NATIONAL LIBRARY OF MEDICINE Bethesda, Maryland Gift of f?/2& The New York Academy of Medicine T ne By 19 H. W.SCHIMPF A LABORATORY GUIDE CHEMICAL ANALYSIS ! i/ BY DAVID O'BRINE, E.M., M.D., D.Sc, Professor of Chemistry and Geology in COLORADO STATE AGRICULTURAL COLLEGE, Chemist of the Experiment Station. "'Longum iter est per prtzcepta, breve et efficax per exempla."—Seneca Ep. VI. FOURTH EDITION, ENTIRELY REWRITTEN AND REVISED. NEW YORK: JOHN WILEY & SONS, 53 East Tenth Street. 1802. ' ■**—*—-■^----- ,-r N. V ArADti^t % ;.;.:: ■ 1924 I Entered according to Act of Congress, in the year 1883, Entered according to Act of Congress, in the year 1888, BT DAVID O'BRINE, In the office of the Librarian of Congress, at Washington. TO HIS ESTEEMED FRIEND AND TEACHER, S. A. NORTON, PH. D., LL. D., PROFESSOR OF CHEMISTRY IN OHIO STATE UNIVERSITY, COLUMBUS, OHIO, THIS WORK IS RESPECTFULLY DEDICATED BY THE AUTHOR. Preface to the Second Edition. This edition has been entirely rewritten, and is practically a new book. The chapter on reagents has been extended, so that it occupies nearly four times the original space. The uses, impurities, and tests for each reagent have been added. The tests in the dry way have been doubled, and are now presented in a more systematic form. To Prof. Egleston, E. M., Ph. D., LL. D., of the School of Mines, Columbia College, I am indebted for th.e scheme of blowpipe analysis on pages 68 and 69. The tests in the wet way have been similarly enlarged, and a scheme for the separation by electrolysis has been added, by Prof. E. B. Knerr, A. M., D. Sc, of Parson's College, Iowa. The space allotted to the acids has been increased, thus enabling me to deal more fully with the subject. Chapter V. is entirely new. The facts, laws, etc., employed in chemistry have been compiled and presented in a convenient form. The comparison of the bases and acids, it is thought, will be found useful to the student. The chapter on water has been carefully read, both in manuscript and in proof sheets, by Prof. C. C. Howard, PREFACE TO THE SECOND EDITION. M. S., of Starling Medical College, Columbus, Ohio. His wide experience in water analysis has contributed largely to its value. The chapter on poisons has been very much enlarged, and to it the recovery of the more expensive reagents has been added. The chap- ter on stoichiometry has been extended by adding the heating power of coal. This chapter has been read, in manuscript and in proof sheets, by Prof. Floyd Davis, M. S., Ph. D., of Drake University, Iowa, and I have profited by his valuable suggestions. My thanks are due to all who have aided me in any way, by criticism or by words of advice; but especially am I under obligations to my friend and teacher, Prof. S. A. Norton, Ph. D., LL. D., of the Ohio State University, Columbus, O. He has carefully and patiently read the entire work in manuscript and in proof, and to him I am indebted for much of its value and accuracy. Any corrections or queries from those using the book shall have my grateful attention. Fort Collins, August, 1888. PREFACE. This little volume is intended for the use of students who possess some knowledge of Chemistry. The object is to present a practical guide in Chem- istry adapted to the wants of the College or the Medical Laboratory. It would be impossible to ac- knowledge the sources of all analytical details or methods; they have been used, and in most cases modified by so many different persons that they are now regarded as common property. The labors of many well known chemists have been laid under contribution. Some of the methods are my own, and every test presented has been verified. There is a dis- cussion of all that is important in the analysis of water, milk and cheese, blood, urine, and poisons. Especial attention is invited to the following subjects: Separation of Bases, and tests; Comparison of Phos- phorus, Arsenic, and Antimony; The Organic Acids; Classification of the Alkaloids; The Ptomaines; and Stoichiometry. My thanks are due to the students and faculty of the Columbus Medical College, and especially to Drs. PREFACE. Hamilton, Kinsman, Lee, and Pooley, for their kind- ness and assistance. I am under special obligations to Prof. Norton, LL. D., of the Ohio State University, for much kind advice and assistance with the proof and many of the tests. The work is presented to the Laboratory student, hoping it may lessen his labor. Ohio State University, Columbus, May, 1883. CONTENTS. CHAPTER I. PAGE How the Reagents are Made, their Uses and Tests................11-50 CHAPTER H. Tests in the Dry Way.............................................51-69 CHAPTER III. Tests in the Wet Way — How to Get a Substance in Solution........................70-73 Silver Group, and Separation...............................73-80 Lead and Arsenic Groups, and Separation..................80-93 Iron Group, and Separation................................94-108 Alkaline Earths, and Separation..........................109-115 Alkalies, and Separation.................................115-120 Zettnow's Separation Without H2S.......................120-122 Separation by Electrolysis................................123-125 CHAPTER IV. Separation of the Acids —Dry Way.............................126-127 Inorganic Acids...........................................128-143 Organic Acids.............................................144-153 CHAPTER V. Comparison of the Bases and Acids.............................155-171 Facts, Hypotheses, and Laws Employed in Chemistry...........172-173 CHAPTER VI. Water Analysis..................................................174-183 Chlorine..................................................... 174 Hardness..................................................... 175 Organic Matter............................................... 176 Forchhammer's Method...................................... 178 Sulphates...................................... ........... 180 Nitrates...................................................... 180 Nitrites................................................... 180 Notes on Water Analysis..................................182-183 CONTENTS. CHAPTER VH. Poisons, Ptomaines, etc..........................................184-190 General Reagents.........................................190-192 Strychnine................................................193-195 Brucine...................................................195-196 Igasurine..................................................... 196 Morphine.................................................196-198 Meconic Acid.............................................198-199 Codeine...................................................... 199 Narcotine................................................... 200 Quinine..................................................200-201 Veratrine.................................................201-202 Aconitine.................................................202-203 Atropine..................................................203-205 Nicotine..................................................205-206 Conine....................................................... 207 Caffeine.................................................. .208-209 L Cocaine...................................................209-210 Antimony................................................210-211 Phosphorus...............................................211-213 Mercury.....................................,............213-214 Arsenic........................,..........................214-216 Lead......................................................216-217 Zinc......................................................217-218 Copper....................................................218-219 How Poisons Destroy Life.................................219-220 CHAPTER VTH. GENERAL STOICHIOMETRY Useful Constants................................................... 221 Thermometric Scales............................................221-222 Gases (expansion)...............................................222-223 Specific Gravity................................................223-224 Calculate % Composition.......................................224-225 Combination and, Decomposition (gaseous form).................225-226 Atomic Weight..................................................226-228 Empirical Formula............................................... 228 Bye Products of Different Kinds.................................228-229 Thermal Units..................................................229-230 Heating Power of Coal..........................................230-233 Index..........................................................234-237 Laboratory Guide, PREPARATION OF REAGENTS. ACIDS. Acids are used as general solvents, both in the concentrated and dilute states. The dilute acid generally contains from three to five molecules of H20 to one of the acid. To neutralize alkaline solutions. Care should always be taken not to add a great excess of acid. The higher oxygen acids, as HN03, HC103, are used as oxidizing agents, as are also their salts when mixed with free HC1 or H2S04, as K2Mn208, KC103. The weak acids, as acetic acid, or their salts, as sodium acetate, are sometimes used in analyses, as in the separation of ZnS from the bases of the iron group. Some organic acids, as tartaric and citric, are used to prevent or hinder the precipitation of the oxides of the iron group. In a mixture of bases and acids it is generally considered that the strong bases are united with the strong acids; if an acid be free, it is presumably a weak acid. 12 LABORATORY GUIDE. 1- Acetic acid (H, C2H302), sp. gr. 1.04, contains 30 per cent. acid. Preparation — Made by allowing 8 per cent, alcohol to trickle slowly over hard wood shavings in a free circulation of air; also as a bye product from the destructive distillation of wood, Tests — On heating an acetate in a tube, the odor of acetone will be perceived. Heat an acetate with alcohol and sulphuric acid, and acetic ether will be given off. Impurities — It may be contaminated by H2S04, HC1, or HN03, and should yield none of the tests which are used for their detection.* This will apply to the impurities in all the reagents. Uses — To acidulate fluids when it is wished to avoid the employment of mineral acids. In separations, as follows: it dissolves calcium phosphate, but does not dissolve calcium oxalate, distinguishing the former from the latter; it also dissolves manganese sulphide, but does not dissolve zinc sulphide. 2. Arsenic (As205), 3. Arsenious (As203) anhydrides. As205 -f 3H20 = 2(H3AsOJ and As203 -f 3H20 = 2(H3As03) acids. Preparation—The As203 is prepared by roasting arsenical pyrites in muffle furnaces through which the air is allowed to pass, and is condensed as a fine white powder. The arsenic acid is prepared by oxidizing arsenious anhydride (As203) with nitric acid —As203 + 2HN03 -f 2H20 = N203 + 2(H3As04). Tests —When heated on charcoal, it gives a garlic odor. In solution As203 with AgN03 yields yellow Ag3AsQ3.f As205 *ln general terms it may be said that the probable impurities in any reagent may be inferred from the materials used in the manufacture of that reagent. tin this book the sign placed over a symbol indicates that a gas is produced or evolved; the same sign---placed under a symbol indicates that a solid is formed and precipitates. PREPARATION OF REAGENTS. 13 with AgN03 yields red brown Ag3AsQ4. Marsh's and Davy's (NaHg) tests are very delicate. Impurities—When in powder (As203 or As205) it may contain powdered chalk or sulphate or arsenite of calcium. These substances can be detected by vaporizing the arsenic, when the impurities will be left behind. The vitreous is the purest. Uses—Arsenious acid is employed in the form of arsenite of soda to determine hypochlorous acid, free chlorine, and iodine The arsenic acid is used as an oxidizing agent. 4. Boric anhydride (B203) and borax, biborate of soda, (Na2B407,10H2O). Borax is found native as tincal. Boric acid is found native as sassolite. Preparation — Boric acid is made by dissolving borax in hot water, and adding strong HC1, when white, pearly looking scales of H3B03 separate out on cooling. Tests — Free boric acid imparts a green tinge to the colorless flame of a Bunsen lamp. The same color may be obtained from a borate by previously moistening it with strong sulphuric acid or with glycerin. Impurities — Borax may contain H2S04, HC1, Pb, Cu, Fe, Ca, or NaCl. Uses — The principal use of borax is for a flux; it dissolves metallic oxides, with "the formation of colored beads. Fused borax is used for the determination of C02 and HN03 by loss. For blowpipe work the crystallized borax is exposed to a gentle heat in a crucible until it ceases to swell. Cool, and pulverize, when it is ready for use. 5. Chromic acid (H2Cr04) has never been isolated. Po- tassium chromate (K2Cr04) and bichromate (K2Cr207) are quite important. Preparation — Pulverized chrome iron ore is mixed with potassium carbonate and potassium nitrate, and is then heated in a current of air in a furnace. The Cr203 is oxidized to 14 LABORATORY GUIDE. *2Cr03, and unites with the potassium to form potassium chromate. When potassium chromate is treated with nitric acid, potassium bichromate is formed—2K2Cr04 -}" 2HN03 = 2KN03-f-H20 + K2Cr207. When a cold saturated solution of potassium bichromate is treated with sulphuric acid, the anhydride Cr03 separates out, as follows: K2Cr207 + 2H2S04 = 2Cr03 + 2KHS04 + H20. Tests—A solution of potassium bichromate treated with acetate of lead forms yellow PbCr04. A solution of Cr03 treated with hydrogen peroxide and ether gives a fine blue color. Impurities — The K2Cr207 may contain K2Cr04 or HN03, and the Cr03 may contain H2S04 or KHS04. Uses — Cr03 is a powerful oxidizing agent: 2Cr03 = Cr203 -\- 03. Heated with H2S04, 0 is set free; heated with HC1, CI is liberated, or chlorochromic acid. A solution of K2Cr04 is used as an indicator in volumetric analysis. A solution of K2Cr207 in free H2S04 is used in volumetric analysis for an oxidizing agent, as in the determination of iron. 6. Citric acid (H3, C6H507, HgQ), a lOjer cent, solution. Preparation — It is made from lemon juice, which contains the acid in the free state (about 5 per cent), by boiling to coagulate the albuminous matters, treating with CaC03, and decomposing the Ca3(C6H507)2 with H2S04, filtering and evaporating. Tests — It melts when heated, and at 175° C. gives off pungent characteristic vapors containing acetone, while aconitic acid is formed in the residue. AgN03 gives a white precipitate, Ag3(C6H5Q7), which does not blacken on boiling (distinction from tartrate). Impurities — It may contain tartaric, oxalic, or sulphuric acids, and the metals lead, copper, and iron. Uses — It prevents or hinders the precipitation of the metals by the alkaline hydroxides. PREPARATION OF REAGENTS. 15 7. Potassium ferricyanide (K3FeC6N6), one part of the salt to twelve parts of water. It should not be dissolved until wanted. Preparation — It is made by oxidizing K4FeC6N6 by CI until the solution will no longer give a precipitate with a ferric salt. It has a red color. Tests—It gives Turnbull's blue, Fe3(FeC6N6)2, when treated with ferrous salt; with ferric salt it gives no precipitate, but the solution becomes brown. Impurities — It may contain CI or K4FeC6N6. Uses — For the detection of ferrous salts and as an indicator in volumetric analysis; also as an oxidizing agent in the presence of alkaline hydroxides. 8. Potassium ferrocyanide (K4FeC6N63H20), one part of the salt to twelve parts of water. Preparation — By heating animal matter with iron filings and K2C03, which results in the formation of KCN. On lixiviating the fused mass with hot water, the KCN acts upon the iron oxide and iron sulphide simultaneously produced by the roasting, and then results in the formation of potassium ferrocyanide, which crystallizes out. Tests — It forms Prussian blue, Fe4(FeC6N6)3, when treated with ferric salts, and with copper it forms a dark brown pre- cipitate of cupric ferrocyanide, Cu2FeC6N6. It forms with most of the metals colored solutions or precipitates. Impurities — It may contain C02, H2S04, HC1. Uses — To make ferricyanide as above described; also to make hydrocyanic acid, and as a general reagent. 9. Gallic acid (C7H605, H20). Preparation — Mix powdered nutgalls with water to form a thin paste, and expose the mixture to the air in a warm place for thirty days; filter, reject the filtrate, boil the residue with water, and filter through animal charcoal; set the liquid aside to crystallize and dry on bibulous paper. 16 LABORATORY GUIDE. TESTS —Add a few drops of potassium hydroxide to gallic acid, and an intense green color is produced. This color is changed to purple red by acids, and is prevented by an excess of alkaline hydroxide or carbonate. The above reaction (green) does not occur with gallotannic or pyrogallic acid. An aqueous solution of the acid should not precipitate alkaloids, gelatin, albumin, gelatinized starch, nor a solution of tartrate of antimony and potassium previously mixed with chloride of ammonium (distinction from tannic acid). Impurities — Tannic acid. Uses — To make pyrogallic acid. When gallic acid, in the absence of water, is heated to 215° C, it is sublimed as pyrogallic acid and carbonic anhydride; at higher temperatures other products are formed: C7H605 = C6H603 -f- C02. 10. Hydriodic acid (HI), an aqueous solution. Preparation — Pass H2S through water in which iodine is suspended, H2S + I2 = 2HI -fj^ Filter off the S, and boil to expel the excess of H2S. It is decomposed by exposure to the air. Tests—AgN03 precipitates yellowish white Agl, blackening in the light. HgCl2 precipitates yellowish red Hg_I2. PdCl2 precipitates black Pdl2. Impurities — Free iodine, which may be known by the solution turning a brownish yellow color. Uses —The tendency of H of HI to combine with O renders that acid a powerful reducing agent. 11- Hydrobromic acid (HBr), an aqueous solution. Preparation —By allowing Br and P to act on one another in the presence of water: 3H20 + 3Br -f- P = H3P03 -}- 3HBr. It is decomposed by exposure to the air. Tests —When a bromide is treated with H2S04 + Mn02, it gives off Br. In solution HgN03 precipitates Hg2Br2, yellowish PREPARATION OF REAGENTS. 17 white, soluble in excess of alkaline bromides. Bisulphide of carbon, chloroform, or ether gives, with free Br, a reddish yellow solution; free Br colors starch solution orange yellow. Impurities — Free bromine. Uses — Most metals and their oxides are dissolved by it. 12. Hydrochloric acid (HC1), sp. gr., 1.12; contains 24 per cent. acid. The dilute acid is made by adding one part of acid to three parts of water. Preparation — Made by heating fused common salt with sulphuric acid : 2NaCl -J- H2S04 = Na2S04 + 2HC1. Tests—AgN03 gives a white precipitate of AgCl, insoluble in HN03 and soluble in NH4HO. When a chloride is heated with Mn02 -4- H2S04, CI is given off. Test by physical properties. Impurities — It may contain Fe, As, CI, S02, and H2S04. Uses — It is a group reagent for Ag, Pb, and Hg'. It is a good test for free ammonia, forming white clouds of NH4C1. It dissolves most metals and their oxides, carbonates, and sulphides. When HC1 dissolves the metals, H is liberated; when it dissolves the sulphides, H2S is evolved. The peroxides, when treated with dilute HC1, fall into two groups, one evolving CI as Pb02, Mn02; the other producing H202, as Ba02. ( NOCl2 + CI ) Aqua regia is 3HCl-f-HN03 =\ or [ + 2H20. ( NOC1 -f Cl2 ) The solvent action is due to the free chlorine. 13. Hydrocyanic acid (HCN or HCy). Preparation — Two parts of the ferrocyanide of potassium in powder are distilled with one and one-half parts of sulphuric acid diluted with two parts of water, the vapor of HCN being carefully condensed. Prepared in this way it contains a very small quantity of H2S04. 18 LABORATORY GUIDE. Tests—When HCN is mixed with an equal quantity of (NH4)2S, and evaporated to dryness by a gentle heat, ammonium sulphocyanate is formed, which gives with the ferric salt a blood red solution. Impurities — H2S04 and K4FeC6N6. Uses — To separate Co from Ni. In electroplating and gilding. 14. Hydrofluoric acid (HF). Preparation—By treating fluor spar with strong sulphuric acid — CaF2 -f H2S04 = CaS04 -f- 2HF. The commercial acid, of a sp. gr. of 1.15, has the formula HF, 2H20. Tests—When free, it etches glass. Impurities — The commercial acid may contain H2S04. Uses — To * decompose silicates and to etch glass. Note — The following mixture will be found very convenient for marking beakers, as it deadens the surface, so that a lead pencil can be used to write on it. Mix equal parts of dry, recently precipitated BaS04 and NH4F in a porcelain mortar, and add, while stirring, liquid hydrofluoric acid. Keep in a gutta percha bottle, shake before using, and expose about fifteen minutes. Use a steel pen to write on glass with this " diamond ink." 15. Hydrofluosilicic acid (H2SiF6). Preparation — Heat a mixture of sand and fluor spar with sulphuric acid. The SiF4 is passed first through a small vessel containing mercury and then through water: (1) Si02 + 2CaF2 + 2H2S04 = SiF4 + 2CaS04 + 2H20. (2) 3SiF4 + 2H20 = 2H2SiF6 + Si02. Tests —It forms difficultly soluble salts with potassium (K2SiF6) and barium (BaSiF6), and is sometimes used to separate these elements from their soluble compounds. Impurities — It may contain H2S04. Uses—As tests for K and Ba. The addition of alcohol increases the insolubility of the precipitates. PREPARATION OF REAGENTS. 19 16. Hydrosulphuric acid (H2S), water saturated with the H2S, made as required for use. Preparation — Treat ferrous sulphide* with dilute sulphuric acid —FeS-f H2S04 = FeS04 H-H^S": if the gas is passed through a saturated solution of water and glycerin, it will keep for six or eight months; the glycerin does not interfere with any reaction. Tests — The odor of rotten eggs. Pb(C2H302)2 gives a black PbS; AgN03 gives black Ag2S. Impurities —When made from FeS it may contain As. In examination for poisons, prepare it from native sulphide of antimony and HC1. Uses — Besides its reducing action, it is largely employed as a group reagent. 17. Nitric acid (HN03), sp. gr. 1.2, contains 30 per cent. acid. A stronger acid is sometimes required, sp. gr. 1.52. Preparation — By heating a nitrate with sulphuric acid: 2KN03 -f H2S04 = K2S04 + 2HN03. Tests—All the normal nitrates are soluble in water. Brucine gives a red color with HN03 ; ferrous sulphate with sulphuric acid gives a brown ring; pyrogallic acid when added to water acidulated with H2S04 gives a brown zone of contact (very delicate). Impurities — It may contain HC1, H2S04. It should be colorless and leave no residue when evaporated. Uses — It dissolves most of the metals to form nitrates (Sb and Sn form oxides). It is one of the best oxidizing agents. 18. Oxalic acid (H2C204, 2H20), one part of the acid to ten parts of water. *FeS is made on a small scale by heating iron white hot in a blacksmith's forge, and running it through sulphur, and collecting the product in water; dry, and it is ready for use: Fe -(- s = FeS. 20 LABORATORY GUIDE. Preparation — By the action of nitric acid on sugar or of the alkalies on sawdust: C12H2201X + 180 = 6(C2H204) + 5H20. By this commercial method, the sawdust yields about one-half its weight of crystallized oxalic acid. Tests—When heated it breaks up into H20, CO, and C02. All the soluble calcium salts produce in solutions of H2C204 white, finely pulverulent CaC204 -f- 3H20, which is nearly in- soluble in H2C204; the addition of ammonia promotes the precipitation. Impurities — It may contain Ca, K, or HN03. Uses — It is a good reducing agent; also used in volumetric estimations, particularly of the alkalies; also to standardize a solution of permanganate of potassium. 19. Permanganic acid (H2Mn208) or potassium per- manganate (K2Mn208). Preparation — Fuse Mn02 with KN03, which gives potas- sium manganate, K2Mn04 ; this is easily decomposd by water, forming a rose red solution of permanganate, K2Mn208. Tests—A ferrous salt in the presence of free H2S04 bleaches a solution of permanganate. Impurities — It may contain HN03, HC1, H2S04, or NH3 Uses — It is one of the best oxidizing agents, and one of the most valuable reagents in volumetric analysis. As it is easily decomposed by organic substances, its solutions must be filtered through previously ignited asbestos or sand. 20. Picric acid (HO C6H2(N02)3) a saturated alcoholic solution. Preparation—When carbolic acid is boiled with fuming nitric acid, the solution, on cooling, deposits beautiful yellow crystals of carbazotic or picric acid. PREPARATION OF REAGENTS. 21 Tests — Solutions of salts of K and of most of the alkaloids precipitate picric acid, or a solution of its soluble salts. The cinchona alkaloids give a yellow precipitate. Impurities — It may contain carbolic acid or nitric acid. Uses—An important reagent for the alkaloids. A test for potassium salts, rendered more sensitive by the addition of alcohol. One of the most delicate tests for albumin in urine, forming a white line at junction of the liquids. Potassium picrate explodes violently both by heating and by percussion. 21. (a) Potassium sulphocyanate (KCNS), one part of the salt in twenty parts of water. Preparation — Fuse cyanide of potassium with sulphur: KCN + S = KCNS. (6) Ammonium sulphocyanate (NH4CNS), one part of the salt in twenty parts of water. Preparation — By digesting HCN with yellow ammonium sulphide: (NHJ2S + 2HCN = 2(NH4CNS) -f H2S. Tests — Both are delicate tests for the ferric salts, giving with them a blood red solution. Impurities — It should be remembered that the above reaction is masked by the presence of non-volatile organic acids. Almost every specimen of potassium sulphocyanate gives a red tint on the addition of pure H2S04 or HC1; this tint is prevented by adding a small piece of zinc. A solution of potassium sulphocyanate thus prepared can alone be safely employed as a test for small traces 'of ferric salt. Uses — They serve as indirect tests for S and HCN. 22. Sulphuric acid (H2S04). The concentrated has a sp. gr. of 1.842; the Nordhausen (H2S207), sp. gr. 1.9. Preparation — By burning S or FeS2, and allowing the product of combustion, S02, to mix with H20 and N02, obtained from the' decomposition of NaN03, which changes 22 LABORATORY GUIDE. S02 into H2S04. The N02 becomes reduced to NO, but in the air becomes again N02. This continuous reaction may be represented as follows: (1) S02 + N02 -f H20 = H2S04 + NO. (2) NO-fO = N02. Tests — BaCl2 gives a white precipitate, BaSQ4, insoluble in dilute acids. Free sulphuric acid is detected by its property of charring sugar. Impurities — It may contain Pb, Cu, As, Fe, HN03, HCl, S02, and N02. Uses — It is used to decompose very many compounds, thereby evolving volatile products like HCl, HN03, and H2S, or anhydrides like C02 and Cr03. The difficultly soluble sulphates are those of Pb, Ba, Sr, and Ca; for these elements it is an especial reagent. The dilute acid is made by pouring the concentrated acid into four parts of water (not conversely). 23. Sulphurous anhydride (S02), solution in water. Preparation — By heating H2S04 with C or S: 4H2S04 + Ca == 4S02 -f 2C02 -f- 4H20. Tests —When free, the odor is characteristic. When a few drops of a solution of its salt are treated with dilute HCl and Zn, H2S is evolved. Impurities — H2S04, as the S02 is easily oxidized to H2S04. Uses—As a reducing agent, and in iodometric analysis. 24. Tartaric acid (H2C4H406). Dissolve the crystals in three parts of water when needed for use. Preparation — Argols are boiled with powdered chalk, forming an insoluble calcium tartrate and a soluble potassium tartrate: 2KHC4H406 4- CaC03 = K2C4H406 -f CaC4H4Ofi 4. H20 4- C02. PREPARATION OF REAGENTS. 23 Calcium chloride is now added to the solution, when all the tartaric acid is precipitated as calcium tartrate: K2C4H406 + CaCl2 = 2KC1 + CaC4H4Q6. The calcium tartrate is boiled with dilute H2S04, when an insoluble calcium sulphate and a solution containing free tartaric acid are formed: CaC4H406 4- H2S04 = H2C4H406 -f CaSQ4. Tests—When heated it gives off the odor of burnt sugar. A solution of KC2H302 precipitates from concentrated solutions of tartaric acid the acid potassium tartrate, insoluble in alcohol (distinction and separation from citric, oxalic, and malic acids). Impurities — Pb, Cu, Fe, and H2S04. Uses — The same as citric acid. 25. Ethyl alcohol (C2H60), sp. gr. .815. Preparation — Made by the fermentation of grape sugar: C6H1206=2C2H60 + 2CO;. If 95 per cent, alcohol is treated with CaO a number of times, and then with metallic Na, a nearly pure absolute alcohol can be obtained. Tests—Add to the solution to be tested a few drops of a 10 per cent, solution of KHO, and warm to 50° C. A solution of I in KI is added until the solution becomes yellowish brown; to it add cautiously caustic alkali to decolorize it; if alcohol is present, a yellow precipitate is formed after a time (iodoform crystals). Impurities — It may contain fusel oil and water. The first can be recognized by its characteristic odor on evaporating a few drops on the hands. The absence of water may be known by the alcohol remaining clear when mixed with an equal bulk of pure benzol. Increased specific gravity will also indicate impurities. 24 LABORATORY GUIDE. Uses—As a solvent for some substances, as LiCl. It is sometimes added to aqueous solutions to render precipitation more complete, as 2KCl,PtCl4. It forms acetic ether with free acetic acid. 26. Ammonium carbonate (2(NH4)20, 3C02), one part of the salt in four parts of water, and one part of ammonia.* Preparation — Made by heating a mixture of ammonium chloride and calcium carbonate: 6NH4C1 4- 3CaC03 = 3CaCl2 4- 2NH3 -f H20 + 2(NH4)20, 3C02. Tests — It gives off the odor of ammonia, and effervesces with HCl, C02 being given off. It should volatilize completely. Impurities — It may contain H2S04 and HCl. It may also contain empyreumatic substances. Uses — It is advantageously used in the place of Na2C03, because it is volatile. It is a group reagent for the alkaline earths. It separates arsenious sulphide from the antimonous sulphide, by dissolving the former but not the latter. 27. Ammonium Chloride (NH4C1), one part of the salt to eight parts of water. Preparation—When nitrogenous substances are subjected to destructive distillation, an impure ammonium carbonate is formed; this, when treated with HCl, forms NH4C1. This is afterwards sublimed. Tests — It should leave no fixed residue on evaporation on platinum. It gives a brown precipitate with Nessler's test for ammonia, and a white precipitate of AgCl with AgN03. Impurities — It commonly contains iron; If it contains iron, pass CI through a saturated solution for a short time ; add a slight excess of NH4H0, warm, and filter. It may contain H2S04 and Ba. *When used as a solvent for arsenious sulphide, the ammonia is omitted. PREPARATION OF REAGENTS. 25 Uses — It forms very soluble double salts with certain elements, thereby preventing their precipitation, as Mn and Mg. It is used to precipitate from their solutions in potassium hydroxide various substances which are soluble in that alkali, but insoluble in ammonia, as alumina and chromic oxide. It is a special reagent to effect the precipitation of platinum as ammonium platinic chloride. It is used in the method of fluxing silicates for the separation of the alkali metals, and in the manufacture of ammonia. 28. Ammonium ferrous sulphate ((NH4)2Fe2(S04),6H20). Preparation — Made by mixing solutions of the molecular weights of ferrous sulphate and ammonium sulphate; evapora- ting and crystallizing the salt.* Tests — In the presence of free H2S04 it bleaches a solution of K2Mn208. The presence of ammonia, iron, and sulphuric acid can be shown by their respective tests. Impurities — It ought to give no reaction for a ferric salt. Uses—A very important volumetric reagent. It is used to standardize K2Mn208 and K2Cr207. 29. Ammonium fluoride (NH4F). Preparation — To hydrofluoric acid add ammonium to strong alkaline reaction (it is best to do this in a platinum dish); heat gently, filter, and evaporate to dryness. Keep in a gutta-percha bottle. Tests—A portion heated on platinum should leave no fixed residue; this test should be applied under good ventila- tion. It gives the tests for NH3 and HF. *The following general statement can be made: Double salts are prepared (1) by mixing together solutions of two salts in equivalent proportions, or (2) by fusion of the two salts. 