m rnm^ 4S* * *v * * - •* v-tofifev- >f*" $te *r* ■ NATIONAL LIBRARY OF MEDICINI Bethesda, Maryland 4-28-13-io-V Gift Of The New York Academy of Medicine Ilk, h IW. By. -19 £k^*LV £* *w..-w * 'Vs&i V ( A LABORATORY GUIDE CHEMICAL ANALYSIS 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 praeccpta, breve et efficax per exempla."—Seneca Ep. VI. SECOND EDITION. ENTIRELY REWRITTEN AND REVISED. NEW YORK: JOHN W I L E Y & SONS, 15 Astor Place. 1889. THF K Y, ACADEMY fyp xfr-T^T^T-NTir JUL 6 1915 UbHAft Y. TO HIS ESTEEMED FRIEND AND TEACHER, S. A. NORTON, PH. D., LL. D., PROFESSOR OP CHEMISTRY IN OHIO STATE UNIVERSITY, COLUMBUS, OHIO, THIS WORK IS RESPECTFULLY DEDICATED BY THE AUTHOR. \ Entered according to Act of Congress, in the year 1883, Entered according to Act of Congress, in the year 1888, BY DAVID O'BRINE, In the office of the Librarian of Congress, at Washington. 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. Egelston, E. M., Ph. D., LL. D., of the School of Mines, Columbia College, I am indebted for the 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, 6 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. 8 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 II. 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.............................12G 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 10 CONTENTS. CHAPTER VII. Poisons, Ptomaines, etc.........................................184-190 General Reagents............................... ........190-192 r 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 Coacine...................................................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 VIII. 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. I- 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 -+-3H20 = 2(H3As04) and As203 + 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 -f 2HN03 -f- 2H20 = N203 + 2(II3As04). Tests—When heated on charcoal, it gives a garlic odor. In solution As203 with AgN03 yields yellow Ag3As03.f A^305 *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 HX03 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 -f- 2HN03 = 2KN08 -f H20 -f- K2Cr207. When a cold saturated solution of potassium bichromate is treated w^,th 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 -J- 03. Heated with H2S04, O 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 II2S04 is used in volumetric analysis for an oxidizing agent, as in the determination of iron. 6. Citric acid (H3, C6H507, H20), a 10 per 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 +_& 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 Hgl2. 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 0 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 -f 3Br -f P = H3P03 + 3HBr. It is decomposed by exposure to the air. Tests—When a bromide is treated with H2S04 -f- 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 -f- H2S04 = Na2S04 -f- 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. ( NOCU + CI ) Aqua regia is 3HC1 + 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 — H2SOt 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 + 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 -f 2CaF2 + 2H2S04 = SiF4 -f 2CaS04 -f 2H20. [2) 3SiF4 + 2H20 = 2H2SiF6 -f- 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 + II2S04 = FeS04 + iL^T: if the gas is passed through a saturated solution of water and glvcerin, 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 + 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: C12H22011 + 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 -j- 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. (b) Ammonium sulphocyanate (NH4CNS), one part of the salt in twenty parts of water. Preparation — By digesting HCN with yellow ammonium sulphide : (NH4)2S -f 2HCN = 2(NH4CNS) + 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 + H20 = H2S04 + NO. (2) NO -f- 0 = 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 + C2 = 4S02 -f- 2C02 + 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 + CaC03 = K2C4H406 -f CaC4H4Q6 -f H20 + 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 -f CaC4H4Q6. The calcium tartrate is boiled with dilute H2S04, when an insoluble calcium sulphate and a solution containing free tartaric acid are formed: CaC4H40G + H2S04 = H2C4H406 + 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 -f 3CaC03 = 3CaCl2 + 2NH3 + H20 + 2(NH4)20, 3C02. Tests — It gives off the odor of ammonia, and effervesces with HCl, CO2 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 NH4HO, 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 -f CaO, H20 = 2~NH3 -4- CaCl2 + 2H20. (2) H20 + NH3 = NH4HO. 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 -f 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 NH4HO, 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 NH4H0. PREPARATION OF REAGENTS. 29 Tests and Uses for 36 and 37—A solution of arsenious acid forms with 36 green CuIIAsQ3 or Cu3(As03)2, and with 37 forms yellow Ag3AsQ3, 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(NHJ2S + 6H20 = ____ Al2(OH)fr + 3(NH4)2S04 + 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 = H^S + 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(0H)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 (CaCOJ. Preparation—A hot solution of CaCl2 is precipitated by (NH4)2C03, with the addition of some NH4HO; 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 + 2HC1 = CaCl2 + 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 -f H2S04 = CaS04 -f 2HFT 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 lapse 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 -f- 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 + 7H20 + Cr2Cl6 + 6Cl. 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 + 3CaC03 -4- C02 + 8H20 -f 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, alsG 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. oO 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 Cu2Cl2 forms a compound having a mother of pearl lustre. Impurities — It may contain CuCl2. Uses — For absorbing CO in gas analysis (Cu2Cl2CO-f- 2H20). The ammoniacal solution of cuprous chloride gives with acetylene a red precipitate of di-acetylene cuprous oxide: 2C2H2 + 2Cu2Cl2 + H20 = 4HC1 -f- 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 -f- 2FeS04 + 2KI = Cu2I2 -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) C2H5OH4-H2S04 = C2H5HS04-|-H20. (2) C2H5HS04 -f- C2H5OH = (C2H5)20 + 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 -f-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. Use>3 — 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. Uses — 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 + 2(H,C2H302) = Pb(C2H302)2 + 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 PbCrQ4. 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 + K2Cr207 + H20 = 2PbCr04 -f 2KC2H302 -f 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 OF 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 + H2S04 = MgS04 -f"C0"2 -4- H20. Dolomite (CaMg2C03) contains Ca, but it forms with II2S04 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 NH4H0 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 -f NH4C1 = NaNH4HP04 + 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 OP REAGENTS. 41 76. Millon's ceagent. Preparation — Dissolve one part of mercury in one part of HNOs (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 + KC1 -f~03. Tests—A mixture of potassium hydroxide and pyrogallic acid absorbs oxygen and blackens the pyrogallate. When 0 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 U 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) -f- 4C1 = K20,C120 -f 2KC1 -f 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 + Ca(OH)2 = CaC03 + 2KH0. PREPARATION OF REAGENTS. 4o 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. Pare 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 -f Zn = ZnK202 + 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 -f 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 + 2KI = HgI2 + 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 (KSb03). 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 -4- KC1 = KN03 -4- 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 + 2HC2H302 -4- H20 = (KN02)6,Co2Q(N02)4,2H,0 -f 4KC1 + 2KC2H302 + 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 NH4HO. 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 insufficient 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 bypassing 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- CaCl2 -f 2NaC03 = 2NaC10 + 2NaCl -f 2CaCQ3. 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), or 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, Pl>S03, 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 -f 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 wrater, 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, in 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 +1)7 It deflagrates upon a glowing coal, giving 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 in the crystalline mass.................. It becomes strongly luminous or phosphorescent. It changes color from — ! yellow, on cooling is again white. dark yellow, '* yellowish .. dark yellow, on cooling is yellow- ish, fusible at red heat........ reddish yellow, on cooling is red- dish yellow, fusible at a white heat....................... Green or reddish to nearly black, on cooling is reddish brown (magnetic)........... Red 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 colored oxides of........... ............ indication of Haloid salts, as NaCl, etc. Alkaline earths, fluorides, etc. Zinc, ZnO. Tin, SnO, Ti02. Bismuth, Bi203. Lead, PbO. Iron, Fe203. Mercury, HgO. Co, Mn, Ni, and Cu. TESTS IX THE DRY WAY. 53 Organic compounds generally blacken from separation of carbon, evolving inflammable products like acetone (CO(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° O, in slender needles, H2C204, with H,S04 evolves CO and C02 ......... volatile at 218° C, forms octahe- White ( dral crystals, As203, with H2S becomes yellow.............. heavy fumes, crystalline needles, Sb2Os, with H2N 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, which heated with dry Na2C03 + C yields 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................. Red 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 I change starch blue...... \ red fumes of Br, which Condensable / change starch yellow___ 1 colorless vapors of As and f S, condensing to red or \ yellow drops............ Sof 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 -J- KI blue.................... of acetone = CO(CH3)2, is in- flammable; the assay heated with H2S04 -f C2H60 yields acetic ether................ odor of frankincense......... fumes which cause violent I 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. Sulphites, sulphates, etc. Cyanogen compounds. Hydrous sulphides and hy- posulphites. Organic compounds, NH4 compounds, and cyanides. Hypochlorites, PtCl4, and AuCl3. 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, N205, NH4N03, and peroxides. Formates and oxalates. 107. Heat the dry substance, together with certain dry reagents, in the matrass. Oxidizing with KC103 + Na2C03 (better on Pt INDICATION OF foil); green indicates Mn; yellow, Cr..... Mn and Cr. H2S reaction with Na2S203; Zn white, Cd and As yellow, Mn and Cr green, Sb red, and Pb, Ag, Hg, Cu, Bi, Ni, Co, / with KHS04 decomposes and Fe, black. I formates, acetates, oxa- „ 0~ .. ] lates, also fluorides, etc.. H,SO± reaction 1 ' ' Liberating these acids. ) withKHS04+Mn02,evolv- [ ing from the haloid salts, \ CI, Br, and I............ Haloid salts. / with black flux (Na2C03 + C) or / NaX03 + KCN, the volatile As, Hg. \ in tubes of very thin glass, with ] Mg wire or Na pellets, heat the Reducing / dried solid, phosphides changed ] from phosphates -f- H20, evolve / odor of decaying fish = PH3... Phosphates. sulphides obtained from sulphates \ -f- H20 or HCl on Ag, give black 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 fumes of burning sulphur = S02. a white to steel gray or red subli- mate, odor of horse radish = Se02, white fumes, fusible to colored drops = Te02.................. As2S3 oxidizes to As203 and S02; a portion sublimes in reddish yel- Evolves ^ low drops....................... colorless vapors of As203, con- denses in beautiful octahedral crystals, and on C gives a garlic odor........................... white dense fumes of Sb203, some- times accompanied by red drops of Sb2S3....................... amalgams and HgO yield Hg easily, 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. INDICATION OF Sulphides. Selenides. Tellurides. Higher arsenides, except those of Ni and Co. Higher arsenides, except those of Ni and Co. Antimony compounds. Mercury compounds. 109. Confirm the most important of these reactions by repeating these tests, and by others in addition. Remember — 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. All Sb compounds fused with Na2C03 -f- KCN yield metallic Sb, oxidizable to white Sb2Os. These reactions are also valuable for the detection of the volatile acids as HCl, HN03, H2C03, 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. It 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 coat- 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.— i light yellow.............. yellowish white........... orange yellow............ white, metal burns with a lurid flame............. J white, coating unchanged / byR.F................. I reddish brown, obtained \ only in a strong O. F... dark yellow............... orange yellow............. ■ reddish brown............. II hen hot / 3Tellow.................... 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. Hg2CL, NH4C1, and some sulphides. Pb. Bi. Cd. Zn. Sn. Ag. Pb. Bi. Cd. Zn. Sn. 58 LABORATORY GUIDE. Leaves an infusible residue; oxidize thoroughlv; INDICATION OF this residue, moistened with Co(N03)2, and again ignited, is while hot — / a blue infusible mass...... A1203, Si02. Alkaline silicates, borates, White and \ and phosphates. luminous.. / a green mass.............. SnO, bluish; ZnO and Ti02, yellowish; Sb. / a pink mass............... MgO, TaO. BaO. 1 a brown red mass......... CaO, SrO, Cr203, Sb2Os. / Some of the residues yield \ characteristic borax beads.. CuO, CoO, Fe203, Mn02, Colorea ' \ Mn and Cr may also be tested / by heating on Pt foil with NiO, and Cr203. \ KN03..................... Mn gives green mass -j- HA Yields a characteristic color to the flame — = red; Cr gives yellow (Easily reducible metals are best tested mass (test by Pb(A)2). on charcoal; and easily volatilized sub- stances on Pt wire.) Moisten insoluble salt with strong HCl. Yellow Na. Violet K, Rb, Cs, In. I Li. I Sr. Red I mixed with yellow, after intense heating and moistening in hydro- \ Ca. / emerald green................. Cu,Th. I bluish green if Se is present___ Te. Green ) pale green to yellowish green... ) yellowish green, moisten salts Ba. 1 with strong H2S04........... B. \ bluish green.................. P. 1 azure blue................... Se Pb. \ azure blue, then green.......... CuCl2. Blue ( light blue in R. F............ 