence of fermentation, a peculiar aroma to the tobacco, which aroma is some-
times compared to the bouquet of wine. The sauced leaves are next submitted to
fermentation, dried at a gentle heat, and finally cut into shreds by means of
machinery. Tobacco leaves are also twisted or spun together; for instance, in the
kind known as twist. Cigars are tobacco enveloped in a smooth leaf. The fact
that cigars are improved by keeping is due to a kind of slow fermentation, during
which the aroma is more fully developed, while noxious substances are eliminated.
Tobacco smoke contains, in addition to carbonic acid, water, and some ammonia,
the products of the dry distillation of tobacco, to which the peculiar flavour is due—
among these substances are nicotine and nicotianin. Zeise found in tobacco smoke a
peculiar empyrematical oil, butyric acid, ammonia, carbonic acid, paraffin, empyreu-
matic resin, traces of acetic acid, oxide of carbon, and carburetted hydrogen.
Curiously enough, burning tobacco does not form carbolic acid nor creosote; hence
tobacco smoke affects the eyes less than does the smoke of smouldering wood. Zeise
experimented on Porto Rico tobacco; but his researches fail to convey any informa-
tion as to the constitution of the essential aroma of tobacco smoke; in this respect it
is with tobacco as with the bouquet of fine brands of wine, chemical reagents cannot
480
CHEMICAL TECHNOLOGY.
detect the d
rence.
But it is certain that tobacco smoke contains conjugated
ammonias, a. as aniline has, in very dilute state, a similarity in odour with the
smoke of god tobacco, it may be present. Carbolic acid may also be produced by
the dry distillion of tobacco. The combustibility of tobacco is not proportional to the
quantity of n. ic acid (nitrates) it contains, because while Kentucky tobacco, rich in
nitrates burns Dadly, the Java, Maryland, Brazilian, and Hungarian tobaccos, poor
in nitrates, burn readily. Schlosing has recently investigated the cause of the
varying degr of the combustibility of tobacco. He found that the portion of
tobacco ash soluble in water always contains carbonate of potash in proportion to the
combustibility of the weed. When tobacco was carbonised by smoking, the soluble
portion of the ash was found to contain only chloride of potassium and sulphate of
potash. A badly burning tobacco is improved by saucing it with the solution of a
potash salt of some organic acid (malic, citric, tartaric, or oxalic acid), and then
drying the tobacco; on the other hand, a good burning tobacco is deteriorated by
treating it with solutions of either sulphate of lime, chloride of calcium, or the
corresponding magnesia and ammonia compounds. The cause of this phenomenon
appears to be due to the fact that the potash salts of the organic acids yield on being
carbonised a bulky, light, and very porous charcoal, which readily burns off, leaving
only ash, while the charcoal formed by the combustion, under the same conditions,
of the organic lime salts is very compact, hard, and burning off with difficulty.
Snuff. For the making of snuff the tobacco leaves are sorted as for smoking
tobacco, but the sauce is chiefly composed of ammoniacal salts and aromatic
substances. The fermented leaves are formed into carottes, thick beet-root shaped
masses tapering from the centre to both ends, but not drawn out into a thin spindle;
these carottes are rasped (rappé) by means of machinery, and thus converted into
powder. After having been sifted, this powder is again moistened and submitted to
another fermentation. Snuff contains nicotine, partly free, partly as a neutral or
basic (probably acetate) salt to an amount of about 2 per cent. Snuff also contains
ammonia combined with an acid. It is to the presence of these substances that snuff
owes its irritating action on the mucous membrane. In order to prevent snuff
from becoming dry glycerine is frequently added.
The aim of the fermentation of the tobacco for the purpose of snuff making appears
to be:-1. The formation of a peculiar oil or ether which imparts aroma.
2. The
partial destruction of the nicotine of the tobacco so as to render it better fitted for
use as snuff.
3. The production of alkalinity by the partial destruction of the
organic acids of the tobacco. 4. Evolution of a specific flavoúr by the formation of
vapours of carbonate of ammonia (probably also of ammonia bases, such as ethyl-
amin), and ´´otine. 5. The conversion of the albuminous matters and other
nitrogenous substances into ammonia, whereby the loss of ammonia by volatilisation
is made up au
a black substance (humus), to which snuff owes its dark colour, at
the same tim formed.
Essential Oils a
tial oils mos
plants is m
containing t
gently rubbi
ins.
TECHNOLOGY OF ESSENTIAL OILS AND RESINS.
These substances almost all occur naturally. To the essen-
J'ants owe their odour and flowers their perfume. The essential oil in
vith enclosed in cells; hence, after bruising a plant, or the parts
›ssential oil, the peculiar odour is more perceptible; for instance, by
between the fingers the leaves of some kinds of geraniums, melissa,
ESSENTIAL OILS.
481
lemon-plant, &c. Essential oils do not impart to the fingers a fatty, but a rather rough,
harsh feeling. A large number of essential oils possess the property of precipitating
silver from its ammoniacal solution in a metallic state; hence the use of essential
oils in silvering glass (See p. 281).
Preparation of Essential Oils. These oils are chiefly obtained by submitting parts of
plants, previously ground to a coarse powder, to distillation with water. Although
the boiling-point of these oils is generally much higher than that of water, the oils
are mechanically carried over in a minute state of division with the aqueous vapour.
When oils, the boiling-point of which is very high, have to be extracted, some common
salt is added to the water to heighten its boiling-point. In order to separate the oil
from the water there is employed a peculiarly shaped vessel called a Florentine
flask. In this way the essential oils of aniseed, chamomile, lavender, peppermint,
cloves, cinnamon, &c., are obtained, while the most common essential oil, viz., that of
turpentine, is obtained by the distillation of Venice turpentine with water.
Preparation of Essential
Oils by Pressure.
The essential oils largely met with enclosed in the cells of the
skin of lemons, oranges, bergamots, and, in fact, all the fruits belonging to the Citrus
species, are obtained by pressing the rind of these fruits. Although the greater
number of the essential oils occur ready formed in various parts of the plants, some
of these oils are the result of the action of water, as, for instance, the essential oil
of bitter almonds, which is formed by the action of water upon amygdalin under the
influence of a pecular albuminous compound called synaptase or emulsin; the
essential oil of mustard seed is formed in a similar manner, but may be artificially
prepared by distilling a mixture of iodide of propyl and cyanide of potassium, &c.
Extraction of Essential Oils Some of the essential oils, more especially those present in
flowers, are so sparingly distributed that they can only be obtained by digesting the
fresh flowers with pure olive oil or with cotton-wool soaked in sweet olive oil, the
fresh flowers being placed in alternate layers between the cotton saturated with oil;
in some cases pure lard is employed. The essential oils may be recovered from the
sweet oil by agitation with strong and highly rectified alcohol. The essential oils of
jasmine, sweet violets, hyacinths, &c., are obtained in this manner.
by means of Fatty Oils.
Properties and Uses of
Essential Oils.
These oils are more or less soluble in water, and the solutions
are known in pharmacy as distilled waters. The essential oils are soluble in alcohol
in proportion to the amount of oxygen they contain. Upon this property is based
the use of these oils in perfumery and for the preparation of liqueurs (cordials).
Perfumery. This branch of industry provides us with scented waters (esprits eaux de
senteur), odoriferous extracts (extraits à odeurs), perfumed fats, pomatums, oils, &c.
Scented waters are really alcoholic solutions of one or more essential oils. The
alcohol used for this purpose requires to be very pure and perfectly free from fusel oil
or other impurity. The oils are dissolved in the alcohol, and in order to blend the
mixture and render it mellow, it is kept for several months in a bottle before being
sold. The old process of distillation is very properly discarded, because, owing to
the high boiling-point of the oils, a portion was left in the still, while the scented
waters thus prepared were inferior in quality. Eau de Mille Fleurs is prepared by
dissolving in 9 litres of alcohol, 60 grms. of balsam of Peru, 120 grms. of oil of
bergamot, 60 grms. of oil of cloves, 15 grms. of neroli oil (oil of orange
flowers, a very expensive oil), 15 grms. of oil of thyme, adding to the mixture
4 litres of orange-blossom water, 120 grms. of tincture of musk, obtained by
digesting 15 grms. of civet and 75 grms. of musk with 2 litres of alcohol. Eau
32
482
CHEMICAL TECHNOLOGY.
de Cologne is obtained by dissolving in 6 litres of alcohol 32 grms. of essential
oil of orange-peel and equal quantities of oil of bergamot, lemon, essence de
limette, essence de petit grains, 16 grms. essence de cedro, and equal quantities of
essence de cedrat, essence de Portugal; further, 8 grms. of neroli oil and 4 grms. of
rosemary.
The perfumed extracts are generally obtained by the exhaustion, by means of
alcohol, of the scented fats and oils prepared from flowers as before described.
Doebereiner first suggested the use of artificial perfumes; among these are an
Chemical Perfumes. alcoholic solution of acetate of amyl as pear oil, valerate of amyl as
apple oil, buterate of amyl as pine-apple oil, pelargonate of ethyl as oil of quinces,
suberate of ethyl as essence of mulberries, while nitrobenzol mixed with nitrotoluol
(commercial nitrobenzol) is termed artificial oil of almonds, and, when very coarse, is
sold as essence de Mirbane, chiefly used for the preparation of aniline. The perfumed
fats (pomatums) of better quality are generally prepared from an infusion of the
flowers with oil or fat at a temperature of 65°, or by a process of digestion in the
cold by placing the flowers in layers between pure lard or cotton-wool soaked in
very pure olive oil; enfleurage is the name given to this operation. The ordinary
pomatums are made simply of lard or marrow-fat coloured with turmeric, annatto, or
alkanet root, and perfumed with a few drops of some essential oil.
Preparation of Cordials. The aim of the preparation of liqueurs (cordials) is to render
brandy a more agreeable beverage by the addition of sugar, glycerine, and aromatic
substances. A distinction is made between finer liqueurs (rosoglio) and ordinary
cordials (aqua vitæ) according to the quality of the materials employed for the purpose.
When a sufficiently large quantity of sugar is used to render the liqueurs thickly fluid
they are designated crêmes, while those made with the juices of fruit obtained by
pressure, sugar, and alcohol, are cálled ratafia. These liqueurs are not prepared to
any great extent in this country; but in France, Italy, Austria, and especially Holland,
the preparation is on a large scale.
The basis of all liqueurs is a very highly rectified and pure alcohol. The
vegetable materials used in the liqueurs may be classified under three heads :—In
the first place, such vegetable substances as contain essential oils and are used
for that reason only, carraway, aniseed, juniper-berries, mint, lemon-peel, orange-
blossom, and bitter almonds. These substances, previously bruised or cut up, are
digested with alcohol, the mixture being next distilled, or, as is more generally the
case, alcoholic solutions of the essential oils are employed and the preparation
performed in the cold. To the second class belong such vegetable substances as are
used for the sake of their essential oil and for their aromatic bitter substances,
chiefly roots, such as sweet calamus, gentian, ginger, orange-peel, unripe bitter
Curaçoa apples (a peculiar kind of orange), wormwood, cloves, cinnamon, vanilla (the
pod of an orchidaceous plant originally brought from Mexico). These substances
having been bruised are digested with alcohol either at the ordinary temperature of
the air or at 50º to 60°, the result being the formation of what is termed a tincture.
To the third class belong fruits, such as cherries, pine-apples, strawberries, rasp-
berries, the juice of which is obtained by pressure, passed through a sieve, and
mixed with alcohol and sugar or syrup, viz., a solution of 4 lbs. of refined loaf- -sugar
in 4 litres of water. The liqueurs generally contain from 46 to 50 per cent of alcohol.
It is customary to colour the liqueurs red with santal-wood, cochineal, aniline red,
or with the Coccus polonicus, as is the case with the celebrated Alkermes de Firense,
RESINS.
483
I
a liqueur made at Florence; yellow with saffron, turmeric, or marigold flowers
(Calendula); green by mixing yellow and blue; blue with tincture of indigo; violet
with aniline violet; while in many cases caramel is used to impart a brown colour.
The so-called crêmes contain for every litre of liquid about 1 lb. of sugar or a corre-
sponding quantity of glycerine. As an instance of the composition of a liqueur,
Maraschino consists of 4 litres of raspberry water, 1 litres orange-blossom water,
1½ litres kirschwasser (a Swiss preparation-from cherries fermented and distilled-a
strong spirituous liquid which contains hydrocyanic acid), 18 lbs. of sugar, and 9 litres of
alcohol at 89 to 90 per cent. Liqueurs are very similar to crêmes, but contains less
sugar. English bitter contains 5 parts of flavedo corticum aurantiorum (outer rind
of dried orange peel), 6 parts of cinchona bark, 6 parts of gentian, 8 parts of Carduus
benedict, 8 parts of centaury, 8 parts of wormwood, 4 of orris root digested with
54 litres of alcohol at 50 per cent, while after filtration 12 lbs. of sugar are added.
Cherry ratafia :—20 litres of cherry juice, 20 litres of alcohol at 85 per cent, 30 lbs.
sugar, and usually 4 to 8 litres of bitter almond water. Peppermint :—21 litres of
essential oil of peppermint dissolved in 1 litre of alcohol at 80 per cent; this solution
is poured into 54 litres of alcohol at 72 per cent sweetened with 60 lbs. of sugar
previously dissolved in 26 litres of water, and coloured with either tincture of indigo
or turmeric.
Resins. By the action of the oxygen of the air most of the essential oils are
gradually thickened, and at length converted into a substance termed resin. Resins
are frequently met with in the vegetable kingdom; in some instances, as with
coniferous trees, resin flows spontaneously from the wood in combination with an
essential oil, so-called Venice turpentine, which hardens by exposure to air. Some
resins are extracted from vegetable matter by means of alcohol, this solution being
either precipitated with water or evaporated to dryness. Resins are either soft, and
are then termed balsams, chiefly solutions of resin in essential oils, or hard. To the
former belong Venice turpentine, Canada balsam, balsam of Peru, Copaiva balsam,
&c.; to the latter, amber (a fossil resin), anime, copal, gum dammar, mastic, shellac,
asphalte. The gum resins are obtained from incisions made in certain kinds
of plants, the milky juice of which hardens by exposure to air; these substances
are partly soluble in water, and yield with it in many instances an emulsion; for
instance, assafœtida, gum gutti, &c. Many gum resins possess a very strong odour
and contain essential oils. Although it is customary to treat of caoutchouc and
gutta-percha under the head of resins, these substances are not related to resins at
all, but belong to a separate class of bodies, among which, according to Dr. G. J.
Mulder's researches, the so-called drying oils must be enumerated.
Sealing-Wax.
Use of Resin as Sealing-wax of modern time (for medieval sealing-wax was really
a mixture of wax with Venice turpentine and colouring matter) is prepared from
shellac, to which some turpentine is added in order to promote fusibility and
prevent brittleness. Red sealing-wax and bright coloured wax are made of a
very pale, sometimes even purposely bleached, shellac, while black and dark
coloured sealing-wax are made of more deeply coloured shellac. In addition to
shellac and turpentine, sealing-wax contains earthy matter, added not only for the
purpose of increasing the weight, but also for preventing the too rapid fusion
of the mass; chalk, magnesia, plaster of Paris, zinc-white, sulphate of baryta,
kaolin, finely-divided silica, are employed for this purpose. Red sealing-wax is
prepared by melting together in an iron pan placed on a charcoal fire 4 parts of
484
CHEMICAL TECHNOLOGY.
shellac, 1 part of Venice turpentine, and 3 parts of cinnabar (vermillion), care
being taken to stir the mixture constantly. Ordinary red sealing-wax is often
composed of:-
Shellac ...
Turpentine
...
Chalk or magnesia
Gypsum or zinc-white
Baryta white
Vermillion
Oil of turpentine
...
:
...
:
:
:
I.
2.
3.
4.
5.
550
620
550 700
600
740
680
600
540
600
300
200
200
100 380
300
300
130 220
·340 300
30С
20
25
1
The cooled but still soft mass is either rolled on a slab of marble and shaped into
sticks, or the fluid mass is run into brass moulds. Perfumed sealing-wax contains
either benzoin resin, storax, or balsam of Peru. The various colours are imparted by
cobalt ultramarine (cobalt blue), chromate of lead, bone-black, &c. Marbled sealing-
wax is made by mixing variously coloured sealing-wax together. Inferior kinds of
sealing-wax-parcel-wax-are coloured with red oxide of iron, while instead of
shellac ordinary resin is used with gypsum or chalk. New Zealand resin, the
produce of the Xanthorrhea hastilis, is now frequently used instead of shellac.
Asphalte.
This material sometimes known as bitumen, is a black, glossy, brittle
resin, probably formed by the gradual oxidation of petroleum oil; it occurs very
largely on the island of Trinidad, on the northern coast of S. America, at the mouth
of the Orinoco, on the water of the Dead Sea (anciently Lacus Asphaltites), and
in some other localties, viz. France, Seyssel, Departement de l'Ain, a limestone con-
taining 18 per cent of asphalt. By boiling this limestone, previously broken up
into small lumps, with water, there is obtained an asphalte, 7 parts of which are
mixed with 90 parts of native asphalte limestone. The materials are ground up
together and are employed for paving purposes, being compressed with heavy and
highly heated irons. Asphalte also occurs at Val de Travers, Switzerland; Limmer,
Hanover; Lobsann, Lower Alsace; and in the Northern Tyrol. Asphalte, or
bitumen, is somewhat soluble in alcohol, readily so in Persian naphtha, oil of turpen-
tine, benzol, and benzoline. It is used in varnish making (iron varnish), in engra-
ving copper and steel, as an etching ground, and as an oil paint. Asphalte mixed
with sand, lime, or limestone, is largely used for paving purposes, being durable and
somewhat elastic; it is employed for this purpose either in a pasty or semi-fused
state, or in powder. Instead of native asphalte, Busse's terresin, a mixture of coal-
tar, lime, and sulphur is sometimes used, as well as coal tar asphalte, obtained from
gas works. The residue of the distillation of coal-tar is often employed instead of
asphalte, and pebbles mingled with coal-tar are now used to form excellent footpaths
in some parts of the metropolis.
་
Caoutchouc. Elastic gum or india-rubber, is derived from the the milky juice of a
series of plants, occurring also in opium; but the commercial article is obtained
from the milky juice of various trees belonging to the natural orders of the Urticeæ,
Euphorbiaceae, Apocyneæ. Among the trees which yield caoutchouc in large quantity
are the Siphonia cahucu, in South America, and the East Indian, Urceola elastica.
Ficus elastica, F. religiosa, F. indicu, also yield caoutchouc. It is obtained by
making incisions in the tree and collecting the exuding juice in vessels of dried clay
INDIA-RUBBER.
485
The juice is solidified by the application of fire or by exposure to the sun's rays; the
variety known as lard gum is usually dried by exposure to the sun. Perfectly pure
caoutchouc is a white, and in thin sheets semi-transparent, substance; its texture is
not fibrous; it is perfectly elastic, becoming turbid and fibrous when strongly
stretched. Excessive cold renders it hard but not brittle. The specific gravity of
caoutchouc is o‘925. Although hot water and steam render caoutchouc soft, it is not
further acted upon by them. It is insoluble in alcohol, not acted upon by dilute
acids or strong alkalies, while for a very long time it resists the action of chlorine.
Strong sulphuric and nitric acids decompose india-rubber, and when red fuming
nitric acid is employed a violent combustion ensues. If when strongly stretched
india-rubber is placed in cold water for a few minutes it temporarily loses its
elasticity, which it regains by being immersed for a few minutes in water at 45°. By
exposure to a gentle heat caoutchouc becomes supple, and finally melts at 200°, with
partial decomposition, forming a viscous mass which does not again become solid on
cooling. When caoutchouc is ignited in contact with air it burns with a sooty flame.
Of all substances with which we are acquainted none would be better suited to gas
manufacture than caoutchouc, which, according to experiments made many years ago
at Utrecht, yields at red heat rather more than 30,000 cubic feet of gas to the ton, the
gas being quite free from sulphur and ammonia compounds, and its illuminating
power very superior to that of the best oil gas. Unfortunately caoutchouc is much
too high priced for this application. Caoutchouc may be kneaded with sulphur
and other substances by the aid of heat, becoming converted into what is known as
vulcanised india-rubber, vulcanite, ebonite, &c. When caoutchouc is submitted to
dry distillation, at much below red heat, it yields only oily fluids, consisting of
carbon and hydrogen (caoutchen, heveen, &c.), which are par excellence solvents for
caoutchouc. Caoutchouc itself contains only carbon and hydrogen, its formula being
CH, (in 100 parts: 87.5 carbon and 12.5 hydrogen); probably, however, caoutchouc
is a more complex mixture of various hydrocarbons.
Solvents of Caoutchouc. India-rubber is soluble in alcohol-free ether, in the oils
(empyreumatic) of caoutchouc, in Persian naphtha, oil of turpentine, sulphide of
carbon, and in chloroform. Industrially the ethereal solution of caoutchouc is
useless, because it contains hardly more than a trace of that substance. As regards
oil of turpentine, it dissolves caoutchouc only when the oil is very pure and with the
application of heat; the ordinary oil of turpentine of commerce causes india-rubber
to swell rather than to become dissolved. In order to prevent the viscosity of the
india-rubber when evaporated from this solution, 1 part of caoutchouc is worked up
with 11 parts of turpentine into a thin paste, to which is added part of a hot and
concentrated solution of sulphuret of potassium (K2S5) in water; the yellow liquid
formed leaves the caoutchouc perfectly elastic and without any viscosity. The solu-
tions of caoutchouc in coal-tar naphtha and benzoline are most suited to unite pieces
of caoutchouc, but the odour of the solvents is perceptible for a long time. As
chloroform is too expensive for common use, sulphide of carbon is the most usual
and also the best solvent for caoutchouc. This solution, owing to the volatility of the
menstruum, soon dries, leaving the caoutchouc in its natural state. When alcohol is
mixed with sulphide of carbon the latter does not any longer dissolve the caoutchouc,
but simply softens it and renders it capable of being more readily vulcanised.
Alcohol precipitates solutions of caoutchouc and gutta-percha.
•
486
CHEMICAL TECHNOLOGY.
Preparation and Use of
India-Rubber.
India-rubber is used to clean paper, rub out black-lead pencil
marks, for making waterproof fabrics (macintosh), rubber sponge, tubing, elastic webs,
lutes, &c.
Vulcanised Caoutchouc.
When caoutchouc is immersed for some time in molten sulphur
it absorbs the latter, and becomes converted into a yellow, very elastic mass. The
properties of vulcanised india-rubber are: elasticity even at low temperatures, while
ordinary india-rubber hardens at 3°. Vulcanised india-rubber is insoluble in the sol-
vents of caoutchouc. It resists compression to a very great extent; hence its use
instead of steel springs on the tramway cars. According to the old method
caoutchouc was vulcanised by being placed for some ten to fifteen minutes in
thin plates in molten sulphur heated to 120°, the weight of the caoutchouc increasing
10 to 15 per cent. The material was subsequently mechanically treated by pressure,
and then heated to 150°. In order to prevent efflorescence of the sulphur,
caoutchouc is sometimes heated to 120°, and then kneaded, by the aid of powerful
machinery, with either kermes (Sb₂S3), or a mixture of sulphur and sulphuret of
arsenic. At the present day Parkes's method is generally adopted; the caoutchouc is
simply immersed in a mixture of 40 parts of sulphide of carbon and 1 part of
chloride of sulphur; it is next placed in a room heated to 21°, and when all the sul-
phide of carbon has been volatilised, the process is in so far complete that it is only
requisite to boil the material in a solution of 500 grms. of caustic potassa to 10 litres
of water, the vulcanised caoutchouc being next washed to remove excess of alkali.
Recently (1870) Humphrey has introduced the use of petroleum ether (benzoline)
instead of sulphide of carbon, as the former fluid dissolves chloride of sulphur
readily. H. Gaultier de Claubry (1860) vulcanises caoutchouc by the aid of
bleaching-powder and flowers of sulphur. This mixture produces chloride of
sulphur, and the caoutchouc treated by it contains some chloride of calcium.
Neither this process nor that of Gérard-the use of a solution of pentasulphide of
potassium of 25° to 30° B., aided by a temperature of 150°, and a pressure of
5 atmospheres or 75 lbs. to the square inch-are practically available on the
large scale. Articles of vulcanised india-rubber are made of ordinary caoutchouc
and then vulcanised. The uses of vulcanised india-rubber are so many and so
generally known that it is hardly necessary to enumerate them.
In the year 1852 Goodyear discovered a process by which caoutchouc is rendered
hard and woodlike, being then termed vulcanite or ebonite. This substance exhibits
a black or brown colour, and is largely used for making combs, imitation jet
ornaments, stethescopes, and a variety of articles. The preparation of ebonite differs
from that of vulcanite only in the introduction of a larger amount of sulphur
(30 to 60 per cent), at a higher temperature, with the addition of other substances,
shellac, gutta-percha, asphalte, chalk, sulphate of baryta, pipe-clay, sulphurets of
zinc, antimony, or copper, &c. Ebonite is capable of taking a high polish; does
not, as is the case with horn, become rough when cleaned with hot water, and is to
some extent elastic. Vulcanised caoutchouc mixed with sand, emery, and quartz,
is used for sharpening agricultural implements, scythes, sickles, &c.
Production and Consumption
of Caoutchouc.
The total quantity of caoutchouc produced in 1870 amounted to
120,000 cwts., of which the island of Java yielded 50,000 cwts.
The consumption is fully equal to the supply, the largest quantity being used in North
America, 35,000 cwts.
Gutta Percha. Plastic gum, gutta or getah-percha, gettannia gum, tuban gum, is a
substance in many respects similar to caoutchouc; it is the inspissated juice of the
GUTTA-PERCHA.
487
Isonandra gutta, a tree growing in Malacca, Borneo, Singapore, Java, Madura, and
adjacent countries.
}
Gutta-percha was at first obtained by felling the trees and collecting the exuding
juice, either in suitable vessels or in shallow pits dug in the soil, or in baskets made
from banyan leaves, the juice being left to coagulate under the action of the sun.
More recently deep incisions are made in the trees and the exuding juice collected.
The lumps of solid gutta-percha thus obtained are united by softening in hot water
and by pressure. The raw gutta-percha of commerce is a dry, red, or marbled mass,
not unlike leather cuttings which have been pressed together; the raw material con-
tains as impurities some sand, small pieces of wood and bark, and sometimes other
inspissated vegetable juices of less value than gutta-percha. The name gutta-
percha really means Sumatra gum, this island being known in Malay language as
Pulo-percha. When perfectly pure gutta-percha is quite white, its ordinary brown
colour being due to an acid insoluble in water, which is present, partly free, partly as
insoluble salts (of magnesia, ammonia, potash, and protoxide of manganese),
of apocrenic acid; but in addition there is a small quantity of organic colouring
matter. Gutta-percha is a mixture of several oxygen-containing resins, which
appear to be the products of the oxidation of a hydrocarbon, the formula of which is
C20H60. Payen found in gutta-percha the following substances:-75 to 80 per cent
of pure gutta-percha; 14 to 16 per cent of a white crystalline resin termed alban ;
and from 4 to 6 per cent of an amorphous yellow resin named fluavil. Previously to
being used gutta-percha is cleansed from dirt by a mechanical process of kneading
in warm water, being then usually rolled into thick plates or sheets. The purified
material exhibits a chocolate-brown colour, is not transparent unless first reduced to
sheets as thin as paper, when the gutta-percha is in transparency equal to horn. At
the ordinary temperature of the air gutta-percha is very tough, stiff, not very elastic
nor ductile. Every square inch of a strap of gutta-percha, if of good quality and as
homogeneous as possible, can sustain a strain of 1872 kilos. without breaking. Its
sp. gr.=0′979. At 50° it becomes soft, and at 70° to 80° it is so soft as to be very
readily moulded, while two pieces pressed together at this temperature become
perfectly joined. By the aid of heat gutta-percha can be rolled into sheets, drawn
into wire, and kneaded into a homogeneous mass with caoutchouc.
Solvents of Gutta-Percha. Gutta-percha is insoluble in water, alcohol, dilute acids, and
alkalies; it is soluble in warm oil of turpentine, sulphide of carbon, chloroform, coal-
tar oil, caoutchouc oil, and in the somewhat similar oil obtained by the dry distilla-
tion of gutta-percha. Ether and some of the essential oils render gutta-percha pasty.
As already stated this substance becomes soft in hot water, absorbing a small quantity,
which is only very slowly driven off. Dry gutta-percha is a very good insulating
material for electricity.
Uses of Gutta-Percha. The natural properties of this substance indicate its use as a sub-
stitute for leather, papier maché, cardboard, wood, millboard, paper, metal, &c., in all
cases not exposed to the action of heat, and where a substance is desired resisting water,
alcohol, dilute acids, and alkalies. The raw material, previously to being moulded into
shape, is purified and kneaded by means of powerful machinery and with the assistance
of hot water (some soda or bleaching-powder solution being added), the aim being
the removal of such impurities as are only mechanically mixed with the gutta-percha as
well as the removal of some of the colouring matter, while a more homogeneous mass is
produced. The purified substance is next submitted to the action of kneading machinery
similar to that in use for working up caoutchouc, while it is rolled out into plates of some
3 centimetres in thickness. Gutta-percha is moulded into tubes by the aid of machinery
similar to that employed for making lead and block-tin tubing. Many objects are made
from gutta-percha by pressing it while soft into wooden or metal moulds. By the use of
488
CHEMICAL TECHNOLOGY.
a solution of gutta-percha in benzol, it may be glued to leather and similar substances.
It is almost impossible to enumerate the various uses of gutta-percha. It is employed
for straps for machinery instead of leather, tubes for conveying water, pumps, pails, sur-
gical instruments, ornamental objects of various kinds, for covering telegraph wires, &c.
Unlike pure caoutchouc gutta-percha becomes gradually deteriorated by exposure to the
atmosphere, so that it can be even readily ground to powder.
Mixture of Gutta-Percha Frequently a mixture of I part of gutta-percha and 2 parts
and Caoutchouc. of caoutchouc is employed. Articles made of this compound
possess the properties of both substances, and may be vulcanised equally as well as
gutta-percha alone. A mixture of equal parts of caoutchouc, gutta-percha, and sulphur,
heated for several hours to 120°, obtains properties similar to those of bone and horn.
Sometimes gypsum, resin, and lead compounds are added to this mixture, which is then
used for making knife hafts, buttons, &c.
Varnishes. By varnish we understand a liquid of an oily or resinous nature
employed for coating various objects, the thin film becoming dry and hard, thus
protecting the object on which it is laid from the action of air and water, and
at the same time imparting a glossy and shining surface. We distinguish oil and
Oil Varnishes. Spirit varnishes. Oil varnishes are usually prepared from linseed oil,
but sometimes, especially for artist's purposes, poppy seed and walnut oil (so-called
drying oils) are used. Linseed oil (raw) becomes slowly converted by the action of
the air into a tough, elastic, semi-transparent mass; but this property is possessed in
a far higher degree by the so-called boiled oil, that is to say-an oil which has been
brought by the action of heat and of oxidising materials into a state of greater
activity, in fact-into a state of incipient slow oxidation, the result of which is the
formation of the substance termed by Dr. G. J. Mulder* linoxine, which in many of
its properties corresponds to caoutchouc. The drying of oil varnishes is not there-
fore due to evaporation (leaving, as is the case with alcohol varnishes, a coherent film
of resin), but to the oxidising action of the oxygen of the air, whereby a coherent
film of linoxine is formed. Linseed oil (raw) is converted into what is termed
varnish by heating the oil with certain substances which more or less readily give off
oxygen, while these substances also act upon the elaine, palmitine, and myristine of
the linseed oil. The greater part of the linseed and other drying oils is linoleine,
3(C32H27O3),C6H5O3, which by slow oxidation becomes linoxine C32H27O11, by
the action of alkalies converted into linoxic acid, HO,C32H2509. The substances
with which raw linseed oil is boiled are litharge, oxide of zinc, and peroxide of man-
ganese. It is certainly preferable to carry this operation into effect upon the water
bath, or at least with vessels provided with steam jackets. The oxides are employed
in coarse powders, which are suspended in a linen bag in the oil. In practice 1 part
of oxide of zinc or litharge is taken to 16 parts of raw oil; and of the manganese
I part to 10 of oil; the oxides become partially dissolved in the oil, while they aid
in converting the palmitine, &c. (not linoleine), into plaster (lead or zinc soap).
Boiled linseed oil usually contains from 25 to 3 per cent of litharge dissolved.
Neither the addition of sulphate of zinc nor such absurdly added substances as
onions, bread crust, or beet-root have any result whatever. Linseed oil intended to
be mixed with zinc-white should not be boiled with litharge, but with peroxide
of manganese. The lower the temperature at which linseed oil is boiled' the brighter
its colour. Mulder found that when raw linseed oil, especially if old, was kept for
12 to 18 hours at a temperature of 100°, it acquired the property of boiled oil.
Sometimes after boiling linseed oil is bleached by exposing it in shallow trays
* This author published some years ago in the Dutch language a highly interesting and
valuable work--practically as well as scientifically--on the drying-oils.
VARNISHES.
489
•
10 centims. deep, best made of sheet lead, covered with sheets of glass, to the action
of strong summer sunlight. Liebig's recipe for making a bright varnish is the
following:-To 10 kilos. of raw linseed oil are added 300 grms. of finely pulverised
litharge, after which there is added a solution of 600 grms. of acetate of lead; the
mixture is vigorously stirred, and after the subsidence of the materials the clear
varnish is ready for use. Borate of manganese is, according to Barruel and Jean,
an excellent so-called siccative (dryer) when added to raw linseed oil, 1 part to 1000
of oil. Mulder's experiments confirm this statement in every respect.
Gold Size. This is used in gilding for fixing gold leaf on wood, paper, &c., and consists
of a solution of linseed oil and lead plaster in oil of turpentine, prepared by first
saponifying linseed oil with caustic soda or potassa, and precipitating the aqueous
solution of the soap with a solution of acetate of lead, the lead soap thus formed being
next dissolved in oil of turpentine.
-are
Printing Ink. This is, when genuine and prepared from good linseed or walnut oil,
anhydride of linoleic acid, C32H2703, mixed with very finely divided lamp-black, and
obtained by heating raw linseed oil for several hours, at a high temperature
(315° to 360°), whereby the fatty constituents-glycerine, palmitine, &c.-
volatilised. Usually the oil is heated in vessels directly exposed to the action
of fire, and as the colour of the ink is black, a deep colour of the residue of the
heating of the oil is not of much consequence. In order to render printing ink more
rapidly drying, some borate of manganese may be heated with it at 315° for some
hours. The quantity of fine lamp-black (best re-ignited in close vessels, or exhausted
with boiling alcohol) usually added to printing ink, amounts to about 16 per cent.
Soap is added in order to prevent smearing and assist in obtaining sharpness
of impression. Coloured printing inks are obtained by adding to boiled oil red or
blue or other pigments; for red vermillion is used. The ink used in lithography
and copper-plate printing is made thicker, a better black being added.
Oil Varnishes. The so-called fat or oil varnishes are solutions of resins in boiled lin-
seed oil mixed with oil of turpentine, benzol, or benzoline. Amber, copal, anime,
gum dammar, and asphalte, are among the more ordinary resins employed for this pur-
pose, the varnishes being made by melting, with the aid of gentle heat, the amber,
copal, &c., to which, while liquid, boiling linseed oil is added. The cauldron in
which this operation takes place should only be two-thirds filled; and the mixture of
oil and resin kept boiling for ten minutes. The cauldron having been removed from
the fire its contents are allowed to cool down to 140°, when the oil of turpentine is
added. The quantities by weight are 10 parts copal or amber, 20 to 30 boiled
linseed oil, 25 to 30 oil of turpentine. Black asphalte varnish is obtained in a
similar manner by treating 3 parts of asphalte, 4 of boiled linseed oil, and 15 to 18
parts of oil of turpentine. Dark coloured amber varnish is not prepared from
amber but from the residue (amber colophonium) of the distillation of the empy-
reumatic oil of amber and succinic acid left in the still from the preparation of
succinic acid. These varnishes are the most durable, but they dry slowly and
are more or less coloured.
Spirit Varnish. The so-called spirit varnishes are solutions of certain resins,
viz. sandarac, mastic, gumlac (shellac), anime in alcohol, aceton, wood spirit,
benzoline, or sulphide of carbon. Good spirit varnish ought to dry rapidly, give a
glossy surface, adhere strongly, and be neither brittle nor viscous. As shellac is
frequently employed, the name of lac varnish is sometimes given to these varnishes.
The spirit, usually methylated spirit, ought to be strong, about 92 per cent. The
490
CHEMICAL TECHNOLOGY.
solution of the resins is promoted by the addition of one-third of their weight
of coarsely powdered glass for the purpose of preventing the resinous matter caking
together, and being thus to some extent withdrawn from the solvent action of
the alcohol. In order to render the coating remaining from the evaporation of
the spirit less brittle, Venice turpentine is usually added. Sandarac varnish
is obtained by dissolving 10 parts of sandarac and 1 of Venice turpentine in 30 of
spirit. Shellac varnish, more durable than the former, is obtained by dissolving
I part of shellac in 3 to 5 of spirits. French polish is a solution of shellac in
a large quantity of spirits, and when this polish is to be applied to white wood, the
varnish is bleached by filtration over animal charcoal. Copal varnish, far superior
to the foregoing, is made by first melting the resin at as gentle a heat as possible
so as to prevent the colouration of the substance, which is next pulverised, mixed
with sand, treated with strong alcohol on a water bath, and filtered. A solution
of turpentine or elemi resin is added to render the varnish softer. Colourless copal
varnish is obtained by pouring over 6 kilos. of previously pulverised and molten
copal, contained in a vessel which may be closed, 6 kilos. of alcohol at 98 per cent,
4 kilos. of oil of turpentine, and 1 kilo. of ether; the vessel containing this mixture
having been closed is gently heated. The solution is clarified by decantation.
Coloured Spirit Varnishes. These are used chiefly for the purpose of coating instruments,
and other objects of brass and coloured metallic alloys, so as to prevent the action
of the atmosphere. Such varnishes are used for imparting a gold-colour to
base metals; for this purpose alcoholic tinctures of gummi-gutta and dragon's blood,
or fuchsin, picric acid, Martius yellow, and corallin, are separately prepared and
added, in quantities found by trial, to a varnish consisting of 2 parts of seed lac, 4 of
sandarac, 4 of elemi, and 40 of alcohol.
Turpentine Oil Varnishes. These are prepared in the same manner as the preceding.
They dry more slowly, but are less brittle and more durable. Common turpentine
oil varnish is obtained by dissolving ordinary resin in oil of turpentine; but this
varnish is liable to crack. Copal is either dissolved in oil of turpentine, without or
after having been melted; in the latter case the varnish being coloured. When non-
melted copal is used it is broken into small lumps, and is suspended in a stout canvas
bag over the surface of the oil of turpentine contained in a glass flask and placed on
a sand bath, the vapours arising from the oil of turpentine gradually dissolving the
copal. Dammar gum resin varnish made with oil of turpentine is prepared by
drying the resin at a gentle heat and dissolving it in three to four times its weight of
oil of tupentine. This varnish, though colourless, is not very durable. Green
turpentine oil varnish is prepared by dissolving sandarac or mastic in concentrated
caustic potash solution, diluting with water, and precipitating with acetate of copper,
the dried precipitate being dissolved in oil of turpentine.
Polishing the Dried Varnish. In order to increase the gloss of varnished surfaces, especially
on metallic objects and coaches, carriages and woodwork in theatres, concert-rooms,
halls, &c., the dry surface is first rubbed over with soft felt, on which some very fine pumice-
powder is laid, and is next polished with very soft woollen tissue on which some oil and
rotten-stone is placed, the oil being rubbed off with starch-powder. Instead of varnishes,
solutions of collodion (fulminating cotton in alcohol and ether) and solutions of water-
glass are sometimes used; while Puscher recommends a solution of shellac in ammonia,
largely used by hatters.
Pettenkofer's Process for In order to remove the cracks often observed in old pictures, Von
Restoring Pictures. Pettenkofer has suggested exposure to the vapour of alcohol at the
ordinary temperature of the air, the picture being placed in an air-tight box, at the bottom
of which is a tray containing alcohol. This method has been tried, but not only has it
CEMENT.
491
failed in many cases, but some pictures have been actually spoiled. According to
Dr. G. J. Mulder's researches, the only effective preservative of pictures is complete
exclusion of air. He suggests that pictures should be well varnished on the painted side
as well as on the back, and next hermetically covered with well-fitting sheets of polished
glass on the front, and some substance on the back impermeable to air. The real cause
of the ultimate destruction of pictures as well as of paint is the gradual but continuous,
yet slow, oxidation of the linoxine, resulting in the crumbling to powder of the pulverulent
matters—pigments, used as colours. It may not here be out of place to state that one of
the best solvents of linoxine (dried paint) is a mixture of alcohol and chloroform, which
may be advantageously used to remove stains of paint, and also of waggon and carriage
grease from silk and woollen tissues.
CEMENTS, LUTES, AND PUTTY.
Cements. In a general sense we understand by cement, substances or mixtures
which, when placed in a pasty state between the surfaces of bodies in close contact,
cause them to adhere solidly after the drying or solidification of the pasty material.
According to this definition, glue and paste are cements, but solder is not. As a
universally applicable cement cannot be met with, it is clear that as regards any
specific cement it should completely answer the purpose for which it is employed.
The substances used for cement are very various, and are of course adapted to the
particular objects they are intended to unite. There are numberless receipts for the
preparation of cements, which may be best classified by stating the name of the most
essential constituent. Thus we have:-1. Lime cements. 2. Oil cements. 3. Resin
and sulphur cement. 4. Iron cements. 5. Starch, or paste. 6. Cements of less
consequence, as, for instance, water-glass cement, chloride of zinc cement, &c.
Lime Cements. Slaked-lime forms with casein, white of eggs, gum-arabic, and glue,
mixtures which after some time become very solid, and are used to unite wood,
stone, metal, glass, porcelain, &c.
Casein cement may be made in various ways, but is most usually prepared by
mixing freshly-precipitated casein, obtained by acidifying milk, previously freed from
whey and separately reduced to powder, with freshly slaked lime. As this mass
hardens very rapidly, it should be used immediately, and not prepared in larger
quantity than may be required. Casein dissolved in bicarbonate of potash or soda
solution, and gently evaporated to a thick consistency, also yields a good cement.
A solution of casein in a concentrated aqueous solution of borax made with cold
water yields a clear thick solution, which, as regards adhesive property, far surpasses
a solution of gum-arabic. A solution of casein in silicate of soda or potash is an
excellent cement for glass and porcelain. When stone, metal, wood, &c., are to be
united, or when the cement is to be used for filling up small cavities, there is usually
added to the mixture of casein and lime a powder made of 1 kilo. of fresh casein,
1 kilo. of quick-lime, and 3 kilos. of hydraulic mortar or lime. According to Hannon
partly decayed and liquefied gluten yields with lime a cement similar to that
obtained from casein.
Oil Cements. The main and essential constituent of these cements is a drying oil in
the shape of an oil varnish (boiled linseed oil). Most of these cements resist the
action of water.
Boiled linseed oil and fat copal varnish may be used as cements to unite glass and
porcelain, but are seldom so employed on account of requiring some weeks to become
dry. Mixed with white-lead, litharge, or minium (red lead), the cement dries more
quickly, but does not become quite hard until after some weeks. When a larger
492
CHEMICAL TECHNOLOGY.
I
quantity of this cement, or rather putty, is required, it is frequently made of boiled
linseed oil with a mixture of 10 per cent of litharge and 90 per cent of either washed
chalk or slaked lime. Zinc-white is sometimes used instead of litharge. This putty
is frequently warmed before use in order to render it softer; it is used for uniting
stone, brick, &c. A mixture of 2 parts of litharge, 1 of slaked lime, and 1 of dry sand,
made into a uniform paste with hot and boiled linseed oil, has been used by Stephenson
as a putty to be placed into the sockets of steam-pipes. By precipitating a
solution of soda-soap with alum solution an alumina soap insoluble in water is
obtained, which, having been dissolved in warm linseed oil varnish, yields, according
to Varrentrap, an excellent cement for uniting stone. Glaziers' putty is a mixture of
chalk and boiled linseed oil, well beaten up together. When this putty is made with
raw linseed oil it hardens very slowly; prepared with boiled linseed oil it may be
kept soft for a considerable time by either being placed under water, or kept in
bladders like lard, or tied up in canvas bags previously soaked with oil. According
to Hirzel, a mixture of litharge and glycerine forms an excellent cement and readily
hardening lute, which, according to Pollack, may even be used to unite iron and iron,
as well as iron and stone.
Resin Cements.
•
Cements made with resin as the main constituent are often used,
because, on becoming cold, they harden at once and possess the property of being
waterproof; on the other hand, these resin cements will not endure a high tempera-
ture without becoming soft, and by exposure to air and sunlight they become so
brittle as to be easily pulverised.
As a cement for glass and porcelain, sandarac and mastic are sometimes used,
because these resins are readily fusible and are colourless. They are applied to the
surfaces to be united in the form of a powder put on with a small hair-brush, after
which the object is heated so as to melt the resins, the pieces to be joined being
pressed together. As far back as the year 1828, Lampadius suggested as an excel-
lent cement a solution of I part of amber in 15 parts of sulphide of carbon.
When this solution is painted over the surfaces to be united and immediately
pressed together, the joint is at once effected owing to the rapid evaporation of the
sulphide of carbon. A solution of mastic in sulphide of carbon may be similarly
used. Shellac alone does not form a good cement, being too brittle when cold, and
contracting too much after having been melted; the addition of some Venice turpen-
tine and earthy powders (see Sealing-wax) compensates these defects. While wood
cannot be joined together with shellac, it is firmly and readily glued by coating the
pieces to be joined with thick shellac-varnish, and then placing between the two
pieces a slip of muslin. Resins are frequently used for lining water-cisterns, and for
rendering terraces, &c., waterproof. Pitch, colophonium, asphalte, mixed with lime,
sulphur, or turpentine, are used for this purpose, the object of the various additions
being to obtain a greater or less degree of hardness. Jeffery's marine glue is
prepared by dissolving caoutchouc in twelve times its weight of coal-tar naphtha and
adding twice the weight of either asphalte or shellac. The mixture is gently heated
to render it uniform. There is a solid and a fluid marine glue in the trade; the
former is used for glueing wood and for caulking, the latter, obtained simply by the
use of a larger quantity of solvent, is used as a varnish; both kinds are insoluble in
water, are not acted upon by change of temperature, and do not become brittle. By
the name of zeiodelite is understood a mixture consisting of 19 parts of sulphur and
42 of powdered glass or earthenware; this mixture having been heated to the
PASTE.
493
melting-point of sulphur, may be used, instead of hydraulic cement, for uniting stones
and bricks. R. Böttger prepares this cement by mixing with molten sulphur an
equal weight of infusoria earth to which some graphite is added. Under the name
of diatite Merrick prepares a mixture of shellac and finely divided silica.
Iron Cement. Among the very many recipes given for the preparation of this cement,
used for luting the sockets and spigots or flanges of cast-iron pipes, and for caulking
the seams of the plates of steam boilers, we quote the following as one of the best:
A mixture of 2 parts of sal-ammoniac, 1 of sulphur, and 60 of finely-pulverised cast-
iron borings or filings. When required for use, this mixture is made into a paste
with water, to which some vinegar or dilute sulphuric acid is added. The parts to
be joined by this cement should be free from fat, oil, or rust. The cement is forced
in with the caulking-chisel and soon becomes very hard. A lute for small leaks in
iron and fire-clay gas-retorts can be made with 4 parts of iron-filings, 2 of clay, and
I of pulverised porcelain saggers. This mixture is made into a paste with a solution
of common salt.
Paste. The material used by bookbinders, and, in fact, wherever paper is to be
glued to paper, is obtained by boiling flour with water or by treating starch with hot
water.
Starch paste is best made by rubbing the dry starch up with cold water, so as to
form a uniform magma, to which, while being constantly stirred, boiling water is
very rapidly added; this paste should not be boiled if required for cementing paper
together. Rye-meal boiled with water yields an excellent paste, which may be
improved by the addition of some glue solution and preserved by alum. Partly
decayed and liquefied gluten forms an excellent paste. Starch-paste to which, while
hot, half its weight of turpentine is added is greatly improved and rendered water-
proof by the addition.
DIVISION V.
ANIMAL SUBSTANCES AND THEIR INDUSTRIAL APPLICATION.
Origin and Properties of Wool.
WOOLLEN INDUSTRY.
Wool is distinguished from hair chiefly by the three fol-
lowing properties :-wool is finer; is not straight, but curled; while it generally
contains less pigment, and hence is white in colour. The quality of wool increases
with the increase of these three characteristics. Wool, like hair, exhibits an organised
structure, consisting histologically of an epithelium, of a rind and of a pith or marrow.
The epithelium of wool consists of small thin plates which overlap each other like
FIG. 251.
FIG. 252.


the tiles on a roof; in this manner the cuticular plates give to the surface a squamose
appearance, which may be coarsely represented as the appearance exhibited by
a fir-cone. Fig. 251 exhibits a piece of wool of an ordinary sheep; while Fig. 252,
magnified to the same number of diameters, exhibits a piece of the very finest
Saxony wool, thus showing the great difference of fineness of these two sorts
WOOL.
495
of wool. The grooves on the surface of the wool are the cause of its rawness to the
touch, and from the existence of these grooves wool admits of being felted. When
the fibre which exhibits this texture is pressed together with a kind of kneading
motion, while the fibre is at the same time softened by the action of steam, the result
is that the fibres are joined to each other in the direction of the scales on their
surface and, becoming entangled, form a firm, dense texture, which is termed felt.
We obtain wool chiefly from sheep; the quality of the wool very much depends
upon the peculiar breed, the climate, fodder, and care taken of the animals. We
distinguish two chief breeds of sheep-viz.:-1. The mountain sheep, having short,
fine, and more or less curly wool. 2. The sheep of the lowlands, having coarse,
sleek, long, hair-like wool. To the first breed of sheep belongs the sheep met with in
the interior and more elevated parts of Germany, also the Spanish merino sheep, of
which there are several varieties, the most remarkable being the infantado and
electoral races. By the latter is understood the variety which in 1765 was imported
into Saxony, being made a present to the Elector, and was the cause of the exist-
ence in that country of a breed of sheep yielding excellent wool. Till comparatively
recently the exportation of the living merino sheep from Spain was prohibited under
pain of capital punishment. The variety of sheep designated Escurial is not
a peculiar race or breed, but an electoral sheep with finer and fuller fleece. Sheep,
like goats, are undoubtedly animals preferring a mountain plateau, and are very sen-
sitive to a damp or moist soil. There are many varieties of the lowland sheep,
among them the heath sheep (lowlands of Germany); the so-called Cretan goat
(Ovisaries strepsiceros) of Southern Europe and Western Asia; the various breeds of
English sheep, Southdown, Leicester, Cotswold, Lincoln, &c., and the Scottis
varieties, Shetland and Hebrides.
The varieties of wool obtained from other animals than sheep are:-
a. Cashmere wool; the fine downy hair of the Cashmere goats inhabiting the eastern
slopes of the Himalaya, 14,000 to 18,000 feet above sea level. The colour is white-grey
or brown. In the state in which it is sent to Europe it is largely mixed with coarse hair,
so that 100 kilos. of the raw material yield after sorting and cleansing only 20 kilos. of
fine hair.
b. The Vicuna wool; the very slightly curly hair of the Llama or Vicuna goat
(Auchenia Vicuna), a native of the high mountains of Peru, Chili, and Mexico. This kind
of wool, or rather woolly hair, was formerly more so than now employed for weaving fine
tissues. Sometimes there is substituted for this wool a mixture of ordinary wool and the
finest hair of hares and rabbits. What is now termed Viguna or Vicuna wool in
the trade is a tissue made of a mixture of wool and cotton.
c. Alpaca wool, or pacos hair; the long, sleek, white, black, or brown hair of the
Alpagua or Alpaco (Pako), a kind of goat which dwells in Peru. This kind of woolly hair
has great similarity with the Vicuna wool, but is not quite so fine.*
d. Mohair, or so-called camel's wool; the long, slightly curly, silky hair of the Angora
goat (Capra angorensis), a native of Asia Minor. This substance is spun and woven into
non-fulled tissues (camlet or plush), and is also mixed up with the half-silk tissues
of which it forms the woof or weft.
Chemical Composition of Wool. Purified and cleansed wool consists chiefly of an albumi-
noid sulphur-containing substance termed keratin (horny matter), but, as met with on
the animals, wool contains much dirt, dust, and suint. The labours of Faist, Reich,
Ulbricht, Hartmann, Märcher, and E. Schulze have greatly increased our know-
ledge of this substance.
* The microscopical texture and properties of this kind of hair have been investigated
and are described in Wiesner's work, "Einleitung in die Technische Mikroskopie."
Vienna, 1867, p. 172 et seq.
496
CHEMICAL TECHNOLOGY.
The following results are those obtained by Faist when analysing various kinds of
merino wool:-
I.
2.
a.
b.
C.
d.
e.
f.
Mineral matter
6.3
16.8
0'94
1'3
ΙΟ
I'2
Suint and fatty matter
44°3
44'7
21'00
40'0
27°0
16.6
Pure wool
...
38.0
28.5
72.00
56·0
64.8
77'7
Moisture
...
114
70
6.06
2'7
72
3'5
100'0
ΙΟΟ Ο
100'00
ΙΟΟ Ο
ΙΟΟ Ο
100'0
Percentage of pure air-
dry wool...
49'4
35'5
78'06
58.7
720
82.2
1. Raw wool, air-dried.-a. Hohenheim wool, with a small quantity of readily soluble
suint. b. Hohenheim wool (the name of a large agricultural establishment and agrono-
mical school near Stuttgardt, Wurtemburg), containing a large quantity of glutinous suint.
2. Washed wool, air-dry.*-c. Hohenheim wool. d. Same variety, with difficultly soluble
suint. e. Hungarian wool, very soft. f. Wurtemburg wool, less soft.
While making researches on wool, Elsner of Gronow estimated the loss which
wool experiences when treated with sulphide of carbon for the elimination of
the suint. The results were:
Washed merino wool
Unwashed wool (laine en suint, raw wool)
Long carded wool
15 to 70 per cent.
...
50 to 80
18
""
Suint is a mixture of secreted and accidental substances, dust, &c. When raw
wool is macerated for some time in warm water, there results a turbid liquid which
contains suspended as well as dissolved matters. The dry substance of the aqueous
extract of suint consists, according to Märcker and Schulze (1869), of:—
Organic matter
Mineral matter
I.
2.
3.
4.
58.92
41'08
61.86
38-14
59'12
60'47
40.88
39'53
1 and 2 relates to wool of mountain sheep. 3 and 4 to full-bred Rambouillet sheep.
The soluble portion contains the potash salt of a fatty acid (suintate de potasse).
The fatty acids contained in suint are, according to Reich and Ulbricht, mixtures of
oleic and stearic acids, probably also palmitinic acid and a small quantity of
valerianic acid, with potash in such quantity, that more recently this material has
been employed to obtain therefrom carbonate of potash and chloride of potassium
100 kilos. of raw wool may yield from 7 to 9 kilos. of potash (See p. 132)
Potash from suint consists, according to Märcker and Schulze, of:-
Carbonate of potash
Chloride of potassium
Sulphate of potash
...
...
86.78
6.18
2.83
4'21
100'00
Silica, alumina, lime, magnesia, oxide of iron,
phosphoric acid, &c.
...
* Washed on the sheep while alive, an operation performed by the farmers, and to be
distinguished from the washing wool undergoes during manufacture.
WOOL.
497
P. Havrez (1870) states that it is more advantageous to extract chloride of potas-
sium and prepare ferrocyanide of potassium from suint than to employ it in
preparing carbonate of potash. Suint is a valuable material in gas manufacture
and the potash salts may afterwards be extracted from the coke.
Properties of Wool.
The value and applicability of wool for the purposes of being spun
and woven depend upon a number of properties, of which the following are the most
important.
Colour and Gloss. Wool is generally white, but that of some of the common kinds
of sheep and also of the alpaca and mohair are either brown, grey, or black.
The gloss of some varieties of wool is a highly prized property. The gloss is not
exactly related to the fineness of the wool, but more to the softness and suppleness of
the fibre, which on being touched by the hand imparts a feeling similar to that
of cotton-wool or silk. The curl or waviness of the wool is due to the fact that the
hair or fibre is bent and more or less curved. When there are many and small
curves the wool is termed small curled, while if the curves are large it is termed
coarsely curled. There is also a difference between wool which exhibits high
curves (strongly waved and curled) and wool exhibiting low curves (weakly waved
and curled). The fineness of wool depends upon the smallness of diameter of the
fibre; generally the finer the fibre the better the wool is suited for the uses
commonly made of it. There are, however, some varieties of wool met with which,
though very fine, are rather tough and straight, and therefore less suited for manu-
facturing purposes. It should be observed that the diameter of the woollen
fibre does not constantly vary with the fineness; while neither the wool-meter
(eriometer) nor the micrometer can sufficiently determine the fineness of the wool for
technical purposes, that property being best estimated by practical experience by the
sense of touch. What is termed quality or uniformity in wool is that the fibre has
through its entire length the same diameter. By softness, suppleness of the wool,
it is understood that the fibre readily admits of being bent in all directions; this
property is usually accompanied by extensibility and elasticity. A fibre of wool may
therefore be somewhat more strongly stretched before breaking, after it has been first
straightened so as to remove the curls. The elasticity of the fibre is shown, when a
hair is broken, by the two ends becoming more or less rapidly contracted and curled
up. By strength we mean that property of wool whereby it bears without breaking
a certain weight, which, according to the quality and fineness of the fibre, varies from
26 to 44 grms. By height is understood the length of the curled hair in its
natural position; while by length we designate the measure (in centimetres) of
a single fibre when so stretched that its curls are no longer perceptible. The length
of the fibre is of great importance in the selection of wool, and constitutes one of the
main distinctions between carded wool and short wool. The teasled wool is
used more especially for the weaving of cloth-milled or fulled cloth. Generally
this kind of wool is strongly curled, and the length of the stretched hair is less than
15 centims. The combed wool (long wool) is used for smooth woollen tissues which
require a middling length, 9 to 12 centims., some strength, and not too much curl.
Preparation of Wool. Before wool is a marketable article it has to be washed, shaved
or sheared off, and sorted.
I. Just before shearing the wool is washed-or as the term more usually runs, the
sheep are washed-for the purpose of cleansing the fleece and of eliminating a por-
tion of the suint. By this washing wool loses from 20 to 70 per cent in weight.
33
498
CHEMICAL TECHNOLOGY.
II. The Shearing of the Sheep.—Usually in our climate sheep are shorn only once
a-year, about the middle of May or beginning of June, but with long-woolled sheep
this operation is performed in September (summer wool), and about the end of March
(winter wool). Lamb's wool is distinguished by its great fineness. Besides the
wool shorn from the live sheep we distinguish skinner's wool, from the skins of sheep
slaughtered for food, and pelt wool from sheep which have died from disease; while
the former kind is shorter than ordinary wool, the latter is deficient in strength and
elasticity, and is therefore of less value.
III. Sorting the Wool.-The different parts of the skin of the sheep yield wool of
different quality; among the parts which yield better kinds of wool are the shoulders,
the flanks, and the thighs. The wool of the following parts is of inferior quality,
viz., neck, withers, back, throat, breast, feet. The peculiar mode of sorting wool
and the denominations given to the several varieties differ in different countries;
generally the terms firsts, seconds, thirds, &c., are employed. While the fineness of
the wool is the main character which distinguishes the various kinds, the sorter also
looks to the length, curl, strength, &c. As met with in commerce, wool contains a
larger or smaller quantity of hygroscopic water, varying from 14 to 16 per cent; and
even when wool is exposed to dry air for a long time, the water amounts to 7 or 10
per cent.
Wool Spinning. The operations of spinning do not in strictness pertain to chemical
technology, because the material operated upon is not chemically treated, and only
mechanically undergoes a change of form. The machinery employed is very complicated,
but has been brought to great perfection.
Before being made into cloth, the wcol, as is the case with cotton, silk, flax, and hemp,
has to be made into yarn. Before this operation can be proceeded with, the sorted wool
is-1. Carded for the purpose of weaving. 2. Or the wool is combed for the making of
smooth woollen goods. Carded wool is ultimately made up into cloth, while combed wool
is made up into such materials as thibet, mousseline de laine, merino, &c. The following
eight operations are those to which carded wool is submitted:-
1. Washing.-The aim of this operation is to eliminate the suint from the wool, and for
this purpose the fibre is submitted to the action of very weakly alkaline liquids. These
even in the carbonated state should be weak, because, when concentrated, the wool
either is dissolved or its strength and elasticity impaired. The alkaline liquids chiefly
used for this purpose are lant (stale urine) mixed with water, tepid soap-suds, or a very
weak solution of soda. The washed wool is rinsed in plenty of cold water, wrung out, and
then dried in the shade. By exposure to direct sunlight wool becomes yellow. 100 parts
of fleece lose by washing from 17 to 40 parts, leaving 60 to 83 parts of pure wool.
2. Dyeing. When this operation takes place immediately after washing, it is only to
impart to it very fixed dyes, such as indigo, or madder; because, as regards most other
dyes, they would be injured by the operation of milling, in which soap, lant, and other
materials are employed. Wool by being dyed often increases considerably in weight,
sometimes as much as 12 per cent.
3. Willowing, or Devilling.—This operation aims at the obtaining of the flocks of wool in
a more uniform mass, while at the same time mechanical impurities, straw, &c., are
removed. The machinery by which this is effected is similar to that used for the same
purpose for cotton.
4. Oiling or Greasing. As wool has a great tendency to become felted, and has to be
submitted to the operation of carding, it might in this process become broken; and in
order to prevent this and give the fibre, which has become harsh, suppleness, it is greased
or mixed with oil. For the finer kinds of wool, olive oil or arachis oil is used, while for
coarser kinds rape-seed and fish oil are employed. Olein, as it is termed, really oleic acid,
a by-product of the manufacture of stearine candles, is often used for this purpose, pro-
vided it be not contaminated with either sulphuric or stearic acids. 100 kilos. of wool for
warp require 10 to 12 kilos. of oil, while 100 kilos. of wool for woof require 12 to 15 kilos.
of oil.
5. The carding of wool aims at the same result as the carding of cotton. The
machinery employed is in each instance similar in construction. Wool is carded at least
twice. The first carding is termed fleece-carding, the result being that the wool is formed
WOOL.
499
into a loose fleece, which is rolled up on a cylinder; the second carding converts the fleece
into loose curls about 1 metre or a yard in length, which are turned over on to the roving
machine. Recently the carding-mill has been so constructed that it also performs the
operation known as roving.
6. Roving. By means of machinery the wool is converted into what is technically
termed slub or half-yarn, which by the following operation, viz.,
7. By spinning is made into yarn. The machinery, while working at a bigh speed,
twists the fibres into a continuous thread or yarn.
8. The finished yarn is wound on reels, the length of the skeins or hanks and the
number of skeins to a bunch varying in different localities. The fineness of the yarn is
abroad designated by the number of hanks which go to the half kilo.; but in Belgium and
France the number of metres of yarn length which go to the kilo. expresses the fineness.
Artificial Wool. Woollen rags are carefully sorted, and by means of machinery converted
into what is termed mungo and shoddy; the former is a short-haired wool obtained from
milled goods; the latter (a longer hair) is prepared from woollen hosiery. The rags having
been well sorted, and all seams, buttons, and ornaments cut off, silk and other linings
separated, are cleansed, again sorted, and then oiled. The rags yield on an average
30 per cent of the weight of buttons, linings, &c., and the 70 per cent remaining yields
some five-sevenths of mungo, prepared by means of a mill. Mungo is not carded; but
shoddy, made by a similar process, is carded after having been again oiled.
Weaving the Cloth. Cloth is a smooth woollen fabric, the woof-yarn passing alternately
over and under chain-yarns. The peculiar felty appearance is given to cloth by the
operation of milling or fulling. The operation of weaving cloth does not differ in any way
from the weaving of linen or cotton fabrics; usually the chain and weft yarn are equally fine.
The cloth as it leaves the weaver's hands is not in the least similar to
Washing and Milling
the Bough Cloth. the finished fabric, but is very like a coarsely woven towel, the chain
and weft being quite loose and every thread distinctly visible; while the felty appearance of
the cloth is entirely absent, this being obtained by the operation of milling, which is preceded
by the burling process, whereby knots, pieces of straw, and other similar impurities are
removed by the aid of small steel forceps. The rough cloth is next washed for the
purpose of removing oil, dirt, and weavers' glue; this washing is assisted by soft soap,
potash or soda ley, and is performed by a washing machine. The operation of fulling or
milling aims not only at a cleansing of the rough cloth (it is not always washed previously
to being milled), but more particularly at the felting together of the fabric, so that the
chain and weft can hardly be distinguished. It is performed by the joint action of
moisture, high temperature, and a peculiar mechanical treatment, by which the threads
are kneaded into each other. As the milling also aims at the complete removal of grease
the water into which the fabric is steeped is rendered alkaline by means of lant, while
soft-soap and fuller's earth (see p. 295) are used to assist the action. Soft soap is only
used for common cloth, while for the finer kinds palm oil and olive oil soaps are employed.
The milling or fulling consists in beating the rough cloth with wooden mallets moved by
machinery; recently the use of cylinders is very general for this purpose.
In order to give to the milled cloth a more pleasing appearance, it is
first teasled and next shorn. 1. The operation of teasling aims at the
loosening of the surface hairs of the felted cloth, and at brushing these in one direction ;
the operation is performed by the use of teasles or weaver's thistle (Dipsacus fullonum)
which acts by the thorns on the seed capsules. 2. The shearing of the cloth is an
operation by which the surface hair is cut off to a uniform length. The shearing is either
performed by hand-a very tedious operation, the cloth being stretched uniformly on a
cushioned table, the operator using peculiarly made shears-or by cylinders, somewhat
similar to lawn grass-cutters in principle of working. There is a distinction between
transversal, longitudinal, and diagonal cylinders. a. The transversal cylinder is placed
lengthwise to the cloth, the cylinder moving from one edge of the cloth to the other.
B. In the longitudinal machine the moving cylinder is placed across the width of the
cloth, which is moved under the shearing-knives. y. In the diagonal machine several
cutting cylinders are placed diagonally above the cloth. The wool shorn off is used in
upholstering, and very largely for the purpose of giving a velvety appearance to some
kinds of paper-hangings.
Teasling and Shearing
the Cloth.
Dressing the Cloth. Before the cloth is ready for sale, it has to be submitted to the three
following operations:-Lustring, brushing, and pressing.
1. The lustring is now performed by stretching the cloth very tightly on a copper
cylinder, the surface of which is perforated with a number of small holes. The cylinder
is placed in a steam chest, and steam having been turned on, the cloth obtains a
permanent gloss and is prevented from becoming rough on being worn. 2. The brushing
of the cloth takes place before and after the shearing, and is effected by machinery, the
500
CHEMICAL TECHNOLOGY.
brushes being fixed to cylinders, and the cloth moved over and under them, while at the
same time either a jet of water or sometimes steam is made to play on the cloth.
3. Finally, the cloth is pressed, having been first folded; between each fold is placed on
the right side of the cloth a piece of glazed millboard and a piece of coarser millboard on
the wrong side; a plank is put between the pieces of cloths, some six to twelve of which
are placed in the press at a time.
Other Cloth Fabrics. In addition to milled cloth several other kinds of woollen goods
are manufactured, which are cloth-like in some particular. Of these the following
are the chief :-Flannel, either smooth or twilled, only slightly milled, once teasled
on the right side, and either not shorn at all or only once; the chain often consists of
carded wool, but is sometimes cotton or silk; the woof is carded yarn. Swan-skin
is fine twilled flannel. Cashmere is finely twilled cloth only once teasled, but shorn as
often as cloth. The hair is short and covers the textile yarn slightly, so that the
twill is distinctly seen. Cashmere is often made with a cotton chain.
Frieze is coarser, stouter, and longer-haired than cloth, is strongly fulled, but less
teasled and also less shorn. After having been shorn, frieze is simply dressed by
being brushed and hot-pressed; it is then brushed over with a solution of tragacanth
in water, next calendered, and lastly slightly oiled with olive oil and again pressed.
A non-twilled and finer kind of frieze is known as "ladies' mantle frieze;" while a
heavier and short shorn frieze is called castories. Kalmuk and thick frieze (Irish
frieze) consists of a heavier yarn and is more strongly milled. Buckskin is a
twilled non-teasled trouser material, the right side of which is shorn and quite
smooth. Kersey is a coarse kind of undressed (neither teasled nor shorn) woollen
fabric used for making cloaks and overcoats for military men, sailors, railway
officials, &c. The coarser kinds of railway rugs and horse-cloths are of a similar
material. Paper-makers' felt is a coarse, twilled,. loosely woven, lightly milled
material, neither teasled nor shorn, used for the purpose of being placed between the
wet sheets of paper. Felted cloth, a fabric first made some twenty years ago without
spinning and weaving at all, has not been found suitable, and is therefore now hardly
ever seen. Wool intended for felting purposes is first cleansed, freed from suint,
next carded and converted into a uniformly thick layer similar to cotton-wool, and is
then felted.
Worsted Wool. It has been already stated that long haired or combed wool is the
material used for the purpose of preparing worsted-yarn-a smooth thread, the
longitudinal fibres of which are placed parallel to each other-this yarn serving the
purpose of weaving such fabrics as thibet, merino, Orleans, &c. There is a distinc-
tion between genuine combed wool or worsted, and half-worsted or sayette-yarn,
which is the link, as it were, between combed and carded wool, and is used for the
purposes of knitting stockings, in carpet-making, Berlin-wool work, &c. Although
half-worsted is always spun from long-haired wool, the fibre is not in this instance
combed, but carded by a peculiarly constructed mill. Combed yarn or worsted
consists either entirely of wool, or is a thread of wool mixed with mohair and
alpaca, or of wool and cotton, or of wool and silk, such yarns being termed fancy
yarns.
The manufacture of smooth woollen fabrics is, as far as weaving and the mechanical
operations are concerned, similar to the weaving and mode of manufacturing other
textile fabrics. Some of the smooth-surfaced woollen fabrics are finished when
woven; others require a dressing which depends upon the taste of the consumers
and upon the peculiar requirements of the trade. The following enumeration
SILK.
501
of the smooth-surfaced woollen fabrics, of which there is an almost endless variety,
may give some idea of the various kinds of goods belonging to this category.
A. Smooth Fabrics.—Barracan used to be formerly woven from camel's hair, but is now
woven from combed wool; it is termed moiréd when it is watered. Orleans consists of a
twisted cotton thread chain and a single woollen weft; the fabric having been woven is
singed, washed, dried, shorn, and hot-pressed. Camlet also was formerly made from
camel's hair, and consists of combed woollen chain and weft. Dress crape is a fabric
made of a strongly twisted worsted yarn-chain and more loosely woven weft; when the
cloth is woven it is dyed black or grey, next wound round a cylinder, and boiled in water
in order to shrink it. Bolting cloth is made of a strongly twisted yarn, and employed for
the purpose of making flour-sieves. Mousseline de laine, chaly, is a woollen muslin with
silk chain, and this class includes a host of fabrics generally known as Bradford fabrics as
well as mixed materials, alpaca, mohair, silk mohair, &c.
B. Twilled Goods.-Merinos with three- or four-threaded twill and two "right" sides
are, after weaving, singed, hot-pressed, and dressed or glazed. When unglazed it is called
thibet. Serges are twilled fabrics with three, four, or five strands. So-called Atlas
fabrics are kalmang and lasting, the latter employed for ladies' shoes, gentlemen's cravats,
furniture, and upholstery work. The fabric from which the press-bags of the oil-mills
are made is also a twilled woollen material woven from very strong and tough wool.
C. Variegated or Patterned Fabrics, such, as are used for trousers, and also woollen
damask. Shawls belong to this class; in some of these the whole fabric is woollen
(Cashmere shawls); in others a silk or cotton thread is mixed. The plaids and tartans
are especially British fabrics.
D. Velvets.-Woollen velvet, woollen plush, and velpel, are merely distinguished from
each other by the length of the hair, which is greater in plush than in velvet, and greatest
in velveteen. Woollen velvets are employed in various ways; for instance, in covering
chairs, sofas, for curtains, &c. These materials are more or less loosely woven, and are
variously shorn and dressed, being known in the trade by such appellations as astracan,
beaver, castorin. Utrecht velvet, &c.
SILK.
Silk. Silk is at once distinguished from cotton, flax, hemp, and wool by being
naturally produced as a very long and continuous thread, whereby the operation of
spinning is dispensed with; but in its stead the operation known as silk-throwing is
required, by which several of the natural fibres of the silk are twisted into one in
order to obtain a stouter yarn.
Silk is the produce of the silkworm (Bombyx mori), an insect which undergoes
four metamorphoses. The worm is produced, in the spring, from the egg, or ovule.
It casts its skin from three to four times, and finally spins a thread, produced, or
rather secreted, by two glands placed near the head, from small apertures, in which
is a glutinous fluid which immediately coagulates under contact with air. Thus
what is termed a cocoon is formed, which serves as a shelter for the pupa
against injury and cold. The thread is double, but is united in one by a peculiar
kind of glue termed serecin, which is laid as a kind of varnish over the whole
surface of the thread, of which it forms about 35 per cent of the weight. After a
period of fifteen to twenty-one days the pupa is metamorphosed into a butterfly,
which, in order to leave its prison, softens a portion of the cocoon with a juice which
it secretes, and then perforates the softened part. For the purpose, however, of
producing silk, the pupa is not allowed to develop so far, but is killed (excepting in
a number of cocoons intended for the full development of the butterflies so that they
may produce eggs), and the thread of the cocoon is carefully wound on a reel.
Sericiculture.
Varieties of Silkworms,
The Bombyx mori is the main supplier of silk. Its food is the
leaves of the white mulberry tree, Morus alba. There are, however, other silk.
producing insects, among which the following are to be noticed :—
502
CHEMICAL TECHNOLOGY.
a. Bombyx cynthia, largely cultivated by the natives of the north-east portion of the
interior of Bengal and also by the Japanese; the former call this worm Arrindy-arria, the
latter Yama-maï. This worm feeds on rice leaves, Ricinus communis. The silk obtained
from this insect, although less brilliant than that which the ordinary silkworm yields, is
very useful, as being durable and strong. This worm will feed on other leaves, such as
that of the weavers' thistle, Dipsacus fullonum, wild chicory, Chicorium Intibus, and the
leaves of the Aylanthus glandulosa. The results of acclimatising this insect in France
and Germany have been satisfactory.
b. Bombyx Pernyi is a native of Mongolia and China; it feeds on oak-leaves. Some
years ago these worms were introduced into France, and have been fed and reared
successfully upon European oak-leaves.
c. Bombyx mylitta, or Tussa worm, is a native of the colder parts of Hindostan and of
the slopes of the Himalaya. Its silk is an important article of commerce in Bengal.
This insect feeds on oak and other leaves, casts its skin five times, and yields large
cocoons. The fibre of this kind of silk is from six to seven times stouter than the silk of
the ordinary worm, but unfortunately the Tussa worm only lives in its free natural state,
and when captive does not produce silk. The following silk-producing varieties belong to
North America:-d. Bombyx polyphemus; on oak and poplar trees. e. B. cecropia; on
elm, whitethorn, and wild mulberry trees. f. B. platensis; on a kind of mimosa,
Mimosa platensis. g. B. leuca deserves further attention.
We quote the following account of the culture and rearing of silkworms:-1. The
mulberry tree. The leaves of the variety known as the white mulberry tree, from
the fact that its fruit is yellow or light red in colour, is the most suitable food for this
insect, but its cultivation belongs to horticultural pursuits, and we cannot enter upon
the subject here. 2. The production of the eggs or ova of the silkworm is effected in
the following manner:-The largest and finest cocoons, and such as have a fine
thread, are selected and preserved; usually the cocoon of the female insect is more
oval than that of the male, which is more pointed at the ends and is somewhat
depressed in the centre. Although these characteristics do not apply in all cases,
sericiculturists become sufficiently adepts in this matter to be able to select a
sufficient number of cocoons of each sex. 100 to 120 pairs of well-formed cocoons
yield about 30 grms. of eggs, about 50,000 in number, from which, however, only
about 70 to 75 per cent of worms are obtained. The cocoons selected for breeding
purposes are allowed to remain on a table covered with a white cotton cloth.
After some twelve days the butterflies make their appearance, and having paired, the
females after a lapse of some forty hours lay 300 to 400 eggs. 3. The eggs are
properly protected from cold in winter and remain in the buildings, called magna-
neries, being placed in a uniform layer on a cotton cloth stretched on a wooden
frame. The eggs are covered with sheets of white paper perforated with small holes.
Upon the sheets of paper mulberry leaves, at first cut up so as to form a kind of
chaff, are placed. In France a contrivance known as a couveuse, that is to say, an
oven in which a suitable temperature is kept up, is now generally used for the
purpose of breeding the worms, which are best hatched from the eggs at a tempera-
ture of 30°, provided moisture is also present. The young brood on leaving the eggs
creep through the holes in the paper, and seeking daylight (there is always free
access of light in magnaneries) begin at once to feed on the mulberry leaves. 4. The
rearing of the worms requires care and attention. They are best placed on paper
laid on wooden frames. The worms grow rapidly and are very voracious. They
cast their skins four times, and after thirty to thirty-two days begin to spin the
cocoons. 5. When the period of spinning approaches, the worms are placed in
small, somewhat conical wicker-work baskets, in which they are comfortably located.
The first thread spun, or rather an entangled flocky mass, is afterwards separately
collected and kept as floss silk. The insect discharges, before beginning to spin
SILK.
503
further, first a solid substance, white or green in colour, and consisting, according to
Péligot, chiefly of uric acid, next a clear, watery, very alkaline liquid, which contains
15 per cent of carbonate of potash, this curious discharge amounting to 15 to 20 per
cent of the weight of the worm.
The formation of the cocoon is finished in about five
days, but the cocoons are not collected for the purpose of reeling the silk until after
seven or eight days, so as to make sure that all the worms have spun.
As far as the chemical composition of silk is concerned, we have to distinguish
between the fibre and its envelope. The fibre consists for about half its weight of
fibroin, a substance which, according to Städeler's researches, is nearly related to
horny matter and mucus, and is identical with these as regards chemical composi-
tion. The formula of silk fibroin is C15H23N5O6. The gum-like envelope of the
silk fibre, which has been termed by Cramer and Städeler silk glue or sericin, is
partly soluble in water and readily so in soap-suds and other alkaline fluids. The
formula of sericin is C15H25N5O8. P. Bolley's researches have proved that in the
silk-producing and secreting glands of the worm only glutinous, semi-liquid
fibroin occurs, which, in coming into contact with air, is acted upon by the oxygen
and then converted into sericin. Raw silk leaves on ignition a small quantity of
ash; Guinon found in Piedmontese raw silk, dried at 100°, 0·64 per cent of ash, con-
sisting of 0.526 lime and o‘118 alumina and oxide of iron. Dr. G. J. Mulder found
in 100 parts ofraw silk:-
White silk from the
Levant (Almasin silk).
Yellow silk from
Naples.
Fibroin
53°40
Glue-yielding matter
...
20'70
Wax, resin, and fatty matter...
1'50
Colouring matter
0'05
Albumin
24'40
54'0
19'1
I'4
25'5
6. Killing of the Pupa in the Cocoon.-—The pupa remains in the cocoon for from
fifteen to twenty days, and is then metamorphosed into a butterfly, which will
perforate the cocoon and thus obtain an exit. It is clear, however, that the cocoons
not intended for breeding purposes should not be kept so long, because by the
perforation of the cocoon the silk is spoiled, or at least greatly deteriorated; therefore
the pupa in the cocoons are killed either by the application of oven-heat or of steam.
Manipulation of the Silk. Six different operations are required to render raw silk fit for
use as an article of commerce and suited for weaving, &c. These operations are:—
1. The sorting of the cocoons, an operation which requires great care and greater
experience, its aim being-(a) the separation of yellow from white cocoons; (B) the
elimination of all damaged cocoons as only fit for yielding floret silk; the damage may
arise in various ways, as, for instance, by mouldiness, injury by other insects, and,
lastly, fouling of the pupa, as well as perforation by the butterfly; (y) selection of
the cocoons according to varying fineness of thread and uniformity of the silk.
2. Winding the silk on a reel is the first operation with the cocoon. By this the
threads of silk which the insect has wound up into a kind of ball is wound off and
brought into the shape of a skein or strand.
As the single fibre of silk is far too thin to be manipulated, the operator usually
unites from 3 to 10 or even 20, making them unite by the operation of reeling; this
is not by any means so readily performed as might be imagined, because it is
difficult to find the end of the thread, whilst the surface of the cocoon is varnished
504
CHEMICAL TECHNOLOGY.
with a gum-like mass which glues the fibres together. Partly by the aid of
hot water and partly by dexterity these difficulties are overcome, and by good
management a thread of 250 to 900 metres length may be obtained from each
cocoon, each yielding from o'16 to 0'20, at the utmost o 25 grms., of raw silk. 1 kilo.
of raw silk requires from 10 to 12 kilos. of cocoons. The silk thus obtained is termed
raw silk, which should be quite uniform as regards thickness and strength of fibre.
That portion--the interior and a portion of the outer layer of the cocoon-which does
not admit of being reeled off is employed for making floret silk, by operations similar
to those in use for wool and cotton-viz., cleansing, disentangling, combing,
carding, and spinning, to produce a silk yarn.
1. The Throwing of Silk.-As the thread obtained by reeling is too fine for
use either for weaving, knitting, sewing, &c., it is usual to unite several threads of
silk by means very similar to those used in rope-making, an operation termed
throwing, known as twisting when the thread of raw silk is simply rotated on
its axis so as to make it stronger. The following are the chief varieties of thrown
silk:-1. Organzine, used as chain for woven silk fabrics, is prepared from the best
raw silk. The threads of 3 to 8 cocoons are united; being first strongly twisted and
next thrown, after which two of such threads are twisted together. 2. Trame used
for woof or weft and for silk cord is made from inferior cocoons. Single-threaded
trame consists of one single twisted raw silk thread made up of the united threads of
3 to 12 cocoons. The double-threaded trame consists of two untwisted threads thrown
to the left but less strongly than in organzine. There is also three-threaded trame, &c.
Trame is softer and smoother than organzine, and therefore fills better than round
threads in weaving. 3. Marabou silk is stiffly thrown and similar to whipcord; it is
made from three threads of the whitest raw silk and thrown in the trame fashion; is
dyed without being previously scoured (boiling the gum out in this instance), and is
again thrown after dyeing. 4. Poil silk is a simple raw silk thread, twisted,
and used chiefly as a basis for gold and silver wire, such as is worn on military
uniforms. 5. Sewing silk is obtained from some 3 to 22 cocoon threads being
twisted together. There are several other varieties of silk thread used for crochet,
knitting, &c.
4. Conditioning or Testing of Silk.-The fineness of raw as well as of thrown
silk is expressed by stating how many yards' or metres' length of the fibre are
contained in a certain weight. The unit abroad is 400 ells or 475 metres. When the
expression is used, that such silk is at 10 grains, it is understood that 475 metres'
length of that particular silk weigh 10 grains; a silk at 20 grains has the same
length but double the weight, and consequently that silk is only half as fine as the
former.
Raw, as well as thrown silk, contains a large quantity of hygroscopic water,
the quantity of which cannot be judged by the external appearance of the material.
The silk usually met with in commerce contains 10 to 18 per cent of hygroscopic
water; and silk may occasionally contain even 30 per cent without appearing to
be moist. As silk is a very expensive material and often sold by weight, it is clear
that this property of taking up water is too important to be left unnoticed; and for
that reason silk is conditioned as it is called, that is, the quantity of water it
contains is duly ascertained.
5. Scouring or Boiling the Gum out of Silk.—Excepting a few instances, such as
for example, in the weaving of fine silken sieve cloths, and for crape and gauze
SILK.
505
fabrics, raw silk has to be deprived of its envelope-the gummy matter already
mentioned, in order to give softness, suppleness, gloss, and especially also to render
the silk fit for being dyed.
The operation of scouring is comprised in the following manipulations :-
1. Removing the gum (dégommer).
2. Boiling.
3. Colouring.
The taking out of the gum is performed in the following manner :-Olive oil soap
is first dissolved in hot water and into this solution at 85° the skeins of silk are
placed hung on sticks. The skeins are moved about in this bath until all the gum
has been uniformly taken out. The silk is next wrung out, rinsed in fresh water
and then dried. Silk may by this process lose 12 to 25 per cent in weight,
according to the quality of the raw silk and the quantity of soap employed. The
scoured silk is ready for dyeing with dark colours, but if required to be dyed with
bright colours it has to be first boiled. To this end it is put into coarse canvas
bags, each containing from 12 to 16 kilos. of silk, and in these sacks the silk is
placed in a soap bath and boiled for 1 hours; the silk is next rinsed in water, wrung
out, and dried. The operation of rosing or colouring aims at imparting to the silk a
slight tint in order to enhance its beauty. The trade distinguishes various hues of
white silk, such as Chinese white, azure white, pearl white, &c. The first of these
hues, a somewhat ruddy tint, is obtained by rinsing the silk in soap-water, to which
some Orleans has been added. The bluish hues are produced by indigo solutions.
The bleaching of scoured silk is effected by the aid of sulphurous acid, the fibre
either being placed in a room where this gas is evolved from burning sulphur, or by
treating the silk with an aqueous solution of the acid. As silk loses a great deal in
weight as well as in body by the scouring, which is, however, required, because raw
silk does not admit of being dyed, it has become the practice to produce a material
called souple, obtained by treating the raw silk with boiling water in which only
a small quantity of soap, 1 kilo. to 25 kilos. of silk, is dissolved. Instead of this
soap solution, an acidified (with dilute sulphuric acid) solution of sulphate of
magnesia or of soda is sometimes used. The silk loses by this process only 4 to 10 per
cent in weight. In order to bleach raw silk without depriving it of its natural
rigidity, the skeins are digested at a temperature of 20° to 30° with a mixture of
alcohol and hydrochloric acid; this liquor becomes green in colour, and the deeper
the hue the whiter the silk. The silk is rinsed in water, and having been dried will
be found to have lost only about 2.91 per cent in weight. The alcohol used in this
process may be readily recovered by neutralising the acid with chalk and by
subsequent distillation.
Weaving of Silk. This branch of the silk industry is very similar to the weaving of
cotton, linen, woollen, and mixed fabrics; very frequently, however, silk yarn
is mixed and woven with other fibres. Often either the chain or woof is made
simply of twisted, not of thrown, silk, the advantage being the production of thicker,
but less coarse fabrics. Dark silk tissues are ready for the market as soon as
woven; they are only folded and pressed. Lighter silk fabrics (atlas and taffetas)
are washed over with a sponge dipped in a solution of gum tragacanth, and are next
hot-pressed or calendered by the aid of iron cylinders either heated by steam or by
placing a red-hot iron in them. Heavy silk fabrics are often, as it is termed,
506
CHEMICAL TECHNOLOGY.
moiréd, that is, while partly moistened are passed between hot rollers. By the aid of
copper cylinders bearing various designs, different patterns are en relief embossed
upon heavy silken and silk velvet fabrics, being gaufred, as it is termed.
Silk fabrics are:-1. Smooth. 2. Twilled. 3. Patterned. 4. Gauze.
5‹ Velvet.
a. To the first category belong: :-1. Taffetas, a light, thin, smooth tissue, made
of scoured silk, the chain being organzine single threaded, the woof trame, and
bi- or tri-threaded. 2. Gros (Gros de Tours, Gros de Naples), a heavy taffetas-like
fabric, woven with heavy thread, and hence having a ribbed appearance when thick
and thin threads are mixed.
b. Twilled fabrics are:-1. The various kinds of serges (Croisé, levantin, drap
de soie, bombasin). This fabric has a right and a wrong side, the former being the
chain side. 2. Atlas, or satin, in all its endless varieties, single, double, half, and
serge atlas.
c. Patterned fabrics. To this class belong all fabrics which either by the
art of weaving or by other means are distinguished by some design (droguet, chagrin,
reps, silk damask, &c.)
d. To the velvet fabrics belong:-1. Genuine velvet; cut or uncut.
2. Plush.
e. To the silk gauzes belong an immense variety of very light materials, as for
instance:- 1. Marle. 2. Silkstramin. 3. Crape. 4. Various qualities of silk webs.
5. Barège.
It is quite beyond the scope of this work to enter into further details on the
subject of the mixed fabrics, of which indeed there is a very large and yearly
increasing variety. Among them we mention here only poplin as made in Ireland, a
beautiful mixed fabric of linen, wool, and silk, and often woven in what is known
as tartan pattern. Mixed woollen silk and cotton fabrics are very largely produced
in this country as well as abroad.
Means of Distinguishing Silk
from Wool and from
Vegetable Fibres.
woollen as well as
Owing to the manufacture of mixed fabrics, it has become
a necessity to be enabled to detect and distinguish silk from
from cotton and linen fibres. Microscopical investigation
aided by chemical tests are resorted to for this purpose.
The animal fibres (silk, wool, and alpaca), are at once distinguished from
the vegetable (flax, hemp, cotton), by the fact that the former are soluble in caustic
potash, and the latter not. The animal fibres on being singed give off a smell
of burnt feathers, and when ignited in the flame of a candle are almost immediately
extinguished, a carbonaceous residue being left. Cotton and linen fibres continue to
burn, do not give off the smell of burnt feathers, and do not leave a carbonaceous
mass when extinguished. Wool and silk are coloured yellow by nitric acid
(1′2 to 1°3 sp. gr.), cotton and linen not so. Nitrate of protoxide of mercury colours
animal fibres intensely red, and upon the addition of a soluble alkaline sulphuret
this colouration becomes black. Linen, or flax, and cotton are not at all acted upon
by this reagent. An aqueous solution of picric acid dyes wool and silk intensely
yellow, but not so vegetable fibres. The colourless liquid obtained (according to
Liebermann) by boiling a solution of fuchsine with caustic potash does not impart
to a mixed fabric of wool and cotton any colour at all; but when the fabric is
thoroughly washed in water, the woollen fibre becomes intensely red-coloured, while
the cotton fibre remains colourless. A solution of ammoniacal oxide of copper in
excess of ammonia dissolves, first silk, next cotton, but not wool. When wool and
floret silk are mixed the latter may be dissolved by successive treatment with
SILK.
507
nitric acid and ammonia, while wool is left. A solution of oxide of lead in caustic
potash or soda may serve to distinguish wool from silk, owing to the fact that, in
consequence of the former containing sulphur and the latter not, the mixture, when
wool is present, becomes black. Nitro-prusside of sodium is undoubtedly the most
delicate test for distinguishing between silk and wool in solution in caustic
alkali, because, owing to the sulphur of the wool, this reagent produces in the solution
a violet colouration.
By the aid of the microscope, cotton, wool, and silk are readily distinguished
from each other. As for cotton (see p. 343), it has been fully described, and its
microscopical appearance illustrated by woodcuts, as also have silk and woollen
fibres. Of the latter we may now state that, whereas cotton fibre consists of only
one cell, wool (as also hair and alpaca), is made up of numerous juxtaposed cells;
FIG. .452
FIG. 255.