26 LABORATORY GUIDE. Impurities — If it leaves no residue, especially of Si02, any other impurity can be neglected. Uses — This preparation may be very advantageously sub- stituted for hydrofluoric acid in the analysis of silicates. ■ 30. Ammonium hydroxide* (NH4HO), sp.gr. 96; contains 10 per cent. NH3. Preparation—Ammonium chloride is heated with slaked quicklime, and the gas passed into cold water: (1) 2NH4C1 4- CaO, H20 = 2NH3 -f CaCl2 + 2H20. (2) H20 + NH3 = NH4H0. Tests — The odor, or by turmeric paper. For traces, Nessler's test gives a brown precipitate. Impurities — It should leave no residue on evaporation in a platinum dish. It may contain C02, HCl, H2S04, Ca, and empyreumatic matter. Uses — To neutralize acids. To precipitate many metallic hydroxides; of these, some are soluble in an excess, as Zn, Cd, Ag, and Cu, while others are not soluble, as Fe. In acid solutions double salts may be formed that would hinder the precipitation, which might be formed in neutral solutions, as free HCl with NH4HO forms NH4C1, which prevents the pre- cipitation of magnesium. When NH4HO neutralizes acid solutions, it enters into combination not only with the free acids, but also frequently displaces and combines with those previously in combination with other bases. These reactions give rise to salts which frequently have the remarkable property of forming with analogous salts of the heavy metals, double salts which are so easily soluble that it is commonly said that ammonium chloride hinders or prevents precipitation of the protoxides of the iron group. *This body has never been obtained in a solid state, but it is convenient to reckon it analogous to potassium hydroxide. PREPARATION OF REAGENTS. 27 31. Ammonium molybdate ((NH4)2Mo04). Preparation — Dissolve one gram of molybdic anhydride, Mo03, in four cubic centimeters of ammonia; pour into fifteen cubic centimeters of HN03 (sp. gr. 1.2). Tests — Phosphoric acid gives in presence of HN03 a yellow precipitate of ammonium phosphomolybdate of variable composition. Impurities-—The Mo03 may contain Pb or Fe. Uses — To precipitate phosphoric and arsenic acids, which are nearly insoluble in nitric acid. Sodium phosphomolybdate is soluble in water, and forms a delicate reagent for alkaloids (Sonnenschein's reagent). 32. Ammonium nitrate (NH4N03). Preparation — Neutralize carbonate of ammonia with nitric acid; warm, and add ammonia to slight alkaline reaction; filter and crystallize. Fuse in a platinum dish. Impurities — It may contain any of the impurities of carbonate of ammonia or of ammonia. The salt should leave no residue when heated in a platinum dish. Tests and Uses — It serves as an oxidizing agent; to con- vert lead into the oxide of lead, or to effect the combustion of carbon in cases where it is desired to avoid the use of fixed salts. Also to make nitrous oxide : NH4N03 = N20 + 2H20. 33. Ammonium oxalate ((NH4)2C204, 2H20), one part of the salt in twenty parts of water. Preparation — Mix a solution of oxalic acid with a slight excess of ammonia and evaporate. Tests—It forms with a soluble lime salt a white precipitate, CaC204, insoluble in oxalic (H2C204) or acetic (H,C2H302) acid; a very delicate reaction. Impurities — It may contain all the impurities of oxalic acid or of ammonia. It should leave no residue when ignited on platinum foil. 28 LABORATORY GUIDE. Uses — It forms in neutral solutions very difficultly soluble compounds with Ca, Sr, Ba, and Pb, precipitating their corre- sponding oxalates. It is especially good for the detection and separation of calcium. 34. Ammonium succinate ((NH4)2C4H404). Preparation — Neutralize succinic acid with ammonia. The succinic acid is made by heating tartaric acid with phosphorus and iodine in the presence of water: H2C4H406 + 4HI = H2C4H404 + I4 + 2H20. The succinic acid may be purified by dissolving in HN03 and recrystallizing. The most advantageous way of making succinic acid is by the fermentation of malic acid: 3C4H605 = 2C4H604 + C2H402 + 2C02 + H20. Tests and Uses — It separates the sesquioxide of iron from other heavy metallic protoxides. Impurities — It may contain tartaric acid or hydriodic acid. 35. Ammonium sulphate ((NH4)2S04), one part of the salt to four parts of water. Preparation — Neutralize sulphuric acid with ammonia and crystallize. Tests and Uses—Used in the separation of the alkaline earths. It precipitates Ba and Sr as sulphates. Impurities — It may contain the impurities of H2S04 or NH3. 36. Ammonio-sulphate of copper. Preparation — Made by adding NH4H0, drop by drop, to a not too concentrated solution of CuS04, until the precipitate at first produced is nearly redissolved; the clear solution to be employed. 37. Ammonio-nitrate of silver is made in the same way with AgN03 and NH4HO. PREPARATION OF REAGENTS. 29 Tests and Uses for 36 and 37—A solution of arsenious acid forms with 36 green CuHAsQ3 or Cu3(AsQ3)2, and with 37 forms yellow Ag3As03, both soluble in NH4HO and in dilute nitric acid. 38. Ammonium sulphide — (NH4)2S is colorless, and (NH4)2S2 is yellow; the higher sulphides are red. Preparation—Pass H2S through NH4HO until it does not produce a precipitate in a solution of MgS04. Tests —All alkaline sulphides, even in very dilute solutions, give a purple coloration with nitro-prusside of sodium. Impurities — It should not contain any free ammonia (test by MgS04) nor ammonium carbonate (test by CaCl2). It should leave no residue when evaporated to dryness and ignited. The solution spoils by long keeping. Uses — It is used as a group reagent. It precipitates as hydroxides Al and Cr from their solutions, with the escape of H2S: A12(S04)3 + 3(NH4)2S -J- 6H20 = _____ Al2(OH)6 4. 3(NH4)2S04 4- 3H2S. It precipitates the rest of the iron group, the lead group, and also, from acid solutions, the arsenic group as sulphides. Used in excess, it dissolves the sulphides of the arsenic group, and CuS to some extent. The phosphates of the alkaline earths and oxalates (except Mg) are precipitated unaltered; as calcium oxalate or phosphate, from a hydrochloric acid solution. 39. Barium acetate (Ba(C2H302)2). Keep in crystals. Preparation — Dissolve barium carbonate in acetic acid, filter, and crystallize. Tests and Uses — To take the place of BaCl2 in precipita- ting H2S04 when it is desired to avoid the introduction of a chloride into the solution, or to convert the base into an acetate. Impurities—It may contain the impurities of acetic acid. 30 LABORATORY GUIDE. 40. Barium carbonate (BaC03). Preparation — Precipitate a hot solution of BaCl2 with (NH4)2C03 mixed with some ammonia; wash the precipitate a number of times, and add water to the consistency of cream. Tests — H2S04 evolves C02, and precipitates the Ba completely as white BaS04, insoluble in all dilute acids. Impurities — It may contain HCl and NH3. Uses — To separate Fe203, Cr203, and A1203 from MnO, ZnO, NiO, MgO, etc., in neutral solutions free from sulphates. 41. Barium Chloride (BaCl2,2H20), one part of the salt in ten parts of water. Preparation — It may be formed from witherite, BaC03, by treatment with HCl, or from heavy spar, BaS04, by fusing with C, thereby producing BaS, and subsequent treatment with HCl: (1) BaS04 + 4C = 4CO -f BaS. (2) BaS + 2HC1 = B^S 4-BaCl2. Tests—H2S04 gives a white precipitate of BaS04, insoluble in acids. Test for chlorine as before described. Impurities — It should be neutral; H2S04 must completely precipitate it. Uses—As a special test for H2S04 and as a group reagent for acids. 42. Barium hydroxide (Ba(OH)2). A saturated aqueous solution at 15° C. contains one part in twenty. Preparation — Fuse the carbonate (witherite) with pow- dered charcoal, and treat with water, or dissolve the oxide in water: BaO -f H20 = Ba(OH)2. Tests — Same as No. 41, for Ba. Uses — To precipitate magnesia, and in the detection and estimation of H2S04 and C02, especially in the atmosphere. and H3P04. PREPARATION OF REAGENTS. 31 43. Barium nitrate (Ba(N03)2), one part in fifteen parts of water. Preparation—Treat BaC03 or BaO with dilute HN03. Tests — Same as No. 41, for Ba. Impurities — May contain HCl. Uses — It can be used to take the place of BaCl2 when it is desirable to avoid the presence of a metallic chloride in the fluid. 44. Barium peroxide (Ba02). Preparation — By heating BaO in a current of air or of oxygen. Tests and Uses — It is used to form hydrogen peroxide as follows : Ba02 -f 2HC1 = BaCl2 + H202. Impurities — It may contain BaO. 45. Bromine (Br), sp. gr. 2.96. Preparation — By treating the "bittern" of salt works with chlorine. Tests — By the odor. By the orange color it gives to starch solutions. By giving with AgN03 a yellowish white precipitate of AgBr. Impurities — It may contain CI. Uses —As an oxidizing agent. It will take the place of CI in most cases. 46. Bromine water (water saturated with bromine). One part of bromine is soluble in thirty-four parts of water; sp. gr. 1.024; is used in preference to Br in some cases. 47. Calcium carbonate (CaC03). Preparation—A hot solution of CaCl2 is precipitated by (NH4)2C08, with the addition of some NH4H0; wash well with hot water, and dry thoroughly. Tests —Ammonium oxalate gives with a solution of calcium a white precipitate of CaC2Q4. Test C02 as before described. 32 LABORATORY GUIDE. Impurities—May contain Ca(OH)2, HCl, and salts of the fixed alkalies. Uses — Used as a flux in the analysis of silicates when testing for the alkali metals. 48. Calcium Chloride (CaCl2,6H20), one part of the salt in eight parts of water. Preparation — Marble is treated with hydrochloric acid: CaC03 4- 2HC1 = CaCl2 -f C02 + H20. The CaCl2 is recrystallized. Tests—Ammonium oxalate gives a white precipitate of CaC204. Test for CI as before described. Impurities — It must have a neutral reaction, and not be colored nor precipitated by (NH4)2S. Uses — It is used as a group reagent for the acids, and in most cases acts like BaCl2. The anhydrous salt serves to dry gases, and for the absorption and estimation of water in organic analysis. 49. Calcium fluoride (CaF2). Preparation — It is found native as fluor spar sufficiently pure for use. Tests and Uses — When treated with H2S04, HF is liberated, which etches glass: CaF2 4- H2S04 = CaS04 +2HE 50. Calcium hydroxide (Ca(OH)2). Preparation — Dissolve quicklime (CaO) in water. Use the clear solution; keep in a well stoppered bottle. Tests and Uses —To detect C02, and to liberate NH3 from ammonium salts. It separates tartaric acid from citric acid — by precipitating the former in the cold, and the latter on boiling. To effect the removal of H2S04 and H3P04. It precipitates Magnesium from its solution as Mg(OH)2, nearly insoluble in water but soluble in NH4C1. PREPARATION OF REAGENTS. 33 51. Calcium oxide (CaO), quicklime. Preparation — The CaC03 is heated, when C02 passes off. Tests and Uses — It is chiefly used to liberate ammonia from ammonium salts, and in making soda lime. 52. Calcium sulphate (CaS04,2H20), gypsum. Preparation — Dissolve gypsum in water; use a saturated aqueous solution. Tests and Uses — Used in the separation of the alkaline earths. CaS04 precipitates Ba immediately, Sr after the lap*?, of some time, and Ca not at all. 53. Carbon disulphide (CS2), sp. gr. 1.27; boils at 45° C. Preparation — Made by passing the vapor of sulphur over heated charcoal: C -|- S2 = CS2. It is nearly insoluble in water, but very soluble in alcohol and in ether. Tests — The odor of its vapor is very offensive. Impurities — It may contain S02, S, and H2S. Uses — It is a solvent for sulphur, phosphorus, iodine, oils, gums, resins, and fats; also used for making thermometers for registering very low temperatures. 54. Chlorine water (water saturated with chlorine). Water absorbs at 10° C, two and fifty-eight hundredths times its volume of chlorine. Keep in a cool place, in a bottle covered with paper. Preparation—When a small quantity of chlorine is required, it can be made in a test tube as follows: Heat HCl with K2Cr207 — K2Cr207 + 14HC1 = 2KC1 -f 7H20 -f Cr2Cl6 + 6CT. Tests — Odor of chlorine. Impurities — May contain HCl and Cr2Cl6. Uses — It possesses most of the properties of the gas. It is an oxidizing agent, and a solvent for Au and Pt. 34 LABORATORY GUIDE. 55. Chloroform (CHC13), sp. gr. 1.48; boils at 61° C. (purified chloroform); chemically known as trichlormethane. Preparation — Made by heating to 65° C, ten parts of bleaching powder, forty parts of water, and one part of alcohol; sp. gr. .834. The following is thought to represent the reaction: 3C2H60 + 8(Ca(OCl)2) = 2CHC13 -f- 3CaC03 + C02 -4- 8H20 + 5CaCl2. Wood spirit, acetone, oil of turpentine, and many essential oils, likewise yield chloroform when treated with chloride of lime. It is almost insoluble in water, but soluble in ether and alcohol. Tests — Heat a few drops of chloroform with aniline and alcoholic caustic soda solution; the characteristic odor of carba- mine is observed. By this process one part of chloroform may be detected in six thousand parts of water. Impurities — It may contain H2S04, Na2C03, CI, C2H40, fusel oil, organic impurities, and water. It must have a neutral reaction, and leave no residue on evaporation. Uses — To remove Br and I from aqueous mixtures. It is a general solvent for gums, oils, and resins, and a group reagent for the alkaloids. 56. Cobalt nitrate (Co(N03)2), one part of the salt to ten parts of water. Preparation — Dissolve cobalt oxide in nitric acid, and recrystallize: Co(N03)2,5H20. Tests—With a borax bead it gives a blue color. Impurities—It may contain other metals, as Ni, and in some cases As. Uses — In the dry way for blowpipe use. It is a good test for Al, Zn, Si, Mg, and Sn. 57. Copper (Cu), metallic. Tests and Uses —It is employed to detect HN03, also to detect Hg and As. It is used in the manufacture of S02 and NO, also in organic analysis of nitrogenous substances, to effect the reduction of the nitric oxide. PREPARATION OF REAGENTS. 35 58. Cuprous chloride (Cu2Cl2), sp. gr. 3.7. Preparation —Boil CuCl2 with HCl and Cu filings; the solution yields, on the addition of water, a white precipitate of Cu2Cl2. Tests—The HCl solution of Cu2Clj, forms a compound having a mother of pearl lustre. Impurities — It may contain CuCl2. Uses — For absorbing CO in gas analysis (Cu2Cl2CO-{- 2H20). The ammoniacal solution of cuprous chloride gives with acetylene a red precipitate of di-acetylene cuprous oxide: 2C2H2 4- 2Cu2Cl2 -f H20 = 4HC1 + C4H2Cu4Q. 59. Copper sulphate (CuS04,5H20), one part of the salt in eight parts of water. Preparation — By treating pure Cu with H2S04. Tests —Ammonia gives a blue solution with Cu; potassium ferrocyanide gives a dark brown precipitate of Cu2FeC6N6. Potassium xanthate is the most delicate test for copper. Impurities—When precipitated by iron it always contains traces of it. Uses — To precipitate HI (when mixed with two and one- half parts of FeS04) as a white cuprous iodide, Cu2I2, the only iodide of copper. The reaction of CuS04 with HI and KI are similar: 2CuS04 4- 2FeS04 + 2KI = CuJ, -f- Fe2(S04)3 -f K2S04. It is used to detect arsenious and arsenic acids, also as a delicate test for the soluble ferrocyanides. 60. Ether ((C2H5)20), commercial ether or ethyl oxide, sp. gr. .750. Contains 74 per cent, ether and 26 per cent, alcohol. Preparation — By acting on alcohol with H2S04 between 130° and 137° C: (1) C2H6OH 4- H2S04 = C2H5HS04 4- H20. (2) C2H5HS04 + C2H50H = (C2H5)20 4- H2S04. 36 LABORATORY GUIDE. Tests — The odor is characteristic. Ether, of the above specific gravity, dissolves in three and eight-tenths parts of water. Absolute ether forms a clear mixture with any proportion of oil of copaiba. Anhydrous ether forms a clear mixture with CS2; if the smallest quantity of H20 be present, the mixture is milky. Impurities—Alcohol, water, and sulphuric or sulphurous acids. Uses — It dissolves the resins, fats, sulphur, phosphorus, iodine, and ferric, mercuric, and auric chlorides. 61. Ferric Chloride (Fe2Cl6), one part of the salt in fifteen parts of water. It should be as nearly neutral as is possible. Preparation — Dissolve iron or iron oxide in HCl, and add a few drops of HN03 to oxidize it. Tests — K4FeC6N6 gives a blue precipitate, Fe4(FeC6N6)3; KCNS gives a blood red color, Fe(CNS)3. Impurities — The ferrous salts. Uses — It is used in detecting the cyanides and phosphoric acid. It forms basic salts with benzoic, succinic, and acetic acids, which are completely precipitated from neutral solutions upon boiling. It gives characteristic colorations with free acetic, formic, and meconic acids, red; with salicylic acid, violet; with tannic acid, black ink; with phenol, creosote, daphnin, morphine, and pseudomorphine, blue. 62. Ferrous sulphate (FeS04,7H20), the dry salt; also, solution, one part of the salt to ten parts of water. Preparation—Take the ferrous sulphate residues in making H2S, concentrate and filter while hot, and let it crystallize under a layer of alcohol. Tests —Ferrocyanides form Everitt's white, K2Fe(FeC N ) and the ferricyanides form Turnbull's blue, Fe3(FeC N ) " Impurities — May contain ferric salts. PREPARATION OF REAGENTS. 37 Uses—As a test for free HN03 ; as a test for ferricyanides, and as a good reducing agent for the precipitation of metallic gold from its solutions. 63. Gold chloride (AuCl3). Preparation — Gold is dissolved in aqua regia, avoiding an excess of HN03. Evaporate on the water bath to dryness, and dissolve in water; it should be neutral. Tests and Uses — It is used as a test for stannous salts, forming the "purple of Cassius." Impurities—If made from gold coin, it may contain Cu. 64. Hydrogen (H). Preparation — Made by the action of dilute H2S04 on zinc — Zn + H2S04 = ZnS04 +H2. Add a drop of PtCl4 when you want to hasten the process. Pass the H through a mercuric chloride solution, and then through a potash solution. If it is desired dry, pass it through H2S04 or a CaCl2 tube. Tests—When burned with 0, water is formed. Impurities—Arsenic, hydrocarbons, and sometimes. H2S. Use3 — To reduce oxides, chlorides, and sulphides to the metallic state, and also to protect certain bodies, such as metallic sulphides, from oxidation during ignition. 65. Indigo solution. Preparation — Treat indigo with fuming sulphuric acid, added slowly, and in small portions at a time. Any considerable elevation of temperature must be avoided by placing the vessel in cold water. tjses — Used to fill prisms to cut off the sodium flame; also as tests for chlorine, and for chloric and nitric acids. A very dilute solution will in time decompose. 66. Iodine (I). It is purified by being resublimed. UsES — it is used in very many volumetric processes. 38 LABORATORY GUIDE. 67. Lead acetate (Pb(C2H302)2,3H20), one part of the salt in ten parts of water. Preparation — Dissolve lead oxide in acetic acid, using an excess of acid to prevent basic salts from forming: PbO 4. 2(H,C2H302) — Pb(C2H302)2 4- H20. Paper soaked in this solution is called lead paper. Dry, and keep in a well stoppered bottle. Tests — H2S precipitates Pb from its solutions as a black PbS; K2Cr207 precipitates yellow PbCr04. Impurities — Generally contains basic salts of lead. Uses — It is used as a special test for certain elements and compounds, as H2S, K2Cr207, H3P04, (NH4)2S, and H2S04, and in the preparation of organic acids. 68. Lead chromate (PbCrOJ. Preparation — Precipitate acetate of lead with potassium bichromate; wash, dry, and heat to a bright redness: 2Pb(C2H302)2 4- K2Cr207 4- H20 — 2PbCr04 4- 2KC2H302 4- 2H,C2H302. Tests — It is insoluble in water. When fused on charcoal with sodium carbonate, Pb is obtained; in like manner the Cr can be oxidized and tested. Impurities — It may contain lead carbonate. Uses — For the combustion of organic substances. It is converted by heat into the sesquioxide of chromium and basic chromate of lead, and gives off 0. 69. Litmus paper. Preparation — Dissolve litmus in water, filter, and divide into two equal parts; saturate the free alkali in one by dilute H2S04 until the color just appears red, and add the other part of the filtrate; draw strips of paper through the solution, and dry on threads. To make the red litmus paper, add H2S04 until distinctly red, and treat as above described. Tests and Uses — The blue is used to detect the presence of acids; and the red, of alkalies, alkaline earths, alkaline carbonates, and the soluble salts of some weak acids. PREPARATION OP REAGENTS 39 70. " Magnesium mixture." Preparation — Dissolve one hundred and one and five- tenths grams of crystallized magnesium chloride, two hundred grams of ammonium chloride, and four hundred grams of ammonium hydroxide (sp. gr. 96), the whole made up to one liter with water. This amount will precipitate thirty-five and five-tenths grams of phosphoric acid. Tests and Uses — Used as a test for arsenic and phosphoric acids and their soluble salts. 71. Magnesium sulphate (MgS04,7H20), one part of the salt in ten parts of water. Preparation — Made from the native carbonate by treating it with sulphuric acid: MgC03 4- H2S04 = MgS04 +W2 -f H20. Dolomite (CaMg2C03) contains Ca, but it forms with H2S04 an insoluble CaS04, while the MgS04 is very soluble; the Mg can be separated in this way from the Ca. Tests and Uses — Used for the detection of phosphoric and arsenic acids, which it precipitates in the presence of NH4HO and NH4C1 as ammonium magnesium phosphate or arsenate, sparingly soluble. It is used to test the complete saturation of NH4HO with H2S in making (NH4)2S. 72. Mercury (Hg), sp. gr. 13.6. Preparation — Cinnabar (HgS) is roasted in a suitable kiln: HgS + 02 = Hg + S02. Tests and Uses—At ordinary temperatures, the only liquid metal. Used in filling thermometers and barometers, and in gas analysis to collect dried gases. It is used to make sodium amalgam. 73. Mercuric Chloride (HgCl2), one part of the salt in sixteen parts of water. Preparation — Dissolve Hg in aqua regia, and crystallize. 40 LABORATORY GUIDE. Tests — KI forms with a solution of HgCl2 a red precipitate of Hgl2, soluble in an excess of either reagent. Impurities — It may contain the mercurous salts. Uses—As a test for tin (as stannous chloride), HI, and KI. Mercuric oxide, sulphide, iodide, iodate, basic carbonate, oxalate, phosphate, arseniate, arsenite, ferrocyanide, and tartrate are insoluble in water. 74. Mercurous nitrate (HgN03,2H20). Preparation — Dissolve one part of Hg in one part of HN03 (sp. gr. 1.2), and let the crystals separate; dissolve these in H20, mixed with dilute (one to sixteen of H20) HN03, by trituration in a mortar; filter, and keep the filtrate in a bottle, with some Hg covering the bottom of the vessel. Tests — It forms with KI a greenish yellow precipitate of Hg2I2. Impurities — The mercuric salt. Uses — Mercurous compounds of ordinary occurrence are insoluble in water, except the normal nitrate. Fixed alkali hydroxides precipitate black Hg20, insoluble in alkalies. NH4HO precipitates black (NH2Hg2)NQ3, insoluble in alkalies and soluble in acids. It serves as a test for many acids, as formic acid. 75. MicroCOSmic salt (NaNH4HP04,4H20), crystals. Preparation—Add a hot solution of disodic hydric phos- phate to ammonium chloride. Free the crystals from NaCl by recrystallization: Na2HP04 4- NH4C1 = NaNH4HP04 4- NaCl. Tests—The tests for phosphorus and for ammonia. Impurities — If it forms a clear colorless bead, the impurities may be disregarded. Uses — For the identification of Si02 by the blowpipe, and also to take the place of borax beads. PREPARATION OF REAGENTS. 41 76. Millon's reagent. Preparation — Dissolve one part of mercury in one part of HN03 (sp. gr. 1.42) ; dilute with twice its bulk of water, and filter after twenty-four hours. Tests and Uses — It is a good test for all " protein " bodies. When heated with albumin, etc., it produces first a yellow and afterwards a red coloration. 77. Oxygen (0). Preparation — Made by heating a mixture of KC103 and Mn02 as follows : KC103 4- Mn02 = Mn02 4- KC1 +"0"3. Tests—A mixture of potassium hydroxide and pyrogallic acid absorbs oxygen and blackens the pyrogallate. When O is burned with H, water is formed. Impurities — Impurities can be removed by passing it through a solution of KHO (sp. gr. 1.27), then through (J tubes containing soda lime, and then through U tubes containing CaCl2. Uses—As an oxidizing agent and in organic analysis in the place of CuO and PbCr04. 78. Platinum vessels (care of). The following precau- tions must be observed in their use: 1. Never fuse caustic alkalies, alkaline earths, nor their nitrates in platinum. Use a silver dish instead. 2. Never fuse the alkaline sulphides with carbon, nor other fusible sulphides, nor cyanides in a platinum dish. 3. Easily fusible metals, or their oxides with carbon, form fusible alloys with Pt. Never fuse organic metallic salts in Pt. 4. Phosphates and carbon at a high temperature give rise to fusible phosphides of platinum. 5. Chlorine, bromine, aqua regia, or mixtures that liberate them, dissolve platinum. 6. Silicon, at high temperatures, combines with platinum. 7. Clean them by fusing in them bisulphate of potash or borax, and polish them with fine sea sand or emery flour, and always keep them polished. When fusing an unknown body on platinum foil, always do it on one corner, never in the center. 42 LABORATORY GUIDE. 79. Platinum chloride (PtCl4,10H2O), one part of the salt in ten parts of water. Preparation — Dissolve clean platinum scraps in aqua regia, and evaporate on the water bath to dryness. The residue should dissolve completely in alcohol. Tests and Uses — It is a quantitative test for K, forming a yellow precipitate of 2KCl,PtCl4; also a test for NH4HO, Cs, and Ru. 80. Potassium bisulphate (KHSOJ. Preparation—As a bye product in the manufacture of HN03; also made by treating the normal sulphate with sulphuric acid. Tests and Uses — Used as an important reagent in the dry way for blowpipe work; also used for cleaning Pt crucibles. 81. Potassium chlorate (KC103), crystals. Preparation — Pass a slow current of CI into a cold dilute solution of KHO: (1) potassium chloride and potassium hypochlorite are formed — 2(K20,H20) 4- 4C1 = K20,C120 + 2KC1 4- 2H20. (2) If this solution is boiled, it is converted into the chlorate and chloride —3(K20,C120) = 4KC1 + 2(KC103). Tests—When heated, oxygen is given off; K gives a violet tinge to a colorless flame. Impurities — KC1 and CI. It is sometimes made from CaO,Cl20, when it may contain calcium sulphate and chloride. Uses—As an oxidizing agent with HCl or H2S04, and in the manufacture of oxygen. 82. Potassium hydroxide (KHO), solid, and a solution of a specific gravity of 1.27. Preparation — Made by treating carbonate of potash with milk of lime, as follows: K2C03 4- Ca(OH)2 = CaC03 -f 2KH0. PREPARATION OF REAGENTS. 43 If the solution of potassium is too strong, the lime will not remove the whole of the carbonic acid. The CaC03 is insoluble and settles out; the liquid is evaporated in an iron or silver dish. Tests — It gives a violet flame, and is strongly alkaline. Impurities — It is hard to free it from carbonates. When KHO is dissolved in absolute alcohol, and the solution evaporated in a silver dish, the residue will be nearly pure KHO. Pure potassium hydroxide is very difficult to make; the above treatment will give a sufficiently pure product. Uses — It expels ammonia from its salts. A solution of a specific gravity of 1.27 (one of KHO to three of water) is used for the direct determination of C02. It is used for the determi- nation of sulphur in organic substances. It precipitates many oxides and hydroxides, some of which are soluble in an excess of KHO, as Al, Cr, and Pb; others are insoluble in excess, as Fe and Bi. It also dissolves some salts, as lead chromate and sulphur compounds. It is used to generate hydrogen by dissolving Zn, in contact with Fe or Pt: 2KHO + Zn = ZnK202 -f H"2. 83. Potassium iodide (KI), one part of the salt to twenty of water. Preparation — Iodine is added to a solution of potassium hydroxide, forming an iodide and an iodate: 6KHO 4- 61 = 5KI + KI03 + 3H20. When KI03 is heated, it decomposes into KI 4- 03. Tests — Mercuric chloride gives a red precipitate of Hgl2, soluble in an excess of either reagent, as follows: HgCl2 -f 2KI = HgI2 4 2KC1. Impurities — It may contain an iodate, and the impurities of KHO and of I. When KI is dissolved in dilute H2S04, it should be colorless; a brown color indicates free iodine. 44 LABORATORY GUIDE. Uses — It is used as a solvent for iodine, and in the estimation of free chlorine. It precipitates silver, mercurous and mercuric, lead, copper, bismuth, and cadmium salts from their solutions as iodides. 84. Potassium metantimoniate (KSbOs). Dissolve when required, as it is not permanent in solution. Preparation — Fuse antimonic acid with a large excess of potassium hydroxide; dissolve, filter, and digest hot in a silver dish, with an excess of potassium hydroxide; decant the alkaline liquor, and stir the residue until it becomes dry. Tests and Uses — It cannot be used in acid solutions. It produces in neutral or alkaline solutions of sodium a white, slow-forming, crystalline precipitate of NaSb03 that is nearly insoluble in cold water. 85. Potassium nitrate (KN03), the crystallized salt. Preparation — It is found native in many hot countries. It is made by boiling together solutions of Chili saltpeter, and potassium chloride : NaN03 -\- KC1 = KN03 -f- NaCl. The NaCl crystallizes out first. The mother liquor contains the KN03. Tests and Uses — It is an oxidizing reagent. 86. Potassium nitrite (KN02), one part of the salt to two parts of water. Preparation — By passing nitrous acid into KHO until it is completely saturated. The nitrous acid may be made by taking two parts of starch, eight parts of HN08 (commercial, sp. gr. 1.4), and eight parts of water, and heating; as soon as the action begins, the flame is taken away. The fumes (N203) are passed first into a cooled empty flask, and then into KHO. Tests and Uses — It serves in the presence of free acid to liberate iodine from its compounds. It detects and separates cobalt by precipitating it as potassium cobaltic nitrite: 2CoCl2 -f 12KN02 -f 2HC2H302 + H20 = (KNQ2)6,Co20(NQ2)4,2H20 -4- 4KC1 + 2KC2H302 4. 2NO. PREPARATION OF REAGENTS. 45 87. Potassium sulphate (K2S04), one part of the salt to two hundred parts of water. Preparation — Purify the commercial salt by recrystalliza- tion, when it will be sufficiently pure. Tests and Uses — It serves to separate Ba from Sr (see No. 52). It is used in preference to H2S04, as it does not, like that reagent, disturb the neutrality of the solution. 88. Silver nitrate (AgN03), one part of the salt in thirty parts of water. Preparation — Silver coin can be used in its preparation. The coin is dissolved in HN03, forming the nitrates of copper and silver. Precipitate the silver by HCl as silver chloride (AgCl); the copper remains in solution, and can be poured off; wash the AgCl until the wash water gives no traces of copper with ferrocyanide. Reduce the AgCl to pure metallic silver by means of Zn and HCl, the nascent hydrogen combining with the chlorine of the AgCl to form HCl, leaving the silver in a finely divided state. Wash and dissolve the silver in the smallest possible quantity of HN03, and evaporate to dryness. It should be neutral to litmus. Tests — Hydrochloric acid completely precipitates it as white AgCl, insoluble in dilute HN03, but soluble in NH4H0. Impurities — Made as above described, it will contain no impurities. Uses —A group reagent for the acids, and a special test for HCl. 89. Sodium acetate (NaC2H302,3H20), one part of the salt in ten parts of water. Preparation — Neutralize sodium carbonate with acetic acid, and crystallize. Tests — It gives the reactions for sodium and acetic acid before described. Impurities — It may contain the impurities of sodium carbonate or of acetic acid. 46 LABORATORY GUIDE. Uses — Sodium acetate added in sufficient amount to solu- tions containing other acids, results in forming salts of these acids, leaving acetic acid as the only free acid. In the presence of this free acid, in not too large excess, Zn is precipitated by H2S as ZnS; Fe203 and A1203 as basic acetates upon continued boiling. 90. Sodium carbonate (Na2COa,10H2O), the crystals, the perfectly dried salt, and a solution containing one part of the salt to eight parts of water. Preparation — It is made by roasting salt cake with an equal weight of chalk and about half its weight of coal. Tests — It gives the tests for sodium and for carbonic acid. Impurities — It may contain Si02, H2S04, HCl, Fe, H3P04, and As. Uses — In the dry way as a flux. When fused it decomposes sulphates, silicates, and arsenious sulphide. It is a special test in the dry way, when KN03 is added, for manganese and chromium, forming a green opaque bead of sodium manganate, or of yellow sodium chromate. It is used to saturate free acids. Its solution precipitates most of the metals as carbonates. 