ALBERT R. MANN LIBRARY AT CORNELL UNIVERSITY Cornell University Library A manual of sugar analysis, including th 3 1924 018 530 000 The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924018530000 MANUAL SUGAE ANALYSIS INCLUDING THE APPLICATIONS IN GENERAL ANALYTICAL METHODS TO THE SUGAR INDUSTRY. WITH AN INTRODUCTION ON THB CHEMISTRY OP CANE-SUGAR, DEXTROSE, LEVULOSB, AND MILK-SUGAR. BY J. H. TUOKEE, Ph.D. I^EW York: D. VAN NOSTKAND, PUBLISHER, 23 MuBKAT Street astd 27 Waeren Street. 1881. Oopyi-ight by I). VAN NOSTRAND, 1881. PREFACE. Notwithstanding the amount and variety of analytical work required for the various interests connected with sugar, there exists no book in English that treats of this branch of analysis, and only a few scattered and incom- plete dictionary articles. The main dependence of the chemist must be on G-erman and French sources, in which languages treatises on sugar analysis are numerous. I have accordingly attempted, with as much success as may be, to supply this deficiency in the special literature of analytical chemistry, believing that there is now, and still more in the near future there will be, a need of such a work in English-speaking countries. An introduction on the chemistry of the more important sugars is given, on account of its intimate connection witli the subject ; the matter is brought strictly up to the time of publication, and in some important respects — as, for ex- ample, in relation to inversion, and the melassigenic action of salts on cane-sugar — I believe to be more full than can be found elsewhere. The formulas and atomic weights used are according to the new system, and the temperatures are Centigrade. 3 PREFACE. I desire to render my acknowledgments to Prof. C. F. Chandler, of Columbia College, New York, for access to his fine private library of technical chemistry ; to Dr. A. Behr, of Jersey City, for the loan of books, and other favors ; and to W. Baker, Esq., Librarian of the School of Mines, Columbia College, New York, for uniform courtesy and help. The Aitthok. New York, July 1881. CONTENTS. CHAPTER I. THE CHEMISTRY OP THE SUGARS AS A CLASS. The Sweet Taste, 9— Chemical Constitution, 10— Classiflcation, 12— Ponnation in Plants, IS — Synthesis, 16 — Rotatory Power, 17 — Fermentation : mucous, 18 ; lactous, 19 ; vinous, 21 ; eellulosic, 25 — Action of Heat, 26 — Oxidizing Agents, 26— Acids, 28— Saccharides, 28— Alkalies, 29. CHAPTER II. CANE-SUGAR OR SACCHAROSE. Occurrence, 31 — Preparation from Natural Sources, 34 — Physical Properties, 35 — Action of Light, 38 — Composition, 39 - Solubilities, 39 — Action of Heat, 41 — Inversion by Heat, 43 — Inversion by Acids, 45 — Action of Sul- phuric Acid, 49 — Oxidizing Agents, 50 — Alkalies, 64 — Sucrates of Potas- sium, 55 ; Sodium, 56 ; Calcium, 56 ; Barium, 60 ; Strontium, 61 ; Iron, 61 ; Copper, 61 ; Magnesium, 63 — Combination of Cane-Sugar with Neutral Salts, 62 — Melassigenic Action of Salts, 64 — Various Reactions, 72 — Para- saccharose, 73 — Inactive Cane-Sugar, 73. CHAPTER III. DEXTROSE, LEVULOSE, AND INVERT-SUGAR. Dextrose, 74 — Pormation, 75 — Preparation, 75 — Properties, 77 — Rotatory Power, 78 — Composition, 79 — Decompositions, 79 — Action of Alkalies, 80 — Various Reactions, 81 — Combinations, 83 — Qualitative Tests, 85 — Paradex- trosp, 86. Levulose, 87 — Pormation, 87 — Preparation, 87 — Properties, 88 — Decomposi- tions, 88 — Calcium Compound, 89. Invert-Sugar, 89. CHAPTER IV. LACTOSE OR MILK-SUGAR. Rotatory Power, 91— Composition, 92— Solubilities, 92 — Action of Heat, 92; of Sulphuric Acid, 93 — Alkalies, 94 — Fermentation, 95. 5 6 COKTENTS. CHAPTER V. DETERMINATION OF SPECIFIC GRAVITY. The Hydrostatic Balance, 96— Mohr's Balance, 96— The Specific-Gravity Flask, 98— Areometry, 100— Gay Lussac's Volumeter, 103— The Densimeter, 105 — Baume's Hydrometer, 106 — Balling's or Brix's Areometer, 110— Table showing Sugar Percentages, Densities, and Baume Degrees, 116-119. CHAPTER VI. DETERMINATION OF CANE-SUGAR- OPTICAL METHODS. Polarized Light, 130— Mitscherlieh's Saccharimeter, 126— The Soleil-Duboscq Saccharimeter, 130— Clerget's Method, 136— Clerget's Table, 141— The Soleil-Ventzke Saccharimeter, 143 — Wild's Polaristrobometer, 152 — Du- boscq's Shadow Saccharimeter, 157 — Schmidt and Haenseh's Shadow Sac- charimeter, 159— Laurent's Saccharimeter, 159— The Equivalence of various Saceharimeters, 163 — The Decoloration of the Sugar Solution, 164 —Errors of the Optical Method, 170— The Optical Inactivity of Invert- Sugar, 173— Influence of various Bodies on the Optical Estimation, 175 — Correction of Measuring Apparatus, 177. CHAPTER VII. DETERMINATION OF CANE-SUGAI^-CHEMICAL METHODS. Method of Peligot, 179— Extraction by Alcohol, 180 ; by Fermentation, 181— Estimation after Inversion, by Pehling's Method, 182. CHAPTER VIII. DETERMINATION OF' DEXTROSE AND INVERT-SUGAR. Section I. Fehling's Method and its Modifications, 185 — Part I. : The Metliod as suited for Technical Work: Volumetric, 186 — Pehling's Solution, 187— Violette's Solution, 188— Monier's Solution, 188— Possoz's Solution, 189— Calculation of Results, 191— Part II. ; The Method as suited to Exact Work : A. Volumetric, 201 ; B. Gravimetric, 303— Mohr's Method, 205. Section II. Determination of Dextrose and Invert-Sugar by other Methods than that of Fehling : Knapp's Method, S06— Sachsse's Method, 207— Estima- tion of Dextrose and Invert-Sugar in presence of each other, 207— Estima- tion of Levulose and Dextrose in presence of each other, 208 — Gentele's Method, 210. CONTENTS. 1^ CHAPTER IX. ANALYSIS OF RAW SUGAR. Composition of Raw Sugar, 311— Estimation of Cane-Sugar, 313— Estimation of Invert-Sugar, 317; of Water, 217; of Ash, 333— Soluble Ash, 334— Alkaline Ash, 225— Sulphated Ash, 236— Estimation of Color, 339— Stam- mer's, Colorimeter, 329— Estimation of Organic Matter, 333; of Insoluble Matter, 236; of Yield, 287— Method of Coefaeients, 237— The Payen- Soheibler Process, 240— Method of Dumas, 347. CHAPTER X. ANALYSIS OP MOLASSES AND SYRUPS. Estimation of Cane-Sugar, 350; of Water, 353— Quotient of Purity, 353— Esti- mation of Color, 358 ; of Alkalinity, 258. CHAPTER XI. ANALYSIS OF THE CANE AND CANE-JUICE. The Cane, 260— Cane- Juice, 261- Estimation of Cane- Juice, Ventzke's Me- thod, 262. CHAPTER XII. ANALYSIS OF THE BEET AND BEET-JUICE. The Beet, 365— Scheibler's Method for Estimating the Sugar, 266— Estimation of Marc and Amount of Juice, 269 — Analysis of Beet-Juice, 270. CHAPTER XIII. ANALYSIS OF WASTE PRODUCTS. Analysis of Scums and solid Residues, 273 — Refinery Scum, 373 — Beet Marc, 375 — Carbonatation Residues, 275 — Waste Waters, 276 — Estimation of Cane-Sugar in very dilute Solutions, 376. CHAPTER XIV. ANALYSIS OF COMMERCIAL GLUCOSE OR STARCH-SUGAR. Composition, 278 — Estimation of Sugar by Fehling's Method, 280; by Fermenta- tion, 281— Anthon's Method, 282— Estimation of Water, 383— Adultera- tion of Raw Sugar with Dextrin, 284 — Detection of Starch-Sugar when mixed with Refined or Raw Cane-Sugars, 284— Chandler and Ricketts' Method, 287. 8 CONTENTS. CHAPTER XV. ESTIMATION OP MILK-SUGAR. By Pehling's Method, 390— OptieaUy, 290. CHAPTER XVI. ESTIMATION OP DEXTROSE IN DIABETIC URINE. By the Optical Method, 393— By Pehling's Method, 394. CHAPTER XVII. THE CHEMISTRY OP ANIMAL CHARCOAL. Composition, Analyses, 396— Mode of Action, 398 — Absorbing Power, 399 — Marks of good Char, 303— Revivification, 303— Alteration by Use, 304— Car- bon, 306 — Carbonate of Lime, 306 — Alkaline Salts, 307 — Sulphate of Lime, 307— Iron, 307— Sulphide of Calcium, 308— Nitrogen, 309. CHAPTER XVIII. THE ANALYSIS OP ANIMAL CHARCOAL. Estimation of Water, 311; of Carbon, 311; of Carbonate of Lime — Scheibler's Calcimeter, 313 — Calculation for Removal of Carbonate by Acid, 818 — Estimation of Calcic Sulphate, 320; of Calcic Sulphide, 321; of Calcic Phosphate, 322: of Iron, 323; of Soluble Matter, 334; of Specific Gravity, 326; of Absorptive Power, 337; by Duboscq's Colorimeter, 339 — Coren- winder's Method, 333— The Potash Test, 333. APPENDIX. Note on the Action of Organic Matter on the Alkaline Solution of Cupric Oxide, 335— Tables, 338. CHAPTER I. THE CHEMISTEY OF THE SUGARS AS A CLASS. The term sugar is applied to a group of bodies resem- bling each other by a number of striking properties ; these properties — partly chemical and partly physical — are as follows : (1) the sweet taste ; (2) the ability to undergo the process of fermentation ; (3) the identity or similarity in chemical composition or relations ; (4) the power that aqueous solutions have of rotating the plane of polarized light ; (5) the general resemblance in physical and chemical characteristics, such as their ready solubi- lity in water, insolubility in absolute alcohol and ether, facility of crystallization in well-defined forms, the simi- larity of their products of oxidation, and their ability to reduce the oxide of copper in alkaline solution, either directly or after conversion into some other sugar by fer- mentation or the action of dilute acids. The sweet taste is very distinctive of sugars, and is possessed in a greater or less degree by nearly all of them, from cane-sugar, which is the type of sweet sub- stances, to some of the rarer saccharoids, which . have this property in a very low degree or not at all. The sugars are not the only bodies, however, possessing a- sweet taste, as glycol and glycerin are sweet, as well as some metallic salts, notably the acetates of lead ; the 10 CHEMISTRY OF THE SUGARS AS A CLASS. two former are, however, allied to the sugars, as they are polyatomic alcohols. The yttria salts and some sUver compounds are also said to have a sugary flavor. The relative sweetening power of cane-sugar to dextrose has been generally placed as two to one ; Parmentier questions this, and gives the following quantities of the two sugars as having an identical sweetening effect : 10 pts. of cane-sugar to 40 pts. of water. 12 " dextrose to 40 " " It has been asserted that levulose is sweeter than cane- sugar, and this seems to be confirmed by the fact that in- vert-sugar is sweeter than cane-sugar, H. Morton placing the excess at ten per cent. The 'sugars are mostly of vegetable origin, though a few, as inosite and dextrose, are found in animals ; they exist in a great variety of plants distributed over every part of the globe. CHEMICAL CONSTITUTION. All bodies known as sugars are composed of carbon, oxygen, and hydrogen ; in the true sugars the hydrogen and oxygen are present in the proportions that form water. For example, dextrose C,H,jO„, has the hydrogen and oxy- gen present in the exact -proportion to make six molecules of water, and the formula may be written thus : C,(H50)° ; the compound, from this point of view, may be considered as a hydrate of carbon. Bodies thus constituted are called carbohydrates, and under this name are included many important substances not classed as sugars, though 'sugar may be derived from many of th^m by the action of dias- tase or acids. The most important of these are : starch. CHEMICAL CONSTITUTION. H »CeH,„0, ; cellulose, wC^H.^O, ; gum, C.,H,,0., ; and dex- trin, C.H,.0.. Most sugars belong to the class of the Jiexatomic alco- hols and the corresponding ethers. An alcohol is a com- pound in which hydrogen, in a saturated hydrocarbon, is replaced by one or more atoms of the univalent radical hydroxyl HO; thus, propenyl alcohol or glycerin (C3H,)"'(HO)3, is derived from the hydrocarbon propane C3H, by substituting three atoms of hydroxyl for the same number of hydrogen, the result being a triatomic alcohol — that is, one containing three atoms of hydroxyl in the place of an equal number of replaceable hydrogen. So vidth higher replacements : mannite CeH„0„ may be consi- dered as derived from the saturated hydrocarbon C.H,, by replacing six atoms of hydrogen with an equal number of hydroxyl atoms, and the formula may be written (CoHj^XHO)", which represents a hexatomic alcohol. Mannite and dulcite are important representatives of the siagars having the composition of alcohols. Sugars of the formula CsH.jO,, or the glucoses^ have two atoms of hydrogen less than the saturated alcohols, and are classed as aldehydes of these alcohols ; this classifica- tion is justified by the fact that dextrose, when acted upon by nascent hydrogen, is converted into mannite, just as acetic aldehyde is changed into ethylic alcohol by the same agent. Sugars of the composition C.^H^jO,,, such as cane-sugar, . are so constituted that one molecule is equivalent to two molecules of the glucoses, minus one molecule of water — as, C„H,,0„ = (2C,H„05 — OH,) ; these are called diglucosio alcoliols. The carbohydrates starch, cellu- lose, and a few others, having the formula CeH,„0„ or 12 CHEMISTRY OP THE SUGARS AS A CLASS. multiples of it, may be regarded as the oxygen ethers or anhydrides of the glucoses or the diglucosic alcohols, in- asmuch as they differ from them by one molecule of water. The most important of the sugars may be arranged, ac- cording to their chemical relations, as follows : Triatomic. Dambonite. (C^H^yCOH)'. Derived from butylene C4H8. I. SATURATED ALCOHOLS. Pentatomic. (CeHOv (OHf Quercite. Finite. Derived from the hydro- carbon CcHt. Hexatomic. (CeH8)v(OH)= Mannite. Dulcite. Isodulcite. Rhamnegite. Derived from the hydro- carbon CeHe. IL ALDEHYDES OF THE HEXATOMIC ALCOHOLS (glucoses). CsH^Oe — H2 ^ CeHisOa. Dextrose. Mannitose. Eucalyn. Levulose. Dulcitose. Inosite. Galactose. Dambose. III. DIGLUCOSIC ALCOHOLS. [Related to the glucoses by C12H22O11 = (zCoHuOe — HjO)]. Saccharose. Melitose. Parasaccharose. Mycose. ) Lactose. Trehalose. ) Melezitose. Synanthrose. Maltose. The above grouping is based on the modem theories of organic chemistry, which may be useful in this application, as they have undoubtedly been in many others. A more convenient, and possibly an equally scientific classification may be made, based on the relations of constitutional iden- CLASSIFICATION. 13 tity or similarity in regard to their empirical formulas, and general cliemical and physical properties. The true sugars or carbohydrates have the characters pre-eminently sac- charine, while the saccharoids differ much from them in atomic constitution and many other properties. The car- bohydrates are classed as fermentable and non-fermen- table. Class I. is again divided into A, Olueoses, and B, Sucroses, the former being capable of fermenting directly without previous conversion into any other body. 14 CHEMISTRY OP THE SUGARS AS A CLASS. d °o> °o O °,o B o si a 1— 1 d c o n ■|d|"|yg" S Q W « 1 > CO Q IB • ^ 1/^ >o b O O d en en CO < e 1— 1 E V (3 d 3 'S < u a cC m i^ O O vO o 2 ts o'w O q ^^ O hH* 'S S -3 |-3 c ^ s s s o o O o o H c O O vO O °o 3d i-l m 4 = n i ^ 'H w z q q S tn ffl ^ u'E uE (O c" o - o S tn „ S" u o >. S £ 1 S •e 1 -g s en z < m ^o go i. o Z s c/5 H r 00 ■^ l-J « « o o o en CO 4 H tn H P4 i § ^ M Q 8 o _ ■lu" >- a: S . oi" O X B ^ O . o u en !-■ s c» b u -^ en V o .c CI Pi en s 1 < > m d en 2 1 1 § ^ s ^ IS ■s .c o O H >--o • o " «^ S5o O m O O 11. .^ 1 10 q B c3 ^ CD S'2§ 1 - ^ 3 1 J ^ < o o Mucic ** • Under the influence of chlorine and bromine some sugars yield two acids containing six atoms of carbon — isodi- glycoethylenic acid Q^^fi^, and gluconic acid CeHi^O,. * Jour, Prak. Chemie, Ixxxix. 383. 38 CHEMISTRY OP THE SUGARS AS A CLASS. The first is formed when a solution of bromine is made to act on milk-siigar ; the second when a current of chlorine is passed through a dilute solution of cane-sugar or dextrose. Levulose and sorbite break up by the action of chlorine into glycollic acid. Reactions with Acids. — Sugars form with acids com- pounds analogous to ethers, acting like polyatomic alco- hols. Concentrated nitric acid, or a mixture of nitric and sulphuric acids, acts upon saccharine bodies, giving rise to nitro-substitution compounds in which the univa- lent radical NOj takes the place of an atom of hydrogen. Thus, in the case of saccharose, the product has the com- position C,2Hj5(N02)'0„. With inosite, hex-nitro inosite is produced, C„H8(N05)°0„. Isodulcite, dextrose, milk-sugar, and trehalose yield nitro compounds whose composition is not exactly known. Sulphuric acid acts on cane-sugar much more strongly than upon the glucoses. A strong syrup of cane or milk- sugar mixed with concentrated sulphuric acid is immedi- ately decomposed with strong intumescence, attended with an evolution of sulphurous acid gas and various volatile compounds, a black carbonaceous residue being left. Dextrose, under the same circumstances, gives without blackening, a sulpho-acid C,,H„SO„ = 4C„H,,0j. SO,, the reaction being precisely similar to that of organic acids with sugar. Phosphoric acid appears to act in the same manner. Saccharides. — The organic acids yield, with sugars, ethereal compounds called saccharides. Berthelot* has produced this class of compounds by heating dextrose with various organic acids, such as acetic, butyric, stearic, *Ann. CMm. Phys., liv. 78. ACTION OF ACIDS AND ALKALIES. 39 but has found, as a general rule, that the number of molecules of water eliminated is one in excess of the number of molecules of the monobasic acid taking part in the reaction. So that the products obtained are ethers of glucosan, and not of glucose, as below : (1) C„H,,0. + SC'^H^O, = CeH.„(C,H,0)^0. + 2H,0. Dextrose. Butyric acid. Dibutyric glucose. (2) CeH.,0, + 2C,H,0, = C,H/C,H,0)=0, + 3H,0. Dibutyric glucosan. By the action of tartaric acid on saccharose, dextrose, and lactose, according to the same chemist, entirely simi- lar derived compounds are formed, which bear the rela- tion to glucosan shown in the equation (2). Mannite also gives compounds likewise related to mannitan. Action of Weak Acids — Inversion. — When cane- sugar is heated with dilute sulphuric acid or hydrochloric it is converted into dextrose and levulose : Melezitose yields two molecules of dextrose ; melitose, one molecule of dextrose and one of eucalyn ; and lactose, two molecules of galactose (Pasteur). Action of Alkalies. — Dextrose is much more easily acted upon by caustic alkalies than saccharose. The de- composition of aqueous solutions of the glucoses takes place slowly in the cold, more quickly on heating, the liquid first turning yeUow and then brown, yielding humus-like bodies. Dextrose thus treated gives glucic acid as the first product of the reaction. The sucroses C,jHj,0„ are not attacked by dilute alkalies in the cold, and but slowly on heating ; they are decomposed by boiling 30 CHEMISTRY OF THE SUGARS AS A CLASS. with concentrated alkaline solutions. When fused with caustic alkalies they yield oxalic acid. Ammonia, in the form of gas or in aqueous solution, when allowed to act on the sugars and some other carbo- hydrates, is capable of forming compounds with them somewhat resembling gelatin, and containing in some cases from 14 to 19 per cent, of nitrogen. Dusart, by heating dextrose, lactose, and starch with aqueous ammo- nia in sealed tubes to l.'50° C, obtained nitrogenous sub- stances which were precipitated by alcohol in tenacious threads, forming with tannic acid an insoluble, non-putre- fying compound. As it has been observed that bone gela- tin approximates in composition to an amide of the carboliydrates, tlie above facts are of considerable inte- rest. C.H„Oe + 2NH3 = CeH,.N,0, + 4H,0. Gelatin. It has also been observed that gelatin, when boiled with sulphuric acid, yields, among other products, sugars re- sembling the glucoses. CHAPTER II. CANE-SUGAR OR SACCHAROSE C„H„0„. Gomifion Sugar — Crystallizable Sugar — Sucrose — Sucre de Canne, Fr. — Rohrzucker, Gr. Occurrence. — Cane-sugar is widely diffused in the vegetable kingdom, being found more generally, and in greater quantities among the grasses. The sugar-cane, Saccharum offieinartbrri, contains often more than twenty per cent, of sugar, unmixed, it is claimed, with any other sugar, when the plant is perfectly ripe. The following analyses of the cane are by O. Popp * : From Martinique and ,, r-.,:-™ FroTi Upper Egypt. Water 72.22 17.80 .28 9.30 .40 72.15 16.00 2.30 9.20 ■35 72.13 iS.IO ■25 9.10 .42 Cellulose Salts lOO.OO 100.00 100.00 The stems of SorgTium mccJiaratum and S. Holcus, when quite ripe, contain 9 per cent, cane-sugar unmixed with fruit-sugar (Goessman) ; the unripe stems carry only starch and grape-sugar. P. Collier f has found in the * Zeit. fiir Chemie, 18T0, 328. t Report to the Commissioner of Agriculture, 1879, and Aug. 1, 1880. Washington, U.S.A. 31 33 CANE-SUGAR OR SACCHAROSE. juice of different varieties- of sorghum from 15.95 per cent, cane and .65 per cent, of grape-sugar, to 13.90 per cent, cane and 1.45 per cent, grape-sugar, when the canes are quite ripe. The juice from the stems of Indian corn or maize {Zea mays), according to the same authority, con- tained 12.09 per cent, cane-sugar and .68 per cent, grape- sugar. The nectar of flowers contains invert-sugar with a considerable proportion of cane-sugar, the latter amount- ing in the case of the fuchsia to three or four times the quantity of fruit-sugar (A. S. Wilson, CTiem. News, xxxviii. 93). Many fleshy roots carry considerable quantities of cane-sugar, notably those of Angelica arcliangelica. Beta tulgaris, Chcerophyllum bulbosum, CMcorium intyhus, Daucus carota, HeliantTius tuberosus, Leontodon tarax- acum, and others. The common beet {Beta vulgaris) averages from seven to eleven per cent, of canersugar, though in particular cases, owing to high cultivation, the amount has reached fourteen per cent.* The beet contains no other sugar besides saccharose. According to W. Stein, t eight per cent, of sugar is obtainable from the mad- der-root, though it contains fourteen per cent., partly un- crystallizable. Cane-sugar occurs in the stems and trunks of trees, as the sugar-maple, Acer saccharinum, the sycamore, some species of Betula, in the vernal juice of Juglans alba, Tilia Europoea, and in several palms, especially Saguerus Rumpliii, or the sago palm, and the Cocos nuci- fera, or cocoanut-tree. The leaves of many plants con- tain sugar. A. Petit found in vine-leaves .92 per cent, of * Payen, Compt. Rend., xl. 769 ; Schmidt, Ann. der Chemie, Ixxxiii. 335. f Journ. fur Prak. Chemie, cvii. 444. SUGAR IN FRUITS. 33 cane and 2.62 per cent, of grape sugar, and also the same bodies in cherry-leaves. The sugar of fruits at the season of maturity is always cane-sugar, but by the influence of a peculiar ferment it may be partially or wholly converted into a mixture of dextrose and levulose, which, is commonly called fruit- sugar. Ripe fruits thus sometimes contain only fruit- sugar, and at others a mixture of cane and fruit sugars. Buignet* gives in the following table the saccharine content of "most of the common fruits, with the amount of acid present : Apricots Pineapples English Cherries . . Lemons Figs Strawberries Raspberries Gooseberries Oranges Peaches (green) . . . Pears (Madeleine). Apples Prunes Grapes (hothouse) " green.... Cane-Sugar, Fruit-Sugar. 6.04 11-33 .00 ■41 .00 6.33 2.0"! .00 4.22 .92 .36 5.28 2.19 5.24 .00 .00 2.74 1.98 10.00 1.06 "•55 4.98 5.22 6.40 4-36 1.07 8.42 8.72 5-45 3-43 17.26 1.60 1.864 ■547 .661 4.706 .057 ■ 550 1.380 1-574 .448 3.900 .115 1. 148 • 633 1.288 -345 2.485 The formation of cane-sugar in fruits is not prevented by the presence of acids (Buignet, loc. cit.) Cane-sugar is also found in melons and dates. Walnuts, hazel-nuts, bitter and sweet almonds contain only cane-sugar (Pe- louze t), while the saccharine matter of others is a mixture of cane and fruit sugar. The sugar of common honey is levo-rotatory, and is composed of fruit-sugar, dextrose. * Arm. Chim. Phys., [3] Ixi. 233. f Gompt. Rend., xl. 34 UANJbi-SUtrAii UK SAUUHAKOSJi;. and cane-sugax. The latter is found cMefly in the honey of the cells, and rapidly disappears on keeping, owing to an accompanying ferment. Cane-sugar is not found in healthy cereals and barley-malt ready formed, but is pro- duced by the action of diastase and water in the crushed grain (Mitscherlich, Peligot, and Stein). The analysis of the manna from Sinai (from Tamarix mannifera) shows, according to Berthelot : * 55 per cent, cane-sugar, 25 ' ' invert-sugar, 20 " dextrin. And that from Kurdistan : 61 per cent, cane-sugar, 16.5 " invert-sugar, 22.5 " dextrin. Preparation from Natural Sources. — For working on the small scale Marggraf recommends that the plant, re- duced to as fine a state of division as is practicable, be treated with strong boiling alcohol, and the solution ob- tained filtered and allowed to cool, when the sugar crystal- lizes out. To obtain cane-sugar from fruits containing also uncrystallizable sugar, Peligot and Buignet f have adopt- ed the following method : Add to the juice an equal •volume of alcohol to prevent alteration, if it is to be kept any length of time before operating, and filter; saturate the filtrate with excess of milk of lime, and again filter. Boil the second filtrate, when a compound of cane sugar •and lime separates, which contains two-thirds of the total . cane-sugar present. Filter, wash the precipitate well with water, diffuse it in water, and decompose with a stream of *.Gompt. Rend., liii. 583. f Arm,. CUm. Pkys., bd. 283. CRYSTALLIZATION OP SUGAR. 35 carbonic-acid gas. The solution filtered from the car- bonate of lime is concentrated by heat {best in a vacuum) to a syrupy consistency, decolorized by bone-black, and mixed with strong alcohol until it becomes cloudy, when it is set aside to crystallize. If the solution, after treat- ment with carbonic acid, yields a turbid filtrate, solution of basic acetate of lead is added, the liquid refiltered, and the excess of lead removed from the second filtrate with sulph-hydric acid gas. Physical Properties. — Cane-sugar when obtained by slow evaporation forms large, transparent crystals, but when the crystallization takes place rapidly they are much modified and striated. When a strong syrup is concen- trated to the proper consistency, it sets, on cooling, to a solid mass of fine crystals, which, after being washed with a pure syrup, constitutes the loaf-sugar of commerce. Sugar crystallizes in the monoclinic system, the forms gene- rally having hemihedral faces, but are often tabular. Fig. I. Figs. 1 and 2 show the crystallization of cane-sugar. Axes : a : 6 : c = .7952 : 1 : .70. Angle of axes & and c = 76° 44'. Angles i?/^' =103° 30'. m m (on the side) = 101° 32'. e'e' (above jp) =99°. a'h' = 64° 30'. 36 fJA^JJi-DCJVUirb v^JX i:3JA.KjVja.JXix\jK3S2*. (See Wolff, Jour. Pk. Ghemie, xxviii. 129). Ordinary forms, m, p, h', a\ e', d^. Harder than any other sugar except lactose. Fig. 3 represents fine crystals of cane-sugar under a moderate magnifying power. Fig.3. Cane-sugar exhibits phosphorescence when broken, or when a strong electric discharge is passed through it. Specific Gravity.— 1.593 (Joule and Playfair), 1.595 (MaumenS), 1.630 (Dubrunfaut), 1.680 (Kopp) ; the latter number, according to Gerlach,* who has carefully experi- mented in this direction, is the most correct — 1.58046 atl7i° * Zeit. f. Buhme., xiii. 283, SPECIFIC ROTATORY POWER. 37 C. "being the figure he obtained : melted barley-sugar 1.509 (Biot). Specific Rotatoey Power. — This constant as given by- different authorities for the line D is : e. WD. Arndtsen 77-394 47.276 33-762 21.608 30.276 27.441 19.971 9986 16.350 14570 5.877 67.02° 67-33° 66.37° 66.75° 66.42° 66.48° 67.08° 67.12° 67.31° 66.04° 66.90° Ann. Chim. Phys. [3],54. 403- Wiener Akad., 52, ii. 486. Polaristrobom, 1S65. J. Pk. Chem. [2], ii. 235. Comft. Rend., 83, 393. Compt. Rend, 80, 1354. Wiener Akad., 69, iii. 162. Pogg, Ann., 148, 350. Stefaa Vf\\(]i.........y.. ...... Tuchschmid Calderon Girard and Lu3'nes Weiss OudciTians c — No. of grammes of material in 100 c. c. of solution. The discrepancies shown above are principally diie to the different conditions as to' concentration and temperature for the various series of experiments. Schmitz * gives a general formula when c = 85.68 to 10.40 : [a] D = 66.453 — .00123621e — . 000117037c"; and for more dUute solutions : [a] D = 66.639 — .0208195c + .00034603c'. According to Tollens, t when c = to 18, and c = 18 to 69, the formulas are respectively : [a] D = 66.8102 — .015553c — .00005246c'. [a] D = 66.386 -f .015035c — .0003986c'. The deviation of the D ray for 1 mm. quartz is 21.67° (Broch). For the transition tint (the mean yellow ray) the figure * Ber. Chem. Oesell., 1877, 1414. ■f Ihid., X. 403. 8 CANE-StTGAR OR SACCHAROSE. a] j = 73.8° is the one generally given, and wMcli cor- ectly corresponds to tlie normal weights of the various accharimeters using the transition tint (within narrow Lmits). The numerical relation of the rotations for the ine D and the transition tint is variously given at — [a] i = 1.13061 [a] D for quartz (Broch), and [a] i = 1.129 [a] D (Montgolfier *), 1.0961, 1.034 ("Weiss, Wiener ATcad., Ixix. 157), or sugar solutions. 'ToUens {Ber. Chem. Gesell., 13, 19, 3297) gives the rota- ory power of cane-sugar in various solvents as follows : 10 per cent, solutions, [a] D = water, 66.667°. " + ethylic alcohol, 66.827°. " + methylic " 66.628°. " + acetone, 67.396°. The temperature exercises no important iniluence on the otatory power (see page 170). Sugar is unalterable in the air. Specific heat, .301. Action of Light. — Kaoult {Joxtrn. Fab. Sucr., 1871) tates that cane-sugar in solution enclosed in a sealed ube from which the air has been expelled by boiling, and :ept for five months exposed to light, was found to have •een half converted into glucose ; a similar arrangement in he dark remained unaltered. Kreuslerf asserts that if he air and germs are completely excluded in the above ex- )eriment no change takes place. This view is confirmed by 'ellett and Motteu {Ber.Belg. Akad., 1877). * Bull. Soc. Chim., xxii. 48^. X <^<""'> I'abr. Sucre, 19, 5. f Zeit. f. Anal. Chettt., xiv. 197. SOLUBILITIES. 39 Composition. — Cane-sugar is composed of carbon, hy- drogen, and oxygen : Equivalents. Centesimally. Carbon 144 22 176 * 42.11 6-43 51.46 Hydrogen 342 100.00 Cane-sugar, whether obtained from the cane, beet, or any other source, is identical in every physical and chemical property, and in constitution. Endosmose. — The endosmotic equivalent, according to Joly, is 7.25, but is not constant, depending on the quality of the membrane, though independent of the temperature (Schmidt, Fogg. Ann., 102). It is proportional to the den- sity of the solution. Solubilities. — Sugar is very soluble in water, the con- centrated' solutions having that peculiar consistency deno- minated syrupy. H. Courtonne,* confirming the results of Berthelot and Scheibler, gives the solubility of saccharose at 12.5° C. and 45° C. : 12i°. 100 grms. of water dissolve 198.647 grms. sugar. 45°. 100 " " " 245.000 " The saturated solution at 12^° containing 66.5 per cent. 45° " 71.0 " The specific gravity of a sugar solution saturated at *Zeit.f. Rubenz., 1877, 1033. 40 CANE-SUGAR OR SACCHAROSE. 17i° is 1.3272 to 1.330 (Anthon*); 1.345082 (Michel and Kraft t). Brixij: gives the following formtda for calculating the amount of contraction produced by the solution of cane- sugar in water : V = .0288747X - .000083613X'' - .000002051X', wherein. X = the percentage of sugar dissolved ; at the maximum, for a solution of 56.25 per cent. X is equal to .9946. Cane-sugar is insoluble in ether and cold absolute alco- hol ; eighty parts of hot absolute alcohol take up one part of sugar, which it deposits on cooling. § Aqueous alcohol dissolves it more readily. Scheibler|| has calcu- lated the following table from his experimental data on the solubility of cane-sugar in dilute alcohol of various strengths : * Zeit. f. Ruhenzueker Ind., 1868, 615. For full tables of solubilities at different temperatures and densities, see page 116 and the end of the volume, t Ann. Chem. Pharm., lii. 195. X Zeit.f. RubenzuoUr Ind., 1854, 304; 1874, 1111. %Ibid., xxii. 346. Ber. Chem. Gesdl., v. 343. SOLUBILITY IN ALCOHOL. 41 Per cent. absolute Ate °C. At 14 •> C. At 40° C. alcohol. By volume Sp. Gr. at Grammes Sp. Gr. at Grammes Sp. Gr. at Grammes i7Ji» C. in zoo c. c. ^IV^ c. in 100 c. c. ■7'/i? C. In 100 c. c. O 1.3248 85.8 1-3258 87.5 105.2 lO I. 2991 80.7 1.3000 81.5 95-2 20 1.2360 74.2 1.2662 74-5 90.0 30 1.2293 65-5 1.2327 67.9 82.2 40 1.1823- 56.7 I. 1848 58.0 74-9 50 1. 1294 45-9 1. 1305 47.1 63-4 60 1.0500 32.9 1.0582 33-9 49-9 70 .9721 18.2 .9746 18.8 31-4 80 ■8931 6.4 ■8953 6.6 13-3 90 .8369 • 7 .8376 .90 2.3 97.4 .8062 .08 .8082 •36 •5 On comparing this table with the one showing the solu- bility of cane-sugar in water (page 116), it wUl be seen that the water in mixtures of alcohol and water poor in alcohol, dissolves more sugar than it can per se ; but for mixtures rich in alcohol the contrary is the case. Sugar has a great tendency to form supersaturated solu- tions, especially when the temperature has been lowered. Contact with a solid body in a fine state of division at once determines a precipitation of the excess of sugar (Sostman, Zeit. f.Hubenz., xxii. 837). Action of Heat. — Pure cane-sugar heated to 100° C, even for a long time, is scarcely altered in the absence of watery vapor ; in the presence of water a relatively con- siderable change takes place (MotteU). At 173° to 177° C. it melts without loss of weight to a clear liquid, which on cooling solidifies to an amorphous mass called barley- sugar, gradually becoming opaque and somewhat crystal- line. If the fused mass is kept at this temperature for a long time it is altered, without loss of weight, into levolu- san and dextrose, as : 42 CANE-SUGAR OR SACCHAROSE. Barley-sugar reduces less of copper oxide in the alkaline solution of tartrate of copper than does dextrose ; sp. ro- tatory power,* 48°. Cane-sugar heated above 180° degrees becomes brown, loses weight, and on cooling, if exposed to the air, ab- sorbs more water than it lost, deliquesces, and behaves with alkalies like dextrose (Peligot). When heated for a long time from 210° to 220° it froths up, the brown color becomes darker, and a large quantity of water is given off containing traces of acetic acid and furf urol ; when froth- ing has ceased the residue left is caramel mixed with some unaltered sugar and a bitter substance called assamar.j; When the temperature is raised, more water is evolved, and an insoluble matter produced, which increases in quantity when the temperature is carried to 250° to 300°. This insoluble body is of complex composition, being com- posed of at least three distinct substances, caramelene, caramelane, and caramelin. According to Peligot,:]: on heating cane or grape sugar to 220°, and treating the resi- due obtained with alcohol, unaltered sugar and a bitter substance are dissolved out, and caramel remains behind, containing on the average, when dried at 180°, Ci^HisOo) or two molecules less of water than cane-sugar. It is soluble in water, precipitated by baryta-water and subacetate of lead, not fermentable, and insoluble in alcohol. When sugar is subjected to dry distillation, carameliza- tion takes place with evolution of gases. The gas given off at first is nearly pure carbonic oxide, and afterward * ToUens, Ber. Oh. Gesell, x. 1403. ^Arm. CMm. Phys., Ixxvii. 154. { J. Ph. Ghem., Ixxxii. 148. INVERSION. 43 carbonic acid and marsh-gas make their appearance. An aqueous distillate forms, which holds a viscid oil and tar, besides acetic acid, acetone, and aldehyde. A voluminous, porous coal remains, constituting 32 to 34 per cent, of the sugar treated. Inversion by Heat.— Water acts precisely as do dilute acids in converting cane into invert-sugar. Dextrose. Levulose. According to G-ayon,* sugar solutions in sealed tubes in- vert in the cold, but much more rapidly when heated. See also Heintz {Zeit. f. Ruhenz., xxiv. 232), Berthelot {Ann. Chim. Pliys., Lxxxiii. 106), and PilUtz {Fres. Zeit., X. 456). A series of experiments made by Pellet f shows the effect of concentration and temperature in causing inversion. The table below gives the amount of invert- sugar formed during ninety-six hours' heating : Sugar in too c. c. At 25° C. At 50° C. At 75° C. lo grm, 30 '• 60 " 90 " ■ 5975 grm. ■5275 " .1025 " Trace. 3.0216 grm. 2.9200 " .6450 " .1500 " 8.8100 grm. 7.1825 " 5.490 " 3.9776 " Maumene,:}: as the result of experiments, which are sup- ported by previously-made observations of Soubeiran, Buignet, and others, claims that invert-sugar is a sub- stance of variable composition, the latter depending upon the facts as to whether the inversion takes place under the influence of heat or acids, the time, degree of heat, rela- * Gompt. Rend., 1877, No. 10. f Jowrn. Fabr. Suere, xix. 10, X Traitide la Fabrication du Sucre, tome i. 118-137. t4 • CANE-SUGAE OE SACCHAEOSB. Ive quantities of acid and sugar, and other circumstances ; ihat it may, according to the above conditions, consist of lextrose, levulose, and an optically inactive sugar (isome- Ic with the two others) in all proportions ; and that the niKture may show the most varying optical rotation. A lolution of cane-sugar, according to Maumene, on being lubmitted to 4)rogressively-increasing inversion, begins to ose its dextro-rotation, which is reduced to zero, after \rhich a left rotation begins to appear, caused by the ex- ;ess of levulose, which attains a maximum ; the rotation hen gradually decreases untU zero is again reached, and hen a plus or minus reading is shown ; and finally there s a tendency to assume a permanent dextro-rotation. Ls bearing on the estimation of cane-sugar by Clerget's )rocess, Maumene allows that if strict attention is paid to he conditions laid down for the method (see page 136), the otation of the inverted solution is constant, and hence no rror from this source will be introduced. Bechamp * attributed the inversion that cane-sugar un- dergoes in the presence of water to the influence of mould r fungi ; but the later experiments of Clasen t seem to dis- irove this. The latter shows that water, acting as an acid, ydrates the cane-sugar, air being an important factor in he change. Mcol,:]: also, has proven that sugar is quickly nd perfectly inverted when heated in sealed tubes to 130°- 35°. A solution of sugar may be preserved for weeks in lose vessels ; but in a dilute syrup, exposed to the air and rotected from dust, traces of altered sugar may be found 1 three days, which increase from day to day. * Corrupt. Rend., xl. 436. f Journ. Prak. Chemie, ciii. 449. X Amsr. Chemist, vi. 817. INVERSION BY WATER. 45 Solutions of cane-sugar brought into intimate contact with the air alter very quickly. In an experiment where a solution of sugar of 10° B. was caused to flow over bits of broken glass in a cylinder open at both ends, at 19°C. it was found that traces of invert-sugar could be discovered after six hours. The alteration after this time went on with greater proportionate rapidity, so that scarcely any crystallizable sugar remained after thirty-six hours (Hochstetter*). When nitrogenous matter is present a few hours suffice for the above change. The best authorities admit that the formation of levulose and dextrose in^ inver- sion is simultaneous. Clasen(foc. cit.) states that a dilute solution of cane-sugar heated immediately after its pre- paration, nearly to the boiling-point of water for several hours, takes on no molecular change. According to Hoch- stetter, a solution of cane-sugar of 25° B., boiled in a dish for one, one and a half, and two hours, at 110° to 112°, un- derwent but slight inversion ; but on passing air into the boiling solution the action took place with much greater rapidity. Lund ascribes this change to the carbonic acid present in the air. ACTION or ACIDS — INVERSION. This change is produced in perfection by the action of dUute acids on cane-sugar solutions ; the mineral acids act more quickly and powerfully than others. The change takes place at ordinary temperatures, but much quicker in the heat and as the acid is more concentrated. If the heating is long continued after the inversion is complete, coloration of the solution takes place, accompanied with the formation of various humus and ulmic compounds. If * Jow. S,-9 l.o6-,2 8.8 ,2 1.0977 12,8 ■4 1.0054 0:8 .7 1.0347 4.8 16.0 i.o6s6 §■« -3 1.0982 12.9 :i 1.0058 0.8 .8 1.05'^t 49 3 -I - 1.0660 : 8.9 -4 1.0586 12.9 1 0062 0.9 -9 1.0355 4.9 .2 1. 