THE Blowpipe Manual. BY DR. THEODORE SCHEERER, Professor of Chemistry in the Royal Saxon Mining School at Freiberg. TRANSLATED BY WILLIAM S. CLARK. AMHERST: STORRS & McCLOUD, PRINTERS. 1869. Translator's Preface. This little manual has been prepared for the use of the students of the Massachusetts Agricultural College. Those who desire further information upon this most important subject are referred.to Plattner's "Art of Assaying with the Blowpipe." Contents. USE OF THE BLOWPIPE IN QUAIITATIVE ANALYSIS. Pae. Introduction..... 9 I. The Blowpipe Flame and Articles necessary in assaying qualitatively with the Blowpipe,.. 13 Oxidizing and Reducing Flames,.. 13 A. The Blowpipe,...... 16 B. The Blowpipe Flame,....16 C. Supports and Holders for the substances to be heated, 16 (1) Charcoal, p 16. (2) Platinum Wire, p 17.. (3) Platinum Foil, p 18. (4) Platinum Spoon, p 18. (6) Platinum Forceps, p 18. (6) Glass Tubes, p 18. (7) Glass Matrasses, p 19. D. Blowpipe Reagents,..... 19 (1) Soda, p 19. (2) Borax, p 19. (3) Salt of Phosphorus, p 20. (4) Other Reagents, p 20. E. Other Articles for use with the Blowpipe,.. 21 II. Qualitative Examination with the Blowpipe,. 22 Order of the Tests,.... 22 1. Test in Glass Matrass,... 22 Substances which, under certain circumstances, may be detected in this way: Water, Sulphur, Selenium, Tellurium, Arsenic, Quicksilver, Oxygen, Ammonia, Fluorine, Chlorine, Bromine, Iodine, Nitric Acid.. 2. Test in open Glass Tube,.... 25 Substances which, under certain circumstances, may be detected in this way: Sulphur, Selenium, Tellurium, Arsenic, Antimony. CONTENTS. VI 3. Test on Charcoal,..... 6 Substances which may be determined by the Incrustation which they give to the coal: Selenium, Tellurium, Arsenic, Antimony, Bismuth, Lead, Cadmium, Zinc, Tin, Molybdenum, Silver, Metallic Sulphides, Chlorides, Bromides and Iodides. 4. Test in the Platinum Forceps, (as well as, in some cases, on the platinum wire or coal,).. 34 Substances which may be detected by-the Color which they communicate to the blowpipe flame: Soda, Potassa, Casia, Rubidia, Lithia, Strontia, Lime, Baryta, Molybdic Acid, Oxide of Copper, Tellurous Acid, Phosphoric Acid, Boracic Acid, Thallium, Arsenic, Antimony, Lead, Indium, Selenium, Chloride and Bromide of Copper. 5. Test in the Borax Bead,.... 42 6. Test in the Phosphorus Bead,... 43 Substances which may be determined especially by the Colors which they impart to the Beads of Borax and Salt of Phosphorus: Oxides of Cerium, Lanthanum, Didymium. Manganese, Iron, Cobalt, Nickel, Zinc, Cadmium, Indium, Lead, Thallium, Tin, Bismuth, Uranium, Copper, Silver, Platinum, Palladium, Rhodium, Iridium, Ruthenium and Gold, Titanic, Columbic, Niobic, Antimonious, Tungstic, Molybdic, Vanadic, Chromic and Tellurous Acids. Table I, in which the above substances are arranged according to the Colors which they give the beads of Borax and Salt of Phosphorus,... 44 Table II. On the Behavior of Metallic Oxides when heated alone upon Charcoal; with Carbonate of Soda on Charcoal; and in the Beads of Borax and Salt of.Phosphorus on the Platinum Wire,... 52 Table III. On the Behavior of the Alkaline Earths and Earths Proper before the Blowpipe,... 66 7. Test with Soda,...... 70 Substances which, under certain circumstances, may VIH CONTENTS. be detected in this way: Silicic, Titanic, Tungstic and Molybdic Acids, Gold, Silver, Platinum, Tungsten, Molybdenum, Antimony, Arsenic, Tellurium, Copper, Bismuth, Tin, Lead, Thallium, Zinc, Cadmium, Indium, Nickel, Cobalt, Iron. 8. Special Tests for the determination of certain substances,.. 1. These substances are: Potassa, Lithia, Boracic Acid, Sulphuric Acid and Sulphur, Nitric Acid, Fluorine, Chlorine, (Chlorides and Chlorates), Bromine, (Bromides and Bromates,) Iodine, (Iodides and Iodates), Magnesia, Columbic Acid, Alumina, Oxides of Zinc, Tin and Antimony, Titanic and Niobic Acids, Zirconia, Oxide of Magnesia, Tellurium, Arsenic, Phosphorus. ABBREVIATIONS EMPLOYED IN TABLES II. AND III. Bx.-Borax or Biborate of Soda. Ch.-Charcoal. Ct.-Coating or Incrustation. OF1.-Oxidizing Flame. RF1.-Reducing Flame. Sd.-Carbonate of Soda. SPh.-Salt of Phosphorus or microcosmic salt, a phosphate of soda, ammonia and water, which when heated loses its water and ammonia and becomes a monobasic phosphate of soda. CONTENTS. VII Alphabetical List of Certain Substances which may be Detected with the Aid of the Blowpipe. Alnmina, p 44, 66, 80. Magnesia, p 44, 66, 80. Antimony, p 25, 27, 41, 44, 52, Manganese, p 45, 66, 81. 71, 80. - Mercury, p 23, 58. Arsenic, p 25, 27, 41, 52, 71, 81. Molybdic Acid, p 30, 38, 44, 68. Baryta, p 37, 44, 66. Nickel, p 45, 55, 71 Bismuth, p 28, 44, 52, 71. Niobic Acid, p 44, 81. Boracic Acid, p 40, 73. Nitric Acid, p 75. Bromine, p 33, 78. Phosphoric Acid, p 39, 83. Cadmium, p 29, 44, 52. Platinum, p 70. Casium, p 35. Potassa, p 35, 72. Cerium, p 45, 54. Rubidium, p 35. Chlorine, p 33, 78. Selenium, p 23, 25, 26, 42. Fluorine, p. 75. Silica, p 44, 71, 74. Glucina, p. 44, 68. Silver, p 31, 44, 60. Chromium, p 45, 54. Soda, p 34. Cobalt, p 45, 54, 71. Strontia, p 36, 44, 66. Columbic Acid, p 44, 80. Sulphur, p 25, 31, 74. Copper, p 38, 42, 45, 54. Tellurium, p 23, 27, 39, 44, 60, Didymium, p 45. 81. Fluorine, p 75. Thallium, p 29, 44, 44, 60. Glucina, p 44, 68. Tin, p 30, 44, 60, 80. Gold, p 56, 70. Titanic Acid, p 44, 62, 80. Indium, p 29, 42, 44, 56. Vanadic Acid, p 45, 62. Iodine, p 33, 79. Uranium, p 45, 62. Iron, p 45, 56, 71. Yttria, p 44, 68. Lanthanum, p 44. Zinc, p 29, 44, 46, 80. Lead, p 28, 42, 44, 56. Zirconia, p 44, 68, 80. Lithia, p 32, 35, 72. Introduction. The blowpipe is a simple instrument which has for several centuries been used by workers of metals ia various countries to produce suddenly an intense heat. Its use having been chiefly to melt the solder employed in fastening together pieces of more infusible metals, it is called by the Germans soldering pipe. The simplest and most ancient form of the blowpipe is a hollow, conical, metallic tube, which at the small end is bent without a sharp turn to a right angle. In using, the larger end of this is taken into the mouth and a stream of air blown into it, which is applied as it issues from the point exactly like the blast from a bellows. The blowpipe may, therefore, be regarded as a small bellows fed by the mouth, and its heating effect depends upon the same principles. In this rude application and form the blowpipe was of no importance to science. This it came first to possess when the careful study of several scientific men had converted it into one of the most valuable instruments for the chemist and mineralogist, as well as for miners and metallurgists. The fol 10 INTRODUCTION. lowing historical sketch shows how this was gradually accomplished. Anthony Swab, a Swedish counselor of mines, who lived in the first half of the eighteenth century, was, so far as is known, the first who undertook to apply the blowpipe to the chemical examination of ores and minerals.' Next to him, the Swedish mineralogist Cronstedt, used the blowpipe for determining and distinguishing minerals, with' special reference to the chemical system of mineralogy published by him in 1758. Engestroem, who in the year 1765 translated this system into English, added a description of Cronstedt's method of using the blowpipe. In the year 1773 this description was translated into Swedish, and soon after, into several other European languages. Imperfect as the application of the blowpipe then was, it attracted immediately great attention from the rapidity and certainty of its results. Nevertheless, the new art, which easy as it appeared required long continued practice, made at first but little progress. It received important assistance from the efforts of Bergmann, who employed the blowpipe for qualitative examinations in the whole province of inorganic chemistry, and showed. how by it' aid very minute quantities of mineral substances could be detected, the discovery of which in any other way would be much more difficult. Bergmann published the results of his experiments in a work, which was printed in Latin at Vienna in 1779, and was translated into Swedish by Hjelm in 1781. Upon the death of Bergmann, which happened soon after, (in 1784), Gahn pursued still INTRODUCTION. 1I further the path struck out by the latter. He attained by persevering zeal to great skill in the use of the blowpipe, without, however, recording anything of his rich experience, which would have been for the most part lost except for his obliging readiness to communicate the art to any one desirous of acquiring it. The young Berzelius, whom Gahn regarded with peculiar interest as a student of science, was thus enabled to possess himself of his knowledge, and upon this foundation to build greater. Gahn had made a good selection; a person better adapted for this further development of the art could scarcely have been found. By him the application of the blowpipe was not only in a high degree perfected and extended, but at the same time by his personal instructions and writings so widely diffused that it has now become an essential part of the knowledge of every chemist and mineralogist. In the year 1821 Berzelius published his excellent "Use of the Blowpipe in Chemistry and Mineralogy," of which since that time several editions have appeared and which has been translated for the use of American students by Professor J. D. Whitney. All the efforts of those who thus far had used the blowpipe in chemical experimentation had been directed to qualitative analysis. Harkort, however, seizing upon the fruitful idea of employing the blowpipe also in quantitative analysis became the founder of a new branch of the blowpipe art. In 1827 appeared as the result of his experiments made in Freiberg the first number of his "Art of Assaying with the Blowpipe" containing 12 INTRODUCTION. the article on silver. He was prevented from issuing the second number, which was to contain the methods of determining lead, copper and tin, by a call to Mexico, where he died a few years after. Plattner, his successor, perceiving the importance of developing the subject, employed himself for many years in applying to practice the idea of Harkort. His perseverance and ingenuity enabled him to bring the art of assaying quantitatively with the blowpipe to a degree of perfection which had been previously thought impossible. Plattner has given the results of his experiments both in qualitative and quantitative assaying in his work, "Art of Assaying with the Blowpipe," of which the first edition appeared in 1835 and the second in 1847, and which has been translated and published in London. The methods of assaying qualitatively and quantitatively with the blowpipe, in the state of perfection to which they have been brought by Berzelius and Plattner, are sciences so extensive that a considerable amount of time and practice are required to become familiar with them. Especially is this true of quantitative assaying, which indeed is seldom acquired by chemists, but is almost exclusively employed by practical metallurgists. The following description of the apparatus, reagents and methods to be employed in qualitative analysis with the blowpipe, is believed to be sufficient for the use of beginners, and even for most of the students in the scientific schools and colleges of the country. I. THE BLOWPIPE FLAME AND ARTICLES NECESSARY FOR ASSAYING QUALITATIVELY WITH THE BLOWPIPE. The blowpipe flame is produced when with the aid of a blowpipe a current of air is driven in accordance with certain rules through the flame of a candle or lamp. The best flame for this purpose is that of an oil lamp with a wide and rather thick wick. The principal requisites to the production of a good flame are first, the steadiness and sufficient durability of the blast; and secondly, the proper application and management of the same. The first will be treated of along with the description of the blowpipe. In regard to the second point, the flame may be made to produce upon the heated substance either an oxidizing or a reducing effect. The oxidizing and reducing flames are the principal agents in the whole art of assaying with the blowpipe. He who understands how to produce these flames of the right kind and of sufficient permanence has overcome one of its most difficult points. To form a reducing flame, the point or jet of the blowpipe is held parallel with the somewhat 14 BLOWPIPE FLAMES. obliquely cut wick and in such a way that it just touches the side of the flame. The result, will be a yellow, luminous flame. An oxidizing flame is produced when the blowpipe jet is introduced into the flame about one-third the width of the wick. At the same time it is well to blow a little harder than in the production of the reducing flame. The oxidizing flame is of a blue color and possesses but little illuminating power. The yellow color and luminous character of the reducing flame result from the solid particles of carbon, which unconsumed, but white-hot, float in the burning gases till they are burnt upon the outside of the conical flame. In the oxidizing flame, which exhibits the blue color of burning carbonic oxide gas, these particles of carbon are wanting. It is not difficult to give the reason for the production of these unlike flames. In the reducing flame the less powerful blast from the blowpipe drives the whole flame before it without causing a complete mixture of the combustible gases with the air; while in the oxidizing flame a more powerful stream of air is thrown directly into the flame, and is thus more thoroughly mixed with the burning gases. In the latter case, therefore, a much more complete combustion must take place than in the former. If a piece of a substance capable of oxidation be held directly before the point of the oxidizing flame, it will be heated by it, and will be oxidized by the surrounding atmospheric air. If a powerful blast be used in this THE BLOWPIPE. 