91. Sodium chloride (NaCl), crystals. Preparation — Common salt is purified by passing into its concentrated solution, hydrochloric acid gas to saturation; the small crystals of NaCl which form are collected on a funnel, drained, and washed with HCl; the NaCl is then dried in a porcelain dish until the HCl has been completely evaporated. Tests — It gives the tests for Na and CI. Impurities — It may contain CaS04 and MgCl2. Uses — It is used for the volumetric assay of silver, and to standardize solutions of silver for the estimation of chlorine. It is usually fused before weighing; if the gas flame acts on the salt, HCl escapes, and sodium carbonate is formed. PREPARATION OF REAGENTS. 47 92. Sodium hypochlorite (NaCIO), the solution. Preparation — (1) Hypochlorites are made by passing CI through a solution of metallic hydroxides. (2) Agitate one part of good bleaching powder with ten parts of water; add sodium carbonate to the solution as long as a precipitate is formed, allowing the solid matter to subside, and use the supernatant liquid: Ca(OCl)2 -f CaCl3 -f 2NaC03 = 2NaC10 + 2NaCl -f- 2CaC03. Tests and Uses — It liberates iodine from KI. It is a good oxidizing agent. It dissolves arsenic spots by oxidation to arsenic acid, distinction from antimony. 93. Soda lime. Preparation — To a solution of sodium hydroxide add twice the weight of the best quicklime, and evaporate to dryness in an iron vessel; heat to a low red heat in an iron or Hessian crucible, and break up the lumps in an iron mortar, passing them through a coarse sieve — eight meshes to an inch. Tests and Uses — It should be free from ammonia, and effervesce but slightly with dilute HCl. It is used as an absorbent for carbonic acid, and in the analysis of nitrogenous organic substances. 94. Sodium nitrate (NaN03), crystals. Preparation — Neutralize sodium carbonate with nitric acid, evaporate, and crystallize. It is found native in an impure state (Chili saltpeter). Tests and Uses — It is a powerful oxidizing agent. It is used to convert the sulphides of tin, arsenic, and antimony into oxides or acids; also to complete the combustion of organic substances. 95. Sodium nitroprusside (Na4C10N10N2O2Fe2,4H2O), one part of the salt in twenty parts of water. 48 LABORATORY GUIDE. Preparation — Digest one part of potassium ferrocyanide with two parts of HN03 and two parts of water until it ceases to produce a blue precipitate with iron salts; when cool, neutralize the mother liquid with sodium carbonate, and then collect the red crystals. Tests and Uses — It gives with the alkaline sulphides a purple color;' a very delicate test. 96. Sodium palladio-chloride (PdCl4,2NaCl), one part of the salt in ten parts of water. Preparation — Dissolve five parts of palladium in aqua regia, add six parts of sodium chloride, and evaporate in a water bath to dryness. Tests and Uses — The brownish solution is a good reagent for detecting and separating iodine from Br and CI. 97. Sodium ammonium phosphate (NaNH4HP04,4H20), *>r microcosmic salt. Preparation — Heat six parts of disodium phosphate and one part of pure ammonium chloride with two parts of water; free from the NaCl by recrystallization and by the addition of ammonia; dry the purified crystals, and pulverize. Tests and Uses—When heated, it first loses its water, then its ammonia, and becomes a glassy, transparent mass of sodium metaphosphate, NaP03, which dissolves many metallic oxides with characteristic colors. In the dry way, it is used for beads ; it is a special test for the determination of silica. 98. Sodium sulphite (Na2S03) and acid sodium sulphite (NaHS03), one part of the salt to five parts of water. Preparation — Made by passing S02 over crystals of Na2C03 until the evolution of C02 ceases. Tests — Lead acetate precipitates white lead sulphite, PbS03, easily soluble in dilute nitric acid, and not blackening when boiled (distinction from thiosulphate). Impurities — It may contain sodium sulphate. PREPARATION OF REAGENTS. 49 Uses — It is a good reducing agent in acid liquids, changing arsenic acid to arsenious acid, chromic acid to chromic oxide, and ferric oxide to ferrous oxide. It separates arsenious sul- phide, which is soluble in it, from the sulphides of antimony and tin, which are insoluble in it. 99. Sodium thiosulphate (Na2S203,5H20), or sodium hyposulphite, one part of the salt in forty parts of water. Preparation — Treat a solution of Na2S03 with sulphur: Na2S03 -|-S = Na2S203. Tests and Uses — It gives a precipitate of S, with evolution of S02, when its solutions are treated with HCl; it has great reducing power, and does not precipitate calcium (distinction from sulphite). It is employed in volumetric analysis. It separates Sn from As and Sb by precipitating, from acid solu- tions, As and Sb as sulphides. It is a solvent for several salts, as AgCl, Hg2Cl2, and CaS04. 100. Stannous chloride (SnCl2,2H20), one part of the salt in six parts of water, acidulated with HCl. Preparation — Dissolve tin in hydrochloric acid, having an excess of tin in the vessel; keep the solution in a well stoppered bottle containing small pieces of tin. Tests and Uses — It is a good reducing agent, and a special test for mercury and gold. 101. Starch solution. Preparation — Pulverize a piece of starch the size of a pea in a mortar, and add water enough to wash it out; this is added to a quart of boiling water, and the boiling is continued for two minutes; use when cold. Starch paper is made by saturating unsized paper in this liquid and drying it. Tests and Uses — Used as a test for free iodine, with which it gives a blue color. 102. Turmeric paper. Preparation — Heat one part of bruised turmeric root with six parts of weak alcohol; filter the tincture obtained, and steep slips of unsized paper in the filtrate; they acquire a yellow tint. 50 LABORATORY GUIDE. Tests and Uses — It is used as a test for the alkalies and for boracic acid. Mix an alkaline borate with HCl to slight acid reaction; a slip of turmeric paper is dipped into it and then dried at 100° C, the dipped portion will show a peculiar wine red tint; this reaction is very delicate. 103. Zinc (Zn), granulated metal. Preparation — Melt Zn in an iron ladle, and pour in a small stream from a height of six feet into a jar of cold water, and dry. Chemically pure Zn is used in Marsh's test. Zinc free from iron is used in volumetric analysis of iron. For ordinary use, zinc free from arsenic is all that is required. Tests and Uses — To generate hydrogen, and for arsenetted and antimonetted hydrogen. It precipitates the less electro- positive metals from their solutions, as Cu. It is used to detect sulphurous acid and phosphorous acid. It is a very valuable exercise for the student to make the reagents, as a laboratory practice, and to always test their purity. In all his work, he must bear this thought in mind, "Trifles make perfection, but perfection is no trifle." CHAPTER II. TESTS IN THE DRY WAY. 104. The following hints will be of use to the student: 1. Have everything neat and clean. 2. Never put anything away dirty. 3. Take the smallest possible quantity of the assay. 4. Know what you do, and why you do it. 5. Do the work yourself 6. Note the characteristic tests, and remember two of them. 7. Look up the properties and reactions of the substance in some work of reference. 8. Never quit a substance until you have mastered it. 9. It is not how much you do, but how well you do it. 10. Caution — Do not expose yourself nor others needlessly to the vapors of the laboratory; as, chlorine, hydrogen sulphide, arsenic, etc.; the bad effects may not be perceptible immediately. Keep accurate notes at the time. The following is the most convenient way to keep a note book: NAME SYMBOL STATE REACTION REMARKS (1) Sodium chloride. NaCl. White crystal-line solid, iu cubes. Decrepitates; can be prevented by being finely pulverized. The decrepitation is caused by the water mechanically in-closed in the crys-tals. (2) Potassium chlorate. KC103. White crystal-line solid, in monoclinic tables Gives off oxygen: KC103 = KC1 +~Cv It deflagrates upon a glowing coal, gives a violet flame. The above can occupy two pages of a note book. 52 LABORATORY GUIDE. 105. Note the physical properties of the substance — its state, solid or liquid. If liquid, evaporate a portion to dryness, and use it in the following tests. (H20, H202, the volatile acids, HCl, HN03, HC2H302, and many organic compounds will leave no residue). If solid, or when rendered solid by evaporation, carefully note its form, crystalline or amorphous, compact or pulverulent, homogeneous, or an evident mixture; also its color, luster, feel, hardness, specific gravity, and sometimes its taste. If it suffers any change upon exposure to the air, stable, deliquescent, or efflorescent. 106. Heat the dry and finely pulverized solid in a small glass tube open at one end (a matrass), at first gently, gradually increasing the heat as seems to be required, noting any changes that occur. It decrepitates from H20 mechanically inclosed INDICATION op It becomes strongly luminous or phosphorescent. It changes color from — / yellow, on cooling is again white. 1 dark yellow, " yellowish .. ] dark yellow, on cooling is yellow-White to < ish, fusible at red heat........ J reddish yellow, on cooling is red-f dish yellow, fusible at a white \ heat....................... Haloid salts, as NaCl, etc. Alkaline earths, fluorides, etc. Zinc, ZnO. Tin, SnO, Ti02. Bismuth, Bi203. Cadmium, CdO. Lead, PbO. Green or reddish to nearly black, on cooling is reddish brown (magnetic)........... Bed to brown, while hot, and on cooling is red, or becomes so on rubbing....... The red salts of Co, the pink salts of Mn, the blue and green salts of Cu and of Ni, lose H20, and at greater heat decompose, evolving acid vapors, and leaving dark Iron, Fe203. Mercury, HgO. Co, Mn, Ni, and Cu. TESTS IN THE DRY WAY. 53 Organic compounds generally blacken from separation of carbon, evolving inflammable products like acetone (C0(CH3)2), and the odor of burnt sugar (C deflagrates with KC103)................................. Alkaline salts of organic acids leave residues of carbonates, which effervesce with HCl: It fuses quietly, and on cooling again becomes solid without being decomposed.......... It gives off aqueous vapor, that condenses in up- per cool part of tube (test by litmus paper): (1) A neutral reaction....................... Water of crystallization, the mass remains fluid while hot......................... Water of crystallization, the mass becomes again dry............................. (2) An acid reaction, salts with weak bases like Al or Zn................................ (3) An alkaline reaction, as NH3............. It yields a sublimate which is without fusing, yellow when hot, Hg2Cl2, with KHO becomes black......................... melting at 205° C, boiling at 295° C, HgCl2, with KHO be- comes yellow................. volatile at 165° C, in slender needles, H2C,04, with H2S04 evolves CO and C02 ......... volatile at 218° C, forms octahe- White ( dral crystals, As203, with H2S becomes yellow.............. heavy fumes, crystalline needles, Sb203, with H2S changes to orange ....................... easily volatilized, in crystalline needles, NH4 salts, with soda lime evolves NH3............. melts, but volatilizes with diffi- culty, and on cooling forms a transparent mass............ INDICATION OF Acetates, tartrates, citrates, etc. Some compounds of the al- kalies. Hydrates, hydrous silicates. Phosphates and Borates. Alums, CuS04, etc. Acid sulphates, fluorides. NH4 compounds. Hg. See below. Hg ealts, heated with dry Na2C03 + C yield glob- ules of metallic Hg. Oxalates; CO burns with a blue flame, and C02 ren- ders Ca(OH)2 turbid. As, heated with C, gives garlic odor. Sb203, which is soluble in H2C4H406. NH3, will brown turmeric paper. PbCl2, blackens with H2S. 54 LABORATORY GUIDE. Yellow needles, fusible to red drops, becom- ing yellow on cooling, but on rubbing again become red...................... Yellow drops, yielding dark red or even black drops when hot................. Bed drops, yielding dark red or even black drops when hot........................ Black drops, both when hot and cold, but becoming red upon rubbing............ I black and compact, As.. formed of globules, Hg.. with violet vapor of I... The mass after melting seems to boil, giving off a gas: violet fumes of I, which change starch blue...... red fumes of Br, which Condensable ( change starch yellow___ colorless vapors of As and S, condensing to red or yellow drops............ of burning sulphur = S02, which bleaches KMn04 and K2Cr207 -f H2S04 to green. of peach kernels = CN, which burns with a rose colored flame, and changes AgN03 to AgCN................... of rotten eggs = H2S, which blackens lead paper........ of ammonia = NH3, which blackens Hg2Cl2............ of chlorine = CI or C120, which turns starch paper-f- KI blue.................... of acetone = CO(CH3)2, is in- flammable; the assay heated with H2S04 + C2H60 yields acetic ether................ odor of frankincense......... fumes which cause violent coughing................... red fumes, soluble in H20___ INDICATION OF Hgl2. Sulpharsenides, As2S2. Sulpharsenides, As2S3. HgS. Arsenides, As. HgO, amalgams. I205, some iodides. Iodates and some iodides. Bromates. Sulpharsenides and persul- phides. Note the odor. Sulphites, sulphates, etc. Cyanogen compounds. Hydrous sulphides and hy- posulphites. Organic compounds, NH4 compounds, and cyanides. Hypochlorites, PtCl4, and AuCL. Acetates. Benzoic acid. Succinic acid. Nitrates and bromates. TESTS IN THE DRY WAY. 55 Colorless and inodorous. ignites a glowing splinter, O, or N20 from the salts of...................... renders Ca(OH)2 turbid, C02; burns with a blue flame, CO; both are bet- ter shown after adding H2S04 to assay......... INDICATION OF I205, N206, NH4N03, and peroxides. Formates and oxalates. 107. Heat the dry substance, together with certain dry reagents, in the matrass. H2SO. reaction Oxidizing with KC103 + Na2COs (better on Pt foil); green indicates Mn; yellow, Cr..... H2S reaction with Na2S203; Zn white, Cd and As yellow, Mn and Cr green, Sb red, and Sn brown............................... / with KHS04 decomposes I formates, acetates, oxa- lates, ateo fluorides, etc.. with KHS04-)- Mn02, evolv- [ ing from the haloid salts, \ CI, Br, and I............ with black flux (Na2C03 + C) or NaX03 + KCN, the volatile elements...................... in tubes of very thin glass, with Mg wire or Na pellets, heat the Beducing ( dried solid, phosphides changed from phosphates -|- H20, evolve odor of decaying fish = PH3... sulphides obtained from sulphates -j- H20 or HCl on Ag, give black stain.......................... INDICATION OF Mn and Cr. Pb, Ag, Hg, Cu, Bi, Ni, Co, and Fe, black. Liberating these acids. Haloid salts. As, Hg. Phosphates. Sulphur compounds. 108. Oxidize the substance by heating in a dry glass tube, open at both ends. 56 LABORATORY GUIDE. / a whitish yellow sublimate, with INDICATION OF / fumes of burning sulphur = S02. Sulphides. / a white to steel gray or red subli- mate, odor of horse radish = Sc02, Selenides. 1 white fumes, fusible to colored \ drops — Te02.................. Tellurides. \ As2S3 oxidizes to As203 and S02; J a portion sublimes in reddish yel- Evolves ( low drops....................... Higher arsenides, except \ colorless vapors of As203, con- those of Ni and Co. / denses in beautiful octahedral 1 crystals, and on C gives a garlic 1 odor................ .......... Higher arsenides, except white dense fumes of Sb203, some- those of Ni and Co. 1 times accompanied by red drops \ of Sb2S3....................... Antimony compounds. \ amalgams and HgO yield Hg easily, Mercury compounds. When strongly treated, the salts of Bi, Pb, and Sn yield yellowish white sublimates, Cd brown, Zn and Th white, better shown in film reactions. 109. Confirm the most important of these reactions by repeating these tests, and by others in addition. Bemember — All NH4 salts when heated with soda lime yield NH3 gas; test by litmus, HgCl2, and odor. All S compounds fused with Na2C03 yield a hepar, which with H20 blackens Ag. All Hg compounds fused with Na2C03 + C (black flux) yield globules of Hg. All As compounds heated with C are reduced to As, and yield lustrous mirror. Note the garlic odor. All Sb compounds fused with Na2C03 -)- KCN yield metallic Sb, oxidizable to white Sb203. These reactions are also valuable for the detection of the volatile acids, as HCl, HN03, H2COs, HC2H302, and also such as can be liberated by H2S04, as HCl, HBr, HI, etc.; also for H2S04 and H3P04. TESTS IN THE DRY WAY. 57 110. Heat a portion of the substance on charcoal before the blowpipe, first alone in the oxidizing flame. ft decrepitates...............................•. It deflagrates— The residue is neutral to litmus paper.... The residue is alkaline to litmus paper... It fuses — Sinks into the charcoal or forms — A crystalline bead...................... A transparent mass. Test for alkaline reaction............................... It evolves an odor — Of ammonia............................. Of burning sulphur...................... Of garlic.............................. Of decaying horse radish................ Yields fumes which form a coating on the coal: Easily volatilized — White to bluish white, White, in R. F., garlic odor........ Dark gray, horse radish odor..... Dark yellow....................... White............................. Not included in the list are some other substances, as....................... Not volatile in the O. F — light yellow.............. yellowish white........... orange yellow............ white, metal burns with a When cold ( lurid flame............. white, coating unchanged by R. F................. reddish brown, obtained only in a strong O. F... dark yellow............... orange yellow............. j reddish brown............. yellow.................... pale yellow................ reddish brown............. INDICATION OF NaCl or calcite. Nitrates, chlorates, iodates. Nitrates and carbonates of alkalies, alkaline earths. Pb3(P04)2. Salts of alkalies, alkaline earths. NH4 salts, some cyanides. Sulphides, hyposulphites. As. Se, Te. As. Se. Te. Sb. Hg2Cl2, NH4C1, and some sulphides. PbO dark yellow. Bi203 orange yellow. CdO reddish brown. ZnO yellowish white. S11O pale yellow. AgO reddish brown. PbO. Bi203. CdO. ZnO. SnO. AgO. 58 LABORATORY GUIDE. Leaves an infusible residue; oxidize thoroughly; this residue, moistened with Co(N03)2, and again ignited, becomes after heating / a blue infusible mass...... j a blue glass............... INDICATION OF A1203, Si02. Alkaline silicates, borates, and phosphates. SnO, bluish; ZnO and Ti02, yellowish; Sb. MgO, TaO. BaO. White and \ / a pink mass............... 1 a brown red mass......... \ a gray mass............... / Some of the residues yield \ characteristic borax beads.. Colored / Mn and Cr may also be tested / by heating on Pt foil with \ KN03..................... CaO, SrO, Cr203, Sb205. CuO, CoO, Fe203, Mn02, NiO, and Cr203. Mn gives green mass -(- HA = red; Cr gives yellow mass (test by Pb(A)2). Na Yields a characteristic color to the flame— (Easily reducible metals are best tested on charcoal; and easily volatilized sub-stances on Pt wire.) Moisten insoluble salt with strong HCl. Violet K, Rb, Cs, In. Li carmine......................... ( crimson......................... Sr Bed ^ mixed with yellow, after intense heating and moistening in hydro-chloric acid............4....... Ca. Green / emerald green................. I bluish green if Se is present___ ) pale green to yellowish green... ) yellowish green, moisten salts [ with strong H2S04......... \ bluish green............. Cu, Th. Te. Ba. B. P. 1 Se Pb Blue ( azure blue, then green....... light blue in R. F........... CuCla. As ( faint, greenish blue....... Sb. 111. Heat a portion of the substance, finely pulverized and mixed with Na2C03 or KCN, in the reducing flame. TESTS IN THE DRY WAY. 59 INDICATION OF As. Hepar is produced, which, when moistened with H20 or dilute HCl, blackens a silver coin. S, Se, Te. Yields a volatile metal, which immediately oxidizes and forms — A white coating on the coal; garlic odor. As. A coating, yellow when hot; white when Zn, Te. A coating, reddish brown, and easily vola- Cd. Yields a reguline metal — Malleable bead toith incrustation— Yellow to red....................... Pb. Yellow.............................. Tl. White.............................. In. Malleable bead with slight incrustation— White, best with KCN............... Sn. Ag. Brittle bead with incrustation— Sb. Orange to yellow.................... Bi. Malleable scales or infusible powder— Red, when rubbed on a hard surface.. Cu. Au. Fe, Co, Ni. Pt, Ir, Mo, W. 112. Heat a portion of the substance in the reducing flame, on a wood splinter coated with Na2C03, and charred; some metals are reduced. Wash away the Na2C03 in a mortar, and test further. Magnetic powders are....... Malleable particles are....... Brittle beads or spangles are. INDICATION OF Fe, Co, Ni. Pb, Ag, Sn, Au. Sb, Bi, Cu, Tl. 113. Bring the washed residues of Nos. Ill and 112 on a slip of glass, dissolve in HN03, HCl, or aqua regia, and test. 60 LABORATORY GUIDE. HN03 solution — Fe(N03)3 gives a blue precipitate with K4FeC6N6, red solution with KCNS. Ni(N03)2 gives a green precipitate with NaHO, which blackens with Br fumes. AgN03 gives a white precipitate with HCl, soluble in NH4HO, and a red precipitate with K2Cr207. Pb(N03)2 gives a white precipitate with HCl and H2S04, and a yellow precipitate with K2Cr207. Cu(N03)2 gives a red precipitate with K4FeC6N6, blue solution with NH4HO. HCl solution — BiCl3 gives a white precipitate with H20, which blackens with H2S. CoCl2 solution is blue when warm, red when cold; test by borax bead. SnCl2 reduces AuCl3 and HgCl2; gives with borax bead and a trace of Cu, red Cu20. Aqua regia solution AuCl3, reduced by SnCl2 or FeS04 to a purplish powder. PtCl4 with NH4C1 gives a yellow precipitate; ignited gives spongy Pt. SbCl3 gives a white precipitate with H20, soluble in H2C4H406, becomes orange with H2S. Note —Some of these reactions are especially useful — The deflagration produced by the nitrates and chlorates. The odor of As, Se, and S. The non-volatile coatings of Pb, Bi, Zn, and Cd. The coloration by cobalt of Al, Mg, Zn, and Sn. The flame coloration of Na, K, Li, Sr, Cu, B, and Ba. The hepar of S and Se. The reguline metals of 111 and 112, with their confirmatory tests. 114. Put the substance in a small test tube, and add HCl and a thin strip of Zn. If a reduction follows, It may color the liquid Violet, indicates Ti02. Blue, indicates W03 or V205, changing finally to brown Mo, Ta, Nb. Green, indicates Cr03; in large excess also Fe203. It may leave a deposit on Zn Black, indicates Pt, Pd, Bi, Sb, Sn, Pb, Cd, Tl. Brown to yellow, indicates Au, red Cu. TESTS IN THE DRY WAY. 61 Brown to gray, indicates Ag, Hg, As, in dilute solutions the others also; repeat for " Reinsch's test" the Hg, As; Sb and Bi with a bright copper strip; heat the mixture, and afterwards heat coated strip in tube open at both ends. It may evolve a gas Due only to the HCl; to HCN, cyanides; to C02, carbonates; to S02, sulphites or hyposulphites, H2S, sulphides. Due also to the reducing action of nascent H; H2S, H2Se, H2Te, H3P, H3As, H3Sb; test by paper moistened with Pb(C2H302)2, AgN03, AuCl3; reactions of the hyposulphites indicate com- pounds of P, As, and Sb. 115. It is well for the student to notice that — The Closed tube is used for detecting bodies that change color when heated, as Zn, 0, and organic compounds, etc.; those that give off odors, as acetates, tartrates, etc.; those that are easily volatile, and yield a sublimate, as Hg, As, I compounds, etc.; those that seem to boil and give off a gas, as 0, CO, CO2, etc.; those that are easily oxidized or reduced with dry reagents, as Pb, As, and Hg compounds. The bent opened tube is used for easily oxidized substances, as sulphides, Sb compounds, As and Hg, etc. Charcoal is used for detecting bodies that decrepitate, as NaCl; that deflagrate, as nitrates, etc,; that evolve an odor, as NH3 and As; that yield coating on the coal, as Pb, Bi, etc.; that yield an infusible and colored residue when it has been treated with Co(N03)2, as Mg, etc.; that yield easily reducible metals, as Pb, etc. Platinum wire is used for easily volatile substances that color the flame, as K, Sr, etc. A modification of the film tests (116) is made by using thin tablets of plaster-of-Paris and an alcoholic solution of iodine. The substance is placed on the tablet, moistened with the solution of iodine, and the blue flame is used, when the volatilized iodides are deposited on the cold surface; when suitably inclined, the reactions are similar to the film tests. 116. Beads of Borax and of Microcosmic Salt. For directions see page 64. COLOR OF THE WITH PHOSPHORUS SALT WITH BORAX BEADS OXIDIZING FLAME REDUCING FLAME OXIDIZING FLAME REDUCING FLAME Yellow to brown. Fe. Ni, U, Ag, Va, Ce. Fe, Ti. Fe, U, Pb, Bi, Sb, Va. Ti, W, Va, Mo, hot. Red. Fe, Ce, Ni, Cr, when hot and strongly saturated. Cu, Fe, Ti, W, containing Fe (blood red) when hot. Ce, Fe, Ni, when cold (reddish brown). Cu strongly saturated (opaque). (Amethyst.) Violet. Mn, D, hot and cold. Ti, Nb, cold, strongly sat-urated. Mn, D, Co added to Ni, hot and cold. Ti, cold. Blue. Co, Cu, hot and cold. Co, W, Nb, hot and cold, strongly saturated. Co, hot and cold. Cu, cold. Co, hot and cold. Green. Cu, Mo, Co or Cu added to Fe, hot. Cr, U, cold. Cr, U, Mo, Va, cold. Cr, Va, cold. Cu, Co or Cu added to Fe, hot. Fe, U, Cr, Va, hot and cold. Gray. Ag, Zn, Cd, Pb, Bi, Sb, Te, Ni, from reduced metal. As with phosphorus salt; also Nb. Colorless. Si02, skeleton bead. Al, Sn, Ta, Nb, W, Zn, Cd, Pb, Bi, Sb, yellowish. Si02, skeleton bead. Al, alkaline earths, Ce, D, Mn, Sn, not clear. Si02, Al, Sn, not clear. Alkaline earths, Ag, Ta, Nb, Te, Ti, W, Zn, Cd, Pb, Bi, Sb. Si02, Al, Sn, not clear. Alkaline earths, La, Ce, Ta, Mn, D, Cu. Note.—Reduction takes place more easily with phosphorus salt (reduction is aided by addition of Sn); in general, the behavior Of the various bodies is quite similar with borax and phosphorus. Salt of phosphorus is especially good for the detection of silica, 117. Film tests. For explanation see page 64. NAMK OXIDE INCRUSTATION WITH AgN03 AND NH3 IODIDE INCRUSTATION AND COATING IODIDE INCRUSTA-TION WITH NH3 BLOWN UPON IT SULPHIDE INCRUS-TATION AND COATING SULPHIDE INCRUS-TATION WITH (NH4)HS METALLIC INCRUS-TATION AND COATING Sb. Black, insoluble in NH3. Orange; breathed up-on, disappears for a time. Disappears per-manently. Orange. Disappears for a time. Black, with brown coating. As. Lemon yellow or brownish red; soluble in NH3. Orange yellow; when breathed upon, dis-appears for a time. Disappears per-manently. Lemon yellow. Disappears for a time. Black, with brown coating. Bi. White. Bluish brown, with a light red coating; if breathed upon, dis-appears for a time. Rose red to or-ange yellow; chestnut brown when dry. Umber brown, with a coffee brown coating. Does not disap-pear. Black, with soot-brown coating. Hg. Carmine and lemon yellow, breathed up-on, does not disap-pear. Disappears for a time. Black. Does not disap-pear. Gray, incoherent coating. Pb. White. Orange yellow to lem-on yellow; breathed upon does not dis-appear. Disappears for a time. Through brown-ish red to black. Does not disap-pear. Black, with brown coating. Cd. Coating becomes blue black. White. White. Lemon yellow. Does not disap-pear. Black, with brown coating. Zn. White. White. White. White. Does not disap-pear. Black, with brown coating. 64 LABORATORY GUIDE. Directions for Beads—A small Pt wire is fused into a glass tube or rod, and the end heated, and dipped into anhydrous borax or salt of phosphorus, and heated to a colorless bead. The substance to be tested is touched by the hot bead, and a portion taken up, and heated in the oxidizing and then in the reducing flame. The chemistry of the process is quite simple. The metallic oxides are dissolved in the bead, and a colored glass forms; of course, the color will vary with the amount of the substance taken. Certain bodies, as the alkaline earths, dissolve in borax, forming beads, which, up to a certain stage of saturation, are clear. When these beads are brought into the reducing flame, and an intermittent blast is used, they become opaque. This is what is known as flaming. Tin, lead, and silver are used to facilitate the reduction of CuO, Fe208, Ti02, and W03. The beads, charged with the substance to be tested, are formed on the Pt wire, and while hot shaken off into a porcelain plate, and when a sufficient number is obtained, they are fused on charcoal into a large bead, and the metal added. Directions for Films — The metallic incrustations are ob- tained by heating a small particle of the substance on an asbestos fiber in the reducing flame of a Bunsen burner, under a glazed porcelain capsule half filled with water to keep it cool. On touching the metallic incrustations with a drop of dilute (20 per cent, of N205) HN03 on a glass rod: instantly dissolve, slowly and difficultly dissolve, unaffected, Pb, Cd, Zn, In. Bi, Hg, Th. Te, Se, As, Sb. The substance to be tested is held in the upper oxidizing flame to form an oxide incrustation. When an asbestos fiber, wrapped with Pt, is soaked in a saturated solution of iodine in alcohol, and burned under the oxide incrustation, it forms the iodide incrustation; the solubility of the iodide incrustation is tested by the moist breath. When (NH4)2S is blown upon the iodide or oxide incrustation, it forms the sulphide incrustation. The oxide incrustation is also rubbed with a glass rod dipped in AgN03, and NH8 vapor blown upon it. TESTS IN THE DRY WAY. 65 118. Minerals are also tested by the fusibility of small splinters held in the platinum forceps in the fusing cone. In using the blowpipe, it is important to remember that a trial of fusibility with the forceps, if not at once producing fusion, should be made on a piece of the mineral not larger than an ordinary pin-head, and it should be either oblong and slender, or thin, and be made to project considerably beyond the points of the forceps, lest the forceps carry off the heat. Von Kobell has arranged a scale by which the fusibility of the substance may be compared with that of certain minerals of known fusibility. 1. Stibnite, fusible in the flame of a candle, in splinters. 2. Natrolite, fusible in the flame of a candle in fine splinters, easily fusible before the blowpipe. 3. Almandine, infusible in the candle flame, but fusible before the blowpipe. 4. Actinolite, fusibility less than almandine, and greater than orthoclase. 5. Orthoclase, fusible in fine splinters before the blowpipe. 6. Bronzite, fusible on the edges in very fine splinters. The various gradations of fusibility are expressed by decimals; thus, 3.8 denotes a mineral which is less fusible than almandine and more than actinolite. 119. Minerals are also tested by the scale of hardness — Mohs's scale, with substitutes: 1. Talc, yields easily to the nail; as, embolite, molybdenite. 2. Gypsum, yields with difficulty to the nail, and does not scratch a copper coin; as, graphite, lead. 2.5. Foliated mica; as, cryolite, halite, galenite. 3. Spar (calcareous), scratches a copper coin, or about the same hardness; as, bornite, serpentine. 4. Fluor spar, does not scratch glass, and is not scratched by a copper coin; as, fluorite, siderite. 5. Apatite, scratches glass with difficulty, and yields readily to the knife; as, calamine, franklinite. 66 LABORATORY GUIDE. 5.5. Scapolite, crystalline variety; as, chromite, cobaltite, lapis lazuli. 6. Orthoclase, scratches glass easily, and yields with diffi- culty to the knife; as, labradorite, oligoclase, turquois. 7. Quartz, yields to the file, but not to the knife; as, boracite, garnet, spodumene. 8. Topaz, does not yield to the file; as, spinel. 9. Sapphire or corundum. 10. Diamond. 120. Minerals are also tested by the streak. The streak of a mineral is made by scratching it with a knife or file, or by drawing it across a piece of unglazed porcelain, and the color of the mark which it leaves behind is observed. The following are a few examples: 1. Metallic streak — tetradymite, bismuthinite, stibnite. • 2. Non-metallic streak — cobaltite, grayish black; manga- nite, reddish brown; pyrolusite, black; franklinite, reddish brown; limonite, brownish yellow. 