0665 9 -.1 1.0991 13.0 i •9 1.0066 1 0.9 9-0 l.03|9 5.0 -3 1.0669 9.0 1.0996 13.0 1.C070 1.0074 i.o .1 1.05 .2 5-05 51 -4 ■.V 1:^7^ 9.1 1 9-1 i l.IOCO I. 1005 13-1 13- IS 2.0 1.O077 I.I- . .3 1.0372 5.2 1.0682 9-2 -9 1.1009 13-2 .1 I. 0081 1.2 1 .4 1.0370 5-2 1 1.0687 9.25 24,0 1.IDI4 13-3 .2 1.C085 \:l 1 :i l.(^ 5-3 1. 0691 9-3 .1 1.IOI9 13.3 ■3 1.C089 I.tqSi 5.3 -9 1.0695 9.4 -2 I . IC23 1.1028 13-4 ■4 1.0093 '■3 ; -7 1.0388 5.4 17.^ 1.0700 .9.4 -3 13-4 :§ 1:001,7 1.4 -o 1.0393 5-4 .1 1.0704 9 5 -4 1.1032, 13-5 l.OIOI 1.4 -9 1.0397 5.5 .2 1.0709 H ,1 I. 1037 13-5 13.5 i I.OICS - 1.5 W-° 1. 0401 W ■3 1. 0713 . 1.1042 1.0109 1.55 .1 1.6 .2 1.04^5 -4 1.0717 9.6 : -7 1.1046 13.6 •9 r.0113 1.0409 5-7 i 1.0722 9-7 .8 1.I05I 13.7 3-0 I.OH7 1.7 -3 1.0413 I. 0418 H 1 .0726 ^:i' .9 I.I0-.6 13-75 13-8 .1 I.0I2I 1.7 -4 1.8 .5 5? -.1 1.0730 ; 25.0 I.IODD .2 I. 0125 1.0422 5.8 1-0735 9-9 ,1 1. 1065 13-9 •3 1. 0121} 1.8 .6 1.0426 5.9 „-9 1-0739 9.9 ! -2 1.1070 13.9 ■4 I. 0133 1.9 .7 1.9 .8 1.0430 il 18.0 1-0744 10. -3 1.1074 14.0 :a I. 0137 1.0434 .1 1.0748 10.0 -4 i:ii 14.0 I.OI4I 2.0 -9 1-0439 6.05 .2 1.0753 10. 1 -.1 14.1 ":? I .0145 2.0 ll.o 1.0443 6.1 -3» 1.07J7 10. 1 14.1 I. 0149 2.1 .1 ii,-<'447 6.2 1 -4 1.0761 10.2 :l 1.1093 14.2 •9 1.0153 2.2 .2 1-0451 6.2 j -.1 1.0766 10.2 1.1097 14.2 40 I -01^7 2.2 .3 1.0455 6,3 1.0770 10.3 ^■9 I. 1102 14.3 .1 I.OIOE 2.3 -4 1.0459 6,3 ' •7 1.0775 10.35 1 26.0 1.1107 14.35 .2 1 .0165 2.3 -5 2.4 , -i 1,0404 h* .8 1-0779 1. 0783 10.4 - .1 i.im 14-4 • -3 1.0169 X.a468 ^■• '■ 10.5 .2 1.1116 14.5 ■4 I. 0173 2.4 -^ 1.0472 6-5. j 19^0 10.5 10.6 •3 1.1121 14.5 14.6 .5 I. 0177 1.0181 1.0476 1. 0481 6.55 6.6 i 1-0792 ■4. I. 1125 .6, 1-0797 • X.0801 10.6 ■.r 1.1130 14.6 .7 J. 0185 2.6 .1 12.0 1.04S5 1.0469 67 10.7 1.1135 14-7 .^ I. 0189 2.7 1 -I ''■2 6.8 I 1.0806 10.7 • lo.i 10.85 ■I -9 1.1140 14.8 ■9 5.0 I .0193 1. 0197 2.7 .2 2.6 .3 I 0493 1.0497 1.0810 1-0815 1.1144 1. 1149 .1 I. 0201 2.8 .4 1.0502 6.9 1 l.o3i9 10.9 27.0 I. 1134 1. 1158 Z.11S3 I. 1168 14.9 .2 1.020;§ 27-7 ! 1,2828 31-85 2 3 I.I55I 1.15^5 19-3 19.4 2 1 1955 tl' 51 I 27^ " 1 59 9 1.2834 1.2840 4 i.isbi ^9-4 3 1.1966 23.7 2 1.2394 27.8 ! 1 1.2845 31 9 1 1,1566 19- 5 4 1.1971 23.7 23.| 23.8 3 1-2399 27-9 2 ;-^5i 31-95 J -1571 I. 1576 19-55 19.5 1 1.1976 1.1982 4 i 1.2405 1.2411 %l ' 3 4 32.0 ■ 32.05 19.65 I 1.1967 23.9 1.2416 28.0 I 1.2869 32.1 9 1.1586 i9-r 1 1.1992 23.9 I 1.2422 28.1 i!2li87 32-15 36 I. 1591 19.8 9 1.1998 24.0 52 1.2427 "§■' I 9 32 2 I 2 1.1596 l.x6oi 19.8 44 19.9 I 12008 24.0 24.1 9 1-2433 1-2439 tl 1 32.3 32.3 3 I 1606 19-9 2 1.2013 24.1 I 1.2444 28.3 l;6o 1.2898 33-4 4 I.i6ir 20.0 3 1.2019 24.2 2 1-2450 '?-3 1 1.2904 32-4 i i I 1616 20.0 4 1.2024 24.2 1 3 \:tl\ =?■■» 2 1.2910 32.5 1 . 1621 20.1 I 1 1.2029 24.3 4 28.4 3 1 .2916 32-5 32.5 32.6 I T.1626 20.1 1 1.20Si 24.35 I 1.2467 ^■s 4 1.2922 , i.iSsi 20 2 j I 1.2043 24.4 1.2472 ■'i8.65 1 — r^" 7 1.2928 37 9 1.1^6 1.1641 20.2 20.3 i 1.2045 1.2-il 24-45 ! 24-5 ; I 1.2478 1.2934 1.2940 32.7 32-7 — — 118 DETERMINATION OF SPECIFIC GRAVITY. tM \U (M (M o 6" Si Degree Baume. er cent. i II ■ a cnO & h A, & 6o.g 1.2946 32.8 67 2 1-3334 36.0 ":i 1.3732 39-1 79-8 1.4145 42.3 9 1.2952 32.8 3 1.3340 36.0 1.3738 39-1 ■9 1.4152 42-2 6i 1.2958 1.2964 32.9 4 1.3346 36.1 ■1 •■3745 39-2 80.0 1.4158 1.4165 42.2 I 32.9 § 1.3352 36-1 1-3751 39-2 .1 42-3 2 1.2970 33-0, '•3359 1.3305 36.2 -9 39-3 .2 1.4172 42.3 3 I. 2981 .33.0 . I 36.2 74.0 39-3 •3 1.4179 I. 4185 42.4 4 33.1 1.3371 36.3 .1 1^3770 39-4 •4 42-4 I -1.2987 33.1 ! 9 36.3 -2 1-3777 39-4 :l 1.4192 42-5 1.2993 33.2 1 68 364 -3 1.3783 39-5 1.4199 42.5 42-6 I 1.2999 33.2 I 1-3390 36.4 ■4 1.3790 39-5 39-S .■^ 1.4205 . — ^ 1.3005 33-3 2 1.3396 36.5 :l 1.4212 42.6 9 1.3011 33-3 3 1.3402 11 1.3803 39-0 ' .9 1.4219 1 .4226 42.7 62 I. 3017 33.4 4 1.3408 i l!38?§ 39-7 81.0 42.7 42.8 I 1.3023 33-4 I I.J415 36.6 39^7 39^| .1 1.4232 2 1.3029 33-5 1.3421 36.7 -9 '■sf^ .2 I --^39 1.4246 42.8 3 1.3035 33-5 I 1-3127 li 75.0 1.3828 39-8 ■3 42-9 4 1.3041 33-6 1-3433 .1 1.^35 39-9 . .4 •-4253 42-9 1 1.3047 33-6 9 1.3440 36.8 ,2 1-3842 39-9 :l ItU 43.0 1.3053 33-7 69 I-344S 36.9 .3 1.3848 40.0 43-0 I 1.3059 33-7 33-1 I 1-3452 36-9 -4 1.3t5l 40.0 .7 I-4273 43.1 1.3065 2 l-3tS8 1.3465 37-0 :l 40.1 .8 1.4280 43-1 9 1.3071 33-8 3 37-0 1.3868 40.1 .9 1.4287 43-2 63 1.3077 33.9 4 "•3471 37 1 -.1 •-3^74 40.2 82.0 1.4293 43-2 I I.30ii3 33-9 I ••3477 1-3484 37- • 1.3IS80 40.2 .1 1.4300 43-3 2 1.3089 34-0* 37.2 ^■9 1.3B87 40. 3 .2 1-4307 43-3 3 1-3095 J)-o,! I 1.3490 37.2 76.0 • ■3894 40.3 .3 I -4314 43-4 4 1.3101 34-1 1.3496 37.3 .1 1.3900 40.4 .4 1.4320 43-4 1 1. 3107 34-1 9 1.3502 37-3 .2 • ■3907 40.4 :l 1.4327 43-5 I-3113 34-2 70 1.3509 37.4 •3 I -3913 40.5 1-4334 43-5 § 1-3119 I-3126 34-2 I 1.3515 37-4 .4 1.392a 40.5 40.6 -.1 I-434I 43-5 43-6 34.3 2 I.3521 37.5 :l 1-3926 1-4348 9 1.3132 34-3 3 1.3528 37-6 1-3933 40.6 .9 1-4354 43.6 64 1.3138 34-4 4 '•3534 i 1-3940 40.7 83.0 1-4361 43-7 1 I -3144 34-4 i 1.3540 37-6 1-3946 40.8 .1 1.4368 43-7 43-8 2 1-3158 34-5 1.3546 37-7 -9 • -3953 .3 •-4375 1-4382 3 1.3156 1 .3162 34-5 34-6 I ••3553 37-7 378 77.0 ;:i^ 40.8 ■3 43-8 4 .1 40.3 -4 1.4388 43-9 i 1.3168 34.6 9 37-8 .2 1-3972 40.9 :l •-4395 43-9 I. 3174 1.3180 1.3186 34-7 71 1^3572 37-9 -3 1-3992 41.0 1.4403 44.0 ? 34-7 34-1 I 2 ••3578 •■3585 ll'.o ■4 41 41.0 ■i 1.4409 1. 4416 44.0 44.1 9 1-3192 34-8 3 •■3591 38.0 J -3399 41.1 •9 ••4423 44-' 65 1.3198 34-9 4 1.3J97 *' -.1 1-4005 41. 1 ;84.o 1-4430 44-2 I 1.3205 34-95 I 1.3604 3i-' 1-4012 41.2 ■ .1 •••1437 44-2 \ 2 1.3211 35-0 1.3610 ^' ■9 1-4019 41.2 ! oS •■4443 44-3 i 3 1-3217 35 05 I 1.3616 ^.2 78-0 1-4025 41.3 ; .3 1.4450 44-3 ■4 1.3223 35.1 1.3623 38.2 -1 1.4032 4"^3 •4 1.4457 44-3 1 1.3229 3515 9 1.3629 38.3 .2 1-4039 41^4 ' 1 1.4464 44-4 1.3235 35-2 72 •.3635 ^.3 •3 1-4045 41-4 1.4471 44-4 I 1.3241 35-25 I 1.3642 38.4 -4 1.4052 41-5 i ;:SS 44-5 1.3247 35-3 2 1.3548 ^■4 -.1 1.4058 1.406s tl 44-5 44.6 9 1.323 35-35 3 '^f ^•5 ■9 1.4492 66 1.3260 35 4 4 38.5 i 1.4072 41.6 85.0 1.44^ 44-6 I 1.3266 35.4 i • .3667 1.4078 41.7 .1 1.4505 44-7 2 1.3272 35.5 1-3674 38.6 ■9 1.4085 41-7 41-8 41.8 .2 1.4513 447 44-1 44-8 3 4 1.3278 35.5 35.^ I 1.36iio 1.3687 ^.7 79.0 -1 1.4092 1.4098 •3 •4 1.4519 1.4520 i 1:3291 35-6 9 1.3693 .2 1.4105 41 -9 -.1 •■4533 44-9 1-3297 35-7 73 1.3699 ^.8 •3 1.4112 41.9 3-4540 44-9 1 1.3303 35-7 1 ••3705 389 •4 1.4119 42.0 :l •-4547 45.0 1.3309 35-8 ; 2 1.3712 38^9 :l 1.4125 42.0 •-4554 1-4561 45.0 9 I -3315 35.8 ; 3 ••3719 390 1.4132 42.1 .9 45.1 67 1.3322 35-9 ■ 4 1-3725 39^o •7 1.4138 42.1 85.6 l.«68 45- • •• 1.3327 35.0 Another table is given, partially supplementary to the last and calculated by the same formulas, but taking in a wider range of densities, and having the desrrees Baume in the first column: TABLE. 119 Table showing Relation between Degrees BaumS, Percentages, and Specific Gravities of Cane-Sugar Solutions. |g Si M boa I" h ft S" li If ^n S" S^3 an a && ll 0" 5I a" mO o- .OO l.OCOO IS- 23-52 1.0992 26. SB 1.2203 39- 73.23 1.3714 r:§S 1.0035 IS- 5 24-43 1.1034 26.5 1-2255 39-5 74-25 I 1.0070 14- 26.27 1. 1077 27. 49.63 40. 75-27 76-29 I 2.69 I. 0105 14-5 1.II20 27.5 50-59 1.2361 40.5 1.3913 2 3.59 i.ot4i 15- 27.19 28.10 1.1163 1.1206 28. 51-55 l:lt^ 41. 77-32 78-35 1.3981 2 4.49 I. 0177 15-5 28.5 52-51 41.5 1:^1 3 5.39 6.2g I. 0213 16. 29.03 1.1250 29. 53-47 1.2522 42. 79-39 60-43 3 1.0286 16.5 29-95 30-87 1.1294 29.5 54-44 1-257S 1-2632 42-5 1.4187 4 7.19 8.09 17- 1-1339 30. 55-47 50-37 43- 81-47 1.4267 1.4328 4 1.0323 ;i:' 31-79 1-1303 30.5 1.2687 43-5 i^-5J 5 9.00 1.0360 32-72 1.1429 31- 57-34 58-32 1-2743 44- PI 1.4400 i 9.00 10. 80 1.0397 18.5 33-«5 34-58 1.1474 31-5 1.2800 44-5 1.4472 10435 19- I-IWO 32 59.29 60.27 1.2857 45- 85.68 1.4545 1.4619 6 11,70 1.0473 19-5 35-50 I. 1566 1-1613 32-5 1-2915 45.5 45. 87.81 88. Si 7 12.61 1.0511 20. 36-44 33- 61.25 1-2973 1.4694- 1.4769 1-4845 ? 13-51 I.QMO 1.0588 1.0627 20.5 37-37 38-30 I -1660 33-5 62.23 1-3032 46-5 14.42 21. 1.1707 34- 63.22 1.3091 47- 89.96 8 15.32 16.23 21.5 39-24 1:IU 34-5 64.21 1-3151 r 91-03 1.4922 9 1.0667 22. 40-17 35- 65.20 66.19 1-3211 92.1^ 1.5000 9 17.14 1.0706 22.5 41-II 1.1852 ¥ 1.3272 48.5 93.21 1.5079 1 5158 10 J8 05 i8.q5 1.0746 23- 42-05 1.1901 67.19 1.3333 49- 94-30 10 •;il 23-5 42.99 1-1950 36-5 68. 19 1-3395 1-3458 49-5 95.40 96.51 1.5238 II 19.B7 20.78 24- S:i 1.2000 37- 69-19 50. 1.5319 II 24-5 1.2050 is^s 70-20 1-3521 50.5 99.85 12 12 21.69 22.60 1.0909 1.0951 25- 25-5 n 1.2101 1.2152 71-20 72.22 1-3585 1.3649 51. 51-5 'ifi CHAPTER VI. Determination of Gane-Sugar — Optical Methods. POLAEIZED LIGHT. Fig,7. ^^ gy Reflection. — When a ray of light, a &, Fig. 7, falls on a polished surface of glass (wood, ivory, lea- ther, or other non-metallic sub- stance), f g h i, inclined to it at an angle of 35° 25', it i^ reflected, and the reflected ray acquires peculiar properties whereby it is said to be polarised. The change which has taken place in the light may be shown as follows : Let the polarized ray be received at c on a second reflecting surface, at the same angle as before. If the surfaces are parallel the ray is reflected ; but if the second surface is caused to turn around c 6, the intensity of the ray constantly diminishes, and when the reflecting planes are perpendicular to each other no light is reflected. If the rotation of the upper mirror be now continued the intensity of the ray gradually increases, and attains a maximum when the surfaces are again parallel. If the incident ray strikes at any other angle than that given the light is more or less polarized ; but the greatest effect for glass is always obtained under the condition mentioned. The angle which the incident ray makes with the normal 120 POLARIZATION BY REFRACTION. 121 corresponds to the greatest effect for any substance, and is called the polar izing angle. For water it is 53° 11'; glass, 54° 35'; air, 45°; and quartz, 57° 32'. By Refraction. — The phenomena of polarization are exhibited not only by reflection, but also by refraction, double or single. All doubly -refracting crystals have the property of polarizing light, and calc-spar may be selected as well illustrating this fact. When a ray of ordinary light passes throiigh a crystal of calc-spar in any direction except that of the shorter diagonal of the rhomb, which is its optical axis, it is divided into two beams of equal in- tensity, the ordinary and the extraordina/ry rays. When the ordinary ray passes through a second rhomb of spar it again experiences double refraction, giving rise to two beams of unequal intensities. If the second crystal be ro- tated jintil the principal planes of the two coincide — that is, when they are in opposite or similar positions — the ordi- nary ray acquires its greatest intensity and the extraordi- nary ray disappears ; continuing the rotation, the extraor- dinary ray reappears and increases in brightness, while the ordinary beam diminishes until the principal planes are perpendicular. When, however, the extraordinary ray suffers a second refraction by means of calc-spar, the con- verse to the above is exhibited. The two rays resulting from the double refraction are found to be polarized. Among other crystalline bodies capable of polarizing light by double refraction may be mentioned tounaaline and selenite (crystallized sulphate of lime). Glass also, sub- mitted to strains or pressure, becomes doubly -refracting. The plane in which a ray of polarized light, incident at the polarizing angle, is reflected or transmitted in the greatest degree, is called the plane of polarization of the ray. 133 DETERMINATION OF CANE-SUGAR. When tlie polarization is produced by reflection the plan of polarization is identical with the plane of reflection The Nichol Prism. — A valuable device for producinj polarized light, or analyzing it, is the Nichol prism, whicl consists of a rhomb of calc-spar slit along the plane pass ing through the shorter diagonal, and having the tw( halves cemented together again by Canada balsam, whos^ refractive index is intermediate between the ordinary anc extraordinary indices of the crystal. Hence, when a ra^ of light, S C, Fig. 8, enters the prism the ordinary ray experiences tota ' reflection on the surface of the bal sam, a b, and takes the directioi CdO, and is refracted out of the crystal ; while the extra ordinary ray, C e, emerges alone. The Mchol prism ha the advantages of perfect transparency and a very com plete polarizing effect. Elliptical, Circular, and Plane Polarization. — L accordance with the principles of the undulatory theory when the ether particles that make up a beam of po larized light vibrate in parallel straight lines, the ray i said to be plane polarized; when the particles describe ellipses around their positions of rest, the planes of th^ ellipses being perpendicular to the ray and the axes paral lei, the light is elUptically polarized. A particular case o the latter is when the axes of the ellipses become parallel when circular polarization is produced. When a ray o light in this condition is refracted by a Mchol prism an( viewed through an analyzer, the rotation of the latte causes no change in the intensity. Circularly -polarize( light is not, however, identical with ordinary light, as ma^ be proved by the interposition of a plate of selenite be ROTATION^ OF THE PLANE. 133 tween the polarizer .and analyzer, when the light becomes elliptically polarized. Kotation of the Plane of Polarization. — Crystals of quartz, calc-spar, and tartaric acid can cause a rotation of the polarization plane around its axis. If a plate of quartz, cut perpendicular to its axis, is placed between the analyzer and polarizer, color is exhibited, the tints chang- ing in the order of the colors of the spectrum as the ana- lyzer is turned. With monochromatic light it is found that when the prisms are adjusted to produce total extinction of light, and the quartz introduced in the path of the ray, the light is partially restored, but that on rotating the analyzer again total extinction is produced. The angle through which it is necessary to turn the analyzer to pro- duce this effect represents the angular rotation which the plane of polarization has experienced. There are two va- rieties of quartz, known as right and left handed — the one rotating the plane of polarization to the right and the other to the left. Fig. 9 represents the rotation of the plane of Fig.9. polarization : the plane A B, originally perpendicular, suf- fers successive rotations to a b, a' &', and a" &",. the angle C W a" being the final angle of rotation. Malus has established the following laws in regard to ro- tatory polarization : I. TTie aviount of rotation is proportional to the thick- 124 DETERMINATION OP CANE-SUGAR. ness of fhe quartz. II. The rotation of the plane of polarization varies for the different rays of the spectrwm, increasing with the refrangihility of the light. Witli a plate of quartz one millimetre thick the rotations obtained for different colors were : Eed 19° Blue 32° Orange 21° Indigo 36° Yellow 23° Violet 41° Green 28° Specific Rotatory Power.— When the polarizer and analyzer are so placed to each other that their principal sections are parallel, and a quartz plate 3.75 mm. thick is interposed in the path of the polarized ray, a peculiar tint is produced. It is a delicate rose- purple, but changes quickly into red or violet by the slightest movement in the position of the analyzer, the alteration of color being much more rapid and decided than for any other shade or color. It is called the transition tint {teinte de passage), and in measurements of the rotative power of various bodies this is often taken as a standard. The rotatory power of li- quids is directly as the length of the column through which the ray passes, and also as the quantity of active substance dissolved, if it is a solution. If e be the amoxmt of substance dissolved in a unit of weight of the solution, I the length of the liquid column, and a the observed angle of rotation for any particular color, as the transition tint, the angle of rotation for the unit of length vidll be — ; but, as the solution of the optically active body is often attend- ed with alteration of volume, it is desirable, in order to ob- tain an expression independent of such irregularities, to SPECIFIC ROTATORY POWER. 125 refer the observed angle of deviation to a hypothetical unit of density — that is, to divide the quantity — by the density, g, of the solution. The expression [a] j = —. — is e I g called the specific rotatory power, and represents the angle of deviation which the pure substance, in a column of the unit of length and density 1, would impart to the ray corre- sponding to the transition tint. For instance, a solution containing .155 gramme of cane-sugar to 1 gramme of liquid has a specific gravity of 1.06, and deflects the polarized ray for the transition tint 24° in a tube 20 mm. long. The spe- cific rotatory power is, therefore, \a\ i= ~ = 7.3°. '- -'•' .155X20X1.06 [a] is the expression for the specific rotatory power in general ; a letter afliixed shows the particular ray of the spectrum at which the deviation was observed : thus, [a] D and [a] j are the expressions for the line D of the spec- trum, and for the mean yellow ray, or transition tint, respectively. The minus sign is prefixed to the degree when the substance rotates to the left. The Polariscope.- — The apparatus for determining the rotatory power is called a polariscope, and consists of an arrangement carrying two Nichol prisms properly placed to serve as analyzer and polarizer, having a space between them, so that a tube, provided with glass plates at its ends and filled with the solution to be examined, may be inter- posed in the path of the polarized ray. In front of the po- larizer is inserted a quartz plate 3.75 mm. thick, so that when the prisms are adjusted with their principal planes parallel the transition tint is visible. The interposition of 136 DETERMINATION OP CANE-SUGAR. the active substance in the tube causes the color to change, and the amount of rotation of the analyzer necessary to re- store the transition tint measures the angle of rotation of the body under examination, from which, with the data given, the specific rotatory power may be calculated. The instruments to be described furnish more elaborate and ac- curate means of 'determining the specific rotatory power. Many organic bodies have the power of deviating the plane of polarization. Among them may be mentioned, DEVIATING TO THE EIGHT, cane-sugar, dextrose, milk- sugar, dextrin, camphor, asparagine, cinchonine, quini- dine, narcotine, tartaric, camphoric, and aspartic acids, oil of lemons, and castor-oU ; to the left, levulose, starch, albumen, amygdalin, quinine, nicotine, strychnine, brucine, morphine, codeine, malic acid, oil of turpentine, and oil of valerian. Optical Saccharimeters.-^The property that solu- tions of cane-sugar have of deviating the polarized ray in a fixed and definite degree has been made the basis of various instruments constructed for the purpose of quan- titatively -estimating that body. These instruments are called optical saccTiarimeters, polariscopes, or polarime- ters. Those treated of in this work are as follows : Mit- scherlich's, the Soleil-Duboscq, the Soleil-Yentzke, Wild's Polaristrobometer, together with Duboscq's, Laurents's, and Schmidt and Haensch' s modifications of the sacchari- metre d penombre of Jellett. mitscherlich's saccharimetee. This instrument consists of two Mchol prisms, enclosed in brass tubes supported on a cast-iron foot by means of a bar, by which the upper part may be made to slide to and MITSCHBRLICH'S INSTRUMENT. 12 fro (Pig. 10). The tube 5 contains the polarizer, and it ma; be made to turn on its axis, being kept in any desired posi tion by a screw at i. The tube a, containing the analyzei is also capable of rotating, and has an arm attached, as we] as a pointer which measures the amount of rotation upoi a fixed graduated circle of brass. The gradiiation of th circle is in degrees from 0° to 360°. There is a space be tween a and b for the reception of the tube C, which ii exactly 200 mm. long and designed to hold the saccharini solution. This observation-tube is made of brass, anc closed at each end by a screw-cap having a small orifice ii its centre ; glass plates are placed between the cap and th( ground ends of the tube, so as to make a tight joint anc to allow the light to pass through the axis of the tube. The theory of the apparatus is very simple : the light en tering by the first prism being polarized, on passing througl 128 DETERMINATION OP CANE-SUGAR. the sugar solution has its plane deviated to the right ; the prisms having their principal sections parallel, it becomes necessary to turn the analyzer through a certain angle cor- responding to the strength of the solution, in order to com- pensate for the rotatory effect of the sugar. To adjust the instrument for use it is important to fix correctly the zero-point, and that on the scale correspond- ing to 100 per cent, of cane-sugar. This is done as follows : For the Zero — The pointer is turned to 0° on the scale, a gas or oil lamp being placed behind the apparatus in such a position that the light may shine through its axis, and the observation-tube, filled with water, having been put in place, ^■ is unscrewed so as to allow the tube b to turn freely, the eye being placed at a. If the apparatus is not set correctly at the time of observation, a colored field will be seen, and the tube h must be turned until the field gra- dually darkens and finally presents the appearance of a round disk with an intense vertical black band in the cen- tre, gradually shading equally on both sides to a lighter tint, and appearing dark green or yellowish at the extreme distance from the centre. When the field presents the above appearance the rotation of the tube 5 is suspended, and i is screwed down so as to secure it. Now, with the apparatus thus set, if a be turned by means of the index, the field becomes gradually lighter until the pointer indi- cates 90°j when it is at its maximum brightness ; if the turning be continued the field darkens again, and at 180° it presents the same appearance as at 0° ; this may be used as a control experiment for the correct -adjustment of the zero-point. If, when the instrument is properly adjiTsted, and the pointer stands at 0° on the scale, a colorless solution of MITSCHBRLICH'S IlfSTRUMENT. 139 cane-sugar Ibe placed in the observation-tube, the field of the saccharimeter loses its dark color and shows a yellow- ish tint, owing to the fact that the plane of pola,ri2ation has . been altered by the sugar solution ; on turning the analyzer in a, the field passes through a series of chromatic changes in the following order: yellow, green, blue, violet, red, orange. To adjust the point corresponding to 100 per cent. of sugar, a solution of 15 grammes pure, dry cane-sugar is made by dissolving in water and diluting to 100 c.c; this is placed in the tube and the analyzer turned. The field passes through a series of colors as above until the normal spectrum of the apparatus is obtauied, which presents an appearance as follows — viz. : the right half of the colored circle must appear of a pure blue ; the centre has a line of violet, which shades off imperceptibly into red on the left. If the instrument correctly indicates at the point for 100 per cent, of sugar, the above appearance of the field is seen when the index of the scale is at 20°. Use of the Instrument. — For use in testing saccha- rine products 15 grms. is taken, dissolved in water, and di- luted to 100 c.c. After decolorization with lead solution, and filtering, some of the clear solution is placed in the observation-tube, and the analyzer turned by means of the arm attached, until the normal spectrum is obtained. The reading of the scale, multiplied by five, gives the percentage of sugar. It is evident that, when the degree of coloration of the material to be tested will admit, any multiple of the normal quantity may be taken and the solution made up to 100 c.c. The factor for multiplying the reading will be correspondingly less. With weak sugar solutions as much as 75 grms. may be weighed, in which case the reading of the instrument gives directly the percentage. 130 DETERMINATION OF CANE-SUGAE. Value as a Saccharimeter.— The chief, and indeed almost fatal, objection to the Mitscherlich apparatus as an instrument of precision is that, in the majority of cases, the actual readings of the scale have to be multiplied by a large factor. Owing to the introduction of more accurate polarizing apparatus, the Mitscherlich instrument is now comparatively little used. THE SOLEIL-DTJBOSCQ SACCHARIMETEE. Biot, early in this century, investigated the principles of circular polarization, and especially the power which quartz plates have of rotating the plane of polarized light. He constructed the polariscope for measuring the rotatory quality of various substances, which, with the aid of cal- culation, was capable of quantitatively estimating sugar. Clerget, following up the researches of Biot, devised a method of determining cane-sugar which is essentially that now employed with the Soleil saccharimeter. The method is Clerget' s, the instrument is Soleil' s.* The appa- ratus has been improved by Duboscq,t the successor of Soleil, and in its present form is called the saccharimeter of SoleU-Duboscq. The Instrument. — The following is mainly Terrell's excellent description: Figure 11 represents the appara- tus, which consists of two metal tubes mounted on an appropriate stand. The light enters at H by a circular opening of about 3 mm. diameter, and traverses the achro' matic polarizing prism P ; B, is a plate of quartz, called the plate of double rotation, and is composed of two halves of equal thickness, cd, cut perpendicularly to the axis of * Soleil, Compt. Rend., xxiv. 973. \ Soleil et Duboscq, ibid., xxxi. 248. THE SOLEIL-DUBOSCQ. 131 crystallization and joined together so that the line of sepa- ration is vertical. The half-disks have contrary rotations, the one being left-handed and the other right-handed. The light passing through T encounters Q, a quartz plate, either right or left handed, and of an arbitrary thickness. From Q the ray reaches K K', which are two wedge-shaped Fig. 1 1. .S H + - MB ainn A C L L N WBiS^f?^ KK' quartz plates, having the same kind of rotation, but differ- ent from that of Q. These plates are each fixed in a brass slide and covered with plane glass plates on each side to protect them from exterior injury or displacement. By means of a rack-work and pinion, to which is fixed the milled head, the slides may be made to move to and * The author is indebted to Dr. H. A. Mott for the above engraving. 133 DETERMINATION OF CANE-SUGAR, fro in opposite directions whUe remaining parallel. By this arrangement, at will the thickness of the quartz through which the polarized ray has to pass may be varied. Finally the light passes to the analyzer A and the quartz plate C. The small Galilean telescope LL' serves to render distinct the field of the instrument. The doubly -refracting prism A is so placed relatively to the diaphragm of the telescope that the passage of one of the rays transmitted by the polarizer is intercepted, so that but one passes, either the ordinary or the extraordinary ray, according as the plate R is 3.75 mm. or 7.5 mm. in thick- ness. It is evident from the construction of the apparatus that on placing the eye at the ocular, S, there is seen the ap- pearance of a luminous disk with a vertical line in the middle, produced by the junction of the quartz plates R. The sum of the thicknesses of the two prismatic quartz plates at a certain relative position is exactly equal to that of Q ; and hence, as the rotations are in different senses, the one being left and the other right handed, or the re- verse, it follows that they neutralize each other and pro- duce no effect on the polarized ray. On looking into the instrument when thus adjusted it wUl be seen that the two half-disks of the field are of the same color. If now we interpose in the space T a tube containing a liquid having a rotatory power, immediately the uniformity of color be- tween the two semi-disks is destroyed ; this is due to the rotatory effect of the liquid, which destroys the mutual compensatory effect of R, and the quartz wedges. For ex- ample, if the solution under examination consisted of cane- sugar, the deviation would be to the right, and this, with that of the right-handed plate of R, produces an inequality at- THE SOLEIL-DUBOSCQ. 133 tended with the production of unequal color in the field. The field may be restored to uniformity by turning the screw, thereby increasing or decreasing the thickness of the quartz at K and compensating for the deviating effect of the liquid. This action of the compensator shows not only whether the solution of the substance examined is right or left rotating, but also the degree as measured by the thickness of quartz necessary to neutralize the devia- tion of the body examined. The latter is measured by fig- 1 2. means of a graduated scale fixed to one of the slides R E' (Fig. 12), while upon the other is a mark serving as an indicator. The scale is graduated into degrees indicating percentages of sugar, on each side of the zero. A displacement of the scale equal to one division is equivalent to a rotative effect equivalent to that of a plate of quartz -^^-^ millimetre thick. Soleil greatly improved his saccharimeter by placing in front of the ocular of tTie telescope a Mchol prism, N (Fig. 11), fixed in a movable case, which may be turned at wUl through an angle of 180°. This arrangement is called the producer of sensitive tints. The prism N destroys to a great extent the influence of the coloration in the liquids submitted to examination, and that of the light employed. It also permits us to obtain, by adjusting it to a certain position, the sensitive tint. The tubes designed to contain the liquids to be tested consist entirely of brass, or glass enclosed in one of brass. The extremities of the tubes are ground, so as to be per- 134 DETERMINATION OP CANE-SUGAR. fectly parallel with each, other and to form a liquid-tight joint with the glass plates that cover them. Around the ends of the tubes there is a thread cut, by which brass caps, perforated in the centre, may be screwed on, a round plate of glass having been previously placed upon the end. The light can thus pass through the axis of the tube Avhile it is filled with solution. An exterior view and section of these tubes may be seen in Fig. 13. The length of the Fig. 13. tubes is exactly 200 millimetres. The small movable tube containing the ocular to which the eye is placed, can be moved so as to adjust the focus in order to get the clearest view of the field. The collar on the ocular-tube, y (Fig. 12), which is connected with N, enables the operator to ob- tain the sensitive tint by rotating the prism. Determination of the Zero-Point. — For this pur- pose the instrument is so placed that the light traverses its axis, and the observation-tube containing distilled water is put in position, as T in Fig. 11. The telescope is then focussed until a distinct view of the field is obtained. If the halves of the disk are different in color the milled head is turned either to the right or left, as may be. neces- sary, until the colors appear to be perfectly identical on either side of the vertical line when the observation is taken ; now the collar near the ocular is turned, and it will MANNER OF USING. 135 be perceived that the color of the field changes through red, blue, yellow, etc., until the sensitive tint is obtained, at which the previously appearing uniformity of the field, may be seen not to exist. A perfect uniformity may be made by turning the milled head cautiously again. The color of the sensitive tiut varies somewhat with different observers, but for most persons it is the rose-violet, or where the lightest color of the spectrum (almost white) just begins to verge upon the red. By practising these manipulations the operator soon becomes skilled in the proper adjustment of the saccharimeter. When the field presents the appearance described, the zero of the scale ought to coincide with the indicator. Should this not be the case the two zeros may be made to agree by turning the screw-button (Fig. 12), placed near the end of the scale. Manner of Using the Instrument. — To use the sac- charimeter for the estimation of cane-sugar, a normal weight of 16.19 grms. is taken, dissolved in water, and the solution diluted up to 100 c.c, being suitably deco- lorized. When the observation-tube is filled with a so- lution thus prepared, and is placed in the instrument previously adjusted so that the field appears of a uni- form tint, it will be seen that the uniformity is de- stroyed, and that the half-disks have different colors, one being complementary to the other. If now the milled head be turned until the equality of color is re- stored for the sensitive tint, the number of the scale to which the indicator points shows directly the percentage by weight of cane-sugar contained in the material ex- amined. A new instrument should be tested to see whether it 136 DETERMINATION OP OANE-SUaAK. makes correct indications at the division of the scale read- ing 100 per cent., and whether the scale is correctly gi-adu- ated, and the optical portions are in proper condition and adjustment. 16.19 grms. of pure, dry cane-sugar are taken, dissolved in water, and the solution made up to 100 c.c. This constitutes the normal solution for the sacchari- meter, and should show 100° on the scale, the zero-point having been adjusted as previously described. A magni- fying-glass accompanies the apparatus to assist in reading the scale. Clerget's Metliod of Inversion. The readings of the Soleil-Duboscq saccharimeter show directly the percentage of cane-sugar when no other opti- cally active body is present. Such bodies are, however, often found in saccharine products submitted to the pola- riscopic test, particularly in beet syrups and juice. Under some conditions invert-sugar may also have a similar action, though this sugar is thought to be without action on the polarized ray when occurring in commercial saccharine products (see page 173). As all of these substances have a specific rotatory power different from that of cane-sagar, deviating the plane either to the right or left, it follows that the reading of the saccharimeter for solutions containing such bodies must be incorrect as indicating cane-sugar, and the error will be in proportion to the amount of opticaUy-active substance pre- sent. Execution of the Process. — Clerget has devised a process for correcting the results of the saccharimeter when taken on solutions containing optically -active invert- CLBRGET'S METHOD. 137 sugar besides cane-sugar. * The direct titre is taken in the ordinary way, and a part of the solution remaining from this estimation is filled into a 50 c.c. flask (which is gradu- ated to 50-65 c.c.) up to the 50 c.c. mark; then concen- trated hydrochloric acid is added to 55 c.c, and the whole heated on a water-bath to 68°-75° for 10 to 15 minutes. This is sufficient to produce complete inversion of the cane-sugar present, while the invert-sugar is unacted on. After the liquid in the flask has attained the temperature of the surrounding air it is placed in the observation-tube and the reading taken. The sugar solution, while being heated with hydrochloric acid^ is apt to become colored. The color can be readily removed by shaking the cold liquid with a very little bone-black. The observation-tube is of peculiar construction. It is larger than the ordinary, lined with glass, and has a tubule in the middle for the introduction of a thermometer-bulb in order to take the Fig 14. temperature of the liquid at the time of reading. Fig. 14 shows the arrangement. * It must be remembered that Ihe process is entirely inapplicable when any optically-active body is present besides cane or invert sugar, and also if the in- vert-sugar itself exists in an inactive condition as regards polarized light. 138 DETERMINATION OP CANE-SUGAR. The tube is 220 mm. long, the increased length being to allow for the influence upon the saccharimetric reading made by the dilution of 10 per cent, on the addition of acid. Calculation. — Clerget found that a solution of 16.35 grms. pure sugar in 100 c.c. of volume, which read +100° in the saccharitneter, showed after inversion a rotation of 44° to the left at zero C— a difference in the rotation of 144, due to the inversion. The optical rotation is much affect- ed by the temperature of the solution after inversion, to the extent that the deviation diminishes by one-half of a degree (very nearly) of Soleil's scale for each degree Centi- grade that the temperature is raised. At 0° C. the action is expressed by T° = 144 - i T. If S represents the sum or difference of the polariscopic readings before and after inversion, T the temperature of the inverted solution when polarized, and R the percent- age of cane-sugar sought, then 144— iT : 100 :: S : R 288 — T : 200 :: S : R, ; whence jj^ 200 S 288 — T This formula, with the experimental data, will enable the operator to calculate the corrected percentage of cane- sugar. Clerget's Table. — To save the trouble of this calculation Clerget has given a table, which will be found on pages 141, 142.* Manner of Using the Table. — When a liquid * See also Tuchschmid, Zeita. f. Ruienz, Ind., 1870, 649. CLBRGBT'S PROCESS. I39 is tested in the saccharimeter, the degree of the scale has to be multiplied by 1.619 to give the number of grammes in a litre. This calculation the columns A and B enable us to dispense witli. By finding in the column A the number of the scale read, the one corresponding under B shows the quantity sought. When the substance is submitted to in- version, the sum or difference * of the direct and indirect readings is taken, and the number nearest it in the column corresponding to the tempemture at which the indirect reading was observed is sought. The horizontal line in which this number occurs is followed to the right, the quantity under A in this line being the corrected percent- age of cane-sugar. For example : I. Direct reading, + 38.7 Indirect " —25 at 15° C. Sum 63.7 The nearest figure to the sum under 15° is 64.1, which cor- responds to 47 per cent, of sugar. II. Direct reading, -f 90 Indirect " -f 10 at 30° C. Difference 80 = 62 per cent, sugar. When the sum or difference does not correspond exactly to a number of the table in the temperature column, the sugar percentage should be taken for that next below and * AVTien the two readings are in the same sense — ^that is, both plus or both minus — ^the difference is taken ; the sum is takea when they are in different senses. 140 DETERMINATION OP CANE-SUGAR. above, and the average of two taken — as 63.7 under 15° C is nearest to 62.8, corresponding to 46 per cent., and 64.1, " " 47 per cent. Average 46.5 In all cases the results are calculated more exactly witl the formula than by the table. 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N ^ o w en ^ m j-oo g; jH « eniC*S9E sjo c^ en 4^' tvao d "-5 n ^mo oo ono m com too t>. t^ p« c^ t« !