15 operation, a portion of the air will pass unconsumed through the point of the flame and increase its oxidizing effect. Not only is the oxidizing flame employed for oxidation, but also, on account of the greater intensity of its heat, for determining the fusibility of substances. It should here be observed that the point is the hottest part of the flame. The reducing flame has the greatest reducing effect when the substance operated on is introduced so far into the flame as to be completely surrounded by it and thus protected from the oxidizing influences of the atmospheric air. It must not, however, be introduced so far into it as to allow it to become covered with carbon, which would diminish the heat, and sometimes produce other injurious effects. A.-THE BLOWPIPE. The most convenient form of the blowpipe is that invented by Berzelius. It consists of five parts, which are so fitted.together that they can be readily taken apart for cleansing or transportation. These parts are a mouthpiece, a narrow tube seven to nine inches long, an air-chamber to collect.lhe condensed vapor of the breath, a small tube inserted into the air-chamber at riglht-angles to the larger one, and a jet with a minute orifice for the escape of the blast. The mouthpiece may be either funnel-shaped to press against the lips, in which case it is made of horn, or a mere extension of the larger tube, formed of bone,. ivory or silver, the tube itself being usually of brass. 16 SUPPORTS FOR ASSAY. The jet should be a conical piece of platinum properly bored and drilled to fit the tip of the shorter tube and to allow the escape of a very small stream of air. Care must be taken that the orifice be not too much enlarged in removing the carbon which may collect upon and obstruct it. This is best done by heating the jet to redness. With sufficient practice it is possible by using the wide mouthpiece to blow uninterruptedly from five to, ten minutes. During this continuous blowing the experimenter must breathe through the nose, using the palate as a valve, and force the air out by means of the. muscles of the cheeks. B.-THE BLOWPIPE FLAME. The flame for use with the blowpipe may be that of coal gas, a candle, or a lamp filled with oil, burning fluid or alcohol. Where gas cannot be had, it will be found convenient to have both an alcohol and an oil lamp. These may be either of glass or metal. C.-SUPPORTS AND HOLDERS FOR THE SUBSTANCES TO BE HEATED. For holding the substances which are to be exposed to the flame of the blowpipe must be employed, of course, materials which are not easily injured by heat. The following articles are most commonly used:1. Charcoal.-The best for this purpose is a well burnt, compact and dry coal of pine ori other soft wood, CHARCOAL. 17 free from knots, and having the rings of growth as close together as possible. Its good quality may be known by its clear, ringing sound when struck. This should be sawed into parallelopipeds six inches in length and two in width in such a way that the rings of growth are cut off at right-angles to two of the long sides. These sides of the coal are the ones for use. The substance to be heated is laid near the edge of the coal, sometimes in a shallow depression made in it. The other two long sides of the coal, which run parallel with the rings of growth or rather with tangents to these, are unfit for use, since in consequence of their heterogeneous structure they often burn with very uneven surfaces and sometimes snap off. A substance is heated upon coal when it is intended to reduce it, to prevent its oxidation, or when the unavoidable reducing effect of contact with coal can exert no injurious influence upon the desired result. 2. Platinum Wire, about 0.4 of a millimeter in thickness. A long piece of this is bent several times around in the form of a ring and the free ends bent up into small hooks. The ring is held upon the index finger of the left hand, and one of the hooks, filled with the substance to be examined, exposed to the flame of the blowpipe. Borax, or salt of phosphorus, is commonly melted first to a transparent bead upon the hook, and then the substance to be tested, in the form of small pieces or as a fine powder, heated with it, in order to observe its reaction with these fluxes both in the oxidating and in the reducing flame. Of course, care 18 PLATINUM AND GLASS. must be taken not to treat in this way metals or other substances which under such circumstances would attack the platinum wire. 3. Platinum Foil.-This is used for fusing substances which must not be subjected to any reducing influence, as is unavoidable upon coal. The platinum foil, which should be about 2 inches long and 1 inch wide, may be laid upon a piece of charcoal or held in forceps. 4. A Platinum Spoon, about half an inch wide. While in use the handle may be fastened to a holder made for the purpose and furnished with a screw for securing it, or may be stuck into a cork. Such a spoon is used for melting certain substances with bisulphate or nitrate of potassa. 5. Forceps, with platinum points. Their form is such that the two platinum points are separated by pressing upon the heads of rivets. Between the extremities of the platinum points is introduced a fragment of the substance to be tested before the blowpipe either with reference to its fusibility or the color which when heated it imparts to the blue flame. The whole forceps are from 5 to 6 inches long. 6. Glass Tubes, about 6 millimeters in diameter, and from 5 to 6 inches long. These are employed chiefly for roasting substances containing sulphur, arsenic, selenium, tellurium or antimony, which when heated with certain precautions in an open tube either deposit various sublimatesupon the inner surface of it or give off an odor by which they may be recognized. BLOWPIPE REAGENTS. 19 7. Glass Mattrasses, which can be easily made by fusing together one end of a glass tube, Their length should be about 3 inches. They are used in heating substances which contain volatile ingredients to protect them as much as possible from the influence of the air. The volatile substance driven off is deposited, in this case, upon the inner surface of' the tube, but not in an oxidized condition as when heated in an open tube. D.-TTHE BLOWPIPE REAGENTS. In most blowpipe experiments the number of reagents employed is very limited and the quantity of these required very small. There are only three reagents which can be said to be extensively used. 1. Soda.-Anhydrous carbonate of soda, which for certain purposes must be free from sulphuric acid. Soda is used principally to assist in the reduction of metallic oxides and sulphides upon charcoal, to decompose silicates and to determine the solubility or insolu. bility of a substance when melted with it. 2. Borax.-Purified borax freed by heat from the greater part of its water of crystallization and pulverized. In using it, the red-hot hook of the platinum wire is dipped into the powder and the portion adhering to it melted in the flame of the blowpipe, and this operation is repeated till the bend of the wire is filled with a globule which both hot and cold must appear perfectly transparent and colorless. The still soft bead of borax is thea dipped into the powder of the substance to be tested, so that a suitable quantity of the same ad 20 SPECIAL REAGENTS. heres to it, which can then be subjected to the influence of the melted borax glass in the flame of the blowpipe. The solubility or insolubility of the assay is to be observed, and also the color of the bead in the oxidizing and in the reducing flame both while hot and after cooling. 3. Salt of Phosphorus, the well known double phosphate of soda and ammonia. It cannot be melted to a bead directly upon the platinum wire without difficulty, (since, so long as ammonia and water are disengaged, it drops off easily), and must, therefore, first be freed from these by heating gradually upon charcoal, and then taken upon the wire. The use is exactly like that of borax. Besides these principal reagents, a few others are, in certain cases, employed, viz: Saltpeter, for oxidizing melted substances. Bisulphate of Potassa, for expelling and determining certain volatile substances, (lithia, boracic acid, nitric acid, hydrochloric acid, bromine, iodine), as well as for the decomposition of titanates, tantalates and tungstates. Nitrate of Cobalt, chemically pure and in solution, especially for testing for alumina, magnesia, oxide of zinc, oxide of tin, and titanic acid, which moistened with the solution of cobalt and heated assume certain characteristic colors. Silica, for various purposes. Fluor-spar, mixed with a certain quantity of bisulphate of potassa, for detecting lithia and boracic acid. Oxide or Oxalate of Nickel, for determining the presence of a large quantity of potassa in salts containing at the same time soda and lithia. Oxide of Copper, for detecting chlorine, bromine and BLOWPIPE IMPLEMENTS. 21 iodine. Tin, in the shape of foil, for assisting in the reduction of substances dissolved in borax, or salt of plhospllorus. The hot bead, resting upon charcoal, is to be touched with tin foil, so that a portion of this remains upon it, and then heated a few seconds in as powerful a reducing flame as possible. Silver, for detecting sulphur and sulphuric acid. The blowpipe reagents may be best kept in bottles, well stopped with ground glass stoppers, —which may be packed in a wooden box constructed for the purpose. In traveling, means should be adopted lo prevent the stoppers from becoming loose and falling out. E.-OTHER ARTICLES NECESSARY IN ASSAYING WITH THE BLOWPIPE. The method of using these articles, of which some are rather convenient than indispensable, requires no explanation. The following are, therefore, merely mentioned: a hammer, a small anvil, a steel mortar, an agate mortar, files of various sorts, a knife, scissors, a magnet, a microscope, &c., &c. 2 II. QUALITATIVE EXAMINATION WITH THE BLOWPIPE. This consists of the performance of certain operations, and the accurate observation of the resulting phenomena, from which the presence or absence of certain substances may be known. These operations may be undertaken most advantageously in the following order, viz: Test of the substance to be examined, first, in a glass matrass, i. e. in a glass tube closed at one end; second, in a glass tube open at both ends; third, on charcoal; fourth, in the platinum forceps; fifth, in the borax bead; sixth, in the phosphorus bead; seventh, with soda. After these tests, it is often necessary to make some experiments for the detection of certain substances, the presence or absence of which could not be positively determined by the preceding operations. 1.-TEST IN GLASS MATRASS. The clean and perfectly dry matrass, containing a small quantity of the substance to be examined, is heated at the lower end at first gently over the flame of a spirit lamp, and then gradually more intensely before the blowpipe, till the glass begins to soften. TEST IN GLASS MATRASS. 23 It is to be noticed whether anything is sublimed or volatilized, as ex. gr. water, quicksilver, sulphur, selenium, tellurium, arsenic. The first three may be readily recognized from their well known properties. In case water is sublimed, it should always be noticed whether it gives an acid or alkaline reaction with litmus paper. When organic substances are present, the fluid deposited on the walls of the tube has a characteristic burnt taste and odor. A microscope is often necessary to detect a small sublimate of quicksilver; its use should indeed rarely be dispensed with in these operations. Selenium gives a red subli mate; if a large quantity be present so that a thick crust is deposited, the color in the lower part of the tube is steel-gray. Tellurium produces a gray sublimate. Arsenic yields a black deposit, which, when the quantity is considerable, has a somewhat'metallic iuster. It must not, however, be concluded, because these reactions de not appear, that these elements are not present, since sulphur, selenium, tellurium and arsenic especially may occur in compounds from which they either can not be liberated by such ignition, or at least not in a pure condition. It is also to be observed that two or more of them may be present in a compound and may be sublimed together, by which the difficulty of recognizing them is more or less increased. This is very often the case with sulphur and arsenic. These sometimes give a sublimate, which below consists of metallic arsenic, but higher up appears successively black, brown, red and yellow; colors due to sulphide of arsenic, which is more volatile than the metal. Oxygen and ammonia, 24 TEST IN GLASS MATRASS. when disengaged from a substance by heat; may also be detected in tile matrass; the first, by introducing a burning splinter of wood; the last, by the introduction of a strip of reddened litmus paper. Commonly, however, ammonia is not given off in a pure state but combined with an acid, and then a white sublimate of an ammoniacal.alt is deposited. By mixing the assay with lime or soda, and then heating it in a mattrass, fiee ammonia is liberated and easily recognized. Some other substances, especially fluorine, chlorine, bromine, iodine and nitric acid, cal be detected in the matrass: since this; however, cannot in most cases be done by heating the substance under examination alone, but only by the use of some particular reagent, the method will be given it the eighth sectiol, which treats of the performance cf special experiments for the detection of certain substances. It is to be observed, secondly, whether the substance heated is in any way altered, ex. gr. changes its color and perhaps in cooling resumes it, varies its form or state of aggregation, exhibits a flash of light or phosphorescence, decrepitates, &c., &c. To treat in a special manner all such cases here would occupy much space, and still not obviate the necessity of more exact chemical knowledge, which the skillful experimenter with the blowpipe must always have at command. The test in the matrass gives in many cases, as appears from the preceding, no distinct proof, but often only indications of the presence of substances which can be determined with absolute certainty only after still further TEST IN THE OPEN TUBE. 25 experimentation. The indications are nevertheless of importance, and afford much assistance towards the final decision. 