FIG. 253.
·
W

B
B
W
the silk fibre being similar to the secreted matter of spiders and other kinds of
caterpillars. The silk fibre (Fig. 253) is smooth, cylindrical, devoid of structure, not
hollow inside, and equally broad. The surface is glossy and only seldom are
any irregularities seen on it. If it is desired to detect in a woven fabric the
genuineness of the silk, it is best to cut a sample to pieces, place it under water
under the object-glass of a microscope magnifying 120 to 200 times, covering it with
a thin piece of glass. The round, glazed, equally proportioned silk fibre, Fig. 254,
is easily distinguished from the unequal and scaled wool fibre (w in Fig. 255), and
from the flat band-like and spiral cotton fibre (B, Fig. 255). Under the microscope
also the admixture of inferior with superior fibres of silk can be easily detected. A
small microscope known as a "linen-prover" is sold for these examinations.
508
CHEMICAL TECHNOLOGY.
TANNING.
Tanning. The operation by which the skins of various animals, more especially
those of the larger mammalia, are converted into leather is called tanning. By
leather we understand a substance, tough, flexible, not harsh; further, distinguished
by resisting putrefaction and by not yielding any glue when boiled in water,
as is the case with tanned hide, sole leather, and the so-called red-tanned leather, or
only after a very continued boiling, as with tawed skins of calves, sheep, or goats.
Whatever the differences which obtain in the practical processes for carrying out the
conversion, the physical principle involved is the same in all. Knapp's general
definition of leather is that it is skin, in which by some means or other the aggluti-
nation of the fibres after drying has been prevented.
To a comparatively very recent period tanning was conducted on an empirical
basis; it is only by a more accurate knowledge of the histological structure of the
skin and of the tannin-containing materials that the real nature of the process has
become known, this knowledge being due chiefly to the researches of F. Knapp and
Rollet.
That which is converted into leather is, however, not the skin or hide, but really
what is known anatomically as the corium, that is to say, the inner portion of
the skins, from which by mechanical (cutting and scraping) as well as by chemical
means (action of lime) the other integuments have been removed. In its most general
sense tanning should:-1. Effect the prevention of putrefaction. 2. Render the
dry skin a supple, fibrous, tough, non-transparent substance, and not horny as would
be the case were the skin simply dried. A well-tanned skin or hide possessing these
properties is termed "well finished." The specific process of tanning is of course
preceded by some preliminary operations, the aim of which is to "dress" the skins or
hides—that is, in scientific terms, to prepare the corium more or less perfectly free
from all other integuments. Tanning in the more restricted sense of the word may be
effected by a great many organic and inorganic substances; but in practice on the
large scale there is employed :-
1. Tannin as contained in oak bark, producing brown-red tanned leather.
2. Alum and common salt-Tawing.
3. Fatty matters-Samian or Oil Tawing.
Anatomy of Animal Skin. Leaving the hair out of the question, the skin of the mam-
malia consists of several layers. The uppermost of these in which the hair is
growing, the epidermis, is very thin, semi-transparent, and consists of cells which
contain nuclei. This epidermis is covered by a more or less horny layer not
possessing any vital properties, which gradually wears off, and is as gradually replaced
by the stratum Malpighii, or Malphigian net, a structure consisting of cells con-
taining fluid and nuclei. It is this layer in which the nerves and finer blood vessels
are imbedded, together with the glands which provide the perspiration. In the tan-
yards this layer is known as the bloom side, or hair side of the skin or hide.
The real corium or derma, situated under the layer just mentioned, does not consist
of cells, but is of a fibrous texture, and is that portion of the skin which after
tanning constitutes the leather; in the living animal it is separated from the
muscles by a more or less strongly developed fat-bearing tissue, the so-called
panniculus adiposus, which is, however, removed in the dressing, the side of the skin
TANNING.
509
or hide to which it was attached being termed the flesh side. All the histological
constituents of skin or hide possess the property of swelling up when put into hot
water, and of becoming after more or less protracted boiling converted into glue,
more slowly when the skin is taken from old, more rapidly when from young
animals. By the action of acetic acid the fibrous tissue of the skin is converted into
a jelly-like transparent mass, in which the fibres are not only not destroyed but pre-
sent with their peculiar structure. Alkaline leys dissolve this tissue but very
slowly; while lime- and baryta-water have no other effect on it than simply the dis-
solving therefrom of the cellular binding tissue which permeates it, and which is an
albumen compound also acted upon by dilute acids.
The various operations of tanning, more particularly the preliminary operations
of steeping and dressing, are based upon the behaviour of the different histological
elements of the skin and hide with alkaline and acid fluids; but the real process of
tanning is based upon the behaviour of the corium with totally different reagents.
This latter substance has the property of combining with tannic acid, several
metallic oxides, viz., alumina, the oxides of iron and chromium, oxidised fatty
matter, the insoluble metallic soaps (compounds of fat acids, viz., stearic, palmitinic
acids, &c., with oxide of lead, &c.), picric acid, pinic acid (present in rosin), and
other organic substances, somewhat in the same way as animal and vegetable
fibre combine with dyes and pigments. In the most extended sense of the word all
these substances are tanning agents, because they possess the property of being
precipitated on and in the fibres of the corium, so that when the latter is dried the
agglutination of the fibres is prevented, and the natural suppleness and softness of
the skin preserved. But in the case of the application of alumina compounds, the
softness is only imparted to the tanned skins by the operations of currying and
dressing.
I. Red- or Bark-Tanning.
Tanning Materials.—This branch of industry employs as raw materials hides and
vegetable materials containing tannin.
These vegetable materials contain essentially an astringent principle termed
tannin or tannic acid, and which, though it differs in some of its properties as
derived from different plants, agrees in being of an astringent taste, exhibiting
acid reaction to test-paper, of yielding with salts of peroxide of iron a deep blue-
black or green-black colour, of precipitating solutions of glue and cinchonine, and
lastly of converting animal skins into leather. It has been proved that the tannin
present in nut-galls—which, by-the-bye, are too expensive for use in tanning opera-
tions-is converted by the action of acids and by fermentation into glucose and
gallic acid, the latter, however, not being suited for tanning purposes. Under the
conditions which obtain during the tanning of hides, the tannic acid contained
in oak bark (tan) cannot be split up similarly to nut-galls, and this negative
property really aids the tanning operations greatly. All kinds of tannic acid are,
when in contact with alkaline liquids, such as lime-water, caustic potassa, ammonia,
and with the simultaneous presence of air, decomposed and converted into brown-
coloured humin substances.
Oak Bark. This substance is for the tanner the most important of all tannin-
containing materials, and cannot be replaced by any other. It is the inner bark of
several kinds of oak, Quercus robur, Q. pedunculata, and is stripped from the trees
and branches when these have attained an age of from nine to fifteen years, the bark
510
CHEMICAL TECHNOLOGY.
when cut into splints being termed tan. According to E. Wolff, the quantity of
tannin contained in oak-bark is as follows:-
Tannic Acid.
Age of the Trees.
In the crude bark covered with the rind
10.86 per cent
41 to 53
""
inside layer of the old bark
14'43
41 to 53
inside of the bark
13°23
41 to 53
crude bark and inside of bark ...
11.69
""
41 to 53
""
inside layer and inside of bark
inside of bark
13'92
""
41 to 53
13.95
14 to 15
15.83
""
2 to 7
The fir bark (produce of
According to Büchner's researches (1867) the quantity of tannic acid contained in
the best kinds of oak bark does not exceed 6 to 7 per cent.
Pinus sylvestris) is one of the best tanning materials, and is frequently used for sole
leather; this bark is stripped off the trees immediately after they have been cut down
for timber. While J. Feser found 5 to 15 per cent of tannin in this bark, Dr. Wagner
found only 73 per cent. In the United States the bark of the Abies canadensis
is used; and an extract is in the trade, which according to Nessler's researches
(1867) contains 14'3 per cent of tannic acid. The extract is imported into this
country under the erroneous appellation of hemlock extract. The bark of the elm
with 3 to 4 per cent tannin, the bark of the horse-chestnut with about 2 per
cent tannin, and beech-tree bark with also about 2 per cent tannin, are all employed
for tanning purposes. The younger branches and twigs of the willow trees yield a
bark (3 to 5 per cent tannin) which is especially suited for certain kinds of glove
leather; while another kind of willow bark is used for the tanning of Russian
leather. In Tasmania and New South Wales the barks of some species of acacia,
viz., Acacia dealbata, A. melanoxylon, A. lasiophylla, and A. decurrens are used.
Among the native European plants which might be advantageously cultivated
for tanning purposes, the Polygonum bistorta deserves to be mentioned: this plant
should contain according to Fraas from 17 to 21 per cent (?) of tannic acid.
Sumac,
This substance is, next to oak bark, one of the most important tanning
materials; it is the product-the leaves and stems-of a shrub, the so-called tanner's
sumac (Rhus coriaria and R. typhina), which grows wild in Southern Europe and
the Levant, and is cultivated in North America and Algeria. The shoots from the
roots are collected and planted in June, and after some three years' growth, the
shrubs are large enough to admit of the branches and leaves being gathered. The
young branches and twigs are cut off, and after drying in the sun, the leaves are
beaten off with sticks or clubs, and next crushed under mill-stones, sifted, and packed
into sacks, and thus sent into the market. The sumac of commerce is a coarse
powder, exhibiting a yellow or blue-green colour, and containing 12 to 16'5 per
cent of tannic acid. By keeping, the tannic acid of sumac is converted into
secondary products, owing to a spontaneous fermentation. Sumac also contains a
yellow dye-stuff which seems to be identical with quercitrin. With sumac should not
be confused another material of the same name, but distinguished as Italian or
Venetian sumac, and derived from the Rhuscotinus, also yielding fustic or yellow
dye-wood. Italian sumac is the pulverised bark of the young twigs and leaves of
this plant, which under the name of ruga grows in Southern Europe and also near
Vienna; it is largely used in the countries where it grows for tanning purposes,
being more particularly employed for preparing goat- and sheep-skins.
TANNING.
511
Dividivi. The material designated by this name is the seed capsule of some trees
found native in Central America, and belonging to the Casalpiniariæ; these seed
capsules are about 6 centims. long, are bent as an S, have a brown-red colour, and
contain olive-green coloured, egg-shaped, polished seeds. In 1768 the Spaniards
brought this material to Europe, where it is used for tanning purposes on account of
the tannin contained in the epidermis of the capsules (more correctly siliquæ, or pods).
The quantity of tannin was found by Müller to be 49 per cent, by Fleck 324 per
cent, while Dr. Wagner found from 19 to 26'7 per cent. Dividivi is rather an expen-
sive tanning material, but is occasionally used for dyeing purposes. Among the
' tannin-containing substances which are occasionally imported from abroad may be
mentioned the bablah, the produce of the Acacia Bablah and allied species. This
material contains, according to Fleck, 20˚5 per cent tannin, while Dr. Wagner found
145 per cent. Algarobilla, the seed capsules of the Prosopis pullida, a native of
Chili, has been also occasionally employed as tanning material in this country.
Although myrobolans, the fruits of Terminalia citra, T. Bellirica, and T. Chebula, are
imported from Bombay, they contain too little tannin to be of any service in tan-yards.
Nut Galls. We understand by this name an excrescence formed on the leaves of the
Quercus infectoria by the puncture of the female insect of the Cynips gallæ tinctoriæ,
or oak wasp, effected in the leaves and young twigs in order to deposit its eggs; the
juices of the tree collect round the egg, and on hardening form the nut-gall. This
material is best collected before the young insect has become fully developed,
because then the gall contains the largest quantity of tannic acid. In the market
three varieties are met with, termed black, green, and white galls. The black and
green variety have been gathered before the insect became fully developed inside the
nut; these galls therefore do not exhibit outwardly any hole or opening, but on
breaking the gall there will be observed in the centre a small cavity surrounded by a
light brown friable substance, which contains the larva of the insect.
Galls are
generally spherical, but exhibit small irregularities of surface, and are of a black-
green or grey colour. The white galls are gathered after the insect is fully
developed, and has by perforating the tissue of the gall escaped. This variety is
more spongy, its colour is a red-brown or brown-yellow. Galls of good quality are
obtained only from warmer countries, for although galls are formed in our climate
upon oak leaves, the quantity of tannin contained amounts to only 3 to 5 per cent.
Fehling found in Aleppo galls from 60 to 66 per cent of tannic acid, while Fleck
found 58.71 per cent of this acid, and 5'9 per cent gallic acid.
Valonia Nuts. These are the dried immature acorn cups of two species of oak,
Quercus ægilops and Valonia camata, both being employed in tanning as well as the
valonia nuts produced by the puncture of the Cynips quercus calycis. The quantity
of tannic acid met with in these substances averages about 40 to 45 per cent. In the
so-called valonia flour, obtained by grinding the acorns belonging to this class,
Dr. Wagner found 19 to 27 per cent of tannin. The acorn cups are imported under the
name of drillot, and according to Rothe these contain 43 to 45 per cent of tannin.
Chinese Galls. Under this name has been known in the trade since 1847, and imported
from Japan, China, and Nepaul, the excrescence upon a kind of sumac, Rhus
javanica and R. semialata, produced by the puncture of the Aphis sinensis. This
gall-nut is rather oblong or bean-shaped, with an irregular surface covered with a
yellow-grey felt; the length varies from 3 to 10 centims., and the thickness from 15 to
4 cent:ms.; the texture is horny; the quantity of tannin varies from 60 to 70 per cent.
512
CHEMICAL TECHNOLOGY.
Cutch.
The substances long known in medicine under the name of catechu and
kino have been for the last fifty years also employed as tanning materials. Theyare
vegetable extracts, that known as cutch (trade term) being obtained by exhausting
with boiling water the pith of the wood of the Acacia catechu, a tree met with in
different parts of the tropical regions of Asia. The liquor obtained by boiling the
pith-wood in water is inspissated, and on cooling forms a solid mass, which is brought
into commerce in various shapes and named after the port of shipment. Bombay
cutch is met with in the shape of large square blocks, through and round which the
leaves of a kind of palm-tree are placed. The colour of the fracture of this substance
is a brown-black with a fatty gloss; externally the mass is dull and friable. Bengal
cutch is prepared from the nuts of the Areca catechu, and occurs in commerce as
large, irregularly-shaped cakes, externally brown, internally more yellow-coloured.
Gambir is a variety of cutch prepared in Sumatra, Singapore, and Malacca, and
especially in the Island of Riouw, from the leaves and stems of the Uncaria Gambir.
The dry extract occurs in commerce in small cubical blocks, which are light, of a
cinnamon-colour, and very friable, the fracture being earthy. All these substances
contain about 40 to 50 per cent of a peculiar kind of tannic acid or catechu tannic
acid, the formula of which, according to J. Löwe, is C15H1406, as well as a peculiar
acid, catechutic acid, C16H1406, not of much use in the tanning process.
Kino.
This drug is very similar to catechu, and is said to be the extract prepared
from various plants, viz. :-
...
...
African kino from
East Indian kino from
West Indian kino from
Australian kino from
...
...
...
Pterocarpus erinaceus,
Pterocarpus Marsupium,
East Indian kino, according to others, from Butea frondosa,
...
Coccolaba uvifera,
... Eucalyptus resinifera.
Kino is met with in small, angular, brittle, brown-red to black-coloured masses,
the powder of which is always brown-red. It is soluble in hot water and alcohol,
yielding a blood-red solution of an astringent and sweet taste. Kino contains from
30 to 40 per cent of a tannic acid similar to that contained in cutch; both of these
materials are especially useful in so-called quick tanning.
the Tanning Materials.
Estimation of the Value of The value of all the tanning materials entirely depends upon
the quantity of tannic acid they contain. The latter is soluble in water, and more or
less completely precipitated from that solution by various reagents, such as glue and
animal skin, acetate of copper, acetate of oxide of iron, cinchonine and quinine,
while a solution of permanganate of potash completely destroys the tannic acid.
Upon these properties the following properties have been based for the approximative
estimation of the quantity of tannic acid present in various tanning materials :—
1. Precipitation by glue or skin :—
a. Weighing of the skin before and after immersion in the liquor containing
tannin, the increase of weight giving the quantity of tannic acid.—(DAVY).
b. Precipitation with gelatine solution of known strength.-(Fehling).
c. Titration by means of an aluminated solution of glue.—(G. MÜLLER).
d. First determine the specific gravity of the tannin solution by means of an
areometer, next remove the tannin by skin, and then again take specific
gravity of liquid, the decrease being proportionate to the quantity of tannin
in the original liquor.-(C. HAMMER).
TANNING.
513
2. Precipitation of tannin by acetate of copper, and estimation of the relation
between tannin and oxide of copper in the precipitate :—
a. Volumetrically.—(H. FLECK); or
b. By the gravimetrical method.-(E. WOLFF).
3. Volumetrical estimation of tannin by acetate of iron.—(R. HANDTKE).
4. Oxidation of tannic acid by permanganate of potash.—(LöwENTHAL).
5. Precipitation of tannin by means of cinchonin, the solution of which is tinged
red by means of fuchsin. I grm. of quercitannic acid requires o'7315 grm.
cinchonine, equal to 4'523 grms. of crystallised neutral sulphate of cinchonin.-
(R. WAGNER).
The Skins. The skins of almost all quadrupeds might be converted into leather by
tanning; but the tanner chiefly prepares his leather from the hides of cattle, occasion-
ally from the hides of horses and asses as well as of pigs. The quality of the
hides not only depends upon the kind of animal, but also upon its fodder and mode
of living, The hides of wild cattle yield a more compact and stronger leather than
the hides of our domesticated beasts; among these the stall-fed have better hides
than the meadow-fed or grazing cattle. The thickness of the hide varies consider-
ably on different parts of the body, the thickest part being near the head and the
middle of the back, while at the belly the hide is thinnest. These differences are
less conspicuous in sheep, goats, and calves. As regards sheep it would appear that
their skin is generally thinnest where their wool is longest.
or
The hides of bulls and oxen yield the best and stoutest leather for soles. In the
raw-untanned-state, and with the hair still on, the hides are termed "green
fresh." Fresh or green hides are supplied to the tanners by the butchers, or are
imported either dry or salted. A hide weighing in fresh state from 25 to 30 kilos.
loses by drying more than half its weight. South America (Bahia, Buenos Ayres, &c.)
exports a large quantity of hides, both dry as well as salted and cured by smoking.
The hides of cows yield generally an inferior grained leather; but South American
cow hides may be worked for light sole leather. Calves' hides, again, are thinner,
but when well tanned, curried, and dressed, yield a very soft and supple upper
leather for boots and shoes. Horse hides are only tanned for saddlery purposes,
while sheep and goat-skins and the skins of lambs are tanned-or more generally
tawed-for the purpose of making wash-leather, maraquin, glove-leather, book-
binders'-leather. Pigs' hides and seals' skins are tanned for saddlery purposes.
The Several Operations. The several operations of the oak bark tanning process may be
reduced to three, viz.:-A. The cleansing and dressing of the hide on the hair and
flesh side; in other terms, the separation of the corium from the other integuments.
B. The true tanning. C. The currying and dressing operation, by which the
tanned hide becomes a saleable article. These three operations are again subdivided
as follows:-
A. The cleansing of the hide:—
1. Steeping and macerating the hide.
2. Dressing the flesh side.
3. Dressing the hair side.
4. The swelling of the cleansed hide.
B. The tanning of the cleansed hide, performed either by placing it in tanks or
pits with oak bark and water, or in a liquor of these previously prepared, or by the
so-called quick method.
34
CHEMICAL TECHNOLOGY.
514
C. The dressing and currying of the tanned hides, by which is understood all the
operations which tend to improve the compactness of texture, or give a better grain
and better appearance to the leather, together with softness, toughness, suppleness
and colour.
Cleansing the Hides.
A. This operation includes:-1. The steeping or macerating of
the hide in water for the purpose of rendering the texture uniformly soft and so
supple that it may be bent without danger of cracking, while, on the other hand, this
steeping also effects a cleansing of the hide by removing from it blood and dirt. The
fresh hides of recently slaughtered animals require a maceration in water for some
two or three days, but dried, cured, or salted hides have to be left macerating for some
eight to ten days. This operation should, if possible, be carried on in a stream of
water; but if there is no convenience, then the hides are placed in large tanks; in
either case the hides are taken out twice daily and put back into the water again.
Cleansing of the Flesh Side. When the hides have become quite soft, they are-
(2) cleansed or dressed on the flesh side by being placed with the hair side down-
wards on a "tree," a stout semi-circular plank, one end of which is placed on the
ground while the other is supported by a trestle, so that the plank is in a sloping
position. The workman has a so-called dressing-knife, a tool to which handles are
fastened, and which is bent so as to form a slight curve; with this knife he shaves,
or, as it were, planes off, from the hide all fatty tissue and integuments which are
situated between the hide and the muscles. At the same time the water is squeezed
out of the hide to some extent.
After a preliminary or first dressing, the hides are again placed for twenty-four
hours in water; the dressing and planing is then quite finished, and the hides
having been well washed, are left to drain on the tree ready for removing the hair.
In some instances the hides are washed by the aid of "possing-sticks," and "fulled
by means of machinery, by which the operation is greatly shortened, so much so,
that two to three days suffice, instead of, as is usual by the aid of manual labour,
eight to ten days.
Cleansing the Hair Side.
3. This operation aims at the removal from the corium of the
epidermis and hair-containing integuments. As the hair and integuments connected
therewith are very firmly attached to the corium, the removal can only be safely
proceeded with, so as to leave the corium uninjured, by the employment of a
menstruum which more or less dissolves and causes the epidermis to swell up. For
this purpose the hides are usually placed in lime-pits, the effect of the lime being the
partial dissociation (in an anatomical sense) of the epidermis, so that it and the
hairs may be readily removed by mechanical means.
The effect is usually obtained by-a. Sweating; b. Liming; c. Application of
rusma or compounds of sulphuret of calcium.
a. A semi-putrefactive fermentation called sweating is employed in the case of
thick hides, such as serve for sole leather, which are not placed in lime owing to the
fact that it cannot be completely removed, and would render the leather brittle.
The operation of sweating consists in placing the hides one upon the other, the flesh
side turned inward, some salt or crude wood vinegar having been first rubbed in, in
a tank, or box, which can be closed so that the heat generated by the fermentation
which sets in may be confined as much as possible to aid the action. As soon as the
evolution of ammonia is perceptible, the hides are ready for the removal of the hair,
which is shaved off, together with the epidermis, by the aid of the dressing-knife.
TANNING.
515
Instead of causing the sweating to be done by fermentation, the hides are sometimes
hung on laths in rooms either heated by means of steam or by fire. A temperature
of 30° to 50° should be kept up, together with a good current of steam, by which the
epidermis is thoroughly softened. In order to prevent any injury to the corium, the
hides are sometimes submitted to what may be termed a cold sweating process,
consisting essentially in placing the hides in water-tight tanks, in which there is a
constant current of fresh water, the temperature being kept at 6° to 12°. The hides
thus submitted to a constantly moist atmosphere become, after six to twelve days,
without any perceptible putrefaction, fitted for the removal of the epidermis and hair.
b. The liming of the hides not only prepares them for the removal of the hair, but
also saponifies the fatty matter; and though the lime soap thus formed is insoluble in
water, it is removed by subsequent mechanical and chemical operations. The
operation of liming is carried on in pits, into which, along with milk of lime, the
hides are placed so as to be quite covered. Usually several (three to five) pits are in
use at once, each of which contains a different quantity of lime. That the milk of
lime should be frequently stirred in these pits is of course evident. The hides
remain in the lime-pits for three to four weeks.
c. The very thin skins of the smaller animals will neither sustain sweating nor
liming and are therefore treated with rusma, a salve-like mixture of orpiment,
I part with 2 to 3 parts of slaked lime. By the rubbing in of this mixture on the
hair side of the skins, the hairs are so softened as to make their removal an easy
matter. Böttger states that hydrosulphuret of calcium has the same effect; hence
the lime of the purifiers of the gas-works has been of late years frequently employed
for treating hides as well as skins, with the additional advantage of yielding a better
leather.
Stripping off the Hair As soon as the hides are sufficiently prepared to admit of the
removal of the hair and epidermis, they are stretched out on the tree and the integu-
ments peeled off by the aid of the blunt dressing-knife. In order to give to the
dressing-knife a better grip, the workman strews some fine sand on the hide, and if
he has to deal with very heavy and thick hides, uses a large and rather sharp knife.
When the hair and the epidermis have been removed, the hides are again washed and
macerated in water, and after this dressed; that is to say, reduced as much as
possible to an equal thickness, while the waste-tail, leg, and head pieces-are cut
off and the hide planed, thereby losing some 10 to 12 per cent in weight.
Swelling the Hides.
The aim of this operation is to remove the lime, and also to
render the corium more capable of readily absorbing the tan materials. This end is
attained by placing the hides in a so-called sour bath, made of refuse malt and
bran, which by acid fermentation yields as active principles propionic, lactic, and
butyric acids.
The lime is removed from the dressed hides when placed in this acid liquid, and
the lime-soap present becoming decomposed, the fatty acids thus set free float on the
surface of the liquid. The soluble lime salts are completely removed from the
hides by a subsequent thorough washing with water. The thickness of the hides is
doubled by the swelling action of the acid liquid, aided by the mechanical action of
the carbonic acid evolved from the carbonate of lime deposited within the fibres of
the hides; while the butyric acid fermentation distends the fibres of the hides by the
gases thereby evolved. When the hides have not been treated with lime but have
been submitted to a "sweating," they do not require the acid bath, but are
516
CHEMICAL TECHNOLOGY.
simply placed in water for the purpose of swelling them. Yet the sour bath is
preferable owing to its more regular action.
Instead of using the preceding mixture for the purposes of removing the lime and
of swelling the hides, they are often placed in acid tan liquor (red tan liquor), that is
to say, a liquor containing exhausted oak bark solution which has served for
tanning; this liquor appears to contain also large quantities of lactic and butyric
acids. The dressed hides are first placed in a diluted red liquor and then in a
stronger liquor, this operation taking some 12 to 14 days. Macbride and Seguin
have proposed to substitute very dilute sulphuric acid (1 in 1500), but although by
the use of this acid the operation of swelling is rendered far more rapid, the quality
of the leather is impaired. Phosphates and animal excreta which contain a
large quantity of uric acid, such as that of dogs and of pigeons, have been, and in
many cases are still, used for the purpose of swelling hides, especially skins of sheep,
calves, and goats.
The Tanning.
B. The main object of the operations just described is first to obtain
the corium as much as possible separated from the other integuments and textures
belonging to the skin, and next to render the corium as much as possible permeable
by the liquor in which the tannin-containing vegetable matter is dissolved.
In
practice it is taken for granted that a dry hide gains one-third in weight by being
converted into leather, consequently it absorbs that quantity of tannin.
The impregnation of the fibres of the hide or skin with tannin is effected by two
different methods, viz.:—
1. By placing the hides between layers of oak bark chips in a tank, so-called
tanning in the bark; or
2. By immersing the hides, first in a dilute, and again in a concentrated aqueous
infusion of oak bark.
Tanning in the Bark. 1. This mode of tanning is at the present time confined to heavy
hides intended for sole leather. The tanks in which this operation is carried on are
made of wood, either oak or fir, are of course watertight, and are usually sunk into
the soil. Brick cisterns lined with cement are occasionally used, but are objec-
tionable, at least when recently built, on account of the deteriorating action of the
lime and cement upon the oak bark. In some parts of Germany tanks constructed
of slabs of slate or sandstone are used. Each tank has sufficient capacity to contain
50 to 60 hides. On the bottom of the tank is first placed a layer of exhausted (spent)
tan, and upon this a layer of some 3 centimetres in thickness of fresh bark, then a
hide with the hair side downwards, again a layer of fresh oak bark, and again a hide,
alternately until the tank is nearly filled, care being taken to put some more bark on
the thickest part of the hides, and to fill not only all interstices with bark, but to put
on the top a layer of some 30 centimetres thickness of spent tan. Water is
next poured into the tank until it stands a few centimetres above the topmost hide;
this having been done, a lid-in England loose planks-is placed on the tank,
the contents of which are left undisturbed for some time. When Valonia flour
is employed with the oak bark only half the quantity of the latter is necessary.
The hides are left in "the first bark" for 8 to 10 weeks, the period being a little
shortened if Valonia flour is also used. Before all the tannin has been absorbed, and
as a consequence the formation of volatile and odorous acids (valerianic, butyric, &c.,
has commenced, the hides are transferred to another tank and again placed between
alternate layers of fresh bark, the only difference in the arrangement being that the
TANNING.
517
hides which were first placed on the top are now laid at the bottom of the tank.
The hides are now left for three to four months, so as to thoroughly absorb the
tannin. They are next placed for some four to five months in another tank which
contains less bark. In the case of very heavy and thick hides the process is
repeated four or even five and six times. The quantity of bark required for
obtaining thoroughly well-tanned leather depends partly on the quality of the bark,
and somewhat on the condition of the hides. Usually the tanners reckon that the
quantity of bark required amounts to four to six times the weight of the dry hides;
and taking the weight of these at an average of 20 kilos.—
For the first tank there will be required 40 kilos. of bark.
second
third
""
35
30
""
""
105 kilos. of bark.
A dried and well-tanned hide weighs about 22 kilos., or 10 to 12 per cent more than
the dry raw hide. A thoroughly tanned hide exhibits when cut with a sharp knife a
uniform texture free from fleshy or horny portions, while the grain on the hair side
should not on being bent slowly exhibit signs of cracking.
Tanning in Liquor. 2. The thinner hides, and indeed most skins (when tanned, as
distinguished from tawing), are placed in infusions of the tannin-containing material.
There are various methods in use for this operation, which is based mainly upon a
thorough uniform swelling of the hides, so that when these are placed in weak
liquors the tannin may penetrate readily and uniformly. The hides are, in fact, very
gradually tanned. When taken from a liquor the fluid is forced by mechanical
means out of the hides before they are placed in a stronger liquor, this liquor
being obtained by exhausting the tanning materials by the aid of cold water. The
thinner kinds of hides are thoroughly tanned in seven to eight, the heavier hides in
eleven to thirteen weeks.
Quick Tanning.
Many methods-some quite impracticable and most of them
thoroughly irrational—have been proposed for converting hides into leather in a very
short time. Of these different methods we briefly mention the following:-
:-1. The
hide is simply placed in an infusion of the tannin-containing material-Macbride's
process, improved by Seguin (1792). Application of hydrostatic pressure to force the
liquor through the hides, kept from contact with each other by a stout woollen
tissue. 2. Circulation of the tannin-containing fluid, several tanks being connected
together by means of pipes, and the liquor being forced through the tanks by means
of pumps (Ogereau, Sterlingue, and Turnbull's methods. 3. The hides are sewn
together so as to form sacks, which are filled with oak bark chips and water and then
placed in an aqueous solution of cutch, to which, in order to increase its specific
gravity, coarse molasses is added-Turnbull's method by increased endosmose.
At the time this mode of proceeding was brought forward, the diffusion of liquids
by dialysis (discovered by Graham in 1861) was unknown. 4. Motion of the
hides in the tannin-containing liquids, the hides being placed in a cylinder
constructed of wooden laths so as to leave open spaces between them. This
cylinder is immersed horizontally in the liquid to a greater or less depth, so that in
every revolution the hides are alternately in and out of the liquid-Brown, Squire,
and C. Knoderer's methods. 5. Application of mechanical pressure to the hides,
518
CHEMICAL TECHNOLOGY.
which having been from time to time removed from the tanning tanks, are placed
upon perforated planks, and either pressed under a heavy roller or are placed in a
press-Jones, Nossiter, Cox, and Herapath's method. 6. Application of hydrostatic
pressure for the purpose of causing the tan-liquor to penetrate the hides, which are
sewn together so as to form bags, which having been filled with oak bark liquor, are
placed in suitably constructed vessels, so that hydraulic pressure may be applied
without fear of bursting the bags; or the hides are fastened by means of screws and
bolts, placed in a framework which is immersed in a well-constructed cistern filled
with tan-liquor, hydraulic pressure being applied-Drake, Chaplin, and Sautelet's
methods. 7. Snyder's method of punctation, consisting in perforating the hide over
its whole surface, the punctation being effected by sharp needles, so as to constitute
artificial pores. The experiments of Knapp have proved the thorough irrationality
of this plan, it having been found that the hide is so permeable to tannin-liquor that
a piece of calf-skin when placed in a solution of tannin of the consistency of syrup
is thoroughly well tanned in about an hour's time. 8. Application of a vacuum
by placing the hides in a vessel from which the air may be withdrawn by the aid of
air-pumps; tan-liquor having been forced into the vessel, the air is re-admitted and
again withdrawn-Knowly and Knewsbury's plan. Knoderer has recently found
that by a judicious combination of the vacuum method, followed by motion and
fulling of the hides in the tan-liquor, the operation of tanning is much shortened.
The reader should bear in mind that the methods here alluded to are not now
in general use.
Dressing or Currying
the Leather.
When the hides have been converted into leather by the
processes described, they are not by any means fit for use nor ready for sale as
a finished material, but require to be dressed, or, as it is technically termed, curried,
an operation not necessarily performed by the tanner-at least, never so in England
and France. The several operations are not similar for all kinds of leather,
but depend to some extent upon the use to which it is intended to be put. For
instance, sole leather is submitted simply to a process the object of which is
to render it sufficiently stiff and compact, so as not to alter its shape by wear.
Sole Leather. The dressing or currying of this kind of leather consists mainly in sub-
mitting it to a mechanical operation of hammering, by which the material is
rendered more compact. As soon, therefore, as the hides are taken from the tanning
tanks, the adhering spent tan is brushed off with a broom, after which the hide
is dried in a cool place, and when dry laid flat upon a polished stone slab, and then
beaten with wooden or iron hammers, an operation in large establishments per-
formed by hammers moved by machinery.
Upper Leather. The dressing of this kind of leather, chiefly used by sadlers and
boot and shoe makers, is a far more complicated process, and depends in a great
measure on the use for which the leather is intended. The first of these operations is
The Paring. the paring or whitening, which means the cutting away, by the aid of a
tanner's shaving-knife, of all portions of the hide which are too thick, so that
the whole hide may be made of uniform thickness. This operation is carried
on upon the tanner's "wooden leg," the hide being placed with the hair-side
downwards. When goat, lamb, sheep, or calf-skins are to be pared, they are
placed on a polished slab of marble, and having been well stretched, the raw or
projecting parts are cut off with the tanner's shaving-knife.
1
TANNING.
519
The Scraping or Smoothing.
The aim of this operation is similar to that of the former,
and more particularly is employed in the case of leather intended for making gloves.
The leather is first dried and next fixed on the "perching-stick," one end of the skin
remaining free, the other being taken hold of by the operator with a pair of forceps.
The skin having been stretched, the perching-knife, a highly polished somewhat
convex steel disc of 18 to 30 centims. diameter, and provided in the centre with an
opening fitted with a piece of leather serving as a handle, is brought into use,
the portions of the skin which require to be pared off being usually indicated by
being rubbed over with chalk.
Graining the Leather. As in consequence of the drying of the leather the grain has
become flat, smooth, and unequal, it is raised by an operation performed by means of
the pommel, also termed the graining- or crimping-board, a piece of hard wood
30 centims. in length by 10 to 12 centims. breadth, flat and smooth on the top, but on
the opposite side, in the direction of the length, somewhat curved, so that it is
thickest in the middle, this part being provided with parallel notches, which are
occasionally sharpened by means of a file; a leather strap is fastened to the top as a
handle. The leather to be grained, having been placed on the dressing-table, is
fastened to the edge of the wooden board by means of iron clamps, and those portions
of the leather, the grain of which has to be raised, having been somewhat bent, are
rubbed with the pommel so as to render the grain uniformly visible,
Raising the Grain Slightly a pommel
with Pommels of Cork.
Polishing with Pumice-Stone. Such kinds of leather as require no grain (for instance, the
leather used in carding machines) after having been pared, are moistened and then
rubbed over on both sides with pumice-stone, being thus rendered smooth; while
leather which requires a higher gloss, such as the coloured leathers, are treated with
made of cork, by which the leather is caused to
assume a velvety appearance. Again, if a still higher gloss is required, the leather
Smoothing with the Tawer's is first smoothed, or rather ironed, with iron or copper
sleekers," and next polished with glass sleekers, a stout cylindrical piece of glass,
03 metre in length by 10 centims. diameter, the leather being placed on a tanner's
Rolling. wooden-leg. Leather intended for saddles, in order to impart to it the
appearance natural to hog's leather, is passed through rollers, the surfaces of which
are provided with blunt points, which, being forced into the leather, give to it the
desired appearance.
Softening Iron.
Finishing Off. In order to remove from the leather any creases and other inequalities
of surface, it is damped, and then smoothed with a flattening-iron, or, if the skins are
thin, with a piece of horn provided with blunt teeth.
Greasing. When the upper leather is required to be very supple and soft, it is
greased; that is to say, it is rubbed with a mixture of fish-oil and tallow, or better,
with the peculiarly modified fish-oil which has been used in "chamoising," having
been recovered by the aid of a solution of potash from the chamois leather skins.
The hides to be greased are first moistened, and having been rubbed with the greasy
matter, are dried in heated rooms, so that the fatty materials, by actually combining
with the hides, become, as it were, tanned and tawed at the same time. The greasing
is therefore not simply an operation of dressing, but in reality a second tanning
(technically tawing) process.
The black colour usually seen on the surface of leather required for saddlery and
boot-making is imparted to the hides by rubbing them with a fresh solution of
oak bark and then sponging them over with a solution of copperas to which some
520
CHEMICAL TECHNOLOGY.
blue vitriol has been added; the hides are then again dressed, and lastly rubbed
with a paste made of fish-oil, tallow, lamp-black, yellow wax, soap, and copperas, the
object of this operation being to protect the leather from the injurious effects of the
shoe-blacking, which usually contains sulphuric acid. (For a shoe-blacking without
acid see
Chemical News,” vol. xxiv., p. 120). Finally, the leather is painted or
brushed over with a mixed tallow and glue solution, and then, having been polished
again with glass, is ready for sale. In order to keep leather supple and soft, it is best
to rub it with a mixture of fish-oil and lard.
Yufts, Russia Leather. Under the name of yufts is understood a peculiar kind of
leather, usually of a red or black colour, which is very water-tight and strong. This
kind of leather used to be made exclusively in Russia, whence it is obtained in large
quantity, the name being derived from the Russian Jufti, signifying a pair, and
apparently due to the fact that in tanning the hides are sewed together in pairs.
The hides usually prepared for Russia leather are those of young cattle; sometimes,
however, the hides of horses and the skins of sheep, goats, and calves are employed.
The operations for preparing yufti are:-1. The cleansing of the hides, performed in
the usual manner with lime. 2. The swelling of the hides in an acid-bath prepared
with malt, exhausted tan-liquor, or with kaschka (excreta of dogs rubbed up with
water). 3. The tanning, not performed with oak bark, but with the barks of various
kinds of willows, fir and birch bark also being used. The dressed hides are first
placed for some days in partly exhausted bark, and are then put into the tanning
tanks along with bark (as above described), or are sometimes placed in a warm
infusion of the tannin-containing materials. The tanning continues for five to six
weeks. 4. The tanned hides are placed on the planing-block for the purpose of
draining, and are next impregnated with diggut or elachert, oil of birch, obtained by
a process of dry distillation from birch wood. This oil contains creosote, phenol (of
a peculiar kind according to Louginine), and paraffin. It is rubbed into the hides on
the flesh side, and when thoroughly impregnated they are stretched until they
become soft and supple. The hides are next rubbed on the hair side with a solution
of alum, and then grained and dried. The dry hides are dyed in pairs, sewn together
so as to form a sack, into which a decoction of dye material is poured. When
a red colour is desired, the dye is prepared from sandal wood, there being added
to the former lime-water, to the latter some potash or soda. In more recent
methods the hides are dyed by being brushed over five or six times with the dye
material. The dry leather is finally dressed by the mechanical operations previously
described. The use of yufts for book-binding and other purposes is well known.
Owing to the empyreumatic oil with which this kind of leather is impregnated
insects do not attack it.
Morocco Leather. By morocco leather is understood a kind of leather which, when
genuine, is obtained from goat or kid skins, is very soft, elastic, highly coloured, and
not lacquered. We distinguish between genuine morocco and the imitation
obtained by the splitting of calf, sheep, and other skins, as chiefly employed in book-
binding.
The preparing of morocco leather is undoubtedly one of the many industrial
discoveries of the Saracens; even at the present day a great deal of morocco leather
is made by their descendants in Northern Africa and in the Levant. The prepara-
tion of good morocco leather requires very great care, and especially as regards the
preliminary operations. The skins are deprived of the hair by the aid of lime and
TANNING.
521
sweating. The tanning material in general use is sumac, the skins being sewn up
so as to form sacks into which water is poured together with pulverised sumac; by
this mode of employing the tanning matter the operation is finished in three days.
Calf and sheep skin are very generally tanned in England by the same method.
The dyeing of morocco leather is not performed in the Oriental countries; the dry
tanned skins are exported under the name of Meschin leather (cuir en croutes) to be
dyed and dressed in Europe.
Dressing Morocco Leather. The skins are dyed and next dressed. The dyeing is per-
formed (u) by means of the dye-vat (for genuine morocco), or (B) with the
brush (for imitation morocco). a. The operation of dyeing with the vat is performed
in a small trough large enough to hold one skin, and filled with dye-liquor at 60°
from a larger tank. The workman pours in no more of the dye material than can be
conveniently absorbed by the skin, which is continually moved to and fro. The
dyed skins are laid out flat, and from two to four dozen placed one upon the other.
The dyeing operation is repeated several (three to five) times, care being taken to
turn the heap over so that the undermost skin is placed on the top of the heap
previous to beginning the dyeing operation again. The dyed skins are washed in
water and next dressed. B. The imitation morocco is dyed by the dye-liquor being
uniformly brushed over the skins; these having been first stretched on a table, the
dye-liquor is brushed over more than once so as to produce a uniform hue. The
effect of the dyeing is greatly enhanced by the dressing of the skins and the fine
grain given to them. The dyed skins are first rubbed on the hair-side with linseed
oil applied by means of a piece of flannel. The calendering or glazing by machinery
is the next operation, after which the peculiar appearance of the surface is imparted
by means of strong pressure or so-called platting. Yellow skins are not glazed,
because their colour would thereby become a brown. The aniline colours are now
largely employed in dyeing skins.
Cordwain, Cordovan Leather. This differs from morocco only by being prepared from
heavy skins, and by retaining its natural grain or not being platted. It is usually
met with dyed red, yellow, or black.
Lacquered Leather. This kind of leather, now largely used by coach-builders and for
making shoes, boots, helmets and other military accoutrements, is an invention of
the present time, its great merit being its property of resisting water, and in being
supple and soft, while the lacquer, if well laid on, should not crack nor peel off.
Only black lacquered leather is generally met with. On the tanned, rarely tawed,
hide, which has not been greased, is very uniformly laid a varnish, which is thick
and tough while cold but thinly fluid when warm; this häving been done, the hide
is placed in a brick-built stove kept at 50°, where the varnish dries after having
become so fluid as to run uniformly over the surface of the leather, which is placed
quite horizontally. The coloured lacquers are generally more thinly fluid and are
dried at a lower temperature. The hides chiefly used for lacquering are cow-hides;
or a thin hide is obtained by splitting thick hides and lacquering them.
The leather in use by pianoforte-makers for covering the hammers is prepared by
a process usually kept a trade secret. This kind of leather requires to be soft and
very elastic. All that is known about the process of preparing this material is that
it is obtained by tanning and tawing (chamoising) combined; the hair having been
removed, but not the epidermis, the hide is first fulled in oil, then washed-in ley,
bleached in the sun, and next tanned in a tepid oak bark infusion. Danish leather
522
CHEMICAL TECHNOLOGY.
is prepared by tanning sheep, goat, kid, and lamb skins with willow bark; such
leather being chiefly used for gloves. It is distinguished by its strength, suppleness,
and bright colour.
Tawing; Preparation of
White Leather.
II. Tawing.
This mode of preparing leather is based upon the peculiar
action of the salts of alumina upon skins, not hides generally.
Four modifications of tawing are known, viz.:-1. Common tawing. This
operation extends only to thin skins, such as sheep and goat skin, &c., which are
treated only with alum and common salt without the application of oil. 2. Hunga-
rian tawing process. Heavier hides not treated with lime are tawed and next
chamoised. Klemm's method of preparing fatty leather is somewhat similar to this
treatment. 3. The French or Erlanger tawing method, by which the skins are
prepared for glove-leather. 4. Tawing by the aid of insoluble soaps, according to
Knapp's suggestion.
Common Tawing.
1. The tawer obtains sheep skin, or occasionally goat skin, either
with the wool off or "in the wool," as the term runs, in the latter case greater care
being required, because the value of the wool, which, by careful working may be
obtained in good condition, refunds a considerable portion of the expense of the
operation by its sale. The various operations of tawing are in a certain measure
similar to those of tanning.
The steeping and planing is carried on as in the tanning process. The workman
places ten skins on the planing-tree, and dresses each skin with the dressing-knife on
the hair as well as on the flesh side; next the wool or hair is shaved off after the skins
have been first treated with the lime; but when "in the wool" the skins are cleansed
with thin lime-water, which is laid on the flesh side of the skin by a brush made of
cow's-hair, so that the wool is not brought into contact with lime. The wool is
removed, not by a planing-iron, but by means of a piece of wood somewhat sharpened.
The wool having been removed, the skins are brushed over with a mixture of equal
parts of lime and sifted ashes; next the head and leg strips of the skin areturne d
inside. Each skin is then folded together and beaten, in order to prevent the wool
being touched by the lime. The skins are left in this condition for eight to ten days
until the wool is loosened. The skins are next thoroughly washed on the flesh side as
well as on the wool side in order to remove the lime and dirt; this having been
done the wool is partly pulled off by the hands, partly removed by a blunt tool.
The skins thus deprived of wool are placed in the lime-pit and further treated as
just described. In order to remove the paste adhering to the skins they are, on
being removed, placed in a tank, where, owing to the quantity of animal matter
dissolved in the water, a fermentation has arisen accompanied by an evolution
of ammonia. By the action of this alkali a large portion of the fatty matter con-
tained in the skins is removed. After being taken from the lime-pit the skins are
placed on the dresser's block, and some parts, such as the ears, skin of tail, portion
of top part of chest, cut off and thrown aside for the glue-boiler. The skins are put
over night to soak in water, and then again placed on the dressing-block in order to
be planed with a blunt iron on both sides of the skin; this operation is repeated
after the skins have been placed in a tank containing water, and while there
thoroughly beaten with a heavy wooden "possing-stick" in order to remove lime.
In the subsequent planing the lime and lime-soap are forced out, and any wool that
TANNING.
523
has remained shaved off. In order to dissolve the last traces of lime the skins are
placed in an acid-tank containing bran and water, in which by fermentation lactic
and acetic acid have been formed. These acids convert the lime of the skins into
soluble salts, while the process causes the swelling of the skins, which thus become
better adapted to absorb the tanning materials. The skins remain in the sour-tank
for two to three days. The tanning material consists for 1 dicker (= 10 skins) of
an alum ley, containing o'75 kilo. of alum, o‘30 kilo. of common salt dissolved in
22.5 litres of boiling water. 1 litre of this liquid is poured into a trough, and
having become tepid, each skin is separately thoroughly washed with and soaked in
it, and then put aside without being wrung out, the skins being placed one upon the
other so as to form a heap. After lying thus for two or three days, the skins are
wrung out and hung up to dry slowly by exposure to air.
I
As regards the theory of the action of the alum ley in the tawing operation, it was
formerly believed that only the chloride of aluminium-formed by double decompo
sition between the constituents of the common salt and the sulphate of alumina of
the alum (the alkaline sulphates being considered useless)—was active, and that a
basic chloride of aluminium (aluminium oxychloride) combined with the skin,
there being left in solution hydrochlorate of alumina. It was also known that
acetate of alumina, if used instead of alum ley, was quite as active and yielded excel-
lent results. The experiments made by Dr. Knapp, sen., with alum, acetate of
alumina, and chloride of aluminium, have proved that no decomposition ensues
when the aluminium salt is taken up by the skin, the quantity taken up being for the
undermentioned salts as follows:-
Of alum
Of sulphate of alumina
Of chloride of aluminium
Of acetate of alumina...
8.5 per cent
279 "
273
""
23'3"
""
The alumina salts do not, however, combine with skin under all conditions in the
same quantity as just mentioned, as experience proves that the skins absorb more
when placed in concentrated than when in dilute solutions. As regards the part
played by the common salt in the preparation of the alum ley, the salt is not there
simply to bring about the conversion of the alumina sulphate into chloride of
aluminium (recent experiments made by Knapp in 1866 have proved that by
employing 1 atom of potash alum and 3 atoms of common salt = 37 per cent, no
mutual decomposition ensues), but the salt is in this process active by itself, partly
aiding dialytically the action of the alum, partly owing to its property-possessed
also by alcohol-of withdrawing from animal tissues the water they contain suffi-
ciently to prevent the fibres to become glued together by the drying of the substance,
thus promoting the formation of leather. The dry and tawed skins will be found to
have become shrunken and stiff, having lost much of their suppleness and flexibility.
In order to remedy these defects the skins previously damped with water are sub-
mitted to a mechanical operation, being placed on the convex side of a curved iron,
and stretched by being drawn between this fixed iron and a movable steel plate,
which is fitted closely upon the other. After having been thus softened, the skins
are stretched on a frame for some time to become dry. When dry they are ready for
sale, the leather thus obtained being largely used under the name of white-skins for
the lining of boots and shoes.
524
CHEMICAL TECHNOLOGY.
Hungarian Tawing Process. 2. This process is distinguished from that just described,
inasmuch as the heavy hides of oxen, buffaloes, cows, horses, &c., are made into
leather for saddlery and other purposes, while sometimes also the skins of wild boars
and of other animals are thus tawed for making flail strings. The raw hides are first
soaked in water to remove blood and impurities. Next the hair is shaved off by
means of a sharp knife. This operation performed, the hides are put into an alum
ley, which for a hide weighing 25 kilos., consists of 3 kilos. of alum, 3 of common salt,
and 20 litres of hot water. This liquor when tepid is poured into an elliptical tub
in which the hide is placed.
One of the workmen then jumps into the tub and by moving the hide about with
his feet soaks it thoroughly with the liquor, in which it is then left for at least eight
days, the operation of treading with the feet being repeated. The hide is now taken
from the tub and hung up to dry, and when dry is stretched and fatted" in by
the following method:-The hide is warmed by being held over a charcoal fire, and
when warm is rubbed on the hair as well as on the flesh side with molten tallow, of
which some 3 kilos. are used for every hide. When thirty hides have been thus
treated, they are one by one again held and moved to and fro over the fire, and next
hung up in the open air to dry. The tallow partly combines with the hide.
The hides thus prepared are converted into a leather of excellent quality, especially
suited for the harness of horses and saddlery work of a more common kind, in
which, as in that used for artillery horses, great strength is required. This leather
is cheap on account of its being prepared in a short time.
Glove Leather.
3. The so-called Erlanger, or French tawing process, is employed
only for the production of the glacé, or kid leather, used for making gloves and ball-
room shoes. The hair side of the skins intended to be converted into this leather
is left unchanged, while as regards wash-leather gloves which are treated (tanned)
with fish oil the hair side is cut off. The skins intended to be converted into kid
leather are treated with extraordinary care, and thus acquire in a very high
degree all the good quality of alum-tanned (or rather tawed) leather. As these
skins are often intended to remain white or are dyed with delicate colours, the
greatest care is taken to prevent any injury, as, for instance, contact with oak wood
or with iron while wet.
Two kinds of skins are employed for conversion into the better varieties of
kid leather; one of these, the more expensive, being the skins of young goats,
fed solely with milk, the other being lamb skin. Each of these skins yields on
an average 2 pairs of gloves. The leather of which ladies' ball-room shoes are
made is obtained from the hides of young calves (so-called calf-kid). The preli-
minary operations of preparing this leather are exactly similar to those already
described for the ordinary white leather; but the tawing operations are quite
different, the skins being put into a peculiar mixture, by which they are not only
tawed, but simultaneously impregnated with a sufficient quantity of oil to render
them soft and give suppleness. The mixture consists of a paste composed of wheaten
flour, yolks of eggs, alum, common salt, and water. The flour by the gluten it con-
tains aids the absorption of the alumina compound, and thus assists the real tawing.
The starch does not enter into the composition of the skins, while the yolk of
eggs acts by the oil it naturally contains in the state of emulsion, this oil giving to
the kid leather that suppleness and softness which is so much esteemed in gloves. It
appears that emulsions made with almond oil (the so-called sweet oil of almonds--a
TANNING.
525
fixed oil), olive oil, fish oil, and even paraffin, may be advantageously substituted for
yolk of eggs. The skins are thoroughly soaked and kneaded in this mixture, to
which, in France, there is sometimes added 2 to 3 per cent of carbolic acid for the
purpose of preventing the too strong heating of the skins when impregnated with
the mixture and packed in heaps. The skins are next stretched by hand and dried
as rapidly as possibly by exposure to air. Having been damped, a dozen of the skins
are placed between linen cloths and trodden upon to render them soft. After this
they are, one by one, planed, dried, and again planed. Either by rubbing with a
heavy polished glass disc or by the appreteur, simultaneously with the application of
some white of egg, or a solution of gum, or of fine soap, a gloss is given to the skins,
the hair side of which is the right side or dyed side. The dyes are applied either by
immersion or by brushing over the leather; the latter, or English method of dyeing
skins, is more ordinarily practised.
According to Knapp's researches very good white kid leather is obtained by tawing
the epidermis (blöss) from lamb or goat skins in a saturated solution of stearic acid
in alcohol. The leather thus obtained is very soft, has a whiter colour than ordinary
glacé leather, and a beautiful gloss.
Knapp's Leather. 4. The preparation of leather with the aid of insoluble soaps,
introduced by Knapp, would appear to have become of some importance. The pro-
perty possessed by oxide of iron of acting as a tanning material has been known for
a long time, and in 1855 Mr. Belford took out a patent in this country for a mineral
tan method, in which oxide of iron was used; but good leather did not result.
The hides do not become really tanned by being immersed in solutions of such
metallic salts, as those of the protoxide and peroxide of iron, oxides of zinc
and chromium; for though the acidity of these solutions is reduced to a minimum
without producing a permanent precipitate, and thereby the deleterious action of the
acid upon the fibres of the hides decreased, and though a certain combination of the
oxide and fibres takes place, no real leather is formed because the substance
when finished is not fitted for contact with water, for then the so-called tanning
is washed out. Knapp's process also is not really a tanning but a tawing operation,
by which the skins are alternately immersed in a solution containing 3 to 5 per cent
of soft soap, and then in a saline solution of oxide of iron, or of chromium,
containing 5 per cent of the salt, from which an insoluble metallic soap is precipi-
tated and impregnated with the fibres. After this operation has been several times
repeated the hides or skins are washed in water and dried. Although the exterior
colour of good sound leather may be imitated, the real qualities of leather are
wanting. Knapp's process is not in use or is so entirely modified by substituting
alum for metallic oxides that the skins are tawed by a combination of the preceding
tawing processes and the oil-tawing process now to be described.
Samian Tawing Process.
III. Sämian or Oil-Tawing Process.
By this name is understood a peculiar process by which the
skins and hides of various animals, such as harts, deer, sheep, calves, oxen (for the
white leather for military use as belts, &c.), are converted into so-called oil- or wash-
leather. The tanning material is oil, fat, tallow, or fish oil, to which recently there
has been added 4 to 7 per cent of carbolic acid. The leather thus obtained is
526
CHEMICAL TECHNOLOGY.
chiefly used for making military breeches, socks, vests, gloves, braces, belts, surgical
applications, and not in small quantity for washing glass and porcelain, owing
to its softness. On this account wash-leather is also largely used by gold and silver-
smiths for polishing trinkets with rouge (very carefully prepared oxide of iron). The
upper or exterior layer of the corium, which owing to its greater compactness does
not possess the ductility and suppleness of the lower or interior layer, is in the
skins intended to be converted into wash-leather entirely cut away, so that no hair
and flesh side are taken into consideration. The cutting away of this layer greatly
promotes the absorption of the oil, which by the joint action of air and heat yields a
product which is a dry compound of fibre and oil, in which the latter physically has
disappeared, inasmuch as the leather is not impervious to water. Wash-leather
differs in this respect from oil or fat leather; still, on immersion in water, the skin does
not glue together and shrink. Thin skins, such as those of goats and lambs, are
not deprived of their hair side, because it would render them too thin for use.
The skins intended to be made into wash-leather are, as regards the first stage of
the operation, treated exactly as described for the skins treated with alum, the only
difference being that the hair is removed together with the hair side portion of the
skins, which are next placed in a bran bath in order to remove the lime. After this
the skins are stretched and conveyed to the fulling machine in order to become
saturated with oil, for which purpose the skins are first laid on a table or bench and
are rubbed with oil, the hair side being placed uppermost. This having been done
they are made into clouts and placed under the stampers of a machine so as to
thoroughly impregnate them with oil. From time to time the skins are taken from
the trough and exposed to the air, then again rubbed with oil and put under the
stampers until enough oil has been absorbed. By the repeated exposure to air
the skins become dry, and oil (fish oil is chiefly used) absorbed; the exposure to air
is continued until the surface of the skins appears quite dry. When the skins have
an odour somewhat similar to that of horse-radish, and have lost their fleshy odour,
they have absorbed a sufficient quantity of oil, while a portion of the oil has been
somewhat changed and has entered into combination with the fibre, another portion
only mechanically adhering to the pores of the skins. The next operation therefore
aims at rendering the process of the combination of the oil with the skins more
rapid by bringing about a fermentation attended with an elevation of temperature;
this is effected by placing the skins in a warm room, heaping them together, and
covering them with canvas to keep in the heat which is generated, care being taken
to air the heap from time to time in order to prevent overheating and consequent
deterioration of the skins. This operation of airing the skins is repeated until by
the spontaneous heating they have acquired a yellow colour and the workmen
know by experience that the oxidation of the oil is finished. A portion of the oil
(estimated at about 50 per cent of the quantity originally employed) is left in the skins
in uncombined state, and is removed by washing with a tepid solution of potash.
From this liquor there separates on being left at rest a portion of fat termed dégras,
and which, as already mentioned, is employed for the dressing of tanned hides.
The skins having been thus deprived of the excess of oil are wrung out, dried, and next
dressed, in order to restore to them their softness and suppleness partly lost in the
drying. Cordovan or Turkey leather, is oil-tawed without the hair side having been
first removed, while the flesh side is blackened in the usual way. This kind of
leather is chiefly used for ladies' boots and shoes. According to Knapp, skins from
TANNING.
527
which the hair has been first removed may be tawed by treating them alternately
with a solution of soap and dilute acids, so that the fatty acids are precipitated into
the fibre. After the tawing the skins thus treated should be thoroughly washed
in water to remove all acid. As regards the constitution of the leather, commonly
known as wash-leather, tawed with oil, nothing is definitely known, but it would
appear that this process of tawing has some analogy to the process of imparting oil
to calico intended for Turkey-red dyeing.
Parchment.
The substance known as parchment is not really leather, because its
fibres are neither tanned nor tawed, as proved by the fact that boiling water readily
converts parchment into a superior kind of glue similar to isinglass, of course too
expensive for joiners' use. Parchment is essentially the well-cleansed and carefully
dried skins of hares, rabbits, and especially of calves and sheep.
Ordinary parchment is prepared from sheep-skins, but the variety known as
vellum, Vélin or Parchement vierge, is far finer, and is made from the skins of young
calves, goats, and stillborn lambs. According to the use intended to be made
of parchment, so is its preparation modified. The skins are first soaked in water
and then placed in the lime-pits. Sheep skins are cleansed by working with cream
of lime in order to preserve the wool. When the hair has been removed the skins
are washed, being placed on the dresser's block, and usually also planed with
a sharp knife to remove the superfluous fleshy parts. This having been done, each
skin is separately stretched in a frame, in a manner very similar to that in use for so-
called Berlin-wool work, the skins being held in position by means of strings, and
dried by exposure in the open air. Parchment intended for drum skins (from
calves' skins), for kettledrums (from asses' skins), does not require any further
operation. If intended for bookbinding the parchment is treated as described,
but after drying it is planed with a tool the cutting edge of which is somewhat
bent in order to impart a rough surface, whereby the parchment is rendered capable
of being written on and dyed. If the parchment be intended—as it used fre-
quently to be formerly before the invention of metallic paper-for memoranda,
written with lead-pencils, to be wiped out if desired with a wet sponge, it is
after planing painted over with a thin white-lead paint, for which a mixture of glue-
water with baryta- or zinc-white is often substituted. The vellum of this country is
generally obtained from sheep skins, which are split into two sheets by means of
cutting-tools. Parchment after having been dried on the frames is dusted over with
chalk and rubbed with pumice-stone. The sieves used in powder mills for granula-
ting the powder are made of parchment obtained from hogs' skins.
Shagreen. Genuine Oriental shagreen (saghir, sagri, sagre), is a variety of tawed
parchment, one side of which is covered with small hard grains. This material
is manufactured in Persia, at Astrakan, in Turkey, and in Roumania, from certain
portions of the skins and hides of wild asses, horses, and other animals. The hides
are soaked in water until the epidermis can be removed easily together with the
hairs by the aid of a dressing-knife; next the hides are again placed in water so as
to swell the material sufficiently to admit of cleansing it, and cutting away on both
flesh and hair side all superfluous material, so as to leave only the corium, which then
has the appearance of a fresh bladder. In order to produce on skins thus prepared
a grained surface, they are put into frames, as described under Parchment, while
on the hair side, allabuta, the hard black seed of the Chenopodium album is
stamped in, either by the feet or forced in by pressure. When the skins are dry they
528
CHEMICAL TECHNOLOGY.
are removed from the frame, the seed shaken off, and the skins thoroughly planed
with a sharp dressing-knife, then put again into water, tawed, and finally dyed. The
tawing is effected by the aid either of alum or of oak bark. The dye of shagreen is
generally green, and is due to salts of copper. After dyeing the skins are soaked in
mutton tallow.
Fish skin, or fish chagrin, is obtained from various kinds of sharks (Squalus
canicula, S. catulus, S. centrina) and other fishes of the same class. The skin of
these animals is not covered with scales, but with more or less projecting hard
points. The skins having been removed from the fish are stretched in frames and
simply dried, being then sent to the market. Formerly sharks' skin was in some
countries used by joiners instead of sand- and glass-paper for preparing wood. The
skins deprived of the projections are dyed and used for covering small boxes, tubes
of small telescopes, &c.
·
GLUE-BOILING.
General Observations. The organisms of all animals, but more especially of the higher
classes, contain tissues which are insoluble in cold as well as in hot water, but
which by continued boiling become dissolved, and yield on evaporation of the solu-
tion a glutinous gelatinising mass, which, by further drying, exhibits, according to the
degree of purity of the material, a more or less transparent and brittle substance, which
in pure state is devoid of colour as well as of smell, becoming swollen in cold water and
dissolved by boiling in that liquid. This substance, i.e., the product of the conver-
sion of the so-called glue- or gelatine-yielding tissues, is what is known in the trade
as glue, and largely used by joiners, carpenters, c., for joining wood, also for
sizing paper, for clarifying various liquids, beer and wine for instance, and as a
cement. Among the glue-yielding tissues the following are the most important :-
Cellular tissue, the corium, tendons or sinews, the middle membrane of the vasa
lymphatica and veins, the osseine or organic matter of bones, hartshorn, cartilage,
the bladders of many kinds of fish, &c. Chemically we distinguish between glutin,
that is to say, glue derived from skins, bones, &c., and chondrin, which has been
obtained from cartilage. In a technical point of view this distinction is hardly
required, as the cartilaginous matter is as much as possible selected from other glue-
making materials, because experience has shown that glutin has a much greater
power of adhesion than chondrin. The latter, however, is largely used as size in
this country.
As already observed, the glue- or gelatine-yielding tissues yield on being dissolved
a gelatinising mass, the aqueous solution of which does not, however, possess to any
great extent a glueing property, which is only imparted to the gelatine by a process
of drying. In considering, therefore, the process of glue-boiling, we have to distin-
guish the animal matter capable of yielding glue, the gelatinous mass obtained
therefrom, and the glue obtained by drying the latter. The temperature required for
obtaining gelatine differs according to the different animal tissues employed; the
consistency of the gelatine obtained from equally strong solutions varies with the age
of the tissues operated upon.
Glue readily dissolves by boiling in water, forming on cooling a gelatincus mass,
even if the quantity of glue is only 1 per cent. Repeated boiling and cooling a
glue solution causes it to lose the property of gelatinising, and the same effect is pro-
duced by acetic and dilute nitric acids. Solutions of alum precipitate glue solutions
GLUE.
529
only after the addition of potash or soda, the precipitate consisting of glue mixed
with basic sulphate of alumina. Glue enters with tannic acid into a combination of
constant composition; hence glue or gelatine may be used for the estimation of
tannin in vegetable matter.
Three different kinds of glue are distinguished by the manufacturers, viz. :—
a. So-called skin-glue, or leather-glue, prepared from refuse hides, skins,
tendons, &c.
b. The glue obtained from bones.
c. The glue obtained from fish-bladders, termed isinglass.
Very recently glue from vegetable gluten and so-called albumen glue have been
prepared.
Leather Glue. This substance is prepared from a large variety of animal refuse, the
chief sources being the following:-Refuse from tan yards, tawing and leather-
dressing works, old gloves, rabbit and hare skins (the hair having been used by hat-
makers), skins of cats and dogs, ox feet, parchment cuttings, surons (skins which have
served the purpose of carrying drugs, especially from America), sinews, guts,
leather cuttings (leather tanned with oak bark cannot be readily converted into glue).
The glue-boiler on an average obtains from the various materials about 25 per cent
of glue, preference being given to the refuse of tawing operations and kid leather
making, because these materials are ready for boiling without requiring any previous
treatment. Glue-boiling involves the following operations
Treating with Lime.
1. Treating the glue-yielding materials with lime.
2. Boiling these materials.
3. Forming the gelatine.
4. Drying the gelatine so as to form glue.
I. The aim of this operation is the cleansing of the refuse and the
prevention of putrefaction. It is effected by placing the cuttings in tanks or lime-pits
and pouring in a thin milk of lime. The materials, while the milk of lime is
frequently renewed, are thoroughly mixed with the lime-liquid and left for fifteen to
twenty days in the pits. By the action of the lime any blood and flesh is dissolved
and the fatty matter saponified. In order to remove the excess of lime, the
materials are placed either in nets or in willow-baskets, and these are immersed in a
brook or river, where a continuous stream of fresh water removes the greater part of
the lime in a few days. The washed material is next exposed in the yard to the
action of the air in order that it may become dry, as well as form a carbonate of
any lime still present in the materials. When the materials are dry they are packed
and sent off to the glue-boilers, who, previous to proceeding with the boiling opera-
tion, macerate the materials again in a weak milk of lime, the maceration being
followed by washing.
Fleck states that a weak alkaline ley (5 kilos. of calcined soda and 7.5 kilos. of
quick-lime to 750 to 1000 kilos. of glue-yielding material) is preferable to the use of
milk of lime. When the glue-boiling and tanning operations are executed on the
same premises, the lime-treated glue materials are put for a few hours into old oak
bark liquor, the acids (lactic, butyric, and propionic acids) of which remove the lime,
while the animal matter is at the same time superficially tanned. This glue tannate
rises during the boiling as scum to the surface and assists in rendering the glue
liquor clear. According to Dullo, the Cologne glue-a very pale and strong glue-
35
530
CHEMICAL TECHNOLOGY.
is obtained from offal, which, after liming, has been treated with a solution of
chloride of lime (hypochlorite of lime), and thereby bleached.
Boiling the Materials. This operation is carried on either in the ordinary manner of
boiling anything with water, or by so-called fractioned boiling, or finally by the
application of steam. As the conversion of the glue-yielding materials into glue
takes place slowly and gradually under the influence of the boiling water, it is clear
that the method of boiling cannot be without influence upon the glue ultimately
produced. The first portions of gelatine which are formed remain in contact with
a boiling-hot mass, and are thereby further changed so as to lose the capability of
gelatinising, while the glue at last obtained exhibits a dark colour and is often not so
strong, although it is generally believed that deep-coloured glue is of a better
quality. A rational mode of glue-boiling would involve the gradual removal of the
solution obtained, while of course fresh water would have to be supplied to replace
the liquor drawn off. The older method of glue-boiling consists in simply placing
the materials with water in a cauldron, care being taken to prevent burning by placing
the materials on a stout wire gauze or tying them in a net and suspending it in the
boiling liquid. Soft water yields a better result than hard. Gradually the materials
become dissolved, and the scum which is formed is taken from the surface with a
large ladle. The refuse of glue of former operations is added to the boiling liquid,
and the operation continued until the liquid is of the required strength, which is
tested by pouring into a broken egg-shell a small portion of the liquor, and by
placing the partly-filled shell in ice-cold water. If the solution gelatinises after a
while, forming a hard and rather stiff gelatine, the liquor is run off by means of a
tap, filtered through a layer of straw placed in a basket, and conveyed to a wooden
lead-lined cistern, externally covered with mats or straw, or some bad conductor of
heat. In some works the liquor is decanted into a deep but narrow boiler, the
furnace of which is so arranged as to impart heat to the top of the vessel only. This
vessel, as well as the cistern, is heated previously to the liquor being poured in. The
liquor is clarified by stirring it with a small quantity of very finely-pulverised alum,
075 to 15 per mille of the liquid. After this the liquid is left to stand all
night. The alum precipitates any lime remaining as sulphate of lime, and also some
organic matter which renders the liquid turbid. Alum, though it prevents the
putrefaction of the glue while drying, impairs its strength. The lime might better
be precipitated by oxalic acid, and the organic matter removed by adding to the
boiling mass some astringent matter, such as oak bark decoction or hops, so that
during the boiling the organic impurities could be taken away as scum.
Fractioned Boiling. By this operation only a comparatively small quantity of water is
added to the animal matter intended to be converted into glue. When the water is
fairly boiling the cauldron is covered with a well-fitting lid, and the steam being kept
in as much as possible, is allowed to act upon the materials so as to convert them
into glue. When, after continued boiling for about two hours, the water has taken
up sufficient gelatine, the liquor is run off and fresh water poured on the materials.
This operation is repeated until the decoction no longer gelatinises, the last liquor
being kept for use instead of water for a following operation. The liquors thus
obtained, excepting the last, are either mixed or each is treated separately. The glue
yielded by the first decoction is stronger than that yielded by the subsequent liquors.
By this method of boiling the saturated liquor does not remain exposed to the action
of heat and water too long, and consequently a better article is produced. In some
GLUE.
531
instances the materials intended to be converted into glue are boiled in a vessel
similar in construction to those in use in bleaching-works and in paper-mills,
arranged in the following manner. At some distance from the bottom a perforated false
bottom is placed, in the centre of which is fixed a wide tube which reaches to about two-
thirds of the height of the cauldron. The materials intended to be converted into glue
are placed upon the perforated bottom and water under it; as soon as the water boils,
the steam produced, not being able to escape rapidly and readily through the materials,
exerts a pressure upon the liquid and forces it through the tube, the consequence being
that a constant stream of boiling liquid falls upon the glue materials, which are rapidly
dissolved.
A more rational mode of conducting this operation consists in employing high-
pressure steam admitted into the mass of the animal materials to be converted into
glue. In this manner a very concentrated solution of glue is obtained in a short
time. In England steam is generally employed, but on the continent its use is the
exception. It has been said that it is advantageous to allow the animal offal intended
for glue to become somewhat decomposed and then to disinfect it with chlorine
and sulphurous acid before boiling it for glue, because by this mode of treatment a
brighter glue is obtained. We are unable to say whether this opinion is correct.
Moulding. As soon as the glue solution has, by standing in the tanks into which it had
been transferred from the boilers, become quite clear and somewhat cooled, the
liquid is poured into moulds, and when solidified the jelly is cut into cakes of the
shape and size met with in the trade.
The moulds, into which the glue solution is poured through a strainer made of
metal gauze, are of wood, and generally a little wider at the top than at the bottom,
so as to admit of an easy removal of the solid material. At the bottom of the moulds
a series of grooves are cut at such a distance from each other as agrees with the size
of the intended glue-cakes. Before the liquid is poured into the moulds, these are
thoroughly washed, and either allowed to remain damp, or if dried are oiled, so as to
prevent the solidifying gelatine adhering to the wood. Recently moulds made of
sheet-iron and zinc have been introduced. The moulds are filled with the lukewarm
glue solution, and when the glue is sufficiently hard it is gently loosened from the
sides with a sharp tool, and the mould having been turned over on a wooden or stone
table, previously damped, is lifted off the block of gelatine, which is next cut into
cakes or slabs. The cutting tool is simply a piano-wire, or more frequently a series
of these stretched in a frame at sufficient distance from each other to make the
cakes of the desired thickness, the frame being placed on small wheels so as to be
easily moved. Glue is met with in the trade as a gelatinous mass, or is sold in
casks under the name of size. It is said that the process of drying impairs the good
qualities of the glue.
Drying the Glue. This operation is performed by placing the gelatine cakes on nets
made of twine stretched in frames and exposed in a dry airy place to the action of
the sun.
The drying is one of the most difficult operations of the glue-making
process, because the temperature of the air and its hygrometric condition exert a
great influence on the product, especially during the first few days. The glue will
not bear a temperature above 20°, berause at a higher temperature it becomes again
fluid, and as a matter of course flows through the meshes of the net and adheres to
the twine so strongly as to require the nets to be put into hot water for the removal
of the mass. Too dry air causes an irregularity in the drying of the glue, and as
532
CHEMICAL TECHNOLOGY.
a consequence the cakes become bent and cracked; while frost causes disintegration,
so as to necessitate a re-melting of the glue; hence it follows that drying in the
open air can only be effected in the spring and autumn. Although the glue-boilers
have tried to dry glue by artificial heat, this plan has not been generally introduced owing
to the fact that a slight excess of heat causes the melting of the gelatine, the more
readily when ventilation is neglected. Drying-rooms, as recently constructed are large-
sized sheds fitted with the required frame-work for receiving the gelatine cakes, and
heated by steam-pipes placed on the floor near the latter. The walls are provided
with openings which can be closed by means of valves, while there are ventilators in
the roof arranged to obtain a proper circulation of air. As the gelatine placed
nearest to the floor of the room becomes most quickly dry, it is, with the frames
upon which it placed, removed after eighteen to twenty-four hours to a higher part of
the drying-room, which is not heated at all if the outer air has a temperature of
15° to 20°. The drying-shed, or room, is by preference built so as to face the north.
When the glue has been thus dried as much as possible, it is generally quickly dried
in a stove in order to impart hardness. It is next polished by being immersed in
hot water, and cleaned with a brush, and again dried.
Glue from Bones. The organic matter contained in bones, forming nearly one-third
part (32.17 per cent) of their weight, consists of a material which, after the bones have
been treated with hydrochloric acid, is very readily converted by the action of high-
pressure steam into glue. The preparation of glue from bones by the action of
hydrochloric acid is the usual mode of proceeding, and the operation is advantage-
ously combined with the making of sal-ammoniac and phosphorus.
The preparation of glue from bones includes the following operations:—I. Boiling
out the Grease.-The bones are put into water and boiled in a cauldron, the fat
floating to the surface. Frequently in order to save fuel the bones are put into an iron
wire basket, which is removed after the boiling has been continued for some time, the
bones thrown out and fresh ones put in, the boiling being continued until a thick
gelatinous liquor is obtained. The fat or grease is removed from the surface of the
liquid by means of ladles. The gelatinous mass obtained by this process is either
used as a manure or is given to cattle as fodder. In some works bones have been
exhausted with sulphide of carbon for the purpose of extracting the grease.
II. Treating the Bones with Hydrochloric Acid.—The bones having been drained are
placed in baskets, and with these are immersed in tanks to more than half their height,
the tanks being filled with hydrochloric acid at 7° B. (= 1·05 sp. gr. = 10'6 per cent
CIH); 10 kilos. of bones require 40 litres af acid. The bones are kept in this
liquor until they become quite soft and transparent. They are next drained and then
with the baskets immersed in a stream or brook with a good supply of running
water to wash out the greater portion of the acid, which is fully neutralised by
placing the bones in lime-water, again followed by washing with fresh water,
the bones being then ready for boiling. Gerland has suggested the use of
sulphurous instead of hydrochloric acid. III. Conversion of the Organic Matter
into Glue.—The cartilaginous substance having been either partly or completely
dried is put into a cylindrical vessel containing a false perforated bottom, and
between that and the real bottom a pipe or tube. To the top of the vessel a lid is
fitted, provided with an opening for a steam-pipe leading from a small boiler.
Shortly after the admission of the steam a concentrated glue solution begins to run
off from the pipe at the bottom of the cylinder; this solution is usually so concen-
GLUE.
533
trated as to admit of being at once run into the moulds, and after having become
solid is treated as before described. After a few hours a weak liquid makes
its appearance, and as soon as this happens the cylindrical vessel is opened, the glue
mass removed with the weak liquid to a copper and boiled, care being taken
to stir the magma constantly. As soon as the glue is dissolved the liquor is poured
into moulds. Glue obtained from bones exhibits a milky appearance due to the pre-
sence of a small quantity of phosphate of lime retained in the substance. Some-
times there is purposely added more or less baryta-white, zinc-white, white-lead,
chalk, or pipe-clay. The glue obtained from bones is sold under the name of patent
glue.
Liquid Glue.
When glue is dissolved in its own weight of water and a small quantity
of nitric acid added to the solution, it loses the property of gelatinising, while the
adhesive property of the glue is not impaired. Dumoulin prefers to dissolve 1 kilo.
of Cologne glue in 1 litre of boiling water, and to add to the solution o‘2 kilo.
of nitric acid at 36 B. = 131 sp. gr. After the evolution of the nitrous acid fumes.
has subsided the fluid is cooled. A better liquid glue is obtained by dissolving good
gelatine or glue of superior quality in strong vinegar and moderately strong acetic
acid, to which one-fourth of its bulk of alcohol is added, and some pulverised alum,
the solution being aided by a water-bath. The action of the acetic acid is the same
as that of the nitric acid. According to Knaffl, a very excellent liquid glue is
obtained by heating for some 10 to 12 hours upon a water-bath, a mixture of 3 parts
of glue in 8 parts of water, to which are added 0'5 part of hydrochloric acid, and
0'75 part of sulphate of zinc, the temperature of the mixture being kept below
80° to 85°. This kind of liquid glue keeps for a very long time and is largely used
for joining wood, horn, and mother-of-pearl. This glue is employed by the makers
of artificial pearls.
Test for the Quality of Glue. Although the quality of glue is best ascertained by practical
use, some of the physical qualities and the external appearance of glue may be
mentioned as indicating a superior article. Glue of good quality should exhibit a
bright brown or brown-yellow colour, should be free from specks, glossy, perfectly
clear, brittle, and hard, should not become damp by exposure to air; when being
bent it should snap or break sharply, the fracture presenting a glassy, 'shining
appearance. When placed in cold water glue should not even after forty-eight
hours in this fluid swell up and increase in bulk nor dissolve. A splintery fracture
of glue indicates that it has not been well boiled. The adhesive property of glue is
often increased by adding certain pulverulent earthy substances. This addition is
regularly the case with Russian glue. Among the substances employed are white-
lead, sulphate of lead, zinc-white, baryta-white, and even chromate of lead. As
different kinds of glue may agree in their external aspect and yet vary as regards
their adhesive power, methods of testing glue have been proposed, some of which
are based upon the chemical, others upon the physical, properties of this substance.
I. Chemical Processes of Testing Glue. Of these we mention the following
Graeger's Method.-Premising that the quality of a glue is dependent on the
quantity of glutin contained, irrespective of the origin of the glue and its freedom
from foreign substances, which might weaken its adhesive property, Graeger estimates
the quantity of gluten by precipitating the glue solution with tannin, and by calcu-
lating from the amount of tannate of gelatine obtained (the composition being taken
in 100 parts at 4274 parts of gluten and 57′26 of tannin), the quantity of pure
534
CHEMICAL TECHNOLOGY.
gluten contained in the glue. Risler-Beunat, while employing the same principle,
prepares two normal fluids, one of which contains io grms. of pure tannic acid
to the litre, while the other contains in 1 litre 10 grms. of pure isinglass and
20 grms. of alum. As equal bulk of these fluids do not saturate each other, the
author determines by titration the relation between them, and dilutes the tannic acid
solution with the requisite quantity of water. In order to test a glue the author dis-
solves 10 grms. of the sample to be tested with 20 grms. of alum in a litre of water,
heat being applied if necessary. Next 10 c.c. of the tannic acid solution are taken,
to which an equal bulk (10 c.c.) of the glue solution is at once added, because one
may be sure that this is not too much, as no sample of glue met with in commerce is
as pure as isinglass. The vessel containing the mixed liquid being well shaken and
the precipitate having settled, another c.c. of glue solution is added to the tannin
solution, which is next filtered through a moistened cotton filter. If one drop of the
glue solution still produces a precipitate in the clear filtrate another c.c. is added to
the tannin solution, and then again filtered, these operations being repeated until the
filtrate is no longer rendered turbid by the glue solution.
These modes of testing glue givẻ only an approximate value of the glue, as its
precise chemical constitution is not known, and is, in all probability, complex; while
it has not been proved that the substance combined with tannin corresponds to the
adhesive power of glue. Finally, it should be observed, that gelatine and glue, though
both precipitated by the same quantity of tannin, are altogether different substances.
II. Mechanical Modes of Testing Glue.-Schattenmann's Method. The glue to be
tested is kept immersed for a considerable time in a large quantity of water at 15°; the
substance swells up, absorbing five to sixteen times its own weight of water. The more
consistent and elastic glue is found to be in this state the greater its adhesive power.
FIG. 256.
α
1
The larger the quantity of water
absorbed the more economical will
the glue be in use. According to
Weidenbusch's experiments, this
method should be employed only
with glue obtained from bones, as
that obtained from animal offal does
not behave similarly. Lipowitz has
proposed the following method:-
5 parts of glue are dissolved in
such a quantity of water that the
weight of the solution is equal to
50 parts. This solution is kept for
twelve hours at 18° in order to
cause the solution to gelatinise.
The gelatine obtained is placed in
a glass vessel, Fig. 256. a is a
piece of tinned iron through which
the iron wire b moves easily. At the
lower end of b is soldered a saucer-
like piece of tinned iron, the convex

side of which is turned downwards. The weight of the wire b and the convex
piece soldered to it is 5 grms., while the funnel, c, put on the top of the wire
GLUE.
535
also weighs 5 grms.
The funnel is of sufficient size to contain 50 grms. of small
shot. According to the consistency the greater weight will it require to force the
gelatine down into the glass, and from the weight required the adhesiveness may
be judged. Heinze has tried this method (1864), and the results of his experiments
prove the correctness of Lipowitz's proposition.
Weidenbusch's method is essentially that suggested by Karmarsch, and consists
in testing the weight required to tear asunder two pieces of wood glued together
with the sample of glue; but it is evident that this plan is not satisfactory, because
it is impossible to obtain wood always of the same quality, while the adhesiveness of
good glue is greater than that of wood itself. Weidenbusch has evidently observed
that the method is not reliable, for he has suggested the following plan:-Small
sticks or rods are made of gypsum, are gently dried, first by heat and next over
chloride of calcium until the rods do not lose weight. They are then saturated
with solutions of samples of glue; the force required to break these rods after drying
determines the strength of the glue, because the force required to break the gypsum
is of a constant value. An apparatus has been contrived by the aid of which the
weight required to tear asunder the dried gypsum rods may be ascertained; the
average weight has been found to be 219 grms. The glue to be tested is dried
at 100º, put over night into cold water, next dissolved in hot water, the solution
being so arranged as to contain one-tenth of glue. This solution is coloured with
neutral indigo tincture in order to render it more easily discernible. The gypsum
rods are left in the solution for a couple of minutes and then dried until the weight
does not vary. When this obtains the rods are broken by the action of mercury,
which is gradually admitted into the apparatus.
Isinglass. The substance met in commerce under the name of isinglass is, if
genuine, the dried interior pulpous vesicular membrane of the air-bladder of certain
kinds of fish belonging to the order of the cartilaginous ganoids, and more
especially of the common sturgeon (Accipenser sturio); the huso, or grand sturgeon
(4. sturio); the A. Güldenstaedti, and A. stellatus. The bladders of these and of kin-
dred species of fish plentifully met with in the Caspian Sea and the estuaries of the
rivers running into it, are cut open, cleansed, stretched, and dried by exposure to sun-
light, and when sufficiently dry to admit of being handled without fear of tearing the
outer muscular membrane, which does not on being boiled yield any glue, is torn off,
while the interior membrane is moulded in various ways (as in rings, lyre-shaped, or
folded as leaves of paper), and bleached by sulphurous acid, then thoroughly dried
by exposure to sunlight.
According to the countries from which it is sent into the trade isinglass is
distinguished,—as Russian (the best kind being obtained from Astrakan); North
American (from Gadus merlucius); East Indian (from Polynemus plebejus), met with in
leaves, also as small sacks, and in the entire bladder; Hudson Bay isinglass (derived
from sturgeons); Brazilian is probably obtained from various kinds of Silurus and
Pimeladus. This isinglass occurs in hollow tubes, in lumps, and in discs. German
isinglass is prepared at Hamburg from the air-bladder of the common sturgeon. In
Roumania and Servia the skin and intestines (not the liver) of cartilaginous fishes
are boiled into a stiff jelly, which, having been cut into thin slices, is dried and sent
into the market as isinglass. As regards the use of this material we have to
distinguish between fish glue and isinglass. The former, if properly prepared, is not
at all distinguishable from ordinary glue as obtained from bones or other animal
536
CHEMICAL TECHNOLOGY.
refuse; but isinglass is not glue, and is only converted into it by boiling. It consists
of fibres or threads, which when placed in water are somewhat dissolved, but
retain their organised structure; this being especially of importance for the use
of this substance in clarifying wine, beer, and similar fluids, as the fibres con-
stitute as it were a close network, which readily takes up the turbidity produced by
small particles. The presence of tannin in liquids which are intended to be clari-
fied by the use of isinglass is advantageous, inasmuch as it promotes the contraction
of the isinglass fibres, whereby the suspended particles present in the fluid to be
clarified are retained; so that in truth the clarifying by isinglass is a kind of filtration,
which cannot be performed either by glue or by a hot saturated solution of isinglass.
For isinglass may, in all other instances, such as the dressing of woven silk fabrics,
the preparation of so-called court-plaster and cements, be substituted good gelatine.
Under the name of Ichtyocolle Française, Rohart some years ago introduced a substi-
tute for isinglass, a compound said to be obtained from fibrin of blood and tannin.
Recently three substitutes for glue have been introduced,
Substitutes for Glue, and New
Preparations obtained
from Glue.
viz. :—1. Gluten glue (colle gluten). 2. Albumen glue (colle
végétale ou albuminoide. 3. Caseine glue (colle caseine). The first is a mixture
of gluten and fermented flour. It is a very sour mixture, endowed with but
very slight adhesive power. Albumen glue is partially decayed gluten, the
substance largely obtained in the manufacture of starch from wheaten flour
thoroughly washed with water, and then exposed to a temperature of 15° to 20°, at
which it begins to ferment and become partly fluid, or more correctly soft, so as to
admit of being poured into moulds which are placed in a room heated to 25° or 30°
for twenty-four to forty-eight hours. The surface having become dry enough
to admit of the cakes being handled, they are taken from the moulds and further
dried by being placed either on canvas or on wire gauze. After four to five days the
cakes are quite dry and fit for being kept in a dry place for any length of time. A
solution of this substance in twice its weight of water constitutes a normal solution,
which may be diluted according to the use desired to be made of it. This kind of
glue may be used for the following purposes :-Glueing wood, cementing glass,
porcelain, earthenware, mother-of-pearl, for pasting leather, paper, and cardboard; it
may further serve as weaver's glue, and as dressing for silk and other woven
fabrics; also for a mordant instead of albumen in dyeing and printing various
fabrics; and lastly, for clarifying liquids.
Caseine glue is prepared by dissolving caseine in a strong solution of borax. The
thick fluid thus obtained has great adhesive powers and may be advantageously
employed by joiners and bookbinders. What is known as elastic glue is a prepara-
tion of glue and glycerine, by the addition of which glue may be rendered
permanently elastic and soft. It is prepared in the following manner:-Glue is
melted in water by the aid of a water-bath, into a very thick paste, to which
glycerine is added in the same quantity by weight as that of the dry glue. The
mixture is thoroughly stirred and then further heated in order to evaporate the
excess of water. The mass is then cast on a marble slab, and after cooling, serves
for the purpose of making printer's inking rollers, elastic figures, galvano-plastic
moulds, &c.
PHOSPHORUS.
537
General Properties.
MANUFACTURE OF PHOSPHORUS
Phosphorus was discovered in 1669 by Brand, at Hamburg, and
prepared by him from urine. In 1769, Gahn, a Swedish chemist, first prepared this
element from bones; his mode of preparation being improved in 1771 by his
celebrated countryman, Scheele. Since the introduction of phosphorus matches, its
manufacture has become one of the most important technical operations. Phos-
phorus occurs largely in the mineral kingdom as phosphoric acid, but for the manu-
facture of phosphorus in sufficient quantity only in such minerals as apatite, phos-
phorite, and staffelite.
Phosphorite is found in various localities, as, for instance, near Diez, Weilburg,
and Amberg and Redwitz in Bavaria. Some of this phosphorite is very rich in
phosphoric acid, a sample of that found near Diez having yielded on analysis (by
Petersen, 1866), 37.78 per cent of phosphoric acid, corresponding to 16'06 per cent of
phosphorus.
Preparation of Phosphorus. Bone-ash is now the only material used by phosphorus makers,
as the commercial preparation of phosphorus has not succeeded by using either apatite
and other varieties of pure phosphorite which contain about 18.6 per cent of phos-
phorus—as well as sombrerite (a mineral met with on the American island of Som-
brero), consisting of phosphate and carbonate of lime, and imported into England for
the manufacture of superphosphates; or the Navassa guano, also imported from the
United States, containing, according to Ulex's researches, one-third of its weight of
phosphoric acid; or phosphate of iron, as proposed by Minary and Soudray,
by distilling that substance with previously well-ignited coke-powder.
Bones, as used by the manufacturers, contain :-
In dry state, but not ignited, from 11 to 120 per cent of phosphorus.
As bone-black
16 to 18.0
""
As bone-ash (white burnt bones) 20 to 25'5
""
""
""
""
""
The composition of bone-ash is exhibited by the following results of analysis :-
Carbonate of lime
Phosphate of magnesia
Tribasic phosphate of lime
Fluoride of calcium...
:
I.
2.
10'07
9'42
2.98
2'15
83°07
84'39
3.88
4:05
The bone-ash is decomposed by means of sulphuric acid, according to a plan first
suggested by Nicolas and Pelletier :-
a. Bone-ash, Ca3(PO4)2
Sulphuric acid, 2H,SO} yield (Acid phosphate of lime, CaH4 (PO4)2
4
(Sulphate of lime, 200
4.
The acid phosphate of lime is heated with charcoal, and converted by loss of water
into metaphosphate of lime:—
b. Ca] (PO4)2-2H₂O=Ca(PO3)2•
H₁
Acid phosphate
of lime.
Metaphosphate
of lime.
538
CHEMICAL TECHNOLOGY.
The metaphosphate of lime yields, when ignited to white-heat with charcoal, two-
thirds of its weight of phosphorus, while one-third remains in the residue:
!
c. Metaphosphate of lime, 3Ca(PO3)2 yield Carbonic oxide, 10CO
(Tribasic phosphate of lime, Ca3(PO4)2
Charcoal, 10C
Phosphorus, 4P.
The ordinary mode of preparing phosphorus includes the following operations:-
In some instances the preparation of phosphorus is cotemporary with other
businesses, viz., glue-boiling, the preparation of sal-ammoniac, yellow prussiate of
potash, &c., but generally in England the phosphorus makers do not even burn the
bones to ashes, but purchase bone-ash and occasionally apatite; this salt, however,
is very difficult to treat with sulphuric acid, and is also objected to on account of its
hardness, for it has to be ground to a very fine powder. English makers only carry
out these four :-
1. Burning the bones and grinding the bone-ash to powder.
2. Decomposition of the bone-ash by sulphuric acid, and evaporation of the acid
phosphate previously mixed with charcoal.
3. The distillation of the phosphorus.
4. The refining and preservation of the phosphorus.
to Ash.
Burning of the Bones 1. The bones to be used for phosphorus making are obtained
either from bone-boilers or from the waste bone-black of sugar-refiners. The aim
of the ignition of the bones is the complete destruction of the organic matter. The
operation is conducted in a kiln very similar to those in use for burning lime. A
layer of brushwood having been put at the bottom of the kiln, bones form the next
stratum, and so on alternately. The wood having been lighted, the combus-
tion of the bones ensues. In order to carry off the fumes, the smell of which is very
offensive, a hood made of boiler-plate is placed on the kiln, and either connected with
a tall chimney, or the smoke and gases are conducted into the fire of the kiln and
burnt. The white burnt bones are withdrawn through an opening reserved in the
wall on purpose, the kiln being kept continuously in operation, as is the case with
some lime-kilns.
100 kilos. of fresh bones yield from 50 to 55 kilos. of white burnt bone-ash, which
is converted into a coarse powder by means of machinery.
by Sulphuric Acid.
Decomposition of the Bone-Ash 2. 100 kilos. of the bone-ash, of which about 80 per cent
is tribasic phosphate, require for decomposition :—
106.73 kilos. sulphuric acid of 1°52 sp. gr.
85.68
73.63
""
""
""
,, I'70,.
1.80
""
""
""
99
Payen advises that for 100 kilos. of bone-ash 100 parts of sulphuric acid at 50 per
cent or 1.52 sp. gr. be taken, The operation of mixing the acid and bone-ash is
effected in lead-lined wooden tanks, or in wooden tubs internally coated with pitch or
coal-tar asphalte. The liquor decanted from the precipitate has a sp. gr. of 105 to
I'07 8° to 10° B. The sediment is lixiviated with water, and the liquor obtained
(= 5° to 6° B.) evaporated with the first liquor in leaden pans. A second lixiviation
of the sediment yields a fluid which is used instead of water for the purpose of
diluting the oil of vitriol. The evaporation in the leaden pans (these are smaller, but
otherwise similar in construction to those used for evaporating sulphuric acid) is
continued until the fluid has attained a sp. gr. of 1'45 = 45° B., when it is mixed
PHOSPHORUS.
539
with charcoal-powder, or rather granulated charcoal, of the size of small peas, in the
proportion of 20 to 25 parts of charcoal to 100 of liquor, and quickly dried after
having been put into cast-iron pots placed on a furnace.
The dry mass consists of phosphate of lime, carbon, and water, to an amount of
5 to 6 per cent. At the commencement of the manufacture of phosphorus the idea
prevailed that in the preceding preparation the phosphoric acid was present in free
state, while the lime had combined with sulphuric acid; but Fourcroy and Vau-
quelin finding that the tri-basic phosphate of lime as met with in bone-ash
(Ca3(PO4)2) was, by the action of the sulphuric acid, converted into acid phos-
phate of lime (CaH4(PO4)2), supposed that more sulphuric acid was required,
an opinion opposed by Javal, who proved that when pure phosphoric acid is inti-
mately mixed with carbon, it yields only a small quantity of phosphorus, because the
acid is volatilised at a temperature lower than that required for its decomposition, or
rather reduction by carbon. Owing to the presence of water in the mixture, there is
given off during the distillation in addition to oxide of carbon, carburetted and
phosphuretted hydrogen.
Distillation of Phosphorus. 3. The mixture of acid phosphate of lime and charcoal is
distilled in fire-clay retorts similar in shape to those used for distilling Nordhausen
sulphuric acid, while the furnace in which these retorts are placed is also similar in
construction and holds twelve retorts on each side. The body of the retorts is
placed on the side of the fire, while the neck passes through an opening in the wall
of the furnace, that portion of the wall being only lightly bricked up, as the retorts,
after the distillation is finished and the furnace cooled, have to be removed, in order to
clear out the residue and introduce fresh mixture. Between each pair of retorts is left
a space o some 12 to 15 centims., in order to afford room for the passage of the flame.
As already mentioned, the heat causes the acid phosphate of lime (CaH4(PO4)2), to be
converted into metaphosphate of calcium (Ca(PO3)2), which, with increased heat,
gives off two-thirds of its phosphorus, there being left in the retorts one-third in the
shape of tri-phosphate of calcium (Ca3(PO4)2). The receivers used in Germany are
constructed in the following manner :-The material is clay, glazed. The receiver
consists of two parts, one of which is a cylindrical vessel open at the top, into
which the other part fits, and is fixed by means of a rim which is prolonged so as to
form a neck, between which and the first part is inserted a tube fitted on the neck of
the retort, while the other end of this tube dips for about 10 centims. into the
receiver, the latter being filled with water. Into each retort 6 to 9 kilos. of the
mixture intended to be operated upon are introduced; the retorts are then placed in
the furnace and the brickwork is restored. This having been done, the fire is
kindled and kept up very gently for some time in order to dry the fire-clay used in
joining the bricks. The receivers are filled with water and fitted to the retorts.
In each receiver a small iron spoon is placed fastened to an iron wire which serves
as a stem. After six to eight hours' firing the heat has been so much increased as to
cause the expulsion of any moisture left in the material placed in the retorts, while
quantities of hydrocarbon gases and oxide of carbon are formed and with
sulphurous acid expelled. Subsequently other gases are given off, and because they
contain some phosphuretted hydrogen are spontaneously inflammable. As soon as
this phenomenon is observed, the joints of the receivers and apparatus connecting it
with the retort are luted with clay, care being taken to leave by the insertion of an
iron wire a small opening for the escape of the gases, which are as speedily as
540
CHEMICAL TECHNOLOGY.
possible removed by well-arranged ventilators from the building in which the
furnace is placed. The appearance of amorphous phosphorus at the small opening
indicates the commencement of the distillation. The spoon is then placed in the
receiver in such a direction that any phosphorus coming over may collect in it.
During the progress of the operation, and as long as any phosphorus distils over,
the evolution of combustible gases continues, and consequently a small blue-coloured
flame is observed at the opening in the lute. The water in the receivers is
kept cool during the operation. After forty-six hours, with a greatly increased firing,
a full white-heat is reached, and the quantity of phosphorus coming over has
decreased so much as to make a continuation of the ignition process wasteful. The
receivers are therefore disconnected from the retorts, and the crude phosphorus, a
mixture of silicide of phosphorus, carburet of phosphorus, amorphous phosphorus, and
other allotropic modifications of this element, is poured into a tub containing water.
The furnace having become cool is broken up and the retorts are removed, the con-
tents taken out with an iron spatula, and the retorts replaced after having been
re-filled with fresh mixture. 100 kilos. of the mixture yield about 14.5 kilos. of
crude and 12.6 kilos. of refined phosphorus. As to Wöhler's method of preparing
phosphorus by the ignition of a mixture of charcoal, sand, and bone-ash, the process
is not well adapted for practical use, because it requires a very high temperature,
FIG. 258.
FIG. 257.


137]
E
A
D
D
B
A
B
G
FIG. 259.
E

which would melt, or nearly so, and at any rate soften, the retorts. Moreover, the
proposed mixture contains only one-third the quantity of phosphoric acid met with
in the mixture now in general use.
the Phosphorus.
Refining and Purifying 4. As already stated, the crude phosphorus is contaminated
with carbon, silicium, red and black phosphorus, and various other impurities, which
in former days were eliminated by forcing the phosphorus through the pores of stout
wash-leather by means of a machine exhibited in Fig. 257, c representing a tightly-
tied piece of wash-leather containing the crude phosphorus, the bag being placed on
a perforated copper support, situated in a vessel filled with water at 50° to 60°. As
soon as the phosphorus is molten, there is placed on the wash-leather a wooden
PHOSPHORUS.
54X
plate, DD, which by the aid of the mechanical arrangement E, and the lever, G G, can
be forced downwards so as to cause the fluid phosphorus to pass through the pores of
the leather, the impurities being retained. More recently French manufacturers
have introduced another system of purifying phosphorus, viz.:-a. By filtration
through coarsely-powdered charcoal, which is placed in a layer of 6 to 10 centims. on a
perforated plate of the vessel A, Fig. 258, two-thirds filled with water, kept by means of
the water-bath, B, at a temperature of 60°. The molten phosphorus placed on a passes
through the layer of charcoal, and is thereby purified. It flows through the open
tap c and the tube E, being collected in the vessel F filled with water, maintained by
means of the water-bath, G, at a temperature sufficiently high to render the phos-
phorus fluid, so that it may, when aided by hydraulic pressure, pass through the
perforated bottom, H, and the wash-leather spread over it. The filtered phosphorus
may be run off by means of the tap J.
According to another process of purification (b), porous, unglazed porcelain or
earthenware plates are fixed in an iron cylinder connected with a steam-boiler. The
steam yielded by the latter forces the molten phosphorus-previously mixed with
charcoal powder for the purpose of preventing the pores of the plates becoming
choked-through the earthenware plates. The charcoal containing some phosphorus
is used in the distillation of the phosphorus. This method of purification
yields from 100 kilos. of crude, 95 kilos. of refined, phosphorus. In Germany crude
phosphorus is purified by distillation, this operation being carried on in iron retorts
of a peculiar make and shaped like the glass retorts used in chemical laboratories.
The neck of these retorts dips for a depth of 15 to 20 millimetres in water contained
in a basin filled to the rim, so that any phosphorus which is discharged into this
water causes it to overflow. The crude phosphorus having been fused under water
is next mixed with 12 to 15 per cent of its weight of moist sand, and this mixture is
placed in the retorts in quantities of 5 to 6 kilos., the object of the mixing with sand
being to prevent the phosphorus becoming ignited during the filling of the retorts.
Crude anhydrous phosphorus yields by this process of distillation about 90 per cent
of the refined product. In a phosphorus manufactory at Paris the crude phosphorus
is purified by chemical means, viz., by mixing with 100 kilos. of the crude substance
35 kilos. of sulphuric acid and the same quantity of bichromate of potash; a slight
effervescence ensues, but the result is that the phosphorus is rendered very pure, and
may, after washing with water, be at once cast in the shape of sticks. The yield of
refined phosphorus by this process is 96 per cent.
Phosphorus.
Moulding the Refined It has long been the custom to mould phosphorus into the shape
of sticks formed by the aid of a glass tube open at both ends, one of these being placed
in molten phosphorus covered by a stratum of warm water. The liquid phosphorus
is sucked by the operator into the tube until it is quite filled. The lower opening of
the tube being kept under water is closed by the finger of the operator; the tube is
instantly transferred to a vessel filled with very cold water, by which the phosphorus
is solidified. It is removed from the glass tube by pushing it out with a glass rod or
iron wire while being held under water. Instead of suction by the mouth, a
caoutchouc bag similar to that used in volumetric analysis for the purpose of sucking
liquids into pipettes may be employed. In the French phosphorus works the glass
tubes are fitted at the top with an iron suction tube provided with a stop-cock. The
operator, who has from one to two thousand of these tubes at his disposal, sucks,
either by mouth or with a caoutchouc bag, the molten phosphorus into the glass tube,
542
CHEMICAL TECHNOLOGY.
and having turned off the stop-cock, rapidly transfers the tube to a vessel filled with
cold water. When all the tubes are filled the phosphorus is removed by opening the
stop-cock and pushing the stick out by the aid of a wire. A clever workman may
mould in this way 2 cwts. of phosphorus daily.
Another mode of performing the moulding has been introduced by Seubert. The
apparatus contrived by him for this purpose is exhibited in Fig. 260, and consists of
a copper boiler fitted on a furnace; to the flat bottom of this boiler is fastened by
hard solder an open copper trough communicating with the water-tank, c. In the
boiler is fitted a copper funnel, a, provided with a horizontal tube, B. This portion
of the apparatus is intended for the reception of the phosphorus, of which it will
hold 8 to 10 kilos. At the end of the horizontal tube, B, is placed a stop-cock, H,
while the portion of the projecting mouth of the tube beyond the cock is widened
out and fitted by means of bolts and nuts with a flange-like copper plate, into which are
inserted two glass tubes, a a. Into the copper trough is let a wooden partition, e c,
which serves the purpose as well of supporting the glass tubes as of preventing
the communication of the hot water in the boiler and a portion of the trough
with the cold water of the tank and the portion of trough nearest to it. The
FIG. 260.

A
B
a
じ
​
vessel a having been filled with refined phosphorus, the water in D is gently warmed
so as to cause the fusion of the phosphorus. As the warm water reaches to the
partition, c c, it is clear that on opening and closing the tap в, some phosphorus will
pass through and flow out of the tubes a a, but that remaining in these tubes will
solidify, and on opening the tap в again the solid sticks of phosphorus may be
removed from the glass tubes by taking hold of the piece of projecting phosphorus,
the phosphorus being immediately immersed under water in the tank c, and kept
there protected from the action of the light. While, according to Seubert, it would
be possible for a workman to mould in an hour's time 30 to 40 kilos. of phosphorus,
Fleck has found, that under the most favourable conditions of temperature, it takes
six hours to mould 50 kilos. of phosphorus. If it is desired to prepare granulated
phosphorus with this apparatus, a stratum of 6 to 8 centims. thickness of hot water is
so carefully poured on cold water as not to mix; next the tap в is opened sufficiently
to cause the phosphorus to form drops, which, immediately on falling into the coll
PHOSPHORUS.
543
water, becomes a hard solid mass. For practical purposes granulated phosphorus is
preferable to the moulded sticks. The phosphorus is stored either in strong sheet-
iron tanks or in wooden boxes lined with thinner (tinned) sheet-iron, these vessels
being capable of holding 6 cwts. of phosphorus covered with a stratum of water fully
3 centims. deep. When large quantities, say, from 1 to 5 cwts, of phosphorus have
to be sent off, it is usually packed in water in small wine casks, and the casks having
been tightly closed, are coated externally with molten pitch, then rolled through
chaff, and lastly covered with stout canvas sewed tightly round the cask. Another
method of packing phosphorus consists in placing it in well-made water-tight sheet-
iron or tinned iron canisters, such as are largely used in London for the purpose
more particularly of conveying oil paints, and which are closed by soldering on a lid
very securely. In some cases these canisters are packed in wooden boxes to the
number of six or twelve according to size and weight.
Preparing Phosphorus.
Other Proposed Methods of Among the many suggestions as to the preparation of phos-
phorus, we may mention Donovan's plan of obtaining this element by the calcination
of a mixture of finely divided charcoal and phosphate of lead, prepared by
digesting 10 kilos. of broken-up bones with 6 kilos. of nitric acid, and 40 litres
of water; this liquid, after having been decanted from the gelatinous material of the
bones, is treated with a solution of 8 kilos. of acetate of lead. The washed and
dried precipitate of phosphate of lead is next ignited, and afterwards, when cold,
mixed with one-sixth of its weight of lamp-black or charcoal powder. Cari-Mon-
trand exposes a mixture of bone-ash and carbonaceous matter at red heat to the
action of hydrochloric acid gas :—
Calcium tri-phosphate, Ca3(PO4)2
Carbon, 8C
Hydrochloric acid, 6C1H
Phosphorus, P2
Chloride of calcium, 3CaCl
Field Hydrogen, 3H₂
Carbonic oxide gas, 8CO
Neither of these methods have been tried practically on the large scale.
Fleck's Process. By this method the preparation of phosphorus is allied to that of
glue- and size-making. The process is based upon the solubility of phosphate of
lime in hydrochloric acid, and the separation of an acid phosphate of lime on the
evaporation of the solution, carried on in earthenware evaporating basins. Theo-
retically, 156 parts of tribasic phosphate of lime (Ca3(PO4)2) require 73 parts of
anhydrous hydrochloric acid, whereby are formed—of chloride of calcium, 111; of
acid phosphate, 100; and of water, 18 parts. By the ignition of 100 parts of acid
phosphate of lime with 20 parts of carbon, are generated-of phosphorus, 21°3;
of tri-phosphate of lime, 52; and of oxide of carbon, 46′7 parts.
By re-heating the tri-phosphate of lime remaining in the retorts with hydro-
chloric acid another portion of acid phosphate of lime might be obtained; and as far
as experiments have been made, it is proved that it is possible to extract all the
phosphorus contained in bones, by working with hydrochloric acid free from
sulphuric acid, and carefully evaporating the acid solution thus obtained. Practi-
cally the process includes the following operations:-1. Cleaning, breaking up, and
exhausting the bones. 2. The evaporation of the acid liquid; crystallisation of the
acid phosphate, and mixing of the latter with charcoal. 3. The distillation and purifi-
cation of the phosphorus; and finally,—4. The glue boiling. The bones, previously
crushed and deprived by boiling of the fat they contain, are macerated in dilute hydro-
chloric acid at 7° B. sp. gr. 1'048, and then in a stronger acid at 30° B.=sp. gr. 1'246,
in which the bones are left until they have become quite soft. The liquid which has
544
CHEMICAL TECHNOLOGY.
served this purpose is afterwards employed with water in preparing the first acid
liquor for the exhausting of the bones. The first liquor, a solution of acid
phosphate of lime (superphosphate) and chloride of calcium, obtains a sp. gr. of
1*118=16° B. This acid liquid is evaporated, but this operation cannot be pro-
ceeded with in leaden vessels, and there is some difficulty in finding very large
evaporating basins made of porcelain or earthenware which will answer the
purpose. As soon as the liquor has reached a density of 30° B = sp. gr. 1°246, it is
sufficiently concentrated to crystallise; on cooling, the crystals, having been by
means of pressure separated from the mother-liquor, are mixed with one-fourth
of their weight of charcoal powder. They are then heated to 100° in the porcelain
or earthenware vessels, so as to obtain a dry mass which admits of being sifted
through a copper-wire gauze sieve, after which the material is put into peculiarly
shaped retorts and calcined for the purpose of yielding phosphorus. The residue
left in the retorts is afterwards calcined with access of air so as to burn off the
charcoal, and the remaining phosphate of lime is again treated with strong hydro-
chloric acid, yielding a concentrated liquor which does not require much evaporation.
The phosphorus obtained by this process is refined as already described, the
softened bones being treated for glue and size.
Gentele, Gerland, Minary,
and Soudry's Methods of
Preparing Phosphorus.
According to a communication published by Gentele in
1857, upon a plan of phosphorus manufacture, he com-
bines that industry with the preparation of sal-ammoniac. The bones are treated
with hydrochloric acid. To the resulting solution crude carbonate of ammonia is
added; this substance being obtained as a by-product of the manufacture of animal
charcoal. The phosphate of lime precipitated is employed in the preparation of
phosphorus, while the solution of chloride of ammonium is evaporated and sublimed.
Gerland (1864) suggests the treatment of bones-first, with an aqueous solution of
sulphurous acid, the heating of the liquor obtained with the view of expelling the
acid, which being again absorbed by a layer of coke (a coke column such as used in
alkali works to absorb hydrochloric acid), the phosphates first held in solution are
precipitated by the elimination of the sulphurous acid. Minary and Soudry (1865)
proposed to prepare phosphorus from a mixture consisting of phosphate of iron and
well-ignited coke.
Properties of Phosphorus.
When perfectly pure and kept under distilled water, which
previously to being employed for this purpose has been by boiling deprived of the
air it held in solution, and has been cooled either under a layer of oil or in
well-stoppered bottles, and in perfect darkness, phosphorus is a colourless and trans-
parent substance; but usually it has a white-yellow colour and waxy appearance.
Its sp. gr. is 183 to 184. When the temperature of the air is not too low
this element is as soft as wax, but becomes brittle in cold weather. Phosphorus
cannot be pulverised; is tough; but when molten in a bottle under warm water and
shaken until the fluid is quite cold, the substance is thereby reduced to a finely
divided state; instead of water it is better to use either alcohol, urine, or a weak
aqueous solution of urea. Phosphorus fuses at 44° to 45°, and remains, especially if
kept under an alkaline solution, fluid for a considerable time though cooled far below
its melting-point, but solidifies suddenly when touched by a solid body. At 290°
phosphorus boils, and it evaporates sensibly at the ordinary temperature of the air.
By slow oxidation (fumes of phosphorus are given off at the ordinary temperature of
the air) there is formed not only phosphorous acid but nitrate of ammonia and
PHOSPHORUS.
545
antozone. Phosphorus is in the state of vapour slightly soluble in water. The solid
element itself is slightly soluble in alcohol and ether, also in linseed oil and oil of
turpentine, the best solvents being sulphide of carbon, chloride of sulphur, and
chloride of phosphorus. At 75° phosphorus ignites in contact with air, and in order
to ignite it by friction this temperature has to be reached. Amorphous or red
phosphorus requires a very high temperature (300°) for ignition. Commercial
phosphorus usually contains some impurities, such as sulphur, arsenic, and sometimes
traces of calcium, due to the lime of the bone-ash used in the preparation. Beside
being used in chemistry, phosphorus is chiefly employed in the making of matches;
also for what is termed liquid fire (a solution of phosphorus in sulphide of carbon), for
the preparation of tar colours, and for hardening some copper alloys.
Amorphous or Red Phosphorus. Dr. Schrötter, of Vienna, discovered in 1848 that the
property possessed by ordinary phosphorus (first noticed in 1844 by E. Kopp)
of becoming coloured red by the action of light, was due to the formation of an
allotropic modification, which has been since termed red or amorphous phosphorus.
This is best prepared by heating ordinary phosphorus, with exclusion of air and
water, in a closed vessel and under pressure, to 250° for a length of time. On the
large scale this operation is conducted in an apparatus invented by A. Albright, of
Birmingham. In Fig. 261, g represents a glass or porcelain vessel, filled for
five-sixths of its capacity with pieces of phosphorus to be heated to 230° to 250°.
The vessel ƒ is placed in a sand-bath, b, heated by the fire. To the vessel g is fitted
an air-tight lid, into which is fastened the bent tube, i, provided with a tap, k, and
dipping into the vessel n, which is filled with water, or preferably with mercury
covered with a layer of water. The tap, k, is left open at the commencement of the
operation for securing the escape of the air contained in g, and as soon as no more
air escapes the tap is closed, and
FIG. 261.
the heat increased so as to con-
vert the ordinary into amorphous
phosphorus. The time required for
the operation depends upon con-
ditions which can only be met by
experience. After the thorough
cooling of the apparatus, the vessel

g
m
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TAAAABUMID Midhunter auTTE HUMAINE
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is opened, and the red phos-
phorus removed. It is then placed
under water and crushed to a pulp
in order to remove any uncon-
verted ordinary phosphorus. Sul-
phide of carbon might be used for
this purpose, but the danger of
ignition (by accident) of the solu-
tion of ordinary phosphorus thus
obtained is prohibitive. Nicklès proposes to separate ordinary from amorphous
phosphorus by shaking up the mixture of amorphous and ordinary phosphorus with
a fluid, the specific gravity of which is less than that of amorphous phosphorus (2*1),
and greater than that of ordinary phosphorus (184). A solution of chloride of cal-
cium at 38° to 40° B. can be used for this purpose; the ordinary phosphorus floats in
this fluid and can then be readily taken up by sulphide of carbon, while the operation
36
546
CHEMICAL TECHNOLOGY.
Properties of Amorphous
Phosphorus.
can be carried on in a closed vessel. When very large quantities of amorphous
phosphorus have to be purified it is best to follow Coignet's plan, consisting in
treating the boiling mixture of the two varieties of phosphorus with caustic soda
solution, whereby the ordinary phosphorus is converted into phosphuretted hydrogen
gas and hypophosphite of soda is formed, the remaining amorphous phosphorus
being purified by washing with water. R. Böttger suggests the use of a solution of
sulphate of copper, which with ordinary phosphorus forms phosphuret of copper.
This substance occurs either in powder of a red or scarlet
colour or in lumps of a red-brown hue; fracture conchoidal, sometimes with an
iron-black hue; sp. gr. = 2'1. Amorphous phosphorus is not soluble in sulphide
of carbon or other solvents of ordinary phosphorus. It is unaltered by exposure to
air; and when heated to 290° is re-converted into ordinary phosphorus. When
mixed and rubbed with dry bichromate of potash red phosphorus does not explode,
and when mixed with nitre it does not burn off by friction, but only by application
of heat and then noiselessly. It explodes, however, when mixed with chlorate
of potash. With peroxide of lead amorphous phosphorus ignites by friction with a
slight explosion, but when heat is also applied a violent explosion ensues.
Owing to its properties and behaviour with several oxides, moreover its non-vola-
tility and non-poisonous properties, amorphous phosphorus is, as well as on account
of its less ready ignition, an excellent material for the making of matches; but
amorphous phosphorus is not in general use for this purpose. It is, however, used
for preparing iodide of phosphorus, which serves for the preparation of iodides
of amyl, ethyl, and methyl, used in the manufacture of cyanin, ethyl violet, and
other coal-tar colours. Sir William Armstrong's explosive mixture for shells
contains amorphous phosphorus and chlorate of potash. From 66,000 cwts. of bones
there are annually prepared in Europe some 5500 cwts. of phosphorus.
REQUISITES FOR PRODUCING FIRE.
Generalities and History. According to the writings of the ancients, Prometheus drew
fire from stones by their concussion. The Romans rubbed together two pieces of
hard wood for producing by friction sufficient heat to ignite dry leaves fallen from
trees; while Darwin and the Prince of Neuwied state that the uncivilised races of
man obtained fire by the rapid rotation of two pieces of wood. Turners at the pre-
sent day employ friction in the carbonisation of wood for ornamental purposes.
During Titus's reign the Romans obtained fire by rubbing decayed wood between
two stones, along with a small thin roll of sulphur. In the fourteenth century, the
tinder-box, with the flint and steel, became known, and also the so-called German
tinder, a prepared cryptogamic plant. Till 1820 these remained generally the
chief means of obtaining fire, aided, of course, by the wooden splints tipped with
sulphur.
In the year 1823, Döbereiner, at Jena, discovered that finely divided spongy
platinum has the property of igniting a mixture of atmospheric air and hydrogen
gas, and he contrived the so-called Döbereiner hydrogen lamp, which has been, and
is still, occasionally employed to procure fire and light. About the same period
there was invented a kind of phosphorus match of the following arrangement.
Equal parts of sulphur and phosphorus were cautiously fused in a glass tube; after
the fusion was completed the tube was tightly corked. If it were desired to obtain
PHOSPHORUS.
547
fire, a thin splint of wood was immersed in this mixture, and some of it having been
fixed to the wood, the latter on being brought into the air became ignited by
the combustion of the mixed substances, which took fire spontaneously in the air.
It is evident that this rather clumsy contrivance never became general. Of far
more importance as suited for practical purposes were the chemical matches or dip
splints, first manufactured at Vienna, as early as 1812. These splints were tipped
with sulphur covered with a mixture of chlorate of potash and sugar, to which
for the purpose of imparting colour was added some vermillion, while a little
glue gave a pasty and adhesive consistency.
#
By touching this composition with concentrated sulphuric acid ignition ensued;
the acid was kept in a small glass or leaden bottle into which some asbestos had
been inserted, which acted as a sponge for the acid. The only friction matches
known up to the year 1844 were discovered and made by M. Chancel, assistant to
the well-known Professor Thenard of Paris, 1805. The Prometheans, first made in
England in or about the year 1830, were contrived on the same principle, viz., the
ignition by friction between two hard substances of a mixture of chlorate of potash
and sugar fixed to a kind of paper cigarette, which contained also a small glass
globule filled with sulphuric acid; however, the high price of this kind of match
prevented its general use. Under the name of Congreves the first real friction
matches were made in 1832. On the sulphur-tipped splints was glued a small
quantity of a mixture of 1 part of chlorate of potash and 2 parts of black sulphuret of
antimony, to which some gum or glue was added. By strongly pressing this compo-
sition between two pieces of sand-paper the mixture became ignited, but frequently
also on becoming detached from the wooden splint flew about in all directions with-
out igniting the sulphur or the wood. It is not well known who was the first to
substitute phosphorus for sulphuret of antimony; but according to Nicklès phos-
phorus matches were already in use in Paris as early as 1805, while in 1809 Derepas
proposed to mix magnesia with phosphorus in order to lessen its great inflammability
when in finely divided state. Derosne (1816) appears to have been the first who
made phosphorus friction matches at Paris. However, it was not before the middle
of 1833 that phosphorus matches became more generally known, when Preshel, at
Vienna (this city is famous for the match and fusee industry in Germany), made not
only phosphorus matches, but also fusees and German-tinder slips tipped with the
phosphorus composition. About the same period F. Moldenhauer, at Darmstadt,
made phosphorus lucifer matches. The South Germans attribute to Kammerer the
invention of phosphorus lucifer matches, while in England, according to the opinion
of the late celebrated Faraday, John Walker, of Stockton, Durham, was the inventor
of lucifer matches, or at least the first maker. The older kind of matches, although
very combustible, ignited with a rather sharp report, owing to the presence of chlorate
of potash in the mixture, while, moreover, the too ready ignition by concussion
rendered the transport of these matches so unsafe, that in Germany, the transport,
as well as the manufacture, became prohibited. In the year 1835 Trevany substi-
tuted a mixture of red-lead and manganese for a portion of the chlorate of potash,
thereby greatly improving the composition. In 1837 Preshel altogether discarded
this salt, substituting peroxide of lead, or, as Böttger advised, either a mixture of
red-lead and nitrate of potash, or of peroxide of lead and nitrate of lead. From this
period the manufacture of matches became an extensive industry, greatly aided by
the manufacture of phosphorus on the large scale.
548
CHEMICAL TECHNOLOGY.
In the course of time other improvements were made, as, for instance, the
substitution for sulphur of wooden splints, thoroughly dried and soaked in wax,
paraffin, or stearic acid, the coating of the composition with a varnish to protect it
from the action of moisture, while, at the same time, the external appearance of
the matches was rendered more ornamental. At the present day matches are a
product of an industry which cannot possibly be much more improved in a technical
point of view, being also a product which, as regards its price, is within the reach
of all.
However useful phosphorus lucifer matches may be, it is a great drawback to their
utility that the combustible composition is a poisonous mixture, while, moreover, the
workpeople engaged in that department of the lucifer-match making in which the
phosphorus is handled are often affected by a peculiar kind of caries of the jaw-
bones, the real cause of which is the more difficult to ascertain as the workpeople
engaged in the manufacture of phosphorus and exposed to its vapours to such an
extent as to render their breath luminous in the dark are not similarly affected.
The discovery of the red or amorphous phosphorus, which is neither poisonous nor
very inflammable, affords a happy substitute for the ordinary phosphorus, but the
former is by no means generally used in the preparation of matches.
Manufacture of Lucifer
Matches.
The operations required are:—
1. The preparing of the splints of wood.
2. The mixing of the combustible composition.
3. The dipping, drying, and packing of the matches.
1. The Preparation of the Wooden Splints.—Generally white woods are used for
this purpose, such as white fir, pine wood, aspen, more rarely fir wood (Föhrenholz),
sometimes beech wood, lime-tree wood, birch, willow, poplar wood, and cedar. The
shape of the splints is usually square in section, but abroad the splints are some-
times cylindrical. The square splints are readily made by hand, simply by splitting
up a block of wood having the length required for the splint. A cutting tool, a large
knife, similar to that which is sometimes used by chaff-cutters, is very frequently
used for the purpose of cutting the wooden splints, while a contrivance similar to
that in use for propelling the hay or straw forward is also employed, being so
arranged as to propel the wood after every cutting stroke the length required for a
splint. More generally the operation of splitting the block of wood parallel to its
fibres and next cutting off the splints to the required length is effected by machinery
consisting of fixed knives, against which the wood is moved with sufficient force to
split it up into splints, which are next cut to the required length. Instead of
splitting the wood by these means, the splints are now in Germany always made by
a kind of plane, invented by S. Romer, of Vienna, by which the wood is cut
up into circular splints. The cutter of this plane differs from that of the ordinary
carpenter's plane, by possessing, instead of the cutting edge, a slight bend, in which
three to five holes have been bored in such a manner that one of the edges of these
holes is sharpened; in practice three holes are preferred. When this plane is
forced against a lath of wood, placed edgeway, the cutting tool penetrates into the
wood, splitting it up into as many small sticks or splints as the cutter contains holes.
When a number of thin splints have been cut from the lath, it is again planed true
with an ordinary plane and then the operation repeated. The dividing of the thin sticks
into splints of the required length is effected by a tool consisting of a narrow trough
about 6 centims. wide and provided with a slit in which works a knife fastened to a
PHOSPHORUS.
549
lever. A clever workman can prepare 400,000 to 450,000 splints daily. In the
south-west of Germany a plane for cutting wooden splints, the invention of Anthon,
at Darmstadt, and similar in action and construction to that above mentioned, is in
general use; but throughout an extensive portion of the empire the manufacture of
the splints has become a separate trade often carried on in woods and forests, the
splints being sold to the lucifer-match makers in bundles ready for dipping.
Instead of making the splints by hand they are occasionally made by a machine,
such as that by Pellitier, at Paris (1820), having on a bench a plane 36 centims. long
by 9 wide, made to move backwards and forwards, while a piece of wood is placed
so that it is caught by the fore-cutter, which consists of a steel knife provided with
twenty-four teeth sharpened like little knives, the second cutter removing the small
laths from the plank of wood. Cochot's machine (1830) consists of a large iron
wheel 1 metre in diameter, on the periphery of which are fixed thirty wooden blocks
lengthway of the size of the splints. When the wheel is turned round the blocks of
wood are caught by the knives fastened to a small cylinder, and the wood is split up
into splints, which are removed from the block by another knife. Jeunot's machine,
patented in 1840 in France, is of a similar construction. Neukrantz, at Berlin
(1845), contrived a tool based upon the principle of the hand-plane, the wood intended
to be cut being moved against a fixed steel cutter, which produced sixteen to twenty
splints at a movement. Krutzsch, at Wünschendorf, Saxony, has improved upon this
plan (1848) by perforating a steel plate with about 400 holes placed as near together
as possible; the edges of these holes having been sharpened, a block of wood is forced
in the direction of its fibres against the plate and thus divided into splints. A piece
of wood 3 centims. in thickness and width, by 1 metre in length yields 400 lengths,
each of which can be cut up into fifteen splints; 6000 of the latter are made in
two minutes. Of the several tools and machines contrived for the purpose of
cutting splints—and the number of these contrivances is very large-we quote the
following of German origin. The machine invented by C. Leitherer, at Bamberg
(1851), consists of what might be termed a kind of guillotine, viz., a box at the bottom
of which is placed the wood to be formed into splints, the fibre of the wood being
vertical. In front of this box is placed a frame-work, in which a heavy block,
provided with four cutters, each terminated by eight to ten narrow tubes (somewhat
similar to cork-borers), can be made to move rapidly, so as to give forty-five strokes
a minute, the wooden block intended to be cut into splints being made to move under
the cutting tool after each stroke. Wrana's machine is in principle the same as
that of Neukrautz, but has been greatly improved, the plane not being fixed, but
supported by a piece of wood. Long's machine, again, consists of a series of
cylinders, between which the block of wood is placed, while knives are so arranged
as to cut the block into splints while the wood moves on by the motion imparted to
the cylinders.
2. The Preparation of the Combustible Composition is carried on in the following
manner :—The glue, or gum, or any other similar substance, is first dissolved in a
small quantity of water to the consistency of a thin syrup, with which, having been
heated to 50°, the phosphorus is incorporated by gradually adding it and keeping the
mixture stirred so as to form an emulsion, to which are next added the other ingre-
dients after having been pulverised. In order to obtain a good composition, it is
essential that there should be neither too much nor too little phosphorus, for an
excess of phosphorus will not only tend to increase unnecessarily the price of the
550
CHEMICAL TECHNOLOGY.
composition, but it has also the effect of rendering it unfit for igniting the sulphur
and stearin wherewith the matches are tipped, because the phosphoric acid gene-
rated by the combustion of the phosphorus is deposited as an enamel-like mass,
which prevents further combustion. It appears that the best proportion is from one-
tenth to one-twelfth of phosphorus.
A much smaller quantity of phosphorus is required if this element is first dissolved
in sulphide of carbon and the solution added to the other constituents of the compo-
sition; the sulphide of carbon while rapidly volatilising leaves the phosphorus in a
very finely-divided state. As phosphorus is very readily soluble in sulphide of
carbon, and as the latter is moderately cheap, the method has the advantage that the
mixing of the materials can take place without the application of heat. It is, how-
ever, evident that the greatest care is required in manipulating such a liquid as
sulphide of carbon, and far more when phosphorus is dissolved therein. C. Puscher
suggested (1860) the use of sulphuret of phosphorus, P₂S, instead of pure phosphorus
in the composition for matches. He prepared a composition containing 3'5 per cent
of this sulphuret, and obtained excellent matches.
Among the metallic oxides which are employed in the mixture, preference is given
either to a mixture of peroxide of lead and nitrate of potash, or to a mixture of the
former with nitrate of lead obtained by treating red-lead with a small quantity of
nitric acid and leaving this mixture for a period of several weeks to dry. Glue, gum,
and dextrine are used as excipients; the first, however, is objectionable because it
carbonises and prevents the combustion. Perhaps a dilute collodion solution or a
mixture of sandarac or similar resin, with benzole, might be used as an excipient
instead of the gum.
The mixtures actually used in the trade are kept secret, but the following recipes
may give some idea of the composition :—
Phosphorus
I.
15 parts
...
Gum senegal
Lamp black
Red-lead
3°0
...
0'5
5'0
Nitric acid at 40° B. (= sp. gr. 1°384) 20
Phosphorus
Glue ...
:
II.
...
•
A mixture of nitrate of
lead and of peroxide of
lead, technically known
as oxidised red-lead.
80 parts (Dissolved in the required
quantity of sulphide of
carbon.
21'0
""
24'4
""
Peroxide of lead
Nitrate of potash
Phosphorus
Gum senegal
Peroxide of lead
...
:
Fine sand and smalt...
24.0 **
III.
3'0 parts
3°0
2.0
2.0
No doubt there is room for great improvements in these compositions.
3. Dipping and Drying the Splints.-In order to fix the sulphur and combustible
composition to one end of the splints, it is clear that these should not touch each
PHOSPHORUS.
551
other, but be so arranged as to leave an intermediate space. A contrivance is
employed, consisting of small planks, 03 metre long by 10 centims. wide, the surface
being provided with narrow grooves placed close together, and just large enough
each to hold a single splint, Fig. 262. The splints are one by one placed in the
grooves, an operation usually performed by girls. One plank having been filled
another is placed on the top of it. The surface of the plank on one side is provided
with a piece of coarse flannel, while the other side is grooved for holding splints.
Each of the planks has at the end a round hole, through which pass iron
rods, Figs. 263 and 264, in the top of which a screw thread is cut, so that as soon as
some twenty to twenty-five planks have been filled with splints and placed one upon
another, they are fastened so as to form a framework. A clever hand can fill during
ten hours fifteen to twenty-five of these frames, each containing 2500 splints.
Recently it has been attempted to perform this work by machinery, and the machine
constructed by O. Walsh, at Paris (1861), enables a lad to frame 500,000 to 600,000
splints in ten hours.
The sulphur intended for dipping the splints is kept in a molten state over a mode-
rate fire in a shallow rectangular trough, in the middle of which a stone is placed as
FIG. 263.
FIG. 262.
FIG. 264.