>• tv csoQ 00 ob 00 w :o so o\a\a>aiaNa>ONaNOoooooOMiHi-iH)MH>wc^e. i.rmeopi^'SMto ON crio^cr^ t^ >-< ^too m ijra) wvD ONcnuo q eotN.q "^t^i-j m«) e^ mo^enio oncocvo ^i^h -rtto w m~ (idid M cn-l-v' t>.30 diw N -tif^ CO cj d « eo "ivD !>.» Q m SJl^-mrvM d>iH ci enrnMs i^d\o i-i cn-tkd t^od d m c« ^m U3\5 r^ r. t^ t^ t« t^ c^ [■'•00 oo 00 00 « 00 00 ONOtotOva>oiON3 oooo oo owMi-iiHhoMMetn n ^Tcn encn cocncncneo ~o -q- p^. iH~-!KO N mcT-ptvo q en t^q -•to o»eokO~d~ Sc\o en en-**0 ^'C0 O >-' en-^-uip^-oo om n enir*o iNid'Q en en^^ tvoo o ► \o i^ t^ K t^ r> t^ Oooo oo 00 00 00 00 o3 0.3 oa>u\ONO o o o o o o •-• h (Mio o'en tNiM TWO en uioientb O ^^.w ^^O w i/'o»e*»o o ^ t^n >ooo c 8CMH M enmno t«.tJiQ w cn^isQ t>cQ o m Q. a'i'~»0» cm-i en Wi'^ t-S?° \o t^t^r>-t«c^r»tN«OQOK}aoooaooD a-ONQ>otot<7>ova^o o ooo o o h « ^mr*^eo O^m en en mo ^^c>Q m eoM^O lent^o "tf-r^M UTOO envo ONent*-0 vco Hid" mo»cnvo o cni^w iroo en^o o^cn t"*o ^«o en moicno o ^ SovO t^^.?t^> r^ t<.t>->(n 00 00 0009 00 wot ON ON ON O^OlOlO o ^.,1-1 moNCnvo o "W-r^i-i moicn i/io 'a-t«.M mo>«*o o ^t^ rirv30 oiM N cnminoQ o«d en eO'g^o t»diQ h - - ■- --"-OOOOOSSoOOO SnO-OnOnOnOiOnO O 5 t^ t'- 1«. t^ r* p- e^ r«o3 00 00 oc i>.M moNcttq q eni en 4-trtoeQ dn-' g o Q o o o I- M"'mqi'Nvq~q"^ en 4- m tied d <■ ooo do M •■ H en '^lo N.ao o >- _ _ _ ^Smmmhmmmmm C'm N'encne'^cnT?) ; «^ q»cn(>.6 -T30~M~u-orenio o~ « vtmo p<>oc^vq o ■* tN. m m o* envo^d'^'t^M m O -O-oo w m ON en r«. o •♦oO en \q On en t^ m moo en >q q ^ t^ "-; d(d M cn^>^<>oo' d H ri -imoai diw « enirvdcd a\Q ei kS V> ■-« r^ t^. ts ►" i>«o oO CO CO 00 oo CO 00 cnONONeTNONOtONO o mo'cn^o o Tfoo e '^qteoiN M ^^ ci)OOcnt-'>i-ii/^dNr4ioo~ KmUm^SSh^SE!" weneiien?n% e*\o o -"foo w'o o eo^-w moNcnvq o -^oo cnNO ONcnt«.M mo'cn^q q ^oo nnc tS'&tlRS.^^t^t^QOQOQOOaWcO OnO-O^OnOXTiOnO^O o &oq^ 2 S "^ t ! a §'?§ S^ g-gggggg) enu3 o ^00 WND o -«o w »ooient-.iH tKO «« O -toa n^O o enb^n moient«.M mo-e q'=nt>.MmqNefH'»o ^joo en^o o CLBRGET'S PROCESS. 143 The Method applied for Saccharimeters in Gene- ral. — The tmderlying fact of Clerget's process— namely, that a sugar solution reading -{- 100° will, after the action of acids, show — 44°, making a difference of 144° due to inversion — is general, and hence may be applied to the re- sults of any saccharimeter. By the following method of proceeding, instead of the one described, fully as accurate results may be obtained with much less trouble, and only the observation-tubes used in ordinary work. The direct reading is taken, and from the normal solution remaining 50 c.c. are placed in a- flask graduated to 50-56 c.c, acid being added to the upper mark, and the sugar inverted as previously described. After inversion the solution is al- lowed to cool, the evaporated water replaced, and the read- ing taken in the ordinary glass tube, the temperature from a thermometer placed near the saccharimeter being also observed. The reading is increased by ten per cent. Care must be taken to keep the temperature in the neighbor- hood of the instrument as uniform as possible, and to bring the solution to the same degree before filling into the tube. If these precaiations are taken the temperature will not vary materially during the observation. The calcula- tion is the same as that already given, either the formula or table being used. THE SOLEIL-VENTZKE SACCHARIMETER. This instrument differs in no essential from the one last described, though the mechanical construction has been greatly improved, the optical parts somewhat changed and arranged in a different manner. These improvements are 144 DETERMINATION OF CANE-SUGAR. due to Ventzke,* and later to Scheibler.f This sacchari- meter, as now made by the best European makers,:}: is one of the most practically useful for the optical determination of cane-sugar, and is to be recommended in preference to the Soleil-Duboscq, though more expensive. Owing to its perfection in mechanical construction it is very easy to work with, and With 5 " " 77.5. With 9 " " 78.3. V. Suga/r-house syrup containing 38 per cent, invert-sugar, polarized 13.1. With 4 ^er cent, lead solution, 13.3. With 8 " " 13.7. Another solution polarized 13.8. With 10 per cent, lead solution, 13.7. The lead solution itself has no action on the polarized ray. * Zeits. f. ZucTceriiid. des Deut. Seiches, 1875, 1054. \Ibid., 1876, 734. i Ibid., 1876, 730. ERROR FROM LEAD-PRECIPITATE. 167 and third product sugars (beet), .25 per cent.; molasses (beet), .63 per cent. Scheibler * gives the following way of eliminating this error, which he calls the method of double-dilution: To 100 c.c. of the sugar solution 10 c.c. of lead solution are added and the saccharimetric reading taken. A second solution is prepared by mixing the same volumes of the saccharine liquid and lead solution, which is dilated to 230 c.c. and polarized. The last reading is doubled and sub- tracted from the first, the difference multiplied by 2.2, and this product taken from the first reading. This last result constitutes the corrected sugar content. Example : A sugar solution gave a saccharimetric reading of 47.10. After dilution 23.40. (1) 23.40 X 2 = 46.80 ; 47.10 - 46.80 = .30. (2) .30 X 2.2 = .66 ; 47.10 - .QQ = 46.44. It often happens that, even after the addition of an ex- cessive quantity of lead solution, the filtered liquid retains a strong brown color, rendering it unfitted to give an accu- rate reading. In this case a shorter observation-tube may be used or the solution made of half the normal strength. This mode of proceeding is, however, open to the objection that the necessary doubling of the reading increases the errors of observation. Bone-Black. — This is the agent best suited to assist lead in the decolorization of raw sugar solutions. For this purpose a quantity of well-dried, powdered black should be kept on hand in a tight bottle with a wide mouth, fitted with a stopper that carries a glass tube the end of which is * Zeits. f. Zucherind., 1875, 1054. 168 DETERMINATION OP CANE-SUGAR, F)s,24. kept cloKsed with a small cork when the bottle is not in use (Fig. 24). The bone-black should be dried at 120° for two hours. After the addition of lead the flask is filled up to the mark with water, shaken, about one-half of the contents poured out, the black dusted into the liquid remaining in the flask, which is agitated vigorously a few moments and filtered. The least quantity of black should be used that will be sufficient to decolorize the solution. An animal black of very superior decolor- izing power may be prepared from bone- black in grains, such as is used in the sugar manufacture. To the char to be treated, about one-third to one-half more hydrochloric or nitric acid is added than is necessary to dis- solve all the phosphate and carbonate of lime present, and the mixture is warmed several hours to promote solution (the more thorough the solution of the mineral matter the higher the decolorizing power of the carbon will be). It is then tho- roughly washed with boiling water until the washings cease to redden litmus-paper. After the washing is complete the carbon is dried at 120° and finely powdered for use, though the grains may be used for filtering in tubes. Bone-black well prepared according to this method has a much greater decolorizing effect than the ordinary, and hence a small quantity may be taken for a test. The most obstinate so- lution may be readily decolorized by its aid with a mode- rate quantity of lead solution. Absorption of Sugar by Bone-Black. — ^Animal char- coal has the property of absorbing sugar from its solutions. ERROR PROM BONE-BLACK. 169 Scheibler * has found that 5.5 grms. dried black shaken with 50 o.c. of a solution containing 13.034 grms. of cane- sugar, renders the polarization .4 percent, to .5 per cent, too low. J. M. Merrick f has, by a series of experiments, fully proven the existence of this source of error in the saccha- rimetric determination. His results agree with those of Scheibler. When the sugar solution is filtered through a column of black, the first third should be rejected and the test made on the remainder of the filtrate, which may be confidently relied upon to contain the normal amount of sugar. The error arising from the absorption of siigar by the bone-black may be corrected by determining the ab- sorption coefficient of the dried black. It is good practice to use both bone-black and lead on all low-grade solutions, but in moderate quantity, as the errors tend to counter- balance each other. For 50 c.c. of the Ventzke sugar nor- mal solution with the specially prepared black, there may be used from J per cent, to 3 per cent, by volume of lead solution, and from J grm. to 1 grm. of char for all products of moderate difficulty. For molasses and the most trou- blesome cases it will be found that very rarely will more than 5 per cent, of lead solution and 1 to 2 grms. of char be necessary. When the bone-black is used in the quanti- ties indicated above no correction need be made for its ab- sorbing power for sugar. Even when working with ordinary bone-black two grammes are generally sufficient for all but the worst cases.:]: * Zeits. f. Zuckerind. des Deut. Beiches, 1870, 318. f Chem. News, xxxviii. 33. X H. A. Mott {Jowm. Am. Chem. Soc, i. 13), working with tlie Ventzke nor- mal solution, has found that ten grammes of char absorb the following quan- tities of sugar : 170 DETERMINATION OP CANE-SUGAR. PEEPABATION OF PUEE StJGAE. The purest loaf-sugar of commerce is reduced to a fine powder, placed in a funnel whose barrel is stopped with a plug of raw cotton or sponge, and 85 per cent, alcohol poured' upon it. This is allowed to percolate through the mass until a volume of alcohol has passed through equiva- lent in bulk to about three times that of the sugar. The latter is then drained, air-dried, powdered again, and final- ly dried in small quantities, at a time when it is needed, at a water-bath heat for half an hour. Sugar thus prepared may be confidently relied upon to indicate one hundred per cent, of cane-sugar with a correct saccharimeter. ERROES INHEEENT IN THE OPTICAL METHOD OF ESTIMAT- IKG- CATSTE-StTGAE. 1. Influence of Temperature. — Though the specific rotatory power of cane-sugar is not dependent in any marked degree on the temperature at which the observation is taken, yet the temperature has some effect, owing to a va- riety of causes, among which are (1) the alteration in the length of the observation- tube by changes of heat, (2) the increase in volume of the sugar solution in the tube and consequent change in density, and (3) the expansions and contractions produced in the quartz plates and other parts of the apparatus. Mategczek * gives a table of the cor- rections to be made at various temperatures for the Soleil- Yentzke and the Soleil-Duboscq instruments, 17^° C. being taken as a standard : With pure sugar, .30 per cent, to .35 per cent. " raw sugars, .10 " .66 " Also, that some bone-blacks absorb in a different ratio from others. * Zeits. f. Zuckermd. des Deut. Beiches, 1875, 877, 891. ERROR PROM TEMPERATURE. 171 Temp, SoUil-Vcntjke. Soleil-Duboscq. Reading at given temp. II. Reading at given temp. II. IO° 100.17 26.004 II 100. 14 26.010 12 100.12 26.016 13 100. 10 26.022 14 100.08 26.028 15 100.05 26.034 100.05 16. 181 16 100.03 26.039 100.03 16.184 17 100.01 26.045 100.01 16.188 I7i 100.00 26.048 100.00 16.190 18 99.99 26.051 99.99 16.192 19 99.96 26.057 99.96 16.196 20 99-94 26.064 99.94 16.200 21 99-91 26.071 99.92 16.203 22 99.88 26.078 99.89 16.207 23 99-85 26.086 99-87 16.2II 24 99-83 26.093 99-85 16.215 25 99.80 26.100 99.82 16.218 26 99-77 26.108 27 99-74 26.116 28 99-71 26.124 29 99.68 26.132 30 99.65 26.139 The numbers in the second column indicate the quanti- ties to be weighed at corresponding temperatures to give a correct reading at 17^° C. If the correction is taken from the first column, the ordinary normal quantity must be weighed. For saccharimeters reading circular degrees, the correc- tion is made by adding the product of the difference in temperature from the normal 17° C. and the factor .011, to the degree read, when the temperature is above 17°, or sub- tracting when it is below. As, for example, the reading is 25° at 20° C. ; then 20 — 17 = 3 X .011 = .033, which, add- ed to 25°, makes 25.033° as the corrected result. This is for solutions of 25 grms. to 100 c.c, approximately. II. Personal Error. — In all saccharimeters where the 172 DETERMINATION OF CANE-SUGAR. reading is taken by a comparison of the equality of tint of two half-disks, there is a small but pretty constant source of inaccuracy in the results, owing to the fact that all eyes are not equally sensitive to minute differences of color. The same observer at different times of the day and in dif- ferent conditions of the eye, from its being more or less fatigued, will give varied readings. Some persons are spe- cifically unfitted for work with the polariscope having a field of two colors, on account of color-blindness ; but this is not true of the shadow saccharimeters or that of Wild. Dr. Landolt * has made a careful determination of this error with the aid of five experienced polarizers, and finds it to be, with the Soleil-Ventzke, the Soleil-Duboscq, and the Wild saccharimeters, from .3° per cent, to .5° per cent., plus or minu§. Probably this will be considered too high ; ±.2° per cent, would better represent the average. The per- sonal error does not necessarily affect the ultimate accuracy of the results, for each operator can set the scale of the in- strument to suit his own eye ; and if more than one use the same instrument, each can have his personal correction. Thus, if one operator reads the zero-point at — .4° and another at zero, the former will have to add .4° to all of his readings, f * Ameriecm Chemist, iv. 18-20. t Tollens (Ber. Deut. Chem. Gea., 1877, 1403) and Schmitz {ibid., 1877, 1414) have proved that the sp. rotatory power of cane-sugar is not constant for solutions of all concentrations. The effect on the results of the optical estima- tion of cane-sugar is too small to be taken into account for technical work, being less than one-tenth of one per cent, in all instruments. Elaborate tables of the correction for the different instruments have been calculated, and may be found in the places cited, and also in Stammer's Lehrbuch der Zucherfabri- kaiion and Landolt's OpUsche DrehungsvermSgen. OPTICALLY INACTIVE SUGAR. 173 EREOB OWING TO PEESENCE OF INVEET-STJGAE — OPTICAL INACTIVITY OF INVEET-SUGAE. All raw sugars and molasses from the cane contain in- vert-sugar, sometimes in large amounts. Inasmuch as the rotatory power of invert-sugar made by acting upon cane- sugar with acids, is strongly to the left, a mixture of the two will give in the saccharimeter a reading too low as ex- pressing the cane-sugar. It has been considered that the invert-sugar in the products of the cane possesses the same rotatory power as that artificially prepared, and it was cus- tomary with some chemists to correct their polariscopic readings by adding to them ^-^ of the invert-sugar as found by the estimation with copper liquor. Recent researches of Girard and Laborde * tend to verify a previous observation of Dubrunfaut — that the invert- sugar in cane products is optically inactive, and hence the use of the coefficient ^ involves an error. The results of the above chemists are based on the examination of (1) syr- ups artificially prepared from raw cane-sugars of many sources ; (2) of molasses from the sugar plantations ; and (3) from the refiner's molasses. The cane-sugar was esti- mated directly with the polariscope, and also very careful- ly by inversion and gravimetric determination with copper liquor. The invert-sugar was determined in the same man- ner. In the majority of the samples examined the per- centage of sugar by the copper method agreed quite close- ly with that by direct polarization, the latter being as often above as below the former. Other investigators, among whom may be mentioned Muntz (/. des Fabricants, xvii. Ko. 5), Morin {Sucrerie * Joum. des Fabriccmts, xvii. No. 5. 174 DETERMINATION OP CANE-SUGAR. Indigene, xii. 158), Gill {Sugar-Cane, July, 1878), slnd. Halse, hare confirmed the conclusions of the French chemists by an extended series of experiments upon raw sugars of all ori- gins, cane-juice, molasses, etc. Morin shows that analyses of raw sugar corrected by the coefficient ^ generally add up over 100, even when large amounts of undetermined organic matters are present. As beet sugars and syrups rarely contain more than traces of invert-sugar, these re- sults have no special application in that direction. Meissl * has recently, by a most elaborate investigation, gone over the ground covered by the authorities named, with the result of completely contradicting both their facts and conclusions. Working with seven low-grade' raw sugars from the cane, carrying from 5 to 13 per cent, in- vert-sugar, and determining the cane-sugar after inversion, and the invert-sugar directly, by Soxhlet's improved mani- pulation with Fehling' s solution (page 201), he finds the cane- sugar by inversion to be always considerably higher than the saccharimetric reading, the difference varying with the amount of invert-sugar present ; that by the use of the coefficient /^ the corrected percentage of sugar agrees closely with that by inversion ; that the syrups extracted from these sugars by alcohol, and containing from 27 to 39 per cent, invert-sugar, give essentially the same results as above. He also proves that the sugars, on complete analy- sis, do not add aip over 100, but the quantity of organic matters not sugar, varies from 1 to 8 -per cent. Meissl consi- ders the conclusion of the chemists cited, as to the optical inactivity of invert-sugar in commercial products, as erro- neous, and ascribes the error to the use of the gravimetric * Zeits. f. Rubenz., xxix. 1034; Stammer's Jahresb, (abstract), xix. 178. POLARIZING EFFECT OP VARIOUS BODIES. 175 method with FeMing's solution, which, he claims, gives re- sults that are too high (page 203). The coefficient ^-^ is inadmissible, however, for general commercial work, because sugars are bought and sold (at least in the United States) on the direct polarization, and it would be clearly wrong to make the correction unless the matter was so understood by the merchant. See also Horsin-Deon.* INFLUENCE OF VARIOUS BODIES ON THE POLAEISOOPIC READINGS. Alcohol. — The presence of alcohol in solutions of cane- sugar does not alter materially the specific rotatory power ; it diminishes the rotatory power of invert-sugar ( Jodin — see Invert-Sugar, page 89). Alkalies. — Caustic soda, ammonia, and potash lower the saccharimetric titre, according to Sostman,t and the effect may be represented quantitatively as follows : Alkali in loo c.c. Strength of solution in sugar. 5 grms. in loo c.c. 10 grms. in loo c.c. 20 grms. in loo c.c I grm. KsO I " Na,0 .426 per cent. .450 " .65 per cent. .907 .915 per cent. 1.217 " * Jr. Fain: Sucre, xx. No. 37. f Sostman, Zeits. f. ZucJcerind. des Deut. Reiches, 1866, 373. 176 DETERMINATION OP CANE-SUGAR. Pellet's * results are somewhat different ; 5 4 grms. sugar in loo ex. 17.3 grms. sugar in 100 c.c. I grm. KOH I " NaOH I " NH.O • 17 •14 .073 .500 •450 •085 Caustic liitne has an important influence in lowering the specific rotatory power of cane-sugar. Muntz f gives the following in this relation : Sugar solution, 10 grammes in 100 c.c. : .409 gramme sugar to \ molecule CaO, [a] D 64.9° .818 " " \ " " " 61.3° 1.637 " " 1 " " " 56.9° 3.274 " " 2 " " " 51.8° Pure cane-sugar being 67.0° In the estimation of cane-sugar, according to various ob- servers, one part of lime lowers the rotation equivalent to— .64 part of sugar (Jodin). .79 " " (Dubrunfaut). 1.12 " " (Bodenbender). 1.22 " " (Stammer). Baryta and strontia have a similar action to that of lime. On neutralization of the alkali or alkaline earth with acetic or phosphoric acids the normal rotation is re- stored. Mineral Salts. — Muntz:]: has found that some salts * Pellet, Zeits. /. Zueherind. des Deut. Reiehes, 1877, 1086. fMiintz, ibid., 1876, 780. iMnntz, ibid., 1876, 785. EFFECT OF SALT OK POLARIZATION. 177 lower the specific rotatory power of cane-sugar. Taking the rotatory power of sugar at [a] T> = 67.0°, he finds, in the case of chloride of sodium: KaCl added. Concentration of sugar solution in lOo c.c. Sgrms. 10 grms. 20 grms. 5 grms. lO " 20 " [rt]D66.I 65-3 63.8 66.2 65-3 63-7 66.3 65.6 61.0 Carbonates of soda, ammonia, and potash, and phos- phate of soda have a small effect, 1 gramme of the salts in the sugar normal solution altering the rotation generally much less than .20 per cent. According to Bardy and Riche,* sulphate, nitrate, chloride, and carbonate of potas- sium, and chloride of sodium have little or no effect on the polarization. Muntz states that sulphates of potassium, sodium, ammonium, and mugnesium, the nitrates and acetates of the same bases, phosphate of soda, chlorates, sulphides, hyposulphides, and chlorides of calcium, mag- nesium, and barium, alter the reading from 2 to 3 per cent, when they are present dissolved in the proportion of 20 to 30 parts to 100 parts of sugar. COEEECTIOH" OF THE MEASURING APPARATUS. The graduated apparatus, as bought from the dealers, is seldom accurate, and requires to be corrected. For this purpose it is best to make standard flasks of 100 c.c. and 50 c.c. capacity, from which pipettes and all other measur- ing apparatus may be adjusted ; the standards should be * Sucrerie Indigene, x. 551. 178 DETERMINATION OF CANE-SUGAR. kept in a safe place and only used for purposes of compa- rison. Flasks should be selected that will hold the re- quired quantity of liquid up to a point a little below the mid- dle of the neck which should not be too short. Clean and thoroughly dry the flask, place it on the pan of a balance in a room whose temperature is about 16° C, and counter- poise with weights ; now, in the case of the 100 c.c. flask, weigh 99.89 grammes of distUled water, or, for the 50 c.c. flask, 49.945 grammes at 16° C, carefully wiping away any drops that may adhere to the neck. When the weighing is completed, mark on the neck of the flask a straight line tangent to the lowest curve of the meniscus formed by the surface of water. The weight of water taken is ex- actly equal to 100 grammes, or 50 grammes distilled water at 4° C, the temperature of water's greatest density. If the flasks are to be marked for two graduations, as 100 c.c. and 110 c.c. in one case, and 50 to 55 c.c. in the other, ten and five grammes of water respectively must be weighed after the 100 and 50 marks are fixed, and another mark made on the neck as before. From the standard flasks standard pipettes, capable of ex- actly delivering 100 c.c. and 50 c.c, may be readily made by careful measurement vdth water, the mark placed on the pipettes indicating the exact volumes they vnll deliver into the standard flasks. By means of the. pipettes the flasks :for general use in the laboratory may be corrected ; for this latter graduation no especial temperature of the water used is required, so long as it does not materially change during the progress of the correction. In this manner it is always easy, in a few moments, to graduate a flask with perfect ac- curacy — and in case of doubt the standard is always at Jhand. CHAPTER VII. Determination of Cane-Sugar — Chemical Methods. Many of these methods have only an historical interest, and such will be but outlined in description ; those, how- ever, that are in actual use wiU be described in as much detail as the necessities of each case demand and the space will permit. METHOD OF PELIGOT. This process is based on the fact that lime enters into combination with cane-sugar in definite proportion, form- ing a sucrate, so that when excess of caustic lime is added to a sugar solution, an acidimetric estimation of the com- bined lime gives indirectly the amount of sugar dissolved. The method is only suited for saccharine products contain- ing no grape-sugar, and it cannot be recommended for ac- curacy. It is executed as follows : Dissolve ten grammes of the sug'ar to be tested in 75 c.c. of water, add ten grammes of finely -powdered caustic lime to the solution, and agitate from seven to ten minutes, or untU the lime is all combined with the sugar ; for v/eak saccharine liquids a less quantity of lime may be used. Throw the milky liquid on a filter, and take 10 c.c. of the clear filtrate, dilute to 300 c.c, add a few drops of litmus solution, and titre with standard acid until the red color of the litmus just ap- pears. The standard acid solution is made by dissolving twenty-one grammes of monohydrated sulphuric acid to a litre with water, that amount of solution being capable of 179 180 DETERMINATION OF CANE-SUGAR. saturating the lime which, combines with fifty grammes of sugar ; hence, 1 c.c. of the acid solution is equivalent to .05 gramme cane-sftgar. : METHOD OF EXTRACTION BY ALCOHOL. This is a method more particularly suited to the estima- tion of the sugar in plants, and where the quantities to be assayed are very small ; when the conditions are favorable it is capable of giving accurate results. It consists in simply extracting the material with cold alcohol of specific gravity .830, and evaporating the alcoholic liquid obtained to dryness. Aqueous alcohol will dissolve small portions of invert-sugar, mineral salts, fat, and coloring matter, but these can be washed from the dried residue by means of absolute alcohol, which does not dissolve the cane-sugar. The process may be conducted as follows : * 100 to 120 grammes of the dried and finely-powdered substance are treated in a small flask with alcohol of .830 specific gravity, and a drop or two of a very dilute solution of caustic alkali is added to neutralize any acidity, the alcohol being allowed to stand in contact with the material under examination, with frequent shaking, for three hours ; filter, add a fresh portion of alcohol, allow to stand two hours with agita- tion, and filter again. Repeat this operation several times, if necessary, as long as anything is taken up by the solvent. Unite the filtrates and evaporate at a gentle heat untU a dry mass is obtained. Lastly, wash the residue repeatedly with absolute alcohol and dry in water-bath until it ceases to lose weight; the residue is calculated as pure cane- sugar. (See also Scheibler's method, page 266.) * "Report on the Growth of the Beet in Ireland," British Mue-Book. ESTIMATION BY FERMENTATION. 181 4 METHOD BY FERMENTATION. The use of this process is open to many objections both from a want of exactness which is inherent in it, but also from the length of time required for its execution. One source of inaccuracy is that the fermentation does not always give the quantities of alcohol and carbonic acid in the normal proportions ; sometimes a secondary fermenta- tion takes place, with the formation of lactic acid and other bodies from which carbonic acid gas is not evolved. The process may be carried out in two ways — viz., I. By the estimation of the alcohol formed, and II. Bp the esti- mation of the carbonic acid. I. By Estimation of Alcohol.— When a solution of cane-sugar ferments, according to the best authorities, 100 parts of the sugar give 51.11 parts by weight of alcohol. The determination is conducted as follows : A rather dilute solution of the sugar is placed in a flask, and dry yeast added in quantity from 4 to 5 per cent, of the liquid, and the whole exposed to a temperature of from 20° to 25° C. When the fermentation is finished, which is in f i>6m 24 to 36 hours for a moderate quantity of sugar, the solutio'n is sub- mitted to distillation, and the amount of alcohol coijitained in the distillate is determined in the usual way. II. By the Estimation of Carbonic Acid.— The so- lution is placed in a flask whose cork has two perforations, one of which carries a small glass tube just passing through the stopper and closed at its outer end during -fhe fermen- tation ; the other carries a tube bent at a right angle and connected vnth a U-tube containing fragments of pumice- stone moistened with concentrated sulphuric acid, which in turn is joined to a second U-tube filled with chloride of cal- 183 DETERMINATION OP CANE-SUGAR. • cium in lumps. The proper quantity of yeast is added to the flask, and the whole system, consisting of flask and tubes, is weighed ; it is then allowed to remain at a tem- perature of 20° to 25° C. until fermentation has ceased. An aspirator is now applied to the chloride of calcium tube, the stopper removed from the glass tube, and a current of air drawn through the arrangement, the flask being meanwhUe moderately heated to facilitate the disengagement of the gas. The U -tubes serve to dry the gas so that no water may escape during the aspiration. The apparatus is now reweighed, and the difference between the first and second weights shows the quantity of carbonic acid produced during the experiment. 100 parts of cane- sugar correspond to 48.89 parts of carbonic acid. When invert or grape sugar is present they will have to be determined separately, and the amount, calculated into cane-sugar, subtracted from the result given by fermenta- tion ; 475 parts cane-sugar = 500 parts invert-sugar. DETERMINATION OF CANE-SUGAR BY FEHLING'S METHOD AFTER INVERSION. Acids have the property of converting cane into invert sugar in definite proportion, so that 19 parts of the former produce 20 parts of the latter. Execution of the Test. — To determine the cane-sugar, 1.00 gramme of the substance, if of a high tenor in sugar, and a proportionately larger quantity if the amount of sugar is lower, is dissolved in about 100 c. c. of water in a half -litre flask, 3 c.c. of strong hydrochloric acid added, and the whole heated for twenty minutes on a water-bath to 70° ; the liquid is then nearly neutralized with caustic or carbonated alkali. When the contents of the flask have ESTIMATION OF CANE-SUGAR BY INVERSION. 183 cooled, the solution is made up to the mark and is then ready for testing. The method of estimating the invert- sugar formed is, according to Fehling, either with Soxh- let's modiiication (page 201) or after the gravimetric method (page 203). For work with any pretension to ac- curacy the simple titration is quite inadmissible. Calculation.— CuO X .4307 Cu X .5394 = cane-sugar. Invert-sugar x .950 = cane-sugar. When invert-sugar is also present in the solution of which the cane-sugar is to be determined by inversion, the former is first estimated as a separate operation, and then a portion of the original solution is inverted as directed above, and the total invert-sugar, including that formed from the cane-sugar, is determined with the copper liquor. An example wiU. indicate the calculation required. The amount of invert-sugar present, as found by the direct test with the copper liquor, is 12.00 per cent.; for inversion 1.00 gramme of the substance is dissolved to 500 c.c, and of this solution 36 c.c. are necessary to precipitate 12 c.c. of the copper liquor ; then 36 X .002 = .072 gramme of substance containing .060 gramme invert-sugar, or 83.33 per cent. ' 83.33 12.00 less invert-sugar originally present, 71.33, which is the figure representing the invert-sugar derived by inversion from the cane-sugar. 19 : 20 :: a; : 71.33 = 67.76 per cent, cane-sugar ; or, 71.33 X x'i^ = 67.76. 184 BETBRMINATION OP CANE-SUGAR. When the oxide or metallic copper is weighed, the calcula- tion is entirely similar. In some cases the heating of the sugar solution with strong mineral acid causes a slight decomposition of the invert-sugar, which is shown by the liquid assuming a brown color. To avoid this Brunner recommends oxalic acid as the inverting agent. CHAPTER VIII. DETEBMINATION OF DEXTROSE AND INVEET-SUGAE. Section I. Fehling' s MetJiod and its Modifications. The basis of this method is a qualitative reaction for the detection of dextrose in the presence of cane-sugar, dis- covered by Trommer, whose results are summed up as fol- lows : (1) An alkaline solution of copper oxide, containing a fixed organic acid, as tartaric, has the oxide reduced to suboxide by dextrose, and cane-sugar under the same cir- cumstances is not at aU, or only slightly, affected ; (2) cane- sugar, when inverted by acids, is converted into a mixture of dextrose and levulose, which acts toward the alkaline copper solution precisely as grape-sugar ; (3) there is a de- finite relation between the amount of oxide reduced and the sugar. The reaction takes place slowly in the cold, and almost instantly at the boiling temperature. By the oxidation of grape-sugar formic, acetic, and oxalic acids are formed. According to Reichardt, gummic acid is also produced ; but this is denied by Claus,* who, however, found oxymalonic acid. Barreswill first took advantage of Trommer' s reaction to make it the basis of a quantitative method for the rapid estimation of cane and grape sugar. The solution pro- posed by him, consisting largely of alkaline carbonates, was found difficult to keep on account of the deposition of * Zeita. fH/r Chemie, 1869, No. 5. 185 186 DETERMINATION OP DEXTROSE AND INVERT-SUGAR. oxide of copper. It was improved by Fehling,* who has investigated the quantitative relations of the bodies taking part in Trommer's reaction. He found that one equivalent of anhydrous grape or invert sugar was capable of reduc- ing the oxide corresponding to ten equivalents of crystal- lized cupric sulphate — ^as : 1 eq. dextrose _ 10 eq. cupric sulphate C.H„Oe = 180 ~ r(CuSO, +5H,(3)=:3492L ^l-il. This has been confirmed by Neubauer.t There are two ways of proceeding in regard to the estima- tion of sugars by the Fehling process — one making use of all the refinements of more recent discovery and requiring a considerable amount of time, being adapted for cases where the greatest accuracy is required ; and the other quickly and easily executed, but quite exact enough for many technical purposes. It is proposed to discuss the subject divided as indicated above. Part I. The Method as Suited for Technical Work — Volumetric. Some recent researches have thrown doubt upon the con- stancy of the relation between dextrose and the amount of copper oxide reduced by it from alkaline solution, which affects both the volumetric and gravimetric methods. A conformity with these results would necessitate an altera- tion in the modje of operating, considerably lengthening it. These considerations, however, do not affect the substantial * Ann. der Ohem. Pharm., Ixxii. 106. •j- Arch, der Pharm., [2] Ixxi. 278. Soxhlet denies that the relation between the copper salt and glucose is fixed, but that it varies according to the circum- stances under which the test is made, from 9.7 to 11.1 equivalents of copper oxide to one of grape-sugar. See results of Soxhlet and others, page 201. FKHLING'S SOLUTION. 18'? value of Fehling' s process as ordinarily carried out for the greater part of commercial work, such as the analysis of raw sugars, syrups, etc., when the tenor is not higher than 20 per cent. There are cases that occur in commercial practice where the greatest possible exactness and care is required, and for which no analytical refinement would be misplaced. The analyst, however, must form his own judgment as to the proper course to pursue under any given circumstances. Fehling's Solution. — The formula for this- solution is as follows : 34.64 grammes pure cryst. cupric sulphate,«dissolved in 160 c.c. dist. water ; 150 grammes neutral potassium tartrate, dissolved in 600 c.c. to 700 c.c. of soda lye sp. gr. 1.12 (equivalent to about 90 grammes of the dry salt). The two solutions are mixed and made up with water to a volume of 1000 c.c. at 15°. Of this 10 c.c. is equivalent to .050 grm. dextrose or invert-sugar ; " " .0475 " cane-sugar. Fehling' s solution, unfortunately, is not very stable, de- positing oxide of copper in the cold, and especially when heated or exposed to light. Violette * and Monier each give a formula for a solution which is said to keep well, but doubtless that of the latter is less to be recommended on account of its strong alka- linity. * Dosage d/u sucre cm moyen des Uquev/rs titrees. 188 BBTBRMTNATION OF DEXTROSE AND INVERT-SUGAB. Violette's Solution. — "- 34.64 grammes pure cryst. copper sulphate. rl87 " tartrate of soda and potash (Rochelle salt). ^78 " caustic soda. The copper salt is to be dissolved in 140 c.c. of distilled water, slowly added to a solution of the tartrate and caus- tic soda, and the whole made up to one litre at standard temperature. 10 c.c. = .050 gramme dextrose or invert-sugar. " — .0475 " cane-sugar. Monier's Solution. — 40 grammes pure cryst. copper sulphate. 3 " chloride of ammonium. 80 " acid tartrate of potash (cream of tartar). 130 " caustic soda. The sulphate is dissolved in 160 c.c. of water, the ammo- nium salt added, the solution mixed with the other ingre- dients dissolved in 600 c.c. of distilled water, and the whole made up to one litre. 10 c.c. = .0577 gramme dextrose or invert-sugar. " = .0548 " cane-sugar. The ammonium chloride furnishes free ammonia, which acts as a solvent for oxide of copper, thus preventing its precipitation on standing. The investigations of several chemists * seem to establish that long boiling of cane-sugar with a strongly alkaline so- lution containing copper oxide causes a reduction of the oxide in small quantity. But, however, if (1) the solution * Lolseau, Armr. Chemist, iv. 391. Pelz, ibid., iv. 113 ; iii. 313. Possoz, Joum. des Fabr. des Sucre, xiv. 50. METHOD OF POSSOZ. 189 is diluted sufficiently, (2) if t7ie reduction fakes place quicTdy, and (3) if the copper liquor used has merely enough alkali, to ensure its permanence, either in the cold or at a boiling heat, the error from this source is tos small to affect the results notably for any purpose to which the method can be suitably applied. Possoz's Solution. — Possoz recommends a copper li- quor which he claims has no action on cane-sugar when used according to the directions given: 40 grammes pure crystallized copper sulphate. 300 " tartrate of potash and soda. 29 " caustic soda. 150 " bicarbonate of soda. The sulphate of copper is dissolved in 150 c.c. of water and the bicarbonate added. The other salts are made into a solution with 500 c.c. of water, the two solutions mixed, boiled for one hour, allowed to cool, and water added to make one litre. The resulting solution is allowed to stand six months before use. 10 c.c. = .0577 gramme dextrose. " = .0548 " cane-sugar. The sugar solution to be tested by this process should be of such a concentration that .100 gramme dextrose or invert- sugar precipitates the copper from 30 c.c. of the copper liquor. The estimation is made by heating to 70° C. with a measured excess of copper liquor, filtering, and determin- ing the copper remaining in the filtrate by a suitable method ; whence the amount reduced by the dextrose may be calculated. The formula following gives a cupric liquor which will be 190 DETERMINATION OF DEXTROSE AND INVERT-SUGAR. found to be perfectly permanent ; used with the necessary precautions, its action on cane-sugar may be altogether dis- regarded for ordinary work. It is the same as Violette's, except that the proportion of alkali contained is somewhat altered : 34.64 grammes pure cryst. copper sulphate. 180 " tartrate of potash and soda. 70 " caustic soda. Dissolve the tartrate and soda in 600 c.c. of distilled water, and to this add the cupric salt in solution, in small quan- tities at a time, shaking after each addition ; when a clear liquid is obtained it is allowed to cool and made up to one litre. 