2.-TEST IN THE OPEN TUBE. A portion of the assay finely pulverized is introduced about a half an inch into the tube, and this gradually heated at the place where the substance lies. The tube should be held a little inclined, so that the current of heated air passes over the assay, and upwards through the upper and longer part. In this way the assay is roasted, i. e. exposed to an oxidizing heat, by which various substalces are volatilized and rendered recognizable. Sulphur is disengaged as sulphurous acid, which may be easily known by its peculiar suffocating odor. Selenium is but little oxidized, and deposits a red or steel-gray sublimate, at the same time giving the very characteristic odor of selenium vapor-resembling that of decayed horseradish-a ready and sure proof of its presence. Arsenic is volatilized as arsenious acid, antimony, as oxide of antimony and tellurium as tellurous acid, all of which form a white sublimate. That of arsenious acid is distinctly crystalline, while the others appear pulverulent. Arsenious acid and oxide of antimony can be driven forward by heat from the place where they have been deposited, but in the case of tellurous acid, this takes place only in appearance, since it fuses to small transparent drops, which may be detected sometimes by the naked eye, though better with the aid of a microscope. The roasting process must be carried on slowly with 26 TEST ON CHARCOAL. a gradually increasing temperature and a good current of air, produced by the inclination of the tube.; since otherwise, unoxidized volatile substances might be sublimed, and the assay fused together so as to prevent further oxidation. To roast a substance as completely as possible, it is necessary after heating it some minutes, to grind it in an agate mortar, and then to repeat the roasting. This alternate heating and grinding must be continued till nothing more is sublimed. 3-TEST ON CHARCOAL. The same things are to be observed in heating on charcoal as in using the matrass. Especially important is it to become familiar with the color and certain other properties of the incrustations which different substances deposit when heated on charcoal. These are more particularly treated of in the following synopsis taken from Plattner's "Art of Assaying with the Blowpipe." SELENIUM melts easily, and gives in the oxidizing or reducing flame brown fumes, and deposits an incrustation which at a little distance from the assay is steelgray, with a slight metallic'luster, and at a greater distance, dull and dark-gray, inclining to violet. This incrustation is readily driven from one place to another by the oxidizing flime, but, if touched with the reducing flame, vanishes, coloring the flame at the moment beautiful ultramarine. When selenium fused on coal,or a deposit from it, is touched with the blowpipe flame a strong odor of decayed horseradish is perceptible, due TEST ON CHARCOAL. 27 to the gaseous, colorless oxide of selenium which is thus produced. TELLURIUM melts very easily, gives off fumes and deposits on the coal, not far from the assay, both in the oxidizing and in the reducing flame, tellurous acid. The deposit is white, with red or dark-yellow edges, and may be driven from place to place by the oxidizing flame, but in the reducing flame vanishes, coloring the flame at the same time green, or, when selenium is present, bluishgreen. ARSENIC volatilizes without fusing, and deposits upon the coal, in the reducing as well as in the oxidizing flame, arsenious acid. The deposit is white, in thin layers, grayish, and at some distance from the place where the assay was laid. It is removed instantly when merely warmed by the blowpipe flame. If heated suddenly in the reducing flame, it vanishes, giving the flame a feeble light-blue color. When volatilized it gives a strong alliaceous odor, which is peculiar to the suboxide of arsenic. ANTIMONY fuses readily, and incrusts the coal with oxide in both flames. The incrustation is white, in thin layers, bluish, and nearer the assay than that of arsenious acid. By a gentle heat from the oxidizing. flame, it may be driven from one place to another without coloring the flame, but, if exposed to the reducing flame it changes its positions with a slight greenishblue color. The oxide of antimony being much less 28 TEST ON CHARCOAL. volatile than the arsenious acid may be easily distinguished from it. If metallic antimony be melted on charcoal and heated to redness, and then allowed to remain undisturbed, it continues a long time red-hot, and gives off dense white fames, which are partly deposited upon the coal, and partly around the globule of metal in white, pearly crystals. This phenomenon depends on the fact that the red-hot fluid globule of metal absorbs oxygen from the air, oxide of antimony is formed, and thus so much heat liberated as is necessary to keep the very fusible antimony in a melted state for some time, till it becomes covered with crystals of the oxide. BISMUTH fuses very easily, and deposits on the coal oxide of bismuth, both in the oxidizing and in the reducing flame. The deposit is, while hot, dark orangeyellow, when cold, lemon-yellow, and in thin layers, bluish-white. The yellow deposit consists of pure oxide of bismuth, and the bluish-white, which is farthest from the assay, of carbonate of bismuth. The bismuth incrustation is deposited a little nearer the assay than that of antimony. It may be driven from place to place by either flame, since the oxide is reduced on the coal at a red heat, and the metallic bismuth then volatilized and reoxidized, but does not, when heated in the reducing flame, impart to it any color. LEAD melts easily, and gives the coal in either flame an incrustation of oxide at the same distance from the assay as that of bismuth. The deposit while hot, is dark lemon-yellow, after cooling, sulphur-yellow, and in TEST ON CHARCOAL. 29 thin layers, bluish-white. The yellow crust is pure oxide of lead, and the bluish-white, carbonate of lead. The yellow deposit when heated in the oxidizing flame changes its place for the same reason as the oxide of bismuth, and without coloring the flame; in the reducing flame it changes its position, tinting the flame with ultramarine. THALLIUM melts, volatilizes and deposits a brown incrustation, coloring either flame a brillant green. CADMIUM melts readily, takes fire in the oxidizing flame, burns with a dark-yellow flame and brown fumes, and deposits on the coal near the assay oxide of cadmium. This exhibits its peculiar color best when completely cold; it is reddish-brown, in thin layers, orangeyellow. The deposit of oxide of cadimum may, since the oxide is easily reduced, be volatilized by either flame, but without imparting to it any color. Around the outer edge of the incrustation the coal sometimes exhibits pavonian tints. INDIUM fuses readily, forms in the oxidizing flame a coating brown while hot, and yellow when cold, and which touched with the reducing flame colors it blue. ZINC fuses easily, takes fire in the oxidizing flame, burns with a very luminous, greenish-white flame and dense white fumes, and gives the coal an incrustation of oxide. This is rather near the assay; while warm, yellow, and when completely cold, white. Heated in the 30 TEST ON CHARCOAL. oxidizing flame it glows, but is not volatilized because it cannot be reduced by the heated coal on which it rests. Even in the reducing flame it is volatilized but slowly. TIN melts without difficulty, and in the oxidizing flame becomes covered with oxide, which may be removed by a puff of air; in the reducing flame the fused metal presents a brilliant surface and incrusts the coal with oxide. The incrustation is while hot, slightly yellow, and somewhat luminous in the oxidizing flame; but, upon cooling, it becomes white. It is so near the assay as to touch it on all sides. It cannot be volatilized. MOLYBDENUM, in metallic form, cannot be fused before the blowpipe, but when heated in the exterior flame gradually oxidizes, and covers the coal, at a little distance from the assay, with molybdic acid, which is deposited in some places, especially nearest the assay, in transparent, crystalline scales, but elsewhere in a pulverulent form. The deposit has while hot, a yellowish color, but on cooling becomes white. The crystalline scales are best produced, by heating the assay as far as possible from the point of the blue flame. The pulverulent molybdic acid can be driven about by either flame, but the place which it leaves appears, after it is completely cold, dark copper red and has a metallic luster, from oxide of molybdenum, which is formed by the reducing effect of the coal on the acid, and which is not volatile. In the reducing flame, metallic molybdenum remains unchanged. TEST ON CHARCOAL. 31 SILVER, held for sometime in a fluid condition by a powerful oxidizing flame, gives a very slight deposit of dark red oxide. In combination with a small quantity of lead, there appears, first, a yellow deposit of oxide of lead, but afterwards, when the silver contains less lead, it colors the coal outside the yellow crust dark red. If the silver contain a little antimony, there appears, first, a white incrustation of oxide of antimony, which, if the blowing be continued, becomes red. An alloy of silver, lead and antimony gives, after the latter metals are mostly volatilized, a copious, carmine red deposit. Such a deposit may also sometimes be obtained by heating alone on charcoal a rich ore of silver. SULPHIDES, CHLORIDES, BROMIDES, AND IODIDES OF THE METALS.-In assaying with the blowpipe, not only are pure metals found, which being somewhat volatile, may be detected by the incrustation which they give the coal when sublimed, but there are also compounds which deposit a white crust upon the coal, that may be driven off by the oxidating flame, and very often resembles closely a deposit of oxide of antimony. Here belong of the sulphides, those of potassium and sodium, which while forming from the slllphates in the reducing flame on coal, yield a white, and not very volatile incrustation of sulphates, produced by the reoxidation of the volatilized sulphides. This, however, does not occur till the sulphates have sunk into the coal, and given off their oxygen. Sulphides of potassium being more volatile than sulphides of sodium, the former are deposited earlier, and in greater quantity than the latter. This deposit, 32 TEST ON CHARCOAL. when touched by the reducing flame, disappears, imparting to the flame, when consisting of sulphate of potassa, a bluish violet color, and, when of sulphate of soda, a reddish yellow. Sulphide of lithium, formed by the reduction of sulphate of litllia on coal, is also volatilized by an intense heat, but more difficultly than sulphide of sodium, and gives, instead of a pure white, a greenish white, thin crust, which touched with the reducing flame vanishes, coloring the flame caimine red. Tlhe sulphides of lead and bismuth also belong here. Each of these sulphides, both in the oxidizing and the reducing flame, affords two different deposits of which the most volatile is white, and is a sulphate. When these deposits are heated in the reducing flame, that of lead disappears, communicating a blue tinge to the flame; that of bismuth vanishes, but does not color the flame. The incrustation nearest the assay consists of the oxide of the metal, and may be recognized from its color, both while hot and after cooling. There are indeed several other sulphides of metals which incrust the coal, when thoroughly heated before the blowpipe, with a more or less abundant white deposit, ex. gr. sulphide of antimony, sulphide of zinc and sulphide of tin; but the deposit consists only of the oxides, and is in the oxydating flame either volatile or fixed. Among the chlorides of the metals, several possess the property, when heated before the blowpipe on coal, of volatilizing and depositing a white incrustation, viz: the chlorides of potassium; sodium mnd lithium, after sinking into the coal in a fluid state, volatilize and give TEST ON CHARCOAL. 33 a white deposit near the assay, (chloride of potassium yields the most abundant, and chloride of lithium the least, which also instead of being pure white, is grayish); chlorides of ammonium, quicksilver and antimony, which volatilize without melting; chlorides of zinc, cadmium, lead, bismuth and tin, which first melt and then afford two incrustations, viz: a white, volatile one of chloride, and a less volatile one of oxide. These in the reducing flame disappear, a part of them with a colored flame. That of chloride of potassium is bluish, inclining to violet, and that of chloride of sodium, reddishyellow, of chloride of lithium, carmine red, and that of chloride of lead, blue; the remainder do not color the fljme. Chloride of copper fuses and colors the flame intense ultramarine. If the blowing be long continued, it may be observed that one part of the assay is volatilized with white fumes lhaving a strong odor of,chlorine, and another deposits on the coal three rings of different colors, of which the one nearest the assay is dark-gray, the next dark-yellow to brown, and the third bluish-white. In the reducing flame a portion of these may be made to change position, coloring the flame at the same time ultramarine. Of the bromides and iodides of metals which appear on coal very similar to the chlorides, should be particularly noticed here the bromides and iodides of potassium and sodium. These melt and are absorbed by the coal, and are then volatilized with white fumes, a part of which forms at some distance from the assay a white crust on thl charcoal. This when touched with the re 34 TEST IN FORCEPS. ducing flame disappears, the bromide and iodide of potassium coloring the flame bluish, inclining to violet, and bromide and iodide of sodium, reddish-yellow. 4.