3. Streak nearly the same as their color — orpiment, lemon yellow; realgar, bright red; arseolite, white; valentinite, white; cinnabar, red; minium, red; salmiac, white • hematite, red. 121. Minerals are also tested by their specific gravity. Ordinary rock has a specific gravity of about 2.5. The ores of the heavy metals have a high specific gravity. Mountain leather and mountain cork, varieties of asbestos, float upon water. Iridosmine has a specific gravity of from 19 to 21. 122. Minerals are also tested by their lustre. Metallic, the lustre of metals; vitreous, lustre of broken glass, as quartz and calcareous spar; resinous, the lustre of yellow resin, as opal, zinc blende; pearly, as talc, magnesia, stilbite; silky, as calcite, gypsum; adamantine, the lustre of diamonds, as white lead ore or cerussite. TESTS IX THE DRY WAY. 67 123. Minerals are also tested by their color, either metallic or unmetallic. The metallic are named after some familiar metal, as copper red, gold yellow, steel gray, etc. The unmetallic are various shades of white, gray, blue, green, yellow, red, and brown; play of colors, as the diamond and precious opal; change of colors, as the labradorite; opalescence, as in opals and in cat's eye; iridescence, as in quartz. 124. Minerals are also tested by their taste, odor, and feel. Taste belongs to soluble minerals — astringent, as ZnS04; sweetish astringent, as alum ; saline, as NaCl; alkaline, as soda; cooling, as KN03 ; bitter, as MgS04; sour, as KHS04. Odor, the odor is given by friction, moistened with the breath, the action of acids, and the blowpipe — alliaceous, the odor of garlic, as by burning As; horse radish odor, by burning selenium; sulphurous, by burning sulphur or pyrites; fetid, the odor of rotten eggs or H2S (it is elicited by friction from some varieties of quartz and limestone); argillaceous, the odor of moistened clay, as serpentine and allied minerals when breathed upon, pyrargillite affording it when heated. Some minerals have a greasy feel, as the steatites and graphite. In some cases, refraction, polarization, electricity, magnetism, in- flammability, and crystalline form give important information. Any one of these tests is insufficient for all of the elements but each is good for several of them. Negative tests are not given, and the student should for himself select those tests which he finds most serviceable under his handling. He should also make out a table, giving his results, in a systematic form. Notice — Borax beads (116) are especially valuable for Mn, Co, Cu, Cr, Fe, Fe -j- Ti, and U; phosphorus beads for Si02; the film tests (117) for Bi, Hg, As, Sb, and Cd; the nascent H (114), for Cr and Mo, by deposits for As (octahedral crystals), and by gas for H2S, H3As, and H3P; the color tests (110) are good for Na, K, Cs, Ru, Ba, Sr, Li, Ca, Cu, B (As, Sb, Pb); the tests of fusibility, hardness, streak, specific gravity, lustre, color, odor, etc., for special mineralogy. 68 LABORATORY GUIDE. 125. Prof. Egleston's Scheme of Blowpipe Analysis. The substance may contain As. Sb, S, Se, Fe, Mn, Cu, Co, Ni, Pb, Bi, Ag, Au, Hg, Zn, Cd, Sn, CI, Br, I, C02, Si02, N205, H20. 1. Treat on charcoal in the O. F. to find volatile substances, such as As, Sb, S, Se, Pb, Bi, Cd, etc. a. If there are volatile substances b. If there are no volatile sub- present, form a coating and test it stances present, divide a part of with phosphorus salt and tin on the substance into three portions, charcoal for Sb (110) or to distinguish and proceed as in 1. between Pb and Bi (110). (a) Yellow coat, yielding with phosphorus salt a black bead; dis- appearing with blue flame; no part of it yielding greenish Sb flame; Pb and Bi. (b) Yellow coat, generally with white border yielding black or gray bead with phosphorus salt, disappearing with blue flame; also the border, disappearing with greenish flame; Pb and Sb. (c) Yellow coat, very similar to (&), but yielding no blue flame; Bi and Sb. 2. If As, Sb, S, and Se are present, roast a large quantity thoroughly on charcoal until no odor of arsenic or sulphurous acid is given off. Divide the substance into three portions, and proceed as in 1. 1. Treatment of the First Portion — Dissolve a very small quantity in borax on Pt wire in the O. F., and observe the color produced. Various colors will be formed by the combination of the oxides. Saturate the bead, and shake it off into a porcelain dish. Repeat this once or twice. (a) Treat these beads on charcoal with a small piece of lead, silver' or gold in a strong R. F. (&) Fe, Mn, Co, etc., remain in the bead. If the bead spreads out on the charcoal, it must be collected to a globule by continued blowing. Make a borax bead on Pt wire, and dissolve in it some of the fragments of the bead, reserving the rest for accidents. (c) Ni, Cu, Ag, Au, Sn, Pb, and Bi are reduced and collected by the lead button (Sn, Pb, Bi, if present, partly volatilize). Remove the lead button from the bead while hot, or by breaking the latter when cold, on the anvil between paper, carefully preserving all the fragments. (d) If Co is present, the bead will be blue. If a large amount of Fe is present, add a little borax to prove the presence or absence of Co. If Mn is present, the bead, when treated on Pt wire in the O. F., will become dark violet or black. TESTS IN THE DRY WAY. 69 (e) If only Fe and Mn, with no Co, are present, the bead will be almost colorless. Look here for Cr, Ti, Mo, U, W, V, Ta, by the wet way. (/) Treat the button (c) on charcoal in the O. F. until the lead, etc., is driven off, Ni, Cu, Ag, and Au remaining behind; or separate the lead with boracic acid. (g) Treat the residue (g) on charcoal in the O. F. with phosphorus salt bead, removing the button while the bead is hot. (h) If Ni and Cu are present, the bead will be green when cold. If Ni only, yellow; if Cu only, blue. Prove Cu by treating with tin on charcoal in the R. F. (i) For Ag and Au, make the special test. 2. Treatment of the Second Portion — Drive off all the volatile sub- stances in the O. F. on charcoal. Treat with the R. F., or mix with soda, and then treat with the R. F. for Zn, Cd, and Sn. If a white coating is formed, test with cobalt solution (110). 3. Treatment of the Third Portion—Dissolve some of the substance in phosphorus salt on Pt wire in the O. F., observing whether Si02 is present or not, and test for Mn with potassium nitrate. 3. Test for As with soda on charcoal in the R. F., or with dry soda in closed tube (110). 4. Dissolve in soda on Pt wire in the O. F. (if the substance is not metallic and does not contain any S), and test for Sb on charcoal, with tin in the R. F. (110). 5. Test for Se on charcoal (110). 6. In absence of Se, fuse with soda in the R. F., and test for S on silver foil (111). In presence of Se, test for S in open tube (111) to dis- tinguish between S and S03. 7. Test for Hg with dry Na2C03 + C in a closed tube (107). 8. Mix some of the substance with assay lead and borax glass, and fuse on charcoal in the R. F. Cupel the lead button for Ag. Test with nitric acid for Au (113). 9. Test for CI, Br, and I with a bead of phosphorus salt, saturated with oxide of copper (110). With Br the flame is blue, with green tint; with I, the flame is green. 10. Test for CI or Br with acid sulphate of potassium. 11. Test for H20 in a closed tube (106). 12. Test on Pt wire or in Pt pointed forceps, for coloration in the flame (110). 13. Test for C02 with HCl (106). 14. Test for N205 with acid sulphate of potassium. 15. Test for Te in an open tube (108). CHAPTER III. TESTS IN THE WET WAY. 126. The first duty of the student will be to get the substance into a state of solution, before he can make any tests. Organic matter, as sugar, tartaric and citric acids, prevents the formation of some precipitates; as, Fe(OH)2, and renders others uncertain. While testing for bases, their presence should be first determined, and these matters destroyed, if necessary. Roast a small portion of the substance in a small tube or on Pt foil; carbon is indicated if the substance chars. Heat on Pt foil after making an intimate mixture with KN03 ; if it defla- grates, carbon is present. If carbon is indicated, roast a portion on Pt foil in free air; if it burns to a white mass, it indicates carbon. Remove organic matters by ignition in free air, when no volatile bodies, as As or Hg, are present; if volatile bodies are present, treat all with HC1 + KC103. Decompose compound cyanides by heating with strong H2S04 in a good draught of air, and expel most of the H3S04 by prolonged heating. 127. When no organic matters are present, make a careful preliminary examination of the substance, to obtain some clue to the kind of solvent required. Test a small por- tion of the substance with each of the liquid solvents named below, until a complete solution is obtained. Determine in each case if a partial solution is obtained, by filtering the liquids and evaporating a portion on Pt foil. LABORATORY GUIDE. 71 128. A substance having a metallic lustre may be a metal* an alloy, or an ore containing S, As, or Sb. Reduce to a fine powder, Boil with strong HN03. It oxidizes most metals, and dis- solves them as nitrates; oxidizes S to H2S04, As to As205. If a white residue is left, it may be Pb(N03)2, PbS04, Sn02, Sb203, etc.; filter and wash. Treat this residue with H20, and boil; Pb(N03)2 dissolves. Add this to the portion already dissolved. Add a strong solution of H2C4H406, and boil; Sb203 dissolves. Test by H2S. Add NH4HO to the H2C4H406 solution, and again boil; PbS04 dissolves. Test by H2S. Sn02 remains. Reduce on charcoal by KCN-|-Na2C03. Dissolve the metallic bead in HCl, and test for SnCl2; or treat this white residue with NH4HS; Sn02, Sb203 dissolve; Pb becomes black PbS. If, on adding H20-|-NH4C1 to the solution in HN03, a white cloudiness appears, Bi may be present. If a colored residue is left, it may be gold, the platinum metals, or carbon, silicon, or sulphur. Pt and Au dissolve in aqua regia. The S ignites when heated on Pt foil, and yields S02. The car- bon may have come from the process of smelting, as in cast iron. It burns away before the blowpipe on Pt foil. The silicon leaves, on ignition before the blowpipe, a white residue. Test by micro- cosmic salt. 129. Substances which have no metallic lustre. Reduce to a very fine powder. Boil a small portion with H20. If all dissolves, or the greater part, treat the entire quantity with H20, and filter. Treat a small portion of the residue insoluble in H20, with dilute HCl. Add H20, and boil. If much dissolves, treat all with HCl. Gases like H2S, S02, C02 may be given off. Sb and Bi solutions become turbid when H20 is added. Treat a small portion of the residue insoluble in H20 and in HCl, with HN03. Treat this last residue with concentrated HCl. Peroxides like Mn02, Pb02 evolve CI. Treat this last residue 72 LABORATORY GUIDE. with aqua regia, or with HC1-|-KC103. The solutions which may have been obtained by these various processes may be examined separately, as is sometimes necessary in testing for acids; or, if Pb, Ag, Hg, are absent, they may be mixed together in testing for bases. In this treatment with acids, Si02 may have dissolved. If this is suspected, evaporate the solution to complete dryness, moisten with HCl, and again dry thoroughly. The Si02 thereby becomes insoluble. By these methods we cannot expect to dissolve AgCl, metal- lic fluorides, sulphates of Pb, Ba, Sr, most silicates, and Si02, many strongly ignited oxides, as those of Fe, Cr, Sn, Al, Sb, Ti, W, Nb, Ta, nor all the free S, nor carbon. If AgCl is present in this residue, it may be dissolved out by (NH4)HO. The others require special treatment, as follows: — 130. Substances which are insoluble in H20, in HCl, in HN03, and in aqua regia. Examine this insoluble residue by the preliminary tests. ( Chapter II.) Test for C and S by Heating on Pt Foil in the Oxidizing Flame — If these are present, oxidize thoroughly. After oxidiz- ing the substance, test by microcosmic salt. It will indicate Si02, Cr, Fe, Ti, W, Ta, Nb; test for the last four by Zn+HCl. Heat a portion on charcoal with Na2C03-f-KCN. It will give hepar with Ba, Sr, Ca, Pb sulphates; reduces metals like Sn, Fe, Pb, Sb, Ag. Test for Al on charcoal and with Co(N03)2. Test for F by treatment with strong H2S04 ; the HF evolved etches glass. The further treatment of these insoluble bodies depends upon the indications which are then obtained. 131. If the very finely pulverized substance is mixed with four times its weight of Na2C03, or better, NaKC03, and thor- oughly fused, (a) BaS04, SrS04, CaS04, PbS04 become Pb, BaC03, SrC03, CaC03. The S04 unites with the Na to form Na2S04; (b) silicates, fluorides, titanates, etc., chromates, alum- inates, stannates, antimonates, give soda salts, soluble in H20. TESTS IN THE WET WAY. 73 If the very finely pulverized substance is mixed with eight times its weight of KHS04 and thoroughly fused, (a) ignited oxides like Fe203, A1203, Cr203, either form salts soluble in H20, or leave a residue soluble in HCl or HN03. (6) This is the best method for titanates, etc. Most of these substances if mixed, when finely pulverized, with two parts of charcoal and twelve parts*of KN03 in a porce- lain dish and ignited, yield a mass which is partly soluble in H20, and the residue in HCl. It is often advisable to treat filings of alloys and substances which contain As, Sb, Sn with NH4HS. This dissolves out the As, Sb, Sn, and leaves most of the metals as sulphides, which are soluble in HN03. 132. When a Solution has been made by any one of these methods, it must be remembered that any excess of an acid must be expelled by evaporation before applying tests for bases; and that any excess of alkali must be neutralized before applying tests for acids. Often when only a single substance, known to be present, is to be determined, special modes of separation may be applied at once. (a) Fluorides are decomposed by H2S04. (6) Silicates are decomposed by HF. (c) The platinum metals, As, etc., are converted to chlorides by chlorine gas. (d) Most of the metallic sulphides and oxides when heated are reduced by H gas, or by nascent hydrogen ; i. e., Zn-{-HCl. 133. In qualitative chemical analysis, the metals or bases are commonly divided into five groups. GROUP I.—SILVER GROUP. This comprises those metals whose chlorides are practically insoluble in water, and which are, therefore, precipitated by the group reagent, hydrochloric acid. These are silver, lead, and 74 LABORATORY GUIDE. mercury (monad mercury or mercurosum), and the rare elements, tungsten, thallium, and niobium. This is called the silver group. When Ag is absent, Pb and Hg are easily detected along with the elements of the next group. 134. Silver (Ag1, 108*). The solution of the nitrate is the one used for testing. The best solvent for silver is HN03. Hot concentrated H2S04 forms sulphate, which is sparingly soluble. Fixed alka- lies do not act upon Ag in the wet or dry way. The nitrate, acetate, and sulphate form anhydrous crystals. The ortho- phosphate and arsenite are yellow; the arseniate, reddish- brown ; the iodide, yellow; the bromide, yellowish-white; the sulphide, black. The salts of silver are chiefly colorless, and the normal salts are neutral to litmus. The oxide, sulphide, chlo- ride, bromide, bromate, iodide, iodate, cyanide, ferrocyanide, ferricyanide, carbonate, oxalate, phosphate, arsenite, arseniate, sulphite, and tartrate are insoluble in H20, or sparingly soluble. The fixed alkaline hydroxides precipitate, in tke absence of organic acids, silver oxide, Ag20, grayish-brown, insoluble in excess of reagent. By reduction of silver salts, an argentous oxide, Ag40, and a corresponding chloride may be formed. By the action of ozone on the metal, Ag202 is formed. Silver combines with CI, Br, and I at ordinary temperatures, and readily with S, P, and As on heating. 135. Tests: — 1. Easily reduced to metallic Ag before the blowpipe, on charcoal. 2. HCl precipitates white AgCl, insoluble in HN03, soluble in NH4H0. 3. H2S or (NH4)2S precipitates black Ag2S, insoluble in dilute acids, in alkalies, alkaline sulphides, potassium cyanide; soluble in boiling HN63. * The atomic weights are whole numbers. TESTS IN THE WET WAY. 75 4. NaHO, KHO, and NH4HO precipitate light-brown Ag2Q, insoluble in excess of NaHO or KHO, but soluble in excess of NH4HO. If the solution is acid NH4HO does not precipitate AgN03. 5. Na2C03 precipitates grayish-white Ag2C03, soluble in NH4HO. 6. Na2HP04 precipitates yellow Ag3P04, soluble in HN03, H3P04, and in NH4HO. 7. KI precipitates yellow Agl, insoluble in NH4H0, soluble in excess of reagent. 8. KBr precipitates white AgBr, slightly soluble in excess. 9. K2Cr207 precipitates dark-red Ag2Cr04, soluble in HN03 and in NH4HO; decomposed by HCl into white AgCl. 10. Zn, Cu, Fe, Mg, Pb, Bi, Hg, reduce silver solutions to the metallic state, best from its solution as cyanide (arbor Dianse). 11. K4FeC6N6 precipitates white Ag4FeC6N6, difficultly soluble in NH4H0. 12. Na2S203 precipitates white Ag2S2Q3, soluble in excess. Light decomposes most compounds of Ag, with blackening from formation of metallic Ag, or of Ag40, or of both. The nitrate and chloride fuse undecomposed, but are decom- posed at higher temperatures. The nitrate, phosphate, iodide, and cyanide are not decomposed by light alone. Almost all the salts of silver are freely soluble in ammonia. AgCl is easily soluble, AgBr is difficultly soluble, and Agl is almost insoluble. 136. Lead (Pbn"iy, 207). It is generally obtained from galena, PbS. It is a soft metal, of bluish lustre, which is easily tarnished. When heated in the air, it oxidizes, first to litharge, PbO, and then to minium, or red lead, Pb304. When either of these oxides is treated with HN03, Pb(N03)2 is formed; but when the higher oxide is used, there remains behind a brown powder, Pb02, known as puce colored oxide of lead. It is possi- ble that red lead is a mixture of 2PbO, Pb02. Only the protox- ide enters into combination with acids, and its salts are generally 76 LABORATORY GUIDE. insoluble in water. Notably the sulphate, oxalate, carbonate, chromate, sulphite, phosphate, oxide, hydroxide, chloride, iodide, bromide, and ferrocyanide are sparingly soluble in water. The nitrate and acetate are soluble in water, either of which can be employed in the tests. Lead combines directly with S, P, As, and most of the metals. The lead salts are non-volatile; most of them are colorless. The normal salts redden litmus paper, and are decomposed at a red heat. 137. Tests: — 1. From solutions of lead acetate or nitrate, the fixed alka- lies precipitate white Pb(OH)2, soluble in excess of the reagent by combination, as potassium plumbite, K2Pb02. 2. Heated before the blowpipe, on charcoal, with dry Na2C03, give metallic Pb, and a yellow coating or incrustation of PbO. 3. Metallic Zn precipitates Pb in crystals (arbor Saturni). 4. H2S or (NH4)2S precipitate black PbS, insoluble in ex- cess ; soluble in HN03, and converted into PbS04 (detects one part in 100,000). 5. H2S04 precipitates white PbS04, insoluble in alcohol, soluble in strong H2S04. PbS04 is soluble in 1,300 parts of water; more readily soluble in some ammoniacal salts. 6. (NH4)2C03 precipitates white PbC03. See No. 7. 7. Na2C03 precipitates basic lead carbonate, PbC03 -f- Pb(OH)2, in various proportions, according to temperature and concentration. 8. HCl precipitates white PbCl2, soluble in 30 parts of water, insoluble in alcohol, and ammonium hydroxide. 9. K2Cr207 precipitates yellow PbCrQ4, insoluble in dilute HN03, and insoluble in NH4HO; soluble in fixed alkalies. 10. KI precipitates yellow Pbl2, soluble in large excess on heating. (Soluble in 1,900 parts of cold and 200 parts of hot water.) TESTS IN THE WET WAY. 77 11. Na2HP04 precipitates white Pb3(P04)2, insoluble in dilute acetic acid, soluble in HN03 and fixed alkalies.: 3Pb(NQ3)2-f 4Na2HP04 = Pb3(PQ4)2 + 6NaNQ3-i-2NaH2P04, if there is an excess of phosphate. 138. Mercury (HgI_n, 200). It is liquid at temperatures between — 40° C. and 360° C. It is slightly volatile at ordinary temperatures. It enters into combination with CI and Br at ordinary temperatures. It combines with I and S in the cold, if triturated with them. It combines with most of the metals at ordinary temperatures, forming alloys, which are called amal- gams. At ordinary temperatures it is but little acted upon by HCl; strong H2S04, when heated, dissolves it with moderate rapidity, evolving S02. HN03 is the best solvent. It forms two oxides, Hg20 black and HgO red or yellow, and two correspond- ing classes of salts, mercurous and mercuric compounds. Their solutions redden litmus. The chlorides: mercurous chloride, Hg2Cl2, is insoluble in water; the mercuric chloride, HgCl2, is soluble in water. The reactions in the dry way are nearly the same for both ous and ic compounds. Only the mercurous compounds will be described here, the mercuric at No. 143. The mercurous salts volatilize upon ignition, and most of them are decomposed by this process; the Hg2Cl2 and Hg2Br2 volatilize unaltered. The salts are generally colorless. Most of the ous compounds (except the normal nitrate) are insoluble in water. 139. Tests: — 1. All compounds of mercury, when dry and heated with dry Na2C03 in a tube closed at one end, give a sublimate of metallic mercury. 2. Copper foil precipitates silvery spots of metallic mercury. 3. NaHO or KHO precipitates black Hg2Q, insoluble in alkalies, soluble in HN03. 4. NH4HO precipitates black (NH2Hg2)NQ3, insoluble in alkalies, soluble in acids. 78 LABORATORY GUIDE. 5. H2S or (NH4)2S precipitates black Hg2S with HgS and Hg, insoluble in HN03, HCl, (NH4)2S; sparingly soluble in K2S Na2S. 6. HCl precipitates white Hg2Cl2, calomel, soluble in NH4C1, in aqua regia, in HN03, blackens by NH4HO. Hg2Cl2 -f- 2NH4HO = NH2Hg2Cl -f NH4C1 + 2H20. 7. KI precipitates greenish yellow Hg2I2, insoluble in H20 and in C2H60. By excess becomes Hg2I2 -f 2KI = Hg + (KI)2HgI2. 8. K2Cr207 precipitates orange Hg2CrQ4 or a basic chro- mate, soluble in HN03. 9. K4FeC6N6 precipitates white gelatinous Hg4FeC6N6; K3FeC6N6, a red brown precipitate. 10. Na2C03 precipitates gray Hg2CQ3, blackening to a basic carbonate and oxide when heated. 11. Soluble sulphates precipitate white Hg2SQ4, soluble in 500 parts H20. 140. Separation of the Silver Group. HCl added to AgN03 -f- Pb(N03)2 -f Hg2(N08)2 precipi- tates white AgCl -j- PbCl2 + Hg2Cl2, filter and boil the precipi- tate with water. RESIDUE. AgCl. Add NELHO. Hg2Cl2. SOLUTION. PbCl2, on cooling, acicu- lar crystals. Add H2S04, precipitates white PbS04. Reduce with carbon and Na2C03 to metallic Pb; dissolve in dilute HN03, and add K2Cr207, yellow PbCrCv Solution. AgCl, add HN03. AgCl. Reduce on charcoal to metallic Ag; dissolve in dilute HN03, add K2Cr207, red Ag2Cr04. Residue. NH2Hg2Cl, black. Reduce in a glass tube with carbon and Na2C03, sublimate of Hg. Dissolve in HN03 and confirm with KI, red Hgl2. See No. 139. TESTS IN THE WET WAY. 79 141. Notes on the first group. 1. The separation of the first group is quite simple. The PbCl2 is dissolved in an abundance of hot water; AgCl in ammo- nium hydroxide; while Hg2Cl2 is left undissolved as a black NH2Hg2Cl. 2. When only one member of the group is present as a pre- cipitate, NH4HO determines which it is; PbCl2 does not change color; AgCl dissolves; Hg2Cl2 blackens. 3. The group reagent, HCl, completely precipitates Ag and Hg, and partially precipitates Pb, as the PbCl2 is soluble in 135 parts of cold water and 30 parts of hot water. 4. In all mixtures of the bases that the student does not make for himself, the condition of the solution (acid, neutral, or alka- line) must be determined before the group reagent is added. The Group Reagent HCl. 5. HCl may precipitate sulphur from alkaline solutions containing Na2S or Na2S203. 6. Saturated solutions of chlorides, as BaCl2, are precipi- tated unchanged as BaCl2, 7. Solutions of Bi, Sb, and Sn may be precipitated as the oxychloride of the metal in question. 8. Certain volatile acids may be expelled; as C02, H2S, and HCN. 9. Certain double salts, as sulphides, cyanides, iodides, thiosulphates, may be broken up and precipitates formed: (KCN)2HgC2N2 + 2HC1 = HgC2N2 + 2KC1 + 2HCN. 10. Alkaline solutions of metallic oxides, as K20, ZnO, may be precipitated when neutralized by acids. 11. HCl may precipitate certain alkaline solutions of boracic, silicic, antimonic (tungstic, molybdic, tantalic, and 80 LABORATORY GUIDE. niobic ), acids, and certain organic acids, as benzoic, salicylic, and uric. N. B. — In using a reagent, use enough to precipitate the substance sought completely, and test the filtrate to ascertain if this has been done; but care should be taken not to add too much — a drop too much is excess. GROUP II. —LEAD AND ARSENIC GROUP. 142. The second group comprises those metals that are precipitated from their slightly acid solutions, as sulphides, by the group reagent H2S. They are Ag, Hg, Pb, Bi, Cu, Cd, and As, Sb, Sn; the rare elements, palladium, rhodium, osmium, ruthen- ium, platinum, iridium, gold, molybdenum, selenium, tellurium, and tungsten. 143. Mercury (Hg11, 200). As mercuric compounds. The oxide, basic carbonate, tartrate, sulphide, ferrocyanide, iodide, iodate, arsenite, arseniate, phosphate, and oxalate are insoluble in water. The chromate and citrate are sparingly soluble. The ous salts of mercury are easily changed by oxydizing agents to the ic salts. The ordinary mercuric salts (except the chloride) which are soluble in water, seem to require the presence of free acid, being partially decomposed by water, with the separation of basic salts. The reactions are modified by the free acid, as in the case of mercuric nitrate. 144. Tests: — 1. In the dry way, the same as the ous compounds. 2. Cu(Zn, Fe) precipitates metallic Hg. 3. H2S or (NH4)2S precipitates white HgSHgCl2; on the addition of an excess of the reagent, it is converted into black HgS, insoluble in HN03 or HCl, soluble in aqua regia and in alkali hydroxides; it is also soluble in free chlorine. (a) HgS + Cl2 - HgCl2 + S. (b) HgS + K2S = K2S, HgS. (c) 2HgS + 2KHO = K2S, HgS + HgO + H20. TESTS IN THE WET WAY. «T The black sulphide, when heated and rubbed, is converted into red (vermilion) without chemical change. 4. Reducing agents (SnCl2, S02, Na2S203) first white Hg2Cl2, then gray Hg. 5. Fixed alkali hydroxides (NaHO, KHO) precipitate red- dish-brown basic salts; with excess of reagent, HgO, insoluble in alcohol and in ammonium hydroxide, soluble in 200,000 parts of water. 6. NH4HO precipitates white (NH2Hg)Cl, soluble in HCl, sparingly soluble in NH4HO. 7. Na2C03 or K2C03 precipitates reddish-brown basic salt, 3HgO, HgC03, converted into the yellow oxide HgO. 8. Soluble iodides (KI) precipitate red Hgl2, soluble in an excess of either reagent. 9. K2Cr04 precipitates yellowish-red HgCr04, soluble in HN03, sparingly soluble in water. 10. Soluble phosphates (Na2HP04 ) precipitate white Hg3(PQ4)2, soluble in acids and in NH4HO salts. 145. Lead (Pbn-IV, 207). See No. 136. 146. Bismuth (Bim, 210). Bismuth melts at 264° C. It readily combines with CI, Br, I, and S. Nitric acid is the best solvent. Bismuth forms one stable oxide, Bi203, yellowish white; the oxide, Bi202, is black; Bi205 is red. The oxides and hydrox- ide, Bi(OH)3, are readily soluble in dilute mineral acids. The bismuth salts are white, non-volatile, and are decom- posed at a red heat (the trichloride is volatile). The chloride is deliquescent; the nitrate, permanent. All the salts have a ten- dency to basic formations, and many are decomposed by a large quantity of water into insoluble basic and soluble acid salts. The most of the normal salts are soluble in water acidulated with their respective acids, or with acids forming soluble bismuth salts; the decomposition of the normal sulphate, nitrate, and chloride is prevented by the addition of organic acids, as citric acid. 82 LABORATORY GUIDE. The sulphide, chromate, borate, sulphite, hydroxide, oxalate, iodide, basic carbonate, phosphate, tartrate, citrate, cyanide, ferrocyanide, ferricyanide, valerianate, and tannate are insoluble in water. 147. Tests: — 1. Fused with Na2COs, gives brittle bead, Bi, and yellow oxide, Bi203, coating. 2. Bi -J- S -}- KI, heated on charcoal before the blowpipe, gives bright scarlet-red incrustation. 3. H2S or (NH4)2S precipitates brownish-black Bi2S3, insol- uble in KCN, (NH4)2S, and dilute acids; soluble in strong HN03. 4. Alkali hydroxides (NaHO, KHO, NH4HO) precipitate, in the absence of tartaric or other organic acids, white Bi(OH)3, insoluble in excess, soluble in HCl and HN03. 5. Na2C03 precipitates white (BiO)2C03, insoluble in excess, soluble in KCN; HCl and HN03 (best). 6. H20 precipitates (best from the chloride) white BiOCl, insoluble in tartaric acid, soluble in HCl and HN03. (a) BiCl3 + H20 = BiOCl -f- 2HC1. (6) Bi(N03)3 + 2H20 = BiON03H20 -f- 2HN03. (c) 4Bi(N03)3 + 6H20 = Bi405(N03)2H20 + 10HNO3. (d) Bi(N03)3+3H20 = Bi(OH)3+3HN03. 7. K2Cr207 precipitates yellow basic chromate, Bi20(Cr04)2, insoluble in NaHO, soluble in HN03. 2Bi(N03)3 + K2Cr207 + 2H20 = Bi2Q(CrQ4)2 + 2KN03 -f 4HN03. 8. KI precipitates brown Bil3, soluble in excess of the reagent, in HCl and HI. 9. SnCl2, in the presence of NaHO or KHO, precipitates black Bi202 (very delicate reaction). 10. K4FeC6N6 precipitates white Bi4(FeC6N6)3. The alka- line cyanides precipitates white Bi(OH)3 with the formation of HCN. TESTS IN THE WET WAY. 83 11. Oxalates (H2C204) precipitate white Bi2(C204)3, in- soluble in dilute acids. 12. Phosphates (Na2HP04) precipitate white BiPQ4, solu- ble in HCl and H2S04. 13. Bi is reduced from bismuthous solutions by Zn, Fe (Sn, Cu, Cd, Pb) as a spongy precipitate. 148. Copper (Cu1"11, 63). When heated, it combines directly with Br, I, S, Si, etc. When it dissolves in an acid, H is not evolved (HI is an exception). HN03 is the best solvent. (a) Cu + 2H2S04 = CuS04 + 2H20-fSO;. (b) 3Cu-f 8HN03=3Cu(N03)2+4H20-f-2NO. (c) CuCl2 is formed when Cu is burned in an excess of CI, or when the hydrated crystalline chloride is heated. Copper forms two oxides: cuprous, Cu20, brownish red; cupric, CuO, black. The cuprous salts, Cu20, Cu2(OH)2, Cu2Cl2, are insoluble in water. The cupric are readily reduced to cuprous by strong reducing agents, acting with alkalies: 2CuS04 -f 4KHO -f- S02 = Cu2S04 + 2K2S04 + 2H20. By ferrous salts in the presence of iodides: 2CuS04 -f 2KI + 2FeS04 = Cu2I2 -f K2S04 + Fe2(S04)3. Metallic Fe and Zn precipitate from cupric salts, metallic Cu without the formation of cuprous salts. The following cupric salts are insoluble in water: Oxalate, borate, hydroxide, basic carbonate, tartrate, cyanide, sulphide, arsenite, ferro and ferri cyanides. The sulphate and acetate are insoluble in alcohol; the nitrate and chloride are soluble. The chloride is also soluble in ether. 149. Tests: — 1. Heated with Na2C03, upon charcoal, it is easily reduced to metallic Cu (red). 2. Fe and Zn precipitate from cupric solutions, Cu (Cu is also precipitated by Bi, Cd, Ni, Co, Sn, P): CuS04 -f- Fe = FeS04 -f Cu. 84 LABORATORY GUIDE. 3. Fixed alkalies (KHO, NaHO) added to saturation pre- cipitate blue Cu(OH)2, insoluble in excess ; when boiled, becomes CuO : Cu(OH)2 = CuO-j-H20, or black, basic hydroxide Cu302(OH)2. Many organic substances, as tartaric acid, will prevent the formation of the precipitate, or redissolve it. 4. NH4HO precipitates (short of saturation) pale blue basic salts, (saturation) deep blue Cu(OH)2 ; the precipitate dissolves to a deep blue solution (supersaturation) : CuS04 + 4NH4HO = (N2H6Cu)0(NH4)2S04 + 3H20. 5. H2S or (NH4)2S precipitates brown-black CuS, soluble in 950,000 parts of water, in KCN, in HN03; sparingly soluble in (NH4)2S. (a) CuS-f 4KCN = (KCN)2CuC2N2 + K2S. (b) 3CuS + 8HN03 3Cu(N03)2-f 3S + 4H20 + 2NO. 6. Na2C03 precipitates greenish-blue basic carbonate, CuC03Cu(OH)2; on boiling, it becomes CuO, and dissolves in NH4HO and KCN to a colorless fluid. 7. K4FeC6N6 precipitates red-brown Cu2FeC6N6, insoluble in dilute acids, but decomposed by KHO; slightly soluble in NH4HO; in dilute solutions, merely a reddish coloration. 8. K3FeC6N6 precipitates yellowish-green Cu3(FeC6N6)2, in- soluble in HCl. 9. Na2HP04 precipitates bluish-white CuHP04, if the re- agent is in excess; Cu3(P04)2, if the copper salt is in excess. Slightly soluble in acetic acid. 10. Alkaline cyanides (KCN) precipitate yellowish-green CuC2N2, soluble in excess and forming (KCN)2CuC2N2, which is unstable. 11. Soluble iodides (KI) precipitate, from concentrated solutions, white Cu2I2. The liquid is dark brown from free iodine When a reducing agent is added, the precipitate is free from iodine TESTS IN THE WET WAY. 85 (a) 2CuS04+4KI = Cu2I2+2I + 2K2S04. (b) 2CuS04 + 2KI + 2FeS04 = Cu2I2-f-K2S04 + Fe2(S04)3< (c) 2CuS04 + 4KI-f H2S03 + H20 = Cu2I2 -f- 2K2S04 + H2S04 + 2HI. 12. SnCl2 precipitates white Cu2Cl2 only in concentrated solutions, soluble in HCl. 13. K2Cr04 precipitates red-brown CuCr04, soluble in NH4HO with green color. 