10 c.c. = .050 gramme dextrose or invert-sugar. " = .0475 " cane-sugar. Selection of Reagents. — The tartrate and caustic al- kali used may be of the best commercial quality, the latter as free from carbonate as possible. In order to obtain a copper salt containing rigidly the theoretical amount of oxide, the following procedure may be adopted : Procure a thoroughly reliable article of chemically piire crystallized cupric sulphate, or make it by recrystallizing the commer- cial salt, and select the clear, well-formed crystals, reject- ing those that are opaque and which generally consist of a more or less wet aggregate of fine crystalline material ; care- fully brush the selected pieces from all fine powder, and pulverize them, repeatedly pressing the powder between sheets of filter-paper to get rid of any adhering moisture. Preserve the salt thus prepared in a closely-stopped bottle until it is to be weighed out for use. If pure sulphate of copper cannot readily be obtained, 8.804 grammes pure me- STRENGTH OP SUGAR SOLUTION. 191 tallic copper, precipitated by the battery or otherwise, is dissolved in nitric acid, and sulphuric acid, in quantity slightly more than that necessary to combine with the cop- per, is added ; the mixture is evaporated to drive oflf the nitric acid, the free sulphuric acid neutralized with caus- tic soda, and the copper sulphate thus obtained is used in the preparation of the copper solution by the above for- mula ; 8.804 grammes of copper is exactly the amount con- tained in 34.64 grammes of the crystallized siilphate. Care must be taken to thoroughly dry the precipitated copper, and at so low a temperature that oxidation will not take place. The copper solution should be kept in a blue glass bottle or one blackened on the outside. Strength of Sugar Solution. — The amount of sugar to be determined varies greatly in different products sub- mitted to the grape-sugar estimation ; it is best to make the sugar solution of such dilution that from 25 c.c. to 50 c.c. will precipitate the copper from 10 c.c. of the copper liquor ; the sugar solution should not be much stronger than this, as it then becomes difficult to hit the end point of the reaction with sufficient delicacy. Calculation of Results — Glucose Normal. — It is convenient to establish a standard strength, for the sugar solution, of 5 grammes of the substance to be assayed to 100 c.c, and this may be called the glucose normal solu- tion. From the varying amounts of grape-sugar contained in the material to be examined it becomes necessary to vary from the glucose normal by weighing out 10, 15, or 20 grammes to 100 c.c. of volume, when the solution becomes double, triple, or quadruple normal; or to weigh 5 grammes of assay, and dilute to 200 c.c, 300 c.c, or 500 c.c, when the solution is called half, third, ox fifth nor- 192 DETERMINATION OP DEXTROSE AND INVERT-SUGAR. mal. The calculation of the results may be greatly- abridged in the following way : The reciprocal of the num- ber of cubic centimetres required of the glucose normal solution to precipitate 10 c.c. of the copper liquor, multi- plied by 100, is the direct percentage of dextrose or invert- sugar sought ; for 10 c.c. copper liquor = .050 gramme grape-sugar, and the normal glucose solution contains in 1 c.c. — .050 gramme of the substance. Suppose in an experiment 30 c.c. of sugar solution is required for 10 c.c. of copper solu- tion ; then 30 X .050 = 1.50 grammes of assay used, containing .050 gramme grape-sugar, .05 1.50 = 3.33 per cent, grape-sugar; the reciprocal of 30 is .0333, which, by displacement of the decimal point, becomes 3.33. A table for thus calculating percentages is appended. TABLE. 193 Table for Calculating the Percentage of Grape or Invert Sugar when THE Number of c.c. used refers to the " Glucose Normal Solution." (5 grammes to 100 c.c^ 1 Sua 1 t L 3 II 1 1% 1 II ■s II ■0" i 2» u ^ti ' Ob u 0- u "e u 51 d '^i i o" «i d «i 0" 0* n d z; Pk"^ Z fc- Z fc" Z P,"^ z fc- Z p." 1 - ^ ICX}.Q 72 1.39 143 .699 214 .467 s •351 356 1 .2809 1 ^ 50.00 73 1.37 144 ^li •465 •350 357 .2801 i 3 33.33 74 135 \% •463 ^l •348 358 •2778 4 2S.Q0 ?s 1-33 .685 217 •461 •347 359 % 20.00 1.32 \% .680 2Z6 •459 289 •346 380 16.66 ?? 1.30 .676 219 •457 290 •345 361 .2770 1 14.29 1.28 149 :| 220 ■454 291 •344 362 .2762 12.50 22 1.26 150 221 ■452 292 ■342 363 •275s 9 ri.ii 1.25 151 .662 222 .450 293 ■341 364 ■2747 10 10.00 81 1.23 152 .6;3 223 ■ 448 294 .340 365 .2740 II §1 82 1.22 153 • 654 224 ■446 l^ 36B .2732 12 §3 1.20 154 .649 fA •444 f ■2725 13 !♦ 5::§ ip .645 .442 l^ ^337 .2717 14 \i il .641 227 .440 ■335 369 .2710 '1 1. 16 IW .637 228 .438 299 ■334 370 .2703 5O i? 1. 15 1. 14 .633 .620 229 230 ■437 ■435 300 301 ■333 •332 371 372 -.11^ 5:l§ ■ 89 1. 12 160 .S25 231 ■ 432 302 ■331 373 .2681 J9 90 I. II 161 .621 232 ■4-)! 303 ■330 374 .2674 20 5.00 91 1. 10 162 .617 233 .429 304 IS 375 ■2667 21 4.76 92 1.09 163 .613 234 ■427 305 376 •2659 22 4-54 93 1.06 164 .610 %l ■425 306 ■327 377 .2632 i 23 4.31 94 .606 ■424 307 .326 378 .2645 .2638 24 4-17 } 1.05 .602 237 • 422 308 ■325 379 2i 4.00 1.04 ii ■ 'm 23a • 420 309 ■324 3«0 .2631 26 385 1.03 .595 239 .4.8 310 .322 38. .2625 .261S : 2^ 3-70 1.02 169 240 .417 311 .321 3S2 3-57 99 1. 01 170 .5^ 241 • 415 312 .320 383 ■2611 29 3-45 100 1. 00 171 .585 242 ■413 313 .319 384 .2604 30 3-33 lOI ■99 172 ■58' 243 .411 314 ■318 3S5 ■2397 31 3-23 102 .gb 1 173 .578 244 ■.t^ 315 ■317 3t6 ■ 23gr ■2*4 32 3-12 103 • 97 174 ■ 575 245 316 .316 337 33 3-03 104 .90 ;?i ■5S ■ 406 1 3' 2 ■315 3^3 ■2577 'M \^ S ■95 .Sffi 247 ■405 318 ■314 389 ■ 2571 l§ ■94 ;^5 .565 248 ■403 319 •313 350 .2564 2.78 107 •■)3 .562 249 ■ 402 1 320 .312 391 -2557 15 2.70 loa .92 !g ■559 250 ■ 400 321 •3" 392 •2551 2.63 109 .917 • 555 251 ■398 322 .310 393 :2i3l 39 2. 56 110 .909 181 .552 252 ■397 323 ■ 309 394 - 40 2.50 III 182 %l 253 ■395 324 :|S 39j .2532 41 .2:^ 112 .803 "t3 254 ■394 IS 396 .2525 42 , 113 .885 184 ■ 543 255 ■392 ■307 397 .2519 43 2.32 114 •877 .11 .540 255 .391 327 ■305 398 .2512 44 2.27 11^ 116 .869 .538 257 IS 328 ■305 399 .2506 45 46 2.22 .862 % ■535 258 329 .304 400 .2500 2.17 "2 118 • 8S5 ■ 532 239 .386 330 ■303 401 :^n 15 2.12 •847 189 :S§ 260 .385 331 ■302 402 2.08 119 .840 190 261 .383 332 ■301 403 .2481 49 2.04 120 191 ■523 262 ■3|' 333 .300 404 .2475 50 2.00 121 192 ■'*\ 263 ■380 334 :i 405 •2469 5' 1.96 122 '.iza 193 .518 264 -379 4o5 ■2463 52 \% 123 ■^ 194 ■515 fA ■377 407 •2457 B 124 196 ■513 ■376 1 408 •2451 54 1.85 ^21 .800 ■5'S 26? ■374 409 •2445 1.82 :f g? ■ 508 ■373 339 ■2950 410 •2439 56 1-79 fi •505 269 ■372 340 ■2941 411 •2433 P 1-75 .781 199 ■ 502 270 .370 341 ■2932 412 •2427 \^ 129 200 .500 271 ■ 369 342 •2924 413 .2421 g 130 201 •497 272 ■368 343 •2915 414 •2415 1.67 131 202 .495 273 ■ 366 344 ■.^ tl •2405 .24061 61 1.64 132 •757 203 •493 274 •365 HI 62 1.6J 133 ■752 204 .485 ■364 '.2Sp 419 .2398 t 1.34 IP .746 .741 ^ .362 ■ 361 iJ2 ■^7 1-54 .735 S§ .483 ■ 360 349 .2865 420 .2381 1-51 139 •730 .481 279 •358 350 .2857 421 .2375 1 1.49 1.47 •725 .719 209 210 .478 .476 280 281 It? 351 352 •2849 .2841 422 423 :^ fig 1.45 140 •714 211 •474 282 •355 353 .2833 424 .2359 70 1-43 J41 .709 212 ■472 283 ■353 354 .2825 ^§ .2353 71 1. 41 142 .704 213 .469 284 •353 355 .2817 .2347 194 DETERMINATION OP DEXTROSE AND INVERT-SUGAR. t 1 °S 1 II ■w u 1 °!3 II 1 p 1 ^ Km 9 "5 S ss s 3 2" o Ot '•• u .5k Ok d ot: ": Og d «| d tj| d s| d "i d d ° ■^S ^ ft" « p.-" !5 ij*"* z; p;- K e.'" « 6.'"' s .2342 456 :3 1 2062 514 .1945 543 .1842 572 .1748 .2336 2C58 m .1942 544 .1838 ; 573 .1745 429 ■2331 .2183 4^ 20 =,3 ■1938 Si .1835 574 .1742 430 •2325 i 4W .2179 2049 u ■1934 .1831 575 •ira§ 431 .2320 i 460 .2174 489 20)5 .1930 fg .1828 576 432 .2315 461 490 2041 519 .1927 .1825 ^l .1733 433 .2309 462 491 2037 520 .1923 549 .1821 .1730 434 .2304 463 .2160 492 2032 521 .1919 .1916 550 .1818 m .1727 ^ .2299 464 .2155 493 2028 522 551 .1815 .1724 tu .2150 494 2024 523 .1912 552 .1812 581 .1721 f^ .2146 t^ 2D20 524 .1908 553 .icoS ^2 .1718 .2278 t^ .2141 2016 '^ .1905 554 .itos ^ .1715 439 ■2137 '^ 2012 'il' m .1802 §* .1712 440 •2273 469 .2132 2008 ^ .1798 .17M .1706 441 .2267 470 .2128 499 2004 557 ■ 1795 442 .2263 471 .2123 500 2000 529 ;!^ 558 i ■J703 443 .2257 472 .2119 lioi 1996 530 f ii'si :ii 444 .2252 473 .2114 502 '^1 531 •■IP 589 Vil ■2247 474 .2110 503 532 .1880 561 .1782 590 .2242 t^ .2105 504 1984 533 .1876 562 -.11^ 591 .1602 til ■2237 .2101 ^i 1980 534 ■Jig 563 592 .1680 .2232 477 .2096 1976 564 •1773 593 .1680 449 .2227 478 :ai IS 1972 :i865 1 .1770 594 .1683 450 .2222 479 1968 gg .1862 .1767 f .j68i 451 .2217 486 .2083 509 1965 .1859 .1678 452 .2212 481 .2079 510 1961 539 .1855 568 .1760 .1675 453 .2207 482 .2075 5" 1957 540 •'S52 569 ■1757 .1672 454 .22OT .2198 483 .2070 512 1953 541 .1848 570 •1754 ^ 455 484 .2066 513 1949 542 .1845 571 .1751 .16^ The use of the table is quite simple. When the volume ■of sugar solution used is very small or fractional, by a change of the decimal point, making a whole number, a more exact figure may be obtained, the operator always knowing approximately the percentage of grape-sugar, s6 as to be able to set down the result correctly. Thus an ex- periment gives 4.1 c.c. of the glucose normal; looking in the table for the percentage opposite 41, we find it to be 2.44, which, by change of the decimal point, gives 24.40 per cent, as the true result. If 410 is taken instead of 41 a still more exact result is obtained — namely, 24.39 per cent. In cases where the strength of the sugar solution varies from the normal, the result of the test in c.c. may be reduced to the standard by multiplying by 2, 3, or 5 re- spectively when the half, third, or fifth normal solution is used ; or by dividing by 2, 3, or 4 for the double, triple, or quadruple jaormal solution. CALCULATION OF RESULTS. 195 Examples : I. 5 grammes of a raw sugar were dissolved to 300 c.c, and on estimation it was found that 36 c.c. were required i'or 10 c.c. of copper liquor ; then ^ = 12, and the corresponding percentage in the table is 8.33. II. 20 grammes of cane- juice made to 100 c.c. required 24.6 c.c; hence 24.6 X 4 = 98.4. Calling this 98.5, we find from the table that 98 corresponds to 1.02 per cent. and 99 " " 1.01 " The average is 98.5 " "1.015 -"a which is the percentage sought. When the estimation of grape-sugar is made on the same sample from which the cane-sugar is determined with the saccharimeter, it saves a great deal of time to have a pipette graduated to deliver 19.21 c.c. when the Soleil- Ventzke saccharimeter is used, and 30.8 c.c. for those hav- ing the normal weight of 16.19 grammes. These pipettes measure precisely 5 grammes of the original substance. In this way, after sufficient of the filtered solution has been taken for polarizing, from the remaining portion (free from lead) the required quantity is taken out with the appropri- ate pipette to make the glucose normal solution or its multi- ples. By this method of proceeding one weighing suffices for two determinations, and a further advantage is that a better average sample is obtained by weighing 26 or 16 ' grammes, while the glucose and cane-sugar determinations are made from identically the same solution. When the sugar solution is sufficiently colored to inter- fere with the copper test, it may be readily decolorized by shaking with a very small quantity of, bone-black and fil- tering. 196 DETERMINATION OF DEXTROSE AND INVERT-SUGAR. Organic matter other than sugar exerts a very sligh-t, if any, influence upon the results of the invert-sugar estima- tion after Fehling* (see note at the end of the volume). * It is entirely inadmissible to use a sugar solution containing lead in Pehl- ing's method, as the results of experiments given below show. This fact was pointed out by H. C. Gill (/. Chem. Soe., 1871, April), who also suggested the use of sulphurous acid as a precipitating agent. Experiments that I have made on the subject confirm Gill's results, and establish further that the preci- pitation of the lead must be very complete, as a mere trace seems to interfere as much with the test as a larger quantity. For this reason sulphates are unsuita- ble as precipitating agents, sulphate of lead being perceptibly soluble in water and sugar solutions. The use of sulphurous acid is, however, not open to this objection. EFFECT OF LEAD SOLUTION. I. Refined sugar containing 4.25 per cent, invert-sugar. A sugar solution required for 10 c.e. copper liquor 35.5 e.c. The same, with excess of lead solution, required 43.5 " The same, with lead solution and excess of NajSOi, re- quired 43.5 " n. Invert-sruga/r from cane-sugar. A solution to precipitate 10 c.c. of copper liquor re- quired 53.5 0.0. The same, with a large quantity of NaaS04, without lead, required 53.6 " The same, with lead solution and excess of Na^SOi, required 90 " III. Molasses sugar containing 2 86 per cent, invert-sugar : A solution required to precipitate 10 c.c. copper liquor, 50.7 c.c. The same, with a large quantity of Na2S04, required 50.2 " The same, with lead solution and excess of NajS04, required 68 " EFFECT OF SULPHirEGUS • ACID. I. A sugar solution required for 10 c.c. copper solution 81.3 e.c. The same, with 5 per cent. SOa solution 31.0 " " "30 " " " 31.5 " " "30 " " " 31.3 " " "50 " " " 313 " II. A solution of sugar required for 10 c.c. copper liquor 30.7 c.c. The same, with 1 per cent. lead solution 37 5 " " 1 and excess. of SOa 32.0 " EXECUTION OP THE TEST. 197 Execution of the Test. — ^10 o.c. of the copper liquor is measured into a porcelain dish or casserole, diluted with its volume of water, and with a good flame quickly brought to a boil. The liquid should show no signs of precipita- tion by ebullition. The sugar solution is added from a burette as rapidly as possible without risk of running in an excess. The color changes from a deep, clear blue to a dull hue, and at the same time the suboxide begins to form. As the operation proceeds the red color begins to manifest itself, and the liquid assumes a bluish- violet tinge, in which the red constantly increases, the shades passing through bluish red, violet red, dark crimson, and finally to a full crimson, when the copper is just thrown down. The last color changes to a bright scarlet as soon as invert-sugar or grape-sugar is present in excess. The experienced ope- rator can easily estimate by the color of the boiling solu- tion how the operation is proceeding, the end point of the reaction being indicated by the full crimson color of the agitated mass, without tinge of scarlet, and by the shade of the supernatant liquid after the suboxide has settled out, which should be a clear pearl white, neither bluish nor yellowish In order that the end point may be determined with greater exactness, it is necessary to remove a little of the liquid in a small pipette, filter, acidify with acetic acid, and add a drop of a very dilute solution of potassium fer- rocyanide, which will strike a brownish-red color as long III. A sugar solution required 30.7 c.o. With 2 o.c. lead solution 39.5 " " a " " " + excess SOj 30.5 " " 1 " " " 37.0 " " 1 " " " -j-exoessSOs 33.5 " " 1 " " " -(- larger excess SOa 31.0 " 198 DETERMINATION OP DEXTROSE AND INVERT-SUGAR. as copper remains in solution. If the color is very faint, a practised operator can estimate the amount of sugar solu- Fig. 25. APPARATUS REQUIRED. 199 tion to be added, to tliat actually run in, to.complete the re- action. Apparatus. — Fig. 25 shows a collection of apparatus suitable for carrying out the method of testing described. The arrangement and choice of implements can be highly recommended where rapid work is, required, especially when a number of tests are made at once. It consists of a burette-stand; two burettes provided with glass cocks, one of 50 c.c. capacity for the sugar solution, and a second of 100 c.c. for the copper liquor ; the casserole over which the burette delivers the sugar solution ; a pipette graduated to take out 5 grammes from the sugar normal solution of the polariscope ; small pipettes (about four inches long) for ob- taining a sample from the casserole ; a rack for holding a number of 3-in. test-tubes, funnels (f in.), and pi- pettes, together with the acetic acid and ferrocy- anide of potassium. The latter are contained in dropping or atropia bottles, shown by Fig. 26. They have a piece of sheet gum stretched and tied over their tops, so that it is only necessary to press upon the gum in order to fiU the tube ^^^. with liquid. When reliance is placed in the disappearance of the blue color alone as the end point of the test, the operation may be performed in a large test-tube held over a sheet of white paper. The color of the liquid, after the precipitate has settled, is best seen by holding the tube in a slanting posi- tion. This method of carrying out the test is not so accu- rate as the one described, and Tiot quicker in execution. 200 DETERMINATION OF DEXTROSE AND INVERT-SUGAR. Pavy's Modification of tlie Volumetric Method.* Dr. Pavy has taken advantage of the fact that caustic ammonia is a powerful solvent for suboxide of copper. In his process he uses a large excess of this reagent mixed with the ordinary copper liquor, so that the reduction takes place without precipitation, the boiling solution be- coming decolorized at the same time. Under the condi- tions specified it was found that six molecules of cupric oxide are reduced by one molecule of dextrose, instead of five molecules as in the process of Fehling (old system). The copper liquor used by Pavy is of the following composition : Cupric sulphate cryst., 34.65 grammes ; Potassio-sodic tartrate, 173 " Caustic potash, 160 " in one litre. 120 c. c. of this solution is mixed with 300 c. c. of solution of ammonia sp. gr. .880, and water added to make one litre. 20 c.c. of this corresponds to .010 gramme of grape or invert sugar. The test is made in a flask of about 80 c.c. capacity, with a cork fitted in the neck carrying a glass tube dipping under water, at the end of the tube being placed a piece of rubber tube cut longitudinally, so as to form a valve to prevent the water from being forced into the flask by con- densation during a momentary stoppage of the operation. 40 c.c. of the dilute test liquor is run into the flask, and while boiling the sugar solution is added, drop by drop, until complete decolorization is effected. The results are said to be quite satisfactory. See original papers {loc. cit.) * Chem. News, xxxix. 77, 197, 349 ; ibid., Steiner, xl. 139. SOXHLET'S METHOD. 301 Part II. The Method as Suited for Exact Work. A. Yolumetric.^Soxhlet' s Researches. — As stated on page 186 (note), Soxlilet, by recent investigations, has demonstrated that the relation of dextrose and invert-sugar to the cupric oxide reduced from alkaline solution is not constant, contrary to the view formerly accepted, but varies within certain limits, according to the circumstances (mainly in regard to dilution) under which the reduction takes place. According to his results, 50 c.c. of a 1 per cent, dextrose solution, or 100 c.c. of a ^ per cent, solution, with the undiluted copper liquor, required for complete reduction from 101.0 c.c. to 101.4 c.c. Fehling's solution. For the P. solution diluted with 1 vol. water, 99.5 c.c. F. sol. u (( 76 Sulphuric anhydride 23.75 Phosphoric anhj'dride 5-59 Carbonic acid 4'06 Chlorine. ..« 4.15 Ferric oxide .55 ' Alumina : .65 Silica 12.38 101.03 Deduct oxygen equivalent to chlorine .93 100. 10 The juice from which this sugar was made is supposed to have been treated only with lime (Wallace).* III. Sulphated ash from one year's work in a refinery laboratory ; Potash 28.79 Soda 87 Lime 8.83 Magnesia 2.73 Ferric oxide and alumina 6.90 Sulphuric anhydride 43.65 Sand and silica 8.29 100.06 —(J. W. McDonald. ■!■) The estimation of the ash is made by incinerating from two to three grammes of the sugar in a small platinum dish at a red heat ; the difference in weight of the dish before and after ignition gives the absolute quantity of ash, which multiplied by 100 and divided by the amount of the assay gives the percentage. Soluble Ash. — A simple incineration of the sugar gives the total ash, regardless of its composition. As insoluble * Chem. Mews, xxxvii. 76. f ^id., xxxvii. 127. ALKALINE ASH. 225 matters, like sand and clay, do not exert any injurious ac- tion on the sugar in the process of refining. It is often desirable to know the soluble part of the ash. This may be determined as follows : Weigh from two to five grammes of substance, dissolve in a little boiling water, filter hot, wash with hot water, and evaporate the filtrate and wash- ings in a tared platimim dish ; ignite the dry residue, burn off the carbon, and weigh. Alkaline Ash. — On account of the great volatility of the alkaline carbonates which form a large portion of sugar ashes, the heating for a sufficient time to oxidize the carbon will result in a considerable loss by volatilization, rendering the result of the estimation too low. It is well known that in general the salts of the alkali metals have a powerful melassigenic effect in preventing cane-sugar from crystallizing, and in inversion, while many, of the other con- stituents of sugar-ash are almost inert in this respect (see page 64). To be able to estimate the amount of alkaline salts in a given ash is, therefore, a desideratum. This result may be reached in the following way : Thoroughly carbon- ize the sugar ; transfer the coal to a small mortar, pulver- ize ; wash well with hot distilled water and filter ; evapo- rate the filtrate and washings, and dry the residue on a water-bath ; or determine the amount of alkaline carbo- nates by standard acid solution in the ordinary process for alkalimetric estimation (page 258). By the carbonization, the salts are mostly transformed into carbonates, and dur- ing the lixiviation the comparatively non-injurious lime salts remain on the filter in great part, together with sand, clay, alumina, magnesium, carbonate, and other matters. Small quantities of caustic lime and other bodies are dis- solved along with the alkaline carbonates, owing to the re- 226 ANALYSIS OF RAW SUGAR. duction of sulphates to sulphides, but by far the greater portion of the dissolved salts consist of sodium and potas- sium carbonates, and alkaline chlorides. Sulphated Ash. — Scheibler* has proposed the incinera- tion of sugars with the addition of concentrated sulphuric acid. The advantages of this method are (1) that the car- bonization in the presence of the acid furnishes a porous coal which burns off rapidly and vnthout much swelling, while in the ordinary way the charred mass is apt to be- come hard and graphitic ; (2) that the bases are converted into sulphates, with the expulsion of chlorine and carbonic acid, whereby the loss by volatilization is greatly dimin- ished, as the sulphates are very stable at a red heat com- pared with chlorides or carbonates. The ash is thus deter- xained : Two to three grammes of sugar are weighed in a Fig. 31. ■ small tared platinum dish, as shown lin Fig. 31, 45 mm. in diameter, 14 I mm. high, with a flat or convex bot- tom ; from fifteen to thirty drops of pure concentrated sulphuric acid are added to the sugar in the dish, and the heat applied at first rather gently, and then to full redness. Nothing is •gained by having too large a flame, as the carbon burns off most rapidly with a moderate red heat. Scheibler has pro- posed the use of a platinum muffle, which, when many de- .terminations are to be made, will be found useful. It is figured at 32. The dimensions of the muffle to hold three -dishes, as described above, are 150 mm. length, 55 mm. width, and 25 to 30 mm. high. It should slightly taper towards one end, which is elevated somewhat so as to al- low the air a good draught through the apparatus. When * Stammer'a Jahresb., iv. 231 ; vii. 367. SULPHATED ASH. 227 the carbon is completely burned off, the dish is allowed to cool and reweighed. If the amount of ash is large, or it is very fusible, it will often happen that the last portions of carbon are oxidized with difficulty. In such a case the dish is allowed to cool, one or two drops of siilphuric acid added, and the dish heated cautiously at first to avoid spattering, and finally brought to redness for fifteen minutes. As the equivalent of sulphuric acid is greater than Fig- 32- that of carbonic acid (in proportion of 40 : 22), it is necessary to reduce the net weight of the sulphated ash to the figure that represents the carbonated ash. Scheibler has found that a subtraction of one- tenth from tLe weight of the sulphated ash will do this approximately. Though the discrepancy mentioned above is not constant for all sugars, yet the results given by the method are near enough to the truth for all practical purposes.* Example : Sugar plus dish 12.121 Dish 10.110 Sugar taken 2.011 * Violette (Amer. Chemist, v. 296) ennsiders that the coefficient ft- should be used in general, and -^ for very pure raw sugars. 238 ANALYSIS. OF RAW SUaAR. Dish plus ash.. 10.120 Dish 10.110 .009x100 .. _. Ash 010 --^:^i^=MveTcent. Less iV 001 .009 The process with sulphuric acid is preferable to the sim- ple incineration for accuracy, general agreement of results, and facility of execution. The soluble ash can also be made by the sulphuric-acid method. It is to be recom- mended that with sugars containing much sand, clay, and other insoluble impurities, the soluble ash be taken, as this represents the amount of the salts which go into solution in the operation of refining. SCHEME FOE THE EXAMINATION OF SUGAR-ASH. Dissolve 10 grammes of the sugar in water, dilute to 100 c.c, and filter : A. Dry filter ; ignite B. Evaporate 25 c.c. C. 50 c.c. ( — 5 gnus. in tared platinum dish ; (=2.5 grammes sugar) sugar) of filtrate are subtract filter ash. of the filtrate in a tared evaporated in a plati- Residue = dish, add sulphuric num dish, carbonized. Sand, Clay, etc. acid, carbonize, burn off the coal washed with coal, and weigh; sub- hot distilled water, and tract -,V from residue. the washings, after fil- = Soluble Asli. tration, evaporated on water-bath to dryness. Result = Alkaline Ash.* D. The alkaline ash is titred with standard acid. Result — Alkaline Carbo- nates. * Alkaline chlorides and carbonates. COLORIMETRY. 239 The relation between tlie snlphated ash and the salts as they exist in the raw sugar is such, according to Landolt, that one part of the former is equivalent to two parts of the latter. This is for beet-sugars. ESTIMATION OF THE COLOR. Several instruments have been invented for effecting a comparison of color between sugar solutions. Of these Payen's decolorimeter and its modification, Ventzke's, have for their object the estimating of the decolorizing power of char. Salleron's, Duboscq's, and Stammer's colorimeters, and Stammer's chromoscope, are more general in their ap- plication, and permit the color-comparison of all saccharine products, solid and liquid, as well as the estimation of the decolorizing power of animal black. None of these appli- ances, with the exception of Stammer's colorimeter {Far- benmdss), have a standard of comparison in the instrument itself ; the results are merely comparisons with standard solutions of caramel, which in practice are found to be exceedingly difficult to make twice alike by the same operator. Hence estimations made with such standards have necessarily a considerable element of uncertainty in them. Staminer's Colorimeter (not to be confounded with his chromoscope) approaches nearest to an absolute stan- dard, the results obtained by different instruments and operators by Stammer's process being generally strictly comparable. The apparatus is shown in Fig. 33. The solution-tube I is closed at its lower extremity by a glass plate, and Is open above, where it is provided with a lip by which the sugar solutions may be poured. I is fixed 230 ANALYSIS OF RAW SUGAR. 33- to the wooden support by two screws, which, when it is necessary to clean the instrument, can be easily re- moved. The measuring- tube III is closed below by a glass plate, and moves freely up and down in the solution-tube I. TI, fas- tened to III, is open be- low, and at its upper ex- tremity is covered by the colored glasses which form the standard of compari- son ; at the lower portion of it are two rings with screws, which are connect- ed with a slide moving in a groove cut in the wooden support shown in the fig- ure. The slide serves as an indicator of a milli- metre scale placed at the back of the wooden frame, for the purpose of measur- ing the perpendicular dis- tance that the joined tubes, II and III, may be raised. The standard consists of two glasses, and a de- gree of color equal to them is called 100. Besides this, the apparatus is provided vdth two separate colored glasses, each eqiial to one of the plates forming the standard, and COLORIMBTRY. 331 may be employed in the place of the standard, being equi- valent to one-half of it in color intensity ; also one or both may be used with the standard glasses, when the combina- tions are equal respectively to one and a half times, and double the normal standard. The eye-piece V consists of an optical arrangement whereby the color due to the so- lution under examination, and that from the colored glasses, are made to appear on either side of a vertical line dividing a circular disk, making a luminous field similar to that of the Soleil saccharimeter. In this man- ner an accurate comparison of color may be obtained. The eye-piece can be fitted on the top of the tubes II and III after the standard glasses are placed in position in the upper part of II. A mirror at the bottom reflects the light upward through the tubes, and a screw behind the wooden frame attached to the tube II enables the operator to elevate or depress at wiU II and III. The whole appa- ratus is mounted on a wooden stand, as shown in the cut. The manner of using is as follows : The operator fills the solution-tube to the proper height with the liquid to be ex- amined, and then, looking through the ocular, by means of the large screw attached to the frame elevates gradually the tubes II and III, until after repeated trials the two halves of the luminous disk appear of the same intensity of color. At this point the screw is turned so as it keeps the apparatus in the position thus obtained, and the read- ing of the scale taken, which shows the amount of perpen- dicular elevation. The more III has been raised, the greater the depth of the column of liquid between the bot- toms of I and III. The color-intensity of this column is compared with standard glasses. A solution before use must be rendered perfectly clear, by filtration if necessary. 232 ANALYSIS OF RAW SUGAR. The color of a solution is in inverse ratio to tlie length of a column of it necessary to produce a given color. If the comparative color be expressed by 100, it follows that the readings in millimetres must be divided into 100 to get the figure expressing the relative color. The apparatus may be cleaned by loosening the screws holding the rings on the bottom of II, when the latter can be raised out of the solution together with the tube III. Calculation. — The estimation of the color of raw sugar, Fullmass, or other material can be calculated on one hun- dred parts of cane-sugar contained, and the result shows the relation of color to the saccharimetric strength. A so- lution of the substance to be estimated is made by dissolv- ing a known weight in water and making the solution up to 100 c.c. It is convenient to take the normal solution in- tended for the polariscope. The clear solution is placed in the colorimeter and the reading taken, which is divided into 100. If the solution is too dark for use with the standard, one or both of the extra colored plates may be put in and the readings (before division into 100) divided by li^ or 2 ; or the dark solution may be diluted, to twice, four times, or any desired volume, the reading being di- vided by 2, 4, etc., to reduce to the standard of the colori- meter. If, on the other hand, the solution is too light, the standard glass may be replaced by one of the extra glasses and the reading multiplied by two. These directions ap- ply to the use of the colorimeter, whether for solids or liquids. Example : 15 grammes of a raw sugar polarizing 85 were dissolved in water and the solution filtered, after making up to 100 c.c. On trial with the colorimeter it was found to be too dark, and the two extra glasses were put in, when the reading was 36. The calculation would then be COLORIMBTRY. 233 as follows : r^- = 18 = ^ = 5.55, which is the number ^, , ,. 15x85 expressing the color corresponding to ^^^, = 12.75 grammes cane-sugar in 100 c.c. of solution. Now, as 12.75 : 5.55 = 100 -.x, a? = 43.5 ; which is the color corre- sponding to one hundred parts of cane-sugar. Monier's* Method with Standard Colors For those not having a colorimeter this process may be found useful, though in every way less satisfactory than the pre- ceding. A series of ten standard colors are prepared by dissolving known weights of caramel in a fixed volume of water, say 25 c.c, in arithmetical progression, the first tube containing one part caramel, the second two parts, the third three parts, and so on. In order to make a compari- son of raw sugar by this method five grammes are weighed, dissolved in water, and the solution made up to the bulk of the standard solutions, after filtration. A comparison is now made between the raw sugar solution and the stan- dards, the one it most nearly approaches in color being that which contains the same amount of coloring matter as the raw sugar. For preparation of the caramel see page 331. ESTIMATION OF THE OEGANIC MATTER NOT SUGAR. In commercial analysis these bodies are determined by difference, the sum of the sugar, grape-sugar, water, and ash being subtracted from one hundred, and the remainder called the organic or undetermined matters. Included in the above term is a great variety of substances, nitroge- nous and non-nitrogenous, of which the chief are organic * Guide pour Vessai et I'cmcdyse des aucres. Paris. 234 ANALYSIS OF RAW SUGAR. acids combined with bases found in the ash, gum, coloring matter, albuminous bodies, and insoluble organic matters, as particles of cane or beet, and cellulose. Some of these bodies are inert in their action on cane-sugar in the process of the manufacture or refining of sugar, while others are very injurious, such as the gummy matters, in hindering or preventing crystallization, and the protein compounds, which tend to set up fermentation of various orders in sugar liquids. Though for most commercial purposes the estimation by difference is sufficient when all the other de- terminations are made correctly, yet in some cases it is desirable to estimate directly the organic substances, and to discriminate, if possible, between them in regard to their greater or less injurious action on sugar solutions. The method by difference is open to the objection that all the errors of the other determinations fall upon the undeter- mined matters and make it too high or too low, as the case may be. This fact greatly lowers the value of the figures representing the organic substances in many commercial analyses. WalkofPs Method. — This is based on the fact that tannin precipitates from raw sugar solutions most of the nitrogenous matters and some other bodies. Two grammes of pure dry tannin are dissolved in distilled water, and the volume made up to one litre; 1 c.c. of this solution contains .002 gramme tannin. About five grammes of the sugar to be tested are dissolved in 200 c.c. of water, the so- lution heated moderately, and the tannin added from a burette. A flocculent precipitate forms, which gradually settles. From time to time a small portion of the liquid is taken out, filtered after the manner described under Esti- mation of Grape-Sugar, page 197 in connection with Fehl- ESTIMATION OP ORGANIC MATTER. 235 ing's solution, and a drop of a solution of ferrous sulphate is added to the filtrate. As soon as a dark color is pro- duced in contact with the iron salt the tannin is in excess, and the end point of the reaction is attained. The weight of tannin employed, calculated from the number of cubic centimetres used, divided by six, represenst the amount of organic matters precipitated. The sugar solution should be perfectly neutral. The relation between the tannin and the organic matters precipitated by it, given above, was ob- tained for beet products, and it is probable that for those of the cane the proportion is different. When the process is used for the latter, the relation might be determined by precipitating an impure sugar solution with a known quan- tity of ^tannin insufficient to completely throw down the matters in solution, collecting on a weighed -filter, drying at 100°, and calculating the amount of tannin correspond- ing to the other substances. Walkoff's process, though somewhat empirical, is capa- ble of giving good comparative results.* Sxibacetate of Lead Method. — The basic acetate of lead, it is well known, precipitates a large portion of the organic substances present in raw sugars. Besides the nitrogenous bodies precipitable by tannin, gummy and coloring matters, and many organic acids, are carried down. Twenty grammes or more of the sugar are dissolved in a moderate quantity of warm water, and an excess of solu- tion of lead subacetate added ; after heating a few minutes the solution is filtered, the precipitate thoroughly washed, diffused in water together with any portions of * Pellet and Peltoii, as the result of an exhaustive examination of the ac- tion of tannic acid on beet-molasses, consider Walkoff's process unreliable, as asparagine is not precipitated. 236 ANALYSIS OF RAW SUGAR. the filter from which, it is difficult to detach the precipitate, and treated with gaseous sulphuretted hydrogen until the lead is all thrown down as sulphide, leaving the organic substances that were combined with the oxide of lead in solution. The precipitated plumbic sulphide is filtered from the solution, washed, and the combiued washings and filtrate evaporated to dryness in a tared dish on a water-bath, the heating being continued till the mass ceases to lose weight. This method, though somewhat tedious to execute, may furnish results of comparative value. Schrotter and Monier have proposed a volumetric method with permanganate of potassium, but it is of very doubtful advantage. For the separate estimation of the organic matters in raw sugar products see Laugier, Guide pour V analyse des matieres sucrees* ESTIMATION OF INSOLUBLE MATTER. These substances include particles of , cane or beet fibre, accidental organic or inorganic impurity, sand, clay, etc. 20 to 50 grammes of the sugar are taken, dissolved in boiling water to make a rather dilute solution, which is filtered through a tared filter, by the aid of a vacuum-pump if ne- cessary. After washing sufficiently, the filter is dried at 100° C. until it ceases to lose weight, and the final weight, after the subtraction of that of the filter, gives the amount of insoluble impurities. To find the proportion of the or- ganic and inorganic constituents, the filter is burned to an ash in a weighed crucible ; after the subtraction of the weight of crucible and filter ash, the remainder is the inor- * Zeit. f. Ruhenz., xxviii. 805; (Stowwer's Jahresb., xviii. 233; Bittmaii, Stammer's Jahresb., xix. 340. ESTIMATION OF YIELD. 