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 with incrustation — Pb. Yellow.............................. Tl. White.............................. In. Malleable bead with slight incrustation— White, best with KCN............... Sn. Ag- Brittle bead with incrustation— Sb. Bi. Malleable scales or infusible powder— Red, when rubbed on a hard surface.. Cu. Au. Fe, Pt, Co, Ni. 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 aud 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 K4FeC6NG, 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 awhile precipitate with HCl and H2S04, and a yellow precipitate with K2Cr207. Cu(N03)2 gives a red precipitate with K4FeCcN6, 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 AuCls, 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 H.C4H406, 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 afterward;*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, 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 OXIDIZINci 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. as to 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. NAME OXIDE incrustation WITH AgN03 and NH3 IODIDE INCRUSTATION AND COATING IODIDE INCRUSTA-TION WITH Nil3 BLOWN UPON IT SULPHIDE INCRUS-TATION AND COATING SULPHIDE INCRUS-TATION WITH 6, Al2(OH)6. Add NaHO or KHO, and boil for Borne minutes (if not boiled, Cr and Al go in solution, and may be separated by boiling afterwards, Cr). Precipitate. Fe2(OH)8, Cr2(OH)e into two portions. Divide Portion I. Fe. Add HCl; test by KCNS, red; K4FeC6N6) Portion II, Cr. Fuse on Pt foil with KNO- thoroughly; dis solve in H20, add a few drops of HC2H302 and Pb(C2H302)2;yeJ- loio PbCr04. Solution. K2A1204. Add HOI to make it acid, then add (NH4)2C03; pre- cipitates white Al2(OH)6. Heated charcoal, on charcoal, moistened Co(N03)2, blue mass. with Note. —In nil 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. 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 K6Co2(N02),2. 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. Ni,03, olack. Filtrate. 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 -j- KN03; green mass, NaMnOi. Add HC2H302, red NaMn04. Solution. K2Zn02. Pass (NH4)2S through whUe Zn S. Heated on charcoal, moistened with Co(N03)2, green mass. Method II. In acetic acid solution. Pass H2S through white Zns. Must contain excess of H2S. Filter; render alkaline by NH4HO, 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 NH4H0 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 Cl, as follows : Fe2Cl6 + 6NaC2H302 = Fe2(C2H302)6 + 6NaCl. Fe2Cl6 -f 6NaC2H302 -f 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(OH)6; Ba, Sr, Ca, and Mg phosphates. Dissolve in hot dilute HCl and KC103. Digest to expel free"Cl7 filter out the S. Nearly neutralize with dilute solution of Na2C03, and add solution of NaC2H302 (strongly acidified with HC2H302) 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 HC2H,0, Fuse A12(P04)2 with VA parts of Si02 plus 6 parts dry Na2C03; dissolve in H20. Add (NII4)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, SrCl2, 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 NH4C1 and NH4HO; filter. Precipitate. Al2(OH)6, Cr2(OH)6, Fe2(0H)6. Test as in No. 176. Filtrate. To this filtrate add |XH4)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. O ^3 179. Separation of the Iron Group in the presence of Phosphates. (Second Method.) fi!tratriStsepfiaraeatd asTroup iv"' ^ Xn4C1' "^ NH*H° t0 ^^^ reactiou; then add (NH^S to complete the precipitation. The PRECIPITATE. and treat with VnM ^ . L tt ', ' AJ, °/ ^ >6; Pho8Phates of A1- Cr- an<* of Ba, Sr, Ca, and Mg. Wash the precipitate thoroughly, Se r^dboftoexnp H% -i ' ^tu^ rGSidUe 1S lGft'teSt " f°r C° and Ni'as in No- I7C- Si0* is sometimes present in the residue. ana dou to expel H2S; if turbid, filter again, and reserves, small portion of the precipitate, and test for phosphoric acid by (NII4)2Mo04. FIRST PORTION. Add a few drops of HN03 and boil. Solution. 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 K4F«6Ne, 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 K2C03, cool, and add an excess of BaC03; let the mixture stand, and,filter. Precipitate. No. 2. Al2(OH)6, Cr2(OH)6 [Fe2(P04)2, Fe2(OH)e, BaC03]. Boil the precipi- tate with NaHO or KHO. Precipitate. Cr2(OH),„ Fe2(OII)£ directed in No. 176. Test as Solution. K2A1204. Acidify with HCl and add NH4H0 and boil. Precipitate, Ah i Oil) 6. SECOND PORTION. Solution. BaCl2, SrCl2, CaCl2, MgCl2. Add H2S04 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 NH4H0 to alkaline reaction, and then (NH4)2S. Warm and filter. Precipitate. MnS, ZnS. Dissolve in HCl, and separate as in No. 176. Filtrate. BaCl2, MgCl2. Remove Ba, Sr, Ca with H2S04 (Portion 2 above). Precipitate Mg as phosphate. See Group IV. O 00 w o w > o O c! M b 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, HN03 with disengagement of II. They combine with Cl, 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 Cl 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 silico- 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 BaC08. 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 BrCr04. The precipitate dissolves in HCl or HN03, and is again precipitated by NHJIO. 5. Na2HP04 precipitates white BaHPQ4, soluble in acids; reprecipitatcd by NII4HO. 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 II30, insoluble in C2H60. 8. NaI03 precipitates white Ba(I03)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, NH4HO, Na2C03, (NII4)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(OH)2, solu- ble in 700 parts of H20 112 LABORATORY GUIDE. 2. Soluble carbonates precipitate CaC03 ; alkaline phos- phates precipitate CaHP04; ammonium oxalate precipitates CaC204. The precipitates are similar to those of Ba and Sr. 3. II2S04 (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 (Na2S03) 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 (NII4)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. NH4HO precipitates some of Mg as Mg(OH)2, leaving the rest as a double salt of Mg and NH4H0, as for example : 2MgS04 -f 2NH4HO = Mg(OH)2 -f (NH4)2S04MgS04. 3. K2C03 or Na2C03 precipitates basic Mg4(C03 )3(OH)2 ; boiling promotes the precipitation; ammonium salts prevent the precipitation. 4. (NH4)2C03 precipitates (in concentrated solutions) MgCOg. The addition of NII4HO promotes separation, while NH4C1 prevents the precipitation. 5. Na2HP04 precipitates (if not too dilute) MgHPO ; pro- moted by stirring with glass rod. In H20, containing NH4HO, 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 MgHAsQ4, 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 NII4('l -+ NH4HO -]- (NH4)2C03. PRECIPITATE. FILTRATE. BaC03, SrC03, CaC03. MgC03 + NH4Cl. Add I1C2II302; solution as acetates. Now add K2Cr207. Mg C 03, K2 C 03, Lic03, Na2C03, and (XH4)2C03. Precipitate. Filtrate. Yellow BaCr'O,. Dissolve in HCl; Sr(C2H302)2,Ca(C2H302)2[K2Cr207]. Make alkaline with NII4HO, and add (NH4)2C03. Test a separate por-tion for Mg by flame green. Add Precipitatks (XII4)2HP04. H2S04, white BaS04; insolullo in acids. SrC03, CaC03. Wash well, to remove K2Cr04; dissolve in HC2H302. Precipitate Of MgHP04. Con- Solution. vert to Mg(N0312; test by CO(N03)2; Sr(C2H302)2, Ca(C2H302)2. Add K2S04 (1 to 200 parts of H20). pink mass. See No. 110. Precipitate. Filtrate. SrS04. Add HCl. Test by flame; crim-son. CaS04. Add (X H4) 2 C2 04, white Ca C2 04; test by flame; brick-red. Xote. — If (NH4)2HP04 is added to the filtrate, the MgIIP04 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 NH4H0, NH4C1, and (XH4)2C03. The BaC03, SrCO ness on water bath; 3, CaC03. Dissolve in HCl; evaporate to dry-Dulverize and treat with absolute alcohol: filter FILTRATE. and wash with alcohol. MgC03, etc. 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; was!': and dissolve in HN03. Evaporate to dryness, powder, and treat with absolute alco-hol; filter and wash with alcohol. 1 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. PscCipitr.tee SrS04 and CaS04. Treat with (NH4) 2S0< + a little NH4HO. Residue. Solution. SrS04. Test as be-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)2C08 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 }'Our 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, (N1I4)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 Cl, 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 non-alkali 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 Cl passed into their solutions converts them into hypochlorites or chlorates. 7. The sulphides are formed by passing H2S 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 H20, 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. Nn4HO, Rb, and Cs 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(X0.2)30; insoluble in alcohol. The dried precipitate explodes when heated. 5. H2SiF6 produces a transparent colorless precipi ate, as follows: 2KN03 + H2SiF6 = K2SiFG + 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. H2SiFG precipitates white Xa2SiF6 ; 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 tD 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 NH4H0. (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 NH4HO—from very dilute solutions; from concentrated solutions it precipitates all the fixed alkalies, except Na and Li. 6. It forms explosive compounds with Cl = (NC13), and I = (NH2I), as follows : 2NH3 +12 = 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 NH4HO 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 sodium carbonate until completely dissolved. Evaporate to dryness, and gently ignite till all the NH4H0 is expelled, Na being substituted for NH4H0. If it blackens, it is heated with HN03. It is dissolved with H,0 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 Nn4H0 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 NH4HO, 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 Woehler's Mineral Analysis, as desirable books for this kind of work. 204. Zettnow* has arranged a scheme without the use of H2S or (NH4)2S. i The solution (a) may contain salts of: (I.) Pb, Ag, Hg; (II.) 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 (d)-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 (Ic). Dissolve PbS04 by solu- tion of (NH4)2C4H406 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., VII. 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, VII., 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 (g): 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 (li): Nitrates of Hg, Bi, Cu, Cd. 7. Residue (i): Sb205, Sn02. Test half of solution Qi) 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.\ 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 (g) 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 Fe,Clt, and digest, before neutralizing and adding BaC03. 8. Precipitate (j): Cr^OH);, Al2(OH)6, with Fe2(OH)6 and an excess of BaCG3. 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 HC2H302 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 II20, while BiOCl. tin case much Cu is present, Cd is tested as follows: The solution is strongly acidulated with IICI, 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 Ma 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 escanes; filter. The filtrate is examined for Zn by K4FeC6N6. 205. Separation 1 A J: _ 5 5 + O" 'S2 A S 0 O < Acetates, al-kali with KOII P: >-' Ag ....... Ag Ag Pr Ag Ag Pr Ag Pr Pr Ag Pr Hg2"....... — C Hg — C Hg Pr Pr Pr Pr Pr Pr Pr P' Pr Hg"......-- Hg Hg Hg Hg Pr Pr Pr Pr Pr ng Pr Pb......... PbO, Cu — C Bi Pr Cu — C Bi Pb Cu Bi Pr Cu Pr Pr Cu Pr Pb Pr Pr Pr Cu Pr Pr Pr Pr Pr Pr Pr - . + Pb+Pb02 Cu Pr — ac Pb+Pb02 Pr Pr 1 Cu......... Bi......... Cd..«...... Cd Cd Cd Cd Cd Pr Cd Pr Pr Cd Pr _ _ - x - X — As As As As As As + As _ — — Sb ........ Sb Sb Sb Sb Pr Sb Pr Sb X Sb Sb ) Sn Au Sn Au Pr Pr Pr Pr . Sn Au Pr Pr Sn Pr Au........ Au Pr Au Au k Pt......... Pt Pt Pt Pt Pt Pt Pt Pr Pr Pt Pt ] Mo........ Mo,03 Mo203 Mo203 Mo,03 Mo2Oa Mo203 Mo203 Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr 1 Cr1" Pr 1 Al ...... Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr 1 e Ur......... — d Ur304 + X Mn02 - d Ur304 + X Mn02 Pr - X Ur304 1 Mn Mn02 Pr Pr Pr Pr Pr Pr Pr 1 Zn......... Zn Zn Co Ni Pr Pr Zn Pr Pr Pr Pr Zn Co Ni Pr Pr Pr Pr Pr Pr — c Zn Zn Pr Pr V Co...... Ni ..... Ni 1 Ba 1 Sr........ Ca......... Mg Pr Pr Pr Na......... K.......... 1 * A. C. J., I., r>. i Classen. a A. P. S., November, 1878. b A. P. S., November, 1887. c A. V. j., VIII., by Electrolysis. /; v. Ta "3 V, O 1 5 a Eh IJ 'A 5 T A "5 So 1« 5 a a '3 o 3 CO to a A* + So — _ _ _ Pr Pr Pr Ag Ag Ag Ag Pr Ag Ag Ag Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Hg Hg Hg Hg ns Hg Pr Pr Ph -p,* -, + Pb+Pb02 Cu - , + Pb+Pb02 Cu — + Pb+PbO, Cu -, + Pb+Pb02 Cu Pb Cu Pb4"Pb02 Cu Pr Cu Pr Pr Pr Cu Pr * Bi Pr Bi Bi Bi Bi Pr Pr Pr Pr ~cd* - X Cd — C Cd Cd Cd Cd Cd Cd Cd As As As As As As - x _ _ _ ?h Sb - X Sb Sb Sb Sb Sb Pr Pr Pr Pr Sn Sn Sn Sn Sn Sn Pr __ AU Pr - X Pr Au Au • Au Au Au Au Pr _ Pt Pt Pt Pr Pt Pt Pt Pt Pt Pt Pr — — _ _ — _ * Mo2Oa Mo203 Mo203 Mo203 Mo203 Mo203 Mo203 - x _ — + Pr Fe Fe Fe Fe Fe Fe+Fe2(OH)6 Fe Fe Pr °r 4- X Cr2 (0H)6 Pr Pr Pr 4 X Al2(OH)6 Pr Pr 4- X Ur(0H)4 Pr Pr Ur304 Ur304 4-Mn02 ?r - X Mn02 Pr 4-Mn02 r,n - X Zn - X Co - X Ni Pr Pr Pr Pr Zn Co — C Zn Co Zn Co Zn Zn Co Zn Co Zn Co Zn Pr + CoO NiO Co Pr Ni Pr Pr Pr Ni Ni Ni Ni Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr 3. rf From neutral, e Uranium solutions should be electrolysed at about 89° —90° C. on a water bath- ELECTROLYSIS. SEPARATION BY ELECTROLYSIS. 206. Any form of battery may be used, or the current from dynamo. The current should be of about such strength as that afforded by two Grove cells. Keep zincs clean and well amal- gamated. Let all connections be clean and tight. Use a deep and rather narrow platinum cup to receive the element deposited, in the majority of cases. A shallow platinum dish, however, gives best results for bismuth, and in such few cases where the deposit does not adhere very firmly to the platinum. Use a platinum spiral made of rather heavy wire for the other elec- trode. _i_ The plus sign (4~) over an element, e. g., Pb02, indicates that the deposition takes place at the positive pole (platinum pole of a Grove cell); the minus sign (—), e. g., Ag, indicates that the element separates at the negative (zinc) pole. Pr indi- cates that the reagent gives a precipitate. A blank space, as under HN03 for Fe, indicates that the, element is not thrown out of that solution by the current. Whenever a precipitate is formed, filter off before electrolyzing, and convert to a solution, if possible, from which the current will throw out the element. The following will illustrate the use of the table: A nitric acid sojution of Hg, Pb, Fe, Zn, Co is to be separated. Pass current. Hg appears at the — pole; Pb02 at the -{- pole; Fe, Zn, Co remain in solution. Remove the liquid to a beaker; add an excess of KOH, filter, and after removing the Hg (by strong HN03) from the crucible or platinum dish, place therein the KOH solution of Zn and pass current. Zn separates at the — pole. Dissolve the Fe2(OH)6 and Co(OH)2, formed by KOH, in H2S04 ; add excess of NH4OH. Co(OH)2 goes into solution; Fe2(OH)6 separates again. Filter; electrolyze the cobalt solu- tion. Co separates at the — pole. Dissolve the Fe2(OH)6 in citric or succinic acid and electrolyze. Fe separates at the negative pole. CHAPTER IV. SEPARATION OF THE ACIDS. 