precisely level as possible. The quantity of sulphur is so regulated that it covers
the stone to a depth of 1 centim. In the operation of dipping, the ends of the
splints are made just to touch the stone and immediately removed, care being taken
to cause, by shaking the frame, any superfluous sulphur to flow into the trough again.
Instead of sulphur the better kind of matches are impregnated with stearine,
stearic acid, or paraffin. The splints having been first thoroughly dried, are placed
in a bath of molten paraffin, and left there for a time so as to allow the wood to
absorb by capillarity.
The tipping with the phosphorus composition is performed similarly to the
sulphuring of the splints, the composition being placed in a uniform layer on a piece
of thick ground glass or on a well-polished lithographic stone (Solenhofen lime-
stone).
The drying of the matches takes place in a room heated by steam, the frames
being hung on ropes or put on shelves. The position of the frames is such that the
552
CHEMICAL TECHNOLOGY.
matches are in a vertical position, and the composition hangs on them as a drop. The
composition of the saloon matches is, after drying, coated with coloured resinous
solutions, and often with a collodion film.
Anti-Phosphor Matches. This variety of match was invented in 1848, by Böttger,
at Frankfort, and was prepared industrially by Fürth, at Schüttenhofen; Lund-
ström, at Jönköping (Sweden); Coignet, at Paris (under the name of Allumettes
hygiéniques et de sureté au phosphore amorphe); De Villiers and Dalemagne, Paris
(under the name of Allumettes androgynes); also by Forster and Wara. These
matches are of two kinds :-a. Those which are free from phosphorus, the
amorphous phosphorus being incorporated with the sand-paper. B. Those which are
free from phosphorus both in the match and on the sand-paper.
To the matches of the first category belong:-1. Matches, the composition
of which is free from phosphorus, consisting simply of a pasty mass, the main con-
stituents of which are sulphuret of antimony and chlorate of potash.
2. The
amorphous phosphorus mixed with some very fine sand or other substance promoting
friction is, with glue, put on to the box in which the matches are contained; or, as is
the case with the androgynes, at the other end of the splint. The friction surface on
the boxes consists of a mixture of 9 parts of amorphous phosphorus, 7 parts of pul-
verised pyrites, 3 parts of glass, and 1 part of glue. The matches ignite readily by
friction on the surface containing this composition, but do not ignite when rubbed on
any other rough surface. These so-called safety matches are largely manufactured
at Jönköping, under the Swedish name of Sakerhets-Tändstickor (security fire
matches). Jettel (1870) uses for the friction surface a compound consisting of equal
parts of amorphous phosphorus, pyrites, and black sulphuret of antimony; for
coating on the two sides of 1000 small boxes, each containing fifty matches, about
80 grms. of this mixture are required. It need hardly be mentioned that in
England safety matches are largely made and of excellent quality, in fact, better than
anywhere else.
non-poisonous" match.
B. Forster and F. Wara, at Vienna, have introduced a
The amorphous phosphorus is mixed up with the combustible composition in
the usual way, so that these matches ignite readily by being rubbed on any rough
surface, but the ignition is accompanied by noise, owing to the chlorate of potash
contained in the mass.
As regards the matches belonging to the second category-viz., such as neither
contain phosphorus nor require a phosphorus-containing surface, we may give
the analysis by Wiederhold, of the composition of those made by Kummer and
Günther, at Königswalde, near Annaberg, in Saxony :-
Chlorate of potash
Oxidised red-lead
Black sulphuret of antimony
...
Gum senegal
8 parts.
8
8
I
"
""
Oxidised red-lead is a variable mixture of peroxide of lead, nitrate of lead, and
undecomposed red-lead. Weiderhold, at Cassel, suggested (1861) the following
ignition mixture :—
Chlorate of potash ...
Hyposulphite of lead
Gum arabic
7.8 parts.
2.6
...
•
...
ΙΟ
ANIMAL CHARCOAL.
553
This is the best anti-phosphorus mixture. Jettel, at Gleiwitz, gives the following
mixtures free from phosphorus:-
Chlorate of potash
Sulphur
Bichromate of potash
Sulphuret of antimony
...
Sulphur auratum, SbS, (Stibium
sulfuratum aurantiacum).
(Antimonium sulfuratum, B.P.)
Nitrate of lead
a.
b.
C.
d.
4'0
7:0
3'00
8.0
|
ΙΟ
ΙΟ
0'4
2'0
1
I
2'0
0'5
8:0
0°25
While R. Peltzer has called attention to the applicability of copper-sodium hypo-
sulphite for the preparation of a phosphorus-free ignition mass, Fleck* has also
remarked the use which might be made of sodium in this respect.
Wax or Vesta Matches.
Instead of the phosphorus composition being fixed to a wooden
splint it is in the wax matches (allumettes bougies) attached to a thin taper made of a
few cotton threads (4 to 6), immersed in a molten mixture of 2 parts of stearine and
I part of wax or paraffin. The tapers, while this mixture is hot, are drawn through
a hole perforated in an iron plate, the opening of which corresponds to the desired
thickness of the taper. The taper is next cut by means of machinery into suitable
lengths; afterwards the phosphorus composition is affixed and the vestas put into
boxes.
Zulzer's machine for cutting the tapers and for making them into matches has the
following arrangement. The wicks having been rolled on a drum are forced between
two cylinders, which impart the fatty composition, and next the tapers are carried by
the machinery across grooves in planks to holes in a movable vertical iron plate,
which is connected with a cutting apparatus intended to divide the tapers into
suitable lengths. As the cutters are placed at the entrance of the holes, the tapers
after having been separated from the main wicks are left dangling in these holes, and
by a mechanical contrivance, the plate containing the holes is lifted sufficiently
to bring another row of holes level with the wick-producing apparatus. When a
plate has been thus filled with tapers it is removed, another put in its place, and the
ends of the tapers immediately immersed in the phosphorus composition, and next
placed in a drying room. Marseilles is the great centre of the wax match industry,
while Austria stands next.
Animal Charcoal,
ANIMAL CHARCOAL.
Animal charcoal is the residue obtained by the dry distillation of
bones. Owing to its introduction (1812) by Derosne, and afterwards re-introduction
with improved filtering apparatus by Dumont (1828), into the sugar refining
industry, animal charcoal, or bone-black, has become one of the most important
substances of chemical technology. When bones are submitted to ignition in closed
vessels with exclusion of air, the organic matter yields a tar known as crude Dippel's
oil, and carbonate of ammonia, while a coal-black residue remains exhibiting
perfectly the organised structure of the bones.
Preparation of Bone-black. The bones are either boiled with water
water or, better,
exhausted with sulphide of carbon to remove the fat, which being obtained in
Jahresbericht der Chem. Technologie (Dr. Wagner), 1868, p. 220.
554
CHEMICAL TECHNOLOGY.
a quantity of 5 to 6 per cent of the weight of the bones, is a valuable by-product of
this branch of industry. The carbonisation of the bones is so conducted that the
volatile products are either burnt or condensed. In the latter case the broken-up
bones are put into iron retorts similar to those used for coal-gas manufacture,
and the volatile products are collected in suitable condensing apparatus, while
the gas after having been purified is sometimes led into a gasholder and used
for illuminating purposes, or when not purified is burnt under the retorts. Ac-
cording, however, to the experience obtained in Germany, bone-black thus made
has a lower decolourising power than when the bones are ignited in iron pots,
the volatile products being burnt at the same time. In Germany, therefore, the older
plan of carbonisation in pots is usually resorted to. In England and Scotland, and also
in Holland, Belgium, and France, retorts are generally used for this purpose. The
carbonisation in pots is carried on in the following manner:-Cast-iron pots are
filled with broken-up bones and placed one on the top of the other, the edges of the
mouths of the pots being luted with clay. The pots are placed on the hearth of a
kind of reverberatory furnace. After awhile the vapours which are forced through
the lute become ignited, thereby enveloping the pots in a sheet of flame, so that the
carbonisation goes on without requiring the firing of the furnace to be kept up.
When the flame subsides the carbonisation is complete. The yield of animal char-
coal amounts by this method of procedure to 55 to 60 per cent the carbonaceous
matter being, however, mixed with about ten times its weight of mineral matter, as
may be inferred from the following results of analysis of a dried sample of bone-
black, which in 100 parts was found to consist of-Carbonaceous matter, 10; phosphate
of lime, 84; carbonate of lime, 6 parts. By exposure to air bone-black absorbs
7 to 10 per cent of moisture. The carbonised bones are broken up and granulated
by machinery, the formation of dust having to be avoided as much as possible
because it has very little value.
Properties of Bone-black. As far back as the year 1811, Figuier discovered that bone-
black possesses the property of withdrawing organic and inorganic substances―viz.,
lime and potash from solutions. It appears that this property is due to surface
attraction (capillary action), although bone-black is also capable of decomposing
chemical compounds. Owing to the fact that bone-black can absorb inorganic
matter, it is largely used for the purpose of withdrawing lime and saline matter from
saccharine fluids in beet-root sugar works. According to Anthon, the property of
bone-black to withdraw lime from solutions is partly due to the fact that carbonic
acid is condensed in the pores of this substance.
By treating bone-black with hydrochloric acid, and thus dissolving the mineral
matter it contains, the residue, after having been well washed with water, dried, and
re-ignited in a closed crucible, has lost in a very great measure its property of with-
drawing from solutions and retaining within its pores inorganic matter. When acid
liquids are to be decolourised by bone-black, it should always be employed after having
been treated with hydrochloric acid. Shoe-blacking manufacturers employ in their
trade a large quantity of bone-black.
Testing Bone-black. The greater the decolourising power of charcoal the better its
quality, though it appears that the decolourising power is not proportionate to the
power of withdrawing lime and saline matters from solutions. In order to ascertain
the decolourising power of any sample of bone-black, its quality in this respect
is compared with that of another of known strength. Payen proposes to take equal
ANIMAL CHARCOAL.
555
bulks of water coloured with caramel, to treat these with equal weights of animal
charcoal, and to filter these mixtures; the charcoal which yields the clearest liquid
being the best.
Bussy obtained the following results by the estimation of the
relative decolourising power of equal quantities by weight of different kinds of
charcoal :-
Ordinary bone-black
Bone-black treated with hydrochloric acid
...
Ditto, ditto, but afterwards ignited with carbonate of potashı
Blood ignited with carbonate of potash
Blood ignited with carbonate of lime
I'O
1.6
...
20'0
20˚0
...
20˚0
15'5
Glue ignited with carbonate of potash
...
Brimmeyr's experiments on the decolourising properties of bone-black led to the
following results:-1. The capability of absorption of this substance does not depend
upon the mechanical structure of the bone-black, but upon the quantity of pure
carbon it contains. 2. The quantities of matter absorbed by bone-black of various
kinds are when reduced to pure carbon-really equivalent, and are probably
independent of the varying chemical nature of the soluble absorbed substance.
3. Bone-black saturated with any substance retains its absorptive power for other
materials of a different chemical nature. 4. Bone-black acts the quicker and better
the less its capillary structure has been interfered with either by mechanical or
chemical means (action of hydrochloric acid). Schultz's results of experiments
agree with those just quoted. The specifically lightest bone-black which contains
the largest amount of carbon is the most strongly decolourising material.
As
regards the sugar (especially beet-root) manufacture, the power of bone-black to
withdraw lime from a solution comes also into consideration; this lime-absorbing
capability is estimated by directly testing the quantity of lime which a given sample
of charcoal can take up.
Revivification (Re-burning)
of Charcoal.
After having served the purpose of decolourising and
absorbing lime for some time in the process of sugar refining, the bone-black
becomes, as it is termed, foul and requires to be revived, for which purpose it is
either first thoroughly washed with hot water or sometimes left to enter into a state
of fermentation, or treated with steam, and finally always re-ignited. The more
usual plan is to wash the bone-black, while still in the filters, with hot water, so as
to remove all soluble matter, the material being next re-ignited. In this manner
bone-black may be restored for use twenty to twenty-five times. This mode of
reviving labours under the disadvantage that during the ignition the organic matter
(ibsorbed impurities) is not quite destroyed, and by choking the pores of the bond-
black impairs its decolourising power. It is therefore preferable to cause the bone-
black to ferment, to treat it next with dilute hydrochloric acid, wash it well,
aid lastly ignite it. The quantity of hydrochloric acid employed for this purpose in
sug r-producing works is very large.
Substitutes for Bone-black Among the substances which have been tried as substitutes
for the use of bone-black, carbonised bituminous shale takes the first place. This
material (the coke of the Boghead coal is an excellent example) absorbs colouring
matter, but does not touch the lime. Moreover it often happens that the coke
is rendered unfit for this use by the presence of a considerable amount of mono-
sulphuret of iron. The coke of sea-weed is perhaps a more suitable material.
556
CHEMICAL TECHNOLOGY.
MILK.
Milk. This fluid is secreted by glands with which all female mammalia are
provided. It contains all the organic and inorganic substances required by the
young animal as food, being intended to feed the young until they are sufficiently
developed to partake of other nutriment. The main constituents of milk are:-
Sugar (lactose), caseine, butter, inorganic salts, such as chlorides of potassium and
sodium, phosphate of lime, and finally water. The average percentage composition
of cow's milk is the following:-
Butter
Lactose and soluble salts
Caseine and insoluble salts
Water
...
3*288
5 129
4'107
12 524 per cent.
87'476
100'000
Milk is a mixture of several insoluble, very minutely divided, emulsioned sub-
stances, suspended in a watery liquid. The specific gravity of milk varies from
1030 to 1045. Under the microscope it becomes evident that the white colour of
milk is due to the so-called milk globules—small globular bodies of a yellow colour,
with a more deeply coloured circumference, and exhibiting a pearly gloss. It was
formerly believed that these globules consisted of an exterior envelope filled with
butter, but the recent researches of Drs. Von Baumhauer and F. Knapp have
proved this opinion to be erroneous. When milk is left standing these globules rise
to the surface and form cream, below which remains a blue transparent fluid
containing the sugar of milk, salts, and caseine, the latter in the form of caseine-soda
When milk is kept for some time a portion of the lactose (sugar of milk) is decom-
posed and converted into lactic acid by the aid of the caseine, which acts as a
ferment. In its turn the lactic acid decomposes the caseine soda, whereby the
caseine is set free and separated as an insoluble substance; this action takes place in
the coagulation of milk. The whole of the lactose or sugar of milk becomes
converted into lactic acid by long keeping.
Lactic acid (C3H6O2) is also formed by the fermentation of starch, cane sugar,
and glucose, under the influence of caseine and a ferment. This acid is met
with in sauerkraut (a favourite dish of the Germans, being a well-preserved
mixture of white and savoy cabbages cut into shreds, and packed in casks
along with salt, coarse pepper, and some water), and in other pickles, in beer,
and in nearly all animal liquids. Lactic acid is also present in some of the
fluids of the tan-yard tanks; in the sour water of starch works where starch
is prepared by the old methods; in the bran bath of dye works; and is con-
stantly met with in the residual liquids of corn spirit distillation. When lactic
acid is heated with sulphuric acid and peroxide of manganese, aldehyde is formed,
which is used in the preparation of aniline green and of hydrate of chloral.
The coagulation of fresh milk is effected by the use of rennet, which is pre-
pared from the stomach of a calf, well washed and stretched out in a wooden frame,
then dried either in the sun or near a fire. The substance thus prepared was for-
merly soaked in vinegar, but experience has proved this to be unnecessary. When
required a small piece is cut off and steeped in warm water, and the liquid added to the
milk previously heated to 30° to 35°. The milk is hereby coagulated, even in large
MILK.
557
quantity, in about 2 hours; 1 part of rennet is sufficient for the purpose of coagula-
ting 1800 parts of milk. The mode of action of rennet is not well understood, but it
does not consist, as was formerly believed, in the instantaneous conversion of a por-
tion of the lactose present in milk into lactic acid, since experiments have shown
that rennet coagulates milk which exhibits an alkaline reaction.
Wh:y. By the term whey is understood the fluid in which the coagulated caseine
of milk floats and which may be obtained either by decantation or filtration. The
whey of sour milk contains very little lactose and a large quantity of lactic acid
(sour whey); while sweet whey, obtained by coagulating milk with rennet contains
all the lactose. Sweet whey containing 3 to 4 per mille of a proteine compound
(termed lacto-proteine by Millon and Commaille) is evaporated to some extent
in Switzerland, with the view of obtaining the sugar of milk in crystalline state. The
Lactose-Sugar of Milk. substance thus obtained is purified by re-crystallisation. Lactose,
C12H22O11+ H₂O, does not possess a very sweet taste and feels sandy in the mouth.
It is soluble in 6 parts of cold and 2 parts of hot water. It is not capable of alcoholic
but only of lactic acid fermentation. By the action of dilute acids sugar of milk is
converted into galactose, a kind of sugar similar to grape sugar, and is then capable
of alcoholic fermentation. Industrially sugar of milk is sometimes employed for the
purpose of reducing a silver solution to the metallic state, as in the case of looking-
glass making. 100 parts of the commercial sugar of milk from Switzerland (a), and
from Giesmannsdorf in Silesia (b), were found to consist (1868) of:-
a.
b.
Salts
...
...
0'03
0'16
Insoluble matter
...
0'03
0'05
Foreign organic substances...
I'14
I'29
Sugar of milk
...
98.80
98.50
100'00
100'00
Means to Prevent Milk
becoming Sour.
By boiling milk the air it has taken up is eliminated and
thereby the conversion of the caseine into a ferment, and the consequent decomposi-
tion of the sugar of milk, prevented. Milk may very readily be kept fresh by
the addition of small quantities of carbonates of alkalies or borax. The coagulation
of milk (not its becoming sour) may be prevented by the addition of some nitrate of
potash, chloride of sodium, or other alkaline salts.
Testing Milk. In localities where milk is consumed in very large quantities-for
instance, in large cities and towns-it is sometimes adulterated by the addition of
rice-water, bran-water, gum-solution, and emulsion of sheep's brain. The most
common adulteration of milk is its dilution with more or less water. Several
methods and instruments have been invented for the purpose of testing the quantity
of caseine and butter present in milk, and it should be here observed that, according
to Dr. F. Goppelröder's excellent researches (1866), it has been found that the
relative proportion of the quantity of these substances varies in milk from one day
to another, and even in the milk drawn at mornings and afternoons. According to
Jones's plan milk is poured into a vertical graduated glass tube; the quality of the
milk varies with the number of graduated divisions occupied by the cream separated
from the milk. It is evident that in this way only the quantity of cream contained
in the sample of milk under examination is found, and nothing learnt about the
degree of dilution of the milk with water, which somewhat influences the rapidity
558
CHEMICAL TECHNOLOGY.
of the separation of the cream. Chevalier and Henry employ for the testing of
milk an areometer, the degrees of which are ascertained by experiment from really
genuine milk. Other methods are based upon the use of tincture of nut-galls or
solution of sulphate of zinc for the purpose of precipitating caseine and butter in a
sample of genuine milk, and next to compare the quantity of these reagents neces-
sary to precipitate in an equal quantity by bulk of any other sample of milk.
Donné's galactoscope may be used for the purpose of testing the purity of milk,
more especially in reference to its adulteration with water, the instrument being
based upon the greater or less transparency of a column of milk of a certain length
which admits through it the rays from the flame of a lighted candle; the more
transparent—that is, the longer the column of milk-the more it is adulterated with
water. Brünner tests milk in the following manner:-To 20 grms. of the milk to be
tested are added 10 grms. of charcoal powder. This mixture is evaporated to
dryness at a temperature of 70° to 80°. The butter is then extracted by means of
ether, and this solution evaporated and weighed. Pure milk yields 3′1 to 3'56 per
cent of butter, cream from 10'6 to 11:06 per cent. C. Reichelt has lately tried to
apply the hallimetrical method (see p. 422) for the purpose of determining the
quantity of water contained in milk.
Uses of Milk.
Milk is used as food and for the preparation of butter and cheese, for
clarifying wine in order to render it less deep coloured, and, if turbid, quite clear.
More recently milk has been largely sold in the so-called condensed state, by which is
understood milk evaporated in vacuo after the addition of sugar to the consistency
of thick honey. This mode of preserving milk was first employed by the Anglo-
Swiss Condensed Milk Company at Cham, Canton Zug, Switzerland, and is now
carried on in various parts of the Continent and in the United States, and also in
England, in Surrey and Berkshire. The average composition of the condensed
milk is:-
Water ...
Solid matter
...
...
...
22.44
77'56
100'00
One-half of the solid matter consists of the sugar which has been added, the rest
being butter, 9 to 12 per cent; caseine and lacto-proteine, 12 to 13 per cent; sugar
of milk, 10 to 17 per cent; salts, 22 per cent. Condensed milk is soluble in cold
water, and yields with 45 to 5 parts of water a liquid similar to genuine, but of
course sweetened, milk.
Butter. This substance is prepared as follows:-Milk of good quality is placed
in a rather cool cellar or other locality for the purpose of causing the cream to
separate. The cream is poured into a clean stoneware or glass vessel kept for the
purpose, and left until by constant stirring it has become thick and sour; it is then
put into a churn, by the action of which the solid fat globules are separated from the
thick fluid in which the caseine with a small quantity of butter remains suspended.
Butter being specifically lighter than water should, it might be thought, separate
very readily from a liquid which contains in solution various substances which are
heavier; but the fact is, that caseine renders the separation of butter from cream
difficult even when the cream is sweet and not thick; when, on the other hand, milk
coagulates before the cream is separated, the butter is lost. Two methods have been
devised for the purpose of obtaining all the butter contained in milk. Gussander, a
MILK.
.559
Swedish agriculturist, has proposed that the separation of cream should be rendered
more rapid, and always completed before the milk becomes sour, while Trommer
prevents the souring of the milk by the addition of some soda.
The churns vary very much in construction; the most simple, which is that most
extensively used, consists of a tall somewhat conical wooden vessel covered with a
wooden lid, through a round opening in which a cylindrical wooden stem passes.
To this stem is fixed a wooden perforated disc, which is moved upwards and downwards
by a similar motion imparted to the stem. The butter having been separated from the
liquid is thoroughly washed and kneaded with fresh water, and next more or less
salted, at least in most cases, although thoroughly well-washed butter may be kept
for a very long time without becoming rancid. The liquid from which the butter is
separated is known as churn-milk or buttermilk; it contains o°24 per cent butter,
3.82 per cent casein, 90.80 per cent water, 5'14 per cent sugar of milk and salts. In
the water lactic acid is present. 18 parts of milk yield on an average I part of
butter, which in fresh condition consists of:—
I.
II.
III.
IV.
Butter fat
.94'4 93'0
87.5
78.5
Caseine, sugar of milk
Extractive matter
}
0'3
0'3
ΙΟ
0'3
Water
5'3
6.7
1125
21.2
I
Owing to the presence of water and caseine, butter after some time becomes rancid.
It is salted in order to prevent this rancidity as much as possible, the salt being
thoroughly mixed with the butter by kneading. To 1 kilo. of butter 30 grms. of salt
are required. According to Dr. Wagner, butter in England is salted with a mixture
of 4 parts of common salt, I part of saltpetre, and 1 part of sugar. In Scotland,
France, Southern and Western Germany, butter is not salted at all, and therefore
only made and sold in comparatively small quantities at a time. Salt butter is
termed in Scotland pounded butter.
By melting butter until the first turbid liquid has become clear and oily, water
and caseine are eliminated, and settling to the bottom of the vessel, the supernatant
fat may be put into another vessel, and will, after cooling, keep sweet without salt
for any length of time. Butter is often artificially coloured either by the aid of annatto,
turmeric, or infusion of calendula flowers.
Chemical Nature of Butter. Butter consists of a mixture of neutral fats—glycerides—
which on being saponified yield several fatty acids, among which the non-volatile
are :—Palmitinic acid, C16H32O2, and butyroleic acid (C12H30O2). The volatile are :—
Butyric acid✶ (C4H8O2), capronic acid (C6H12O2), caprylic acid (C8H18O2), caprinic
acid (C10H2002). The last four constitute in the shape of glycerides the butyrin or
peculiar fat of butter, and impart to that substance its peculiar odour and flavour.
Cheese. Cheese is prepared from caseine. It is made either from skimmed or
unskimmed milk. In the former case a lean, dry cheese is obtained; in the
latter a fat cheese, such as Cheshire, Cheddar, American, and the bulk of
Holland cheeses. Lean cheese is made in Germany by pouring the skimmed
and already sour milk upon a cloth, through the pores of which the whey passes,
* This acid is formed not only by the saponification of butter, but is also met with in
secreted perspiration, the juices of the stomach, and results from the fermentation and
decay of sugar (in weak solutions), starch, fibrine, caseine, &c.
560
CHEMICAL TECHNOLOGY.
while the caseine remains on its surface as a pasty mass, which is put by hand into
the cheese-moulds, these being next exposed to air.
Fat cheese is made of sweet milk just drawn from the cows, the milk being
coagulated by rennet after having been heated to 30° to 40°. The gelatinous mass
thus obtained is broken up and pressed by hand, and the whey gradually removed
by the aid of wooden ladles. The caseine having been freed from whey is next well
kneaded with some common salt and then put into wooden moulds with two or three
small holes at the bottom for the purpose of allowing the whey to flow off when the
cheese is pressed. The newly made cheese is usually every alternate day dipped in
warmed whey, next wiped dry, put into the mould again, and pressed. When the
crust has sufficiently formed and the cheese become so hard as to admit of being
handled, some salt is rubbed into its surface and it is then placed in a cool well-aired
room upon a shelf to dry, and become as it is termed ripe. The vesicular appearance
of some kinds of cheese (the Gruyère cheese exhibits this in a high degree) is indi-
rectly due to the incomplete removal of the whey, the sugar contained becoming
during the ripening converted into alcohol and carbonic acid, which by its
expansion while escaping produces the vesicular texture. Dutch cheese does not
exhibit this appearance on account of being strongly pressed and containing much salt,
by which the fermentation of the sugar of milk in the cheese is prevented. The
quality of the cheese depends to some extent upon the temperature of the room in
which it ripens. At Allgäu 1 cwt. of Swiss cheese of the first quality is produced
from 600 litres of milk, while for the second quality 720 to 750 litres of milk are
taken for the same weight. The theory of cheese formation is not well known, but
it appears that fermentation plays an important part in it. W. Hallier has proved
that freshly made cheese is filled with ferment nuclei (Kernhefe).
Cheese cannot be formed without this ferment, and by the addition of suitable
ferments the duration of the cheese-ripening process and the quality of the cheese
may be to some extent regulated at will. By exposure to air cheese undergoes
changes which may be best observed in skimmed-milk cheese. When new or young
its colour is white. By being kept so that it does not dry, it turns yellow and often
becomes transparent, waxy, and then exhibits the peculiar odour of cheese. When
cheese gets very old it becomes a soft pasty mass, this change commencing at the
outside and progressing towards the interior. The waxiness of cheese is due either
to an evolution of ammonia or of acid. Mild cheese usually exhibits an acid reaction,
while strong cheese is ammoniacal. Chemically speaking, skimmed-milk cheese is
a compound of caseine with ammonia or ammonia bases, amylamine for instance.
The so-called dry cheeses, green Swiss cheese, consists of an infusion of herbs,
Melilotus, &c., with volatile fatty acids, valerianic, capric, caproic acids, and indif-
ferent substances, leucin, &c. The composition of sweet milk cheese (a) and of sour
skim-milk cheese (b) is exhibited by the following table :-
Water
...
Caseine ...
Fatty matter...
Ash
...
:
:
α.
b.
...
36:0
44'0
29'0
45'0
30.5
6'0
4'5
5°0
100'0
ΙΟΟ Ο
MILK.
561
The results of the researches of Payen on cheese are quoted below in 100 parts for
the following kinds :-1. Brie. 2. Camembert. 3. Roquefort. 4. Double cream
cheese. 5. Old Neufchatel cheese. 6. New Neufchatel cheese. 7. Cheshire.
10. Parmesan cheese.
8. Gruyère. 9. Ordinary Dutch.
I.
I.
2.
3.
4.
5.
Water
...
45'20 51'90
34'50
9'50
34°50
Nitrogenous matter
18.50
18.90
26.50
18.40
13.00
Nitrogen
2.93
3'00
4'21
2.92
3.31
Fatty matters
25'70
21'00 30'10
59'90
41'90
Salts
5.60
4'70
5'00
6.50
3'60
matter and loss
Non-nitrogenous organic 5:00
4'50
3'90
5'70
7'00
II.
-་--
6.
7.
8.
9.
IO.
Water
...
36.60
35'90
40'00
36'10
27.60
Nitrogenous matter
8:00
20'00
31°50
29'40
44'10
Nitrogen
I'27
4'13
5'00
4'80
7:00
Fatty matters
40'70
20.30
24'00
27'50
16:00
Salts
0'50
4'20
3'00
o'go
5'70
Non-nitrogenous organic)
14'20
7.60
1'50
6.10
6.60
matter and loss
The varieties mentioned under I. exhibit an alkaline reaction, and contain with
ammonia cryptogamic plants, or, as it is termed, are mouldy. The varieties under
II., so-called boiled, strongly pressed and salted, cheese, exhibit an acid reaction, as
also does freshly prepared caseine. A portion of the fat contained in the cheese is
even from the first decomposed into glycerine and fatty acids.
Emmenthaler (a) and Backstein (b) cheese are composed, according to Lindt's
researches (1868), as follows:-
Water ...
Fatty matters
Caseine
Salts
...
a.
b.
37'4
36'7
45°2
35.8
30.6
30'5
28.2
37'4
28.5
29'0
23°2
24°4
3'5
3.8
3'4
2.4
100'0
ΙΟΟ Ο
ΙΟΟ Ο
ΙΟΟ Ο
The results of E. Hornig's recent analyses (1869) of different kinds of cheese are:—
I.
2.
Water
Fatty matters
...
Caseine
Salts ...
Loss...
...
...
0'02
0'04
3.
4.
38.66 56.60 51°21 57'64 36.72 34'08
20'14 17:05 9'16 20°31 33.69 28.04
34'90 18.76
18:51 25*67
33.60
23°28
24.09
6.17 6.78 6'01 3°51 3'71 5°58 6.17 5°45
0'13 0.81
0'02 0°32
5.
6.
7.
8.
59'28
49°34
10'44 20.63
24.25
'O'21
0'02
100'00
ICO'OO 100°00 100'00
100'00
100'00 100'00 100'00
37
562
CHEMICAL TECHNOLOGY.
1. Dutch cheese.
2 and 3. Ramadoux cheese, made in Bavaria. 4. Neufchatel
cheese. 5. Gorgonzola cheese. 6. Bringen or Liptau cheese, from the Zyps
Comitat, Hungary. 7. Schwarzenberg cheese. 8. Limburg 'cheese, made in the
environs of Dolhain-Limburg, in Belgium.
Freshly made caseine mixed with lime is used as a kind of cement. Caseine is
also used in calico-printing as a mordant; and a solution of caseine in borax is used
instead of glue. In the seeds of the leguminous plants, peas, beans, lentils, &c., is
met with a nitrogenous substance which is soluble in water and precipitable there-
from by weak acids; this material is very similar to caseine, and according to
M. J. Itiers's accounts, peas and beans are in China boiled with water and strained,
and to the liquid thus obtained some solution of gypsum is added, whereby the
vegetable caseine (legumine) is coagulated, and the coagulum thus obtained is
treated as that of milk, obtained by the addition of rennet to the latter. The mass
so obtained gradually becomes like cheese in all respects.
MEAT.
Generalities. That which we term butchers' meat is the muscular substance of
slaughtered animals, together with more or less fat and bone, so that the meat
exhibited for sale contains on an average in 100 parts:-
Muscular tissue
Fat and cellular tissue
Bones
Juices
...
16
3
ΙΟ
71
ΙΟΟ
Muscular tissue is histologically composed of a variety of complex tissues and
fluids, the basis of which is animal fibre or fibrin, an organised proteine compound.
The muscular fibre held together by cellular tissue forms the muscles, fat being
deposited in the cellular tissue and in cells peculiarly constructed for that purpose.
Blood-vessels, lymph-vessels, nerves, and other organised tissues are dispersed
through the muscles and serve a variety of physiological purposes. The muscular
tissue is impregnated with a proteine fluid in which are met with a variety of other
substances, as kreatinin, hypoxanthin, kreatin, inosite or muscular sugar, lactic acid,
inosinic acid, extractive matter, and inorganic salts-among these chloride of
potassium and phosphate of magnesia.
Constituents of Meat. The average result of a great number of researches recently made
on the large scale concerning the quantity of water contained in the meat of fattened,
and half- or non-fattened animals, are the following:-
In the non-fattened meat
""
half-fattened meat
fully-fattened meat
:
:
Lamb. Sheep. Bullock.
Pig.
62
58
56
50
54
49
40
46
39
33
fat meat
It hence appears that with an increase of fat the quantity of water present in meat
decreases, a portion being replaced by fat. Well fed and fattened meat contains for
equal weights about 40 per cent more dry animal matter than non-fattened meat
while in highly fattened meat it may amount to 60 per cent.
MEAT.
563
The difference in nutritive value of the meat of well-fattened bullocks as compared
with that of non-fattened is exhibited in the following percentage results obtained by
Breunlin:-
Water
Ash
...
Fat...
Muscle
...
1000 grms. contain :-
:
:
Fattened.
Non-fattened.
38.97
59.68
1'51
I'44
23.87
8·07
36.65
30.81
100'00
100'00
Muscular
Meat.
Fat.
Ash.
Water.
Meat from fattened bullocks ...
Meat from non-fattened bullocks...
356
239
15
390
308
81
14
597
Difference
+48
+158
+I
-207
Consequently the meat of fattened bullocks contains in 1000 parts 207 more of
solid nutritive matter than the meat of the same in unfattened condition.
The Cooking of Meat. Meat is either roasted or boiled. By boiling, meat is very essentially
altered in composition according to the time it is boiled and the quantity of water
used to boil it in. The fluid in which meat has been boiled contains soluble alkaline
phosphates, salts of lactic and inosinic acids, phosphate of magnesia, and a trace of
phosphate of lime. In order to be of the highest nutritive value, meat should retain
all its soluble constituents; hence boiled meat loses much in nutritive power. The
albumen contained in meat is lost by boiling according to the usual plan. Meat
intended to be boiled should be immersed in boiling water to which some salt has
been added, the meat being put in while the water boils violently, whereby so great
a heat is at once imparted to the outer portions of the meat as to coagulate the
albumen, which then acts as an impermeable layer, retaining the juices in the meat.
Liebig's directions for making good broth are the following:-Lean meat is minced,
mixed with distilled water, to which a few drops of hydrochloric acid and common
salt are added. After having been digested in the cold for about an hour, the liquid
is strained through a sieve, and upon the residue some distilled water is again
poured so as to extract all soluble matter. In this way an excellent and highly
nutritive cold solution of extract of meat is obtained; this may be drunk without
being heated, and contains albymen in solution, which is coagulated by heating.
100 parts of beef yield an extract containing 2.95 parts of albumen and 3'05 parts of
other constituents of meat not coagulable by heat. Chevreul obtained from 500 grms.
of beef containing 77 per cent water, 27:25 grms. of extract, in which were 3'25 grms.
fat; deducting these there remain 4.8 per cent extract. The bulk of this fluid extract
was 1.25 litre, the weight 1013 grms., and it contained :-
Water
Organic matter
Alkaline salts
...
Soluble in alcohol
Insoluble in alcohol
Earthy phosphates...
:
991'30
9'44
3°12
8.67
0'46
1013'09
564
CHEMICAL TECHNOLOGY.
Broth made from beef contains only 3 parts of meat substance inclusive of glue
and fat.
Under the best conditions, 1 kilo. of beef yields :—
Soluble in cold water
60 |
Insoluble in cold water
Coagulated albumen
Albumen in solution
Glue-yielding substance
29'5
30.5
6'9
...
1701 Fibrous matter
164'0
Fat
Water...
...
20
750
The Boiling of Meat.
We have already stated that the meat intended to be boiled
should be immersed in boiling water and the fluid kept boiling for a few minutes, so
much cold water being next added as will reduce the temperature of the liquid to
70° or 74°. At that heat the liquid should be kept for some hours to produce a very
savoury, sweet, succulent piece of boiled meat. If, however, it is desired to make a
strong broth, lean meat is first minced, next well exhausted with cold water, and then
slowly heated-best on a water-bath—and just allowed to come to the boil over a slow
fire. The liquid is strained from the solid meat, and the latter put into a clean cloth and
well pressed. The residue is fit only for the making of manure.
The broth may be
coloured with caramel if desired. Broth so made contains all the soluble consti-
tuents of meat, and exhibits an acid reaction owing to the free lactic and inosinic
acids. Broth does not owe its good properties to the gelatine it contains, this
substance being present in very small quantities, while the so-called bouillon
tablettes obtained from bones are altogether unfit for food. These tablettes should
not be confused with solid meat-extract cakes of Russian make, which contain,
according to Reichardt (1859) :-
Water driven off at 100°
Ash
Fat
Nitrogen
:
...
15'13 per cent.
475"
...
0°22
""
Substance soluble in alcohol at 80 per cent
10'57
38.09
""
""
I
When broth is boiled for a long time it becomes deep coloured and assumes
the very agreeable flavour of roast meat. Evaporated upon a water-bath it yields a
pasty deep brown-coloured mass, 18:27 grms. of which yield, with 1 lb. of hot water
and the addition of some salt, a very strong and excellent soup. 32 lbs. of bones
with the adhering scraps of lean meat yield 1 lb. of this extract. Extract of meat as
generally met with is now made in South America by several firms, viz., at Fray-
Bentos, Uruguay, Gualeguaychu (Entre Rios). 1 kilo. of this extract contains all the
soluble portion of 34 kilos. of meat without bones, or 45 kilos. of average butchers'
meat. Australian extract of beef (the American extract is of mutton and beef mixed,
manufactured by R. Tooth) is largely imported into Europe. The chief test for the
purity of the extract of meat is its solubility in alcohol at 80 per cent, next the
quantity of moisture it contains, and the absence of albumen and fat. 60 per cent of
the extract at least should be soluble in alcohol. The quantity of water amounts to
about 16 per cent, the nitrogen to 10 per cent, and the ash to 18 to 22 per cent,
consisting essentially of phosphate of lime and magnesia, chlorides of the alkalies,
among which potassium chloride predominates.
Preservation of Meat.
Among the many methods employed for the preservation of meat,
that by complete exclusion of air ranks foremost. Appert's plan of packing meat in
MEAT.
565
tin canisters, from which the air is completely exhausted, is generally the follow-
ing:-The meat, or very concentrated soups, game, &c., is put into tin canisters,
which are thoroughly filled. A lid is then soldered on, in which a small hole is made
for the purpose of entirely filling any interstices with gravy. This having been
done, the small hole is soldered over, after which the canisters are placed in a
cauldron filled with brine and boiled therein for a half to four hours, according to
the size of the canisters. When any of them is not well soldered, there will
issue from the leakage smaller or larger vesicles of air and vapour, and where
such is the case hot solder is applied to the spot. By this boiling the albuminous
substances are coagulated and converted into a less-readily putrescible modification.
The oxygen of the air contained in the canisters is partly converted into carbonic
acid, partly deozonised, and thus rendered ineffective for the production of putres-
cence. After having been submitted to the action of boiling heat for some time, the
canisters are placed in a room heated to 30°, and left there in order to test whether
putrefaction can set in, manifested by the bulging outward of the top cover, which,
if the operation has been thoroughly successful, is usually somewhat concave in con-
sequence of a vacuum having been formed inside the tin. After having been thus
tested for several days, the canisters may be considered sound, and will keep for an
indefinite period. Dr. Redwood's method of preserving meat under a layer of
paraffin, and Shaler's plan of preserving meat in dry carbonic acid gas at o°, are in
principle the same as Appert's method.
Preservation of Meat by
Withdrawal of Water.
Meat may be preserved by drying it or salting it, both methods
being based upon the withdrawing of the water. Although drying is the best
method of preserving meat, it is an operation attended with very great diffi-
culty. The natives of North and South America cure meat by cutting it into
thin strips, removing the fat, and rubbing Indian-corn meal on the surface. Thus
prepared, the meat is exposed to the heat of the sun and dries rapidly, forming a
flexible non-putrescent mass, which in North America is termed Pemmikan, in
South America Tassajo, and in South Africa Biltongue. 100 parts of beef, which is,
after drying, rolled up so as to form a compact mass, yield 26 parts of tassajo. The
drying of meat is in Europe never effected on a large scale, partly on account of the
low temperature, partly on account of the necessity of cutting the meat into pieces,
rendering it in many instances unfit for culinary purposes.
Many preparations of flour and meat extract have been introduced at different
times under the name of meat-biscuit, first made in 1850 by Gail Bordon, at
Galveston, in Texas, U.S., and greatly improved upon by C. Thiel, at Darmstadt.
The latter minces fresh lean meat, next exhausts it with water, and uses the liquid
obtained for mixing with the flour instead of water. The large biscuit manufacturing
firms in England, especially Huntley and Palmer at Reading, prepare patent meat-
biscuits or wafers, made with Liebig's extract of meat and Hassall's flour of meat.
On the Continent, E. Jacobsen, at Berlin, prepares a similar biscuit, more especially
with the view of preparing soup. To the mixtures of animal and vegetable matter
prepared so as to be suitable for keeping for a length of time belong the pea-
sausages, first made by Grüneberg in Berlin, and largely used during the late war
as an excellent food for the German armies.
Salting Meat. This method of preserving meat, based upon the principle of with-
drawing water, has been used from time immemorial. The salt, while penetrating
into the meat and thereby hardening it, displaces the water and aids the preservation
566
CHEMICAL TECHNOLOGY.
of the substance. The freshly-slaughtered meat is first rubbed with coarse salt, and
then left in a cask with salt for some days. It is next pressed and put into another
cask, the wood of which has been previously soaked with brine. Some salt is then
added, and lastly the brine, which had been obtained by pressing the meat, is
poured over it, and the lid of the cask put on. Frequently some nitrate of potash
and sugar are added, as well on account of the antiseptic property of these substances
as for imparting a bright red colour to the meat.
Salt, however, not only withdraws water from the meat, but also, as has been proved
by Dr. Liebig's researches, some of the very best and essential portion of the juices of
the meat, including albumen, lactic and phosphoric acids, magnesia, potash, kreatin,
and kreatinin. Hence it is clear, that unless these substances are in some way or other
added to the salted meat, its use as food for a lengthened period cannot fail to become
injurious to the system, and it is surmised that scurvy is due to this condition of salt
meat. Liebig has suggested that meat, instead of being treated with dry salt, should
be salted with a strong brine made up of common salt, Chili saltpetre, chloride of
potassium, and extract of meat. The salt to be used for making this brine should be
previously purified by the application of a solution of phosphate of soda, whereby
lime and magnesia are precipitated. Cirio's method of meat preservation, which was
exhibited in 1867 at the Paris Exhibition, consists in placing the meat in vacuo and
then forcing brine into it. By this process the nutritive value of meat is much
impaired owing to the loss of the juices.
Smoking or Curing Meat. The rationale of this process and the preservative action of the
smoke have not been scientifically elucidated. In the first place the heat of the smoke
dries the meat, while, further, smoke contains a creosote, which, according to the
more recent researches of Hlasiwetz, Gorup-Besanez, Marasse, and others, essentially
consists of a mixture of C-H8O2, C8H1002, and C,H12O2. This creosote possesses
the property of coagulating the albuminous substances of meat, and once coagulated
and thereby rendered insoluble these substances are not capable of decay, or only
so after a very great lapse of time. Smoke, moreover, contains some pyroligneous acid
and other creosote-like substances (oxyphenic and carbolic acids), which undoubtedly
play some part in the preservative action.
Vinegar is an excellent preservative of meat, especially in hot summer weather.
Abroad meat is frequently put into a clean linen cloth which is thoroughly soaked
with vinegar, some salt also being sprinkled on the cloth. Meat kept for a few days
in this manner is very tender and readily digested. It is very probable that vinegar
might be advantageously employed on the large scale for the preservation of meat
together with complete exclusion of air. In order to prevent the vinegar extracting
the juices of the meat, the latter should be exposed to the action of the vapours of
strong vinegar.
Lamy more recently, and Braconnot, Robert, and De Dombasle, nearly half a cen-
tury ago, proposed to preserve meat by the aid of sulphurous acid gas, pieces of meat
weighing some 2 to 3 kilos. being exposed to the action of this gas for ten minutes,
while larger pieces of 10 kilos. and more, are exposed to the action of the gas for 20 to
25 minutes. After having been exposed to fresh air for some minutes for the purpose
of getting rid of the excess of the gas, the meat is coated with a brush with a solu-
tion of albumen in a decoction of marsh-mallow root, to which some molasses have
been added. Very recently meat has been preserved by first drying it in a current of
hot air and next coating it with a film of caoutchouc or gutta-percha, by immersing
ᎷᎬᎪᎢ .
567
the meat in a solution of these substances in chloroform or sulphide of carbon. It is
very generally known that a temperature below freezing-point is a most perfect pro-
tection against decay of animal.matter; hence ice is largely used for the preservation
of fish in summer time. Meat as well as game and poultry are best preserved in hot
weather in ice pits. In no country of the world is so much use made of this mode
of preserving meat and vegetables as in Russia, where the very severe winter is
turned to good account by the preserving of all kinds of animal food; in fact, oxen,
sheep, hogs, deer, and all kinds of game and poultry are brought to market in a frozen
condition, and may be kept so for any length of time without impairing the goodness
or taste after cooking. At St. Petersburg large stores of frozen animal food and
game brought from distances of hundred of miles are kept throughout the winter. At
the Dornburg, near Hadamar (Province of Nassau, Prussia), a natural permanent
ice store exists wherein perishable food is kept stored in large quantity. The
artificial production of ice by means of Carré's machine is employed in New South
Wales for the freezing of meat, which is next packed in ice ready for transport.
DIVISION VI.
DYEING AND CALICO PRINTING.
Dyeing and Printing in General
ON DYEING AND PRINTING IN GENERAL.
The object of the art of dyeing is to impart to textile
fibres, chiefly in the shape of woven tissue, but in many instances as yarn, some
colour or other. Dyeing is distinguished from painting by the fact that the
pigments are fixed to the animal and vegetable textile fibres according to certain
physico-chemical principles, and are not, as in painting, simply fixed by adhesion to
the surface, although painters and artists occasionally use the same pigments.
Printing consists in the duplication of coloured patterns, and is a very important part
of dyeing.
Dyes. The materials employed for the production of colours, the dyes and pigments,
are partly of mineral, animal, and vegetable origin, partly artificially obtained-that
is, the products of modern chemistry. Among the very large number of inorganic
pigments few only are as such fit for use, and if employed at all it is by an indirect or
circuitous process, that is, they are produced upon the woven fabric itself. For
instance, chromate of lead is obtained by first impregnating the woven tissue with
acetate of lead, after which the fabric is treated with a solution of bichromate or
neutral chromate of potash, the result being the formation of a solid adhering
chromate of lead. Among many other inorganic pigments may be enumerated—
Berlin blue; hydrated oxide of iron, for drab, nankeen, or rust colour; bistre colour,
hydrated oxide of manganese; chrome-green, oxide of chromium. Among the dyes
of animal origin are―The ancient Tyrian purple, derived from a mollusc, a native of
the Mediterranean, now not used; kermes (Coccus ilicis); cochineal (Coccus cacti); lac
dye (Coccus lacca). A much larger number of dyes are obtained from the vegetable
kingdom. It appears from recent researches, that a large number of the so-called
vegetable pigments are present in the plants themselves in a colourless condition,
becoming coloured by the action of the atmosphere. It is impossible to mention any
general properties of the vegetable pigments, because excepting the fact that they are
all coloured, they are not possessed of any property common to all. Nearly all dyes
fade by the combined action of sunlight and moist air. Chlorine destroys most
colours; while many dyes are bleached, not destroyed, by sulphurous acid. We owe
to the researches of modern chemistry a class of pigments which surpass in beauty
almost all the native dye materials. These chemically prepared dye materials are
chiefly derived from coal-tar, more particularly from benzol, toluol, carbolic acid,
anthracen, and naphthalin. The pigments derived from these substances are
DYEING.
569
commonly termed aniline or coal-tar colours, fuchsin, magenta, aniline blue and violet,
Manchester yellow, aniline orange, picric acid, aniline brown, coralline, alizarine
(artificially prepared from anthracen), magdala red, aniline black, and aniline green.
Among the chemically prepared colouring matters should be mentioned those
obtained by the decomposition of the alkaloids (cinchonine, quinine, &c.), chinoline
blue, quinine green (thalleiochine), and also murexide, a product of the decomposi-
tion of uric acid.
Lake Pigments.
The so-called lakes are compounds of starch, alumina, oxide of tin, oxide
of lead with sometimes carbonate of lime, baryta, or oxide of antimony, with the colouring
matter of madder, cochineal, woad, logwood, tar-colours (viz. coralline, fuchsin, aniline
violet), but as yet these substances are not prepared in definite proportions. By paints
we understand substances which as a rule are insoluble in water and are mixed with
either weak glue solution, being then termed water-colours, or with linseed oil, called
oil-paints. To these pigments belong white-lead, red-lead, ultramarine, Berlin blue,
vermillion, chrome-yellow, bone-black, &c. The ordinary water-colours are insoluble
in water, being finely suspended therein by the aid of gum, white of egg, gum
tragacanth, &c. The pastel pigments used for drawing are made up of various
pigments, mixed with pipe-clay, soap, and some tragacanth mucilage, and moulded
into cylindrical sticks.
Colouring Materials.
粤
​Dyeing means strictly the tinging or colouring of absorbent
substances by impregnating them with solutions of colouring matters. It is thus
opposed to painting, which consists in laying a colour upon the surface to be
coloured. In the art of dyeing some colouring matters are applied by immersing
the tissue to be coloured in the decoction or solution of the pigment. Some sub-
stances are applied to the surface of the woven fabric by the intervention of what
is technically termed a mordant, which is in the case now under consideration
only a means of obtaining adhesion, as when, for instance, ultramarine is fixed by
the aid of white of egg. Sap-colours are substances more or less soluble in water,
covering very slightly, and more or less translucent, as sap-green, gamboge, carmine
solution, many of the tar-colours, &c.
The Coal-Tar Colours.
Coal-Tar. This substance is very largely obtained as a by-product of the dry dis-
tillation of coal for the purpose of gas manufacture, and is a most complex mixture
of a very large number of substances, among which are fluid and solid hydro-
carbons (benzol, toluol, cumol, cymol, anthracen, naphthalin); acids (carbolic or
phenylic, cresylic, phlorylic, rosolic); bases (aniline, chinoline, odorine, picoline,
toluidine, coridine, &c.), and asphalte-forming materials. Leaving the small quantity
of basic substances out of the question, 100 parts of tar consists of the following
substances:
Benzol
Naphtha
Naphthalin
Anthracen
Carbolic acid
Pitch
:
...
:
:
:
I'5
35°0
22'0
ΙΟ
9'0
35
100'0
570
CHEMICAL TECHNOLOGY.
By fractional distillation of tar we obtain, on the one hand, light oils, from which
benzol and its homologues are separated; on the other hand, heavy tar oil, which is
used for making carbolic acid; while, lastly, anthracen is separated from the pitch.
Approximatively, the following table shows the quantity of the various materials
obtained by the dry distillation of coal:-
100 kilos. of coal yield
100 kilos. of tar yield
"
""
""
I
""
""
""
་
35
"
""
3'00 kilos. of tar.
0.75 to 1 kilo. of anthracen.
3'00 kilos. of crude benzol.
1'50 kilos. of pure benzol.
3'00 kilos. of nitro-benzol.
2:25 kilos. of crude aniline.
3'37 kilos. of crude aniline red.
1'12 kilos. of pure fuchsin.
For the preparation of 1 kilo. of pure fuchsin 60 cwts. of coal are required.
Benzol. Chemically speaking, benzol or benzine is a fluid hydrocarbon, 66H6, dis-
covered in 1825 by Faraday among the products of the dry distillation of oil, in
the liquid resulting from the strongly compressed oil gas. In 1833 Mitscherlich
obtained this body by distilling benzoate of lime. Leigh, at Manchester, 1842, first
discovered benzol in coal-tar; and to Mansfield's researches is due the method
of separating benzol from tar by a process available on the large scale.
The benzol as met with in commerce is a mixture of benzol boiling at 80 4° with
toluol, C-H8, boiling at 108°; xylol, C8H10, boiling at 130°; cumol, C,H10, boiling at
151°; and cymol, C10H12, boiling at 175°; benzol and toluol, however, predominate.
Abroad benzol is sold to the aniline makers at a certain specified percentage
of benzol, C6H6; for instance, benzol at 30 to 40 per cent contains by bulk or
weight, as may be agreed upon, the above percentage of the compound C6H6, the
Ꭱ
FIG. 265.
m
n
rest being 60 to 70 per cent of
toluol and xylol, forming a fluid
which is suitable for making aniline
red, while for aniline blue or black a
fluid at 90 per cent benzol, C6H6, is
required. The boiling-point of the
benzols usually employed for making
the so-called tar-colours varies from
80° to 120°, while the specific gravity
varies from 0·85 to 0·89.

Benzol is prepared from light tar
oil which boils below 150°. The
apparatus invented by Mansfield for
this purpose is shown in Fig. 265.
A is the still placed on a furnace,
R; c is filled with cold water. As
soon as the oil in the still begins to
boil, the vapours are condensed in в and flow back into A; this continues until
the water in c has been heated to a certain temperature, when the vapours are
condensed in the cooler, D, the liquid flowing at n into the carboy, s. As soon as the
water in c begins to boil, all the substances contained in the tar-oil and volatile
DYEING.
571
at 100° are condensed and collected in s. A very pure benzol is prepared with this
apparatus. By opening the tap m, the hydrocarbons which boil above 100° can
be rectified. The stopcock, i, is used for emptying the still. In the benzol works the
apparatus exhibited in Fig. 266 is used. A is the still, в the condenser, c a water
W
FIG. 266.

B
וויון
1140
ווווווניות
ACIKCHA
BTS and IN KA
Lust-tata
TOPAD 20
Po
FIG 267.

D
H
m
ETIZO
tank. At the commencement of the operation the water in c is heated by means of
the steam-pipe D, which communicates with the steam boiler. The tube & is attached
to the still; i is a contrivance for filling, b for emptying it. The condensed water is
572
CHEMICAL TECHNOLOGY.
When it is desired to pre-
carried off by means of H. By freezing benzol and pressing the solid substance
obtained it may be rendered quite pure.
In the year 1860, Dr. E. Kopp, at Turin, showed that the preparation of benzol
might be advantageously effected by the use of an apparatus similar in construction
to that employed in spirit distilleries. Coupier has constructed an apparatus upon this
principle, which is shown in Fig. 267. A is the still; at в the crude benzol is
poured in; c is a steam-pipe for heating the still and its contents. The vapours
evolved from the boiling liquid are carried into the column N, which acts as a dephleg-
mator, by which a first fractionation is effected. The volatile vapours which are not
condensed in N are carried to the apparatus D, which is filled with a solution of
chloride of calcium. This apparatus is kept at a uniform temperature determined by
the thermometer, t, and maintained by the steam-pipe m.
The steam conveyed by the heating pipe escapes by P.
pare pure benzol the chloride of calcium solution is heated to 80°. The vapours which
are conveyed to G are a mixture of benzol, toluol, &c. As the temperature of the
receiver & does not exceed 80°, the vapours of toluol and other homologous
compounds, as xylol, are condensed; while the vapours still uncondensed are carried
to the receivers H, I, and K, losing or depositing there the last traces of the less
volatile hydrocarbons, becoming finally condensed in L, surrounded with cold water,
and trickling down into the carboy, M. The fluid condensed in G, H, I, and K, flows
back into the column N. As the receiver G contains the heaviest oils these are
carried, for the purpose of dephlegmation, to the lower portion of the column, while
the products condensed in ê are conveyed by pipes into the upper portion of
the column. When it is desired to prepare toluol instead of benzol the chloride of
calcium apparatus is heated to 108° to 109°.
H. Caro, A. and K. Clemm, and F. Engelhorn have suggested, instead of making
benzol from coal-tar, it should be extracted from coal-gas by causing this to be passed
slowly through tar-oils which have a higher boiling-point than benzol, toluol, &c., and to
extract by distillation the benzol, &c., from these heavy oils after they have become
saturated. The heavy oils can serve the same purpose again, while as regards the
depreciation of the illuminating power of the gas caused by the withdrawal of the
hydrocarbons, benzol, &c., present in the gas as vapours, the authors suggest the
saturation of the gas with petroleum oil (benzoline). This mode of making benzol is
not yet practised on the large scale.
Nitro-benzol The benzol is converted into nitro-benzol by the aid of nitric acid; the
H
commercial article is a mixture of nitro-benzol, C6 {No₂, nitro-toluol, C,
NO2,
H3
NO2,
and nitro-xylol, C8 NO₂
C. Collas first prepared this substance on the large scale at Paris under the name of
Essence de Mirbane. The apparatus employed formerly for the making of this prepara-
tion was contrived by Mansfield, and consists of a convoluted glass tube, which
towards its top or upper end is bifurcated so as to form two separate tubes fitted
with funnels. Into one of these a continuous stream of benzol, and into the other
strong nitric acid, is caused to flow; and while these liquids are carried downwards
by gravitation through the windings of the tube the combination takes place, and
the warm liquid is so far cooled that it can be collected at the lower end of the tube.
The crude nitro-benzol thus obtained is rendered pure by first washing it with water
and next with a dilute solution of carbonate of soda.
E. Mitscherlich discovered nitro-benzol in 1834, and
DYEING.
573
Para-nitro-benzoic acid, a substance isometric with nitro-benzoic acid, is found in
the washings of the nitro-benzol.
It is preferable, however, to prepare nitro-benzol from a mixture of 2 parts of
nitric acid at 40° Beaumé (sp. gr. 1°384) and 1 part of concentrated sulphuric acid,
the operation being carried on in closed vessels very similar to those in use for
making aniline. The upper part of the apparatus is fitted with a tube for conveying
the nitrous acid fumes to a chimney, while an S-shaped tube connects the apparatus
with the tank containing the acid mixture. The quantity of benzol intended to be
nitrated is introduced into the apparatus at one time; the mixed acids are gradually
poured into the benzol, and the reaction aided by a stirring apparatus. Any benzol
volatilised by the heat generated by the reaction is condensed by an apparatus fitted
to the reaction vessel and is thus saved. The end of the reaction is indicated by
the liquid becoming colourless and being separated into two distinct strata by the
addition of water. The acid is first diluted to 50° B. (sp. gr. 1'532) and the fluids
are separated by decantation. The nitro-benzol is purified by washing with water,
the dilute acid mixture being used either in the making of sulphuric acid or in
other chemical processes, such as the preparation of superphosphates. On E. Kopp's
suggestion nitro-benzol is now made by the aid of a mixture of nitrate of soda and
sulphuric acid. 100 kilos. of benzol yield 135 to 140 of nitro-benzol.
We distinguish three different kinds of nitro-benzol, viz. :—1. Light nitro-benzol,
boiling between 205° and 210°. This is used in perfumery and soap-making in very
large quantities under the name of artificial oil of bitter almonds, or Essence de
Mirbane, sp. gr. = 1'20 (= 24° B.) 2. Heavy nitro-benzol, boiling between 210° and
220°, possessing a peculiar fatty smell. It is not used in perfumery, but chiefly for
the preparation of aniline red; sp. gr. 1*19 (= 28° B.) 3. Very heavy nitro-
benzol, boiling between 222° and 235°, sp. gr. = 1167 58° B.) Of disagreeable
odour, this kind is chiefly used for the preparation of aniline intended for making
aniline blue.
Aniline, The crude aniline used for the preparation of the so-called tar or
aniline colours is essentially a mixture of aniline, CH-N, toluidine, CÂHÎN, and the
pseudo-toluidine discovered by Rosenstiehl, a body isomeric with toluidine. This
kind of aniline is known in the trade as aniline oil. Pure aniline and pure toluidine
only yield pigments under special conditions. Aniline was discovered at Dahme, in
Saxony, by Dr. Unverdorben, in 1826, among the products of the dry distillation of
indigo, and in 1833 Runge, at Oranienburg, near Berlin, discovered its presence in
coal-tar. Runge also discovered that aniline yielded, when brought into contact
with a solution of hypochlorite of lime (bleaching-powder), a beautiful violet colour;
hence the name kyanol (blue colouring oil). Dr. von Fritzsche, St. Petersburg, 1841,
thoroughly investigated the substance obtained by Dr. Unverdorben from indigo,
ascertained its composition, and called it aniline, from anil, the Portuguese term for
indigo. In the year 1842 Zinin found that when nitro-benzol was treated with
sulphuretted hydrogen, there was formed a base which he termed benzidam. The
further researches of O. L. Erdmann and Dr. A. W. Hofmann, brought the fact to light
that Dr. Unverdorben's crystalline, kyanol, benzidam, and aniline were the same
substance, to which the name aniline was then finally given. We owe to the exten-
sive researches of Dr. A. W. Hofmann our present knowledge of aniline and its
compounds.
Coal-tar contains 03 to 0'5 per cent of aniline, but its extraction from tar is
CHEMICAL TECHNOLOGY.
574
attended with so many difficulties that it is preferred to prepare aniline from nitro-
benzol by a reaction discovered by Zinin; that is to say, to bring nitro-benzol into
contact with reducing agents. I molecule of nitro-benzol, C6H5N₂O 123, yields
I molecule of aniline, C6H₂N = 93. In practice it is assumed that 100 parts of nitro-
benzol yield 100 parts of aniline.
Although sulphuretted hydrogen completely reduces nitro-benzol to aniline, the
trade working on the large scale prefers to follow Béchamp's method, the treatment of
nitro-benzol with iron-filings and acetic acid. The apparatus in use for carrying
It
out this operation was devised by Nicholson, and is exhibited in Fig. 268.
consists essentially of a cast-iron cylinder, A, of 10 hectolitres (220 gallons) cubic
capacity. A stout iron tube is fitted to this vessel reaching nearly to the bottom of
the cylinder. The upper part of this tube is connected with the machinery G, while
FIG. 268.