237 ganic insolvhle impurities (sand, clay, etc.) The diffe- rence between the latter and the total constitutes the organic insoluble impurities. ESTIMATION OF THE YIELD. It is important to be able to estimate the amount of cane- sugar obtainable in refining from a given sample of raw su- gar. The buyer or seller who has no knowledge of chemis- try finds it very convenient to make use of a single figure summing up the results of the chemical analysis which, perhaps, he is able to but imperfectly interpret. It has long ago been observed that two raw sugars having the same polarization give quite different results in refining, as to yield in crystallizable sugar ; and this is rightly attri- buted to the varying nature and quantity of the impurities, which either tend to destroy the cane-sugar by inversion or to "prevent its crystallization. Method of Coefficients. — It is also a well-recognized fact that saline matters have a particularly injurious effect on the cane-sugar in refining, and that in the syrups from which no longer any sugar can be crystallized, there is a more or less fixed relation between the salts and the un- crystallizable cane-sugar. These considerations gave rise to the method of valuing raw sugars that is in extensive use in France, and, somewhat modified, is adopted in the French government laboratories for sugar analysis. This method assumes that for every part of ash in the raw sugar five parts of cane-sugar are prevented from crystallizing, and that for each part of glucose or grape-sugar one or two parts (according to commercial convention) are carried per- manently into the molasses. Thus, a sugar containing 238 ANALYSIS OF RAW SUGAR. Sugar 93.00 Glucose 2.00 Ash 1.00 by the method of the coefficients would give (1X5) + (2.00 X 1) = 7, or (1 X 6) + (2.00 X 2) = 9, which, subtracted from the amount of cane-sugar, shows a yield of 85 or 83. The above is the method in the form most used, though many have considered the coefficient 5 too high, and figures varying from 3.5 to 5 have been pro- posed, and to a certain extent adopted. In raw beet-sugars containing very small quantities of grape-sugar the glucose factor is neglected. A commission appointed by the French government, composed of MM. Aime Girard, De Luynes, and other chemists, have recommended this mode of valuing raw su- gars, which has been adopted, and is now the officially recognized method. The scheme submitted by the above chemists is as follows : From the percentage of cane-sugar given by the saccharimeter is subtracted the sum of — (1) Four times the weight of the ash (ash burned with addition of sulphuric acid, and one-fifth subtracted) ; (2) Twice the glucose when the titre is 1 per cent, or above ; the glucose multiplied by 1 when the titre is be- tween 1 per cent and f per cent. ; when the titre is below i per cent, the glucose is neglected ; (3) If per cent, for waste in refining. Thus the sugar .whose analysis was given above would show a yield of '(1 X 4) + (2.00 X 2) -f 1.50 = 9.50 ; 92.00 - 9.5 = 82.5. The method of coefficients described, and used in France THE SALINE COEFFICIENT. 239 for the commercial valuation of raw sugars, though doubt- less justified for certain beet and high-grade cane sugars, is open to serious objection. The results given by it necessa- rily vary a great deal, approaching near the truth for some, but falling far short for others, being generally too low. On this account the system has never obtained outside of France. The various saline impurities have individually very unequal injurious effect on cane-sugar, some being almost inert and others very hurtful ; besides which the organic impurities have also an injurious action. The soluble portion of the ash, the only one that can have any melassigenic action, in raw cane-sugars is frequently not more than one-half to three-fourths of the total, while with raw beet-sugars nearly the whole is soluble, and consists largely of the most melassigenic salts — namely, those of potassium. Further, the ash in all raw sugars varies with many circumstances — the methods of manufacture, the soil, manure, etc. — and to lay down a hard-and-fast rule to measure its injurious action is not only empirical, but, from, the nature of the case, must be very unreliable. The error of the method in giving results that are too low is much more apparent with raw cane, than with raw beet su- gars. Take, for example, a number of type analyses of Cuba sugars ; 340 ANALYSIS OP RAW SUGAR. Good cen- Fair 'cen- Good mus- Fair mus- Molasses- trifugal. trifugal. covado. covado. sugar. 96.50 .80 92.50 2.10 90.00 3.00 86.00 81.50 Glucose 4-50 6.50 .60 1.65 .55 3.20 1.25 2.00 4.00 Ash • 35 1-75 ■ 75 5-0O 1. 00 6.50 1.50 6.50 Water 100.00 100.00 100.00 100.00 100.00 ^^ ^-^ ,_^ ^~. (^ cji ^ t^ \0 ^^ 0.*. X X 8 + en ii li 1 + !?■ i + ^f? b p "8 It will be readily seen by those who are experienced in these matters that the above yields for the higher grades, more closely approximate the actual refining results, while for the lower grades the calculated yield falls much short of the actual. PATEN'S PROCESS, MODIFIED BY SCHEIBLER. {Haffinationwerths — ReTidements.) Raw sugar, washed with" alcohol of about eighty-flve per cent, saturated with cane-sugar, is deprived of its syrup. This consists in part of glucose, and partly of cane- sugar that has lost the ability to crystallize owing to the presence of various foreign bodies, together with most of PATEN'S METHOD. ' 241 the other impurities, as coloring matters, salts, etc. The residue from this operation is the cane-sugar a/itually crys- tallized in fhe raw product, plus the cane-sugar held dis- solved in the water present, and precipitable hy the wash- ing solutions. Payen's original method is executed in the following way : The wash-liquor is made by saturating one litre of 88 per cent, alcohol to which 50 c.c. of strong acetic acid is added, with finely-pulverized cane-sugar. The object of the acid is to decompose sucrates and render the saline matters more soluble. Ten grammes of the sugar to be ex- amined is first treated with absolute alcohol to deprive it of water, and then with 50 c.c. of the alcoholic sugar solu- tion, the assay being placed in a small tube the solu- tions poured upon it and allowed to filter through. A second and third washing is given if necessary, the last wash-liquor consisting of 96 per cent, alcohol saturated with sugar. The purified material is then brought on a tared filter, dried at 100°, and weighed. The method remained in this form for many years and was but little used. In 1871 Dr. Scheibler, of Berlin, in competition for a prize oifered by the Society of the Beet- Sugar Industry of the ZoUverein, revived the process of Payen, and so improved the manner of executing it as to make it a practically useful method. It cannot be properly claimed that Payen's method gives the absolute yield that raw sugars will show in refining, for that depends not only upon the manner of working, whereby greater or less perfection is attained, but also upon the fact that the organic or inorganic impurities may differ in amount or kind independently of the percentage of crystaUizable sugar present. For example, two raw 243 ANALYSIS OP RAW SUGAR. sugars giving a yield by this process of 90, the one con- taining one per cent, of total impurities of a slightly melas- sigenic nature, and the other three per cent, of a more in- jurious character : it is evident that the amount of sugar obtainable in refining will be very different from the two sugars. As a relative standard, however, the method, when properly executed, is capable of giving valuable in- formation in regard to the worth of raw sugars, as, cceteris paribus, the more crystallizable sugar present the greater the yield. The only legitimate interpretation of the results by Payen's method is to consider the latter as an analytical process for determining the total cane-sugar present, ex- clusive of that permanejitly in the form of syrup. The following is a description of the manner of making the estimation with the improvements of Scheibler and others.* There are four liquids used, viz. : No. 1, consisting of 85 per cent, alcohol to which 50 c.c. of acetic acid is added to the litre, and the mixture allowed to stand in contact with a large excess of powdered sugar for a day, being shaken at inter- vals. Tfo. 2. Alcohol of 92 per cent, saturated, as above, with sugar. No. 3. Alcohol of 96 per cent. , also saturated with sugar. No. 4. A mixture of two-thirds absolute alcohol and one- third ether. 'The solutions 1, 2, and 3, after saturation, are preserved * Stammer's JaftresS. .• Seheibler, xii. 179, 195, 311; xiii. 144, 148; xiv. 139; Kohlransoh, xii. 203; xiii. 152; Bodenbender, xii. 196, 207; Lotman, xiv. 145. American Chemist, iii. 330; iv. 85. PAYEN'S METHOD. 343 in the two-necked bottles shown in Fig. 34, provided with a syphon delivery -tube, c, for drawing off the solu- tion. The bottles are loosely filled with lumps of pure white sugar, as is also the sy- phon ; & is a chloride of cal- cium tube to prevent moist air from entering. The solu- tions may be saturated with sugar by allowing them to stand in contact with a large excess of the pulverized sub- stance, and agitating at inter- vals until the operation is complete. The bottle for holding No. 4 is similar to the above, the syphon being of much smaller calibre. The washing-liquids should be placed conveniently for use in a situation as little liable to changes of temperature as possible. The washing of the raw sugar takes place in the appara- tus figured at 35, one-fourth of the natural size. A is a flask graduated to 50 c.c, which is closed by a rubber stopper of two perforations, one carrying the tube n, through which the wash-liquids are added, and another, o, which reaches nearly to the bottom of the vessel, and is enlarged at its lower extremity, as shown in the cut. This enlargement serves to hold the filtering material, which consists of little cylinders of the felt iised by pianoforte manufacturers, and which fits tightly in the tubes. B is a, 344 ANALYSIS OF RAW SUGAR. flask whicli acts as a reservoir for the solutions after they have been in contact with the ravs^ sugar in A, and from which they are drawn off through a rubber tube connect- ing with the flasks, by a suction applied to B by a small tube as shown. An ordinary Bunsen water- air pump, or any other aiyangement capable of providing a moderate exhaust, is suitable for the purpose. Fig- 35' Execution of the Test. — The sample of raw sugar to be tested should be ground in a mortar, if necessary, to break up all small lumps. The half normal quantity of the Ventzke-Scheibler saccharimeter * is weighed (13.024 grammes) and transferred to A. In the case of very moist sugars that would stick to the weighing-dish, it would be better to weigh directly into A, previously tared. The first step of the washing is to run from No. 4 a volume of liquid equal to twice that of the sugar, and allow it to stand * Or any other quantity to suit the saceharimeter used. PAYEN'S METHOD. 345 for ten minutes, with frequent agitation to thoroughly dis- integrate the mass of sugar and to allow the alcoholic mix- ture to do its work well. The object of this operation is to remove the water and at the same time to precipitate any cane-sugar dissolved in it. If the acid solution {No. 1) were allowed to act directly on the moist sugar, it would be so diluted by the water present as to be capable of dissolv- ing cane-sugar, and hence make the result too low. If the sugar contains over four per cent, moisture, it is advisable to partially dry the samples after weighing. When the alcohol and ether have remained long enough, the tube r is connected with o, and by means of the air-pump the liquid is drawn into B ; then solutions 2 and 3 are added succes- sively to A, shaken up with the sugar, and similarly with- drawn. The object of the last two solutions is to take up the last traces of alcohol and ether. Solution No. 1 is now run into A in quantity equal to twice the bulk of the sugar, and allowed to stand, with frequent shaking, for ten or fif- teen minutes. After this has been drawn off, a second and third portion, if necessary, is used, until the solution ceases to take up anything more, and the sugar under treatment has reached its maximum purity and whiteness. The washing with No. 1 solution is the most important in the process, and the time of washing and volume of wash- liquor employed must be left to the judgment of the ope- rator, as they vary a great deal for different kinds of sugars. After the last portion of No. 1 has been carried off, successive quantities of Nos. 2, 3, and 4 are syphoned into A in the order named, and, after being shaken a few moments with the contents of the flask, removed. Finally the flask A is gently heated while the pump is still in ope- ration, to facilitate the removal of the last traces of alco- 346 ANALYSIS OP RAW SUGAR. hol and ether. When the washings are finished the flasks are disconnected, the filtering-tube o (Fig. 35) taken out, carefully washed from any adhering particles of sugar into the flask by a wash-bottle, sufficient water added to dis- solve the sugar together with a drop or two of lead solu- tion, and the^ contents of the flask finally made up to 50 c.c, filtered, and polarized. The direct reading of the sacchariraeter gives the percentage of crystallizable sugar. The method of Payen-Scheibler, though apparently complicated, is in reality quite simple and easy of execu- tion. Considerable care and some experience with it are, however, required to get good and unvarying results. The chief difllculty with the method — one which is especially prominent in a climate subject to such sudden changes as that of the United States — is that the solutions which at ordinary temperatures are saturated may become under or super-saturated, causing sometimes very serious errors un- less constant care is taken. Even when the solutions are kept in bottles coated on the inside vdth sugar and almost filled with it, it has been known, in consequence of a sud- den fall in the temperature of the laboratory, that the liquids, though not actually depositing in the storage bot- tles, were in a state of supersaturation, and as soon as a solid body was shaken with them, such as the raw sugar to be assayed, an immediate deposit of sugar was formed, sufficient to raise the test from 6 per cent, to 8 per cent, above the true amount. In case the solution is in this con- dition, or by a rise in temperature becomes capable of dis- solving more cane-sugar, the difficulty may be surmounted by agitating briskly a portion of the solution for five minutes with a large excess of powdered sugar before DUMAS'S METHOD. 347 using. It is important to observe, also, that the contents of the washing-flask A should remain at the same tempe- rature, which should be the same as that of the solutions, throughout the operation ; direct handling is therefore as much as possible to be avoided. In consequence of the time necessary for a reliable de- termination by this method, or the misleading results of the estimation made in inexperienced or incompetent hands, the Payen-Scheibler method has never been generally used as a guide to the buyer of raw sugars, though it de- serves to be.* METHOD OP DUMAS. M. Dumas found that alcohol of 85 per cent, by volume, containing fifty grammes of strong acetic acid to the litre, when saturated with cane-sugar, marked 74° on the alco- holometer of Gay-Lussac. For testing a sample of sugar, 100 c.c. of the normal liquor, prepared as above, is agitated with 50 grammes of the sugar to be tested, the solution filtered, and the areometer fioated in it. If it marks 74°, the sugar contains 100 per cent, pure sugar ; if it descends to 69°, the percentage is 95. Each degree lost by the areo- meter corresponds to one per cent, less in the titre of the sugar. For sugars of 88 per cent, and upward this process may be made to give good results, but for lower products the * Lotman {Stammer's Jah/reab., xiii. 156) has made an extensive series of analyses of raw beet and cane sugars, in which he compares the yield according to Scheibler's method with that by the method of coefficients. The results show that, with a few exceptions, Scheibler's yield is from .20 per cent, to 10.15 per cent, higher than by the latter method, the difference increasing as the sugars become lower in grade by a pretty even ratio. ^48 ANALYSIS OF RAW SUGAR. results are unreliable. P. Casamajor* has proposed a modification of Dumas' s method, which he highly recom- mends as giving good results on aU classes of raw sugars except melados, or those containing a similar amount of water. He prepares the saturated alcoholic solution by- agitating methylic alcohol of 83^° Tralles with powdered sugar. The solution, when fully saturated, marks 77.1° at 15° C. on the alcoholometer. The process for testing raw sugars is carried out as follows : 19.8 grammes of the sugar are weighed, well pulverized, and mixed in a mortar, as quickly as possible to avoid evaporation, with 50c.c. of the standard solution ; the mixture is poured upon a filter, and the density of the filtrate is taken with the areometer. To the degree of the alcoholometer, corrected for temperature, is added the difference between 100 and the alcoholometric degree of the standard solution. The sum represents the percentage of cane-sugar sought. The readings of the Tralles instrument must be reduced to 15° C. ; and to do this, for solutions between 60° and 70°, the number of degrees of temperature above 15° C. are multiplied by .37, and the product subtracted from the ori- ginal reading of the areometer ; for solutions above 70° the factor is .36, and for those below 60° the factor become^ .38. It is also advisable to make a correction on account of the volume of the normal solution used : At 15° C. 19.8 grammes of sugar taken for a vol. of 50 c.c. 20° " " " " " " 50.25 25° " " " " " " 50.5 30° " " " " " " 60.8 35° " " " " " " 51.2 * Jour, of Amer. Chem. Soc. , 1879, vol. i. No. 6. For further details the reader is referred to the author' s paper,* which states that the results obtained by this pro- cess, even on very low grade sugars, agree closely with du- plicate assays made with the optical saccharimeter. * Chem. News, xl. 74 et seq. CHAPTER X. ANALYSIS OP MOLASSES AND STETJPS. Under this head may be included all sugar solutions above a density of 15° or 20° Baum6, such as the brown and filtered liquors of the refinery, and the heavy syrups and molasses of the cane and beet sugar manufacture. Estimation of tlie Cane-Sugar. — This estimation is made writh the saccharimeter, as described under raw SUGAR. The solutions should be v?eighed as quickly as possible to avoid evaporation. Molasses and impure syrups in general require a rather large quantity of lead solution and bone-black for decolorization. In some cases the ordinary method of procedure fails to give a solution light enough to admit of a saccharimetric reading, and it becomes necessary to either use the half-normal solution or the half-tube (100 mm.); the reading in either case must be multiplied by 2. When these means fail, it is best to proceed as follows : Weigh three times the normal quanti- ty, dilute to 300 c.c. after adding lead solution, and filter. The solution, if still too dark, is submitted to a further fil- tration through a tube containing well-dried bone-black in grains, care being taken to reject the first third of the fil- trate, as some sugar is retained by the char.* In beet-sugar solutions there are generally impurities which affect the polarized ray sufficiently to cause the * If the prepared black described on page 168 is used, the filtration with a tube is rarely or never necessary. 350 ESTIMATION OP CANE-SUGAR. 261 estimation of sugar -wdth. the saccharimeter to be more or less incorrect. These impurities are : Malic acid. Polarizing to the left. Aspartic acid " " {in alkaline solution). Invert-sugar. ii Metapectic acid. a Beet-gum. a Dextran. the r Asparagine. a Aspartic acid a (m acid solution). Glutaminic acid. a a The dextran and the beet-gum have a very high rotatory power. Eissfeldt and FoUenius * have published a process (for beet-juice) whereby these interfering impurities are either destroyed or precipitated, by warming the solution to be tested successively with alkaline solution of copper oxide containing a large excess of alkali, solutions of basic ace- tate of lead, and ferrocyanide of potassium, filteiing, and polarizing. The results are said to be good. Sickelfalso weighs 13.024 grammes beet-juice, adds 1 c.c. of lead solution, and makes the liquid up to 50 c.c. with absolute alcohol, filters, and polarizes. The aspara- gine, aspartic acid, malic acid, gum, and dextran remain in the precipitate, while the presence of the alcohol neutral- izes the rotatory effect of invert- sugar. Tannic acid added to the warmed sugar solution precipi- *ZeU. f. Rubem., 1877, 728. \lhid., 1877, 779. 252 ANALYSIS OF MOLASSES AND SYRUPS. tates many of the bodies which are optically active. When this agent is used, basic lead acetate, in quantity more than sufficient to precipitate all of the tannic acid, must be add- ed after the latter. The tannic acid solution is prepared by dissolving 50 grammes of tannin in 200 c.c. of 90 per cent, alcohol, and diluting to one litre. On account of the large precipitate formed when tannin is used in connection with lead in very low products, the results are apt to be too high from the influence of the precipitate (page 166).* Clerget's method is hardly to be recommended to meet the difficulties in the case of optically-interfering impurities. Where the sugar is to be estimated with accuracy it will be advisable to have recourse to the method of inversion and estimation by Fehling's solution (estimation of cane-sugar, page 182). When the saccharine material is alkaline from the presence of caustic lime or alkalies, the solution should be barely acidified by acetic acid before the addition of the lead acetate, in order to neutralize the effect which alkalies have upon the polarized ray. Estimation of Invert-Sugar. — As with raw sugar, page 217. The solution for titration must be dilute. Estimation of Asli. — As vdth raw sugar, page 222. The solution, after the addition of sulphuric acid, ought to be heated cautiously, for fear of loss by spurting. Estimation of the Water. — For purposes not requir- ing much accuracy this determination may be made with the Balling saccharometer, the reading indicating percent- ages of dry matter, which subtracted from 100 leaves the * Champion and Pellet (Sucrerie Indigene, xii. 276) add 10 c.o. strong acetic acid to 100 c.c. of juice, or a proportional quantity to molasses, after the filtra- tion from the lead precipitate in the ordinary process of decolorizing. This is said to completely neutralize the optical efEect of asparagine. ESTIMATION OF WATER. 353 water. For an accurate determination of water in sugar solutions, about twelve grammes of coarse, well-dried sand are weighed in a suitable dish or a watch-glass, together with a small rod and a glass bixlb. This gives the first weight. Then allow from one to two grammes of the solu- tion to drop into the bulb from a pipette, and reweigh. Finally break the bulb with a gentle pressure, taking care not to allow any fragment to faU from the dish, and care- fully mix the syrup with the sand by means of :the rod untU a uniform mass is obtained. Dry at 100° C. for four or six hours. The bulbs can be easily blown over a com- mon Bunsen lamp, and should have a small projecting neck and be thin enough to break easily. The diameter is about 12 mm. Example : Weight of dish, sand, rod, bulb, and syrup. ..22.121 grms. '< " " " " 20.104 " Syrup taken - 2.017 " The enserrible after drying 4 hours 21.120 " " " 6 " 21.119 " 22.121 — 21.119 = gQ^^ — = 49.67 per cent, water. Estimation of Organic Matter not Sugar. — ^By difference, or one of the methods given under raw sugar. Quotient of Purity or Exponent— T'/ie Direct Method. — The most direct, and in general the most conve- nient and reliable, way of obtaining this expression is to divide the percentage of impure sugar, or total solid mat- ter, into the percentage of pure sugar multiplied by 100. The former is represented by the degree Balling of the so- 354 ANALYSIS OF MOLASSES AND SYRUPS. lution reduced to standard temperature, while the latter is the polarization. The quotient expresses the percentage of pure sugar contained in the dry sv^stance — i.e., the total soluble matter if it were deprived of water. Gasamajor' s Method. — This has the advantage of requir- ing no weighing ; but where a balance is at hand the direct method is preferable both on account of absolute accuracy as well as the agreement of the results among themselves. According to the original method,* the solution to be tested is diluted so as to stand between 5° to 15° Brix ; the degree Brix is taken, corrected for temperature, and the solution, after proper decolorization, is polarized as it stands, with- out weighing or dilution. The polarization is multiplied by a factor corresponding to the percentage of dry matter by Brix, the product being the quotient sought. The cal- culation may be made by the formulas — Q = sx^^ (1) Q = SX^^ (3) in which D is the degree Brix, P the corresponding speciiic gravity, S the polarization, (1) is intended for use with instruments requiring the nor- mal weight 16.19 grammes, and (2) with the SoleU-Ventzke. I have found that the results given by this process ap- proach nearer those of the direct method, and agree better among themselves, by having the solution less dUute than that given above ; in this case the factor is decreased. The * Amer. Chemist, vol. iv. 161. QUOTIENT OP PURITY. 255 following table, calculated by Mr. Gr. S. Eyster, of Boston, for use with this modification of the method, gives the fac- tors by which the reading of the saccharimeter is to be in- creased, for the Soleil-Ventzke instrument. Example : Reading of saccharimeter 50.1 Corrected degree Brix 25.7 Then from table- Factor for 25.7° = .914 50.1 X .914 = 45.79 quotient. The solutions should be taken as strong as it is conve- nient, up to 27° Brix. 256 ANALYSIS OP MOLASSES AND SYRUPS. z l-l o O < H Z o N s o a & Cd U trt f^ r1 "1 S Q S < c t/1 2 ^ a z s o u a q 8 8 8 ■§ o q J>i 1 1 in m m 1 S" o q o 0^ ON CO in M l-l m CO On c^ M On M o -^ l-t o o> 9 O ° 8 ON ON t 1 CO CO OO 00 in M N CO o CO CO in CO in m w o CJ m M 1 o in ON On O m ON o R CO CO OO t>. CO m m M 3; in HI CO M N ON « 8 C) C4 M m M 1-4 R O o m in ON o 0^ O m CO 1 vO 1 CO CO CO ON CO M 8 CO CO 1 t-t O o ON in ON M ON O ON 00 i- -? »n in M CO CO CO CO CO H O CO O m M o R i-i o M l-H I-I 8 CO ON CO CO OO '^ M ON in CO CO m CO t-t in C4 R M M R i-« o c 00 vO N On CO CO M m OO m CO CI CO M in f o CO CO M o HI O CO o l-l o o M o w 8 CO On 8 o» CO O m m CO M CO in s- m i-i O CO CO M in N CO O 00 o CO q o ° M ON O CO ON OO O CO m OO " CO m m M o CO CO QO CO CO w m CO M M O OO q o CO 6 o 00 CO ON o CO ON CO g 5 CO m N in H o t H CO R M o 74 1 I-I CO q M o in OO 1 NO in o r*. CO ON M s M 7» CO ? C4 CALCULATION TO DKY SUBSTANCE. 357 The estimation of the quotient of purity is of great value in the various stages of the manufacturing and refining of sugar, showing as it does, in a single figure, the proportion of pure sugar to impurities. It is pre-eminently the test for the refiner, who in general does not wish to know Jiow much sugar he has in a given solution, but how pure it is ; its value for his purposes is altogether independent of the amount of water contained. To the buyer or seller, on the contrary, a knowledge of the percentage of pure sugar in the sample as it stands, otherwise known as the "direct test" or the "polarization," is of the greatest importance, and the percentage of water has a direct bearing upon it. Calculation of the Results of an Analysis into Equiva- lents in the Dry Substance. — It. is often desirable for pur- poses of comparison to have the results of an analysis reduced to terms of the dry substance. The reciprocal of the degree Brix multiplied by 100, is a factor by which the percentage of sugar, grape-sugar, and ash is increased to reduce them to the basis of dry mass ; thus in a syrup hav- ing the following composition : 55° Brix. Cane-sugar 45.00 Grape-sugar 3.10 Ash 82 the factor corresponding to 55 is 1.818 ; then in the dry substance we have : Sugar 45.00 X 1.818 = 81.81 Grape-sugar... 3.10 x 1.818 = 5.63 Organic matter by difference .. . 11.07 Ash 82X1.818= 1.49 100.00 258 ANALYSIS OF MOLASSES AND SYKUPS. These figures represent the quotients of purity respec- tively of the sugar, grape-sugar, organic matter, and ash. If the dry substance is estimated by drying, instead of the spindle, the results are, of course, more accurate. The table on page 193 may be used to obtain the factors neces- sary in the above calculation. Estimation of the Color. — The determination of the color in relation to the sugar is made according to direc- tions given under Raw Sugar, page 229. For sugar solu- tions, however, it is generally only necessary to estimate the color reduced to the normal standard of the colori- meter. Estimation of the Alkalinity. — Products of the beet- sugar manufacture often contain caustic lime or alkalies. When these bodies are present in sufficient amount, it be- comes necessary to determine them. For this purpose a standard alkaline solution is made by dissolving exactly 53 grammes of pure sodium carbonate, that has been heated -some time to drive off moisture, in water, and diluting to one litre. A standard acid is also prepared by mixing 140 grammes of nitric acid, sp. gr. 1.385, or an equivalent amount of any other strength, with water, and diluting to about 1,100 c.c. The relation between the acid and alkali is now found by titration, using litmus or cochineal solution .as an indicator. Suppose 20 c.c. of acid saturates 22 c.c. of alkali ; then to make the acid solution normal — that is, to contain in one litre the number of grammes of the body dissolved corresponding to its combining weight (such so- lutions will consequently saturate each other volume for volume) — every 20 c.c. of acid must be diluted with two c.c. of water to bring it to the strength of the alkali, or for one litre 2 X 50 = 100 c.c. To one litre of the acid solu- ESTIMATION OF COLOR. 259 tion is added, accordingly, 100 c.c. of water, and the mix- ture well shaken. Molasses and heavy syrups are often too much colored to allow of the use of litmus or cochineal solutions, so that the point of saturation has to be determined with delicate litmus-paper. Seventy-five grammes of molasses are weighed and di- luted with water to 250 c.c; two portions of 100 c.c. each, equivalent to 30 grammes of the molasses, are taken out for trial with the acid solution, the first to obtain an ap- proximation of the alkalinity, and the second for a sepa- rate and more accurate determination. The alkalinity is generally calculated in terms of calcic oxide CaO. 1 c.c. of the test acid = .028 gramme CaO. CHAPTER XI. Analysis of the Cane and Cane-Juice. THE CANE. Estimation of Cane-Sugar. —It is difficult to obtain a sample faithfully representing the whole cane, as the amount of sugar differs in various parts. This variation is particularly marked at the joints. It is best to take three portions between the joints— from the base, top, and middle Fig. 36. of the cane, together with one of the joints ; slice the pieces and press out the juice in a small metallic roller- press (Fig. 36), moistening the pressed cane with hot water two or three times, and renewing the pressure to wash out the sugar contained as closely as possible. The juice from the press is diluted to the smallest number of cubic centimetres that it vsdll be convenient to calculate upon. For example : Eight times the normal quantity for the Ventzke-Scheibler instrument, equal to 208.4 grammes of the cane, is weighed, pressed, and washed until about 380 c.c. of juice is obtained. This, for convenience, is diluted 260 CANE-JUICB. 361 to 400 c.c. after the addition of lead solution, filtered, and polarized. If the polarization is 32, then, as eight times 32 the normal was weighed, -_ = 4, which is multiplied by 8 4, on account of the dilution to 400 c.c. instead of 100 c.c, the standard volume gives 16. This is the percentage of cane-sugar in the sample treated. The sugar may also be estimated by extraction with alco- hol (page 180) on the dried assay. The grape-sugar may be determined in a measured por- tion of the juice pressed from the cane, before the addition of lead solution or after its removal by sulphurous acid. See estimation of invert-sugar. The ash and water are estimated in the manner already described in other places. It has only to be remarked that the slices should be made quite thin to ensure good drying, which is commenced at a temperature of 80°, and gradually raised to 110°. CANE-JUICE. The total impure sugar is estimated by the Brix sac- charometer. Vivien's areometer (page 115) may also be found useful for this purpose. For hot countries, where cane-juice has in all cases to be tested, it is well to have hydrometers standardized at 25° C, instead of 15° or 17^°, as is the usual practice. The Cane-Sugar is estimated by the saccharimeter, two or three times the normal quantity being weighed. The sugar can be more quickly determined, however, in cane-juice or any other weak saccharine solution by Ventzke's process, which dispenses with the weighing. This method is carried out by taking the density of the 263 ANALYSIS OP THE CANE AND CANE-JUICE. juice with tlie Brix spindle, finding the corresponding spe- cific gravity from the table on page 116, and calculating the percentage of sugar according to the following formulas : = S (1) = S (2) = S (3) Px .2605 D PX .1619 D Px .1500 D in which P is the polarization of the juice as it stands without weighing ; D = the density, and S the percentage of sugar. Formula (1) is for use with the Ventzke-Scheib- ler saccharimeter, (2) with the Soleil-Duboscq, and (3) for those instruments of which fifteen grammes is the normal weight. If the juice needs an addition of lead, it is filled into a 100 c.c. flask, and a measured volume of the lead so- lution added from a graduated pipette, the saccharimetric reading being increased in proportion to the dilution. Ex- ample : Cane-juice of 10° Brix (sp. gr. 1.04), to which 3 c.c. of lead solution to 100 c.c. were added, was found to po- larize 32 ; 32 -J- 3 per cent. = 32.96. According to the for- mula (1) 32.96 X . 2605 „ „^ Yq^ = 8.25 per cent, cane-sugar. A table is herewith given, reckoned according to formula (1) for the Soleil-Scheibler saccharimeter, which dispenses with the calculation. An example wiU show the manner of using it : A solution whose corrected per cent, of sugar by the Brix areometer is 9.5 polarizes 27 ; in the horizontal VBNTZKE'S METHOD. 263 column opposite 9.5, under 2, is found .502, wMch multi- plied by 10 gives 6.020 Under 7 in like manner occurs 1.757 Percentage of cane-sugar = 6.777 Table for Estimating the Percentage of Sugar by Weight, in weak Sugar Solutions : Abridged from one calculated by Oswald. Reading of the Saccharimeter. Degree Bnx. Sp. Gr. I 2 3 4 5 6 7 8 9 10 1. 000 .260 521 .7S1 1.042 1.302 I ~~ 823 2.084 2.344 2.605 "^5 1. 0019 .260 520 .780 1.040 1.300 1 560 I S20 2.080 2.340 2.600 t.o 1.003Q I .CO 58 .259 IS .778 1.038 1.297 I 557 I 816 2.076 2.335 2-595 1-5 :l% .777 1.036 1.295 I 554 I f'3 2.072 2.331 2.500 2.0 1.0078 r.? • 775 1.034 1.292 I 55; ^ ^ 2.068 2.326 2.585 2-5 1.0097 .258 ■774 1.032 \-M I 548 I 2.064 2.322 2.580 3-0 1.0117 •257 515 .772 1. 020 1.028 545 I 802 2.060 2.317 2.575 3-5 I. 0137 .257 514 1.28s I 542 1 799 2.056 l:^ 2.570 4.0 I.OI57 .256 513 '76§ 1.026 1.282 I 795 2.052 2.56s 4.5 1. 0177 .256 512 1.024 1.280 I % 2.048 2.304 2.559 5.0 I. 0197 , -255 5" ;766 1^022 1.277 I 533 1 2.044 2.299 2^554 11 I. 0213 ■255 510 .765 1^020 1.275 I 530 I '§5 2.040 2.295 2^549 1.0237 •254 P 1. 018 1.272 I 527 I '*S 2.036 2.200 2.285 2^544 6-5 1.0257 I .0278 ■25» 1762 1,016 1.270 I 1.267 I 524 1 778 2.032 2.539 7.0 .253 507 .760 1. 014 521 I 77+ 2.027 2.281 2.534 u 1.0298 .253 ij6 .758 1. 012 1.265 I 518 1 1 2.023 2.276 2.529 I. 0319 .252 505 .757 1. 010 1.262 I 515 I 2.019 2.272 2-524 8.5 .252 504 .756 1.008 1.260 1 512 I 2.015 2.267 2.519 9.0 .251 503 ■754 1.006 1.257 I ^ ; 760 2. on l'.^ 2.514 9-5 i!o38o .251 502 .753 1.004 1.255 I 757 2.007 2.509 10. I. 0410 .250 501 .751 I.C02 1.253 I 503 I 753 2.003 2.254 2.504 10.5 1.0422 .250 500 .750 1.000 1.250 I 500 1 750 1.999 2-249 2.499 11. 1,0443 1.0464 .249 1^ .748 •998 1.247 I 497 I 746 1-995 2-245 2.404 2.4K II. 5 ■^ .747 •giS 1.245 I 494 1 743 \% 2.240 12.0 1.0485 , 1.0506 '^ ■745 •994 1.242 1 % I 739 2.236 2.484 12.5 .248 .744 .992 1.240 I 735 1.983 2.231 2-479 13.0 1.0528 .247 495 .742 ■i 1.237 I 484 1 732 1.979 2.227 2.474 13-5 1.0549 .247 494 ■ 741 1.235 I 482 I 728 1-975 2.222 2.469 14.0 1. 01570 .246 493 ■?i .986 1.232 I f.i I 725 1.971 2.218 2.464 14.5 I. 0591 1.0613 .246 492 .984 1.230 I 722 1.967 2.213 2.459 15.0 .245 491 ■736 .982 1.227 1 473 I 718 1.963 2.209 2.454 16.0 i:il .245 i ■735 .980 1.225 I i?7 ; 714 1-959 2.204 2.449 .244 •733 .978 1.222 1 ''5 1.955 2.200 2.444 16.5 .244 •732 .976 1.220 1 464 I 708 1. 951 2.195 2-439 17.0 1.0700 .243 f8? •730 .974 1.217 1 461 I 704 1.948 2.191 2.186 •2.434 Hi 1.0722 .243 .729 •972 1.215 1 458 I 701 1.944 2.429 1.0744 1.0765 .242 485 :??i .970 1.212 1 455 I 697 1.949 2.182 2.424 18.5 .242 484 ■968 1.210 I 452 I 694 1.936 2.178 2.420 19.0 19. 5 1.0787 I. OHIO .241 .241 483 482 ■724 ■723 .966 .964 1.207 I 1.205 I Si I 1 1.932 1.928 2.169 2.415 2.410 20.0 1.0833 .240 481 •721 .962 1.202 I 443 I i3 1.924 2.164 2.405 20.5 1.0855 .240 480 .720 .960 1.200 1 440 I 680 1.920 2.160 2.400 21.0 1.0878 •239 ^t .718 .958 I. 197 I 437 I 676 1. 916 2.155 2.395 21-5 1.0900 •717 .956 1.195 I 434 I i 1. 912 2.151 2:385 22.0 !■! til •715 •954 1.192 I 431 I 1.908 2.146 22.5 :2i8 .714 .952 I. TOO I 1.187 1 428 1 1.904 2.142 2.380 23.0 .237 475 • 712 ■950 425 I 662 1.900 3 -137 ^•375 Grape-Sugar. — (See chapter x.) Ash. — (See chapter x.) 264 ANALYSIS OP THE CANE AND CANB-JUICE. Estimation of Water.— Sj the Brix spindle or by dry- ing, according to tlie accuracy required (page 252). The quotient of purity is a very useful determination, and may be made by the direct method: Pol. X 100 „ Brix = ^^P- CHAPTER XII. Analysis of the Beet and Beet-Juice. THE BEET. Preparation of the Sample. — The top and small radi- cles are cut off, and the beet is washed to free from mecha- nical impurities, being dried with a coarse towel. If de- sired, the weight before and after this treatment may be taken. If a single beet is to be operated upon, the whole, after the above preparation, is reduced to a fine pulp by grating or any other means. For a sample representing a quantity of beets or the growth of a field, it is necessary to take a number of roots differing in size and variety. Beets taken from the same field, and apparently submitted to the same conditions, are found to vary a great deal in their saccharine richness. By successive slices, made parallel to the axis of the beet, cut out a square prism, of such thickness as will be determined by the size of the roots. Fig. 37 will illustrate this. The dotted line represents in projection the prism. The different por- tions thus obtained from all the roots consti- tuting the average are reduced to pulp and mixed together. Champonnois has invented a boring rape which serves very well to cut out a portion of the beet as above described, and which pulps it at the same time (Fig. 38). 365 366 ANALYSIS OF THE BEET AND BEET-JUICE. Estimation of Cane-Sugar — About 200 grammes of the pulp are placed in a small filtering-bag and pressed in a hand-press slowly until the juice ceases to iiow with the strongest pressure obtainable ; the marc is then moistened with boiling water, the pressure renewed, and this opera- tion repeated until all soluble matter has been extracted and the residue is dry, care being taken to avoid undue di- lution of the solution. Three to four cubic centimetres of tannin solution are added, and about three times that volume Fig. 38. of lead solution, and the whole made up to an exact volume, filtered, and a portion polarized. Any of the modifications suggested in the case of molasses (page 251) may be tried. The calculation is in all respects similar to that for estimating the sugar in the cane. Scheibler's Method for estimating Sugar in the Beet.