207. The examination of the bases should always precede the examination of the acids, except H2S04, HCl, and HNOs. The reagents added in the separation of the bases must be borne in mind when testing for the acids, or the original solution must be examined. We may find, while searching for the bases, As203, Sb203 C02, Si02, Cr03, H2S, H3P04, H2C204, H2S03, and some others. S, Se, and Te give a hepar on silver coin; H3P is self- enkindling. Certain bases form with certain acids, compounds insoluble in water. H2S04 formfe with Ba, Sr, Ca, and Pb, difficultly soluble sulphates; HCl forms with Ag and Pb, corresponding chlorides; P205 forms with Ba, Sr, Ca, and Mg, corresponding phosphates. See the tests for the bases for example. Heating separates the acids into two great groups: organic and inorganic. Most of the organic acids blacken when h ated to redness; the most noted exceptions are acetic, formic oxalic and the volatile organic acids and their salts. The chlorides of Pb, Ag, Hg, Sn, and Sb, and the sulphide of As are not easily decomposed by H2S04. C02, S02, H2S, HCl, HF, and HN03 are liberated in thp free state, while HI, HBr, HCN, Cr03, HC103, and H2C204 arc- decomposed into colored or colorless gases. The reaction may be modified if there is more than one acid in the substance to be examined. SEPARATION OF THE ACIDS. 127 Deflagration on charcoal indicates acids rich in oxygen; as, chlorates, nitrates, permanganates, chromates, bromates, iodates, etc. Should deflagration take place on charcoal, great care should be used in afterwards treating a portion of the substance with H2S04, as explosions may occur. 208. If not in the solid state, evaporate the solution to dryness and heat in a small tube with four times its weight of strong sulphuric acid, or bisulphate of potassium. 1. Xo action ensues. It may be silicic, selenic, phosphoric, tungstic, iodic, molybdic, sulphuric, boric, titanic (arsenic and chromic found among the bases). 2. Vapors are evolved. (a.) Colored gases. Indicates Violet vapors, coloring starch paste blue........Iodic acid. Reddish vapors, coloring starch paste orange .. Bromic acid. Greenish-yellow explosive gas....................Chloric acid. Yellow vapor; smell of chlorine (C120)..........Hypochlorous acid. Brownish-yellow, irritating vapors...............Nitrous and nitric acid. (b). Colorless gases. With odor of vinegar..........................Acetic acid. With odor of rotten eggs.......................Hydrosulphuric acid. j Sulphurous acid. With odor of burning sulphur................j Thiosulphuric acid. j Cyanic acid. With odor of peach kernels..................-j Ferrocyanic acid. With odor of burnt sugar..................... Tartaric acid. Irritating odor, gives white fumes with NH,.. .Hydrochloric acid. Fuming gas, etches glass........................Hydrofluoric acid. Evolves oxygen, changes to brown or green---Chromic acid. Odorless, gives turbidity with lime water.......Carbonic acid Eurns with blue flame and renders lime water turbid........................CO + C02 = Oxalic acid. Some of these acids are best liberated by mixing the sub- Btance with MnO, and then treating with H2S04, or KHS04. 128 LABORATORY GUIDE. Dilute H2S04-|-Zn colors the fluid—* Indicates Violet or lilac.................................Titanic acid. Blue.........................................Tungstic and vanadic acid. Blue, then green and brown..................Molybdic acid. Blue, then muddy or brown.................Tantalic and niobic acid. Green........................................Chromic acid. 209c Inorganic Acids. The acids can not be separated into groups with that accuracy with which we separate the bases, yet their identification is facilitated by grouping them. If the solu- tion is acid, neutralize with NH4HO; if alkaline, neutralize with HN03. The acids of As, Crf etc., have been detected as bases by H2S. Many of the bases can be precipitated by boiling the solu- tion with an excess of Na2C03, and filtering. The acids will be present as soda salts. This method should be used only when time is a consideration. 210. ( 1.) BaCl2, in the presence of HCl, precipitates sul- phuric (H2S04) and hydrofluosilicic (H2SiF6) acids. Sulphur and Sulphuric Acid. Sulphuric acid dissolves most metals, but is not as generally applicable as HCl or HN03. With evolution of H: Zn, Al, Fe, Mn, Sn, Mg; with evolution of S02 : Hg, Ag, Cu, Bi, and Sn. The sulphates of Ba, Pb, Sr, and Ca are insoluble or sparingly soluble in water, and the soluble salts of these elements are used for tests for H2S04. Sulphuric acid liberates most other acids, and forms sulphates with their bases. The salts of Sn, Hg, Ag, and Sb are liberated with difficulty. See No. 22. Free H2S04 may be detected in sulphates by means of cane sugar, as follows : (1) Concentrate the liquid on the water bath (in a porcelain dish), add a fragment of white sugar; a greenish- * Take a small beaker, add the supposed acid; now add H2S04 and Zn as in making H. The nascent H reduces the acid, and changes the color of the solution as above indicated. SEPARATION OF THE ACIDS. 129 black residue indicates H2S04. (2) The alkaloid, veratrine. gives, with free H2S04 (best when heated), a red color; more delicate than test No. (1), but more expensive. 211. Tests: — 1. To detect S in albumin, take a solution of Pb(C2H302)2, add NaHO until clear; add the albumin to the solution, and boil (black colored sulphide). 2. In the dry way, see No. 107, hepar test. 3. An alkaline solution of sulphur with nitroprusside of sodium gives a violet color. See No. 95. 4. In the wet way, see tests under No. 22. 5. The normal sulphates of the alkalies of Ca, Mg, Ag, Mn are neutral to litmus paper. The sulphates of the metals of the alkalies, alkaline earths, and PbS04 are not decomposed when heated to redness (MgS04 an exception). The sulphates of Co, Ni, Cu, Cd, Zn, and Ag require a great heat to decompose them. Sulphates fused with Na2C03 on porcelain without reducing agents do not stain a silver coin. See No. 107 (distinction from sul- phides). 212. Hydrofluosilicic acid. See No. 15. 213. Tests: — 1. BaCl2 precipitates white BaSiF6. 2. KC1 precipitates gelatinous K2SiF6. 3. H2S04 decomposes it, liberating HF, which etches glass. By heat, it is resolved into fluorides and silicon fluorides : BaF2 + SiF4. 4. NH4HO in excess precipitates silicic acid, with the forma- tion of ammonium fluoride. 5. Heated with microcosmic salt, no skeleton bead is formed, because all of the silica volatilizes as SiF4. The Na salts are much like K in No. 2 above, being diffi- cultly soluble. * 130 LABORATORY GUIDE. 214. (2.) BaCl2 in neutral solutions precipitates phosphoric (H„P04), boric (H3B03), oxalic (H2C204), hydrofluoric (HF), carbonic (H2C03), silicic (H4Si04), sulphurous (H2S03), hypo- sulphurous (H2S203), arsenious (H3As03), arsenic (H3As04), iodic (HI03), and chromic acids (H2Cr04). 215. Phosphoric acids. There are three modifications, the ortho, pyro, and meta phosphoric, having three, two, and one mole- cules of H20 combined with P205. 216. Orthophosphates. Tests: — 1. BaCl2 precipitates white BaHPQ4 (from dimetallic phos- phates), soluble in HCl and in HN03, sparingly soluble in NH4C1. 2. CaCl2 precipitates (in neutral or alkaline phosphates) white CaHP04, soluble in HC2H302 and in NH4C1. 3. "Magnesia mixture" (No. 70) precipitates white MgNH4PQ4, soluble in NH4HO, HC2H302, and slightly soluble in NH4C1. 4. AgN03 precipitates light-yellow Ag3PQ4, soluble in HN03 and in NH4HO. 5. (NH4)2Mo04 4-HN03 gives a yellow precipitate of ammonium phosphomolybdate of a variable composition. The pre- cipitate is soluble in an excess of phosphoric acid, and is pre- vented by organic substances like tartaric acid. 6. Albumin, or gelatin, is not precipitated, nor by solutions of orthophosphates mixed with acetic acid. 7. In the dry way, see No. 107. Dissolve the phosphate in a borax bead, and add tungstate of sodium; blue in reduction flame. 8. Fe2Cl6 in the presence of a small quantity of HCl or HN03 and a quite large excess of NaC2H302 gives a yellowish- white gelatinous precipitate of Ff>2(P04)2 ; an excess of Fe0Cl ■—-------- 2 6 gives a red color, and is slightly soluble. SEPARATION OF THE ACIDS. 131 217. Pyrophosphates. Tests: — 1 BaCl2 fails to precipitate the free acid, but precipitates its salts, Ba2P207 ; soluble in HCl. 2. AgN03 precipitates white Ag4P207, soluble in HN03 and in NH4HO. The precipitate forms best by the addition of an alkali. 3. Ammonium molybdate with nitric acid does not give a precipitate until orthophosphate is formed. Most pyrophosphates of the heavy metals (Ag an exception) are soluble in alkali pyro- phosphates (distinction from orthophosphates). MgS04 precipitates Mg2P207, soluble in excess of either solution. NH4HO fails to precipitate it from these solutions. On boiling, it separates again; by this reaction you can detect pyro in the presence of phosphoric acid. 4. White of egg or albumin is not precipitated by solution of the acid, nor by a solution of the salts, when mixed with acetic acid. 218. Metaphosphoric acid. "Magnesia mixture" gives no precipitate; albumin gives a precipitate. AgN03 precipitates white AgPQ3, soluble in alkali metaphosphate solutions; distinction from pyrophosphates. It gives no precipitate with ammonium molybdate. Metaphos- phates do not coagulate albumin unless acetic is added. Fusion with Na2C03 converts meta and pyro into orthophos- phates. 219. Boric or boracic acid (H3B03). See No. 4. 220. Tests: — 1. BaCl2 and CaCl2 precipitate white Ba3(B03)2 and Ca3(B03)2. 2. AgN03 precipitates white AgB03 ; normal borates form in part brown silver oxide. 3. When the free acid is moistened with glycerin and burned, it gives a green flame. When burned with alcohol, green flame. When moistened with H2S04, green flame. 132 LABORATORY GUIDE. 4. The free acid turns turmeric paper brownish red, becoming more intense when the paper is dried. When mixed with HCl to acid reaction and dried as before, it becomes red. 221. Oxalic acid. The oxalic acid is here placed with the inorganic acids. See No. 18. 222. Tests: — 1. H2S04 and heat decompose it into CO, C02, and H20. If the mixed gases are passed into NaHO, the CO which escapes burns with a blue flame. 2. BaCl2 precipitates white BaC204, soluble in HCl or HN03. 3. AgN03 precipitates white Ag2C204, soluble in NH4HO and in hot HN03. 4. All the soluble Ca salts precipitate white CaC204, soluble in HCl and in HN03, but nearly insoluble in oxalic acid and acetic acid; ammonium hydroxide promotes the precipitation. 5. When the acid or oxalates are mixed with MnQ2 (free from C02) -f- H20 -f- a few drops of H2S04, C02 escapes: Mn02 -f K2C204 -f 2H2S04 = MnS04 + K2S04 -4- 2H20 + 2C02. Oxalic acid is a good reducing agent. The oxalates of the alkaline metals are soluble in water; the rest are almost insoluble in water. The oxalates of the easily reducible metals, as Ag, Cu, Hg, when roasted, give off C02 and leave the metal in the metal- lic state; the less reducible metals, as Zn, Mg, are left as oxides. and give off CO and C02. Ferrous oxalate is yellow. 223. Hydrofluoric acid. See No. 14. The fluorides of the alkali metals are soluble in H20. The fluorides of the alkaline earths are sparingly soluble in H20. The fluorides of Ag, Hg, are readily soluble; of Cu, Zn, Pb, and Fe, sparingly soluble. 224. Tests : — 1. BaCl2 precipitates white BaF2, soluble in HCl and HN03. SEPARATION OF THE ACIDS. 133 2. CaCl2 precipitates, after some time, CaF2; NH4H0 hastens the precipitation. It is insoluble in alkaline fluids; slightly soluble in HCl or HNOg in the cold. Brazil-wood paper is turned yellow by HF. 225. Carbonic acid (H2C03) has not been isolated. C02 is commonly called carbonic acid. The carbonates of the alkalies are soluble in water. The carbonates of the other metals are insoluble, except a few bicarbonates. All strong acids decompose the carbonates, with effervescence of C02, which reddens moist litmus paper. The metallic carbonates are insoluble in alcohol [ (NH4)2C03 an exception]. The carbonates of the alkalies are not decomposed by heat; the carbonates of the alkaline earths are slowly decomposed at a white heat; all other carbonates are readily dissociated. Basic acetate of lead, solutions of Ba(OH)2 and Ca(OH)2, are delicate tests. See No. 106. 226. Silicic acid. See No. 116, in the dry way. It can be obtained by passing silicic fluoride into water: 3SiF4 + 4H20 = H4Si04 + 2H2SiF6 ; or by passing C02 into a solution of a soluble silicate: Na4Si04 -f 4H20 + 4C02 = H4Si04 -f 4NaHC03. Silicates are determined by the separation of Si02. Only alkaline silicates are soluble in water. Silicic acid is soluble in mineral acids ; silicic anhydride is insoluble. When an alkaline silicate is acidulated with HCl (or HN03) and evaporated to dryness on the water bath, and this operation repeated once or twice, the silica is in an insoluble form as Si02- See No. 90. Solutions of alkaline silicates are decomposed by ail acids. Mix one part of Si02, or a silicate, with two parts of cryolite and four to six parts of H2S04, in a platinum crucible, and heat cautiously, holding near the surface a thick platinum wire, in the loop of which a drop of water is held. A white pellicle of silicic acid is formed on the drop of water. 227. The remaining six acids of this group are precipi- tated or decomposed by the group reagents for the bases. 131 LABORATORY GUIDE. Ag Group. H2S03 decomposed by HCl with evolution of S02. H2S203 decomposed by HCl with evolution of S02 and separation of S. As Group. H3As03 precipitated by H2S as yellow As2S3. H3As04 precipitated by H2S as yellow As2S3. HI03 decomposed by H2S with formation of an iodide and separation of S. Fe Group. H2Cr04 precipitated by (NH4)2S as Cr2(OH)6. 228. Sulphurous acid. The sulphites of the alkalies are soluble in water. The normal sulphites of the other metals are sparingly soluble. Sulphurous acid is oxidized to sulphuric acid by the air. It reddens and bleaches litmus. It is a good reducing agent. The sulphites are easily decomposed by other acids, liber- ating S02 (carbonic, boracic, and, in some cases, hydrosulphuric acids are exceptions). 229. Tests:— 1. BaCl2 precipitates white BaS03, soluble in HCl; distinc- tion from sulphate. 2. H2S03 and Zn + HCl givellTsT Test by odor. 3. AgN03 produces a white precipitate, Ag2S03 ; blackens on heating; easily soluble in dilute HN03 or in excess of alka- line sulphite. 4. Sulphites, when mixed with SnCl2 -f- HCl, give a yellow- ish precipitate of SnS2. 5. Sulphurous acid -|- HCl and a clean strip of Cu when boiled together, blackens the Cu. 6. Its reducing action upon colored salts'; as, chromic, per- manganic. It decolorizes iodized starch, and the blue precipitate with K3FeC6N -f- Fe2Cl6. SEPARATION OF THE ACIDS. 135 7. If a solution of an alkaline sulphite, to which acetic acid is added (just sufficient for acid reaction), and ZnS04, with a small quantity of sodium nitroprusside, the fluid acquires a red color; if the quantity is small, the color is hastened by the addi- tion of a small quantity of K4FeC6N6. Thiosulphates do not show this reaction. 230. Thiosulphuric or hyposulphurous acid. It does not exist in a free state. Most of its salts are soluble in water. It gives white precipitates with Hg, Pb, and Ag, which soon become yellow, brown, and black. The reactions in general are similar to sulphurous acid. Since BaS04 is insoluble, BaCl3 separates sulphates from sul- phites and thiosulphates. CaCl2 forms a precipitate with sul- phite; no precipitate with thiosulphates. The reactions with HCl and AgN03 are different; the HCl liberating S02 and S, the silver precipitate being redissolved by thiosulphate, and subsequent blacking of the precipitate. When thiosulphates are treated with iodine, an iodate and a tetrathio- nate are formed : 2BaS203 -4- I2 = Bal2 -|- BaS406. Sulphites do not give this reaction. 