""
the surface of the tube is fitted with steel projections. The tube serves to admit
steam as well as acting as a stirring apparatus. Sometimes, instead of this tube, a
solid iron axle is employed, and in this case there is a separate steam-pipe, D.
Through the opening at K the materials for making aniline are put into the
apparatus, while the volatile products are carried off through E. H serves for
emptying and cleaning the apparatus. The S-shaped tube connected with the
vessel B acts as a safety-valve. When it is intended to work with this apparatus,
there is first poured into it through к 10 kilos. of acetic acid at 8° B. (= sp. gr. 1'060),
previously diluted with six times the weight of water; next there are added 30 kilos.
of iron-filings or cast-iron borings, and 125 kilos. of nitro-benzol, and immediately
after the stirring apparatus is set in motion. The reaction ensues directly, and is
attended by a considerable evolution of heat and of vapours. Gradually more iron
DYEING.
575
is added until the quantity amounts to 180 kilos. The escaping vapours are
condensed in F, and the liquid collected in R is from time to time poured back into
the cylinder, A. The reduction is finished after a few hours. The resulting thick
magma exhibits a reddish-brown colour, and consists essentially of hydrated oxide of
iron, aniline, acetate of aniline, acetate of iron, and excess of iron. Leaving the
acetic acid out of the question, the process may be elucidated by the following
formula:-
C6H5NO₂+H₂O+Fe₂-C6H₂N+Fe2O3.
Nitro-benzol.
Aniline. Peroxide
of iron.
This magma is either first mixed with lime or is put into cast-iron cylinders shaped
like gas-retorts, and submitted to distillation, the source of heat being either an open
fire or steam. The product of this operation, consisting of aceton, acetaniline,
aniline, nitro-benzol, &c., is rectified by a second distillation, care being taken to
collect only the product which comes over between 115° and 190°; but a
product which comes over at between 210° and 220° is very suitable for
the preparation of aniline blue. The aniline oil thus obtained is a somewhat
brown-coloured liquid, heavier than water, and pure enough for the preparation of
the aniline colours. According to Brimmeyer, acetic acid is not necessary, and a
very good result may be obtained by mixing nitro-benzol with 60 parts of pulverised
iron with acidified water (2 to 25 per cent of hydrochloric acid upon the weight of
nitro-benzol), and leaving this mixture to stand in a retort for some three days
before distilling off the aniline oil. In the aniline-oil works of Coblentz Frères, at
Paris, nitro-benzol is reduced by the aid of iron-filings, a portion of which have been
coated with copper by being immersed in a solution of the sulphate.
The composition of the aniline oil-essentially a mixture of aniline, toluidine, and
pseudo-toluidine-depends upon the nature of the benzol and nitro-benzol used for
its preparation. The aniline oil boiling between 180° and 195° (sp. gr. = 1'014 to
I'021 = 2° to 3ºB.) is prepared from nitro-benzols which boil between 210° and 220°,
and the aniline it yields is chiefly used for aniline red; while for aniline blue a very
heavy nitro-benzol is employed, and for aniline violet a nitro-benzol which boils at
210° to 225°. The following table exhibits the boiling-points of the substances which
have been mentioned:-
Benzol
Toluol
Nitro-benzol
...
80°
108°
213°
Nitro-toluol
Aniline
Toluidine
...
...
225°
182°
...
198°
As regards the annual production of aniline oil it is now (1871) 3,500,000 lbs., of
which 2,000,000 lbs. are consumed in Germany, and the remainder in Switzerland,
England, and France
Aniline Colours.
I. Aniline Colours.
The aniline oil serves for the industrial production of the so-called
aniline or toluidine colours:-1. Aniline red. 2. Aniline violet. 3. Aniline blue.
4. Aniline green. 5. Aniline yellow and aniline orange. 6. Aniline brown. 7. Ani-
line black.
Aniline Red. 1. This pigment or dye, also known as fuchsin, azaleine, mauve,
solferino, magenta, roseine, tyraline, &c., is the combination of a base, which
Dr. A. W. Hofmann has named rosaniline, with an acid, usually acetic or hydro-
576
CHEMICAL TECHNOLOGY.
chloric. In Germany and Switzerland fuchsin is the hydrochlorate of rosaniline,
C20H19N3,CIH; while in England the acetate is used, the formula being
C20H19N3,C2H403.
The base rosaniline is a colourless substance, but its readily crystallising salts are
coloured. The composition of this base is expressed by the formula, C20H19N3,H₂O;
and it is formed by the combination of 2 atoms of toluidine with 1 atom of aniline
and the elimination of 4 atoms of H, which become oxidised—
2C,H,N+C6H₂N+30=2H2O+C20H19N3,H₂O,
Accordingly the constitutional formula of rosaniline is:—
C6H4)
2C-H6 N3C20H19N3
H3
According to Rosenstiehl's researches (1869) all the different kinds of fuchsin ot
commerce contain pseudo-rosaniline, a base isomeric with rosaniline.
Aniline red can be obtained from aniline oil by the application of various reagents,
as, for instance:-Chloride of tin, Verguin's method; perchloride of carbon, Hof-
mann and Natanson's methods; pernitrate of mercury, Gerber-Keller;* perchloride
of mercury, Schnitzer; nitric acid, Lauth and Depouilly; antimonic acid, Smith;.
arsenic acid, Medlock, Girard and de Laire; aniline oil, nitro-toluol, hydrochloric
acid and metallic iron, Coupier. 100 parts of aniline oil yield 25 to 33 parts of
crystalline fuchsin.
Notwithstanding the great danger arising from the use of arsenic acid, and the
difficulty of disposing of the very poisonous residues of this mode of preparing fuch-
sin, the majority of the manufacturers of this dye prefer to use the arsenic acid
method. According to Girard and de Laire's method 1 cwt. of aniline oil and 2 cwts.
of hydrate of arsenic acid at 60° B. (= 1'71 sp. gr.) are heated together for 4 to 5
hours at a temperature which should not exceed 190° to 200°. The red fused mass
¡fuchsin mixture or smelting) formed by this operation is broken into small lumps
and then boiled with water, and as soon as the mass is dissolved it is filtered through
felt or linen bags, and the filtrate poured into tanks for the purpose of obtaining
crystals. After the lapse of 2 to 3 days the mother-liquor, a very poisonous liquid,
which covers the crystals, is run off into perfectly water-tight tanks made of stone and
coated with asphalte, and in order to precipitate the arsenic and arsenious acids
there is added a mixture of washed chalk and lime, the ensuing precipitate being
employed for making arsenical preparations.† The crystalline mass is purified by
re-crystallisation. In the French fuchsin works the fused mass is dissolved in
water and hydrochloric acid, and next neutralised with soda. The fuchsin is thus
obtained as a crystalline cake, which is dissolved by being boiled with water, and this
solution allowed to crystallise. The fuchsin thus obtained always contains arsenic
and when it is desired to use a salt of rosaniline for colouring liqueurs and sweet-
meats it is necessary to use a preparation made with either chloride of carbon or
bichloride of mercury.
The salts of rosaniline exhibit by reflected light a green
golden hue; by transmitted light the colour is red. The hydrochlorate of rosaniline
is usually called fuchsin, the acetate, roseine, and the nitrate, azaleine. The solutions
* The fuchsin prepared by the aid of this reagent is known as rubin, and is employed
for dyeing silk and for colouring liqueurs and sweetmeats.
† According to Dr. Bolley, the arsenical fluids obtained can be rendered again fit for use
by distillation with hydrochloric acid. On being diluted with water the arsenious acid
contained in the distillate is thrown down.
DYEING.
577
of these salts in water or in alcohol exhibit a well-known and very magnificent
carmine red. The tinctorial power is exceedingly high, since I kilo. of fuchsin
is sufficient to dye 200 kilos. of wool. The tannate of rosaniline is very difficultly
soluble in water. Fuchsin is the basis of nearly all other aniline colours; for
instance, fuchsin yields violet or blue with aniline oil; fuchsin and iodide of ethyl,
blue or violet. The action of the arsenic acid in the formation of rosaniline may be
represented as follows:-
C20H25N3+3As2O5
C6H-N
2C6H₂N)
Aniline
oil.
=
C20H19N3+3As2O3+3H₂O.
Arsenic Rosaniline. Arsenious Water
acid.
acid.
Aniline Violet, 2. This pigment, also known as aniline purple, anileine, indisine, phena-
nicine, harmaline, violine, rosolan, mauveine, was discovered in 1856 by Dr. W. H.
Perkin, and is prepared by the action of bichromate of potash and sulphuric acid.
This substance has also been prepared by other reactions, for instance, by the treat-
ment of a salt of aniline with a solution of bleaching-powder (Bolley, Beale, Kirk-
ham); with peroxide of manganese (Kay), and peroxide of lead (Price), both in the
presence of sulphuric acid; by the action of permanganate of potash upon a salt of
aniline oil (Williams); by treating aniline oil with chlorine (Smith); with ferri-
cyanide of potassium (Smith); with chloride of copper (Caro and Dale). Indus-
trially, only Dr. Perkin's method with the bichromate and sulphuric acid is used.
The base of the violet thus obtained is mauveine, C2-H24N.
The so-called Violet Impérial obtained by Girard and de Laire by the action
of chromate of potash upon a mixture of aniline oil and hydrochlorate of rosaniline
at 180°, differs from the preceding product, while another violet is obtained according
to Nicholson by heating fuchsin to 200° to 215°. When a salt of rosaniline is heated
with excess of aniline there are formed, before blue colours ensue, violet pigments, of
which, according to Hofmann—
"
The red-violet is monophenyl-rosaniline.
The blue-violet is diphenyl-rosaniline.
This latter yields on being further heated triphenyl-rosaniline or aniline blue.
Accordingly,-
Rosaniline red is
Monophenyl-rosaniline (red-violet) is
Diphenyl-rosaniline (blue-violet) is
Triphenyl-rosaniline (blue)
...
C20H21N3O.
C20H20(C6H5)N3O.
C20H19(C6H5)2N3O.
C20H18 (C6H5)3N3O.
The violet is now named the old or Nonpareil violet; and we have the new
or iodine violet, Hofmann's violet or dahlia colour, distinguished by the presence of
the alcohol radicals, ethyl, methyl, and amyl, instead of phenyl. These new violets
are obtained by heating to 100° or 110° fuchsin with alcohol as a solvent, and
the iodides, or more recently, the bromides, of the alcohol radicals, the mixture
being kept in closed cylindrical vessels. According to the length of time this
reaction is allowed to take place there are formed :—
Monethyl-rosaniline,
Diethyl-rosaniline, or
Triethyl-rosaniline.
The most ethylised base exhibits a blue-violet colour, while the less ethylised
リ
​38
578
CHEMICAL TECHNOLOGY.
exhibits a red hue. The methylated and ethylated violets are far more brilliant than
the phenylated. The Violet de Paris, introduced by Poirrier and Chappat, is the
product of the action of chloride of tin and similar compounds upon the methyl or
ethyl aniline.
Aniline Blue. 3. This colour, also known as azuline and azurine, was first obtained in
1861 by de Laire and Girard by heating together for some hours a mixture of fuch-
sin and aniline oil, and treating the product of this reaction with hydrochloric acid.
The blue pigment produced is known in commerce as bleu de Paris or bleu de Lyons ;
in dry state it is a copper-coloured shining material, not exhibiting green or yellow
by reflection, the characteristic of fuchsin and aniline violet. In order to purify the
auiline blue it is dissolved in strong sulphuric acid, and this mixture heated to 150°
for 1 hours. By the addition of water to this solution the blue is precipitated in a
modified and soluble form and is then called bleu soluble. We quote here the
following methods for preparing this blue:-Rosaniline and aldehyde (Lauth);
rosaniline and crude wood-spirit (E. Kopp); rosaniline and alkaline solution of
shellac (Gros-Renaud and Schäffer), this is termed bleu de Mulhouse; also by oxida-
tion of methylaniline (J. Wolff); rosaniline and bromated oil of turpentine (Perkin);
rosaniline and isopropyl iodide (Wanklyn); rosaniline and ethylen iodide and
bromide (M. Vogel); rosaniline and iodide and bromide of aceton (Smith and Sie-
berg). The conversion of hydrochlorate of rosaniline (fuchsin) by heating with
aniline oil into aniline blue is elucidated by the following formula:—
C20H19N3,CIH+3C6H¬N
Rosaniline salt. Aniline.
C20H16 (C6H5)3N3,HC1+3NH3.
Aniline blue.
C6H4)
Ammonia.
The aniline blue thus prepared is rosaniline, 2C-H6 N3, in which 3 atoms of basic
H3
hydrogen have been substituted by 3 atoms of phenyl, C6H5; or, in other words,
this aniline blue is triphenyl-rosaniline, the hydrochlorate of which is―C38H32N3C1.
When a salt of rosaniline is heated with toluidine, the toluidine blue (tritolyl-
rosaniline), C41H37N3 = C20H16(C7H)3N3. When aniline blue is heated, the products
of the dry distillation contain diphenylamine, C.₂HIN, a white crystalline compound,
which when moistened with nitric acid yields a magnificent blue colour. Diphenyl-
amine and its homologue phenyl-tolylamin, C13H13N, which yields by dry distilla-
tion bleuine, Cз9H33N3, are employed for the preparation of blue pigments. Dr. A.
W. Hofmann found that when rosaniline is heated for a considerable length of time
with iodide of ethyl or iodide of amyl, the result is that the most ethylated or
amylated product (triethyl-rosaniline, or triamyl-rosaniline), yields aniline blue
(iodine blue). Naphthyl also may be introduced into fuchsin to form, according to
Wolff, a brilliant blue colour termed naphthyl blue. Under the names of Bleu de
lumière or Bleu de nuit, is known a blue dye which appears blue in daylight as well
as in artificial light. A blue with a violet hue is known as Bleu de Parme.
Aniline Green. 4. We are acquainted with two varieties of this colour, viz. aldehyde
green and iodine green. The former, also called emeraldine, was discovered in 1863.
by Cherpin, chemist in M. Usèbe's Works at Saint Ouen, and is obtained by
treating a sulphuric acid solution of sulphate of rosaniline with aldehyde. By
cautiously heating this mixture, a deep green pigment is obtained which contains
sulphur; the formula of this compound is, according to Dr. A. W. Hofmann,
C22H27N3S2O. When required for use hyposulphite of soda is added and the
DYEING.
579
compound boiled therewith in water; this solution is used for dyeing silk, and instead
of the soda-salt sulphuret of ammonium or sulphuretted hydrogen may be used.
The green-coloured material can be precipitated by a mixture of common salt and
sodic carbonate, while a mixture of 2 parts of sulphuric acid and 50 to 70 parts of
alcohol is a solvent for this substance. This aniline green is especially beautiful
when seen by candle-light. The other kind of aniline green is the so-called iodine
green, discovered (1863) by Dr. A. W. Hofmann, as a by-product of the manufacture
of the methylated and ethylated rosaniline violets.
Iodine green is obtained by the following process:-1 part of acetate of rosaniline,
2 of iodide of methyl, and 2 of methylic alcohol, are heated together for several
hours under a high pressure, or on the small scale in a sealed tube. When the
operation is finished the result is a mixture of violet and green pigments dissolved in
methylic alcohol. The volatile substances having been driven off by distillation the
mixture of pigments is put into boiling water, wherein the green is completely
dissolved, while the violet remains insoluble; the former is precipitated by a cold
saturated solution of picric acid in water, the ensuing precipitate—picrate of iodine
green—is collected on a filter, rapidly washed with the smallest possible quantity of
water, and after having been partly dried, brought into commerce as a paste
(en pâte). The crystalline iodine green, free from picric acid, has the formula
C25H33N3OI2.
Aniline Yellow.
Aniline Orange.
5. By the preparation of the red-coloured pigments from aniline oil,
there is formed, as well as fuchsin, a resinous substance, from which Nicholson
obtained a brilliant yellow-coloured pigment, the aniline yellow, aniline orange,
aurin, or hydrochlorate of chrysaniline, which dyes wool and silk brilliantly yellow.
Chrysaniline is a base of the formula C20H17N3. The most interesting salt of this
base is the nitrate, which is insoluble in water. The residue of the preparation
of fuchsin is treated with steam, and as soon as a portion of the base has been dis-
solved, it is precipitated by the aid of nitric acid. Schiff obtained aniline yellow by
the action of antimonic acid or hydrated oxide of tin upon aniline; M. Vogel
obtained a yellow pigment by the action of nitrous acid upon an alcoholic solution of
rosaniline. This aniline yellow has the formula, C20H19N2O6; it is soluble in
alcohol, not so in water.
Aniline Black
and Aniline Brown.
6. Aniline black, C¿H-NO6, a deep aniline green formed by the
action of oxidising agents upon aniline oil, was observed as early as 1843 by Dr. J.
von Fritzsche, and was formerly prepared from the residues of the prepara-
tion of aniline violet with bichromate of potash; but now we obtain aniline black by
the action of chlorate of potash and chloride of copper upon hydrochlorate of
aniline, as recommended by Lightfoot. As has been proved by Cordillot, these two
chemical reagents may be replaced by ferricyanide of ammonium; or, according to
Lauth, by freshly precipitated sulphuret of copper. According to Bolley, the last
substance acts by becoming oxidised to sulphate of copper, and simultaneously
carrying oxygen on to aniline. The black made according to this method being
insoluble has to be formed on the woven textile fabrics themselves, and is hence also
called black indigo or indigo black. More recently, again, the so-called Lucas black
(Peterson's black) has been obtained, its most valuable property being that it is
a ready made black, which for its full development only requires a weak oxidation.
It is a black fluid mass consisting of hydrochlorate of aniline and acetate of copper,
which mixed with some starch paste is printed on the fabrics. The black becomes
580
CHEMICAL TECHNOLOGY.
oxidised by exposure to air; the oxidation is rendered more rapid by ageing
the fabrics in a room heated to 40°. Aniline black is used both in dyeing and
printing textile fabrics.
7. Aniline brown (Habana brown) is prepared according to de Laire by heating a
mixture of aniline violet or aniline blue with hydrochlorate of aniline to 240°, until
the mixture becomes brown-coloured The brown thus obtained is soluble in water,
alcohol, and acids, and can be at once employed in dyeing. Another kind of aniline
brown (Bismark brown) is obtained by fusing fuchsin with hydrochlorate of aniline.
Carbolic Acid Dyes.
II. Carbolic Acid Colours.
The portion of heavy coal-tar oil which distils over at 150° to 200°,
consists chiefly of carbolic acid (phylic acid phenol). As brought into commerce by
C. Calvert and Co., C. Lowe and Co., and a great many other eminent firms both in
this country and abroad, carbolic acid is a crystalline mass which becomes slightly
reddened by exposure to air, fuses at 34°, and boils at 186°. It is prepared according
to Laurent's method by treating the heavy oils of tar with alkalies. There are three
homologous phenols in this preparation:—
Carbolic acid, C6H6O,
Cresylic acid, C-H8O.
Phlorylic acid, C8H10O.
Carbolic acid is soluble in 33 parts of water. Calvert's carbolic acid, as used in the
colour-works, is prepared by cooling a mixture of the Laurent acid in water. At +4°
a hydrate of carbolic acid, CáН¿0+H₂O, is separated, and by elimination of water it
becomes pure carbolic acid, which fuses at 41º. While carbolic acid is very largely
used in several degrees of purity for a variety of purposes as an antiseptic, disin-
fectant, &c., more than 50 per cent of all the carbolic acid manufactured is used for
the purpose of preparing the following pigments and dye materials :-
1. Picric acid.
2. Phenyl brown.
3. Grénat soluble.
4. Coralline.
5. Azuline.
Picric Acid. Picric acid, trinitro-phenylic acid, C6H3(NO2)3O, obtained by the action
of nitric acid upon carbolic acid, or better, by treating crystallised phenyl sulphate
of sodium with nitric acid. is a yellow substance crystallising in foliated structure,
difficultly soluble in cold, readily in hot water, and also soluble in alcohol. It is
used for dyeing wool and silk yellow, and with aniline green (iodine green), indigo,
and Berlin blue, it is used for dyeing silk and wool green.*
In France annually some 80 to 100 tons of picric acid are prepared, but the bulk is
used for the manufacture of the picrate gunpowder (see p. 157). The ammonia salt
of the trinitro-cresylic acid is met with in the trade as Victoria yellow as a dye
material. When treated with cyanide of potassium, picric acid yields isopurpuric
acid, while the trinitro-cresylic acid yields with the same cyanide cresyl-purpuric acid
(V. Sommaruga); the potassium and ammonium salts of the respective acids yield the
grenate brown.
* It has of late become usual to employ, instead of pure (non-explosive) picric acid, the
soda salt of that acid, under the name of picric acid and aniline-yellow. This has given
rise to very serious accidents, owing to the highly explosive nature of the salt.
DYEING.
581
Phenicienne. 2. Phenyl brown was first prepared by Roth in 1865 by causing nitro-
sulphuric acid to act upon carbolic acid; the resulting substance, phénicienne or
phenyl brown, is an amorphous powder, a mixture of two pigments, viz., a yellow,
according to Bolley, dinitrophenol, C6H4(NO2)2O, and a black-brown substance
which is similar to the humus compounds. Phenyl brown is used for dyeing wool
and silk.
Grenate Brown. 3. Grénat soluble, which has been very recently introduced by
J. Casthelaz in Paris as a substitute for orseille, is nothing more than the well-
known isopurpurate of potash, which was first discovered by Hlasiwetz, and is
formed by the action of cyanide of potassium upon a solution of picric acid according
to the following reaction, as described by Zulkowsky:—
C6H3(NO2)3O+3KCN+2H2O=C8H4KN5O6+NH3+KCO3.
Picric acid. Cyanide of
potassium.
Isopurpurate
of potash.
Am- Carbonate
monia. of potash.
As Grenate brown when dry is explosive with the least friction, it is kept in the
state of a paste, to which some glycerine is added for the purpose of keeping it moist.
Coralline. 4. Coralline, or pæonine, a scarlet dye material, is formed, according to
Kolbe and R. Schmidt, by heating a mixture of carbolic, oxalic, and sulphuric acids
until the colour has been sufficiently developed. When the reaction is finished the
mass is washed with boiling water for the purpose of eliminating the excess of acid.
The residue is next dried, pulverised, and submitted at 150° to the action of ammonia.
The relation existing between the rosolic acid, discovered in tar by Runge, and
coralline is at present not fully established, but according to Caro's researches these
substances are identical. Rosolic acid may be formed from carbolic and cresylic
acids (as rosaniline is from aniline and toluidine) according to the following
formulæ :-
C6H6O·+2C7H8O=C20H16O3+3H2.
acid.
Carbolic Cresylic
acid.
Rosolic
acid.
Azuline. 5. Azuline (phenyl blue). When coralline is heated with aniline oil (com-
mercial aniline) there is obtained, according to J. Persoz and Guinon-Marnas, a blue
pigment, which is termed azuline, or azurine.
Nitro-benzol.
Pigment directly from It has been attempted to prepare pigments directly from nitro-
benzol. Laurent and Casthelaz state that a red pigment is obtained by keeping a
mixture of 12 parts of nitro-benzol, 24 parts of iron-filings, and 6 parts of hydrochloric
acid for twenty-four hours at the ordinary temperature of the air. There is formed
a solid resinous-like mass, which is first exhausted with water and the solution
precipitated with common salt. The pigment thus obtained is said to be a substitute
for fuchsin, and as such capable of being used as a dye and for calico-printing.
Naphthaline.
III. Naphthaline Pigments.
This material, CroHs, was discovered in the year 1820 by Garden in
coal-tar, and was afterwards the subject of researches by Faraday, A. W. Hofmann,
M. Ballo, and others. According to Berthelot it may be synthetically prepared by
substituting for 2 atoms of hydrogen of the benzol 2 atoms of acetylen (C₂H₂):-
C6H6¬2H+2C₂H₂+C6H4(C2H2)2=C10H8.
Benzol. Acetylen.
Naphthaline.
582
CHEMICAL TECHNOLOGY.
Naphthaline is a crystalline substance, exhibiting rhomboids when in very thin
scales. Its odour is peculiar and somewhat similar to that of storax; it has a burning
taste. When cooled, after having been fused, it appears as a white crystalline mass
having a sp. gr. 1*151. It fuses between 79° and 80°, and boils between 216° and
218°. When treated with nitric acid, naphthaline yields phthalic acid, which accord-
ing to circumstances and by elimination of carbonic acid may be either converted
into benzol or into benzoic acid:*-
There exists between the
a. C8H604-2CO₂=C6H6.
Phthalic acid.
Benzol.
ß. C8H6O4—CO₂=C7H6O2.
Phthalic acid.
derivatives of benzol and naphthaline a great analogy,
which not only extends to the composition and reaction, but even to chemical and
physical properties. The analogy of composition is exhibited by the following
tabulated form:-
Benzol (hydride of phenyl), C6H6.
Nitro-benzol, C6H5(NO2).
Aniline, C6H,N.
Rosaniline, C20H19N3.
Naphthaline (hydride of naphthyl), CroH8.
Nitro-naphthaline, CH(NO2).
Naphthylamine, CroH,N.
Base of the naphthaline red, C30H21N3.
Naphthylamine, C10H9N3, the base which corresponds to aniline, is prepared from
naphthaline in exactly the same manner as aniline is prepared from benzol, by con-
verting naphthaline by the aid of nitro-sulphuric acid into nitro-napththaline, which
is next converted into napthylamine by Béchamp's process (see p. 574). As proved
by M. Ballo (1870) the naphthylamine may be readily eliminated from the reduced
mass, treated with iron and acetic acid, by distilling it with the aid of steam.
Naphthylamine crystallises in white acicular crystals, fuses at 50°, and boils at
about 300°. Its taste is sharp and bitter. It is almost insoluble in water.
Naphthylamine serves for the preparation of the following dyes:-
1. Martius yellow,
2. Magdala red,
3. Naphthaline violet,
4. Naphthaline blue.
Martius Yellow. 1. This pigment, better known in England as Manchester yellow, or
naphthaline yellow, Jaune d'or, is the calcium or sodium compound of binitro-naph-
thalinic acid (C10H6(NO2)2O), obtained by adding to a solution of hydrochlorate of
naphthylamine nitrite of soda until all the napththylamine has been converted into
diazonaphthol. The fluid which contains diazonaphthol is next mixed with nitric
* The large quantity of benzoic acid now consumed in the preparation of some of the
tar colours, and employed for other chemico-technical purposes, is no longer obtained
from the benzoin resin (gum benzoin, as it is often termed); but this acid is prepared
either from hippuric acid present in the urine of horses, or it is a derivative from
naphthaline. The naphthaline-benzoic acid may be prepared by two different methods,
viz.:-1. By converting naphthaline into phthalic acid, and converting this acid, by
heating it with lime, into benzoate of lime, from which, by the addition of hydrochloric
acid, the benzoic acid is set free and precipitated. 2. By converting phthalic acid into
phthalimide, C6H5NO2, and converting this substance by distilling it with lime into benzo-
nitrile, C-H5N, the latter by boiling with caustic soda solution being converted into
benzoate of soda, from which solution the benzoic acid is set free and precipitated by the
addition of hydrochloric acid. In the year 1868 Merz obtained from cyannaphthyl a new
acid, to which the name of naphtoe acid is given (formula C₁1H8O2), a substitute for
benzoic acid.
DYEING.
583
acid and then heated to the boiling point, the binitro-naphthylic acid is thrown down
in yellow acicular crystals. The conversion of naphthylamine into binitro-naphthylic
acid (binitro-naphthol) may be elucidated by the following formulæ :—
a. C10H,N+HNO2=2H2O+C₁0H6N₂.
Naphthylamine.
Diazonaphthol.
B. C10H6N2+2HNO3=2N+H2O+C10H6(NO2)2O.
Diazonaphthol.
Binitro-naphthylic acid.
As proved by M. Ballo, the latter acid may be directly formed by the action of
nitric acid upon naphthylamine. Manchester yellow imparts directly to wool and
silk, without the intervention of any mordant, yellow hues, which may be made
to differ in depth of colour from lemon-yellow to deep golden-yellow. 1 kilo. of the
dry calcium or sodium compound dyes 200 kilos, of wool brilliantly yellow. While
picric acid dye is volatilised by steam, the Manchester yellow perfectly admits of the
operation of steaming. In this country this dye material is frequently employed
for the purpose of modifying the hue of magenta.
Magdala Red. 2. This pigment, naphthaline red, C30H21N3, was discovered in 1867
by Von Schiendl at Vienna, and has been the subject of researches by Durand,
Ch. Kestner, Dr. A. W. Hofmann, and others. It is generated from naphthylamine
by the elimination of 3 molecules of hydrogen from 3 molecules of the base:—
3C10H9N-3H2=C30H21N3.
Naphthylamine. Magdala red.
On the large scale the preparation of Magdala red is effected in two stages. In
the first the naphthylamine is converted into azodinaphthyl-diamine by the action of
nitrous acid:-
a.
a. 2C10H,N+HNO2 = 2H2O+C20H15N3•
Naphthylamine.
Azodinaphthyl-diamine.
In the second stage the azodinaphthyl-diamine is treated with naphthylamine, the
result being the formation of Magdala red.
B. C20H15N3+C10H9N = C20H21N3+NH3.
Azodi- Naphthyl-
naphthyl-diamine. amine.
Magdala
red.
The Magdala red of commerce, a black-brown, somewhat crystalline powder, is the
chloride of a base of the composition described. As regards tinctorial powder Mag-
dala red is not less valuable than fuchsin, while it surpasses the latter in being a
very fast colour. When treated with iodide of methyl and iodide of ethyl, naphtha-
line red yields violet and blue-coloured derivatives.
Naphthaline Violet.
Naphthaline Blue and 3 and 4. Violet and blue naphthaline pigments may be prepared
in various ways; for instance, by phenylising naphthylising, methylising, or
ethylising Magdala red; also by treating naphthylamine with mercuric nitrate
(Wilder), by substituting for hydrogen in aniline and toluidine the radical naphthyl,
CroHy. J. Wolff, as early as 1867, obtained a very brilliant naphthyl blue in
this manner; again, from rosaniline and mono-bromnaphthaline, and from rosaniline
and naphthylamine (M. Ballo). Very recently Blumer-Zweifel as well as Kiel-
meyer have produced naphthylamine violet on cotton and linen fabrics, by treating
584
CHEMICAL TECHNOLOGY.
naphthylamine while present on the woven tissues with chloride of copper, chlorate
of potash, and, in fact, all such reagents as may be employed for the production of
aniline black* (see p. 579).
Anthracen Pigments.
IV. Anthracen Pigments.
Anthracen (para-naphthaline, photen), C14Hro, is present in coal-
tar to an amount of 0'75 to 1'0 per cent, and was discovered by J. Dumas in 1831,
while in 1869 it was first employed by Graebe and Liebermann for the purpose
of obtaining anthracen red or artificial alizarin. Anthracen occurs in that portion
of the products of the distillation of coal-tar which being rather thick are known
in this country by the designation of green grease, and, as such, used as a
coarse lubricating material. The green grease consists of heavy oils, some
naphthaline, and about 20 per cent of anthracen. By means of the hydro-
extractor, and by submitting the raw material to strong pressure, crude (con-
taining 60 per cent pure) anthracen is obtained. This raw material is purified by
being treated with benzoline (petroleum spirit), aided by heat, and again aided
by the centrifugal machine, fusion, and sublimation, these operations resulting at last
in the production of pure anthracen. This substance then appears as small foliated
crystals, white, void of odour, fusing at 215°, and subliming at a higher temperature
without decomposition. This body is sparingly soluble in alcohol and benzol, more
readily in sulphide of carbon. With picric acid it yields a compound exhibiting ruby-
red crystals; while under the influence of oxidising agents it is converted into
anthrachinon (oxanthracen, oxyphoten), C4H8O2, which in its turn is converted into
alizarine, C4H8O4, by a circuitous process.
'14·
According to the original method of preparing alizarine, the anthrachinon,
C₁H8O2, obtained from anthracen by the action of oxidising agents, such as nitric
acid, was first converted into bibromide of anthrachinon, C₁4H6Br₂O₂, by treating
anthrachinon with bromine, and this bromated compound was further treated either
with caustic potash or caustic soda at a temperature of 180° to 200°, the bibromide of
anthrachinon becoming converted into alizarine potassium (or alizarine sodium,
if caustic soda has been used), from which the alizarine is set free by the addition of
hydrochloric acid :-
a. C14H6Bг₂O₂+KOH= C14H6K2O4+2BrK+2H₂O.
Anthrachinon.
Bibromide of
ß.
Alizarine
Potassium.
B. C₁₁H6K₂O4+2CIH = C14H8O4+2CIK.
Alizarine
Potassium.
Alizarine.
Alizarine is now prepared from anthrachinon by treatment at a temperature of
260° with concentrated sulphuric acid of 184 sp. gr., the anthrachinon being
converted into a sulpho-acid; this acid is next neutralised with carbonate of lime, the
fluid decanted from the deposited gypsum, and carbonate of potash added to it for the
* It is evident that by combining suitable aniline, naphthyl, and cetyl compounds, the
greatest variety of blue and violet pigments may be prepared. The following blue
pigments were obtained in the summer of 1867, these researches being undertaken in con-
sequence of the results obtained by J. Wolff in the same direction. 1. Fuchsin and
bromide of naphthyl. 2. Fuchsin and cetyl bromide. 3. Naphthylamine, fuchsin, and
aniline oil. 4. Cetylamine, fuchsin, and aniline oil. 5. Naphthylamine, fuchsin, and
cetylamine. 6. Cetylamine, fuchsin, and naphthylamine.
DYEING.
585
purpose of precipitating all the lime. The clear liquid is then evaporated to
dryness, the resulting saline mass is converted into alizarine-potassium by heating it
with caustic potash. From the alizarine-potassium thus obtained the alizarine is set
free by the aid of hydrochloric acid. According to another method, the preparation
of anthrachinon is avoided, and anthracen employed directly, by first converting it—
by the aid of sulphuric acid and the application of heat-into anthracen sulpho-
acid, C28H18SH403. After having been diluted with water, the solution of this acid
is treated with oxidising agents (peroxides of manganese, lead, chromic acid, nitric
acid), and the acid fluid is next neutralised with carbonate of lime. When peroxide
of manganese has been used the manganese is also precipitated as oxide. The
oxidised sulpho-acid having been previously converted into a potassium salt, the
latter is heated with caustic potash, alizarine-potassium being obtained.
There is no doubt that anthracen may be converted into alizarine by other means;
and it is very likely that from other hydrocarbons (benzol, toluol, naphthalin) present
in coal-tar, anthracen and anthracen red may be obtained.
The industrial manufacture of artificial alizarine, carried on in the first place by
the inventors of this process-Graebe and Liebermann; and taken up by J. Gessert,
at Elberfeld; Brönner and Gutzkow, at Frankfort-on-Maine; Brüning, at Höchst
(near Wiesbaden); Greiff, at Cologne; and by Perkin, in London-is one of the
brightest pages in the history of chemical technology. Although for the present
anthracen red cannot compete with madder, it will, in all probability, become in
a very great measure a substitute for that dye-stuff and garancine.
Cinchonine Pigments,
V. Pigments from Cinchonine.
The preparation of pigments from cinchonine-an almost waste
by-product of the manufacture of quinine on the large scale--may be conveniently
considered as an appendix to the coal-tar colours. Cinchonine is submitted to
distillation with hydrate of soda in excess, the resulting product being about
65 per cent crude chinoline (chinoline oil), a mixture of the three following homo-
logous bases :-
Chinoline
Lepidine
...
Kryptidine or dispoline
Lepidine is the chief constituent of this mixture.
:
C₂H,N.
CIOH,N.
CITHIN.
When chinoline oil is heated with iodide of amyl the result is the formation
of amyl-lepidin-iodide, which on being treated with caustic soda solution, yields a
very brilliant blue pigment—cyanine, lepidine blue, or chinoline blue, C30H39N2I. This
substance is a crystalline compound, exhibiting a metallic green gloss and golden
yellow hue; it is difficultly soluble in water, readily in alcohol. The formation of
cyanine may be elucidated by the following formulæ :-
a. C10H₂N+C5H11I = C15H20NI.
Lepidine. Iodide of Amyl-lepidin-
Amyl. iodide.
ß. 2C15H20NI+NaOH= C30H39N₂I+CaI+H₂O.
Amyl-lepidin-
iodide.
Cyanine
;
586
CHEMICAL TECHNOLOGY.
Red Dre Materials,
Madder.
Red Pigments occurring in Plants and Animals.
Madder is the root of the Rubia tinctorum, a perennial plant
cultivated in Southern, Central, and Western Europe; while in the Levant the
R. peregrina, and in the East Indies and Japan the R. mungista (mungeet),
are partly cultivated, partly met with in the wild state. According to the researches
made in England, the dye imported under the name of mungeet from India is
not the root, but the reedy stem of a species of Rubia, and as a dye it is inferior. The
native country of the madder plant is the Caucasus. All these plants are perennial.
The root varies in length from 10 to 25 centims.; it is not much gnarled, and is
generally a little thicker than the quill of a pen. Externally the root is covered with
a brown bark; internally it exhibits a yellow-red colour. Madder is met with in the
trade in the root (technically racine if European), and in powder exhibiting a
red-yellow colour, and possessing a peculiar odour. Avignon madder, however, has
hardly any smell at all; but the odour is particularly marked in Zeeland, or so-called
Holland, madder. The powdered madder is always kept in strong oaken casks, so
as to exclude air and light. The best kind of madder is that grown in the
Levant (Smyrna and Cyprus), and met with in the trade under the name of lizari or
alizari, in roots which are usually rather thicker than the roots of the European
varieties, owing partly to the fact that the Levant madder is generally of four to five
years' growth, while in Europe the roots are of two to three years' growth only.
Dutch madder, chiefly grown in the province of Zeeland, is met with decorticated
(robé), the outer bark and sometimes the splint bark having been removed. The well
dried roots are broken up by means of wooden stampers moved by machinery, to
reduce the bark and splint bark to powder, while the very hard internal portion of
the root is left untouched, this being separated from the powder by means of sieves.
The powder is put into casks and termed beroofde. During the last ten or twelve
years, the old madder sheds (meestoven) in Zeeland have been superseded by large
manufactories, in which the madder root is treated as it is in the Vaucluse (France),
and ground up entirely, so that the former distinct qualities of madder are no longer
met with. When the whole root is pulverised the madder is termed onberoofile, non
robé. Besides the Dutch madder, that from Alsace and from the Vaucluse,
Avignon, occur very largely in the trade. What is known as mull madder is the
refuse and dust from the floors of the works, and is the worst quality. In addition to
colouring matter, madder contains a large quantity of sugar, of which W. Stein (1869)
found as much as 8 per cent. While it was formerly considered that madder
contained no less than five different colouring substances, it appears from recent
researches that this root in fresh state only contains two pigments, viz. rube-
rythrinic acid (formerly termed xanthin), and purpurine. According to Dr. Rochleder,
the former of these is converted under the influence of a peculiar nitrogenous
substance present in the madder root into alizarine—the essential colouring matter of
madder-and into sugar:-
C20H22O11 = C14H8O4+C6H12O6+H₂O.
Ruberythrinic Alizarine.
acid.
Sugar.
According to the researches of Graebe and Liebermann, alizarine is a derivative
from anthracen, C14H10, the formula of the former being C14H8O4. As already men-
tioned (see p. 585), Graebe and Liebermann have succeeded in converting anthracen
DYEING.
587
into alizarine (1869). Alizarine is yellow, but becomes red under the influence of
alkalies and alkaline earths. Madder contains a red pigment, purpurine, or
rubiacine, C14H8O3, which by itself, as well as in combination with alizarine, yields
a good dye.
Madder Lake. We understand by this term a combination of alizarine and purpurine
(the colouring matter of madder) with basic alumina salts. Madder lake is prepared
by first washing madder with water, distilled or at least free from lime salts,
and next exhausting the dye-stuff with a solution of alum, the liquor thus obtained
being precipitated with carbonate of soda or borax. The bulky precipitate having
been collected on a filter is thoroughly washed and dried.
Flowers of Madder. The preparation made from madder on the large scale and known
in the trade as flowers of madder (fleur de garance), is obtained from the pulverised
madder by steeping it in water, inducing fermentation of the sugar contained in it,
and next thoroughly washing the residue, first with warm, next with cold water. The
residue after subjection to hydraulic pressure to remove the water, is dried at a gentle
heat, and having been pulverised again is used in the same manner as madder for
dyeing purposes. The operation of dyeing with the flowers of madder requires a
less elevated temperature of the contents of the dye-beck. It would appear that by
the preparation of the flowers of madder the pectine substances of the root are
eliminated which otherwise become insoluble during the operation of dyeing.
Azale. When flowers of madder are treated with boiling methylic alcohol (wood-
spirit), the solution obtained filtered, and water added to the filtrate, a copious yellow
precipitate is obtained, which having been washed with water and dried constitutes
the material known as azale (from azala, Arabian for madder), which has been
suggested for use as a dye material in France. Probably this substance is crude
alizarine; as obtained from madder or garancine it is met with in the trade sometimes
under the name of Pincoffine, having been first discovered and prepared by Mr.
Pincoffs, at Manchester.
Garancine. This preparation of madder contains the colouring principles of the root
in a more concentrated, pure, and more readily exhaustible state. In order to
prepare garancine, madder (generally this term is given to the pulverised root) is
first moistened uniformly with water, and next there is added part of sulphuric
acid diluted with I part of water. This mixture is heated by means of steam
to about 100° for one hour, and the magma then thoroughly washed with water
for the purpose of eliminating all the acid. This having been done the garancine
is submitted to hydraulic pressure for the purpose of getting rid of the greater part
of the water, after which the material is dried and lastly ground to a very fine
powder. By the action of the sulphuric acid, some of the substances contained
in madder and more or less interfering with its application as a dye, are eliminated
by the washing of the garancine, while the colouring matter remains mixed with the
partly carbonised organic substances. As regards its tinctorial value I part of
garancine may be taken as equal to 3 to 4 parts of madder. As madder when
employed in dyeing does not become quite exhausted, the fluids of the dye-beck are
Garanceux. strained from the solid residue, and this is treated with half of its weight
of sulphuric acid. The mass is next treated as has been described under Garancine,
and constitutes after drying what is known as garanceux, being used generally for the
production of what are termed sad colours (black, deep brown, lilac). As a matter of
course garanceux is of less tinctorial value than garancine.
588
CHEMICAL TECHNOLOGY.
Colorine. The substance met with in commerce under the name of colorine is the
dry alcoholic extract of garancine, and consists essentially of alizarine, purpurine,
fatty matter, and other substances soluble in alcohol present in garancine. E. Kopp
commenced some years since to exhaust madder with an aqueous solution of
sulphurous acid, thereby obtaining the pigments of madder in a (for technical pur-
poses) pure condition. These preparations, which are already extensively used, are
distinguished as:-Green alizarine (Alizarine verte), which from Alsace madder
is obtained to an amount of about 3 per cent, containing with the alizarine a green
resinous material; yellow alizarine (Alizarine jaune), the former substance without
the resinous material, this having been eliminated by suitable solvents, as purpurine
and flowers of madder. The tinctorial value of purpurine amounts to 10 times, and
that of the green and yellow alizarine to 32 to 36 times, that of madder. Madder of
good quality yields on the large scale :-
Purpurine
Green alizarine
Yellow alizarine
Flowers of madder
:
1*15 per cent.
2'50
""
0'32
""
...
39'00
""
:
Brazil or Camwood.
By this name are designated several varieties of wood belonging
to the Casalpinia, and used for dyeing purposes. The best kind is the so-called
Pernambuco or Fernambuco wood, obtained from the Casalpinia brasiliensis s. crista ;
externally it is yellow-brown, internally its colour is a bright red, while the wood
is heavy and rather hard. Its name is derived from that of the state of the Brazilian
Empire, in which the tree grows abundantly. It is met with in commerce in chips
and large logs. The sapan wood obtained from Japan, and derived from the
(C. sapan) is an inferior kind, while the varieties known as Lima or Nicaragua wood,
or Bois de Ste. Marthe (C. echinata), and the brasilet wood (C. vesicaria), are all of
less value. All these kinds of wood contain a colouring matter termed brasiline,
(according to Bolley the formula is C44H40014+3H2O), a colourless substance,
crystallising in small acicular crystals, the aqueous solution of which turns gradually
carmine-red by exposure to air, a change brought on almost instantaneously either
by boiling the solution or by the action of alkalies. Brazil wood is used in dyeing
for the production of a beautiful red colour, which is not fast. This wood is also used
for the preparation of round lac, for which purpose, however, the red and violet tar-
colours are now more often employed. Red ink is commonly made with brazil wood
according to the following recipe :-Brazil wood, 250 grms.; alum, 30 grms.; cream
of tartar, 30 grms.; water, 2 litres. Boil down to 1 litre, strain the liquid, and next
add of gum arabic and sugar candy each 30 grms. A better red ink is obtained by
dissolving 2 decigrammes (4 grains) of carmine in 1827 grms. (5 drms.) of liquid
ammonia, and adding a solution of 1 grm. (18 grains) of gum arabic in 2 fluid ounces
of water. Red inks are now frequently prepared from solutions of fuchsin to which
some gum and alum are added, or by dissolving commercial aurine, a modification
of rosolic acid, in a solution of carbonate of soda.
*
Sandal Wood. There is a red and a yellow variety of this wood in commerce. The
red wood is derived from Pterocarpus santalinus, a tree growing in Ceylon and other
parts of India. The wood is imported in logs exhibiting a straight fibrous texture,
and externally a deep red, internally a bright red. The colouring matter contained
in this wood is of a resinous nature and is named santaline. According to the
DYEING.
589
researches of H. Weidel (1869), sandal wood contains a colourless body, santal,
C§H6O3, which appears to be converted by oxidation into santaline. Sandal wood is
used for the preparation of coloured lakes, coloured furniture polish, for dyeing wool
brown, dyeing leather red, as a pigment in tooth powders, &c. The same pigment is
found in barwood, derived from Baphia nitida, an African tree; this wood is said to
contain no less than 23 per cent of santaline, while sandal wood only contains
16 per cent of this substance.
Safflower. The drug to which this name is given consists of the dried petals of the
flowers of the Carthamus tinctorius, a thistle-like plant belonging to the family of the
Synanthereæ, a native of India, and cultivated in Egypt, the southern parts of
Europe, and also to some extent in parts of Germany. Safflower contains a red
matter. carthamine, insoluble in water, and also a yellow substance soluble in
that liquid. The quality of this drug is better according to its greater purity from
mechanical admixtures, such as seeds, leaves of the plant. Carthamine, C14H1607, or
Rouge végétal, is prepared in the following manner :-The safflower is exhausted
with a very weak solution of carbonate of soda, and in this fluid strips of cotton-
wool are dipped, after which the strips are immersed in vinegar or very dilute
sulphuric acid for the purpose of neutralising the alkali. The red-dyed cotton strips
are next washed in a weak solution of carbonate of soda, and the solution thus
obtained is precipitated with an acid; the carthamine thrown down is first carefully
washed, and next placed on porcelain plates for the purpose of becoming dry.
Carthamine when seen in thin films exhibits a gold-green hue, while when seen
against the light the colour is red. When carthamine has been repeatedly dissolved
and precipitated it is termed safflower-carmine. Mixed with French chalk (a
silicate of magnesia), carthamine is used as a face powder. Safflower is used for
dyeing silk, but the red colour imparted is, although brilliant, very fugitive.
Cochenille, or Cochineal, This substance is the female insect of the Coccus cacti, found on
several species of cacti, more especially on the Nopal plant and the Cactus opuntia.
This insect and the plants it feeds on are purposely cultivated in Mexico, Central
America, Java, Algeria, the Cape, &c. The male insect, of no value as a dye
material, is winged, the female wingless. The female insects are collected twice
a year after they have been fecundated and have laid eggs for the reproduction
of young, and are killed either by the aid of the vapours of boiling water or more
usually by the heat of a baker's oven. Two varieties of cochineal are known in
commerce, viz., the fine cochineal or mestica, chiefly gathered in the district of
Mestek, a province of Honduras, on the Nopal plants there cultivated; and the wild
cochineal, gathered from cactus plants which grow in the wild state. This latter
variety is of inferior quality. Cochineal appears as small deep brown-red grains, at
the lower and somewhat flattened side of which the structure of the insects is some-
what discernible. Sometimes the dried insect is covered with a white dust,
but frequently the material is met with exhibiting a glossy appearance and
black colour. The white dust, very frequently fraudulently imparted by placing the
grain with French chalk or white-lead in a bag, is according to the results of
microscopical investigation, the excrement of the insect, exhibiting when seen under
the microscope the shape of curved cylinders of very uniform diameter and a white
colour. Cochineal contains a peculiar kind of acid-carminic acid-which, by the
action of very dilute sulphuric acid and other reagents, is split up into carmine-red
(carmine)—also present in the insect, together with the acid-and into dextrose :-
590
CHEMICAL TECHNOLOGY.
C₁₂H18010+3H₂O = С₁₁Н₁₂O₂+C6H12O6
17.
Carminic
acid.
ΙΟ
Carmine-
red.
Dextrose.
What is commonly termed carmine is prepared by exhausting the cochineal with
boiling water; to the decanted clear fluid alum is added, after which it is left
standing. By another method carmine is prepared by exhausting the pulverised
cochineal with a solution of carbonate of soda, white of egg is next added to
this solution for the purpose of clarifying it, and afterwards the solution is precipi-
tated with an acid. The washed precipitate is next dried at 30°. So prepared,
a finer and better kind of carmine is obtained, but the common carmine-carmine
lac and round lac-is prepared by treating an aluminous solution of cochineal with
carbonate of soda; the larger the quantity of alumina contained in these preparations,
the coarser the quality.
Lac Dye.
This dye-stuff is obtained from a resinous substance, stick or grain lac,
or gum resin, and is derived from a variety of the cochineal insect in the following
manner-The Coccus lacca, a native of India, pierces the branches of certain kinds
of fig-trees from which a milky juice exudes, which, while becoming inspissated,
encloses the insects and at last forms a hard resinous mass tinged with the dye-stuff
contained in the insects. This pigment is extracted from the resinous matter by
means of a solution of carbonate of soda, and the solution obtained is precipitated by
alum solution. The lac dye is not very different from cochineal. The dye materials
contained in kermes (Coccus ilicis), Coccus polonicus, and Coccus fabæ are similar to
that contained in cochineal, but are now quite obsolete; even cochineal is far less
used since the coal-tar colours have been introduced.
Orchil and Persio. By orchil, persio, and cudbear, we designate red dye-stuffs which are
met with in commerce in pasty masses. Orchil is prepared from several kinds of
sea-weed, Roccella tinctoria, R. fuciformis, R. Montagnei, Usnea barbata, Usnea
florida, Lecanora parella, Unceolaria scruposa, Ramalina calicaris, Gyrophora
pustulata, and others, which having been well dried, are first ground to a
very fine powder. This is mixed with urine and left to enter into putrefactive
fermentation. The carbonate of ammonia formed by the decay of the urine acting
upon the peculiar acids-lecanoric, alpha and beta orcellic, erythrinic, gyrophoric,
evernic, usninic, &c.-contained in these sea-weeds converts these non-nitrogenous
substances into orcine, C-H8O2, this reaction being accompanied by the elimination
of water, and usually also with the elimination of carbonic acid. By taking up
nitrogen and oxygen orcine is converted into orceine, CH-NO3, constituting the
essential colouring matter of orchil. This substance appears as a red paste, exhi-
biting a peculiar violet odour (viola odorata) and an alkaline taste. Before the coal-
tar colours were discovered, this dye material was prepared chiefly in England and
France, from weeds imported from the Canary Islands, or collected on the Pyrenees
and imported from Lima and Valparaiso. Persio, cudbear, or red indigo, is much
the same kind of product as orchil; the former was formerly prepared in Scotland
from sea-weeds found on the coast. At a later period it was made in large quantity
in Germany, in France, and in England. Persio was a red-violet powder. Some
ten years ago two preparations of orchil were brought into commerce under the
names of orchil carmine and orchil purple (pourpre Français). These substances
contained the orchil dyes in a very pure condition, Since the tar-colours have made
DYEING.
591
their appearance, the dyes obtained from the sea-weeds, very beautiful but very
perishable colours, have in a great measure become obsolete.
Less Important Red Dyes. Among the less important red dyes and colouring matters are the
alkanet root (Anchusa tinctoria); dragon's blood, a red-coloured resin from Dracaena
draco; harmala red from the seeds of the Peganum Harmala, a plant growing in the
Steppes of Russia; Chica red, or carajura, from the leaves of the Bignonia chica, a tree
growing in Venezuela; purple-carmine, or murexide, obtained from uric acid by treating
it with oxidising substances (nitric acid for instance) and next with ammonia.
Blue Dye Materials.
Indigo.
Blue Dye Materials.
Indigo is the chief blue dye. Although known to the Romans and
Greeks, who used it for painting purposes, it was not used as a dye stuff in Europe
until about the middle of the sixteenth century. Indigo is a substance which is
widely dispersed in the vegetable kingdom. It is found in large quantity in the
leaves of several species of the anil plants, Indigofera, belonging to the family of the
Papilionacea. Indigo is also met with in woad, Isatis tinctoria, Nerium tinctorium,
Marsdenia tinctoria, Polygonum tinctorium, Asclepias tingens, &c. The indigo is not
met with in the plants ready formed, but is generated when the freshly-pressed juice
of the plant is exposed to the action of the atmosphere.
According to the results of a series of experiments, it appears that in the living
plant the colourless pigment is present in combination with a base, lime or an
alkali. Dr. Schunck states that the indigo plant contains a material which he has
termed indican, which either by fermentation or by the action of strong acids is
converted into indigo blue and a peculiar kind of sugar, indigo glycine, according to
the following formula :—
C52H62N2034+4H₂O+C16H10N2O3+6C6H10O6.
Indican.
Indigo blue. Indigo glycine.
The indigo of commerce is prepared from the indigo plants in the East and West
Indies, Southern and Central America, Egypt, and other parts. In Hindostan indigo
is prepared from the Nerium tinctorium. The following five varieties of the indigo
plant are more particularly employed for the preparation of this dye material; the
plants are:-Indigofera tinctoria, I. anil, I. disperma, I. pseudotinctoria, and
I. argentea. The plant requires a warm climate and a soil so situated that it is not
liable to become inundated. When the plants have grown to maturity they are cut
down with a sickle close to the soil and transferred to the factory, where the indigo
is extracted from the plant by the following process:-The factory is fitted with large
water tanks, filtering apparatus, presses, a cauldron, drying-room, and, lastly, with
fifteen to twenty tanks of brickwork laid in hydraulic cement and plastered inside
with the same material. Into these tanks the branches, twigs, and the leaves
are placed, and water is run in, care being taken to force the green plants
down under the water by the aid of stout wooden balks wedged tight against
the sides of the tanks. At the usual high temperature of the air in the
tropical regions fermentation soon sets in, and the liquid contained in the tanks
assumes a bright straw-yellow or golden-yellow colour, a large quantity of gas is
evolved, and after a lapse of nine to fourteen hours, the liquid, having become of a
deeper yellow hue, or almost the colour of sherry wine, is run from the fermenting
tanks into a very large tank of similar construction, into which, when as full as may
be judged convenient, a number of workmen enter, provided with long bamboo poles,
592
CHEMICAL TECHNOLOGY.
and commence stirring the fluid vigorously for the purpose of exposing it as much
as possible to the action of the air. During this operation, continued for some two
or three hours, the colour of the liquid gradually changes to pale green, and the
indigo may then be seen suspended in the liquid in very small flocks. The liquid is
then left to stand, and the suspended matter gradually subsiding, the water is
gradually run off by the aid of taps or plugs fitted into the tank at different
heights. At last the somewhat thick, yet fluid, precipitate of indigo is run into a
cauldron, where it is boiled for about twenty minutes in order to prevent it fermenting
a second time, for by this second fermentation it would be rendered useless. The
magma is left in the cauldron over night and the boiling resumed next day
and then continued for three to four hours, after which the indigo is run on to large
filters, consisting first of a layer of bamboo, next mats, and on these stout canvas, all
placed in a large masonry tank. Upon the canvas is left a thick, very deep blue,
nearly black paste, which is thence taken and put into small wooden boxes,
perforated with holes and lined with canvas; a piece of canvas is put on the top of
the paste, and next a piece of plank is fitted closely into the box. So arranged, a
number of these are placed under a screw-press for the purpose of eliminating, by a
gradually increased pressure, the greater portion of the water, and thus to solidify the
pasty material. On being removed from these boxes the cakes of indigo are trans-
ferred to the drying-room, and there, daylight and direct sunlight being carefully
excluded, gently dried by the aid, in some cases, of artificial heat. In order to
prevent the cracking of the cakes, the drying has to be effected very gently, and lasts
usually for some four to six days. The dried cakes of indigo are next packed in stout
wooden boxes and then sent into the market. The exhausted plants are used for a
manure, for although the boughs on being planted in the soil would again grow, they
would not yield either in quality or quantity enough indigo to pay the expenses of
culture. 1000 parts of fluid from the fermenting tanks yield o°5 to 0.75 parts of indigo.
Properties of Indigo. The indigo met with in commerce exhibits a deep blue colour,
dull earthy fracture, and when rubbed with a hard substance (the better kinds of indigo
even when rubbed with the nail of the thumb), give a glossy purplish-red streak. In
addition to a larger or smaller quantity of mineral substances, indigo contains a
glue-like substance, or indigo glue; a brown substance, indigo brown; a red pigment,
indigo red; and the indigo blue, or indigotine, C16H10N2O3, the peculiar dye
material for which the drug is valued. The quantity of indigo blue contained in the
several kinds of indigo of commerce varies from 20 to 75 and 80 per cent, and
averages from 40 to 50 per cent. Indigo may be purified according to Dumas's
process by digestion in aniline, whereby the indigo red and indigo brown pigments are
dissolved and eliminated. According to Dr. V. Warther (see "Chemical News,"
vol. xxiii., p. 252), Venetian turpentine, boiling paraffin, spermaceti, stearic acid, and
chloroform, are, at high temperatures, solvents for indigo blue. (See also "Chemical
News,” vol. xxv., p. 58, “ On the Solubility of Indigo (Indigotine) in Phenic Acid.”)
Testing Indigo. The quality of indigo is ascertained by its deep blue colour and light-
ness (see "Chemical News," vol. xxiv., p. 313). G. Leuchs found that in forty-nine
samples of this material the best contained 60.5 per cent, the worst 24 per cent of
indigotine, the specific gravity of the former being low and of the latter high. Indigo
should float on water, and when of good quality it should not, on being broken to
pieces, deposit at the bottom of the vessel filled with water in which it is contained
a sandy or earthy sediment. On being ignited, indigo should leave only a compara-
DYEING.
593
tively small quantity of ash. When suddenly heated, indigo should give off a
purplish-coloured vapour, sublimed indigotine, and the drug should be perfectly
soluble in fuming sulphuric acid, yielding a deep blue fluid. That kind of indigo
which on being rubbed with a hard body exhibits a reddish coppery hue is termed
coppery-tinged indigo, indigo cuivré. In order to test indigo more accurately, a
weighed portion is dried at 100' for the purpose of ascertaining the quantity of
hygroscopic water contained, which should not exceed from 3 to 7 per cent.
Next the dried indigo is ignited for the purpose of ascertaining the quantity of ash it
yields. For good qualities of the drug this amounts to 7 to 9.5 per cent. Numerous
methods have been proposed by practical dyers as well as by scientific men for the
purpose of ascertaining the value of indigo; that is to say, the quantity of
indigotine it contains. Some of these processes are either too tedious, and cause
great loss of time, or are not sufficiently exact. A commercial sample of indigo may
be treated first with water, next with weak acids, then with alkaline solutions and
alcohol, and the ash and hygroscopic water having been estimated, the residue of
the different operations will be the indigotine, the process being based upon the
insolubility of the latter in the different solvents used for the removal of the impuri-
ties met with in the sample under examination. Mittenzwei proposes to reduce the
indigo by means of an alkali and protosulphate of iron, to pour over the surface of
the liquid a layer of petroleum oil for the purpose of excluding air, to take by the
aid of a curved pipette a known bulk of the indigo-containing fluid, and to introduce
this fluid at once into a test-jar placed over mercury, and containing a known and
accurately measured bulk of pure oxygen. As I grm. of white indigotine (soluble)
requires for its conversion into blue (insoluble) indigotine 45 c.c. of oxygen, the
quantity of gas absorbed gives the quantity of indigotine. This method yields very
correct results, but requires an experienced manipulator.
Berzelius's Indigo Test
by Reduction.
Take 5 grms. of pure quick-lime prepared from white marble or
from well-washed oyster-shells, put the quick-lime into a porcelain mortar, and mix
the lime with sufficient water to form a thin milk of lime; next take 5 grms. of the
sample of indigo very finely powdered, and add it to the milk of lime, mixing
thoroughly, and then pouring the fluid into a flask capable of containing 1200 c.c.
Rinse the mortar with water so as to make up a bulk of 1 litre, next add to the
contents of the flask 10 grms. of crystallised sulphate of iron, and immediately after
cork the flask and let it stand for several hours in a moderately warm place or on a
sand-bath, taking care to shake the vessel frequently. After the liquid has become
cool and the sediment deposited, a small syphon of known cubic capacity is filled
with distilled water, and by the aid of this instrument 200 c.c. of the fluid contained
in the flask are transferred to a beaker-glass. Some pure hydrochloric acid having
been added to the fluid, it is left to be acted upon by the air until the reduced and
soluble indigotine has become insoluble and blue-coloured. The precipitate is
collected on a tared filter, well washed, dried, and next weighed. This weight cor-
responds to the quantity of pure indigo blue present in 1 grm. of the sample.
Penny's Test.
This test is based upon the application of bichromate of potash and
hydrochloric acid. 10 parts of finely-pulverised indigo are digested with twelve times
its weight of fuming sulphuric acid at a temperature not exceeding 25° for a period
of twelve hours. When the indigo has been entirely dissolved the fluid is poured
into 1 pint (= 0.568 litre) of water, next 24 grs. of concentrated hydrochloric acid are
added, and the fluid is then gently heated, after which it is titrated with a solution
39
594
CHEMICAL TECHNOLOGY.
of bichromate of potash in water, this solution being added as long as a drop of the
fluid taken with a glass rod and placed on a piece of white filtering-paper exhibits a
trace of green or blue colouring matter. The operation is finished when the liquor
tested exhibits a bright brown or ochrey-yellow speck upon the filtering-paper.
8 parts of bichromate are required for decolourising 10 parts of pure indigo blue.
Chloride of iron may be used for converting indigo blue into isatine. Probably the
observation made by Stockvis at Amsterdam (1868), that indigo blue is soluble in
chloroform, might be rendered available for the testing of indigo.
Indigo Blue.
This substance, also known as indigotine, may be obtained from the
indigo of commerce, either by carefully conducted sublimation, or, as already stated,
by treating indigo with lime, protosulphate of iron, and water. The formula of
indigo blue is C16H10N2. When indigo blue is, in the presence of alkaline substances,
brought into contact with bodies which readily absorb oxygen-for instance, with
protosulphate of iron, sulphites, &c.—there is formed, with simultaneous decomposition
of water, white indigo or reduced indigo, C16H12N2O2. The use of indigo as a dye
material is in great measure based upon this reduction. By the action of oxidising
substances, such as permanganic acid, chlorine, chromic acid, a mixture of
so-called red prussiate of potash (ferricyanide of potassium) with potash, soda, oxide
of copper, &c., indigo blue is converted into isatine, C16H10N2O4. Indigo blue
dissolves in concentrated sulphuric acid, but becomes thereby radically changed and
cannot be brought back to its primitive state, forming as it does with the acid a
chemical compound-sulphindigotic acid, or, as it is termed by dyers, sulphate of
indigo. When this acid solution is treated with carbonate of potash, there is formed
indigo carmine or blue carmine, soluble indigo, a deep blue precipitate soluble in
140 parts of cold water. This indigo-carmine is used as a water-colour pigment;
while mixed with some starch and a little gum-water it is formed into balls or other
suitable shapes and used as washing-blue, ultramarine being also employed for the
same purpose.
Logwood, or Campeachy.
∙14
This dye material is the wood, freed from bark and splint, of
the logwood tree, Hæmatoxylon campechianum, a native of Central America, and
cultivated in several of the West Indian Islands. The colouring matter contained in
this wood is called hæmatoxyline, С16Н14О6, a pale yellow, transparent, aciculated
crystalline body. By itself it is not a pigment, but is a colourable material, which
becomes coloured when brought into contact with strong alkalies, more especially
with ammonia and the oxygen of the air. The solution of hæmatoxyline in water is
quite colourless, but becomes at once purple-red by the smallest addition of ammonia.
The colouring matter thus formed is termed hæmateine. Logwood is used for the pur-
pose of dyeing blue and black. Extract of logwood is very frequently prepared.
As with other similar extracts, it should be made in vacuum pans withdrawn from the
oxidising action of the air, because the hæmatoxyline contained in logwood becomes
thereby altered. The makers of the extracts of dye-woods invariably use vacuum
apparatus.
Litmus. This colouring matter, also sometimes termed tournesol, is only very rarely
used as a dye for textile fabrics, the colour imparted being very fugitive; but litmus
is employed to impart a bluish tinge to whitewash-lime, further for colouring test-
papers, for giving a red hue to the red champagnes, &c. Litmus is obtained from the
seaweeds that yield archil, cudbear, and persio, potash being employed with the
ammoniacal liquor. The difference in the preparation consists in the fermentation
DYEING.
595
and oxidation being carried further, the result being that the red pigment (orcin) is
thereby converted into a blue-coloured material azolitmine:—
Orcin, C,H8O2
Ammonia, NH3} yield
Oxygen, 40
(Azolitmine, CH,NO4
and
Water, 2H2O.
The fermented mass is mixed with gypsum and chalk, moulded into lozenges, dried,
and sent into commerce.
That known as litmus on rags, tournesol en drapeaux, is prepared in the southern
parts of France (almost exclusively at Grand Gallargues, Département du Gard)
from the juice of the Croton tinctorium in which coarse linen rags are repeatedly
steeped, and these having been submitted to the action of the ammonia evolved from
stable manure or from lant, become purple-red coloured. Weak acids turn this
colour to yellow-red, which is not again turned to purple-blue by alkalies, the effect
of these being to render the colour somewhat green. The tournesol en drapeaux is
largely used in Holland for imparting a colour to the crust of certain kinds of cheese
made in that country, the effect being that the cheese thus externally dyed is by far
less liable to decay and to be attacked by cheese-mites. The pigment is also used
for colouring a peculiar kind of paper, extensively employed for the covering of
sugar-loaves. It is also used for imparting a tinge to liqueurs, sweetmeats, &c.
Yellow-Wood, Fustic.
Yellow Dyes.
Yellow-wood is the hard wood of the dyer's mulberry tree,
botanically termed Morus tinctoria or Maclura aurantiaca. It is imported chiefly
from Cuba, San Domingo, and Hayti. This wood has a yellow and in some parts
yellow-red colour, due to a colourless crystalline body, morine, C12H805, present in
combination with lime, and also to a peculiar kind of tannic acid, morine-tannic acid, also
termed maclurine (formula, C13H10O6), both often met with deposited in the wood in
large quantities. Morine becomes yellow by exposure to air and the simultaneous
influence of alkalies. When treated with caustic potash maclurine is split up into
phloroglucine and protocatechutic acid. Yellow-wood is employed for dyeing yellow
and also black, in consequence of the large quantity of tannic acid it contains. The
commercial extract of this wood is termed cuba extract.
Young Fustic, French Fustet. This is a green-yellow wood, exhibiting brown-coloured
stripes, and derived from a European shrub, the Rhus cotinus of the botanists, a plant
belonging to the southern parts of Europe. The prefix "young" is given to it on
account of the smallness of its branches as compared with that of the yellow-wood,
which is distinguished as old fustic. The fustet contains a peculiar colouring
matter termed fustine, and in addition large quantities of tannic acid. It would
appear that fustin yields quercetine by being split up in chemical sense.
Annatto, or Arnotto Is a yellow-red pigment, chiefly used for dyeing silk. It is met
with in commerce as a thick paste of the consistence of putty, and is prepared in
America, the West and East Indies, from the pulp of the fruit of the Bixa Orellana.
According to Chevreul, annatto contains two different pigments; one of these exhibits
a yellow colour and is soluble in alcohol and water, while the other, a red-coloured
matter, is readily soluble in alcohol but not in water. Piccard states that the formula
of the latter is C5H604. Annatto is soluble in weak caustic and carbonated alkaline
solutions.
596
CHEMICAL TECHNOLOGY.
Yellow Berries, or
simply Berries.
This drug is the fruit of various kinds of shrubs which are known
by the general name of the dyer's buckthorn, the Rhamus infectorius, R. amyg-
dalinus, R. saxatilis of the botanists, grown in the Levant, Southern France, and
Hungary. The size of these berries varies very much, two sizes being chiefly met
with and distinguished in commerce, viz., the large bright olive-coloured full-sized,
and the smaller shrivelled deep brown berry. The former are gathered before they
are quite ripe, while the others have been left after full maturity for a considerable
time on the twigs. These berries contain a fine golden-yellow pigment named
chrysorhamnine and olive-yellow xanthorhamnine. According to Bolley the former
is identical with quercetine. Berries are used in calico-printing, for the colouring of
paper-pulp, and for the preparation of lake colours.
Turmeric Is the dried root of the Curcuma longa and C. rotunda, a plant growing in
India and Java, belonging to the natural order of the Scitaminea. The root is met
with in egg-shaped tubers or flattened lumps, exhibiting a dirty yellow colour. The
pigment contained is termed curcumine, C8H1002. As a dye turmeric is chiefly used
in silk-printing and dyeing, also for woollen fabrics for dark and full shades of
colour. Upon cotton it dyes without mordant, but the colour is very fugitive.
Turmeric test-paper is used for the detection of alkalies and boracic acid, by which
it is turned red-brown.
Weld.
This dye material consists of the dried herb and stems of a plant botanically
known as Reseda luteola, a native of the southern parts of Europe and frequently
cultivated for the use of dyers. French weld is considered the best. The pigment
it contains is known as luteoline.
Quercitron Bark.
This dye material, as its name indicates, is the inner bark of the
black oak, Quercus tinctoria. It is a native tree of North America, and the drug is
imported in the state of powder. The colour of this substance is bright yellow, and
it contains tannic acid in addition to a yellow pigment, quercitrine, C33H30017.
When quercitrine is treated with dilute acids it is split up, yielding quercetine,
C27H18012, a lemon-yellow powder met with in commerce under the name of flavine.
According to Hlasiwetz's opinion, quercetine contains the complex of morine. Owing
to the beauty of the colour it yields, quercitron bark is, with picric acid, the chief
yellow dye of the present day. Among the more or less important yellow dyes, we
mention :-Saw-wort, Serratula tinctoria; dyer's brown, or greenwood, Genista
tinctoria; the wongshy, Chinese annatto, or yellow pods, the seed capsules of the
fruit of Gardenia florida, a plant belonging to the family of the Rubiacea; purrhee,
or Indian yellow, Jaune Indien, a dye material imported from India, the origin of
which is not known (it is the magnesia salt of purreic or euxanthic acid, and is
stated to be obtained from the urine of camels); Morinda yellow, from the Morinda
citrifolia. Since the tar-colour industry has sprung up, picric acid (see p. 580) is
frequently used as a yellow dye, and mixed with either indigo or aniline blue, as a
green dye for silk and woollen fabrics. 'In order fully to exhaust the picric acid
dye-beck. some sulphuric acid should be added to it. More recently the so-called
Manchester yellow (see p. 582) is frequently employed instead of picric acid. The
latter is not used upon cotton.
Black Dyes.
Brown, Green, and Brown dyes, aniline brown excepted, are mixtures of red, yellow,
and blue, or of yellow or red with black. Frequently a brown is dyed by the use of
oxidising agents with tannin-containing pigments, such as willow, oak, or walnut
barks with cutch, the extract of the wood of the Areca and Acacia catechu, &c. The
DYEING.
597
latter is technically termed chemick brown. Manganese, or bister brown, is obtained
from the hydrated oxide of manganese. Black is obtained from tannate or gallate of
protoperoxide of iron or from logwood decoction and chromate of potash* or from
aniline black (see p. 579). Green is produced by mixing yellow and blue, or by the
use of the Chinese green Lo-kao, obtained from Rhamnus chlorophorus and R. utilis ;
or by the use of sap-green from the berries of the Rhamnus catharticus; finally,
aniline green (aldehyde green and iodine green, see p. 578) is used, and yields a most
beautiful dye.
Bleaching.
BLEACHING.
The operation of bleaching aims at more or less perfectly whitening
or decolourising the yarns spun from flax, hemp, jute, cotton, or of the textile
fabrics woven from the same. Vegetable fibre resists the action of most chemical
agents in use in the bleaching, while the foreign or incrustating or colouring matters,
occurring chiefly on the surface of the fibre, are rendered soluble or completely
destroyed. The bleaching of the fabrics and fibres which, such as linen or cotton
tissues, consist mainly of 'cellulose, is based on this principle. The method of
bleaching wool and silk differs from that of the vegetable fibres, inasmuch as
the chemicals used for the latter would exert upon the former a solvent action, not
only as regards the impurities, but the substance itself.
In the operation of bleaching, partly chemical and partly mechanical means
are employed. On the large scale, setting aside all theoretical considerations which
do not fall within the scope of this work, the operation of bleaching cotton fabrics
consists of the following operations :—
1. Singeing, followed by "rot steep" or "wetting-out steep."
2. Liming-boiling with milk of lime and water for 12 to 16 hours.
3. Washing out the lime and passing in hydrochloric acid "sours" or weak vitriol.
4. Bowking in soda-ash and prepared resin, 10 to 16 hours.
5. Washing out the bowk.
*
Ordinary black ink which, if really made with galls, consists essentially of gallate of
protoperoxide of iron kept in suspension in water by the aid of gum arabic, is indeed a
dye liquor. A very good black ink may be made as follows:-1 kilo. of coarsely pulverised
nut galls and 150 grms. of logwood chips are exhausted with 5 litres of hot water;
600 grms. of gum arabic are dissolved in 2 litres of water; and 500 grms. of sulphate of
iron in some litres of water; each of these solutions being made separately. This done the
gall-logwood infusion is mixed with those of the gum and copperas; a few drops of
essential oil of cloves or of gaultheria (winter green oil) having been added, there is added
as much water as will bring the bulk of the liquid up to 11 litres. While this kind of ink
attacks and corrodes steel pens, it has the additional disadvantage that after a time the
writing becomes yellow. In 1848 Runge called attention to an ink originally invented by
Leykauf at Nürenberg, and improved upon by C. Erdmann at Leipzig and sold by him.
This ink is made up of 1000 parts of a logwood decoction (1 part of wood to 8 parts of
water) and I part of yellow chromate of potash, some bichloride of mercury being added
for the purpose of preventing the formation of mould. This ink is cheap and very per-
manent; the colouring principle is a combination of hæmateine and oxide of chromium.
Leonhard's so-called alizarine ink is made by exhausting with water, so that 120 parts of
fluid are obtained from 42 parts of galls and 3 of madder. To this mixture is added
12 parts of sulphindigotic acid, 5.2 parts of green copperas, and 2 parts of pyrolignite of
iron solution. Rouen's blue ink, frequently used in France, consists of a decoction of
750 grms. of logwood, 35 grms. of alum, 31 grms. of gum arabic in 5 to 6 litres of water.
For an excellent extemporaneous ink, see "Chemical News," vol. xxv., p. 45. Copying
inks are only more concentrated ordinary inks, to which more gum and sugar are added.
Marking ink for linen is a solution of silver (see p. 105), or aniline black produced on the
woven fabric (see p. 579).
598
CHEMICAL TECHNOLOGY
6. Passing through a solution of chloride of lime (hypochlorite of lime).
7. Passing through weak hydrochloric acid.
8. Washing, squeezing, and drying.
The singeing is not a part of the bleaching process properly considered; its
purpose is to remove the loosely adhering filaments, and improve the appearance of
the cloth if required for printing.
The “rot steep" (so-called because the flour or size with which the goods were
impregnated was formerly allowed to enter into fermentation and putrefaction)
is intended to thoroughly saturate the cloth. The liming takes place in kiers
or kettles capable of holding from 500 to 1500 pieces of cloth. The lime is very
carefully slaked and brought to a smooth milk of lime, being sifted so that no
small lumps of quick-lime shall get into the kier. The lime is equally distributed
upon the cloth as it enters the kier. The cloth is pressed into the liquor and
the boiling commenced and continued for a period of 12 to 16 hours. At the end of
that time the liquor is run off and clear water run in to cool the pieces of cloth,
which are then taken out and washed. The utility of the liming consists in its
action upon the greasy matters, forming with them a kind of insoluble soap, which is
easily removed by the subsequent processes. The souring after liming removes all
excess of lime and breaks up the insoluble lime-soap, leaving the greasy matters upon
the cloth, but in such an altered state as to be easily dissolved in the bowking which
follows. Hydrochloric acid is sometimes used in this souring, but more commonly
dilute sulphuric acid is employed. The bowking or boiling with alkali and soap has
for its object the removal of the greasy matters; it dissolves them, and all the dirt
held by them now comes out of the cloth, leaving the cotton nearly pure. The alkali
used in this process is soda-ash. The soap is made from resin and called prepared
resin. The last process is that of passing the goods through a clear solution of
bleaching-powder for the purpose of destroying the slight tinge of colour of a buff
or cream shade still adhering to the cotton. The solution of bleaching-powder
is very weak, so that probably a piece of calico of the ordinary size does not take up
more than the soluble matter from of an ounce of bleaching-powder. The goods
are allowed to remain some time in soaking with the chloride of lime solution,
and are next passed through sours for the final operation. The dilute hydrochloric
acid has the effect of setting the chlorine free from the bleaching-powder and thus
completing the destruction of the colour. At the same time it removes the lime and
likewise any traces of iron (iron moulds) that may exist in the cloth. Linen is not
so easily bleached as cotton, and it appears to suffer considerably by boiling with
lime and by contact with bleaching-powder. It is, therefore, generally bleached by
continual boilings with alkali and a few sourings with bleaching-powder; or as lime
is injurious, the hypochlorites of potash or soda are substituted. Woollen goods or
yarns are bleached by treating them with very mild alkaline liquors, which remove
the fatty matters, lant and soap with soda crystals being the substances usually
employed. Sulphurous acid gas-or, as it is termed in the trade, vapour of burning
brimstone—is used to finish wool, giving it whiteness and lustre. The following is
an outline of the process as described by Persoz for bleaching woollen goods; it
is for 40 pieces each 50 yards long:-1. Passed three times through a solution of
25 lbs. of carbonate of soda and 7 lbs. of soap at a temperature of 100° F.; add ₫ lb.
of soap after every four pieces. 2. Wash twice in warm water. 3. Passed three
times through a solution of 25 lbs. of carbonate of soda at 120° F., and add ₫ lb. of
DYEING.
599
soap again after every four pieces. 4. Sulphured in a room for twelve hours, using
25 lbs. of sulphur for the forty pieces. 5. Passed three times through a solution of soda,
as in No. 3. 6. Sulphured again, as in No. 4. 7. Soda liquor again, as in No. 3.
8. Washed twice through warm water. 9. Sulphured a third time as in No. 4.
10. Washed twice in warm and then in cold water. II. Blued with extract of
indigo (indigo-carmine) according to taste.
Bleaching of Silk.
The operation of bleaching silk is always preceded by removing
(decorticating, degumming) the gummy substance attached to and externally
covering the fibre. This is effected by boiling the raw silk in soap and water.
For the purpose of bleaching silk nothing but water, soap, and sulphur (for making
sulphurous acid) are used. Occasionally some soda crystals are employed to
save soap but as alkalies injure, and if incautiously used destroy, the fibre, they
must be employed with extreme care. Bran is sometimes used with soap in order to
neutralise any excess of alkali (bran contains, or rather develops, when it becomes
wet, lactic acid). The process is terminated by passing in an extremely diluted
sour (solution of sulphuric acid in water) so weak as scarcely to be acid to the taste.
Sulphuring is only required for silks intended to be left either white or to be dyed or
printed with bright and light colours. This operation requires great care and should
be seldom resorted to.
This is an outline of the process of bleaching as carried on in practice on the
large scale in this as well as in other countries. The theoretical consideration of
the mode of action of the substances employed belongs to theoretical chemistry, and
is treated under the heads of Chlorine, Sulphurous Acid, Oxidising Substances, &c.;
and as far as the textile fibres are concerned, under Cellulose for flax, hemp, jute,
cotton, and the Animal Fibres for wool and silk. The meadow bleaching of cotton
and linen fabrics is still resorted to in some extent, but only in connection with the
processes already referred to. None of the novelties proposed for bleaching
purposes-among these, for instance, the use of permanganate of potash (Tessié du
Motay's process) as a bleaching agent-have been found by practical bleachers of
great experience to be either better, more manageable, or cheaper than the methods
sanctioned by lengthy experience and daily use.
Dyeing.
DYEING OF SPUN YARN AND WOVEN TEXTILE FABRICS.
Just as animal charcoal and arable soil are possessed of the property
to assimilate in their pores colouring matter and some inorganic substances without
the latter being altered, so also do animal and vegetable fibres possess the property
of absorbing from solutions, and fixing in a more or less insoluble condition, dyes
and some of the constituents of mordants. This combination, or more correctly
union, is often so loose that it is readily broken up by repeated treatment with
solvents (viz. simply washing with water or soapsuds), especially if aided by heat
Thus, for instance, a textile fibre dyed (rather tinged, for dyeing implies fixity) with
sulphindigotic acid, or a solution of Berlin blue in oxalic acid, may be decolourised
again by repeated washing in water. A fibre can only be called dyed in the strict
sense when the dissolved dye material has been united in insoluble condition with
the fibre, for which purpose often the intervention of a third substance, viz., a
mordant, is required, the union thus formed resisting the action of solvents, that is
to say—repeated washing with warm water and soap. The colour thus produced is
termed fast, and resists the action of light, air, soap-water, weak alkaline solutions,
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CHEMICAL TECHNOLOGY.
and weak acids. A dye which does not resist these agents is termed fugitive.
Dyeing is partly based on chemical principles, but as regards the taking up or fixing
of the dye by the fibre, it would appear to be only a physical attraction, capillarity,
as there does not exist between a certain quantity of fibre and of dye an atomistic
relation. Moreover, neither fibre nor dye have lost, after fixation has taken place,
their characteristic properties.
The insoluble condition of the union between fibre and dye may be obtained
in various ways, viz.-1. By removal of the solvent, as, for instance, oxide of copper
dissolved in ammonia may be fixed on the fibre by simply evaporating the latter
fluid; chromate of zinc dissolved in ammonia may be fixed in the same manner. The
precipitation of carthamine from its alkaline solution by the aid of an acid, and the
precipitation of some of the tar colours from their alcoholic solutions belong to the
same category. The insoluble condition can be produced by—2. Oxidation, the pre-
viously soluble dye being rendered insoluble by taking up oxygen (ageing process).
The ferrous and manganous sulphates becoming converted by oxidation into
insoluble hydrated oxides; and further, those dyes of vegetable origin which,
in addition to tannic acid, also contain a peculiar dye material, such as quercitron,
sumac, yellow-wood, fustet, &c., belong to this category. When any textile fabric is
impregnated with an aqueous or alkaline infusion of these substances, and then aged
or stoved (technical terms for exposure to action of air in what are termed ageing-
rooms), the dye material becomes brown, and is then no longer soluble in water. This
is more rapidly effected by treating the textile fabrics, previously impregnated with
the solutions of the drugs, with oxidising substances—for instance, chromic acid or
bichromate of potash. Another instance of this kind is the process of dyeing black
with logwood and chromate of potash, whereby the hæmatoxyline of the wood
is oxidised, and the chromic acid reduced to chromic oxide. To some extent
the dyeing blue with indigo in the vat (blue vat), to be more fully described pre-
sently, belongs to the same category; but in this case the production of the colour is
due to the gradual absorption of oxygen, while simultaneously hydrogen is evolved
from the white indigo, the hydogen combining with oxygen and forming water. The
formation of aniline black upon tissues by the aid of ozone-forming substances
(chlorate of potash, ferricyanide of ammonium, chromate of copper, freshly precipi-
tated sulphide of copper) belongs to this class. In many cases the insoluble condi-
tion (3) is obtained by double decomposition; as, for instance, blue is produced by
hydroferrocyanic acid and oxide of iron; green by arsenite and sulphate of copper ;
yellow by chromate of potash and a soluble lead salt. This mode of fixation of pig-
ments is only employed with mineral colours. The most important and most
ordinary method of fixing dyes is (4) by the aid of mordants. We understand by a
mordant, a solution of some substance which, not being itself a dye, has an affinity as
well for the fibre as for the dye material, and is thereby capable of effecting the
fixation of the latter to the fibre.
The more important mordants are:-Alum; sulphate, acetate and hyposulphite of
alumina; aluminate of soda; and acetate of iron; according to Reimann [1870],
amorphous silica may be used for fixing several dye materials; tin mordants; fatty
substances, Gallipoli oil, in Turkey-red dyeing; tannic acid, for madder colours :
chineal colours; aniline dyes on cotton and linen fabrics; albumen, dried white of
egg, gluten, caseine, and fatty oils (linseed oil also sometimes). The fabrics to
be dyed are impregnated with the mordants, which are next fixed, an operation
DYEING.
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differing according to the nature of the mordant as well as the specific dye it is
required for; but in general terms, ageing, dung-bath, bran-bath, and soaping, are
employed, after which the woven fabric is placed in the dye solution contained in the
dye-beck. Most of the dyes of organic origin can be fixed only by the aid of mordants.
Bancroft considers dyes as substantive and adjective. By the former is under-
stood those which without the aid of a mordant become fixed upon the textile fibres
in an insoluble condition: to these belong all mineral pigments; and among
the vegetable colouring substances-indigo, turmeric, annatto, safflower, also most of
the tar-colours, although, as already mentioned, tannic acid is used for fixing
fuchsin and similar tar-colours. By adjective colours or dyes is understood
such as require an intermediate substance (a mordant in fact) to become fixed upon
the fibre in an insoluble condition. These intermediate substances are termed mor-
Mordants. dants; they not only serve for fixing the dye to the textile fibres, but also
produce in the mordanted goods such an alteration that the parts of the tissue where
the composition is applied appear white when the goods are taken from the dye-
beck. The substances which produce this effect are technically termed dischargers,
or discharge compositions; among them are phosphoric, tartaric, oxalic, arsenious
acids, &c.; but in practice the goods are first uniformly dyed, and the discharge then
applied so as to act only where it is desired to exhibit a pattern. What are termed
resists are not mordants, but only compositions applied to the woven fabric at
certain parts where it is desired that no deposition of colour or mordant shall takę
place. Mordants may modify the original colour that a dye yields; as, for instance,
with alumina compounds madder yields red, pink, and scarlet; with salts of iron,
according to the degree of concentration, lilac, purple, black; and brown with cer-
tain salts of copper. For the purpose of clearing and brightening (avivage), the
dyed or printed goods are passed through solutions of either dilute acids, weak
or strong alkalies, soap-suds, bran-bath, solutions of bleaching-powder, or also
of some other dye material.
Dyeing Woollen Fabrics.
Wool is sometimes dyed in the flock or fleece, that is to say,
when not spun; sometimes in yarn or worsted and as a finished woven fabric (cloth,
broadcloth, &c.). As there is always some refuse wool in the operations of weaving,
fulling, and dressing the woollen tissues, it is advantageous to dye wool in the condi
tion of spun yarn. When the dye intended to be applied to wool is fast, the textile
fibre is first mordanted. For this purpose the woollen fibre is treated with a solution
of alum and cream of tartar (bitartrate of potash); or with the latter salt and tin-salt
(chloride of tin); or, again, cream of tartar and green vitriol; for certain colours,
chloride of tin and pink salt (see p. 75) are used.
Dyeing Wool Blue. The imparting of a blue colour to wool is one of the most
important operations of dyeing woollen goods. It is frequently effected with indigo,
which produces the most beautiful and fast colours; but indigo is used only for the
better and heavier kinds of woollen fabrics; lighter tissues-merinos for instance-
are often dyed with Prussian blue (not a fast colour), while common woollen goods,
flannels, &c., if dyed blue at all, are dyed with logwood and blue vitriol (sulphate of
copper). In order to ascertain whether a woollen tissue has been dyed with indigo,
Frussian blue, or copper salts, the following tests may be employed. Woollen
tissue dyed with indigo does not change its colour by being boiled with caustic
potash, or by being moistened with concentrated sulphuric acid. When Prussian blue
is the dye used, the tissue becomes red-coloured by being boiled with caustic potash,
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CHEMICAL TECHNOLOGY.
and becomes discoloured by being moistened with strong sulphuric acid. Woollen
goods dyed with logwood and copper salts are reddened by being moistened with
dilute sulphuric acid, and on being incinerated, the tissue leaves an ash containing
copper.
Indigo Blue. Woollen goods are most frequently dyed blue with indigo by means of a
solution of white indigo (reduced indigo) in an alkaline fluid, the goods being blued
by exposure to air—that is to say, by the oxidation of the indigo taken up by the fibre,
the dye becoming simultaneously fixed. The principle of this mode of dyeing with
indigo (technically known as blue vat), may be elucidated by the following formula:—
C16H12N₂O₂+0=C16H10N2O2+H20.
Blue Vats.
The greatest consumption of indigo is in forming the blue vats, in which
woollen or cotton goods, more rarely linen, are dyed by simply immersing them in
the solution of white indigo. The same vats are not equally adapted for wool
and calico, there being, as will be seen in the following details, a wide difference in
their composition. According to the general accounts, the lime and copperas vat
(see below) is not well adapted for woollen goods; still in the most recently
published French treatise on woollen dyeing, there is no mention made of any
other kind of vat; the following proportions and directions being given for setting
a vat for dark blue:-1200 gallons of water; 34 lbs. of quick-lime; 22 lbs.
of green copperas; 12 lbs. of ground indigo; 4 quarts of caustic potash solution at
34° sp. gr. 1°288. The indigo is ground very fine by trituration in properly
constructed mills, this being a point of the utmost importance. In the above recipe
the potash is mixed with 5 gallons of water in an iron pan, and the indigo added.
The mixture is gradually heated to ebullition and kept boiling for two hours
with uninterrupted stirring; this softens and prepares the indigo for dissolving. The
lime is well slaked so as to be very fine, and is next passed through a sieve in the
state of milk of lime. It is then mixed with the indigo and potash; the copperas
(protosulphate of iron), previously dissolved, is added to the vat and well stirred ;
then the mixture of lime, potash, and indigo is poured in, and the whole well stirred
for half an hour. If the proportions are well kept, the vat will be fit for working
in twelve hours; if, however, it looks blue under the scum, it is a sign that the
indigo is not wholly dissolved, and more lime and copperas should be added, and the
vat left undisturbed for another twelve hours. The vat is worked at a temperature
of 70° to 80° F. This is the ordinary composition of a vat for dyeing cotton, but is
not, at least in England, in use for dyeing woollen goods.
The usual blue vats for wool contain neither copperas nor lime, or but a small
quantity of the latter; as, for instance-Water, 500 gallons; indigo, 20 lbs. ;
potash (carbonate, pearl-ash), 30 lbs,; bran, 9 lbs.; madder, 9 lbs. The water
is heated to just below its boiling-point; the potash, bran, and madder are first put
into the vat, a well-made wooden tub of convenient size, and then the indigo
previously very finely ground. Cold water is added so as to reduce the temperature
to 90° F., and that temperature is maintained constantly by means of a steam-pipe.
The ingredients are well stirred every twelve hours. The vat is generally ready for
use in forty-eight hours after setting. This vat does not work longer than about
a month, and is somewhat expensive on account of the potash. Another-the
so-called German-vat is much more manageable, and may be worked for two
years without emptying, being freshened up as required. It is composed of the fol-
lowing ingredients:-2000 gallons of water are heated to 130° F., and there are added
DYEING.
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20 lbs. of crystals of soda (common carbonate); 2 pecks of bran; and 12 lbs.
of indigo; the mixture being well stirred. In twelve hours fermentation sets in;
bubbles of gas rise; the liquid has a sweet smell, and has assumed a green
colour. 2 lbs. of slaked lime are now added and well stirred, the vat is again heated
and covered up for twelve hours, when a similar quantity of bran, indigo, and soda,
with some lime, are added. In about forty-eight hours the vat may be worked; but
as the reducing powers of the bran are somewhat feeble, an addition of 6 pounds of
molasses is made. If the fermentation becomes too active, it is repressed by
the addition of lime; if too sluggish, it is stimulated by the addition of bran and
molasses. Like all the other blue vats for wool it is worked hot. Another kind of
vat may be called the woad vat, because a considerable quantity of woad is added to
it, and also madder, which in this case acts simply by reason of the saccharine
matter it contains. The proportions are :-Pulverised indigo, 1 lb.; madder, 4 lbs. ;
slaked lime, 7 lbs., boiled together with water and poured upon the woad in the vat.
After a few hours fermentation sets in, and fresh indigo is added according to the
depth of colour required to be dyed. The pastel vat is set with a variety of woad
which grows in France, and which is richer in colouring matter than the common
woad. It is possible that the colouring matter of the pastel adds to the effect; but it
is more likely that while it furnishes fermentescible matters useful in promoting the
solution of indigo, it is added as a remnant of ancient usage. Before indigo became
again known in Europe (the dye was known to the Greeks and Romans), in the 17th
century, woad was the general blue dye material. The method of dyeing the woollen
fibre and fabrics is very simple. The wool, thoroughly wetted out, is suspended on
frames, and dipped in the vat for an hour and a half or two hours, being agitated all
the time to insure regularity of colouring. The pieces are then removed, washed
in water, and treated with weak hydrochloric or sulphuric acids to remove the alkali
rêtained. As regards blue vat for cotton dyeing, in some exceptional cases when
thick and heavy goods have to be dyed, the so-called German vat is used; but
generally all calicos are dyed blue by means of the cold lime and copperas vat. The
materials used are lime, protosulphate of iron, ground indigo, and water. The
chemical action consists, in the first instance, in the formation of sulphate of lime
and protoxide of iron; the latter substance having a considerable affinity for oxygen,
removes an atom of it from the blue indigo, converting it into white, which dissolves
in the excess of lime, and is ready for dyeing. The proportions are as follows:-
900 gallons of water; 60 lbs. of green copperas; 36 lbs. of ground indigo; 80 to go
lbs. of slaked lime, stirred every half hour for three or four hours, then left twelve
hours to settle, well raked up again, and as soon as settled ready for dyeing.
Saxony Blue- As already stated, indigo dissolves in concentrated sulphuric acid,
forming (because it is not a solution in the ordinary sense of the word) sulphindigotic
acid, which is employed in dyeing wool in the following manner :-First, I part of
indigo is treated with 4 to 5 parts of fuming sulphuric acid; next, this solution
is poured into a vessel containing water; and into this mixture flock wool is
immersed for twenty-four hours. After this time the wool is removed from the
vessel and drained, and transferred to a cauldron filled with water, to which has been
added either carbonate of ammonia, or of soda. or of potash, and boiled for
some time. The solution thus obtained, technically known as extract of indigo
or as indigo carmine, is used for dyeing wool which has been previously mordanted
with alum There is formed on the wool sulphindigotate of alumina.
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CHEMICAL TECHNOLOGY.
+
Recovering Indigo
from Rugs, &c.
In order to recover the indigo from scraps and rags of woollen and
other fabrics dyed indigo blue, the materials are treated with dilute sulphuric acid,
which is heated to 100º. The wool is dissolved, while the indigo is left as an
insoluble sediment. Military uniforms yield from 2 to 3 per cent of indigo. The
acid solution is next neutralised with chalk, and a sulphate of lime is obtained
which, owing to the nitrogenous matter intermingled, may be usefully employed as a
manure.
on Wool.
Berlin or Prussian Blue Wool is dyed with the so-called Prussian blue (ferrocyanide of
iron) by two methods, one of which consists in saturating the wool with a solution of
a salt of peroxide of iron (generally the persulphate, or preferably the pernitrate),
after which the wool is passed through a solution of ferrocyanide of potassium
in water, acidulated with sulphuric acid. The other process producing so-called Bleu
de France is based upon the decomposing action which the atmosphere exerts on the
ferro- and ferri-cyanhydric acids. The goods are immersed in a solution of either the
ferro- (yellow) or ferri- (ruby red) cyanide of potassium (commonly yellow or red
prussiate) in water, to which are added sulphuric acid and alum. Afterwards the
goods are aged, or exposed to the air in rooms in which steam is simultaneously
admitted to elevate the temperature and assist the action of the oxygen of the air.
The result is that the ferro- or ferri- cyanhydric acid is decomposed, hydrocyanic
acid being evolved, while there is deposited on the fibres of the woven fabric ferro-
cyanide of iron, Prussian or Berlin blue. Meitzendorff has recently invented a
method of dyeing this blue by which a colour is produced very similar to that
obtained by the so-called Saxony blue. He prepares a solution containing ferro-
cyanide of potassium, chloride of tin (SnCl4), tartaric and oxalic acids; this solution
is heated and the wool kept therein for some time. The oxalic acid dissolves
the Prussian blue, which of course can only act as a dye when dissolved, any
of it left undissolved being lost. The tartaric acid increases the brilliancy of the
colour.
Dyeing Blue with Logwood
and a Copper Salt,
For this purpose logwood is boiled in the dye-beck with
water, and to the decoction are added alum, cream of tartar, and sulphate of copper.
The wool is boiled in this fluid, and is next cleared by being boiled in a fluid con-
taining logwood, tinsalt (protochloride of tin), alum, and cream of tartar. The goods
dyed in this manner do not, as is the case with the indigo goods, become white by
Instead of logwood, archil and cudbear are frequently used for so-called half-
wear.
fast colours.
Dyeing Yellow.
On the Continent, weld, which has become quite obsolete for dyeing
yellow on wool in the United Kingdom, having been entirely superseded by
quercitron bark, is still used for producing a yellow dye, on account of the fact that
weld, when brought into contact with an alkali, becomes less red-coloured than is
the case with the other yellow dyes.
In dyeing with weld its colouring matter is extracted by water, and the decoction
added to the goods intended to be dyed. With alum it dyes a very fine clear yellow,
tolerably permanent in soap, but not resisting air and light. Weld has not more than
one-fourth the tinctorial power of quercitron bark, and on this account, as well as on
that of its great bulk relative to its weight, it is not used in this country. Fustic,
yellow-wood, is very extensively employed in dyeing, and is the most suitable yellow
matter for working with other colours in compound shades. With aluminous
mordants it gives yellow of an orange shade; with iron mordants it gives drabs,
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DYEING.
605
greys, and olive. As a yellow colouring matter it is considered to be of far less
power than quercitron bark weight for weight, while it is also inferior in purity of
colour; but as fustic withstands the action of acids and acid salts better than bark,
it is used in greens, blacks, and mixed colours where yellow is required. Young or
French fustic (also known as Venice sumac) is used for imparting yellow to merinos.
A golden yellow is produced upon wool with either picric acid or Manchester
yellow.
Dyeing Wool Red. Madder is the chief colouring matter employed for imparting to
wool a red or scarlet colour. The process of dyeing 'wool with madder consists in
mordanting the woollen tissue, fibre, or yarn, and in immersing it in the dye-beck
containing madder with water. The wool is mordanted by being immersed in a
warm solution of alum and cream of tartar. The dyeing is effected by placing the
mordanted goods in the dye-beck or madder-bath, the quantity of madder being
equal to half the weight of the woollen goods. In practice the goods are, of course,
slowly moved into, through, and out of the dye-beck, proper mechanism being
provided for this purpose. After having been dyed, the goods are thoroughly
washed, so as to remove excess of dye as well as any mechanically adhering
particles of madder. Dyeing red with cochineal is effected upon wool in the same
manner as with madder. Scarlet is red with a yellowish hue, while a peculiar hue of
red is termed crimson, often produced by cochineal. Woollen fabrics are mordanted
in a mixture of water, cochineal, cream of tartar, and tinsalt, and next dyed
by boiling with more cochineal and tinsalt. Wool is very readily dyed with all the
tar-colours (red, blue, green, grey, yellow, brown, violet), the affinity of wool for
these colours being so great, that the solution of any of these pigments may be com-
pletely deprived of its colouring matter by contact with wool.
Green Dyes. Green dyes are usually obtained by combining blue and yellow. Wool
is first dyed blue, and having then been mordanted with cream of tartar and alum, is
dyed with fustic, or, on the Continent, with weld. The green cloth used for covering
billiard-tables and other furniture is dyed in the following manner :-A weak decoc-
tion of fustic is prepared, and into this some Saxony blue is poured, while there is
next added alum and cream of tartar. The woollen fabric is immersed in the bath
and boiled for two hours. It is next thoroughly washed and brightened by being
again immersed in a dye-beck filled with a fresh fustic decoction, to which a smaller
quantity of Saxony blue has been added. All kinds of woollen tissues, worsted, half-
wool, alpacas, delaines, &c., may be dyed green by means of lo-kao (Chinese green),
and iodine green.
Mixed Shades. Mixed shades are produced on the fabrics by means of cochineal,
madder, French fustic, fustic, in a manner similar to that used for dyeing green.
Black Dyes. Excepting only aniline black, all black dyes may be considered as combi-
nations of iron with tannic or gallic acid; but the best and fastest blacks on broadcloth
are such as have as a first dye either madder or indigo. The woollen goods are mor-
danted with sulphate of iron (green copperas) and dyed by immersion in a decoction of
logwood, galls, sumac, &c. The so-called Sédan black (this town is celebrated for its
cloth manufacture) is produced by dyeing the cloth blue with woad, when after
careful washing the cloth is placed in a dye-beck containing water, sumac, and log-
wood, and is boiled for some three hours, after which sulphate of iron in a solution
of known strength is added. This operation is repeated until the cloth has assumed
an intensely black colour. Half-fast black colours are produced on cloth by dyeing
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CHEMICAL TECHNOLOGY.
them blue with Prussian blue, after which the operation just described is gone
through. Common black is produced by dyeing with logwood, sumac, some fustic,
and a mixture of green and blue vitriol. Chromium black, invented by Leykauf at
Nüremberg, is obtained in the following manner:-The cloth is mordanted with a
solution of bichromate of potash and cream of tartar, after which it is dyed in a
decoction of logwood. The so-called pyrolignite of iron (crude acetate of iron
prepared from scraps of old iron and crude acetic acid) is now very generally used as
a mordant instead of the green copperas. This acetate, also known as black or iron
liquor, is prepared on the large scale and sold as a liquid at a sp. gr. of 109 to 1*14.
White Cloth. This cloth, in use especially for military uniforms, is obtained by first
thoroughly washing, fulling, and carefully sulphuring the cloth, which is next.
passed through a bath containing chalk and a small quantity of size, after which
it is dried, beaten, and well brushed.
Silk Dyeing. Silk is usually dyed in skeins unspun, but having been first decorti-
cated, that is to say, deprived of the layer of gummy matter which forms the outer
covering of cocoon silk. It is then scoured, bleached, and sulphured; the latter only
when the silk is to be dyed with very bright colours and delicate light hues. Silk is
dyed in cold dye solutions. It is dyed black by any of the following processes :—
1. Logwood and iron mordant;
2. Logwood and bichromate of potash ;
3. Galls and other substances containing tannic acid with iron salts as mordant
4. With aniline black, according to the recipes of Persoz, jun., and others, by the
use of chromate of copper and oxalate of aniline.
The first and second are simply known as ordinary blacks, while the third is
known as fast black. The ordinary black is obtained by simply mordanting the silk
with nitrate of iron, and then dyeing it in a decoction of logwood. This cheap dye
is more particularly applied to light silken fabrics. The colour is reddened even by
weak acids, such as lemon and orange and other fruit juices. The fast black is far
more expensive, but it is not affected by weak acids, while it affords the additional
advantage of largely increasing the weight of the silk (in raw state as well as in spun-
yarn silk is sold and bought by weight), as this textile fibre absorbs from 60 to 80,
and even 100 times its own weight, and silk used for shoe-laces even 225 per cent of
the dye material. When desired the silk-dyer has to return for 100 lbs. of raw silk
from 160 to 180 or 200 lbs. weighted black-dyed silk. In Germany an indigenous
gall, locally known as Knoppern, French avèlandes, containing some 30 to 50 per cent
of tannic acid, is used in the extract to dye silk black. In England nut-galls
imported from the Levant are employed for this purpose. Although the increase in
weight of the silk by black dyeing is advantageous to the dealers, the deposition of
so much foreign matter in the fibre of the silk not only injures its wearing qualities,
but also gives rise to the disagreeableness of the dyeing coming off while the mate-
rial is being worn. Microscopic research has proved that the dye adheres very
loosely to the silk. The process of dyeing silk black with galls is very simple. The
fibre is first steeped in a solution, or rather infusio-decoction, of galls, technically
known as "galling," after which the silk is placed in a solution of nitrate of iron.
This black is sometimes dyed on silk previously dyed with Prussian blue, but far
more frequently a bluish shade is given to black by first dyeing the silk with log-
wood, copperas, and some sulphate of copper.
As regards the weighting of the silk, it is essentially due to the fact that silk, as
DYEING.
607
an animal product, has the property of combining with tannic acid and thereby
becoming heavier. The larger, therefore, the quantity of tannic acid contained in
the dye-bath, or the oftener the galling of the silk is repeated, the heavier the fibre
will become within certain limits. It is not quite indifferent whether a per-salt or a
proto-salt of iron be employed, the former being preferable. The previously galled
silk becomes, when passed through a solution of a per-salt of iron, at once coloured
black; but when it is passed through a solution of a proto-salt of the same metal, the
silk becomes at first coloured only black-violet, and gradually deep black by exposure
to air. Although in every case the result is the same, the use of a per-salt is advan-
tageous, and becomes necessary with a small quantity of tannic acid, while for a
heavy weighting of the silk, the proto-salt of iron only can be employed. It is stated
that the dyeing of silk with aniline black by means of chromate of copper and oxalate
of aniline yields excellent results. Silk is dyed blue either with indigo, Berlin blue,
ogwood, or aniline blue. The indigo vat has not been much used for imparting a blue
colour to silk since the discovery of fixing Prussian blue upon silk; and if indigo
is used at all it is as indigo carmine, or the so-called distilled blue, purified sulphin-
digotic acid. In order to dye silk with Prussian blue, it is first immersed in a
solution of nitrate of iron. This salt is generally in use in England, while in France
a persulphate of iron made by dissolving green copperas in nitric acid is employed,
and known under the name of Raymond's solution, the blue produced being termed
Raymond's blue; Napoleon blue is produced by the addition of a tinsalt to the iron
bath, followed by treatment with a solution of ferrocyanide of potassium acidulated
with sulphuric acid. The latter blue, more brilliant than the former, is usually
prepared in England, a tinsalt being invariably added to the iron mordant. The
mordanted silk is next passed through a boiling soap-solution, then washed, and next
steeped in a solution of ferrocyanide of potassium acidulated with hydrochloric acid.
The brilliancy of the dyed silk is greatly enhanced by passing it through water con-
taining ammonia. Dyeing silk with aniline or naphthaline blue is a very simple
process, it being only necessary to put the silk into a solution of the dyes,
the solvent being alcohol or wood-spirit, or in the case of soluble aniline blue,
water. The silk is left in the solution until it has assumed the desired hue. Until
the discovery of fuchsin, silk was always dyed red and pink by means of cochineal,
safflower (carthamine), and archil; but now silk is generally dyed with fuchsin,
coralline, and Magdala red (naphthaline red). The process is as simple as that
just described for aniline blue. Aniline red is the brightest, purest, and deepest of
all red dyes for silk, but it is not so fast as Magdala red. Archil is still largely used,
but aniline violet or mauve is in close competition with it. Yellow is produced upon
silk by first mordanting with alum and dyeing in a decoction of weld, to which, if it
be desired to impart an orange hue, some annatto is added, or, preferably, Man-
chester yellow. By cautious treatment with nitric acid silk may be dyed yellow,
some xanthroproteic acid being formed, while without any mordant picric acid pro-
duces a bright lemon-yellow on silk, the colour becoming deeper by treatment with
alkalies. Ordinary green is produced upon silk by dyeing it yellow by means
of either weld, quercitron, fustic, or picric acid, and then dyeing it blue with indigo-
carmine, aniline blue, or sulphindigotic acid. Fast green is obtained by dyeing the
silk blue with Bleu Raymond, and next treating it with fustic. During the last few
years aniline green (emeraldine) has been generally used for dyeing silk green. Lilac
is produced upon silk by means of aniline violet, archil, or logwood and tinsalt.
608
CHEMICAL TECHNOLOGY.
Calico Dyeing.
Cotton is dyed either in yarn or woven fabric, but more generally as
yarn. Cotton is far more difficult to dye than wool, and requires, especially for
obtaining fast colours, stronger mordants. Blue is produced upon cotton (calico it
is termed in fabric) by means of the copperas-vat (see Indigo); further by Berlin or
Prussian blue, logwood, and green copperas; and finally by being passed through a
solution of oxide of copper in ammonia; the fibre, yarn, or tissue exhibiting after
drying a beautiful bright blue colour. Yellow is produced with Avignon berries,
weld, fustic, quercitron, annatto, acetate of iron (nankeen), and chrome-yellow.
Green is obtained by the copperas-vat followed by dyeing with fustic. Brown is
produced with a salt of iron and with quercitron or madder, or simply by means of
hydrated oxide of manganese. Black is either fast, aniline black, or is produced by
dyeing blue by the aid of the copperas-vat, next mordanting with acetate of iron, and
then dyeing in a bath consisting of galls and logwood. The aniline colours can be
fixed upon cotton only by the aid of a specific mordant-a solution of tannin in
alcohol; or the fibre of cotton is first animalised, as it is termed; that is to say,
impregnated with either albumen or casein, the fibre being to a certain extent made
similar to that of wool or silk and rendered absorbent of aniline dyes. Cotton may
be mordanted with Gallipoli oil, or with soft-soap for certain dyes.
Turkey Red.
As regards dyeing cotton and calicos red, madder is the chief dye material, while
probably at no distant period artificial alizarine from anthracen will become an important
material. We distinguish between ordinary red and Turkey, sometimes termed
Andrinople red; the former is produced upon cotton goods mordanted with acetate
of alumina (commonly called red liquor or red mordant); the latter is obtained by
complicated manipulation, the rationale of which is not quite elucidated by science.
This beautiful and very fast red, improved by washing, is produced by
the following distinct operations:-The well-bleached cotton goods are first padded
in a mixture of Gallipoli oil and pearl-ash containing about 200 lbs. of oil, 40 lbs. of
pearl-ash, and 100 gallons of water, a quantity sufficient for about 4000 yards of
calico. The pieces are next exposed to air in summer and to the heat of a stove in
cold weather for twenty-four hours; then padded again in a mixture of oil, potash,
and water, and again dried and exposed, and so on for as many as eight different
treatments for dark colours. The excess of oil, or rather that which has not suffered
change by oxidation and the alkali are now removed by steeping in an alkaline fluid,
and the pieces well washed. The next process is the galling and aluming; 60 lbs.
of ground nut-galls are exhausted with hot water, and to this liquor are next added
120 lbs. of alum and 10 lbs. of acetate of lead, after which the liquor is made up to
120 gallons. The pieces are padded in this liquor, dried, and aged three days, then
fixed by passing in warm water containing ground chalk, being next washed and
dyed in madder mixed with a little sumac and with blood. For dark shades of
colour the fabrics undergo another galling and aluming after dyeing, and are then
aged, fixed, and dyed a second time. After this last operation the goods exhibit a
very heavy brown-red colour, and they are brightened by two or three soapings or a
passage in dilute nitric acid. In other processes sheeps' and cows' dung are mixed
with the oil and other modifications introduced. Garancine is largely used in Turkey-
red dyeing. By its use the operations of clearing and brightening (avivage) have
been much shortened. All that has been suggested as regards the rationale of the
Turkey-red dyeing process, and more especially as regards the action of the Gallipoli
oil (huile tournante, an inferior kind of olive oil which, when mixed with a weak
PRINTING OF WOVEN FABRICS.
60g
solution of pearl-ash, should, if of proper quality, form a perfect emulsion, which, after
twenty-four hours' standing, should not exhibit any globules of oil floating on the
surface), is not sufficiently substantiated to afford a secure basis for further reasoning.
Linen is dyed by processes similar to those in use for cotton, but owing
to the peculiar structure of the flax fibre, its affinity for dyes is much lower than that
of cotton.
Dyeing Linen.
Fabrics.
THE PRINTING OF WOVEN FABRICS.
Printing of Woven This very important branch of the dyer's art aims at producing
coloured patterns upon calico, linen, and woollen and silk tissues. Calico printing is
the most important portion of this industry, which is based upon the same principles
as dyeing, but is in the practical execution far more difficult, partly because the
colours have to be applied to certain portions only of the fabric, while others either
remain colourless or are discharged, partly also because it frequently happens that
many colours have to be applied close to each other. The colours employed in calico
printing are of two different kinds; first, such as are directly applied to the cloth by
the aid of blocks or plates upon which the patterns and designs to be produced upon
the calico are engraved-to the colours thus applicable belong, also, the ochres,
Berlin blue, madder-lake, indigo, cochineal, and most of the tar colours; secondly,
the other kind of colours are such as are produced by immersing the calico printed
with various mordants in dye-baths—madder, cochineal, logwood, weld, sumac, cutch,
&c., belong to this category.
There exist various methods of printing, of which the following are the chief:-
1. From the thickened and mordanted colours.
2. The thickened mordant only is applied by means of engraved copper cylin-
ders to the cloth, which, after the mordant has been thoroughly fixed, is put
into the dye-beck.
3. The entire piece of cloth is either mordanted or a colour is printed, while to
such portions of the cloth as are to remain white or are intended to be
afterwards of another colour or colours, or pattern, a resist is applied,
sometimes printed from blocks, or more frequently from cylinders, the effect
being that on the portions of the cloth thus protected the dye does not
become fixed.
4. Coloured patterns may be, and in practice are, largely produced by first
dyeing the mordanted cloth (calico nearly always requires a mordant)
uniformly with one colour, and removing this colour in certain portions
of the cloth by what are technically termed discharges, that is to say,
chemicals which destroy the dye.
In order to fix certain kinds of colours they have to be submitted to the action of
steam (steam colours); while such inorganic substances as ultramarine, emerald
green, &c., or among the semi-organic, the lakes of madder for instance-which are
applied mechanically by the aid of albumen, caseine, gluten, and also require for
fixing the aid of steam-are technically termed surface-printed colours.
Mordants. The mordants employed in calico printing are chiefly such salts as are
comparatively loose combinations of acid and base, so that the latter can readily unite
with the fibre. Among the mordants chiefly used the acetates of alumina (see p. 263)
and iron occupy a first place, while alum or a solution of aluminate of soda is more
rarely used. Acetate of lead is the mordant for producing chromate of lead; various
40
610
CHEMICAL TECHNOLOGY.
combinations of tin (see p. 75) are also employed as mordants. The application of a
mixture of caseine and lime has been recently proposed as a mordant; for this
purpose caseine, technically known in England as lactarine, and prepared from milk
(of which it is the curd), is dissolved in dilute caustic ammonia, and the solution thus
obtained is mixed with freshly prepared milk of lime. The caseine-lime mixture is
used for steeping the cloth intended to be dyed; the caseine-lime becomes insoluble
by the application of heat, after which the fabric is so thoroughly mordanted that it
resists washing with alkaline fluids. In order to prevent the stiffness of the cloth
when the caseine-lime is used as a mordant, it has been suggested to mix the fluid,
previous to its application to the woven fabric, with some Gallipoli oil; the calicos
to which this mordant is applied behave as regards the dyes like wool, and readily
take the same colours. Cheese, which does not contain too much fat, or skim milk
cheese, when digested with ammonia, produces a solution which can be used instead
of caseine. Tannic acid, albumen, dried white of eggs re-dissolved in water, and
vegetable gluten are used as mordants in calico printing.
Thickenings. In order to give the colours or mordants used in printing, either by
block or cylinder, a sufficient consistency, they are mixed with what are technically
known as thickenings. As such are used:-Senegal gum, tragacanth, leiocome,
British gum, dextrine, salep, flour, gluten, pipe-clay with gum, glue and size, sulphate
of lead, sugar, molasses, glycerine, starch, sometimes chloride and nitrate of zinc.
The purity of the colours and mordants depends in a great measure upon the quality
of the thickenings. British gum, prepared from starch, is most frequently used. As
regards the selection of the thickening, it should be borne in mind that very acid
mordants cannot be mixed with starch, because it loses its consistency with acids;
while again, some metallic preparations-for instance, basic or sub-acetate of lead,
solutions of tin, nitrate of iron, and of copper-cause gum to coagulate, and hence gum
should not be used as a thickening with these substances.
Resists, or Reserves. As already stated, there is used in calico printing a composition
which, on being applied to the cloth, prevents the deposition or fixing of colour to
the portions of the cloth where the resist composition is placed, the result being
that these portions are left white. Most frequently the resist is employed with the
view of preventing the fixation of indigo to certain portions of the cloth, so that it
remains white where the resist has been applied. The resists are composed of pasty
excipients, such as pipe-clay, fat, oil, sulphate of lead, to which are added and with
which are incorporated substances which readily yield oxygen, for instance, sulphate,
nitrate, and acetate of copper, or a mixture of red prussiate of potash (ferricyanide of
potassium), and caustic soda solution. In some instances resists are composed so
that they act as a mordant (alumina or iron mordants) for other dyes, the portions of
the cloth protected by the resist from contact with indigo, and left white, being dyed
by immersion in a dye-beck containing another dye-stuff, which may be madder or
quercitron bark. This kind of printing is sometimes termed lapis, in consequence of
the remote similarity which some of these patterns bear to lapis lazuli. The so-
called white resist for cylinder printing consists, as an example, of acetate or
sulphate of copper, acetate of lead thickened with gum, or dextrine solution. This
composition having been printed by means of the cylinders, the pieces are the next
day put into the indigo-vat and kept there until the desired depth of colour has been
obtained, after which they are passed through a bath containing dilute sulphuric
acid until the places where the resist has been applied have become white. The
•
PRINTING OF WOVEN FABRICS.
611
rationale of this process is the following:-As soon as the reduced indigo (white
indigo) in the vat comes in contact with the oxide of copper, it is converted at the
expense of the oxygen of the oxide into blue indigo, which is precipitated in insoluble
state on the resist. By the treatment with dilute sulphuric acid the hydrated sub-
oxide (red oxide) of copper is dissolved, and with it the indigo blue washed out.
Instead of the salts of copper white resists are used, and composed of bichloride of
mercury and sulphate of zinc; the former acts in a manner similar to the salts of
copper, while the latter enters into an insoluble combination with the reduced (white)
indigo, which is precipitated where the resist has been applied.
Discharges. Discharges are for the purpose of producing by chemical means white
patterns on certain parts of the dyed cloth. This end may be attained by dissolving
a previously applied mordant or as is the most usual method-by destroying or
discharging the dye which has been distributed over the whole surface of the cloth.
As regards the first method, certain acids-phosphoric, arsenic, lactic, oxalic, hydro-
fluosilicic acids are made to combine with the base contained in the mordant;
while for the purpose of discharging the previously applied colour, there are
used such substances as bleaching-powder, chromic acid, a mixture of red prus-
siate of potash and caustic soda-ley, permanganate of potash, a paste composed
of bromine mixed with water and pipe-clay, nitric acid, &c. All these agents have
an oxidising effect, whereas protochloride of tin and protosulphate of iron, also used
for this purpose, acting by absorbing oxygen, are reducing substances. Among the
Acid Discharges. acids, tartaric acid is generally used for the purpose of discharging
alumina and oxide of iron employed as mordants; sometimes this acid is mixed with
bisulphate of soda. A piece of cloth dyed red or blue, to which is in certain parts
applied a mixture of tartaric acid, pipe-clay, and gum (the latter as thickening
to give consistency), becomes immediately bleached when the cloth so prepared is
immersed in a solution of bleaching-powder.
Discharges.
Oxidising Agents as Of late fluoride of potassium has been used as a discharge for
Berlin blue. The discharging of indigo blue by oxidising agents is due to the for-
mation of isatine from the indigo blue, the former being soluble, the latter insoluble
in water, so that the soluble substance can be removed by washing :-
C16H10N2O2+20= C16H10N204.
Indigo blue.
Isatine.
Indigo is discharged by chromic acid, employed in practice as bichromate of
potash, the acid being reduced while giving off oxygen to chromic oxide. More
recently Mercer has proposed to bleach goods dyed with indigo by the application of
a mixture of potash and ferricyanide of potassium; for this purpose the indigo-dyed
cloth is soaked in a solution of red prussiate of potash, and then caustic
potash thickened with British gum is printed on. The potash converts the
ferricyanide into ferrocyanide, and by the oxygen thus set free the indigo blue is
coverted into isatine :-
Ferricyanide of potassium, 4K,FeCу6"
Caustic potash. 4KOH
Indigo blue, C16H10N₂O₂
Reducing Agents as
Discharges.
yield
{
Ferrocyanide of potassium, 4K4FeCу6.
Isatine, C16H10N2O42H₂O.
Protochloride of tin, known as crystals of tin and as tinsalt, is the
most important of the reducing agents applied to goods dyed with oxide of iron.
When the protochloride is placed in contact with oxide of iron, the result is the for-
mation of readily soluble protochloride, which is removed by washing, while
612
CHEMICAL TECHNOLOGY.
simultaneously there is deposited on the fibres of the cloth stannic acid (more cor-
rectly proto-peroxide of tin), which may serve as a mordant for red and yellow dyes.
Calicos may be printed by :-
Calico Printing.
1. Dyeing in the dye-beck.
2. By block or cylinder printing (topical colour-printing).
3. By resist or discharge printing.
In the process of dyeing in the dye-beck (madder style) the thickened mor-
dant, to which usually some faint colouring matter is added for the purpose of
recognition (the reader should bear in mind that the mordants are colourless,
or at least nearly so), the pattern produced on the white calico is imprinted
by the aid either of blocks or cylinders, upon which the desired pattern is
engraved.
The process of block printing takes place upon a table over which a piece of thick
woollen cloth is stretched. The calico to be printed is laid on this cloth, and by the
aid of blocks the mordant is transferred to the calico. The blocks, made of pear-tree
wood, box-wood, or fir-wood, have the pattern engraved en relief, or wrought by means
of brass wires fastened in the wood in such a manner as to form a certain figure. The
former blocks are called engraved, the latter dotted or stippled blocks, while in some
cases the two methods are used simultaneously. In order to distribute the mordant
uniformly a frame or chase is employed, on which, by means of nails, a stout piece of
canvas is stretched, the frame being made to float on the top of a thick solution
of gum or linseed mucilage, placed in a suitably constructed vessel. On a frame a
piece of oil-cloth is fastened to prevent percolation of the fluid; next the mordant is
brushed over the cloth of the frame quite uniformly. The printer puts his block on
the cloth thoroughly moistened with mordant, so that the projecting engraved
portions of the block become uniformly moistened, and the block having been trans-
ferred to the calico is pressed thereon, the pressure aided either by a smart blow
given by the printer's fist or by a wooden mallet, care being taken to print every
portion of the engraving equally on to the woven fabric. When several mordants
are placed on to the frame by the aid of separate brushes and thence printed on to
the cloth, the result is the production of the so-called iris or fondu prints. In order
to accelerate the operation of printing, machinery is now usual-for instance, the
Perrotine, invented by Perrot, at Rouen, in 1833. This machine works with
three to four wooden formes (Perrotine formes upon which the patterns are fastened by
nails), these patterns being cast in a manner similar to stereotype plates, consisting
of a readily fusible metallic alloy. The arrangement of this machine is of course
such, that the formes are as wide as the cloth intended to be printed. Instead of this
machine cylinder printing has become general. The cylinders are made of copper,
and on these the pattern is engraved. The cylinders are revolved in a framework by
means of machinery. By the aid of a wooden cylinder covered with cloth which
dips into the vessel containing the mordant, the copper cylinder is fed with mordant,
while a kind of blunt knife, known technically as the doctor, scrapes off from the non-
engraved portion of the copper cylinders any superfluous colour, which is thus con-
fined to the engraved portion forming the design.
Before the mordanted cloth can be dyed it has to be kept for some time in
order that the alumina and iron mordants may combine intimately with the fibre of
the cloth. Moreover, the cloth, before being immersed in the dye-beck, has to
undergo the operation technically known as cleansing; that is to say, after the mor-
PRINTING OF WOVEN FABRICS.
613
dant has become dry, the thickening and faint colouring matter have to be removed,
together with any mordant uncombined with the fibre. For goods intended to
be madder dyed the cow-dung bath is required. Usually some chalk is added for the
purpose of saturating the acetic acid or the mordant. Although all calico printers
agree that the cow-dung bath is necessary, the rationale of the action of this bath has
not as yet been explained. According to Mercer and Blyth, for cow-dung may be
substituted certain phosphates and arseniates, and these chemists propose the use of
phosphate of soda and phosphate of lime. More recently silicate of soda has
been used instead of cow-dung. In England cow-dung is no longer, or at least only
very rarely, used. After the goods have been treated with cow-dung or its substitutes,
they are washed and then dyed. In the case of dyes the colouring matter of which
readily soluble in water, infusions or decoctions are used; cochineal, quercitron
bark, weld, safflower, &c., are thus used. But other dyes, the colouring principle
of which is less readily soluble, such as madder and garancine, are put with
It
hot water into the dye-beck in which the mordanted goods are immersed.
is clear that when several different mordants have been printed on to the cloth,
several different colours can be obtained by the same dye material. With madder,
for instance, all shades of pink and red, black, brown, violet, and lilac can be pro-
duced when alumina and iron mordants and mixtures of these have been used
as mordants. As the dye only takes where the mordant has been applied, it can
be readily removed from the other portions of the cloth; this removal of superfluous
dye is effected by washing, treating with hran and soap, and grass bleaching opera-
tions, technically termed clearing. In some cases madder-dyed goods are cleared
with the aid of solutions of bleaching-powder or Javelle ley (see p. 223). Some dyes
require in order to become bright and brilliant the operation known as avivage or
clearing, but of a special nature; this is more particularly applicable to Turkey-red
dyed goods, which after removal from the dye-beck are submitted to a boiling under
pressure with soap-suds and chloride of tin.
Topical or Surface Colours. The process of applying thickened colours and mordants
simultaneously is known as topical or surface printing, the colours, pigments, being
termed topical or surface colours. Of these two varieties are known, one of which
is printed in the state of solution, becoming gradually fixed and insoluble on the fibre
itself; the other is applied in the insoluble state with thickening and plastic
substances, by the aid of which the colours adhere to the fibre, so that by simple
washing they are not removed-ultramarine is applied in this manner. Many of these
styles of printing require for fixing as well as for clearing the application of steam,
from which they derive their name of steam colours, now very extensively used.
The printed goods are dried for two or three days, and next stretched on frames, and
thus arranged exposed to the action of steam at 100°, in properly constructed rooms.
The length of time this operation is continued depends in practice upon several con-
ditions, and varies in different establishments, but is generally twenty to forty-five
minutes at a time. The precise action of the steam is not well known. China blue,
deriving its name from a resemblance to the colour of old china ware, is produced by
a very complex process, of which the following is a brief outline. The indigo in its
natural state is very finely ground and mixed with deoxidising bodies, such as
sulphate of iron, acetate of iron, orpiment, or protochloride of tin, and thus applied to
the cloth; the goods thus printed are aged and afterwards dipped into clear lime-
water; this serves to "wet out" and to form an insoluble, or at least difficultly
614
CHEMICAL TECHNOLOGY.
Discharge Style.
+
soluble, compound of the gum paste or starch of the thickening with the lime. The
piece is next placed in the copperas vat for ten minutes, the lime-water which
adheres to the cloth precipitating a little oxide of iron over its whole surface, but it
does not appear that the slightest dissolution or deoxidation takes place. The piece
is now taken to the lime vat again, in which it is gently moved about; by this opera-
tion the indigo is deoxidised and dissolved, but does not spread beyond the design,
for the reason that it is surrounded with fibres saturated with water and coagulated
gum, while by the excess of lime present, the solubility of the deoxidised indigo is
greatly lessened. The piece is again dipped into the copperas vat and again into the
lime vat several times, the last dip being in lime for a long time. The goods, thickly
coated with a cream of lime, are put into clean water, and afterwards into a dilute
acid, then washed and cleared in weak soap and warm weak acid. China blue is a
fast colour, but very dark shades cannot be obtained by this process, which is rather
costly on account of the time and labour it requires. Steam blue is obtained by
printing with a solution of ferrocyanide of potassium thickened with starch,
acidulated with tartaric acid and a small quantity of sulphuric acid, after which the
calico is dried, aged, and lastly steamed. Yellow is produced by first treating
the goods with acetate of lead, and next passing them through a solution of bichromate
of potash. Green is produced with a mixture of chromate of lead and Berlin blue.
As employed in practice on the large scale, the term discharge is
given to a composition which has the power of bleaching or discharging the dye
already communicated to a fabric. The discharging of mordants by the aid of
agents-chiefly acids-which dissolve or otherwise render ineffective the constituents
of the mordants, seldom occurs in practice, and only then a few special styles. As
a rule, discharge is effected with uniformly dyed goods, more especially indigo and
Turkey-red dyed fabrics, upon which it is desired to produce white patterns; while
sometimes upon a portion of the white ground thus obtained other colours are produced.
The agents used to produce the discharge vary with the dye which has been applied as
well as with the colour afterwards desired to be produced on the white ground,
while, moreover, the discharge ought not to injure the fibre of the cloth. Oxalic,
tartaric, citric, more or less dilute sulphuric and hydrochloric acids, bisulphate
of potash, nitrate of lead, solutions of bleaching-powder, weak chlorine water, and
bichloride of tin are used, being properly thickened with suitable materials, while
some are so contrived as to serve as mordants for colours to be subsequently applied;
for instance, for blue, a mixture of tartaric acid, Berlin blue, tinsalt, farina, and
water, is used; for yellow, nitrate of lead with tartaric acid, starch, and water; for
green, a mixture of yellow and blue; for black, a logwood decoction to which
nitrate of iron has been added. The pieces thus prepared (these discharges having
been printed on) having been put into and passed through a solution of chloride
of lime, the dye previously applied is destroyed where the discharge is printed, and
in its stead the new colour is produced according to the pattern. Chromic acid, or an
acidulated solution of bicromate of potash, is sometimes used as a discharge,
the oxide of chromium produced yielding a brown colour.
Aniline Printing. As regards the application of these colours to calico printing they
may be termed steam colours. The printing and fixing is effected by the following
methods:-1. The thickened mordant is printed on, and next fixed either by drying
or by ageing and steaming after drying, the fabric being dyed in a solution of the
aniline colour (red, violet, blue), the colour becoming fixed to the mordanted portions
PRINTING OF WOVEN FABRICS.
615.
only of the calico. 2. The thickened mordant is mixed with the aniline dye, and
thus printed, and the fixing effected by steaming. The mordants for these colours
are:-Dried albumen, blood albumen, viz., that bleached by the action of ozone
obtained by means of oil of turpentine; vegetable gluten in various forms, for
instance, that dissolved according to W. Crum's plan in weak caustic soda ley, or
according to Scheurer-Rott in a weak acid, or gluten dissolved in saccharate of lime
according to Liès-Bodard, or finally gluten dissolved by incipient putrefaction, as
suggested by Hanon. Instead of gluten caseine may be used dissolved either in
caustic ley or in acetic acid; glue and tannate of glue are also used (Kuhlmann and
Lightfoot). Other mordants for these colours are tannin, fat oils, and preparations
thereof, as oleo-sulphuric acid, palmatino- and glycerin-sulphuric acid. Further,
certain resins, among which shellac dissolved in borax is one.
Gluten is largely obtained as a by-product of the preparation of starch from
wheaten or other flour. When required for use as a mordant, the gluten is allowed
to remain in moist state, and by incipient putrefaction becomes sour, and hence fluid.
The mass is purified by first treating it with carbonate of soda; 5 kilos. of the sour
gluten require for saturation about 560 grms. of a carbonate of soda solution at
1'15 sp. gr., whereby the gluten is again rendered insoluble, and after having been
washed is re-dissolved in caustic soda ley, 5 kilos. of the gluten requiring 435 grms.
of a caustic soda solution at 1080 sp. gr. This solution is next diluted with 3.5 litres
of water. The fluid is printed on the calico, which is next dried, aged, and steamed,
after which it is rinsed in water and dyed in a solution of the aniline colour. The
gluten is sometimes mixed with the aniline colour and printed on with it, after which
the calico is steamed a first time, then washed, and steamed a second time. Gluten
may be used without the preparation with carbonate of soda by leaving it to putrefy
until it has become very fluid; it is then mixed with about one-third of its weight of
caustic soda solution of the above 1080 sp. gr. When caseine (lactarine, it is tech-
nically termed in England) is used for mordanting calico previous to the application
of aniline dyes, it is dissolved in caustic soda, and after the calico has been printed
with this mixture the aniline colour is printed on.
The method of printing with aniline colours as devised by (3) Gratrix and Javal,
differs considerably from the preceding, and consists (a) in preparing an insoluble
compound of the aniline colour with tannic acid, which, having been thickened with
Senegal gum, is printed on to the cloth which has been previously mordanted with
tinsalt or any other suitable mordant; or (B) there is printed on the previously
animalised cotton, that is to say, cotton mordanted with albumen, lactarine, or
gluten, or cotton mordanted with tinsalt, a thickened decoction of galls, by which in
the first place a tannate of albumen, &c., in the second one of tin, both insoluble in
water, are formed. The calico having been dried is then passed through an
acidulated aniline solution. The aniline-tannin compound mentioned under (a) is
prepared by adding to an aniline solution as much decoction of galls (better still
solution of tannin) as is required for the complete precipitation of the dye material.
This precipitate is collected on a filter, washed, and dissolved in alcohol or acetic
acid, and having been thickened with gum, the solution is used for printing. When
printed the goods are steamed and washed either with or without soap, according to
the shade which it is desired to give to the colour. A red colour requires a soap-
wash. According to the second method the calico is treated with a solution of stan-
nate of soda, after which a thickened solution of tannin, or a tannin-containing
616
CHEMICAL TECHNOLOGY.
material is printed on to the cloth, which is steamed and the mordant further fixed.
The dyeing operation is carried on in a dye-beck used as for madder, the beck being
filled with water, acidulated with acetic acid, and heated to 50%. The cloth is put
into this liquid, and gradually the dye dissolved in acetic acid is added. When the
requisite quantity of the dye has been added, the contents of the dye-beck are heated
to the boiling-point. Aniline black is produced (see p. 579) upon the cloth by means
of chlorate of potash, chloride of copper, ferricyanide of ammonium, or freshly pre-
cipitated sulphuret of copper. Naphthylamin violet (see p. 583) is now produced by
a similar process.
and Dressing.
Hotpressing, Finishing, The printed, washed, and rough-dried cotton goods are next
finished, that is to say, starched, dried, often calendered, hot-pressed,
folded, and again pressed. In England these operations form a distinct branch of the
dyeing art usually not performed by the printers. For chintz white wax is added to the
hot starch in order to impart a better gloss. In order to give muslins a somewhat velvety
appearance spermaceti is added to the starch while being boiled with water.
Printing Linen Goods. Linen goods are, as a rule, neither dyed nor printed, and only a few
indigo-dyed articles on which white patterns are produced are in the trade. As regards the
Printing Woollen Goods. printing of woollen goods, flannels more particularly, block-printing
is most frequent. The goods are mordanted with chloride of tin. The fixing of many of
the colours imparted to woollen goods is effected by steaming. We distinguish, moreover,
in the printing of woollen goods-1. Golgas printing; and (2) Berill printing. As regards
the former method, now almost obsolete, the golgas, a very thin and light flannel fabric, is
first mordanted with alum and cream of tartar, and next placed between wooden or
leaden plates partly perforated with a pattern, and strongly pressed in a peculiarly
constructed hydraulic press, where it is possible to force dye solutions through the goods,
which are only wetted by these solutions and consequently dyed where the dye liquor can
pass through, the strong pressure preventing the liquid running over the flannel in
any other direction. By the berill printing process the surface colours, thickened with
starch, are printed on to the flannel with hot brass formes; the starch not being removed,
the result is the formation of relieved and coloured patterns. The processes and methods
Printing Silk Goods. of printing silk goods are generally the same as for calicos; either sur-
face printing is resorted to with fixing by steam, or various mordants are printed on to
the silk, which is next dyed in the dye-beck. A peculiar kind of printing on silk is based
upon the property of nitric acid producing upon silk a permanent yellow colour, as well as
of destroying most other dyes, and yet acting on resins and fatty substances only slowly.
Mandarin Printing, This mode of printing on silk is termed mandarin printing, and the
tissue, chiefly silk handkerchiefs, to which it is applied, mandarins. In order to etch with
nitric acid on the indigo-dyed silk, there is printed on to it a resist, composed of resin and
fat, after which the tissue is kept for 2 to 3 minutes in a mixture of 1 part of water and
2 parts of nitric acid heated to 50°. The goods are then thoroughly rinsed in fresh water
and boiled in a soap solution, to which carbonate of potash is added. The portions of the
silk where no resist has been placed are thus made beautifully yellow.
Bandanas. On genuine madder-red dyed silk white patterns are etched by a process
similar to that just described for golgas printing. The goods are placed between leaden
plates in which the pattern is cut out, and then submitted to strong hydraulic pressure;
next a solution of bleaching-powder acidulated with some sulphuric acid is forced through
the goods, by which the madder dye is destroyed. The pattern thus etched may be after
washing, the pressure remaining and water being forced through, dyed yellow by first
forcing a solution of acetate of lead and next one of chromate of potash through the
woven fabrics, kept of course in the press.
DIVISION VII.
THE MATERIALS AND APPARATUS FOR PRODUCING ARTIFICIAL LIGH1.
Artificial Illumination
in General.
Very few among the large number of bodies which at a high tem-
perature, either by combustion or at a red heat, evolve a permanent light are suited
for use as materials for artificial illumination. The number of bodies which comply
with the conditions demanded in artificial illumination is very small. These condi-
tions are the following:-
1. That by the combustion of the body a sufficient degree of heat be evolved to
maintain the combustion. 2. That when the burning body happens to be solid, it be
previous to the combustion converted into gas or vapour, as otherwise no flame is
generated, which is absolutely required for the purpose of illumination. 3. That the
burning body evolve in the flame solid bodies or very dense vapours as an essential
condition of the illuminating property of the flame. 4. That either the body itself or
the raw material from which it is obtainable be present in large quantity and be
readily obtainable. 5. That the products of combustion be gaseous and harmless to
the health.
It is a generally known fact that any great accumulation of heat imparts to bodies
the property of emitting light. This is more conspicuous in solid and fluid bodies,
because their molecules are placed more closely together than happens to be the case
with gases and vapours. At a temperature of 500° to 600° a solid body becomes
red-hot, while at about 1000° white heat occurs. A gaseous body heated to these
degrees of temperature emits only a very feeble light. In order to render a gaseous
body (and as already mentioned only gaseous bodies are suited for illuminating
purposes) luminous during its combustion, it should contain the vapours of some of
the higher hydrocarbons (for instance, benzol, acetylen, naphthaline, &c.), and that
these by becoming white-hot should yield light, or that there be present in the flame,
by itself non-luminous, a solid body which is thus rendered white-hot; for instance, a
spiral platinum wire in a hydrogen flame, a piece of caustic lime in the oxy-hydrogen
flame, a cylindrical piece of zircona or magnesia in a hydrogen or coal-gas flame
fed by oxygen, oxide of magnesium in the flame of burning magnesium (magnesium
light), solid phosphoric acid in the flame of burning phosphorus, &c. Leaving out of
the question for the present such lights as are not generally available, as those just
alluded to, and also the electric light, it is clear that for all practical purposes we
can avail ourselves of only such materials for illuminating purposes as yield a flame
618
CHEMICAL TECHNOLOGY.
which emits light in consequence of the vapours of heavy hydrocarbons present
therein. These hydrocarbons are indeed contained in all the substances which are
either used for illuminating purposes or from which illuminating materials are
prepared, as, for instance, tallow, palm oil, and the fatty acids, viz., stearic and
palmitic, wax,. spermaceti, paraffin, rape-seed oil, the various paraffin and petroleum
oils, camphine (highly rectified oil of turpentine), coals, bituminous schists, boghead
coal, wood, fats, and resins.
Flame. Every solid and fluid body which becomes either volatilised, or decom-
posed into gaseous matter at a temperature below that required for its combustion,
can burn only in the shape of gas. The ensuing light is what we call flame.
The well-known shape of flame is due to the pressure of the ambient air, because
the latter, becoming heated and being rendered specifically lighter, ascends. When
the illuminating material consists of molten paraffin, stearic acid, or oil (colza, rape-
seed, or petroleum), it is sucked upwards in the interstices of the wicks acting as
capillary tubes, and in the immediate neighbourhood of the flame these substances are
converted into gases and vapours, the nature of which closely agrees to that of purified
illuminating gas.
Sir Humphry Davy was the first to elucidate the nature of flame and the
cause of its luminosity as well as of the unequal luminosity of different kinds of
flames. In our day the researches of Hilgard, H. Landolt, Pitschke, Blochmann,
Kersten, and more particularly of H. Deville, Volger, Lunge, Dr. Frankland, and
others, have greatly contributed to our knowledge of flame. When closely observed
we can distinguish in flame three distinct portions, viz. :—(1) an outer luminous layer,
or so-called veil; (2) a central nucleus, which is red-hot; and (3) an inner and lower
portion, in which the gaseous substances about to become ignited are heated. The
opinion formerly held about the cause of the emission of light by flame was that by
the combined action of a very high temperature and the oxygen of the atmosphere,
which first combines with the hydrogen, carbonaceous matter is separated, which,
being heated to a bright white heat emits light. By the researches made by Hilgard
on the flame of burning candles, and of Landolt and H. Deville, who experimented
with a gas-flame, we have been taught that a very quick and rapid diffusion of air
and the products of combustion takes place, and that in the interior of the flame a
decrease of the quantity of the combustible gases and an increase of the products of
combustion occurs. But all these researches do not enable us to explain many of
the most ordinary phenomena observed in luminous flames. We do not, for example,
know what relation there exists between the chemical composition of an illuminating
substance and its illuminating power; consequently, gas analyses made for the
purpose of testing gas are in that respect of very little value. According to the
researches of O. Kersten, confirming those of O. L. Erdmann, the atmospheric oxygen
combines, at least in gas flames, first with the suspended particles of free carbon and
next with the hydrogen. The combustion, Kersten states, does not take place in the
centre of the flame, but only at the veil and that portion of the luminous mantle
which is nearest to the veil, because we cannot admit that any trace of oxygen can
pass through a layer of red-hot hydrogen and carbon. The products of combustion
observed in the centre of the flame are not formed there, but have been carried there
by diffusion. The total heat of the flame is consequently derived from the limit of
the zone of combustion. The temperature of the centre of the flame and of the
mantle increases of course towards the top, and hence the most luminous portion of
ARTIFICIAL LIGHT.
619
the flame is that where the carbon is separated by the intense heat, below the thin
layer of the dark central cone. Higher, where the heat which decomposes the
hydrocarbons into their constituents reaches upwards to the middle, the entire
centre is luminous, and hence a solid flame is exhibited. As, then, the free carbon
comes nearer to the layer rich in oxygen, it is converted into carbonic acid, and is
the more luminous the more energetic this combustion. In the veil oxide of carbon
and hydrogen burn simultaneously. The reason why this veil does not exhibit at
its lower part a luminous mantle is because the mass of the gases in the interior is
too cold for admitting a separation of hydrocarbons.
The non-luminosity of a flame, even that of pure olefiant gas, due to the too
contracted space occupied by the temperature of the veil, may be observed when a
gas flame is turned down as low as possible; in this case a complete combustion
takes place before any decomposition can ensue, just as happens in the lower blue
portion of a luminous flame. The luminosity, therefore, depends upon the composi-
tion of the gas before it is burnt, and not upon a subsequent combustion of the
carbon. It has been assumed that the luminosity of gas flames is due to the
momentarily eliminated particles of solid carbon becoming white-hot; but
according to Dr. Frankland's researches, made in 1867, it is not the particles of solid
carbon, but rather the dense vapours of the higher hydrocarbons, those having
a high boiling-point, which, while ignited at an elevated temperature, cause the
luminosity of the gas flame. There are present in illuminating gas compounds of
great density, which in the state of vapour, similar to what may be observed of the
vapour of arsenic, may render flame luminous; among these are the vapours of
benzol, naphthaline, and probably of many other of the constituents of coal-tar. These
vapours remain in the flame in undecomposed state up to the moment that they reach
the outer layer or envelope of the flame, where they become consumed when coming
in contact with the oxygen of the air. It has been customary to adduce as a proof
that the luminosity of the flame is due to eliminated particles of carbon, the fact that
when a piece of porcelain is held in the flame carbon is deposited thereon; but it has
not been proved that this substance is pure carbon; on the contrary, when the
deposit is submitted to analysis, it is always found to contain hydrogen, and any
chemist who desires to obtain pure carbon from lamp-black knows well enough that
this substance has to be strongly ignited in close vessels before all the hydrogen it
contains has been eliminated. In order to accelerate this process of purification,
chlorine gas is passed over the lamp-black placed in a combustion-tube, or better, a
porcelain tube, and raised to nearly a white heat. Lamp-black is probably nothing
more than a conglomerate of the densest light-emitting hydrocarbons, the vapours of
which become condensed upon the surface of the cold porcelain. How could a flame
be so transparent as it really is were it filled with solid particles of carbon? How
could it be the same for photometrical assays if the flame be placed with its broad or
narrow edge towards the photometer if the light of the flame were due to solid
particles of carbon? It is possible that in a slight degree an elimination of carbon
actually takes place as a consequence of the decomposition of hydrocarbons, but the
main source and cause of the luminosity of a gas-flame is the combustion of the heavy
hydrocarbons. It is clear that the temperature of the flame has some influence on
its luminosity. According to H. Deville's experiments (1869) the degree of
the luminosity of a flame is intimately connected with the density of the vapours
present therein, while the dissociation does not appear to be without some influence
620
CHEMICAL TECHNOLOGY.
upon the condition of the flame. Under ordinary conditions an illuminating material
to be burnt in air free from draughts, and so that no smoky flame be produced,
should contain upon 6 parts by weight of carbon 1 part by weight of hydrogen,
as nearly obtains in olefiant gas, paraffin, wax, and stearic acid. Oil of turpentine,
which contains upon 1 part by weight of hydrogen 75 parts by weight of carbon,
burns with a sooty flame. This is the case in a higher degree with benzol, which
upon 1 part of hydrogen contains 12 of carbon, or with naphthaline, in which the
proportion is 1:15. In order to burn the excess of carbon (as already stated,
according to Dr Frankland's researches, this is not pure carbon, but a conglome-
ration of dense hydrocarbons) which becomes eliminated, an increased supply of
air is required, such as is created by a lamp-glass. Such flames as do not eliminate
carbon, as, for instance, those of marsh-gas and alcohol, yield only a faint light
when burning. The luminosity of gas is at once destroyed when atmospheric air
is mixed with the gas, as may be observed in the Bunsen burner; the same effect
obtains when the gas is mixed with other indifferent gases or vapours.
Artificial light is procured:
I. From substances solid at ordinary temperatures, and prepared in the shape of
candles made of such materials as tallow, palm oil, stearic, palmitic and elaidic acids,
wax, spermaceti, and paraffin.
II. By employing fluid substances, chiefly in lamps, and which may be brought to
the following categories :-
a. Non-volatile oils, such as rape-seed, olive oil, fish oil.
b. Volatile oils which are either-
a. Essential oils, as, for instance, camphine (refined oil of turpentine); or
B. Mineral oils, obtained from tar, from peat, lignite, bituminous slate, boghead coal,
and consisting of mixtures of fluid hydrocarbons, met with in commerce under a
variety of names, such as solar oil, photogen, ligroine, kerosen, paraffin
oil, &c.; or
y. Native earth-oil or petroleum, which, after having been refined, is sold in England,
commonly under the name of petroleum oil, to distinguish it especially from
Young's patent paraffin oil.
III. By means of gaseous substances obtained by the dry distillation of coals,
bituminous slate, peat, wood, petroleum residues, resins, and fatty substances, all of
which when submitted to a high temperature above a cherry-red heat, become decom-
posed, yielding a solid residue rich in carbon (coke), tar, and gases; or again, by other modes
of treatment, as with the so-called water-gas, obtained by passing steam over red-hot
charcoal.
In the gaseous illuminating substances the luminous body is either :-
a. Yielded by the flame itself, as is the case in the ordinary gas flame; or,
b. Introduced externally, as in the so-called platinum light, by the aid of platinum
wire; in the lime-light by means of lime; in the magnesium- and zirconium-
light from cylindrical pieces of these substances; or by the so-called carburation
of the gas with the vapours of fluid hydrocarbons.
Light from Candles.
I. Artificial Light obtained by Means of Candles.
Leaving out of the question the use in some very poor districts of
splints of resinous wood for the purpose of procuring artificial light, candles are the
only shape in which solid materials are employed for illuminating purposes. A
candle consists of the solid illuminating material, palmitic and stearic acids, paraffin,
tallow, or wax, cast in the well-known cylindrical shape, and provided in the
direction of its longitudinal axis with a cotton-wick, the thickness and plaiting of
which should be arranged in proper relation to the diameter of the candle. We
describe in the following pages the manufacture of:—
1. Stearine candles.
2. Paraffin candles.
3. Tallow candles.
4. Wax candles.
ARTIFICIAL LIGHT.
621
1
Manufacture of Stearine
Candles.
•
1. Palm-oil and tallow are now in Europe the raw materials
for the manufacture of these candles, while lard is used for this purpose in the
United States (Cincinnati). The researches of W. Heintz, which complete those
made by Chevreul, have taught us that these fats consist of palmitic, stearic, and
oleic acids, and glycerine. The acid which Chevreul has designated as margaric
acid has been proved to be a mixture of palmitic and stearic acids. The so-called
"stearine candles" are frequently made of a mixture of stearine (viz., a mixture of
palmitic and stearic acids) and soft paraffin. Candles of this description are known
abroad as Apollo and Melanyl candles. The manufacture of stearine candles
consists in two chief operations, viz. :-
A. The preparation of the fatty acids;
B. The conversion of these acids into candles.
A. The preparation of the fatty acids can be effected by saponification with lime,
by means of sulphuric acid and subsequent distillation, by means of water and high-
pressure steam, and by means of steam and subsequent distillation.
by Means of Lime.
Preparation of Fatty Acids I. Saponification of the Fats by Means of Lime.-The raw
fats employed in this operation are beef or mutton tallow, and palm oil. The
mutton tallow contains a larger quantity of solid fatty acids, and is more readily
saponified, but beef tallow is cheaper. The Russian tallow, of which large quantities
are met with in commerce, is usually a mixture of beef and mutton tallow. As palm
oil is imported into Europe in large quantities and is comparatively low in price, it
has become in many stearine candle manufactories the fat chiefly used.
Stearine yields 95'7 parts of stearic acid (melting at 70°) C18H3602.¨
Palmitine
Oleine
94.8
90'3
""
palmitic acid
oleic acid
""
62° C16H3202.
-12° C18H3402.
Stearine, palmitine, and oleine, are glycerides. The stearine is tri-stearine,
C57H11006; palmitine is tri-palmitine, C51H98O6; and oleine is tri-oleine, C37H10406.
By the saponification with milk of lime, the calcium salts of the three fatty
acids, stearic, palmitic, and oleic, are formed, and glycerine is separated. The
operation of saponification is conducted in the following manner:-Of tallow or
of palm oil about 500 kilos. with 800 litres of water are put into wooden lead-lined
vats or tuns, of 20 hectolitres cubic capacity, and next by the aid of steam conveyed
into the vessel by a leaden pipe coiled spirally. When all the tallow has been
melted there are gradually added to it some 600 litres of milk of lime, containing
70 kilos. of lime — = 14 per cent of the weight of the tallow, care being taken to stir
the mixture continuously. After heating for some six to eight hours the formation
of the lime-soap is complete. The somewhat yellow glycerine solution is run off
from the solid granular lime-soap and used for preparing glycerine. According to
theory, starting from the supposition that upon 3 molecules of fatty acids found com-
bined in the neutral fat there is 1 molecule of glycerine, 100 parts of fat would
require only 8.7 parts of caustic lime, but in practice 14 per cent of lime is generally
used because it has been found that the saponification is rendered easier, but a larger
quantity of sulphuric acid is also required.
The lime-soap thus obtained is decomposed by means of sulphuric acid, either con-
centrated, or as so-called brown or chamber acid. This operation is carried on either
in the vessel in which the saponification took place, or in a similarly constructed vessel
622
CHEMICAL TECHNOLOGY.
or in stoneware basins. also fitted with a steam-pipe. The quantity of sulphuric acid
required for the decomposition of a mixture composed of 500 kilos. of tallow and
70 kilos. of lime amounts to 137 kilos. The acid is first diluted with water to 12° B.
= sp. gr. 1 086 (in this condition the acid contains 30 per cent, H₂SO4), and is next
poured on to the lime-soap, with which it is thoroughly stirred, while steam heat
is applied simultaneously. When the fatty acids have been set free the supply of
steam is shut off, and the fluid mixture left for some time, the melted fatty acids
rising to the surface, while the gypsum settles at the bottom of the liquid. The
melted fatty acids are transferred to a lead-lined tank, and in order to remove the
last traces of lime and sulphate of lime, first washed with dilute sulphuric acid, and
next with water, the steam heat being kept up to maintain the acids in a fluid state.
The quantity of purified fatty acids thus obtained is the following :—
500 kilos. of tallow 459'5 kilos. of fatty acids.
500
""
""
500
463'0
478'0
""
500
487'5
99
""
""
""
2000 kilos. of tallow 1888 0 kilos. of fatty acids,
equal to 94.8 per cent. The yield depends on the kind of tallow used, on its purity,
and the mode of operating for its saponification.
100 parts of the fatty acids give:--
a. 43°3 parts of solid fatty acids
b. 45'8
c. 46°2
""
""
""
39
""
29
d. 48°4
On an average 45'9 parts of a mixture of stearic
and palmitic acid.
When the fatty acids have been as much as possible freed from lime, gypsum, and
sulphuric acid, by means of repeated washing with water, they are kept in molten
condition for some time in order that the water may be thoroughly eliminated.
Next, the fatty acids are cooled and become solidified, after which they are
submitted to strong hydraulic pressure in order to remove the oleic acid, this opera-
tion being repeated and then performed with the aid of heat. The acids are then cast
into large square blocks, or cooled in moulds similar in shape to those used for large
cakes of chocolate, and capable of containing 2 kilos. of the fatty acids. In some
works moulds made of enamelled iron are used for this purpose. The fatty acids are
left in these moulds for the purpose of crystallising slowly; in winter twelve hours,
in summer twenty-four hours, are required for attaining this end. The more slowly
the crystallisation proceeds the better, because the more readily the fluid portion can
be separated by pressure from the solid mass. The solidified mass is next
submitted to hydraulic pressure, in order to eliminate the fluid fatty acids retained
between the crystals of the solid mass. The first operation of pressing is performed
at the ordinary temperature. The solid cake of the fatty acids is for this purpose
put into a press-bag, which may be made of any strongly woven fabric, horsehair
cloth being often employed. The press-bag having been filled is placed between
plates of iron or zinc, and then transferred to the table of a hydraulic press, capable
of exerting a pressure of 200,000 kilos. The oleic acid which runs off is collected in
channels and thence conveyed by a pipe to a cistern. This material is used in soap-
making, also for lubricating wool, and more recently as oleic acid ether mixed
with alumina for the purpose of softening leather. When the hydraulic press does
ARTIFICIAL LIGHT.
623
not remove any more fluid from the solidified crystalline acids, hot-pressure is
resorted to. For this purpose hydraulic presses of a peculiar construction and
placed in a horizontal position are employed; the arrangement of these presses, the
plates of which are heated by means of steam is, however, too complicated to be use-
fully described. The pressed fatty acids are next purified. This is effected by
treating them in a molten state with very dilute sulphuric acid (3° B. =1'020 sp. gr.),
and washing them with water, an operation repeated two to three times, the fatty acids
being of course kept molten all the time. The wash-water to be employed for this
purpose ought to be free from lime, and if such water is not obtainable, the lime
should be removed by means of oxalic acid. The purified fatty acids are next main-
tained in a molten state for some time, in order to eliminate the water mechanically
adhering to them. Sometimes the fatty acids are clarified by the aid of white of
eggs beaten to a froth, and added to the water of the last operation, in the proportion
of 2 eggs to 100 kilos. of fatty acids; or the stearic acid is re-molten in water
containing oxalic acid. The fatty acids thus obtained are either cast into thick
slabs and thus sent to the candle factory, or the molten acids are directly converted
into candles.
It is evident that annually a large quantity of worthless gypsum must result as a by-
product of the decomposition of the lime-soap by the use of sulphuric acid.
It may
therefore be worth while to suggest that caustic baryta should be substituted for lime,
because by the decomposition of the baryta-soap with sulphuric acid, there would be
formed baryta white (sulphate of baryta), the value of which will cover the expense of the
sulphuric acid; but, on the other hand, caustic baryta is a great deal more expensive than
caustic lime. It is true that the sulphate of baryta separates more readily and completely
from the liquor, and a purer glycerine can be obtained from it. Cambacère's suggestion
(1855) to saponify with alumina was made with the view of obtaining a more valuable by-
product. Alumina does not saponify fats, but aluminate of soda (employed for the purposes
of saponification for some years in the United States under the name of natrona refined
saponifier) does so, the result being the formation of an alumina-soap, while the soda is set
free and may be used again for the purpose of re-dissolving fresh portions of alumina. As
in the operations made with the native minerals cryolite and bauxite, aluminate of soda is
obtained as an intermediate product, which may be further treated for sulphate of
alumina and soda; the proposal to use an alumina-soap instead of a lime-soap deserves
every consideration, the more so as the fluid obtained by the decomposition of the
alumina-soap with sulphuric acid may be directly employed for the preparation either of
sulphate of alumina or of alum. The alumina-soap may be decomposed at the ordinary
temperature by acetic acid, and acetate of alumina obtained (see p. 263). The lime
saponification process has been in a great measure thrown into the background since the
invention of the far more profitable saponification process with sulphuric acid and super-
heated steam.
Less Lime.
Saponification with II. Saponification Process with a Smaller Quantity of Lime and
the Application of Superheated Steam.-De Milly has essentially changed the pro-
cess of the saponification of the neutral fats; he found that the quantity of lime
used in the saponification, which in his works at Paris had been already diminished
from 14 to 8 or 9 per cent of the quantity of the fats, could be decreased even to
4 or to 2 per cent, provided the mixture of lime-water and fatty matter was heated to
a higher temperature than that usually employed. De Milly put into a steam boiler
2300 kilos. of tallow and 20 hectolitres of milk of lime, which contained either
50 kilos. of lime = 2 per cent, or 69 kilos. 3 per cent, after which this mixture was
heated to 172° by means of steam, having a temperature of 1823 = 10 atmospheres, or
150 lbs. pressure per square inch. The result was, that after seven hours the saponi-
fication was complete, the contents of the boiler consisting partly of an aqueous
solution of glycerine, partly of a mixture of free fatty acids, and a small quantity of
a lime-soap. The boiler having been emptied was again filled, and the operation
624
CHEMICAL TECHNOLOGY.
repeated, so that in twenty-four hours 6900 kilos. of tallow could be operated upon.
It is evident that this method of saponification is very profitable, in consequence of
requiring much less sulphuric acid for decomposing the lime-soap.
Several opinions have been enunciated explanatory of this process; but, if we bear
in mind (1) that kind of action which Berzelius designated as catalytic, where a
comparatively very small quantity of any substance may call forth a decomposition
under favourable conditions of a very large quantity of another substance; and
(2) recollect that Wright and Fouché have more recently (De Milly's experiments
were made about twenty-five years ago) found that water at a high temperature
causes the dissociation of fats and oils into glycerine and fatty acids, it is clear that
while the small quantity of lime may have facilitated the saponification, the result
obtained by De Milly is mainly due to the very high temperature of the water
employed in the operation. This is clearer from the fact that a process of saponifi-
cation is successfully in use based solely upon the application of water at a high
temperature.
Saponification by Means of
Sulphuric Acid,
III. Saponification by Means of Sulphuric Acid and Subse-
quent Distillation by Means of Steam.—It was known to Achard, in the year 1777,
that the neutral fats are decomposed by concentrated sulphuric acid in a manner
similar to the decomposition effected by caustic alkalies. This fact was again
brought forward in 1821 by Caventon, and 1824 by Chevreul, but was not scientifi-
cally investigated until 1836 by Frémy, and not industrially applied until the year
1841, when Dubrunfaut introduced the distillation of the fatty acids on the large
scale. The crude fatty matter usually submitted to this process of saponification is
of the kind that cannot be saponified by the lime process by reason of its impurities;
thus, for instance, palm and cocoa-nut oil, bone and marrow fat, fat of slaughter-
houses, kitchen-stuff, the products of the decomposition, by means of sulphuric acid,
of the soap-water obtained from wool-spinning and cloth-making works, residues of
the refining of fish and other oils, residues of tallow-melting, &c.
This process of saponification by means of sulphuric acid as carried on in the large
establishment for stearine candle-making of Leroy and Durand, at Gentilly, near Paris,
consists of three operations, viz.:-
a. Saponification with sulphuric acid.
B. Decomposition of the products of saponification.
7. Distillation of the fatty acids.
=
a. In order to eliminate the greatest impurities first, the crude fatty matters are
molten and kept in the liquid state for some time, so that the coarser impurities may sub-
side. The fatty matters are then transferred to a kind of boiler made of iron boiler-plates
lined inside with lead, and fitted with a stirring apparatus and a steam-jacket, connected
by means of pipes with a steam-boiler, so that the apparatus may be heated. Into this
vessel sulphuric acid at 66° B. 18 sp. gr., is poured, the quantity of this fluid being
regulated according to the nature of the fatty matters operated upon. Kitchen-stuff, fat
from slaughter-houses, and the like require 12 per cent of their weight of acid; palm oil
requires from 6 to 9 per cent according to quality. The fatty substances having been put
into the vessel, the stirring apparatus is set in motion, and the steam turned on for the
purpose of supplying heat to the vessel. The temperature to which the vessel is heated
varies, in Price's Works, Battersea, being 177°, while at Gentilly, the heat is seldom higher
than from 110° to 115°. During the operation the mass foams, becomes brown, and evolves
sulphurous acid, partly due to the action of a portion of the concentrated sulphuric acid
upon the glycerine, partly to its action upon the impurities present among the fatty
matters. The neutral fat is converted into a mixture of sulpho-fatty acids and sulpho-
glyceric acid. The saponification is complete after some fifteen to twenty hours' appli-
cation of heat. According to De Milly's new process (1867) the tallow is heated to 120°,
along with 6 per cent of sulphuric acid, and the action of the latter is limited to two to three
ARTIFICIAL LIGHT.
625
minutes; it is thereby possible to obtain 80 per cent of the solid fatty acids in a condition
at once fit for making candles without re-distillation, only 20 per cent having to be
distilled.
B. Decomposition of the products of the sulphuric acid saponification. The mass is
left to cool for three to four hours and is next transferred to large wooden tanks
lined with lead, and previously filled one-third with water. At the bottom of these tanks
steam pipes are fitted, by means of which the fluid contents of the vessel are soon heated
to 100°. The sulphuric acid and the fatty acids are dissociated, and these bodies, partly
combined with a larger quantity of hydrogen and oxygen than was present in the fatty
acids from which they were formed, partly also in an unaltered condition, are found
floating on the surface. After having been repeatedly triturated with boiling water, the
fatty acids are tapped or poured over into a vessel filled with water heated to 40° to 50°,
for the purpose of allowing the impurities to become deposited. The clarified fatty acids
are next heated in a vessel placed on an open fire in order to evaporate all the water, after
which they are submitted to distillation.
y. The distillation requires several precautions. Distillation with an open fire would
convert the fatty acids into oil, gas-tar, and a carbonaceous residue, if the heat were
sufficiently high. But when the temperature is properly regulated, the fatty acids
are protected from the direct action of the fire. Air should be completely excluded from
the distilling apparatus. With these precautions the fatty acids distil over without
undergoing any essential alteration. These conditions are complied with by the use of
superheated steam at a temperature of 250° to 350°. The fatty acids are put into a roomy
retort supported by brickwork, and fitted with a steam tube as well as a condensing tube
connected with a receiver, in which the fatty acids are collected.
When the several fatty acids are fractionally collected from the beginning to the end of
the distillation their melting-points are:-
From Kitchen-stuff
From Palm Oil.
Ist product
54.5°
2nd
""
52.0°
3rd
*
48'0°
4th
46.0°
5th
""
44.0°
6th
7th
""
41.0°
39.5°
and Bone Fat.
44'0°
41°0°
41.0°
42.5°
44'0°
45'0°
41'0°
The water condensed with the fatty acids runs off from the receiver through a tap. At
the beginning of the operation the water constitutes half of the produce; towards the end
only about one-third. With a retort capable of containing 1000 to 1100 kilos. of material
the distillation takes some twelve hours. The end of the operation is indicated by the
coming over of coloured products. There remains in the retort a black tarry matter, the
quantity of which amounts in the case of palm oil distillation to 2 to 5 per cent, and for
kitchen-stuff to 5 to 7 per cent. This residue is not removed after each distillation but
left in the retort until it has accumulated to such an extent as to render its removal
necessary. The first products of the distillation of palm oil saponified by means of fatty
acids are so solid, that by pressure they do not yield any fluid acid, and are at once fit for
the manufacture of candles. The products which come over afterwards are further
purified by hydraulic pressure, re-melting, and washing with water. The substance
obtained by pressure, more or less pure oleic acid, is used for soap-making only in this
country, although abroad it is burnt in some kinds of lamps. The oleic acid obtained by this
process is essentially different from that obtained by the lime saponification process. The
quantities of fatty acids obtained by this process of saponification are the following :—
From Suint
"',
Olive oil residues
Palm oil
Fat from slaughter-houses
Oleic acid
•
•
47 to 55 per cent.
47 to 50
75 to 80
""
60 to 66
25 to 30
99
Chloride of zinc, which in many respects (see p. 81) is similar in its action to sulphuric
acid, has been proposed as a substitute for the latter. For countries into which sulphuric
acid has to be imported chloride of zinc might be of greater advantage, being capable
of recovery and less dangerous and difficult in transport. When, according to the
researches of L. Kraft and Tessié du Motay, a neutral fat is heated with anhydrous
chloride of zinc, a complete incorporation of these substances takes place between 150°
41
626
CHEMICAL TECHNOLOGY.
and 200°; and by continuing the heating for some time, and washing the materials with
warm water, or better with water acidulated with hydrochloric acid, there is obtained
a fatty matter, which on being submitted to distillation, yields the corresponding fatty
acid, while only a small quantity of acroleine is formed. The chloride of zinc, becoming
soluble in the water used for washing, may be recovered by evaporating the fluid. The
yield of fatty acids by this process is the same as that obtained by the use of sulphuric
acid, while the fatty acids also agree as to their physical properties. The quantity
of chloride of zinc required amounts to 8 to 12 per cent of the fat.
and High Pressure.
Saponification with Water IV. Some sixteen years ago another agent, capable of bringing
about, in a manner similar to alkalies and acids, the dissociation of fatty matters into
glycerine and fatty acids, was introduced, this agent being simply superheated steam
at high pressure:—
C₂H;
3(C16H310) } 03+3H₂O = C3H5
Tripalmitine.
Η
JH
} 03+3H20=C3H; } 03+3 {6H₂,0} 0.
13,0}0.
¡C16H31
Water. Glycerine. Palmitic acid.
The idea of submitting fatty matters to a similar method of treatment is not a new
one, for in the researches of Appert (1823) and Manicler (1826) some hints are given
on the decomposition of fats by means of superheated water; but the aim of these
technologists was different, for in their experiments they employed steam to separate
the tallow from the cellular tissue it is contained in, and for that purpose a tempera-
ture of 115° to 121° was quite sufficient, while at a temperature of 180° and a pressure
of 10 to 15 atmospheres (= 150 lbs. to 225 lbs. pressure to the square inch) water
can exert a far more energetic action upon the neutral fats, dissociating them and
thus setting free their constituents. The knowledge of this interesting fact is due to
the researches of Tilghmann and Berthelot, who almost simultaneously made this
discovery in the year 1854, while shortly after Melsens, at Brussels, obtained the
same result. As regards the industrial application of this discovery, Tilghmann and
Melsens made further researches; their modes of operating are very similar.
Tilghmann adds to the neutral fat about to be decomposed one-third to one-half
of its bulk of water, and pours this mixture into a sufficiently strong vessel in which
the fluids can be submitted to the action of heat, viz., a degree nearly as high as the
melting-point of lead, 320°. This vessel is so arranged that during the operation it
can be closed so as to prevent on the one hand the evaporation of water, and on the
other admit of a sufficiently strong pressure. The process is carried on continuously
by causing the fluids to circulate through a tube heated to the required temperature.
Melsens uses a Papin's digester, in which the fat to be decomposed is heated to 180° to
200º, with 10 to 20 per cent water, to which 1 to 10 per cent of sulphuric acid has been
added. Wright's and Fouché's apparatus consists of two hermetically closed copper
vessels placed one above the other and connected together by means of two tubes, one
of which reaches nearly to the bottom of the lower vessel, and ends in the upper one
just above the bottom.
The second tube is fixed into the lid of the lower vessel and passes through the
upper vessel reaching nearly to its cover. The upper vessel is the steam-generator,
while the decomposition goes on in the lower vessel. When it is intended to work
with this apparatus, the steam-generator is filled with water nearly to the point at
which the first tube ends in it. The second vessel is then filled with molten fat so
that this material reaches the top of the second tube. There remains thus a free
space between the fat and the lid of the second vessel, which space is termed by the
patentees chambre d'expansion, expansion room. Heat being applied to the generator,
ARTIFICIAL LIGHT.
627
the steam formed is carried by the second tube into the expansion room, and
becoming condensed forces it way downwards through the specifically lighter fat
and flows through the first tube again into the generator. In this manner the
neutral fat is intimately mixed at a high temperature and under high pressure with
water, and completely dissociated in a short time into fatty acid and glycerine.
Manufacture of Fatty Acids
by means of Superheated
Steam and Subsequent
Distillation.
V. Allied to the process just described is the operation carried
on by the well-known Price's Candle Company, Limited, at
Battersea. Gay-Lussac and Dubrunfaut have already tried to
apply to industrial purposes the fact that neutral fats are dissociated by distillation,
yielding fatty acids; but notwithstanding that these savants employed steam, the results
obtained did not answer the expectation, because a portion of the fatty matter was
decomposed, yielding acroleine and leaving a carbonaceous residue. Wilson and Gwynne
were more successful with their experiments, and by using a distilling apparatus similar
to that described on p. 625, they obtained by means of superheated steam the complete
dissociation of the neutral fats into fatty acids and glycerine; while by closely watching
and regulating the temperature, they not only could completely saponify the neutral fats,
but also distil the fatty acids and glycerine over without undergoing any decomposition.
The retorts have a cubic capacity of 60 hectolitres, and are heated by direct fire to a
temperature of 290° to 315°. A malleable iron steam-pipe conveys steam at a tempe-
rature of 315° into the molten fatty matter. The admission of steam is continued for
twenty-four to thirty-six hours according to the kind of fat. The saponification proceeds
regularly and the products distil over and are collected at the lower aperture of the
cooling apparatus. The fatty acids are at once fit for candle making purposes, while the
glycerine is purified by a subsequent distillation with steam. As already mentioned, the
proper temperature has to be scrupulously maintained, for if the temperature falls below
310°, the saponification proceeds very slowly; but if the temperature rises much above
that degree, a portion of the fatty substance is decomposed and acroleine is formed in
large quantity.
Candle Making.
B. The wick is a very important portion of stearine candles, and,
indeed, of all kinds of candles, because in the interstices of the wick the molten fatty
matter of the candle is drawn upwards to the flame. The wick ought therefore to
consist of porous substances, and in the case of candles-for lamps it is not so requi-
site-it should be combustible.
It is essential that the wick be of uniform thickness through its entire length and
free from knots or loose threads. The yarn ordinarily used for making wicks is the
lightly-twisted cotton thread known in the trade as No. 16 to 20 for tallow candles,
and No. 30 to 40 for stearine candles. It is evident that the more uniform the wicks
the better fitted they are for capillary action, and hence, provided the illuminating
material be pure enough, a uniform combustion. Formerly the wicks were always
twisted, and for tallow and wax candles this is still frequently the case, the single
threads being placed next to each other and then turned so as to form a very elon-
gated spiral. In order to obviate the snuffing of the burning candles, Cam-
bacères introduced the plaited wicks, which, while burning, become so twisted that
the end of the portion of the wick which protrudes from the tallow or stearine is kept
just outside the flame, so that it may be consumed to ash by the ambient air.
Before the wick can be used in candles it has to be prepared, because unprepared
wick leaves by its incomplete combustion a considerable quantity of a carbonaceous
residue which greatly impairs the capillary action. When stearine candles were
first made it became necessary to impregnate wicks with substances which should
promote the combustion, and De Milly found (1830) that boracic and phosphoric
acids would answer this purpose, because these acids, while combining with the
constituents of the ash of the wick, caused the ash to form at the top of the burning
wick a glass bead, which by its weight turned the wick out of the flame, thereby
increasing the combustibility. In the French candle factories the wicks to be
628
CHEMICAL TECHNOLOGY.
prepared are put for three consecutive hours into a solution of 1 kilo. of boracic acid
in 50 litres of water. The previously plaited wicks are next either wrung out or put
into a centrifugal machine to get rid of the first excess of moisture, after which they
are dried by being placed in a` `acketted tinned-iron box, which is heated by means of
steam. Some alcohol should be added to the aqueous solution for the purpose of
wetting the wicks more perfectly. Payen recommends a pickling liquor for wicks,
composed of a solution of 5 to 8 grms. of boracic acid in 1 litre of water, to which
3 to 5 per mille of sulphuric acid is added. In some Austrian stearine candle factories
phosphate of ammonia is used to impregnate the wicks; while Dr. Bolley calls
attention to the use of a solution of sal-ammoniac at 2° to 3° B. as a cheap pickling
for wicks.
Moulding the Candles.
The blocks or cakes of stearic acid obtained as described are not
sufficiently pure for moulding. The edges of the blocks are often more or less coloured
and soft, owing to some oleic acid not having been pressed out, while the surface of the
blocks is contaminated with oxide of iron and the hair of the press-bags. In order to
purify the blocks or cakes (in this country they frequently weigh from 1 to 3 cwts.) the
edges are pared off and the surface is scraped, the refuse so obtained being again sub-
mitted to hot-pressing. The blocks thus treated are next put into tubs lined with lead,
and dilute sulphuric acid of 3° B. = 1020 sp. gr. having been poured over them, the fluid
is heated by means of steam, the aim of this operation being to remove oxide of iron and
destroy the fibres of the press-bag, and not, as is sometimes stated, to decompose the last
traces of stearate of lime, which of course cannot be present. When the action of the
sulphuric acid has been continued for a sufficient time, it is run off and the last trace of
the acid removed by washing the stearic acid, of course again molten, with boiling water.
The molten stearic acid is then clarified by means of a certain quantity of white of egg,
which is thoroughly stirred through the molten mass heated to the boiling-point of the water
mixed with it. The impurities which become mixed and incorporated with the white of
egg settle at the bottom of the vessel. The great tendency of the stearic acid to crystal-
lise in large foliated crystals caused at the commencement of the stearine-candle making
business a difficulty, candles of unequal transparency as well as of great brittleness being
obtained. The defect was remedied by the addition of a small quantity of arsenious acid,
but as this proved detrimental to health (arseniuretted hydrogen as well as some arsenious
acid being evolved during the burning of such candles), the use of this acid was abroad
prohibited by law, and in England condemned by public opinion. Instead of the use of
arsenious acid, some 2 to 6 per cent of white wax has been added to the stearic acid
while molten, continually stirring until nearly solidified previous to pouring the stearic
acid into the candle-moulds previously heated to the melting-point of the stearine.
By the cooling and stirring a kind of fluid-fat paste was obtained which does not crys-
tallise. Now some 20 per cent of paraffin is added to the stearic acid, and its tendency to
crystallise altogether suspended.
The candle-moulds are made of an alloy of tin and lead, usually consisting of 20 parts
of tin to 10 of lead. The moulds are narrow, somewhat conical tubes, highly polished
internally in order to impart a smooth surface to the candles. The wick is fixed in the
longitudinal axis of the moulds, being fastened at one end (the top of the finished candle)
in a small hole at the bottom of the mould, and at the other end fastened to a funnel, through
which the fatty acid is poured into the mould. The shape of the moulds used in the
French stearine candle works is exhibited in Fig. 269. a is a mould consisting of two
parts, viz., the mould proper and the funnel. b exhibits these two parts fitted together,
and c a longitudinal section with the wick inserted, while d is the wire hook with which
the wick is passed through the mould. For the moulds now generally used one moulding-
basin or box is employed to contain thirty moulds. This basin or moulding-box is
exhibited in Fig. 270. AD is a large sheet-iron or tinned box in which the moulds are
placed. This box is fitted into another of similar shape, в B, which by means of steam is
kept at a temperature of 100°• As soon as the moulds are heated to 45°, the box A D is
removed from в B, and the molten stearic acid is poured into the moulds. When the
moulds and the candles contained have become quite cold, the latter are removed. Now
moulding machines are generally employed, so that this operation is performed uninter-
ruptedly, the construction of these machines being such that the reeled wick is drawn
through the moulds while the candles remain joined together by a short piece of wick
until after the moulding is complete, the candles when cold being taken from the moulds
and the wicks cut through to separate them. Cahouet's and Morgane's machines are
chiefly used.
ARTIFICIAL LIGHT.
629
Before the stearine candles are pared and polished they are in some works bleached by
being exposed to the action of the sun's rays and to dew in open air. The candles
are carried to the bleaching-ground by mechanical self-acting means, consisting of a cloth
without end, and which is connected with a slightly sloping table, upon which the candles
are placed, and caught by the cloth, which is fitted with a series of rounded wooden laths
fastened across the cloth, whereby the candles are held in position. For the purpose of
exposing the candles to the action of the air they are placed on a frame-work similar to
that of a table, instead of the top of which are stretched two textures of lead-wire, each of
these textures in a horizontal plane distant from each other about half the height of a
candle. The meshes of the upper wire net are so wide that a candle can be passed through
it, while the meshes of the lower wire net are narrower. The candles are one by one put
into the meshes, the pointed portions of the candles being placed upwards, while the base
rests on the lower wire net. In this position the candles are left for some time according
to the season of the year. When bleached the candles are pared and polished by
machinery.
Tallow Candles.
2. Refined, purified tallow is used for making the dip as well as thẻ
moulded tallow candles. The dips are made by the repeated immersion of the wicks in
molten tallow. On the small scale this operation is performed in the following manner :-
The tallow trough having been filled with molten tallow, the wicks looped on a wooden or
a
FIG. 269.
с
d