* — The estimation, as given above, will show only ap- proximately the amount of sugar, on account of impurities present in the juice obtained, which have a considerable effect upon the polarized ray — as well as the generally im- perfect extraction of the sugar. Scheibler's process, * German Patent, No. 3573, Stammer's Jahrb., 1879. SCHEIBLER'S METHOD. 26? Fig. 38I though requiring spe- cial apparatus, avoids these errors, and gives results very near the truth. It is essentially an extraction of the sugar from the finely- divided beet without previous drying, by means of alcohol, in the heat. The apparatus is shown in Fig. 38^. J) is an upright glass con- denser fitted tightly to A by a rubber cork. A and B are glass tubes of the form shown, A be- ing placed within B, and making a close joint at the upper ends, the lower portion of A being free and open. Near the top of the latter are two or moi'e openings, five to six mm. in diameter, o 0, communicating be- , tween the annular space and the interior of A. B is fastened with a rubber cork to the flask c, which is graduated to 50 c.c. The narrowed end of B ex- 268 ANALYSIS OP THE BEET AND BEET-JUICE. tends some distance into c, in order that none of tlie boil- ing sugar solution may be spurted into the former. In the cylinder A is placed a small filter, a, which may be of cot- ton, felt, or other suitable material. For the execution of the test from 20 to 25 grammes beet-pulp are placed in A, which has been previously tared, by means of a long-stemmed funnel, so that the mass fills the tube nearly to o o. A is then reweighed, and the dif- ference of the two weighings gives the amount of assay taken. The cylinders A and B are now adjusted as shown in the cut, and the condenser fixed in position. Now 25 c.c. alcohol of 90 to 94 per cent. Tralles (.8339 to .820 sp. gr.) are placed in the flask, and by means of a sand or water bath heated to boiling. It is perhaps better that the alco- hol should be added through the top of the condenser at d^ through which it passes to the beet -pulp and falls in c. The vapor from the boiling alcohol, ascending into the space between A and B, passes through o o, and is liquefied in the condenser (kept cool by a stream of water), from which it drops in A, and, coming in contact with the assay, extracts the sugar, the solution dropping into the flask, where it parts with its alcohol, which is again made to pass through the substance to be extracted. The flame should be so regulated that the drops from A should succeed each other at regular intervals, and not too quickly. As a rule, from a half to three-quarters of an hour' s boiling is suffi- cient to complete the operation, after which the apparatus is allowed to cool, the last drops of the solution from A being received in the flask, which is filled to the mark with distilled water, after the addition of a few drops of lead, filtered, and the sugar estimated with the saccharimeter. The alcoholic sugar solution, after dilution to 50 c.c, ESTIMATION OP MARC. 269 should show about 41 per cent. Tralles. For many varie- ties of beets the strengths given for the alcohol cannot be strictly adhered to, as when the latter is too dilute a trou- blesome frothing takes place on boiling. According to Scheibler and ToUens {loc. cit), the con- tinued boiling of the alcoholic solution causes no sensible alteration of the sugar dissolved, even when the beets ope- rated upon are slightly acid. The method has been ex- haustively and critically examined by Tollens * and others, with the result of establishing its substantial accuracy as showing the absolute amount of sugar in the beet, and its great superiority over processes previously in use. Estimation of the Marc and the Amount of Juice. —Twenty grammes of the pulp are made into a thin paste with boiling water, poured upon a weighed filter, and tho- roughly washed, with the aid of a vacuum if necessary. The filter is then dried at 110°. Example : Watch-glasses + filter -f marc at 110° = 22.100 " -f " at 110° =21.260 Weight of marc 840 .840 X 100 , o , = 4.2 per cent. 20 ^ The percentage of marc subtracted from 100 gives the per- centage of juice, as 100 — 4.2 = 95.80 per cent, juice. The amount of juice may be obtained by an indirect method which gives results agreeing very well with the above. The water is determined in the pulp by drying, * Zeit. f. Ruhenz., May, 1880; Stammer's ie^J-iwcA., Brganzungsband, 102. 270 ANALYSIS OF THE BEET AND BEET-JUICE. and also in tlie juice ; then the percentage of juice is found by the formula -4- X 100, in which s is the percentage of IS water in the pulp, and S that in the juice. The marc is ob- tained by difference. Sclieibler's Method. — The percentage of marc, and from it that of the juice, may be obtained with greater accuracy than by the methods described, in connection with Scheibler's process for determining the sugar in the beet (page 266). The contents of the tube A, after the extrac- tion of the sugar, are desiccated by passing a stream of dry air through the latter, after which it is weighed and the amount of marc calculated. Scheibler claims that the re- suits obtained by the formula -^ x 100 are erroneous, as the direct polarization of the juice is never quite correct, owing to the presence of about five per cent, of sugar-free water in the beet {colloidal water). Grape-Sugar is generally present in very sma,ll quanti- ties. To estimate it a weighed portion of the pulp is ex- tracted with water, and the grape-sugar determined in the expressed liquor by Fehling's method, with the usual pre- cautions (see estimation of dextrose). Water is determined by drying the pulp or the thinly- sliced beet at 100°. The Estimation of Ash. — As in raw sugar (page 222). ANALYSIS OF BEET-JUICE. The Baume hydrometer is largely used to afford a rela- tive comparison as to the value of beet-juice. The Brix spindle is, however, preferable, in that the readings corre- ANALYSIS OP BEET-JUICE. 271 spond, within certain limits of error, to the percentage of impure sugar in solution. Estimation of Cane-Sugar. — By the saccharimeter, twice or thrice the normal quantity being taken and di- luted up to 100 c.c, af|;er the addition of about 2 c.c. tan- nin and 6 c.c. of lead solutions. The cane-sugar may also be readily determined by Ventzke's metho^ (page 261). As with beet- molasses, though in a less degree, this estima- tion is rendered more or less incorrect by the presence of optically active impurities in the juice. For modifications of the usual method to be pursued to meet this source of error, see the chapter on the analysis of molasses (page 250). Estimation of Grrape-Sugar. — As in the case of the beet. Estimation of the Ash. — With sulphuric acid, as with the beet. The juice should be carefully evaporated to avoid loss, before the charring takes place. Estimation of Water. — By drying in sand with bulb (page 252) for accurate work, by preference in vacuo — or with the Balling spindle. Quotient of Purity. — Divide the degree Balling, cor- rected for temperature, into the percentage of cane-sugar by polarization X 100. Stammer gives as the valuation-co- efficient ( WerthzahJ) of beet- juice, an expression obtained by multiplying the quotient into the percentage of cane- sugar, and dividing by 100. This is only useful for compa- rative purposes. Estimation of Organic Matter not Sugar. — This is determined by difference or any of the methods given in chapter ix. Where the water is estimated by the areome- ter the results are always low, owing to the error of the 272 ANALYSIS OP THE BEET AND BEET-JUICE. instrument in impure solutions, and consequently tlie mat- ters determined by difference are too high. To correct this error, Stammer has proposed to subtract one-fifth of the organic matter thus found, and add it to the water. This correction would equally apply to all impure sugar solu- tions, whether from the beet or cane. Estimation of the Alkalinity. — On the juice with- out dilution (page 358). Estimation of the Color. — As with raw sugar and molasses. The wet analysis of beet-juice may be reduced to dry substance, as shown on page 257. Note. — The matter given in relation to the analysis of cane and beet Juice applies equally to any weak sugar solu- tion, such as the "sweet water" from char-washing, etc. CHAPTER XIII. Analysis of Waste Products. ANALYSIS OF SCUMS AND SOLID RESIDUES. These consist of the refinery scums ; the marc of the beet freed from all obtainable sugar ; the bagass, or residue from the cane-presses ; and the precipitates produced in the process of carbonatation and defecation in the beet- sugar manufacture. The only estimation commonly made upon these bodies is that of the sugar. Before these resi- dixes are thrown out in the course of the manufacture, it is of considerable importance to make sure that there is no undue proportion of sugar present. They should be test- ed systematically, and sufiiciently often to form a proper control of the work. Refinery Scum. — This is the matter caught in the bag-filters when the crude solution of raw sugar is filtered preparatory to being run upon the char. It consists of the insoluble matters contained in the raw sugar, as sand, foreign matters of all kinds, particles of cane-fibre, the substances precipitated by caustic lime in defecation, and the coagulated albumen and bodies carried down with it, when blood is used in the process of defecation. Estimation of Gane-Sugar. — From a large average sam- ple, a smaller one is prepared by taking- out portions and thoroughly mixing them together. Weigh 13.04 grammes for the Ventzke-Scheibler, or the normal quantity for other 373 274 ANALYSIS OP WASTE PRODUCTS. saccharimeters, add enough boiling water to make a uni- form paste, and gradually dilute with the hot water untU the weighing-capsule is nearly full and a uniform thin magma is obtained free from lumps ; pour this upon a filter in a funnel provided with a filtering cone, and filter by the aid of a vacuum into a flask or cylinder graduated to 100 c.c, imtil all the liquid has passed through ; add small portions of boiling water at a time, stirring up the insoluble matter on the filter as much as possible with the stream from the wash-bottle, and continue the washing un- til the filtrate measures nearly 100 c.c; if the solution is alkaline, barely acidify with acetic acid, add a few drops of lead solution, allow to cool, fill to the mark, shake, add a little powdered bone-black, filter, and polarize. The reading (by the Ventzke-Scheibler instrument), multiplied by two, gives the percentage of cane-sugar. This method is accurate enough for nearly all purposes ; but where •greater exactness is required the ^ scum may be extracted with a larger quantity of hot water, and the sugar deter- mined in an aliquot part of the filtrate after inversion, by Fehling's method. If the grape-sugar is to be determined, the solution is made to 100 c.c. before the addition of the lead, and an ali- quot part of it taken for the grape-sugar estimation. From the remainder a 50 c.c. flask is filled, a measured volume of lead solution added, the solution filtered and polarized. The reading must be corrected for the dilution caused by the addition of the lead. The water is determined by drying one gramme at 100° to 110° C. The asTi is determined by incineration without the addi- tioni of sulphuric acid. CARBONATATION RESIDUES. 275 Beet Marc. — The cane-sugar may be determined in tlie same manner as witli refinery scums, or better after Schei- bler's method with alcohol (page 266). If the residue is very poor in sugar, it would be advisable to estimate the latter by the inversion with hydrochloric acid, and Fehl- ing's method, after extraction with a large quantity of hot water. The other estimations may be made as in the case of refinery scums. Residues from the Carbonatation Process.— These form the precipitates produced by adding a large excess of caustic lime to the sugar solutions, and precipitating the solution of calcic sucrate with a stream of carbonic acid gas. They are frequently alkaline from imperfect carbona- tation, and the sugar contained is in the state of sucrate. The estimation of the cane-sugar may be made similarly to that of refinery scums, except that it is necessary to first diffuse the solid matter through water, and pass a stream of washed carbonic acid gas to break up the combi- nation of the sugar with the lime ; filter from the precipi- tated calcium carbonate, and determine the sugar in the filtrate by the saccharimeter, or with alkaline copper solu- tion after inversion. E. Perrott * gives a method that is equally applicable to the determination of cane-sugar in all sucrates. One hun- dred grammes of substance are taken, mixed well with 380 c.c. of water, at the same time breaking up all lumps, and 20 c. c. of carbonate of ammonia solution. The mixture is allowed to stand ten minutes after agitation, and filtered. Prom the filtrate 200 c.c, representing 50 grammes of assay, are taken, diluted to 400 c.c, and the cane-sugar determined by Fehling's method after inversion. * Sucrerie Indigene, ix. 11. 276 ANALYSIS OF WASTE PRODUCTS. Bagass. — Two hundred grammes are reduced to as fine a state of division as possible, mixed well with boiling wa- ter, placed in a small filtering-bag, and pressed with a hand-press. The washing is repeated with fresh portions of water, and the pressing renewed until all sugar is ex- tracted. As the solution is commonly too dilute to test to advantage with the polariscope, it is best to take an ali- quot part of that obtained, corresponding to a known weight of bagass, and to estimate the grape-sugar directly, and the cane-sugar after inversion, by Fehling's method. WASTE WATERS. Under this head are included the last washings of the bag and char filters, and those of the diffusion and macera- tion processes of the beet-sugar manufacture. It is espe- cially important to know when the washings no longer contain enough sugar to make it advantageous to save them. Ten c.c. of the waste waters are evaporated at a water-bath heat in tared dishes, and the net residue repre- sents the amount of solid matter contained, of which from twenty to seventy-five per cent, may be sugar. If it is wished to estimate the amount of sugar, a larger portion is evaporated -with the addition of a few drops of hydro- chloric acid, and the amount of invert-sugar determined by Fehling's method. Estimation of Cane-Sugar in Dilute Solutions. In testing very dilute solutions for sugar the follovsdng method of procedure may be adopted : Evaporate the solu- tion after careful neutralization, if necessary, to from one- fifth to one-twentieth of its bulk, on a water-bath at a low heat, and determine the grape-sugar directly, and the cane- ESTIMATION OP SUGAR IN DILUTE SOLUTIONS. 277 sugar after inversion by Fehling' s method. As a rule, for very dilute solutions, the mere presence of sugar of any kind is sought to be demonstrated, so that it is only neces- sary to evaporate with the addition of a little hydrochloric acid, and determine the invert-sugar found. CHAPTER XIV. ANALYSIS OF COMMERCIAL GLUCOSE OR STARCH-SUGAR. Grape-Suga/r — Corn-Sugar. Starkezucker, Kornzucker, Or. — Bucre de Fecnle, Fr. This product is prepared from corn-meal or starch, either by the action of mineral acids at a boiling tempera- ture, or by means of diastase. It occurs commercially in three forms — viz. , in the condition of a dry granular or fine powder ; as a solid in lumps containing varying amounts of water ; and as a thick yellowish or white syrup. The fol- lowing analyses will show the composition of different va- rieties : I. By Steiner.* I. • 11. III. IV. Water 1550 •30 45.40 28.00 930 1.50 traces. .08 6.00 2.50 26 50 40.30 1590 7.00 1.80 .03 distinctly blue. 13.30 .40 76.00 5 00 5.30 .20 •05 7.60 1. 10 42.60 39-80 8.90 Ash Maltose Dextrin '. Carbolivdrates . . .'. Acid (as S04Ha) Iodine reaction 100.08 100.03 100.25 100.00 * Stamvmen's Jahrb., 1879, 379 ; Dingier, cexxxiii. 263. 278 ANALYSES OP GLUCOSE. 379 The first is of Grerman origin, white and soft ; the rest are English, produced by the action of dilute, sulphuric acid on corn-meal at high pressure. II. Powdered. Granulated. Lumps. Syrup. Sugar by copper test.. Undetermined bodies Water 81.63 9.06 8.76 .55 74.27 IT. 89 13-34 • 50 71.26 12.57 15-71 .46 50 30 19 I Ash 100.00 100.00 100.00 100.00 In III., the next series of analyses, by Neubauer, the sugar is estimated by the fermentation method : I. 11. in. ■ IV. 57-20 18.38 24.42 63.02 13.32 23.66 61.43 22.45 l6.I2 59-25 23-59 17.16 Non-ferment bodies (dextrin, etc.) Water 100.00 100.00 100.00 100.00 The non-fermentable, or bodies classed as undetermined, consist of dextrin, unaltered starch, and, according to Haarstick,* of the arniylin of Bechamp. They have a high dextro-rotation. The solid varieties of commercial glucose show Mrotation in a marked degree, while with the syrups this property is generally absent. The latter differ from the former in that the conversion of the starch into sugar is not carried so * stammer's Jahrb., 1876, 176. 280 ANALYSIS OE COMMERCIAL GLUCOSE. far, and hence the amount of organic matter not sugar in them is proportionately large. ESTIMATION OF THE SUGAR BT FEHLIKG'S METHOD. On account of the presence of maltose with the dextrose, sometimes in large amounts as shown by Steiner' s results, this determination cannot show anything definite as repre- senting dextrose. The amount of copper oxide reduced by the two sugars differs very much, 100 parts of maltose reducing 141.5 parts CuO, while the same quantity of dex- trose throws down 220 parts CuO. The results of this test have accordingly only a relative value. As to the action of dextrin upon the heated copper liquor, Rumpf and Heinzerling,* as the result of their investigation, state that solutions of (1) caustic soda and cupric sulphate at the boiling-point do not act on dextrin entirely free from sugar, which corrects Gerhardt's observation, who asserted that dextrin caused a reduction of the oxide in the sulphate ; (2) solutions of alkaline tartrates, and Fehling's solu- tion each act upon dextrin, making the results of the dextrose estimation too high in direct proportion to the length of time the heating is continued. When the reduc- tion is quickly effected, and the heating continues only a few minutes, they have found that the error in the estima- tion of dextrose in the presence of dextrin in starch-sugars is too small to sensibly affect the results. The execution of the test is in all respects according to directions already given. See chapter viii. * Zeit. f. Anal. Chemie, ix. 358. ESTIMATION BY FERMENTATION. 281 ESTIMATION OF THE DEXTROSE BY EEBMENTATION. * A solution of the sugar to be examined is made contain- ing a known amount, and the percentage of dry matter de- termined. The solution is then submitted to fermentation with yeast, and, after the expulsion of the alcohol and car- bonic acid formed, the percentage of dry matter is agai"!! determined, and the difference between the amounts of dry substance estimated before and after fermentation gives the sugar originally present. The results are a little low as compared with those given by Fehling' s method, because in the vinous fermentation all of the sugar does not break up into alcohol and carbonic acid, but about five per cent, is converted into glycerin, succinic acid, and other bodies, which, being non-volatile at the temperature of boiling water, remain in the liquid after the evaporation. Example : One hundred grammes of starch-sugar are dissolved, diluted to one litre, and the specific gravity taken. Suppose it is 1.03 : we find from Balling's table (page 116) that this corresponds to a percentage of dry sub- stance of 7.463, and as 100 c.c. weigh 103 grammes, 100 grammes of the solution contain 9.708 grammes of the ori- ginal assay, and 9.708 : 7.463 :: 100 : a? = 76.87 per cent. The composition of the solution, then, is 76.87 percent, dry substance. 23.13 " water. 100.00 For the fermentation 500 c.c. of this solution are taken, * Neubauer, Wagner's Jahresb., 1875, 806. 282 ANALYSIS OF COMMERCIAL GLUCOSE. a sufficient quantity of fresh beer-yeast added, and the whole placed in a fermentation apparatus arranged so that dried carbonic acid can escape. Compare matter on page 181. The system is then weighed, and allowed to remain at the proper temperature for three or four days until the ac- tion is complete. This point may be ascertained by weigh- ing at intervals! When the apparatus ceases to lose weight the operation may be considered as finished. The liquid in the flask is filtered, boiled down to one-third of its volume to drive off alcohol, and, after cooling, made up to its original bulk. If the density after fermentation is 1.0082, which corresponds to 2.05 percent, dry matter, 100 c.c. weigh 100.82 grammes and contain 2.068 grammes dry substance ; or in 500 c.c, 10.340 grammes. As the 500 c.c. of solution contained 50 grammes of the original sugar, then — '- — w?^ = 20.67 per cent, unfermentable mat- ter ; 76.87 - 20.67 = 56.20 per cent, of fermentable sugar. ANTHOK'S METHOD. This is based on the fact that the impurities present in commercial starch-sugar have a greater density than that of the sugar contained. The process, though somewhat empirical, is said to give results accurate enough for most purposes. A saturated solution of the sugar to be examined is made by adding a large excess of it, in as fine a state of division as possible, to water, and allowing the mixture to stand, with frequent agitation, for twelve hours, or until fully saturated. The specific gravity of the clear solution thus produced is obtained either by the specific-gravity balance ESTIMATION OP WATER. 283 or by weighing (chapter v.) From this the percentage of impurities may be found in the accompanying table : TABLE. Density of sat. Per ct. of Density of sat. Per ct. of Density of sat. Per ct. of solution. impurities. solution. impurities. solution. impurities. 1.2060 1.2350 15 1.2587 30 1.2082 I 1.2368 16 1.2603 31 1. 2104 2 1.2386 17 I.2618 32 I. 2125 3 1.2404 18 1.2633 33 I.2147 4 1.2422 19 1.2649 34 1. 2169 5 1.2440 20 1.2665 35 1. 2189 6 1.2456 21 1.2680 36 1.2208 7 1.2473 22 1.2695 37 1.2228 8 1.2489 23 1.2710 38 1.2247 9 1.2506 24 1.2725 39 1.2267 10 1.2522 25 1.2740 40 1.2284 II 1.2535 26 1.2755 41 1.2300 12 1.2548 27 1.2770 42 1.2317 13 1.2561 28 1.2785 43 1.2333 14 12574 29 ESTIMATION OF THE WATEE. Two to three grammes are weighed and dried with sand (page 219). In the case of solid glucose, the portion to be tested is placed on" the weighing-dish, separated from the sand, and melted with a gentle heat. When liquefied it is mixed with the sand in the usual manner. The dextrin and other matters are estimated by differ- ence, after the ash is determined by incineration, with the addition of sulphuric acid.* * Estimation of the Dextrose optically. — This determinaCion cannot be made by the optical method, on account; of the presence of a large and varia- ble amount of dextrin, maltose, and other bodies, which are optically active, and whose specific rotatory powers are different from, and much greater than, that of dextrose. The specific rotatory power of dextrin varies from [a] ]"= 139° to 212° ; while that of maltose is [a] D = 139 3°. If it is desired, for purposes of comparison, to polarize starch-sugar, the solution before it is placed in the tube of the saccharimeter for observation, should be heated for five minutes to 100° to get rid of the birotation, and obtain at once the lowest reading. 284 ANALYSIS OF COMMERCIAL GLUCOSE. THE DETECTIOIir OF DEXTEIN AND STAECH-SUGAB WHEN MIXED WITH RAW AND BEFINED SUGARS. I. The Adulteration of Raw Sugar with Dextrin. — Commercial dextrin has been added to raw sugars in order to give them a higher polarization, and consequently a greater market value ; .40 of one per cent, of dextrin raises the saccharimetric titre about one per cent. Two qualitative tests are commonly resorted to for detecting dextrin under these conditions, though neither is entirely reliable : 1. Alcohol of 95 per cent, added to a concentrat- ed solution of sugar containing the adulterant gives a white, thread-like coagulum, while more dilute solutions show only a cloudiness in a greater or less degree. The salts present in raw sugar, and particularly sulphate of lime, give a similar precipitate. 2. A solution of iodine in iodide of potassium produces with dextrin, according to the method of manufacture, a wine or violet red, while some varieties do not give any coloration. * The presence of dextrin may be detected with certainty by Chandler and Rickett's method (page 287). For the determination of cane-sugar the process of inversion and estimation with copper liquor will have to be resorted to (chap, viii.) f II. Detection of Starchi Sugar or Syrup when mixed with Raw or Reined Sugars. — The presence of these sub- ■ * Boivin and Loiseau(W«p'»ier's Jahresh., 1870,399) give the following as the marks of sugars containing dextrin : 1. On burning they give ofi the odor of heated bread. 3. They are very difficult to filter, and the filtrates are apt to be cloudy. This is particularly the case when lead solution has been used in clarifying. 3. Owing to imperfect mixture, separate lumps of dextrin may be separated and appropriately tested. f Lactose or milk-sugar in raw sugar may be detected by treating the latter with twelve times its weight of 80 per cent, alcohol, which dissolves the sugar and leaves the lactose. DETECTION OF GLUCOSE IN CANE-SUGARS. 385 stances may in general be shown by paying attention to the following points : 1. Sugars mixed with powdered or granu- lated corn glucose, on solution in water invariably leave white particles of the glucose undissolved ; 2. Owing to the birotation exhibited by solid starch and corn glucose, it will be observed, on submitting a commercial sugar con- taining it to the polariscopic test, that the reading does not remain constant, but gradually becomes less until a point is reached when the diminution of the reading ceases. If the solution is observed immediately after it is prepared (withoht heat), as little as three to five per cent, of starch- sugar may be thus detected. This test only applies when the sugar is mixed with solid glucose, as the syrup does not show birotation. 3. On account of the high rotatory power of starch-sugar, a refined sugar mixed with it will show a larger percentage of cane-sugar by the saccharime- ter than the true one ; hence the analysis generally adds up over one hundred. This will apply whether the material used for mixing is solid glucose or the syrup. With these three tests it is easy to determine qualita- tively the presence of starch or corn glucose in any sample of sugar, whether raw or refined, in amounts from two per cent, upwards. There exists no accurate method for determining the amount of commercial glucose in any refined or raw sugar mixed with it. The glucose itself varies greatly in compo- sition, and the invert-sugar contained in raw and refined sugars acts toward Fehling's solution precisely as does the sugar in glucose. The ordinary optical method cannot be employed, because the reading of the saccharimeter given by a mixture of cane and starch sugars is a resultant of the rotations of the two sugars, together with that of the 386 ANALYSIS OF COMMERCIAL GLUCOSE. impurities present in tlie latter. The rotation of starch- sugars from different sources and in different conditions, whether solid or liquid, varies within exceedingly wide limits. Clerget's method is equally inapplicable, except as a qualitative test, for the reasons stated above. The un- suitableness of this method for the quantitative estimation is specially profliinent on account of the optical properties of the maltose, dextrose, dextrin, and soluble starch pre- sent, it being remembered (page 136) that Clerget's process is intended for solutions of cane-sugar containing no rota- tory substance other than optically active invert-sugar of known specific rotatory power. Casamajor* recommends the use of methylic alcohol marking 60° of Gay Lussac's alcoholometer, saturated with starch-sugar, as a qualitative test for the latter when mixed with commercial cane-sugars. The suspected sugar, after drying, is thoroughly washed with the test solution, which dissolves the cane-sugar and impurities, leaving the glu- cose in grains and powder. It seems probable, as the author suggests, that this method might be so modified as to give fairly good results quantitatively, perhaps better than ^n-ith the very unsatisfactory methods hitherto proposed, by col- lecting the undissolved starch-sugar on a weighed filter, after all soluble matters have been removed by the alco- holic sugar solution, and the strongest methylic alcohol (92i° Gay Lussac), applied successively. Drs. Chandler and Ricketts f have devised a method for estimating the right-rotating substances in the glucose added to a commercial sugar. *Jowr. Am. Cliem. Soc, ii. 438. \Ibid., vol. i. CHANDLER AND RICKETTS'S METHOD. 287 CHANDLER AND EICKETTS'S METHOD. This consists in inverting the. mixed sugars with acids, as in Clerget's process (page 137), and observing the rotation in a water-bath tube at 92° C. (temperature of water-bath). Invert-sugar at 87.2° C. has no eifect upon the polarized ray, owing to the fact that the rotation of levulose is nexx- tralized by that of the dextrose which is constant for all temperatures (see invert-sugar, page 89). Hence, when a mixed sugar of commerce is inverted, the cane-sugar is converted into invert-sugar, which, with that originally present, is optically inactive at the temperature named. The dextrose and other bodies from the starch-sugar pre- serve their specific, rotatory effect. When, therefore, a pure commercial sugar is inverted, at 87.2° the rotation is null, while if any corn glucose is present a rotation to the right will be shown, and in proportion to the amount pre- sent. To calculate the results given by this process a standard starch-sugar was taken which gave ' ' an average rotation to the right at 92° C. of 87 divisions of the saccharimeter scale (Ventzke-Scheibler), w^en the sample tested 63 per cent, by Fehling's method. Hence, if 26.048 grammes be 26.048 X t¥b the amount taken for observation, — §7 X 100 ~ 18.864 grammes is the amount of dry substance necessary to read 100 divisions on the scale, or each division is equal to .1886 gramme." 26.048 grammes of the suspected sugar is taken for the Ventzke-Scheibler instrument, inverted with hydro- chloric acid, and the solution observed in the tube heated to 92° C. Each division of the scale read corresponds to .1886 gramme reducing substances, as shown by the cop- per test, added to the sugar under examination, in the form 288 ANALYSIS OP COMMERCIAL GLUCOSE. of corn glucose or staroii-sugar. Figs. 39 and 39 a show Fig- 39' 1 the arrangement adopted. The middle portion of the sac- charimeter is so modified as to admit of the interposition CHANDLER AND RICKBTTS'S METHOD. 289 of a water-bath, in tlie space ordinarily intended for the observation-tube alone. This is heated from below by two or f onr small spirit-lamps, and an opening is made in the cover of the water-bath for a thermometer whereby the temperature of the water is regulated. The form of the tube is shown in Fig. 39 a, which is merely the ordinary Fig. 39 a. one provided with a tubule for the introduction of a ther- mometer into the tube itself. This method in many cases is capable of giving useful results, and though a decided advance over previous meth- ods for the optical estimation of sugar in the presence of starch-sugar, yet it must not be . forgotten that when the composition of the adulterant varies considerably from the above standg-rd, or that of any other standard taken, the results, considered quantitatively, will be misleading. CHAPTER XV. ESTIMATIOIiT OF MILK-SUGAE. I. By Fehling's Method. — Milk-sugar reduces the al- kaline solution of oxide of copper in a different proportion from dextrose or invert-sugar. One equivalent of milk- sugar reduces 7.40 to 7.67 eq. (Soxhlet *), 7.40 to 7.44 eq. (Rodewald and Tollens f). 10 c.c. of the standard copper liquor is equivalent to .067 gramme sugar. Copper X .7635 ) ..-, ^^ V = milk-sugar. Copper oxide X .6096 j The estimation is precisely similar to that made for dex- trose and invert- sugar, except that it is necessary to heat somewhat longer, as the reaction, though complete, does not take place so rapidly as with dextrose. Either the volumetric or gravimetric methods may be used. To estimate the sugar in milJc, it is necessary to coagulate the caseine with a few drops of hydrochloric or acetic acids, and filter, before proceeding with the operation. II. By the Optical Method. — When the normal weight of 32.680 grammes for the Ventzke-Scheibler saccharime- ter, and 20.50 grammes for the Soleil-Duboscq and other saccharimeters in which the normal weight is 16.19 grammes for cane-sugar, is taken, each degree of the scale, when the 200 mm. tube is used, corresponds to one per * See references for Soxhlet's work, pages 201, 303. t Scheibhr's Neue Zeit., iv. 67-86. 390 ESTIMATION OF MILK-SUGAR IN MILK. 291 cent, milk-sugar. As milk-sugar exhibits the phenomenon of birotation, it is necessary to heat the freshly-prepared solution for a few mimxtes before taking the reading in the saccharimeter. For the estimation of milk-sugar in milJc, the fat and caseine must be first removed, the latter being strongly levo-rotatory ; 50 c.c. of the milk is mixed in a porcelain dish with 25 c.c. lead solution of moderate strength, and the mixture heated to gentle ebullition and allowed to cool ; it is then washed into a 100 c.c. flask, which is filled to the mark, and the solution filtered. The clear filtrate is then examined, the 200 mm. tube being used. The - read- ings must be doubled on account of the dilution from 50 c.c. to 100 c.c. If the milk exhibits an acid reaction it must be neutralized with soda solution (Landolt). CHAPTER XVI. Estimation of Dextrose in Diabetic Urine. I. BY THE OPTICAL METHOD. Foe ordinary cases the mode of proceeding is exactly as in tlie case of dilute sugar solutions in chapters xi. and xii., the urine being decolorized with lead and bone-black when necessary. Owing to the fact that the specific rota- tory power of dextrose is considerably lower than that of cane-sugar, when the various saccharimeters are employed the normal quantity to be weighed, in order that the read- ings may indicate percentages, must be greater, and in pro- portion to the relative specific rotations of the two sugars. Taking [66.5] D for cane-sugar, and [53] D for dextrose, we have 66.5 : 53 : : 26.05 : x — 32.683 grammes, which is the dextrose normal weight for the Soleil-Scheibler instrument. Calculating similarly for the others, we have, when the normal quantity for the saccharimeters is weighed and made to 100 c.c, 1° of the Laurent and Soleil-Duboscq instruments = 2.031 grammes, 1° of the Soleil-Ventzke instrument = 8.268 grammes, 1° of the Wild instrument (sugar scale) = 1.255 grammes, 1° of the Mitscherlich instrument = 9.410 grammes, in one litre. Schmidt and Haensch have made a modification of the SoleU instrument, so that the scale reads directly the num- 392 ESTIMATION OF DIABETIC SOGAR. 223 ber of grammes dextrose in 100 c.c. ; tMs is called the dia- hetometer. When the urine contains albumen it must be removed before the sugar can be estimated, as the former body has a strong rotation to the left. For this purpose the secre- tion is heated in a dish, with acetic acid added to acid reac- tion, until the albumen separates in flocks, which is then fil- tered oflf," washed, and the urine with the washings made up to the initial volume ; or the urine, acidified with acetic acid, may be dUuted with a concentrated solution of so- dium sulphate to double its bulk, when the albumen sepa- rates and may be filtered off. Biliary acids, though right-rotating, are seldom present in quantities sufiicient to affect the substantial accuracy of the optical method. When the urine contains less than 2.00 grammes of sugar to the litre, or the normal secretion is to be tested, the above mode of proceeding is unsuitable. Landolt * gives the following method for use under these circumstances : To one or two litres of the urine neutral acetate of lead is added, and the solution filtered ; the filtrate is mixed wilh basic lead acetate and ammonia, the precipitate formed containing all the sugar present. This precipitate is dif- fused in alcohol and treated with sulphuretted hydrogen gas, the lead sulphide filtered off, the solution decolorized, if necessary with animal charcoal, evaporated to a known volume, and tested in the saccharimeter. If biliary acids are present in the urine, they will be found in thealcoliolic solution, and invalidate the optical test to some extent. To prove whether these acids are present or not, a portion of * Das optisehe Drefmngsvermdgen, p. 185. 294 ESTIMATION OP DBXTEOSB IN DIABETIC UKINE. the alcoliolic solution is evaporated to dryness, tlie residue taken up with water, and the solution obtained allowed to ferment with yeast for two days, or until the sugar is de- stroyed. • If the filtered residual solution shows a right rotation, biliary acids are present, and a correction for them must be made. II. The Qualitative Test. — "Fifteen or twenty drops of the urine to be tested, previously decolorized with a little powdered bone-black and diluted with four or five c.c. of water, are treated with a half cubic centimetre of sodium or potassium hydrate solution, and then a very dilute solu- tion of copper sulphate added drop by drop. Too large an amount of the copper salt should not be added, as in that case black oxide of copper separates on boiling, obscuring the red color of the cuprous oxide when only a small quantity of sugar is present. The clear blue solution is heated nearly to ebullition, without shaking, when a yel- low cloud forms on the surface, followed by a precipitation of red cuprous oxide. ' ' A second mixture prepared in the same way is allowed to stand quietly, without previous heating, from six to twenty -four hours, when, if sugar is present, there wiU be a precipitate formed in this case also. This control experi- ment is of great importance, and ought never to be omit- ted, since most of the sub.stances which reduce copper so- lution, like sugar, do so only when heated, or after pro- longed boiling, and not, like diabetic sugar, in the cold" (Neubauer). The Quantitative Estimation. — This determination is ESTIMATION OF SUGAR BY COPPER TEST. 295 made in all respects according to tlie ordinary volumetric method, or, for very accurate work, after the modification of Soxhlet. See chapter viii., section i. The gravimetric method is of doubtful accuracy, on account of the possible precipitation of earthy phosphates or other salts, under some conditions. It is best to decolorize the urine with a small quantity of powdered bone-black. If albumen is present it must be separated by heating to boiling with a slight excess of acetic acid, filtering, and washing the precipitate. Uric acid is probably the only body ordinarily present in urine which reduces the copper solution. According to many experiments of Neubauer, the uric acid in normal and diabetic urine has no appreciable effect on the results of the copper test. When uric acid is present to an abnor- mal amount, it may be removed by treating the solution, previously diluted to contain f per cent, sugar, with a slight excess of basic lead acetate, filtering, adding a solution of sulphurous acid until all lead is removed, and again filter- ing. The clear lead-free filtrate may be used for the sugar estimation. CHAPTER XVII. THE CHEMISTRY OE ANIMAL CHARCOAL. Bone-Black — Bone-Char — Animal Char — Animal Black — Knochenkohle, Gfr. — Charbon d'Os, Fr. Composition. — Animal charcoal is the carbonaceous residue left by the distillation of bones in close vessels. Dr. Wallace gives as the average composition of a good char : Carbon* ii.oo Carbonate of lime 8.00 Phosphates of lime and magnesia 80.00 Alkaline salts 40 Sulphate of lime 20 Oxide of iron 10 Silica 30 100.00 * The carbon is much higher than that of the bone-black made in this country. The following analysed give a good idea of the composi- tion of American chars : I. 2. 