231. Iodic acid. It is made by the action of HN03, or other oxidizing agent, upon iodine. It is a white crystalline solid. It is decomposed by heat into I and 0; it is readily solu- ble in water. The alkaline iodates are the only salts of this acid which are freely soluble in water. Iodates are decomposed by reducing agents. The alkali metals form acid iodates. P reduces iodates to iodides; tartaric acid gives a yellow zone when iodates and iodides are together. 232. Tests: — 1. BaCl2 precipitates white Ba(I03)2, soluble in HN03. 2. AgN03 precipitates white AgI03, soluble in NH4HO, but only sparingly soluble in HN03. 136 LABORATORY GUIDE. 3. SO2 and H2S decompose it. Test for free I by starch or with bisulphide of carbon. An excess of either (S02 or H2S) converts the acid into hydriodic acid. » 4. If an iodate and an iodide are mixed and treated with a strong acid, they react upon each other: 5HI -f HI03 = 61 + 3H20. Test the free iodine. 5. Iodates give off oxygen, and, in some cases, iodine and oxygen. Iodides do not give off oxygen. Morphine reduces iodic acid with separation of iodine. Most of the iodates are insoluble in alcohol; separation from iodides. 6. Salts of lead precipitate white Pb(I03)2. 7. Fe2Cl6 precipitates yellowish-white Fe2(I03)6, soluble in an excess; boiling decomposes it. 233. (3.) Acids precipitated by AgN03 and not by BaCl2 : Hydrochloric (HCl), hydrobromic (HBr), hydriodic (HI), hydro- cyanic (HCN or HCy), hypochlorous (HCIO), nitrous (HN02), hydrosulphuric or sulphuretted hydrogen (H2S) 234. Hydrochloric acid. See No. 12. Free chlorine is told by the red color it gives when added to ferrous salt and potassium sulphocyanate; also by the blue color which it gives to a mixture of KI and starch paste. The normal chlorides are soluble in water, except those of the first group (Ag, Pb, Hg). Chlorine gives, with a phosphorous salt bead on a platinum wire, CuO dissolved in it to make it opaque, a blue colored flame, due to CuCl2. When a solid chloride is heated with K2Cr204 -4- strong H2S04, a brown gas, changing to red drops, chlorochromic acid (Cr02Cl2). Add NH4H0 in excess, yellow (NH4)2Cr04. On the addition of an acid, the yellow changes to a reddish- yellow (NH4)2Cr207. SEPARATION OF THE ACIDS. 137 235. Hydrobromic acid. See No. 11. 236. Tests: — 1. AgN03 precipitates yellowish-white AgBr; changes to gray; soluble in KCN, sparingly in NH4HO, insoluble in HX03. 2. HN03 decomposes HBr and the bromides (except Ag, Sn, and Hg). 3. Mn02 -J- H2S04 -J- RB,r = Br; recognized by its odor 4. Cl passed through a solution of a bromide, decomposes it, liberates Br and colors it yellow. 5. Bisulphide of carbon, chloroform, or ether, gives, with free Br in solution, reddish yellow; free Br colors starch solution orange yellow. 6. The solubility of the bromides is intermediate between the chlorides and iodides. The general statement can be made, that all bromides are soluble in water, with the exception of the first group of bases. 237. Separation Of Cl, Br, and I. There are quite a num- ber of methods for separation of Cl, Br, and I. 238. Tests: — 1. A solution of the mixture is placed in a large test tube? a little Mn02 and water; add one drop of dilute (one to ten) H2S04. A brown color indicates I. Boil; violet vapors are given off. When these cease, then add 2 C. c. of H2S04, and boil; brown vapors of Br. Boil till brown vapors cease. When cold) add an equal volume of H2S02 and heat; green vapors indicate Cl. 2. The solvent action of NH4HO on the chlorides (AgCl, AgBr, Agl) (see No. 135) separates the chlorides from the iodides. A hot, concentrated solution of (NH4)2C08 dissolves the chlo- rides, but only dissolves traces of the bromides, and none of the iodides. 138 LABORATORY GUIDE. 239. Hydriodic acid. See No. 10. 240. Tests: — 1. A solution of one part of CuS04 and two and one-naif parts of FeS04 precipitates from neutral solution dirty-white, Cu2I2. The precipitation is hastened by NH4H0. Chlorides and bromides are not precipitated by this reagent. 2. The CuO bead is similar to the chloride No. 234. The iodides in analysis are identified by liberated iodine. 3. Lead salts precipitate bright-yellow Pbl2. 4. Ozone, chlorine, bromine, nitric acid, sulphuric acid, acidulated potassium nitrite, and chromates, decompose iodides. 5. Mn02 -f H2S04 + RI =T 241. Hydrocyanic acid. See No. 13. The solution is feebly acid to test paper. The cyanides of the alkaline earths, alkalies, and mercuric cyanide are soluble in water. 242. Tests: — 1. AgN03 precipitates white AgCN. The solubility is very like AgCl. i 2. Mercurous nitrate (HgN03) precipitates gray Hg, and Hg(CN)2 and Hg(N03)2 in solution. 3. Copper salts precipitate yellowish-green Cu(CN)2, soluble in an excess of the reagent. 4. Lead salts precipitate white Pb(CN)2, soluble in a large excess of the reagent; precipitated on boiling. 5. HCN in the presence of K^FeC^N^. Acidify with H2S04 or H2C4H406, shake with ether, which takes up only HCN, but not K4FeC6N6. Confirm by other tests. 6. Blood red coloration on heating an alkaline-cyanide solu- tion with picric acid. 7. Soak filtering paper in freshly prepared (three to four per cent.) tincture of guaiacum, let dry, and now moisten it with a one-fourth per cent, solution of CuS04 : blue color (1: 300,000). SEPARATION OF THE ACIDS. 139 8. Take a little KHO and FeS04, and warm the mixture*for a short time, a very little Fe2Cl6, and the whole slightly acidu- lated with HCl to dissolve the ferrous and ferric hydroxides, when Prussian blue will appear if HCN is present: (a) 2KCX + FeS04 = Fe(CN)2 -f K2S04. (b) Fe(CN)2+ 4KCN = K4FeC6N6. (c) 3K4FeC6N6 + 2Fe2Cl6 = Fe4(FeC6Nfi )3 + 12KC1. 9. A solution of HCN is added in excess to one part of KHO and three parts of finely pulverized HgO, which dissolves in a solution of the alkalies only in the presence of HCN. This is regarded by Fresenious as a positive test for HCN. 243. Hypochlorous acid. See No. 92. 244. Tests: — 1. AgN03 precipitates white AgCl. 2. Concentrated solutions when boiled give off 0. 3. Pb(N03)2 precipitates white PbCl2; changes to orange red, and .finally brown Pb02. 4. MnCl2 precipitates dark-brown MnO(HO)2. 5. Indigo and litmus solutions are decolorized on the addi- tion of this acid. All hypochlorites are soluble in water, and are quite unsta- ble, whether solid or in solution. 245. Nitrous acid. See No. 86. 246. Tests: — 1. Dilute H2S04 with iodide of potassium-starch paste: blue color. 2. (a) Acidify with H2S04, add aniline-sulphuric acid; a few minutes after, a few drops of a clear solution of naphthylamin sulphate: deep red color, (b) Meta-diamidobenzal: yellow to brown color. 140 LABORATORY GUIDE. 3. Evaporate nearly to dryness, and rub with a few drops of a solution of sulphate of aniline, odor of carbolic acid. Carbolic acid gives, with HN02, red, brown, and then green colors. 4. Heat a mixture of one part solution HgN03, one part of carbolic acid (1: 100), and three parts H20 to boiling, and add ten parts of the liquid to be examined; red color indicates nitrous acid (1:500,000). 5. Pure HN02 is hardly known. Indigo solution is bleached by nitrites. Nitrites liberate iodine from KI, decolorize K2Mn2Od when acidulated with H2S04. With very dilute acids, nitrites form brown ring, 2(FeS04)2NO, with a crystal of FeS04. Nitrates do not give these reactions. The nitrites are all soluble in water; AgN02 sparingly soluble. Forms reddish-yellow, sparingly soluble, (KN02)6Co203(N203)2. Heated on charcoal, nitrites deflagrate like nitrates. 247. Hydrosulphuric acid (sulphuretted hydrogen). See No. 16. Described under group reagents. 248. (4.) Acids not precipitated by any reagent: Nitric (HN07), chloric (HC103), and perchloric (HC104). 249. Nitric acid. See No. 17. 250. Tests — 1. Molybdic acid with sugar gives blue color. 2. Heat one part of carbolic acid and four parts of sulphuric acid: when cold, boil nitrates (as water residue): gives deep- brown to red color. 3. Nascent H and HN03 form ammonia. 4. Cu with HN03 gives N02, red fumes. 5. Nitrates deflagrate on charcoal. Free nitric acid is distinguished from nitrates by (1) giving the brown with ferrous salt; (2) by coloring woolen threads yellow. A feather can be used as a test in this case. In most cases in nitrates, H2S04 must be used to liberate the HN03. SEPARATION OF THE ACIDS. 141 251. Chloric acid. See No. 81. 252. Tests : — 1. H2S04 decomposes chlorates, C1204 ; greenish-yellow gas, explosive. Use small quantities. 2. A solution of a chlorate with H2S04 and a solution of sulphite of soda bleaches indigo. The S02 deprives chloric acid of its 0, and the liberated Cl bleaches the indigo. 3. Heat chlorate with KCN on Pt foil; violent deflagration ensues. Use small quantities. 4. If chlorates are treated with HCl, as follows : 2HC103 -f 2HC1 = 2H20 -f 2C1 -j- C1204. 5. Solution of sulphate of aniline (containing toulidin) mixed with two volumes qf H2S04. Intense blue color indicates chlorates. 6. AH chlorates are soluble in water. Chlorates, when strongly heated, give off oxygen and become chlorides. This reaction enables us to separate chlorates from nitrates by AgN03. 253. Perchloric acid. Tests: — 1. All perchlorates are soluble in water; most of them freely. Potassium salts precipitate white KC104, sparingly solu- ble in water, insoluble in alcohol. 2. Ba and Ag salts are not precipitated. 3. H2S04 (in the cold), HCl, S02 fail to decompose the aqueous solution. Indigo is not bleached (difference from all other acids of chlorine). 4. On ignition, perchlorates act like chlorates, but are more explosive. 254. Acids identified by ferric chloride (Fe2Cl6). 255. Tests: — (a) A precipitate is formed. 1. Hydroferrocyanic, blue (in the presence of free HCl). This is decomposed by KHO into Fe203 and K4FeC6N6. 142 LABORATORY GUIDE. 2. Phosphoric acid, yellowish white; insoluble in HC2H302, soluble in HCl, Fe2Cl6, and Fe(C2H302)3. If free HCl is present, it should be neutralized by adding NaC2H302 before adding H3P04. 3. Tannic acid, dark blue (ink). The origina. compound precipitated by gelatine. 4. In neutral solutions, boracic acid yellowish; benzoic and succinic acids give light brown. Confirm. (b) A color is produced in the presence of HCl. 5. Hydroferricyanic acid, brownish; ferrous salts produce blue precipitate. 6. Sulphocyanic acid, blood red; not removed by HCl; . removed by HgCl2. In neutral solutions, the color vanishes on adding HCl. 7.» Acetic acid, reddish brown. Test ether'by making acetic ; i. e., add H2S04 -j- C2H60, and heat. 8. Formic acid, reddish brown. When the original solution is treated with AgO or HgO, C02 is evolved. 9. Sulphurous acid, reddish brown; on boiling, the color vanishes. When HCl is added to the original solution, S02 is evolved. 10. Meconic acid, blood red; unchanged by AuCl3. 11. Gallic acid, black. The original solution is not precipi- tated by gelatine. 256. Acids decolorizing indigo solution. (a) Alone, without addition of an acid. 1. Chlorine, bromine, hypochloric, chlorous, hypochlorous acids, hypochlorites, strong nitric acid, alkaline metallic sul- phides, and caustic alkalies. 2. On the addition of HCl or II2S04, and heating: Chlo- rates, nitrates, iodates, bromates, manganates, and the ic oxides of manganese and lead. Color water with a few drops of indigo solution, and add the substance drop by drop until the change takes place. 257. Separation of some of the Organic Acids. Remove the metals of the diflferent groups, neutralize the solution with NH.HO, add CaCl2, shake well, and let stand thirty minutes. PRECIPITATE. Oxalic and tartaric acids. Wash the precipitate and add cold NaHO, and filter. Residue. CaC204. Con- firm by No. 222. Filtrate. H2C4H40a. Confirm by No. 260 and No. 24. FILTRATE. Add to the filtrate three volumes of strong alcohol, and filter. Precipitate. Citric, malic, and succinic acids. Wash with alcohol, dis- solve in HCl, add NH4HO, boil, and filter. Precipitate. Calcium citrate. Dissolve in IICI, and test by heating with H2S04, when C02, CO" are given off without darkening; on further heating S02, the mixture blackens. See Nos. 262 and 6. Filtrate. Malic and succinic. Add alcohol, filter, wash, and dis- solve the residue in HN03; evaporate to dryness on the water bath. Add Na2C03 solution, boil, filter, neutral- ize with HCl, heat, and add CaS04 to a portion: a white precipitate; malic acid. Con- firm by No. 265. To the re- maining portion add Ca('l2 in excess, filter, add alcohol to the filtrate: a gelatinous pre- cipitate; succinic acid. Con- firm by No. 268. Filtrate. Benzoic acid and others. Heat to expel alcohol, neutralize exactly with HCl, and add Fe2Cl6; filter. Precipitate. Ferric benzoate. Wash the precipitate. Warm with NII4H0; filter; evaporate to near dryness. Add HCl and obtain shin- ing crystals of benzoic acid. Confirm by No. 270. Filtrate. Acetic, formic, etc. Examine for these in the original solu- tion . See No. 278 for acetic; No. 280 for formic. Uric, gallic, and tannic acids are sep- arately tested. Gal- lic and tannic can be separated by dia- lysis. CO > H I— O o H w o o 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 (H3C6Hs07 or Hglj ), 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 -f K2C204 -4- 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 + K2C204 -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 -4- 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 KoCr207 : yellow color (succinic acid); green, without odor (citric acid); green, with fruity odor, malic acid. 2. Precipitate tartaric and citric acids by CaCl2 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 -j- 2AgBr; also, by nitrous acid on asparagin, and' on aspartic acid: (a) C4H8N203 4- 2HN02 = C4H605 4- 2H20 4- N4. (b) 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 NH4H0. 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 NH4HO in slight excess when mixed with ten volumes of alcohol, while malate of ammonium goes into solution. 2. AgN03 precipitates white Ag2C4H4Q5; 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 H2S04. Heated in the air, succinic acid burns with a blue flame, free from soot. Most of the succinates are soluble in H„0. 148 LABORATORY GUIDE. 268. Tests: — 1. CaCl2 gives no precipitate, but on adding alcohol a gelatinous precipitate of CaC4H404 ; 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, BaC4H404. 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(C2H302)2 precipitates (from alkali benzoate, not from free acid) doeculent 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 4- C2H5N02. 271. (3.) Acids precipitated by AgN03 in strong neutral solutions: Ferrocyanic (H4FeC6N6), ferricyanic (H3FeC6N6) sulphocyanic (HCNS), acetic (HC^^O^, 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^FeC6X6 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 fcrro 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. AgN03 precipitates orange Ag3FeC6N6, insoluble in dilute UNO., 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. Sulphocyanates 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). 