FIG. 270.

D
B
thin iron rod are immersed in the tallow. According to the weight it is desired to give to
the candles, from sixteen to eighteen wicks are looped on to the dipping-rod, care being
taken to place them as much as possible equidistant from each other; this done the wicks
are dipped vertically into the molten tallow. At the first dip, when the wicks are to be
soaked, the molten tallow should be hot, because hot tallow penetrates more readily into
the insterstices of the cotton. After the first dip the dip-rods are placed on the edge of
the tallow trough, and next alternately hung over the dripping frame after the somewhat
twisted wicks have been put straight again. The dripping frame is simply a wooden
frame-work, on the edges of which the dipping-rods rest, while the wicks are suspended
over the tallow trough or another suitable vessel. When all the wicks looped on to the
dipping-rods have received their first dip, and the tallow in the trough has been so far
cooled as to begin to exhibit at the sides of the vessel signs of solidification, the second
dip is proceeded with and the operation continued until the candles have assumed the
desired thickness. As the lower portion of the candles would become frequently thicker
than the upper, this defect is obviated by keeping the lower end of the candle for a
moment in the molten tallow, so that the excess adhering to the candle may be molten off
630
CHEMICAL TECHNOLOGY.
again. In order to keep the tallow in the trough at a uniform degree of fluidity it is
now and then stirred with a wooden rod. At the last dip the candles are put into the
trough at a somewhat greater depth in order to form the upper conical portion. The
lower end of the candles exhibits a non-symmetrical cone, which is either cut away or
removed by placing the candles for a moment on a copper plate heated by steam and
provided with a channel for running off the molten tallow.
Moulded tallow candles are made in a similar manner to stearine candles. The tallow
used for the moulded candles is usually of better quality than that used for dip candles,
at least on the continent of Europe; not so in England and America, where very highly
refined tallow is used for dips by the better class of makers, the thus refined tallow being
harder owing to the mode of purifying. What are termed composite candles (unknown
on the Continent) are made by precisely the same method as the moulded stearine
candles, the wicks also being plaited. Moulded tallow candles have been entirely super-
seded by composites, excepting that in some of the central parts of Europe, locally
moulded tallow candles are here and there made. One of the largest London firms states
that the manufacture of candles (almost all moulded, viz., composites, stearine,
paraffin, ozokerite, spermaceti), for exportation from this country to all parts of
the world, is increasing to such an extent that the candle making business in Russia,
Turkey, Greece, Italy, Spain, Portugal, Sweden, and Norway, is becoming rapidly
extinct, not being capable to compete on the small scale with the large makers in this
country and in France, where, however, the late lamentable events have very seriously
interfered with this branch of industry.
Paraffin Candles.
Paraffin is obtained from native petroleum (Rangoon oil) or from
among the products of the dry distillation of peat, brown coal, lignite, bituminous
slates, boghead mineral or ozokerite (a peculiar mineral, wax-like, and yielding
paraffin-it occurs in Galicia and Bohemia in large quantities) It is, after having
been purified, the substance from which the beautiful paraffin candles are made by
precisely the same methods and apparatus as are used and have been described for
stearine candles. The paraffin employed for making candles is a mixture of
paraffins having different melting-points.
Paraffin obtained from boghead coal fuses at
""
""
,,
45'5° to 52°.
56.0°
46.7°
brown coal
peat
Rangoon oil or tar
ozokerite
61.0°
""
65'5°
""
As the German paraffin candle makers use almost exclusively a paramin from
brown coal (lignite), and peat, and of a comparatively low melting-point (45° to 53°),
stearic acid is added for the purpose of raising the temperature at which the
paraffin melts. The quantity of stearic acid (technically stearine) added, depends as
much upon the point of fusion of the paraffin as upon the season of the year,
summer candles being made with a larger quantity of stearine than winter candles.
The quantity of stearine thus added to paraffin amounts to 3 to 15 per cent, while as
already mentioned, paraffin to an amount of 15 to 20 per cent is added to stearine
candles. A small quantity of stearine is always added to paraffin candles for the
purpose of preventing these candles becoming bent while standing in a candlestick.
The first paraffin candles ever made were manufactured by Messrs. Field, of Lam-
beth, from paraffin extracted from Irish peat, now very many years ago, long
before paraffin was seen or known elsewhere than as small specimens in chemical
laboratories. Paraffin candles are always moulded, and the moulds are heated
to above the melting-point of the paraffin (60°, or better even 70°), in order to pre-
vent the paraffin crystallising. The molten paraffin is heated to about 60° when it is
cast into the moulds; these when well filled are left standing for a moment and then
cooled by immersion in cold water, whereby the candles suddenly solidify, and are
ARTIFICIAL LIGHT.
631
thus prevented becoming crystalline and opaque, instead of transparent as desired.
Plaited wicks are used in the paraffin candles, and these wicks are treated with
boracic acid. For black paraffin candles the paraffin is heated to nearly its boiling-
point with anacardium shells, the resin of which is dissolved by the paraffin,
the latter becoming very dark brown, and exhibiting after cooling a black colour,
similar to that of coals. These black candles burn without smoke or smell, provided
the wick be thin; this is a requisite in all paraffin candles.
Candles from Fatty Acids. We must not neglect to call attention here to a fatty acid,
sebacylic acid, CroH804, which might perhaps be used to impart to paraffin and other
kinds of candles a higher melting-point. This acid may be obtained by the dry distilla-
tion of oleic acid, or better by treating castor oil with a highly concentrated caustic soda
solution. In the latter instance, the sebacylic acid is derived from the ricinoleic acid
(castor oil is in Latin termed Oleum Ricini) :·
Ricinoleic acid, C18H3403
Caustic soda solution, 2NaOH
298!
80)
yield
378
Sebacylate of soda, C10H16Na2O4
( = 184 fatty acid.)
Caprylic alcohol, C8H180
Hydrogen, H₂
=
246
= 130
2
378
According to these formulæ, 100 parts of castor oil will yield rather more than 81 parts
of fatty acid. This fatty acid is no doubt also contained in the products of the distillation
of the fatty substances formed by sulphuric acid, the sebacylic acid being then derived from
oleic acid. The high melting-point (127) of sebacylic acid and its ready combustibility
render this body a very fit material for being mixed with readily fusible candle materials,
and especially with paraffin of low fusion-point (45°). Moreover, this acid will impart to
the candles hardness and gloss. As this acid further also prevents the crystallisation of
stearic acid, it might be usefully added to such fatty substances as have a great tendency
to crystallise; an addition of 1 to 5 per cent of sebacylic acid to the candle materials,
renders them as hard as wax. The simultaneous formation of caprylic alcohol, which
can be used for varnish and lacquer making, enhances the industrial value of sebacylic
acid; still castor oil is too expensive for this purpose, but the purification of sebacylic
acid, obtained no matter from what source, is not easy, requiring manipulations which on
the large scale would become expensive.
Wax Candles. 4. Wax, or more particularly bees'-wax, is a fatty substance secreted
by the bees, and employed by them for the purpose of building the cells in which
they preserve the honey. According to the researches of J. Hunter and F. Hubner,
it is now generally admitted that the wax-containing particles gathered by the bees
from flowers are used exclusively as food for the young brood, while the wax is a
product of the animal organism of the bees, and a conversion product of sugar. In
order to obtain the wax the bees are either killed or forced from their dwelling by
smoke, after which the honey-containing cells or honeycombs are taken from the
hive, and the honey eliminated by pressure, or by being allowed to flow out sponta-
neously. By washing in hot water the wax is purified, and on cooling, the cakes of
yellow wax are obtained, the outer dirty crust having been removed by scraping. The
crude wax thus obtained exhibits a more or less yellow colour, is soft and readily
kneaded at the ordinary temperature of the air, but becomes brittle at a lower tem-
perature; its fracture is granular; specific gravity varies between 0‘962 and o‘967 ;
fusion-point between 60° and 62°. While the granular texture of the yellow wax is
due to the impurities it contains, it is for that reason as well as for its unsightly
colour, not suited for candle-making, and has therefore to undergo bleaching. This
is performed in the following manner;-First, the yellow wax is put into a tinned
copper cauldron filled with boiling water, to which is added o 25 per cent of alum, or
cream of tartar, or sulphuric acid, and this mixture thoroughly stirred. After a few
minutes the liquid is run off into a tub or cask, the impurities are left to settle, while
632
CHEMICAL TECHNOLOGY.
the wax is prevented from solidifying by covering the tub with a lid, and wrapping
it up in a woollen blanket. Next the wax is converted into thin ribbon by means of
machinery, in order to increase the surface and facilitate the bleaching action of the
air and light. The ribbons are placed on pieces of canvas stretched in frames, and
these are placed on meadows or grass-plots exposed to the action of the sun and air,
and left until the colour has disappeared. In order to bleach the interior, the
ribbons are again molten and again converted into ribbons, and this operation
repeated until the wax is thoroughly bleached. The bleaching takes, according to
circumstances, the state of the weather and the kind of the wax operated upon, from
twenty to thirty-five days, for completion. The loss of weight of wax incurred
amounts to 2 to 10 per cent. The bleached wax is molten again, passed through
strainers, and then moulded into large square cakes or thin circular tablets. As
regards the bleaching of wax by artificial means (chemical bleaching) many
suggestions have been made, but in practice these leave much to be desired. The
application of chlorine and bleaching-powder has the disadvantage that solid and
very brittle chlorinated products are formed, and by remaining mixed with the wax
impair its combustive quality, and cause candles made of such wax to give off hydro-
chloric acid. The process of bleaching wax, patented in 1859 by Arthur Smith, by
the use of bichromate of potash and moderately dilute sulphuric acid, answers very
well in practice; the bleaching is performed in a few hours, and wax by this plan is
bleached and purified as perfectly as by exposure to air and light; but the toughness
of the wax is somewhat impaired, so that it is not suitable for such purposes as
modelling, flower-making, &c. In reference to the chemical properties of wax, John
first found wax to be a mixture of two substances differing from each other by their
solubility in alcohol; one of these substances, soluble in boiling alcohol, is cerotic
acid, C27H54O2 (formerly known as cerin); the other sparingly soluble in alcohol is
known as myricin, and consists, according to Brodie, of palmitate of myricile,
C46H92O2 = C16H31 (C30H61)О2. In addition to these bodies wax contains 4 to 5 per
cent of a substance fusing at 28° and named cerolein, to which is due the solidity
of wax.
The relative proportions of cerotic acid and myricin present in bees'-wax
vary considerably, and this variation is the cause of the alteration of the fusion-
point observed in different kinds of wax.
Other kinds of Wax. 1. Among the more or less wax-like substances are the following:-
Chinese wax, imported in large quantity from China, is derived from a peculiar kind
of coccus insect, known entomologically as the Coccus ceriferus, which dwells on
certain trees, more especially the Rhus succedanea, upon which it deposits a wax-like
substance, in its physical appearance very similar to spermaceti. This quasi-wax
is snow-white, crystalline, brittle, fibrous, and fuses at 82°. When submitted to dry
distillation it yields cerotic acid and ceroten, a paraffin-like body. According
to Brodie, Chinese wax consists of cerotate of ceryl, C54H108O2 = C27H53 C27H55)02.
2. Andaquies wax, the product of an insect met with in the regions watered by the
Orinoko and Amazon rivers, fuses at 77°, has a sp. gr. of o'917, and appears to be
similar in composition to bees'-wax. 3. Japanese or American wax, met with in the
trade in round concavo-convex cakes, covered with a whitish dust. This soft brittle
material fuses at 42°, is soluble in boiling alcohol, and is said to consist of palmitine.
4. Carnauba wax, imported from Rio de Janeiro, is said to be the outer coating of
the leaves of a kind of palin tree named the Kopernicia cerifera; it fuses at 83.5°,
and is used on account of its high fusion-point to improve candle-making materials
ARTIFICIAL LIGHT.
633
of low fusion-point.
5. Palm wax, obtained from the bark of the Ceroxylon
andicola, a palm-tree met with on the higher peaks of the Cordilleras. The wax is
scraped from the bark, and the scrapings are boiled with water, and the wax thus
molten is collected from the surface of the liquid, in which the impurities remain.
This kind of wax fuses at 83°-86°, and is very likely identical with the Carnauba
wax. 6. The Myrica wax, from the Myrica cerifera, is obtained by boiling the
fruit of the plant with water. It is imported from some of the Southern States of
the Union. The variety of this wax known as Ocuba wax is obtained from the
same plant and in the same manner, in the district of Para, Brazil, along the banks
of the Amazon river. This wax has an olive-green colour, and fuses at 36° to 48°.
It is used in America for making candles. We may add here that of all countries in
Europe, if not in the world, Corsica produces the largest quantity of wax. In
ancient as well as medieval times, the inhabitants paid their taxes in wax, and
supplied 200,000 lbs. annually. Since wax is to honey in quantity as I to 15,
the Corsicans must have gathered 3,000,000 lbs. of honey.
The Making of Wax Candles. Wax candles are most frequently made by pouring the molten
wax on to the wicks. For this purpose the wicks are hung upon frames and covered with
metal tags at the ends to keep the wax from covering the cotton in those places; these
frames are carried to a heater, where the wax is melted. The frames can turn round, and
as they turn a man takes a vessel of wax and pours it first down one, and then the next,
and so on. When he has gone once round, if the wax is sufficiently cooled he gives
the first wick a second coat, then the third, &c., until they are all of the required thick-
ness. The candles are now rolled on a marble slab or wooden board for the purpose of
imparting the proper shape. The conical top is moulded by properly shaped tubes, and
the bottoms are cut off and trimmed. The moulding of wax candles is now rarely if ever
performed, but if executed, it is done in precisely the same manner as described for
stearine and paraffin candles. Wax, however, is not a very suitable material for moulding,
in consequence of its shrinking on cooling, as well as its pertinacious adherence to
the moulds. The wick for moulded wax candles must be previously soaked with wax in
order to prevent the candles becoming as it is termed honey-combed. The wax is molten
on a water-bath, and glass moulds are used in preference to metal ones, as well for
the smooth surface glass imparts as for the more ready removal of the candles when cold.
In order to prevent the breaking of the glass moulds, they are covered with gutta-percha.
The large sized altar candles, which often weigh from 15 to 20 kilos., are not made
by either of the two methods described, but by hand. The wick, partly made of linen,
partly of cotton yarn, is first soaked with wax, or covered with that material cut into long
strips, rendered soft and kneadable by the aid of warm water, and next made up to the
required thickness by rolling on more wax; or a quantity of wax is rolled by hand into
the required shape, and the wick inserted by cutting a longitudinal channel in the mass of
wax into which the wick is placed. The channel is filled up with wax and the candle
finished by rolling. Very recently (1870) Messrs. Riess have constructed a press for
making wax candles. The arrangement of this machine seems to be somewhat similar to
the press used for making continuous lengths of lead and block-tin pipes. This wax
candle press is heated by steam so as to render the wax soft. The wick is inserted into
the wax in such a manner that it is concentrically surrounded with wax when ejected
from the spout of the cylinder of the press, thus forming a continuous candle, which is
cut up into lengths.
The wax tapers of various thickness are made by a method of which the following is
an outline:-In the first place, these tapers are not made of pure wax, but of wax and
tallow mixed, in order to impart flexibility; while for coloured wax resin and turpentine
are added to the tallow. The wick of the tapers should be very uniform, and the strands
of yarn intended for this purpose are reeled on a cylinder or drum placed at one end of the
workshop, while at the other end is placed a similar drum. Between these drums is placed a
shallow copper pan, which can be kept warm by means either of steam or a charcoal fire.
This vessel is filled with the molten wax, and provided with a hook at the bottom, below
or through the opening of which the wick is drawn. At the edge of the pan a draw-iron
is fixed, provided with circular, somewhat conical, apertures of different size, arranged
in the same way as those described (see p. 25) for wire-drawing. The wick is drawn
through the wax, put under the hook, and through the aperture of the drawing-iron, and
634
CHEMICAL TECHNOLOGY.
next reeled on the other cylinder or drum, which is very slowly turned round in order to
give the wax time to solidify. When all the wick has been thus coated with wax,
the taper is, when required to be rendered thicker, drawn a second, and even a third and
fourth, time through the wax, and a larger-sized aperture of the drawing-iron. The end-
less taper thus formed is cut up into the requisite lengths.
Bees'-wax is used for many minor purposes, as is well known. Amongst them, as of
interest, may be noted its selection by the British Government for a lubricating material
for small-arm cartridges and also for breech-loading cannon. This is due partly to its
power of resisting oxidation, and its consequent freedom from corrosive action upon
metal surfaces (lead, &c.), and partly to its peculiar action as a lubricating material, by
producing an extremely smooth surface upon the bore of the arm as it is swept through
upon the discharge. It also prevents particles of paper or powder residue from attaching
themselves to the metal, and thus is the best anti-fouling agent known.
Sperm or Spermaceti
Candles.
Spermaceti is the solid portion of the oil of the sperm whale,
Physeter macrocephalus, a cetacean belonging to the mammalia, and living in some of
the seas of the southern hemisphere of our globe. The spermaceti is obtained from
the oil by filtration, and is subsequently hardened and whitened by pressure, and
refining with a weak alkaline ley. In some cases a very large and full-grown sperm
whale may yield 100 cwts. of sperm oil, containing from 30 to 60 cwts. of spermaceti.
This material as met with in commerce is a white, mother-of-pearl like, glossy,
foliated, crystalline, semi-transparent substance, fatty, and lubricating to the touch,
of sp. gr.
0943, fusing at 43°, and distilling unaltered at 360°. It is soluble in
about 30 parts of boiling alcohol, becomes yellow by exposure to air, and may be
pulverised. According to Mr. Smith and Dr. Stenhouse, spermaceti consists of pal-
mitate of cetyl, C34H64O2 = С16H31 (C16H33)O2; but according to Heintz (1851), sper-
maceti is a combination of cetyl with stearic, palmitic, myristic, cocinic, and
cetinic acids. Spermaceti candles are made extensively, if not exclusively, in
England, where they were first manufactured about 1770. These candles have
always been greatly prized for their transparent whiteness, high illuminating power,
and regular burning; and notwithstanding their costliness, are largely used and
exported to British India. In order to check the great tendency of spermaceti
to crystallise, 5 to 10 per cent of white wax or a little paraffin is added to the fused
mass intended to be moulded into candles, by a process exactly similar to that
already described for stearine candles.
Glycerine.
он
Glycerine, C3H§O, (as triatomic alcohol, CHO3, or C₂H, OH
OH
is present in the shape of glycerides in combination with solid and fluid fatty acid
to an amount of 8 to 9 per cent, and may be separated by treatment with bases
(potash, soda, lime, baryta, oxide of lead), or with acids (sulphuric acid), and certain
chlorides (chloride of zinc), also by means of superheated steam, or very hot water
without the formation of steam, in closed vessels. Glycerine is also formed as a con¹
stant product by the alcoholic fermentation of dextrose, levulose, and lactose. Accord-
ing to Pasteur's researches, the quantity of glycerine thus formed amounts to about
3 per cent of the weight of the sugar. Glycerine was first discovered by Scheele
whilst engaged in preparing lead plaster. Industrially, glycerine has been used for
only twenty-five years, in consequence of the large quantity of glycerine obtained as
a by-product in the manufacture of soap as well as of stearine candles. The vinasse
of the potato, and molasses from beet-root sugar distillation, and likewise the
residue of the distillation of wine, vinasse proper, as carried on in the South of
France, contain large quantities of glycerine.
As regards the preparation of glycerine on the large scale, it is mainly a question
ARTIFICIAL LIGHT.
635
of purification of the glycerine obtained in the industrial preparation of the stearic
acid from neutral fats above described. When the lime saponification process is
used, the glycerine remains dissolved in the water after the separation of the in-
soluble lime-soap. The lime also dissolved having been eliminated by either sulphuric
or preferably oxalic acid, the evaporation of the liquid to the consistency of a syrup
will yield a glycerine pure enough for many technical purposes. When the decom-
position, or rather dissociation, of the neutral fats is effected by means of superheated
steam, the glycerine and fatty acids (see p. 634) are both obtained in pure state, pro-
vided the heat be kept at or below 310°, because otherwise a portion of the glycerine
is decomposed with evolution of vapours of acroleine. The fact that, when fats are
saponified with sulphuric acid, the sulpho-glyceric acid in aqueous solution yields
readily by evaporation glycerine and sulphuric acid, may be applied for the prepara-
tion of glycerine. The soap boiler's mother-liquor, now the most important source
of crude glycerine, may be made available for its production, according to Reynold's
patent, in the following manner :-The mother-liquor is first concentrated by evapo-
ration; the saline matter which is thereby gradually separated being removed from
time to time. When the fluid is sufficiently concentrated-ascertained by the boiling-
point having risen to 116°—it is transferred to a still, and the glycerine distilled off
by means of superheated steam carried into the still. The distillate is next concen-
trated and brought to the consistency of a syrup in a vacuum pan.
According to the researches of A. Metz (1870) :—
A sp. gr. (at 17·5°) of 1·261 corresponds to 100 per cent of anhydrous glycerine.
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Glycerine has become largely employed owing to its oily consistency, also to the
fact that at ordinary temperatures it is fluid, and does not freeze when quite concen-
trated even at — 40°;* further to its stability, its pleasant sweet taste when quite
pure, its harmlessness, its great solvent power for many substances, and, lastly, to
its low price.
Among the many applications of glycerine are the following:-For keeping clay moist
for modelling purposes; for preventing mustard from drying up; for keeping snuff
damp; preserving fruit; sweetening liqueurs; and for the same purpose for wine, beer,
and malt extracts. Glycerine is also useful as a lubricating material for some kinds of
machinery, more especially watch and chronometer works, because it is not altered by
contact with air, does not become thick at a low temperature, and does not attack such
metals as copper, brass, &c. Glycerine is used in the making of copying inks, and of a
*The freezing of glycerine, observed in 1867, by Mr. W. Crookes, in London; by Sarg, at
Vienna; and Dr. Wöhler, at Göttingen, proves, however, that under certain conditions,
and while being transported from one place to another, glycerine may become solid even
at a temperature not so low as the freezing-point of mercury.
636
CHEMICAL TECHNOLOGY.
great many cosmetics. In order to render printing ink soluble in water-its insolubility
is, however, its greatest advantage-it has been proposed to use glycerine for its prepara-
tion instead of linseed oil. Glycerine is an excellent solvent for many substances, including
the tar-colours (aniline blue, cyanine, aniline violet) and alizarine. In order to render
paper soft and pliable glycerine is added to the pulp. To the quantity of pulp required for
making 100 kilos. of dry paper, 5 kilos. of glycerine, sp. gr. 1'18, are sufficient. It is not
out of place here to mention the following useful weavers' glue or dressing, composed of—
Dextrine, 5 parts; glycerine, 12 parts; sulphate of alumina, 1 part; and water, 30 parts.
By the use of this mixture the weaving of muslins need not be-as was formerly the case-
carried on in damp darkened cellars, but may be performed in well-aired and well-lighted
rooms. It is said that leather driving belts, made as usual of weakly tanned leather,
when kept in glycerine for twenty-four hours, are not so liable to fray. A glycerine solu-
tion is now largely used instead of water for the purpose of filling gas-meters, as such a
solution does not freeze in winter nor evaporate in summer. Santi uses glycerine for the
compasses on board screw-steamers, in order to protect the inner compass box against the
vibrations caused by the motion of the propeller. It is impossible to enter here into
minute details on the use of glycerine; suffice it to observe further that it is employed for
preserving anatomical preparations, for rendering wooden casks impervious to petroleum
and other oils; for the preparation of artificial oil of mustard or sulpho-cyan-allyl, made
by treating glycerine with iodide of phosphorus, whereby iodide of allyl is formed, which
on being dissolved in alcohol, and next distilled with sulphocyanide of potassium, yields
sulpho-cyan-allyl. When glycerine is treated with very concentrated nitric acid or with a
mixture of strong sulphuric and nitric acids, it is converted into nitro-glycerine (trinitrine
or glyceryl nitrate) (see p. 158), largely used for various purposes, the preparation of
dualine and dynamite, &c. A mixture of finely powdered litharge and very concentrated
glycerine made into a paste forms a rapidly hardening cement, especially useful as a cover
for the corks or bungs of vessels containing such fluids as benzol, essential oils, benzoline,
petroleum, &c., the cement being impermeable to these liquids.
Illumination with Fluid
Substances.
II. Illumination by Means of Lamps.
The fluid substances in use as illuminating materials are
either:-a. Fixed, or fatty oils. b. Volatile oils, which again are either essential
oils, as, for instance, camphine; or products obtained from tar, as photogen and
solar oil; or, finally, native, as petroleum. Among the fixed or fatty oils, rape-seed
oil, colza oil, olive oil, fish oil, and the dry papaver-seed or poppy-seed oil, are
chiefly used.
the Oils.
Purifying or Refining In order to refine these oils so as to render them more suitable
for combustion in lamps, they are treated with about 2 per cent of their weight of
strong sulphuric acid, or with a concentrated solution of chloride of zinc. These
substances do not act upon the oil, but destroy or coagulate any impurities, as muci-
laginous and colouring matters, present. The acid or chloride of zinc is removed by
washing with water, after which the oil is filtered, and in order to remove any
mechanically adhering water, it is kept for a considerable time at a temperature of
about 100°, being heated by means of steam circulating in pipes fitted in the tanks.
Now oil is frequently extracted from the seeds by means of sulphide of carbon (see
p. 199). The oils which serve for the purposes of illumination are termed lamp-oils.
The introduction of paraffin and petroleum oils has caused a very considerably
decreased consumption of the fixed fatty oils.
Lamps. Lamps were known and used even in remote antiquity, and were invented,
it is believed, by the Egyptians. While it cannot be denied that as regards outward
form the lamps of the ancients were graceful, their technical construction was rude,
and remained so—not taking into account some minor improvements made in the
seventeenth and eighteenth centuries, among which improvements are the introduc-
tion of the glass cylinders by the Parisian apothecary Quinquet, and the invention
of the hollow and circular burner by Argand, 1786—until chemistry discovered a
ARTIFICIAL LIGHT.
637
sound theory of combustion and illumination, and until physicial science ascertained the
principles of the supply of oil and means of estimating the illuminating power of the
flame of lamps, and further until the refining of oil supplied a purer and more fluid
illuminating material. A still greater step to improvement in light obtained from
lamps was the discovery of the petroleum and paraffin oils and the construction of
lamps suitable for their combustion. These oils have now become of general use
wherever gas is not obtainable. In passing, it may be observed that in no country is
gas so extensively made on the small scale as in Scotland, where farm-houses,
country seats, and other dwellings, not conveniently situated near to public gas-works,
are very generally provided with small gas-works, in which the excellent Cannel
coal of the country is employed, yielding a very pure and highly illuminating gas at
a reasonable cost, and with the advantage that gas is allowed by the insurance com-
panies as light in stables and other places where readily inflammable materials are
kept, while lamp and candle lights are absolutely prohibited in such places, for
fear of causing fire. Some of the many inventions and improvements of oil lamps
made during the last forty-five to thirty years are quite forgotten; the moderator
colza lamp has been nearly superseded by improved paraffin and petroleum oil lamps,
and as we do not treat in this work on the history of technology, but on technology
as now developed, we cannot enter into any further historical details, but proceed
with our subject.
Viewing lamps generally, we observe the same parts as in a candle, viz., the
illuminating material and the wick. As regards the illuminating material, it is in
lamps as well as in candles fluid, the difference consisting in that with candles the
fatty material is molten near the end of the wick, a cup of molten fat being formed,
while with lamps the illuminating material is fluid at the ordinary temperature, and
therefore kept in a vessel or reservoir from which the wick is uninterruptedly and as
uniformly as possible supplied. The differences observed in the construction of the
various kinds of lamps depend partly upon the illuminating material employed
(colza oil, petroleum oil, sperm oil, &c.); partly upon the shape of the wick and upon
the mode of supplying air to the flame, either with or without a glass chimney;
further, upon the shape of the oil reservoir and its position in reference to the wick;
and finally and chiefly, upon the method and means by which the illuminating
material is carried to that portion of the wick where the combustion is intended to
take place; that is to say, whether the illuminating material is only absorbed by the
capillary action of the cotton wick, or whether this action is aided by hydrostatic or
mechanical means.
Colza oil and mineral oil-be the latter obtained from the tar yielded by the dry
distillation of certain kinds of coal or peat, or be it derived from native petroleum—
differ from each other as regards their properties as illuminating materials in the
following particulars:-1. Colza oil is not volatile at the ordinary temperature, and
not even when heated to above 100°. It is hence devoid of smell, and is not by itself
ignitable unless it be first heated to a such a high temperature (about 200°) as to
give off products of dry distillation-in fact, become decomposed and converted into
oil-gas.
The mineral oil, even that kind which is termed odourless, possesses some
odour, and loses in weight or is gradually volatilised by exposure to air. At a
higher temperature it is volatilised and can be distilled over unaltered, while at a
still more elevated temperature it is nearly all converted into illuminating gas.
2. Colza oil consists of carbon, hydrogen, and oxygen, according to the formula
638
CHEMICAL TECHNOLOGY.
C18H1202. In the dry distillation which this oil undergoes in the wick just below
the flame it is converted into elayl gas and carbonic acid:-
=252
Colza oil, 2C10H1802=340, yield (9 molecules of elayl gas, 9C₂H¸
carbonic acid, 2CO2 = 88
2
""
""
340
consequently 25.8 per cent of the colza oil becoming carbonic acid does not con-
tribute anything to the illuminating power of the flame, but deprives the half of the
volume of the elayl gas of its illuminating power. Refined colza oil burns in
well-constructed lamps very completely, yielding only the odourless products of
combustion, viz., carbonic acid and water. 3. Petroleum oils are mixtures of
different hydrocarbons, very probably of the higher members of that homologous
series of which marsh gas is the primary. Petroleum oil begins to boil at 250°, and
is at a higher temperature decomposed, yielding gaseous products, marsh gas and
elayl gas, and soot, or unburned carbonaceous matter. The quantity of carbon
contained in petroleum oil is far larger than that contained in colza oil; hence the
former when burning in contact with air and without a glass chimney exhibits a sooty
flame, but this changes at once into a very bright flame when by the addition of a
glass chimney the increased draught of air causes the complete combustion of the
excess of carbon. While colza oil only reaches the flame in the state of gas, the
petroleum oils come into the flame as vapour, and the construction of the petroleum
oil lamps ought to be so contrived that the combustion be as complete as possible in
order to prevent any disagreeably odorous vapours or gaseous matters escaping un-
consumed. As regards accidents from fire, petroleum or paraffin oil lamps are, with
proper precautions and good quality of oil, not attended with greater danger than
that of the use of colza oil. 4. As is well known, colza oil is a fatty lubricating oil,
while paraffin or petroleum is not so: in consequence of this difference the former
may be used in lamps in which the oil is carried to the wick by mechanical means—
either by clockwork or spiral springs acting upon one or more more pistons, as in the
Carcel and moderator lamps. Because the fatty nature of colza oil as well as its
lubricating property keeps the packing of the pistons oil-tight as well as lubricated,
it is clear that the paraffin oils cannot be used in such lamps.
Independently of the illuminating material, the construction of a normal lamp
should be such, that (1) it yields a maximum of light uniformly for a definite time
(three to eight hours). This condition, a consequence of the complete and equal
combustion of the illuminating material, can only result from (a) the use of a
purified illuminating material; (3) the use of a wick of uniform thickness and
structure; (y) the uniform supply of illuminating material to the flame; (d) by suffi-
ciently strong heat at the point where the combustion takes place, so that the
conversion of the illuminating material into gases may be complete; (ɛ) by the
regulation of the supply and access of air. Too small a supply of air often gives
rise to a sooty flame, while too large a supply causes a lowering of the temperature
of the flame, and hence also separation of soot and formation of odorous products
of incomplete combustion; and even if these results do not occur and a complete
combustion obtains, too large a supply of air impairs considerably the illuminating
power of the flame; (2) the means of regulating the size of the flame must be
perfect. 2. The lamps ought to be so constructed that the light evolved be not
wasted. The well-known reflectors and lamp caps aid the illumination greatly.
ARTIFICIAL LIGHT.
639
The reservoir for the oil should be in the first place so situated that its shadow falls
on some unimportant part of the field to be illuminated; and secondly, so arranged
that the point of gravitation of the lamp be maintained.
Various kinds of Lamps. Taking the manner of conveying the illuminating material by
means of the wick to the flame as a basis for the division of lamps into various kinds,
we distinguish the following:—
1. Suction lamps, in which the oil is simply sucked up by the capillary action of the
cotton wick from the reservoir. According to the situation of the oil reservoir with
reference to the wick, suction lamps can be subdivided into :-a. Those in which the
oil reservoir is placed at about equal height with the flame of the burning wick.
B. Lamps in which the oil reservoir is placed higher than the burner. These lamps have
a detachable oil reservoir, which, having been filled, is inverted into a fixed vessel,
an arrangement common in reading-lamps for burning colza oil. 2. Pressure lamps, in
which in addition to the capillarity of the wick, mechanical or physical means are
employed for the purpose of forcing the illuminating material to the wick. In this variety
the oil reservoir is placed at the foot of the lamp. According to the method of forcing
the oil to the wick, pressure lamps are:-a. Aërostatic, in which the principle is that of
Hero's fountain; into the closed oil reservoir air is forced, and this while trying to make
equilibrium with the outer air, presses upon the oil and forces it upwards through a
tube to the burner. B. Hydrostatic lamps, based upon the principle of the communicating
tubes, in which the heights of fluids of different specific gravity making equilibrium
together stands in the inverse relation to their specific gravity. The fluid which has to
make equilibrium with the oil and force it up towards the cotton wick should be specific-
ally heavier than the oil. 7. Statical lamps, in which the oil is forced from the reservoir
at the foot of the lamp to the burner by the pressure either of the weight of a solid body
(for instance, a leaden weight), or by the direct weight-pressure of a piston moving down-
wards in the oil reservoir. 8. Mechanical lamps, in which the oil contained in the
reservoir is forced upwards to the burner either (a) by means of pumps set in motion by
wheelwork similar to that of a large watch (Carcel lamps with clockwork), or (b) by the
pressure of a spiral spring acting upon a solid piston (moderateur lamps). In the mechanical
lamps the oil is carried to the wicks in larger quantity than is required for the momentary
consumption; this excess of oil returns continually to the oil reservoir. The lamps here
alluded to are only suited to burn colza oil, and we ought to observe that those mentioned
under a, ß, and y, are obsolete, for the very good reason that they have been superseded
by better and more simple contrivances; this applies also to the clockwork lamps which
were, even when well made, very liable to get out of order and required very pure oil to
work well. 3. The lamps for burning the paraffin and petroleum oils are all simple
suction lamps, the reservoir being placed under the wick and in its axial prolongation.
The lower specific gravity and the greater fluidity of the oils greatly aid the capillary
action of the wick, and renders all pressure apparatus superfluous. The so-called
benzoline sponge-lamps also belong to the category of suction lamps, the very volatile and
highly combustible benzoline (obtained from the crude petroleum) being absorbed by the
sponge, more commonly cotton waste or tow, and thence slowly carried by capillary action
into the wick.
1. To this kind belong all the lamps in which the oil is simply carried to
the flame by the capillary action of the cotton wick, the oil reservoir being placed somewhat
below the burning end of the wick. According to the situation of the oil reservoir in
reference to the wick, suction lamps can be divided into (a), those in which the oil
reservoir is placed nearly at the same height as the burning wick. Here we have to
observe the two following conditions, viz. :-(a) the burning wick is placed in the oil
reservoir itself, as may be observed in the kitchen lamp and antique lamp; or (b), the oil
reservoir and burner are separated from each other, the reservoir being placed by the side
of the burner, or, as is the case in the ring lamps, at the circumference of the burner,
which is in the centre. B. Those lamps, the oil reservoir of which is placed higher than
the burner, as, for instance, in the so-called reading lamp.
Suction Lamps.
Among the suction lamps are the following:-In the antique lamp, Fig. 271, the wick, a
skein of cotton, is placed in an open or closed oil vessel, the burning end of the wick
simply protruding from the spout. This kind of lamp is technically very imperfect,
because, in the first place, the wick has to suck up the oil, when the level of that fluid
gradually sinks by the burning of the lamp, to a height far too great for its capillary
power; hence the flame will by lack of sufficient oil become gradually more and more
lurid, and at last extinguished altogether before all the oil is consumed. In consequence
of the thickness of the wick the combustion is incomplete, owing to want of sufficient
640
CHEMICAL TECHNOLOGY.
access of air, the lamp thus burning with a sooty flame; while the body of the lamp
throws a great shadow. This last defect is less marked in a kind of kitchen lamp, exhi-
bited in latal projection in Fig. 272, and viewed in plan in Fig. 273, as by means of the
spout the distance between the oil reservoir and the flame is increased, or, in other words,
the angle, c a b, rendered more acute. The so-called Worm's lamp, Figs. 274 and 275, in
former days much used in the Rhine provinces, should be noted on account of the shape of
the wick, t, which is composed of a flat woven cotton band, instead of a skein of cotton yarn,
and thus the access of air to all parts of the wick is so regulated that complete combustion
FIG. 272.
FIG. 271.
FIG. 273.


9

Po
KATTITURNITINE FIN
of the oil takes place. The wick is put into the wick-holder, c, which is soldered to the ring,
d, loo ely fixed on the rim of the glass globe, which serves as an oil reservoir. By means
of the rackwork and pinion, e and e', the wick can be turned upwards and downwards, and
the flame thus regulated. The part a is placed in a candlestick or in any other suitable
stand. A glass and globe may be placed over and around the flame. Although this
lamp is an improvement on the old-fashioned kitchen lamp, it has many defects.
FIG. 275.
FIG. 274.


C
d
d
عبدالله
The Lamp with Constant
Oil Level.
In order to obviate the constant decrease in the intensity of the
light as the level of the oil sinks by its consumption, as happens in
the lamps already described, it is simply necessary to keep the oil in the burner as much
as possible at the same height. This can be effected in suction lamps by placing the oil
reservoir higher than the burner, but in doing this it becomes necessary so to arrange the
construction of the lamp that the oil be gradually carried to the wick in such quantity as
is required for its proper burning. This is practically carried into effect as exhibited in
Fig. 276, which shows in vertical section a kind of lamp in England known as a
reading lamp. The oil reservoir of this lamp is a movable vessel, a, of tinned
iron, and closed by means of a valve, which when the vessel is placed vertically,
as exhibited in the cut, leaves the neck or mouth of the oil flask open in a downward
ARTIFICIAL LIGHT.
641
direction, so as to admit of the oil running into the space bb; but as soon as the oil has
risen to the level, ee', the fluid acts as a hydraulic valve, and no more oil can flow out of
a until by the burning of the lamp the level has been lowered. The tube d carries the oil
to the wick-holder; while at c a small hole is made for the purpose of giving free access
of air to the space between the sides of the vessel a and the cylindrical box in which it
is placed. When more oil might flow to the wick of this kind of lamp than can be burnt
in a given time the flame is extinguished, but, as usually constructed, these lamps, unless
they be tilted, or exposed to a very warm atmosphere (in which case owing to the expan-
sion of the air in the vessel a the oil
is forced out of it) answer the purpose
very well, giving when burnt with
suitable wicks and well-refined colza
oil a good light, but less intense than
that obtainable from the better kinds
of paraffin oil lamps.
Pressure Lamps.
2. These are distin-
guished from suction lamps by the
mode in which the oil reservoir is
situated in reference to the burner,
the former being not placed on a
level with or higher than the latter
but below it, the place assigned to
the reservoir being the foot of the
lamp; and as the capillary action of
the wick is not sufficient to enable
it to suck the oil upwards to so great
a height, an arrangement is required
to lift the oil towards the wick, while
any excess of oil above that which the
flame at the wick is capable of con-
suming trickles downwards, and is
either conducted into the oil reservoir
or collected in a separate vessel. The
pressure lamps are certainly, as far as
colza oil lamps are concerned, the
best in every respect; but the dif-
ferent varieties of these lamps to be
here noticed have been superseded by
the moderateur.
According to the contrivance by
means of which the oil in pressure
lamps is forced up to the wick, we
distinguish :-
a. Aërostatical Lamps. In these
lamps the principle of Hero's foun-
tain is employed. Air is forced into
the closed oil reservoir, and this air
while trying to gain its equilibrium
with the outer air, forces the oil
through a very narrow tube upwards
to the burner. These lamps have,
owing to great complicity of con-
struction, difficulty of management,
and of filling with oil, never been of any real practical use.
FIG. 276.

6. In the hydrostatic lamps, also now obsolete, though in use in France in the earlier
part of this century, the oil is forced to the burner by the pressure of a column of liquid
upon the oil. The physical principle involved is, that of the two vessels or tubes com-
municating with each other, and filled with liquids of different specific gravity, the
height of these fluids is inversely as the specific gravities of the fluids. The fluid which
has to make equilibrium with the oil ought of course to be specifically heavier than
the oil, and ought neither to act injuriously upon the metal of which the lamp is made
nor upon the oil; while the liquid should not freeze very readily. Mercury, solution of
common salt, molasses, solutions of chloride of calcium, and similar liquids, have
been proposed as fluids to act in the manner alluded to.
42
642
CHEMICAL TECHNOLOGY.
y. Statical Lamps.--In these lamps the oil contained in the reservoir at the foot of the
lamp is either forced up to the burner by the pressure of a solid body exerted upon the
oil, or by the pressure of a piston, acting directly and by its own weight, forcing the oil
upwards through a narrow tube. In the first instance the oil is put into a bag made of any
impermeable and sufficiently pliable material-leather, caoutchouc, or waxed silk, for
instance—and this bag is placed in a reservoir, and next a weight is made to press upon the
bag, to which is fitted a small tube communicating with the burner. The second arrange-
ment with the piston was the forerunner of the mechanical lamps; but as statical
lamps are no longer made further details are unnecessary.
Mechanical Lamps. d. These lamps are fitted with a mechanical contrivance by the aid of
which the oil is forced from the reservoir in the foot of the lamp to the burner, the quan-
tity of oil thus supplied to the latter exceeding the requirements at any given moment of
the burning flame. While in all the lamps mentioned the contents of the burner is a
constant column of oil, which decreases steadily from the top downwards, or is renewed
from time to time, the oil in the mechanical lamps is a constantly flowing stream, which
yields the wick the requisite quantity for combustion, while the excess flows downwards
into the reservoir.
Two kinds of mechanical lamps are especially noteworthy, viz. :-
Clockwork Lamp. 1. The clockwork lamp, pump lamp, Carcel lamp, invented in 1800, by
the lamp maker Carcel, at Paris, and afterwards improved upon. The pump or pumps-for
in the better kinds there are two, unless the single pump is double acting-which forces
the oil from the reservoir in the foot of the lamp is moved by clockwork, provided with a
strong spring which is wound up. The pump is a combination of suction- and force-
pump; in some lamps of this kind, instead of a pump an Archimedean screw is employed
for the same purpose. In the socket of the clockwork the oil reservoir and pump are placed.
The tube through which the oil is forced upwards to the burner is carried through
the shaft of the lamp. The oil reservoir and the clockwork are separated from each
other by a horizontal metallic plate.
An apparatus of simple construction often employed in the Carcel lamp is shown
in section in Fig. 277. The body of the lamp forms the cylinder, in which the horizontal
piston m is moved to and fro, while the space n above it is connected with the oil pipe
FIG. 277.
n
FIFERITTEROD
C
a
leading to the burner. The space below the body or
cylinder of the pump is connected with the oil reservoir,
and divided into two compartments by means of a par-
tition, and further provided with two valves, made either of
oiled silk or of gold-beaters' skin. When the piston
moves in the direction from d to c, oil enters from the
reservoir through b, while the oil then present in the
space between c a and m, is forced through c into the space
n, and thence into the oil pipe. The space n serves also
the purpose of an air vessel, for the compressed air acts as
a regulator to the constant flow of the oil. When the
piston moves in the direction from c to b, oil enters through
a, and through d into n. The clockwork which moves the
piston rod of m is placed below the oil reservoir. The
arrangement of the pump is such that the burner of
the lamp is supplied with a larger quantity of oil than
is required for the immediate consumption of the flame, the result being that the
wick and the burner are kept cool, and the carbonisation of the wick at the flame is pre-
vented, and thereby the capillary action of the cotton left unimpaired. The excess of oil
flows again into the reservoir. The clockwork of these lamps requires winding up
about once in twelve to fifteen hours; and for burning seven to eight hours, the action is
so very uniform that a light of equal intensity is maintained for that time. Some
of these lamps are fitted with an external knob, which can be used for the purpose of
stopping the clockwork by arresting the motion of the regulating wings.
Moderateur, or Moderator 2. This lamp was invented in 1837 by Franchot, and as it is more
simple, less liable to get out of order, and is cheaper than the clock-
work lamp, it has in a great measure superseded the use of the latter. The essential part
of this lamp is a large, well-packed piston, which resting on the oil contained in the
reservoir, is forced downwards by means of a spiral spring, the oil finding no outlet but
through a small opening, into which is inserted a narrow tube leading to the burner. A
moderateur lamp is exhibited in Fig. 278, the upper part of the cut being a front,
the lower a sectional view. The oil reservoir is placed in the hollow body of the
lamp, made of metal; this reservoir serves also as pump body or cylinder for the
piston a, made of a metallic disc, fitted with a leather rim as packing, and also acting as a

Lamp.
ARTIFICIAL LIGHT.
643
valve. To the piston is fitted the rod B, which through nearly its entire length is
provided with teeth, biting in those of the small wheel, D, forming a rack and wheel-work
contrivance, which admits of drawing the piston upwards by turning the handle of D.
When thus wound up the expansion of the spiral spring which is held at E forces
the piston downwards. When the reservoir is not filled with oil, the piston rests on
the bottom of the vessel; and when oil is poured into the cup of the lamp, it flows
downwards into the reservoir and on to the upper surface of the piston: if this is
next moved upwards or wound up, there is a vacuum formed below it, and the
FIG. 279.
FIG. 278.
FIG. 280.



鹉​的
​B
DEL
LELETALLIE
(NSGELES USA.
atmospheric air pressing upon the oil forces it downwards by reason of the flexibility of
the leather packing acting as a valve, until all the oil is below the piston and the latter
fully wound up, when the oil forces the leather packing so tightly against the sides of the
reservoir that there is no way of escape but by the tube c, which communicates with the
burner. The spring is very accurately adjusted, and its expansion regulated to the bulk of
oil which is consumed, so that the wick is properly supplied. After the lapse of some
hours the lamp has to be wound up again. In order to prevent the oil passing through
the tube c in too large a quantity at once and being forced out of the burner as a jet, there
644
CHEMICAL TECHNOLOGY.
is brought into play a contrivance which is technically termed the moderateur, consisting
of (Figs. 279 and 280) a peculiarly bent wire, &, which is placed in the tube c, and is sol-
dered to the inner tube of the lower part of the burner. The lower and movable portion
of the tube c is, when the piston is fully wound up, so placed that & fits and dips into c,
while, when the piston moves downwards, c is also lowered, and not partly plugged by &.
By this arrangement the flow of the oil is rendered uniform and independent of the
greater force of expansion exerted by the spiral spring when the lamp has been fully
wound up. To some of these lamps an arrangement has been fitted, consisting of a dial
and hand, exhibiting externally the position of the piston, so that it may be seen
when the lamp again requires to be wound up, and in some cases an alarum has been
added for the purpose of giving audible warning when the operation is required. With
good colza or sperm oil an excellent light is obtainable, while the machinery is not very
liable to get out of order.
Oil Lamps.
FIG. 281.
с
Petroleum Oil and Paraffin 3. The fluids commonly termed paraffin or petroleum oils, and
also known as kerosen, photogen, pyrogen, &c., are always burnt in
suction lamps, the oil reservoir being placed either below or by the side of the wick.
Mechanical lamps, such as the moderateur lamp, for instance, cannot be used for petroleum
oils, because these oils do not lubricate the leather
of the piston. As the mineral oils are not viscous,
the capillary tubes of the wick can more readily
suck up the oil from the reservoir, so that by the
lowering of the level of the fluid a loss of intensity
in the light is hardly perceptible. Owing to the
large quantity of carbon contained in these oils,
a smokeless flame is produced only by a powerful
current of air, which is obtained partly by the glass
chimney and partly by the adjustment of the wick,
which should project very slightly above the rim
of the burner; while in the paraffin oil lamps
provided with flat wicks the object is promoted by
the brass cap put over the flame and provided with
an opening, below which the admixture of air and
vapours of the oil takes place, and also a strong
current of air called forth to aid the combustion.
In reality the petroleum and paraffin oil lamps are
vapour lamps; that is to say, the vapours of these
liquids yield the luminous flame, not the gases
resulting from the decomposition of the oil, as
obtains in the case of colza oil and candles. In
order to guard against the possibility of an
explosion, the paraffin oil lamps are all so con-
trived that the fluid contained in the reservoir
does not become heated, and for this purpose the
current of air which sustains the combustion is
made to cool the burner.

d..
a
f
b
Among the many paraffin oil lamps one of the
best is that of Ditmar, at Vienna. This lamp,
Fig. 281, consists of a metal oil reservoir, b, which
surrounds the wick tube and is connected with
that tube by means of a horizontal tube, through
which the oil is conveyed to the wick. a is an
aperture for filling b with oil, and closed by a
metallic screw-plug. The wick is a circular argand
burner with double currents of air and with glass
chimney, c. The metallic bearer or gallery, f, of
the chimney can be made, as in moderateur oil lamps, to slide upwards and downwards
for the purpose of adjusting the height of the bent narrowed portion of the glass
so as to produce the best flame. This narrowed part of the glass should stand about
three-eighths of an inch above the wick, as indicated by the dotted lines d and e,
so that the greater part of the flame, which should be about 6 to 8 centims. high,
is above the narrowed portion of the glass. If the glass is too high the flame either
smokes or is ruddy, and when too low the flame is small and hardly emits any light.
The oil reservoir of this lamp does not become heated, since it is kept cool by the strong
current of air drawn in by the combustion. In one of the recently published numbers of
the "Journal of the Society of Arts," the petroleum lamps of Silber are very highly
ARTIFICIAL LIGHT.
645
commended.
These lamps yield a light equal to that of twelve to forty wax-candles,
while the construction is such that they can be used with either mineral or fatty
oils alternately, and without the necessity of trimming the wicks. We have already
alluded to the so-called benzoline or sponge lamps (see p. 639).
Historical Notes.
III. Gas.
General Introduction and For many hundreds of years it has been known that fossil coals
yield a combustible gas, and even in very ancient times the observation has been
made that large quantities of combustible gases were sometimes evolved from coal
and other mineral seams, also from salt-mines, &c. The soil contains in many
localities such a quantity of gas that by boring a hole the escaping gas may be
employed for the purposes of illumination. In the neighbourhood of Fredonia,
State of New York, a native permanent source of gas exists, which having been
accidentally discovered by the pulling down of a mill situated on the banks of the
river Canadaway, has been, by boring into the bituminous limestone, enlarged, and a
gasholder constructed. The native gas now serves for the purpose of illuminating
the locality. The quantity of gas collected in twelve hours amounts to about
800 cubic feet, and consists, according to Fouqué's researches, of a mixture of marsh-
gas (CH4) and hydride of ethyl (C2H6). In the Szlatina salt-mine, situated in the
Marmaro Comitate (Hungary), illuminating gas is constantly evolved at a depth of
90 metres below bank from a marly clay which is interspersed between the layers of
rock-salt. This phenomenon was known in 1770, and the gas is now collected in a
gas-holder and used for lighting up the mine. A small quantity of gas is also
evolved in the Stassfurt rock-salt mines. The Rev. Mr. Imbert, who as a
missionary has travelled through China, states that in the Province of Szu Tchhouan,
where many bore-holes for rock-salt have been made to a depth of about 1500 to
1600 feet, gas is permanently emitted and conveyed in bamboo tubes to places where
it is used for lighting as well as heating purposes, more especially the heating of
salt-pans in which the brine is evaporated. In Central Asia and near the Caspian
Sea there are at several localities so-called eternal fires, which are due to the
constant evolution of gas from the soil. Similar phenomena are observed at Arbela
in Central Asia, at Chitta-Gong in Bengal, and elsewhere, while now and then large
volumes of gas emitted in the coal-pits and conveyed to bank by means of iron pipes
are suffered to burn for several days.
As regards the artificial production of gas from coals, Clayton and Hales, 1727 to
1739, made the first observations on this subject; while the Bishop of Llandaff,
1767, exhibited how the gas evolved from coal might be conveyed in tubes. Dr.
Pickel, Professor of Chemistry at Würzburg, lighted his laboratory, 1786, with the
gas obtained by the dry distillation of bones. At about the same period Earl Dun-
donald made experiments on gas-lighting at Culross Abbey; but it should be
observed as regards these experiments that they were made more with the view to
obtain tar, and the gas evolved by the distillation of the coals was considered a
curiosity. The real inventor of practical gas-lighting is William Murdoch, who in
1792 lit his workshops at Redruth, Cornwall, with gas obtained from coals. His
operations remained unknown abroad for some ten years, and hence the French
consider Lebon as the inventor of gas-lighting, since he lit (1801) his house and
garden with gas obtained from wood. The first more extensive gas-work was
established in 1802 by Murdoch, at the Soho Foundry, near Birmingham, the
property of the celebrated Boulton and Watt; and in 1804 a spinning-mill at
646
CHEMICAL TECHNOLOGY.
Manchester was lighted with gas. From that period gas-lighting became more and
more generally adopted in factories and workshops, but not before the year 1812 did
this mode of lighting become introduced into dwelling-houses and streets, a few of
which in London were lit with gas in this year; while in Paris gas was first
introduced in 1820. From that year gas-lighting may be said to have become of
general importance in Europe, and now there is hardly any important place on the
Continent where it is not in use, while as regards the United Kingdom in no portion
is gas-making and lighting so general over town and country as in Scotland.
Among the more recent improvements in this direction are Pettenkofer's wood and
peat gas manufacture, and Hirzel's gas from petroleum residues. The principle of
gas-lighting is, as has been already stated, the same as that of candles and oil lamps,
but the raw materials in use for gas-making are not by themselves suited for
illumination, and it is therein that the great improvement is to be found.
Gas-Lighting.
Raw Materials of These are coals, wood, resin, fatty substances, oil, petroleum, and
water, and according to the material employed the gas obtained is designated as coal,
wood, resin, oil, petroleum, and water gas.
Coal Gas.* I. Coals consist of carbon, hydrogen, oxygen, and small quantities of
nitrogen, mineral matter, or ash, and contain, further, a larger or smaller quantity
of iron pyrites. Technically we distinguish in England gas coals, steam coals, and
household coals. As regards the first—the so-called cannel coals usually excepted—
they belong to the class termed caking coal, for the reason that this kind of coal
when submitted to heat softens and becomes agglutinated. According to H. Fleck,
the best kinds of gas-coals contain upon ICO parts of carbon 2 parts of fixed
(gebundenen) and 4 parts of disposable (disponiblen) hydrogen. Among the best gas-
coals are the so-called cannel coals, the term cannel being a corruption of candle, as
in former times pieces of these coals were in some parts of Scotland and Lancashire
used by the poorer people to burn instead of candles. Cannel coal is chiefly found
in Scotland and Lancashire, although there exist seams of cannel coal in some of the
pits of Durham and Northumberland. The Boghead coal, or Torbane Hill mineral,
is not properly speaking a cannel coal, and will-excepting as specimens in
museums—soon have disappeared altogether; for gas manufacture it has already
become quite obsolete. In France and Belgium-in addition to large quantities of
imported English gas-coals and Scotch cannel-the coals of Mons and Commentry
are used, while in Germany the Saxony, Silesian, Westphalian. and Rhenish coal-
pits yield excellent gas-coals. Gas-coal should be as much as possible free from
sulphur, and should further contain only a small quantity of ash; but in practice
these points are less attended to, because the defects of one kind of coal are by good
gas-makers counterbalanced by the better properties of other kinds.
I cwt. (=50 kilos.) of German coals yields on an average 14 cubic metres, or
500 English cubic feet of gas, and 35 kilos. or 150 parts by bulk of coke. In
England it is usual to compute the quantity of gas yielded per ton of coals; on an
I cubic metre=35.31 English cubic feet.
40.22 Bavarian
32.34 Rhenish
31.65 Vienna
""
1000 cubic feet English = 28.31 cubic metres.
1138 Bavarian cubic feet.
915 Rhenish
896 Vienna
""
"
ARTIFICIAL LIGHT.
647
average the Newcastle coals yield about 9000 to 9500 cubic feet of gas per ton of
coals; cannel coals vary in yield from 10,000 to 12,000; as regards the Boghead variety
it gave about 15,000 cubic feet of gas, but much depends upon the mode of distilla-
tion and the length of time this operation is continued. It should be borne in mind
that the best illuminating gas is given off during the first hours of the distillatory
process; the latter products, though adding greatly to the bulk of the mixture, contain
much of the comparatively useless gases and diluents. The mode of decomposition
of the gas-coals may be elucidated by the following diagram, 100 parts of coal con-
sisting of:-
Carbon
Hydrogen
Nitrogen
Sulphur
...
:
::
78.0?
4'0
1'5
08} yield
Coke
Illuminating gas
...
70-75
...
Tar
30-25
Ammoniacal water
...
Chemically combined water 5'7
Hygroscopic water
Ash
5°0
50j
Products of the Distillation.
100'0
These may be classified into four chief products:
Carbon
I. Coke. Sulphuret of iron (Fe-S8)
II. Ammoniacal
liquor.
Ash
90-95
IO-
10- 5
100
100'0
Main constituents. Sulphide of ammonium, (NH4)2S
Carbonate of ammonia, 2(NH4)2CO3+CO2
Chloride of ammonium, NH4Cl
Cyanide of ammonium, NH CN
Sulphocyanide of am-
·4
monium,
NH CNS
(Benzol,
C6H6
Toluol,
C4H8
Xylol,
C8H10
Fluid. Cumol,
C9H12
Cymol,
C10H14
Propyl,
C₂H,
¿Butyl,
C4H9, &c.
Hydro-
carbons.
Naphthaline,
C10H8
Acetylnaphthaline,
C₁₂H10
Fluoren,
(?)
Anthracen,
C14H10*
Solid.
III. Tar.
Methylanthracen,
C15.
C₁SH12
Reten,
C16H12
Chrysen,
C18H12
Pyren,
С16Н10
Carbolic,
C6H6O
Cresylic (cresol),
C-H8O
Phlorylic (phlorol),
C8H100
Rosolic,
C20H1603
Acids.
Oxyphenic,
C6H6O2
Combinations
of oxyphenic
acid and acids
homologous C8H1002 of methyl
therewith.
* Has become important as a source of alizarine, in consequence of the discovery of
Creosote, consisting of (C-H8O2
three
substances,
(CH1202 homologous
Graebe and Liebermann, 1859.
648
CHEMICAL TECHNOLOGY.
III. Tar.
Pyridine, CH5N Leucoline, CH,N Coridine, C10H15N
Aniline, C6H-N Iridoline, CroHON Rubidine, CHIN
Bases. Picoline, C6H3N Cryptidine, CHIN Viridine, C12H1N
Lutidine, C,H,N Acridine, CrzHgN
Collidine, CgHIN
II
Asphalte forming compoundsEmpyreumatic resins
IV. Illuminating
gas.
Manufacture of Coal Gas.
Anthracen
Carbon.
Acetylen,
C₂H₂
Gases.
Elayl,
C2H4
Trityl,
C3H6
(Ditetryl,
4
C₁H8
a. Illuminating
Benzol,
C6H6
or light-yield--
Styrolen,
C8H8
ing constitu-
Naphthaline,
C10H8
ents.
Vapours.
Acetylnaphthaline, C12H10
Fluoren,
(?)
Propyl,
C3H7
Butyl,
C4H9
Hydrogen,
H2
CH4
CO
CO2
Ammonia,
NH3
Cyanogen,
CN
CNS
y. Impurities.
Sulphuretted hydrogen,
SH2
S2C
N
B. Diluents, or light-
bearers.
Methylhydrogen,
Carbonic oxide,
Carbonic acid,
Sulphocyanogen
Sulphide of carbon,
Sulphuretted hydrocarbons.
Nitrogen,
Whether coals, resin, wood, peat, or other materials are
employed, the manufacture of gas involves the three following chief operations,
viz. :-a. The obtaining of crude gas by the process of distillation. b. The separa-
tion of tarry and other condensable matters. c. The purifying of the crude gas so
as to render it fit for use.
a. The distillatory process or making of crude gas is effected by the application of
a high temperature—above red-heat-and exclusion of air, and is carried on in
vessels which are technically termed gas retorts or simply retorts.
Retorts. The retorts were in the earlier days of gas-lighting always made of cast-
iron and of cylindrical shape, but for the last twenty years fire-clay retorts have
become very generally used, though they have not altogether superseded the use of
cast-iron retorts, which were found inconvenient for only two reasons, viz., for
wearing out too rapidly, and for not admitting of being raised to the very high
orange-heat, which has been adopted for the distillation of some kinds of cannel
coals. As regards the size of the retorts, this varies according to the requirements
of the works, but generally the retorts are sufficiently large to hold 100 kilos. of coal,
leaving from 0.5 to 0.6 of the interior space unfilled for the purpose of affording
room for the expansion of the coals. The diameter of such a retort is about
54 centimetres in the larger axis, and 43 to 45 centimetres in the smaller axis, by a
length of 2.5 to 3 metres. One end of the retort is usually closed, although in some
large gas-works, as at Edinburgh, Glasgow, Paisley, fire-clay retorts of very great
length and open at both ends are in use, being fired by two furnaces situated at each
end. In some of the London gas-works, retorts are in use not made of fire-clay, in
ARTIFICIAL LIGHT.
649
one or more pieces, but built up with fire-bricks or slabs of fire-clay, of a peculiar
shape, and made for the purpose in Wales; these slabs are put together with a
cement of pure quartz sand and about 1 per cent of lime, or a clay which becomes
pasty and adhesive in very great heat. Retorts of this kind are cheaper and stand
five years' wear. Retorts made of heavy boiler-plate rivetted together, as well as
forged iron retorts, welded together like the iron mercury bottles, are also in use, but
of course are, in the furnaces, protected from the direct action of the fire by properly
built arches and coverings of fire-bricks.
of Retorts.
Mouth-piece and Lid The retorts are always fitted with a separate mouth-piece, to which
during the process of distillation the lid is fastened; this mouth-piece is always
made of cast-iron, even in the fire-clay retorts, to which it is fitted by a flange on the
retort, the flange of fire-clay being provided with six to eight holes for putting in the
screw bolts for the purpose of making a good joint. In order to get a gas-tight joint
a mixture of iron filings and gypsum is used, which is made into a paste with an
aqueous solution of sal-ammoniac. The mouth-piece is fitted with a short tube for
FIG. 283.
FIG. 284.
FIG. 285.
FIG. 282.


D


n
ル
​72
n
B
the purpose of giving vent to the gases and vapours evolved during the distillation
As the mouth-piece is placed outside the furnace, it is generally of longer duration
than the retorts, and these are moulded to suit the mouth-piece.
Fig. 282 exhibits the front view of a mouth-piece of a Q-shaped retort. Fig. 283
exhibits a section. B is the opening at the retort end; n is the lid for closing
the retort during the distillation. At ss, Fig. 282, are seen the cast-iron eyes
intended to support the malleable iron bars for the support of the lid. 00, Fig. 283,
is the flange wherewith the mouth-piece is fitted to the retort. D is the short piece
of tube. Fig. 284 is a front view of the cast-iron lid of the retort; and Fig. 285, a
view of the side of the lid turned towards the retort. As will be observed, the lid fits
accurately into the opening of the retort. The method of closing or rather tightly
fastening the lids of gas retorts is exhibited in Fig. 286, being a side view of
the mouth-piece. mm are the malleable iron bars on which the lid is supported by
means of the projections, nn, Fig. 284. Through the bars mm are cut openings,
through which the cross-bar p is put, and in its centre a hole with screw thread, into
which is made to fit a screw-bar and handle, a. By turning the screw, the lid is
forced tightly against the rim of the mouth-piece; but in order to secure a gas-tight
joint, a lute is used consisting of some clay or spent purifier lime and clay mixed.
Another mode of fastening the lid is exhibited in Fig. 287, being also a side view.
The bars mm are in this instance bent at one end where the cross-bar a is
to be placed. To that cross-bar is fitted at right angles another bar, н, provided
650
CHEMICAL TECHNOLOGY.
at one end with a heavy iron ball, and at the other with a knee-bend, so that by
pulling the ball downwards the lid, n, is tightly fastened.
Retort Furnaces.
The retorts are placed in a furnace in the manner exhibited in
Fig. 288, that is to say they are placed horizontally and supported by brickwork—
technically benches. The mouth-piece projects from the furnace, each of which may
contain two to three, five to seven, or even twelve to sixteen retorts, as in large gas-
works, in which case the lower rows are of fire-clay, the higher of iron.
FIG. 286.
n
p
n
B
FIG. 287.


H
B
Distillation.
0
Charging the Retorts, and The retorts are in some works charged by means of a large
scoop, which being filled with the quantity of coals the retort is intended to be
charged with, is carried by four men and then lifted into the retort, and being over-
turned fills the retort, after which the scoop is withdrawn and the lid of the retort
fastened on. But in many gas-works the coals are thrown into the retorts with shovels.
As soon as the retorts, which previously to being filled are always heated to red-
heat or higher, are charged, and the lids closed, the evolution of gas is very strong,
and continues so for some time, until after some four to five hours the distillation is
finished, or at least the gas then given off is not worth collecting. In Scotland the
distillation is not continued so long, three or three and a half hours being deemed,
with good firing, quite sufficient, cannel coals giving off their gas more freely than
caking coals. The lids are now loosened and the gas at the mouth of the retorts
kindled in order to prevent explosion by its becoming, as would be the case if
the lids were at once removed, mixed with air. The red-hot coke left in the retort is
raked out and at once used for firing the furnaces, or put into iron wheelbarrows
and wheeled out of the retort-house into the yard, there to be quenched with water
and kept for sale. Cannel coals do not as a rule yield a good coke, but only broken-up
black shaly breeze, which, however, along with some dead oil, is used in the Scotch
gas-works for heating the retorts. On an average one-third of the coke obtained is
required for firing the retorts.
The Hydraulic Main. We understand by the hydraulic main a vessel with which are
connected the ascending tubes leading from the retorts. As a rule the hydraulic
main is placed on the top of the furnace in which the retorts are ignited. The
diameter of the ascending tubes varies of course with the size of the retorts, but is on
an average 12 to 18 centimetres. The hydraulic main, of which в, Fig. 288, is
a section at right angles to the longitudinal axis, is a wide pipe of cast-iron or
of boiler-plates rivetted together, and having an average diameter of 30 to 60
centims. It is either cylindrical or -shaped, and extends over the entire length of
the row of furnaces. The hydraulic main is intended to act as a receiver for all the
ARTIFICIAL LIGHT.
65

HIDLEG
FIG. 288.
K
K
I
85=
CHEMICAL TECHNOLOGY.
volatile products of the distillation, while at the same time it affords to every single
retort a hydraulic valve, shutting it off from the other retorts, and preventing
effectually any gas finding its way back to the retorts when opened at the mouth.
The mode of connection between the retorts and the hydraulic main is shown in
Fig. 289. A is the ascending tube; в the saddle-pipe; c the dip-tube carried down-
wards into the hydraulic main; D is the main; and m the liquid-viz. tar, or at the
first starting of a gas-work, water. Fig. 290 exhibits a somewhat different mode of
connecting the retorts and hydraulic main. There is fitted to this main a syphon
tube for running off the excess of tar to the tar cistern, and on the top of the main
is, as exhibited in Fig. 288, a wide iron tube for carrying off the gas to the
condensing apparatus.
FIG. 290.
FIG. 289.