3^ 4- 5. 6. 1- 8. Moisture 3-37 8.05 6.71 trace. .18 •43 81.26 256 7^67 7-54 .08 2.45 7.76 8.76 trace. onR 2.39 7^55 7.42 trace. •17 •57 81. go 2.78 8.17 7.60 .06 .11 •57 80.71 4-43 8.70 7.84 trace. .04 78.99 2.07 8.47 6.08 trace. .05 83^33 1.76 9.08 7.19 trace. .10 8V.87 Garb, lime Sulphate of lime. . Iron Sand, clay, etc Undetermined * . . Lbs. per cu. ft. . . . .32; .32 81.53' 80.602 100.00 42.7 100.00 45^50 100 00 48.5 100.00 45^5 100.00 100.00 474 100.00 1 00.00 These analyses represent chars of the best quality, in grains of medium size. * Alkaline salis^ phosphates of lime and MgO, etc. ANALYSES OF CHAB. 297 ^ to M j>. vo r^ c i CM t^ O w O t^ 5 m • \n t^ M CO w O CJ N O O I^ • HI o cc fi • cc 1- O ■* O U^ O c o ^ in CO H OQ 'C r-* & H O^ H- 1^ =^ w r^ y; a^ ■^ m flS vD en ^ _ O c^ 2 ta C h- « 8 o r^ T}- m es c t^ !>. « ^ £ vd 0^ -* d c o CO CT. >j . r-» oc Cfl r^ ^ o\ c Oi (D O O^ O^ - ■^ CT» H o t^ CT> CC iL ^ CC c ■!l- xn CC ■* -d- O o r^ cn O^ t- o a* "^ o> t>. M ^ r^ E; g m t^- ^ ■* C M m vC o> ■* ■<* t^ C c o> c t^ y ■* CO *c OO h- c ai *~ k^ !r (0 XI E ■;;! o a. c E bo ^ ) "- a: i h t a. O : T IS a H ^ c c J3 ■ S o L, -O 2 * 1 O ) "o ;; Q CJ U C/3 tn J5 en p ' ^ •a e O z 298 CHEMISTRY OP ANIMAL CHARCOAL. Historical. — The decolorizing power of animal cliar was first noticed by Lowitz, but Figuier in 1811 proposed its use as a decolorizer. In 1812 Derosne introduced it into the sugar manufacture, and in 1821 Bussy and Payen thoroughly investigated its properties and mode of action. It was first used for sugar solutions on the large scale in a state of fine powder, and consequently after one operation it became useless for another. Dumont, however, in 1828, made a great advance in the practical application of animal black, by employing it in grains and filtering the sugar so- lution through a column of it. Afterwards, the char was submitted to a process of revivification by washing and burning, essentially the same as practised at the present time. Mode of Action. — The effects of animal charcoal on sugar solutions may be classed under two heads, though the physical action is the same in either case — ^viz., the removal of color, and the absorption of other soluble matters. The two actions seem to be dependent to some extent, and the color of the filtered solution is in most cases a good index of the amount of purification effected, though not always, for the coloring matter in sugar so- lutions that have been much heated is entirely removed with great difficulty, while the absorption of salts and other matters takes place in a normal degree. Filhol gives a table showing the decolorizing powers of various sub- stances as compared with bone-black washed with hydro- chloric acid, which is called 100 : NITROGEN IN CHAR. 299 Litmus. Red Wine. Molasses. Cold. Hot. 96.86 90.28 100 Cold. Hot. Cold. Hot. Hydrated sesquioxide of iron. . " oxide of lead Barium sulphate 128.9 54 54 77 100 7272 79-41 2596 42.18 100 51.91 103.83 46.15 49-13 100 5224 84.37 25.96 42.18 100 Calcic phosphate or carbonate . . Magnesium carbonate Bone-black 109 100 The absorptive power of bone-black is owing to the pre- sence of carbon in a minute state of division. The phos- phate of calcium constitutes a framework, as it were, for the carbon, and, after the calcination of the bones, remains in a very porous condition ; hence the lighter the char for a given bulk the better it absorbs. Presence of Nitrogen. — The carbon contains from one to one and a half per cent, of nitrogen, which diminishes to about one-half per cent, when the char has been used some time. This substance seems necessary for the decolorizing effect, as no vegetable charcoal destitute of nitrogen has the same properties. Nitrogenous chars prepared in dif- ferent ways have the property of absorbing color in va- rious degrees. A table from Muspratt illustrates this : Decol. Power. Ordinary animal black ■■ •• '■ " " treated with hydrochloric acid .. . 1.6 Ordinary black calcined with K jCOa 20.0 Blood " " 20.0 " " chalk ii-o " " phosphate of lime lo.o Albumen " KjCOs i5-5 Gluten " " 15-5 Oil " phosphate of lime 1.9 Absorbing Power of Char.— Brimmeyr' s experiments, 300 CHEMISTUr OP ANIMAL CHARCOAL. confirmed by Schultz, on the absorbing power of animal charcoal, gave rise to the following conclusions : 1. The absorptive power does not depend on the mechanical struc- ture, but upon the amount of carbon contained. 2. Char which has lost its power for absorbing one substance is capable of taking up another body of a different chemical nature. 3. The quantities of matter absorbed by bone-char of various kinds are, when considered in relation to the amount of carbon present, really equivalent, and probably independent of the varying chemical nature of the ab- sorbed substance. 4. Bone-char acts the quicker and better the less its capillary structure has been altered by mechani- cal or chemical means. The following analyses, taken from actual work in a sugar refinery, show the absorptive action of char for solu- ble impurities : Sugar Grape-sugar Organic matter not sugar. Ash Raw Liquor. 93-50 2.14 3.56 .80 Filtered Liquor. 95-30 2.25 2.00* -45+ 100.00 100.00 100.00 Char Wasliings. 78.50 3-23 11-05 7.22 * 43.82 per cent absorbed. t 43-75 F^ cent, absorbed. Walkoff * gives an admirably clear, graphical representa- tion of the progress of a filtration, showing the absorption of alkalies and coloring matter, and the progressive purifi- cation of the sugar solution (Fig. 40). The perpendicular * TraiU Complet, tome ii. 191. ABSORPTIVE POWER OF CHAR. 301 lines show the hours of filtration, and the others the rela- tive proportion of sugar in dry substance, alkalinity, and decolorization during the progress of the operation. Absorption of Salts and Organic Matters. — The soluble substances taken up by char are either organic or mineral, th.e former consisting of gums, coloring matter, albumen, etc., and the latter of inorganic bases combined with organic or mineral acids. The organic bodies, nota- bly albumen, are retained by the char with great tenacity, so that long washing with hot water, or even steaming. Fig. 40. / „ .. , l\ Hours Quotient o\ ^^ / Decoloration 200 225 / ot f urity 78 79 80 81 S"i /C| \1 2 3 i 6 6 7/ g\ k^linity 1,3 1 / 1 1.2 1 / 250 1.1 'aA \ 275 1,0 0,9 82 83 84 85 86 87 88 89 90 91 92 \ \ / 1 ^ Decoloration 325 W / / l\ 0,8 W / ^ \ 350 0,7 W ^ \ 375 0,6 W yf^ / \ 400 0,5 V J w // \ 425 0,1 \' / A / i 450 0,3 \ \ / 475 0,2 \ / ■ — AlkaRnity 500 0,1 525 0,0 550 faUs to remove aU of the absorbed material ; some inor- ganic salts are also obstinately retained. The soluble mat- ters submitted to the action of the char are taken up in varying amount, depending on the nature of the body. 302 CHEMISTRY OP ANIMAL CHARCOAL, Walkoff,* working with, weak solutions of potash and soda salts, arrives at the following results, the conditions being the same in all experiments, and the temperature 15° C. : Per cent, absorbed. Potassium hj'drate (at 60° C). . 13.5 " (ati5°C.).. 16.6 " carbonate 25.0 phosphate 30.7 " nitrate 6.5 " chloride 3.0 " ••••• 1-3 " citrate 12.2 " sulphate 22.4 Per cent, absorbed. Sodium carbonate 24. " " (at 60° C.).. 18.3 " phosphate 32.3 ,... 28.0 " nitrate 5.0 " sulphate 20.4 Magnesium sulphate 4g.o Sodium chloride i. Bodenbenderf has also examined the subject and ex- tended the research so as to include salts of organic acids. In the table, under I. are included dilute solutions of the salts, with 5 per cent, of cane-sugar added, and under II. more concentrated solutions without sugar : Percent. ^ absorbed. I. 11. 21.50 16.50 48.10 69.97 45.40 48.20 8.10 9-15 Potassium acetate , 28.70 13.51 "■75 The absorbing powers of char for different alkaline salts were found to be in the following order, commencing with the weakest : Potassium chloride, sodium chloride, potas- * TraiU Complet, tome ii. 306. f Slammer's Jahresb., x. 339. REVIVIPICATIOK. 303 slum nitrate, sodium nitrate, potassium acetate, sodium acetate, potassium sulphate, sodium sulphate, magnesium sulphate, potassium carbonate, sodium carbonate, and so- dium phosphate. The amount of purification effected by char in a sugar solution is directly as tJie amount of the former used to a given weight of sugar, as the temperature, and as the time lohich the solution is in contact with the coal. Marks of a Good Char. — Good animal charcoal has a dull black color, without presenting any appearance of in- cipient fusion on the surface, and does not contain an undue proportion of cellular particles, which come from small and inferior bones, and have by no means the deco- lorizing effect of the char made from the large bones. It should adhere strongly to the tongue, and not contain much fine powder, but be hard and tough to resist the great wear to which it is subjected during filtration and revivifi- cation. The size is regulated by the density and tempera^ ture of the liquor to be filtered. Revivification. — After bone-char has served the pur- poses of filtration, water as hot as possible is run in at the top of the filter, which displaces in part the sugar solution remaining in contact with the char, and at the same time it mixes with the rest, forming a dilute solution of sugar and the impurities taken up from the liquor ; this dilute solu- tion is known as "sweet water." By the action of the heated water the char gives up the greater portion of the absorbed matter, which goes in part to the sweet water and the remainder to the ^^ waste water, ''^ which is the wash- water that no longer contains suflBcient sugar to make it profitable to save. The "sweet water" is generally boiled down with one of the lower products, and should on no ac- 304 CHEMISTRY OP ANIMAL CHAECOAL. count be used to dissolve comparatively pure raw sugars for refining. From tlie above it follows that the purification of sugar solutions by bone-black consists in removing the impuri- ties from the first products, but, instead of eliminating them entirely, adding a large portion of them to the lower or half -refined* products, where their injurious influence comes less into play. The second step in the revivification consists in heating the washed char in closed retorts, out of contact with the air, at a sufficiently high temperature to perfectly carbon- ize any organic matter remaining in it, and to bring the char back to the physical condition in which its absorbing properties are exerted to their fullest extent. Alteration by Use. — The following analyses, taken from actual work, show the progressive changes that have taken place in bone-black used in a refinery where raw su- gars from the cane were worked : ANALYSES OF CHAR. 305 «; M Tf so w H M CO H . ■ «o Tj- J r^ CO d M . o o en en en , CO lO a o 4 CO t^ H m '^ u! o N ■•i- ? OS oo M cn , en m C7N ''S- • ir> en * »n ^ !? O^ in CM •Th m CO cn . in CO c a^ '^ ' • m M o ■ in m ° -^ w u^ ^ ■* N « en ^ ■* a O^ ■* o H c/l in m c^ u^ ■* o •^ -i- 1 t-" to « '^f cn , O o> -^ ' hJ « . ^ vO \n O -* N 't en « en JS m M s in '■* CO tn en M in , , O O O M ^ • ' r^ w-j OS ■< ^ fu^ ^ CO en «n o t^ tH •* Si*.-^ • e^ CO ^o-a Tt m fi is 1 V P 1- H 3- t C S IH a. •C5 O O o m C o pd ,13 ■3 " 1- u ho Q o g C in 3 306 CHEMISTRY OF ANIMAL CHAKCOAL. An examination of the table shows that the char by use undergoes a change, which will be examined seriatim, in relation to the various constituents of the black. Carbon increases owing to the fact that some organic matters absorbed are held with great tenacity, and no prac- tical amount of washing is sufficient to remove all traces of these bodies. The consequence is that, in the burning in the process of revivification, the residual organic matter is carbonized in the pores of the coal, and, instead of increas- ing the decolorizing effect of the coal, the opposite is the case, as a quantity of inert non-nitrogenous carbon is de- posited in the body of the grain, making it more dense and decreasing the amount of cellular surface. A large per- centage of carbon in a new char is often a mark of poor quality, being caused by imperfect and insufficient burning of the bones. As a rule old and new char may be distin- guished by the proportion of carbon contained. Carbonate of Lime. — The tenor of this salt is rapidly reduced when the char is first used for filtration, and then generally remains stationary for a long time at from 4.50 per cent, to 3.50 per cent., but finally, in very old chars, the percentage may be lowered to less than the last figure ; in this case tliere is too little of the salt for normal work- ing. Its office is mainly to ensure neutral liquors by satu- rating any free acid which may exist in the solution, or may be formed by the lactic-acid fermentation, where the temperature of filtration is too low. As the solutions ought always, whether in filtering or washing, to be not lower than 180° F. , there can be no danger of this fermentation so long as this condition is complied with. By taking proper care to have the raw liquor sufficiently limed, . and the temperature high enough in the filters, the amount SULPHATE OF LIME— IRON. 307 of carbonate of lime in the cliar will remain high enough almost indefinitely. In the beet-sugar manufacture, where the liquors and juices often contain a large excess of caustic and other lime-salts, the percentage of carbonate is apt to be high rather than low. It has in that case to be removed by treatment with hydrochloric acid. An excess of the car- bonate is injurious to the char in the same way as is any other insoluble inert body, which stops up the pores and reduces .the available filtering surface. Hard water con- taining much carbonate of lime is not suitable for washing char, as the lime-salt is retained. Alkaline Salts. — These consist largely of ammoniacal compounds, and are only found in considerable quantity in new char. If suffered to remain they go into the liquor and act injuriously by their melassigenic properties. On this account new char should be thoroughly washed and burned before using. Sulphate of Lime. — This salt acts by filling up the pores of the coal, and may be derived from the sugar treat- ed or the water used in washing the char ; it is strongly re- tained by the char, but thorough washing is the remedy in this as in many other cases. Iron is a highly injurio^^s body, and is derived from the sugar treated or from rusted, insufficiently -painted filters and piping, and also from the retorts of the kilns in which the black is burned. When existing in the char it is sure to get into the filtered liquors, and especially the sweet waters, more particularly when they are a little acid. It accumulates in the yellow sugars or lower products of the refiner, giving them an undesirable dull grayish cast which greatly lowers their marketable value. Such sugars also 308 CHEMISTRY OP ANIMAL CHARCOAL. darken tea to whicli they are added, by the formation of tannate of iron. All new black purchased for refining pur- poses should carry very low percentages of iron. To prevent iron from getting into the char in the course of manufacture, the filters should be well scraped and paint- ed as often as is necessary, and the liquors should be neu- tral. InsoluWe matter which resists the solvent action of strong acids on the char consists partly of quartz, sand, or clay — which in moderate amount is not objectionable — and also of hydrated silica derived from weak sugar solutions that have soured and precipitated the dissolved silica. This is caught in the char, and acts in the manner of sul- phate of lime or other finely-divided matters. Sulphide of calcium is apt to accumulate in char that has been used some time and v/hich contains much sul- phate of lime. The sulphate is reduced in contact with the organic matter or carbon in the reburning of the char, forming the soluble sulphide which goes into the liquors. Sulphide of calcium, coming in contact with the iron in the liquors, strikes a yellowish green color, which develops,^ even after the solution has run off the coal, from the forma- tion of ferrous sulphide, and very seriously interferes with the operation of making salable sugars, especially for the lower products. Calcium sulphide is one of the worst im- purities that can exist in bone-black used for purposes of filtration, and any sample containing more than a very small quantity vnll fail to give a satisfactory working on the large scale. In contact with an acid sugar solution sul- phide of calcium also gives off hydrosulphuric acid, w^hich at favorable temperatures is believed to predispose the su- gar solutions to fermentation. In the series of analyses THE EXHAUSTION OP CHAR. 309 given on page 305, the last, showing .41 per cent, of calcium sulphide, represented char which was rejected as being no longer fit for filtration, and chiefly owing to presence of the sulphide. Nitrogen appears to greatly aid in the decolorizing ac- tion of the carbon in animal black, and, as a rule, the higher the amount the better the char. It is often a question submitted to the chemist as to whether a given char is so far exhausted as to decolorizing properties that it would be desirable to replace it with new. Many things have to be considered in this relation, the chemical analysis alone not always being a sufiicient guide, as cliars which analyze poorly sometimes decolorize very well. No general rule can be laid down for the mat- ter, and the chemist will have to rely largely upon the re- sults obtained in working on the large scale with the.black in question, extending over a sufficient length of time, and including all the necessary analytical details ; above all, reliance should be placed on his general experience gained in this special department. There is appended a series of analyses of bone-blacks, I.* showing both old and new chars, and II. f char of English and American origin that has been used in filtration : * MaumenS, Traite Complet. f W. Arnott, Amer. Gftemist, i. 216. 310 CHEMISTRY OP ANIMAL CHARCOAL. Carbon 10.21 76.94 7.42 .12 .01 • 67 .22 •34 4.07 8.44 80. 31 8.77 .40 .04 • 35 •43 1.71 • 55 9.88 80.11 7-76 .08 .04 • 17 .92 1.04 12.07 76.35 7.09 .11 .33 .12 •79 1. 14 10.65 78.52 7.21 .20 .08 • 17 .06 ■ 73 2.38 24.22 64^35 4.82 .84 • 14 .12 • 43 1-35 3-73 26.12 62.40 3-35 .88 .16 .24 • 56 4.08 2.21 Phosphate of lime.. Carbonate of lime.. Sulphate of lime. . . Sulphide of calcium Alkaline salts Oxide of iron Sand Water Real density Apparent density : In powder In grain Decolorizing pow- er : In powder In grain 100.00 2.89 1.070 .776 142 93 100.00 2.928 .996 .804 94 71 100.00 2.903 .944 .769 116 88 100.00 2.937 1.081 .778 104 65 100.00 2.943 • 975 • 771 165 lOZ 100.00 2.939 1. 144 1.688 62 8 100.00 2.937 1.388 1. 196 51 7 II. Origin. Carbon Phosphates. . . Carbonates . . . Sulphates. . . . Oxide of iron Alkaline salts Sand, etc 12.90 82.04 3-23 .27 • 51 ■ 25 .80 16.35 77-93 3^30 .29 •33 .20 1. 60 g.02 85^44 3.10 .42 .48 .20 1-34 8.24 87.48 2.00 .58 • 57 -15 .98 11.40 80.61 5.98 .92 •43 .20 -46 11.20 83.80 3-33 -14 •32 .20 I-OI 10.20 83-43 4.76 -17 • 51 .10 -83 10.45 84-50 3-75 .27 -43 ■ 15 -45 CHAPTER XVIII. The Analysis of Animal Charcoal. ESTIMATION OP WATER. Dry for two hoars at 140° C. The sample should not be powdered. ESTIMATION OF CAEBON. Dissolve four or five grammes of the finely-powdered char in about 35 c.c. of pure hydrochloric acid diluted with its bulk of distilled water ; heat on a water-bath in a flask or beaker-glass for half an hour, with frequent agitation, until the soluble part has all been taken up. Dilute to about 200 c.c. with hot distUled water, allow to settle, and pour on a filter that has been previously washed with di- lute acid dried at 100° and weighed. When ° Fig. 41. the liquid has all filtered, add more hot water to the flask, shake well, allow to subside, and pour off the clear solution from the undis- solved matter ; add water to the flask a third time, vpith a little hydrochloric acid, and transfer the carbon to the filter in the usual way. Continue the washing on the filter with hot water, at first acidulated, and final- ly with pure water, until the washings have no longer an acid reaction, or a drop, when evaporated on platinum foil, leaves little or no residue. Dry the filter at 100° until it 311 312 ANALYSIS OF ANIMAL CHARCOAL. ceases to lose weight, the weighing being performed in the same vessel (watch-glasses or a weighing-flask, Fig. 41) in which the filter had been previously tared. After the last weighing, transfer the filter with the carbon to a weighed crucible, burn off the carbon, and reweigh. The residue in the crucible, after the subtraction of the fil- ter ash, constitutes the insoluble residue, which, taken from the last weight at 100°, gives the amount of pure carbon. Example : Amount of char taken 4.500 grammes. Residue + weighing-flask -f filter at 100°. 20. 570 Weighing-flask + filter at 100° 20.150 Carbon -f- insoluble matter 420 Insoluble matter 019 Carbon 401 Crucible after ignition ] 5.140 " 15.120 .020 Filter-ash 001 Insoluble matter 019 ■401 X 100 ^^^ ^ , ^QQ — = 8.91 per cent, carbon. ■019 X 100 ^^ p^^ ^^^^ insoluble matter. 4.50 Note. — Char should be weighed in a close vessel for pur- poses of analysis, either between watch-glasses or in a weighing-flask, as, according to the state of the atmosphere, or the amount of water in the char itself, there will be a SCHBIBLER'S CALCIMETER. 313 gain or loss during the time necessary to take an accurate weight. Fig, 42.* ESTIMATION OF CAKBOSTATE OF LIME. For work where ordinary accuracy is required, this esti- mation had best be performed according to Scheibler's * The author is indebted to Messrs. Elmore & Richards, of New York, for the above engraving. 314 ANALYSIS OF ANIMAL CHARCOAL. process.* The results for low percentages are accurate enough for all technical purposes. We give Scheibler's description. The apparatus is represented by Fig. 42, and consists of the following parts : 1. The evolution-flask A, in which the assay is acted upon by hydrochloric acid, which is placed in the rubber tube S. The glass stopper of A is perforated, and carries a tube, to which is joined a rubber tube, r, connecting A with B. The latter has a gum stopper fitted with three glass tubes ; the one joined to r extends a short distance into the vessel, and has fastened to it, by the neck, a thin caoutchouc bag, K, capable of being easily distended by a slight pressure ; q is closed by a pinchcock while the estima- tion is being made, and serves to bring B into communica- tion with the air when necessary. The glass tube u also passes through the stopper of B and connects with (2) The graduated tube 0, which is divided into twenty- five equal parts (about 4c.c. each), each division being sub- divided into tenths. The lower end of this is in communi- cation with (3) The straight control-tube D, open at the upper end, and at the lower having a tube of smaller calibre passing to the bottom of the two-necked flask E, as shown in the fig- ure, the connection between the two being regulated by the pinchcock p. E is the reservoir for the water, and C and D are filled from it by pressure exerted by the breath of the operator through w, the cock p preventing the reflux of the water. C, D, and u are fastened to an upright board by suitable means, and the bottles are supported on a shelf fastened to the upright board. » stammer's Jdhresb., 1861-2, 344. SCHEIBLEK'S CALCIMETER. 315 In addition to the apparatus, the following requisites are necessary to the performance of the test : 1. A normal weight of 1.702 grammes. 2. A centigrade thermometer graduated from 12° to 30°. 3. Diluted hydrochloric acid of specific gravity 1.120. 4. A solution of chloride of copper. 5. A. solution of ammonium carbonate. For the execution of a test the normal quantity of pulver- ized char (1.702 grammes) is placed in A, which must be dry, and the tube S, filled with acid to the mark, is carefully placed in the bottle. E is then filled with water, and the operator forces the liquid into D and C until it reaches a little above the zero-point in C, when it is allowed to flow out by opening p until the level in is at 0. Care must be taken that the water is not caused to overflow into B, for in that case the apparatus would have to be taken apart and dried. The stopper being now placed in A, a connection with B is made by the tube r. If the level of liquid in D and C are then unequal, the equality may be restored by opening the cock q for a few seconds, and which for the rest of the operation remains closed. The test may now be proceeded with. The vessel A is held, as shown in the cut, so that the acid may come in con- tact with the char, and the bottle gently shaken to cause the acid to thoroughly mix with the assay. The pressure of the gas evolved distends the rubber bag and depresses the column of water in C. The cock^ is now opened to let the water in D flow out, the operator aiming to keep the level in C and D as near the same as possible during the progress of the determination. When all the gas has been given off, and the level of the liquid in C becomes station- ary, p is closed after bringing the water in D to the same 31G ANALYSIS OF ANIMAL CHARCOAL. level as that in C, and the volume and temperature read off. New char sometimes contains a small quantity of caustic lime. When thig is the case the finely-powdered char before being tested is evaporated on the water-bath, after being thoroughly moistened with a solution of carbonate of ammonia. ' The presence of sulphide of calcium in char introduces a slight eiTor in this method, as it is decomposed in contact with the acid, setting free sulphuretted hydrogen, which would be reckoned as carbonic acid gas. This difficulty may be met by the addition of a small quantity of cupric chloride to the acid used. The apparatus should be placed in a position where the temperature is as equable as possible. The estimation is made in duplicate, and the average taken as the true result. The following table gives the percentage of carbonate of lime from the volume and temperature readings : TABLE FOR SCHEIBLBR'S CALCIMETEE. 317 z o (a < o > § K S S ^ R g ■J hJ < h -r O 'e«i 14 f=l f-i < a [i3 o X «i m o X H Q ES H O g'S'>B isasffi&s a jsigaRS aaTa-s H c m^.r» t-g - a ajusre jsog g.g fj « 5f KfR-RKSRSa-aSf^^SifS S S&S S^.8 S£-B s M « m-^irno iNoo oio m n jn^jruo «j»>QO g'S fj « i? in " hi cJ co^»f*d tied d>d M (^ m3-»^*D t^oo 0(d jj « en V 'g.'RSggS.SaSfi'fta'S.^ffiS'S^ SJS-S'g.S^R -« «„f >«=■.« 0,0 - 3 jJJS^ jv» g,o g 5j gj jj •£.813335 g?g.R3s«s,sn*Sias-a S-3 &g sa M N §.*SSR^ „ « m*,™. «-«. 0,0 - g S'« J8 'R^S. s: - " ""™ "^ ''s a a 3 ffrira &« ss s a ffs ss a-ag s»8 ssss-ffs s g^asassassss - " ""^ '■» "g a a ffjffs^ E^s g'S s a i?? ss s.'ss^ g'aaasg«8&'ss'?S'S'goS sas " " ""™' •-» "^g s a ffffsre &^ g-s s a a if? ,g£-S8 ffsa 3>s-2 STiTffa-srffa a a a 2 g sg^s ,8S8asS-B:?&ffSSSSS8SS8S88S8aS M « tutvo •sOO CO ".« entioo ^*co 0*0 ^ « SO^lO 1" M N co'^irio tv» ono m n m-tu-\o t>.oo o-o M « W'i-.n 318 ANALYSIS OP ANIMAL CHARCOAL. An example will show the use of the table : A sample of char gave a volume of 15.4 at 25° C. 15.0 volumes = 14.27 at 25° .4 " = .37 at 25° 14.64 per cent, calcium carbonate. The carbonate of lime in animal black may be estimated very accurately by several processes depending upon the expulsion of the gas, determining the weight lost, and cal- culating the carbonate of lime from the carbonic acid lost : CO, X 2.2727 = carbonate of lime. For details of these and other methods the reader must be referred to standard works on analytical chemistry. Calculation for Removal of Carbonate by Acid. — In the beet-sugar manufacture, and in refining where the water used for washing the char is very hard, calcic carbo- nate accumulates in the char to an abnormal extent, and it is often desirable to remove the excess by washing with hydrochloric acid. Taking 7 per cent, as the normal amount, Scheibler has given a table whereby the amount of hydrochloric acid of any strength required to reduce the carbonate to the prescribed limit may be calculated : TABLE. 319 Oi 1 1 g 1 1 1 1 1 1 f i s S 1 1 1 in 1 f a 3 " !? *s >s &■ & •s " s S s " " ST s- U3 ■8 a Si 00 1 § 1 1 1 1 i 1 1 1 1 1 1 « 1 1 1 o s g, ff 2- 3- M !? m -s ■a f^ t>. 00 =S s S s s " & S' tv 1 1 3 i S! 1 t ^^ 1 i 1 f 1 a' 1 a 1 1 K ' M » S a a- u " S? " ■s •g r^ S" s s ff ST e 1 O 1 1 % 1 1 1 1 1 1 1 t S ^ t 1 1 en 1 3 .s "a s " - " " a " H S s s ^ jn *s t^ ^ s 1 IS ^ 1 § g s 1 f 1 t 1 1 i 1 1 1 00 1 1 1 = CO 00 o» o^ o» CJi s s s a B a a s* S" K" •a ■s go 5 ■* i 1 « 1 1 1 1 ■a € t 1 1 1 1 1 1 VO t^ ts ^« !>. t«. 00 00 00 CO o. lO lO V3 lO tH t>. *^ 00 00 Ot o - <« 1 1 f 1 o9 S ^ 1 f 1 1 1 1 1 1 t -8 1 1 > m CO eo m CO CO ■* T^ ■* "«*• ■* ■* 1- .o .n ir vO QO P« tN at o o „ ^ , V3 00 ^ o> * * s s !S ^ S8 ^ s S! a CO a ^ 'S 3- ST « ff %j6 S s s a 8. S' ■S K t^ ?. to ft 3, s= s S VO ■8 8 r^ H M M H - " M hi M M •^ " M M M - M u o lo o m o to o in o IT o in o O o o o o o Qn in ^ ^ J? S a a " s S s ON o< M p^ -g I/' S !? 320 ANALYSIS OF ANIMAL CHARCOAL. Example : A char contains 12.30 per cent, calcic car- bonate, and the acid at command has a density of 1.166, or 30° B. 'Now, 12.30 — 7.00 = 5.30 per cent, carbonate to be removed. From the table we iind — 5.0 parts CaCOs require 11.40 parts acid, .3 " " '-' .68 " 12.08 parts, of sp. gr. 1.166, or, in a ton of 2000 lbs. of char, 2000 X 12.08 per cent. — 241 lbs. of commercial acid of the indicated strength. ESTIMATION OF CALCIC SULPHATE. For this and the succeeding determination the char should be very finely pulverized and passed through an 80- mesh sieve. Twenty grammes are taken, placed in a porce- lain dish on a water-bath, moistened with distilled water, 80 c.c. of pure concentrated hydrochloric acid added, and the whole heated for an hour with frequent stirring. At the end of that time the semi-fluid mass is washed into a 250-c.c. flask, diluted to the mark, and the mixture filtered. To 200 c. c. of the clear filtrate, corresponding to 16 grammes of the original substance, is added, in the heat, its bulk of water, together with a slight excess of barium chloride, and allowed to stand at rest from six to twelve hours. The precipitated barium sulphate is now filtered from the clear solution, and, after washing two or three times with boil- ing water in the beaker, is treated with about 5 c. c. of a strongly acid solution of ammonium acetate, heated for five minutes, diluted with boiling water, and the precipitate and fluid transferred to the filter. After a further washing, the ESTIMATIOJf OP CALCIUM SULPHIDE. 321 filter is dried and tlie weight of the barium sulphate deter- mined in the usual manner. Barium sulphate X .58334 = calcium sulphate.* ESTIMATION OF CALCIUM SULPHIDE. Twenty grammes of the finely-powdered char are treated in a porcelain dish on a water-bath, after first moistening with water, with 40 c.c. of fuming nitric acid free fronl sulphuric acid, added in small portions at a time to pre- vent too violent a reaction. The mixture is heated, with frequent stirring, for half an hour, when 40 c.c. of pure con- centrated hydrochloric acid are added gradually, and the whole kept heated, with stirring as before, for twenty min- utes longer. The contents of the dish are now transferred to a 250-c.c. flask, and when cold the fluid is diluted to the mark and filtered ; 200 c.c. of the filtrate, corresponding to 16 grammes of char, after dilution with an equal volume of water, are treated with a slight excess of barium chlo- ride, and the amount of sulpliate formed determined as in the estimation of calcium sulphate. It is of the first importance that, in this and the preced- ing estimation, the reagents used sTiould he absolutely free from sulphur in any form. For the calculation of the results, the amount of the ba- rium salt found in the determination of calcic sulphate is subtracted from that as obtained above, and the remainder * The error owing to the volume occupied by the undissolved carbon has been experimentally proved to be without sensible efiect on the results, and likewise that from the slight solubility of barium sulphate in a liquid contaiar ing a considerable amount of free hydrochloric or nitric acids. 332 AliTALTSIS OF ANIMAL CHAKCOAL. is the barium sulphate corresponding to the calcic sul- phide : Barium sulphate X .3089 = calcic sulphide. Example : 10 grammes of char containing .50 per cent, sulphate of lime, when treated for the estimation of sul- phide, gives .230 gramme BaSO,. Now, the barium sul- phate from the calcic sulphate would be 10.000 X .0050 — .050 gramme CaSO„ and -^M_ = .0857 gramme BaSO,. .58324 ® .2300 — .0857 = .1443 gramme BaSO„ iurnished by the oxidation of the sulphide ; hence, /.1443 X .3089> 10 ^^ X 100 = .445 per cent. CaS. lies and Fahlberg' s * method, though more tedious in execution than the above, gives very good results ESTIMATION OF CALCIC PHOSPHATE. About one gramme of the powdered char is ignited in a crucible until the carbon is burned off ; the residue is then dissolved in 50 c.c. pure nitric acid, and the solution made up with water to 100 c.c. ; 25 c.c. of this solution is taken and treated gravimetricaUy by precipitation with molyb- denum solution, or by the volumetric method with ura- nium acetate. For details of these methods the reader is referred to Fresenius's or other standard works on analyti- cal chemistry. * Ber. Chem. Gesell, 1879, xi. 1187. ESTIMATION OP IRON. 333 This determination is rarely necessary, except upon the exhausted char, when it is desired to estimate its value for fertilizing purposes. ESTIMATION OF THE IKON. The iron may be determined in the filtrate from the car- bon, or from an ignited portion of the char, dissolved in strong hydrochloric acid. When the tenor of the iron is very low about 10 grammes should be taken for the assay. To the strongly acid solution, platinum foil and a piece of iron-free zinc are added to reduce the sesquioxide to protox- ide. When the liquid no longer gives a red coloration with a drop of ammonic sulphocyanate solution, the reduction is complete. The iron in the ferrous condition is then deter- mined by a standard solution of potassium permanganate. Preparation of the Standard Solution. — This solu- tion is prepared by dissolving about 2^ grammes of the crystallized salt in water and diluting to one litre. To find the exact amount of iron that the solution is equivalent to, 1.500 grammes pure crystallized oxalate of ammonia are dis- solved in water, and the solution made to 350 c.c; 50 c.c. of this are taken, diluted with the same bulk of water, about 5 c.c. of pure concentrated sulphuric acid added, and,, after warming to 60°, the permanganate solution ftom a burette is run in. At first the color does not disappear rapidly, but this soon alters, and as the liquid to be stan- dardized is dropped in the color becomes instantly dis- charged as long as any of the salt remains unoxidized. As soon as the color becomes permanent, and the solution is of a very faint rose-color, the end point of the reaction is attained ; 71 parts of ammonic oxalate are equivalent to 56 parts of iron. 324 ANALYSIS OP ANIMAL CHARCOAL. Example: 1.620 grammes oxalate of ammonia was dis- solved to 250 c.c, and 50 c.c, equal to .340 gramme of tlie salt, taken for tlie titration, wMch recLuired 42 c.c. of the permanganate. Hence 42 c.c. is equivalent to .340 gramme oxalate, or 71 : 56 : : .340 : x = .2682. • ^ = .006385 gramme iron for 1 cubic centimeter of the standard solution. The standardizing should be done in duplicate. Pure metallic iron in the form of pianoforte-wire may be used in the place of the ammonic oxalate, by the solution of a weighed portion of it in pure sulphuric acid in an at- mosphere of carbonic acid or steam to prevent oxidation.* ESTIMATION OP SOLUBLE MATTER. To 25 grammes of the finely-powdered char are added 200 c.c. of warm water (not above 65°), and the mixture allowed to stand for a half -hour, with frequent agitation. The insoluble matter is allowed to settle, the clear liquid poured off through a filter, and about 100 c.c. more of wa- ter added to the residue, which is treated as before, but for a shorter time, and, after settling, the supernatant liquid is filtered. The washing is repeated once more, the undis- solved residue, together with the liquid, is transferred to the filter, and the insoluble matter remaining on it is washed until free from anything soluble. The combined * Chlorine is set free when permanganate is added to a solution containing hydrochloric acid, which tends to introduce an error in the results of iron de- terminations made under such conditions. Por the small amounts of iron in bone-char, however, the influence of this error in the above estimation may be altogether neglected. (See Presenius' Quant. Analysis, Am. ed., 198.) ESTIMATION OP SOLUBLE MATTER. 335 filtrates are evaporated in a platinum dish over a water- bath to dryness, with the addition of sufficient hydrochlo- ric acid to give the solution a faint acid reaction, in order to prevent the escape of ammonia as carbonate and sul- phide. The addition of the acid alters the combination of some of the bodies present, but the error introduced is slight. The weight of the dried residue is the total soluble mat- ter. After the last weighing the dish is ignited only for a time sufficient to burn off the carbon, and the inorganic re- sidue constitutes the soluble mineral matter, while the dif- ference between this and the total is the organic soluble matter. W. Thorn* determines the organic matter in char by taking 60 grammes, heating with 25 c.c. soda-lye of 1.4 sp. gr. and 200 c.c. of water, and washing out the yellow solu- tion with hot water. The alkaline solution obtained is su- persatxirated with sulphuric acid and titred with solution of potassium permanganate ; 5 parts of organic matter = 1 part of salt, or 1 c.c. of normal permanganate solution = .158 gramme organic matter. This process may give good comparative results. ESTIMATION OF STTGAE. One hundred grammes of powdered char are heated with two or three times its weight of hot water for a half-hour, with occasional shaking ; the clear solution, after settling, is filtered and the washing repeated twice ; and finally the residue is brought on the filter and further washed until all soluble matter is removed. The filtrates are evaporated on * Wagner's Jahresb., 1875, 813. 326 ANALYSIS OF ANIMAL CHARCOAL. a water- bath, in a porcelain dish, to about 80 c.c, caustic alkali being added to very slight alkaline reaction. The solution, after cooling, is made up to 100 c.c, and polarized after the free alkali has been saturated by acetic acid. If the amount of sugar is too small for the saccharimetric test, resort must be had to the inversion method, which is more accurate in this case and should be generally preferred. When this method is used the liquid may be evaporated with the addition of hydrochloric acid to invert the sugar, and the invert-sugar formed estimated by Fehling's me- thod, either gravimetrically or volumetrically. When the char is properly washed the amount of sugar remaining in it is extremely small, and cannot be estimated by the po- larimetric method. ESTIMATION OF SPECIFIC GEATITY. 