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 Cl, 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 4~ 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 bv the fermentation of milk, cane, and grape sugars. It is also found in vegetable matters that have turned sour. Sarcolactic or \, 152 LABORATORY UUIDE. paralactic acid exists in muscular flesh. With bases, it forms 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 4- 2H20 4- H2S04 = NH4HS04 + 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 odo^r 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. IIg. Insol. in (NH4)2S, and in HNO3. Sol. in potassium sul-phide. First white, then yellow and red brown to black, HgCl2 -r x HgS. Insol. in HNO3. (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, Hg2Cl2. Sol-uble in HN03,and in aqua regia as HgCl2— blackened by NH4HO. Soluble in 12,000 parts boiling H2O. Sol. in NH4C1. Sodium hydroxide, (NaHO.) 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 brojyn, Ag20. Sol. in excess—Sol. in HN03,HC2H302, and NH4HO. Black, mercuroso-ammonium salts.Sol. I11HNO3. 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.) 1 Grayish white, Ag2C03. Sol. in NH4HO. Yellow precipitate basic salt,soon be-comes black. Red brown, basic salt + x HgO. By heating becomes yellow oxide, HgO. Sulphuric Acid, White, AgaS04. Sparingly sol. in ex-cess, and in H2O. White, Hg2S04. Sol. 500 parts H2O. (H2 SO4) ► REACTIONS. Group I—Continued. 157 Lead. Black, PbS. Insol. in (NH4)2S. Sol. in HNO3. White,PbCb. Sol.in 135 parts H2O— 30 parts hot H2O. Insol. in alcohol, and NH4HO. Copper. Brown black, CuS. Sol. in 950,000 parts H2O. Sol. in HNO3, Sparingly sol. in (NH4)2S-Sol. in KCN. CUCI2, freely soluble. CU2UI2. Insoluble in H2O. Bismuth. Crown black, B12S3 Sol. in HNOj — Insol. in KCN. BiOCl. Insoluble in H2O. Cadmium. Yellow, CdS. Sol. in HCl. Insol. in KCN. White, Pb (OH)a. 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 HOI and HNO3. White, Cd(OH)2. Insol. in excess. Soluble in acids. White, Pb(OH)2. Insol in excess, While precipitate Basic lead carbonate, White, PbS04. Sol. in 13,000 parts II2O. Greenish blue pre clpitate, 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 fin NH4CI. Sol. in KCy and preci pi tat ed from this solution by (HN4)2S. Blue precipitate, basic copper car- bonate, when heated becomes black brown. CuO. White, (Bi0)2 CO3. Insol. in excess. Sol. inHCl,andinHN03, White, CMCO3. Insol. in excess- precipitate not com- plete in presence of NH4C1. Sol. in 3% parts H2O. 158 LABORATORY GUIDE. Group I—Continued. Reagents. Silver. Mercurous. Mercuric. Potassium chromate, K2CTO4. Dark red,Ag2Cr04. Sol. in HNO3, and in NH4HO. Red basic chromate. Sol. in HNO3. Yellowish red, HgUr04 Sol. in HNO3. Potassium ferrocy-anide, K4FeCy6. White, Ag4FeCy6. Insol. in NH4HO. White, Hg2FeCy6. Stannous, chloride, SnCl2. White, AgCl. Dark gray, Hg White, Hg2Cl2, with excess metallic Ilg. 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 -f-S2, appears slowly, hastened by boiling. Orange red, Sb2S3. Sol. in HCl, in alkalies and in alkaline sulphides. Orange, SD2SS. 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. Sb2S5. Sol. in excess. REACTIONS. 159 Group I—Continued. Lead. Copper. Bismuth. Cadmium. Yellow PbCr04. Sol. in fixed alkalies. Sparingly sol. in HNO3. Insol. in NH4HO. Red brown, CuCr04. Sol. inNH4HOwith green color. Yellow, Bi2(Cr04)3. 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 NaH«>, black B1O2. in concentrated so-lutions. Yellow Pbl2. 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. in 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 HU1 and H2UVH4O6. Easily reduced by KCN. White, NaSb03. Sol. in excess. Potassium Sb203 anhydride. hydroxide, KHO. Ammonium hydroxide, NH4HO. Sb203. Insol. in excess. ND4Sb03. 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 sb203. White, AgSb03. Sol. inNH4IIO. Copper sul-phate, CUSO4. Yellowish green, Cu3(As03)2. Sol. in HN03,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 White, Hg3(As03)2. Sol in acids. --- Basic antimoni-ous chloride. HgCl2. - 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, yfl-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)2C03. 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(OIl)4. Sol. in excess. in HCl. Reduced to metal by KCN — Su(OH)--. Sn(OH)4. Soluble in excess. Yellow, KzPtC16. Sol. in 12,083 parts absolute alcohol. Soluble in exi-i-ss. Su(OII).!. Iusol. In excess. Sn(OH)4. Slightly sol. in excess. Yellow, (NH4)2PtC16. Sol. in 20,535 parts absolute alcohol— sparingly sol. in cold H2O. Yellow, (NH3)2AU2 O3. In-sol. in excess. [Fulminating gold.] Silver ciiloride and metallic silver. AgCl. Light brown, AgCl-fPt02. Light brown, AgCl-r-Au203. AVith S11CI2, white, C112CI2. Sol in acids. S11CI2, first white IIsr2Cl2—with excess black Hg. Sr.. 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 (NH4)2S. Nearly insoluble in dilute HCl. Soluble in aqua regia. Hydrogen sulphide, H2S. W^iite, ZnS. In neutral or acetic acid solutions. Black, NIS in neutral solu-tions. Sodium hydroxide NaHO. White, Zn(0H)2. Soluble in ercess, reappears on heating. Apple green, N1(0H)2. In-soluble in excess. Soluble iu 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(0H)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, Ni3(P04)2. Soluble in NH4HO. Barium carbonate, Ba0O3. 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 NH4.HO. Yellowish green, Ni3(FeCy6)2. Insoluble In HCl. REACTIONS. 163 Group III—Continued. Cobalt. Iron, (ons) Manganese. Black, CoS. Insoluble in excess. Insoluble in HC2H3O2. Nearly insol. in HCl. Sol. in aqua regia. Black, FeS. Sol. in IICI and HC2H3O2. In the air oxidizes. Flesh colored, MnS. Soluble in HCl and HC2H3O2. In the air, oxidizes. Black, CoS in neutral solutions. Blue, hydroxide or basic salts. Insoluble in excess. Soluble in NH4IIO 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 iu excess with brownish red color. White, Fe(0H)2 becomes green and brown. Incom-plete precipitation. White, Mn(0H)2. In the presence of NH4Ulnot pre-cipitated. On standing be-comes brown. Mn203and 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, Mii2FeCy6. 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, TJO2S. 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 and reprecipitat-ed by NH4CI. White, FeP04. Sol. in excess. Insoluble in HC2H302. Green, CrP04. Yellowish white, TJO2HPO4. 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-i-2U02FeCy6. ferrocyanide, K4FeCy6. Potassium Blood red, Fe(CNS)3. Solution. sulphocyan-ate, KCNS. Red solution. 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)2U207. Reagents. Ammonium. carbonate, (NH4)2C03. Sodium hydroxide, (NaHO). REACTIONS. Group III—Continued. 165 Aluminium. White, A12(0H)6. White, Al2(OH)6. Sol. in excess. On heating with NII4CI reprecip- itnted. Iron, (ic) Chromium. Brown red,basic carbonate. Brownish red, Fe2(OH)6. Insol. in excess. Grayish green, Cr2(QH)6. Sol. in excess. Bluish green. Cr2(OH)6. Sol. in excess— with green color, on heating reprecipitates. Cranium. Yellow, 2(NH4)2tt>3+ (UO)2C03. Sol. in excess. Precip- itated by fixed alkalies Yellow, Na2U207. Sol. in (NH 4)2003. Group IV—Metals precipitated by (NH4)2C03 but not by H2S. Reagents. Magnesium. Barium. 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, MgC03+XMg (OH) 2. Sol. in 10,000parts II2O. 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.S0I. in 50,545 parts of H2O, containing NH4HO. White, CaC03. Sol. in 10.C01 parts cold H2O. Sol. in HNO3, and HCl. H2O containing NH4HO. requires 65,24G parts to dissolve it. Sodium hydroxide, (NaHO). While, Mg(0H)2. Sol. in ammoni-um salts. White, Ba(OH)2, only in concen-trated solutions. White, Sr(0II)2. difficultly sol. in H2O. White, Ca(OH)2, diffi-cultly sol. in H2O. Ammonium hydroxide, (NH4HO). White, Mg(OH)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 alcohol. Ammonium oxalate, (NH4)2C204) White, BaC204. Sol. in 2,590 parts H2O. Sol. in HC2H3O2. Quite sol. in dilute H2C204. White, 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 Yellow, BaCr04. Difficultly sol. Yellow, SrCr04. Moderately sol. inH20. Whitish, CaCr04. Easily soluble. (K2Cr04). Hydrofiuosi-licicacid, (H2SiF6). White, BaSiF6. Sparingly sol. in H2O. --- White, CaSiF6. Easily soluble. REACTIONS. Group V—Metals not precipitated by H2S nor by (NH4)2CC>3. Reagents. Potassium. Ammonium. Lithium. Sodium. Sodium White, H2CO3. Slightly sol. in H2O. (Na2C03). Sodium White, Li3P04. Sol. in 2,539 parts of H2O. Sol. in 3,920 parts of dilute am-monia. Phosphate, (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 Wliite crystal, KHC4H406, forms better alter shaking. Sparingly sol. in H2O. Sol. in HCl and in alkalies. White crystal, NH4HC4H4O6. Slightly sol. in H2O. Sol .in al-kaline solutions, and the mineral acids. acid (H2C4H4O6). Totassium White crystal, Na2H2Sb207. Insol. in alcohol. Sparingly sol. in H2O. Sol. in al-kaline solutions antimoniate, (K2H2SD2O7). Nessler's reagent, sol. of Hgl2 in KI-J-KHO. - Yellowish brown, NHg2I. Hydrofiuosi-licic acid, (H2S1F6). Translucent, K2SiF6. Insol. in alcohol. Sol. in 790 parts H2O. Sol. in IICI. White, Na2SiF6. Difficultly sol. in H2O. Flame Violet. Red. Yellow. reaction. 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. Ag2S04 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 acids, and in NH4CI. Yellow, Ag3P04. Sol. in HNO3. Sol. in NH4H0. Pyrophosphoric acid, H4P2O7, White, 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. AgP03. 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,Ag3 ASO4. Sol. in HNO3. Sol.inNH4HO Arsenious acid, H3ASO3. White, Ba3(As03)2. Sol. in NH4C1. Sol. in acids. White, Ca3(As03)2. Sol. in NH4C1. Sol. in acids. Light Yellow, Ag3As03. Sol. in HNO3.Sol.inNH4H0 Chromic acid, H2CTO4. Yellow, Ba0rO4. Sol. in HOI and HNO3. Insol. in HC2H3O2. Light yeUow,0aurO4. 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 aeids. Sol. in NH4CI: White, Ca3(B03)2. Sol. in acids. Sol. in NH4Clandin CaCL-. White, Ag3B03. Sol. in HN03. Sol. in NH4HO. Phosphorous acid, H3P03. White, Ba3(P03)2. Sol. in HC2H3O2. White, Ca3(P03)2. Sol. in NH4CI. 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. Sol. 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 H103. with SO2,is reduced to Agl. Hydrofluoric acid, White, bulky BaF2. Sol. in HCl in HNO3. in NH4C1. White gelatinous CaF2. Sol. in HCl and in NH4CI. Insol. in HO2H3O2. HF. Hydrofluosilicic acid White, BaSiF6. In-sol. in HCl 2 (not in the free acid). Sol. in NH4CI. Insol. in KHO. Less sol. in warm than cold water. White precipitate Ferric Chloride. Silver Nitrate. Sucoinic acid, C4H6O4. Its alkaline salts give a light yel-low precipitate. White precipitate. Benzoic acid, C7H6O2. Flesh color. Soluble in HCl. White precipitate. Soluble in hot water. Salicylic acid, C7H6O3. Deep violet oolor. White precipitate. Soluble in hot water- Gallic acid, C7H6O5. Bluish black precipitate. Reduced to metallic Ag. Tannic acid, CmHioOsc Bluish black color. White precipitate. REACTIONS. Reactions of the acids—Continued. Lead Acetate, Special Reactions. White, PbCla. Soluble in 30 parts hot water. With H2SO4 + Mn02 Cl is given off. With Cr03, red Cr02Cl2 is given off. White, PbBr2. Soluble in hot water. When liberated by Cl and treated with CS2 or O4H10O, gives a red color. Yellow, Pbl2. Soluble in hot water, on cooling yields golden colored crystals. When treated with strong HN03, I is set free, and gives with Crf2 or better CHCI3 violet color,in stronger solutions blue. White, Pb(CN)2. Soluble in HNO3. Insoluble in KCN. When treated with (NH02S and gently evaporated to dry-ness forms with ferric salts a blood red .color. Warmed with KHO+FeS04 and a little Fe2C16, and then acidulated with HCl, forms Prussian blue. White, PMCNSK With Fe2C16 blood red color, add HgCte the color vanishes. Black. PbS. See page 3. In alkaline solution with nitroprusside of sodium violet color—very delicate reaction. Organic acids—Continued. Lead Acetate. Special Reactions. Reducing agent- With concentrated H2SO4, CO2 is given off. With Fe2C16, red brown solution, on heating precipitates On heating with C2H6O -\- H2SO4 forms acetic ether. On heating with AS2O3 forms cacodyl. White,PbC204. Sol. in HNO3, Insol. in HC2H3O2. The acid K and NH4 salts difficultly soluble. White. Pb04H406. Sol. in HNO3. Slightly sol. in NH4CI. Insol. in alcohol. With MnOz + H2SO4 heated, CO2 is given off. When heated on Pt foil gives odor of burned sugar. White, PbC4H40s. Melts on heating. Add CaCb -\- C2H6O white CaC4H40s even in dilute neutral solutions. Sol. in water. Insol. in alcohol. White, PbHC6Hs07. Sol. in HNO3, and in ammonium citrate. Melts when heated, and at_175~C gives off pungent, char-acteristic vapors, containing acetone. It prevents the precipitation of iron and the other heavy metals by the alkalies. Solution of lime gives no precipitate in the cold, (while Tartaric, Racemic and Oxalic acids do.) Lead Acetate. Special Reactions. White, PbC4H404. Sol. in. excess of either. Sol. in HNO3 Melts at 180DC. With Fe2CI6. a brownish red bulky pre-cipitate of basic ferrio succinate—quantitative method of estimation. Its alkaline salts give a white precipitate. Melts at 120°C. Sublimes. Where heated in a test tube with HNO3 nitrobenzole is evolved, odor of bitter almond oil. White precipitate. Melts at 15o°C. Its vapors causes irritation in the throat, and has a sweetish sour taste. When heated with methylic alcohol and concentrated sulphuric acid, salicylate of methyl is evolved, having the odor ot winter green. Melts at200°C The alkaline solution absorbs oxygen.with Cu(C2H302)2 brown to black precipitate. Yellowish precipitate. With molybdate of ammonia a red color, removed by oxalic acid,precipitates gelatin and albumin,(distinctions from gallic acid). Has an astringent taste. 