D
H
m:.
Cooling or Condensing
Apparatus.
b. The volatile products of the distillation which are not con-
densed in the hydraulic main are carried off with the permanent gases. The reader
should observe that a comparatively very high temperature prevails in the ascending
tubes and hydraulic main. These volatile products are gas, steam vapours of tar,
the steam containing in solution and suspension various ammoniacal compounds.
Before the gas can be purified it has to be cooled and deprived of a number of sub-
stances which are in fact impurities, inasmuch as they would impede the flow of gas
through the pipes if they were not got rid of. The condensing process may be carried
on in various ways, but on the large scale the most efficient is the very simple
expedient of causing the gas to pass through a series of cast-iron pipes, as exhibited
in Fig. 291, in vertical section; also in D, Fig. 288. These tubes, placed in the open
air—in warm climates or in hot summer weather arrangements being made to cool
the pipes externally by a stream of water-are connected with each other at
the top, and rest in a large cast-iron tank, p, which by means of partitions is
divided into compartments not communicating with each other, being hydraulically
ARTIFICIAL LIGHT.
653
locked. Each compartment is fitted with an inlet, m, and an outlet, n. In this tank
the gas-water or ammoniacal liquor and tar are collected, while the height these
fluids should occupy in the tank is regulated by a tube, d, or as seen in Fig. 288, at н,
by a syphon tube. The condensed liquids flow to the brickwork tank, q, and thence
to the tar cistern. The inlet tubes dip to some depth into the fluid so as to force the
gas to pass through it. The size, number, and height of these condensing tubes
depends on the quantity of gas which has to be cooled in a given time; on an
average 50 to 90 square feet of surface of tubes is allowed for 1000 cubic feet of gas
to be cooled per hour.
The Scrubber.
In many of the larger gas-works the gas, after it has issued from the
tube condenser, is passed through an apparatus tormed the scrubber, for the purpose
of more completely depriving it of tarry matter before sending it on to the purifiers,
FIG 291.

HHHI
I
and also for getting rid of the ammonia and sulphur compounds. The rationale of
the mode of action of the scrubber is similar to that often employed on a minute
scale in practical chemistry, when a gas or vapour is passed through a glass tube
filled with pumice-stone, so that in a limited space a great surface is provided.
The scrubber consists of cylindrical cast or malleable iron chambers of sufficient
size, and filled with lumps of coke or fire-brick, which are constantly moistened with
water. Fig. 292 exhibits a sectional view of a scrubber, also seen in Fig. 288 at oo.
The cylinder has a diameter of 1 to 1 metres, by a height of 3 to 4 metres;
the vessel is filled with coke, which is kept moist by means of water introduced by
the rotating perforated tube, H. The inlet of the gas is at i; it proceeds upwards
through the column of coke and on reaching the top passes off downwards through
m to the second scrubber. At the lowest bend of the exit or outlet tubes a
syphon pipe is fitted for the purpose of draining off water and tarry matters which
654
CHEMICAL TECHNOLOGY.
collect in the reservoir, M.
additional pressure to be
The use of the scrubber-the gas hardly requires any
carried through it-effects a saving of the purifying
materials, lime, &c., by causing the gas to be thoroughly washed and cooled;
in other terms—mechanically purified.
Exhauster. This apparatus, also termed the aspirator, is placed between the
hydraulic main, being connected with the gas leading pipe, or between the
condensers and the purifiers. It is intended
to suck or pump the gas from the retorts so as
to diminish their internal pressure. This
pressure amounts in some cases to nearly
15 lbs. to the square inch, and it was found
that under that pressure a great deal of gas
was lost through the pores of the fire-clay
retorts, especially when new, being then not
coated with a film of graphite which after-
wards acts as an impermeable layer. The aspi-
rators also serve ίν remove the gaseous
mixture as rapidly as possible from the red-
hot retorts and coke, and thus prevent the
partial decomposition of valuable illuminating
constituents of the gas, by which decompo-
sition, moreover, the retorts, iron as well as
fire-clay, become lined with a graphite-like
coke, which impairs the conducting power for
FIG. 292.

A
1.
heat, as well as decreases the internal cubic capacity of the retorts. The intro-
duction of exhausters dates from 1839, when Grafton made and tried the first. His
arrangement was-a box filled with water for about three-fourths of its capacity,
while in the box, on an axis projecting outside, through gas- and water-tight stuffing
boxes, four circularly-bent scoops were fixed, so that on a rotating motion being
imparted to the axis, and thereby to the scoops, a partial vacuum was formed, and the
gas inspired into the apparatus, and thence carried off by side tubes. This apparatus
has never been of any practical use in gas-works. Next, the so-called bell
exhauster was used; the principle of this apparatus-similar in construction to
that in use in paper mills-being in reality nothing else than a hydraulic air-
pump, consisting of two or three large bell-shaped iron vessels, connected together
and placed in tanks filled with water, and moved slowly upwards and downwards by
mechanical power. Under each of these bell-shaped vessels an inlet and outlet
pipe is fitted provided with valves. There have been a great many variously
constructed exhausters proposed; some of these, Anderson's for instance, are
similar to the cylinder blowing machines in use with blast furnaces; others
again are similar in construction to the double-acting air-pumps of low-pressure
marine steam-engines; some to centrifugal pumps. With the fire-clay retorts,
now very generally adopted in gas-works, the use of exhausters is almost a
necessity, and the apparatus is always fitted up with new gas-works. Of course an
accessory of the exhauster is a small steam-engine and boiler.
Purifying Gas.
c. The crude gas having been passed through the apparatus just
described, and mechanically purified, is sent on, as it is technically termed, to the
purifiers, in order to eliminate by chemical means such substances as sulphuretted
ARTIFICIAL LIGHT.
655
hydrogen, carbonic acid, and various ammoniacal compounds, carbonate of ammonia,
sulphuret of ammonium, cyanide of ammonium, &c.; and also some of the compound
ammonias, as, for instance, aniline, iridoline, &c. At the outset of the gas-lighting
industry, quick-lime was the only material employed for purifying purposes, this sub-
stance being at first employed in the form of a thick milk of lime, the purifier being
so constructed that the crude gas was brought into intimate contact with the fluid,
which, in order to prevent the lime from forming a sediment, was kept in constant
motion by a stirring apparatus; while the purifier, made of cast-iron, was provided
with inlet and outlet pipes for the gas, a pressure gauge, and the necessary syphon
pipes and valves for letting out the waste milk of lime and re-filling the vessel.
Variously arranged wet lime purifiers have been devised, and among them some
which act also as exhausters; but notwithstanding the very satisfactory results
obtained by the use of wet lime purifiers, the gas being very effectually freed from
carbonic acid, sulphuretted hydrogen, and ammonia, there is the defect-first, of
the back pressure on the retorts and other apparatus; and secondly, a difficulty
in the mode of so disposing of the very fœtid waste lime liquor as not to create a
nuisance; hence it is that the wet lime purifiers have been almost entirely super-
seded by the so-called dry lime purifiers. These are large square iron boxes fitted
inside with movable trays resting on ledges and provided with sieve-like perforations,
and either made of iron gratings or iron plates, or even wooden boards, on which the
previously slaked and somewhat moist lime is carefully placed in layers of uniform
thickness to a height of 20 centimetres, there being in every purifier box from five to
eight frames. The purifier is usually divided into two compartments by a partition,
so that the gas which enters from the bottom of one compartment has to ascend
through the layers of lime of the inlet compartment, and to descend through those of
the outlet compartment. The gas passes through the layers of dry lime readily
enough and almost without producing any back pressure, and there is no necessity
to render the lime more porous by the addition to it of either moss, sawdust, chopped
straw, &c. As to the quantity of lime required for the purpose of purifying a cer-
tain volume of gas, it is stated that for 1000 cubic feet of crude gas from
Newcastle coals, 2'6 kilos. of unslaked quick-lime are required. With careful
selection of the gas-coals to be carbonised, and a well-conducted distillation and
mechanical purification of the crude gas, the lime purifying process, especially
if wet and dry purifiers both are used, as is the case in some of the largest gas-
works in Scotland, yields excellent results, and there is no need for any other
purifying materials; while the spent lime, as is the case in Scotland, is found useful as
a manure, as well as for building purposes with some fresh lime and sand. It is, how-
ever, true that in many places the gas thus made is too impure for use in dwelling
houses, and a more complete elimination of the ammonia and some of the sulphur
compounds is found to be absolutely necessary. Since 1840 an immense number of
gas-purifying materials and contrivances have been brought forward and tried but
again abandoned. It is entirely beyond the scope of this work to enter into more
than a very slight sketch of the various gas purifying processes; but we give the
following particulars on this subject.
It cannot create any surprise when we find that acids and metallic salts should have
been called in to aid the absorbing of the ammonia and sulphuretted hydrogen from coal-
gas. Protosulphate of iron has been here and there resorted to, of course in aqueous
solution. Mallet (1840) commenced the use of the residue of the chlorine manufacture,
crude chloride of manganese, for the same purpose. Far more important is the method
656
CHEMICAL TECHNOLOGY.
first suggested in 1847 by R. Laming, and now generally known as the Laming puri-
fying process. As originally patented, the mixture was composed of protochloride of iron
with quick-lime or chalk, and in order to keep the mass porous sawdust was added.
Instead of protochloride of iron, sulphate of iron is now more generally used, and mixed
with previously sifted and slaked lime, and one-fifth to one-fourth of its bulk of sawdust.
The mass is then placed in beds or layers exposed to open air, moistened with water, and
is, after twenty-four hours, fit for use in the same apparatus as is employed in the dry lime
purifying process. According to the results of the scientific researches of A. Wagner
(1867), Gélis (1862), of Brescius, Deicke, and others, the peroxide of iron of the Laming
mixture becomes converted by the sulphuretted hydrogen into sesquisulphuret of iron
(Fe2S3), and by exposure to air-revivifying process, for which purpose old purifiers are
used, air being forced through-the sulphur is separated again, and oxide of iron
mechanically mixed with sulphur is left. This mixture may be used several times, and
as mentioned in the earlier pages of this work, the sulphur may be advantageously
extracted from this mixture. Gauthier-Bouchard, at Paris, has proved that the spent
Laming mixture may be used on the large scale for manufacturing Berlin blue and yellow
prussiate of potash; while Menier, at Marseilles, prepares annually 12 to 15 tons of sulpho-
cyanide of ammonium from the spent gas-purifying materials. Very recently (1869) the
proposition has been made to withdraw the benzol contained in illuminating gas by
passing the gas through heavy oils of tar, from which the benzol, to be used for aniline
making, is to be separated by fractioned distillation, and the gas again rendered luminous
by passing it through benzoline, light petroleum spirit. It is evident that considering the
great bulk of gas to be operated upon, this proposal or suggestion will be difficult to carry
out in practice, and also costly in consequence of the apparatus required.
Gas-holders, These apparatus, sometimes but less correctly termed gasometers,
serve as well for the purpose of storage of the great bulk of the gas as for causing a
sufficient pressure, so as to regulate its flow through the street mains and burners.
The gas-holder consists of three parts, viz. :—1. The tank, a cylindrical water-tight,
more or less deep vessel, with vertical sides, filled with water as a hydraulic lute.
2. The bell, or rather inverted cylinder, which can move freely between the stand-
pillars by the aid of grooved rollers or pulleys, which work on iron bars fitted
against the stand-pillars. 3. The large inlet-pipe which communicates with the
purifiers, and the outlet-pipe which communicates with the street mains, each being
supplied with valves and syphon-boxes for the purpose of collecting any water
which might condense or otherwise find its way into these pipes.
The tank was in former days made of wood, then, when the size of the gas-holders
was increased, of cast-iron plates fitted with flanges provided with holes for
screw-bolts, the joints being filled with cement so as to make a water-tight vessel.
Now the tanks are constructed by digging to a greater or less depth into the soil, the
bottom and sides being laid in brickwork with a water-tight cement backed by a
puddling of clay. In some few cases the tank is constructed as exhibited in Fig. 293,
where a cone remains covered by brickwork, but as water is generally plentiful, and
is less costly than the expense attending this arrangement, it is not usual. The
bell or holder is always made of sheet-iron plates rivetted together, care being taken
either to put red-lead putty, or brown paper soaked with red-lead paint or thick
boiled tar between the overlappings of the plates so as to obtain good joints. The
plates are inside and outside painted with iron-paint or coated with boiled coal-tar.
Formerly, with gas-holders of a capacity varying from 30,000 to 80,000 cubic feet,
the bell was suspended by means of iron chains led over pulleys fastened to the
stand-columns and provided with heavy weights for the purpose of counterbalancing
the too great weight of the iron holder and to regulate the pressure exerted upon the
gas; but with the very large holders now in use, and the practice of building them
of thinner iron plates, the holders are simply made to move freely between the
stand-columns as exhibited in Fig. 293. In order to gain space with the same depth
ARTIFICIAL LIGHT.
657
of tank, the so-called telescopic gas-holders are constructed, being, in fact, one or more
cylinders fitting into each other and capable of sliding upwards and downwards, the
topmost cylinder only being fitted with a roof, while a gas-tight joint is obtained by
FIG. 293.

།།།
་་་་་
་་་་
a hydraulic lute. The inlet and outlet mains are of cast-iron, and open just a few
inches above the level of the water in the tank (Figs. 288 and 293). A peculiar
construction of gas-holder, invented by Pauwels, at Paris, and in use in some of the
gas-works of that city, is exhibited in Fig. 294. The inlet and outlet pipes, a and b,
FIG. 294.

KU
are in this gas-holder connected with the roof, and consist of several pieces with
joints fitted with gas-tight stuffing-boxes, the arrangement being readily understood
from the engraving. The advantage is that all chance of flooding of the inlet and
outlet pipes is prevented, but the arrangement is expensive and not compatible with
telescopic gas-holders; moreover, the level of the water in the tanks of gas-holders
43
658
CHEMICAL TECHNOLOGY.
is rarely, if ever, subject to any great increase in height, because a drain-pipe is
fitted to the upper rim of the tank for carrying off rain-water. Gas-engineers well
enough know that it is difficult in many cases to prevent leakage from tanks so
effectually that there should be much risk of the sudden flooding of the inlet and
outlet pipes by a rush of water. Small gas-holders are often provided with a scale,
the divisions of which correspond to certain quantities of cubic measure; but large
gas-works are nearly all fitted with a station-meter, through which all the gas made
has to pass previous to entering the gas-holders, and by means of this meter a
control is kept over the quantity of gas made. The cubic capacity of every gas-holder
is of course accurately known. The size of the gas-holders varies; some at very
small works, for villages, railway-stations, country-seats, &c., are only 1000 to 3000
cubic feet capacity, while there exist gas-holders of enormous size, 45 metres diameter
by 20 in height, which contain 1 million cubic feet. According to Riedinger's rule, the
cubic capacity of a gas-holder should be equal to 2 to 2 times the average daily
quantity required.
I
The filling of a gas-holder is proceeded with in the following manner:-The outlet
main-pipe having been shut off by the closing of the valve fitted to it, gas is admitted
through the inlet-main into the holder; the gas accumulating in the latter exerts a
pressure upon the water in the tank, which consequently is depressed inside the
holder and rises higher outside it, while gradually the holder is lifted by the force of
the gas, the inlet valve being shut off as soon as the holder is filled to within about
20 centimetres of its height. When the outlet valve is then opened the gas flows into
the street mains, the pressure being obtained from the weight of the holder. In
order to ascertain the quantity of the gas made, it is measured by a large gaso-
meter, technically termed a station-meter, and placed between the purifiers and
the inlet to the gas-holders. The construction of these station-meters is very similar
to that of the ordinary wet gas-meters.
Very little is known as to the composition of the gas at the different stages of its
manufacture from the moment it enters the hydraulic main to the moment it enters
the street mains. The experiments of Firle, made at Breslau in 1860, are very
valuable, but only relate to a special inquiry.
Firle tested coal-gas:-(a) after it left the condenser; (b) after it left the scrubber:
(c) as taken from the washing-machine; (d) as taken from the purifier containing
Laming's mixture; (e) as taken from the lime-purifier, consequently thoroughly
purified gas as sent into the holder :-
Hydrogen
Marsh-gas
...
Carbonic oxide...
Heavy carburetted hydrogens...
Nitrogen
Oxygen
Carbonic acid
..
Sulphuretted hydrogen
a.
...
b.
d.
37'97 37'97 37'97 37'97 37'97
39'78 38.81 38.48 40°29 39:37
7:21 7.15 711
4'19 4'66
C.
e.
3'93
3'97
4.46
4'66
4'29
4.81
4'99 6.89 7.86
9'99
0'31
0'47 0*15 0'48
0.61
3.72
3.87 3:39 3:33
0'41
1'06 1'47 0'56 0:36
0'95 0'54
Ammonia
Referring these figures to bulk, and taking 1000 cubic feet of crude gas as the unit
quantity, we find the following proportions:-
ARTIFICIAL LIGHT.
659
Cubic feet.
Hydrogen
Marsh-gas
Carbonic oxide
:
::
:
Heavy carburetted hydrogens
Nitrogen
Oxygen...
Carbonic acid
•
Sulphuretted hydrogen
Ammonia
: :
:
:
a.
C.
d.
e.
...
380
380
380
380
380
390
388
384
403
394
72
71
7Ι
39
30
...
42
46
45
46
43
48
50
69
79
100
3
5
2
5
6
40
39
34
33
4
15
15
5
ΙΟ
5
I w
3
1000
999
990
988
966
The above results exhibit the changes which the composition of the gas undergoes
during the purifying process as well as the action of the different apparatus. When
1000 cubic feet of gas composed as stated in (a) enter the purifying apparatus, in
each of these there is taken up of the absorbable gases, chiefly carbonic acid,
sulphuretted hydrogen, and ammonia, the under-mentioned quantities :-
For 1000 cubic feet in cubic foot measure:—
Carbonic acid
Sulphuretted hydrogen
Ammonia
Carbonic oxide
Oxygen
::
Washing- Laming's Lime-
Scrubber. machine. purifier. purifier.
H.
Ι
5
I
29
I
ΙΟ
2
3
5
5
I
32
3
I
The original bulk of the gas decreases consequently steadily, and there remain of
1000 cubic feet of crude gas after leaving:—
The scrubber
The washing-machine
The Laming's purifier
The lime-purifier
...
994 cubic feet.
971
936
""
914 ""
""
This is correct, premising that the other constituents of the gas are unabsorbed,
which really is so, as we may neglect the very small quantities of marsh-gas and
heavy hydrocarbons, which are kept mechanically arrested in each purifying appa-
ratus. The bulk of the gas is, however, slightly increased by an addition of
atmospheric air. 1000 cubic feet of the crude gas (a) contain 51 cubic feet of oxygen
and nitrogen; this quantity is increased :—
In the scrubber by
In the washing-machine by
In the Laming's purifier by
In the lime-purifier by
4 cubic feet.
20
33
""
55
By this addition the total bulk of the gas in each apparatus is again increased, and
amounts (taking account of the variable quantity of marsh-gas and heavy carbu-
retted hydrogen compounds) for 1000 cubic feet unit quantity:-
660
CHEMICAL TECHNOLOGY.
After leaving the scrubber, to
""
""
"
999 cubic feet.
washing-machine, to
Laming's purifier, to .
lime-purifier, to...
•
990
""
988
**
...
966
It is understood that temperature and pressure remain constant during
fying process.
Distribution of Gas.
Generally, in the United Kingdom, and as regards coal-gas also
abroad, the gas is conveyed to the localities where it is to be burnt by means of cast-
iron pipes laid underground. But so-called portable gas (gas portatif) is still
made abroad and conveyed to the consumers in large gas-tight bags placed in cars,
the bags being emptied at the houses of the consumers into small gas-holders. The
materials from which this kind of gas is made are generally such (refuse of oil, oil of
bones, very crude olive oil, resins, &c.) as yield a gas of far higher illuminating power
bulk for bulk than coal-gas, so that a comparatively small bulk of gas will suffice for
even a large number of burners. The pressure exerted upon the gas in the holders
causes it to move through the pipes. The amount of this pressure is, however,
usually regulated at the works by a peculiar mechanical contrivance, so as to make
it as uniform as possible over the total length of the mains and service-pipes. Coal-
gas being lighter than air has a tendency to rise, and for this reason it is considered
preferable to build gas-works at the lowest level of the locality it is intended to
supply, because a less pressure is sufficient for moving the gas through the mains.
The pressure at the burners should be from o'05 to 0'15 of an inch, water-gauge
pressure, while at the gas-works a pressure of 21 to 5 inches (water-gauge) is quite
sufficient to force gas to any distance within a circuit of several miles.
The street mains are made of cast-iron, and laid under the pavement at a suitable
depth, varying from o'6 to 16 metre. The service-pipes in England and on the Con-
tinent are of malleable-iron or of lead, but in Scotland cast-iron pipes (even quarter
and half-inch) are preferred and in general use. The large mains are put together
by placing the spigot into the socket-end of each pipe alternately, and caulking in
greased or tarred tow and pouring in molten lead. In Scotland the mains are now
generally put on the lathe, and the spigot and socket ends turned true, so as to give
a gas-tight joint simply by the aid of some red-led paint and putty and a collar of
soft greased tow. Although carefully laid, the gas-mains give rise to more or
less loss by leakage, which is stated to amount in some instances to 15 or 20, and
even 25 per cent of the gas made and sent into the mains; but if street mains are
cast vertically and the iron be of good quality, each pipe properly tested by hydraulic
pressure for its soundness before being laid, and, moreover, first immersed in hot
coal-tar and the joints well secured, leakage may be very much reduced, if not
altogether prevented. The mains should have a sufficiently large bore for the
quantity of gas to be conveyed through them, so as to reduce friction. They are not
laid quite level even in level streets, but slope gently; while at the lowest level
so-called syphon-pots are placed for the purpose of collecting any condensed water—
the gas is almost saturated with water by being in contact with it in the gas-holders,
although after some time a thin layer of empyreumatic matter covers the surface of
the water, thereby preventing the gas becoming excessively saturated. These
syphon-pots are fitted with a narrow iron tube reaching nearly to the surface of the
pavement, being closed by a screw-cap, which, being unscrewed, a hand-pump may be
screwed on, and any condensed water pumped out of the syphon-pot or box. For the
ARTIFICIAL LIGHT.
661
purpose of connecting the burners with the service-pipes narrower tubes are used,
made either of pure block-tin or of an alloy of lead and tin or of lead and copper;
the latter are, however, not so readily bent, and have the disadvantage that there
may be formed in them acetylen-copper, which, as proved by Crova, is a very explo-
sive compound.
Hydraulic Valve.
FIG. 295.
The valve represented in Fig. 295 is now almost superseded by valves
of a totally different description, termed slide-valves, and worked similarly to
those in use for the water-mains common in London
streets. The valve represented in the engraving
is placed near the gas-holders, and may serve either
for shutting off the inlet-pipe to the holder or for
the same purpose at the outlet-pipe. The valve con-
sists of an iron vessel, I KLM, filled with water. The
pipe A communicates with the gas-holder and B
with the street main. The drum-like vessel, CE FD, is
suspended over the pipes and is counterbalanced by the
weights x and y. When the latter are removed the drum
sinks, and the partition н, dipping in the water, cuts off
the communication between A and B.

•
O4
E
UH
AM
A
B
K
Pressure Regulator. This contrivance, acting automati-
cally, is arranged for the purpose of regulating the
supply of gas from the gas-holders to the mains. It
consists essentially of a small gas-holder connected with
a conical valve placed in the outlet-pipe, while the small
gas-holder to which it is fastened is very accurately
adjusted, or provided with counterweights, by means of which its position may be set at a
certain supply either per hour or evening, as the case may be. If from some cause or
other the consumption of gas increases the gas-holder will sink, and the opening in
which the conical valve plays becomes larger, and consequently more gas passes through; if,
on the other hand, the supply decreases, the consequence will be that too much gas enters
the small holder from the large ones, and the former rising draws the conical valve with it
upwards, thus more or less completely plugging the outlet-pipe.
Testing Illuminating Gas. The cause of the luminosity of the flame of gas is the ignited
carbonaceous matter. Everything, therefore, which impairs the separation of the
carbonaceous matter or chemically affects their proper ignition, decreases the
luminosity of the flame; among these deteriorating causes are-1. Excessive
admission of air or of oxygen. A coal-gas flame burning in oxygen will be found to
have lost its luminosity, and the same occurs, as is well known and exhibited in the
Bunsen gas-burner, when gas is mixed with air previous to being ignited. 2. Car-
bonic acid. When red-hot or white-hot carbonaceous matter comes into contact
with carbonic acid, there is formed carbonic oxide (CO2+C=2CO), which burns
with a blue, non-luminous flame. As elayl-gas (C2H4) becomes decomposed by red
heat into methyl-hydrogen (marsh-gas, CH4) and carbon (C), and as the latter
reduces an equivalent quantity of carbonic acid to carbonic oxide, it is evident that
the carbonic acid deprives half its bulk of elayl-gas of its illuminating power. Sup-
pose an illuminating gas to contain 6 per cent of elayl-gas, and also 6 per cent of
carbonic acid gas, the result will be the elimination of the luminosity of 3 per cent
of elayl-gas. This proves the great importance of the complete removal of carbonic
acid from gas by the lime-purifier.
Very little has been experimentally proved as to the relation existing between the
illuminating power of a flame and the quantity of the separated carbonaceous
particles; it is probable, however, that this relation is a direct one, and that there-
fore the luminosity of a flame is the stronger the larger the quantity of carbonaceous
particles separated, provided, however, that the temperature of the flame be very
high, because otherwise the flame will be either ruddy or smoky. Although by an
662
CHEMICAL TECHNOLOGY.
increased access of air (as in the case of petroleum lamps provided with a glass
chimney) the combustion may be increased so as to create a very high temperature
of the flame and thereby a very white light, it is probable that this expedient (espe-
cially if applied to ordinary coal-gas) would cause a too sudden combustion of the
carbon, rendering it useless for illuminating purposes. Supposing the illuminating
power of a flame to be proportional to the quantity of carbonaceous particles sepa-
rated, and applying this principle to some of the carburetted hydrogens occurring in
purified illuminating gas, taking account more particularly of the gases (CH2) so
composed that by ignition they become decomposed into methyl-hydrogen and
carbon, we have:-
Vol.
Vol.
Vols.
1 elayl, C2H4, which yields r'o of methyl-hydrogen and 2 of vapour of carbon.
I trityl, C-H6,
I ditetryl, C4H8,
I'5 ""
ΙΟ
99
""
""
3"
""
", 4",
"
""
and may assume the illuminating power of these three gases to be as 2:3:4. Taking
the illuminating power of elayl-gas to be 100, the illuminating powers of the gases and
vapours contained in purified coal-gas may be represented by the under-mentioned
figures, the vapours having been calculated at a sp. gr. o:-Elayl, 100; trityl, 150;
ditetryl, 200; propyl, 250; butyl, 350; acetylen, 450; vapour of benzol, 450;
vapour of naphthaline, 800.
The following figures exhibit the quantity of elayl-gas, for which can be substituted
a combustible gas (hydrogen or marsh-gas) impregnated with the vapours of hydro-
carbons at o° and 15° for yielding an equal amount of light. Impregnation with-
At 15°.
Vapour of propyl,
is equivalent to
At oº.
II 500
benzol,
""
""
9.630
·
""
naphthaline,
O'116
""
>>
25'700 vols. elayl.
23.700
""
00'016
When, therefore, 100 litres of hydrogen at o° or at 15° are saturated with vapours
of benzol, the illuminating power of the resulting mixture is equal to that which
would ensue by mixing 100 litres of hydrogen with 9'6 or 23.5 litres of elayl-gas.
•
In order to saturate 100 English cubic feet of hydrogen- or marsh-gas with vapours
of hydrocarbons, there are required of :-
Vapours of propyl
""
butyl
benzol
:
At o°.
500'00
17:00
214'50
0°32
At 15°.
1128.00 grammes
58:00
""
522'00
0'32
naphthaline
For the purpose of carburetting hydrogen-gas with vapours of benzol to saturation,
2145 grms. of benzol at o°, and 5220 grms. of the same at 15°, would be required
for 1000 cubic feet of gas.
Illuminating Gas.
Methods of Testing In order to ascertain the relative value of illuminating gas four
different modes of testing are now in practical use, viz.:-1. Gasometrical test.
2. Specific gravity test. 3. Photometrical tests. 4. Erdmann's gas-testing apparatus.
1. The gasometrical test requires for its proper management an accurate know-
ledge of Bunsen's method of gas analysis.* Be it sufficient for our purpose here to
Anleitzung zu einer technischen Leuchtgasanalyse giebt Adolf Richter; Dingler's
polyt. Journal (1867), Bd. clxxxvi., p. 394.
ARTIFICIAL LIGHT.
·663
mention that a mixture of anhydrous sulphuric acid and ordinary concentrated oil of
vitriol has the property of absorbing the heavy hydrocarbons contained in illumina-
ting gas, which absorption is best effected by bringing into an eudiometer containing
the gas to be tested, a piece of coke moistened with the acid, and fixed on a piece of
platinum wire. In order to ascertain the quantity of carbon of these compounds,
the test, in which the decrease of bulk of the gas indicates the relative quantity
of the hydrocarbons, is combined with two separate eudiometrical tests, the gas
being first ignited by itself with an excess of oxygen, and the operation repeated
with the gas after it has been acted upon by the sulphuric acid. The quantity of
CO2 obtained in the last instance is then deducted from that obtained by the first
operation. Chlorine and bromine are very frequently employed to absorb the
heavier hydrocarbons present in gas, these haloids combining with the hydrocarbons
as a fluid residue. According to a method of gas analysis originally devised by
O. L. Erdmann, and described by C. O. Grasse,* the gas first freed from any carbonic
acid it may happen to contain is burnt from a burner connected with a small
gas-holder, by the aid of oxygen; the water and carbonic acid formed are collected
and weighed. 2. The estimation of the value of an illuminating gas by specific
gravity is frequently employed in practice, as experience has proved that as a rule a
higher illuminating power of gas (provided it be well purified and freed from
carbonic acid), is intimately connected with its higher specific gravity; but it does
not follow that a light gas is useless, while there ought to be taken into account the
durability of the gas, by which is understood the length of time a cubic foot of the
gas will burn under a certain pressure (as low as possible) from a given burner,
and yield a certain light to be tested either by comparison with another kind of coal-
gas or standard sperm candles by the photometer. In Scotland, the gas engineers
when testing cannel and other coals always take into consideration and minutely esti-
mate by means of very accurate apparatus these particulars, care being taken to manu-
facture the gas on the large as well as on the small scale, taking say cwt. of coals, and
to compare both. In most of the large Scotch gas-works, a separate experimental gas-
work, with two or three retorts, and all the necessary apparatus, is to be met with, as
it has been found that only by the use of judiciously selected mixtures of different
cannel coals, a gas of high illuminating power, great purity, and average durability,
can be supplied at the price now generally adopted per 1000 cubic feet.
Illuminating gas consists of a mixture of various gases and vapours, having
different specific gravities, viz., elayl-gas, o'976; methyl-hydrogen, o'555; hydrogen,
0*069; carbonic oxide, o‘967; carbonic acid, 1.520. The specific gravity of the
vapours present in coal-gas varies of course according to the bodies which are met
with in the gas in the state of vapour; among these benzol is one of the most
important for illuminating purposes. The estimation of the specific gravity of illu-
minating gas as a test of its quality is only of value if taken in connexion with other
tests applied to the same gas. Dr. Schilling has constructed an apparatus for the
purpose of taking the specific gravity of illuminating gas. This apparatus is based
upon the fact that the specific gravities of two gases issuing from narrow apertures
in a thin plate under equal pressure are to each other as the squares of their time of
efflux. There are several more readily managed apparatus for estimating the
specific gravity of illuminating gas, and among them those made by Mr. Wright, of
Westminster. 3. Photometrical tests and apparatus, Bunsen's, Wight's. Desaga's
* Journal für Prakt. Chemie (1867), cii., p. 257.
664
CHEMICAL TECHNOLOGY.
(Bothe's tangental photometer), and others are frequently employed for testing
the value of gas and comparing its illuminating power with that of lamps o1
candles. As the kind of burner employed in these experiments has very great
influence on the results, photometrical estimations of the value of gases require great
care. 4. Erdmann's gas tester, introduced on the Continent in many gas-work
since 1860, is a very useful and readily manageable instrument, based upon the fact
that, as the value of an illuminating gas depends mainly upon the quantity of heavy
hydrocarbons contained, that quantity may be measured by estimating the amount
of atmospheric air required to deprive the flame of the burning gas of a given size
of all illuminating power.
Gas-meters. At first, in the early days of gas-lighting, the bargain between consumer and
seller was to pay a certain sum per burner per hour, or to contract for a certain sum per
annum for a given number of burners kept lighted from dusk till a certain hour of the
night, at which time it was customary to have the turncocks of the gas-works at hand or
their respective beats, to turn off the supply of the house, by shutting a tap placed
on purpose in the service pipes; but although here and there in small towns in Italy,
France, Spain, and Germany, this arrangement still exists, it is the exception and not the
rule; the latter being that the gas is sold by cubic measure as registered by instrument!
termed gas-meters, the construction of which is especially in the United Kingdom-
brought to such a high standard, that Mr. Rutter's remark is perfectly true-that gag
is measured with greater accuracy than anything else either measured or weighed in
commerce.
We distinguish between dry and wet meters; the construction of the former is briefly
the following:-In a gas-tight metallic box are placed two or three bellows-like vessels,
which instead of being inflated by air, are inflated by the gas entering from the service
pipe. When inflated to some extent an arrangement of springs and levers forces the gai
FIG. 296
FIG. 297.


out of the bellows again into the exit-pipe leading to the burners. The cubic capacity of
the chambers (as the bellows-like arrangements are called) having been accurately
adjusted, the movement of their walls is communicated to wheel-work, which being con-
nected with dials, indicates in tens, hundreds, and thousands, the consumption of gas in
cubic feet.
Dry meters are preferred on account as well of not being liable to be affected by
frost as of not causing the sudden extinguishing of the gas-lights for want of water, as may
occur with wet meters. Wet meters are constructed upon a plan devised in 1817 by
Clegg, and improved by Crossley and others. Figs. 296, 297, 298, and 299, are
drawings of this kind of meter, which consists in the first place of an outer cylindrical
box of cast-iron, closed on all sides. In this box is placed a drum of pure block-tin,
divided into four compartments, bearing upon a bell-metal axis, and immersed for rather
more than half its circumference in water. By the pressure of the gas and the ensuing
ARTIFICIAL LIGHT.
665
depression of the water the drum revolves, each of its compartments becoming alternately
filled with and emptied of gas. On the axis of the drum is an endless screw, which
by mechanical means is connected with the wheel-work of the dials. The drum is very
accurately adjusted, so that at every complete revolution a certain cubic quantity of gas
passes through and is registered. Fig. 296 exhibits the apparatus with the front plate
removed; Fig. 297 shows the side of the meter; Fig. 298 is sectional plan; and Fig. 299
is a section through the box. a is the box; a' the drum; b its axis; c the endless screw,
FIG. 299.
FIG. 298.


SH
bearing in the wheel, d, and carrying by means of e the movement of the drum on to the
wheelwork of the dials, f. g is the inlet-pipe for the gas, which flows into the valve box,
h, and passing by the valve, i (kept open as long as the meter contains sufficient water for
its action), flows through the bent tube, 7, into the bulged cover of the drum, or
technically antechamber, m, and thence into the several compartments of the drum.
Thence the gas enters the space, n, to which is fitted the outlet pipe, o. i is the valve;
p the float; q the funnel tube for filling the meter with water; r the waste water cistern;
s the plug by the removal of which the waste water may be run off. As long as no gas-
burners are in use the meter connected with them is inactive, but when the gas is burnt
the drum rotates, and by its communication with the wheelwork registers the quantity of
gas consumed. Instead of filling wet meters with water they may be filled with glycerine,
which does not freeze nor evaporate. Wet meters should be placed perfectly level.
As regards their size they are made to supply from three lights up to many thousands if
required. By an Act of Parliament gas-meters are tested in order to ascertain that they
register properly within the limits of the Act. The inspectors of gas-meters have
been provided with very accurate sets of apparatus made according to four sets of standard
apparatus, of which one each is in the hands of the Corporations of London, Edinburgh,
and Dublin; while the fourth is in the custody of the Comptroller of the Exchequer,
at Westminster. These apparatus are masterpieces of highly finished workmanship.
Burners. These are made so as to produce all shapes of flame, and are of different
materials, iron, steel, porcelain, steatite, brass, platinum-lined, &c. The bore from which
the flame of the burning gas issues should be arranged, as regards its width, for the
quality of the gas consumed-cannel coal gas-burners, for instance, being provided with
narrower openings than those for common coal-gas. We have single jet burners, double
jet burners, bats'-wing, fish-tail, cockspur, and other varieties; also Argand burners of
various sizes, bored with six to thirty or forty-eight holes, or as in the Dumas burner, a slit
instead of the holes. The quantity of gas consumed by different kinds of burners varies,
of course, greatly for the same kind of gas under the same pressure. Much gas is wasted
because sufficient care is not taken by the consumers to have really good burners.
Gas Lamps. Of these there is an almost endless variety, from the most simple and unpre-
tentious to the highly ornamented and expensive chandeliers.
Manufacture.
By-products of Coal-gas Among these such as are of important commercial advantage to
coal-gas works are:-1. Coke. 2. Ammoniacal liquor. 3. Tar. 4. Spent gas-lime.
5. Sulphur obtained from the Laming mixture. In some localities Berlin blue
is made from the cyanide of calcium of the Laming mixture (see p. 656).
1. Coke, of which we shall speak more particularly under the heading of Fuel,
€66
CHEMICAL TECHNOLOGY.
as gas-coke is more porous and spongy than the oven-coke and hence better adapted
for use in stoves. In Germany the gas-works have now very generally adopted the
plan of selling the coke broken up into small nut-sized lumps, this operation being
performed by means of machinery; the breeze is mixed with some tar and burnt
under the retorts at the works. 2. The ammoniacal liquor is essentially an aqueous
solution of carbonate of ammonia, 2(NH4)2CO3+CO2. The quantity of ammonia
contained in this liquid must of necessity vary according to certain conditions, as
the quantity of water contained in the coals, the larger or smaller amount of
nitrogen they contain, the degree of temperature and duration of the process of dis-
tillation. The higher the temperature the more nitrogen will be converted into
ammonia, while otherwise a portion of it is converted into aniline, lepidine, chinoline,
&c., and also into cyanogen. Estimating gas-coals to contain on an average 5 per
cent of hygroscopic water and o'75 per cent of nitrogen, 100 kilos. of such coal will
yield under the most favourable conditions 910 grms. of ammonia (NH3). It
has been found that I cubic metre of ammoniacal water yields on an average
(see p. 230) 50 kilos. of dry sulphate of ammonia ([NH4]2SO4), so that 20 hecto-
litres yield 100 kilos. of this salt. I ton of Newcastle gas-coal yields 45 litres
of ammoniacal liquor, 1 litre of which yields from 74 to 81 grms. sulphate of
ammonia. 3. Coal-tar, formerly a source of inconvenience to many gas-works, and
at any rate a substance of very little commercial value, has become since 1858, of
great importance as the raw material for the coal-tar colours. As already stated, tar
consists of fluid hydrocarbons-benzol, toluol, propyl; solid hydrocarbons-naph-
thaline and anthracen; of acids-carbolic, cresylic, phlorylic; of bases—aniline,
chinoline, lepidine, &c.; and lastly, of resinous, empyreumatic, and asphalte-forming
matters. The quantity as well as the quality of the tar obtained by the distillation
of coals for gas-making depends partly upon the kind of coal used and partly upon
the heat applied to the retorts; as at a very high temperature, for instance with the
fire-clay retorts, the quantity of tar is less than at a lower temperature. Owing as
well to the carbolic acid contained in tar as to the empyreumatic substances, it
has antiseptic properties, and is hence used for preventing the decay of wood
exposed to wind and weather, for coating iron, &c. Coal-tar is also used for the pur-
pose of mixing with small coal, saw-dust, peat dust, &c., for making artificial fuel,
and recently, when mixed with sifted pebbles, as a substitute for asphalte
to form excellent footpaths. In order to separate the constituents of tar from
each other, it is poured into a large iron still, and heated to 80° to 100°, for
the purpose of distilling off the light hydrocarbons along with any ammoniacal water
the tar may contain. After thirty-six hours the distillation is further proceeded
with, and as the latent heat of the volatile products to be obtained is very small, the
still ought to be made as low as possible, and the helm ought to be well protected
against any cooling influence. At the bottom of the still a tap is fitted for the pur-
pose of removing, at the end of the distillation, the molten pitch which remains. In
some cases, however, the distillation is pushed further so as to leave only a
carbonaceous residue, the still being made red-hot at the bottom; the residue
is removed after the cooling of the still by opening the man-hole. The distillation
of 750 to 800 kilos. of tar takes twelve to fifteen hours. At first the heat should not
be too strong, and in many tar distilleries high-pressure steam is passed through a
coil of pipes placed in the still, in order to assist, together with open fire, the first
ARTIFICIAL LIGHT.
667
stage of the distillation.
but on an average 0.830.
The light tar-oil is again distilled, and the distillate treated with strong sulphuric
acid, next with caustic soda solution, and then again distilled. The treatment with
sulphuric acid aims at the removal as well of basic substances (ammonia, aniline), as
of naphthaline, while, by means of the caustic soda, the carbolic acid is fixed. The
quantity of sulphuric acid to be used for this purpose amounts to 5 per cent of the
weight of the tar-oil; while the soda solution of 1.382 sp. gr. (= 40° B.) amounts to
2 per cent of that weight. The liquid thus obtained is the benzol of trade;
it remains colourless on exposure to air, and is a mixture of various substances with
benzol, toluol, and xylol as chief constituents. It is easily converted into nitro-
benzol (see p. 572), the starting-point for many of the coal-tar colours. The coal-tar
naphtha, now usually sold after the benzol has been completely removed by
fractional distillation, is used as a solvent for caoutchouc resins, fixed oils, gutta-
percha, and for burning in lamps peculiarly constructed for the purpose, and
only used in open air. Coal-tar naphtha is also used for carburetting gas of low
quality. When the crude oil of tar is cooled down to -10°, naphthaline is
deposited from it, which, as already mentioned (see p. 581), is used for the prepa-
ration of some dyes, and also for the manufacture of benzoic acid. The heavy oil of
tar is purified with concentrated sulphuric acid and caustic soda ley, and freed from
fœtid sulphur compounds by distillation over a mixture of sulphate of iron and
lime. By fractional distillation between 150° and 200° creosote is obtained,
being a mixture of carbolic or phenylic, cresylic, and phlorylic acids. This is
the raw material used for the preparation of carbolic acid and picric acid (see p. 580),
also for certain blue and red pigments, for creosoting wood, for preserving anatomical
preparations, &c. Lunge obtained from a ton of tar:-
The light tar-oils obtained exhibit first a sp. gr. of 0·780,
The heavy tar-oil comes over at 200°.
Benzol at 50 per cent
Best naphtha
...
Burning naphtha
Creosote
...
Ammoniacal liquor
...
2.88 gallons
2.69
3'5I
83·25
""
3'00
:
:
""
And 11 cwts. of pitch.
13.00 litres.
12'00
15'08
""
""
3'74 hectolitres.
13.5 litres.
The heavy oils of coal-tar and the pitch are now largely used for the preparation
of anthracen, from which artificial alizarine is made. The pitch is further usefully
employed in lacquer and varnish making, and also for asphalting pavements.
4. The gas-lime is used abroad for the purpose of removing the hair from
hides and skins intended to be tanned, the sulphuret of calcium contained in the
lime acting as a depillatory. In some localities the spent lime is employed for making
Berlin blue from the cyanide of calcium contained in the lime, and for the prepara-
tion of sulphocyanogen compounds, owing to the sulphocyanide of calcium it
contains. As already mentioned, spent gas-lime is largely used in Scotland as a
manure, which at the same time destroys a great many injurious insects.
5. Sulphur is prepared from the Laming mixture (see p. 198), and used for making
sulphuric acid; it might, perhaps, be better to extract the sulphur from the mixture
by means of steam at 130°. The Laming mixture is occasionally treated with
heavy tar-oils for the purpose of eliminating the sulphur.
668
CHEMICAL TECHNOLOGY.
Composition of Coal-ga
The following figures exhibit the composition of purified coal-
gas in 100 parts by bulk :-
Hydrogen
...
I.
44'00
II.
41'37 39.80
III.
IV.
V.
VI.
VII.
51'29
50'08
46'0
277
Marsh-gas (methyl-hydrogen) 38°40
38°30
43°12
36.45
35°92 39.5 50'0
Carbonic oxide
5'73
5'56
4.66
4'45
5'02 7.5
6.8
Elayl
Ditetryl
...
...
4°13
5'001
4'75
4'91
5'33
3.8
13'0
Nitrogen
Oxygen
Carbonic acid
:
:
:
:
3'14 4'34
4'23 5'43
4'65
1'41
1.89
0'5
0'4
0'41
0'54
0'37
3'02 1'08
I'22 0'7
O'I
Aqueous vapour
...
2'0
2'0
I. and II. Heidelberg coal-gas. III. Bonn coal-gas, analysed by H. Landolt. IV. and
V. Chemnitz, Saxony, coal-gas analysed by Wunder. VI. London coal-gas (1867).
VII. London cannel gas (1867).
Wood-gas. II. As already mentioned (p. 645) the French engineer Lebon was
engaged in 1799 with the making of gas from wood, and brought out an apparatus
termed by him a thermolamp, which, however, was neither found to answer for
heating nor for illuminating purposes, as the illuminating power of the gas
obtained by his process from wood was very inferior and could not compete with the
coal-gas which became known soon after. The reason why wood, as converted into
gas by Lebon's apparatus, did not give satisfactory results is explained by Dumas,
by proving that under the conditions of the distillation of wood employed by
Lebon, the gas evolved consists chiefly of marsh-gas and carbonic oxide, both of
which can scarcely be considered luminous gases. In the year 1849, Dr. M. von
Pettenkofer, at Munich, resolved to experiment on the manufacture of gas from
wood, and he found that, as stated by Dumas, when wood is submitted to distillation
in a manner similar to coal, the gas produced is entirely unfit for illumination,
as in addition to carbonic acid, there are only formed carbonic oxide and marsh-gas.
But Dr. Pettenkofer also found that when the vapours of tar and empyreumatic oils
given off by the carbonisation of wood at a comparatively low temperature are
further heated by passing through a red-hot retort, a very large quantity of heavy
hydrocarbon gas remains among the products, so that then wood yields a better gas
than coal.
While coals are not perceptibly acted upon by a temperature as high as 200°, wood
gives off combustible vapours at 150°; and in order to understand the process of
wood-gas manufacture, we must distinguish between the temperature at which wood
is carbonised or converted into charcoal and empyreumatic vapours, and the tem-
perature at which these vapours are converted into permanent gas suited for illumi-
nation. Coals, resin, and oils yield an illuminating gas at once, when submitted to dry
distillation in gas retorts, because the temperature of carbonisation and of formation of
gas are nearly the same; consequently the vapours formed by the dry distillation of
these substances are far higher in illumination power than obtains in the case of wood.
Therefore the apparatus in use for coal- and oil-gas preparation are not suited for making
wood-gas. Some of the substances rich in carbon and hydrogen met with in wood-tar
(Stockholm tar) boil, by themselves, at a higher temperature (200° to 250°) than that
at which they are formed from wood; and the illuminating power of wood-gas is in
a great measure due to their conversion, by a higher temperature, into permanent
ARTIFICIAL LIGHT.
669
gases. The manufacture of wood-gas, therefore, requires in the first place a retort
in which the wood is converted into vapour, and another retort or generator
in which the vapours are rendered gaseous. At first the carbonising retort, of
the same shape as the ordinary coal-gas retorts, was connected with a series of iron
tubes, which were made red-hot, and through which the vapours given off by the car-
bonisation of the wood, at a temperature of 250° to 300°, were passed to be
converted into gas; but now large retorts are used for this purpose, about three
times as large as the carbonisation retort, which holds 60 kilos. of wood, and there
is, therefore, ample space for the conversion of the vapours into gas. As regards the
quality and quantity of gas obtained from different kinds of wood, there is no very
great difference, as may be inferred from the under-mentioned results of the
researches made by W. Reissig, who operated upon aspen wood (1); linden wood (2);
larch wood (3); willow wood (4); fir-tree wood (5); and white wood or Memel
timber (6). .
50 kilos. (1) gave of purified gas 592 cubic feet, and 99 kilos. of charcoal.
50
""
(2)
""
50
""
(3)
50
(4)
50
""
(5)
50
(6)
620-640
›, 9—11
""
550
""
", 12'5
660
"" 9°0
""
648
9'5
""
564
*
9'2
""
""
""
That the crude wood-gas contains a large quantity of carbonic acid may be
inferred from the following results of analysis by Pettenkofer, the gas having been
made of wood as much as possible free from resin :-
Heavy hydrocarbons
Marsh-gas (methyl-hydrogen)
Hydrogen
Carbonic acid...
Carbonic oxide
6.91
11.06
15.07
25.72
40'59
One volume of the heavy hydrocarbons contained 2.82 volumes of vapour
of carbon. The carbonic acid is removed from the crude gas by means of hydrate
of lime. According to Reissig's researches, the composition of purified wood-gas is
the following:-
Heavy hydrocarbons
Hydrogen ...
...
Light hydrocarbon gas (marsh-gas)
Carbonic oxide
...
::
I.
2.
3.
4.
7.24
7.86
9:00
7.34
31.84
48.67 29.76
29.60
35°30 21'17 20.96
24.02
25.62 22.30 40·28
39'04
100'00
100'00
100'00
100'00
Method of Wood-Gas
Manufacture.
The wood, chiefly fir-wood, is first dried for twenty-four hours in
a drying room, generally brick-built, and heated by the waste heat of the retort
furnaces. The carbonising retort is filled with 50 to 60 kilos. of wood and the lid
screwed on; the distillation is finished in 1 hours, and after the removal of the
carbonic acid there is obtained about 16 cubic metres (nearly 600 cubic feet) of good
illuminating gas. In some places, where wood-gas is regularly made, it is preferred
670
CHEMICAL TECHNOLOGY.
to distil with the wood some Scotch boghead coal or Bohemian foliated coal (Blattel
kohle).
Wood-Gas Burners. The construction of the burners is of great importance with regard
to wood-gas illumination. The sp. gr. of this gas amounts on an average to o‘7,
while that of ordinary coal-gas scarcely every reaches o˚5; the lighter. the gas the
more readily and rapidly it flows out and expands in the air, and the heavier the
gas the more slowly and difficultly it issues and expands. A light gas will not on
issuing into the air separate its particles, while, on the other hand, a heavy gas will,
by exerting greater friction, mix with the air; in order that this effort shall not
injure the luminosity or the gas, the openings in wood-gas burners must be con-
siderably larger than in coal-gas burners. When wood-gas is burnt with rather
strong pressure from coal-gas burners calculated to consume 70 to 100 litres
(3 to 4 cubic feet) per hour, the flame is scarcely luminous, while when burnt from
burners with large openings, wood-gas yields a light exceeding that of coal-gas.
According to the experiments made in 1855 by Drs. Liebig and Steinhill, the illu-
minating power of coal-gas and wood-gas used each at 4 cubic feet per hour was
found to be:-
For coal-gas
= 10*84 normal wax-candles.
wood-gas = 12'92
""
""
so that the average illuminating power of coal-gas stands to that of wood-gas as 6 : 5.
The advantage of wood-gas manufacture over that of coal-gas (only of course in locali-
ties where wood is very abundant and coal either not to be had or at great cost) is
evident enough, because, in addition to less complicated apparatus than required for
coal-gas, the manufacture of wood-gas yields far more valuable by-products, wood char-
coal being the chief of these. Wood, moreover, yields weight for weight more gas
than coal in a shorter time and of higher illuminating power, while the gas is abso-
lutely free from sulphur and ammoniacal compounds, so that by the burning of wood-
gas no sulphurous acid can be formed. As the distillation of wood-gas proceeds
rapidly, one retort kept continuously in action for twenty-four hours will yield
10,000 cubic feet, while for coal-gas only 4000 cubic feet are obtained with one retort
in the same time. On the other hand, wood-gas requires for purifying purposes a
very large quantity of quick-lime. The wood-tar, about 2 per cent of the weight of
the dry wood, and the wood-vinegar-100 parts of wood yield o˚5 to 0'75 parts of dry
acetate of lime-are usefully applied; the tar, however, is in some localities burnt
under the retorts.
Peat-Gas. III. When peat is submitted to dry distillation, there is obtained, as with
coals, an aqueous distillate, tar, and carbonised peat or peat-coke. Vohl obtained by
the dry distillation of an air-dried peat, taken from a high moorland in the canton
Zurich, Switzerland, from 100 parts:-
Gas
Tar ...
...
Aqueous distillate
Peat-coke...
:
...
...
:
The products of the dry distillation of peat are :—
Fluid and solid
hydrocarbons.
Peat oil, 0·820 sp. gr.
...
17.625
5'375
...
52'000
25'000
Heavy oil (lubricating-oil), 0·885 sp.gr.
Paraffin.
ARTIFICIAL LIGHT.
671
Bases.
Ammonia.
Carbonic.
Sulphuretted hydrogen.
Cyanhydric.
Acetic.
Acids.
Propionic.
Butyric.
Valerianic.
Ethylamine.
Picoline.
Lutidine.
Aniline.
Cæspitine.
Gaseous products.
Carbolic.
Heavy hydrocarbons.
Light hydrocarbons.
Hydrogen.
Carbonic oxide.
The apparatus in use for making wood-gas answers the purpose of making peat-
gas. W. Reissig, who has for a long time been engaged in experimenting on
peat-gas manufacture, used a fat peat from the neighbourhood of Munich, con-
taining very little ash and 14 to 15 per cent of water. On an average 1 Bavarian
cwt. of this peat yields 426 Bavarian cubic feet of gas; 134 lbs. of this peat yield
337 English cubic feet of gas. The gas is evolved at first very rapidly, as
is also the case with wood, but the evolution of gas from peat decreases more
uniformly and steadily than it does from wood. Reissig's experiments prove that
peat-gas may be prepared of very good quality; he found the purified peat-gas to
consist of:-
I. Heavy hydrocarbons
Light hydrocarbon gas
9'52
42.65
Hydrogen ...
27.50
Carbonic oxide ...
20*33
Carbonic acid and sulphuretted hydrogen
traces
...
100'00
The analysis of another gas, made with a very excellent peat, gave the following
result:-
Water-Gas.
= 9°52
II. Heavy hydrocarbons (ditetryl, = 3.64
Light hydrocarbons...
Hydrogen
...
Carbonic oxide ...
Carbonic acid and sulphuretted hydrogen
Nitrogen
...
:
:
...
13.16
33.00
35'18
18:34
0'00
...
0'32
100 00
IV. The manufacture of water-gas essentially consists in forcing steam
through iron or fire-clay retorts filled with red-hot charcoal or coke. The steam is
decomposed, yielding a mixture of hydrogen, carbonic oxide, and carbonic acid gases,
with a small quantity of marsh-gas. The purified gas, consisting essentially of
carbonic oxide and hydrogen, is, although not luminous when burnt by itself, suitable
for illuminating purposes under the following conditions:-1. By placing on the
burners small platinum cylinders which, by becoming white-hot, yield a strong light
-Gengembre's and Gillard's plan. 2. By impregnating the gas with vapours of
hydrocarbons, a more common plan, the original idea being due to Jobard (1832) of
Brussels.
672
CHEMICAL TECHNOLOGY.
The determinations of the compositions of water-gas vary very much. Jacquelain
and Gillard state that the crude gas obtained by them is a mixture of hydrogen and
carbonic acid, which, after having been purified by means of lime, consists essentially
of hydrogen. But it is stated by others, and not without good reason, that the
purified gas contains carbonic oxide and hydrogen; and Langlois's results agree
with this account. The formation of 1 molecule of carbonic oxide requires 1 mole-
cule of steam, the hydrogen of which is set free, C+H₂O=CO+H₂, When the
carbonic oxide meets again with steam at a higher temperature, it, as has been
experimentally shown by Dr. Verver, withdraws oxygen from the steam, forming
carbonic acid, while some hydrogen is again set free: CO+H₂O=CO₂+H2. Only
when the carbonic acid is not withdrawn rapidly enough from the retorts is its
re-conversion into carbonic oxide by contact with the red-hot charcoal possible.
Gillard's Gas.
Platinum Gas.
I
In the year 1846, Gillard established at Passy, near Paris, a gas-
work for the purpose of manufacturing hydrogen by the decomposition of water.
At first the steam was decomposed by passing it through retorts filled with
ret-hot iron wire, the idea being to re-convert the oxidised iron to the metallic state;
but as this process did not answer, Gillard commenced decomposing the steam by
passing it through a retort filled with red-hot charcoal. The crude gas thus
obtained is readily freed from the large quantity of carbonic acid it contains, by
crystallised carbonate of soda, which is converted into bicarbonate of soda. The gas
is burnt from an Argand burner provided with numerous small holes, and the
flame, not luminous by itself, is surrounded by a net-work of moderately fine
platinum wire, which on becoming white-hot is luminous. In Paris this gas is
known as platinum-gas (gaz-platine). It is free from smell, burns without smoke or
soot, and for this reason is preferred by gold and silversmiths and electro-gilders.
The illuminating power of this gas exceeds that of coal-gas in the proportion,
according to Girardin, of 130: 127. The flame is quite steady, because the light-
producing substance is a solid body at a white heat.* According to Dr. Verver's
researches there are used at Narbonne, France, for the production of 1 cubic metre of
this gas 0.32 kilo. of wood-charcoal, and for heating the retorts 141 kilos. of coals.
Carburetted Water-Gas. While engaged in his experiments on the oil obtained by the
strong compression of oil-gas, Faraday proved that if marsh-gas, which burns
with a scarcely luminous flame, is impregnated with this oil, it becomes a very
luminous gas. Lowe proposed, in the year 1832, that common coal gas should
be rendered more luminous by impregnating it with vapours of tar-oil or petroleum.
He also showed that with the aid of steam and red-hot coke a mixture of carbonic
oxide and hydrogen might be obtained and rendered luminous by impregnation with
these vapours. Afterwards Jobard, at Brussels, took up the subject and communi-
cated his researches to the French gas-engineer Selligue, who having at an earlier
period (1833) been engaged with similar researches, entered upon the subject with
great energy, and employed carburetted water-gas for illuminating purposes on the
large scale. Selligue used the oil obtained from a bituminous shale for the purpose
of carburetting the water-gas, the oil being obtained in the same manner as such oil
is now made from various kinds of cannel coal and bituminous shales. Selligue's gas-
making apparatus consisted of a battery of three vertical retorts kept continuously
* Schinz has lately published an essay on this gas; see Dr. Wagner's "Jahresbericht
der chem. Technologie," 1869, p. 731.
ARTIFICIAL LIGHT.
€73
red-hot, two of these retorts being filled with charcoal or coke of good quality
and very free from sulphur. Into the first of these retorts, which are connected
together, steam is introduced, forming with the red-hot charcoal carbonic oxide and
hydrogen. This gaseous mixture passing through the second retort, also filled with
charcoal, is there deprived of any carbonic acid, which is converted into carbonic
oxide. This is the reverse of the method of water-gas making now employed,
where the carbonic oxide is converted into carbonic acid, to be next removed from
the gaseous mixture by means of lime. The very hot mixture of hydrogen and
carbonic oxide is next passed into the third retort, which is filled for two-thirds of its
height with iron chains kept red-hot, while a continuous stream of the oil of the
bituminous shale flows from a reservoir through a syphon-pipe into this retort (to
every 10,000 litres of gas 5 kilos. of oil are admitted), and upon becoming decomposed,
mixes with the carbonic oxide and hydrogen, forming a gaseous mixture, which,
notwithstanding the large quantity of carbonic oxide contained, burns with a highly
luminous flame, the gas being at the same time of great durability. A gas-furnace
upon Selligue's plan and containing six retorts in two batteries, together of 6 cubic
metres capacity, yielded in twenty-four hours 24,000 to 28,000 hectolitres (=84,768
to 98,896 English cubic feet) of excellent gas, with a consumption of 1231 kilos. of
oil of bituminous shale, 400 kilos. of wood-charcoal, and 16 hectolitres of coal for
firing the retorts.
Selligue's process has given rise to the following methods:-1. White's hydrocarbon
process, in which steam and gas are made from coals (originally resin was employed, but
cannel coals have been substituted) under the influence of a jet of superheated steam
passed through a red-hot retort. 2. Leprince's process, Gas mixte Leprince, is an
improved hydrocarbon process, the products of the decomposition of steam and coke
being carried at a suitable temperature and in the same retort (provided with a partition
and thus divided into two compartments) over coals in process of carbonisation.
3. Isoard's process, with superheated steam and coal-tar mixed. 4. According to
Baldamus and Grüne's plan, steam and a fluid hydrocarbon are decomposed simul-
taneously in the same retort. 5. Kirkham's plan and that of others, the impregnation of
water-gas with fluid hydrocarbons, benzol, photogen, petroleum, naphtha, &c. 6. Long-
bottom's proposal to carburet air by impregnating it with vapours of benzol, or, according
to Wiederholt's plan, with petroleum naphtha, the benzoline as used in sponge-lamps.
White's Hydrocarbon White in so far modified Selligue's plan in causing water-gas and
steam to be forced through a retort in which cannel coal, boghead, or
resin are submitted to distillation. White's process, as yet rarely employed, came under
notice through the researches which Dr. Frankland instituted at Clarke and Co.'s gas-
works at Ancoats, near Manchester.
Process.
Dr. Frankland found the gas made by White's process to contain about 15 per cent of
carbonic oxide, no carbonic acid, and some 45 per cent of hydrogen. This increase of
hydrogen, without an equivalent increase of carbonic oxide, can only be explained by the
action of the steam upon the marsh-gas evolved in the retort filled with cannel coal,
probably according to the following formulæ :—
Marsh-gas, CH4
Steam, H₂O } yield
Carbonic oxide, CO.
Hydrogen, 3H2.
The composition of the gas, made with and without water-gas, was as follows:-
Gas from Boghead coal:-
Heavy hydrocarbons
Marsh-gas..
Hydrogen
❤
Carbonic oxide..
Carbonic acid
Oxygen and nitrogen
Without
water-gas.
With
water-gas.
•
24'50
14.12
•
58.38
22.25
10'54
6.58
45'51
14°34
3.78
100'00
100'00
44
€74
CHEMICAL TECHNOLOGY.
The advantages of White's hydrocarbon process are not only the increase of hydrogen
and decrease of carbonic oxide and marsh-gas as met with in ordinary coal-gas, but are to
be found in the mechanical action of the products of the decomposing steam by carrying
off very rapidly the heavy hydrocarbons from the retort, so that these are withdrawn in
time from the decomposing influence of high temperature, thereby lessening the forma-
tion of tar. Dr. Frankland summarises the results of this process as follows:-a. It can
be employed without great expense in any gas-work. b. The quantity of gas yielded
increases from 46 to 290 per cent. c. The illuminating power increases from 14 to 108 per
cent. d. Less tar is made, a portion being converted into gas. e. The heat and forma-
tion of carbonic acid accompanying the combustion is much less, as this gas contains
more hydrogen and less carbon.
Gas.
Leprince's Water-Gas. This is only a modification of White's process, consisting chiefly
in the use of retorts divided by means of horizontal partitions into three rooms or
chambers, in which the two phases of the process, viz., the partial decomposition of water
by means of coke or charcoal, and the carburation of the gas by means of the volatile
products of the dry distillation of gas-coals, are carried on simultaneously. The Gas mixte
Leprince is used in the broad-cloth factory of Simonis at Verviers, and at the Vieille
Montagne zinc-works, both in Belgium, also at Maestricht and some places near Luik Liège.
Isoard's Gas. In this process tar is used instead of charcoal or coke for the purpose of
decomposing the steam.
Baldamus and Grune's According to this plan the decomposition of steam and of the hydro-
carbons is carried on simultaneously in the same vessel, so that the
hydrogen contained in the steam is not evolved in free state, but in combination with
carbon as a light-giving hydrocarbon. The gas-making material, brown coal, peat,
bituminous shale, &c., is fully utilised without any by-products, for the tar is entirely
converted into gas, forming with the hydrogen of the water a real hydrocarbon.
Carburetted Gas. The process proposed by Kirkham and several others simply consists in
the impregnation of water-gas with the vapours of fluid hydrocarbons, benzol, photo-
gen, petroleum, &c. This impregnation may take place at the works where the gas is
made, but better where the gas is consumed, just before issuing from the burners. Not-
withstanding that a great many apparatus have been contrived for the purpose of carbu-
retting water-gas and ordinary coal-gas, the process has never answered very well,
because it is difficult to find suitable materials for carburetting, and because erroneous
calculations have been made in respect of the quantity of carburetting materials required
to render a non-luminous gas luminous. If, for instance, benzol (C6H6) be the hydro-
carbon to be used for carburetting purposes,
1000 cubic feet of gas require at 0°, 2342 grms.
,, 15°, 5694
""
benzol.
} be
The improvement of coal-gas by impregnating it with the vapours of some volatile hydro-
carbon has been frequently suggested and practically tried in England; but, although
various apparatus have been contrived for this purpose, such apparatus being generally
fixed to the outlet-pipe of the house-meters, the results have not been so satisfactory as to
lead to a general introduction of these so-called carburetters. Among other reasons why
these appliances have been discarded, is the fact that the gas. especially in London, con-
tains sulphuretted hydrocarbon compounds in very small quantity, which, by becoming
dissolved in the hydrocarbon used for impregnating the gas, accumulate in the carbu-
retter, and are, when fresh carburetting oil is added, carried on to the burners and escape
partly in the state of vapour, causing a very foul atmosphere in the rooms where the gas
is burnt.
Air-Gas. Longbottom suggested to free air from carbonic acid and moisture, and then
to impregnate it with the vapours of very volatile fluid-hydrocarbons, such as benzine and
benzoline. Air can be used as an illuminating gas in this way, but it requires burners
with wide openings and a low pressure, because if the current of the gas be too rapid the
flame is cooled too much and readily extinguished. Apparatus for preparing air-gas have
been devised and constructed by Marcus, Mille, Methei, and others.*
Oil-Gas, Resin-Gas. V. The fatty, or so-called fixed oils, are among the best gas-making
materials, yielding a very pure gas and of high illuminating power. This follows
from their composition:-Lefort found the formula of rape-seed oil to be C10H1802;
olive oil and poppy-seed oil, C18H3202; linseed oil, C15H28O2; hemp-seed oil,
C₁H2202. The fatty oils yield by dry distillation chiefly elayl-gas or a mixture of
II
* See "Jahresbericht der chem. Technologie," 1866, p. 701; 1868, pp. 763 and 765.
1
ARTIFICIAL LIGHT.
675
hydrogen and marsh-gas with the vapours of fluid hydrocarbons, the illuminating
power of which is equal to that of elayl-gas. As oils yield further only a small
quantity of carbonic acid gas and no sulphuretted hydrogen, oil-gas does not require
any purifying, and hence the apparatus may be very simple; while, owing to the high
illuminating power, smaller gas-holders, smaller pipes, and burners of different con-
struction are required. But notwithstanding all these advantages, oil-gas is a thing
of the past. The Binnenhof, at the Hague, with some of the adjacent public build-
ings, was lighted with oil-gas until within some ten or twelve years, when the
apparatus requiring renewal was removed, and coal-gas, as in the other parts of the
town, substituted. The sp. gr. of oil-gas amounts on an average to o'76 and o'90,
but may be as high as I'I. Half a kilo. of oil yields 22 to 26 cubic feet of gas, equal
to go to 96 per cent.
Gas from Suint.
By this we understand a gas prepared from the fatty materials
present in the soap-suds used in washing raw wool and spun-yarns. The water
containing the suint and soap-suds is run into cisterns and is there mixed with milk
of lime and left to stand for twelve hours. A thin precipitate is formed, which, after
the supernatant clear water has been run off, is put upon coarse canvas for the
purpose of draining off any impurities, sand, hair, &c., while the mass which runs
through the filter is put into a tank, in which it forms after six to eight days a pasty
mass, which having been dug out and moulded into bricks, is dried in open air.
At Rheims the first wash-water of the wool is used for making both gas and potash,
because the water contains no soap and only suintate of potash (see p. 132).
Havrez, at Verviers, has recently proposed to employ suint, which, by-the-bye, is
very rich in nitrogen, for the purpose of making ferrocyanide of potassium.
The dried brick-shaped lumps are submitted to distillation, yielding a gas which
does not require purification, and which possesses an illuminating power three times
that of good coal-gas. The wash-water of a wool spinning-mill with 20,000 spindles
yields daily, when treated as described, about 500 kilos. of dried suinter, as the sub-
stance is technically termed. I kilo. of this substance yields 210 litres of gas.
Annually about 150,000 kilos. of suinter are obtained, and this quantity will yield
31,500,000 litres =1,112,485 cubic feet of gas. Every burner consuming 35 litres
of gas per hour, and taking the time of burning at 1200 hours, the quantity of gas
will suffice for 750 burners, and as a spinning-mill of 20,000 spindles only requires
500 burners, there is an excess of gas supply available for 250 other burners, or the
owner may dispose of 5000 kilos. of suinter, which is valued at Augsburg at about
3s. per 50 kilos., and at about 4s. at Mulhouse.
Oil, or Oil from
Gas from Petroleum VI. The so-called posidonian schist of the lias formation, met
Bituminous Shales. With near Reutlingen, in Würtemberg, yields by dry distillation
about 3 per cent of tar, which on being submitted to distillation, yields an oil
which cannot be burned in lamps owing to its containing sulphur; but the oil is an
excellent material for gas manufacture, According to Haas, I cwt. (50 kilos.) of the
oil, valued at 16s., yields 1300 English cubic feet of gas, so that 1000 cubic feet
inclusive of fuel (½ klafter of wood; the klafter is a cubic measure by which wood
is sold, and is =108 cubic feet) and labour cost 16s., a low price considering the high
illuminating power of the gas. The gas, according to W. Reissig's researches (1862)
was found to consist of:-
Σ
676
CHEMICAL TECHNOLOGY.
Heavy hydrocarbons
Marsh-gas
25'30
64.80
...
Carbonic oxide
Hydrogen
...
Carbonic acid
...
Oxygen and nitrogen
:
...
...
...
:
:
6.65
3'05
0'20
traces
100'00
According to experiments made at Stuttgart, the illuminating power of this gas is
2.5 to 35 times that of coal-gas.
Petroleum-Gas. In America and on the Continent of Europe petroleum is now used
for the purpose of gas-making, being either converted into gas or used to carburate
water-gas.
According to the method of Thompson and Hind (1862) the petroleum is converted
into gas by causing it to pass through a red-hot retort, which, in order to increase
the contact surface, is filled with lumps of fire-brick or is fitted with a series of tray-
like iron plates, and the gas so obtained mixed with that made by passing steam over
red-hot charcoal. The crude gaseous mixture is washed by causing it to bubble
through hydrochloric acid and then through a series of purifying apparatus, so that
the gas collected in the gas-holder is devoid of smell. The arrangement of the
retort used in this process is the following:- The retort is placed horizontally; to the
lid is fitted a hollow cylinder which is filled with coke or charcoal. In the space
between this cylinder and the sides of the retort is placed a serpentine iron plate.
Through the lid of the retort two tubes are carried; one of these, communicating
with the serpentine iron plate, is destined for the introduction of the petroleum oil,
while the other is used for passing in the steam, and communicates with the cylinder
filled with coke or charcoal. At the other end of the retort a tube is fitted for
carrying the gas to the purifier. When the petroleum is converted into gas without
water-gas, I cwt. of Pennsylvanian oil yields 1590 cubic feet of gas, which, when
purified, consists, according to Bolley, of:-
Heavy hydrocarbons
Light hydrocarbons
Hydrogen ...
...
...
:
I.
II.
31.6
33'4
45'7
40°C
32.7
26.0
ΙΟΟ Ο
100'0
H. Hirzell prepares gas from the residues of the refining of petroleum, which are
less volatile, as well as from petroleum itself. Hirzel's apparatus, already largely
used in Germany, Austria, Russia, and elsewhere, is especially adapted for the
purpose of making gas for railway-stations, barracks, factories, hotels, and isolated
country seats; its mode of action will be readily understood with the aid of Fig. 300.
D is a wrought-iron vessel containing petroleum or the residues of the refining.
This vessel is fitted with a suction- and force-pump, E, the piston of which can be
filled with petroleum by winding up the clockwork with which it is connected. As
soon as the retort is red-hot, weights are put on the piston, after which the pendulum
of the clockwork is set in motion and the rope unreeled, allowing the piston to sink
slowly into the pump-body, thus forcing the petroleum through i uniformly into the
retort a. The petroleum is converted into gas, and this is carried through the tube d
ARTIFICIAL LIGHT.
677
FIG. 300.
into the receiver, B, and thence
through the condenser, c, which is
filled with pieces of brick, into
a gas-holder. In в the pipe dips
under the surface of the petro-
leum, so that a hydraulic valve
is provided, preventing the gas
from returning to the retort. In
order to keep this column of
petroleum at the same height,
there is fitted to e the U-shaped
tube c, by means of which any
superfluous oil entering c is run
off into a pail. The tube b,
fitted to the gas-tube d, is, by
means of a pipe, connected with
a water-pressure gauge, by the
aid of which the pressure in the
retort during the operation can
be ascertained; this pressure
amounts usually to 8 to 12 centims.
of water. The lid, e, of the con-
denser, c, is kept gas-tight by the
rim dipping in water poured into
an annular space. The working
of this apparatus is very simple.
The clock-motion is maintained
for an hour, and in that time
about 200 cubic feet of gas are
made. If by any chance the
tubes are choked, the manometer
will indicate the accident. When
in regular use the apparatus
should be cleaned once in five or
six weeks, and after every twelve
distillations the retort should be
opened and the crust of coke
picked off with a sharp iron bar.
Petroleum-gas is the best that
can be made, and it has the ad-
vantage that even under strong
pressure and intense cold it does
not deposit tarry matter, nor
does it lose any of its illumi-
nating power. It is absolutely free
from ammoniacal and sulphur
compounds and from carbonic
acid. The sp. gr. of petroleum-