14. Sugar, organic compounds, arsenious acid, with fixed alkali hydroxides, reduce cupric salts to cuprous oxide. 15. K(C2H5)COS2 (potassium ethyl X anthate) precipi- tates brownish Cu(C2H5COS2)2; changes to a bright yellow. (KC2H5COS2 is made by dissolving KHO in absolute alcohol, and adding bisulphide of carbon; filter, and dissolve the precipi- tate in water.) 16. For detecting traces of Cu — When the end of a Pt wire is inserted! just within the eye of a large sewing needle, around which the wire is wound, and the coil left in a solution of Cu acidulated with acetic acid, at 30° C, for a few hours, a black- brown stain or coating on the Pt wire indicates Cu. (Hager.) 150. Cadmium (Cdn, 112). It has a tin-white color, melts at 350° C. HN03 is the best solvent. It forms a single oxide, CdO, yellowish brown; the hydroxide Cd(OH)2 is white. Both dissolve readily in HCl, H2S04, HN03. The soluble normal salts redden litmus paper, and are decomposed at a red heat. Of the metals Ag, Hg, Pb, Bi, Cu, Cd, Cd is the only metal which can displace H in dilute H2S04. The phosphate, oxalate, carbonate, sulphide, hydroxide, cyanidO; ferrocyanide, and ferricyanide are insoluble in water. The chloride vb& bromide are deliquescent, and soluble in water and alcohol. 86 LABORATORY GUIDE. 151. Tests:— 1. Heated on charcoal with Na2C03, it is reduced to Cd; it is easily oxidized to CdO with brown incrustation. 2. H2S or (NH4)2S precipitates yellow CdS, insoluble :n dilute acids, alkalies, alkali sulphides, of cyanides. If the solu- tion of Cd contains a large excess of acid, H?> S produces a precipitate only after dilution with water. The CdS is soluble in hot HCL, HN03, and H2S04. 3. Mg precipitates from acid and ammoniacal solutions gray Cd; Zn also precipitates it. 4. Alkalies (NaHO, KHO) precipitate white Cd(OH)2, in- soluble in excess; NH4HO forms the same precipitate, soluble in excess. In the fixed alkalies, the presence of organic substances prevents the precipitation. 5. Na2C03 or (NH4)2C03 precipitates white CdCQ3, insol- uble in excess; ammonium salts impede or prevent the precipi- tation. 6. KCN precipitates white Cd(CN)2, soluble in excess as (KCN)2Cd(CN)2; H2S precipitates this solution as CdS. 7. KI precipitates white Cdl2 only in very concentrated solutions. 8. K4Fe6C6N6 precipitates yellowish-white Cd2 (FeC6N6); K-jFeC6N6 precipitates yellow Cd3(FeC6N6)2. Both precipi- tates are soluble in HCl and in NH4HO. 9. Oxalates and oxalic acid precipitate white CdC204, diffi- cultly soluble in acids. The chromates (alkali) form yellow CdCr04 only in con- centrated solutions. Phosphates form white CdHP04, readily soluble in acids. 152. Arsenic (Asm-V, 75.) It is a steel-gray, brittle, non- metallic element, volatilizing at 356° C, the vapor having an alliaceous odor. It combines with CI and Br in the cold, and TESTS IN THE WET WAY. 87 with I and S by the aid of heat. It is slowly attacked by the mineral acids; its proper solvent is aqua regia or CI with water. Hot solutions of KHO or NaHO dissolve it. (a) 2As + 10C1 -f- 8H20 = 2H3As04 -f 10HC1. (b) As-4-3KHO = K3As03+3H. As is slowly oxidized in moist air, at ordinary temperatures, to a black "sub-oxide" (fly powder), which is probably a mixture of As and As03. Arsenic forms two important oxides, As203 and As205, arsenious and arsenic anhydrides. 153. Tests: — As203 (Crystalline and Amorphous.) Specific gravity, 3.738. Is a good reducing agent. Forms arsenites with the metals. Forms arsenious acid, H3As03, which is easily converted into sulphides, As3S3 (orpiment), with hydrogen, AsH3 ; with chlorine, AsCl3 ; with bromine, AsBr3 ; with iodine, Asl3. 1. H2S precipitates yellow As2S3; best from HCl solu- tion ; soluble in alkalies and alkaline sulphides, insoluble in HCl. 2. AgN03 precipitates yel- low Ag3As03, soluble in dilute acids, NH4HO, or NH4HO salts. 3. CuS04 precipitates yel- lowish-green Cu3(As03)2, solu- ble in NH4HO, and in NH4C1. As205 (Amorphous.) Specific gravity, 3.734. Is an active oxidizing agent. Forms arseniates with the metals. Forms arsenic acid, H3As04. Forms sulphides, As2 S5 (penta-sulphide). 1. H2S precipitates yellow As2S3 -4- 82 ; from acid solu- tions, appears slowly, hastened by boiling. 2. AgN03 precipitates rcd- dish-brown Ag3AsQ4, soluble in acids, NH4HO, or NH4HO salts. 3. CuS04 precipitates green- ish-blue CuHAs04, soluble in NH4H0, NH4C1. 88 LABORATORY GUIDE. 4. (NH4)2S precipitates As2S3 only in acid solutions, soluble in excess of (NH4)2S. 5. Ferric salts and fresh fer- ric hydroxide precipitate basic ferric arsenites, insoluble in HC2H302, soluble in HCl. Used as an antidote in case of poisoning. As2U3 ; 4. (NH4)2S precipitates As7S5 only in acid solutions. soluble in excess, as (NH4)3AsS4. 5. Ferric salts and fresh ferric hydroxide precipitate yellowish" white Fe2(As04)2 when alkali acetates are added, insoluble in HC2H302. " Ammonio-magnesian mix- ture" precipitates white MgNH4As04. 7. In the dry way, As, on charcoal, gives white fumes of As203 volatilizes unchanged. Both give off a garlic odor. When As, or As203 is heated in a glass tube with char- coal, it gives a steel-gray coating. KCN -J- Na2C03 reduce arsenic from all its compounds. As203 + 3KCN = 2As + 3KCNO. As2S3 -f 3Na2C03 -f- 3KCN = 2As -f 3Na2S + 3KCNO + 3C02. 8. Dry As203 -4- NaC2H302, heated in the bulb of a reduction tube, gives arsen-dimethyl oxide or (cacodyl oxide) As2(CH3)40, recognized by its offensive odor. 9. Metallic Cu reduces As203 from HCl solution as an iron- gray film or crust, Cu5As2. This must be confirmed, as Sb, Hg, Ag, Bi, Pt, PI, and Au are also reduced by copper. 10. Arsenic is reduced to the elemental state by hydrogen by several methods and combines with it to form AsH3 (arsine).* Arsenious hydride (AsH3) burns with a bluish flame; a piece of cold porcelain reduces the temperature, and prevents the oxida- tion of the arsenic, which is deposited in dark steel-gray spots. ♦ The hydrogen can be generated by the action of H2S04 on Zn; by the action of NaHO on Zn; by sodium amalgam; by the action of Mg on strong solution of NH CI ■ by the action of Al on strong KHO. Phosphates interfere with the tests, in alkaline solutions, by sodium amalgam, Mg, and Al by forming phosphorus hydride. Sulphur and sulphites interfere; also, mercury salts and many organic substances, it is not formed in the presence of oxidizing agents, as free CI, HN03, etc. TESTS IN THE WET WAY. 89 Antimony forms similar spots, but they are distinguished as fol- lows : The arsenic spots are steel-gray to black lustre; antimony, velvety-brown to black. The arsenic spots dissolve in sodium hypochlorite; the antimony do not dissolve in the hypochlorite solution. The arsenic spots are soluble in ammonium carbonate, and insoluble in hydrochloric acid; the antimony spots are insol- uble in ammonium carbonate, and soluble in hydrochloric acid. For other differences, see 117. Arsenic is distinguished from the bases by the fact that alkali hydroxides and carbonates do not precipitate arsenious com- pounds from solutions. 154. Antimony (Sbm-V, 122). It is a bluish-white, easily pulverized metal. It fuses at 425° C, and slowly volatilizes at a white heat. It burns at a red heat, and forms Sb203. Its proper solvent is aqua regia. A boiling solution of tartaric acid slowly dissolves precipitated antimony. Antimony forms two oxides, Sb203 and Sb205, antimonious and antimonic anhydride, and SbCl3, and SbCl5, each having corresponding salts. 155. Tests: — Sb203 (white). 1. SbCl3 is decomposed by water. The SbOCl is soluble in H2C4H406. 2. H.,S precipitates orange- red Sb2S3 from acid solutions. The precipitate is soluble in HCl, in alkalies, and in alka. line, sulphides. 3. (NH4)2S, the same as No. 2, soluble in excess. Sb205 (yellowish). 1. SbCl5 is decomposed by water. (H2Q)2Sb2Q5.) 2. H2S precipitates orange Sb2S5 from acid solutions. The precipitate is soluble in HCl, in alkalies, and in alkaline sul- phides. 3. (NH4)2S, the same as No. 2, soluble in excess. 90 LABORATORY GUIDE. 4. AgN03 (in the presence of KHO or NaHO) precipitates black Ag40, insoluble in NH4HO The Ag20 is also precipitated, but is soluble in NH4H0, and leaves Ag40 un= dissolved. 5. KI, in HCl solutions, yel- low color. AgN03 (in the presence of KHO or NaHO) precipitates white AgSb03, soluble in NH4HO. KI, in HCl solutions, dark- brown precipitate of I. 6. All compounds of antimony are reduced, in the dry way, by KCN -f- Na2C03, on charcoal, to a brittle metallic globule. 7. The same reducing agents can be used with antimony as with arsenic. The differences are stated in No. 153. See also 117 for film tests. 8. KHO, NaHO, NH4HO, Na2C03, and (NH4)2C03 pre- cipitate from antimonious salts Sb(OH)3. The precipitate is soluble in an excess of KHO or NaHO in the cold, nearly insolu- ble in NH4HO; soluble in Na2C03 on heating. 156. Tin (Snn-IV, 118). It is a white metal, fusible at 230° C. It tarnishes but little in the air. Its proper solvent is HCl or aqua regia, being dissolved into stannic and stannous chlorides, according to circumstances. Tin forms two stable oxides and corresponding salts: SnO stannous oxide, Sn02 stannic oxide. The stannous compounds are good reducing agents; the stannic compounds are feeble oxi- dizing agents. TESTS IN THE WET WAY. 91 157. Tests: — Chloride, SnCl2 (ous). Oxide, SnO (ous). 1. Stannous sulphide, oxide, hydroxide, phosphate, oxy- chloride, and oxalate are insol- uble in water, 2. Alkali hydroxides pre- cipitate white Sn(OH)2, soluble in excess, as with KHO forms K2Sn02 ; insoluble in NH4HO. Alkali carbonates and BaC03 give the same reaction. 3. H2S and sulphides pre- cipitate dark-brown SnS, soluble in HCl, in alkalies; moderately soluble in yellow ammonium sulphide. 4. HgCl2 precipitates white Hg2Cl2, with excess black Hg. 5. K3FeC6N6, white precipi- tate. 6. K3FeC6N6 + FeCl3 gives a precipitate of Prussian blue. 7. AuCl3 with free HCl or HN03, a purple precipitate — "purple of Cassius." 8. Tin is reduced by zinc from acidulated stannous or stan- nic solutions as a gray, spongy mass (Sn). 9. On charcoal, with Na2C03 -\- KCN, tin salts are reduced to globules of Sn. Chloride, SnCl4 (ic). Oxide, Sn02 (ic). 1. Stannic sulphide, oxide, hydroxide, and phosphate are insoluble in water. 2. Alkaline hydroxides pre- cipitate white H2Sn03, soluble in excess, insoluble in NH4H0. Alkali carbonates and BaC03 give the same reaction. 3. H2S and sulphides preci- pitate yellow SnS2, soluble in HCl, in alkalies, alkaline sul- phides. 4. HgCl2, no precipitate. 5. K3FeC6N6, no precipi- tate. 6. K3FeC6N6 + FeCl3, no precipitate. 7. AuCl3, no precipitate. 158. Separation of the Lead and Arsenic Groups. Hg, Pb, Bi, Cu, Cd. I As, Sb, Sn. Pass H2S through their slightly acid solutions. Precipitate HgS,'Pbs, Bi2S3, CuS, CdS, As2S3, Sb2S3, SnS. Wash thoroughly, then boil with (NH4)2S.__________ RESBDUE. HgS, PbS, Bi2S3, CuS, CdS. Boil this precipitate with just enough HNO, to dissolve it. See note 6. Residue. HgS; test as before given for Hg. Also (PbS04) and S. Solution. Pb(N03)2, Bi(N03)3, Cu(N03)2, Cd(N03)2. Evaporate to get rid of excess of HN03; now dilute. Add H2S04.=> Precipitate. PbS04; re- duce to me- tallic lead on charcoal ; test as before with KI or K2Cr04. Filtrate. Bi2(S04)3, CuS04, CdS04. excess. Add NH4HO in Precipitate . Bi(OH)3; dissolve in HCl; evapo- rate to small bulk. Add to a large vol- umeofwater. BiOCl, white, insoluble in H2"TT Filtrate. Cu(0H)2, Cd(OH)2; blue in dicates Cu. Add KCN until blue disappears. AddH2S. Filtrate. CuC2N2 Precipitate CdS, yellow. SECOND METHOD. Add H2S. Precipitates CuS, CdS. Add dilute H2S04. Residue. CuS. Confirm. Solution. CdS04. Add H2S. CdS, yellow. SOLUTION. (NH4)AsS2, (NH4)SbS2, (NH4)2SnS3. Add HCl to produce distinct acid reaction. Precipitates. As2S3, Sb2S3, SnS,. Boil with HCl. Residue. As2S3, yel- low. Boil with KC103 plus HCl. Solution. H3As04. Add "mag- nesia mix- ture." White MgNH4As04. Solution. Confirm by Marsh's test or Reinsch's test. Sb2Cl6, SnCl4. Dilute, place in an evaporating dish with Pt and Zn, and add a very little HCl. Precipitates. Sb, Sn. Filter off the ZnCl2 tate with HCl. Now boil the precipi- Residue. Sb; dissolve in HCl, plus a few drops of HN03. Now add it to H20, white SbOCl. Dissolve in H2T; add H2S, orange Sb2S3; reduce on charcoal to brittle bead, Sb. Solution. SnCl2. HgCl2 to _ then to black This reduces Hg2Cl2, white, Hg. Or evaporate to dryness, and reduce with KCN plus Na2C03, on charcoal, to ductile Sn. * Also an equal volume of alcohol. CO to tr1 i> W o > H O SJ k! Q d M o TESTS IN THE WET WAY. 93 159. Notes on the separation of Lead and Arsenic Group. 1. The solution should have free mineral acid present, as HCl, to precipitate arsenious sulphide; if too acid, it must be evaporated, or antimonious sulphide is not completely precipi- tated. 2. The precipitated sulphides are more or less colored, and are easily distinguished from sulphur by their heavier specific gravity. 3. Pentad arsenic requires several hours to precipitate it; completely only from hot solutions. 4. The precipitated sulphides are well washed before treat- ment with ammonium sulphide. Use the smallest possible quan- tity of (NH4)2S. 5. Copper sulphide is slightly soluble in ammonium sulphide. Copper sulphide is not soluble in Na2S2 or K2S2, and they can be used to dissolve out As, Sb, Sn; but they dissolve mercuric sulphide, and should not be used when mercury is present. 6. If silver was not removed in the first group, it may be tested for, in the nitric solution of this precipitate, by HCl. See separation note. 7. Beyond general indications, the color of the precipitate affords no safe guidance. A pure yellow indicates arsenic and tetrad tin. If copper is absent, and it is orange-yellow, antimony is apt to be present; if black or brown, it denotes dyad tin (Pt or Au). 8. The sulphides of As, Sb, Sn are sometimes separated by treating the precipitates with (NH4)2C03, which dissolves the sulphide of arsenic. The sulphides of antimony and tin, dis- solved in boiling HCl (under the hood), evaporate the excess of acid; dilute with water, add Pt and Zn : the Sb will be depos- ited on Pt; the Sn forms on Zn; sometimes the Sn floats in small fragments. These elements can be confirmed by the tests before described. This method gives good results. 9. Free nitric acid decomposes the H2S, and should be expelled before the H2S is added. 94 LABORATORY GUIDE. GROUP III. —IRON GROUP. 160. Those metals which, from neutral or alkaline solu- tions, are precipitated, by the group reagent ammonium sulphide, as sulphides, Fe, Mn, Co, Ni, Zn; as hydroxides, Al and Cr. The rare elements: Uranium, indium, thorium, cerium, lanthanum, didymium, titanium, tantalum, niobium, yttrium, erbium, vana- dium. The oxides and hydroxides of this group are insoluble in water. The hydroxides of Co and Ni dissolve in NH4HO; Zn dissolves in excess of any alkali; Al in the fixed alkalies, slightly in NH4HO. Cr203 redissolves in cold solution of fixed alkalies ; it is again precipitated on boiling this solution. The oxides of Al, Crs and Fe, after ignition, are difficultly soluble in acids. The presence of organic substances, as tartaric acid, sugar, etc., prevents the precipitation of this group by alkalies. H28 precipitates only ZnS from acetates of this group. The free acids redissolve the other sulphides : FeCl2 -f H2S = FeS + 2HC1, the FeS being soluble in HCl. It must be borne in mind that H2S is a reducing agent, and that it precipitates the "ous" sul- phides. NH4HO -|- NH4C1 (the latter on account of Mg, Mn, and Al) will fully precipitate only Al, Cr, and ic Fe. (NH4)2S precipitates all the metals of this group from alka- line solutions as sulphides (except Al and Cr). The sulphides of. Fe, Zn, Mn, Co, and Ni are soluble in dilute acids, which keep them in solution during the second group precipitation; but they are insoluble in water. The soluble carbonates precipitate the metals of this group: Zn, Co, and Ni as basic carbonates; the "ous" Fe and Mn as normal carbonates; the "ic" salts of Fe, Al, and Cr as hydroxides. The soluble phosphates precipitate this group. The only phosphates which may occur in a sulphide precipitate are those of Al, Mg, Ca, Cr, Ba, and Sr. In the dry way, they are not easily reduced on charcoal, Zn being the most easily reduced and volatilized. Co, Ni, and Fe TESTS IN THE WET WAY. 95 are reduced to magnetic oxides. The most of them give character- istic beads; none of them give characteristic flame reactions. 161. Iron (Fe11"111, 56). It forms alloys in all proportions with manganese, chromium, tungsten, nickel, cobalt, copper, gold, platinum, aluminum, antimony, silicon, sulphur, phosphor- us and arsenic ; in limited proportions only, with zinc, tin, bis- muth, and carbon. It scarcely alloys at all with lead, silver, and mercury. Iron, in the laboratory, forms two important oxides, FeO and Fe203, and their corresponding series of salts. HCl is a good solvent for iron. 162. Tests:— FeO (black). The chloride is Fe2Cl4. The sulphate is FeS04. The ferrous compounds are oxidized to ferric compounds by all oxidizing agents, as CI, KC103 -f HCl, Br, HN03, etc. Are good reducing agents. The salts, or solution, have a green color. The oxide, hydroxide, sul- phide, carbonate, phosphate, oxalate, borate, cyanide, tar- trate, tannate, ferrocyanide, and ferricyanide are insoluble in water. Ferrous sulphate is insoluble in alcohol. Ferrous carbonate and sul- phide are formed in the wet woa- Fe203 (reddish brown). The chloride is Fe2Cl6. The sulphate is Fe2(S04)3. The ferric compounds are reduced to ferrous compounds by reducing agents, as H2S, S02, SnCl2, H, etc. Are moderate oxidizing agents. The solution has a browr ^ sh- yellow color. The sulphite, gallate, borate, hydroxide, oxalate, tannate, phosphate, and ferrocyanide are insoluble in water. Ferric sulphate is soluble in alcohol. Ferric carbonate and sul- phide are not formed in ordi- nary conditions in the wet way. 96 LABORATORY GUIDE. 1. Alkali hydroxides precip- itate white Fe(QH)2; NH4C1 or (NH4)2S04 dissolves or pre- vents its formation. 2. Alkali carbonates precip- itate white FeC03, soon chang- ing to reddish-brown Fe2(OH)6. 3. H2S precipitates only the acetate FeS. 4. (NH4)2S precipitates black FeS, finally changing to Fe20(SOJ2. 5. 3FeS04 + 2Na2HP04 + 2NaC2H302 = Fe3(PQ4)2 + 3Na2S04 + 2HC2H302. 6. K4FeCfiN precipitates 6^ 6 white (Everitt's) K2Fe(FeC6N6); changes to Prussian blue in the air. 7. K3 Fe C6 N6 precipitates 1. Alkali hydroxides precip- itate reddish-brown Fp2(OH)6, insoluble in alkalies or ammo- nium salts. 2. Alkali carbonates precip- itate Fe2(OH)6. 3. H2S + Fe2Cl6 = 2FeCl2 + 2HC1 + S. 4. (NH4)2S precipitates FeS + S. 5. Fe2Cl6+2H3P04 4 6NaC2H302 = Fe2(PQ4)2 4- 6NaCl + 6HC2H802. 6. K4FeC6N6 precipitates (Prussian blue) Fe4(FeC6N6)3> insoluble in acid, decomposed by alkalies. 7. K3 Fe C6 N6, no . precipi- tate ; solution becomes brown. dark-blue (Turnbull's) Fe3(FeC6N6)2, insoluble in acids. KCNS gives no reaction 8. KCNS gives blood-red with ferrous salts. color. 9. The beads are described in article 116. 10. NaC2H302 precipitates, from nearly neutral ferric salt (when heated to boiling and filtered hot), a basic ferric acetate; complete separation of all the iron. Strong HCl will decompose ferrocyanide of potassium and give a blue. This must be borne in mind when testing for iron. TESTS IN THE WET WAY. 97 163. Aluminum (Alm, 27.5). It is a silver-white metal, fusible at 700° C. HCl is the best solvent. H2S04 dissolves Al from many of its native compounds. It forms double salts as alums. A1203 with traces of Si02 and Fe203 forms corundum, sapphire, ruby. The A1203 is employed as a mordant. Organic acids prevent the precipitation of Al as hydroxide or basic salt. Most insoluble salts of Al are changed to soluble compounds by the action of fixed alkali hydroxides. It forms an oxide, A1203 ; a chloride, A12C16; a sulphate, A12(S04)3; a nitrate, A12(N03)6. The phosphate, hydroxide, and oxide are the principal insoluble compounds. 164. Tests: — 1. Alkali hydroxides precipitate grayish-white Al2(OH)6, soluble in fixed alkali hydroxides, slightly in NH4H0, but not if NH4C1 is present. 2. H2S does not precipitate it, but (NH4)2S precipitates Al2(OH)6, with escape of H2S. 3. Alkali carbonates precipitate white Al2(OH)6 with escape of C02. 4. The basic acetate of aluminum is precipitated like 10 in No. 162. 5. Alkali phosphates precipitate white A12(PQ4)2, soluble in fixed alkali hydroxides, but not in acetic acid. 6. For tests in the dry way, see No. 110. 165. Chromium (CrII"IV', 52.4). It is a steel-gray metal. The metal is quite rare. Its compounds are basic and acid. The compounds of Cr are analogous to those of Al. LABORATORY GUIDE. 166. Tests: Basic. Cr203 (bright green). 1. The phosphate, oxide, and hydroxides are insoluble in water. The carbonate and sul- phide are not formed in the wet way. 2. Fixed alkali hydroxides precipitate bluish-green Cr2(OH)6, soluble in excess on long boil- ing, or by the addition of NH4C1. All Cr is precipitated as Cr2(OH)6. 3. H2S does not affect its solutions, whether acid, neutral or alkaline. 4. (NH4)2S precipitates Cr2(OH)6, with escape of H2S. 5. Oxidizing agents change it to chromic acid. 6. N H4 H 0 precipitates Cr2(OH)6, slightly soluble in excess. 7. BaC03 precipitates Cr2 (OH)6 with some basic salt. 8. Na2HP04 precipitates Cr2(P04)2, insoluble in acetic Acid. Cr03 (scarlet red.) 1. It is a powerful oxidizing agent. Its salts are poisonous, and have a metallic taste. 2. Alkali metals form yellow normal chromates or reddish bi- chromates. Most soluble salts of Cr03 have permanent forms. Ba, Pb, Bi, Ag chromates and the ous chromates of Mn and Hg are insoluble in water. 3. H2S reduces to green solution. 4. (NH4)2S precipitates (in neutral or alkaline) Cr2(OH)6. 5. Reducing agents reduce it to chromic oxide. 6. Lead salts precipitate yel- low PbCr04, soluble in HNO HC2H302, 3) diffi- insoluble in cultly soluble in KHO. 7. Barium salts precipitate yellow BaCr04, soluble in HCl and HN03. 8. AgN03 precipitates dark- red Ag2CrQ4, soluble in HN03 acid. | and in NH4HO. 9. The most delicate test for Cr, as Cr03, is by means of H202 (hydrogen peroxide) and (C2H5)20 (ether), giving a fine blue color, with one part in 40,000 of water. TESTS IN THE WET WAY. 99 10. Tests in the dry way, see Nos. 107, 110, 114,116. Note.— Fe, Al, and Cr form sesquioxides, K203, which may be obtained by igniting their corresponding hydroxides. 167. Cobalt (CoIMV, 58.6). It is a steel-gray, hard, mag- netic metal; does not oxidize in the air at ordinary temperatures. It slowly dissolves in HCl, H2S04 ; readily in HN03. There are two oxides, CoO, cobaltous oxide; Co203, cobaltic oxide. The former is a light-brown powder; the latter is black. There are two chlorides, CoCl2 and Co2Cl6. When Co203 is dissolved in HCl, cobaltic chloride (Co2Cl6) is formed; when this is heated, it is converted into cobaltous chloride (CoCl2) with evolution of chlorine. The cobaltous salts, containing water of crystallization, are red; the anhydrous salts are mostly blue. The cobaltous salts are generally stable compounds, not easily oxidized; cobaltic salts are very unstable compounds, not permanent in solution, and easily reduced by heat alone to the ■ous state. The cobaltous sulphide, borate, oxalate, phosphate, basic carbonate, hydroxide, cyanide, ferrocyanide, and ferricya- nide are insoluble in water. Most of these salts form soluble com- pounds with ammonia. The sulphate is efflorescent; chloride acetate, and nitrate are deliquescent 168. Tests: 1. Fixed alkalies precipitate blue basic salts. This absorbs oxygen and becomes olive-green hydroxide; if boiled before oxida- tion in the air, becomes rose-red Co(OH)2 ; does not dissolve in excess. NH4HO causes the same precipitate, but it is soluble in excess. 2. Alkali carbonates precipitate peach-red basic salts; on heating, become violet and blue. They are soluble in excess and in (NH4)2C03. 3. (NH4)2S precipitates from neutral, and H2S, from the x acetate, and from the alkaline solutions, black CoS, readily solu- ble in HX03, but best in aqua regia 100 LABORATORY GUIDE. 4. Na2HP04 precipitates light-red CoHP04, soluble in acids and in NH4HO. 5. Oxalates precipitate reddish-white CoC2Q4, soluble in mineral acids and in NH4H0. 6. KCN precipitates brownish-white CoC2N2, soluble in excess, and in HCl. When boiled with KCN, the precipitate dissolves as (K3CoC6N6), which is not precipitated by NaClO. 7. K4FeC6N6 precipitates grayish-green Co2FeC6N6, insol- uble in HCl. 8. K3FeC6N6 precipitates dark-brown Co3(FeC6N6)2, insol- uble in HCl. When to a solution of Co or Ni excess of NH4C1 -+- NH4H0 is added, and then K3FeC6N6, a blood-red color indicates Co. If Ni is present, and the solution is boiled, a copper-red precipitate forms; if only Co is present, a dirty green, on boiling. 9. KN02 4* (HC2H302 to strongly acid reaction), the mix- ture kept moderately warmed, precipitates yellow K6Co2(NQ2)12, as follows: (Stadtler gives a different formula.) 2CoCl2 + 10KNO2 + 4HX02 = K6Co2(N02)12 + 4KC1 4- 2NO + 2H20. This reaction separates Co from Ni, as Ni is not precipitated by this reagent. 10. To a dilute solution of cobaltous nitrate, add tartaric or citric acid, then an excess of ammonium hydroxide and a few drops of potassium ferricyanide; a deep-red color appears, even when largely diluted. 11. Tests in the dry way, see No. 116. 169. Nickel (Nin-IV, 58.8). It is a bright, hard, malleable, difficultly fusible metal. It is attracted by the magnet. The best solvent is HN03. In nearly all its compounds it closely resem- bles Co. It forms two oxides, NiO, nickelous oxide, gray-green, and Ni203, nickelic oxide, black. Both oxides dissolve in acid, and form nickelous salts. The salts of Ni have a green color; the anhydrous are yellow; the nitrate and chloride are deliquescent or efflorescent, according to the moisture in the atmosphere. The TESTS IN THE WET WAY. 101 phosphate, oxalate, borate, sulphide, hydroxide, carbonate, cya- nide, ferrocyanide, and ferricyanide are insoluble in water. Many of these become soluble by the action of NH4H0. 170. Tests:— 1. Fixed alkali hydroxides precipitate pale-green Ni(0H)2, soluble in NH4H0 to greenish-blue liquid. NH4HO precipitates Ni(0H)2, but it is soluble in excess to blue color, and it is again precipitated by KHO or NaHO as Ni(OH)2. The presence of organic acids, sugar, impedes the precipitation by alkalies. 2. Alkaline carbonates precipitate green basic carbonate (2NiC03, 3Ni(OH)2), soluble in (NH4)2C03, or in excess, with blue or greenish-blue color. 3. H2S and (NH4)2S precipitate black NiS somewhat solu- in NH4HS. 4. Na2HP04 precipitates greenish-white Ni3(P04)2, soluble in NH4HO. 5. H2C204 precipitates green NiC2Q4, complete after twenty- four hours. 6. KCN precipitates pale-green NiC2N2, soluble in excess. When boiled with NaCIO, black Ni(OH)3 precipitate. See test No. 6, cobalt. 7. K4FeC6N6 precipitates greenish-white Ni2FeC6N6, insolu- ble in acids, soluble in NH4HO, decomposed by fixed alkalies. 8. K3FeC6N6 precipitates greenish-yellow Ni3(FeC6N6)2, insoluble in HCl. 9. Render the solution of Ni alkaline by NH4H0, and add a solution of potassium sulphocarbonate*; a deep brownish-red fluid is obtained, black by reflected light; when dilute it is pink color—characteristic test for Ni. 10. Tests in the dry way, see No. 116. * Note —The solution is made by taking a five per cent, solution of KHO, saturating one-half with H2S, adding the other one-half, and then one-twenty-fifth of the volume of CS2, digesting at a gentle heat, and separating the dark orange-red fluid from the undissolved CS2. Keep in a well closed bottle. 102 LABORATORY GUIDE. 171. Manganese (MnIMV, 55). It is a hard, brittle, slightly magnetic, easily oxidized metal. It is related to Zn, Fe, and Cr. It forms the following oxides: MnO, Mn304, Mn203, Mn02, Mn207. The first is a powerful basic oxide; the last is an acid- forming oxide, yielding HMn04 when brought into contact with water. ~&e three intermediate oxides are feebly basic (Mn02 acts as a weak acid). The chlorides : Manganous, MnCl2, light- pink ; manganic, Mn2Cl6, brown liquid, which readily changes to 2MnCl2 4" Cl2. The sulphates: MnS04, reddish-yellow manga- nous sulphate; Mn2(S04)3, greenish manganic sulphate. The higher oxides of manganese dissolve to manganous chloride, with evolution of CI, when heated with HCl; to manga- nous sulphate, with evolution of O, when heated with H2S04. The higher compounds of manganese are reduced to ous condi- tion from all its combinations by boiling with HCl; the ous is the only stable form. Manganous Salts. They are rose color, the oxide grayish green. The oxalate, hydroxide, sulphide, phosphate, carbonate, sul- phite, and borate are insoluble in water. The nitrate, bromide, iodide and chloride are deliquescent. 172. Tests: — 1. Alkali hydroxides precipitate white Mn(OH)2; changes in air to brown Mn202(OH)2. 2. (NH4)2S precipitates (from neutral and alkaline solu- tions) flesh-colored MnS, soluble in HCl and HC2H302. In the air oxidizes. 3. H2S does not precipitate acid solutions; from neutral solutions only imperfectly. 4. Na2HP04 (from neutral solutions) precipitates white Mn3(PQ4)2; turns brown in air; soluble in dilute acids. 5. Alkali carbonates precipitate white MnC03; brown in the air; before oxidation, slightly soluble in NH4C1. TESTS IN THE WET WAY. 103 6. KCN precipitates white MnC2N2, soluble in excess. It darkens in the air. 7. K4FeC6N6 precipitates whitish-red Mn2FeC6Nfl, soluble in HCl. 8. K3FeC6N6 precipitates brown Mn3(FeC6N6)2, soluble in acids. Manganic Salts. 173. Tests:— 1. They are from a reddish-brown to purplish-red color. The chloride exists only in solution. The sulphate is soluble in dilute H2S04, but is reduced to MnS04 by dissolving in H20. 2. H2S and (NH4)2S reduce manganic salts and precipitate MnS. (The (NH4)2S reduces Mn2Cl6.) 3. The alkali hydroxides and carbonates precipitate Mn202(0H)2. 4. K4FeC6N6 precipitates gray-green Mn4(FeC6N6)3 5. K3FeC6N6 precipitates brown MnFeC6N6. 6. The ic compounds are changed by heat to Mn304. 7. When mixed with H3P04 and evaporated to dryness and heated gently, a violet or blue mass; when heated with H20, a purple-red phosphate. 8. In the dry way, the ous and ic act alike; and the ous compounds are best identified by oxidation, yielding color pro- duct. This test can be nicely shown by the electrolysis of a manganese compound in presence of HN08; when but a trace, gives a pink solution. 9. In the dry way, see 107, 116. 174. Zinc (Zn11, 65). It is a hard, bluish-white metal, brittle at ordinary temperatures; at 94° C. to 149° C, it becomes ductile and malleable; at higher temperatures, it again becomes brittle. It melts at 411° C. It burns with a bluish-green flame, giving off white fumes, and coats the charcoal with oxide. It 104 LABORATORY GUIDE. dissolves in HCl and H2S04, giving off H ; in HN03 with NO or N02. Pure zinc dissolves very slowly in acids or alkalies, unless in contact with Cu or Pt. The oxide, ZnO, is white; the chloride, ZnCl2, is white, deliquescent salt. The carbonate (Smithsonite), ZnC03, occurs native, and is an important ore of Zn; the sulphate, ZnS04, ic isomorphous with MgS04, and strongly resembles it. The basic carbonate, arseniate, phosphate, oxalate, oxide, sulphide, hydroxide, and ferrocyanide are insoluble in water. The most of the insoluble salts are dissolved in alkali hydroxides. The nitrate, iodide, acetate, bromide, chlorate, and chloride are deliquescent. The sulphate is efflorescent. 175. Tests: — 1. Alkali hydroxides precipitate white Zn(OH)2, soluble in excess of either precipitant; reappears on heating, more readily from NH4HO than from KHO or NaHO. 2. H2S precipitates (from neutral or acetic acid solutions) white ZnS. 3. (NH4)2S precipitates (from salts with acids and alkalies) white ZnS; a complete precipitation. It is insoluble in KHO, HC2H302, and in excess. 4. Alkali carbonates precipitate white basic carbonate Zn5(OH)6(C03)2, soluble in KHO and NH4HO, sparingly solu- ble in (NH4)2C03. 5. KCN precipitates white ZnC2N2, soluble in excess. 6. Na2HP04 precipitates white Zn3(P04)2, soluble in alka- lies, in KHO, in NH4H0, in strong acids. 7. K4FeC6N6 precipitates white Zn2FeC6N6, soluble in HCl. 8. K3FeC6N6 precipitates brownish-yellow Zn3(FeC6N6)2, soluble in HCl and in NH4HO. 9. Tests in the dry way, see 106, 110, 117. It will be noticed that Zn gives the only white sulphide, and that nearly all its precipitates are white. 