1. Apparent Specific Gravity. — This is simply a com- parison of the weight of equal volumes of water and char. The determination is made by filling a tared half-litre flask with char, accompanied with a gentle shaking, and taking the weight, which, after subtracting that of the flask, gives that of the half -litre of char. This divided by the weight of the same volume of water gives the apparent specific gravity. This determination is of little use in estimating the value of char, unless the size of the grains in each sample compared is the same, and also that all conditions of the experiments are similar, such as the amount of shaking, etc. The apparent specific gravity is often expressed in another form as the weight of one cubic foot of the mate- rial ; it may be calculated by the formula — SPECIFIC GRAVITY. 327 p^ W X 28.315 453.6 ' in which. P equals the avoirdupois pounds in one cubic foot, and W the weight in grammes of one litre. 3. Absolute or Real Specific Gravity. — Place 50 grammes of the char in a tared 100-c.c. flask partially iilled with distilled water, boU for some minutes to free from air, fill to 100 c.c. after cooling, and weigh. The cal- culation is illustrated by an example : Char + flask + water 180 grammes. Char (50 grammes), flask (55 grammes). 105 " Water 75 " As the flask without char would hold 100 grammes of water, 25 grammes must have been displaced by char; hence g = 2.000 sp. gr. The sp. gr. thus obtained is independent of the pores in the coal, and hence the greater the density, other things being equal, the poorer the quality of the char. ESTIMATION OF THE ABSORPTIVE POWEE. I. The Absorptive Power for Color and Soluble Matter determined on the Large Scale (by Stam- mer's colorimeter. Fig. 33). For this purpose the sugar solution is compared before and after flltration. The color of the liquors referred to the sugar present, is determined according to directions given 328 ANALYSIS OF ANIMAL CHARCOAL. in chap. ix. ; the difference in the solutions, before and after filtration represents the color absorbed. The amount of organic matter and salts taken up is also determined. It is essential, in order that these results should be of any value, that an average sample of each liquor should be ope- rated upon, and it should be especially assured that no "sweet water'*- or syrup foreign to the liquors under ex- amination be allowed to mix with them. The following is an example taken from actual working : Liquor. Per cent, ab- sorbed. Before filtration, j After filtration. Sugar 88.40 523 541 .96 91.30 5.67 2.38 .65 56.0 32-3 574 Glucose Organic matter not sugar Ash Color referred to percent, of sugar. 100,00 54 100.00 23 An estimation made as the above, if from correct samples, is of great value in forming an opinion as to the condition of the char in actual use, and should never be neglected where it is practicable to make it. II. Estimation of the Decolorizing Power in the Laboratory. — This method has to be resorted to in the examination of char for purchase, or when a comparatively small sample is at the disposal of the operator. Dilute any sample of dark-colored molasses or syrup with five times its weight of water, and determine the color of the solution by the colorimeter. Next weigh 100 grammes of the coal to be examined, place it in a flask with 300 c.c. of the dilute DECOLORIZING POWER. 32y sugar-liquor, heat on a water-bath to 100° for one hour, shaking at intervals, filter, allow to cool, make up any loss by evaporation by adding water, and observe the color again. The difference before and after this treatment re- presents the decolorizing power of th0 char. Example : Before filtration 28 After " 18 10 gg = 35.70 per cent, of the original color absorbed. It is important that the conditions in all respects should be the same, in this determination, when made at different times and on different samples. A well-defined method of procedure should be laid down, not to be varied from in any case, as — the char should always be used of one degree of fineness, and the sieve used to bring it to that if necessary ; the dilution and composition of the sugar-liquor should be as nearly as possible the same, as well as the proportion by weight of char to volume of liquor employed, degree of heat, time of the experiment, amount of shaking, etc. ESTIMATION- OF THE COLOR WITH BUBOSCQ'S COLORIMETER. A A' are two glass cylinders with plane bottoms (Figure 43), one of which is destined to receive the solution to be examined, and the other the standard liquor. Two tubes, B B', of small diameter, closed at the lower ends by glass plates, and capable of upward and downward motion by means of a rack andpinion, are placed behind the instrument on the upright support. Each pinion has a pointer, which measures upon the divided scale the respective distances 330 ANALYSIS OF ANIMAL CHARCOAL. between the bottoms A A' and B B'. The upper part of the instrument carries a system of prisms and a small tele- scope, D, which enables the operator to see the relative color of the solutions under examination after the manner of Stammer's colorimeter. A movable mirror placed at E throws the light through the solutions. In the form of the Fig- 43- apparatus shown the light reflected from E had a tendency to enter the tubes out of the exact centre. To remedy this Duboscq has lately made an improvement which consists DUBOSCQ'S COLORIMETER. 331 in interposing between the mirror and the bottom of the tubes a system of two birefrigerent prisms, joined together at their bases so that the line of contact is exactly between A A' extended. The type-liquor is made by dissolving two grammes of caramel in water and diluting the solution to one litre. The caramel is prepared by heating refined sugar for one and a half hours on a paraffin-bath at a temperature not above 215°. A little of the mass should be taken out at the end of that time, inverted by heating with acid, and tested with copper-liquor for sugar ; if any is present the heating must be continued until all the sugar has been de- composed. The caramel should be preserved in a tight bottle. The use of Duboscq's colorimeter is as follows : Of raw sugar or syrup a known weight is dissolved in water, and the solution made to 100 c.c. and observed in the instru- ment. At the commencement of the experiment B B' should stand at the same height, A' being filled with the type-liquor and A Ajvdth the sugar solution to be examined. If the colors of the luminous field of the apparatus appear unequal on either side of the vertical line, A is elevated or depressed by its appropriate pinion until equality of tint is obtained. The relative heights of the two columns of col- ored solution is measured in millimetres on the back of the instrument. The proportion of caramel or coloring matter is in inverse ratio to the heights of the liquid columns. Thus the standard caramel solution contains in 100 c.c. .200 gramme caramel, from which datum the percentage of coloring matter in a sugar solution of known strength may be readily calculated. Example : The heights of the liquid columns as measured on the scale are 20 mm. for the stan- 332 ANALYSIS OF ANIMAL CHABCOAL. dard and 40 mm. for the solution to be compared ; then, as 100 c.c. of the former contain. 200 gramme caramel, we have 20 : 40 : : a; : .200 = .100 gramme coloring matter in 100 c.c. of the solution tested, which divided by the amount of the original substance in 100 c.c. gives the percentage. To test the decolorizing power of char by Du- boscq's Method, a weighed portion of the char is mixed with a known volume of the type-liquor and heated for a half or one hour, with the precautions as to the relative conditions of experiments mentioned on page 329. The difference in color before and after decolorizing shows, by a calculation similar to the one above, the actual amount of caramel removed. Duboscq's process may be used with Stammer's instru- ment, and, in as far as it relates to the decolorizing power of char, Duboscq's is theoretically a better method than Stammer' s, because the type- liquor is of supposed constant composition in the former, thus approaching an absolute standard, while with the latter a solution of constant color or composition cannot always be had. Unfortunately for the accuracy of Duboscq's process, it is practically exceed- ingly difficult, if not impossible, to prepare the standard caramel solution at different times having exactly the same tinctorial power. This fault in the method does not, how- ever, affect the general usefulness of the colorimeter as a measurer of color in sugar solutions. coeenwinder's methob for estimating the absorbing power of char by a solution of calcic stjcrate. To prepare the sucrate solution, dissolve 125 grammes of THE POTASH TEST. 333 sugar in 600 to 800 c.c. of water, add 15 to 20 grammes caustic lime, boil five minutes, allow to cool, and make to one litre. To 100 c.c. of this solution 50 grammes of the char to be examined are added, and the whole left to stand for an hour, with frequent agitation, and then filtered. When the operation is finished, a part of the lime salt is absorbed, and this is to be estimated. By determining the amount of lime by standard nitric acid in 50 c. c. before and after the action of the char, the desired result is obtained. (See estimation of alkalinity, page 258.) ■raEST TO DETERMINE THE COMPLETEWESS OF WASHING AND BURNITSIG. This is by boiling for a few moments small portions of the char with solutions of sodium or potassium hydrate of 20° B. A yellow or brown color shows the presence of or- ganic matter, and the greater the amount the greater the intensity of the color. The char, if properly burned, will give no reaction by this test, while the simply washed but unburned article should not give more tha,n a lemon-color for ordinarily good syrups filtered, or a somewhat darker color for lower products. One circumstance may render the indications of the above test fallacious — that is, when iron and sulphide of calcium are present in the char to a considerable extent, as often happens in old chars, they act upon each other in the pre- sence of .caustic alkali, producing a yellowish or greenish tint in the solution, due to the formation of ferrous sul- phide. This indication may be distinguished from that of the simple action of alkali on organic matter by the ten- dency of the solution in the former case to acquire a tint 334 ANALYSIS OP ANIMAL CHARCOAL. of green on standing, and by the fact that the reaction readily takes place in the cold. Char capable of giving a decided green color under the above circumstances gene- rally carries a high percentage of the sulphide, and is en- tirely unfit for the best uses (page 308). APPENDIX. NOTE CONCERNINa THE ACTION OP THE ORaANIO MATTER NOT SUGAR OCCURRING IN CANE AND BEET PRODUCTS, ON ALKALINE SOLUTION OF COPPER OXIDE. It has been asserted that the organic matters present in impure commercial sugars and syrups have a considerable reductive effect on the copper solution employed in Fehl- ing' s method and its various modifications for the estima- tion of invert-sugar. To avoid this supposed source of error, it has accordingly been recommended that sugar solution before testing, should be treated with excess of basic lead acetate, filtered, the metallic salt remaining in solution precipitated vrith sulphurous acid, and the result- ing liquid after filtering again, used for the sugar deter- mination. In order to prove whether the organic matters acted as asserted with Fehling's solution, the author has made some experiments on the most impure saccharine material obtainable from a variety of sources. The manner of conducting the experiments was as follows: The hot solution of the substance operated upon was treated with excess of basic lead acetate and the pre- cipitate washed thoroughly with a large excess of hot water. To be assured that no sugar should remain in the 335 336 APPENDIX. precipitate as lead suorate, th.e washed magma, after diffu- sion through water, was saturated with carbonic acid by allowing the gas to bubble through the diffused mass for six or eight hours, or longer. After this treatment the precipitate was again well washed, and then, after mixing with water, decomposed by sulphuretted hydrogen, the lead sulphide filtered off, and the resulting dissolved or- ganic matters evaporated to dryness at a gentle heat and weighed. The substance thus separated was heated with Fehling's solution (Violette's), near the boiling-point, for some minutes, the resulting cuprous oxide converted in cu- pric oxide, and weighed, special correction being made for the filter-ash (page 203). The results are given below ; .100 gramme organic matter of the different origins given, caused the reduction of the following amounts of copper oxide : West India molasses 027 gramme CuO Residual syrup from sugar-refining . . .030 " " Beet-molasses 0124 " " Muscovado raw sugar 0246 " " Manilla " 0170 " " .100 gramme invert-sugar reduces. . .2206 " a In order to test whether any sugar might have been re- tained in the precipitates before decomposition with lead, a control experiment was made by adding tartrate of soda and potash to a solution of pure invert-sugar, and precipi- tating with basic acetate of lead. This produced a volumi- nous precipitate similar to that thrown down from impure sugar solutions. The tartrate of lead was treated in the same manner as the compounds of lead and organic matter, NOTE. 33'J' as detailed above, and the tartaric acid obtained after tlie decomposition with sulphnretted hydrogen was heated with the copper solution. .100 gramme reduced .003 gramme CuO. From this it may be concluded that little or no sugar was retained in the organic lead compounds operated upon. As a general result of these experiments, it may be proved by calculation that organic matters in impure su- gars have too small an influence upon the results of the copper test to make it necessary to remove them from the sugar solutions in most cases. When the saccharine ma- terial contains a considerable proportion of these com- pounds, for very accurate work such removal may be desirable. 338 APPENDIX. TABLES. I. Partial List of the Atomic Weights. Aluminium. . Antimony Arsenic Barium Bismuth Boron Bromine... . Calcium Carbon Chlorine Chromium. . . Cobalt Copper Fluorine Gold Hydrogen Iodine Iron Lead Magnesium . . Manganese . . Mercury Nickel Nitrogen Oxygen — Phosphorus. . Platinum. . . . Potassium . . . Silicon Silver Sodium Strontium Sulphur Tin Zinc Symbol. Al 13-75 27-5 Sb 122. 122. As 75- 75- Ba 68.5 137- Bi 2IO. 210. B II. II. Br 8o. 80. Ca 20. 40. C 6. 12. CI 35-5 35-5 Cr 26.2 52.4 Co 29.5 59- Cu 31.7 63.4 F 19. 19. Au 196. 196. H 1. 1. I 127. 127. Fe 28. 56. Pb 103.5 207. Mg 12. 24. Mn 27.5 55- Hg 100. 200. Ni 29-5 59- N 14. 14- O 8. 16. P 31- 31- Pt 98.94 197.9 K 39-1 39-1 Si 14. 28. Ag 108. 108. Na 23- 23. Sr 43-75 87-5 S 16. 32. Sn 59- 118. Zn 32.5 65. TABLES. 339 1-1 o H <: a H z K u z o U a z \ 33.20 3 7-25 1.2990 1.3480 69.1 li.i'i'S" 105-5 34.20 : 8.30 1. 3106 1. 3613 71.2 _ - l^2^( io6. 106.5 35.00 3 35-50 : 9.10 9-65 ' 1.3200 1.3260 1.3720 1.3780 72.4 . - 73-4 107. 107-5 36.00 4 36-50 4 0-15 Q.70 1-3325 ^-3385 1-3855 1-3925 74-4 , 75-2 - i\^7^ 108. 37.00 4 1. 10 1-3450 1-3985 76-4 — = /i.6>Qt'2- 108.5 109. 37-50 A 37-90 4 1-75 2.10 I.3510 1-3562 1.4080 1. 4120 77-4 77-8 - - W.lSb 109.5 no. 38.25 4 38-50 4 2.50 2.80 1.3606 1.3640 I.4180 1-4215 78-7 79-5 - - \u9'l(p 110.5 III. 38.75 4 39-00 4 3.00 3-30 1.3670 1.3700 1.4245 1.4290 80.0 80.6 - - 11.^76" 111.5 112. 39-30 4 39.60 4 3-65 4.00 ^ 1-3740 1.3770 1-4335 1.4380 81.4 82.2 -11.^54, 112.5 113. 39.80 4 40.00 ^ 4.20 4-40 1. 3810 1-3835" I-4415 1-4500 82.9 83.6 - - a 10^ 114. ■ 40-30 ... 1-3875 84.2 115. 40.60 1-^915^ ... 85.2 liG. 40.90 ... 1-3955 85-8 117. 41.20 ... 1.4000 86.5 118. 41-45 ... 1.4030 87.2 119. 41.65 1.4060 87.9 120. 41.90 1.4085 88.5 125. 42.80 ... 1.4215 ... 91.2 130. 43-50 ... I-4315 92.2 342 APPENDIX. V. Boiling-points of Sugar Solutions (after Gerlach). Per cent, sugar. Boiling-point, C. ID. 100.4 a (a. 74. 20. 100.6 X i.ed 30. lOI.O m.-» 40. IOI.5 Mf^-7 50. 102.0 a, r. 6 60. 103.0 a,/ ?■ ■^ '9- 106.5 . 112. ajs. ^ 9 ^. 90.8 130.0 VI. Volumes of Sugar Solutions at Different Temperatures (Gerlach). Temp. C. 10 per cent. 20 per cent. 30 per cent. 40 per cent. 50 per cent. lOOOO lOOOO lOOOO lOOOO 10000 5 10004.5 10007 10009 100 1 2 10016 10 IOOI2 IOOI6 10021 10026 10032 15 1 002 1 10028 10034 10042 10050 20 10033 IOO4I 10049 10058 10069 25 10048 10057 10066 10075 10088 30 10064 10074 10084 10094 101 10 35 10082 10092 IOIO3 I0II4 10132 40 lOIOI IOII2 IOI24 10136 10156 45 I0I22 IOI34 IOI46 10160 10180 ; 50 IOI45 IOI56 IOI7O 10184 10204 i 55 IO170 IOI83 10x96 10210 10229 ] 60 IOI97 10209 10222 10235 10253 65 10225 10236 10249 10261 10278. 70 10255 10265 10277 10287 10306 75 10284 10295 10306 10316 10332 80 IO316 10325 10335 10345 10360 85 10347 10355 10365 10375 10388 ' 90 10379 10387 10395 10405 10417 95 10411 IO418 10425 10435 10445 100 10442 10450 10456 10465 10457 TABLES. 343 VII. The Amount of Lime contained in Milk of Lime of Various Den- sities (Mategczek). I K. CaO I K. CaO Degree Baume. Degree Brix. contained in — litres milk of lime. Degree Baume. Degree Brix. contained in — litres milk of lime. 10. i8.o 7.50 21. 38.3 4. 28 II. 20.0 7.10 22. 40.2 4.16 12. 21.7 6.70 23- 42.0 4-05 13- 23-5 6.30 24. 43-9 3-95 14. 25-3 5.88 25. 45-8 3.87 15- 27.2 5-50 26. 47-7 3.81 i6. 29. 5-25 27. 49.6 3-75 17- 30.9 5.01 28. 51.6 3-70 i8. 32-7 4.80 29. 53-5 3-65 19- 34.6 4.68 30. 55-5 3.60 20. 36.5 4.42 VIII. Density of Lime Sucrate Solutions (Peligot). Per cent, of sugar. Density of sugar solutions. Density when satu- rated with CaO. The sucrate solution contains in 100 parts : CaO Sugar. 40.0 37-5 35-0 32.5 30.0 27-5 25.0 22.5 20.0 17-5 15-0 12.5 10. 5.0 2.5 1.122 1. 116 I. no 1. 103 1.096 1.089 1.082 1.075 1.068 . 1.060 1.052 1.044 1.036 1.027 I.O18 I.179 I.175 I.I66 1-159 1. 148 I-I39 1. 128 I.ii6 1. 104 1.092 1.080 1.067 1-053 1.040 1.026 21. 20.8 20.5 20.3 20.1 19.9 19.8 19-3 18.8 18.7 18.5 18.3 18.I 16.9 15-3 79.0 79.2 79-5 79-7 79-9 80. 1' 80,2 80.7 81.2 81.3 81.5 81.7 81.9 83.1 84.7 344 APPENDIX. l-l o (n •« ei ri «■ o m 7J m a fcj O ei r1 IS a y a ^ "l- C5 15 < o > Qb£>0 ifo "^O irioio t-ivD N t^com t1-5»u^ih t^wwo li^'M t^ en q> in Pj oo tMOO ^'-'oo 5-'-'00«d n a t^^ OiO>OOMMMWrOvo 1~* l-«aO CTiOio O MiNNrotn'* iniTMD i>. CCD OOO " M M M'^^ir' «M«««««N«NNwwNWMNMNr»wcocnencncn>VAMa9 ^M 0*0 S-M o* ■^■^■^'^■vr^^irximrwrnryriiTiKrfO-'O^O^yO^'^ t^f».t« tv t^ t-. tscocOOOCOCOQO 0»OiOia\WOiO O O oio>oooiHHMcd'oddd6ddddddddddddo'6dddwMMHMWMMMMMHMMMMMiHNP»« wi m **■ m -*vo 00 WHO n t^ooo ^eno\N emrto cq»0 umd^moq i>.ao ^.tno mr^^oii- tp-iiroo li-o ti»^ M o ^r*.\D "^N « o ooooo t- in »ii in m irt in m »n t-oa 55 oio m e*1^*\o f^o-m ^^o om '^r«i-i mtv. H N w eo ■* »'*o r^fld a« d* d « « en ■* »nio f>-» oi o m « m ■* irioto oi o m « co ■^o t^^o d- m r« «i tr^o ti eopieoe'icomcOeneomeo^^'V^"^^"*^ V^mmini/'inminin»i>ovoio\o>o*o>o»o'o t>. t>i t^ t». c^ r^ w inQ0>4 tTc^o ^^.m TTtNO eor^o ^jo m mot coo oi^yo w lAO'w t^w inoiN t»wo O ^o-eoao m tv ■* ^ ^ in tn »i-AO vo "o ^o^^t<•.i-«oocQco o>a\o O t«.F^c^p«r«c<>CN.pot^r^ t^i-sc^ t^ t^r>r>>b^>:oaoa3coaoaoaocoaoaocooOcocOQOOoaoaoaoaocoooaocoaD a%a« MOO O>O>00 t>.(^^D^O if»ninT*-'*"»C0e')MCO« N mmw N W NN N NN N « CO eO CO m '^ * iT »r*o »o !*• « <5*i-3-i'YO r>.oo 0(0 1-1 pj eO'^i^AO r^ao o^d w m tn-4-iAg t-*QO diO m « m'^miO r«*o o>d m « m^0'oS>o'o>o p*r^e»»c». t^t^ t>. t'.i>.c-.«5ooooooooco omou"oino»no>noinoirioino»nOinomoino i/io inomoi''Oinot''oino »nOi''oi'"0 cnm«*-^inirfco»o i^t*.ooao cio^r; o mmnn en en ■^ ^Mn u~\o "o r^rvjooo o-oiO o w mpj pjeneo'^'^'n NW noranetMNn nmnn eoeotncnefuncnentnenwicnmeoeo even co cncn^T■*v^■*^v^J■-s■^* tr\o rniH t^f- cw<) cnot^in« o or^o o ^Tt-^oi'T*»0 m cn-»vD en>o c<« m-*»-.N wvo m n t^cnOM 5nfs.o ^rs^ '^roo wio o\Fnt^t^ ■q-oo eor^o ■*oo n-t*oo Tt-CT>cnjo m t>.Mvo m\o o ino*»n bo>-i»iiHN(>< Ncncn'*:'^-'^ lOioiniovo r% t>>r5 r».r^ t»»» OOOOOOOOOOQOOOOOOOqOOO^OOOMWMMMMMMMHMMl-MMMWM t«.u~enooo t^-*M Qoovo t^m q o*inmu>ovovo t>,r>.roaoooa3 0o ota^oioo m hhm em n cnmcn^d--^Tf inuYO^oio tvr<»oooo oOcoo3aoooaoaoaoaooacooocooooocoaocococoaoo>d>oio«otO>Q>OiOiOiOOiO'0>OtO>0«0<<^o>oi lO eno ^*^o O -*eni-i coeocncnTfo o f^^Mvg h t^O (^cn O O't^t^^«*»n(^t«.o cn^-Q »no«o cn>^rs. mM r^rtoo movo woo tJ-oVo n oimMoo '*o c^-com t>.^M t^Tj-i-i o*o cno r^incnoanS eowo't^i^cn ■H H CI C4 en ^■^iniTAO ^xt«.QOoo CO O m « n eO^^f^Oxo t^eooo o»0 m m n en"*^»'">o t^tsoo a*d g en-nt^o enmrvQ e^iri^.o N p^ln^sON « t^o r>.t«*oiw w ^^5^o^o o. t^ rC. [C.cd od oJ og d*d\^dsd o d owtn MPtPipi enEncnio ^OlovOlOvolou^^o^o^ooxo^o«oS^o^ov5^^oVo^o p^ l>. t^. t^ c t^ ts.t^ ►^ t^ t> S. K K Offlo rN»o inintnpj m o aoioo ^aO m ■»*■ tn pi p» w o owooo p~vovo mrr^cnp* m m M e^ co^ufo r^n 0ioiO M N cn^imo p^ioco co <-• n en'^'nio t>.ao 9o ■«■ ■* inomo inoino momo mo mo momo mo mo ino mo mo mo mo mo I'^O "". o mo ino m ' M HI PI M cncO^'*"imvovo c^^acooo 0»0»00>-P».sOQ0 coiooi-ii-ipjpt fH a «< z < s f- a o o o Ix. in o fa pq o & rn ( ) M » a ■=1 m H !(5 W (', o a 0- IS < a g ^' n f/i f, H Q 5 z ^ D Z C O Oh o to Ci n O z < m X H H a (■! a Id H ^ ^ H H a ^ Lh O X Z o •^ h. B «< H E3 "o c as |- GH o c ^' ^iiZ a 0(1.° an TABLES. 345 X. Table showing the Equivalence of the Centigrade Thermometer Scale with that of Fahrenheit. c. F. C. F. C. F. + IOO +212. +63 +I45'4 +26 +7B.8 99 210.2 62 143-6 25 77- 98 208.4 ■ 61 141. 8 24 75.2 97 206.6 60 140. 23 73-4 96 204.8 59 138.2 22 71.6 95 203. 58 136.4 21 69.8 94 201.2 57 134.6 20 68. 93 199.4 56 132.8 19 66.2 92 197.6 55 131. 18 64-4 91 195.8 54 129.2 17 62.6 go 194. 53 127.4 16 60.8 89 192.2 52 125.6 15 59- 88 190.4 51 123.8 14 57-2 87 188.8 50 122. 13 55-4 86 186.6 49 120.2 12 53-6 85 185. 48 118.4 II 51.8 84 183.2 47 n6.6 10 50. 83 181. 4 46 1 14. 8 9 48.2 82 179.6 45 113- 8 46.4 . 81 177.8 44 III. 2 7 44-6 80 176. 43 log. 4 6 42.8 79 174-2 42 107.6 5 42. 78 172.4 41 105.8 4 39-2 77 170.6 40 104. 3 37-4 76 168.8 39 102.2 2 35-6 75 167. 38 100.4 I 33-8 74 165.2 37 g8.6 32. 73 163.4 36 g6.8 — I _ 30.2 72 161.6 35 95. 2 28.4 71 159-8 34 93-2 3 26.6 70 158. 33 91.4 4 24.8 69 156-2 32 89.6 5 23- 68 154-4 31 87.8 6 21.2 67 152.6 30 86. 7 194 66 150.8 29 84.2 8 17.6 65 149- 28 82.4 9 15-8 64 147.2 27 80.6 10 14- 346 APPENDIX. XI. Table showing the Equivalence of the Fahrenheit Thermometer Scale with that of the Centigrade. F. C. F. C. F. C. -|-2I2 +100. +170 +76.67 +128 +53-33 2II. 99-44 169 76.11 127 52.78 210 98.89 168 75.55 126 52.22 209 98.33 167 75- 125 51-67 208 97.78 166 74-44 124 51.11 207 97.22 165 73-89 123 50.55 206 9.6. 67 164 72.33 122 50. 205 96.11 163 72.78 121 49-44 204 95-55 162 71.22 120 48.89 203 95- 161 71.67 119 48.33 202 94-44 160 71. II 118 47-78 201 93-89 159 70-55 117 47-22 200 93-33 158 70. 116 46.67 igg 92.78 157 69.44 115 46.11 igS 92.22 156 68.89 114 45-55 197 91.67 155 68.33 113 45- 196 91. II 154 67.78 112 44-44 195 90-55 153 67.22 III 43-89 194 90. 152 66.67 no 43-33 193 89.44 151 66.11 109 42.78 192 88.89 150 65-55 108 42.22 igi 88.33 149 65. 107 41.67 190 87.78 148 64.44 106 41. II 189 87.22 147 63.89 105 40.55 188 86.67 146 63-33 104 40. 187 86.11 145 62.78 103 39-44 186 85-55 144 62.22 102 38.89 185 85. 143 61.67 lOI 38.33 184 84.44 142 61. II 100 37-78 183 83-89 141 60.55 99 37.22 182 83.33 140 60. 98 36.67 181 82.78 139 59-44 97 36.11 180 82.22 138 58.89 96 35-55 179 81.67 137 58.33 95 35- 178 . 81. II 136 57.78 94 34-44 • 177 80.55 135 57-22 93 33-89 176 80. 134 56.67 92 33-33 175 79-44 133 56.11 91 32.78 174. 78.89- 132 .•- 55.55 90 32.22 173 78.33: 131 55- 89 31.67 172 77-78 .130 54-44 88 31.11 171 77.22 129 53-89 87 30-55 TABLES. 347 XI. — {Continued. ) F. C. F. C. F. C. +86 +*30- +61 +16. 11 +37 +2.78 85 29.44 60 15.55 36 2.22 84 28.89 59 15- 35 1.67 83 28.33 58 14.44 34 I. II 82 27.78 57 13.89 33 0-55, 81 27.22 56 13-33 32 0. 80 26.67 55 12.78 31 0.55 79 26.11 54 12.22 30 — I. II 78 25.55 53 11.67 29 1.67 77 25. 52 II. II 28 2.22 76 24.44 51 10.55 27 2.78 75 23.89 50 10. 26 3-33 74 23-33 49 9-44 25 3-89 73 22.78 48 8.89 24 4.44 72 22.22 47 8.33 23 5- 71 21.67 46 7.78 22 5-55 70 21. II 45 7.22 21 6.11 69 20.55 44 6.67 20 6.67 68 20. 43 6.II 19 7.22 67 19.44 42 5-55 18 7-78 66 18.89 41 5- 17 8.33 65 18.33 40 .4-44 16 8.89 64 17.78 39 3.89 . 15 9-44 63 17.22 38 3-33 14 10. 62 16.67 XII. Changes in Volume of Sugar Solutions when Diluted with Water (after Gerlach). Per cent of sugar Found density at Mean calculated Volume after mix- in solution. ll%"C. density. ing. 70 1.3507 1.3507 1. 0000 60 1.2900 1.28626 .99710 50 1.2329 1.22769 -99577 40 1. 1794 1.17422 .99560 30 1. 1295 1.12521 . 99620 20 1.0832 1. 08013 .99716 • 10 1.0404 1.03852 .99819 1. 0000 1. 0000 1. 0000 INDEX. PAGE Absorptive power of bone-black 299, 301 estimation of 327, 332 Acid, acetic 42, 185, 211 aconitic 211 aspartic 211, 251 butyric 21,211 formic 185, 211 glucic 81,211 gluconic 27, 88 glutaminic 2<^i gummic 185 hexepic 51 hydrochloric 50 isodiglycoethylenic 27 lactic 21,211 levulinic 49, £8 malic 211, 251 melassic 55, Bi, 211 metapectic 251 mucic 27 nitric 28, 93 oxalic 501 211 oxymalonic i£.3 racemic 27 saccharic t. 27, t;5 sulphuric 28, 49 tannic 251 tartaric 27, 211 tnjienic 51 Acids, reactions of sugars with . ., 28 action on milk-sugar 94 Adulterationof raw sugar with dextrin. ... 284 Alcohol, inBuence on results in polarizing . . 75 method of extraction by 180 Alkalies, action on sugars 29 action on cane-sugar 54 action on milk-sugar 94 action on dextrose je, influence on results in polarizing. 175 Alkaline salts in bone-black 307 Alkaline ash 225 Alkalinity, estimation of 258, 272 Alterationof charby use 304 Alum as a decolorizing agent 164 Alummaas a decolorizing agent 164 PAGE Ammonia, action on sugars 30 action on cane-sugar 1^ action on dextrose 81 Amylin 279 Analyses of bone-black 296, 297, 310 of starch-sugar 278, 279 of sugar-ashes 223, 224 Anhydrides of the glucoses 12 Animal charcoal 296 analysis of 311 chemistry of . 296 Anthon's method 282 Apjohn 209 Appendix 335 Arabinose 14 Areometer, the 96, 100 Areometers, of constant weight 100 of constant volume 100 of even scale 101 of uneven scale loi Ash, estimation of , 263, 270, 271 estimation in raw sugar 222 estimation in molasses. 252 analyses of 223, 224 Asparagine 211 Assamar 16, 42 Atomic weights, table of 338 B Balling's areometer no Bardy and Riche 177 Barfoed's test 85 Barley-sugar 42 Barreswill 185 Baume's hydrometer 106 graduation of 107 correction for temperature iro Bschamp on inversion 64 Beet, the 265 estimation of sugar 266 estimation of juice 270 estimationofsugar in juice 271 samplingof. 265 Behr, inversion by adds 46 Berthelot 16, 28 348 INDEX. 349 PAGE Betaine 212 Biliary acids < ■■ 293 Biot 15 Birotation 18, 79 Boivin et Loiseau S9i 284 Bodenbender 30T Boiling-points of sugar solutions 341, 342 Bone-black as decolorant ;.'../. ^ 167 absorption of sugar by i£8 analyses of 296, 297, 310 absorbing power of 299, 301 alteration by use 334 alkaline salts in 30/ density of, absolute 327 density of, apparent 326 nitrogcnin 309 washing and burning of 333 Borax combined with sugar 63 Bomeite 14 Bomeose 14 Brix areometer 112 correction for temperature 114 errorof 112 Bromine, action on sugars 27 Buignet 16,33 c Calcimeter, Scheibler's 313 Cane, the 260 , estimation of sugar in zSo Cane-juice, estimation of sugar in 261 Cane-sugar, determination of 120 inrawsugar 211 estimation in raw sugar 213 estimation in molasses 250 occurrence of 31 estimation in dilute solutions , . . 276 Caramel 42 Carbohydrates 10 Carbon in bone-black 306 cstimationof ' 3" ' Carbonate of lime in bone-black 306 estimation of 3i3 removal by acid 318 Casamajor's mod. of Dumas's method 248 method for quotient 254 Champion and Pellet 68, 71 Champonnois's rSpe 265 Chancel on contraction by inversion 90 Chandler and Ricketts's method 287 Charbond'os 296 Chlorine, action on sugars 27 on cane-sugar 51 Chylariose 87 Centigrade and Fahrenheit scales 346 Circular polarization 122, 179 Clerget's method 136 table 138 Coefficients, method of 237 Collier on the sorghum 31 Colloidal water 270 PAGE Color, estimation of 229, 258, 272 estimation by Duboscq's colorimeter. ^ 329 Colorimeter, Stamraer'sTTTTT. 223 Duboscq's 329 Colorimetry after Monier 233 Compounds of dextrose 83 Contraction in sugar solutions 40, 90 Copper oxide hydrated, action on sugar -26 Copper sulphate for Fehling's solution. — 190 Corenwinder's method 332 Corn-sugar 278 Correction for temperature no, 113 Correction of measuring apparatus 177 Courtonne on the solubility of cane-sugar. . 39 D Damhose 14 Dambonite * 14 Decolorization of sugar solutions 1S4 Decolorizing power of char 328, 332 Densimeter, the : 105 Detection of starch-sugar in cane-sugars . . . 284 Determination of cane-sugar 120, 179 method of Peligot 179 by alcohol iSo by fermentation 181 by inversion and Fehling's method.. .. 182 Determination of dextrose and invert-sugar by Fehling's method 185 Dextran 251 Dextnn as an adulterant of raw sugars 264 Dextrose 74» 75 preparation from starch 75 preparation from urine 76 properties 77, 78 solubilities 77 action of heat on 79 action of acids on 80 action of alkalies 82 action of cupric salts 82 varioiJs reactions 81 combinations 83 combination with water 83 combination with bases 83, 84 combination with sodium chloride 84 qualitative test for, in urine 294 Diabetic sugar 74 estimationof 292 Diabetometer 293 Diastase 15 Double-dilution, method of 167 Di-glucosic alcohols 11, 12 '": Duboscq's shadow saccharimeter 157 ' colorimeter 329 . Duri n, cellulosic fermentation 25 Dulcite 14 Dumas's method 247 Dupr^ 209 Eissfeldt and Follenius 251 . 350 INDEX. Elliptical polarization Errors of optical method by temperature personal error from presence of invert-sugar. .. from use of lead solution from volume of lead precipitate. , ErjrthromanniCe Erythrozyme Eacalyn Exponent of sugar solutions 122 170 170 170 173 165 166 14 95 14 253 Fahrenheit and Centigrade scales, table of. 347 Fehling 186 Fehling's method for estimation of dextrose and invert -sugar 185 for estimation of cane-sugar 182 for exact work 201 for starch-sugar 280 for millc-siigar 2go Fehling's solution 187 Fermentation, estimation of cane-sugar by . 181 analysis of starch-sugar by 281 influence of saline matters on 24 butyrous ig cellulosic 25 lactous 19 mucous 18 vinous 21 Fifter ash for Fehling's method 204 Filtering cylinder 215 Flourens's tables 340, 341 FormatiojT of sugar in plants 15 Fruit-sugar ■..., , 74, 87 Four-fifths method 217 G Galactose 14 Gay Lussac's volumeter 103 Gentele's method ^ 210 Gerlach 340,34^,345 Gil] 165, 174, 196 Girard, preparation of levulose 87 Girard and Laborde 173 Glucose normal solution igi Glucose. . .- 74, 278 Glucoses, the ii Glutaminic acid 251 Grape-sugar 74, 278 Gravimetric estimation by Fehling's method 203 Gunning on the melassigenic action of salts fig H Hamzucker Heat, action on sugars , Hesse on sp. rot. power of lactose . . Hexatomic alcohols Hochstetter on inversion by heat. . PAGE Honey-sugar 74 Honigzucker 87 Homeman 27 Hundert polarization 150 Hydrometer, Baume's 106 Hydrostatic balance, the 96 I leery 16 Inactive cane-sugar 73 Influence of various bodies on polarization, 173 Inosite 14 hex-nitro 28 Insoluble matter, estimation of, in raw sugars 236 Inversion of sugars 129 Inversion of cane-sugar by heat 43 by acids 45 byCOa 48 by sulphurous acid 49 Invert-sugar 89 optical inactivity of 173 estimation of. 1E5, 217 Invertin 23 Iron in bone-black 3°? estimation of 323 Isodulcite 14 J Jackson i5 Jellett 156 prism, the 1^7 Juice beet, estimation of 269, 270 K Knapp's method 206 Knochenkohle 296 Komzucker 278 Krumelzucker 74 L Lactate, calcium 21 Lactin, lactose 91 La Grange on the melassigenic action of salts 70 Lamp, oil 151 Laurent's monochromatic 154 Landolt on personal error 172 Laurent's saccharimeter 159 monachromatic lamp 154 - Lead acetate, basic, preparation of 164 Lead precipitate, error from 166 solution, experiments on error caused by 165 Left-rotating bodies 126 Levulinic acid 49, £7 Levulose, decompositions 87, £8 preparation of 87 properties 87, &8 Light, monochromatic or sodium 154 INDEX. 351 PAGE Lime, action on cane-sugar . 55 Lindo's test 86 Linksfmchtzucker 87 Lowig 17 Lotman 247 Lowenthal and Lenssen on inversion 48 M Malic acid 251 Maltose 14 Maluson the laws of polarized light 123 Mannite 14 Mannitose 14 Marc, estimation of sugar in 275 Marc, estimation of in the beet, by direct method 269 by indirect method 269 after Scheibler 270 Marcker 204 Marks of a good char 303 Marschall on the melassigenic action of salts 6g Mategczek 343 Maumenc 24, 43 Mazzara's test 86 Measuring apparatus, correction of 177 Meissl on inactive invert-sugar 174 Mcissl 203 Meiezitose 14 Mctapectic acid 251 Melassigenic action 64 Metezose 14 Metezite 14 Milchzucker 91 Milk, carbohydrates from 94 Milk-sugar, estimation of. 290 Milk-sugar, specific rotatory power 91 hydrates 92 combinations 92» 94 solubilities 92 action of heat 92 action of acids 93 fermentation of 95 Milk of lime, contents of, in CaO 343 Mitscherlich's saccharimeter 126 Mohr's method for dextrose 205 Monier'a copper solution 187 Morin on inactive invert-sugar 173 Muffle for ash estimation 227 Muntz 176 on inactive invert-sugar , 173 Mycose 14 Mycoderma aceti 21 N Neubauer 186,281, 295 on estimation ofdextrose and levulosc 208 Nichol's prism 122 Nitrogen in bone-black 299, 309 Nucite 14 o PAGE Organic matter, action on Fehling's solution 335 estimation by difference 233 estimation after WalkoflF 234 estimation by lead subacctate 235 estimation in molasses 253 estimation in beet-juice 271 Optically inactive invert-sugar 173 Optical saccharimeters .« 126 rotatory power of sugars 17 Oxygen and air, action on cane-sugar 52 Oxidizing agents, action on sugars 26 action on cane-sugar ^o p Paradextrose 86 Farasaccharose 72 Pasteur ig, 20, 22, 24 Pavy's modification of Fehling's method . . . 210 Payen-Scheibler's process for yield 240 Pefigot 17,179.343 Pellet 65, 176 Peniciliunt glaucum 20 Personal error 170 Phosphate of lime, estimation in char 3 J2 Picric-acid test for dextrose £6 Pinite 14 Plagne 19 Plane of polarization 121 rotation of 123, 124 Pohl .' 16 Polarized light by reflection 120 by refraction 121 Polarization, elliptical 122 circular 122 Polariscope, the 125 Possoz's copper solution iSg Popp, analyses of sugar-cane :■ i Press, car.e 260 Pure sugar, preparation of 170 Q Qualitative tests for cane-sugar 52, y tests for dextrose 85 Quercite 14 Quotient of purity 253, 271 R Raflinationwerthes 240 Raffinose - 14 Rag-sugar 74 Reichenbach 16 Renard 17 Rendements 240 Residues, carbonatation 275 Revivification of char 303 Rhamnegite 14 Richard 15 Right-rotating bodies 126 Right-handed sugar 74 353 INDEX. PAGE Rodewald and Tollens 290 Rohrzucker 31 s Saccharose 31 Saccharum ojfficinarum. 31 Saccharin.*. 17 Saccharides 28 Saccharitneters, Duboscq's shadow 156, 159 Laurent's 1^9 Mitscherlich's 126 shadow 156 Soleil-Duboscq 130 Soleil-Ventzke 143 Schmidt-Hansch 159 Wild's 152 Saccharimeters, equivalence in degrees of various 163 Saccharometer, Vivien's iiS Balling's or Brix no Saccharomyccs cerevisia 23 Sachsse's method 207 Salts in raw sugar 211 combination oi cane-sugar with 62 invcrtive action of 65 action on crystallization 67 solubility in sugar solutions 72 Sampling of raw sugars 212 Scheibler's modification of Paycn's process 240 method for estimating the sugar in the beet 266 method for estimating the sugar in marc 270 calcimeter 313 improvements on the Soleil-Ventzke saccharimeter 144 Scheibler on the solubility of cane-sugar in aqueous alcohol 41 Schleimzuckcr 87 Schmitt's test for dextrose 86 Schmidt and Hansch's shadow sacchari- meter * 159 Schmitz, formula for specific rotatory power of cane-sugar 37 Scheme for ash analysis 228 Schultz on absorbing power of bone-black.. 300 Scums, refinery 273 Scyllite 14 Senkwage ico Sensitive tint : 135 Shadow saccharimeters 156 Sickel 251 Sodium chloride, combination with cane- sugar 62 with dextrose 84 Soleil-Duboscq saccharimeter 130 Soleil-Ventzke saccharimeter 143 Soluble ash 224 Sorghum Holcus 31 Sorghum saccharatum 31 Sorbite 14 PAGE Sorbose 14 Sostman 175 Soxhlet 186, 201, 203, 290 Specific gravity of bone-black, absolute 327 apparent ; 326 Specific-gravity flask, the 96> 98 Specific gravity, determination of 96 Specific rotatory power 124 Stammer's colorimeter 229 Starch-sugar 74. 278 Starkezucker 278 Steiner's analyses of starch-sugar 278 Sucrate of lime solutions, table 343 Sucrates C5 of calcium 56 of potassium ?5» 56 of sodium 36 of barium , 60 of copper 61 oflead 60 of strontium 61 of iron 61 of magnesium 62 Sucre de canne 31 Sucre de fccule 278 Sucre delait 91 Sucre de rasin 74 Sucroses 14 Sucro-carbonate of lime 59 Sugars as a class 9 Sugar, common 31 crystallizable 31 in the nectar of flowers 32 in roots 32 in the beet 32 in stems of trees 32 in leaves 32 in fruits 33 inmanna 34 preparation from natural sources 34 preparation of pure 170 physical properties 35 crystallization of 3^ density 36 specific rotatory power 37 endosmose 39 composition of 39 action of light on 38 solubilities 39* 4^ solutions, tables of 339, 340 action of heat on 41 inversion of, by heat 43 mversion of, by acids 45 action of alkalies on 54 combinations wit'i salts 62 melassigenic action on 64 in bone-black, estimation of. 325 Sulphate of lime in bone-black 307 estimation of 320 Sulphatedash 226 Sulphide of calcium in bone-black 308 estimation of 321 INDEX. 353 PAGE Sweetness, relative, of cane-sugar and dex- trose 1 10 Sweet taste of sugars g of metallic salts 9t ^° Synanthrose 14 Synthesis of sugars 16 T Table, Clerget's , 138 Tables for Scheibler's calcimeter 317, 319 Table of densities and degrees Baume 109, 110 for Balling's areometer 114 of reciprocals 193 of atomic weights 338 of temperatures and concentrations. . 339, 340 of boiling-points for sugar solutions. . 341, 342 of the volumes of sugar solutions at various temperatures 342 showing CaO in milk of lime 343 showing weight of a cubic foot and gallons of sugar solutions 344 of Centigrade and Fahrenheit 345 of Fahrenheit and Centigrade 346 showing relation of percentages, den- sities, and degrees Baume of sugar solutions ' 116 showing . relation of degrees Baume, percentages, and densities of sugar solutions lig Tannin in polarization 251 for estimation of organic matter 234 Tollens, formula for specific rotatory power of cane-sugar 37 Torulaaceti 21 Traubenzucker. . Trehalose Trommer Tunicin u Urine, estimation of sugar in . Ventzke's saccharimeter process for sugar estimation Violette's solution Vivien's saccharometer Volumeter of Gay Lussac Volumes of sugar solutions at various tem- peratures FACE 74 14 185 75 130 261 "5 103 w Walkoffonthe absorbing power of bone- black 30O] 302 Walkoffs method 234 Wallace on the composition of char 296 Waste products, analysis of 273 waters 276 Water, estimation of 217, 252, 264, 270, 271, 283 inbone-black 311 Weighing capsule 213 Wild's polaristrobometer 152 Yeast Yield, estimation of . SCIENTIFIC BOOKS PUBLISBED BT D. VAN NOSTRAND, 23 Murray Street and 27 Warren Street, NEW YORK. Any Book in this Catalogue, sent free by mail on receipt of price. "Weisbach's Mechanics. Fourth Edition, Revised. 8to. Cloth. StO.OO. A Manual OF Theoretical Mechanics. By Julius Weisbach, Ph. D. Translated from the fourth angmented and improved German edition, vrith an introdnctioa to the Calculus, by Eckley B. Coze, A. 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