172 LABORATORY GUIDE. FACTS, HYPOTHESES, AND LAWS EMPLOYED IN CHEMISTRY. I. BELATING TO GASES ONLY. Charles (1787). The volume of a gas is directly proportioned to its absolute tempera- ture—T—273° C. Mariotte or Boyle (1662). The volume of a gas is inversely proportioned to its external pressure. The elastic force of a gas exactly corresponds to its external pressure. The density of a gas is directly proportioned to its external pressure. The volume and density of a gas vary both with temperature and pressure. Graham (1832). The rate of diffusion of gases is inversely proportioned to the square root of their density. Avogadro (1811). Equal volumes of different gases contain the same number of mole- cules. Gay Lussac (1805). Two gases combine by simple volumetric ratios; as, HH, HCl, H20 — H3N, H4C, condensing in all cases to two volumes. The vapor density of a gas is half its molecular weight. Deville (1857). Overheated compound gases become dissociated; as, NH3, HCl, the vapor density becoming the mean of the molecular weights. Meyer (1842). Even elementary molecules may dissociate; as, I2. Compare vapor density of S at different temperatures. Clausius and Maxwell (1867). The elastic force of a gas may be expressed in terms of a "dynamical theory," in which the factors are the number of gaseous molecules (N), their mass (M), their rate of motion (V). The elastic force, % MNV2. By general agreement, hydrogen is taken as the standard unit: I. For density or specific gravity of gases —relative weight of equal volumes. II. For molecular volume —its volume in the free state; 11.2 liters weigh gram. III. For atomic weight, H being 1, O —15.9633; O being 16, II —1.0023. IV. For combining power —chlorine, potassium, and other elements being reckoned its equivalent. II. BELATING TO ALL ELEMENTS. Dalton (1804). Elements combine in definite and invariable proportions by weight, H being 1, Cl—35.5, K—39.1, etc. These proportions may, and do increase by multiples; as, N20, NO, N203, N204, or N02, N205. The simplest rational combining proportion of an element is its Atomic Weight, in H20, 0 — 16; in H3N, N —14. Wollaston (1809). The least combining proportion of an element is its equivalent- in HsO, 0 = 8; in H3N, N = 4.6. The densities of gaseous elements determine their atomic weight (H being 1). Accurate analyses of well defined compounds and assisted by comparison of anal- ogous compounds, are required for ascertaining the atomic weight of the other elements. Assisting in this determination, or confirming the weight assigned, are: FACTS, HYPOTHESES, AND LAWS. 173 Dulong and Petits (1819). The atomic heats of all elements is the same (sn. heat X at. wt. = 6.4, nearly). Kopp's. Compounds analogously constituted have the same molecular heat. Mitscherlich's (1819). Solid compounds analogously constituted have the same crystal- line form; i. e., are isomorphous, K20 with Na20, FeO with MgO, Fe,0, with A1203. Prout's Hypothesis (1815). Maintains that the atomic weights may be expressed in whole numbers (nearly true for about 39). III. THE STBUCTUBE OF COMPOUNDS. Berzelius (1818). All elements may be arranged in an electro chemical series (+ posi- tive, — negative), from caesium to oxygen. Compounds are dual, containing -f~ and — constituents; as oxygen ternary com- + - pounds basic and acid K20 S02. ' Compound radicals exist which are units like the atoms of elements; as, K(CN), NH2(H). Gerhardt and Laurent (1837). All compounds may be arranged in groups after types, HH, IK'l, H20, H3N, II4C — taken once or more than once. Kekule (1858). Elements have a combining power or valency —odd perissads, even T. II III IV v VI VII VIII artiads, from 1 to 8, H, O, N, C, P, S, Cl, Os. I II in Compound radicals have also combining power—(HO), (CO), (PO). Polyvalent elements and radicals may partially saturate each other, forming con- densed nuclei or radicals. The opened and closed chain. The lower hydrocarbons are generally in open or cleft chains. The aromatic hydrocarbons start from a closed chain. Mendelejeff (1870). In accordance with these facts and accepted theories, all the elements may be arranged in groups and series, thereby forming "periods," in each of which several elements exhibit gradational properties —physical, chemical, and physiological. IV. FOBMATION OF COMPOUNDS. Compounds are formed by direct union of their constituents, by substitution, and by double exchange. Bertholett's (1801). Solids separate from mixed solutions by reason of the less solubility of a compound formed by exchange. Gases volatilize from heated mixtures, which give rise to compounds of easy volatility. Bunsen's (1860). The relative mass of the bodies present in a mixture has a controlling influence on the result. It takes time to effect most chemical changes — varying from almost instantaneous explosions to very slow crystallization. In ordinary chemical work, many successive littles are better than one large addi- tion of a reagent. Heat hastens the solution, and retards the precipitation of most of the elements. CHAPTER VI. EXAMINATION OF WATER. The results of water analyses are reported in parts per 1,00$,000, parts per 100,000, and grains per gallon. The English gallon* of water weighs 70,000 grains, and 70 cubic centimeters of water weigh 70,000 milligrams; so 70 cubic centimeters (C. c.) of water is a miniature gallon where milli- grams correspond to grains. Total solids. Seventy C. c. of the water is taken and evapo- rated, in a platinum dish, on the water bath to dryness; the increased weight is the total solids. Separate portions of this residue are taken for the determination of C02, H2S04, etc. Another and larger portion is taken for the determination of the bases. 286. Chlorine is usually in combination with sodium as NaCl. An excess (pure water contains hardly any) commonly indicates contamination with sewage. Chlorine is determined by nitrate of silver: AgN03 -f- NaCl = AgCl -+- NaN03. The molecular weight of AgN03 is 170, and the atomic weight of Cl is 35.5; 170 parts of AgN03 precipitate 35.5 parts of chlorine, or 4.79 parts of AgN03 = 1 part of Cl. Dissolve 4.79 grams of AgN03 in one liter of distilled water; one C. c. of this solution will precipitate one milligram of chlorine. The operation is con- ducted as follows : Seventy C. c. of the water is placed in a clean and white porcelain dish, or in a broad beaker that rests upon a * An English gallon is equal to about 1.2 American gallons. EXAMINATION OF WATER. 175 sheet of white paper. Three C. c. of a neutral solution* of pure chromate of potash are added and well mixed. The beaker can be one-half filled with distilled water, in order to make it more dilute, when the change from the white AgCl to the red Ag2Cr04 is more easily seen. AgN03 is run in from a burette, with con- stant stirring, until the color becomes permanently tinged with red. The number of C. c. used indicates grains of Cl to the gallon. If the water to be examined is acid, it must be neutral- ized with Na2C03. An acid condition of the water may dissolve the Ag2Cr04. If the amount of chlorine is small, the water can be boiled down one-half or one-fourth its volume before being tested. If the amount of chlorine is large, it can be diluted with three or four times its volume of distilled water. It is a good plan to have the same quantity of distilled water in a beaker of the same size with the same amount of K2Cr04, so as to compare the first tinge of red AgiCr04 that forms. In every case of doubt make a blank trial with distilled water, or with water containing a known quantity of chlorine.\ This remark will apply to all the elements tested in water analysis. A little calculation will enable the student to use any solution that he has made of silver or other reagent; but if he has to make them, the solutions described will save him some calculation. 287. Hardness. Ten grams of good castile soap are dis- solved in a liter of thirty-five per cent, alcohol, when one C. c. will precipitate one milligram of carbonate of lime. This must be verified by testing it with 1.11 grams fused CaCl2 dissolved in one liter of water, when one C. c. = one milligram of CaC03 (CaC03 molecular weight = 100, while molecular weight of CaCl2 is 111). The soap solution, if not correct, can be made stronger or weaker until it is correct in strength, or its value can be found and the factor used. Seventy C. c. of water is taken. This is * Fifty grams of K2Cr04, diluted to a liter; AgN03 is added to a permanent red to precipitate any accidental chlorine in the salt; filter, and use the filtrate. t Dissolve 1.65 grams of pure NaCl in a liter of distilled water. One C c. con- NaCl tains .001 milligram of chlorine. It is found as follows:-----= 1.65. Cl tf 176 LABORATORY GUIDE. diluted with three or four times as much distilled water, and 70 C. c. of the mixture is used as a test. The soap solution is run in, with constant shaking, until the lather lasts five minutes when the vessel is placed upon the side. The number of C. c. of soap solution used gives the degrees of hardness. An example will illustrate it. Seventy C. c. of the water was diluted with 210 C. c. of distilled water. Seventy C. c. of this mixture required ten C. c. of soap solution, the whole would require forty C. c. of the soap solution; but seventy C. c. of distilled water requires one C. c. of soap solution, therefore the water required 40 — 3 = 37 degrees of hardness. When this hardness is occasioned by the presence of calcium and magnesium as soluble bicarbonates, boiling the water converts them into insoluble carbonates, which precipitate, and the water becomes soft. This hardness' is called temporary, while permanent hardness, being caused by the presence of sul- phates, is not remedied by boiling. The total hardness is deter- mined before boiling, the permanent hardness after boiling; the temporary hardness is the difference between the two. Lime and magnesia solutions act very differently towards soap solution. Lime forms immediately; magnesia, more slowly, and requires one and one-half times (75 is to 42) as much soap as lime. The lime can be precipitated with oxalate of ammonia, and the fil- trate tested for the hardness due to magnesia. 288. Organic matter. The following solutions will be required: 1. Nessler's reagent is made by taking thirty-five grams of KI, thirteen grams of HgCl2, and 800 C. c. of water. The materials are heated to boiling, and the salts dissolve; to this is added a cold saturated solution of HgCl2 in water until the red precipitate just begins to be permanent; to this is added 168 grams of KHO or 120 grams of NaHO, whichever is most con- venient, and the whole made up to a liter with distilled water. It is allowed to settle, and then put away in a large bottle, well corked. The solution is poured into a small bottle, as required for use; two cubic centimeters are used for a test. EXAMINATION OF WATER. 177 2. Permanganate solution is made by dissolving eight grams of K2Mn208 and 200 grams of KHO in a liter of water. Use fifty C. c. for each analysis. Always examine the permanganate solution for ammonia by distilling the solution and adding as much distilled water, free from ammonia, as has been distilled off. In case you can not free it from ammonia, distill it until the amount of ammonia becomes constant, and subtract this from the ammonia found in the water. 3. Standard solution of ammonia — Dissolve 3.15 grams of NH4C1 in a liter of distilled water. Each C. c. contains one NH Cl 53 5 milligram of ammonia, * = -—- = 3.15; every 3.15 parts of NH4C1 contains one part of NH3. This solution can be diluted, as you may require a solution containing Tfa of a milligram in each C. c. 4. The distilled water that is required for making up the solutions, and the various standards of ammonia, must always be examined to see that they are free from ammonia. All the apparatus must be perfectly clean, and, if possible, kept only for this purpose. It is well to have a room set apart for the analysis of water away from the working laboratory and from the fumes of ammonia. It is well to have one C. c. pipette graduated into one-tenth C. c, and to have a series of pipettes holding 1, 2, 3, 5, 10, 25, and 50 cubic centimeters. The Nessler glasses should be of white glass, and graduated into 50, 100, and 150 C. c. each. One-half liter of the water is placed in a clean flask that is connected with a Liebig condenser. Heat is applied by means of a sand bath, and the distillate is collected in the Nessler tubes. When fifty C. c. of the distillate have come over, the Nessler tube is changed. The first fifty C. c. should be Nesslerized by adding two C. c. of Nessler reagent, and noticing the color produced. The next step is to get the same depth of color by adding a meas- ured volume of 'the standard solution of dilute ammonia to fifty C. c. of pure distilled water to which two C. c. of Nessler's solu- tion has been added. The tubes are placed side by side upon a sheet of white paper, and the depth of color compared by looking 178 LABORATORY GUIDE. down the tubes, or standing off a few feet and looking obliquely through the liquid. When the solutions are of equal depth of colors, the Nesslerizing is accomplished, and the amount of ammonia in the unknown solution equals the amount of ammo- nia added from the standard solution. The distillation is con- tinued until 200 C. c. have come over. The first 50 C. c. contain three-fourths of the total free ammonia, but it is well to Nesslerize each fifty C. c. as it comes over, when the sum of four tests will be the free ammonia. The distillation is stopped for a few moments, fifty C. c. of the permanganate solution is added, and the distillation continued. Each fifty C. c. is Nesslerized as it comes over until it is free from ammonia, which usually requires 150 C. c. The sum of these is the albuminoid ammonia. The subtraction for the ammonia in the permanganate solution should be made here, if required. 289. The method by Forchhammer, of oxidizing the organic matter by K2Mn208, is now employed, with various modifications : K2Mn208 -f- 3H2S04 = K2S04 -f 2MnS04 + 3H20 + UJ. This available oxygen is, by some, made directly the basis of comparison. As regards the time during which the sample of water should be exposed to the action of the permanganate, authorities differ somewhat. Tidy is in the habit of registering the reduction (in the absence of iron and H2S), which occurs in three minutes, as due to nitrites. The operation is continued for one hour, and three hours at a temperature of 60° F. It is well in all the reports to state the time. The operation is usually conducted as follows : 100 C. c. of the water is placed in a flask of 200 C. c. capacity, and to it fifteen C. c. of dilute II2S04 (one acid and three water) is added. From a burette, 10 C. c. of ccnti-normal permanganate solntion is added, and the flask is heated to boil- ing for fifteen minutes. Should the color disappear, more per- manganate is added until the color remains permanent during the boiling. Ten C. c. of a centi-normal solution of oxalic acid is added, and the mixture again heated. The red color is EXAMINATION OF WATER. 179 discharged. Enough of the centi-normal permanganate is again added to give it a red tinge. The same quantities of oxalic acid and permanganate should exactly neutralize each other in color, and the excess of the permanganate over the oxalic acid indicates the amount required for oxidation of the water. The number of C. c. of permanganate in excess is multiplied by .3135 (the amount of milligrams of K2Mn208 in each C. c. of centi-normal solution). Multiplying the result by five, we get the number of milligrams of organic matter in 100 C. c. of the water tested: multiplying the number of C. c. of K2Mn208, read off directly, by 15,675, you obtain the number of milligrams in a liter. Drink- ing water should not contain more than fifty milligrams of organic matter per liter (equal to 2.9 grains per gallon). The action of permanganate upon oxalic acid is as follows : 5H2C204 -f- K2Mn208 -f 3H2S04 == 8H20 -f 10CO2 -f- K2S04 + 2MnS04. The molecular weight of K2Mn208 is 313.56; y1^ of this amount, in grams in a liter of water, is a normal solution; j-J-g- is a deci-normal; x J0 0 is a centi-normal = .3135 grams to a liter. Each C. c. will contain .3135 milligrams of K2Mn208. This is multiplied by an arbitrary constant five (Kubel, Woods, Mohr). (Frankland uses 2.38 times for river water, and 5.8 times for well water.) .3135 X 5 X 10 = 15.675 for a liter (100 C. c. is T\ of a liter). This method is rapid, easy of execution, and reasonably correct. It is very difficult to handle with any certainty the organic matter in water, owing to the decompositions that may take place from the fermentation of albuminoids, peptones, amido-derivatives of mono and bibasic acids of the fatty series (as valerianic, butyric acids); from the aromatic series (as cresol, indol, etc.) The 'fats may split up into glycerin and fatty acids, which may be transformed by oxidation into acids of lower groups; from the carbohydrates there may be formed by fermentation a number of alcohols, aldehydes, and acids of 180 LABORATORY GUIDE. the fatty series. Waters in connection with cesspools may con- tain the constituents of urine and their products of decomposi- tion. Where the residues of vegetation are decaying, substances of the humus class may be present; hence the organic impuri- ties of water may differ in their properties. Fixed and volatile bodies, permanent and unstable compounds, may occur together; hence there cannot exist any simple method for determining the total amount of organic matter in water. 