06 638
D
678
CHEMICAL TECHNOLOGY.
gas is o'69, and it consists chiefly of acetylen (C₂H₂). It is burnt from burners
which consume per hour only one-quarter of a cubic foot to a maximum of 2 cubic
feet. 200 cubic feet of this gas are equivalent to 1000 cubic feet of coal-gas. At the
suggestion of L. Ramdohr (1866), the sodium carbolate (creosote soda), which is
obtained in large quantities in the paraffin and mineral-oil works, is used for gas-
making under the name of creosote-gas.
Resin-Gas. VII. When the substance known as Venice turpentine, a mixture of oil
of turpentine and resinous matter, is submitted to distillation with water, there
remains colophonium, or commonly resin, which essentially consists of sylvic and
pinic acids, these being isomeric and corresponding to the formula CoH3002.
Before the late American war colophonium was imported in very large quantity into
Europe, and was used in England as well as on the Continent for the purpose of gas
manufacture.
When decomposed under the influence of heat colophonium yields an oily fluid,
so-called resin oil, which, when submitted to red-heat, is converted into gas. This
oil is very complex, and contains bodies which are volatilised below red-heat, an
inconvenience in gas-making, because these compounds as soon as formed become
volatilised instead of being converted into gas. Consequently it is necessary to pass
the first products of the decomposition through several retorts in order to convert
them completely into gas, thereby complicating the apparatus and increasing the cost
of fuel. Another difficulty in the making of resin-gas is occasioned by the fact that
colophonium is a solid substance which, in order to be fitted for gas-making, so as to
supply the retorts uniformly and constantly, has to be first liquefied. This has been
in some instances effected by dissolving the resin either in oil of turpentine or in
resin oil, while in other instances the resin has been first molten, and then caused to
flow into the retorts filled with coke or lumps of fire-brick to increase the surface.
The hot gas from the retorts is washed with cold water in order to free the gas from
any adhering resin oil. It is next purified from the carbonic acid it contains (on an
average about 8 per cent) by passing it through a solution of caustic soda.
100 lbs.
of resin yield about 1300 English cubic feet of gas, a quantity which is greatly
increased when the White- Frankland hydrocarbon process is employed.
employed. This
process, however, is obsolete in consequence of the very fluctuating supply of resin
since the last American war and the greatly increased price of that article.
The lime-light, Tessié du Motay's oxyhydrogen light, the magnesium light, and the
electric light have to be considered as appendices to the illuminating and artificial
light producing materials.
Lime-Light. When a mixture of two volumes of hydrogen and one volume of oxygen
is ignited, each gas being supplied from a separate gas-holder, we obtain what is
known as the oxyhydrogen blowpipe, the heat evolved being sufficient to fuse
platinum. The flame of this mixture is not luminous, but if it is made to impinge
against a piece of quick-lime, the latter being rendered intensely white-hot, emits a
light of very great intensity. For the general purposes of artificial illumination the
lime-light is not suitable, arising partly from the high price of oxygen; but for
scientific purposes and for signals, the lime-light, also known as the Drummond-, or
sideral-light, is very manageable. According to the "Journal of Gas Lighting"
(1869) the authorities of the British War Department have arranged to use the lime-
light in military barracks and cavalry stables, having instituted a series of
experiments in the yard of the Queen's Barracks. The illuminating apparatus and
ARTIFICIAL LIGHT.
679
reflecting mirror were placed on a temporarily-erected wooden frame-work, 18 feet
high, and when the lime was ignited the yard was lighted up so strongly, that at
100 yards distance from the light the smallest type could be read. A smaller light
surrounded by a glass globe was tried, and found to be so efficient, that at 30 yards
distance from the light a pin could be distinguished lying on the pavement. The
light-apparatus tried in one of the barrack-rooms was still smaller, but lighted the
room very brilliantly.
Tessie du Motay's Method
of Illumination.
For some years Tessié du Motay's method of illumination has
been often before the public. During the latter part of 1871 and the earlier months
of this year, this method has made considerable progress in improvement, and is
used in some parts of Paris and Vienna, and has been tried at the Crystal Palace.
The gas-mixture used is either water-gas-a mixture of hydrogen and carbonic
oxide-or hydrogen only, or also coal-gas, burnt with a regulated supply of oxygen
instead of air. The oxygen is obtained by the decomposition of the vapours of
sulphuric acid or from manganate of sodium, or by the decomposition of oxychloride
of copper. The flame of the oxyhydrogen gas is made to play against a small
cylindrical piece of magnesia or zirconia; but more recently (1869) Tessié du Motay
has somewhat altered his method, by causing the oxygen to become saturated with
a solution of naphthaline in petroleum. It appears that the latest and most practi-
cally available method is the feeding of good coal-gas with oxygen, a very excellent
light being produced.
Mr. Crookes has found a supply of good coal-gas best adapted to the oxy-hydrogen
flame, the oxygen being supplied from a burner quite separate from the hydrogen burner,
and having a broad slit from which the gas issues. The oxygen should be supplied at a
steady but full pressure. The material upon which the flame impinges may, with advan-
tage, be of dolomite. Under these conditions, Mr. Crookes has always found the lime-
light to work satisfactorily. The dolomite does not crack nor splinter, as is the case with
quick-lime or magnesia. There are also the advantages in employing separate burners, of
decreased expense of apparatus, and of perfect safety.
MM. Deville and Gernez proposed some time since to make a series of experiments to
ascertain, in a chamber containing compressed air, whether the tension of steam (which is
said to be complementary to the tension of dissociation) in the flame of the oxyhydrogen
blowpipe is augmented by exterior pressure, and if the augmentation extends to the tem-
perature of the flame. In a cylindrical chamber of forty metres contents, and the sides
of which have been proved to eleven atmospheres, is arranged the necessary apparatus.
The operators enter the cylinder, and the air is compressed by means of a steam-pump,
when the experiments are proceeded with as in the open air. The endeavour has at pre-
sent been confined to ascertaining the condition of various substances at the moment they
combine in homogeneous flames, and the resulting temperatures. The homogeneous
flame employed is that of carbonic oxide and oxygen. With this flame and a pressure of
17 atmospheres platinum melts, flying off in sparks with a facility it never exhibits
in air; it melts in those portions of the flame which in the air would only heat it to red-
ness. We must then deduce that the temperature of these flames augments with
the pressure they support, and, consequently, the quantities of matter which combine
are greater, and the dissociation diminished. Dr. Frankland has shown that the
brilliancy of the flame of hydrogen gas increases considerably with the pressure, so that
with a pressure of twenty atmospheres it surpasses that of a normal candle. Similarly
when a mixture of oxygen and hydrogen is ignited in an eudiometer the flame is intense,
while in open air it is scarcely visible. M. Deville thinks that if the quantity of heat
disengaged by a substance burning with brilliancy be measured, the result would not be
the same in operating with an opaque calorimeter as with one which transmits the light
and chemical rays. This remark when worked out will probably produce results of tech-
nical interest.
Magnesium Light. The very intense light which is produced by the burning of magne-
sium (see p. 114) has been of late frequently employed for photographing purposes.
Magnesium lamps-as exhibited in 1867 at the International Exhibition, at Paris-
680
CHEMICAL TECHNOLOGY.
are arranged for the use of magnesium wire or magnesium dust, while in each
instance a spirit-flame is employed to ensure the continuity of combustion. In the
lamps with wire, this is pulled forward by the aid of clockwork; while in the lamps
burning the dust, this, mixed with very dry and fine sand (one-third magnesium and
two-thirds sand), in order to ensure to the magnesium particles a sufficient access of
air, is, on opening a stop-cock, supplied from a reservoir. The magnesium light was
used on a large scale in the Abyssinian war, several cwts. of magnesium having
been supplied by Mr. Mellor, the director of the Magnesium Metal Company, at
Manchester.
Chatham Light.
Under this name is known in England a kind of flash-light, obtained
by blowing a mixture of pulverised resin and magnesium dust through the flame of
a spirit-lamp. This flash-light is used for military signals.
Electric Light.
Although the electric light has not been generally employed it
deserves a lengthy notice. As is well known, the discharge of an electric spark, or
a continuous voltaic or magneto-electric current, is capable of producing in pieces of
graphite an intense light; and when this is obtained by suitably constructed apparatus,
it may be rendered available for practical purposes. More recently Professor
Jacobi has, with the assistance of M. Argeraud, of Paris, made a series of experi-
ments on street lighting with the electric light. Upon the tower of the Admiralty
buildings at St. Petersburg, an electric light apparatus was placed, and with it three
of the largest streets of the city, viz. Newsky Prospect, Erbsen Strasse, and Wos-
nesensky Prospect, were illuminated at night from seven until ten o'clock. The
light was intense, and the very clear sky appeared as by sunlight, while the gaslights
became lurid. The battery employed was a carbon battery of 185 cells. In 1854,
the works for the construction of the Napoleon docks, at Rouen, were for several
nights illuminated with the electric light for three to four hours consecutively;
800 men were at work, and could continue their labour at a distance of 100 metres
from the source of light. A Bunsen battery of large size with 100 cells was
used. This light was very cheap, the cost per man being about three farthings;
while the labour could proceed as in daylight. Several lighthouses, among them the
North Foreland on the Kentish coast, and also that of Cape la Hève near Havre,
have been fitted with apparatus for the electric light. This light is also used in
many cases in dissolving views, and for the illumination of pleasure gardens at
London, Paris, Berlin; and permanently for lighting the slate quarries situated near
Angers, France. The electric light has been tried for submarine illumination with
success, and also for photographing purposes. Colonel von Weyde invented a
submarine electric illuminating apparatus, used by the French men-of-war in the
late conflict between France and Germany. In Spain, in 1862 and 1863, the electric
light was frequently employed during the night in the construction of railways. The
magneto-electric apparatus invented by Dr. Siemens (1867) is of great importance,
as proved by the experiments made at Burlington House. By means of this machine
it becomes possible to obtain electric currents at a cheap rate, of enormous power,
and especially adapted for lighthouses.
By the exercise of great ingenuity, the difficulties attending the maintenance of the
carbon points at an equal distance have been overcome. The lamps in which this result
is effected are, however, more or less complicated, expensive, and liable to get out of
order. The electric lamps of Foucault, Serrin, and Duboscq, described admirably in
Dr. Schellen's "Spectrum Analysis," and engravings of which are to be met with in most
treatises on physics, are delicate pieces of mechanism peculiarly unsuited to the rough
•
ARTIFICIAL LIGHT.
681
handling to which apparatus in use for technical or signalling purposes must be sub-
mitted. The electric lamp devised by Mr. Browning is simple in construction, but even
this requires more attention than could be bestowed upon the source of light for general
purposes.
The purity of the carbon points has much to do with the intensity of the light
emitted by batteries of the same strength; while their distance from each other is also of
consequence. 50 or 60 Bunsen's elements will yield a light equal to that of 400 to 1000
stearine candles, according to the purity of the carbon points. Taking the sunlight at
noon on an August day to be represented by 1000, Foucault and Fizeau have found the
chemical power of the light obtained, under the best conditions, from 46 Bunsen's
cells, expressed by the number 235. Despretz states that the light from 100 Bunsen
elements produces much discomfort to the eyes, while that from 600 elements, even at a
glance, is sufficiently intense to cause considerable injury. But the duration of the
electric light as obtained from battery power is not continuous. Whether from polarisa-
tions in the battery or from many other causes, the light sometimes fails for several con-
secutive minutes. It becomes then necessary to have recourse to some source of elec-
tricity in which these objections are eliminated. To a great extent this is the case
with magneto-electricity. The light from Messrs. Wilde's large machine is the most
powerful artificial light which has ever been produced, giving about eight times the light
of former magneto-electric machines. Like most practical applications of science, the
important results which Mr. Wilde has obtained depend more upon an ingenious combi-
nation of several known facts, united with considerable engineering skill, than upon any
really new and striking discovery. The principle of the machine can be expressed in a
few words. It consists in the application of a current from an electro-magnetic machine,
armed with permanent magnets, for the purpose of exciting a powerful electro-magnet;
this electro-magnet being now used as the basis of a still larger electro-magnetic machine,
for the purpose of having induction currents generated by its agency. In other words, by
well-known means, an electric current can be obtained by the rotation of an armature
close to the poles of a magnet. If this electric current be passed round an electro-
magnet, it may be made to produce a far greater amount of magnetism than was
possessed by the first magnet. There is no difficulty, therefore, in comprehending how,
by the mere interposition of a rotating armature, and the expenditure of force, a small
and weak magnet may be made to actuate a very powerful magnet. But as the power of
the magnet increases, so does the power increase of the electric current which may
be generated by induction in an armature rotating between its poles. We have, therefore,
only to pass this No. 2 induced current from No. 2 magnet round a still larger magnet,
No. 3; and by rotating an armature between its poles, we can get a still more energetic
current, No. 3. Theoretically there is no limit to this plan-it is a species of involution;
and when it is considered that each conversion from magnet No. I to magnet No. 2, &c., or
from induced current No. 1 to induced current No. 2, &c., multiplies the power very many
times, it will not be surprising that after three involutions the induced current possesses
such magnificent powers.*
Ι
Some erroneous opinions are pretty generally entertained as to the actual discovery
claimed by Mr. Wilde, and the splendour of the result, for achieving which he deserves
the very highest credit, is liable to cause earlier investigators in the field to be overlooked;
this would be most unfair, for it is through their instrumentality that the way has
been paved for the success now achieved. In 1838, Abbés Moigno and Raillard proved
that by taking an electro-magnetic machine, the original magnet of which would sup-
port only a few grammes, and passing the electric current generated by it round a
large electro-magnet, the latter could be made to support a weight of 600 kilogrms. The
Abbés carried the multiplication of power only so far as to obtain the more powerful
magnet, No. 2, from the weak magnet, No. 1.
With the three armatures of Mr. Wilde's machine driven at a uniform velocity of 1500
revolutions per minute, an amount of magnetic force is developed in the large electro-
magnet far exceeding anything which has hitherto been produced, accompanied by the
evolution of an amount of dynamic electricity from the quantity armature so enormous
as to melt pieces of cylindrical iron rod fifteen inches in length and fully one quarter of
an inch in diameter. With this armature in, the physiological effects of the current can
be borne without inconvenience. When the intensity armature was placed in the 7-inch
magnet cylinder, the electricity melted 7 feet of No. 16 iron wire, and made a length of
21 feet of the same wire red-hot. The illuminating power of the current from this arma-
ture was of the most splendid description. When an electric lamp, furnished with rods
* See "A New Era in Illumination," by W. Crookes, F.R.S.; "Quarterly Journal of
Science," October, 1866.
682
CHEMICAL TECHNOLOGY.
of gas carbon half an inch square, was placed on the top of a lofty building, the
light evolved from it was sufficient to cast the shadows of the flames of the street lamps
a quarter of a mile distant upon the neighbouring walls. When viewed from that
distance, the rays proceeding from the reflector have all the rich effulgence of sunshine.
With the reflector removed from the lamp, the bare light is estimated to have an intensity
equal to 4000 wax candles. A piece of ordinary sensitised paper, such as is used for
photographic printing, when exposed to the action of the light for twenty seconds, at a
distance of 2 feet from the reflector, was darkened to the same degree as a piece of the
same sheet of paper was when exposed for a period of one minute to the direct rays of
the sun at noon on a very clear day in the month of March. Paper could be easily set on
fire with a burning-glass introduced in the path of the rays from the reflector.
It will be of interest, apart from all questions as to economical production, to ascertain
what is the theoretical quantity of coal required to be consumed in the production
of this amount of electric force. Mr. Wilde says that a 7-horse engine is required to
drive the machine. One horse-power is equal to 1,980,000 foot-pounds per hour; that
multiplied by seven is 13,860,000 foot-pounds per hour, which therefore represents
the actual power required to drive the machine. Now, by multiplying the British
Fahrenheit units of heat produced by the combustion of one pound of coal by Joule's
equivalent, 772 foot-pounds, the result will be the total heat of combustion expressed in
foot-pounds. In the best coal this is as high as 12,000,000 foot-pounds. We arrive,
therefore, at the conclusion that, to overcome the friction of the different parts of the
machine; to whirl a mass of metal, weighing several hundredweights, round with
a velocity of 1500 revolutions per minute; to generate a current of electric force far sur-
passing anything before produced; and, after allowing for the waste inherent in its pas-
sage through the conducting wires and electric lamp, to cause it to blaze forth with an inten-
sity of light paling the rays of the sun; to keep up this intense development of energy
for one hour-requires an expenditure of force represented by the combustion of less than
183 ozs. of coal. This is the theoretical calculation; but if reduced to actual practice, the
results are scarcely less astonishing. The efficiency of an engine, i.e. the ratio of the
work actually performed to the mechanical equivalent of the heat expended, varies in
extreme cases between the limits o'02 and 0.2. Taking an average efficiency as o'1, or one-
tenth, we find that the ordinary consumption of coal required to work a 7 horse-power
engine, midway between excessive wastefulness on the one hand, and rigid economy
on the other, is 10 × 18 ounces, or 11 lbs. of coal per hour, worth about one halfpenny.
This is, of course, only one item in the cost-to it must be added the expense of carbon
rods for the lamp, which will be about ten inches per hour, worth perhaps a penny;
there must also be added interest of the cost of purchase of machines, expense of main-
tenance and repairs, which will perhaps bring up the total expense per hour to
sixpence or eightpence. Comparing this with the hourly expense of the electric lights
already in existence, we find, according to the Abbé Moigno, that the French machine
costs altogether sixpence per hour for a light equal to 900 wax candles; whilst the actual
working expenses of maintaining the electric light at Cape La Hève, during a period of
twenty-seven months have been, exclusive of salaries, about one shilling per hour,
or inclusive of salaries, two shillings. According to a calculation made by the Abbé
Moigno respecting the economy of the light evolved by the French machines, it appears
that to maintain a light equal to 4000 wax candles for one hour would cost-with gas,
£1 2s. 6d.; with colza oil, £1 7s.; and with the electricity produced by a Bunsen's pile,
£1 15s. 6d. The annual expenditure at a first-class lighthouse on the old system is, on an
average, £400 per annum; and on the assumption that the light burns for 4000 hours per
annum, that would come to two shillings per hour. The expenses of the old and
the electric system are therefore not very dissimilar; and the problem of the adoption
of electricity to supersede oil must be decided on grounds of convenience and efficiency
alone.
II
One cause of inconstancy in the electric lamp which hinders the adaptation to the pur-
poses of lighthouse illumination is the unequal consumption of the carbon points. From
experiments recently conducted for the Trinity House, Mr. Stevenson finds that the
employment of a modified form of vacuum-tube removes this objection. The subject
upon which we cannot enter more fully here is very exhaustively treated in Mr. Stevenson's
recent work on the illumination of lighthouses.
The following Table exhibits the comparative illuminating power of the principal
artificial lights :-
ARTIFICIAL LIGHT.
683
a.
Light-producing
Substance.
Wax
Stearic acid
...
Spermaceti...
Tallow
grms.
9'02
B.
?
Consumption Intensity of light.
per hour in (1 wax candle
=
100).
102'00
d.
Light obtained
from 10 grms. of
this material.
Ε.
Illuminating
power (wax
candles
ΙΟΟ
100).
III 02
9'94
95'50
96.03
84
::
::
8.87
108.30
123'17
108
8.87
90'25
101'70
90
Paraffin (1st quality)
8.83
94'69
83
(2nd }
8.49
139.87
123
""
Colza oil.
Moderator lamp
40.69
694'00
170'07
159
Kitchen lamp
7:33
45.67
62.30
55
Reading lamp, with-
out glass chimney
9.86
114 ΟΙ
115.80
102
Photogen
20'02
149'03
131
Solar oil
26.82
225'64
199
...
::.
Petroleum
174'40
180
186'01
195
15:06
8.09
According to Dr. Frankland's researches, the following quantities of illuminating
materials exhibit equal illuminating power:
Young's paraffin oil from Boghead coal
American petroleum (No. 1)
""
Paraffin candles
Spermaceti candles
Wax
""
Stearine
Tallow
(No. 2)
...
...
...
:
:
...
:
:
...
:
:
4'53 litres.
5'70
5.88
""
8.42 kilos.
10*37 "
""
11.95
12'50
16.30
""
Paraffin Oils.
PARAFFIN AND SOLAR OR PETROLEUM OILS.
Paraffin was discovered in the year 1830 by Karl von Reichenbach
among the products of the dry distillation of beech-wood tar, and has obtained its
name from parum, little, and affinis, related to, on account of its incapability of
chemically uniting with other substances. Paraffin is not acted upon by alkalies or
acids, nor is it decomposed at a red-heat. It was afterwards found that paraffin is
also formed by the dry distillation of peat, brown coal, Boghead, and some cannel
coals, but not by the dry distillation of real coal. Paraffin is found native and occurs
in large quantities in:-1. Petroleum, Rangoon and Persian, which sometimes con-
tains 6 to 40 per cent. 2. In impure state, under the names of ozokerite, neft-gil,
or mineral wax. 3. In bitumen, asphalte as contained in some schistose rocks, and
as met with at Trinidad and elsewhere.
Manufacture of Paraffin. The mode of obtaining this substance differs according to its
being an educt or a product. It is an educt as obtained from petroleum, ozokerit,
neft-gil; but a product of the dry distillation of brown coal, peat, and the Boghead
shale.
684
CHEMICAL TECHNOLOGY.
•
from Petroleum.
Preparation of Paraffin 1. That petroleum contains paraffin was known in the year 1820,
when A. Buchner discovered in the earth oil of the Tegernsee, in Upper Bavaria, a
solid, fatty substance, which was afterwards ascertained by V. Kobell to be paraffin.
Hence Buchner is locally considered to be the discoverer of paraffin; while later
researches have proved that the earth oil of Baku, on the Caspian Sea; of Amiano,
near Parma; and of Gabian, Hérault, France; contain this substance to greater or
less extent. The idea of using these oils for the industrial preparation of paraffin
dates only from 1856, when some samples of petroleum which were found to contain
a large quantity of paraffin were imported into Europe. The American petroleums
contain only a very small quantity of paraffin; but in those derived from Burmah
and Rangoon, Gregory, De la Rue, and H. Müller found 10 per cent. Bleekrode
investigated a sample of Java petroleum which contained 40 per cent of paraffin.
The mountain naphtha of Eastern Galicia is with great advantage employed for pre-
paring paraffin. According to Jacinsky, 45,000 cwts. of this material were in 1866
obtained from this naphtha.
The Rangoon oil obtained from Burmah as a native product flowing from springs
in the neighbourhood of the river Irawadi is, according to De la Rue's patent
(1854), treated in the following manner for the purpose of preparing paraffin and
hydrocarbon oils. The crude oil is first put into a still, which can be heated by fire
externally while steam is admitted internally. By this operation about 25 per cent
of a fluid is obtained, which on being submitted to fractional distillation yields
hydrocarbon, the sp. gr. of which varies from q'62 to o‘86, while the boiling-point
varies from 26°7° to 200°. The lightest and most volatile of these hydrocarbons is
used as an anesthetic, under the name of Sherwood oil, while the heavier oils
are burnt in paraffin lamps. The residue of this first distillation—about 75 per cent
of the original quantity—is again distilled, but with steam at 150° to 200°; and the
products of variable volatility are separately collected. The last portions of the dis-
tillate contain chiefly paraffin, which is in crude state separated from the liquid
by the application of artificial cold. The heavy oil is used as lubricating oil, and the
paraffin is purified as already described.
and Neft-gil.
Paraffin from Ozokerite Paraffin is prepared from ozokerite and neft-gil, on the island
Swätoi-Ostrow, in the Caspian Sea, about a verst (=1066'78 metres) from the
peninsula Apscheron, on the Caucasian shore. The neft-gil is carried by ships from
Truchmenia. Paraffin is largely manufactured in Galicia from the mineral wax
which occurs near Drohobicz and Boryslaw, also on the northern slopes of the Car-
pathian mountains, and in other parts of the Austrian Empire. The chief works are
found at Aussig, Florisdorf, Ostrau, Vienna, New Pesth, Temisvar, &c. Mineral wax
is also largely found in Texas.
Neft-gil, according to F. Rossmässller, is treated in the following manner:—
15 cwts. of the crude material is put into iron stills provided with a leaden worm, and
submitted to fractional distillation, yielding 68 per cent of distillate, consisting of
8 per cent of oil and 60 per cent of crude paraffin. The oil thus obtained is yellow,
opalescent, possesses an ethereal odour, and a sp. gr. of 0'75 to 0.81. Each distilla-
tion yields a quantity of a light oil boiling below 100°, which is used for the purpose
of purifying the paraffin. The crude paraffin obtained by the first distillation is
tolerably pure, has a yellow colour, and can at once be treated by the hydraulic press
and centrifugal machine. The oil from these operations is again submitted to
fractional distillation in order to obtain more paraffin. The pressed paraffin is
ARTIFICIAL LIGHT.
685
molten and treated at 170° to 180° with sulphuric acid, which is next neutralised by
means of lime, and the paraffin again rapidly distilled; then again submitted
to strong pressure, and the material obtained treated with 25 per cent of the light
oil; then again molten, again pressed, and finally treated with steam for the purpose of
eliminating the last traces of essential oil. The material obtained by this treatment
is a perfectly pure, colourless material, free from smell, transparent, and so hard as
to exhibit in large blocks an almost metallic sound. The fusion-point is 63°
Rossmässler states that the raw material yielded to him in a week's time, after
a previous continued distillation of two months, 148 cwts. of paraffin ready
for second pressure. The Galician ozokerite yields by distillation only 24 per cent of
paraffin, and 45 per cent of paraffin oil, also termed ozokerite oil.
Paraffin from Bitumen.
c. Paraffin is made in England from bitumen, asphalte, mineral
tar, and the bituminous organic matter present in certain shales; among these, the
so-called Kimmeridge clay, Boghead coal, and a few cannel coals. The asphalte
occurring in Trinidad, Cuba, Nicaragua, Peru, California, and other countries, is
used for the purpose of preparing paraffin and paraffin oils. The Cuba and Trinidad
asphaltes yield 175 per cent paraffin. The extensive deposits of bituminous shale in
Hungary are treated for paraffin and oil at Oravicza. According to Wünschmann, the
shale yields 5 to 6 per cent of paraffin, 49 per cent of oil suited for burning in lamps,
and 6 per cent of lubricating oil.
Preparation of Paraffin by
Dry Distillation.
The preparation of paraffin by the dry distillation of peat,
brown-coal, coal-shale, Boghead coal, &c., involves two operations:-
-1. The prepa-
ration of tar. 2. The application of the latter to the preparation of paraffin oil
and paraffin. The coal-tar of the gas-works does not contain paraffin, but naphtha-
line and anthracen.
Preparation of the Tar, 1. This operation is one of the most important and difficult of
the industry, and during the last fifty years many enterprises undertaken for the
application of fossil fuel to the preparation of illuminating materials have failed
solely on account of the imperfect preparation of the tar. The making of the tar is
carried on in retorts or in peculiarly constructed ovens, the distillation being in many
cases assisted by the application of superheated steam. The principle of the con-
struction of the tar oven is very simple, being that by a portion of fuel burning in the
lower part of the oven, a layer, more or less thick, of superincumbent fuel, is sub-
mitted to a slow carbonisation, resulting in the production of tar, which flows down-
wards, while the gaseous products are lost. In order to prevent its violent combus-
tion, the fuel is covered with a layer of clay. But as experience has shown that this
mode of distillation is not well suited for the production of tar intended to yield
paraffin and the oils, it is not general in practice on the large scale, although it has
the advantage of being a continuous and uninterrupted process. According to
report, an oven constructed by L. Unger, the manager of a paraffin works at Döll-
nitz, near Halle, yields suitable products, while a saving is effected in labour as well
as in the quantity of fuel required for the distillation.
Horizontal retorts are frequently used for the preparation of tar, but experience
has taught that if in the construction of the furnaces containing the retorts the
arrangement is similar to that of a gas-works where four to eight retorts are worked
in one furnace, no satisfactory results can be obtained, one of the reasons being that
the principles of gas- and of tar-making are entirely opposed. It appears to be
necessary to construct a furnace for every retort, and that the furnace should be
686
CHEMICAL TECHNOLOGY.
oven.
of such dimensions as to be suited to hold a retort 10 feet long, 30 inches wide, and
15 inches high, forming in section a shallow oval. More recently there have been
built in Bohemia and elsewhere brickwork retorts, shaped somewhat like a baker's
These seem to answer well, but are difficult to repair although of small first
cost. Vohl observed that a quantity of 20 to 25 per cent of water present in the
fossil material very greatly assists the formation and increases the yield of tar,
owing to the superheated steam formed from the water during the distillation
carrying off the vapours of the tar rapidly from the hot retort. This has given rise
to the construction of Lavender's tar-producing apparatus, the principle of which is
the same as that of Violetti's wood-charring apparatus used for the preparation of
the charcoal in gunpowder manufacture. Lavender's apparatus consists of an iron
cylinder provided with holes at the bottom for the purpose of admitting superheated
steam, while to the top of the cylinder a tube is fitted for carrying off the products of
the distillation. It would appear that L. Ramdohr's method of preparing tar from
brown-coal by means of steam yields a tar which contains 22 to 24 per cent of
paraffin and 36 to 38 per cent of oil.
Condensation of the
Vapours of the Tar.
The condensation of the products of the dry distillation is one of
the most important operations, and greatly influences the yield of tar. Vohl has
lately proved that even when the construction of the retorts is not of the best, an
average yield of tar may be obtained by attention to the condensation of the vapours.
The complete condensation of the vapours of the tar is one of the most difficult
problems the paraffin and mineral oil manufacturer has to deal with, while the means
usually adopted for condensation, such as large condensing surfaces, injection of cold
water, and the like, have proved ineffectual. It has often been attempted to condense
the vapours of tar in the same manner as those of alcohol, but there exist essential
differences between the distillation of fluids and dry distillation. In the former case
the vapours soon expel all the air completely from the still and from the condenser,
and provided, therefore, that—in reference to the size of the still and bulk of the
boiling liquid-the latter be large and cool enough, every particle of vapour must
come into contact with the condensing surfaces. In the process of dry distillation
the case is entirely different, because with the vapours, say of tar, permanent gases
are always generated. On coming into contact with the condensing surfaces, a
portion of the vapours are liquefied, leaving a layer of gas as a coating, as it were,
on the condensing surface. The gas being a bad conductor of heat, prevents to such
an extent the further action of the condensing apparatus, that a large proportion of
the vapours are carried on and may be altogether lost. A sufficient condensation of
the vapours of tar can be obtained only by bringing all the particles of matter which
are carried off from the retorts into contact with the condensing surface, which need
neither be very large nor exceedingly cold, because the latent heat of the vapours
of tar is small, and consequently a moderately low temperature will be sufficient to
condense these vapours to the liquid state. The mixture of gases and vapours may
be compared to an emulsion, such as milk, and as the particles of butter may be
separated from milk by churning, so the separation of the vapours of tar from the
gases can be greatly assisted by the use of exhausters acting in the manner of
blowing fans. It is of the utmost importance in condensing the vapours of tar that
the molecules of the vapours be kept in continuous motion, and thus made to touch
the sides of the condenser. The condenser should not be constructed so that the
vapours and gases can flow uninterruptedly in one and the same direction. The
ARTIFICIAL LIGHT.
687
temperature at which the distillation is conducted greatly influences the yield of tar,
and consequently of the paraffin and oil. As regards the influence of the shape of
the retorts and mode of distillation, H. Vohl made the undermentioned comparative
researches by distilling French and Scotch peat in horizontal retorts (No. I.), in
vertical retorts (No. II.), and in ovens somewhat like coke-ovens (No. III.)
100 parts of peat yield of tar,-—
French peat
Scotch peat
I.
II.
III.
5'59
4'67
2:69
9'08
6.39
4'16
The sp. gr. of the tar from the different kinds of apparatus was as follows:
French peat
Scotch peat
را
I.
II.
III.
...
...
o'920
o'935
0'970
I'006
0'970
I'037
It appears from these results that horizontal retorts yield the largest, and ovens
the smallest, quantity of tar; moreover, the duration of the operation of distilling is
shortest in horizontal retorts, which also yield less gas, while in the ovens both tar
and coke are burnt away to a considerable extent by the too great supply of oxygen.
Properties of Tar. The tar obtained from the retorts in distilling peat, brown-coal,
lignite, bituminous shales, Boghead coal, &c., at as low a temperature as possible,
and hardly higher than dull red-heat even towards the end of the operation, exhibits
a coffee-brown colour, generally an alkaline, in some instances an acid, reaction, and
possesses the very penetrating odour characteristic of tar. By exposure to air the
colour of the tar becomes deeper, and sometimes even brownish-black. This tar
often semi-solidifies at a temperature of 9° to 6º, owing to the paraffin it contains.
The sp. gr. varies from o 85 to 0.93, and consequently the tar floats on water. The
so-called steam-tar, obtained by the aid of superheated steam from brown-coal
(according to Ramdohr's plan, 1869) always has an acid reaction, and is completely
saponified by alkalies; this tar becomes solid at a temperature of 55° to 60°, and can
therefore be preserved in solid blocks in summer time. Its sp. gr. is o‘875.
As regards the quantity of tar obtained from 100 parts of raw material, the fol-
lowing results are most general :—
Foliated bituminous
""
shale,
Brown-coal,
Tar.
Sp. gr.
Crude paraffin.
Per cent.
Siebengebirge
Hesse
20'00
0.880
0'750
""
25'00
0.880
I'000
Prussian Saxony
7:00 O'910
0'500
10'00
""
0'920
0'750
6:00
""
""
0'915
0'500
""
5'00
0'910
O'250
Bohemia
II'00
0.860
""
Westerwald
""
5'50
o'910
""
3'50
o'910
Nassau
""
4'00
o'910
""
3:00 O'910
Frankfort
9'00
0.890
Lignite,
Shale,
Silesia
3:00
o'890
O'25
Vendée
14'00
0·870
1'000
688
CHEMICAL TECHNOLOGY.
Tar.
Sp. gr.
Crude paraffin.
Per cent.
Shale,
Westphalia
5:00
0'920
0'050
Schist,
Peat,
Würtemburg
963
o'975
O'124
Neumark
5'00
o'910
0'330
Hanover
9'00
o'920
0*330
""
Erzgebirge
5'70
0'902
0'350
5'30
o'905
0*400
Russia
5.861
""
Boghead coal,
>>
7:00
Scotland
33'00
0.860
1-14
Cannel coal,
Peltonian coal,
Coarse coal,
1—1'3
1'000
""
9:00
O'910
I-1*25
Mode of Operating
with the Tar.
The first thing to be done with the crude tar is to separate the
water, which is effected by pumping the tar into the dehydrating apparatus. These
apparatus consist of tanks of boiler-plate, placed within a larger tank, so that a space
of 10 centims. intervenes, into which water is poured and maintained by means of
steam at a temperature of 60° to 80° for ten hours. After this time the ammoniacal
water and other impurities, together about one-third of the bulk of the crude tar,
have become separated, while the small quantity of water still adhering to the tar is
of no consequence in the further operations. The tar is decanted by opening a stop-
cock or valve placed near the top of the tank, and the ammoniacal water is removed
by opening a stop-cock at the bottom.
Specifically light tars are of course readily separated from the water, while heavy
tars are more difficult to deal with. If to the ammoniacal water of such tars salts
are added, for instance, common salt, Glauber salt, chloride of calcium, and the like,
the specific gravity of the water is increased, and the heavy tar more readily sepa-
rated; but according to Dullo these means are either too expensive or do not quite
answer the purpose. The complete separation of the tar from the water is of the
greatest importance, because in the subsequent distillation the presence of water may
cause the tar to boil over and give rise to serious accidents by coming in contact
with the fire under the stills.
Distillation of the Tar.
This operation is usually carried on in cast-iron stills large
enough to hold 20 cwts. of tar. In order to prevent the flame impinging on the
bottom of the still, it is protected by a fire-brick arch. The still is usually built in
two separate parts, which are joined with a flange and bolts, so that if the lower part
is burnt out, only that requires to be renewed.
The helms of these stills are rather flat and the spout very wide. The vapours of
the various oils have a high density and low latent heat, so that these vapours have
a tendency to condense readily and flow back into the still; therefore the helm is
covered with sand or ash, being bad conductors of heat. When the tar is thoroughly
dehydrated, the distillation proceeds quietly and without ebullition; but if any water
be mixed with or adheres to the tar, the liquid in the still boils violently and is very
apt to boil over. At below 100' the tar loses the very volatile sulphide of ammonium
and the pyrrhol bases, while gases are evolved which ought to be allowed to escape
by a safety-valve. The true distillation begins at 100°, yielding at first a distillate
ARTIFICIAL LIGHT.
689
Treatment of the Products
of Distillation.
consisting of very strong ammoniacal liquor and some light oils. The boiling-point
of the tar is not constant, the oil coming over uninterruptedly when the temperature
has risen to above 200°; then the boiling-point becomes somewhat constant, while
with the oil some water comes over, due to the chemically-combined water of the
carbolic acid being set free. The distillation then again becomes somewhat inter-
rupted, and can be maintained only by stronger firing of the retort. The oils now
distilling over become solid on cooling, owing to the large proportion of paraffin they
contain. The distillation is continued to dryness, the asphalte left in the still being
removed after about four or five operations, and for this purpose the still is some-
what cooled and the molten asphalte run off by a tap at the bottom of the still. If
the distillation is carried to dryness, some water finally distils over, due to the
decomposition of the organic matter. A still of 500 litres capacity can be distilled
off in twelve to fourteen hours, if the operation is pushed so far as to decompose
the asphalte, leaving only a carbonaceous residue; but if the asphalte is to be col-
lected, the distillation must be stopped after eight to ten hours. The still is sepa-
rated from the condensing apparatus by a massive wall, through which the spout of
the helm is passed into the leaden worm serving as a condenser, and kept cool by
being placed in a wooden tank filled with cold water. But as soon as the paraffin
magma begins to come over the water is allowed to become warm, in order to
prevent the paraffin solidifying in the worm. The gases which are evolved towards
the end of the distillation are carried off by a pipe communicating with the chimney.
The mixed products or raw oils obtained by the distillation
are poured into a large cast-iron cylinder and mixed with a solution of caustic soda
so as to cause the latter to act upon, and intimately combine with, the acid sub-
stances (homologues of carbolic acid)-simply termed creosote in the works—and
pyroligneous acid-which impart an offensive odour and dark colour to the oils.
When the mixture of the oils and caustic soda solution has been effected, the fluid is
run into an iron tank and allowed to settle; the creosote-soda is then removed, and
the oil washed with water to eliminate any adhering alkali. The crude oil is next
similarly treated with sulphuric acid for the purpose of removing basic substances,
which impart odour and colour. The quantity of acid to be used and the duration
of its action, aided sometimes by heat, depend upon the nature of the crude oil—
5 per cent of acid of 170 sp. gr. and five minutes action are sometimes sufficient,
while in other cases 25 per cent of acid will be required, and three hours' contact
with the oil. The action of the sulphuric acid should be carefully watched, as it may
injure the quality of the oil by decomposing some of the lighter hydrocarbons, whereby
sulphurous acid is given off. The mixture of acid and oil is allowed to settle;
the former is run off, and the latter washed first with water then with very dilute
soda ley, and is finally poured into the rectifying stills. The solution of creosote-soda
is neutralised with the sulphuric acid from the preceding operation, the result being
that crude carbolic acid is obtained, which is used for various purposes; such as
impregnating wooden railway sleepers, as a disinfecting material, or for preparing
certain tar-colours (see p. 580). More recently the creosote-soda has been used for
gas manufacture, leaving a coke containing soda, the soda being abstracted by
lixiviation with water.
Crude Oils.
Rectification of the This operation is conducted precisely as the distillation of the tar.
The oils are separated according to their greater or less volatility and specific
45
6go
CHEMICAL TECHNOLOGY.
gravity, or are kept mixed, as paraffin oil, at a sp. gr. of 0·833, and sent as such to the
market. When the oil which comes over begins to solidify on cooling or exhibits a
sp. gr. of o88 to o‘9, it is separately collected and placed in a cool situation for the
purpose of crystallising the paraffin.
The vessels in which the paraffin magma
is placed for the purpose of solidifying are rectangular iron tanks, fitted with a tap,
or are conical, sugar-loaf shaped vessels, made of iron or wood, and from 16 to 2
metres high, and 1 metre wide at the top, being provided with a tap for the purpose
of removing the oily matter which has not solidified after the lapse of about two
to four weeks. This thick oil is next cooled to far below the freezing-point of water,
in order to obtain more paraffin and other hydrocarbons mixed with it. Any
still non-solidified matter is, when it has a low specific gravity, again refined by dis-
tillation, and will yield paraffin oil; but if its sp. gr. is high-say from o'925 to 0.940—
it is used as a lubricating oil, known abroad as Belgian waggon grease.
Refining of the Crude
Paraffin.
The crude paraffin is in England sold to the refiners, who are
also paraffin-candle makers; but on the Continent every manufacturer of crude
paraffin refines his product and converts it into candles. The crude paraffin, so-
called paraffin butter, is treated in various ways: some manufacturers crystallise it
by the aid of cold, and press it for the purpose of removing any oil; others again
first treat the crude material with caustic alkali ley, next with sulphuric acid,
and then again distil it or leave it to crystallise. The caustic soda ley removes
from the paraffin all the acid substances and other impurities it may contain. The
partly purified paraffin is now treated with 6 to 10 per cent of sulphuric acid,
whereby alkaline and resinous matters are removed. The loss in bulk of the crude
material by these operations amounts to about 5 per cent. The purified paraffin is
next allowed to remain in a very cool place for some three or four weeks; after
which the nearly solid mass is filtered, then submitted to the action of centrifugal
machines, and finally strongly pressed. The oil which is separated from the
paraffin is again distilled, yielding paraffin oil and paraffin butter. The solid paraffin
is molten, cast into blocks, and these submitted to very powerful hydraulic pressure.
The pressed cake is next treated at 180° with 10 per cent of sulphuric acid for two
hours, then washed with hot water, again cast into blocks, again pressed, and
then washed with a solution of caustic soda. Instead of treating the paraffin with
active agents, it has been proposed to use neutral solvents for the removal of the
oily materials; for this purpose, benzol, light tar oils, benzoline, and sulphide
of carbon, have been employed in the following manner :-The crude paraffin
is first hot-pressed, and the pressed mass fused with 5 to 6 per cent of the solvent;
having been again cast into blocks, these are pressed, and the operation repeated if
necessary. The paraffin having thus been made quite white and pure, is again fused
and treated with high-pressure steam, forced into the molten mass for the purpose of
volatilising the last traces of the solvents. The sulphide of carbon, first employed
by Alcan (1858) for refining paraffin, is used in the following manner :-The paraffin
is melted at the lowest possible temperature, then well mixed with 10 to 15 per cent
of sulphide of carbon, after which the cooled and solidified mass is strongly pressed,
the expressed fluid being submitted to distillation for the purpose of recovering the
sulphide of carbon. The paraffin is next fused and kept in liquid state for some
time for the purpose of eliminating the adhering sulphide of carbon.
Preparing Paraffin.
Hubner's Method of Instead of following the preceding method with the crude tar,
Hübner treats it first with sulphuric acid, and next distils the tar, separated from the
ARTIFICIAL LIGHT.
691
acid, over quick-lime. The crude paraffin obtained is pressed, and then further
refined by treating it with colourless brown-coal tar oil. The advantages of this
method-by which one distillation is saved-—are ;—
a. A larger yield of paraffin.
B. A material of better quality and greater hardness than by the usual method.
With the paraffin the so-called paraffin oils are obtained; but this industry
has been greatly crippled by the extensive importation of paraffin oils (really
petroleum oils) from America, so that the aim of the paraffin makers is to increase
the yield of paraffin. By Hübner's method of distillation over quick-lime,
40 to 50 per cent of impurities (chiefly empyreumatic resins and creosote) are
removed, which by the old process are only got rid of at greater expense by the use
of caustic soda.
Yield of Paraffin. As regards the yield of paraffin, paraffin oil, and lubricating oil, from
the various kinds of raw materials, we quote the following particulars. At the Ber-
nuthsfeld works, near Aurich, the excellent peat yields 6 to 8 per cent of tar;
20 per cent of paraffin oil, of sp. gr. = 0.830; and o'75 per cent of paraffin. H. Vohl
obtained from 100 parts of peat-tar from the peat of undermentioned localities :-
Celle (Hanover)
Coburg
Lubricating Oil.
Sp. gr., 0.860.
Paraffin Oil.
Sp. gr., 0.820.
Paraffin.
34.60
36.00
8.01
...
...
20'62
26.57
3'12
19'45
19'54
3°31
14'40
8.66
0'42
20°39
20°39
3*36
II'00
19'48
2.25
Damme (Westphalia)
Zurich (Switzerland)
Russia
...
Westphalia
...
:
Paraffin oil.
Sp. gr., 0.820.
33°50
33°41
Brown-Coal. In the works situated in the Weissenfels brown-coal mineral district,
1 ton (=275 to 300 lbs.) of the mineral yields 35 to 50 lbs. of tar. 100 lbs. of this
tar yield 8 to 10 lbs. of hard paraffin suited for candle-making, and further 8 to 10
lbs. of soft paraffin for use in stearine-candle making, as well as 43 lbs. of paraffin
oil.
Hübner's works at Rehmsdorf, near Zeitz, yield annually from 360,000 cwts.
of brown-coal about 40,000 cwts. of tar, yielding 18.000 cwts. of crude oil,
4000 cwts. of refined paraffin oil, and 6000 cwts. of paraffin.
100 parts of retort-tar (in contradistinction to steam-tar) from brown-coal yield:—
Brown-coal from-
Aschersleben, Prussia
Frankenhausen
...
Lubricating oil.
Sp. gr., 0.860.
Paraffin.
40'00
3°3
40'06
6.7
Münden
""
17.50
26.21
5'0
Oldisleben
17.72
26.60.
44
Analysed by
Cassel
""
16.42
27 14
4.2
Vohl.
Der Rhön, Bavaria
10'62
19'37
1'2
Tilleda,
Prussia
16.66
18:05
44
Stöckheim, near Düren
Bensberg, near Cologne,,
Tscheitch, Austro-Hungary..
Eger
Herwitz
Schöbritz
""
""
17.50
26.63
3°2
16:36
19'53
3.4
9'04
28.86
3·2)
:
9'14
54'00
52
22'00
48°32
Analysed by
C. Müller.
5°2
21.68
46.33
4'3/
692
CHEMICAL TECHNOLOGY.
Ramdohr obtained (1869) from steam-tar from brown-coal on an average-
na
15 per cent fusing at 56 to 58°!
7 to 9
22 to 24 per cent paraffin
36 to 38 per cent of oil.
paraffin {7
and
38° to 47°
With careful management steam-tar may yield 28 to 30 per cent paraffin.
The quotations of the yield from cannel and Boghead coals vary very much.
100 parts of tar from bituminous shale were found to yield :-
Mineral oil. Lubricating oil. Paraffin.
English bituminous shale ...
24:28
40'00
0'12
Bituminous shale from Romerickberg, Prussia
25.68
43'00
ΟΙΙ
Westphalia
27.50
13.67
I'II
""
Oedingen on the Rhine
19
18:33
38.33
5'00
According to Müller (1867), 100 parts of Galician mineral wax (ozokerite) yield
24 per cent of paraffin and 40 per cent of oil.
Properties of Paraffin. Pure paraffin is a white, wax-like, tasteless, and inodorous sub-
stance, with a slightly fatty appearance. Its sp. gr. is o'877. It is harder than tallow,
but softer than wax. Its properties vary, however, according to the raw materials
from which it has been obtained. Paraffin from Boghead coal has been obtained,
after melting, in a very crystalline state, and with a fusion-point at 45'5°; while,
again, it has been obtained granular as bleached wax, with a fusion-point of 52°.
Paraffin from Rangoon oil was found to fuse at 61°, and that from peat at 46'7°. The
paraffin from the tar of Saxony brown-coals fuses at 56°, and the oil paraffin at 43°.
The native paraffin from ozokerite fuses at 65'5°. The composition of the various
kinds of paraffin is:-
Carbon
From Saxony
Brown-coal.
...
85'02
From
Ozokerite.
From Boghead
From Peat.
mineral.
From
Petroleum.
85:26
85.00
14'74
15:36
84'95-85*23
15'05-15:16
85:15
15:29
Hydrogen. 14'98
From these figures the conclusion may be drawn, contrary to the view generally
adopted, according to which all varieties of paraffin should be mixtures of hydro-
carbons constituted as CnH₂ (whether the paraffin be obtained from brown-coal, peat,
ozokerite, or petroleum), that paraffin is a mixture of hydrocarbons homologous with
marsh-gas, many of which contain no less than C27. Paraffin is insoluble in water,
but soluble to some extent in boiling alcohol; 100 parts, however, dissolve when
boiling only 3 parts of paraffin. Paraffin is soluble in ether, oil of turpentine, oil of
olives, benzol, chloroform, and sulphide of carbon. Paraffin boils above 300°,
and may be distilled without undergoing any alteration. Acids, alkalies, and
chlorine do not at all act upon paraffin at the ordinary temperature; but when
chlorine is caused to pass into molten paraffin, hydrochloric acid is evolved and
chlorinated products formed. Paraffin may be fused with stearine, palmitine,
and resins in all proportions. Paraffin is used for making candles (see p. 630), but
has been employed now and then as a lubricating material; also for preserving
timber; for rendering wine and beer casks water-tight; for the purpose of preventing
the foaming and boiling over of the sugar solutions in the vacuum pans at the
beginning of the ebullition. It has been suggested to use paraffin for preserving
meat; for waterproofing fabrics (Dr. Stenhouse's process); for use instead of wax
ARTIFICIAL LIGHT.
693
for waxing paper (employed in pharmacy under the name of charta cerata); instead
of stearic acid for soaking plaster-of-Paris objects. Finally, paraffin is used in the
manufacture of the better varieties of matches, as a waterproof varnish for coating
the phosphorus composition; and in chemical laboratories to replace oil in the oil-
baths.
Paraffin Oil.
As already mentioned, the dry distillation of Boghead mineral, brown-
coal, peat, and bituminous shales, yields tar, the quantity of which varies according
to the nature of the raw material and other conditions, mode of distillation, degree
of heat, &c. As regards the nature of tar we cannot say that it is fully elucidated.
Until the year 1830, tar was considered to be simply a solution of empyreumatic
resins, rich in carbon, in empyreumatic oil or oils, the nature of these substances
being left undecided. The late Baron von Reichenbach was the first who seriously
investigated the nature of tar, and the result was the discovery of paraffin and
of eupion, a very volatile liquid, highly inflammable, and found to boil at 47° to 169º,
consequently a mixture of various substances. Notwithstanding the high merits of
Reichenbach's researches, the constitution of tar was not fully elucidated. In
an industrial point of view tar has many important applications, especially for the
preparation of illuminating materials; for by a rectifying and fractioned distillation,
tar yields paraffin and paraffin oils, when the heavy oils and acids have been
previously separated. Paraffin oils-met with in the trade under various names,
such as solar oil, photogen oil, ligroine oil, &c.—are very similar to petroleum oils,
and consist like them of carbon and hydrogen, and are, when thoroughly rectified,
almost colourless and free from smell.
The mineral oils now met with in commerce are distinguished as:-Photogen,
prepared in Saxony, and consisting of a mixture of oils boiling between 100° and
300°. It is a colourless, very mobile fluid, exhibiting a characteristic ethereal smell,
and a sp. gr. of o·800 to 0·810; but the sp. gr. of its constituent oils varies from 0.76 to
086. Formerly there were met with in the trade light photogens of a sp. gr. of 078,
consisting chiefly of a so-called essence, of 0.72 sp. gr. and boiling below 60°; but this
oil was found to be too inflammable, and is now used as benzoline (also known as
naphtha, ligroine, Canada oil, &c.) in the sponge-lamps, and for other purposes.
Solar oil, or German petroleum, is a colourless or faintly yellow-coloured fluid of
about the same consistency as colza oil, and of a sp. gr. of 0·830 to 0832. The
boiling-point lies between 255° and 350°; cooled to -10° it should not deposit
paraffin, while its vapour is not inflammable below 100°. Pyrogen is a kind of
paraffin oil invented by Breitenlohner and prepared from residues of crude oils which
contain carbolic acid, paraffin, and other substances, and exhibit a sp. gr. of 0.895
to 0˚945; these materials, which accumulate in tar-works, are converted into pyrogen
by a process presently to be described, yielding a light straw-yellow oil of 0.825 to
0*845 sp. gr. Engine-oil, or lubricating oil, also known as Vulcan oil, is a thickly
fluid oil imported in large quantities from the United States, and which deposits,
when submitted to cold, a large quantity of crystals of paraffin. This oil is obtained
largely in the paraffin oil and petroleum-refining works. According to A. Ott's
account, the American lubricating oil is not obtained by distillation, but simply by
defecating a specifically heavy native petroleum with charcoal so as to eliminate
the colour. This lubricating oil is sometimes mixed with a certain percentage of
vegetable or animal fats. The oil is largely used for lubricating cotton-spinning
machinery, but notwithstanding its extensive employment, the production far exceeds
694
CHEMICAL TECHNOLOGY.
the consumption; it should be as much as possible re-converted into paraffin oil and
pyrogen. In America and on the Continent a large quantity is employed for
making gas.
Preparation of Mineral Oil.
The manufacture of these oils is a collateral industry with the
manufacture of paraffin. The products of the distillation of tar are first treated with
a solution of caustic soda. This operation aims at the removal of carbolic and acetic
(pyroligneous) acid compounds, which impart to the oil a disagreeable odour and
dark colour. The quantity of soda to be used may vary from 5 to 6 or even 20 per
cent, and the operation requires, in some instances, the aid of heat for about two
hours, while in others, again, the end is attained in two minutes and at the ordinary
temperature of the atmosphere. The mixture of soda ley and other substances is then
run into a large tank for the purpose of depositing the soda ley and combined com-
pounds, which, when settled, are run off, and the oil washed with water until it has
become free from alkali. The oil is next treated with sulphuric acid of 17 sp. gr.,
the quantity of which may vary from 5 to 25 per cent, while the duration of the
operation may vary from one minute to three hours. The treatment with sulphuric
acid greatly influences the quality of the oil, because it might happen that, by this
treatment, oils originally free from sulphur would become impregnated therewith,
in consequence of the fact that the more volatile portions of these oils are essentially
mixtures of aldehydes and ketones, bodies which readily combine with sulphurous
acid. The mixture of oil and sulphuric acid is run into a tank for the purpose of
depositing the specifically heavier portions of the liquid; the supernatant lighter
oil is afterwards tapped off, and washed with plenty of water, then with weak caustic
soda ley, being finally rectified by distillation. According to H. Vohl, paraffin oils are
sometimes bleached with hydrofluoric acid, whereby fluorine compounds are stated
to be formed, which, on burning the oil, give off noxious vapours. The alkaline and
acid liquors used in the operation are utilised in the following manner :-The crude
alkaline carbolic acid liquor is saturated with sulphuric acid, and crude carbolic
acid obtained. The latter is used for various purposes, among which are the
creosoting of timber, for disinfecting, &c.; or it is used for preparing pyrogen by
causing the vapours to pass through a red-hot tube, the condensing product being,
after treatment with soda ley and sulphuric acid, as well fitted for burning in lamps
as paraffin oil. Perutz submits the alkaline liquid containing carbolate of soda to
distillation in an iron still, pushing the operation on to dryness, and obtaining a
mixture of carbolic acid with light fluid hydrocarbons. If it is desired to prepare pure
carbolic acid, the liquid which comes over between 140° and 240° is separately
collected and treated in the ordinary manner. The residue left in the still, a mixture
of alkalies and coke, is calcined, the ash lixiviated, and the resulting liquor
causticised with lime. The sulphuric acid is employed for preparing sulphate of
iron. The rectification of the oils is performed in the ordinary manner. 100 parts
of peat tar yield of rectified products:-Sclar oil of 0·865 sp. gr., 26′4; photogen,
0*830 sp. gr., 20'7; paraffin, 23'3; crude carbolic acid (peat-tar creosote), 11'o
parts. 100 parts of Saxony brown-coal tar yield on an average :-Paraffin, 10 to 15
photogen, 16 to 27; solar oil, 34 to 38; creosote, 5 to 10; coke, 15 parts. The
commercial value of these articles fluctuates and depends on the demand and supply.
There were prepared in 1870 in Prussia from 5 millions of cwts. of brown-coal in
sixty-seven different works, 100,000 cwts. of paraffin and 250,000 cwts. of mineral on
paraffin oil.
ARTIFICIAL LIGHT
695
Petroleum.
T'etroleum Oil, and
its Occurrence.
Since the year 1859 native petroleum has become a most important
illuminating material. Petroleum was known to the ancients and was used by them
for various purposes. Greece obtained it from the Island of Zante; and the
petroleum from Agrigentum was burnt in lamps under the name of Sicilian oil.
The inspissated oil which was used under the name of mineral-pitch, or asphalte,
as a cement in building Babylon, was obtained from the neighbourhood of
the River Euphrates. Mineral pitch was used by the ancients for embalming
their dead, while it would appear that some black-coloured earthenware was
prepared with asphalte gently burnt in. In some parts of Central Asia large
quantities of inspissated petroleum occur, and the Dead Sea is especially a locality
where this substance is met with; hence the name of lacus asphaltites. In the Island of
Trinidad a large lake (Pitch Lake) occurs, filled with mineral pitch, which according
to the prevailing temperature is more or less soft. Petroleum is found in a great
many localities in different parts of the world—Amiano, near Parma, where this oil
has been used for burning in street lamps; Tegernsee, Bavaria, the oil-spring
having been known since 1430, but yielding only 42 litres annually; Neufchâtel,
Switzerland; Sehnde, near Hanover; Kleinschöppenstedt, Brunswick; Bechelbronn,
Alsace; Coalbrookdale, England; in the Pyrenees, and other portions of Spain and
France; also in Galicia. In far larger quantity petroleum occurs on the Caspian
seaboard at Apscheron, and especially on the Island of Tschellekan (394° N. lat.),
where more than 3400 sources are found, which yield annually 54,000 cwts. of
petroleum. At Rangoon, in Burmah, petroleum occurs in such large quantity that
annually 400,000 casks, weighing 6 cwts. each, are exported thence. But in no
country is petroleum found in such inexhaustible quantity as in the United States,
in a tract parallel to the Alleghany mountains, and extending from Lake Ontario
into the Valley of the Kanawha, in Virginia. The oil region includes the western
counties of the State of New York and Pennsylvania, and part of Ohio. The most
important petroleum-wells are at Mecca (Trumhall Co., Ohio), and at Titusville, Oil
City, Pithole City, Rouseville, McClintockville (Venungo Co., Pennsylvania, the
country of the Seneca Indians). This territory is termed Oil Creek. The wells are
bored to a depth of 22 to 23 feet: some wells are flowing wells, the oil being yielded
spontaneously; other wells are pumped. In Canada petroleum is met with in
different localities; as, for instance, at Gaspe, near the St. Lawrence, and in Lambton
Co.; also on the western portion of the peninsula formed by the lakes Huron, Erie,
and Ontario, in the Enniskillen district. California yields enormous quantities of
petroleum, which occurs also in many parts of South America, and in the islands of
Java, Borneo, and Timor.
Origin and Formation
of Petroleum.
As regards the origin and formation of petroleum, several hypo-
theses have been brought forward. According to some the formation of petroleum is
intimately connected with the occurrence of hydrocarbons met with—according to
the observations of Dumas, H. Rose, and Bunsen-in compressed condition in many
rock-salt deposits, from which they are set free either in the state of gas or as
naphtha, when the salt comes into contact with water or is broken up. The crack-
ling salt of the Wieliczka mine gives off marsh-gas; but by condensation CH4 might
yield homologous hydrocarbons, C6H14 and C-H16, which form the bulk of the vola-
tile portions of petroleum and paraffin, the composition of the latter varying between
696
CHEMICAL TECHNOLOGY.
C20H42 and C27H56. The association of petroleum, rock-salt, and combustible gases
is met with in a great many localities; as, for instance, in the Bavarian Alps, in Tus-
cany, Modena, Parma, the Carpathian mountains, on the Caspian Sea, in India, and
also in America. According to another view, petroleum is the product of the
slow decomposition of vegetable and animal matter, and results from a re-arrangement
of their elements. The American geologists suppose petroleum to be due to the dry
subterraneous distillation of accumulations of sea-plants and marine animals, and
that the petroleum is forced upwards by water, always present in the bored wells.
Of course the hypothesis involves the action of subterraneous heat at great depth,
which, according to existing observations on the increase of temperature in deep coal
mines, reaches the boiling temperature of water at 8000 feet. According to
Berthelot's view (1866), there should be formed subterraneously, from carbonic acid
and alkali metals, acetylides, which again should yield with aqueous vapour acetylen,
C₂H₂, which in its turn should be converted into petroleum and tar products.
Petroleum.
Refining of Crude Almost all the native petroleums require to be refined before they
can be used as illuminating material, the mode of refining differing according to the
nature and consistency of the oil. The oils met with at Apscheron, in Russia, and
in the neighbourhood of Baku, are nearly all colourless, and can be directly used for
burning in lamps after having been simply rectified by distillation. The Rangoon
oil contains so large a quantity of paraffin that it has at the ordinary temperature
the consistency of butter, and is therefore employed for extracting paraffin. The
native petroleums of many of the East Indian islands contain sulphur compounds,
and cannot therefore be burnt in lamps until they have been treated with caustic
soda and sulphuric acid, and rectified by distillation. The specific gravity of the
native petroleums met with in Canada and the United States varies very much;
that from Venungo Co., Pennsylvania, has a sp. gr. of o8, while oils in other
localities have a sp. gr. of 0.85 to 09. Galicia produces large quantities of native
petroleum, which is refined in some twenty-two works, situated near Boryslav and
Drohobicz; while a large quantity of paraffin oil is obtained as a by-product of the
distillation of paraffin from ozokerite. The lighter petroleums yield about 90 per
cent of photogen and solar oil, but the heavier kinds yield only 40 to 50 per cent, the
remainder being tar. The methods of refining native petroleums consist in treat-
ment with caustic soda, sulphuric acid, and finally fractioned distillation.
Constitution of Petroleum. As far as researches have been instituted, all the native
petroleums, irrespective of consistency and specific gravity, are mixtures of the
higher series of the homologous compounds, of which marsh-gas, CH4, is the first
term.* Amyl hydrogen, hydride of amyl, C5H12, boiling at 68°, and hydride of
caproyl, C6H14, boiling at 92°, constitute the more volatile portion of crude American
petroleum; these burn like marsh-gas with a faintly luminous flame.
stituents of the oil used in lamps are represented by the hydrocarbons C-H16 and
C12H26. The higher series of the marsh-gas group exhibit a butter-like consistency,
and are composed according to the formulæ C20H42 and C27H56, and belong to the
paraffins met with in petroleums.
* Ronalds proved in 1865 that the gases
essentially hydride of ethyl (C2H6), and
second and third terms of the above series.
those of Ronalds, for he found that the
mixture of the hydrides of propyl and
and hydride of ethyl,
The con-
evolved from crude American petroleum are
hydride of propyl (C3H8), which are the
with
The researches of Fouqué (1869) agree
gases evolved from petroleum are partly a
butyl, and partly a mixture of marsh-gas
ARTIFICIAL LIGHT.
697
Technology of Petroleum. According to an Act of Congress crude petroleum may not be
exported, owing to its high degree of inflammability, and a sample of every cask of
petroleum is to be tested. The oil ought not to give off inflammable vapours
(hydride of butyl below 38° C. = 100° F. In the United Kingdom, as elsewhere,
legislative measures have been taken in order to insure safety in the petroleum
trade. Consequently crude petroleum is chiefly refined by submitting it to fraction 1
distillation in order to separate from it the naphtha of 0715 sp. gr. (the benzoline of
the shops), which begins to boil at 60°. Wiederhold found that the naphtha yields
by fractional distillation :-
48.6 per cent of 0'70 sp. gr. boiling at
45'7
5'7
073
0*80
100° (a)
200° (b)
above 200° (c)
(c) is refined petroleum; (a) is too volatile for burning in lamps; (b) may be used in
properly constructed or sponge lamps. H. Vohl calls petroleum naphtha, canadol
or Canada oil, and applies it to the carburetting of illuminating gas; and also as a
solvent for caoutchouc, colophonium, mastic, dammar, copal, amber, shellac, oils
and fats, and for preserving anatomical preparations. The most volatile and lightest
portion of the naphtha (sp. gr. 065, boiling-point between 40° and 50°), known
as Sherwood oil, keroselen, petroleum ether, and rhigolen, is used as an anesthetic,
and applied externally in neuralgia. The less fluid petroleum oils are used as
lubricating oils under a variety of names-Globe oil, Vulcan oil, Phoenix oil, &c.
Crude petroleum is used as fuel in the Russian navy, in steamers on Caspian Sea,
and by the United States navy in some cases; it has been tried with success in
France as fuel for locomotive engines. Refined petroleum, the paraffin oil of
the London shops, is an opalescent fluid, somewhat yellow, boiling at 150°, not
miscible with water, alcohol, 'and wood-spirit; but readily miscible with ether, oil of
turpentine, and sulphide of carbon. Petroleum dissolves, especially when hot,
asphalte, elemi, Venice turpentine, and caoutchouc. As is well known, petroleum is
largely used for burning in lamps. The fluid known as kerosine, also used for
burning in lamps, has a sp. gr. of 0.78 to 0.825. Pitt oil seems to be identical, and
both are prepared from American petroleum by distillation. As a great confusion
exists in the names of the various distillation products of petroleum, we quote the
following particulars communicated by Kleinschmidt, of St. Louis :—
Oils distilling over below
""
at
37'7° sp. gr.
""
76.6°
137.0°
""
""
""
""
148.0°
183°-219°
""
•
""
0·60°
=
· 90°—97° B. — Rhigolin.
0'63-0.6180°-90° B.
80°-90° B. = Gasolin.
0·67—0·63 = 70°—80° B. — Naphtha.
0'73-0·67 = 60°-70° B. - Benzine.
= 40°—60° B.
0'78-0.82
- Kerosen.
In order to give
-
At higher temperatures paraffin and illuminating gas come over.
some idea of the enormous consumption of petroleum, it may be mentioned that the
imports in the German Customs Union,* amounted in 1866 to 918,954 cwts., and in
the first half-year of 1870 to 1,260,630 cwts.
* Embraces all the States of Germany, including the Grand Duchy of Luxembourg,
but no Austrian territory.
DIVISION VIII.
FUEL AND HEATING APPARATUS.
Fuel.
A. FUEL.
We understand by fuel such combustible materials as may be burnt with the
view of obtaining heat. Wood, peat, brown-coal, coal, anthracite, wood-charcoal,
peat-charcoal, coke, petroleum, combustible gases, such as carbonic oxide and
hydrocarbons, are fuel. Excepting the gases, all kinds of fuel are closely related to
each other as far as regards their origin, because fuel consists of cellulose or has
been formed from it. Native fuel, coal, wood, peat, anthracite, consists of carbon,
hydrogen, and oxygen, with larger or smaller quantity of ash (silica, alumina,
oxide of iron, alkalies, and alkaline earths), and as regards coals, also nitrogen,
sulphur, and phosphorus. Only hydrogen and carbon are combustible substances,
and these, therefore, determine the value of fuel by complete combustion, leaving
only ash, water, and carbonic acid. In wood-ash, carbonate of lime, in the ash
of mineral fuel, alumina, chiefly prevail. The effect of fuel depends upon :-
a. Combustibility.
b. Inflammability.
c. Calorific effect.
Combustibility. By combustibility is understood the greater or less readiness with
which fuel is kindled and continues to burn after having been kindled. This
property depends upon the composition of the fuel. A porous fuel kindles more
readily than a denser and more compact fuel. With regard to the relation
between combustibility and composition, it has been found that the more hydrogen a
fuel contains, the more readily it burns.
Inflammability, By the inflammability of fuel we understand its property of
bursting into flame when kindled; and as flame is due only to burning gases,
it is evident that the fuel containing most hydrogen is that which burns with
the most intense flame. In the case of coke, charcoal, and similar fuel, there can be
no flame other than that due to the formation of carbonic oxide owing to incomplete
combustion.
Calorific Effect.
The heat evolved by the complete combustion of fuel may be
measured in two different ways:—
1. As regards the quantity of heat evolved.
2. As regards the degree of temperature or intensity of the heat.
FUEL.
699
When the heat evolved is measured according to its quantity, we obtain the com-
bustive power, the specific or absolute calorific effect, of the fuel.
When the degree of heat is measured, the heating power or pyrometrical effect
of the fuel is ascertained. These two measurements together determine the
technical value of a combustible material. When the absolute calorific effect of a
fuel is referred to its cost, we determine its combustible value in the locality where it
is to be consumed.
Determination of
Combustive Power.
As we do not possess a particular measure for heat, we have,
when desirous of determining the quantity of heat yielded by a fuel, to institute
trials for the purpose of ascertaining the relative quantity of heat evolved by various
kinds of fuel, in order that by comparison we may find how much more heat is
evolved by one kind of fuel than by another. If the results thus obtained are
referred to a given bulk of the fuel experimented with, we obtain its specific calorific
effect; but if it be referred to a given weight, we obtain the absolute heating effect.
The following table exhibits the heat of combustion of several substances:
Hydrogen
Carbon (when completely burned and yielding car-
bonic acid)
Carbon (when yielding carbonic oxide)
Carbonic oxide
Marsh-gas
Elayl-gas
Crude petroleum
Ether
Alcohol
Wood-spirit
Oil of turpentine
Wax
·
•
•
•
•
•
·
•
•
yields 34,462 units of heat.
8080
99
""
2474
2403
""
13,063
""
11,857
""
II,773
""
9027
""
7183
""
5307
10,852
Wood
Wood-charcoal
• •
Peat
Compressed peat
Coal (anthracite)
Fat
•
•
·
10,496
>>
3600
99
7640
""
3000
""
""
4300
""
""
6000
""
9000
""
The absolute heating effect is determined according to the methods of Karmarsch
and of Berthier, or by elementary analysis.
Karmarsch's Evaporation
Method.
According to this method, applied by Dr. Playfair to English
coals, by Brix to Prussian, by Hartig and Stein to Saxony coals, the quantity
of water is determined which I lb. of the fuel will evaporate. According to
Regnault's formula, 652 units of heat are required to convert 1 kilo. of water at o°
into steam at 150°. Consequently—
Ι
I kilo. of carbon
= 12'4 kilos. of water
652
3+,462
can evaporate (8080)
(3,45
I kilo. of hydrogen
652
= 52'9
Experiments instituted by Dr. R. Wagner and others gave the following results :-
Red beech wood
3'78 kilos. of steam.
Zwickau caking coal
(6'0 per cent ash)
6'45
Bohemian coal from Nürschau
(19.0
5'58
Forge or smith's coals from Saarbrück (21′5
6'06
""
Ruhr coals
· (55
""
}
6'90
""
Cannel coal
(4:0
""
)
774
700
CHEMICAL TECHNOLOGY.
Berthier's Reduction
Method.
According to the law of Welter (which, however, is not confirmed
by experience, since recent researches have proved that, especially as regards
hydrogen, great deviations from the law exist), the quantities of heat evolved from
different kinds of fuel are relatively proportioned as the quantity of oxygen required
for their combustion. Assuming this to be correct, it is easy to ascertain the
absolute calorific effect of fuel if its composition is known, it being only required to
calculate the amount of oxygen which will effect the complete combustion of the
constituents of the fuel, careful account being taken of the oxygen it contains.
Practical experience has proved that Berthier's method yields results which, owing
to a constant error, are about one-ninth below the truth. The fuel to be tested
by this method is finely pulverised, and 1 grm. is mixed with a quantity of litharge
slightly more than required for the complete reduction to metallic lead, the minimum
quantity being 20, and the maximum 40 grms. This mixture is put into a fire-clay
crucible, and covered with a layer of 20 to 40 grms. of litharge. The crucible is
covered with another crucible and placed in a charcoal fire, where it is gradually
heated. When the contents of the crucible are fused the fire is increased for a few
minutes, and the crucible then cooled and broken up in order to obtain the
lead button, which is usually clean. This experiment has to be repeated with
the same kind of fuel two to three times, and the results should not differ from each
other more than o'r to o°2 grm. G. Forchhammer employs instead of litharge a mix-
ture of 3 parts of that oxide with 1 part of chloride of lead (consequently an oxy-
chloride of lead), which mixture previous to use is fused in a crucible, and
after cooling, pulverised. Pure wood-charcoal yields, when ignited with litharge or
with oxychloride of lead, 34 times its weight, and hydrogen 103.7 times its weight of
metallic lead; the hydrogen, therefore, rather more than three times as much as the
charcoal (carbon). By means of these data it is possible to estimate the absolute
calorific effect of any kind of fuel. As I part of carbon can by its combustion raise
the temperature of 8080 parts of water 1°, and as pure carbon yields, according
to Berthier, 34 parts of lead, every part of lead reduced by the fuel under examina-
8080
=237'6 units of heat. The application of Berthier's
に
​-)=237'6 units of heat.
tion is equivalent to 34
method is suited only to fuel which contains but a small quantity of hydrogen,
owing, as already observed, to the incorrectness of the law of Welter; and the
method is not applicable to fuel which becomes decomposed below red heat, as in this
case a portion of the gaseous matter evolved does not react upon the lead.
Example :— 1 grm. of compressed peat yields 17.76 grms. of lead, equal to 4124-5 units
of heat (since 237·6 × 17·76 = 41245); in other words, I kilo. of compressed peat yields
4124'5
6.3 kilos. of steam at 150° (since
652
Elementary Analysis.
=
6.3).
Although it has been proved that, as regards isomeric organic
bodies, the quantity of heat evolved by their combustion is not precisely proportional
to the quantity of oxygen* required for that combustion; and whereas the same
quantity of oxygen may yield, under different conditions, different quantities of heat,
it may still for all practical purposes be assumed, that as regards fuel of the same or
similar composition, the results of elementary analysis give the means of ascer-
* The composition of butyric acid and of acetic ether is the same, and is expressed by
the formula C4H8O2; yet the former yields on combustion 5647 units of heat, and
the latter 6292.
FUEL.
701
taining the calorific value of such fuel, provided the quantity of ash it contains
be first determined.
Example: :-1 grm. of compressed peat yielded on analysis o‘4698 grm. of carbon, and
0'0143 grm. hydrogen, equivalent to 4288.7 units of heat; because-
Carbon, 0*4698. 8080 =
Hydrogen, o‘0143. 34,462
3795'9
492.8
4288.7
The compressed peat contained—
3178
= 48.28 per cent water.
15.50 per cent of hygroscopic water, and
chemically combined water
Requiring for evaporation 255:3 heat-units; hence 4288′7—255′3 = 4033′4 units of heat.
The evaporating power of the compressed peat is therefore-
4033'4
652
=
6.19 kilos.
Stromeyer's Test. According to this method (1861) the fuel is ignited with oxide of copper,
the residue treated with hydrochloric acid and chloride of iron, whereby the latter is
partly reduced to protochloride, which is estimated by permanganate of potash. This
method yields very correct results, but is rather tedious.
Specific Calorific Effect. By specific calorific effect we understand the relative quantities
of heat evolved by equal bulks of different kinds of fuel. The specific calorific effect
is obtained by multiplying the absolute calorific effect by the specific gravity of the
fuel under trial.
Pyrometrical Calorific Effect. The pyrometrical calorific effect of a fuel is that indicated by
the temperature resulting from its complete combustion. As there does not exist any
pyrometer the indications of which are sufficiently reliable to be converted into
thermometrical degrees, we have to content ourselves for the present with an
approximative knowledge of the pyrometrical calorific effect as deduced from calcula-
tion. The pyrometrical effect of a fuel is equal to the heat-units of absolute heating
effect divided by the sum of the relative quantities by weight of its products of com-
bustion, each of these quantities by weight being multiplied by the corresponding
specific heat. The flame-yielding substances of the combustible matter of wood and
coals are, therefore, possessed of a lower pyrometrical effect than the non-inflam-
mable carbonised substances; while in reference to the absolute calorific effect, the
reverse obtains. This is due to the fact that the aqueous vapour formed by the
combustion of hydrogen takes up nearly four times as much heat to acquire a
certain temperature as does carbonic acid. The difference of pyrometrical effect of
fuels is far greater when they are burnt in oxygen than when they are burnt in air.
In order to approach in practice as nearly as possible the pyrometrical effect of
theory, it is necessary to burn all the carbon completely to carbonic acid, because
the temperature of its combustion to carbonic oxide amounts in air to only 1427°,
with 2480 units of heat; while if the carbon is burnt to carbonic acid the tem-
perature rises to 2458°, with 8080 heat-units. This complete combustion
may be
greatly promoted by proper treatment of the fuel; for instance, by keeping wood-
charcoal and coke in drying houses for a considerable time; by compressing peat to
increase its density; by preparing dense coke; heating the fuel previous to
introducing it into the furnace; by the use of heated air; and, lastly, by effecting
the combustion with compressed air.
The temperature of combustion is not only the product of the act of combustion
702
CHEMICAL TECHNOLOGY.
itself, but is essentially modified by the action of the active principles of the air
during the combustion. For complete combustion there are required :—
I
For 1 kilo. of carbon, at
15°, 97 cubic metres of air.
hydrogen, at 15º, 28′0
I
""
From these data we deduce the following quantities of air as required for the
complete combustion of the subjoined quantities of fuel:-
1 kilo. of wood (with 20 per cent of hygroscopic water)
5'2 cubic metres of air.
I
wood-charcoal ...
9'0
""
""
""
I
I
>>
pit-coal
coke
I
I
brown-coal
:
:
...
...
9'0
>>
:
:
:
9°0
"
"9
""
""
peat
...
...
73
= 73
In practice on the large scale these quantities of air require to be doubled in order
to obtain complete combustion.
of Heat.
Ι
Mechanical Equivalent The law of the conservation of energy teaches that heat can be
converted into labour, and inversely labour into heat; and that I unit of heat corre-
sponds to 424 metrical kilos. of labour. When heat does work it is dispersed in the
proportion of 424 units of work for 1 unit of heat; consequently the number 424.
expresses the mechanical equivalent of heat. By a foot-pound is understood the
force required to lift a weight of 1 pound 1 foot high. When instead of the pound
the kilo., and instead of the foot the metre are taken, the term kilogrammetre is
employed. 1 kilogrammetre = 6:37 Rhenish foot-pounds; 1 English foot-pound is
equal to 013825 kilogrammetre; 75 kilogrammetres = 542 English foot-pounds;
I horse-power (33,000 pounds lifted 1 foot high in 1 minute) is equal to 760390
kilogrammetres; I unit of heat per English pound is equal to ths of a French calorific
unit per kilo. The starting-point of the mechanical theory of heat is the axiom first
put forward by R. Clausius, that "in all cases in which heat does work a propor-
tional quantity of heat is dispersed or consumed, and inversely, by the performance
of an equal amount of work, the same quantity of heat can be regenerated."
Wood.
Wood.
Wood consists of several structurally different parts, which may be seen in
the transverse section of the wood, viz. :-The axis, or pith, a rather spongy,
regularly shaped tissue of parenchyma cells, which radiate towards the bark. This
is surrounded by the wood, consisting of an aggregation of bundles of vascular
tissue. The wood is surrounded by the bark, and between wood and bark is
deposited a very thin layer of cells filled with a turbid fluid, from which the further
growth of the tree proceeds by the gradual deposition of newly formed cells towards
both the wood and bark side. The bark is externally covered with a layer of
peculiarly shaped cells, which with the rind form the bark, covered by, in young
trees, epidermis. The pith-cells become obliterated in old trees, and leave a hollow
tube. The wood-cells become thicker by the deposition of cellulose, and as this
deposition increases in spring but decreases in summer and autumn, the effect is the
formation of the so-called annual rings, which are separated from each other by the
more compact and harder layers deposited in autumn. The wood-cells are internally
hollow, and are separated from each other by intercellular meatus, which contain
usually air, but sometimes also gum, resin, &c. The largest quantity of cellulose is
FUEL.
703
deposited in the wood and vascular cells, which essentially constitute the wood; the
wood is the harder and more compact, when in a given space the cellulose is
deposited in larger quantity, while in the so-called soft wood the walls of the cells
are thinner and their number smaller in a given space. The trees of which the
wood is used as fuel in Central Europe are :—
Leaved trees.
...
Oak (Quercus pedunculata and robur) fit for felling in 50- 60 years.
Red beech (Fagus sylvatica)
...
White beech (Carpinus betulus)
Elm tree (Ulmus campestris and effusa)
Ash tree (Fraxinus excelsior)
...
Alder (Alnus glutinosa and incana)
Birch (Betula alba and pubescens)
Coniferous trees.
White fir (Pinus abies)
...
Red fir (Scotch fir) (Pinus picea)
Common fir (Pinus sylvestris)...
Larch or larix tree (Pinus larix)
""
""
80-120
"
110-120
""
20-30
""
...
""
"
20-30
""
20-30
""
""
20- 25
""
50-60
""
19
""
70-80
80-100 ""
...
19
50-60 ""
Oak, beech, elm, birch, and ash, are hard woods. Sycamore, larch, and common
fir are half-hard; while poplar, lime tree, willows, are soft woods.
Constituents of Wood.
Wood essentially consists of woody fibre, small quantities of ash
and sap, and a variable quantity of hygroscopic water. Woody fibre, or cellulose,
constitutes about 96 per cent of dry wood, and is composed of C6H10O5; in 100 parts,
of-Carbon, 44‍45; hydrogen, 6'17; oxygen, 49°38. The vegetable sap consists
chiefly of water, but contains organic as well as inorganic matters, partly in
solution and partly suspended. The inorganic constituents of the sap (the ash left
after the incineration of the wood) are the same in all kinds of wood (see p. 123).
In practice it is assumed that wood leaves about 1 per cent of ash; but there is a
difference for certain portions of the tree, the trunk yielding about 123 per cent of
ash, the branches and knotty parts 134 and 154, and the roots 2:27 parts of ash
respectively.
The quantity of water contained in wood is generally larger in soft than in hard
woods. 100 parts of wood recently felled are found to contain on an average the
following quantities of water:-
Beech
Birch
...
...
18.6
30.8
Common fir ...
Red beech
Oak...
34.7
Alder
Oak (Quercus pedunculata)
...
35'4
Elm
:
:
:
White fir
...
37 I
Red fir
Air-dry wood may be considered as consisting of:-
39'7
39'7
41.6
44'5
45°2
40 parts of carbon (inclusive of 1 part ash).
40
""
""
chemically combined water.
40
""
hygroscopic water.
Wood dried at 130°-at which temperature all the hygroscopic water is driven
off-is composed of:-
50 parts of carbon (inclusive of 1 part ash).
50
""
""
chemically combined water.
704
CHEMICAL TECHNOLOGY.
Air-dry beech wood, as used for fuel, contains in 100 parts:-
Carbon
Hydrogen
Oxygen
...
·
Water and ash ..
:
...
39°10
4'90
36:00
20'00
100'00
Heating Value of Wood.
wood.
The heating value of soft wood is greater than that of hard
The wood from coniferous trees is, on account of the resin it contains, the
most readily inflammable. Birch wood is very similar to coniferous wood. Resinous
woods yield the longest flame. According to Winkler's researches on the heating
power of the various kinds of wood, it appears that for 1 klafter of red fir wood
might be substituted :—107 klafter of lime-tree wood, 0.94 klafter of common fir,
o`92 klafter of poplar, o'91 klafter of willow wood, 0·89 klafter of tanne, 0‘70 klafter
of beech, o'665 klafter of birch, 0·65 klafter of sycamore, 0·635 klafter of elm,
0'59 klafter of oak.* Scheerer assumes that the absolute calorific effect of the
different varieties of uniformly dried wood is the same, and that the specific caloric
effect of wood containing the same amount of hygroscopic moisture is proportionate
to the specific gravity. The pyrometric heating effect of kiln half-dried wood, with
10 per cent of moisture, is, according to Scheerer, = 1850°; while that of fully kiln-
dried wood is = 1950°. According to Péclet, the combustion of clean dry wood
evolves a temperature of 1683°, provided the oxygen of the air supplied for com-
bustion be all consumed, for if that is not the case, or only half the oxygen be
consumed, the temperature is only 960º, as happens in stoves of the ordinary
construction.
According to Brix's investigations, the evaporative power of different kinds of
wood is as subjoined:—
Dried.
Undried.
Per cent.
Per cent.
Fir wood, containing water, per cent
16.1
4'13
5 II
Elm wood,
""
147
3·84
467
Birch,
""
12.3
3972
4'39
Oak,
""
18.7
3'54
4'60
Red beech,
22.2
""
3:39
463
White beech,
""
12.5
3'62
4:28
That is to say, 1 kilo. of fir wood, containing 16'1 per cent of water, evaporates
4*13 kilos. of water.
Wood Charcoal. Nearly all organic compounds become decomposed by heat, and leave
carbon if access of air is prevented. If the escape of gases and volatile vapours
evolved when wood is submitted to dry distillation is permitted, a residue is left
known as wood-charcoal Among the volatile products of this operation are gaseous
substances, such as carbonic acid, carbonic oxide, and marsh-gas, while the con-
densable portion of the volatile products consists of tar and an aqueous fluid. This
latter consists of crude pyroligneous (acetic) acid (see p. 469) and of wood-spirit.
The tar contains a large number of fluid and solid substances, among which are
paraffin, creosote (oxyphenate of methyl), oxyphenic and carbolic acids (that is to
say, true carbolic acid, cresylic acid, and phlorylic acid), and several hydrocarbons;
* A klafter is a cubical measure = 108 cubic feet.
FUEL
705
all these substances are combustible. The following diagram exhibits the chief
products of the dry distillation of wood:-
Acetylen.
Illuminating Elayl.
gas.
Carbonic oxide.
Carbonic acid.
a. Real wood.
Wood.
b. Hygroscopic B. Tar.
water.
Carbonisation of Wood.
Benzol.
Marsh-gas.
Naphthalin (?)
Hydrogen.
Benzol.
Oxyphenic acid.
Naphthalin (?)
Cresylic acid.
Paraffin.
Phlorylic acid.
Reten.
Empyreumatic resins.
Carbolic acid.
Creosote.
Aceton.
Propionic acid.
Wood spirit.
y. Pyroligneous (Acetic acid.
acid.
8. Wood charcoal.
Wood is carbonised chiefly for the purpose of concentrating the
fuel or combustible matter it contains, to obtain a more readily transportable
material, and for the purpose of
converting the wood into a fuel for
use in metallurgical and technical
processes in which wood, as such,
cannot be employed.
con-
Wood may be carbonised with
the sole view of making tar (Stock-
holm tar), or with that of making
wood-gas or charcoal. In the latter
case the wood is very frequently
carbonised in the forests where it is
felled, in heaps, pits, or ovens.
A regularly
Heaps. structed heap of blocks
of timber covered with a layer of earth
and charcoal-dust is formed, the wood
being placed vertically or horizon-
tally as regards the direction of
the axis of the heap. In the first
case the heap is termed a "stand-
ing," in the other a laid" heap.
The axis is a pole or several poles of
wood.
Carbonisation in
"
Construction of The building of the
the Heap. heap is commenced by
putting up the axis pole or poles.
Vertical heaps are, according to
their construction, distinguished in
Germany, as :-a. Wälsh heap, Fig.
301. b. Slavonian heap, Fig. 302.
c. Schwarten heap, Fig. 303.
The Walsh, or Italian heap (Fig.
301) is constructed with a hollow
central support of planks or stout
laths, kept apart from each other by
the balks, n. The heap contains
two or three layers of wood and is
conical in shape. The layer of earth
on the wood is termed the chemise.
resinous wood is placed for kindling the pile.
FIG. 301.

FIG. 302.
и

FIG. 303.

In the lower part of the hollow pole or shaft
46
706
CHEMICAL TECHNOLOGY.
The Slavonian heap (Fig. 302) is distinguished from the former by the fact that the
axis is a solid pole and by the channel, b, by means of which the wood is fired. A third
kind of vertical heap, termed the Schwarten, is in use in Norway, the name being derived
from the word "Schwarten," signifying irregular. Three of the larger logs form the
central pole, aa, round which light combustible material is placed for the purpose of
kindling the heap; while the blocks of wood are next built up. The horizontal heaps
have the outward appearance of the former, but the blocks of wood are placed horizontally
and radially. The pole or axis is a solid shaft, and air holes or channels are made in the
wood. In order to prevent the layer of earth which covers the heap falling in and choking
the progress of the smouldering fire, a layer of leaves and twigs is first placed on the
wood, and on that the earth, mixed with charcoal-dust. At first the heap of wood is not
quite covered with earth, an uncovered space of some 6 to 12 inches being left at the foot
of the heap for the purpose of admitting air. The layer of earth usually has a thickness
of 3 to 5 inches, but at the top it is thicker. In order to protect the heap from the effects
of strong wind, it is usual to put up what are termed wind-blinds, simply planks of wood
placed close together and supported by stout poles.
There are two methods in use for kindling or firing the heaps of wood:--1. Kindling at
the bottom, access to the centre of the heap being obtained by a channel, into which
ignited straw is introduced. 2. Ignition from the top, or roof, by throwing into the
central shaft ignited charcoal and wood-shavings.
Charcoal Burning. We have to distinguish three stages or phases in this operation :-
1. The sweating. 2. The full combustion., 3. The slow smouldering. In order that the
fire may spread through the heap, it requires at first a more plentiful supply of air, and
for that purpose the heap is left entirely uncovered, or at least left open at the bottom.
The first effect of the firing is that a large quantity of watery vapour and products of dry
distillation are formed within the heap, which becomes consequently wet, or begins to
sweat. During this time there is the risk of explosion of the mixture of air with hydro-
carbon gases and vapours, by which explosion the overthrow of the heap, or if not so
violent, a shaking of the covering layer of earth, may take place. It may happen, also,
that at this period the combustion becomes internally so active as to completely consume
more or less of the wood. Any holes which may be observed externally are at once filled
up with earth, grass, wet wood, clay, or any suitable material. When the vapours issuing
from the bottom of the heap become brighter in colour, complete ignition of the wood has
commenced, and it then becomes necessary to prevent the access of air by covering the
entire heap with earth mixed with charcoal-powder; this operation is termed the encom-
passing (umfassen) of the heap, which is left in that condition for three, four, or six days,
the high temperature being sufficient to complete the carbonisation of the wood without
further access of air. In order to insure the complete carbonisation of the outer portions
of the heap, the combustion must be carefully conducted from the top and centre out-
wards by partially removing the covering layer towards the bottom, and by making small
channels at various parts of the covering, an operation known as the slow smouldering or
burning off. When the smoke which issues from the channels becomes bright and blue-
coloured, the charcoal is well burnt, and therefore the channels and apertures are all
closed with earth, in order to extinguish the fire. In this condition the heap is left for
twenty-four hours. Then the layer of earth is raked off, and dry earth thrown on the
heap for the purpose of filling the insterstices between the still red-hot charcoal, which
becomes gradually extinguished. As soon as the heap is quite cold externally, it is once or
twice gently watered by means of a watering-pot, then broken up, and the charcoal taken out.
Carbonisation in Beds. This mode of charcoal-burning is in use in Southern Germany,
Russia, and Sweden, and is a continuous operation in so far as the wood is gradually
carbonised, fresh green wood being added while the charcoal is withdrawn. The wood is
sawn into logs and not hewn to smaller blocks. The carbonisation-bed is a rectangular
wooden box, Figs. 304 and 305, the latter being a vertical section. The bed is, in
fact, a kind of kiln, of which a a are the poles and outer logs, h the covering layer of
earth, the hearth. While the slow combustion proceeds from b towards the
opposite end, the charcoal formed is gradually withdrawn. The burner, or workman, has
to see that the combustion proceeds regularly and keeps parallel to the sides of the bed.
Carbonisation in Ovens This process is an imitation in brickwork of the carbonising process
in heaps, because the carbonisation of the wood is effected by the
combustion of a portion of wood of the heap. The oven, or kiln, admits of a more perfect
collection of the products of the dry distillation-tar, pyroligneous acid, &c., but the
charcoal is not quite so good as that obtained by the preceding methods. The shape and
mode of construction of these kilns may vary, as will be presently seen.
or Kilus.
Fig. 306 exhibits one of the most simply constructed kilns. The wood is placed either
vertically or horizontally, being thrown into the kiln through the opening, a, or carried in
FUEL.
707
through the doorway, b, which also serves as the channel through which the firing of the
wood is performed. During the ignition all the apertures of the kiln are closed with
brickwork, with the exception of a small opening at b and at a. The small apertures seen
at the top of the kiln are intended for the escape of the smoke.
α
BO
D
FIG. 304.

In the kiln exhibited at Fig. 307, the doorways, a and b, are intended for the intro-
duction of the wood, and also for withdrawing the charcoal. ccc are draught-holes
provided with plugs. The iron pipe, d, is intended for carrying off the volatile products of
FIG. 305.
Ъ

a
>
the dry distillation. During the operation a and b are closed with brickwork or with
tightly-fitting iron doors lined with fire-clay slabs. The tar is collected in a reservoir.
Below b a small aperture indicates the mouth or outer opening of the firing channel.
FIG. 306.

=
==
The kiln represented in Fig. 308, in vertical section, is constructed for the admission of
air through the ash-pit, e, and fire-bars, r; the wood is introduced through a and b; q is
the pipe for carrying off the volatile products.
708
CHEMICAL TECHNOLOGY.
Carbonisation of Wood
The carbonisation of wood is also effected in closed vessels :-1. Retorts.
in Ovens. 2. In tubes or cylinders, heated air, blast-furnace gases, or super-
heated steam being sometimes used for the purpose of carbonising the wood. As regards
the carbonisation of wood in retorts, this is effected by placing the wood in cast-iron
FIG. 307.

KEY
or fire-clay retorts, which are heated externally, and are provided with pipes for conveying
away the volatile products of the carbonisation, this process being carried on chiefly for
万
​FIG. 308.
obtaining tar or wood-gas. In the case of
tubular kilns, the firing of the wood is effected
by the aid of a series of iron tubes, placed in
the kiln and connected outside with a source
of heat as well as with a chimney-stalk. The
hot air and flame of a furnace are passed
through these tubes, or may be directly led
into the kiln, provided the hot air and flame
are deprived of their oxygen. Upon these
principles is constructed the kiln invented by
Schwarz, and known as the Swedish kiln, of
which Fig. 309 exhibits a vertical section. b is
the carbonisation space enclosed by the brick-
work, a. Through the apertures, cc, the hot
air is admitted which effects the carbonisation.
The liquid products of the dry distillation are
collected on the sloping floor of the kiln and
conveyed by means of the syphon-tubes, ee,
into the tar-vessels, ff. The vapours of the

FIG. 309.

ן:
h
g
h
f
vola tile fluids (pyroligneous acid, wood-spirit, &c.), pass through the tubes, gg, into the
condensing vessels, h h, which are connected with a high chimney (see í, Fig. 310), to aid
FUEL.
709
the draught of the apparatus. The openings, dd, serve for the introduction of the wood.
There are no fire-bars in the hearth of this kiln.
The carbonisation of wood with the view of producing tar is best effected by the method
in general use in Russia, of which Hessel has given (1861) the following description.
The wood, generally of coniferous trees, is cut up with an axe, being distinguished as
FIG. 310.

Brawican and Luczina; the former wood from the trunk of the trees, the latter the
knotty roots. The wood is heaped up on a plot of ground, Fig. 311, which is somewhat
elevated above the level of the soil, and is funnel-shaped, the whole being constructed of
clay and lined with roofing-tiles, on which the tar collects and flows off into a vessel
placed in the vault, as exhibited in the cut. The wood is heaped in six to eight layers,
and is first covered with hay or dung, next with a layer of a few inches in thickness of
sand or earth. The wood in the heap is ignited at the bottom, where forty to fifty
FIG. 311.

apertures are left in the covering, these apertures being closed with wet sand as soon as
the combustion of the wood becomes active, and has spread through the whole heap.
After about six days' smouldering, the top of the heap falls in and a strong flame bursts
out. After ten to twelve days the tar begins to collect and is removed daily. The
smouldering of the wood continues for three to four weeks; the quantity of charcoal
obtained is very small. According to Thenius, wood-tar is obtained by a similar process
in Lower Austria from the wood of the black fir, which does not yield turpentine; but in
Bohemia a very resinous wood is used for tar-making. 100 parts of fir wood yield in
Russia 17.6 parts of tar and 23.3 parts of charcoal.
Since the year 1853 there has been in use in Sweden an apparatus for the distillation of
tar from wood, known as a thermo-boiler. According to Hessel's description, this
apparatus consists of a boiler-shaped iron vessel, A, Fig. 312, of about 8 cubic metres
capacity, and fitted with a man-hole for introducing the wood. This vessel is heated by a
fire at a, and the flues, bb. In order to heat the wood rapidly to 100°, a jet of steam is
710
CHEMICAL TECHNOLOGY.
The
forced into the vessel through e. The tar which might collect and condense in the vossel
is carried off by the aid of the pipe c to B, while the vapours of tar and other volatile
products are conveyed through d into B'. The matter there condensed flows through
h to B, while the more volatile products are rendered liquid in the condenser, c.
combustible gases are returned to the fireplace. In addition to tar, there are, at the
outset of the operation, also obtained oil of turpentine and pyroligneous acid. The
charcoal, which is extinguished by means of steam, is removed from the boiler by the
opening a. According to an investigation by Thenius (1865), with the view of ascertaining
whether the tar obtained in making wood-gas is equally fitted for naval purposes and for
boiling down to pitch as the tar obtained by other methods, it was found that such is not
the case.
This agrees with Dr. Owden's researches, made at his extensive acetic acid and
wood-spirit works at Sunderland, where the tar obtained is burnt, or used with lime and
FIG. 312.

d
f
h
fire-clay for making a kind of asphalte. Owing to the cheapness of coal in the locality,
the wood-charcoal is almost a waste product.
Properties of Charcoal. We distinguish between hard wood and soft wood charcoal, and
as regards the latter, again between charcoal obtained from leaf-bearing trees and
from coniferous trees. According to the degrees of carbonisation, we distinguish
between well-burnt black-coal and the so-called charbon roux, a more or less deep
brown torrified charcoal, often used in gunpowder making.
According to the size, charcoal is—at least abroad-divided into :
1. Coarse log-coal, the largest and most compact lumps.
2. Forge-coal, compact lumps about 4 inches diameter.
3. Coal from the centre of the heap, small lumps and porous.
4. Small coal, nut and pebble-sized lumps, mixed with dust.
5. Raw coal, or not well-burnt lumps.
As regards the yield of charcoal by bulk, this may be referred either to the real
volume of the mass, after deduction of interstices present in the heap, or to the
apparent volume without that deduction being made. We can compare :—
a. The apparent volume of the wood with the apparent volume of the charcoal.
b. The real volume of the wood with the real volume of the charcoal.
c. The real volume of the wood with the apparent volume of the charcoal.
The first method may be called the production according to the apparent
volume (I.); the second, the yield according to the real volume (II.); the third, the
yield according to both volumes (III.) :—
FUEL.
711
Method (I.) gives the following results:—
Oak wood
...
Red beech wood ...
Birch wood ...
...
Dwarf beech wood (as grown for hedges abroad)
Fir wood
718-74.3 per cent charcoal.
""
73.0
99
68.5
99
""
57°2
""
63.6
According to the real volume (II.) the average of several experiments gave a yield
of 476 per cent. According to both volumes (III.), the following results were
obtained at Eisleben :-
Oak wood
...
Weight.
Apparent
volume.
Both
volumes.
21.3 per cent 718 per cent 987 per cent
Red beech wood
Birch wood
...
...
22.7
73'0
""
20°9
99
""
68.5
20'6
57°2
25'0
""
63.6
Dwarf beech wood
Fir wood
Composition of Wood-
Charcoal.
100'4
""
942 ""
78.6
;;
87.2
""
وو
Omitting the small quantities of hydrogen and oxygen present in
charcoal, its average composition in air-dry state is the following:-
Carbon
Hygroscopic water
Ash...
:
85 per cent
I2 ""
3
Combustibility and
Heating Effect.
The combustibility of freshly burnt charcoal is very great, for it
continues to burn, with proper access of air, when once ignited; but as charcoal
does not contain any volatile combustible matter, it requires a great heat to become
ignited, more especially as it is a very bad conductor of heat.
The heating effect of various kinds of wood-charcoal is shown by the figures of the
subjoined table, the heating effect of carbon being taken as the unit:-
| | | |
33'57
33°51
33'74
32.40
32.79
33953
33'49
33.71
2450
Pyrom.
I part of
charcoal re-
duces of
lead.
I part of
charcoal
On an average 75°7 parts. heats water
from oº-
100°.
Well-burnt charcoal, air-dry
Well-burnt charcoal, quite dry
0'97
0.84
Birch wood
""
""
Ash wood
33
Red beech wood,,
Red fir wood
Sycamore wood
""
""
19
Oak wood
Alder wood
Linden wood
""
Fir tree
""
| | | | | | | | | Absol.
Specif.
2350
0'20
0'19
0.18
0'17
O'16
0'15
0'13
O'IO
Willow wood
The evaporative power of fir wood charcoal containing 10.5 per cent of water and
27 per cent of ash amounts to 675 kilos., viz., 1 kilo. of the charcoal evaporates
675 kilos. of water. This charcoal, in perfectly anhydrous state and with 3'02 per
cent ash, evaporates 7:59 kilos. of water.
Charbon Roux ; Torrified
Charcoal.
As the complete carbonisation of wood entails a loss of about
40 per cent of fuel, it has been recently tried to prepare a kind of charcoal exhibiting a
brown-black colour, and obtained from wood by torrifying rather than by carbonising
712
CHEMICAL TECHNOLOGY.
it, experience having shown that such a charcoal is obtained when the air-dry
wood has lost by torrifying some 60 to 70 per cent of its weight. This kind of char-
coal is intermediate to real black charcoal and kiln-dried wood; it contains more
oxygen, is readily pulverised, but is less porous than either kiln-dried wood or
ordinary charcoal, than which it is far more inflammable, and is hence preferred in
gunpowder making. Charbon roux, or torrified charcoal, is a very useful and
important fuel for industrial and metallurgical purposes.
Freshly prepared torrified charcoal has the following composition :-
Carbon...
...
...
Chemically combined water
Ash
...
The composition of this charcoal after keeping is:
Carbon...
...
...
Chemically combined water
ļ
74'0 per cent
24'5
1'5 "" ""
66.5 per cent.
22'0
Hygroscopic water
Ash
...
""
ΙΟΟ
39
1'5
Roasted Wood; The Association for Promoting Chemical Industry at Mains prepares an
Bois Roux. intermediate product to wood and torrified charcoal, to which the name
red wood (roasted wood, bois roux) is given. It is made from beech wood, and is the by-
product of the preparation of acetic acid and creosote. It has all the external appearances
of wood, but the colour, which is deep brown. It is highly inflammable, and consists on
an average of :--
Carbon
Hydrogen
Ash
Water (moisture or constitutional?)
Oxygen
52.65 per cent
5.78
0'43
4'49
36.64
According to R. Fresenius's researches, the evaporative power of air-dry beech wood is
to that of bois roux as 54°32: 100.
Peat.
Peat.
This is the product of the spontaneous decay of vegetable matter, more
especially of marsh plants, mixed with various mineral matters, sand, clay, marl,
lime, iron pyrites, iron ochre, &c. Peat is especially formed in places where shallow,
stagnant pools of water abound, in which the plants grow, while at the same time
the peat is precluded access of air. The following plants are chiefly met with in peat
bogs and form the peat:-Eriophorum, Erica, Calluna, Ledum palustre, Hypnum,
and also Sphagnum, a plant especially fitted for the formation of peat, because
it never wholly dies, but continues to vegetate towards the surface of the water or
bog, while the older parts decay.
The different qualities of peat are partly due to the plants from which the peat is
formed, but chiefly to the more or less complete decay these plants have undergone,
to the mineral substances mixed with the peat, and to the compression to which
it has been submitted by the weight of other mineral materials deposited upon
it. Abroad, and in countries where peat abounds, several varieties are dis-
tinguished, such as-1. Moor peat, chiefly derived from kinds of Sphagnum, and
found in several parts of the United Kingdom as very young peat-for instance, at
Aldershot, and on moor lands. 2. Heath peat, in Holland known as plaggenturf, is
the surface soil of heather-growing places. 3. Meadow-land peat, decayed coarse
FUEL.
713
grass mixed with a soft subsoil. 4. Wood or forest peat, met with in forests,
and formed by the decayed wood, leaves, &c. 5. Marine peat, formed by the decay
of sea plants, various kinds of Fucus, &c.
Peat is directly obtained by simply cutting it with a spade from the surface of the
soil, either with or without the necessity of first removing a layer of other soil,
while some peat can be obtained only by dredging for it under water. In the
latter case a mud is dredged up which (as happens in Holland, where the land peat is
known as hoog veen, while the peat from under water is termed laag veen), has to be
dried gently in open air, and afterwards cut up in brick-shaped lumps, and
further air-dried. Peat is often artificially compressed for the purpose of obtaining
a more compact fuel. The quantity of water contained in freshly dug peat is very
large, and by keeping this peat in dry situations it may lose 45 per cent of its
original weight. Assuming the organic matter of peat to consist of—
Carbon ...
Hydrogen
Water
:
The best solid air-dry peat consists of—
or of—
Solid peat mass (inclusive of ash)
Hygroscopic water
Carbon
Hydrogen
...
Chemically combined water
Hygroscopic water
...
...
:
...
60 per cent.
""
2
38
""
...
...
75 per cent.
25
""
45'0 per cent.
I'5
28.5
25'5
""
The following analyses exhibit the composition of peat-ash, which is characterised
by containing a far larger quantity of phosphoric acid than wood-ash.
According to E. Wolff, two kinds of peat-ash from the Mark (a and b), and another
from South Bavaria (c, analysed by Dr. Wagner) contain:-
Lime
Alumina
a.
b.
15*25 20'00
...
Oxide of iron
:
:
20'50 47'00
5'50
7'59
Silica
41'00
13.50
Phosphate of calcium and gypsum
3'10
2.60
Alkali, phosphoric)
C.
18:37
45'45
7.46
20.17
acid, sulphuric 8:55
acid, &c.
Drying Peat. The use of peat as fuel and its value as such depend in a great measure
upon the quantity of water and the mineral substances it contains. Peat may be
more or less dried:
1. By exposure in stacks in open air, or better in sheds where the peat is protected
from rain, but where a free circulation of air obtains. Air-dried peat contains 25 per
cent water.
2. By artificial heat, kiln drying at 100° or 120°, in kilns or stoves heated by a distinct
fire-place, or by waste heat from other operations.
3. By compressing peat. The compression has the following advantages:-a. Ren-
dering the peat more compact and thus increasing its pyrometric effect. t. Lessening its
bulk, and consequently lessening the cost of transport.by water, in which mode of trans-
port the cost is calculated by bulk or cubic measurement. c. The compression aids
714
CHEMICAL TECHNOLOGY.
the drying. The operation of compressing freshly dug peat, simple as it appears, has been
found in practice to be accompanied with difficulties which hitherto have not been, and
are not likely to be, overcome, for several reasons, among which is the fact that peat, as a
heterogeneous material, cannot be dealt with satisfactorily by compression. But a step in
the right direction towards the utilisation of the enormous masses of peat soil has been
made, by submitting the soil first to a kind of grinding lixiviation, which converts it into a
homogeneous mass, from which the greater part of the mineral matters can be eliminated.
In the works at Staltach, near Munich, the following process has been introduced
by Weber for preparing peat. The peaty material having been brought from the moor in
lumps is put into a kind of pug-mill moved by steam-power, and which reduces the peaty
substance to a uniform paste. This paste is moulded, compressed, and dried in a stove.
Schlickeysen has invented a machine of improved construction; in its application
it is unnecessary to pour any water on the peaty material, consequently the drying pro-
cess is less tedious and expensive. Dr. Versmann's peat-preparing machine consists
chiefly of a funnel-shaped stout sheet-iron vessel provided with small holes on its
periphery and internally fitted with an iron core-piece, which bears cutters fastened
spirally on its surface. By the action of these cutters the peaty matter is reduced to
a pulp, and in that state issues from the holes, while any coarse particles, such as pieces
of root, vegetables, &c., are discharged at the lower opening of the funnel-shaped
iron vessel. On the Haspel moor peat bog situated between Augsburg and Munich,
there has been in use up to the year 1856 a peat-preparing machine, originally invented
by Exter, at Munich, and consisting essentially of solid iron cylinders, provided with
strong teeth 6 centims. long, and arranged in the same manner as obtains in bone-
crushing mills. The peaty material is reduced with the aid of water to a pulp, which
is next pressed, moulded, and dried. The unreduced vegetable matter and roots are
separated from the peaty mass by the machine. Challeton's peat-preparing machine,
invented in 1824, and worked at Montanger, near Corbeil, Seine et Oise, France, consists
of a set of cylinders, 13 metres in length, and fitted with cutters. The peaty mass is
first cut into shreds and is next transferred to another portion of the machinery, in the
particulars of its construction very similar to a coffee-mill. With the assistance of some
water the peaty material is converted into a pulp, which is next lixiviated, and thus
deprived of mineral impurities. The thin, pasty, peaty mass is run into a large tank or
pit dug in the soil, and left there until it has acquired sufficient consistency to be moulded.
This mode of treating peaty matter has been employed at Rheims and St. Jean on
the Bieler Lake, Switzerland. By Challeton's process--100 cwts. of peaty material
(veen)* yield 14 to 15 cwts. of peat, containing about seven-eighths less ash than in
natural state.
It is evident that a process of lixiviation, however suitable in regard to its application to
peaty matter, is, in a certain sense, an irrational mode of treating a substance which has
to be again dried thoroughly, and which, even after being submitted to the several
operations, is not a fuel equal to coal. It is, therefore, a very great improvement in
the utilisation of peat-soil that the peaty matter should be treated in a different manner,
or by the so-called dry compression process, as carried out by Gwynne and Exter.
According to this method the peaty mass is first deprived of its natural excess of water by
means of a hydro-extractor; next pulped, and this pulp dried by artificial means; the
material obtained is ground to powder, which is finally moulded with the aid of strong
pressure and the simultaneous application of heat. The peat thus prepared is of a deep
brown-black, a hard, stone-like material, excellently suited for use as fuel, especially
for manufacturing and metallurgical purposes. Another process of peat preparation con-
sists in first cutting and drying the peat in air. The air-dried peat is ground to a coarse
powder and then dried in a stove. The dried peat is moulded and pressed by means of an
eccentric press, heat (50° to 60°) being simultaneously applied. Peats from the Kolber
moor (a), and from Haspel moor (b), thus prepared, were found to contain in 100 parts:-
b.
Ash
Water
a.
4'21
8.34
15'50
15'50
Carbon
46'98
49.82
Hydrogen
4'96
4'35
Nitrogen
0.72
Oxygen
27.63
26.99
100'00
100'00
* There is no word in English equivalent to the Dutch Veen, a term applicable to all
soils which consist either entirely or chiefly of peaty matter. There is no equivalent
term also in German, but there is in the Danish and Russian languages.
FUEL.
715
Heating Effect of Peat.
The combustibility and inflammability of peat are, owing to the
large quantity of ash and water it contains, less than that of wood.
According to Karmarsch the absolute heating effect of:-
100 kilos. of yellow peat
94'6 kilos. of air-dry fir wood.
100
brown
""
107.6
100
hard
**
19
104'0
100
pitch
110'7
""
""
100 cubic metres of yellow peat
33.2 cubic metres of fir wood.
100
brown
100
hard
100
pitch
89.7
144'6
184'3
""
""
These results agree with those obtained by Brix. Karsten states that for evapora-
tive and boiling operations-
21 parts by weight of peat are = 1 part by weight of coal
4 parts by volume
= 1 part by volume
""
According to Vogel, the evaporative effect of peat is the following:-
Water.
Air-dry fibre
...
10 per cent
Machine-made peat.
...
Compressed peat
12-15
10-15
""
""
Evaporative effect.
5'5 kilos.
5'0-5'5",
5.8-6.0
""
New Method of During the last twenty years peat has been employed for the preparation of
Utilising Peat. paraffin, peat-creosote, and paraffin oil. As far back as the year 1849, Reece
tried to utilise Irish peat in the preparation of paraffin; and the experiments of
Drs. Kane and O'Sullivan proved that i ton of Irish peat yielded about 136 kilos. of
paraffin, 9 litres of paraffin oil, and 454 litres of lubricating oil. According to Wagen-
mann, the peat of the Isle of Lewis, Scotland, yields from 6 to 8 per cent tar, and
this again yields 2 per cent of photogen or paraffin oil, 1.5 per cent of solar oil, and 0′33
per cent of paraffin.
Carbonised Peat.
Carbonised Peat.
In many parts of Germany, and of all countries where peat bogs
abound, the use of peat as fuel is out of all proportion to the enormous quantity of
material left untouched; this is due to the fact that peat is as fuel in many respects
a very inferior material. Its bulk in reference to its heating effect is very large; its
combustion evolves a very disagreeable odour ånd pungent smoke, so that peat
is therefore not suited for heating rooms. On this account peat is carbonised. As
peat varies greatly in composition, the carbonised peat or peat-coke also varies, and
the composition of the peat-coke may be represented as follows:—
Carbon
Hygroscopic moisture
Ash
...
Superior quality.
86
ΙΟ
4
Inferior quality.
34
ΙΟ
56
Nothing is known as to the absolute and specific calorific effect of peat-coke, since
no experiments have been instituted. Ordinary peat-coke appears to approximate
charcoal in its specific calorific effect, but peat-coke is otherwise inferior to charcoal
because it is less dense, and cannot on account of its dusty ash produce an intense
heat. Peat-coke is not suited for fuel in blast-furnaces or other metallurgical opera-
tions, but answers well for heating steam boilers, evaporating pans, and similar
716
CHEMICAL TECHNOLOGY.
apparatus. But peat-coke made from compressed peat is a highly valuable fuel for
metallurgical operations, so that it becomes a matter of importance to find a means of
compressing peat inexpensively. In Holland, peat, especially that known as spon
turf, or hoogeveensche turf, is very largely used for industrial purposes, and on
account of not containing sulphur is used at the Utrecht mint for melting silver and
gold.
Brown Coal.
Brown-Coal.
This mineral fuel is also the product of a peculiar decomposition of
wood, but the decay has in this instance been more complete. It is not easy to draw
a clear line of demarcation between brown-coal and coal, when only the properties of
these substances are to be considered. Therefore the palæontological and geological
relations have to be taken into account when it is required to estimate the value of a
fossil fuel. In general it may be said that any fossil coal of more recent date than
the chalk formation may be termed brown-coal; while all fossil coals found below
the chalk formation are really pit-coal. As the latter contain more nitrogen than the
former, this fact may be utilised in testing to distinguish between pit-coal and brown-
coal. Brown-coal, on being heated in a dry test-tube, yields fumes which exhibit an
acid reaction, because brown-coal is somewhat similar to cellulose; whereas, if the
same test be applied to pit-coal, ammoniacal fumes are given off (containing
ammonia, aniline, lepidin, &c.), which exhibit an alkaline reaction. When finely pul-
verised pit-coal is boiled for some time with a rather concentrated solution of caustic
potash, the fluid remains colourless; but when brown-coal is similarly treated,
the liquid becomes brown-coloured by the formation of humate of potash. This test
does not, however, apply to the brown-coal found in the tertiary formation of
the northern slope of the Alps. E. Richter and Hinrichs state, that when pit-coals
are dried at 115°, and caused to lose a very small quantity in weight, this loss disap-
pears again, in consequence of an oxidation which takes place; while if brown-coal
is so treated, the subsequent increase in weight is not observed.
According to the various degrees of decay, several kinds of brown-coal are
distinguished :—1. Fibrous brown-coal, fossil or bituminous wood, lignite, is similar
to wood, the structure of stem, branches, and roots being apparent. 2. Common
brown-coal forms compact brittle masses, exhibiting a conchoidal fracture. 3. Earthy
brown-coal is a mixture of brown-coal and earthy matter. In several parts of Ger-
many and the Austro-Hungarian.Empire, brown-coal of excellent quality is found,
especially suited for the purpose of preparing paraffin and paraffin oils.
Brown-coal is frequently found mixed with the rhombic variety of iron pyrites. When
that mineral and earthy matter predominate, there is formed what is termed alum-
shale, under which name, however, is also known a kind of clay mixed with bitumen
and iron pyrites. The average quantity of ash contained in brown-coals amounts to
5 to 10 per cent. The ash contains chiefly alumina, silica, lime, magnesia, oxides of
iron and manganese; while the quantity of hygroscopic moisture in freshly dug
brown-coal may amount to 50 per cent. The substance contains in air-dry state
20 per cent water, and the average composition of brown-coal may therefore
be quoted as:—
Carbon
Hydrogen.
...
Chemically combined water
Hygroscopic water
...
:
:
:
...
...
48-56 per cent.
I-2
>>
31-32
20
99
FUEL.
717
The combustibility of brown-coal is less than that of wood, while its inflamma-
bility varies between that of wood and pit-coal. The heating effect of brown-coal
is with-
Hygroscopic
water.
Per cent.
Ash.
Per cent.
Air-dry fibrous brown-coal, containing 20 and o
0*48
0'55
1800
20
""
"9
13
་
ΙΟ
""
0'43
earthy
conchoidal
Kiln-dried fibrous brown-coal
20
0.61
""
0'79
1975
20
ΙΟ
99
""
0'55
20
0
""
0.69
0.88
2050
20
10
""
""
0.62
20
O
0.61
""
20
ΙΟ
>>
";
""
0'55
""
earthy
20
""
O
0*76
""
""
""
20
IO
0.69
conchoidal
20
O
""
""
""
0.85
| | | | | |
2025
2125
2200
20
ΙΟ
""
0.76
Bohemian brown-coal
Bituminous wood
Earthy coal
Lump coal
It appears from this table that the absolute and pyrometric calorific effect of air-
dry brown-coal is more than twice that of kiln-dried wood; and this remark applies
to the specific calorific effect of brown-coal, which is more than twice that of the best
wood.
The evaporative effect of brown-ccal is the following:
Water.
28.7 per cent.
Ash.
10.6 per cent.
Evaporative effect.
5.84 kilos.
23°7
"9
3'9
5776
""
47°2
4.8
""
5'55
""
47'7
3°I
5:08
".
Brown-coal as Fuel.
Brown-coal is a less suitable fuel and its applications are far more
limited than those of pit-coal, for brown-coal cannot be used in those cases where a
caking coal is required. Brown-coal is useful as fuel for certain chemical operations-dis-
tillation, evaporation, &c.-and may be used for heating rooms in dwelling houses, when
burnt in well-constructed stoves. Earthy brown-coal is not well fitted for use as fuel,
unless it has first been lixiviated with water, moulded into bricks, compressed, and dried.
It has been found in practice that brown-coal freshly dug is a better fuel than brown-coal
which has been exposed to the air for some time, because by the combined action of air
and moisture, even when the material does not contain pyrites, a slow combustion takes
place, whereby the combustibility of the material is greatly impaired.
As already
observed, from brown-coal paraffin and paraffin oils may be extracted.
Pit-coal, or Coal.
Coal. Iron ores and coal are the most useful minerals, and the most important of all
inorganic products of nature. Without coals the industry of the world as now
existing would have been simply impossible. Coals supply heat and are a source of
power; and cheap coal is a most important incentive to extensive industry.
Coals are the mummified and carbonised remnants of an ancient flora belonging to
a former phase of existence of our globe; and they exist as a distinct geological for-
mation, which extends in some localities over an area of several square miles.
As regards the mode of formation of coal different opinions are current. The
Absol.
Specif.
Pyrom.
718
CHEMICAL TECHNOLOGY.
simplest view is that a peculiar kind of decay, aided by the internal heat of the
earth, and modified by the pressure of superincumbent rocks and sedimentary
deposits, has taken place among the plants, which have been gradually converted
into a more or less pure carbon. Hence anthracite is a nearly pure carbon; while
the different varieties of coal which contain bituminous and volatile matter are
less completely decayed. The hydrogen and oxygen escape in combination with
carbon as marsh-gas and carbonic acid and as petroleum. Anthracite must be viewed
as the final product of the slow process of decay through which brown-coal and pit-
coal pass.
Cellulose
Peat from Vulcaire
Lignite
Earthy brown-coal
Coal (secondary formation)
(coal
Anthracite
...
}
Carbon.
Hydrogen. Oxygen.
52·65
5°25
42.10
50'44
5'96
33·60
66'96
5'27
27.76
74.20
5.89
19'90
76.18
5.64
18.07
90'50
5:05
4'40
92.85
3'95
3.19
The most important explored coal deposits in Europe are:-In England:* The
South Wales coal formation extending over an immense area; the Staffordshire and
Yorkshire coal basins, the latter of which stretches to the Durham and Northum-
berland basins, and these again to those met with in the Southern parts of Scotland.
2. In Belgium: The basin of the Maas, near Liège, and those of the Sambre and
of Mons. 3. In France: The basins of the Loire, of Valenciennes, of Creuzot and
Blanzy, of Aubin, of Alais. 4. In Germany: The Silesian coal basin, those of the
Saar, of the Ruhr, a tributary river of the Rhine, the basins near Zwickau and
Plauen, &c. 5. In Austria: the Bohemian coal basin at Pilsen, and those of
Brandau and Schlan. The largest of the European coal deposits or basins is very
small compared with those situated in North America. The largest of the American
deposits is that which stretches from near Lake Erie to the Tennessee river, through
the states of Pennsylvania, Virginia, Kentucky, Tennessee, and known as the
Apalachian coal field. The coal fields of Illinois and of Canada are not much
smaller.
Accessory Constituents
of Coal,
Iron pyrites, or mundic, as the pitmen term it, is in the tesseral
or in the rhombic shape, a very common accessory constituent of coal, which
by being impregnated with this material may not only become unfit for use in
certain operations, but is liable to crumble to dust, as is the case with many kinds of
the Welsh coals which are thoroughly incorporated with pyrites, because the pyrites
on coming into contact with air are oxidised and increase in bulk, forcing the
coal asunder. This oxidation may become so active as to give rise to spontaneous
combustion of the coal even in the seams. Galena, copper pyrites, and black-jack
(native black sulphuret of zinc), also occur occasionally in coal. Among the earthy
minerals, carbonate of lime, gypsum, heavy spar, clay, ironstone, and blackband (an
iron ore), are frequently met with.
Classification of Coals. Abroad coals are classified with respect to their behaviour under
combustion, as—1. Caking coals, which on having been reduced to powder and then
* The yield of coals in great Britain is annually increasing, for in 1860 it amounted to
So millions of tons; in 1868 to 104 millions; in 1869 to 108 millions; and in 1870 to 113
millions of tons.
FUEL.
719
ignited in a closed crucible to red heat, cake together. 2. Sintering coals, the
powder of which agglutinates without fusing. 3. Sandy coals, the powder of which
neither cakes nor agglutinates when ignited. In England coals are usually classified
as-1. Gas coal. 2. Household coal. 3. Steam coal.
Comparing the elementary composition of the coals with their chemical and
physical properties, it appears that caking coals contain a bitumen consisting of
carbon and hydrogen ready formed, or what is more likely formed at a high tem-
perature. The larger quantity of oxygen present in sintering coals causes less
bitumen to be formed; while in sandy coals a still smaller quantity of bitumen
is formed. The most recent researches on coal disprove the opinion, that with
an increase of the quantity of oxygen the caking should decrease, and that,
consequently, the coals which contain the largest quantity of oxygen should be
sandy coals. Coals exhibiting almost the same elementary composition behave very
differently when exposed to heat.*
Anthracite.
This carbonaceous mineral is to be considered as the final product
of the process of decay which has converted plants into coal. Anthracite is found
in the metamorphic rocks deposited in seams between clayey slate and greywacke,
also between deposits of mica slate. Anthracite is amorphous and thereby distinguished
from graphite; it is deep black coloured, brittle, exhibits a conchoidal uneven
fracture, burns with a scarcely luminous flame, and without producing smoke.
It does not become soft in the fire, but frequently decrepitates.
Jacquelain's analysis of several anthracites led to the following results:-
From Swansea
Sablé
...
Vizille
Isère Department, France
Carbon. Hydrogen. Oxygen. Nitrogen. Ash.
90*58
3.60 3.81
0'29
I'72
87°22
2.49
1'08
2:31
6'90
94'09
1.85
""
285
I'90
94'00
I'49
0'58 4'00
Anthracite is an excellent fuel for many purposes, and yields, especially with the
blast, a very strong heat. It is therefore largely used in Wales in metallurgical
operations, for burning lime and bricks, and in stoves for household purposes.
In Pennsylvania, anthracite is met with and used largely in the reduction of iron
ores.
Caking Coal.
I
I
In addition to its behaviour under combustion, this coal is charac-
terised by its deep black colour, ready inflammability, and by yielding when heated
in closed vessels a compactly fused coke. Designating, with Fleck, the quantity per
cent of carbon in ash-free coaly matter as C, the free hydrogen as W₁, the combined
hydrogen as W, the oxygen and nitrogen as S; then (C+(W+W₁)+S=100).
W₁ is found by calculation on the supposition that 8 per cent oxygen holds in com-
bination 1 per cent of hydrogen; consequently W₁=§; and this deducted from the
total quantity of hydrogen, gives as difference the free hydrogen W. The caking
property of a coal is due to the proportion that upon 100 parts of carbon there should
not be less than 4 of hydrogen. Caking-coals are especially suited for gas manu-
facture, though Fleck designates as such, in the widest sense, all coals containing
upon 1000 parts of carbon at least 20 of combined hydrogen. But as the value of
such a gas-coal depends upon the free hydrogen, which with carbon will yield volatile
* E. Richters has recently described a method for the comparative determination of
different kinds of coal. See Dingler's Polyt. Journ., vol. 195, p. 72.
=3
720
CHEMICAL TECHNOLOGY.
hydrocarbons, for the purpose of rendering the flame luminous, coal containing upon
100 parts of carbon 2 parts of combined (or fixed) and 4 of free or disposable
hydrogen may be considered as the best gas coal and the strongest caking coal.
Because they contain a larger quantity of hydrogen than other kinds of coals,
caking coals are more readily inflammable and evolve the strongest flame. Strongly
caking coals, however, are not well suited for use as fuel by themselves, owing to the
fact that by the fusion, as it were, they undergo, they greatly impede access of
air at the open fire-bars. Caking-coal is an excellent fuel on the forge-hearth,
because by caking together it forms a receptacle for the blast from the bellows, and
increases the heating effect. The peculiar kind of small coal used by blacksmiths is
known in the French language as charbon de forge, houille maréchale, and is in
England termed smithy-coal.
Sandy-coal is the poorest quality. It contains much oxygen, suffers great
contraction when converted into coke, leaving a sandy, small coke. This kind of
coal contains less than 4 per cent of free hydrogen; it is used as fuel for burning
bricks, lime, and for similar purposes where a cheap fuel is required.
Sintering-coal exhibits an iron-grey colour, is frequently very lustrous, far less
readily ignited than caking-coal, often contains much pyrites, and is employed where
a strong and lasting heat is required. It is, therefore, used industrially on the large
scale as a steam coal, as fuel for metallurgical purposes, &c. This kind of coal
yields only a small quantity of gas, and when burnt for coke in coke-ovens it is
scarcely changed in bulk, yielding a loose somewhat porous coke. 100 parts of the
combustible portion of this coal contain less than 4 parts of free and less than 2 parts
of combined hydrogen. Some kinds of anthracite belong to this class of coal; but
the real anthracite is to be viewed as a native coke produced in a peculiar manner,
not comparable with the process of coke-making as carried on industrially.
The physical properties of coal may be judged from the quantity of hydrogen
* contained, and we find that :-
Caking coals
Gas and caking coals
Gas and sandy coals
Sintering coals
contain upon 100 C., more than 4 W1, less than 2 W.
100 C.,
100 C., less than 4 W1,
4 W1, more than 2 W.
2 W.
""
100 C.,
4 W1, less than 2 W.
Assuming coals to contain on an average 5 per cent of hygroscopic and 5 per cent
of chemically combined water, the average composition is:-
Carbon
Hydrogen
...
Chemically combined water and hygroscopic water
Ash...
:
69-78
3-4
13-23
3
The composition of the ash varies, greatly depending, not only as regards quality,
but also the quantity of the constituents, upon a variety of causes, among which the
geological age of the coal, the formation in which it is found, and others, have great
influence. The ash consists chiefly of an alumino-silicate, or of gypsum and
sulphuret of iron, mixed with larger or smaller quantities of lime, magnesia, carbonic
acid, oxides of iron and manganese, with very small quantities of chlorine and
iodine. Ash which contains much alumina and little silica is infusible. Ash con-
taining much silica, but not any or only a small quantity of oxide of iron, sinters,
but does not fuse; but ash which contains oxide of iron and alkaline silicates readily
FUEL.
721
forms a slag, and may give rise to loss of fuel by enveloping the particles of coal. The
quantity of ash found by incinerating coal in a small crucible varies from 0'5 to 20
and 30 per cent. By washing coals, small coal especially, a portion of the mineral
matter may be eliminated.
Calorific Effect. The subjoined table exhibits for average coals the calorific effect,
specific gravity, and composition:-
Composition:-
Carbon
Hydrogen...
Chemically com-
bined water
Hygroscopic water
Anthracite.
Caking coal. Sintering coal.
Sandy Coal.
85
78
75
69
3
4
4
3
5
8 5 5
2 5 5
II
18
55 5
5
5
Ash
Calorific effect:-
Absolute
0*96
0'93
0.89
0'72
Specific
1'44
I'17
1'16
1'06
Pyrometric...
2350°
2300°
2250°
2100°
I part reduces lead
26-33
23-31
19-27
21-31
I part heats water
from 0°-100
60'5—74'7
52.87-20
44'06-16
50'0-71'0
Sp. gr.
1'41
I'13—126
1'13-1'30
2'05—1'34
It is assumed in practice that the heating effect of a good coal is very nearly that
of wood-charcoal, and twice that of dry wood. In smelting operations the heating
effect of coals is taken by bulk to that of wood by bulk as 5: 1, and by weight as
158. According to Karsten's researches:-
100 parts by bulk of coal in the reverberatory furnace = 700 parts by bulk of wood.
by weight
=250"
100
""
In boiling operations:-
100 volumes of coal
100 parts by weight of coal
peat.
Evaporative Effect
of Coals.
99
by weight of wood.
= 400 volumes peat.
= 400 volumes of wood
160 parts by weight of wood = 250 parts by weight of
This forms the most important industrial investigation which can
be made with coals. In order to ascertain the evaporative effect, we must know-
1. The quantity of hygroscopic water contained. 2. The quantity of ash or non-
combustible matter it contains. 3. The composition of the organic matter.
As Hartig's experiments have proved that the evaporative effect of the organic
matter of coal is the same for nearly all kinds of coal (= 8·04 to 8.30 kilos. of steam),
the evaporative effect of any given sample of coal can be ascertained by estimating
the quantity of water and ash it contains. According to W. Stein, the practical
evaporative effect on the large scale may be taken as equal to two-thirds of that
which has been calculated from the chemical composition of the coal. The practical
evaporative effect of the coals in use in Southern Germany is, according to laboratory
experiments and experiments made on the large scale, the following:-
47
722
CHEMICAL TECHNOLOGY.
Ash.
Practical
evaporative effect.
Ruhr coals,
I. quality
5'00
7'20
Zwickau black pitch-coal,
I.
6'06
...
6'45
II.
15'41
5.61
Bohemian coal,
I.
6.60
5.80
II.
6.90
4'90
III.
"}
"
10'30
4'20
21.50
6:06
I.
II.
6.30
2972
8:40
3.86
""
Saar coal,
Stockheim coal,
The average evaporative effect of the Hartley steam coals is 14 lbs. of water for
I lb. of coal.
Boghead Coal..
This mineral, also known as Torbane Hill coal, found in the neigh-
bourhood of Bathgate, a town situated between Edinburgh and Glasgow, belongs,
with the blattel-coal of Bohemia, to a peculiar fossil fauna, and is especially suited
for the manufacture of paraffin and oils, owing to the large quantity of bituminous
matter it contains. Boghead coal is now solely employed in the preparation of
paraffin and oils; and the supply, which is very limited, because the seam is almost
exhausted, has been secured by Mr. Young, of Bathgate Works.
100 parts of Boghead coal contain :-
Carbon...
Nitrogen
Hydrogen
Sulphur
Oxygen
Water
Ash
60°9
65°3
0'7
0'7
9'1
9'1
0'3
O'I
4'3
5'4
0'3
0'5
24'I
18.6
Boghead coal was formerly employed for gas-making, 1 ton yielding 15,000 cubic
feet of a highly illuminating and very durable gas. Many varieties of the Scotch
cannel-coals are suitable and are used for the preparation of paraffin and oils, and
have therefore so greatly increased in price that these coals—the Wemyss, Rigside,
and others—are now seldom employed for gas manufacture.
Petroleum as Fuel.
Petroleum as Fuel.
Native, as well as artificially prepared petroleum, is, under certain
conditions, a very valuable heating material. The sp. gr. of this oil varies, at o°,
from 0'786 to o‘923, while its coefficient of expansion for 1º varies from 0'00072 to
0'000868. The experiments as to the application of petroleum as fuel for marine
purposes in America have proved that petroleum is three times more efficient than
coal; and as the complete combustion of petroleum does not produce smoke, but
simply evolves carbonic acid and watery vapour, a tall chimney is not required.
Coals may be burned in marine boilers with the same effect, proved by a series of
experiments made about fifteen years ago, on the large scale, by the late Dr. Rich-
ardson, of Newcastle-upon-Tyne, in conjunction with Messrs. J. A. Longridge and Sir
William Armstrong. As petroleum contains 14 per cent of hydrogen, the condensa-
tion of the gases of combustion yields a large quantity of water which may serve for
FUEL.
723
feeding the boilers, while the heat thus set free may be employed for the purpose of
heating the feed-water. According to H. Deville, there is no difficulty in regulating
the supply of petroleum, and it is not necessary to heat it previously. According to
Fr. Storer, I kilo. of crude petroleum evaporates 10 36 kilos. of water, while 1 kilo.
of anthracite coal evaporates only 5'1 kilos. of water. The theoretical evaporative
effect of the purest petroleum is 18′06 kilos., as may be deduced from the percentage
composition of petroleum, viz. :-
C. 0.86
H
0°14
...
8080=6948
34,462=4824
11,772 units of heat;
I1,772
18'06 kilos.
652
I
The heating effect of different kinds of petroleum has been ascertained by
H. Deville (1866-1869) to be as follows:-
Heavy oil from West Virginia
Light oil from
Light oil from Pennsylvania
10,180 units of heat.
10,223
9,963
""
""
""
""
Heavy oil from Ohio
Oil from Java (Rembang)
:
10,399 ",
10,831
""
""
Oil from Java (Cheribon)
9,593 ""
""
Oil from Java (Soerabaya)
10,183
Petroleum from Schwabwiler (Alsace)...
10,458
99
Petroleum from East Galicia
10,005
Petroleum from West Galicia
10,235
Crude shale oil from Autun (France)...
9,950 ""
More recently, R. Foote, Wyse, Field, Aydon, H. Deville, Dorsett, and Blyth, have
constructed petroleum furnaces suitable for steam-boilers, which answer the purpose well.
Petroleum lamps are used abroad, instead of spirit-lamps, for domestic purposes, viz.,
heating tea- and coffee-urns, tea-kettles, &c.
Coke.
Coke.
By coke we generally understand carbonised coal; and in England there is
no other description of coke than oven- and gas-coke, referring of course to the mode
of production.
Coke is prepared for the purposes:-1. Of increasing or rather concentrating the
quantity of carbon in coal, and thus to obtain a fuel which will yield a more intense
heat than coal. 2. For the purpose of converting coal into a fuel deprived of its
volatile constituents, so as to obviate the unpleasant smell emitted by the combustion
of coal when used to heat rooms in dwelling-houses. 3. For the purpose of
converting coal into a fuel which does not become pasty when ignited, coal, in con-
sequence of this property, being unsuitable for use in blast, cupola, and other
furnaces. 4. For the purpose of eliminating from the coal a portion of the sulphur
contained as pyrites. Before being converted into coke, coal, and especially small
coal or coal mixed with slaty shale, fire-clay, and other heterogeneous mineral
matter, is washed, as it is technically termed, the operation consisting in a process of
purification by means of suitably constructed machinery, and the aid of a stream of
water, the rationale of the process being that the mineral matter, which is about
three times heavier than the coal, is deposited. The machinery in use for this
purpose is similar in construction to that employed for washing metallic ores. By
this method of purifying coal, the quantity of ash (mineral matter) it contains may be
724
CHEMICAL TECHNOLOGY.
reduced from 10 or 12 to 4 or 5 per cent; but it should be borne in mind that 7 to 8 per
cent of the coal is lost as dust. Bessemer has suggested the use of a solution
of chloride of calcium, so concentrated that the coal may float on its surface, while
the mineral matter will sink. The residues of coal-washing may contain so much
iron pyrites as to be fit for use in the preparation of sulphuric acid (see p. 203).
The operation of coking is carried on in heaps, in ovens, or in retorts; but in the
latter case the object is not so much to prepare coke as to obtain gas, tar, and other
products from coal. The construction of coke-ovens according to Knab's plan,
admits of obtaining from the coal, tar, ammoniacal water, and other volatile products.
Cok'ng in Heaps. This method of converting coal into coke is very similar to that in use
for converting wood into charcoal; but the central shaft, I to 1.5 metres in height, is in
this instance made of fire-bricks, having a diameter of 03 metre, and provided with
several lateral air-holes, Fig. 313, by means of which the mass of coals is brought in
FIG. 313.

a
connexion with the central shaft. The largest lumps of coal are placed next to the shaft,
being filled up with small coal, technically termed cinders and culm. At the bottom of
the heap channels are constructed radiating towards the centre. The bottom of the shaft
is filled with dry wood, which is kindled from the top. The opening at the top is not
closed with the iron cover fitted to the shaft as long as any smoke from the smouldering
coal is emitted. When no more smoke is emitted, the air-channels at the bottom of the heap
are stopped with wet sand and coal-dust. In England the cooling of the glowing heap is
hastened by pouring on cold water, whereby a greater degree of desulphuration of the
coke is obtained.
Coking in Ovens. In the present day coal is converted into coke almost exclusively in
ovens constructed for this purpose; because it has been found that by the use of
ovens the operation is more readily conducted, while a larger quantity and a better
quality of coke are obtained. As regards the construction of coke-ovens, some are
so built that the gases and vapours evolved during the operation of coking, escape
without being utilised. Others again are so arranged that the combustible gases are
employed as fuel for coking the coal, or as fuel for steam-boilers or other purposes.
This kind of oven is constructed with or without admission of air. To the latter
class belongs Appolt's coke-oven, which is essentially similar to a vertical gas-retort,
fitted with apertures for the exit of the evolved gaseous matter. Other coke-ovens
again are so constructed that the tar and volatile products of the dry distillation of
the coal may be condensed, collected, and utilised. Knab's coke-oven is thus arranged.
Among the coke-ovens of older construction is one, Fig. 314, in use at the
Gleiwitz ironworks in Silesia. A is the body of the oven or kiln, with lateral
openings, ooo, which can be closed by dampers or iron plugs; similar apertures are
made in the bottom of the oven. The top of the kiln is vaulted, with the large
FUEL.
725
opening, b, which serves, as well as the lateral doorway, a, for the introduction of the
coals. The large lumps are placed at the bottom of the kiln, which is entirely filled,
with the exception of a small space towards the top of the doorway, ieft for the pur-
pose of throwing in ignited coals. The doorway, a, is bricked up, only a small channel
being left for the introduction of the ignited coal. ƒ is an iron pipe for carrying off
the volatile products of the smouldering of the coals; d is an iron lid fitting tightly
in the opening b. At the commencement of the operation all the openings of the
oven, excepting those at ƒ and those at the bottom, are closed; and as soon as there
appears at the lower apertures an orange-coloured glow, these openings are closed,
and those of the next row opened, and kept open for about ten hours; the third row
of openings being then unplugged and kept open for sixteen hours; finally, the
fourth row is opened for about three hours, after which the oven is left to cool-all
openings being plugged-for twelve hours. The door, t, is then broken up, and the
coke drawn from the oven by means of iron rakes. This description of oven contains
35 to 40 cwts. of coal, and the average yield of coke is 53 per cent by weight and
74 per cent by bulk. The gases and vapours issuing from ƒ are carried to a
condenser. I cwt. of coals yields 10 litres of tar.
The coking of small coal, culm, coal-dust, either previously washed or not,
is carried on in ovens similar in construction to those used for bread-baking. Small
coal, especially of the caking quality, yields excellent coke, and in many instances,
this fuel is now guaranteed not to contain more than 6 per cent of ash. The mode
of construction of coke ovens for small-coal coking differs in various countries.
Fig. 315 exhibits a vertical section of such an oven in use by the Leipzig-Dresden
Railway Company. The coking-room, a, is 3°3 metres high. The doorway, d,
I metre high and wide, can be closed with an iron door, provided at the top with four
FIG. 315.
FIG. 314.