-TEST IN THE PLATINUM FORCEPS. It having been settled by previous experiments that the assay does not when heated attack platinum, a small fragment or splinter is taken in the forceps and exposed to the point of the exterior flame. Substances which attack platinum may be heated on coal, or, if easily fusible, on the platinum wire. The object is not only to determine the fusibility of the assay, but also the presence of certain substances which under these circumstances impart more or less distinctly a color to the blue flame of the blowpipe. Some substances impart a yellow, others a violet, carmine red, green, or blue color. Plattner, in his work previously quoted, gives on this subject the following particulars: YELLOW.-Soda and its salts, when fused on the platinum wire in the point of the blue flame, possess the property of increasing the size of the exterior flame, and coloring-it intense reddish-yellow. This reaction is not prevented by the presence of a large quantity of other salts, whose bases also color the exterior flame, though not so intensely as soda. For the appearance on coal, see page 32. If a small splinter of a silicate containing soda be ignited'or fused in the point of the blue flame, it increases more or less the outer flame, according as it is more or less fusible and contains more or less TEST IN FORCEPS. 35 soda, tinging it at the same time reddish-yellow. If the blowing be long continued, this color remainsunchanged, or becomes more intense. VIOLET.-Potassa, Caesia and Rubidia, and most of their salts, except the borate and phosphate, when fused in the point of the blue flame, color the exterior flame distinctly violet. If, however, the salt be mixed with only a very minute quantity of a salt of soda, the reaction is so changed that while near the assay a slight violet tinge may be perceived, further from it appears the intense reddish-yellow of the soda. If the mixture contain several per cent. of a salt of soda, the reaction of potassa is wholly suppressed, and only that of soda can be perceived. The reaction of potassa is also prevented by the presence of a small quantity of a salt of lithia. For the appearance of some salts of lithia on coal, see page 32. Many minerals containing lithia and fusible in the point of the blue flame communicate a red color to the exterior flame. This is especially true of the micas from Altenberg and Zinnwald,; which color the outer flame very strongly; this color diminishes, however, in intensity, as soon as the thin strip is melted to such an extent that it can no longer be kept perfectly fluid in the flame of the blowpipe. There are also minerals which give along with the red of lithia still another color, and in such a manner that both appear either separate or mixed. If, for instance, a minute quantity of pulverized triphyline, (phosphate of lithia, iron and maganese), be 36 TEST IN FORCEPS. fused on the platinum wire in the blue flame, ihere appears in the outer flame a carmine-red streak from lithia, surrounded by a green flame resulting from the phosphoric acid. In the forceps this is difficult to observe because the triphyline is too easily fused. If a small piece of amblygonite from Cursdorf, which consists chiefly of phosphates of lithia and alumina, be fused in the forceps in the point of the blue flame, there appears in the exterior flame a yellowish-red streak, which is surrounded by a reddish-yellow flame resulting from the presence of soda. This color continues as long as a portion of the assay is kept in a fluid state. Silicates containing lithia, which alone impart no red tinge to the exterior flame, do so, according to Turner, wilen melted with fluor-spar and bisulphate of potassa on the platinum wire in the point of the blue flame, as will be explained in section 8. STRONTIA.-Chloride of strontium fused on the platinum wire in the point of the blue flame produces instantly an intense red color in the outer flame. Many other salts of strontia, ex. gr. carbonate of strontia, (strontianite), and sulphate of strontia, (coelestine), when exposed to the point of the blue flame in the forceps color the outer flame at first slightly yellowish, but afterwards carmine-red. The presence of baryta prevents the reaction of strontia. LIME.-Chloride of calcium tinges the exterior flame red, though not- so intensely as chloride of strontium. Most pure calcites as well as massive carbonates of lime TEST IN FORCEPS. 37 produce at first a feeble yellowish color in the exterior flame, but afterwards when the carbonic acid is driven off, a red, which is, however, less intense than that from strontia. The presence of baryta prevents the reaction of lime. Fluor spar, while fusing, colors the outer flame as deep red as calc-spar. Gypsum and anhydrite produce at first only a feeble yellowish tinge, but afterwards a rather intense red. Phosphate and borate of lime do not give a red, but a green color. Of the silicates, none afford the reaction of lime except table-spar, which imparts to the exterior flame a slight reddish tinge. GREEN.-There are seven substances which color the exterior flame green, viz: baryta, molybdic acid, oxide of copper, tellurous acid, phosphoric acid, boracic acid and thallium. BARYTA.-Chloride of barium when fused on the platinum wire produces in the exterior flame a green color which at first appears only light-green, but afterwards becomes an intense yellowish-green. The color is most beautiful when only a very small quantity of the salt is used. Carbonate of baryta, (witherite), and sulphate of baryta, (heavy spar), when held in the forceps and strongly heated in the point of the blue flame also tinge the exterior flame yellowish-green, though not so deeply as chloride of barium. The presence of lime does not prevent the reaction of baryta. For instance, baryto-calcite, consisting of carbonates of lime and baryta, causes in the exterior a greenish-yellow color; 3 38 TEST IN FORCEPS. if, however, the blowing be long continued, it may be perceived that the point of the flame is also sometimes of a reddish tinge. MOLYBDIC ACID.-Molybdic acid, or oxide of molybdenum, when attached to the moistened platinum wire and ignited in the blue flame, colors the exterior flame bluish-green, exactly like baiyta, molybdic acid at the same time volatilizing. If a thin scale of natural sulphide of molybdenum be held by the platinum forceps in the point of the blue flame, it does not fuse, but immediately imparts to the outer flame a yellowish-green tinge, resulting from the molybdic acid formed by its oxidization. OXIDE OF COPPER.-Oxide of copper, alone as well as in combination with certain acids which do not themselves give a colored flame, for instance, with carbonic, acetic, nitric and sulphuric acids, communicates to the exterior flame an emerald-green color. Metallic copper, when heated on.'oal in the flame of the blowpipe, is easily oxidized. and then tinges the outer flame emerald-green. The iodide of copper causes also a very intense emerald-green color in the exterior flame. Ores of lead containing copper color the outer flame in the center blue from the lead, (see below), and upon the outside, especially near the point, emerald-green. Silicates containing copper, when heated in the forceps with the point of the blue flame, sometimes impart to the exterior flame a very intense emerald-green color, ex. gr. dioptase, and chrysocolla. TEST IN FORCEPS. 3 This color is also produced by.hose in which the oxide of copper constitutes an unessential, and only the coloring part of the mineral, ex. gr. turquoise. TELLUROUS ACID.-Tellurous acid, suspended on the moistened platinum wire, and heated in the point of the blue flame, melts, gives off fumes and colors the exterior flame green. If the tellurous acid, deposited on coal from heating an ore of tellurium, be touched with the point of the blue flame, it vanishes with a green, or when selenium is present, with a bluish green flame. PHOSPHORIC AcID.-According to Fuchs and Erdmann, phosphoric acid, plosphates and minerals containing phosphoric acid, sometimes alone, and sometimes after being pulverized and moistened with sulphuric acid, impart to the exterior flame a bluish green color. This reaction is so reliable that with suitable care very minute quantities of phosphoric acid may be detected in mineras, when a little of the paste, formed by moistening the powder of the mineral with sulphuric acid, is taken on the platinum wire and exposed to the point of the blue flame. The same is true also of compounds, which from containing a large admixture of soda or other intensely coloring substance, do not alone give the reaction of phosphoric acid. If the salt contain water, it must first be driven off by heating on coal before the blowpipe, and then the anhydrous substance pulverized, moistened with sulphuric acid, and exposed to the blue flame on the platinum wire. If soda be present, the outer flame is tinged very distinctly bluish green at the 40 TEST IN FORCEPS. moment the phosphoric acid is liberated by the action of the sulphuric acid, but afterwards assumes the intense reddish yellow of the soda. As the bluish green. lasts in some cases but a shoit time, it must be observed whether the outer flame is colored bluish green or not, at the instant the assay is touched with the point of the blue flame. Phosphate of lead as well as pyromorphite, heated alone, tinges the edges of the blue flame of oxide of lead with a permanent green. BORACIC ACID.-Both natural and artificial boracic acid, when melted on the platinum wire in the point of the blue flame, impart to it a deep yellowish green, (siskin-gi een.) If, however, the acid be not perfectly free from soda, there results in the outer flame a green color, which is more or less mixed with yellow. Borax alone produces no green, but only the yellow of soda. Anhydrous borax, however, when pulverized and moistened with sulphuric acid, and exposed to the point of the blue flame, gives for a short time an intense green, which changes to yellow as soon as the salt is decomposed and the free sulphuric acid expelled. Minerals containing boracic acid, when heated on the platinum wire with the point of the blue flame, after being pulverized and moistened with sulphuric acid, almost all communicate to the exterior flame a green color. Another and very reliable method of detecting boracic acid in minerals from the siskin green color of the outer flame has been proposed by Turner, and will be found in section 8. THALLIUM.-Substances containing thallium, when TEST IN FORCEPS. 41 strongly heated, color the flame bright green, which is changed to yellow and thus obscured by the presence of much soda. BLUE. —There are some substances which when ignited or fused in the inner flame, color the exterior flame blue, viz: arsenic, antimony, lead, indium, selenium and compounds of copper with chlorine and iodine. ARsENIc.-Metallic arsenic and the arsenides of those metals which do not communicate any color to the exterior flame, as ex. gr. copper-nickel, cabaltine, &c., &c., when heated by the blue flame on coal, are surrounded by a blaze of a light blue color. If the incrustation of arsenious acid deposited on the charooal be touched suddenly by the blue flame, it being very volatile may be distinctly observed to disappear with the same light blue blaze. When arseniates whose bases impart no color to the exterior flame, as ex. gr. nickel bloom, cobalt bloom, iron sinter, &c., are exposed in the forceps to the blue flame, they communicate an intense light blue to the outer flame. In many cases a blue color appears even when the base possesses the property of coloring'the flame, as ex. gr. arseniate of lime, (pharmacolite.) ANTIMONY. When metallic antimony is fused within the blue flame on charcoal, the fluid globule of metal is surrounded by a scarcely perceptible blue blaze; but, if the resulting white crust of oxide of antimony be touched with the blue flame of the blowpipe, it disappears tinging the flame greenish blue. 42 TEST IN THE BORAX BEAD. LEAD.-When metallic lead is melted on coal within the blue flame, the fluid metal is surrounded by a blaze of an ultramarine color, and the coal is incrusted with oxide of lead. The oxide of lead may be driven by the blue flame from one place to another, tinging the flame at the same time with blue. Salts of lead, whose acids do not themselves impart a deep color to the exterior flame, communicate to this an intense ultramarine, when fused with the point of the blue flame, either on the platinum wire or in the forceps. INDIUM.-Compounds of inldium color the flame blue. SELENIUM.-If selenium be melted on coal in the blue flame, it volatilizes, coloring the flame intense ultramarine. A deposit of selenium on charcoal presents the same appearance in the reducing flame. CHLORIDE OF COPPER.-Natural or artificial chloride of copper, ignited on the platinum wire in the blue flame, tinges the external flame at first intense ultramarine, but afterwards green from the oxide of copper formed. BROMIDE OF COPPER.-Bromide of copper, treated in the same way as the chloride, colors the flame at first greenish blue, but afterwards imparts the green of oxide of copper. 5.-TEST IN THE BORAX BEAD. Since this test serves especially to detect the oxides of metals, it is of the first importance that, if the substance to be examined contain unoxidized metals, it should be roasted to oxidize them. Metals combined with sulphur, arsenic, &c., are not only difficultly soluble in borax, but TEST IN THE PHOSPHORUS BEAD. 43 present appearances differing mpre or less from those of the oxides. The roasting of the pulverized substance may be performed on coal or in a glass tube. It must be repeated several times to produce the most complete oxidation and volatilize perfectly sulphur, arsenic, etc. Before every new roasting the substance must be ground in all agate mortar. Sulphides and arsenides of metals may be advantageously subjected to alternate oxidating and reducing roastings. The latter are effected by mixing the pulverized assay with coal or plumbago powder, and then heating it in a glass tube or on charcoal. The same directions apply to the next test. 6.-TEST IN THE PHOSPHORUS BEAD. In this case, as in the preceding, it is important to observe accurately the colors which the beads present while hot, while cooling, and when cold, both in the oxidizing and reducing flames. Beads, in which certain substances are dissolved, possess the property of becom. ing cloudy or opaque, when treated with an intermittent flame. This process is called flaming. The same result may also generally be produced by a slow and gentle heating. of the previously cooled bead. The cloudiness of the bead is also often caused merely by the addition of a larger quantity of the assay. 