176, Separation of the Iron Group. Phosphates and Oxalates absent. Boil the filtrate of lead and arsenic groups to expel II2S. Add a few drops of HN03 or (KC103 plus HCl), and boil an instant to oxidize the Fe; immediately add NH4C1, and NH4H0 in excess. PRECIPITATE. Fe2(OH)6, Cr2(OH)G, Al2(OH)6. Add NaHO or KHO, and boil for some minutes (if not boiled, Cr and Al go in solution, and may be separated by boiling afterwards, Cr). Precipitate. Fe2(OH)6, Cr2(OII)£ into two portions. Divide Portion I. Fe. Add HCl • test by KCNS, red; K4FeC6N6, blue. Portion II. Cr. Fuse on Pt foil with KNOn thoroughly; dis solve in H20, add a few drops of II('2II302 and Pb(C2H302)2;y*J- low PbCr04. Solution. K2A1204. Add IICl to make it acid, then add (NH4)2C03; pre- cipitates white A12(QH)6. Heated on charcoal, moistened Co(N03)2, blue mass. with Note. —In all cases handle quickly and wash thoroughly, and see that the other groups are well washed out. Always test the filtrate, to see that the precipitate is all down. FILTRATE. Co, Ni, Mn, Zn in solution. Add (NH4)2S and heat gently; filter and wash the precipitate with dilute (NH4)2S, and with H20. Treat the well washed precipitate with cold dilute (1 to 12) HCl. If the filtrate is brown, it indicates the presence of Ni. V^___ Residue. NiS, CoS. Test for Co with borax bead. Dissolve in HN03 plus 3HC1. Method I. Evaporate to near dryness; di- lute, add HC2H302 and KN02. Precipitate. Filtrate. Yellow KeCo2(N02)12. Ni(N02)2. Add NaHO; gives Ni(OH)2, pale green. Method II. The solution of Co and Ni is evaporated to near dryness. Add H20, then KCN, until the precipi- tate is dissolved; then boil and add a few drops of HCl. Now make strongly alkaline with NaHO, and add Br or NaCIO; heat. Ppecipitate. Ni203, black. Filtrate. CoC2N, Solution—Method I. ZnCl2, MnCl2. Add NaHO or KHO, and digest without warm- ing. Precipitate. Mn(OH)2, Add Br. black Mn02. Heated on Pt with Na2C03 -\- KN03; green mass, Na Mn Oa. Add HC2I1302, red NaMn04. Solution. K2Zn02. Pass (NH4)2S through white Zn S. Heated on charcoal, moistened withCo(N03)2, green mass. Method II. In acetic acid solution. Pass H2S through white Zns. Must contain excess of H2S. Filter; render alkaline by NH4II0, and add (NH4)2S; flesh-colored MnS. 106 LABORATORY GUIDE. 177. Notes on separation of Iron Group. 1. In many cases when one member of a group is precipi- tated, it mechanically brings down other members of the group with it; in some cases there is a chemical action of one base with another. 2. The NH4C1 dissolves manganous hydroxide, and NH4HO in excess dissolves Co, Ni, and Zn hydroxides. To dissolve the Mn, the NH4HO must be in excess, and the Mn must be in the ous condition. 3. If too much HN03 is added, manganic compounds may be formed, but enough must be added to oxidize the iron. 4. Organic acids (citric, tartaric) and sugar prevent pre- cipitation by alkalies. They may be removed by heat and HN03. The ignited residue is acidulated with HCl, and car- bonaceous matter filtered off. 5. In separating Fe, Al, and Cr by fixed alkalies (KHO or NaHO), they should be strong enough to dissolve Al, and the mixture boiled long enough to precipitate Cr. 6. In the presence of phosphoric acid, the separation becomes quite difficult. There must be only free acetic acid in the solution. It must be strong enough to prevent the precipitation of Ca3(P04)2. As it dissolves some ferric phosphate, the sepa- ration is not very complete. 7. Fe2Cl6 is taken as the reagent, together with NaC2H302, to neutralize the CI, as follows: Fe2Cl6 + 6NaC2H302 = Fe2(C2H302)6 -f 6NaCl. Fe2Cl6 + 6NaC3H302 + 2H3P04 = Fe2(P04)2 + 6NaCl + 6HC2H302. 178. Separation of the Iron Group in the presence of Phosphoric Acid. Boil the filtrate from Group II. to expel H2S; oxidize with a few drops of HN03, and boil a short time. Add NH4C1 and an excess of NH4H0. Filter, and precipitate by (NH4)2S, and filter. Wash the precipitates separately, digest them together with (NH4)2S, filter and wash. PRECIPITATES. FeS, MnS, CoS, NiS, ZnS; A12(P04)2, Cr2(P04)2; Al2(OH)6, Cr2(0H)6; Ba, Sr, Ca, and Mg phosphates. Dissolve in hot dilute HCl and KC103. ^ Digest to expel free CI; filter out the S. Nearly neutralize with dilute solution of Na2C03, and add solution of NuC2n302 (strongly acidified with IIC2H302) as long as a precipitate forms. Digest with gentle heat, and filter while hot. PRECIPITATE. Fe2(P04)2, A12(P04)2) Cr2(P04)2. Boil the precipitate, for some time, with KHO or NaHO. Residue. Fe2(P04)2 and Cr2(P04)2. Divide into two portions, and treat as directed in No. 176, separation of Cr and Fe. Solution K2A1204 with K3P04. Acidulate with HCl, and add excessof NH4H0; A12(P04)2, not soluble in HC2H30, Fuse A12(P04)2 with \y2 parts of Si02 plus 6 parts dry Na2 C 03; dissolve in H20. Add (Nn4)2C03 in excess; filter and wash. The residue contains allu- minum sodium silicate. The solution, the sodium phosphate. SOLUTION. Fe2Cl6, A12C16, Cr2Cl6, or H3P04; MnCl2, CoCl2, NiCl2, ZnCl2, BaCl2, SrCl2l CaCl2, MgCl2. Add Fe2Cl6, drop by drop, as long as a precipitate forms, and until the liquid bacomes red, and heat gently. Filter; test the precipitate for Fe2(P04)2. Save the filtrate, and add to it Nn4Cl and NH4H0; filter. Precipitate. Al2(OH)e, Cr2(OH)6, Fe2(0H)6. Test as in No. 176. Filtrate. To this filtrate add (NH4)2S, and digest and filter. Precipitate. MnS, CoS, NiS, ZnS. Separate as in No. 176. Solution. May contain Ba, Sr, Ca, Mg. Save this for the next group —Group No. IV. 179. Separation of the Iron Group in the presence of Phosphates. (Second Method.) To the filtrate from Group II. add NH4C1, and NH4H0 to alkaline reaction; then add (NH4)2S to complete the precipitation. The filtrate is separaetd as Group IV. PRECIPITATE. FeS, MnS, CoS, NiS, ZnS, S; Al2(On)G, Cr2(OH)6; phosphates of Al, Cr, and of Ba, Sr, Ca, and Mg. Wash the precipitate thoroughly, ana treat with cold dilute HCl. If a black residue is left, test it for Co and Ni, as in No. 176. Si02 is sometimes present in the residue. and b01110 exPel H=s!lf turbid, filter again, and reserve a small portion of the precipitate, and test for phosphoric acid by (Nn4)2Mo04. FIRST PORTION. SECOND PORTION. Add a few drops of HN03 and boil. Solution. Solution. BaCl2, SrCl2, CaCl2, MgCl2. Add H2S04 and filter. Fe2Cl6, A12C16, Cr2Cl6, MnCl2, (CoCl2, NiCl2), ZnCl2, H3P04, and BaCl2, SrCl2, CaCl2, MgCl2. 1. Test a small portion for iron by KCNS, or test the original solution with K4FeC6N6, or K3FeC6N6. 2. To the remainder, add Fe2Cl6 till a drop is precipitated yellow by NH4H0 (all H3P04 is precipitated), concentrate to a small bulk, add H20, nearly neutralize with K2C05, cool, and add an excess of Ba(03; let the mixture stand, and filter. Pecipitate. BaS04, SrS04, (CaS04). Fuse on charcoal, and dissolve the sul-phides in HCl; and separate as in Group IV. Solution. No. 2. MnCl2, ZnCl2, BaCl2, SrCl2, CaCl2, MgCl2. Add HCl and boil to expel C02. Add NH4HO to alkaline reaction, and then (NH4)2S. Precipitate. No. 2. Al2(OH)e, Cr2(OH)G [Fe2(P04)2, Fe2(OH)6, BaC03]. Boil the precipi- Warm and filter. tate with NaHO or KHO. Precipitate. Precipitate. Solution. MnS, ZnS. Dissolve in HCl, and separate as in No. 176. BaCl2, MgCl2. Remove Ba, Sr, Ca with H2S04 (Portion 2 above). Precipitate Mg as phosphate. See Group IV. Cr2(OH)6, Fe2(OH)e. Test as directed in No. 176. K2A1204. Acidify with HCl and add NII4H0 and boil. Precipitate, Al2(OH)0. o 00 TESTS IN THE WET WAY. 109 GROUP IV. —ALKALINE EARTHS. 180. 1. Those metals whose carbonates are insoluble in water are precipitated by the group reagent (NH4)2C03 as carbonates, Ba, Sr, Ca, Mg. If much NH4C1 is present, Mg is not precipi- tated, but is to be found in Group V., or as a distinct division of the IV. Group (precipitated as phosphate). 2. The group can be precipitated as phosphates, if it were not for being so intractable in further operations. 3. The precipitation of Ba, Sr, and Ca by (NH4)2C03, in the presence of NH4C1, is not very complete; in the presence of NH4H0, the carbonates are rendered more insoluble. 4. When only one member of the group is present, a solu- tion of CaS04 (not too little) precipitates Ba immediately, Sr after some time, Ca not at all. 5. In the above, Ca may be tested by (NH4)2C204, white CaC204. They can also be identified by their flame reactions. 6. The metals of this group are heavier than water, and decompose it; at common temperatures, Mg slowly. Ba, Sr, Ca oxidize in dry air, Mg in moist air. They dissolve in HCl, H2S04, UNO3 with disengagement of II. They combine with CI, I, Br, 0, S, P at elevated temperatures; Mg unites directly with N. Mg burns in the air with dazzling light. The metals of this group are dyads. 7. The oxides may be formed by the ignition of their car- bonates, nitrates, or any of their salts containing volatile acids; or by expelling H20 from their hydroxides. 8. The chlorides are formed by dissolving the oxides, hydrox- ides, carbonates, sulphides in dilute HCl. Dry CI converts Ba, Sr, and Ca oxides at a red heat into chlorides (MgO an excep- tion). The chlorides of this group are not decomposed on being heated in a current of H. 9. Ba, Sr, and Ca oxides combine readily with H20 to form hydroxides (MgO combines only slowly). They can also be pre- pared by boiling their solutions with NaHO. The following is the 110 LABORATORY GUIDE. order of the solubility of their hydroxides : Ba(OH)2, Sr(OH)2, Ca(OH)2, Mg(OH)2, the last being almost insoluble in H20. 10. The solubility of the sulphates is in the reverse order of their hydroxides, BaS04 being the most insoluble. When the sul- phates are heated with carbon, they are converted into sulphides. 11. The nitrates are formed by dissolving the oxides, hydoxides, or carbonates in dilute HN03. 12. The salts of this group are colorless, unless the acid is colored. 13. The silicates, carbonates, and normal phosphates are insoluble in H20. 14. Compounds of Ba, Sr, and Ca moistened with HCl impart characteristic colors to non-luminous flame. See No. 110. 181. Barium (Ba11, 137). The metal is but little known. It is represented as a yellowish metal. The sulphate, sulphide, chromate, carbonate, iodide, phosphate, oxalate, and eilico- fluoride are insoluble in water. 182. Tests: — 1. Fixed alkali hydroxides precipitate (only from concen- trated solutions) white Ba(OH)2, soluble in fifty parts of water. 2. Alkali carbonates precipitate white BaC03. The precipi- tation is hastened by heat and by NH4HO; it is incomplete in presence of NH4C1 or NH4N03. The BaC03 is soluble in HN03 and HCl, and in 14,137 parts of water. 3. Soluble sulphates (and H2S04) precipitate white BaS04, which is but slightly soluble in hot concentrated H2S04. The BaS04 is soluble in 200,000 parts of water. 4. K2Cr04 and K2Cr207 precipitate yellow BaCr04. The precipitate dissolves in HCl or HN03, and is again precipitated by NH4HO. 5. Na2HP04 precipitates white BaHPQ4, soluble in acids; reprecipitated by NH4HO. 6. (NH4)2C204 precipitates white BaC2Q4, slightly soluble in HC2H302 and in H2C204, readily in HCl and HN03. TESTS IX THE WET WAY. Ill 7. H2SiF6 precipitates white BaSiF6, slightly soluble in H20, insoluble in C2H60. 8. NaI03 precipitates white Ba(IQ3)2, soluble in 1,746 parts of water. Other members of the group do not give this precipitate. 9. Flame reactions, see No. 110. 183 Strontium (Sr11, 87). The color is yellow, somewhat darker than that of Ca. The SrO is a grayish-white powder; the Sr(OH)2 is about the same color. The hydroxide is less soluble, the sulphate and chromate more soluble than the corresponding Ba compounds. The chlo- ride is slightly deliquescent; the nitrate and acetate, efflorescent. 184. Tests: — • 1. NaHO, NH4H0, Na2C03, (NH4)2C03, Na2HP04 form precipitates which closely resemble those produced by these re- agents with Ba salts. 2. H2SiF6 gives no precipitate; neither does K2Cr207 until enough KHO is added to its solution to convert it to K2Cr04. The K2Cr04 slowly precipitates SrCr04, soluble in acetic acid; reprecipitated by KHO. 3. (NH4)2C204 precipitates white SrC204, soluble in HCl and HN03, sparingly soluble in H2C204 and HC2H302. 4. Flame reactions, see No. 110. 185. Calcium (Ca11, 40). The metal has a light-yellow color. Calcium oxide is quick lime; calcium hydroxide is slaked lime. The oxalate, phosphate, and carbonate are insoluble in H20. The iodate, sulphate, sulphite, and hydroxide are insolu- ble in C2H60, and slightly soluble in H20. The nitrate, chlo- ride, and iodide are soluble in C2H60. The bromide, iodide, chloride, nitrate, and chlorate are deliquescent. 186. Tests: — 1. Fixed alkali hydroxides precipitate white Ca(QH)2, solu- ble in 7C0 parts of H20 112 LABORATORY GUIDE. 2. Soluble carbonates precipitate CaCQ3 ; alkaline phos- phates precipitate CaHP04; ammonium oxalate precipitates CaC204. The precipitates are similar to those of Ba and Sr. 3. H2S04 (not CaS04) precipitates white CaS04, soluble in a concentrated solution of (NH4)2S04 ; distinction from Ba and Sr. 4. K2Cr207 or H2SiF6 do not give a precipitate (distin- guished from Ba). 5. Neutral alkaline sulphites (Xa2S03) precipitate CaS03, soluble in HCl and in HN03 and H2S03. 6. Alkaline arsenites precipitate CaHAs03, soluble in acids and NH4HO. The other members of the group give this precipi- tate only in concentrated solution. The precipitate forms slowly, and salts of ammonia must be absent. 187. Magnesium (Mg11, 24). The metal has the color of silver. The carbonate, hydroxide, phosphate, and arseniate are insoluble in water; the tartrate, sulphite, and oxalate are spar- ingly soluble in water. The hydroxide and carbonate are solu- ble in ammonium salts (except (NH4)3P04). The iodide, nitrate, acetate, chlorate, bromide, chloride are deliquescent. 188. Tests: — 1. The fixed alkalies and the other alkaline earths precipitate Mg(OH)2, soluble in ammonium salts. 2. NH4H0 precipitates some of Mg as Mg(OH)2, leaving the rest as a double salt of Mg and NH4HO, as for example: 2MgS04 + 2NH4HO = Mg(OH)2 -f- (NH4)2S04MgS04. 3. K2C03 or Na2C03 precipitates basic Mg4(C03)3(0H)2 ; boiling promotes the precipitation; ammonium salts prevent the precipitation. 4. (NH4)2C03 precipitates (in concentrated solutions) MgCQ3. The addition of NH4HO promotes separation, while NH4C1 prevents the precipitation. 5. Na2HP04 precipitates (if not too dilute) MgHP04; pro- moted by stirring with glass rod. In H20, containing NH4H0. it is soluble in 44,000 parts of water. TESTS IN THE WET WAY. 113 6. H2S04, 2HFSiF4, and K2Cr04 do not produce a pre- cipitate of Mg salts. 7. (NH4)2Cr04 produces (in concentrated solutions) MgCrQ4. NH4C1 with NH4HO interferes with the formation of the precipitate. 8. Na2HAs04 precipitates MgHAs04, soluble in acids, even acetic acid. 9. Tests in the dry way, see No. 110. 189. Separation of the Alkaline Earths—Group IV. Method I. Boil the ammonium sulphide filtrate from Group III., to decompose the ammo- nium sulphide. Add NH4C1 + NH4H0 -f (NH4)2C03 PRECIPITATE. BaC03, SrC03, CaC03 Add HC2n302; solution as acetates. Now add K2Cr207. Precipitate. Yellow Ba Cr 04. Dissolve in HCl; flame green. Add H2S04, white BaS04; insoluble in acids. Filtrate. Sr(C2H302)2,Ca(C2H302)2[K2Cr207].Make alkaline with NH4H0, and add (XII4)2C03. Precipitates SrC03, CaC03. Wash well, to remove K2Cr04; dissolve in HC2H302. Solution. Sr(C2H302^2, Ca(C2H302)2. Add K2SO, (1 to 200 parts of H20). Precipitate . SrS04. Add HCl. Test by flame; crim- son. Filtrate. CaS04. Add (NH4)2C204, white CaC204; test by flame; brick-red. FILTRATE. MgC03 + NH4C1. Mg C 03, E2 C 03, LiC03, Na2C03, and (NH4)2C03. Test a separate por- tion for Mg by (NH4)2HP04. Precipitate Of MgHP04. Con- vert to Mg(N03)2; test by CO(N03)2; pink mass. See No. 110. Note. —If (NH4)2HP04 is added to the filtrate, the MgHP04 is precipitated and the alkali metals converted into phosphates. The phosphoric acid may be removed by acetate of lead, and the lead removed by (H2S) hydrosulphuric acid. Boil, to get rid of H2S, and filter, if required. 114 LABORATORY GUIDE. 190. Separation of the Alkaline Earths —Group IV. Method II. The group is precipitated as in Method I., by NH4HO, NH4C1, and (NH4)2C03 The BaC03, SrC03, CaC03. Dissolve in HCl; evaporate to dry-ness on water bath; pulverize and treat with absolute alcohol; filter and wash with alcohol. FILTRATE. MgC03, otc. RESIDUE. FILTRATE. Treat as in Method I. BaCl2. Dissolve in H20 and with H2S04; test by flame; green ish color. SrCl2 and CaCl2. Evaporate to dryness, dis-solve in H20, and precipitate with (NH4)2C03; was1 and dissolve in HN03. Evaporate to dryness, powder, and treat with absolute alco-hol; filter and wash with alcohol. Residue. Filtrate. Sr(N03)2. Test by flame; carmine. Ca(N03)2. Test by flame; brick-red. Also by (NH4)2C204. Filtrate. Method II. SrCl2 end CaCl2. Add a few drops of H2S04. Psocipitetes SrS04 and CaS04. Treat with (NH4)2S0^ +a little NH4HO. Residue. Solution. SrS04. Test as bo-fore. CaS04. Test as be-fore. 191. Notes on the separation of Group IV. 1. The NH4C1 is added to form a double salt with Mg that is very soluble and not precipitated with (NH4)2C03 ; NH4HO is added to make alkaline to litmus; it is now gently warmed and (NH4)2C03 added. 2. The absolute alcohol dissolves but a small portion of BaCL. TESTS IN THE WET WAY. 115 3. The NH4IIO is added to render the carbonates more insol- uble. The carbonates of Ba, Sr, and Ca are all slightly soluble in NH4C1. Those of Ba and Ca are more soluble than Sr. 4. The separation by the first method depends upon the fact that the BaCr04 is insoluble in dilute acetic acid, while the chro- mates of Sr and Ca are soluble in that liquid; also upon the fact that SrS04 is almost insoluble in acidulated solutions, while CaS04 is sufficiently soluble to be kept in solution. 5. If the Mg is precipitated by (NH4)2HP04, the NH4HO may be gotten rid of by heat, and the H3P04 as described under Method I. If Na2HP04 is used, you add Na to your solution, which would be an important consideration in making an analy- sis of the residue in water analysis. GROUP V. —ALKALIES. 192. The members of this group (K, Na, Li, and NH4), the chlorides, sulphides, and carbonates, are soluble in water, and are not precipitated by the group reagents HCl, H2S, (NH4)2S, (NH4)2C03. The rare metals of this group are Li, Rb, Cs. The members of this group decompose water (exception NH4). They are all monads, and strongly electro positive, in this order: Cs, Rb, K, Na, and Li; Cs being strongest. They combine directly with CI, Br, I, S, etc. 193. Tests: — 1. The hydroxides of Al, Cr, Zn, Pb, Sn, and Sb dissolve in the fixed alkalies. The oxide of Ag and the hydroxides of Cu, Zn, Ni, and Co dissolve in volatile alkali. 2. The chlorides of the fixed alkali metals color a non- luminous flame, and give well-defined spectra with the spectro- scope. 3. Alkali hydroxides precipitate all non7alkali metals as hydroxides (except Hg, Ag, Sb). NH4HO does not precipitate Ba, Sr, Ca. 116 LABORATORY .GUIDE. 4. The hydroxides and normal carbonates of the alkali metals are not decomposed by heat alone. 5. The oxides may be obtained by burning the metal in oxygen. 6. The hydroxides are prepared by heating carbonates with Ca(OH)2 until the clear solution no longer effervesces with HCl. A current of CI passed into their solutions converts them into hypochlorites or chlorates. 7. The sulphides are formed by passing HaS into their solu- tions to saturation. 8. The chlorides are formed by dissolving the alkalies, or their carbonates, in HCl. When dissolved in HN03, nitrates are formed; when dissolved in H2S04, sulphates are formed. 9. The sparing solubility of lithic phosphate and carbonate in H20 renders it nearly allied to Mg. 194. Potassium (K1, 39). It has a bluish-white color, and a specific gravity of .865. It melts at 62.5° C. The platinic chloride, acid tartrate, silico-fiuoride, phospho- molybdate, tri-nitrophenate, and perchlorate are but slightly solu- ble in water. The above list and tho carbonate and sulphate are insoluble in alcohol. None of the salts are absolutely insoluble in water. 195. Tests: — 1. De Koninck test :* yellow precipitate, 6KN02, Co2(N02)6. The addition of a few drops of acetic acid hastens the reaction. 2. PtCl4 with HCl precipitates yellow crystalline (KCl)2PtCl4; evaporate to dryness on the water bath. The precipitate is not dissolved by alcohol. 3. H2C4H406 or NaHC4H406 precipitates white granular KHC4H406. Alcohol promotes precipitation. * De Koninck test: 6NaN02, Co2(N02)6 (sodio-cobaltic nitrite). Dissolve ten grams of NaN02 and four grams Co(N03)2, in separate portions of R20, and mix; add two C. c. of HC2H302, and make up to one hundred C. c. The presence of Mg, Ca, Ba, Sr, Fe, Zn, Al does not interfere with this reagent. NH4HO, Rb, and Ca form precipitates similar to potassium. This test is more delicate than PtCl4. TESTS IN .THE WET WAY. 117 4. Tri-nitrophenic acid (No. 20) precipitates yellow KC6H2(N02)30; insoluble in alcohol. The dried precipitate explodes when heated. 5. H2SiF6 produces a transparent colorless precipi ate, as follows: 2KN08 + H2SiF6 = K2SiF6 + 2HN03. 6. Flame reaction violet. See No. 110. 196. Sodium (Na1, 23). It is bluish white. Specific gravity, .985. It melts at 95.5° C. The metantimoniate and silico-fluoride are sparingly soluble in water. The acetate, phosphate, sulphate, sulphite, and car- bonate are efflorescent. The nitrate, hydroxide, and chlorate are deliquescent. 197. Tests: — 1. KSb03 (in neutral or alkaline solutions) precipitates white NaSb03. The reagent should be dissolved as wanted; it is not permanent in solution.*. 2. (NaCl)2PtCl4 crystallizes from its concentrated solutions in red prisms. 3. A crystal of red potassium bichromate (K2Cr207), illu- minated by this yellow flame so as to transmit or reflect its light, appears colorless. Paper coated with mercuric iodide, Hgl2 appears white; blue cobalt glass, or a solution of indigo, causes the yellow flame to disappear. 4. H2SiF6 precipitates white Na2SiF6; difficultly soluble in water. 5. Flame reaction yellow. See No. 110. * Metantimoniate of potash (KSb03) is made by fusing antimonic acid with large excess of potassium hydroxide, dissolving, filtering, evaporating, and digesting syrupy solution in a silver dish with large excess of potassium hydroxide, decanting the alka- line liquor and stirring the residue to granulate; then dry. It cannot be used in acid solutions. 118 LABORATORY GUIDE. 198. NH4HO (see No. 30). It is tested by its odor; by litmus paper, blue; the same action on red logwood; blackening mercurous salts; forming white, solid fumes with HCl. 199. Tests: — 1. Nessler's test :* (KI)2HgI2 produces a brown precipitate of NHg2I. This is a very delicate test. 2. HgCl2 forms "white precipitate," NH2HgCl. 3. AgCl is dissolved by NH4HO. (Applicable in the ab- sence of iodides, bromides, thiosulphates, sulphocyanides.) 4. PtCl4 and H2C4H406 form precipitates like those of K in form, color, and solubility. 5. Sonnenschein's reagentf precipitates from neutral or acid solutions NH4H0—from very dilute solutions; from concentrated solutions it precipitates all the fixed alkalies, except Na and Li. 6. It forms explosive compounds with CI = (NC13), and I = (NH2I), as follows : 2NH3 -4- I2 = NH4I + NH2I. 200. Lithium (Li1, 7). The lightest solid element. Specific gravity, .589. Melts at 180° C. It is the least oxidizable of the alkalies. It is found widely distributed in nature—in mineral waters, ashes of plants, in the analysis of minerals (spodumene, petalite, and lepidolite). The silico-fluoride, carbonate, and phos- phate are sparingly soluble in water. Many of its salts (chlorate and chloride) are very deliquescent. * To a solution of HgCl2 add solution of KI till the precipitate is nearly all redis- solved; then add solution of KHO; let stand until the liquid becomes clear; decant. Use the clear solution. Keep from the air when not in use. t Sodium phosphomolybdate for NH4H0 and acid solutions of the alkaloids is made by taking the yellow precipitate formed when mixing acid solutions of ammonium molybdate and sodium phosphate. This precipitate is well washed and heated with podium carbonate until completely dissolved. Evaporate to dryness, and gently ignite till all the NH4H0 is expelled, Na being substituted for NH4HO. If it blackens, it is heated with HN03. It is dissolved with H20 and HN03 to strong acid reaction. Solution 1 to 10 parts of H20. Keep from vapors of NH4H0. TESTS IN THE WET WAY. 119 201. Tests: — 1. Na2HP04 precipitates Li3P04 ; soluble in 2,530 parts of water; more soluble in ammonium salts (while Mg is less solu- ble.) The precipitate is hastened by boiling. 2. Nitrophenic acid (see No. 20) forms a yellow precipitate, quite insoluble in water. 3. Na2C03 precipitates white Li2CQ3; slightly soluble in H20. 4. Flame reaction of LiCl is carmine red. See No. 110. 202. Separation of the Alkalies—Group V. METHOD I. METHOD II. The filtrate from Group IV. may contain K, Na, Li, and NH4HO. Evaporate a por-tion to dryness and heat with KHO or NaHO. NH3 passes off. Test by odor, lit-mus, and HCl. 1. If NH4H0 is present, heat to expel it. 2. Precipitate the lithium as phosphate by (NH4)HP04. 3. Get rid of the H3P04 (No. 189, note). 4. Separate K and Na by PtCl4; the 2KC1, PtCl4 is precipitated; 2NaClPtCl4 in solution. 1. If NH4H0 is present, heat to expel it. 2. Convert K, Na, and Li into platino-chlorides (No. 195). 3. Dry and extract the Na and Li salts with a mixture of alcohol and ether, con-taining a little HCl; wash with a mixture six parts of absolute alcohol and one part of ether. 4. The residue is K2PtCl6; the Li and Na in solution. 5. Evaporate to dryness and ignite to reduce the Pt. 6. Dissolve in HCl and precipitate the Li as phosphate; Na in solution. 203. Notes: — 1. For traces of NH4H0, use Nessler's test (No. 199) with the original solution before any of the groups are precipitated. 2. As some of the salts of K (as KC10, or KN03) are added as an oxidizing agent in some of the groups, it is well to test the original solution for K. 3. Na is everywhere, and it is not generally added to a mixture of the solutions for qualitative separation. 120 LABORATORY GUIDE. 4. The rare elements are two expensive to give qualitative students. Only advanced students should handle them; and they require special directions that would be out of place in a book of this kind. I can recommend "Select Methods," by Wil- liam Crookes, second edition, also Wcehler's Mineral Analysis, as desirable books for this kind of work. 204. Zettnow* has arranged a scheme withou« the use of H2S or (NH4)2S. i The solution (a) may contain salts of: (I.) Pb, Ag, Hg; (H.) Ca, Ba, Sr; (III.) NH4, Na, K; (IV.) As, Sb, Sn, Hg", Cu, Cd, Bi; (V.) Fe, Cr, Al; (VI.) Mn, Mg, Co, Ni; (VH.) Zn. Add HCl to the solution (a); agitate, filter, and wash. Precipitate (&) — PbCl2, AgCl, Hg2Cl2. i Solution (c) — Salts in solution (a), except Ag and Hg. 1. The Pb in precipitate (b) is separated by hot H20 and filtration; then precipitate with H2S04. The Ag is dissolved by NH4HO, and repre- cipitated by HN03, leaving Hg as a black residue. See separation of Group I., No. 140. The solution (c) is treated with dilute H2S04, the precipitate filtered and washed. Precipitate (<£)-CaS04, BaS04, PbS04. Solution (e) — Classes III., IV., V., VI., and VII. of solution (a). 2. Precipitate (d): The CaS04 is in cold water, and precipitated by (NH4)2C204. See, also, Ca under filtrate (k). Dissolve PbS04 by solu- tion of (NH4)2C4H4Os with NH4HO, and the solution acidulated with HC2H302 and precipitated by K2Cr207. The residue contains BaS04 and SrS04; boil with Na2C03, filter, and wash out Na2S04; dissolve the carbonates in HCl, and evaporate to dryness; treat with absolute alcohol, and filter. The residue, BaCl2, test by flame; also precipitate by solu- tion of SrS04. The solution contains SrCl2; test by flame. A small part of solution (e) is tested for the alkalies: NH4HO is tested by Ba(OH)2 and boiling; odor. The Ba is removed by (NH4)2C03 or dilute H2S04; filter. The residue is examined for K and Na. See No. 202. 3. The rest of solution (e) may contain Classes IV., V., VI., VTL As, Sb, Sn, Hg", Cu, Cd, Bi; Fe, Cr, Al, Mn, Mg, Co, Ni; Zn. The major * Eyster has a scheme. See American Chemical Journal, VH., p. 21-26. TESTS IN THE WET WAY. 121 part of solution (e) left with excess of H2S04 from formation of precip- itate (d), is treated with Zn and Pt foil in Marsh's apparatus. The gas is tested for As and Sb, or the gas passed into AgN03. See No. 153. The Zn will reduce metals of Class IV. Heat the generating flask ten or fifteen minutes, and filter. 4. Deposit (/): Sb, Sn, Hg, Cu, Cd, Bi. 5. Filtrate (gr): Fe, Cr, Al; Mn, Mg, Co, Ni; Zn as sulphates. De- posit (/), well washed, is treated in an evaporating dish with strong HN03, and filtered. 6. Solution (h): Nitrates of Hg, Bi, Cu, Cd. 7. Residue (i): Sb205, Sn02. Test half of solution (h) with SnCl2 for Hg. To the other half add HCl and boil; then add excess of NaHO. The precipitated hydroxides of Bi, Cu, Cd are treated on the filter (after washing) with NH4HO and NH4C1. The Bi is left undissolved;* the Cu and Cd pass into solution. The Cu is recognized by its color and by precipitation with K4FeC6N6, after acidulation. The Cd is distinguished from Cu by precipitation by NaHO in ammonical solution.f Residue (i) is washed, and boiled with HCl, which dissolves the anti- monic acid and leaves the metastannic acid undissolved. The solution is tested with Pt and Zn for Sb. The residue is dissolved, with action of nascent hydrogen, made by treating Zn with HCl, and tested with HgCl2 for Sn. Treat filtrate (gr) with HN03 for oxidation. Test a small portion with KCNS for iron (blood red); neutralize with NH4HO. Treat the remaining portion with BaC03; filter. In the presence of H3P04, add Fe2Cl6 and digest, before neutralizing and adding BaC03. 8. Precipitate (J): Cr2(OH)|, Al2(OH)6, with Fe2(OH)6 and an excess of BaCOs. 9. Filtrate (k): Mn, Mg, Co, Ni; Zn as sulphates. Precipitate (j) is treated with dilute H2S04; precipitates BaS04; boil to expel C02 from the filtrate; add NaHO and boil; oxidize Cr to chromate; test with HC.H^ and Pb(C2H302)2, yellow chromate of lead. Treat another part with NH4C1 in excess to precipitate Al. If NH4C1 * The residue is dissolved in HCl, and the solution treated with much H20, white BiOCl. tin case much Cu is present, Cd is tested as follows: The solution is strongly acidulated with HCl, Na2S203 is added, and then boiled; while hot, it is treated with small additions of Na2S203, to completion of black precipitate; the liquid is milky with S. After being filtered, test for Cd by NaHO. 122 LABORATORY GUIDE. is not added in sufficient quantity, Mn, etc., may be precipitated. (See No. 177, notes on separation of Iron Group.) From filtrate (k) get rid of Ba by H2S04; filter, and add (NH4)2C03 to precipitate MnC03; filter; test for Mn on Pt foil with KC103 + Na2C03; green. Test for the Ca, which has not been precipitated (d) by NH4HO, then add NH4C1 and (NH4)2C204. To the filtrate add Na2HP04 to precipitate Mg3(P04)2. Filter; evaporate to dryness; it may contain Co and Ni. Dissolve in HCl, and separate as in the Iron Group. Test for Zn by taking a portion of solution (e) and treat it with H2S04 and HCl; filter; heat gently with excess of NaHO and filter. The filtrate contains the Zn as sodium zincate; nearly neutralize with (NH4)2C03; treat with NH4C1 as long as NH3 escapes; filter. The filtrate is examined for Zn by K4FeC6N6. 205. Separatio n by Electrolysis. O W o GO a B o pa o + a a o M + Om ^O a 5- CO a CO 2 "3 oj p OJ o < *3 M fe < + o fca ao 'S M O 1 M 2 p 'En 03 oS E-|M- 2 'S cS _C o 03 ► H M o o W > a M o CO 144 LABORATORY GUIDE. 258. The common organic acids consist of the following groups: (The organic acids can not be detected with the same certainty as the inorganic acids.) (1.) Acids precipitated by CaCl2 in the cold or on boiling: Tartaric acid (H2C4H406 or H^), citric (H3C6H507 or HgC"), and oxalic (H2C204 or H20). See No. 221 for oxalic acid. Malic acid (H2C4H405) is not precipitated by CaCl2. 259. Tartaric acid. See No. 24. It occurs in the form of colorless, transparent crystals. It dissolves in hot and cold water; also in alcohol. The solution is acid to litmus paper, and if kept for a short time, becomes mouldy, and decomposes. There are four physical isomers of tartaric acid: Dextro-levulo- racemic, and inactive. It can be produced artificially by acting upon milk sugar with HN03; by treating dibromosuccinic (C4H4Br204) with Ag20 in the presence of H20: C4H4Br204 + Ag20 + H20 — C4H606 + 2AgBr. HI or iodide of phosphorus converts it into malic or succinic acid. In the presence of oxidizing agents it is converted (usually) into carbonic, formic, and oxalic acids. When fused with KHO, it breaks up into an acetate and an oxalate: C4H606 -f- 3KHO = KC2H302 + K2C204 -f- 3H20. 