€
*
Ι
air holes. The chimney stalk, b, is rather more than 1 metre high. At each side of
the doorway an iron hook, e, is fixed, for the purpose of supporting the rakes used
by the labourers when drawing the coke. In this description of oven 50 Dresden
bushels of small coal and coal-dust are converted into coke in seventy-two hours.
The coke obtained is very compact; but if the oven be lightly filled, a more spongy
coke is the result. Fig. 316 exhibits the construction of the coke-oven at the
Zaukerode colliery, near Dresden. The bottom or hearth of the coking-kiln is of a
circular shape slightly inclined towards the doorway. The width of the hearth
I Dresden bushel = 103.8 litres.
726
CHEMICAL TECHNOLOGY.
FIG. 316.
is 3.6 metres. The top of the vault c is 3'08 metres above the hearth. bb are two
chimneys, each 13 metres in height, for carrying off the volatile product. The cast-
iron door is so arranged that at the top of the doorway an opening is left for
the admission of air into the oven; e is a hook serving the purpose mentioned in the
description of Fig. 314. Fig. 317
exhibits the vertical section, and
Fig. 318 the ground plan of the
coke-ovens in use at the collieries
situated in the Saar district. The
hearth of the kiln is egg-shaped,
3 metres long and 2 metres wide;
while the height of the kiln is at
most only 1 metre. The chimney,
175 metres high, also serves for the
introduction of the coals. The
admission of air to this oven is
regulated by a channel at a height
of 0.3 metre above the hearth; this channel, Fig. 318, communicates on both sides of
the doorway, t, with the outer air, and communicates by means of the channels, ooo,
with the interior of the oven. The door, t, fits rather tightly in the doorway.
A quantity of 1 to 1.25 cubic metres (from 40 to 50 cubic feet) of small coal is con-
verted into coke with this oven in 24 to 30 hours.

FIG. 317.
b

B
Among the coke-ovens constructed to utilise the escaping gases and heat for
the purpose of making coke, that of Appolt deserves notice. The first of these ovens
was built in 1855 at St. Avold. This coke-oven is distinguished from those
described by its peculiar shape, which is that of a vertical shaft, heated externally,
the heat being supplied by the ignition of the gases and vapours evolved from the coals
while becoming coked. Fig. 319 exhibits a vertical section, and Fig. 320 a horizontal
section of this oven. In order that the heat may reach the centres of the shafts, aa,
their shape is that of a parallelogram, 0°45 by 1°2 metres, and 4 metres deep; 12 of
such shafts form one oven. The separate shafts, the walls of which consist of
hollow double walls, b, are connected with each other as well as with the lining
walls, which forms a series of intercommunicating channels. Every compartment is
provided with an upper and a lower aperture, through the former of which the coals
are introduced, while through the latter-closed during the coking operation with an
iron trap door—the coke is withdrawn. The apertures e e in the brickwork serve for the
purpose of carrying off the gases and vapours which are burnt in the channels by the
FUEL.
727
aid of the air rushing in at ff. The heat produced by this combustion converts the
ccals into coke, and the products of the combustion are carried off through the
channels g and h. The dampers, R, serve to regulate the draught. The channels g
communicate with the horizontal channel, i, the channels h with the channel j;
FIG. 318.

X
0
0
t
the channels i and j are carried into the chimney stalk, k. The compartments of
the kiln, Fig. 319, are united at the top by a contraction of the brickwork, leaving to
each only a small opening, closed by a cast-iron lid, fitted with an iron tube for the
purpose of conveying a portion of the gases and volatile matter. On the top of the
FIG. 319.
FIG. 320.


g f
a
a
W
Th
n
9
101110
10110
oven rails are placed, on which an iron truck runs, laden with the charge-25 cwts.-
for each compartment. The coals are discharged into the compartments by
opening a trap-door in the bottom of the truck. Under the vaulted brickwork, u,
of the oven, trucks can be run for the purpose of being laden with the coke.
728
CHEMICAL TECHNOLOGY.
In order to set the oven in operation dry wood is thrown into the compartments, and
this having been kindled, coals are thrown upon it. The interior of the oven soon
becomes hot by the combustion of the gases issuing from the openings e. When the
heat of the oven is sufficient to effect the decomposition of the coals and the combus-
tion of the volatilised products, the compartments are charged, the iron lid being
tightly luted to the top with clay. The charging is so conducted that the twelve
compartments of the oven are filled in twenty-four hours, after which the coke in the
first compartment is ready for being drawn, and fresh coal put in, an operation which
is continued every second hour. As may be expected from the mode of construction,
Appolt's coke-oven is rather expensive in the first building, the cost abroad being
about £600, while an ordinary coke-oven may be built for £72 to £120; but Appolt's
oven yields daily about 240 cwts. of coke-66 to 67 per cent from Duttweil coal,
which in ordinary coke-ovens yields only 61 per cent. It should be mentioned, that
with Appolt's ovens, the coke from the inner and outer compartments is not of the
same quality and compactness, owing to the higher degree of heat prevailing in the
former.
We may mention briefly the following contrivances for preparing coke, based upon the
same principle as Appolt's. Marsilly's oven is covered with a brick arch, communicating
with a flue through which the gases and vapours are carried under the hearth of the oven,
and by burning there heat it. Jones's oven is similarly constructed, but with the differ-
ence that the combustion of the gases and vapours is made to take place in the coking
kiln. This arrangement, used only with very dry, non-bituminous coals, certainly assists
the coking process, because the air is heated previous to entering the kiln. Frommont's
double cooking oven, in use on the Maas, in Belgium, as well as in Westphalia, and
at Saarbrücken, is a stage oven, so constructed that the gases formed in the lower coking
compartment are carried through channels to the upper hearth; thence with the
gases formed in the upper compartment, are conveyed under the hearth of the lower
oven, and thence through lateral channels to the chimney, so that the heat is thoroughly
utilised. Gendebien's coking-oven is distinguished from that of Frommont, in so far that
one of the upper coking compartments is placed over two of the lower; these ovens are
chiefly used on the Sambre (Belgium). The coke-ovens according to Smet's plan are
inclusive of the principles of all ovens built to utilise the heat of the combustible gases.
Dubochet's coking-oven, constructed in 1851 by Powell, is a tubular oven with sloping
hearth, consisting of two shallow curved parts placed one above the other, and separated
by doors. The upper part is the distillatory furnace or oven, the gases and vapours
there evolved being conveyed under the oven, and burnt with admission of air, the heat
evolved by this combustion serving to coke the coals. The coke is caused to fall into a
cooling oven, from which it is removed when extinguished. The combustible gases evolved
by this process are sometimes employed for the purpose of heating a steam-boiler
belonging to the coal-washing machinery. In the coke-oven built upon Knab's plan, the
gases evolved from the coal are, previous to being burnt, deprived of the tar and
ammoniacal water carried off by them. For this purpose the gases are conveyed to two
large cylindrical vessels filled with coke, and in which nearly all the tar is deposited;
thence the gases are conveyed to a system of tubes connected with water reservoirs for the
purpose of eliminating the ammoniacal products. The purified gases are then conveyed
to the furnace to be there burnt from a large circular burner, to the centre of which air is
admitted. The necessary motion is imparted to the gases by bell-shaped exhausters,
w.ich draw the gases from the furnace through the purifying apparatus and force them to
the burner. According to the statement of Gaultier de Claubry, there are 150 tons of
coal converted daily into coke, in eighty-eight ovens belonging to the Société de Carbonisa.
tion de la Loire, near St. Etienne. The yield in 100 parts is :—
Coarse coke (large lumps)
..
70'00
Tar
Small coke
I'50
Ammoniacal water
•
Breeze
2.50
Gas
Graphite
0*50
Loss
4'00
9:00
10*50
I'92
It is questionable whether the coke thus obtained is equal in quality with that obtained
by the ordinary coke-ovens; because experience proves that all coke prepared in close
FUEL.
729
vessels, is rather porous and less suitable for use on locomotive engines and in blast-
furnaces.
Very small coal and dust are converted into coke in ovens built similarly to those used
for baking bread. The large quantities of refuse coal, screenings, &c., formerly waste, to
be found in enormous heaps near coal-pits, and to effect their removal being frequently
set on fire, burning for month after month, producing huge volumes of smoke, are now
utilised and made into excellent coke, after having been first washed.
The coke drawn from the ovens is extinguished with water or under ash. The former
plan, however, is most frequent, and has the advantage of giving to the coke a peculiar
silvery gloss. There is, however, more than one objection to this mode of extinguishing
coke, because in the first place the coke absorbs and retains some water, which as it has to
be evaporated when the coke is burnt, absorbs a portion of the heat generated by the
combustion. Secondly, the weight of the coke is increased, and may be increased
fraudulently to a large extent, as some portions of the coke-the more porous lumps-take
up 120 per cent of their weight of water, while the dense metallic portion takes up only
1 per cent., and the coke from the bottom part of the oven 13 per cent. On an average
the coke takes up by being extinguished by water 6 per cent of its weight; but cold coke
takes up when thrown into water hardly half as much.
Properties of Coke. Well burnt coke or oven coke, is a hard, uniform, compact, solid
mass, difficult to break, and not honeycombed, nor very porous. Its colour is black-
grey or iron-grey, with a dull metallic gloss. Good coke should contain very little
sulphur. All the sulphur contained in coal, chiefly as iron pyrites, cannot be com-
pletely eliminated by the coking process, as the sulphuret is only reduced to a lower
degree of sulphuration. In the north of England it has been found, that if the coal,
even when highly sulphurous, is first treated with a strong brine and powdered rock-
salt, a coke very free from sulphur is obtained. The sulphur in coke is objectionable,
from its action upon the ironwork of the furnaces, the fire-bars, &c.
Composition of Coke
and its Value as Fuel.
The average composition of good coke is the following:—
Carbon
Ash
Hygroscopic water
...
85-92 per cent.
3- 5
5-10 ""
Owing to the great density and compact structure of coke, and the fact that it does
not contain any combustible gases, it is ignited with difficulty, and requires for kind-
ling a strong red heat, with a blast for continued burning. '
According to a series of experiments in Prussian ironworks with coke in furnaces
with hot blast:
100 parts by weight of coke =
ΙΟΟ
""
bulk
""
80 parts by weight of charcoal.
250
""
Brix found that a coke made from upper Silesian coals, and containing 5'9 per
cent of water and 2.5 per cent of ash, yielded for every kilo. burnt 7:15 kilos. steam.
Artificial Fuel.
Artificial Fuel.
Under this name we understand an originally pulverulent, combus-
tible fuel, such as small coal or coke, breese, sawdust, refuse wood, &c., mixed with
tar or thin clay liquor, and by strong pressure subsequently moulded in the shape of
bricks. Compressed peat and compressed spent tan are in a certain sense artificial
fuel.
Peras.
Under this name is known an artificial fuel first prepared from caking coal
by Marsais, the viewer and manager of some collieries near St. Etienne. The small
coal, screenings, dust, and other refuse, are first lixiviated for the purpose of
730
CHEMICAL TECHNOLOGY.
removing mineral impurities, such as gangue, clay, pyrites, &c. The purified coal
is drained, then ground to powder by suitably constructed mill-work, afterwards
dried by the application of heat, then mixed with 7 to 8 per cent of thick coal-tar,
and finally moulded into bricks by the aid of strong pressure, the brick-shaped
lumps weighing each about 20 lbs. Peras is less fragile than ordinary coal, and being
of a uniform shape, can be better stored than coal, taking up about one-fifth less room,
a matter of considerable advantage on board steamers. Similar to peras are the
patent coals made by Wylam and Warlich.
The so-called moulded charcoal, or Parisian coal, introduced about fifteen years
ago by Popelin-Ducarré, is an artificial fuel composed of charcoal refuse with coal-
tar. The small lumps and dust of charcoal are mixed with 8 to 12 per cent of water,
then ground to powder, and to 100 kilos. of the powder are added 33 to 40 litres of
coal-tar. This magma is thoroughly incorporated and next moulded into cylinders.
These are dried, and finally carbonised in a muffle-furnace. This fuel is far less
fragile than ordinary charcoal, better fitted for transport, burns better than coke, and
even when only slightly kindled, continues to burn in air, which is not the case with
coke.
Briquettes.
When strongly caking coal is heated in closed vessels to 260° to 400°,
and then compressed in moulds, the result is the formation of a hard brick-shaped
fuel, very suitable for domestic use as well as for steam production.* It has been
found that the manufacture of briquettes can be advantageously combined with the
preparation of tar for the purpose of extracting benzol, carbolic acid, naphthaline,
asphalte, and anthracen.
Gaseous Fuel.
Gaseous Fuel. The utilisation of certain combustible gases and mixtures of these
gases as fuel has been practically solved only during the last few years, although in
metallurgical operations the idea of such utilisation is of more remote date. The
combustible gases used on the large scale as fuel are those evolved from blast-
furnaces, and from coke-ovens and other apparatus in which these combustible gases
are formed as the by-product of industrial operations. The composition of the blast-
furnace gases varies of necessity according to the kind of fuel used, the temperature
of the furnace, the shape, build, and height of the latter, the pressure on the blast, &c.
The combustible gases escaping from these furnaces consist chiefly of carbonic oxide,
hydrocarbons, hydrogen, carbonic acid, nitrogen, and of ammonia where coal or coke is
used as fuel. The so-called generator gases are those combustible gases which are
evolved from solid fuel, coke, peat, or wood, by its carbonisation in a separated
furnace, kiln, or oven, with or without the aid of a blast. These combustible gases may
be utilised in various ways and obtained from fuel which is not otherwise applicable
as such. According to Ebelmen these gases are composed as follows:-
Generator gases obtained from :-
Nitrogen ...
Carbonic acid...
Wood-charcoal. Wood.
Peat.
Coke.
64'9
532
63·1
64'8
0.8
11.6
14'0
1'3
Carbonic oxide
...
34'I
34.5
22.4
338
Hydrogen
0'2
0'7
0'5
ΟΙ
* See Th. Oppler, "Die Fabrikation der künstlichen Brennstoffe, insbesondere der
gepressten Kohlenziegel oder Briquettes," Berlin, 1864; also "Jahresbericht der chem.
Technologie," 1864, p. 760; 1866, p. 333; 1868, p. 800.
WARMING.
731
There has long been in use in England a gas mixture obtained by passing
high-pressure steam over red-hot coke contained in retorts. Siemens's regenerative
gas-furnace, described on pp. 24 and 273, belongs to this category. Combustible
gaseous bodies are largely utilised in metallurgical operations, puddling-furnaces,
zinc-smelting, &c.
Purposes.
Gas for Heating It has of late years been frequently suggested that a cheap gas
should be manufactured for heating purposes. In Berlin a company has been
formed under the technical guidance of C. Westphal and A. Pütsch, the object being
to prepare gas from brown-coal at Fürstenwald, a distance of about 38 kilometres
from the city. The intention is to construct twelve retort-houses, each to contain
seventy furnaces provided with ten retorts, to be fired as in Siemens's regenerative
gas-furnace. The purified gas is to be forced by blowing-machines, actuated by
steam-engines of 360 nominal or 500 indicated horse power, into a main pipe of
13 metres diameter constructed of boiler-plates and carried above ground supported
on iron pillars. The gas will be collected at Berlin in twelve gas-holders, each of
750,000 cubic feet capacity. The pressure of the gas in the mains and service-pipes
within the city will be 1.5 centims. water-gauge, in order that pipes of smaller
diameter may be used. According to Ziureck, the composition of the gas obtainable
from the brown-coal is, at a sp. gr. of o'5451, as follows:-
Hydrogen
Carbonic oxide
Marsh gas
Nitrogen.
...
Carbonic acid
...
Condensable hydrocarbons
:
...
•
•
42.36 per cent.
40'00
II.37
3.17
""
2 ΟΙ
""
""
1'09
A gas of this composition will answer admirably for heating purposes. 3000 cubic
feet of it are in heating effect equal to 1 ton of brown-coal, and equal to ¦ ton of
pit-coal, the ton being equal in this case to 275 to 300 lbs. The price will be 7id.
per 1000 cubic feet, so that the heating effect yielded by it as compared with the
price of a ton of coals will be about 4s. 6d. The works are constructed for an annual
production of 9500 millions of cubic feet of gas, or a daily supply of 23 millions of
cubic feet.
Heating Apparatus.*
Warming. We understand by warming the heating of any room or space by heat
evolved from the combustion of fuel. The room or space may be an apartment in a
dwelling-house, a church, a steam-boiler, a glass-house, a hothouse in a botanical
garden, &c. It is the aim of technology to apply the fuel so as to yield by its most
economical use the greatest amount of heat. In order to obtain by the combustion
of fuel as nearly as possible its absolute and specific calorific effect, the combustion
should not only be complete, but the gaseous products should suffer the highest
degree of oxidation; in other words, neither smoke nor any combustible gases
* The following works afford very valuable information on this subject :-C. Schinz,
"Die Wärme Messkunst," Stuttgart, 1858; E. Péclet," Traite de la Chaleur," 3rd edition,
Paris, 1861-62, 3 vols; and for stoves for domestic use, "Die Badische Gewerbezeitung,'
edited by H. Meidinger.
99
732
CHEMICAL TECHNOLOGY.
should be evolved. The practical importance of this principle is exhibited by the
following:-
I part of carbon yields, when burnt to carbonic oxide, 2480 units of heat.
carbonic acid, 8080
I
""
In order to obtain complete combustion, the fuel should be supplied with the
requisite quantity of air, while the vitiated air should be carried off with the gaseous
products of the combustion. This supply of air or draught can be assisted artificially
by means of blast- or exhaust-apparatus; but in most cases the draught is natural,
i.e., produced by the calefaction of the air, which becoming specifically lighter,
ascends.
All heating apparatus consist of three distinct parts-the fire-place or hearth, the
heating-room, and the chimney. The hearth is that portion where combustion takes
place. The heating-room is the portion of the apparatus where the heat generated
is utilised, and the chimney is a channel, usually placed in a vertical position, and
often connected by means of flues with the heating-room and hearth—through which
the gases evolved by the combustion of the fuel are carried off, and a draught
created maintaining an efficient combustion of the fuel.
The hearth or fire-place may vary greatly in shape and mode of construction.
The most primitive, but also the most defective kind of hearth, is that on which the
fuel, usually wood or peat, is placed on tiles or bricks under the chimney. Such
arrangements are still in use in many remote country places, especially in the
country districts of Ireland and Scotland, where faggots of wood and peat are thus
burnt. In this manner a very great amount of heat is wasted and the supply of air
not properly regulated; there is an excess of air supplied, and hence loss of fuel.
The air required for the complete combustion of the fuel should be made to pass
through the fuel, which for that purpose is placed on a grating, consisting of bars of
iron or fire-brick. The space under the fire-bars is called the ash-pit, through which
the air is supplied to the fuel. The hearth is usually provided with iron-doors,
which are opened when fresh fuel has to be introduced. This plan is accompanied
with the objection, that during the period of feeding and raking up the fire, a large
quantity of cold air enters the hearth, and causes the combustion to become irregular
and much smoke to be produced. The use of the so-called stage fire-bars, placed in
the manner of steps, one above the other, is not attended with this defect.
When the fuel contains much sulphur, the iron fire-bars are soon worn out, owing
to the formation of sulphuret of iron; in order to prevent this, it is often usual to
leave a layer of clinkers and slag on the bars for the purpose of protecting them from
the direct action of the fuel. In order to regulate the draught, dampers or similar
contrivances are fitted to the flues, chimney, or funnel.
a. Heating Dwelling Houses.
Heating Dwelling Houses. The heating of dwelling-houses and public buildings, halls,
theatres, churches, &c. (in connection with the ventilation), can be effected in
various ways, either by radiant or conducted heat. According to the construction
of the heating apparatus, we distinguish :-1. Heating by flues. 2. By stoves, or
with hot air. 3. Air heating. 4. By means of steam or hot-air pipes. 5. Hot-water
heating. 6. Heating by means of gas.
Direct Heating. The direct heating of rooms by the combustion of wood and other
fuel on an open hearth, or in chaufing-dishes and small stoves without chimneys, is
WARMING.
733
undoubtedly the most ancient and primitive method of heating. In the centre of
the huts in Ireland and the Highlands of Scotland, a rough hearth is constructed,
while the smoke evolved by the fuel escapes through a hole in the roof. In some
parts of France, Italy, Spain, and Turkey, rooms are heated by means of a chaufing-
dish containing burning charcoal, by the combustion of which the air of the room is
vitiated, becoming unfit to be respired by the lungs. It is evident that for this
reason and owing to the risks of fire this mode of heating is very dangerous.
Chimney Heating. This mode of heating, in general use in England and the larger
towns of Scotland, Ireland, and Wales, is of ancient use, and is based upon the
heating of the air of the rooms by the direct radiation of the heat of the fire. It is
undoubtedly the most imperfect and wasteful method, as there flows into the chimney
a very large excess of air above that required for maintaining the combustion of the
fuel, the consequence being that strong draughts of cold air are felt near the windows
and doors of the rooms, while a downward current of air is frequently created,
causing the chimney to smoke. This mode of heating only suits countries enjoying
an average mild climate and possessed of plenty of fuel. It would appear that
among the reasons why this mode of heating is continued is the pleasure of seeing
the fire and of warming the feet by it, notwithstanding that the other parts of the
body remain comparatively cool. The arrangements of the method of warming by
the radiant heat from chimneys are in the most primitive form the following:-
the lower part of the wall from which the chimney is built, a niche or recess is
constructed in which the fuel burns; but in grates of better construction, the recess
is not very deep, and less contracted where it issues in the chimney, while frequently
the hearth is fitted with a sliding door, and a valve or trap-door in the upper part of
the flue leading into the chimney.
-At
In order to utilise a portion of the conducted heat, yet still to leave the heating to
be effected chiefly by radiation, the flow of hot air into the chimney is to some extent
intercepted, so as to form a combination of the methods of stove- and chimney-
heating.
Stove Heating.
This method of heating is in general use in the colder parts of the
Continent, in America, Canada, &c. A well constructed stove should not consume
too much fuel, the combustion of which should be complete, while the heat generated
should be uniformly radiated, and only a very small quantity allowed to escape into
the chimney. As a stove is placed at some distance from the chimney, the radiating
as well as the conducted heat is utilised. The loss of heat is prevented by a series
of flues; but in order to keep up a sufficient draught, the air escaping into the
chimney should have a temperature of at least 75°. The fuel is generally intro-
duced into the stove from the room, although some kinds of stoves are so constructed
that they may be fed with fuel from the outside of the house similarly to the hot-
house stoves; this method of construction entails a larger consumption of fuel and
some loss of heat.
Stoves are made of cast-iron, sheet-iron, and fire-clay. Iron readily absorbs heat,
and as the sides of the stove are usually not very thick, the heat is rapidly and
readily dispersed. As iron stoves may become red-hot, the air surrounding the
stove is chemically changed in consequence of the permeability of red-hot iron to
carbonic oxide. This gas, according to the experiments of Deville and Troost, 1868,
is absorbed and evolved by red-hot iron to o˚0007 to 0.0013 its volume. Fire-
clay stoves yield a very uniform heat, given off only slowly and gradually.
734
CHEMICAL TECHNOLOGY.
Compound stoves are those in which the hearth is made of cast-iron, on which is
placed a sheet-iron column closed at the top, and provided with a lateral opening
communicating by sheet-iron pipe with the chimney.
We distinguish according to the material of which stoves are constructed:-
a. Those simply of iron.
b. Those of fire-clay.
c. Compound stoves.
Iron stoves are usually so constructed that the heat generated by the combustion
of the fuel is rapidly communicated to the air of the room. The heat generated in
fire-clay stoves is communicated to the great mass of fire-clay of which the
stoves are constructed, so that even long after the fire has been extinguished
the stove continues to give off heat; these stoves are especially used in Sweden
and Russia.
Iron Stoves.
The construction of these stoves varies greatly. When made of cast-
iron the shape is frequently cylindrical, a short pipe being cast on, to which is fitted
a sheet-iron pipe leading to the chimney. In some cases the length of this pipe is
considerable, in order that the heat evolved by the combustion of the fuel may be
better utilised.
Sometimes iron stoves are constructed with an outer mantle which is perforated
and usually exhibits an ornamental appearance; this mantle is placed at some few inches
distance from the inner stove, in which the combustion of the fuel takes place.
Fire-clay Stoves. These stoves, made of a peculiar kind of clay, are externally glazed
similarly to the so-called Dutch tiles. The construction of these stoves is very massive.
They consist of a series of channels made of burnt clay and put together with a
mixture of the same clay unburnt and gypsum. The thickness of the pipes forming the
channels is 7 inches. The number of channels or flues is four to six, or even twelve.
The Russian stove, Fig. 321 in ground plan, is fitted with six flues. Fig. 322 is a front,
FIG. 321.
C
کی
4
3.
Fig. 323 a side view, and Fig. 324 a vertical section.
a is the vaulted fire-place, the flame and smoke
evolved by the combustion of the fuel being carried
upwards in flue 1, downwards in flue 2, again up-
wards in flue 3, again downwards in flue 4, again
upwards in flue 5, and again downwards in flue 6,
and thence into the chimney by means of an iron
pipe fitted to the stove.
Each of these stoves has a separate chimney, a
tube 18 to 30 centimetres wide, carried straight up to
above the roof of the house. These narrow
chimneys, also in use in Edinburgh, Glasgow, and
other Scotch towns, are constructed of fire-clay
tubes fitted into the stone of the walls. As a Russian
stove is really intended to be a store of heat, it has to be hermetically closed as soon as
the fire is extinguished; this is effected by the following contrivance, termed in the Russian
language, Wiuschke. Near the junction of the last flue and the stove-pipe a plate of cast-
iron, Figs. 325, 326, and 327, is fitted to the stove, the plate being provided in the centre
with an opening of 21 to 24 centimetres diameter. This opening has an internal vertical
flange or collar of 2 centimetres, and an external vertical flange of 3 centimetres height.
An iron cover, a, Fig. 327, fits closely on to the inner flange, and a larger cover, b, fits on
to the outer flange, thus securing a tight joint. These ovens are heated with wood,
which is sawn into small blocks. No smoke is evolved, because the high temperature pre-
vailing in the flues consumes the smoke completely, and the wood is not used until it is
thoroughly dry. The Swedish stove is usually cylindrical in shape, and very tall, reaching
nearly to the ceiling of the rooms. The flues (four in number) of these stoves are of
rather complicated construction. They communicate laterally with each other. The
chimney pipe is placed at the top and is provided with a damper, closed when the fire is
extinguished. The fuel, dry wood, required for one heating of the stove, is put into the
stove at one charge, and when the combustion has ceased, the damper and the stove door
are tightly closed.

WARMING.
735
Feilner has constructed a stove of this description, Figs. 328 to 331,
which is a modification of the Russian stove. Fig. 328 shows a front view, and Figs. 329
FIG. 324.
Compound Stoves.
FIG. 322.
FIG. 323.


2
شمی
9
b
α
and 330 vertical sections. The section exhibited in Fig. 329 is through the ground plan,
Fig. 331, as indicated by the dotted line AA. The section shown in Fig. 330 is according to the
FIG. 325.

FIG. 327.
O
FIG. 326.
dotted line BB and the section exhibited in Fig. 331 to the line cc.
stove is constructed of iron surrounded by a burnt clay mantle or box.
FIG. 329.
The hearth of this
The products of
FIG. 330.
FIG. 328.



l
N
l
n
n
クレ
​D
D
A
D
n
D
C
a
736
the combustion are forced
thence issue into the flues.
FIG. 331.
CHEMICAL TECHNOLOGY.
through a cylindrical tube, of 12 to 18 centims. width, and
The combustion is very complete, no soot or smoke being formed.
This stove is divided into two compartments by means of a
vertical wall; and horizontal shelves are fitted to this wall,
thus forming a series of channels or flues, through which
the products of combustion are made to pass. The length
of these flues varies, according to the size of the stove, from
9 to 20 metres. As the hearth is so placed as to be a sepa-
rate part of the stove, the room becomes heated as soon as the
fire is lighted. In the lower part of the stove a kind of air-
heating is arranged, because by two openings, a a, Fig. 328,
cold air enters and becomes strongly heated while passing
through the stove. When the combustion of the fuel has ceased
the damper in the pipe leading to the chimney is closed; the clay portion of the stove having
then been so strongly heated that one firing answers for a whole day. bbb is the brick-
work foot of the stove; cc are supports for carrying the cast-iron bed-plate, dd, of the
iron hearth; e are the side plates; ff the top plate of the fire-room; g is a tube fitted to
the top plate, and intended for carrying off the gases and other products of the combus-
tion of the fuel. On the top plate are placed fire-bricks supporting hh, which is made of
boiler-plate, and provided with a circular hole so situated as to be free from the tube g.
On this boiler-plate are roofing tiles, which reach to the side walls of the stove, and are
covered with sand or dry ash. This construction is necessary for the purpose of pre-
venting the iron hearth in its expansion forcing asunder the brickwork.

ļ
The vertical partition wall, i, is built of brick; it supports k. I are also built of
brick. n n are so short that each of the openings is 7 inches distant from the opposite
side. The smoke is carried upwards through the openings o o. p p is the iron pipe,
which communicates with the chimney. The heat and gases generated by the combustion
of fuel in this stove proceed from the hearth, e, through g, are returned by k, flow along i,
pass through the opening o into the flue n, and finally into the pipe, which communicates
with the open air.
Henschel's stove, constructed to burn brown-coal, deserves notice. Fig. 332 exhibits a
vertical section, and Fig. 333 a horizontal section at the line a B. This stove consists of
FIG. 332.

a
Fig. 333.

A
B
a
two iron cylinders, the outer, a, being of cast-iron, the inner, b, of stout sheet-iron
The outer cylinder is supported by the ash-pit, c d, fitted with fire-bars towards the upper
ond. The inner iron cylinder does not reach to the fire-bars, and is closed at the top by
WARMING.
737
a tightly-fitting cover, g, while the outer cylinder is closed by the lid h. When it is
intended to heat this stove it is first filled with brown-coal, thrown in from the top after
removal of the lids. The fuel is kindled at i, through k. The combustion can only take
place on the fire-bars, the hot air flowing upwards between the two cylinders, and thence
into l, the iron pipe leading to the chimney. The fuel contained in the inner cylinder
gradually sinks downwards as the combustion proceeds. The ash is removed by imparting
motion to the crossed iron bars, m, Fig. 333, to which are fitted pieces of iron passing
between the fire-bars. The handle, n, projects outside the stove. Any smoke which
This kind of stove
might reach the upper part of the stove is carried off by the pipe o.
having once been filled with fuel continues to supply heat for forty-eight hours.
Meidinger, of Carlsruhe, has constructed many very excellent stoves of this description.
This method of heating is effected by means of stoves, but is dis-
tinguished from the ordinary stove-heating by the situation of the stove, which is
in most cases not placed within the space or room to be heated, being within a
chamber from which the heated air is conveyed by channels to the space intended
to be warmed. The aim of air heating or central heating is to heat a large space
uniformly with one stove, or to heat by means of one fireplace all the rooms and
apartments in the same building, when it is not found convenient to construct fire-
places in each apartment. There are in use three modes of air heating, which
differ from each other in the method of ventilating the space to be heated.
Air Heating.
(a.) The cold air enters the heating apparatus, becomes warm, and is conveyed through a
pipe or channel into the room or space to be heated, while an equal bulk of vitiated air
escapes from the imperfectly-closed windows and doors.
(b.) The heated air is returned to the heating apparatus, becomes again warmed, and
re-enters the room. While the method (a) has the advantage of constantly supplying
fresh air to the room, thus creating an uninterrupted ventilation, the method (b) has the
advantage of saving that quantity of heat which is lost in the efflux of warm air in the
first method.
(c.) The outer air becomes heated at the fireplace, and is then conveyed to the room to
be warmed. The vitiated air from the room is conveyed through a flue to the fire, this
air serving the purpose of maintaining the combustion. This method combines all the
advantages of (a) and (b), while, with constant ventilation, a saving of fuel is effected.
As regards the methods of employing air heating, we distinguish according to the
construction of the apparatus:-
(a.) Air heating by means of a mantle oven.
(b.) Air heating by means of a heating chamber. •
The first method is very similar to ordinary stove-heating, and only distinguished
from it in the respect that the stove is surrounded by an outer mantle of bricks
or fire-clay slabs, some 6 to 8 inches from the stove. This mantle is provided with
openings, through which the heated air escapes, and is uniformly distributed through
the room.
In warming with a separate chamber we have to consider the form of the chamber,
a small vaulted room, built of brickwork, and containing the furnace. The heating
chamber should be comparatively very small, so that the heated air shall be carried
as rapidly as possible to the room intended to be warmed. The channels for
carrying off the heated air are placed at the top of the heating chamber, while the
channels for conveying the cold air are situated at the bottom. The space between
the furnace and the walls of the heating chamber measures from 12 to 16 centims.,
but the vault is elevated 1 to 13 metres above the top of the furnace.
The furnace or stove is the most essential part of this air-heating apparatus. It
is made either of cast-iron or of boiler plate; and as regards size 1 square foot of
heating surface is capable of heating 800 to 1000 cubic feet of air. Another kind
of air-heating apparatus consists of the following arrangement :-A series of rows
48
738
CHEMICAL TECHNOLOGY.
of cast-iron tubes, which communicate, are so placed in a furnace or oven that cold
air enters into the lowest row of the series, while the heated air escapes from
the upper row. Since the hot air having become specifically lighter always tends
to rise, it is clear that the apparatus should be placed in the cellar or lowest room
of the building to be heated. The hot-air pipes should be as vertical as possible.
The apertures through which the hot air gains admission to the rooms to be
heated are best situate in the floor, in this case generally a double one; or the hot-
air pipes are placed in channels covered with an iron grating, and sometimes
provided with a damper so that the supply can be regulated.
Heating with hot air is usually attended with a serious defect, viz., that the air
is exceedingly dry or even burnt. This defect can be remedied only by supplying
air with aqueous vapour by placing in the current of hot air shallow basins filled
with water, or by suspending wet sponges near the pipes. Dr. von Pettenkofer has,
however, proved that these expedients do not quite answer the purpose. Air heating
is not very suitable for dwelling-houses, but answers best for public buildings, which,
as churches, theatres, and concert rooms, require to be only occasionally heated, the
defect of the too great dryness of the air being in these instances counterbalanced
by the watery vapour exhaled in the process of respiration by the persons assembled,
and by the gas lights.
Caloriferes. A system of air-heating by means of so-called calorifères has become
rather general in the United Kingdom, North America, Sweden, Russia, Holland,
Belgium, and also to some extent in Germany. It is usually employed in large
buildings, but is also applicable to dwelling houses. Among the best of this kind of
heating apparatus are those supplied by the London Warming and Ventilating Com-
pany, who employ the modification of a plan successfully introduced by Sir Golds-
worthy Gurney in both houses of Parliament. Steam, hot water, gas, and coal or
coke, in open or enclosed fire-places, are equally available for the process, while
the cost is less and the effect greater than with any other known means. The
apparatus are successfully in use in St. Paul's Cathedral, York Minster, eighteen other
cathedrals, 1000 churches in England, and a large number of government, public,
and private buildings, and mansions. Abroad, Hartmann at Augsburg, Boyer and
Co. at Ludwigshafen, Bacon and Perkins at Hamburg, have invented more or less
excellent calorifères. Those by Reinhardt and Sammet, at Mannheim, appear to be
of very great efficacy; they are so contrived that the fuel is thoroughly burnt, not
even any soot or smoke being left, while the air is rendered agreeably moist by the
gentle dripping of water on the hot-air gulls. The temperature of the air can
be kept uniform for days and weeks consecutively. As this apparatus if used in a
dwelling-house is placed in the cellar and the whole house heated, there is no dust
nor other inconvenience attending the ordinary fire-places. This apparatus con-
sumes only a small quantity of fuel, and requires as an attendant an ordinary
labourer. In the air-heating apparatus invented by Boyer and Co., Ludwigshafen,
now in use in many large buildings in Münich, Würzburg, and other Bavarian
towns, the heating pipes are not made of wrought-iron but of charcoal cast-iron,
while the dimensions and shape are so arranged as to expose the pipes as little as
possible to injury from the fire, and yet to afford a large heating surface. For every
kilo. of coals hourly burnt, 2.5 square metres of heating surface are present. In order
thoroughly to utilise the heat of the products of combustion, these products are
caused to pass through a series of pipes, some of which are coated with a smooth
WARMING.
739
layer of mortar, for the purpose of preventing loss of heat by radiation. The heat
of the products of combustion escaping into the chimney is below 100°; and these
products consist only of watery vapour and carbonic acid. In order to render the
hot air supplied by this apparatus pleasantly moist, water is evaporated with
the heated air at the rate of 15 to 2 litres per 100 cubic metres heating surface.
Flue Heating. This mode of heating, now confined to hothouses for plants, and even
there superseded by better methods, consists chiefly in carrying the products of
combustion of a stove or furnace through a series of pipes which are placed within
the room to be heated, and are at the opposite end to the furnace connected with a
chimney. If this plan is adopted for heating dwelling-houses, the furnace is placed
in the cellar; but experience has shown that this method of heating, except in the
case of hothouses, is too crude, and, moreover, dangerous, as by overheating of
the flues fire may ensue.
Hot-water Heating. Instead of heating air directly, it is often heated intermediately by
water, which, owing to its high specific heat, is eminently adapted to this purpose.
This kind of heating is known as hot-water heating. I kilo. of water at 100° emits,
while cooling to 20°, 80 units of heat, capable of heating 32 kilos., or 24'61 cubic
metres of air to 10°. The system of hot-water heating is based upon the placing of
a vessel filled with hot water in the space to be heated, care being taken to keep up
the temperature of the water. In the ordinary hot-water apparatus, the fluid is
never heated higher than its boiling-point, and is usually kept many degrees below
that temperature; hence this method is termed low-pressure water heating.
This low-pressure or ordinary hot-water heating is maintained-
a. By circulation through a closed boiler which is heated.
FIG. 334.
d
b. By circulation and syphon action between an open and a heated vessel.
a. In this method there is fitted to a boiler, quite closed, a series of pipes, through
which the hot water is conveyed from and the cooled water returned to the boiler.
The principle of the circulation of the water may be elucidated by Fig. 334. The
water is heated in A, c is the ascending tube, dƒ are the
tubes through which the water is returned to the boiler.
The tube e serves for the purpose of filling the apparatus
with fresh water, as well as for the escape of any air or
steam which might be evolved. The hot water ascending
in c causes a circulation in the apparatus, which when once
commenced is maintained as long as the heating is con-
tinued. From time to time it is necessary to unscrew the
cap at e, for the purpose of adding a small quantity of water.
Usually e is provided with a stop-cock, which admits of the
introduction of a funnel. For 100 cubic feet of space to be
heated, 20 to 30 square feet of heating surface are required.
The heat of the warm-water apparatus is imparted to the
rooms through stoves, usually made of sheet-iron. These stoves are cylindrical
in shape, 2 to 3 metres high, by 03 to 07 metre diameter, and fitted with a
series of pipes in which the air becomes heated by a larger hot-water tube.
b. The other method of hot-water heating by means of an open boiler with
syphon action, or the so-called thermo-syphon of Fowler, as compared with the first
method, has the disadvantage that from an open boiler a considerable loss of heat is
unavoidable, while it is difficult also to prevent accumulation of air on the upper

740
CHEMICAL TECHNOLOGY,
part of the syphon tube. The height to which the tubing can be carried is in this
system, too, limited to the height equivalent to the atmospheric pressure, about 30 feet
for a column of water.
Perkins's so-called high-pressure hot water system, wherein the temperature
of the water in immediate contact with the fire is raised to 150°, 200°, and even 500°,
consists of a closed tube filled with water. One-sixth of the length of this tube is
coiled and placed in a furnace; the other five-sixths are heated by the circulation of
the hot water. The tubes are of malleable iron, capable of resisting a pressure
of 3000 lbs. per square inch. More recently the hot water from native hot springs,
or obtained from bored artesian wells, has been, as for instance at Baden-Baden,
employed for the purpose of heating. At Baden-Baden the hot water (67) from a
native spring is used to heat a church.
Heating with Steam. This method of heating is based upon the latent heat contained in
steam. 1 kilo. of steam at 100° contains so much latent heat that by it 5.5 kilos. of
water can be heated from 0° to 100°.
A steam-heating apparatus consists of a boiler, steam-pipes, and pipes, which re-
convey the condensed water to the boiler. The boiler may be constructed in the
usual manner. The steam pipes are of cast-iron and placed vertically, or if hori-
zontally, with a gentle slope towards the boiler. If several stories of a building
have to be heated, a main steam-pipe is carried to the highest story, and branch
pipes are fitted to it. The pipes are here and there fitted with air valves for the pur-
pose of permitting the expulsion of the air compressed by the steam. The boiler, if
low-pressure steam be used, should also be provided with an air valve, in order to
prevent the collapse of the boiler by the outer atmospheric pressure if the generation
of steam ceases. Heating by means of steam is advantageously applicable in works
where steam is used as a motive power.
Combination of Steam and Very recently it has been proposed to combine steam- with hot-
Hot-water Heating. water-heating, and to heat from one central locality a series of
buildings and houses, in the same manner as these are now supplied from one central
reservoir with gas or water.
Gas-Heating. It is well known that illuminating gas is now very generally used for
the purpose of heating, being in this application best mixed with air, as is the case,
for instance, in the Bunsen burner.
Gas is used for cooking in stoves specially constructed for the purpose, and also for
heating apartments and buildings. As a rule it may be assumed that the combus-
tion of 5 cubic feet of gas is sufficient to elevate the temperature of 1000 cubic feet
of air 12°, and one-fifth of this quantity of gas suffices by its combustion to keep the
temperature constant.
Heating without
There is no doubt that an inexhaustible supply of heat exists as latent
Ordinary Fuel. heat, which can be set free by friction, or, in other words, by the conversion
of mechanical force into heat.
Notwithstanding many mechanicians have constructed apparatus for producing heat by
mechanical force, none of these have been found practically available, and some were found
to be extremely wasteful. The heat generated by the fermentation of manure is usefully
applied to heating hothouses, by placing under the manure heap thin sheet-iron pipes,
which convey the heat into the hothouse.
Boiler Heating.
B. Boiler Heating and Consumption of Smoke.
Steam-boilers are as a rule built in brick-work, and in their con-
struction, as well as that of the furnace they are fitted with, economy of fuel is the
great object. The furnace is of course built with fire-bars and ash-pit. The grate
WARMING.
741
or fire-bars consist of parallel cast-iron bars, the size and shape of which depend
upon the kind of fuel to be used, while as regards the space between the bars expe-
rience has taught that the sum should not amount to more than one-fourth of the
total surface of the grate. A large grate has the advantage of more freely admitting
air to the fuel, while obstruction by clinker and slag is less to be feared. The
operation of firing with a large grate is more easily conducted, and can take place at
longer intervals of time. Of course the grate must be kept entirely covered with
fuel. Small grates may be preferable in some instances, especially where a vivid
combustion is required. Grates for wood fuel may have half the surface required for
coal, as with the former the openings between the bars do not become choked with
clinker and slag. According to E. Köchlin a grate for burning in one hour 350 kilos.
of old oak wood should be of 1 square metre surface with square metre for space
between the bars. Usually, however, the grates for wood fuel are made four times
smaller than those for coal.
The fire-place or furnace should of course be constructed of sufficient height,
width, and depth to admit of the proper combustion of the fuel. The fuel should be
thrown into the furnace in sufficiently large quantity at once to keep up the steam
adequately. Too frequent firing is not economical, because a large quantity of cold
air is admitted, which cools the boiler and interferes with the proper combustion of
the fuel. The dimensions of the furnace doors must bear a proper proportion to the
size of the furnace, and these doors must close tightly so as to prevent draughts of
air impinging on the burning fuel.
Apparatus.
Smoke-Consuming While we cannot here enter into any further details on boiler-
furnaces, a subject really belonging to engineering, we may now turn our attention
to smoke-consuming furnaces, contrived with the view not only of abating the
nuisance arising from the smoke evolved in huge volumes from large factory and
other chimneys, but also for the saving of fuel, it having been ascertained that by
the ordinary combustion of 1 ton of coals 25 lbs. of soot are evolved, having a
heating power of four-fifths of the coal. The loss occasioned by the carbon thus
carried off amounts to th, or not quite 1 per cent.
Σ
When green coals are put in quantity on a bright boiler furnace, there is suddenly
evolved an immense volume of combustible gases and vapours containing a large
amount of carbon (benzol, toluol, carbolic acid, anthracen, naphthalin, paraffin, &c.,
the oxygen of the air contained in and supplied to the furnace being usually insuffi-
cient to cause the complete combustion of these substances, so that only the hydrogen
burns, while the carbon is separated as smoke and soot, the evolution being promoted
by the comparatively cool state of the boiler-plates, as well as by the large influx of
cold air at the time of firing. The contrivances for preventing and consuming
smoke are based upon different principles; for instance:—a. Air is sometimes
conveyed to the fire-bridge by means of a separate pipe or channel. b. Two
adjoining furnaces are connected and alternately fired in such a manner that the
smoke of the furnace last fired is consumed in the high red heat of the other furnace.
c. The fresh fuel is spread over only the front of the fire nearest the furnace-door, so
that the evolved gases may be consumed by the red-hot fire on the bars. d. The
feeding is effected by mechanical means, uninterruptedly, in such a manner that the
fuel on the bars remains in a high state of incandescence. e. The construction of
very high chimneys has been resorted to for the purpose of supplying a rapid current
of air; but this expedient, a very expensive one, does not answer the purpose, and
leads to loss of heat.
742
CHEMICAL TECHNOLOGY.
We may mention briefly the following smoke-preventing and consuming appa-
ratus:-
1. Mechanical removal of the smoke by washing the products of combustion. In
some chemical works near Newcastle-upon-Tyne the smoke of the different furnaces
is washed by a spray of water previous to being passed into the chimney. For this
purpose the smoke of the different furnaces of the work is conducted into subter-
ranean brick-work channels, so constructed with knee-bends that the smoke is caused
to flow upwards and downwards alternately, while at the mouth of the furnace-flue a
continuous spray of water is caused to impinge upon the smoke, whereby all solid
particles are thrown down and are removed from the channels as soot. There is in this
case only one chimney, in which the draught is kept up by means either of a blast of
air or a jet of injected steam. Jean, at Paris, has somewhat modified this method by
causing the smoke and waste steam of a high-pressure engine to be conveyed into a
subterranean channel covered with a layer of water several centimetres in depth,
while a jet of cold water is made to play upon the smoke and steam. The channel
FIG. 335.

ab
P
Π
is provided with a kind of water-wheel, which does not quite touch the surface of the
water, but is fitted with brushes, which, touching the water, project it as spray
through the channel. The water becomes heated, and serves after filtration as feed
water.
2. Application of improved fire-bars, to be distinguished as (a) immovable, and
(b) movable.
The
Step Grate. Among the immovable grates are the step- and stage-grates.
former consists of a series of step-like stages of fire-bars, to which the poker has
access from the ash-pit. By the heat of the fire on the lower steps the fuel on the
higher step is converted into coke, and only after this process has continued for some
time is the partly-coked fuel raked down to a lower step, while fresh green coal is
placed on the higher. The air enters this kind of grate not only through the space
between the bars, but also laterally through the grated space between the steps.
Caking-coal, or coal which makes much slag, does not answer as fuel in this grate,
but small coal, refuse peat, sawdust, &c., are well adapted. Instead of iron fire-bars
MM. Longridge and Mash make use of slabs of fire-clay, provided with channels
and perforations so as to constitute a grating.
WARMING.
743
Etage or Stage Grate.
This is a modification of the grate just described, and was invented
by Langen (1866). The green fuel is not placed above the burning fuel, but under
it, for which purpose the grate is constructed in stages, the fire-bars being inclined
to the horizon at an angle of about 28°. There is between each etage, or stage, of
the grate a space of about 12 centims. The fuel becomes coked, and the volatile
products pass, mixed with air, through several stages of incandescent fuel, thus
insuring complete combustion.
Movable Grates. The leading idea of these grates is to effect the firing by mechanical
means. Among these the chain grate and rotating grate deserve notice.
Chain Grate.
Notwithstanding the expensive nature of this invention, it has been
found useful in practice and is employed in many establishments.
It consists
JULE
a
ZAZA
FIG. 336.

(Fig. 335) of two endless flat chains, GG, which run on two octo-geared rollers.
Between these chains the fire-bars are placed longitudinally, so that the grate
consists of an endless series of bars. The distance of the two rollers from each
other determines the length of the grate. A rotating motion is imparted at o in such
a manner that the grate moves through 27 to 30 millimetres per minute. The fresh
fuel is thrown in at B, and is carried continuously towards the fire. The height of
the layer of fuel is regulated by means of the slide-damper, n, which can be moved
by means of the lever, p. The chains and rollers are supported by the truck, 1,
running on the iron rails, H H. The velocity of the grate is so regulated that the
fuel is entirely consumed when arriving at the end of the fire-place. There are
several serious defects in this apparatus. It is complicated, soon out of repair,
requires a considerable amount of force to maintain its motion, and it does not
altogether prevent smoke, while, finally, it is found wasteful for fuel.
744
CHEMICAL TECHNOLOGY.
Rotating Grate. This contrivance, invented by Collier, consists of a rotating disc
which supplies the coal to the furnace uniformly through a slit cut below the furnace
doors. This apparatus has never been extensively in use.
Improved Fuel Supply.
3. Among the numerous suggestions for the better feeding of fur-
naces are the following:-
Collier's feeder (1823) consists essentially of two horizontal crushing rollers
provided with projections, so that the coal is broken up into uniform lumps, and
then thrown into the fire by wheels provided with scoops revolving 200 times a
minute. This mechanism requires a half nominal horse-power to maintain its motion.
Stanley's feeder, Fig. 336, consists of a funnel, a, fitted with toothed crushing
rollers. The crushed coals fall on the distributor, b, which rotating with great
velocity throws the coals uniformly on to the fire. Notwithstanding the defects of
this invention, the chief being that it is not possible for the stoker to fire hard if
required, this apparatus certainly prevents smoke, but is also liable to be quickly
out of repair.
Pult Fires. Pult fires were first introduced by Wedgwood for porcelain furnaces.
The characteristic feature is the mode of admitting air, which instead of entering as
usual from below is forced downwards. The grate is placed in a sloping position.
The fire-doors remain open, while the ash-pit is quite closed. This arrangement
fulfils certainly all the conditions of complete combustion, but in practice has not
answered and is only applicable with wood fuel.
Vogl's Grate. The fire-bars in this grate are placed at an angle of 33°. The coals are
supplied by means of a funnel, and the bars can be shaken up and down by mechanical
means.
Boquillon's Grate. An arrangement of rather complicated nature intended to be applied to
house stoves, and so constructed that the green fuel is brought under the glowing fuel.
The grate consists of a horizontal movable cylinder, upon which the fuel rests. When
fresh fuel is added, this cylinder is turned so as to cause the fuel to be placed below the red-
Apparatus of Cutler hot cinders. In practice this grate has not answered, being too compli-
cated. In many cases it has been attempted to feed the fires in an ascending
mode, as, for instance, in Cutler's grate, improved upon by Arnott in 1854. The coals
are burnt from an iron vessel which is by mechanical means lifted over the fire, the supply
of coals in the vessel being regulated to last for twenty-four hours. In George's apparatus
the fuel is supplied to the grate by means of a screw propeller.
and George.
Apparatus with Unequal 4. Among the apparatus in which smoke is prevented by an
Distribution. unequal distribution of fuel on the grate, that of Duméry, deserves
notice. This arrangement is distinguished from those of Cutler and George by the fresh
fuel being put on from both sides of the grate under the red-hot cinders. For this
purpose the grate is strongly curved upwards, exhibiting a saddle shape. The fuel
is forced on to the grate by mechanical means in such a manner that it is first placed on
the lowest fire-bars, and gradually forced towards the centre. This principle was known
to Watt in 1785, and was applied by him in a slanting grate.
Tenbrinck also places the grate in a sloping direction, so that the coals tumble towards
the fire-bridge, and accumulating there as incandescent coke cause the complete combus-
tion of the fuel. In Corbin's grate a partition of fire-brick is employed. Fairbairn (1837)
appears to have been the first to contrive smokeless grates. In his double grate the fur-
nace is provided with two hearths, two grates, and two furnace doors. The grates
are separated from each other by a partition of fire-bricks. The stoking is so regulated
that while the one furnace is in full combustion, the other is supplied with fresh fuel, this
operation occurring at regular intervals and alternately. The result is that the smoke
and gases evolved are burnt by the highly incandescent fuel of the other furnace. De
Buzonnière contrives to force the smoke of one furnace under the incandescent fuel
of the other. With a properly regulated supply of air and regularity of stoking, it has
been proved, by a series of experiments made on the large scale with a 40 horse-power
marine multi-tubular boiler, by the late Dr. Richardson, of Newcastle-on-Tyne, and by Messrs.
Longridge and Sir William Armstrong, that with all kinds of coal and with every variety
WARMING.
745
of steam boiler, smokeless and complete combustion of the fuel may be obtained without
difficulty, the plan being attended with a considerable saving of fuel and production of its
highest calorific effect.
Consumption of Smoke
Air Currents.
Gall's Fire-place.
5. Nearly all attempts in this direction have proved an utter
by the Aid of Collateral failure in practice. Parkes's (1820) split bridge was constructed with
the view of causing the air to flow partly as usual under the grate, partly to act at the
end of the furnace so as to effect a complete combustion. Palazot's invention, highly
commended by Burnat, Tresca, and others, appears to be somewhat similar. Chanter's
arrangement consists essentially of two grates placed parallel to each other. The green
fuel is put upon one of these, and having been coked by the incandescence of the fuel on
the other grate is raked on to that, thus insuring complete combustion increased by
lateral jets of air.
Gall, reversing the rule that the dimensions of a factory chimney should
bear a proportionate relation to the quantity of fuel to be burnt, has constructed
chimneys, the highest point of which above the buildings is only o'6 metre, and which,
therefore, simply serve to carry off the products of combustion. As the difference of
temperature is the cause of the draught of a furnace, Gall maintains a very high tem-
perature in the combustion room; and in order to carry this out all the causes of loss of
heat are reduced to a minimum in the following manner:-a. While in the ordinary mode
of stoking the heat of the combustion room is necessarily lowered by the influx of cold
air, the grating in Gall's arrangement is partitioned in such a manner that each compart-
ment is gradually supplied with fresh fuel, by which arrangement the formation of smoke
is prevented. b. The furnace is constructed so that the stoker cannot possibly put on too
heavy a charge of green coals, while he is compelled to spread these uniformly over the
fire. c. The loss of heat by radiation from the brick-work, fire-doors, &c., is prevented
by causing the air required for the combustion of the fuel to pass these hot surfaces.
d. Gall retards the velocity of the gases which escape to the chimney, while the surface of
the grate and the section of the chimney are enlarged. Indeed, the entire arrangement is
quite different from that in ordinary use, as the fire-bars are placed 3 metres below the
boiler, while the grate is very deep. It was found, however, that when well built there
was a sufficient draught, and steam could be kept up. Nothing is stated as regards
the nature of the gases issuing from the chimney.
Resumé. As regards smoke consuming and preventing apparatus, it is only too
evident that most of these do not answer the purpose so completely as might
be expected. Practical experience has, however, taught that if the conditions
of complete combustion are well attended to in the construction of the furnace, that
with proper management and regular mode of stoking, adequate supply of air,
and the application of the well-known means of preventing loss of heat by radiation,
with coal, peat, or any other fuel, the combustion may be so conducted as to
be smokeless; and at the same time the fuel thoroughly utilised.
OCT 17 1916
ACETATE of alumina, 263
lead, 64
Acetometry, 468
INDEX.
Adamantine or diamond-boron, 256
Adulteration of white-lead, 72
Aërostatical lamps, 641
Air drains, 475
gas, 674
Alabaster glass, 290
Albumen glue, 536
Alkali for treating gold, 106 -
Alcohol, 424
and its technically important pro-
perties, 424
vinegar from, 461
Alcoholometry, 447
Alizarine, 584
Alkalimetry, 224
Alloys and preparations made and
obtained from metals, 4
of copper, 51
gold, 109
lead, 62
rickel and copper, 41
silver, 103
platinum, 96
Aloe hemp, 341
Alpaca wool, 495
Alum and sulphate of alumina, uses
earths, 257
of, 263
flour, 258
roasting, 257
from Bauxite, 259
blast furnace slag, 260
felspar, 260
manufacture, material of, 256
preparation, 257
from alum-stone, 257
clay, 258
alum-shale and alum earths,
257
cryolite, 258
production, 256
properties of, 260
shale, 257
works, preparation of green vitriol
as a by-product in, 32
Alumina acetate, 263
sulphate of, 261
Aluminate of soda, 262
Aluminate 8, 256
Alnminum, applications of, 114
preparations. 113
properties of, 113
Amalgamation, extraction of silver by,
97
process, American, 98
European, 97
American amalgamation process, 98
Ammonia-alum, 260
Ammonia and ammoniacal salts, 226
as a by-product of beetroot sugar
manufacture, 236
carbonate, 238
from bones, 235
gas-water, 230
lant, 234
inorganic sources of, 228
nitrate, 238
preparation of liquid, 227
sulphate, 238
Ammoniacal liquor, 666
salts, technically important, 236
Amorphous phosphorus, 545
Ananas hemp, 341
Aniline, 573
black, 579
blue, 578
brown. 579
colours, 575
green, 578
orange, 579
printing, 614
red, 575
violet, 577
yellow, 579
Annatto or arnotto, 595
Annealing, 20
Annular kilns, 317
Anthracen pigments, 584
Anthrachinon, 584
Anthracite, 719
Antichlor, 349
Antimonial preparations in technical ·
use, 84
Antimony, 82
black sulphuret of, 85
cinnabar, 85
oxide, 14
properties of, 84
sulphuret for refining gold, 106
Apparatus for consuming smoke, 741
Apparatus for distilling, 432
heating, 731
Areometer, 447
to test milk, 558
Arrow-root starch, 360
Arsenic, 85
acid, 86
li
INDEX.
Arsenic, red, or realgar, 87
sulphurets, 86
yellow sulphuret, 87
Arsenious acid 85
Artificial illumination, 617
Asphalte, 484
Assay, dry, 103
hydrostatical, 104
of silver, 103
wet, 104
Augsburg method of mash-boiling, 410
AUGUSTIN'S method of silver ex-
traction, 99
Aurum musivum, mosaic gold, 75
Aventurin glass, 291
Azale, 587
Azaleine, 575
Azuline, 578, 581
Azurine, 578
ALDAMUS and GRUNE'S gas,
674
BALDAMUS a
BALLING'S saccharometrical beer test,
420
Bandanas, 616
Bar шon, 20
properties of, 26
Bark of oak, 509
or red tanning, 509
Bauxite, preparation of alum from,
259
Beer brewing. 403
materials, 403
constituents of, 418
processes of brewing, 405
testing, 420
wort fermentation, 405, 414
Beet, chemical constituents of, 368
molasses, 382
sp cies of, 367
washing and cleansing, 371
Beet-root juice, components of, 373
evaporating, 380
filtration through animal char-
coal and evaporation of, 374
separating the juice from, 371
sona from, 171
sugar, 367
manufactory, ammonia as a by-
product of, 236
Bell-metal, 51
Benzol, 570
Berlin blue, 36
soluble, 37
Berlin or Prussian blue on wool, 604
BERTHIER'S reduction method, 700
BERZELIUS's indigo test, 593
Bessemer steel 27
Bicarbonate of soda, 190
Bismuth, applications of, 77
occurrence and mode of obtaining,
76
Bismuth, properties of, 77
Bisulphate of soda, 214
Bitumen, paraffin from, 685
Black-jack, mode of obtaining zinc
from, 79
Black platinum, 95
suphuret of antimony, 85
Blast, blowing engine and, 12
Blast-furnace, chemical process going
on in the intenor of, 13
description of, 11
gases, 15
process, 10
temperature of at different points,
15
Blasting powder, new kinds, 154
Bleaching. 597
glass, 270
Bleaching-powder and hypochlorites,
214
preparation, 214
properties of, 220
theory of the formation of, 220
Blistered metal, refining, 49
Blowing engine and blast, 12
Blue va's, 602
vitriol, 54
applications of, 56
Boghead coal, 722
Bohemian crystal glass, 268
Boiler heating, 740
Boiler plate, rolling, 24
Bois roux, roasted wood, 712
Bombay hemp, 341
Bone-ash decomposition by sulphuric
acid, 538
Bone-black preparation, 553
properties, 554
substitutes, 555
Bones, ammonia from, 235
glue from, 532
BOQUILLON'S grate, 744
BOUCHERIE'S method of mineralising
wood, 477
Boracic acid, formation, 250
production, 250
properties and uses, 251
Borax, 252
from boracic acid, 252
octahedral, 255
purifying. 254
uses of, 255
Boric or boracic acid and borax, 249
Brandy distilling, relation of to agri-
culture, 448
Brazil or camwood, 588
Brass, 52
tinning of. 75
Bread baking, 451
composition of, 459
impurities and adulteration, 460
making, modes of, 451
oven, 454
Bremen blue, 56
INDEX.
Bremen green, 56
Brewing by steam, 418
beer, 403
process, by products of, 423
Brick material. 311
moulding, 312
Bricks 310
and lime kilns for burning, 325
field burning of, 318
fire, 319
floating, 318
from dried clay, 314
the burning of, 315
Brine, boiling down, 168
common salt from, 168
concentrating 168
Briquettes, 730
Bromine preparation, 193
Bronze, 51
Brown coal, 691. 716
Brunswick-green, 56
Buckthorn dyers, 596
Burners for wod gas, 670
Burning of the bricks, 315
Butter, 558
chemical nature of, 559
C4 Cak⋅ng
YADMIUM, 82
Cak ng coal, 719
Calcining or roasting the ores, 48
Calcium-soap 249
Calico dyeing 608
printing, 612
discharges. 611
resists or reserves, 610
thickenings, 610
Calorifères, 738
Calorific effec', 698
Campeachy 594
Camwood or Brazil, 588
Candle making, 627
Candles from fatty acids, 631
light from, 620
moulding 628, 633
paraffin, 630
sperm. 634
stearine, 621
tallow, 629
wax, 631
Cane-sugar, 364
Caoutchouc, 484
and gutta-percha, mixture of, 488
production and consumption of, 486
solvents of, 485
vulcanised, 486
Capsule, or sagger, 301
Carbolic acid dyes, 580
Carbon, 211
imparting to wrought-iron, for
steel-making, 28
sulphide, 210
Carbonate of ammonia, 238
potassa, 118, 121
Carbonised peat, 715
Cardboard, 354
Carinthian cast-steel, 27
Carmine-red, 589
Carrara and Parian, 304
iii
Cartridges of needle-guns, mixture for
igniting, 157
Cassava starch, 360
Casein as a cement, 562
glue, 536
Cashmere, 500
wool, 495
Casselmann's green, 57
CASSIUS's purple, 111
Cast-iron, 16
crude, re-melting, 18
enamelling, 20
grey 16
white, 16
Cast-steel, 29
Caustic potassa, 133
soda, 189
Cement, artificial, manufacture in
Germany, 330
Cements, 327
artificial, 328
lutes and puity, 491
Cementation process, 107
Centrifugal drier, 381
machine, 391
Ceramic or earthenware manufacture,
293
Cere»ls, vinous mash from, 426
Chair grate, 743
Chamber acid, 206
Charbon roux, torrified charcoal, 711
Charcoal, animal. 553
Berlin blue as a by-product in
manufacture of, 37
burning, 706
combustibility and heating effect,
711
properties of, 710
revivification of, 555
sulphur obtained by the reaction of
sulphurous acid on, 198
torrified, or charbon roux, 711
wood, 704
Chatham light, 680
Cheese, 559
Chemical metallurgy, 4
Chestnut starch, 360
Chili-saltpetre, iodine from, 192
preparation of nitrate of potassa
from, 138
Chimney heating, 733
Chinese galls, 511
China gras-, 340
Chlorate of potassa, 223
Chloride of sulphur, 211
zinc, 81
potassium, 119
Chlorine, 214
iv
INDEX.
Chlorine, apparatus for preparing, 216
Chlorine, condensing apparatus, 217
preparation without manganese,
215
production residues, utilisation, 218
residues, other methods of utilising,
219
Chlorometry, 221
Chlorometrical degrees, 222
Chromate of lead, 64, 66
zinc, 81
Chromates of potassa, applications of,
65
Chrome-alum, 67
Chrome, oxide or chrome green, 67
red, 66
yellow, 66
Cinchonine pigments, 585
Cinnabar, 91
Clay, kinds of, 294
pipes, 309
preparation of alum from, 258
for brick-making, 311
ware dense, 296
kinds of, 296
porous, 297
Clays and their application, 293
colour of, 294
plasticity of, 294
technically important qualities of,
293
Clinkers, Dutch, 318
Cloth, bough, washing and milling, 499
dressing, 499
fabrics, 500
teasling and shearing, 499
white, 606
weaving, 499
Coal, 717
Boghead, 722
brown, 716
caking, 719
Coal-tar. 666
accessory constituents of, 718
colours, 569
Coal-gas, 646
Berlin blue as a by-product in
manufacture of, 37
composition of, 668
manufacture of, 648
manufacture, by-products of, 665
Coals, calorific effect, 721
classification of, 718
evaporative effect of, 721
Cobalt and potassa, nitrate of prot-
oxide of, 39
bronze, 39
colours, 37
green, 39
metallic, 37
protoxide, chemically pure, 39
speiss, 38
ultramarine, 38
Cæruleum, 39
Cochenille, or cochineal, 589
Cocoa-nut fibre, 341
Cocoon, killing of the pupa in, 503
Coke, 665, 723
composition and value as fuel, 729
properties of, 729
Coking in heaps, 724
in ovens, 724
Collodion, 162
Colorine, 588
Coloured fires, 157
Colours, aniline, 575
coal-tar, 569
topical, or surface, 613
Colza oil, 637
Common pottery, 310
Coolers for water, 309
Copper, 43
alloys, 51
amalgam, 54
and nickel alloys, 41
blistered or crude, 49
from oxidised ores, 49
hydrometallurgical method of pre-
paring, 49
ores, treating of for extraction, 44
pigments, 56
preparations of, 54
properties of, 50
refining, 46
smelting, English mode, 47
solution for electro-plating, 116
stannate of oxide of, 58
sulphate, 54
tinning of, 75
Colate engravings, reproduction,
115
Copperas, 31
Coralline, 581
Cordwain, Cordovan leather, 521
Cordials, preparation of, 482
Cork pommels to raise the grain of
leather, 519
Cotton, 342
combing or carding, 342
detection in linen fabrics, 343
fabrics, 343
species, 342
spinning, 342
substitutes, 343
Crucibles, 321
distillation of zinc in, 79
Crude iron, statistics concerning the
production of, 18
Cryolite, decomposition of by ignition
with carbonate of lime, 259
with caustic lime by the
wet way, 259
glass, 291
preparation of alum from, 258
soda from, 188
Crystal-glass, 285
INDEX.
Cupola, or shaft furnace, 18
Cutch, 512
Cyanide of potassium, 35
AMASCENE, 30
DAD
Decoction method of preparing
the wort, 409
Decomposition furnace, new, 173
Defuseling, 445
De-liming, or saturating the juice with
carbonic acid, 373
the juice, other methods, 374
DEVILLE AND DEBRAY'S method of
extracting platinum, 95
Dextrine, 361
Diamond boron, or adamantine, 256
Dinas bricks, 321
Discharge style, 614
Discharges, calico printing, 611
Distillation of the mash, 431
Distillery apparatus, 432
continuous, 440
Dividivi, 511
DORN'S apparatus, 433
Drain tiles, 318
DUMONT'S filter, 375
DUNLOP's process, 218
Dutch clinkers, 318
tiles, 318
Dye-materials, blue, 591
red, 586
Dyeing and printing in general, 568
blue, and with logwood and a
copper salt, 604
calico, 608
linen, 609
spun yarn and woven textile fab-
rics, 599
silk, 606
wool blue, 601
woollen fabrics, 601
red, 605
yellow, 604
Dyes, 568
black, 605
brown, green, and black, 596
carbolic acid, 580
green, 605
red, less important, 591
yellow, 595
Dynamite, NOBEL'S, 160
EFF
FFERVESCING wines, 399
Elayl platino-chloride, 96
Electric light, 680
Electro-metallurgy, 114
Electro-plating with gold and silver,
115
Electro-stereotyping, 117
Electrolytic law, 114
Electrotyping, 115
Emerald green, 58
Enamel, bone glass, 290
Enamelling of cast-iron, 20
Engraving steel, 31
Etage or stage grate, 742
Etching by galvanism, 117
Etruscan vases, 309
European amalgamation process, 97
Explosive compounds, technology of,
148
AGGOT gradation, 168
FA
Fatty acids, candles from, 631
manufacture, 627
Fayence ware, 307
flowing colours, 309
ornamenting, 308
Felspar, 293
mode of obtaining potassa from,
122
Fermentation, 386
after, in the casks, 416
alcoholic or vinous, conditions of,
389
of the grape juice, 393
potato mash, 429
beer wort, 414
mash, 427
sedimentary, 415
surface, 417
Ferments, substitutes for, 456
Fibre vegetable, technology of, 338
Filter for beet-root juice, 375
Fire-bricks, 319
Fire clay stoves, 734
Fire-gilding, 110
Fireplace gulls, 745
Fire, requisites for producing, 546
Firework mixtures, commonly used, 156
Fireworks, chemistry of, 148
chlorate of potassa mixture, 156
friction mixtures, 156
grey-coloured mixtures for, 156
Flame, 618
Flannel, 500
Flax, 338
combing, 340
beating or batting, 339
hot-water cleansing, 339
spinning, 340
Flaxes from New Zealand, 341
FLECK's process of preparing phospho-
rus, 543
Floating bricks. 318
Flowers of sulphur, 197
Flue heating, 739
Franklinite, 9
Frieze, 500
Fritte porcelain, French, 304
English, 304
FUCHS's beer test, 422
Fuchsin, 575
Fuel artificial, 729
and heating apparatus, 698
vi
INDEX.
Fuel, brown coal as, 717
combustibility of, 698
determination of combustive power,
699
elementary analysis, 700
inflammability of, 698
ga-eous, 730
petroleum as, 722
pyrometrical
calorific effect, 701
specific calorific effect, 701
supply improved, 744
STROMEYER's test. 701
value of coke as, 729
Fulling soaps, 245
Fulminating mercury, 92
Furnace, cupola or shaft, 18
reverberatory, 18
working copper ores in, 44
Fustic, yellow dye 595
Fusel oils, removing, 445
ALACTOSCOPE to test milk, 558
Gall-nut, 511
GALL'S apparatus, 435
fireplace. 745
Galvanism, application of, 114
etching by, 117
Galvanography, 117
Galena, 59
Garancine 587
Garanceux, 587
Gas, BALDAMUS and GRUNE's, 674
burner-. 665
carburetted, 674
charging the retorts and distilla-
tion, 650
co ling or condensing apparatus, 652
distribution of, 660
exhauster, 654
general introduction and historical
notes, 645
heating 740
GILLARD S platinum, 672
for hea ing purposes, 731
illuminating testing, 661
from pest, 670
petroleum, 676
petroleum oil, or oil from bitu-
minous shales, 675
suint, 675
Gas, retorts, 648
the scrubber, 653
Gas-water, 671
ammonia from, 230
Gaseous fuel, 730
Gases, blast-furnace, 15
heating with, 24
GATTY's process, 219
GAY-LUSSAC s chlorometric method,
221
GENTELE'S method of preparing phos-
phorus, 544
GERLAND'S method of preparing phos-
phorus, 544
German iron refining process, 21
- silver, 53
Germination of the softened grain, 406
Gilding, 110
by the cold process, 110
wet way, 110
porcelain, bright, 303
GILLARD'S gas, 672
Glass, aluminium-calcium alkali, 269
aven'urin. 291
bleaching 270
bottle, 282
classification of the various kinds,
268
clear melting, 275
cold stoking, 275
coloured, and glass staining, 289
crown, 277
cryolite, 291
crystal, 285
defects in, 276
definition and general properties
of, 268
filigree or reticulated, 292
ice, 291
making, raw materials, 269
material melting, 275
melting and clearing, 280
optical, 286
oven, 271
painting, 289
pearls, 292
plate, 279
casting and cooling, 281
wood, 668
holders, 656
hydraulic valve, 661
ISOARDS 674
lighting, raw materials of, 646
lime, 667
manufacture, sulphur as a by-pro-
duct, 198
meters, 664
oil, resin, 674
pre-sure regulator, 661
products of the distillation, 647
purifying, 654
or window. 276
polishing, 281
platinising, 282
potassium-calcium, 268
potassium-lead, 269
preparation of the material and
melting, 274
pressed and cut, 283
refuse, utilisation, 270
relief, 291
sheet or cylinder, 278
silvering, 281
by precipitation, 281
sodium-calcium. 268
technology of, 268
INDEX.
vii
Glass, the melting vessel, 270
tools for, 277
various kinds, 276
water, 283
GLAUBER'S salt, 213
Glue boiling, 528
drying, 531
from bones, 532
leather, 529
liquid, 533
substitutes for, 536
test for quality of, 533
treating with lime, 529
Gluten glue, 536
Glycerine, 634
Glyphography, 117
Gold alloys, 109
applications of, 110
chemically pure, 108
colour of, 109
and silver, electro-plating with,
115
extraction from other metallic ores,
106
poor materials, 106
leaf for gilding, 110
mode of extracting, 105
mode of extracting by means of
mercury, 106
mosaic, 75
Gun-metal, 51
Gunpowder, 148, 156
caking or pressing, 150
composition, 152
drying. 151
granulated, polishing, 150
granulation of the cake, and sort-
ing the powder, 150
manufacture, 148
mechanical operations, 149
mixing the ingredients, 149
products of combustion of, 153
properties of, 151
pulverising the ingredients, 149
sifting the dust from, 151
testing strength of, 154
white, 154
Gutta-percha and caoutchouc, mixture
of, 488
solvents, 487
uses of, 487
Gutter tiles, 318
Gypsum, 333
casts, 336
grinding, 335
hardening of, 336
kilns or burning ovens for, 334
nature of, 333
uses of 335
ABANA brown, 580
occurrence and mode of extracting, Hamatinon astralite, 291
105
properties of, 108
refining, 106
salts, 111
size, 489
smelting for, 106
solution for electro-plating, 116
testing the fineness of, 109
treating with alkali, 106
Grain germinated drying, 407
Grape-juic fermentation, 393
Grape-sugar, 383
preparation, 384
uses of, 386
Grapes, pressing, 391
Grate, BOQUILLON'S, 744
chain, 743
étage or stage, 743
rotating, 744
step, 742
VOGL'S. 744
Grates, movable, 743
Greea vitriol, 31
preparation of, as a by-product
in alum works, 32
Grenate brown, 581
GRUNEBERG'S method of estimating
the value of potash, 226
Gun-cotton, 160
as a substitute for gunpowder, 162
other uses, 162
properties of, 161
Hæmatite iron ore, 8
Heat, mechanical equivalent of, 702
Heating apparatus, 731
by flues, 739
hot air, 737
water, 739
direct,732
dwelling-houses, 732
with gases, 24
steam, 740
without ordinary fuel, 740
Heaton steel, 28
Hemp, 340
substitutes, 340
Hides, cleansing, 514
swelling, 515
stripping off the hair, 515
HOFMANN S process, 219
Hollander mill, 347
Hops, 404
adding, 412
quality of, 404
substitutes for, 405
Hot-pressing, finishing, and dressing
616
Houses, heating, 732
Hungarian tawing process, 524
Hyalography, 292
Hydraulic main for gas, 650
mortar, 327
valve, 661
viii
INDEX.
Hydrocarbon process (WHITE's) for
water-gas, 673
Hydrochloric acid, 211
properties of, 213
uses of, 213
Hypochlorites alkaline, 223
Hyposulphite of soda, 201
Hyposulphurous acid, 199
CE-GLASS, 291
ICE
Illumination, artificial in general,
617
TESSIE DU MOTAY'S method, 679
with lamps, 636
India-rubber,preparation and use of,486
Indigo, 591
properties, 592
recovery from rags, 604
testing, 592
Indigo-blue, 594, 602
Ink for marking, 105
printing, 489
Iodine from carbonised sea-weed 192
Chili-saltpetre, 192
preparation, 191
properties and uses of, 193
Iron, 8
cast, 16
cement, 493
crude 16
extraction, 9
process, theory of, 10
foundry work, 18
malleable, tinning of, 75
metallic, green vitriol from, 32
minium, 32
ore hæmatite, &
magnetic, 8
marsb, 9
pea, 9
spathose, 8
refining by mechanical means, 24
German, 21
Swedish, 22
sheet, tinned, 75
stones, 734
wire manufacture, 25
Isinglass, 535
ISOARD'S gas, 674
JUTE, 341
AOLIN, 293
KA KARMARSCH'S evaporation
method, 699
Kelp, 130
•
preparation of iodine from, 191
Kilns, annular, 317
for burning lime and bricks, 325
gypsum, 334
lime, continuous, 324
Kino, 512
occasional or periodic, 323
KNAPP's leather, 525
Kneading machines, 453
L
AC dye,590
Lacquered leather, 521
Lactose, sugar of milk, 557
Lake pigments, 568
Laming mixture, 667
Lamp with constant oil level, 640
Lamps, 636
for illumination, 636
petroleum oil and paraffin oil, 644
pressure, 641
statical, mechanical, clockwork,
moderator, 642
suction, 639
various kinds, 639
LAMY'S refining apparatus for sulphur,
196
LANGIER'S apparatus, 443
Lant, ammonia from, 234
Lead acetate, 64
alloys, 62
•
basic chloride of as a substitute
for white-lead, 71
chloride, white-lead from, 71
chromate, 64, 66
containing silver, mode of pre-
paring, 100
metallic, applications of, 62
obtained by calcination, 60
precipitation, 59
occurrence of, 59
oxide, 63
combinations of, 64
preparations of, 63
properties of, 62
sulphate, white-lead from, 70
peroxide, 64
Leaden pans, concentration in, 207
Leather, cordwain, Cordovan, 521
dressing or currying, 518
finishing, 519
for gloves, 524
glue, 529
graining, 519
greasing, 519
KNAPP S process, 525
lacquered. 521
morocco, 520, 521
polishing with pumice-stone, 519
preparation of white, 522
Russia, 520
8' le, 518
the paring, 518
the scraping or smoothing,
upper, 518
LEBLANC's process, theory of, 183
LEPRINCE'S water-gas, 674
Ley, 242
evaporation of, 180, 257
Light, materials and apparatus for
producing artificial, 617
INDEX.
ix
Line and tricks, kilns for burning, 325
lime-burning, 322
cements, 491
light, 678
preparation of fatty acids by means
of, 621
properties of, 322, 225
slaking, 326
sulphite of, 201
treating glue with, 529
uses of, 326
Linen-dyeing, 609
fabrics, detection of cotton in, 343
goods priating, 616
Litharge, 63
revivification of, 61
Lithophanie, 303
Litmus, 594
Liquation process, 47
Liquid glue, 533
Lixiviation, 257
Loam, 296
Logwood, 594
and a copper salt to dye blue, 604
London board, 354
Lucifer matches manufacture, 548
LUNGE'S apparatus, 232
Lustres, 309
Lye, raw, breaking up of, 136
boiling down, 136
treatment of, 136
MACHINE for paper-cutting, 353
paper, 352
Machines for moulding bricks, 312
Madder, 586
flowers of, 587
lake, 587
Magdala red, 583
Magenta, 575
Magnesium, 114
light, 679
Maguetic iron ore, 8
Malachite, 43
Malleable, bar, or wrought iron, 20
MALLET'S apparatus, 230
Malt, the bruising of, 408
Malting, 405
Mandarin printing, 616
Manilla hemp. 341
Manganese and its preparations, 111
soap, 249
testing the quality of, 111
Marking ink, 105
Marl, 295
Marsh iron ore, 9
Martin steel, 28
Martius yellow, 582
Mash boiling thick, 409
distillation of, 431
from potatoes, 427
roots, 429
with sulphuric acid, 428
Mashing, 408
Massicot, 63
Matches anti-phosphor, 552
lucifer, manufacture of, 548
wax or vesta, 553
Mauve, 575
Meat, constituents of, 562
the cooking of, 563
generalities, 562
preservation of, 564
salting 565
smoking or curing, 566
the boiling of, 564
Meerschaum pipes, artificial, 337
Mercurial compounds, 91
Mercuric chloride, 91
Mercury, applications of, 91
extracting by Spanish method, 89
extraction of gold by means of, 106
fulminating, 92
method of decomposing by the aid
of other substances, 90
method of extracting, pursued in
Idria, 87
occurrence and mode of obtaining,
87
or quicksilver, 87
preparations of, 91
properties of, 91
Metal, coarse, roasting or calcining,
49
Metals. alloys and preparations from, 4
steel and other, 30
Metallic iron, green vitriol from, 32
Metallochromy, 117
Metallurgy, chemical, 4
meaning of the term, 4
Meters for gas, 664
Milk, 556
means to prevent becoming sour,
557
sugar of-lactose, 557
testing, 557
Millifiore work, 292
MINARY'S process of preparing phos-
phorus, 544
Mineral green and blue, 57
oil, preparation of, 694
potash, 121
Mineralising wood, 476
Minium, red-lead, 63
Mobair, 495
MOHE'S method, 225
Moire-metallique, 75
Molasses, 566
beet, 382,
potash from, 122
Mordants, 601, 609
Morocco leather, 520, 521
Mortar, 326
hardening, 327
hydraulic hardening of, 331
Mosaic gold, 75
X
INDEX.
邕
​Moulds, making, 19
Muffles, distillation of zine in, 78
Muriatic acid, 211
Must, chemical constituents of, 391
Mycoderma aceti, vinegar with the
help of, 466
NA
APHTHALINE blue and naptha-
line violet, 583
pigments, 581
Neapo itan yellow, 85
Neft-gil, paraffin from, 684
Nettle cloth and muslin, 341
Nickel and copper alloys, 41
and its ores, 39
metallic preparation, 41
properties of, 43
silver, 53
Nitrate of ammonia, 239
potassa, 134
silver, 105
from Chili-
preparation
saltpetre, 138
soda, soda from, 189
tin, 76
Nitric acid, 142
bleaching, 143
condensation, 144
density of, 146
fuming, 147
in saltpetre, quantitative esti-
mation of, 140
manufacture, other methods,
145
uses of, 147
Nitro-benzol, 572
pigment directly from, 581
Nitro-glycerine, 158
Nobel's dynamite, 160
Nut-galls, 511
AK bark, 509
OAK
Oil, blue, 57
cements, 491
colza mineral, 637
gas, resin gas, 674
varnishes, 488
Oils crude, rectification of, 689
essential and resins, 480
extraction by fatty oils, 481
preparation of, 481
paraffin, 683
purifying or refining, 636
treatment of the products of dis-
tillation of, 689
Oleic acid soap, 245
Olive-oil soap, 243
Optical glass, 286
Ores, 4
calcining, or roasting, 48
dressing of, 5
oxidised, copper from, 49
preparation of, 5
Ores, smelting, 48
smelting of, 5
Orchil and Persio, 590
Orpiment, 87
Ovens, coking in, 724
for burning gypsum, 334
for porcelain, 301
or kilns, carbonisation of wood in
706 70S
Oxide of antimony, 84
Oxidised silver, 105
Oxysulphuret of antimony, 85
Ozokerite and neft-gil, paraffin from,
684
PEONINE or coralline, 581
Pans for evaporating beet-root juice
375
Paper-cutting machine, 353
different kinds, 351
drying, 351
history of 345
machine-made, 352
making, 345
manufacture by hand, 346
materials of manufacture, 346
pressing, 351
pulp-bluing, 350
sheets straining, 350
sizing 351
sizing the pulp, 350
Papier-maché, 355
Paraffin candles 630
crude, refining of, 690
from bitumen, 685
from ozokerite and neft-gil, 684
HUBNER'S method of preparing,
690
manufacture, 683
oils, 683, 693
oil lamps, 644
preparation by dry distillation, 68
from petroleum, 684
properties of, 692
yield of, 691
Parchment, 527
paper, 355
Parian and Carrara, 304
Paste, 493
Pasteboard making, 353
PATTINSON'S method of refining silver,
101
Pea-iron ore, 9
Pearls, blown, 292
solid, 292
Peat, 712
glass, 292
carbonised, 715
drying, 713
gas, 670
heating effect of, 715
new method of utilising, 715
INDEX.
XI
Pecquer evaporating pan, 376
PENNY'S indigo test, 593
PENOT S test, 221
Peras, 729
Percussion caps, 93
powders, 156
Perfumes chemical, 482
Perfumery, 481
Permanganate of potassa, 112
Petroleum as fuel, 722
constitution, 696
crude, refin ng, 696
oil and its occurience, 695
gas from, 675
lamps, 644
origin and formation of, 695
technology, 697
PETTENKOFER's process for restoring
pictures, 490
Phenicienne, phenyl brown, 581
Phenyl blue, 581
Phosphorus, distillation of, 538
FLECK S process, 543
making, burning the bones to ash,
538
manufacture, 537
other proposed methods of pre-
paring, 543
preparing by GENTELE, GERLAND,
MINARY, and SONDRY'S methods,
544
properties of, 544
and preparation, 537
red or amorphous, 515
refined, moulding, 541
refining and purifying, 540
Physic, or nitrate of tin, 76
Picric acid, 580
Pictures, PETTENKOFER'S process for
restoring. 490
Pig or crude iron, 9
Pikaba hemp, 341
Pigments from cinchonine, 535
lake, 568
naphthaline, 581
red, 586
Pipes of clay, 309
Platinum, WOLLASTON'S method of
extracting, 94
Porcelain articles, preparation with-
out moulds, 299
bright gilding, 303
casting 299
clay, 293
drying, 299
the mass, 297
faulty ware, 302
French fritte, 304
glaze applying, 300
glazing, 299
kneading the dried mass, 298
grinding and mixing the material,
297
hard, 297
ornamenting, 303
oven, 301
painting, 302
oven, emptying and sorting the
ware, 302
silvering and platinising, 303
tender, 304
moulding, 298
the potter's wheel, 298
Portland cement, 329
Potash from molasses, 122
from the ashes of plants, 122
GRUNEBERG's method of estimating
the value of, 226
purified preparation of, 133
Potassa and cobalt, nitrate of prot-
oxide of, 39
carbonate of, 118
chlorate of, 223
chromates, applications of, 65
mode of obtaining from felspar, 122
neutral or yellow chromate of, 64
nitrate of, 134
permanganate of, 112
salts from sea-water. 122
sea-weeds, 129
suint, 132
the Stassfurt salt minerals,
118
PISTORIUS'S apparatus, 435
Pit coal, 717
Plaster of Paris forms, moulding in,
299
Platinum alloys, 96
black, 96
vinegar, with the help of, 467
gas, 672
hammered or cast, 95
method of DEVILLE and DEBRAY,
95
occurrence of, 93
ores, 93
properties of 95
retorts, 207
spongy, 95
sources whence derived, 118
sulphate of, 121
yellow prussi>te of, 32
Potassium, chloride of, preparation, 119
cyanide, 35
Potatoes, mash from, 427
starch from, 357
Potato-mash fermentation, 429
starch drying. 358
Potter's clay, 295
Pottery common, 310
Printing and dyeing in general, 568
ink, 489
linen goods, 616
silk goods, 616
woollen goods, 616
of woven fabrics, 609
7
xii
INDEX.
Prussian blue cn wool, 604
Puddling furnace, 22
process, 22
Pulp, bleaching, for paper, 349
Pult fires, 744
Pumice-stone to polish leather, 519
Purple, CASSIUS'S, 111
Pyrites distillation, green vitriol from
residues of, 32
preparation of sulphur from, 197
use of for the preparation of sul-
phurous acid, 206
Pyrotechny, 148
Q
chemical principles of, 155
UARTATION, 107
Quercitron bark, 596
Quicksilver or mercury,
RAG
87
AGS, cutting and cleaning, 347
for paper, additions of mineral
to, 346
substitute for, 346
Raw lead, 61
Realgar, 87
Red arsenic, 87
Red lead, 63
phosphorus, 545
prussiate of potash, 35
Refined steel, 29
Refining copper, 46
Resins, 483
Resin cements, 492
gas, 678
oil gas, 674
Resin-tallow soaps, 245
Resin, use of as sealing wax, 483
Resume, 745
Retort furnaces, 650
Retorts for gas, 648
glass, concentration in, 208
platinum, 207
Reverberatory furnace, 18
Rhea grass, 341
Rice starch. 360
RINMANN'S, or cobalt green, 39
Rock salt, 165
mode of working, 167
Roll sulphur, 197
Roofing tiles, 318
Roots, mash fr ›m, 429
Roseine, 575
·
ROSE'S apparatus, 232
Russia leather, 520
Rough steel, 27
Kusina, 87
Russian stoves, 734
SAC
ACCHARIMETRY, 369
Saccharometrical beer test, BAL-
LING'S, 420
Sago, 361
Safflower, 589
Sal ammoniac, application of gases to
the manufacture of, 16
Salines, method of obtaining common
salt in, 164
Salt, common, direct conversion of
into soda, 188
method of obtaining in salines,
164
method of preparing from sea-
water, 163
occurrence of, 163
properties of, 169
uses of, 170
Saltpetre, 134
and sulphur mixture, 156
crude, refining, 137
mode or obtaining, 135
occurrence of native, 134
of the earth, treatment of, 135
quantitative estimation of nitrig
acid in, 140
testing, 140
uses of, 141
Salt-springs, mode of working, 167
Samian, or oil-tawing process, 525
Sandal wood, 588
Sanitary ware, 321
Sap, chemical alteration of the con-
stiruents of, 475
elimination of the constituents of,
474
Saponification, theory of, 242
with lime, 623
sulphuric acid, 624
water and high pressure, 626
SAUERWEIN's method f decomposition
cryolite with caustic lime, 259
Saxony blue. 603
SCHAFFNER'S sulphur regeneration
process, 185
SCHEELE'S green, 57
Schist or alum-shale, 257
SCHWARZ's arparatus, 436
SCHWEINFURT green, 58
Sealing-wax, use of resin as, 483
Sea-weed carboni-ed, indine from, 192
Sea-weeds, potassa salts from, 129
Sea-water, method of preparing com-
mon salt from, 163
potassa salts from, 122
Sericiculture, 501
Shaft or cupola furnace, 18
Shagreen, 537
Shear-steel, 29
Sheep-shearing, 498
Shot manufacture, 62
Siderography, 31
Siderolite and terralite ware, 307
SIEMENS'S apparatus, 440
Silica ultramarine preparation, 267
Silk, 501
Silk bleaching, 599
dyeing, 606
INDEX.
xiii
Silk goods, printing, 616
manipulation, 503
scouring or boiling the gum out,
504
testing, 504
to distinguish from wool and vege-
table fibre, 506
weaving, 505
Silkworms, 501
Silver, alloys of, 103
alloy for plate, 103
and gold for electro-plating, 115
and its occurrence, 96
assay, 103
chemically pure, 102
extraction by amalgamation, 97
AUGUSTIN'S method, 99
the dry way, 100
from i's ores, 96
sundry hydro-metallurgical me-
thods of, 99
German or nickel, 53
mode of preparing the lead con-
taining, 100
nitrate of, 105
oxidised, 105
properties of, 102
reduction by means of zinc, 102
refining process, 100
smelting for, directly, 97
solution for electio-plating, 116
ultimate refining of, 102
Silvering, 104
- by the wet way, 105
fire or igneous, 104
in the cold, 104
Sizing the paper, 351
Skins, 513
Skin of animals, anatomy of, 508
Slaking lime, 326
Smalt, 38
Smelt, the mixing of the, 5
Sulting for gold, 106
silver directly, 97
white metal, 49
of nickel ores, 40
the ore, 5
operation, products of, 7
process, course of, 13
Smoke consumption, 745
Smoke-consuming apparatus, 741
Snuff, 480
Soap-boiling,
raw materials
239
Soap chief varieties of, 243
insolub'e, 249
mak ng 239
tests, 248
transparent, 248
u-es of, 248
Soaps, toilet, 247
various, 247
Soda-alum, 261
of,
Soda-ash, 171
Soda, aluminate of, 26
bicarbonate of, 190
caustic, 189
crude, conversion of sulphate into,
174
lixiviation of, 176
direct conversion of common salt
into, 188
from chemical processes, 172
cryolite, 188
Li rate of soda, 189
soda plants, and from beet-
root, 171
furnace, with rotatory hearth, 175
hyposulphite of. 201
manufacture, 170
occurrence of native, 170
preparation from sulphate of soda
187
stannate of, 76
sulphate, 213
sulphate uses of, 214
ultramarine preparation, 266
waste, sulphur from, 198
waste utilisation, 184
Sodic nitrate, 141
Soft soap, 246
Solferino, 575
SONDRY S process of preparing phos-
phorus, 544
Spathic iron cre. green vitriol from, 32
Spathose iron ore, 8
Sperm,.or spermaceti candles, 634
Spinning cotton. 342
Spinning flax, 340
Spirit from dry distillation of wood,
472
manufacture raw materials, 425
varnish, 489
Spirits from the by-products of sugar
manufacture, 430
from wine and marc, 430
the preparation or distillation of,
424
Spongy platinum, 95
Stags, 5
Stage, or étage grate, 743
Stamp machine. 347
STANFORD and MORIDE's method of
preparing iodine from carbonised
sea-weed. 192
Stannate of soda, 76
Starch. 355
comm rcial, constituents and uses
ot, 360
from potatoes, 357
nature of, 356
rice, chestnut, Cassava arrow-root,
360
sources of, 357
Starch-meal, boiling with dilute sul-
phuric acid, 384
xiv
INDEX.
Starch sugar composition, 386
Statistics concerning the production
of crude iron, 18
Statistics of steel production, 31
Steam brewing, 418
for heating, 740
Stearine candles, 621
Steel, 26
and other metals, 30
engraving, 31
from malleable and crude cast
iron, 29
production, statistics of, 31
properties of, 29
hardening, 29
Step grate, 742
Stereochromy, 285
Stibium, 82
Stoneware, 305
lacquered, 307
ovens, 306
Stove heating, 733
Stoves, compound, 735
iron, 734
of fire-clay, 734
Strass, 288
Styrian cast-steel, 27
Sugar-beet, vinegar from, 466
Sugar-candy, 382
Sugar-care, 364
components, 364
Sugar, draining the crystals, 381
history of, 362
manufacture, 362
beetroot, 367
spirits from the by-products of, 430
nature of, 362
of the grape, 392
preparation from the beet, 370
preparation of moist, raw, or loaf,
380
raw, preparation from the sugar-
cane, 365
production, 367
refining, 366
removing from the form, 381
solution, evaporating and purify-
ing, 385
starch, composition, 386
varieties of, 366
Suint, gas from, 675
potassa, salts from, 132
Sulphate of alumina, 261
alumina and alum, uses of, 263
ammonia, 238
copper, 54
pota ɛa, 121
soda, 213
zinc, 81
or decomposing furnace, 172
Sulphates of alumina, 256
Sulphide of carbon, 210
Sulphite of lime, 201
Sulphur, 194
as a by-product of gas manufac▾
ture, 198
Sulphur, by heating sulphuretted
hydrogen, 198
chloride, 211
flowers of, 197
for refining gold, 107
from soda waste, 198
obtained by the reaction of sulphu-
rous acid on charcoal, 198
preparation of from pyrites, 197
production by the reaction of
sulphuretted hydrogen upon sul-
phurous acid, 198
properties and uses of, 199
regeneration process, SCHAFFNER's,
185
smelting and refining, 194
Sulphurets of arsenic, 86
Sulphuric acid, 201
concentration, 206
decomposition of bone-ash by,
538
green vitriol from. 32
for refining gold, 107
fuming 202
manufacture, other methods of,
208
mash with, 428
ordinary or English, 203
present manufacture of, 203
properties of, 209
saponification by means of, 624
separation from the sugar solu-
tion, 385
Sulphurous acid, 199
use of pyrites for the preparation
of sulphurous acid, 206
Sumac, 510
Sun hemp, 341
Swedish iron refining, 22
TAL
ALLOW candles, 629
Tanning, 508, 516.
in liquor, 517
the bark, 516
materials, 509
estimation of value of, 512
quick process, 517
the several operations, 513
Tar, condensation of the vapours of,
686
distillation of, 688
mode of operating with, 688
preparation of. 685
properties of, 687
Tawer's softening iron to smooth the
leather, 519
Tawing, 522
common, 522
Temperature of blast-furnace at dif-
ferent points, 15
INDEX.
XV
Tempering. 20
steel, 30
Terra-cotta. 311
Terralite and siderolite ware, 309
Thickenis 610
THOMSEN'S method of decomposition
of cryolite by ignition with car-
bnate of lime, 259
Tiles drain and gutter, 318
roofing and Dutch, 318
Tin, 73
applications, 74
nitrate of, 76
preparatio s of, 75
proper'ies of, 74
Tinned sheet iron, 75
Tinning 75
of copper, brass, and malleable
iron. 75
Tinsalt, 75
Tobacco, 477
leaf, chemical composition of, 478
manufacture, 478
smoking. 479
Tow, or tangled fibre, 340
Tubes, distillation of zinc in, 79
Turkey red, 6C8
Turmeric, 596
TURNBULL'S blue 37
Turpentine oil varnishes, 490
Tyraline, 575.
CHATIUS'S steel, 28
UCH
Ultramarine, 264
artificial, 264
cobalt, 38
constitution of, 267
conversion of green into blue, 266
green preparation, 265
manufacture, 264
na ive, 264
properties of, 267
sulphate of, preparation, 265
VACU
ACUUM pans, 377
Valonia nuts,
nuts, 511
Varnish. polishing dried, 490
spirit, 489
Varnishes, 488
oil, 489
spirit, coloured, 490
turpentine oil, 490
Vases, Etruscan, 309
Vegetable fibre, technology of, 338
Vellum, 527
Verdigris, 58
Vicuna wool, 495
Vienna yeast, 450
Vine and its cultivation, 390
Vinegar and its origin. 460
formation, phenomena of, 462
from alcohol, 461
the sugar-beet, 466
Vinegar from wood distillati n, 469
making, elder method, 462
quick process, 463
testing, 467
with the help of the Mycoderma
aceti, 466
platinum black, 467
the manufacture of, 460
Vinous fermentation, 387
mash firm cereals, 426
Vintage, 390
Vitriol blue, 54
applications of, 56
d. uble, 55
green, 31
from metallic iron and sul-
phuric acid, 32
from the residues of 1yrites
distillation, 32
in bede, preparation of, 32
preparation of, as a by-product
in alum works, 32
uses of, 32
white. 81
Violet and blue naphthaline pigments,
583
imperial, 577
VOGL'S grate, 744
Voltaic electricity, copper obtained
by, 50
Volumetrical method, 224
Vulcanised caoutchouc, 486
WA
ALKERITE, 295
Warming, 731
Water, 405
cooler-, 309
gas, 671
carburetted, 672
LEPRINCE'S, 674
hot, for heating, 739
Wax candles, 631
making, 633
or Vesta matches, 553
Weaving silk, 505
the cloth 499
linen threads, 340
Weld, 596
WELDON'S chlorine process, 219
Wheat starch, preparation of, 358
Whey, 557
White gunpowder, 154
lead, 67
adulteration of, 72
application of, 72
Euglish method of manufac-
turing, 68
French method of preparing, 69
from chloride of lead. 71
sulphate of lead, 70
manufacture at Clichy, appa-
ratus used in, 69
properties of, 71
xvi
INDEX.
White-lead, theory of preparing, 70
vitriol. 81
Wine, 390
clearing and fining, 399
constituents of, 393
drawing off and casking, 393
making, 390
the residue or waste, 399
must, improving the, 401
Wines, ageing and conservation of, 397
effervescing, 399
maladies of, 396
Wire, iron, manufacture, 25
WOLLASTON'S method of extracting
platinum from its ores, 94
Wood, 702
charcoal, 704
composition of, 711
BOUCHERIE's method of mineral-
ising, 477
carbonisation of, 705, 708
constituents of, 703
drying, 474
gas, 668
burners, 670
heating value of, 704
in general, durability, of, 472
preservation, 472 474
roasted. rois boux, 712
spirit, 472
vinegar, 469
WOOD's alloy, 82
Wool and vegetab'e fibre, to distinguish
silk from 506
artificial, 499
carding. 498
chemical composition of, 495
colour and gloss, 497
dyeing, 498
Jed, 605
oiling or greasing, 498
origin and properties of, 494
preparation, 497
properties of, 497
spinning, 498
Wool sorting, 498
washing, 498
willowing or devilling, 498
Woollen fabrics, dyeing, 601
goods, printing, 616
industry, 494
Wootz-steel, 30
Worsted wool, 500
Wort, boiling, 411
cooling, 413
extractives of, 411
preparation of, 408
preparion, infusion method, 410
387
YEAS dry, 449
so-called artificial, 450
Yellow chromate of potassa, 64
dyes, 595
prussiate of potash, applications
of, 35
sulphuret of arsenic, 87
wood, 595
Yufts, Russia leather, 520
Z¹
IERVOGEL'S method of silver
extraction, 99
Zinc and tin solution for electro-
plating. 116
applications of, 80
chloride, $1
chromate, 81
distillation in crucibles, 79
muffles, 78
tubes, 79
method of extracting, 77
mode of obtaining from sulphuret
of zinc, 79
occurrence of, 77
preparations of, 80
properties of, 79
reduction of silver by means of,
102
sulphate, 81
white, 80