290. The sulphates are determined by heating 100 C. c. of the water to boiling, adding a few drops of HCl and a slight excess of BaCl2. The precipitate is washed, ignited, and weighed. The BaS04, multiplied by the factor .34331, gives the amount of S03; or by .42051, gives the amount of H2S04. This multiplied by ten gives it for a liter. 291. The nitrates. Seventy C. c. of water to be tested is mixed with an equal volume ten per cent, solution of pure sodium hydroxide, and boiled briskly until reduced to one-naif its volume; it is then made up to its original bulk with pure distilled water. A piece of aluminium foil three or four inches square, rolled around a clean glass rod to keep it from floating, is added, and the bottle set aside for three or four hours. The liquid is distilled in a small retort, and the distillate Nesslerized. The ammonia is to the nitric acid as seventeen is to sixty-three. It is well to have the bottle protected from ammonia by a cal- cium chloride tube filled with pumice or glass beads wetted with HCl or H2S04 to prevent any NH3 from the atmosphere from entering the apparatus. The water residues may be tested quali- tatively for nitrates by heating one part of carbolic acid with four parts of sulphuric acid; the mixture is diluted with an equal volume of water. When boiled with nitrates, it gives a brownish- red color. 292. The nitrites. The reagents required are : (1) Dilute sulphuric acid (one of acid two of water); (2) five grams of meta-phenylene-diamine in an acid solution (HCl or H2S04) of water made up to a liter; (3) .406 grams of pure silver nitrite EXAMINATION OF WATER. 181 are dissolved in boiling distilled water, when pure potassic or sodic chloride is added till no further precipitate of silver chlo- ride occurs. Make up to a liter. When the silver chloride settles, dilute 100 C. c. of the clear liquid to a liter. Keep in the dark and in bottles completely filled. One C. c. = .01 milli- gram of N203. The color it gives is a "Bismarck brown." One hundred C. c. of the water to be tested is poured into a Nessler tube and one C. c. each of the dilute sulphuric acid and the solution of meta-phenylene-diamine consecutively added. The color produced is compared with a standard solution of the nitrite, as in the estimation of ammonia by the Nessler test. (This detects one part in 30,000,000.) The reaction which takes place is thought to be expressed as follows: NH2 NH2 C6H4 -f NOHO =20H2 + C6H4 ^NH2HC1 N2C1 Meta-amido-diazobenzene-chloride. NH2 NH2 NH2 C6H4 + C6H4 = HCl 4- C6H4 NH2 ^N2C1 ^NH2HC1 ^ N2 — C6H3 ^NH2HC1 Triamido-azobenzene hydrochlorate (yellow coloring matter). 293. The following method is sometimes used. The rea- gents are: (1) The standard solution of silver nitrite above mentioned : 2AgN02 = N203 + Ag20 or ^g^ = 4.06 (intro- ducing the molecular weights and performing the division; .406 grams of AgN02 gives 100 milligrams of N203 to the liter. 182 LABORATORY GUIDE. (2) A solution of sulphanilic acid. (3) A solution ot naph- thylamine in alcohol. One hundred C. c. of the water is acidu- lated with pure sulphuric acid; six or eight drops of sulphanilic acid are added; in a few minutes afterward, a few drops of a colorless solution of naphthylamine, when a magenta red color is produced. This color can be compared with a known quantity of silver nitrite as above described. 294. To convert parts per 100,000 into grains per gallon, multiply by .7. To convert grains per gallon into parts per 100,000, divide by .7. To convert grams per liter into grains per gallon, multiply by 70. Milligrams per liter is the same as parts per 1,000,000. 295. Notes : — When the free ammonia exceeds .08 parts per million, it is quite sure to come from urea. In such a case the water will be loaded with chlorides. Good water should not contain more than one part of free ammonia in 10,000,000. A large quantity of albuminoid ammonia, with little free am- monia, and absence from chlorides, indicates vegetable contami- nation. Good water should not contain more than one part in 10,000,000. Human urine contains 824 parts of sodic chloride, or about 500 parts of chlorine in 100,000 parts. Water containing more than twenty milligrams of chlorine per liter (1.4 grains per gal- lon), derived from other sources than a saline subsoil should be rejected. It should not contain more than one part in 100,000. The hardness of water should not be more than .2 gram of CaO per liter, or its equivalent of magnesium. Water should not contain over fifteen parts of nitric acid per 1,000,000. Water containing nitrites is apt to be due to sewage contami- nation, and any thing over .1 milligram per liter can be suspected. In estimating the total solids, it may be necessary to dry the residue at 110° C. to 120° C. before it is weighed. Care must be taken not to expel the carbonic acid, etc. EXAMINATION OF WATER. 183 In every case of doubt a blank experiment should be made with pure distilled water under the same conditions as the experi- ment. The solution of meta-phenylene-diamine can be decolorized, if necessary, by filtering through animal charcoal. The silver nitrite can be made by precipitating silver nitrate with potassium nitrite, washing and drying. The search for impurities in water will vary largely with the purpose for which the water is to be used ; e. g., for steam boilers, for laundries, or for a beverage. In the last case, such impurities as may have come from animals, and especially from diseased animals, should be sought after with scrupulous care, and if found, the water should at once be rejected as unfit for use. CHAPTER VII. POISONS-PTOMAINES, ETC. 296. The name "ptomaines" has been given by Selmi to bodies which have been detected in exhumed corpses, and resem- ble the vegetable alkaloids in their chemical reactions and physi- ological effects. These ptomaines are usually produced in bodies which, after a brief exposure, have been excluded from the air, for they occur in buried bodies, sausages, and tinned foods, and, in most, though not in all, cases, the production is in the internal portion. Panum and Schwenigner have investigated the poisonous effects produced by food in certain stages of putrefaction or fer- mentation, and have found that different physiological actions are produced at different stages of decay; while Sonneschein and Zuelzer found in the fluid produced by anatomical maceration an alkaloid which resembles atropine in its action. The poisons of putrefied sausages produce similar effects, and also contain other bodies which cause tetanic symptoms. In many cases of poison- ing by food, as, for instance, by cheese, the bad effects were not due to vegetable growths or to microscopic organisms. Many individuals have derived from the putrefaction of maize, a body that will produce tetanic symptoms. The relation of these pro- ducts of putrefaction to certain diseases is evident from the fact that Sonneschein's alkaloid is found in the bodies of patients dying of typhus fever, and many persons poisoned by decaying food show marked typhus symptoms. It becomes a matter of grave importance to the chemist to be able to distinguish between these poisonous bodies, which are the POISONS. 185 result of putrefactive processes, and the vegetable principles, which, when administered, may produce death. Some chemists have thought it possible that conine might be produced in animal substances, as from butyric acid and ammo- nium, with the separation of 2H20, thus : Butyric acid. Ammonia. Conine. 2C4H8C2 4- XH3 — 2H20 = C8H15N. It is very doubtful if the synthesis of such bodies is a com- mon occurrence. The chemical constitution of most of the char- acteristic ptomaines are (according to Brieger, 1885) diamines, and are more simple in composition than the vegetable alkaloids. They are, generally, quite strong reducing agents. Brieger says there is no distinctive test for them. There is, therefore, all the uncertainty about the properties of these bodies which is inherent in conclusions based upon reactions on minute quantities, and in physiological experiments undertaken with substances the purity of which is doubtful. 297. The general method of Selmi was to make an alco- holic extract, after the method of Stas ; to filter, and evaporate the alcoholic extract in a vacuum, at from 30° to 35° C. An aqueous solution was then made from this extract, and the solution shaken up with solvents (the solution itself remaining acid, or rendered alkaline with Ba(OH)2). From both the acid and the alkaline liquids, ptomaines were extracted by means of ether, that differed in their chemical reactions and physiological proper- ties. Ptomaines were also extracted by chloroform and amylic alcohol. Ptomaines from fatty matters are extracted by washing the fatty substance with water acidulated with sulphuric acid, and then extracting the solution with ether, first acting on the acid liquid, and then on the same alkalized by Ba(OH)2. 298. Tyrotoxicon or "cheese poison." It has been long known that ice cream, milk, cheese, etc., have given rise to poisonous symptoms. Prof. Vaughan has recently extracted a diazobenzin (C6H5.N:N) compound, as follows: The filtrate 186 LABORATORY GUIDE. from the milk, or the filtered aqueous extract of cheese, is neutralized with Na2C03, and then shaken up with half its volume of pure ether; after the separation of the ether, it is allowed to evaporate spontaneously in a suitable vessel. The residue from the ether is dissolved in water, and again extracted with ether. The aqueous solution of the ether is added to a saturated solution of KHO, and evaporated on the water bath (C6H5N2OK) (at 100° C. it may explode). Mix a few drops of pure sulphuric acid with pure carbolic acid, on a white porcelain dish (it should remain colorless); now add a few drops of the residue left after the spontaneous evaporation of the ether. If the tyrotoxicon is present, a yellow to an orange color will be produced. 299. A poison is any animal, vegetable, mineral, or gase- ous substance which, when applied externally, or taken into the stomach or circulatory system, causes such a change in the ani- mal economy as to produce disease or death. Its action may be chemical or physiological. The physiological may be corrosive, irritant, or neurotic. The chemical poisons are organic and inor- ganic. The action of the poisons may be local or remote — local, when confined to the part to which the poison is applied, as in the case of strong acids, etc.; remote, when the action extends to distant organs. Poisons have a wonderful power of selecting organs or tissues peculiar to themselves — strychnine, the spinal cord; opium, the brain; hydrocyanic acid, the lungs; digitalis, the heart. Death is, in most cases, due to remote action. The action of the poison on the system may be modified by — 1. The quantity. 2. The molecular or physical condition of the poison — most active as a gas or vapor, next as a liquid, and least as a solid. 3. Chemical combination, (a) It may be increased as when morphine is given with acetic or hydrochloric acid, (b) It may be diminished, as. when sulphuric acid and caustic soda are given together. 4. Mechanical mixture, when its action ,may be delayed. POISONS. 187 5. The manne| of giving it, by the mouth, wound, etc. 6. The habits of the person; and closely connected with this is the idiosyncracy of the person. 7. The condition of the person as to health. It is retarded by sleep and food. The evidences of poisoning are (1) symptoms, (2) post mor- tem appearances, and (3) chemical analysis. As the symptoms of many poisons and diseases are alike, the burden of proof remains for chemical analysis. 300. Before the chemical analysis is taken up, a few words might be said as to general treatment: 1. Get the poison out of the system as soon as you can. 2. If you cannot remove it, neutralize it, if possible. 3. Assist its elimination by cathartics and diuretics. 4. Treat the symptoms, as they arise, upon general prin- ciples. The first may be secured by emetics and the stomach pump. The second requires antidotes, of which there are three classes, chemical, mechanical, and physiological. In general terms, the following are considered as the requisites of an antidote: 1. It should be easily accessible. 2. It should be capable of being administered by any one. 3. It should be capable of being taken in very large quanti- ties without injury. The organs examined are usually the stomach and the liver. 301. 1. It is recommended for the student to take the pure poison (say strychnine), and see if he can confirm it by all the tests given in the book. 2. To add it to food, making it as nearly as possible like the contents of the stomach, and then to try to separate and iden- tify the poison. 3. To take some small animal, as a dog or cat, and admin- ister a poisonous dose, and to notice the following: (a) The 188 LABORATORY GUIDE. quantity taken, which is always weighed. £b) The length of time before symptoms of poisoning began, (c) The duration of the symptoms until recovery or death, (d) The character of the symptoms, (e) The post mortem appearances. The first requisite of every analyst is cleanliness. See that everything is absolutely clean by washing it first with acid, and rinsing it with water three or four times; then again washing it with an alkali (as NaHO or KHO), and again rinsing with water three or four times; and lastly, with distilled water several times; also, test the purity of every reagent used. In almost every step of the work you may find difficulties which it is impossible to pre- dict, the remedies for which must be suggested by your general knowledge of chemistry. The inorganic poisons are generally quite easily detected, and usually will not give any trouble. The organic poisons are detected with difficulty, and more readily pass off, in some cases leaving no traces behind. For this reason they are first sought. In all cases, only one-third to one-half the con- tents of the stomach, or other organ, is taken; the rest is kept in case of any accident in the work. Before beginning the work of the analysis, it is well to note accurately the manner in which the samples have been packed; whether the seals have been tampered with; whether the vessels or wrappers themselves were likely to contaminate the articles sent; and then to make a very careful observation of the appear- ance, smell, color, and reaction of the matters, not forgetting to take the weight if solid, the volume if liquid. In short, find out all you can about the case. In examining the stomach, first of all empty the contents into a clean glass vessel; open the stomach, and spread it out on a clean, white plate, and note in writing its internal appearance. Examine it very carefully with a good glass, especially the surface. In some cases it may be required to have it photographed. You may sometimes find pieces of leaves, fruit, seeds, and the like, or powders that adhere to the walls of the stomach. A knowledge of the food eaten may be of importance. Any or all of these may give a clue to the cause of death. Whatever is found, let it be carefully preserved. POISONS. 