260. Tests:— 1. A cold solution of lime (leaving the reaction alkaline) pre- cipitates white CaC4H406, soluble in cold solution of KHO; on boiling, it is reprecipitated, dissolves on cooling (distinction from citrate), and is dissolved by acetic acid, while oxalic acid, pre- cipitate of lime, is not. Lime precipitates citric acid only when heated. 2. When heated with (one gram with ten C. c. concentrated) H3S04 at 100° C. for forty minutes, citric acid gives yellow color, if one per cent, of tartaric acid is present, a distinct brown shade; more marked with larger proportions. SEPARATION OF THE ACIDS. 145 3. A drop of ferrous sulphate solution added to a solution of tartaric acid, or a soluble tartrate, then a few drops of hydro- gen peroxide, and the mixture finally treated with excess of NaHO, a fine violet coloration is produced; it is sometimes almost black. The color is discharged by S02. Acidulated permanga- nate or sodium hypochlorite may be substituted for the hydrogen peroxide in the foregoing test, if care be taken to avoid excess, but the results are not so good as with the peroxide. 4. AgN03 precipitates white Ag2C4H4Q6, soluble in NH4HO. On boiling, the precipitate turns black; by reduction of silver, gives mirror coating on the glass. The above must be a normal tartrate and not free tartaric acid. 261. Citric acid. See No. 6. It forms large, transparent crystals. It is very soluble in hot and cold water, and also in alcohol. The solution is acid to litmus paper, and, like tartaric acid, decomposes on keeping. Heated with KHO, it yields an acetate and oxalate, as follows : C6H807 -f- 4KHO = 2KC2H302 -f- K2Cj04 -f 3H20. Citric acid chars when heated. The charring is attended with pungent fumes, which cannot be mistaken for those of tar- taric acid. When citric acid is heated with dilute H2S04 -J- Mn02, or an acidulated solution of K2Mn208, it is oxidized with formation of carbon dioxide and acetone. Citric acid has been obtained synthetically by many chemists. 262. Tests: — 1. (Citric, succinic, and malic acids.) Precipitate with CaCl2, decompose with dilute H2S04, and boil the filtrate with K2Cr207 : yellow color (succinic acid) ; green, without odor (citric acid); green, with fruity odor, malic acid. 2. Precipitate tartaric and citric acids by CaCl, with a hot and neutral solution of CuCl2, when soluble cupric citrate and an insoluble tartrate remains. Separation. 3. Heat five grams of citric acid with thirty C. C. of NH4HO for six hours in a sealed tube at a temperature of 146 LABORATORY GUIDE. 120° C.: yellow color and small crystals are formed. When poured into an evaporating dish and cooled, it becomes blue; in a few days, green. Malic, oxalic, and tartaric do not interfere with this reaction. Itaconic acid gives the same reaction. One hundredth of a gram of citric acid can be detected. 4. Two grams of the sample of acid are dissolved in twenty C.c. of proof spirit (sp. gr. .920), the solution filtered from any residue, and made up to 45 C.c. with proof spirit; five C.c. of a cold saturated solution of KC2H302 in proof spirit are added, and the liquid stirred for a few minutes. The tartaric acid is pre- cipitated as KHC4H406. The filtrate contains citric acid; boil off the alcohol, precipitate with lead acetate, remove the lead by H2S, and determine the free acid. 5. CaCl2, AgN03, Pb(C2H302)2. Precipitate citric acid with corresponding citric salts. See tartaric acid. 263. Oxalic acid has been described in No. 221. 264. Malic acid (H2C4H405). It is found in the acids of apples, pears, and various other fruits. Nearly all the malates are soluble in water. It crystallizes with great difficulty. It is acid to litmus paper, and becomes mouldy on keeping. It can be produced artificially by the action of Ag20 on monobromosuc- cinic acid 2C4H5Br04 + Ag2OH20 = 2C4H605 + 2AgBr; also, by nitrous acid on asparagin, and on aspartic acid: (a) C4H8N203 + 2HN02 = C4H605 + 2H20 + N4. (6) C4H7N04 + HN02 = C4H605 + H20 + N2. Fused with KHO it splits up, like tartaric and citric acids, into oxalic and acetic acids. Concentrated H2S04 decomposes the acid and the malates in the solid state with evolution of CO. The mixture blackens only after long boiling. 265. Tests: — 1. Acetate of lead precipitates white'crystalline PbC4H405 ; it comes down better when neutralized by NH4HO. When SEPARATION OF THE ACIDS. 147 boiled, it melts to a transparent, waxy semi-liquid. It is spar- ingly soluble in water. If this precipitate is treated with NH4HO, dried on water bath, pulverized, and moistened with alcoholic ammonia, only malate of ammonium dissolves out when treated with absolute alcohol (distinction from tartaric, citric, and oxalic acids). These acids are insoluble in the presence of NH4H0 in slight excess when mixed with ten volumes of alcohol, while malate of ammonium goes into solution. 2. AgN03 precipitates white Ag2C4H405; on boiling, turns gray. 3. When only one of the four acids is present in a solution, lime water precipitates tartaric and oxalic acids in the cold; citric acid on boiling. Malic acid is not precipitated. Calcium tartrate is soluble in NH4C1, whilst the oxalate is not. Note—CaCl2 precipitates, in the cold, tartaric acid from neutral solutions; (2) by boiling CaCl2, rendered alkaline by Ca(OH)2, citric acid; (3) not precipitated from hot or cold solutions by CaCl2, but is precipitated on adding alcohol to the solution malic acid. Oxalic, boracic, phosphoric, hydrofluoric, carbonic, arsenious, and arsenic acids are precipitated from neutral solu- tions by CaCl2; but these will have been removed before the organic acids are reached. 266. (2.) Acids precipitated by ferric chloride (Fe2Cl6), and not by CaCl2 : Benzoic (C7H602), succinic (C4H604) acids, These acids sublime without alteration. They are but little acted upon by HN03. 267. Succinic acid. See No. 34. It is bibasic. It occurs ready formed in amber and in certain lignites. It emits a suffo- cating vapor below the melting point (180° C). Fused with KHO, it yields a carbonate and an oxalate, and gaseous hydro- carbons. It can be produced from malic and tartaric acids by acting on them with HI. It is not attacked by concentrated H3S04. Heated in the air, succinic acid burns with a blue flame, free from soot. Most of the succinates are soluble in H20. 148 LABORATORY GUIDE. 268. Tests:— 1. CaCl2 gives no precipitate, but on adding alcohol a gelatinous precipitate of CaC4H4Q4 ; soluble in NH4C1. 2. Fe2Cl6 (in neutral solutions of succinates of the alkali metals) precipitates a brownish, pale-red, bulky FeC4H4Q4, solu- ble in mineral acids. NH4HO decomposes it. 3. Pb(C2H302)2 precipitates white amorphous PbC4H404, soluble in excess of either; in a short time it separates out in a crystalline form. 4. Alcohol, ammonium, and barium chloride produce a white precipitate, BaC4H4Q4. 269. Benzoic acid is monobasic. It is contained in gum benzoin. It volatilizes completely when heated, with partial decomposition, and forms needles; the fumes provoke coughing. When kindled, the crystals burn with a smoky flame. It can be produced artificially by oxidizing bitter almond oil, or by boiling hippuric acid with HCl, or from the washings of wool (suint). Benzoic acid is sparingly soluble in cold water, freely soluble in hot water and in alcohol. 270. Tests: — 1. Fe2Cl6 precipitates bulky, flesh-colored Fe(C7H502)3. NH4H0 decomposes it; it dissolves in a little HCl. 2. Pb(C2H303)2 precipitates (from alkali benzoate, not from free acid) floeculent lead benzoate, soluble in excess, insoluble in sodium benzoate. 3. A mixture of alcohol, ammonium, and barium chloride, or calcium chloride, produces no precipitate in solutions of ben- zoic acid or of alkali benzoates. Note—This group of acids can be separated by their solu- bility. Succinic is readily soluble in water; benzoic, sparingly soluble. They can be detected by precipitating with Fe2Cl6. Warm the washed precipitate with NH4HO, filter, concentrate, SEPARATION OF THE ACIDS. 149 and divide into two parts. Add to one part HCl; to another, barium chloride, alcohol, and ammonium. These acids do not prevent the precipitation of the hydrox- ides of the heavy metals by alkalies. Benzoic acid from Siam benzoes decolorizes an alkaline solution of K2Mn208. Acids from other sources alter the color to nearly green. The student can make benzoic acid by heating putrid cow's urine with lime, filtering, concentrating the filtrate, and precipi- tating the benzoic acid with an excess of HCl. The hippuric acid of the urine breaks up into benzoic acid and glycocine: C9H9N08 + H20 — C7H602 + C2H5N02. 271. (3.) Acids precipitated by AgN03 in strong neutral solutions: Ferrocyanic (H4FeC6N6), ferricyanic (H3FeC6N6) sulphocyanic (HCNS), acetic (HC2H302), and formic (CH202) acids. 272. Ferrocyanic acid. See No. 8. This acid belongs to both groups, being precipitated by Fe2Cl6. 273. Tests: — 1. AgN03 precipitates white Ag4FeC6N6, insoluble in dilute HN03, soluble in KCN. This has been sufficiently described under No. 8. K^FeC^N^ gives a precipitate with Sb, Al, Bi, Cd, Ca, Co Cu, Fe (ous white then blue), ic deep blue; Pb Mg, Mn, Hg (ous and ic), Mo, Ni, Ag, Sn, U, and Zn. The ferro is separated from ferri cyanide by the insolubility of alkali salts in alcohol (ferro precipitated, ferri not precipitated); also by reactions with ic and ous Fe and with Cu. Ferro is the ous cyanide; ferri is ic cyanide< Ferrocyanide gives colored reactions with many of the alkaloids. The above reactions are given in Reactions for Bases and Acids, pages 158, 162, and 164. 274. Ferricyanic acid. See No. 7. 275. Tests: — 1. AgNOs precipitates orange Ag3FeC6N6, insoluble in dilute HN03, soluble in KCN. 150 LABORATORY GUIDE. 2. FeS04, blue precipitate (Trumbull's blue), Fe3(FeC6N6)2; insoluble in dilute acids. K3FeC6N6 gives precipitates with Bi, Cd, Co, Cu, Fe (ous), Mn, Hg (ous), Ni, Ag, Sn (ous), Zn. See Reactions for Bases and Acids, page 162. 276. Slllphocyanic acid. See No. 21. Sulphocyanatcc of the metals of the alkalies, alkaline earths, Fe (ous and ic), Mn, Zn, Co, and Cu, are soluble in water. 277. Tests:— 1. The ferric reaction is the most distinctive (blood red). in 2. It gives reactions with Co, blue; Cu, black; Fe, blood i red; Pb, yellowish; Hg, white ("Pharaoh's serpents") ; Pt, deep red; Ag, white. It is written HCNS or KCyS. The absolute acid decomposes quite rapidly, with evolution of C02, CS2, H2S, HCN, H3N, and other products. 278. Acetic acid. See No. 1. It is monobasic. It exists in the juices of many plants, especially of trees. In the liquid state it has a density of 1.063, and boils at 120° C. Its vapor is inflammable. On account of its solidifying below 16°, it has received the name of glacial acetic acid, in contra-distinction to a mixture of water and acid, which does not crystallize; this mix- ture is commonly called acetic acid. It does not redden litmus until mixed with water. The most powerful oxidizing agents attack it with difficulty. Most of the acetates are soluble in water. Metallic acetates give the following reactions: 1. Subjected to dry distillation, acetone is given off; charac- teristic odor. 2. Heated with As203, odor of cacodylic oxide; very poisonous 3. Heated with H2S04, acetic acid is evolved. 4. Neutral solution and ferric chloride (avoiding excess) give a deep-red liquid containing ferric acetate. When this is boiled the liquid becomes colorless and reddish-brown ferric oxyacetate. SEPARATION OF THE ACIDS. 151 HCl changes the red ferric acetate to yellow (difference from sulphocyanate). The metallic acetates are soluble in water; Ag and Hg (ous) but sparingly soluble. 279. Formic acid (HCH02). It is monobasic. All its salts are soluble in water. It occurs in ants, in caterpillars, and in several secretions of the human body. It is present in the juice of the stinging nettle and other vegetables; in some cases in mineral waters. It is commonly made by distilling dry oxalic acid with glycerin. Oxydizing agents like CI, Br, Cr03, K2Mn208, convert it into carbonic acid. It has a penetrating odor, and when con- centrated produces intense irritation on the skin. 280. Tests: — 1. Fe2Cl6 gives the same reaction as acetate (blood red). 2. AgN03 precipitates white AgCH02 ; darkens on standing. 3. HgCl2 is reduced to Hg2Cl2 or Hg. Acetates do not give this reaction. It is a good reducing agent. 4. When heated with H2S04 -f- C2H60, ethyl formate (C2H5CH02); fragrant odor of peach kernels. 5. At a gentle heat, strong H2S04 evolves C02 from a formate or formic acid. Strong alkalies produce an oxalate. Note — To separate acetic from formic acid: Saturate the free acids with slight excess of calcined magnesia or carbonate of lead, filtering, evaporating the filtrate to a small bulk, and adding a large proportion of alcohol. The formates of Mg or Pb are precipitated, while the acetate remains in solution. 281. Acetic, formic, lactic, propionic, and butyric acids may be distilled with water (lactic with difficulty). Acetic and formic acids have been described. 282. Lactic acid (H2C3H403). Four isomeric lactic acids are now believed to exist. Ordinary lactic acid is formed by the fermentation of milk, cane, and grape sugars. It is also found in vegetable matters that have turned sour. Sarcolactic or 152 LABORATORY GUIDE. paralactic acid exists in muscular flesh. With bases, it forma neutral salts; they are all soluble in water and in alcohol, but are insoluble in ether. Concentrated lactic acid is a colorless, odorless, syrupy liquid of a very acid taste. Specific gravity, 1.248. Acid containing 75 % has a sp. gr. 1.212. At 130° C. it begins to boil. Lactic acid is miscible in all proportions with water, alcohol, glycerin, and ether, but slightly soluble in chloroform, and insoluble in carbon disulphide and petroleum spirit. It does not reduce Fehling's solution; but it decolorizes K2Mn208, both in acid and alkaline solutions. Hot HN03 converts lactic acid into oxalic acid. 283. Tests: — 1. Calcium lactate under the microscope shows crystalline needles in tufts with short stalks, like double paint brushes. Zinc lactate shows spherical groups of needles. 2. Lactic acid may be separated from those organic acids which form insoluble lead salts, as lead lactate is soluble and remains in solution; or by barium, as barium lactate is soluble in alcohol. 284. Propionic acid (HC3H502). It is obtained by boil- ing ethyl cyanide with sulphuric acid: C2H5CN + 2H20 + H2S04 = NH4HS04 -f C3H602. It separates from its solution in water as an oily layer on the addition of CaCl2. It resembles acetic acid. It has the disagree- able odor of rancid butter and acetic acid. It is contained in crude oil of amber, in sour cocoanut milk, and in certain wines when the fermentation has been pushed too far. It boils at 140° C, and has a density of .996 at 19°. The propionates are all soluble in water. The free acids are evaporated to dryness with PbO, the resi- due treated with cold water, and the liquid filtered. Basic propi- onate of lead dissolves, while most of the acetate, formate, and acrylate remains insoluble. If the solution is boiled and stirred quickly, the propionate separates out as a crystalline precipitate. SEPARATION OF THE ACIDS. 153 285. Butyric acid (HC4H702). There are two isomers, normal butyric and isobutyric acids. The normal butyric acid is a colorless liquid, having the odor of rancid butter and acetic acid. It is soluble in water, alcohol, and ether in all proportions; it is insoluble in concentrated solution of CaCl2 or NaCl. It may be separated from aqueous solution by saturating the liquid with CaCl2, and then agitating with ether. The etherial layer is allowed to evaporate spontaneously. Also by fractional distil- lation. All the metallic butyrates are soluble in water. The butyrate of copper forms bluish-green monoclinic crystals, while valerianic acid separates in oily drops when treated with copper acetate (separative). The most delicate and characteristic test is the formation of ethyl butyrate on heating with alcohol and sulphuric acid. The ether has a fragrant odor of pine-apple. CHAPTER V. COMPARISON OF THE BASES AND ACIDS. 156 LABORATORY GUIDE. Reaction of the Bases—Group I. Metals precipitated from their solutions by H2S. Reagents. Silver. Mercurous. Mercuric. Hydrogen Sulphide, (H2S) Group Reagent. Black, Ag2 S. Insol. in alkaline sul-phides. Sol. in HNO3. Ag2S is sol-uble in 35,000 parts of H2O. Black, HgS. Hg. Insol. in (NH4)2S, andinHN03. Sol. in potassium sul-phide. First white, then yellow and red brown to black, HgCl2 + x HgS. Insol. 111HNO3. Soluble in K2S. Sol. in aqua regia and alkalies. Sol. in 20,000 parts H2O. Hydrochloric acid, (HCl.) White, AgCl. Light changes it to violet. Insol. in acids. Sol. in NH4HO, in KCN, and in Na2S203. Sol. in 1,000,000 parts H2O. White, Hg2Ck. Sol-uble in HN03,and in aqua regia as HgCl2— blackened by NH4HO. Soluble in 12,000 parts boiling H2O. Sol.inNH4Cl. Sodium hydroxide, (Na HO.) Light brown, Ag20. Sol. in HNO3, and NH4HO. Sol. in 3,000 parts H2O. Black, Hg20. Sol. in HNO3. Insol. in NH4HO. Insol. in alcohol. Yellow, HgO. Sol. in 200,000 parts of H2O—Insol. in alco-hol, and NH4HO. Ammonium hy-droxide, (NH4HO) Light bro wn, Ag20. Sol. in excess—Sol. in HN03,HC2H302, and NH4HO. Black, mercuroso-ammonium salts.Sol. in HNO3. Insol. in alkalies. [Mercury, silver and gold do not form hydrox-ides.] White, mercuriam-monium salts. Sol. in HCl, sparingly sol. in NH4HO. Sodium Carbonate, (Na2 CO3.) Grayish white, Ag2C03. Sol. in NH4HO. Yellow precipitate basic salt.soon be-comes black. Red brown, basic salt -f x HgO. By heating becomes yellow oxide, HgO- Sulphuric Acid, (Hz SO4) White, Ag2S04. Sparingly sol. in ex-cess, and in H2O. White, Hg2S04. Sol. 500 parts H2O. REACTIONS. 157 Group I—Continued. Lead. Copper. Bismuth. Cadmium. Black, PbS. Insol. in (NH4)zS. Sol. in HNO3. Brown black, CuS. Sol. in 950,000 parts H2O. Sol. in HNO3, Sparingly sol. in (NH4)2S-Sol. in KCN. Brown black, Bi2S3. Sol. in HNO3— Insol. in KCN. Yellow, CdS. Sol. in HCl. Insol. in KCN. White, PbCl2. Sol. in 135 parts H2O— CuCl2, freely soluble. CU2UI2. Insoluble in H2O. BiOCl. Insoluble in H2O. 30 parts hot H2O. Insol. in alcohol, and NH4HO. White, Pb (OH)2. Sol. in excess. Sol. in HNO3. Insol. in NH4HO. Blue, Cu(OH)2 heat-ed becomes black, CuO. Soluble in acids. White, BiO(OH). Insol. in excess. Sol. in HUlandHN03. White, Cd(OH)2. Insol. in excess. Soluble in acids. White, Pb(OH)2. Insol in excess. Greenish blue pre-cipitate, basic copper ammonium salts. Sol. in excess with blue color. Sol. in KCy. White. BiO(OH). Insol. in excess. Sol. in HClandHN03. White, Cd(OH)2. Sol. in excess, and in NH4C1. Sol. in KCy and precipitated from this solution by (HN4)2S. White precipitate. Basic lead carbonate, Blue precipitate, basic copper car-bonate, when heated becomes black brown. CuO. White, (Bi0)2 CO3. Insol. in excess. Sol. in HCl, and inHN03. White, Cd ( O3. Insol. in excess-precipitate not com-plete in presence of NH4C1. White, Pb SO4. Sol. in 13,000 parts Sol. in 3% parts H2O. H2O. 158 LABORATORY GUIDE. Group I—Continued. Reagents. Silver. Mercurous. Mercuric. Potassium chromate, K2Cr04. Dark red, Ag2 CrC>4. Sol. in HNO3. and in NH4HO. Red basic chromate. Sol. in HNO3. Yellowish red, Hg0rO4. Sol. in HNO3. Potassium ferrocy- White. Ag4FeCy6. Insol. in NH4HO. White, Hg2FeCy6. anide, K4FeCy6. Stannous, chloride, SnCl2. White, AgCl. Dark gray, Hg White, Hg2Cl2, with excess metallic Hg. Potassium Iodide, (KI). Yellowish Agl. Greenish Hg2l2. Sol. in excess. Red, Hgl2. Sol. in excess of either. Group II—Metals precipitated in acid, or neutral solutions by H2S, but not in alkaline. Reagents. Arsenious. Arsenic. Antimonious. Antimonic. Hydrogen Sulphide, (H2S.) (Group reagent.) Yellow, AS2S3. Sol. in alkalies and alkaline sul-phides. Insol. in HCl. Yellow, AS2S3 -r S2, appears slowly, hastened by boiling. Orange red, Sb2S3. Sol. in HCl, in alkalies and in alkaline sulphides. Orange, Sb2Ss. Sol. in HCl, in alkalies and al-kaline sulphides. Ammonium Sulphide, (NH4)2S. AS2S3, only in acid solutions. Sol. in excess. AS2S5, only in acid solutions. Sol, in excess. Sb2S3. Sol. in ex-cess. Sb2Ss. Sol. in excess. REACTIONS. Group I—Continued. 159 Lead. Copper. Bismuth. Cadmium. Yellow PbCr04. Sol. in fixed alkalies. Sparingly sol. in Red brown, OuCr04. Sol. in NH4HO with green color. Yellow, Bi2(Cr04)3. HNO3. Insol. in NH4HO. White, Pb2FeCy6. Red brown, Cu2FeCy6. Slightly sol. in NH4HO. White precipitate. Bismuth ferrocyan-ide. Sol. in HCl. Yellowish white, Cd2FeCy6. Sol. in HCl. White, PbCl2, only White, CU2CI2, only in concentrated so-lutions. Soluble in HCl. In the presence of KHO or NaHo, black Bi02. in concentrated so-lutions. Yellow P0I2. Soluble in excess upon heating. White, CU2I2 the liquid contains free Iodine. Brown, BH3. White Cdl2. Only in very con-centrated solutions. Group II.— Continued. Stannous. Stannic. Platinum. Gold. Brown, SnS. Sol. in HCl, in alkalies, moderately sol. in yellow ammonium sulphide. Yellow, SnS2. Sol. in HCl, in alkalies, in alkaline sul-phides, in alkaline carbonates. Dark brown, PtS2. Insol. in HCl. Mod-erately sol. m alka-line sulphides. Sol. in aqua regia. Dark, AU2S3. Insol. in HCl. Sol. in alka-line sulphides, in aqua regia. SnS. Sol. in yellow ammonium sul-phide. SnS2. Sol. in excess. PtS2. Sol. in excess. AU2S3. Sol. in excess 160 LABORATORY GUIDE. Group II—Continued. Reagents. Arsenious. Arsenic. Antimonious. Antimonic. Sodium hy-droxide, NaHO. White, Sb203. Sol. in excess. Sol. in HCl and H2C4H4O6. Easily reduced by KCN. White, NaSb03. Sol. in excess. Potassium Sb203 anhydride. hydroxide, KHO. Ammonium hydroxide, NH4HO. Sb203. Insol. in excess. NB4Sb03, near-ly insol. in ex-cess. Silver nitrate, AgN03. Yellow Ag3As03. Sol. in HNO3, and in NH4HO. Reddish brown, Ag3As04. Sol.in HNO3, and in NH4HO White precipi-tate, AgCl and £b203. White, AgSb03. Sol. in NH4HO. Copper sul-phate, CUSO4. Yellowish green, Cu3(As03)2. Sol in HNO3, and in NH4HO. or NaHO. Greenish blue, Cu3(As04)2. Sol. in HNO3, NH4HO. White precipi-tate. Basic anti-monious chlo-ride. Light brown precipitate. Cop-per antimoniate, Mercuiic chloride, HgCl2. White, Hg3(As03)2. Sol in acids. --- Basic antimoni-ous chloride. Arsenic. Antimony. Metallic zinc, Zn. Generate H3AS—the spots on por-celain are steel gray to black. They dissolve in NaClO. Warmed with (NH4)2S, forms yellow spots. Soluble in (NH4)2C03, insoluble in HCl. With vapor of iodine, yel-low arsenious iodide. Readily volatile when heated. Generate H3Sb—the spots on por-celain brown to black. They do not dissolve in NaClO, warmed with (NH4)2S forms orange yellow spots, insoluble in (NH4)2( O3. Soluble in HCl. With vapor of iodine, carmine red antimonious iodide. Not readily volatile when heated. REACTIONS. 161 Group II—Continued. Stannous. Stannic. Platinum. Gold. White, Sn(OH)2. Sol. in excess, White, Sn(OH)4. Sol. in excess. in HCl. Reduced to metal by KCN— Sn(OH)2. Sn(OH)4. Soluble in excess. Yellow, K2PtC16. Sol. in 12,083 parts absolute alcohol. Soluble in excess. Sn(0H)2. Insol. in excess. Sn(OH)4. Slightly sol. in excess. Yellow, (NH4)2PtC16. Sol. in 26,535 parts absolute alcohol— sparingly sol. in cold H2O. Yellow, (NH3)2AU2 O3. In-sol. in excess. [Fulminating gold.] Silver chloride and metallic silver. AgCl. Light brown, AgCl+Pt02. Light brown, AgCl-f-Au203. With SnCl2, white CU2CI2 Sol in acids. SnCl2, first white Hg2Cl2—with excess black Hg. Sn. Sn and in neutral. Sol: Sn(OH)4. Black, Pt. Brown, Au. 162 LABORATORY GUIDE. Group III—Metals precipitated by H2S in alkaline solutions. Reagents. Zinc. Nickel. Ammonium sulphide, (NH4)2S. (Group reagent). White, ZnS. Insoluble in H, C2H3O2, and in KHO. Black, NiS. Slightly solu-ble in (NHO2S. Nearly insoluble in dilute HCl. Soluble in aqua regia. Hydrogen sulphide, H2S. White, ZnS. In neutral or acetic acid solutions. Black, NiS in neutral solu-tions. Sodium hydroxide NaHO. White, Zn(OH)2. Soluble in encess, reappears on heating. Apple green, Ni(OH)2. In-soluble in excess. Soluble in NH4HO, and (NH4)2C03 with a blue green color. Ammonium hydroxide, NH4HO. White, Zn(OH)2. Soluble in excess. In presence of NH4HO salts no precipitate. Green, Ni(OH)2. Soluble in excess with blue color. In the presence of NH4HO salts no preciptiate. Sodium carbonate, Na2C03. White precipitate, basic salt, Soluble in NaHO and in NH4NO. Apple green, precipitate of basic salt. Sodium phosphate. Na2HP04. White, Zn3(P04)2. Soluble in alkalies. Soluble in KHO and NH4HO, also in strong acids. Light green, Nis(P04)2. Soluble in NH4HO. Barium carbonate, BaC03. In the cold, no precipitate if sulphates are absent. In the cold no precipitate if sulphates are absent. Potassium ferrocyanide, K4FeCy6. White, Zn2FeCy6. Soluble in HCl. Greenish white, Ni2FeCy6. Insoluble in HCl. Potassium ferricyanide, K3FeCy6. Brownish yellow, Zn3(FeCy)2. Soluble in HCl and NH4HO. Yellowish green, Ni3(FeCy6)2. Insoluble in HCl. REACTIONS. 163 Group III—Continued. Cobalt. Iron, (ous) Manganese. Black, CoS. Insoluble in excess. Insoluble in HC2H3O2. Nearly insol. in HCl. Sol. in aqua regia. Black, FeS. Sol. in HCl and HC2H3O2. In the air oxidizes. Flesh colored, MnS. Soluble m HCl and HC2H3O2. In the air, oxidizes. Black, CoS in neutral solutions. Blue, hydroxide or basic salts. Insoluble In excess. Soluble in NH4HO and in (NH4)2C03 with violet color. White, Fe(OH)2, soon oxi-dizes to green and brown red. Insoluble in excess. White, Mn(OH)2, soon oxidizes to brown, Mn203. Insoluble in excess Blue, hydroxide or basic salts. Soluble in excess with brownish red color. White, Fe(0H)2 becomes green and brown. Incom-plete precipitation. White, Mn(OH)2. In the presence of NH4CI not pre-cipitated. On standing be-comes brown. Mn203 and precipitates. Peach red, basic salts. On heating becomes violet and blue. White, basic salts, becomes brown in the air. Soluble in NH4HO salts. White, MnC03. Somewhat soluble in NH4HO salts. Light red, Co3(P04)2. Soluble in NH4HO. White, Fe3(P04)2. Soluble in NH4HO. In the air becomes blue or green. White, Mn3(P04)2. Soluble in NH4HO salts. In the cold, no precipitate, if sulphates are absent. In the cold no precipitate. See (ic) iron. In the cold, no precipitate, if sulphates are absent. Green, Co2FeCy6 becomes dark. Insoluble in HCl. White, Fe2FeCy6 -f- y K4FeCy6 becomes blue. Insoluble in HCl. NaHO separates Fe(OH)2. Whitish red, Mn2FeCy6. Soluble in HCl. Dark brown, Co3(FeCy6)2. Insoluble In HCl. Dark blue, (Fe3FeCy6)2. Insoluble in HCl, NaHO decomposes it. Brown, Mn3(FeCy6)2. Soluble in HCl. 164 LABORATORY GUIDE. Group III—(Section containing sesquioxides.)—Continued. Reagents. Aluminum. Iron, (ic) Chromium. Uranium. Ammonium sulphide, (NH4)2S. (Group rea-gent.) White, Al2(OH)6. Black, FeS-f S. Soluble in acids forming a ferrous salt. Greenish gray, Cr2(OH)6. Brownish black, UO2S. Moder-ately soluble in (NH4)2S. Insol. in presence of (NH4)2C03. Barium carbonate, BaC03. White, Al2(OH)6. Light brown, basic salts. Greenish basic salt. Yellow, U02(0H)2. Sodium phosphate, Na2HP04. White, AIPO4. Sol. in alkalies an d reprecipitat-ed by NH4C1. White, FeP04. Sol. in excess. Insoluble in HC2H3O2. Green, CrP04- Yellowish white, UO2HPO4. Sol. in excess, also in NH4HO. In Fe(C2H302,)2 but not in HC2H3O2. Prussian blue, Fe4(FeCy6)3. Insol. in HCl. NaHO precipi-tates Fe2(OH)6. Red brown, K4FeCy6-f-2U02FeCy6. ferrocyanide, K4FeCy6. Potassium Blood red, Fe(CNS)3. Solution. Red solution. sulphocyan-ate, KCNS. Ammonium hydroxide, NH4HO. White, Al2(OH)6. Slightly soluble in excess. Brown red, Fe2(OH)6. Greenish blue, Cr2(OH)6. Slightly soluble in excess with violet color, pre-cipitated on boiling. Yellow, (NH4)2TJ207. REACTIONS. 165 Group III—Continued. Reagents. Aluminium. Iron, (ic) Chromium. Uranium. Ammonium. carbonate, (NH4)2C03. White, Al2(OH)6. Brown red,basic carbonate. Grayish green, Ci'2(OH)6. Sol. in excess. Yellow, 2(NH4)2C03-r-(UO)2C03. Sol. in excess. Precip-itated by fixed alkalies Sodium hydroxide, (NaHO). White, Al2(OH)6. Sol. in excess. On heating with NH4CI reprecip-itated. Brownish red, Fe2(OH)6. Insol. in excess. Bluish green, Cr2(OH)6. Sol. in excess— with green color, on heating reprecipitates. Yellow, Na2U207. Sol. in (NH4)2C03. Group IV—Metals precipitated by (NH4)2CQ3 but not by H2S. Reagents. Magnesium. Barinm. Strontium. Calcium. Sodium phosphate, (Na2HP04). White, MgHP04, only in concen-trated solution. In presence of NH4HO and in dilute solution Mg(NH4)P04. White, BaHP04. Sol. in acids— reprecipitated by NH4HO. White, SrHP04. Sol. in acids, reprecipitated byNH4HO. White, CaHP04. Sol. in acids, reprecipitated by NH4HO. Flame. Yellowish green. Carmine. Yellowish red. 166 LABORATORY GUIDE. Group IV—Continued. Reagents. Magnesium. Barium. Strontium. Calcium. Ammonium carbonate, (NH4)2C03. (Group reagent.) White, MgC034-XMg (OH) 2. Sol. in 10,000 parts H2O. Sol. in ammonium salts White, BaC03-Sol. in 14,137 parts H2O. Sol. in HNO3 and HCl. White, SrC03. Sol. in 18,015 parts of H2O. Sol. in 56,545 parts of H2O, containing NH4HO. White, CaC03. Sol. in 10.601 parts cold H2O. Sol.in HNO3, and HCl. H2O containing NH4HO. requires 65,246 parts to dissolve it. Sodium hydroxide, (NaHO). White, Mg(OH)2. Sol. in ammoni-um salts. White, Ba(OH)2, only in concen-trated solutions. White, Sr(OH)2. difficultly sol. in H2O. White, Ca(OH)2, diffi-cultly sol. in H2O. Ammonium hydroxide, (NH4HO). White, Mg(0H)2. Sol. in ammoni-um salts. Sulphuric acid, (H2SO4) or a soluble sul-phate. White, BaS04. Sol.in 200,000 parts H2O. Sparingly sol. in acids. White, SrS04. SoL in 6,895 parts H2O. White, CaS04. Sol. in 500 parts H2O. Insol. in alcohol. Ammonium oxalate, (NH4)2C204) Wbite, BaC204. Sol. in 2,590 parts H2O. Sol.in HC2H3O2. Quite sol. in dilute H2C204. Wnite, SrC204. Sol. in 12,000 parts H2O. Slightly sol. in H2C2O4. Slightly sol. in NH4 salts. White, CaC204. Sol. in 500,000 parts H2O. Insol. in H2C204,or HC2H3O2. Potassium chromate, • Yellow, BaCr04. Difficultly sol. Yellow, SrCr04. Moderately sol. inH20. Whitish, CaCr04. Easily soluble. (K2Cr04). Hydrofluosi- White, BaSiF6. Sparingly sol. in H2O. White, CaSiF6. licicacid, (H2S1F6), Easily soluble. REACTIONS. Group V—Metals not precipitated by H2S nor by (NH4)2COs. Reagents. Potassium. Ammonium. Lithium. Sodium. Sodium White, Li2C03. Slightly sol. in H2O. (Na2C03). Sodium White, Li3P04. Sol. in 2,539 parts ofH20. Sol. in 3,920 parts of dilute am-monia. Phosphale, (Na2HP04). Platinic Yellow, K2PtC16. Sol. in 12,083 parts of absolute alco-hol. Slightly sol. inH20. Yellow, (NH4)2PtC16. Sol. in 26,535 parts of absolute alcohol, ---- chloride, (PtCl4). Tartaric White crystal, KHC4H406, forms better alter shaking. Sparingly sol, in H2O. Sol. in Ht 1 and in alkalies. White crystal, NH4HC4H4O6. Slightly sol. in H2O. Sol .in al-kaline solutions, and the mineral acids. acid (H2C4H4O6). Potassium White crystal, Na2H2Sb207. Insol. in alcohol. Sparingly sol. in H2O. Sol. in al-kaline solutions antimoniate, (K2H2Sb207). Nessler's reagent, sol. of Hgl2 in KI-)-KHO. Yellowish brown, NHg2l. Hydrofluosi- Translucent, K2SiF6. Insol. in alcohol. Sol. in 790 parts H2O. Sol. in HCl. White, Na2SiF6. Difficultly sol. in H2O. (H2SiF6). Flame Violet. Red. Yellow. reaction. 