44 TABLE I. 1.-OXIDIZING FLAME. A.-BORAX. COLORS OF SUBSTANCES WHICH EXHIBIT THESE COLORS. TZ BZADS'. In the Hot Bead. In the Cold Bead. Silica, Silica, Alumina, Alumina, Oxide of Tin, Oxide of Tin, Tellurous Acid, Baryta, 5 Stroutia,'l Tollurous Acid, Lime,;a Coto Cca. }[aneesia,,z g Baryta, lMagnessia,,t; Strontia, Colorless. G1ucina, a Lime, Yttria, M agnesa, Zirconia, N- u Thoria,'c t Yttria, Oxide of Lanthanum, Ziro ia, Oxide of Silver, Th oa, Columbic Acid, Oxide of Lanthanum,. 4 Niobic Aacid, Oxide of Silver, Columbio Acid, ~ Niobic Acid, Titanic Acid,, 0 Titanic Acid. Tunristi Acid, ^ Tuniatic Acid, Molybdic Acid, S lMolybdic Acid, *' Oxide of Zinc, B Oxide of Zinc, Oxide of Cadmium, Oxide of Cadmium, Oxide of Indium, ^. Oxide of Indium, Oxide of Lead, %t Oxide of Lead, Oxide of Thallium, ^ x Oxide of Thallium, Oxide of Bismuth, 5 9 Oxide of Bismuth, Oxide of Antimony. S. Oxide of Antimony, Titanic Acid, (yellow), _ Tungstic Acid. (yellow),' Molybdic Acid, (dark- yellow),) UYeow, red- Oxide ot Zinc, (slightly -dis yellow yellowish), to red and.Oxide of Cadmium, 8 reddih (slightly yellowish), brown. Oxide of Lead, (yellow), Oxide of Bismuth, (red-: dish yellow), *'Oxide of Antimony, (yellowish). 45 TABLE I.-CONTINUED. 1.-OXIDIZING FLAME. A.-BORAX. COLORS OF SUBSTANCES WHICH EXHIBIT THESE COLORS. TEE BEADS. In the Hot Bead. In the Cold Bead. Oxide of Ceriun, (by flaming, enamel-white). Oxide of Cerium, (red). Oxide of Iron, (yellow). Oxide of Iron, (dark red), Oxide of Uranium. (by flaRed, yellow, Oxide of Uralnum (red), ming, enamel-yellow). or purple. Vanadic Acid, (yellow), Vanadic Acid. (yellow). Oxine of Chromium, Oxide of Nickel, (reddish (dark-red), brown), Oxide of Manganese, (red, inclined to violet). Oxide of Nickel, Colot tf Oxide of Manganese, Oxide of Didymium. Amethyst. Oxide of Didymium. Oxide of Cobalt, Blue. Oxide of Cobalt. Oxide of Copper, (blue to greenish-blue). Green. Oxide of Copper. j Oxide of Chromium, (inclined to yellow)......... [,~~~~~~~~~~ 46 TABLE I.-CONTINUED. 2.-REDUCING FLAME. A.-BORAX. COLORS OF SUBSTANCES WHICH EXHIBIT THESE COLORS. THE BEADS. TH BEADS. In the Hot Bead. In the Cold Bead. Silica, Silica, Alumina, Alumina, Oxide of Tin, Oxide of Tin. Baryta, Strontia, Lime. Baryts, Manesia, trontia, lucina, Lime, a Yttria, Magnesia, Zirconia, Glucina, Thoria, Yttria,' Oxide of Lanthanum, Zirconis, Oxide of Cerium, Thora, Columbie Acid, Oxide of Lanthanum, Oxide of Didymium, Oxide of Cerium, Oxide of Manganese. Coluibic Acid. Niobic Acid, in small quantity. Colorless. Oxide of Didymium, Oxide of Manganese. Niobic Acid, in small quantity. Oxide of Silver,'t Oxide of Silver, - Oxide of Zinc,'a Oxide of Zinc,' a Oxide of aCadmium, e o Oxide of Indium, Oxide of Indium, Oxide of Lead, Oxide of Lead, ^ Oxide of Thallium, g; Oxide of Thallium, Oxide of Bismuth, O' Oxide of Bismuth, Oxide of Antimony, Oxide of Antimony,, ~ Oxide of Nickel,. o Oxide of Nickel, a. Tellarous Acid,. t Tellurous Acid. Titanic Acid, Titanio'Acid, Yellow to Tuugstic Acid, Tungatio Acid, brown. Molybdio Acid, Molybdio Acid. Vanadic Acid. Oxide of Cobalt, Blue. Oxide of Cobalt. Titanic Acid, By faing, enamel-lue. 47 TABLE I.-CONTINUED. 2.-REDUCING FLAME. A.-BORAX. COLORS OF SUBSTANCES WHICH EXHIBIT THESE COLORS. THE BEADS. TEE BEADS. In the Hot Bead. In the Cold Bead. Oxide of Iron, (bottle-green). Oxide of Iron, Oxide of Uranium, " Oxide of Uranium, Oxide of Chromium, (emeraldG Oxide of Chromium, green). Vanadic Acid, (emerald-green). Ox'de of Silver, I a Oxide of Silver, Oxide of Zinc,.. Oxide of Zino,.. Oxide of Cadmium,. I ~ Oxide of Cadmium, I I g rayl ad Oxide of.Lvead Grlyandy Oxide of Lertad, " Oxide of Lead, I' cloudy. Oxide of Bismuth,;- Oxide of Bismuth, (The cloOdi- Oxide cf Antimoxide o Antiny, nes oftn Oxide of Nickel, ~ Oxide of Nickel, pVpear first Tellurous Acid. Tellurou A. distinctly.c. A during the uc _ _____ cooling. o By long ctin B long continNiobic Acid, ued blowing and Niobic Acid, ued blowing and (in large quantity. ( in large quantity. Red to brownish- Oxide of Copper. Oxide of Copper. red and cloudy. 48 TABLE I.-CONTINUED. 1.-OXIDIZING FLAME. B.-SALT OF PHOSPHORUS. COLORS OF SUBSTANCES WHICH EXHIBIT THESE COLORS. TlB BEADS. TE BEADS. In the Hot Bead. In the Cold Bead. Silica, (very little soluble.) Silica, (very little soluble.) Alumina.-._ Alumina. Oxide of Tin, t Oxide of Tin, Tellurous Acid, ~ Tellurous Acid, Bary ta. Strontia,' Lime, -.' Baryta, Magnesia,' Strontia, Glucina, Lime, Yttria,, Magnesia, X Zirconia, (ilucina, Thoria, GluYttrian, Oxide of Lanthanum, Zir onia, Niobic Acid. Thoria, Colorless. Oxide of Lanthanum, Oxide of Cerium. Columbic Acid,,, Niobic Acid, Titanic Acid... Columbic Acid, Tungstic Acid, c Titanic Acid, Oxide of Zinc, ^ Tunstio Acid, Oxide of Cadmium, c Oxide of Zinc, Oxide of Indium, S I Oxide of Cadmium, Oxide of Lead, * g Oxide of Indium Oxide of Thallium, C- Oxide of Lead, Oxide of Bismuth, " Oxide of Thallium, Oxide of Antimony. ~ I Oxide of Bismuth, Oxide of Antimony. Columbic Acid, Titanic Acid, Tuntstic Acid, I Oxide of Zinc, Oxide of Cadmium, Oxide of Lead, Oxide of Silver, Oxide of Bismuth, Oxide of Iron, Yellow, red- Oxide of Antimony. Oxide of Nickel, dish yellow O. Oxide of Uranium, (yellowsh to red and greexn reddish Oxide of Silver, Vanadic Acid, broewn. Oxide of Cerium, Oxide of Iron, Oxide of Nickel, Oxide of Uranium. Vanadoe Acid, Oxide of Chromium. 49 TABLE I.-CONTINUED. 1.-OXIDIZING FLAME. B.-SALT OF PHOSPHORUS. COLORS OF SUBSTANCES WHICH EXHIBIT THESE COLORS. THE BEADS. In the Hot Bead. In the Cold Bead. Color of Oxide of Manganese, Oxide of Manganese, amethyst. Oxide of Did im. Oxi of Didymium. Oxide of Cobalt, Blue. Oxide of Cobalt. Oxide of Copper, (to greenish blue.) Molybdic Acid, (alight yellow. ish green). Oxide of Copper, Oxide of Uranium, (yellowish Green. Molybdic Acid, (yellowish green. green). Oxide of Chromium, (emerald green). 50 TABLE I.-CONTINUED. 2.-REDUCING FLAME. B.-SALT OF PHOSPHORUS. COLORS OF SUBSTANCES WHICH EXHIBIT THESE COLORS. THE BEADS. In the Hot Bead. In the Cold Bead. Silica, (very little soluble>. Silica, (very little soluble). Alumina. Alumina Oxide of Tin. Oxide of Tin, Baryta, Strontla, Baryta, Lime, Strontia, Magnesia, Lime, lucinma, Magnesia, Yttria. Ina, YGlucina, Zirconia, lun Yttria, Ttloria, Zirconia, Oxide of Lanthanum, Thoria Oxide of Cerium, Cvlulubic Acid, Oxide of Didymium, Oxde of anthanm Colorless. Oxide of Manganese. Oxide of nthanum Oxide of Cerium, Oxide of J)idymium, _ Oxide of Manganese, 6 Columbib Acid. Oxide of Silver, ~ Oxide of Zinc, o,. Oxide of Cadmium, S Oxide of Silver,. Oxide of Indium, Oxlde of Zinc, Oxide of Lead,.. Oxide of Cadmium, o'e Oxide of Thallium, ^ " Oxide of Indium, Oxide of Bismuth,' m Oxide f Lead, Oxide of Antimony, ~ Oxide of Tnallium, Oxide of Nickel. Oxide of Bismuth, Tellurous Acid. I Oxide of Antimony,' ~ Oxide of Nickel, o. Tellurous Acid.. Oxide of Iron, (red), Titanic Acid, (yellow), Oxide of Iron, Yellow to Ti Aid, tainin Tinic Acid, (containing Iron). b'ood-red Niobio Acid, Iron, (blood. Niobic Acid, " and brown. Tungstio Acid, J red). Tungstio Acid, " " Vanadic Acid, (brownish). Oxide of Chromium, (reddish), 51 TABLE I.-CONTINUED. 2.-REDUCING FLAME. B..-SALT OF PHOSPHORUS. COLORS OF SUBSTANCES WHICH EXHIBIT THESE COLORS. THE BEADS. In the Hot Bead. In the Cold Bead. Violet. Niobi Acid quantity). Niobic Acid, (in large quantity.) Violet. Niobic Acid (in large quant. Titanic Acid. Oxide of Cobalt, Oxide of Cobalt, Blue. Tun-stic Acid Tungstic Acid, Niobic Acid, (in very large quan- Niobic Acid, (in very large quan____tity ) tity.) Oxide of Uranium, Oxide of Uranium, Molybdic Acid. Green. Molybdic Acid. Vanadic Acid, Oxide of Chromium, Gcra and Oxide of Silver, (cloudi Oxide of Zinc, (The cloudi- Oxide of i Cad, ness often Oxide of Cadmium., appears first Oxide of Lead, istinct^y Oxide of Bismuth, while the Oxide of Antimony, ing) Tellurous Acid. ~Red to redaisw and Oxide of Copper. Oxide of Copper. cloudy. 52 TABLE II.-BEHAVIOR OF THE METALletallic Oxides in On Charcoal alone. With Carbonate of Soda Alplwabetic Order. OF1: It is displaced without change, and deposited upon another part On Ch very readily reof the Ch. duced in OF1 and RFI. I RFI It is reduced and The metal fumes and coats 1. ANTIMONI- volatilized. A Ct of an- the Ch with antimonious ouS ACID. timonious acid is deposit- acid. OUS zC. ed on the Ch, and a greenish blue color imparted to the flame. On Ch reduced, with 2, A D, eTuTic emission of arsenical 2. ARSENIOUS Volatile below red heat. fumes, which are characAcIpD. terized by a strong garlic odor. OF1: On platinum foil it fuses readily to a darkbrown mass, which on cooling becomes pale yel8. TEROXIDE low. On Ch in OFl and RF1 OF BISMUTH. reduced to metallic bis- Easily reduced to memuth, which, with long tallic bismuth. blowing, vaporizes, coating the Ch with yellow oxide. The Ct, when touched with the RFI disappears without coloring the tfame. OF: On platinum foil unchanged. RF: On Ch It disap- OFI: Inuoluble. 4. OXIDE OF pears in a short time and RFI: On Ch readily redeposits all over the Ch duced; the metal vaporCADMIUM. a dark yellow or reddish izes and deposits a dark brown powder; the col- yellow or reddish brown or can only be clearly Ct on the Ch. discerned after cooling. 53 LIC OXIDES BEFORE THE BLOWPIPE. With Bx on Platinum Wire. With S Ph on Platinum Wire. OFl: Dissolves with effervescence to a limpid glass, which while hit OFL; Dissolves in large quanti- is slightly yellowish. ties to a limpid glass. which while RFII: On Ch the saturated head bot a ppearsyellowish, hutaftercool- becomes at first c!oudy, but afterint cdlorless. wards clear a^ain, owing to the RIl: The glass when treated only volatilization of the reduced antihr a short time in tile OF becomes iony. Treated with tin, the glass on Chl grayish aml cloudy from par- tecomes alter cooling gray, even if tiTls of reduced antimony. With but very little antimonious acid is tin it becomes gray or black, present. With strong blowing it becomes clear again. 0 0 OFI: Readily dissolved to a limr OFI: A small quantity is easily pidt yellow glass lhlillh on cooling dissolved to a clear yellow gla-s, becomes colorless. When a greater which on cooling becomes colorless. quantity ot oxide is present the On a slarge additio(n of oxide the glass may e tmade enamnel white by glass while hot is yellowish red, he- flamning, and on a still larger addlcomes yellow on cooling, and when tion it becomes by itielf enamelcold is opalescent. white on cooling. RFI: On Ch the glass becomes at RFI: On Ch, particularly when first gray tand cloudy, the oxide is tin i4 added, the glass remains colorreduced to metal with eflerve,~ence, less and ltlimpid wllen hot. hut beand the head becomes clear again. counes on cooling dark-gray and An addition of tin accelerates tle opaque. reaction. OFI: Soluble in large quantity to OFI: Soluble in large quantity to a limpid yellowish glass, becoloing a limpid glass which wilile hot is almost col(rless on cooling. When yellowi-h, but colorless when cold slighly saturated it may be mlade Vwhen saturated it becomes enaenolenl.mel-white by flaming, and when white on coolitig.:, still more oxide is present it be- RFI: On'h tile oxide becomes comes by itself enamel-white on slowly and imperfectly reduced. cooling. The reduced metal deposits a very RFl: Placed on Ch it enters into feeble Ct of dark yellow color. The ebullition; the oxide is reduced, olor is only clearly seen when bhe the reduced metal Vaporizes immedi- mass is cold. An addition ol tin faately and deposits a dark yellow Ct. cilitates the reduction. 4 54 TABLE II.-CONMfetallic Oxides in tlpkabeta ici Order. i On Charcaal alone. WFit Carbonate of Soda. Alphabetical Order. 5. SESQUIOX- Insoluble. TheSd pauses nDEv ni?' C- into tile 1h; thie SesquioxIDE OF CE- Not changed. (le is reducedt to )pr.toxile R111~UM. \vv~wilch reilitlinn (on the CI, as a lilght gray powder. OFI: On platinum wire solutle to a (lark yellowish hrol.un gIlass, whlic. Oil coolin.,,' becoumes opaque and 6. SESQTTIOX- yellw.que IDE OF CfHRO- Not changed. R'FI; The glass becomes Opaquell(t an rctln ()e n coolMIUM. ji, Oil, (:h it eLnnot,e reduced to inetal; tle:'d pnsses ilnto the Cli. and the oxide r'etitliS behind as a vreetl I)pwJer. OFI: On platinum wire a OFT: Not changed. *ery small quantity is dis7. OXIDE OF RFI: It is rel:uced to solved( to a trallsparent,etal, hut does not fuse:mallos of a,pale reclidish c,1COBALT. the mass isi attrat ted by tih ort,, wl'llh tn cooling b;mriaget, and, by frietion. coines i ray assumtes metallic lustre. JtF1: On Ch reduced to a gany nmagnetic powder. OFT: Fuses to a black OFT- Fue.i to lnes lea OFI: On platinum wire luced where it is in ontacit siLuh)le t, o a h lb i I glass'f with the (fI.,reen color; on coolin,_ it B~. OXIDE OF Reduced to mtlbeco, mes opamque a-id white. 8. OXIDE O t tetmperature telow thli RFI: On 0:;lt easily reCOPPER. Ineltin poc to in etal, whichO when WVhen the heat is increased te re is suffi: glohule of metailic cop ently hi-h f s to one os per is obtained. ore globLies. 55 TINUED. With Bx on Platinum're. With S Ph on Platinum Wire. OFI: Soluble to a limpid glass of dark yellow or red color, which ~changes on cooling to yellow. When OFI: As with Bx, but on cooling higlXly saturatedl with oxidi thie glats Iololrless. becomes on cooling enaulel white. RFI: Perfectly colorless, hot and RFl: Tne yellow glass hecomne:;old. Never beoomesuopaqueon coolcol.rless. A lighly saturated tea(,ng, however large the amount of oxbecomes on cooliug enamel-white antl ide. crystablline. OF1: Dissolves but slowly, but colors intensively. If little of the oxide is present the glass, while lot, is yellow, when cold, yellowish green; with more oxide it is.dark red, while hot, becomes yellow on OFI: Soluble to a limpid glass cooling, and when poertety cold has which, when hot, appears reddish; a fine yellowish green o.lor. when cold it has a fue green color. RFI: The glass is,.reen, hot and R A in OI. cold. The intensity of the color depends on the amount of oxide present. Tin cause* no change. OFl: Colors very intensively.-'F As with ~The glass appears pure smalt-biue. OFI: As with Bx, but for the same hut antl ould. An excess of oxideq the color is not imparts to the bead a deep bluisbh quttso deep. blaok color. R I: As OF1. tFl: As ia OFI. OFI: A small addition of oxide snakes the lass appear green while bot, but iUit when cold. A lart, OFI: As with Bx. but for the same qua;ntity imparts to it a very deep.. qu.ntityo. oxid tle colo green color, while hot, becominq,,c tso greenish blue when cold.. l ee ). RFI. A glas containintr a certain 1tFI: A glass containing a largo uantity ot oide beoe clorles quantity ofoxiidebecomes d8ark reen, but on coolin- becomes opaque and which1te nio.ent o soldhc red, (suboxide.) On Ch tie copper tlon changes suddenly to brownish Ir predpanidopaque. A slhss containing snay oe precipitated in the metallic rettd an opaque. A glass contaninn.state, the bead Uec.~ui n conse- hut little oxide, wlell ireatedl on Uh quenoe colorless. A la Ontnin "ith tin appears colorless, while hot, protoxide when treated on h withut esonihred dp tln, becomes on cooling brownish red on 0oolin. and opaque. 56 TABLE II.-CONMetallic Oxdero in On Charcoal alone. With Carbonate of Soda. Alphabetical Order. When heated to ignition Does not disrolve in the 9 P TEROXIDE it hecomes re(uced to met- Sd, hut is easily reduced. al in OFi and RFI. The in hoth flames. The metal OF GOLD. metal fuses easily to al fues readily to a rlohule.,hlohule. The Sd passes into the Ch. RFI: Is reduced and forms 10. OXIDE OF a yellow Ct, and when RFI: Is reduced to soft T TTINDIUM. etrlonly heated colors the metallic glohules, like lead. INDIUM. flame intense blue. _______________ OF1: Insoluble. RFI: On Ch it is reduced; the mass. when placed in a 11. SESqUIOX- O1: Not changed. mortar, pulverized and reRFI: Becomes black and peatedly narhed with waIDE OF IRON. magnetic. ter to remove the adherent Ch particles, yields a gray metallic powder which is attracted by the magnet. OFI: Does not dissolve in 12. BINOXIDE At a red-heat becomes the Sd, hut hecomes re-. INOxIDE reduced; the reduced metal duced; the metal cannot OF 1RIDIUM. s infusible he fused to a globule. RFI: As in Ol. Minium, when heated on platiulm foil. blackens; on increasing the temperature it chanoes into yellow ox OFI: On platinum wire ide, which finally fues to redily dolved to a li yellow as. readily dissolved to a lim elOn Cl ad I uid glass which, on coolalmost instantaneou.ly re- in, hecomes yellowish and 13. OXIDE OF du'sd to metal which, with Ch reduced to continued bl)owimg, vapo)r Rtl On Ch reduced to LEAD. maes. and covers the Ch with metal which, with continyellow oxide, surrounded ued blowingj overs the (h ny a laint white ringofear- with oxide. honate. The Ct, when touched with the RFI disappeari, imparting to the fnme an azure-blue tinge. 57 TINUED. With Bx on Platinum Wire. With S Ph on Platinum Wire. As with Carbonate of Soda. As with Carbonate of Soda. Bead colorless, after flaming gray Bead colorless, turns gray when and opaque. tin is added. OH. When at a certain poinutof 4faturation the glass, while hot, appears yellowish red, and bec mUae OFI: A small amount of oxide n' cooling at first yellow, tten causes the glass to look -yellow.reenish and, finally, colorless. On while hot, colorless, when cold - _ very lare addition. of oxide it When more of the oxide is present tppears, while hot, deep red, beeomthe gl^as. while hlt, appears red. ng, on cooling, brownish red, then and yello. when cold; A still'f a dirty green color, and finally larger quantity makes the glsronih red. dark red, while hot, and dark FI A glass containing but little yellow, when cold. if the oxide suffers no visible lFI: The glass becomes bottle.hanQe. When moro of the oxide green. Treated on Oh with tin i P s present it is red, while hot. and, becomes, at first, bottle-green, but n coolin, hecoms at first yellow, afterwards pure hitriol-greeen.ish, and inally, reddish. treated with tin on Ch the glas,,)n cooling, becomes at first green, and finally colorless. As with Carbonate of Soda. As with Carbonate of Soda. OFI: Easily soluble to a limpid yellow glass which, on cooling. OFI: As with Bx. But to obbecomes colorless. It much oxide ain a glass which appears yellow, is present, it may be made cloud).viile hot, a large addition ol the by flaming A still larger ad'lition )xide i? required. of oxide causes the beal to becomt RFI: On Ch the glass becomes ename'-yellow, on cooling.;rayish and cloudy. This phenomeRtl: The lass diffuses Itself oro ion is better observed wien tin Is the Ch' and beconies cloudy. Witl. Mdded; hut the glass can never be continued blowing the oxide h linade quite opaque. If much of reduced to metal, with efferves the oxide is present, the Ch becomes cence, and the glass becomes cleal soated. again. 58 TABLE II.-CON-'ltetallic Oxides in On Charcoal alone. With Carbonate of Soda. Alphabetical Order. OFi: On platinum wire or foil a very small quanOFI: Insoluble. When tity dissolves to a trans14. SFSQUIOX- the temperature is suffi- parent green mass, which cilptly high hbtlt the se- on cooling becomes opaque IDE OF MAN- quioxide and thl peroxide anld luil.lh green. are converted into a reddish RFl: On Ch it cannot he GANESE. brown potwder. reduced to metal; the Sd RFI; The same effect. passes into the Ch and leaves the protoxide be hind. Heated in a matrass t(, 15. PROTOX- redness. it is reduced and Instantly reduced and vaporized. The vapors conIDE OF MER- volatilized. dense in the neck ot' the Ima trass and form a metallic CURY. coating. OF1: Fuses, becomes brown, vaporizes, and de- OFI: On platinum wir po-its on the Ch ia yellow dissolves with effervescence Ct, which nearest to thelto a limpid glass which. assay is crystalline. On on cooling, becomes milk cooling the Ct becomes white 16. MOLYBDIC whit and the crystals col- RFI: Fusion with effer'.."orless. lveFcence. The {used mass ACID. RFI: The greater part of is absorbed by the Ch, and the assay is absorbed byjpart of the acid is reduced the Ch. and'may be reduced to metal which inay be ohto tnetal at a sufficiently tained as a steel-gray powhigh temperature; the met- der. atl is in the shape of a gray ____ powder. OFI: Not changed. RFI: On Oh reduced to OFI: Insoluble. 17. OXIDE OF "etal; the spongy mass RFI: Easily reduced to cannot,e fused to a glo- metal in the shape of bright NICKEL. bule. but assumes metallic white scales. which are atlustre hy Irnct.on; it is at- tracted by the magnet. tracted by the magnet. 59 TINUED. With Bx on Platinum Wire With a Ph on Platinum W.'re. OFl: Colors very intensively. The OFI: A considerable addition of glass, while hot, is violet,. on cooliln manlganese nust he au t e l to pIroduce it assumes a reddishl tinae Whenia coloredl glass; it then appears, much mnang;anese is ad.led, th#-,lass'while hot, brownish violet, and bJeole.* quite black an'd opaque: reddish violet when cold. but never but the cilr can he. seen whenh theopque. I las contains. so glass. while suit, is flatcened wth the small a quantity of lman;galese that fo ceps. it appears colorless, an a;ldiition of RF:' Thlp..las becomes clorless. lnitre will produce the charao;eristie If thie color was very dark, tle plhe-c(oloration oinlenon is hest observed on Ch wit RFI: Becomes very soon coloraddition ot tin. less. 0 0 OFI: ERsily soluble to a limpid Hlass; if but little of the acid is OFI: Dissolved in large quanti- present it is yellohwilh green, while ties to a linpid gl^ass w.iich. while lit, hut w'en cold altuost olorless. hot. appeari yellow, but colorless on On Ch the glass bec,)omes very coolinr. A very lar e amount of dark, and on cooling assumes a sacid causes tite glass to appear dark beautlful treen color. yellow, while hot, and opaline wheu lRFI: The glass assumes a very cold. dark, dirty green color which, on RFI: A highly saturate beah i oeolllng. necoutes beautiful bright beoimies brown and opaque when grreen. Thesamo on Ch; tin deepens still more acid is present. the color a little. OFI: A small quantity colors the OFI: Soluble to a reddish glass bead violet, while hot; when cold wtich, on c oling-, becomes yelow. pale reddish hrown. Alore oxide A larger addition causes the glass makes the coloration deeper. to a, ppear hrownish red. while hot, RFI: The -lassF becomes gray and andl redlish yellow when cold. cloudly, or even opaque. With RFI: 0. Platinum wire not continued blowing the minute clh.i ed. 0.1 C'h wt tin ithecames, particles of.reduced metal collect t first, gray;anl opaque; with tozether and., the glass becioes continued blowing. the nickel colorless. This takes more readily becomes reduced, andi the glass clear placed on C, especially when tin again andcolorless. s added. The nickel then unites with the tin to a globule. 60 TABLE II.-CONAlphabetical Order. Xcta^ic O^z~ides in On Charcoal alone. With Carbonate of Soda. OFI: Converted into o.mio acid, which without depositing a Ct. volatilizes 18. BINOXIDE with its peculiar pungent Easily reduced to an In^ f odor. u fusible metallic powder. OF OSMIUM. RFI: Easily reduced to a dark brown and infusible metallic powder. 19. PROTOX19. PRorox- Reduced at a red heat: Insoluble: The Sd passes IDE OF PALLA- hut the metallic particles into the Ch, and leaves the.DIUM. are infusible. Palladium bdhind. 20. BINOXIDE OF PLA\TINUM. Like Palladium. Like Palladium. Instantly reduced. The 2. PROTOX Eily reduced to metal-s nt Chn 21. PROTOX-:lie silver, which unites to assesta into the Ch, and IDE OF SILVER. one or more globules. te lutes to one or -1~ b ~~more globules. OFI: Fuses. and Is reduced with effervescence' The reduced metal becomes Soluble, on platinum(. rnpU Instantly vaporized and wire. to a limpid and color22. TELLU- covers the Cll with tellu- less glass, which on coaling ROUS ACID. rous acid; the Ct usually becomes white. has a red or dark yellow On Ch reduced and volaedge. tilized, depositing a Ct o RFI: As in OFI; the outer tellurous acid. flame appears bllish green colored. 23. OXIDE OF Volatizes coloring flame The color of Soda obTHALLIUH. green. scures the green color. OFI: The protoxide burns, like tinder, to binoxilue. The binoxide becomes very OFI: On platinum wire luminous and- appears, it forms with Sd, with effer24. BINOXIDE while hot. yellowish. butvescence, an infusible comOF TIrN. assumes on cooling a dirty pound OF UIN..hite color. RFI: On Ch reduced to RFI: With a powerful metallic tin. and continued flame it may be reduced to metal. 61 TINUED. With Bx on Platinum Wire. With S Ph on Platinum Wire. 0 0 OF1 and RFI: Reduced, but not dissolved; the nletailic particles As with Bx. cannot be fused to a globule. Like Palladium..Like Palladium. OFI: In part dissolved, and in OFt: Imrarts to tie head a art redued. oolin te lassllowih olor. Whn muh of the ecomes opalescent or milk white, oxide is present the griu^ when accordin' to the amount of oxide oide is present the aap when pres. The ~r rho cold, is opalesent and appears *pl. Th e glass at frst becomes yellowish at day-light, reddish at RV.~The z^ass at first becomes ^c nle-lght. I I gray, but afterwards limpidt and RFI: AswithBi. ~oiorie'. ^'I. "s R ithBx. OTI. Soluble to a limpid and colorle's glass which..on CCh, becomes grav from reduced mptal A with Borax. RPil: On Ch hecomes at first gray.th Bo afterwards colorless. The Cli becomes coated with tellurous acid Glass. Colorless when saturated, As with Borax. opaque on coollng. OFI: A very small quantity dissolves slowly to a limpid anti colorless glass, which remains so OFI: As with Borax. on cooling. RFI:'he glass, containing oxide, RFl: From a highly saturated suffors no change. glas a part of the oxide may be reduced on Cn. 62 TABLE II.-CON]letaftlic Oxides in.lphabetical Order, On Charcoal alone. With Carbonate of Soda. OFI Asumes on ht OFI: On Ch It dissolves 25. TITANIC in a elow co r. an e l s n coo OFl: On platinum wire it dissolve sto a liiupidl and coI Not chant ed; at a dee)p yellow glass, which very lhihl teinperature con- on cooling becomes crystal206 TUNGSTIC verted into oxide, but does line and opaque. and of A nCD..... f f rloe white or yellowish color. ACID. I RFI: Blackens, being RFI: With very little Sd converted nto oxide, but on Ch it is reduced to metdoes nut fuse. at; with mIore Sd it iornu s a yellow comn pound of mnetallie lustre, which passes into the Ch. OFI. Insoluble. With a 27. SESQUI Oere Infito le oie but ds certain amount of Spq d the suineTa e irty yloih.ibrown, and with muore R F: Blackens, owento RFI Wlh very little O NIUM. Etheformationof protoxide. utio C s trede to metplace. Fusihe. Whore it is in 28. VANADIC ontact with the h it be Unites tellow fnpound ofsible maetss clies reduced and passes which is absorbed by- the ACID. Into the, Cl. The rest Oi- h. sumes the lustre and color). of graphite. 