168 LABORATORY GUIDE. Reactions of the acids. Soluble Salts of the following Acids. Barium Chloride. Calcium Chloride. Silver Nitrate. Sulphuric acid, H2SO4. White, BaS04, Insol,in acids. White, CaS04. Sol. in 480 parts H2O. in 3 parts HCl. White, Ag2S04, only in concentrated sol. Sulphurous acid, H2SO3. White, BaS03. Sol. in HCl. White, CaS03. Sol. in HCl. White, breaks up by heating into Ag2, Ag2»04 and SO2. Thiosulphuric acid, White, BaS203, only in concentrated sol. White precipitate. Sol. in Na2S203, H2S2O3. quickly breaks up & yields black Ae2S, Ortho Phosphoric acid, H3PO4. White, Ba3(P04)2. Sol. in acids also in NH4CI. White, Ca3(P04)2. Sol, in acid*, and in NH4C1. Yellow, Ag3P04. Sol. in HNO3. Sol.in NH4HO. Pyrophosphoric acid, H4P2O7, WhUe, Ba2P207. Sol. in HCl. White, Ca2P207. Soluble in excess. White, Ag4P207. Sol. in HNO3. Sol. in NH4HO. Metaphosphoric acid, HPO3. White.Ba(P03)2. Sol. in excess of HPO3. White, Ca(P03)2. White. AKf03. Sol.in HNO3. Sol.in NH4HO. Arsenic acid, H3ASO4. White, Ba3(As04)2. Sol. in NH4C1. Sol. in acids. White, Ca3(As04)2. Sol. in NH4CI. Sol. in acids. Red brown,Asr3 ASO4. Sol.in HNO3. Sol. in NH4HO Arsenious acid, H3ASO3. White, Ba3(As03)2. Sol. inNH4Cl. Sol. in acids. White, Ca3(As03)2. Sol. in NH4CI. Sol. in acids. Lizht Yellow, Ag3As03. Sol. in HNO3.Sol.inNH4H0 Chromic acid, H2Cr04. Yellow, BaCr04. Sol. in HCl and HNO3. Insol. in HC2H3O2. Light yellow,Cacr04. Only in neutral so-lutions and easily sol. in H2O. Dark red, Ag2Cr04. Sol. in HNO3. Boracic acid, H3BO3. White, Ba3(B03)2. Sol. in acids. Sol.in NH4Ci: White, Ca3(B03)2. Sol. in acids. Sol. in NH^Olandin CaCL-. White, Ag3B03. Sol. in HNO3. Sol. inNH4HO. Phosphorous acid, H3PO3. White, Ba3(P03)2. Sol. in HC2H3O2. White, Ca3(P03)2. Sol. inNH4Cl. White. Ag3P03. Black metallic Ag when heated. Silicic acid, H4Si04. White, Ba2Si04. White, Ca2Si04. Yellow Ag4Si04 in concentrated solu-tions. Sol. in HNO3 andinNH4HO. Carbonic acid, H2CO3. White, BaC03-Pol. in acids. White, CaC03. Sol. in acids. White, Ag2C03. Sol. in HNO3. Nitric acid, HNO3. Chloric acid, HCIO3. Iodic acid, White, Ca(I03)2 dif-ficultly soluble. Sol. in HN03- White, AgI03. sol. in NH4HO Treated HIO3. with S02,is reduced to Agl. Hydrofluoric acid, White, bulky BaF2. Sol. in HCl in HNO3. in NH4CI. White gelatinous CaF2. Sol. in HCl and i n N H4CI. Insol. in HC2H3O2. HF. Hydrofluosilicic acid White, BaSiF6. In-sol. in HCl C-o. 3. A liter of air is measured at 0° C. and 700 m. m. What volume will it occupy at 720 m. m. and 18° C? 273:273 + 18 720:700 I "1,000: a. Solve for x. IV. The specific gravity of a body is its weight compared with the weight of an equal volume of the standard. Hydrogen and air are the standards for gases, water for liquids and solids. In the above, normal conditions of temperature and pressure are understood. IT equals weight in air; w equals loss of weight in water. W .". Specific gravity equals — (for solids). 1. A body weighs in air, 450 grams; in water, 240 grams. Required, the specific gravity. 450 — 240 = 210; 450 ~ 210 = 2.2, nearly. 2. Five grams of a powdered mineral is put into a counter- poised sp. gr. bottle which holds 100 grams of water; the bottle is then filled with water. Thus charged, it is found to weigh 102.6 grams. What is the specific gravity of the mineral? 102.6 — 5 = 97.6; 100 — 97.6 = 2.4, therefore 5 ~ 2.4 = 2.08. 3. What is the volume of 20 grams of HCl? The specific gravity of the gas is 18.25, and .0896 gram of H occupies 1 liter. 0896 X 18.25 = 1.635 grams of HCl occupy 1 liter; one gram of HCl occupies fi„_ = .6116 of a liter, and 20 grams occupy .6116 X 20 = 12.232 liters. 224 LABORATORY GUIDE. (a) The density of a simple gas is its atomic weight; if this is divided by 14.43 it will give the density as compared with air. 1 fi Oxygen is 16 times heavier than hydrogen, or = 1.1 times heavier than air. (b) The density of a compound gas is % its molecular weight. 12 -4- 32 The molecular weight of C02 =—-J-— = 22; t. e., 22 times 22 . heavier than hydrogen, or . =1.5 times heavier than air. 4. A piece of cork weighs in air 82 grams. A tin sinker weighs in water 785 grams. The two together weigh in water 355 grams. What is the specific gravity of the cork? Let a = wt. of cork in air. Let b = wt. of sinker in water. Let c = wt. of both in water. Then sp. gr. of cork = a + l_c = 82 + 785_355 = -^ V. To calculate the percentage composition of a compound from its formula: 1. Calculate the percentage composition of potassium nitrate (KN03) : K = 39, N = 14, 03 = 48; 0 = 48 * 10°; „ 14 X 100 v 39 X 100 T, , , . , , . N =----r-fvj—~ 5 -^ ==----iTvj----• ^ne molecular weight is (39 + 14 + 48) = 101. 2. How many pounds of mercury and chlorine in 112 pounds of pure corrosive sublimate (HgCl2)? Hg = 200, Cl2 = 71; 200 parts of Hg combine with 71 parts of chlorine. Hg = |^ of 112; CI == ffc of 112. 3. How much mercury is contained in 125 pounds of an ore of which 75% is mercuric sulphide (HgS)? Hg = 200, S = 32; 75% of 125 pounds = 93.75 pounds of HgS. 200 39 Hg = 23T °f 9375' S = ~M °f 9375- GENERAL STOICHIOMETRY. 225 VI. To calculate the quantity of material to yield, liberate or produce a given weight of a substance. 1. We want 50 pounds of oxygen. How many pounds of potassium chlorate must we take? KC103 = KC1 + Og". The molecular weight of KC103 is (K = 39, CI = 35.5, ~Os =48) 48 122.5; 0==-To25"; 48:122-5: :50:z; whence a; =127.6 pounds. From IV. the volume can be easily calculated. 2. Silver is to be precipitated from 100 grams of silver nitrate by means of metallic zinc. How much Zn will be required? 2AgN03 + Zn = Zn(NQ3)2 + Ag2. The molecular weight of AgN03 = 170. .*. 340 parts of AgN08 require 65.2 parts of zinc. 65 2 One gram of AgN03 requires -7^- grams of zinc. 65 2 One hundred grams of AgN03 require -^+- X 100 = 19.17 grams of zinc. 3. What quantities of mercury and of sulphuric acid are necessary to furnish a kilogram of sulphurous anhydride? Hg + 2H2S04 = HgS04 + 2H20 + SO~7. 200 + 196 = 296 + 36 + 64. Dividing by 64, we have 3.12 and 3.06, the respective amounts. VII. Combinations and decompositions of bodies in the gaseous form. 1. How many cubic feet of oxygen are required to consume completely one cubic foot of marsh gas, and how many cubic feet of carbonic anhydride and of water will be formed? CH4+04 = C02+2H20. Volumes 2 + 4 = 2 + 4 (H20 itself is two volumes). . •. Two cubic feet of marsh gas require four cubic feet of oxygen, and there are formed two cubic feet of carbonic anhydride and four cubic feet of water vapor; now, one cubic foot of marsh gas requires two cubic feet of oxygen, and one cubic foot of carbonic anhydride and two cubic feet of water vapor are formed. 226 LABORATORY GUIDE. 2. x volumes of ammonia are decomposed by chlorine. How many volumes of chlorine are required? 8NH3 + 6C1 = 6NH4C1 + N2. Sixteen volumes of NH3 require 6 volumes of CI; 1 volume of NH3 requires | volume of CI.; x volumes of NH3 require f x volumes of CI. 3. How many liters of chlorine must be used to form 100 grams of lead chloride (PbCl2)? Pb + 2C1 = PbCl2. 207 + 71 = 278. From the equation we see that a molecular weight of lead chloride requires a molecular volume of chlorine to form it. 11.2 liters of chlorine gas weigh 35.5 grams; so it requires 22 4 22.4 liters of chlorine . ■. 1 gram = -^-, 22 4 100 grams = -^ X 100 = 8.06 liters, nearly. 4. If air contains 23% by volume of oxygen, how many liters of air will be necessary to burn completely 1 kilogram of carbon? C + 02 = C02 ; 12 parts, by weight, of carbon combine with 32 parts of oxygen, or 1 kilogram of carbon requires 2f kilograms of oxygen. 11.2 liters of hydrogen weigh 1 gram; air, being 14.43 times heavier, weighs 14.43 grams, or 1 liter weighs ' = 1.29 grams A kilogram of air occupies as many liters as 1.29 is contained in 1,000, or 775.2 liters. 2f kilograms will have a volume of 775.2 X 2.66 = 2,062 liters, if the air was pure oxygen; but as it contains only 23% of oxygen, it will be as many times 2,062 as 23 is contained in 100 = 4.35 times; 2,062 X 4.35 = 8,969.7 liters of air. VIII. How the atomic weight of an element is obtained. 1. If it is a gas, by comparing the weights of the same volume under like conditions of temperature and pressure with hydrogen. GENERAL STOICHIOMETRY. 22T 2. If a metal, the product of its specific heat by its atomic weight is a constant quantity, about 6.34. The specific heat of a body is the amount of heat required to raise a unit weight of the substance from 0° C. to 1° C, the thermal unit being the amount of heat required to raise one gram of water through 1° C. In a general way, by making an analysis of their com- pounds— if possible, gaseous compounds — and carefully com- paring the results. Sometimes a formula is assumed. The formulae of com- pounds used are very necessary. Much assistance is derived from (1) Mitscherlich's law of isomorphism, (2) law of specific heat, (3) by substituting in equal successive portions, as from H20, KHO, K20, etc. The density of a gas is one-half its molecular weight. 1. Stas found, after adding 7.25682 grams of potassium chloride to 10.51995 grams of silver dissolved in nitric acid, that .0194 grams of silver remained in solution. Calculate from these data the atomic weight of potassium (the other atomic weights supposed to be known). 10.51995 — .0194 = 10.500.55, the amount of silver used. At. wt. Ag : at. wt. CI :: wt. Ag : wt. CI. 108 : 35.5 :: 10.50055 : x, or 3.45157. 7.25682 — 3.45157 = wt. of K, or 3.80525. Wt. CI : wt. K :: at. wt, of CI : at. wt. K. 3.45157 : 3.80525 :: 35.5 : x, x = 39.1. 2. Erdmann and Marchand obtained 109.6308 grams of mer- cury from 118.3938 grams of the red oxide. Calculate the atomic weight of mercury, supposing that of oxygen to be known. HgO - Hg = O. 118.3938 — 109.6308 = 8.7630, the weight of the oxygen. Wt. of O : at. wt. of O :: wt. Hg : at. wt. of Hg. 8.7630: 16 :: 109.3608 : x, x = 200, nearly. 3. Stas found that 91.462 grams of metallic silver, when heated in a stream of chlorine, yielded 121.4993 grams of pure 228 LABORATORY GUIDE. KHS04. silver chloride. Calculate from this the atomic weight of chlo- rine. 121.4993 — 91.462 = 30.0373 the amount of CI. Wt. of Ag : at. wt. Ag :: wt. CI : at. wt. CI. 91.462 : 108 :: 30.0373 : x, solve for x. IX. The percentage composition of a compound being given. Required, its empirical formula. 1. A substance has been found to contain in 100 parts: Hydrogen.............. 2.04 -f 1 = 21 Sulphur................ 32.65 -^ 32 = 1 l H2S04. Oxygen................ 65.31 -f- 16 = 4 J 100.00 Rule — Divide the percentage by the atomic weight, reduce the quotients to their simplest relation in whole numbers. 2. Potassium equals............ 28.73 -^ 39 = .73 = 1 " Hydrogen " .............73-f 1= .73 = 1 Sulphur " ............ 23.52 -f 32 = .73 = 1 Oxygen " ............ 47.02 -f 16 = 2.93 = 4 100.00 3. Iron equals............ 70.01 -^ 56 = 1.25 -f 62 = 2 ) Oxygen equals......... 29.99 -+■ 16 = 1.87 -7 62 == 3 j Fe2°3, 100.00 X. Students have experienced some difficulty in solving problems when the bye products are of two different kinds and vary in amount. 1. How much (molecular weight) KHS04, K2S04, and HN03 will be formed when 120 parts of KN03 and 94 parts of H2S04 are used in making nitric acid. (a) KN03 + H2S04 = KHS04 + HN03. (b) 2KN03 + H2S04 = K2S04 + 2HNOs. (c) 3KN03 + 2H2S04 = KHS04 + K2S04 + 3HN03. (d) There will be as many parts of nitric acid formed as there are of potassium nitrate taken. (e) If equal quantities are taken, only the bisulphate (KHSOJ is formed. GENERAL STOICHIOMETRY. 229 (/) If two parts of KN03 to one of H2S04, only the nor- mal sulphate (K2S04) is formed. (g) The bisulphate (KHS04) is first formed. (h) The number of parts of normal sulphate (K2S04) is found by subtracting the number of parts of sulphuric acid from the number of parts of potassium nitrate. (i) If the number of parts of normal sulphate be sub- tracted from the number of parts of sulphuric acid, it leaves the number of bisulphate. The answer can now be written out, as follows: 120KNO3 + 94H2S04 = 120HNO3 + 26K2S04 + 68KHS04. XI. Thermal units. The specific heat of a body is expressed by a number which shows the amount of heat necessary to raise a given weight of the body one degree (0° to 1° C.) of temperature as compared with the amount necessary to raise the same weight of water one degree. The latent heat of a liquid body means the amount of heat required to change the body from the solid to the liquid state without change of temperature. The latent heat of a vapor is the amount of heat necessary to change the body from the liquid to the vapor form without changing its temperature. Atomic heat of a body is the amount of heat necessary to raise an atomic weight of the body through one degree of temper- ature. So far as elementary bodies are concerned, their atomic heats are inversely as their atomic weights. The amount of heat required to raise one pound of oxygen 1° C, is one-sixteenth of that required to raise one pound of hydrogen 1° C. 1. Five kilograms of water have to be raised through 10° C. How much charcoal (calling it pure carbon) would it be neces- sary to burn to do this? Carbon in burning develops 8,080 units of heat (see No. XI.) 8,080:50:: 1: x, x = .00618 kilograms or 6.18 grams. 230 LABORATORY GUIDE. 2. Eleven hundred and twenty pounds of iron ore have to be raised to the top of a shaft 1,000 feet deep. What weight of char- coal would develop, during its combustion, force enough to do this? 1,120 X 1,000 = 1,120,000 foot pounds required. One pound of coal, in its combustion, develops 8,080 units of heat; but the mechanical work which this heat is capable of doing is: 8,080 X 1,390, or 11,231,200 foot pounds. . •. 11,231,200 : 1,120,000 :: 1 : x, when x = .09 pound. 3. A piece of zinc falls from a height of 1,000 feet; to what temperature, centigrade, will the zinc be raised by the arrest of motion? When water falls from a height, every 1,390 feet fallen generates 1° C. 1,390 : 1,000 :: 1 : x, x = temperature, to which water would be raised by a fall of 1,000 feet; x = .769° C. Sp. heat Zn : sp. heat of H20 :: temp, of H20 : temp. Zn. .0927 : 1 :: .769 :x, x = 8.3°C,nearly. 4. How many pounds of carbon must be burned in order to melt just 1,000 pounds of ice? How many to evaporate 100 pounds of water, the temperature of which is 10° C. The latent heat of water, 79.25, to melt 1,000 lbs. of ice = 1,000 X 79.25 = 79,250. The units of heat developed by the combustion of one pound of carbon = 8,080 .-. 8,080 : 79,250 :: 1 : x, x= 9.8 pounds of carbon. For the second part of the question. Units of heat required to raise the water to the boiling point, 100 X (100 —10), or 9,000. Units of heat required to evaporate the boiling water = 535.9 X 100 = 53,590. The total units of heat required, 9,000 + 53,590, or 62,590. 8,080 : 62,590 :: 1 : x, x = carbon required in pounds = 7.75. 352. Heating power of coal. Calorific power of hydrogen.................................... 34,462 " " " carbon...................................... 8,080 " sulphur ..................................... 2,221 Specific heat of carbonic anhydride..............................2164 " " nitrogen........................................2440 " " " water vapor....................................4805 " " " sulphurous anhydride......................... .1554 GENERAL STOICHIOMETRY. 231 Latent heat of steam (thermal units), 537° C. Parts of nitrogen to one of oxygen in air (by weight), 3.314. Weight of 100 cubic inches of air (about 2 grams), 31 grains. The value of a fuel may be estimated in two ways, as calorific power and as calorific intensity. Calorific power means the total quantity of heat developed in the combustion of a given weight of the substance; caloric intensity means the maximum tempera- ture developed in the process. The absolute amount of heat must be constant under all conditions. The result must be very different in the matter of temperature, as it is influenced by the nature of the products of combustion, the rapidity of the development of heat compared with the rapidity of its dissipation among sur- rounding bodies. A fuel may have a high absolute heating power and give a low temperature, or a low heating power and give a high thermo- metric intensity. There are cases in which both of these results are valuable. There being no absolute unit of heat, the heat required to raise one pound of water one degree in temperature (or one kilogram one degree) is usually assumed as the standard. 353- The ultimate analysis (made in the Laboratory of the Experiment Station) of a Colorado coal is as follows: Carbon.............................................. 80.00 Nitrogen.........................•................ 1-50 Sulphur............................................. 2.00 Hydrogen........................................... 6.00 Oxygen.............................................. 6.20 Ash................................................ 4.30 100.00 From the calorific power of hydrogen we learn that in the combustion of one pound of hydrogen enough heat is produced to raise 34,462 pounds of water one degree in temperature, carbon 8,080, etc. The calorific power of carbon (8,080) multiplied by the amount 80 = 646,400 units. From the hydrogen must be sub- tracted enough to combine with 6.2 pounds of oxygen to form water (in water there is H = ^ O = H>8 times as mucn oxygen 232 LABORATORY GUIDE. as hydrogen) ; 6.2 — 8 = .77 pounds of hydrogen to combine with the 6.2 pounds of oxygen, leaving 6 — .77 = .5.23 pounds of hydrogen which can take part in the combustion; this multiplied by the calorific power of hydrogen, 34,462 X 5.23 = 180,236.26 units as the value of the hydrogen. The calorific power of sulphur, 2,221 X 2 pounds = the heat units for sul- phur = 4,442 units. The sum total = 646,400 + 180,236.26 + 4,442 = 831,078.26 heat units. But heat is required to convert the water formed in the process of combustion (and hygroscopic) into steam, reckoning from 100° C. The amount of water formed will be nine times the amount of hydrogen, 6 X 9 X 537 = 28,998 units, and leaves 831,078.26 — 28,998 = 802,080.26 heat units for 100 pounds, or 8,020.8 for one pound of fuel. The calorific power of this coal would generate heat sufficient to raise 8,020 pounds of water in temperature 1° C, or 8,020 -i- f- = 14,436 pounds 1° F. 354. To ascertain the maximum intensity or thermometric value, it is necessary to consider the specific heats of substances resulting from the combustion. This result is obtained by divid- ing the calorific power by the sum of the products of each of the results of the combustion by its specific heat. In the case of our coal, we have from the combustion of 100 pounds — C + 02 = C02, or 3.66 times the C = C02 ; 80 X 3.66 = 292.8 pounds C02; H2 + O = H20, or 9 times the H = H20; 6 X 9 = 54 pounds H20; S + 02 = S02, or 2 times the S = S02; 2X2 = 4 pounds S02; making 292.8 + 54 + 4 = 350.8 pounds of the several products. By the reaction nothing but oxygen has been added. If from this sum (350.8 pounds) the C, H, and S be subtracted, it leaves the amount of oxygen required for their formation (80 + 6 + 2 = 88), 350.8 — 88 = 262.8 pounds of oxygen, deducting the 6.2 pounds found in the coal (262.8 — 6.2=254.6); this 254.6 pounds of oxygen must come from the atmosphere; to obtain this quantity GENERAL STOICHIOMETRY. 233 of oxygen from the air, it is accompanied by 843.74 pounds of nitrogen (254.6 X 3.314); the coal contains 1.5 pounds of nitro- gen, making a sum total of 843.74 + 1. 5 = 845.24. The specific heat of the ash is quite small — about .2, and is usually neglected, not materially affecting the results : 292.8 pounds C02 X specific heat .2164 == 63.36 54 " H20 X " " .4805 = 25.94 4 " S02 X " " .1554 = .62 845.24 " NX" " .2440 = 206.23 For 100 pounds of coal = 296.15 for one pound = 2.9615. It takes as much heat to raise the temperature of the pro- ducts of combustion from one pound of this coal 1° C. as will heat to the same temperature 2.9615 pounds of water. By divid- ing the calorific poiver 8,020.8 by this number (8,020.8 -f- 2.96), we obtain 2,712° C. as the temperature produced by the complete combustion of this coal. INDEX. Acids— page Uses of.............................. 11 Acetic............................12, 150 Aqua regia........._____........... 17 Arsenic........-.................... 12 Arsenious___..........___________ 12 Benzoic______.......______.....- 148 Boric......—................—.13, 131 Butyric______.....................153 Carbonic..........____.............133 Chloric.......................------141 Chromic........................--13, 128 Citric—......—................14, 145 Ferricyanic......................15, 149 Ferrocyanic_______..........—.15, 149 Formic............................— 151 Gallic......................—...... 15 Hydriodic........................16, 138 Hydrobromic.....................16, 137 Hydrochloric______..............17, 136 Hydrocyanic.....------.........17, 138 Hydrofluoric_________..........18, 132 Hydrofluosilicic___......-.......18, 129 Hy.drosulphuric.....------........ 19 Hypochlorous........—......---47, 139 Hyposulphurous.................... 135 Iodic .--.................----------135 Lactic......__________..........--- 151 Malic-—.....................-.......I46 Molybdic............................ 128 Nitric......______..............-19, 140 Nitrous____......................44, 139 Nitrophenic or picric..........--- 20 Oxalic.......-.................—19, 132 Perchloric______.....—......----141 Permanganic__________........... 20 Phosphoric------..........--.....130 Ortho......______.............. 130 Meta —......-.........-........131 Pyro.............................131 Propionic..............---......--- 152 Silicic__________................62, 133 Succinic........---........------I4" Sulphocyanic_________.....—21, 150 Sulphuric................—.....21, 128 Sulphur.............................i28 Sulphurous........---.......---22, 134 Sulphanilic-----...................I82 Tantalic...................-------I28 Acid s — Continued. page Titanic.............................. 128 Tartaric..........................22, 144 Uric................................. 143 Alcohol.............-__........_........ 23 Alkalies.................................115 Alkaline earths............______.....109 Alkaloids (poisons)___................184 Aconitine...........................202 Antimony...................._____210 Arsenic_______...............____214 Atropine___............___........203 Brucine........___.................195 Caffeine........................____208 Cocaine............._____________209 Codeine........................____199 Conine........._..........___......207 Copper_____........................218 Destroy life_____________......... 219 Directions...................._____187 Igasurine..............___________196 Lead................................216 Meconic acid................._____198 Mercury________________________213 Morphine........................... 196 Narcotine......___............____200 Nicotine........_________.........205 Phosphorus.........................211 Ptomaines...............----......181 Quinine______.........______.....200 Reagents............................190 Strychnine......................---193 Tyrotoxicon...................____185 Veratrine____.................___201 Zinc.................................217 Aluminum, tests........ ______....... 97 Ammonium — Carbonate.......................___ 24 Chloride............................ 24 Hydroxide.......................... 26 Ferrous sulphate---------........ 25 Fluoride................---------- 25 Molybdate.......................... 27 Nitrate_____....................... 27 Nitrate of silver.................... 28 Oxalate------........-........... 27 23G INDEX. Ammonium —Continued. page Succinate...................._____ g8 Sulphate____________............. 28 Sulphate of copper................. 28 Sulphide _.......................___ 29 Analysis in the dry way______....... 51 " by beads......_____........— 62 " on charcoal______......___ 57 " in closed tube_____________ 52 " by open tube_____........... 55 " by color_________........... 67 " by cobalt nitrate__________ 58 " by feel.............—........ 67 " by films..........___........ 63 " by flame coloration.......... 58 " by fusibility.................. 65 " by hardness___.............. 65 " by lustre___________......... 66 " by odor.......____.........57, 67 " by reduction (Zn and HCl).. 60 " by streak___.....______..... 66 " by taste______............... 67 " by wood splinter..........— 59 Antimony_______________............. 89 ous.............______......______ 89 ic...................—.............- 89 Arsenic___________________________ 86 ous.................._____.......... 87 ic....................______........ 87 Barium, tests____...................... 110 Acetate...................._______ 29 Carbonate..-........................ 30 Chloride -.........._____.......... 30 Hydroxide.......................... 30 Nitrate___.............___________ 31 Peroxide —......................... 31 Bismuth_____.......________________ 81 Bromine..............---......______ 31 Bromine water...........___.......... 31 Cadmium______....................... 85 Caesium......----...................58, 115 Calcium, tests___________........___111 Carbonate----.......____.......... 31 Chloride............................ 32 Fluoride.............._______..... 32 Hydroxide---...................... 32 Oxide.........------------....... 33 Sulphate___........................ 33 Carbon disulphide...................... 33 Chlorine water......................... 33 PAGE Chloroform............................_ 34 Chromium___....._____........______ 97 ous.................................. 98 ic—................................. 98 Cobalt nitrate_____________.........34, 99 Copper........-----------..........34, 83 " sulphate........................ 35 Cuprous chloride________............. 35 Directions — How to keep note book............ 51 For beads and films_____......... 64 For analysis in dry way..........51-69 For poisons.........................187 Distillation, water______........______175 Electrolysis, separation_____.....____123 Ether....................______........ 25 Ferric chloride......................... 36 Ferrous sulphate......_______........ 36 Film tests............................... 63 Flame reactions.........______....... 58 Gold chloride_______________........ 37 Groups (separation) — Alkalies.....______.................119 Alkaline earths..................113-114 Iron.....----------------105, 107-108 Lead and arsenic................... 92 Silver..........._________........_ 78 Hydrogen.........._________________ 37 " peroxide....._____..........166 Indigo solution___...........____..... 35 Indigo solution bleached..........___142 Iodine.................................._ 37 Iron................................____ 95 ous.................................. 95 ic.................................... 95 Incrustation and coating.............. 59 Lead — Acetate...........____............38, 75 Chromate_________..............38, 75 Tests for............................ 75 Lithium___________..........__........jjg Litmus paper_________________...... 38 Magnesium wire........................ 55 Tests______________.......____ _ ijo Mixture____,______............ 39 LABORATORY GUIDE. 237 PAGE Manganese..............................102 ic-.................................. 103 ous..................................102 Mercury...............................39, 80 Tests for..........................77, 80 Mercuric chloride....................39, 80 " iodide......___.............. 78 " nitrate....................___ 77 " oxide......................... 77 " sulphide..................... 78 Mercurous chloride______............. 78 " nitrate...................... 40 Microcosmic salt___................... 40 Millon's reagent_______________...... 41 Molybdenum______......---......... 60 Nessler's test........................... 176 Nickel__________......_________.....100 Niobium___.................---........ 74 Nitrates (water)................------180 Note book, how to keep..........---- 51 Notes on sep. of Pb and As groups... 93 " " " Ag group............ 79 u •' '4 ^e " ............ 94 44 44 44 Ye " __________ 106 44 '4 44 alkaline earths......114 » '• " alkalies............- 119 Organic acids..............-........... I44 Acetic...............---.....--.....15° Benzoic----------.................I48 Butyric........----................153 Citric...........-...........-........I45 Ferricyanic......-----............. I49 Ferrocyanic--------..........----149 Formic........-..................... 151 Lactic------..........------......lgl Malic............-........—-......I46 Oxalic___........................... I32 Proprionic-------------.......... 152 Succinic...............------......I47 Sulphocyanic------...............150 Tartaric...........—........-----I44 Oxygen............-.................--- 41 Platinum vessels, care of.............. 41 " chloride....................— 42 Potassium tests..............---------116 " bisulphate------.......... 42 " chlorate..................... & PAGI Potassium hydroxide.................. 42 " iodide..................____ 43 " metantimoniate............ 44 " nitrate...................... 44 " nitrite....................... 44 " sulphate___................ 45 Problems (stoichiometry)....._____221-233 Ptomaines..............................184 Qualitative analysis in the dry way .. 51 " " " " wet " .. 70 Quantitative of water........________174 Reagents — Preparation__________...........11-50 Poisons (see poisons). Water (see water). Rubidium............................... 115 Selenium...........___......________ 56 Separation of acids....................143 " of bases..................73, 122 " blowpipe______.......... 68 CI, Br, I.................... 137 Silver chloride.......................... 74 " chromate____________.......... 75 " nitrate................—.......45, 74 Sodium..........................____55, 117 " acetate_______........-........ 45 " carbonate___________________ 46 " chloride___....._____________ 46 " hypochlorite___................ 47 " lime____........................ 47 " nitrate..................------ 47 " nitroprusside---.........----- 47 " palladio-chloride............... 48 " phosphates (ammonium)...... 48 " sulphite_________............. 48 " thiosulphate.................... 49 Solution of indigo-----------------142 Stannous chloride-----............... 49 Strontium.............----.............Ill Starch solution................---..... 49 Thallium....................--......... 71 Tin.................------.............. 90 ic......-............................. 91 ous................................... 91 Tungsten.........-..................... 74 Turmeric paper........................ 49 Venadium................--............ 94 238 INDEX. PAGE Water..................._..............174 Ammonia, free.....................177 Ammonia albuminoid___..........178 Chlorine............................174 Forschammer's___........_______178 Hardness_________.................175 Nitrates___..............___.......180 Nitrites............................. 180 Notes...............................182 Water — Continued. page Organic matter............___.....176 Solids............................... 174 Sulphates...........................180 Yttrium..........-----................. 94 Zettnow's chart........................120 Zinc..................................... 50 " tests................................ 103 .-.«iJ.«»..^*»+4. *M..rlH 41>l«lHfH..W4*4mUllHHIimU4HU(l ................ ., —;;..,,.., >.., 111,, m u i s m . 11 u n 11 n 111., ,unMi,u.i.i;;,ni>i;i»..nr yintitiiiMi .....•^^"♦'•^••~--«'r;niiir"i>n...ji/!'tU«r.«(iJ»U4u4 . ......!.;....i................ >......«...►)......i I....I.H......II, I),., nil II I, III.1)1 In, ii, in Hl.lio I,fill (ill f ....n^.i.A^i.im.-i~u«+m;^«4UiiHMii.w)ii*- lilmuiMWli I AUmMMUiMU, uuuiutumuuti,..... ............----i*^i.«u-iW4ii.iiiiii>uu;n«i lIHHm ___ .................i...,...i.,.»i..^;..,i;i,i,iiin.i: Hlilrt illdiui ...............at..........ii4;,ii.,iiinuiiwii luiili lull IH ............~;..,~^.-iMMUMM llilltWjIttHimill ............-^ivi.~i»U«ill«l*ii*Wi*4i.m>ll»4l itimlitiiuu. .......~.i..i^i~iu*uni~^iiuuniiiUiivtMwuiiu inrnm itiu>mu&+H ....-----..........i;ti.i,l„tt^„Ui;.,y,iH>UU IIHIlillflllW •.......—♦.-...»u.iMk.t.ii>wwi;iruH HIli+HU llUimiililn -......^_.,.-«^ii~i^i.iiim«.iiiiniiii ,iiiiniiti»iii4tHlliiiHii1iii • ......„...;i_;i.U.iil.HI«li4)i»;Uii*4il«IH; llHltillj) ■ ■■ •.......•• ...—...i-ii.i;ui;w..-.i«ii..wmiin;n; mum;' .....~...........;«,,..iu,i^;>.;i»wiiu»w»wiiii»i»iiiHw lummmr ,.- ....... . ---->,l...l.nKMiilWUill>IUIi nn. ::...■ .1 ■.!! i,i,\nuUH».>H .....----^.---...~*.,„ny,lMii^Uii>M»iUU»UUiU .„...„-._---„ ...,,j,r^^^t.)WI.»H»;itllWllltUUIlW)>. ■».~i...^,.^,.-..,ii^v.t>,;,yWu.i)i.i,i),ii,ui.»iiw^ ....... ... ...a... ...i.iwi^i^iiiiiiiiiiiiiiiiiiimiitiwiiiiUii^iiii iiiiiiiiiiiiiiiiH«iiH»UMi!iir .—........... .....^u;nwuiHnii»wiHmii«ini ii.Miii- HwHHiifiiii,M'i»4MiHJ*WHHIV ......^.—... .. u»-i.,ii,..i.i)niiiii liwiaiMiUiinuiiiiiiw .IHtMllllUumtUtlU ■iw»iiiw;wiiinmiiiwiiin m« Htlili .WUilliMDMiliUI WHIWI:'..... i~>*i«i.;Mi4ikH»ji»m««i .ilU.,i.l>..U.| ,iuiiinUHH:iiii»iJiHmi)H . .^U*^il.lU4i..U.il.i,lHl|,IH||li|)H|lHlH4mi;___ ..■,...;ii.iuiiijiinmijiu»niinmiiwnw)iwMiinii..... -iii;miH»ii».UM>».ii iiiiwiiiiiiiiii -H.XPIIIUVMIlUllUWIHIMIIHllHimtWMIHIlMil. :: HiiHiiHiilii.ii i .... -.„---^....auuir.uiiii»iiiiiiiniiiiHiil.iiiiiiwiiiiiJimi.iiiiiii4lllliiiilHlilllli ,1*^-1* l; i^-..,ii)niiiii;iiiiiiUiiiiwi>4iii»miiiwwtUi»w»iiwtiiiwi ,,..^^„... „.^WWIilinilWluifat{WW4>Mtll4>4M>tWIIW4IIH»)f ^-.*^>^>».II^Mti>»HIIM»l|l||U>wU«(nmitmH»lll»)WHI.,.. ,_^.,.^i.i, iwm»ni)iiniiiiMw4»»nitnm»w>i»wr ' H4h,1»I»IIKI)HMHWI1HIH IIHHIIH. , .>,l,—.«HM»»J»M»4t«»»U»H i. ^wii.,i^i...m.MiiiiiiKHitmiw mum' mIMMUIIIMWIWIHIHI' HIIHWHK r^»l«iM»fc>i*fHJ»»U»lli HH4HL..... 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