63 TINUED. With Bx on Platinum Wire. With S Ph on Platinnm Wire. OFI: ERsily soluble to a limpid O1N: Eisily dissolved to a limpid ass which. when gontaining a glass which. when cntainlng a large larga quantity. appears yellow. quantity. appears yellow, while hot, while hot, hut beciines colorless on but becomes colorless on cooling. cooling. When containing a very RFI; Appears yellow, whilehot, larg.e quantity it is enamel-whiite. hut. on coolini. reddens and finally when cold. assumes a violet color. It iron is RFI: When containing but little present the glass, on cooling, titanic acid the glass becomes becomes brownish red; with tin on yellow, when nmore. dark yellow to Ch the glass becomes violet, unless brown. A saturated glass becomes the amount of iron be very considenamel-blue by flaming. erable. OFI: Easily dissolved to a limpid and colorless bead. which, when OFI: Like titanic acid. hhighly saturated, appears yellow, RFI: - A glass. containing but while hot. RFl:. with little blowing the little tunzrstio acid, is not chanted:lass ppear. while bot. of dirty When imore, it becomes yellow and, glass ppear. while hoto of a dirty on cooling, yellowish brown. On Ch the same reaction is produced strong blowing it becomes. on cool. wilh a less saturated bead. Tin ing. bluish green. On Ch with tin, deepens the colors. deep green. If iron is present, the elass, on cooling. becomnes brownish red; with tin on Ch the glass becomes blue or. if the amount of iron is considerable, green. OFI: Behaves like sesquioxide of IrQn. When highly saturated the OFI: Dissolves to alimpid yellow glass may be made enamel-yellow glass which. on cooling, becomes by flaming. yel:owishl-reen. RFl: Behaves like Pesquioxide of RFl: The glass assumes a dirty Iron The green bead, when at a green color which, on cooling, certain-point of saturation, may he changes to a fine green. With tin made black by flaming. On ChlonCh the color deepens. with tin it becomes dark yellow. OFI: Dissolved to a limpid glass which, when the quantity of OFI: Soluble to a limpid glass vanadio acid is small. appears whiih if sufficient vanadio acid is colorless, when largrer, yellow. and present. appears dark yellow..while which, on cooling, becomes gieen- hot. and becomes light yellow on' ish. cooling. RFI: The glass, while hot, appears RFI: As with Borax. brownish, and assumes a fine green color on cooling. 64 TABLE II.-CONlalletic O ridcsi On Charcoal alone. Wtt Carbonate of Soda. ~l~pkabeticl l rhder. OF1: When heated becomes yellow and, on cool- O: nsoluble. 29. OXIDE OF nIg, white again. It fuses OF: Ins olbl e not, hut becomes very lum- reduced. The metal vaporZINC. i""u^' ^^ ^ ^"~reduced. The metal vapr. ZINC I:ou. iizes and coats the Ch with ZIN. RF Is slowly reduce; with oxide. With a powerthe reduced mtieta1 become.' n ~o^' WitnapOWer thue reduced iietal becomes hful flame the char toeristi rpidly re-oxidized and the i flame i ti oxrtide deposited on another zin flame i sometimes propart of the Ch.duced. ~oxide depositedeon TINUED. With Bx on Platznum Wire. With S Ph on Platinum Wire. OFI: Dissolves readily and in large quantity to a limpid glass which appears yellowish while hot; on cooling it Is colorless. When much of the oxile is present the glaas may be made enamel-white by flaming; and on a still larger addition it becomes enamel white on As with Borax. cooling. RFI The saturated glass becomes at first gray and oloudy and finally transparent again. On Ch the oxide becomes reduced, the metal vaporizes and coats the Ch with oxide. 66 TABLE III.-BEHAVIOR OF THE ALKALINE BEFORE THE On Ch alone and in the With Carbonate af Soda Forceps. on Ch. The Hydrate fuses, boils. intumesces, and is finally abso-rbed by the Ch. The Carhonate fuses readily to a Fuses with Sd to a homo. 1. BARYTA. transparent glas.s, which oi gleneous mass, which is abcooling becomues enamel-sorued by the Ch. white. In the forceps it colors the outer flame yellow ish -reen. The Iydrate behaves like hydrate of baryta. The Car- Caustic Sirontia is insolu honato fuses only at the hle The C.irbonat minxed edges. and swells out with its own volume of Sd 2. STRON- In arborescent ramifications luses into a limpid glass, ". -~l~ ^ l whltch emit a brilliant lighlt, which becomes enauiel-white TIA. and when heated witli tle on cooling. At a greater RlP impart to it a reddish heat the inass enters into tinge; shows after cooling ebullition, and caustic Stronalkaline reaction. In the fir- tia is formed, which is abcel), colors the outer flame sorbed by the Ch. pnurple. Caustic Lime suffers no alteration. Tle Carblonalte loses carbonic acid. becolne. Insoluble. The Sd pansses 3 T. T-IM wliter anid inore luriinLous, into the Ch and leaves the. L ME. |wt and shows after cooling, al- Ltne unaltered on its burkaline reaction. In the for- fIae. ceps it colors the outer flame pale red. 4. MAGNE- Undergoes no alterations. The Carbonate becomes cau- It behaves like Lime. SIA. stio and iutnmous. Forms an infusible com5. ATTLUMTINA Not changed. pound, with slight intumescence. The excess of Sd is absorbed by the Ch. 67 EARTHS AND THE EARTHS PROPER, BLOWPIPE. With Bx on Platinum Wire. With S Ph on Platinum Wire. The Carbonate dissolves with effervescence to a limpidl aulahs, which when in'a certain state of saturation may he made opaque by As with Borax. flaming; when still more saturated it heomnme opaque on cooling, even without flamini. Like Baryta. Like Baryta. Readily dissolved to a limpid Soluble in large quantities to a plass. which becomes opaque by limpid glass which, when sufficient flamiu-. The Carbonate dissolves Lime ln present, becomes opaque by with efferveecence. -On a large adati- flaming. When saturatad, the glass tion of L;me the glass crystallizes becomes enamel-white on cooling. on coolinl, but does not become enamel-white. Readily soluble to a limpid glass, It behaves like Lime, but does not which becomes opaque by flaming. crystallize so well. When saturated. it becomes on cooling enamel-white. Dissolves slowly to a limpid glass. which remains so on cooling, Soluble to a limpid glass. which and which cannot be made cloudy remains clear under all circunmtanby flaming. A ltrge quantity of ces. If too much Alumina is added, Alumina makes the glass cloudy; the undissolved portion becumes on cooling, it assumes a crystalline translucent. surface. 08 TABLE Ill.-CONOn Ch alone and in the Wi'h Carbonate of Soda Fprceps. on Ch. 6. GLUCINA. Not changed. Insoluble. 7. YTTRIA. Not cnanged. Insoluble. 8 ZIRCONI I le ut omittin a Insoluble. ICOIA very brilliant light. 69 TINUED. With Bx on Platinum Wire. With S Ph on Platinnm Wire. Soluble in largo quantities to a limpid glass, which hecomes opaque by flaming When Glucina is pres- As with Borax, ent in excess it becomes enamelwhite on cooling. Like Glucina. Like Gluaina. Like Glucina. Dissolves more slowly than with Borax. 5 7.-TEST WITH SODA. The substance to be examined is pulverized, mixed with soda, moistened a little and spread on coal. At first it should be heated gently, but after the moisture is driven off the temperature should be raised as high as possible. It should now be observed, first, whether the assay effervesces, and fuses with the soda; or second, whether it is reduced; or third, whether neither one nor the other occurs, in which case the melted soda sinks gradually into the coal,-and the assay remains unchanged. Silicic, titanic, tungstic and molybdic acids effervesce, and fuse with the.soda. Silicic and titanic acids under these circumstances melt to a bead. The former only gives, (when not too much soda is employed), a bead which remains transparent after cooling, while that of the latter becomes, in cooling, opaque and crystalline. Tungstic and molybdic acids are absorbed by the coal as tungstate and rmolybdate of soda. It should also be noticed hero that salts of baryta and strontia forni, when fused with soda, compounds which are absorbed by the coal. All the oxides of the noble metals, as well as the oxides and acids of molybdenum, tungsten, antimony, TEST WITH SODA. 71 arsenic, tellurium, copper, quicksilver, bismuth, tin, lead, zinc, cadmium, nickel, cobalt and iron are reduced on coal with soda, when heated by the reducing flame. Arsenic and quicksilver are instantly volatilized, and sometimes leave behind a scarcely perceptible deposit on the coal. Antimony, tellurium, bismuth, lead, thallium, zinc, cadmium and indium are partially volatilized, and form on the. coal distinct incrustations. The fixed metals, when thus reduced, are found either melted or unmelted in the soda, and are best detected by grinding the part of the coal into which the soda has sunk in an agate mortar, and carefully washing off the particles of coal with water. Those metals which are fusible and malleable remain in the mortar as flat pieces and scales, and the infusible and unmalleable as a powder with a metallic luster. Instead of soda, it is better, according to Plattner, to use with those oxides which are reduced with difficulty, oxalate of potassa. Soda is, moreover, employed as a special reagent for detecting manganese, especially when present in very small quantity. When a substance containing manganese is fused on platinum foil in the oxidizing flame with soda, or better with a mixture of soda and saltpeter, a mass is obtained which is colored green, or when cold bluish green, by manganate of soda. 8. —-SPECIAL TESTS. By the methods thus far given for assaying with the blowpipe, it is not always possible to decide with certainty upon all the substances which may appear, but it is often 72 SPECIAL TESTS. necessary to undertake for this purpose still further experiments. These experiments, which have Ibr' their object the special determination of certain substances, or serve to confirm results previously obtained, are briefly given below. POTASSA.-The presence of potassa in substances, -whi- besides this contain so much soda or lithia as to prevent its reaction on the blue flame of the blowpipe, (see Test in the Platinum Forceps), can, when the quantity is sufficiently large, be proved by dissolving in a bead of borax, colored brownish by oxide of nickel, a portion of, the assay, and observing the color of the bead when cold. A more or less distinct bluish tinge denotes the presence of potassa. Since the reaction depends, of course, upon the quantity of the assay in the bead, it must be gradually increased to the required amount. The bead must be heated on the platinum wire in the oxidating flame. LITHIr.-Silicates which contain only a small quantity of lithia, as, for instance, many turmalines and scapolites, either do not redden the exterior flame at all or only very slightly. In this case it is necessary to adopt the method proposed by Turner, by which even a small amount of lithia may be detected. The process is as follows: The silicate is pulverized as finely as possible and made into a paste with a mixture of one part of ruor-spar with one and a half parts of bisulphate of potassa and a little water, and fused on the platinum wire in the blue flame, the color of the exterior flame being carefully noticed. According to Merlet, it is often SPECIAL TESTS. 73 necessary in order to be positive in regard to the reaction to use two parts of the mixture with one part of the assay. If the silicate contains a small quantity of lithia, the outer flame will be colored red, though not so brightly as from lithia alone, the color inclining strongly to the violet of the potassa. If the silicate be free from lithia, only the violet color of the potassa appears. If it contains soda, it is not always possible to obtain a.distinct reaction from the lithia. If boracic acid be present in the silicate, as in turmalino, the outex flame exhibits first a green tinge denoting the presence of the. acid, but afterwards a wine or less intense red from the lithia. Another method of detecting lithia when mixed with soda is said to be to dip the assay, moistened with hydrochloric acid, into melted wax and then heat it in the blue flame, by which, at the first moment, a red color is produced. Bn3RcIc ACID.-Turner has proposed the following method of testing for boracic acid in salts and minerals: The assay is to be pulverized as finely as possible and made into a paste with water and a flux consisting of four and a half parts of bisulphate of potasha and one part of fluor-spar, which is perfectly free from boracic acid, and fused on the platinum wire in the blue flame. While the mass is fusing fluo-boracic acid is formed which is driven off and colors the exterior flame a deep yellowish green, (siskin-green.) The green color of the flame continues, however, only so long as fluo-boracic acid gas is disenggasd. If, therefore, the quantity of boracic acid be smll,'strict attention must be given, 74 SPECIAL TESTS. since the color lasts only the few seconds in which the materials of the bead are operating on each other. According to Merlet, it is often necessary, in order to obtain a reliable result, to employ with one part of the assay three or four parts of the flux. SILICIC ACID.-This may be most easily detected in silicates by heating a small splinter or fragment in a bead of salt of phosphorus. The silicic acid, being nearly insoluble in the salt, is separated from the soluble parts and forms a more or less transparent mass of the form of the assay used, which is called a siliceous skeleton. SULPHURI I ACID AND SULPHUR.-In sulphates, sulphide?, and indeed in all substances containing sulphur, the smallest trace even of this element may be detected by mixing the assay with two or three parts of soda, or according to Plattner, with the same quantity of oxalate of potassa, (which is perfectly free from sulphuric acid), and heating the mixture in the reducing flame on charcoal. The melted mass, when cold, is laid, with that part of the coal into which it has sunk, on a piece of bright silver and moistened with water. If sulphur be present and has accordingly formed sulphide of sodium, there appears sooner or later a black or brown stain of sulphide on the silver. It must, however, be 6bserved that selenium gives the same reaction. Von Kobell gives the following directions for determining whether the sulphur in a mineral belong3 to a sulphide or to a sulphate. The finely pulverized assay is filsed with hydrate of potassa in a platinum spcon before the blowpipe. The SPECIAL TESTS. 75 platinum spoon with its contents is then placed with ^ bright piece of silver in a small porcelain dish of water. If the substance contains a sulphide, the silver is blackened, but if a sulphate, it remains perfectly bright. In the latter case, the sulphur must first be provedpresent on coal with soda, and, of course, that portion which is melted in the platinum spoon must not have been exposed to any reducing influence. NITRIC ACID.-Nitrates heated in a matrass give off first oxygen, and then nitrous acid, which may be recognized from its yellow color as well as peculiar odor., Nitrates of potassa and soda deflagrate when heated on charcoal. A small quantity of nitric acid may be detected in a substance by heating a portion of it in a matrass with a little more than an equal weight of bisulphate of potassa. The color of the nitrous acid gas may be most distinctly seen by looking directly into the open end of the matrass and thus through as thick a stratum as possible of the mixed gases. FLUORINE.-When hydrofluoric acid in small quantity occurs in minerals with any of the heavier metals and a small quantity of water, it is only necessary, according to Berzelius, to heat the assay in a glass tube closed at one end, and into the open end to introduce a strip of moistened Brazil-wood paper. Hydrofluosilicic acid is driven off by the heat and deposits not far from the assay a ring of silica, and the Brazil-wood paper is turned straw-yellow by the action of the resulting hydrofluoric 76 SPECIAL TESTS. acid. This reaction may be obtained, when as in some micas the hydrofluoric acid amounts to no more than three-fourths of one per cent. If the substance, whether a mineral or a slag, exhibits no reaction of hydrofluoric acid either on the glass or the Brazil-wood paper, it should, according to Berlzelius, be treated as follows: The pulverized assay is mixed with salt of phosphorus, which has been previously melted on coal and then pulverized, and heated at one end of an open glass tube, so that the current of hot air shall pass over it and through the tube. Minerals containing no silicic acid, treated in this way, give off water and hydrofluoric acid, which passing through the tube may be recognized as well by its suffocating odor as by its power of attacking the glass which is rendered dim throughout its entire length, especially in those places where moisture is deposited. If a strip of moistened Brazil-wood paper be held before the current of air at the upper end of the tube, it is turned yellow by the hydrofluoric acid. If the substance contain silicic acid, fluoride of silicon is given off, which is, however, decomposed by the water formed by the combustion of the alcohol or oil, and the silica remains dissolved in it. When the water'condensed in the tube is evaporated, the silica remains behind and may be distinctly seen. If the tube be washed with water and dried, the etcling effect of the hydrofluoric acid may be observed on the glass. A strip of moistened Brazil-wood paper introduced into the tube at the beginning of the experiment is colored yellow. Since in such experiments it is necessary to fuse the substances, it often SPECIAL TESTS. 7T happens in using glass tubes that the glass becomes so soft that the blowing-must be suspended. To avoid this difficulty, Smithson fastens to one end of the glass tube by means of a metallic wire a piece of platinum foil so that it forms a half-tube or canal outside the glass tube. The assay is now laid on the foil and the blast so directed as to drive the products of the ignition into the tube. The use of the wire may be dispensed with by cutting down the sides of a strip of foil for two thirds of its length and then rolling it together and introducing the other third into the glass tube. This has the advantage of preventing the assay, during or after the fusion, from coming in contact with the glass. Plattner always obtains in this way satisfactory results with both minerals and slags, whether the fluorine constitute an essential part of the substance or be present only as an accidental ingredient. According to Merlet, substances which do not contain too small a quantity of fluorine may be tested by heating them, after being finely pulverized, in a mat rass with equal parts, (according to Berzelius with four parts), of fused bisulphate of potassa, till sulphuric acid begins to be set free. The heat, which may be that of a spirit lamp or of the blowpipe flame, should not be applied to the bottom of the matrass but to the side, since otherwise the mass is apt to rise in the tube. The empty part of the matrass becomes thus lined with silica which is deposited by the decomposition of fluosilicic acid gas. The tube may then be cut off just above the melted mass, rinsed- with water and dried with bibulous paper. If the quantity of fluorine be considerable, the walls of the 78 SPECIAL TESTS. tube are etched throughout; if the quantity be small, they show only here and there a dim spot. This method is, however, not so good for detecting minute quantities of hydrofluoric acid as that with salt of phosphorus in the open glass tube. CHLORINE, (CHLORIDES AND CHLORATES).-According to Berzelius, the presence of chlorine in its compounds is detected as follows: A bead of salt of phosphorus is heated in the oxidizing flame and a sufficient quantity of oxide of copper added gradually to render it nearly opaque. A portion of the substance to be tested is attached to the still fluid bead, which is then heated in the reducing flame. If chlorine be present, the bead is surrounded by a flame of a beautiful blue inclining to purple, which continues as long as chlorine remains. A fresh portion of the assay renews the reaction. No other acid found in minerals, except bromine, produces a similar flame. A second method, also given by Berzelius, for detecting chlorine in the metallic chlorides, which are soluble in water, is to lay upon a bright piece of silver a little sulphate of iron or copper, moisten with a few drops of water, and then to place in it a portion of the chloride. The silver becomes after a while stained of a deep bronze color. According to Merlet, the insoluble chlorides may be tested for chlorine in the same way by first melting them with soda on the platinum wire so to form soluble chloride of sodium. BROMINE.-According to Berzelius, the metallic SPECIAL TESTS. 7 bromides give with salt of phosphorus and oxide of copper the same reaction as the chlorides; but the blue color imparted to the flame by bromine inclines not to purple, but to green, especially on the edges. To distinguish with certainty the bromides and bromates from the chlorides and chlorates, it is necessary, according to Berzelius, to fuse them in a matrass with bisulphate of potassa. When thus treated, the former give off bromine and sulphurous acid, (and the latter, chlorine and sulphurous acid), and fill the matrass with reddish-yellow vapors which may be distinctly recognized by their offensive odor resembling that of chlorine, notwithstanding the presence of sulphurous acid. If the quantity of bromine in the assay is small and the foregoing method be employed, it is important when the color cannot be observed from the side of the matrass, to look directly into it through the thickest possible stratum of gas. If the assay contain chlorine, this is also given off under these circumstances, but the yellow color is in small quantities scarcely perceptible. When iodine is also present, a mixture of yellow vapors of bromine and violet vapors of iodine is obtained. IODINE, (METALLIC IODIDES AND IODATES).-Metallic iodides, according to Berzelius, when tested in the bead of salt of phosphorus and oxide of copper, communicate to the exterior flame of the blowpipe a beautiful deep green color. When fused with bisulphate of potassa in the matrass, they give off sulphurous acid and iodine which is partly sublimed and partly fills the tube with 80 SPECIAL TESTS. violet vapors. To discover a small amount of iodine in mineral water which has been freed from the greater part of its chloride of sodium by evaporation, a solution of starch in boiling water and water saturated with chlorine is generally employed, an insoluble compound being thus formed, which possesses a remarkably fine blue color. Heine uses, with better results, instead of chlorine water nitric acid, and tests as follows: The neutral fluid to be examined for iodine is mixed with a small quantity of a solution of starch in hot water, and stirred with a glass rod while a few drops of nitric acid are added. If iodine be present even in very small quantity, there appears directly an intense blue color. MAGNESIA, COLUMBIC ACID, ALUMINA, OXIDES OF ZINC, TIN AND ANTIMONY, TITANIC ACID, NIOBIC ACID, ZIRCONIA.-All these substances, when moistened with a solution of nitrate of cobalt and ignited, assume certain characteristic colors. The pulverized assay should be made into a stiff paste with water, spread on coal and gently heated. After the water is evaporated a drop of the solution of cobalt is to be added, which is absorbed by the dry porous mass. This should then be gently heated to decompose the nitrate of cobalt, and afterwards strongly ignited by the oxidating flame. When the assay is perfectly cold, these substances exhibit the following colors: Magnesia, rose red, (not intense); Columbic Acid, similar to magnesia. Alumina, beautiful blue, (smalt blue). SPECIAL TEMTS. 81 Oxide of Zinc, beautiful yellowish-green, (siskin green); Oxide of Tin, bluish-green; Oxide of Antimony, dirty green; Titanic Acid, yellowish-green, (less beautiful than oxide of zinc); Niobic Acid, dirty green. Zirconia, dirty violet. The purity of the substances is an important requisite to the proper production of these colors. Impurities from other oxides give rise to more or less indistinct, dirty colors; the presence of the alkalies and of silicic acid causes, (by their melting with the oxide of cobalt,) a blue color. OXIDE OF MANGANESE.-ExceePdingly minute quantities of the oxide of manganese-even less than onetenth of one per cent.-may be detected by fusing the finely pulverized assay in the oxidating flame on platinum foil with two,parts of soda and one part of saltpeter. The fused mass is more or less intensely colored by the manganate of soda; when hot, it appears green, when cold, bluish-green, (turquois-color). TELLURIUM.-A test for tellurium, proposed by Berzelius, is to grind the assay with soda and coal, and heat the mass to fusion in a matrass, and drop upon it when cold a small quantity of recently boiled water. This after a little time is colored more or less intensely purplish red from the dissolved telluret of sodium. ARSENIC.-A small quantity of arsenic in a metallic! compound, as for instance, in nickel, cobalt, or any alloy containing arsenic, can often be detected with sufficient 82 SPECIAL TESTS. certainty neither in the matrass nor on coal. Plattner employs for this purpose the following method: One part, (50 to 75 milligrams), of the finely pulverized metallic compound is heated in a platinum spoon as hot as possible with five or six parts of saltpeter. The metals are thus oxidized and arseniate of potassa formed. The spoon is then boiled with water in a porcelain vessel till the melted mass is perfectly dissolved from it. After the metallic oxides have settled to the bottom the solution is poured off into a porcelain dish, mixed with a few drops of sulphuric acid and evaporated, to drive off all nitric acid, to dryness, or, if too much sulphuric acid has been added, till only bisulphate of potassa remains, which on cooling solidifies. In either case, the mass is ground in an agate mortar with about three parts of oxalate of potassa and a small quantity of coal. The mixture is then put into a matrass, warmed at first gently'to drive off all moisture, which may be removed by means of a roll of bibulous paper, and heated to redness. The arsenic acid is reduced to metallic arsenic, which is sublimed and deposited in the narrow part of the matrass. If, when the quantity of arsenic present is very small, the sublimate of metallic arsenic is not distinct, the neck of the matrass should be cut off with a file and the part, in which the sublimate is, heated in the flame of the spirit lamp. If this consist of arsenic, it is volatilized and may be detected by the odor. According to Plattner's experience, the oxalatV of potassa and coal may be advantageously employed also in other cases for the detection of arsenic. Compounds SPECIAL TESTS. 88 which contain arsenic and arsenious acids are, when treated as above, completely reduced and give a ring of metallic arsenic. Even sulphuret of arsenic, when pulverized with four or five parts of oxalate of potassa and a little coal, and the mixture heated in a matrass, is completely decomposed, sulphide of potassium being formed and metallic.arsenic sublimed. A similar result is obtained, according to Fresenius and Von Babo, when the finely pulverized substance containing arsenic is put into a matrass with six parts of a mixture of equal parts of cyanide of potassium and dry soda and heated gradually to redness. It is particularly important to the success of these tests that the mixture to be heated be perfectly free from water, since a small quantity of this not only causes the mass to swell up and rise in the matrass, but may also easily produce the oxidation of the sublimated arsenic. The following method is also adapted to the detection of a small quantity of arsenic: The finely pulverized substance is ground with five or six parts of saltpeter and fused in a platinum spoon. The fused mass is treated with boiling water as given above, and to the solution filtered from the residue is added a slight excess of acetic acid. The fluid is then boiled to drive off all the carbonic acid, and a crystal of nitrate of silver laid in the solution. If arsenic be present, it having been oxidized by the previous treatment to arsenic acid, forms arseniate of silver which is easily recognized from its reddish brown color. PHOSPHORUS.-Small quantities of phosphorus, which 84 SPECIAL TESTS. it is impossible to detect by the test in the platinum forceps, may be discovered as follows: A- mixture is prepared of one part of saltpeter, three parts of soda and one of silicic acid. The substance to be tested for phosphorus is ground i: an agate mortar with five parts of the above mixture and the whole fused in a platinum spoon. The fused mass is then boiled in water and the solution poured off from the residue and treated with a solution of carbonate of ammonia. By long continued boiling, the silicic acid which was dissolved in the carbonate of soda is precipitated and filtered off. The filtered fluid is rendered slightly sour by acetic acid, boiled to expel all the carbonic acid, and the phosphorus then tested for with nitrate of silver as in the preceding method. The appearance of a yellow precipitate of plosphate of silver denotes the presence of phosphorus, which, if originally present in an unoxidized condition, has by the above treatment been oxidized to phosphoric acid. THE END.