189 302. The following is a general process for the separation and identification of poisons : One-half the contents of the stomach is placed in a strong flask, and if neutral or alkaline, it is feebly acidulated with tar- taric acid. The flask containing the substance or liquid under examination, may be gently heated on the water bath. Volatile substances, prussic acid, hydrochloric acid, phosphorus, etc., if present, will distill over, and can be carefully examined by redis- tillation and the various appropriate tests. When all the volatile substances have passed over, the substance is dried. This can be effected by a Bunsen filter pump, and dried over sulphuric acid. When dry, it is reduced to a coarse powder and extracted with petroleum ether (benzin) in a large Soxhlet apparatus. The petroleum extract, when evaporated, leaves the fatty matter con- taining traces of some of the alkaloids. When this is treated with dilute sulphuric acid, the alkaloids are dissolved out, leav- ing the fat behind. The substance remaining is practically free from water and fat. It is digested in the cold with absolute alcohol for three hours, and the alcohol is filtered off and allowed to evaporate spontaneously. It can now be treated with ninety per cent, of hot alcohol, filtered, and the filtrate evaporated. The dry residue is exhausted with ether. The, ether and water being driven off, it can be treated with water, and the extract examined for alkaloids and organic acids. 303. A few metallic poisons (as corrosive sublimate) are soluble in alcohol, and must not be overlooked. The residue, after being acted upon by petroleum, alcohol, ether, etc., is placed in a retort, and distilled once or twice to dryness with a known quantity of strong hydrochloric or sulphuric acid. The residue is carbonized and treated with dilute hydrochloric acid, filtered, and tested with H2S for Zn, Cu, Pb, etc. See Nos. 158, 178. The distillate that came over (before it was carbonized) is also tested by H2S. It is customary to take one-third for organic poisons, one-third for inorganic, and to keep one-third in case of accident. This method does not give good results with phosphorus or oxalic acid. The phosphorus can be distilled in the dark (in the 190 LABORATORY GUIDE. absence of alcohol or ammonia), and condensed with a Liebig's condenser. One part in 200,000 can be shown in this way. Bisulphide of carbon can .be used to dissolve it out if in large « quantities. The oxalic acid can be detected by digesting the substance or fluid with HCl, filtering, neutralizing with NH4HO, and allowing it to precipitate. The filtrate is treated with acetate of lime. The first precipitate contains all the oxalic acid in combination with lime; the second, that which was in the free condition. These precipitates are washed with acetic acid, and identified.* As but one poison is usually found in the above solutions of ether, alcohol, chloroform, etc., no special trouble will be found in identifying it. 304. In applying a reagent to a solution of an alkaloid, add a drop or two of the reagent to an equal quantity of the solu- tion of the alkaloid on a glass slide placed over black paper. A magnifying glass will also be found useful. The following general reagents will be found useful: 305. Iodine in potassium iodide solution (Wagner, 1866). Twenty grams of iodine and fifty grams of potassium iodide in a liter of water. The precipitates are brown and flocculent. A very slight addition of the reagent is sufficient. The alkaloid may be recovered by washing the precipitate and dissolving it in an excess of aqueous sulphurous acid and evaporating on the water bath. The sulphurous acid expels the hydriodic acid, the alka- loid remaining as a sulphate. In cases where the alkaloids are expensive, this method can be used. *The alkaloids are divided into two divisions, volatile and non-volatile. To the first belong nicotine and conine. The second has three subdivisions: first, those that are precipitated by potash, soda, or a solution of their salts, and redissolve in an excess of the precipitant — morphine is the most important one; second, those that are precipi- tated by potash or soda, but do not redissolve to any great extent by an excess of the precipitant, and are precipitated by bicarbonate of soda from acid solutions — narco- line, quinine, and chinchonine; third, those that are precipitated by potash or soda, and do not redissolve to any great extent by an excess of the precipitant, but are not precipi- tated by a bicarbonate of the fixed alkaline metals — strychnine, brucine, veratrine, and atropine. '" POISONS. 191 306. Potassium mercuric iodide (Mayer's solution). Dis- solve 13.525 grams of crystallized mercuric chloride in a beaker of water containing 300 C. c. of water; in another beaker, with the same amount of water, dissolve 49.680 grams of potassium iodide. Mix the solutions, and make up to a liter with water. It is applied only in acidulous (HCl or H2S04) solutions. The solution to be tested should not contain alcohol or acetic acid. The precipitate is curdy or flocculent, and generally a yellowish-white color. The alkaloid can be reclaimed from the precipitate by treating the washed precipitate with stannous chloride and potas- sium hydroxide to strong alkaline reaction, and then exhausting with ether, chloroform, or benzene as a solvent for alkaloids. 307. Phosphomolybdate (Sonnenschein). The yellow pre- cipitate formed on mixing acid solutions of ammonium molyb- date and disodic hydric phosphate (the ammonium phospho- molybdate) is well washed, suspended in water, and heated with sodium carbonate until completely dissolved. The solution is evaporated to dryness, and ignited till all the ammonia is expelled, sodium being substituted for ammonium. If the molybdenum is reduced (blackening), the residue is heated with nitric acid, and again heated. One part of the residue is dis- solved in ten parts of water, with the addition of strong nitric acid. It must be kept from contact with vapors of ammonia, both during its preparation and while kept for use. The colors of the precipitates are orange yellow to brown yellow. Acidified solutions yield the best results. Most of the precipitates are amorphous, and are soluble in ammonia. Alkaloids that are strongly reducing give some shade of blue. If the precipitated alkaloid is treated with potassium or sodium hydroxide solu- tion, it can be dissolved out with ether, benzene, amyl alcohol, or chloroform. 308. Potassium cadmium iodide (Marme, 1866). Saturate a boiling concentrated solution of potassium iodide with cad- mium iodide, and add an equal volume of a cold saturated solu- tion of potassium iodide. It precipitates the aqueous solutions, 192 LABORATORY GUIDE. acidified with sulphuric acid; soluo^e in excess of the precipitant or in alcohol. In dilute solutions, precipitation is apt to occur. The precipitate is at first amorphous, but becomes crystalline. The alkaloids can be recovered from the precipitates as directed for potassium mercuric iodide. 309. Potassium bismuth iodide (Dragendorff, 1866). Pre- pared from bismuth iodide, in the way directed for the last named reagent. It can be used for aqueous solutions of alkaloid salts when strongly acidified with sulphuric acid. 310. Picric acid (Hager, 1869). In a dilute alcoholic solu- tion. The precipitates form best from sulphuric acid solution. They generally have a yellow or yellowish-white color. The alka- loids can be recovered from their picrate precipitates by adding an alkaline solution and exhausting with water, or by evaporat- ing to dryness with a solution of potassium or sodium carbonate, and extracting with alcohol. 311. Concentrated sulphuric acid containing molybdic acid (Froehde's reagent). A solution of .001 gram of molybdic acid or alkali molybdate in one C. c. of concentrated sulphuric acid, freshly prepared by the aid of heat, and used when cold. 312. Metatungstic acid (Scheibler, 1860). Add phosphoric acid to a solution of tungstate of sodium as long as a precipitate is formed, and dissolved. The precipitates are. white and floccu- lent. 313. Tannic acid (Berzelius) in solution with eight parts of water and one part of alcohol. The precipitates are white to yellowish, and are soluble in ammonia. 314. Platinic chloride (see No. 79) and auric chloride (see No. 69) are sometimes used; also the mineral acids. The color tests may vary with the impurities of the alkaloid or reagent, with the concentration, time, and temperature. In case of any doubt, compare it with the known alkaloid in question, under the same conditions of temperature, etc. Never jump to conclusions on the result of your analysis. POISONS. 193 135 Strychnine (C2iH22N202) was discovered^in 1818 by Pelletier and Caventou. It is found in the seed of Strychnos nux vomica, S. Ignatii, S. Colubrina, and Upas Tieute, of the natural order Loganiaccx. The quantity varies from one and five-tenths to four per cent. Brucine is often used to adulterate it, and it occurs with it in the bean. Five grams of the finely powdered nux-vomica seeds are packed in the percolator of a continuous extraction apparatus, and heated with forty C. c. of alcoholic chloroform, containing twenty-five per cent, of alcohol, for two or three hours. The alcoholic solution is treated with twenty-five C. c. of ten per cent, dilute sulphuric acid. The acidulous watery solution is separated from the chloroform and made alkaline with ammonia, and shaken up with twenty-five C. c. of chloro- form ; the chloroform is gently evaporated, and the weighed resi- due heated to 100° C, on the water bath. This gives the total alkaloids. 1. The brucine can be separated from strychnine by precipi- tating the sulphates with ferrocyanide. The strychnine is precipi- tated; brucine is not precipitated unless concentrated. 2. When treated with twenty-one per cent, (by weight) alco- hol, brucine is dissolved; strychnine undissolved, or but slightly dissolved. Nitric acid gives blood red with brucine; strychnine, no color reaction. The best solvent is chloroform. The medicinal dose is from one-thirtieth to one-twelfth of a grain; the smallest fatal dose is from one-fourth to one-half a grain. When taken in poisonous doses, the symptoms come on suddenly. The patient has violent tetanic convulsions; the pain is intense; the pulse rapid; the mind clear; vomiting is uncommon. The post mortem appear- ances are engorgement of the lungs, congestion of the brain and spinal cord, the fingers are clinched, and the body opisthotonos. The treatment is by emetics and the stomach pump. The use of chloroform, tannic acid, opium, camphor, and chloral hydrate has been recommended. Strychnine is remarkable for its stability under ordinary influences of decomposition. 194 LABORATORY GUIDE. 316. Tests: — 1. Mayer's solution gives a precipitate. 2. Sonnenschein's reagent gives a precipitate which dis- solves in ammonia without coloration. 3. Alkali hydroxides give crystallizable precipitates; solu- ble in excess only in the case of ammonia. 4. It is white, and has an intensely bitter taste, perceptible in a solution diluted to 600,000 to 700,000 parts. The bitter taste is followed by some degree of metallic after taste. When heated on Pt foil, it melts and burns like resin, with a black, smoky flame. 5. Most specimens of strychnine when dissolved in nitric acid give a red color, due, possibly, to brucine; if dissolved with sulphuric acid, it is colorless. If to this solution oxygen be added, or any oxidizing agent, as a small crystal of bichromate of potash, ferricyanide of potassium, black oxide of manganese, or peroxide of lead, there is a beautiful play of colors — purple, violet, and crimson. Black oxide of manganese is the best reagent for the above, and potassium bichromate is the worst. Dr. Letheby uses a galvanic battery to generate the oxygen. Curarine gives the same reaction with sulphuric acid and potas- sium bichromate; but curarine is colored by sulphuric acid alone, while strychnine is not*. Morphine interferes with this reaction. Sulphomolybdic and iodic acids produce no immediate change of color in strychnine, while they do in morphine. (To separate strychnine from morphine, make it alkaline and treat with chloro- form ; it dissolves the strychnine but not the morphine; or abso- lute alcohol, which dissolves the morphine but not the strych- nine.) The fact that, morphine is given by physicians should caution the student to be careful in distinguishing between them. 6. Sodium bicarbonate, or potassium sulphocyanate, or mer- curic chloride, or iodide of potassium produces a white precipitate ♦ Curarine gives, with sulphuric acid, a red color; strychnine gives none. Cura- rine may be separated from strychnine by means of benzene, in which the former is insoluble. Cod liver oil gives a similar reaction; distinguished by the taste. Aniline, pyroxanthine, papaverine, narceine, veratrine, and solanine belong to this list. POISONS. 195 8. Dr. Hall's physiological test is made by injecting a dilute solution of strychnine into the thorax or abdominal cavity of a frog, causing tetanic convulsions. Locally there is but slight irritation. Its tetanic effects are due to its action on the gray nerve tissue of the spinal cord. Many of the tests are delicate when examined with a microscope. 317. Brucine (C23H26N204) was discovered by Pelletier and Caventou in 1819. It has been thought by some to be a dimethoxy-strychnine, C21H20(OCH3)2N2O2, and to be capable of being converted into strychnine(?). Brucine is found with strychnine in the Strychnus nux vomica, S. Ignatii, S. Colubrina, and Upas Tieute, of the natural order Loganiacex. The best source of brucine is the false angustura bark, which contafns but little strychnine. "The effect of brucine is similar to that of strychnine, but requires ten or twelve times the amount of strychnine to produce the same effect. It is excreted far more rapidly than strychnine — so rapidly that when given by the stomach to animals it produces little effect. It is soluble in alcohol, chloroforms benzene; almost insoluble in ether. In sepa- rating it from organic mixtures, see strychnine. The ordinary salts of brucine are soluble in water and in alcohol, but not in ether. The symptoms of brucine are like those of strychnine, but they come on more slowly and are less violent. The mode of treatment is the same for both poisons. 318. Tests: — 1. The general reagents for alkaloids give the customary pre- cipitates with brucine 2. The physiological test of brucine, with a frog, is, quali- tatively, nearly the same as that for strychnine, but larger quan- tities are required. 3. When brucine is treated with nitric acid (sp. gr. 1.42), it gives a blood red color; if it is heated, it changes to yellow. When cold, and a trace of protochloride of tin is added, the color changes to a deep purple; an excess of acid or of tin bleaches it. 196 LABORATORY GUIDE. 4. Bichloride of platinum gives a yellow precipitate of the double chloride of platinum and brucine, decomposed by caustic alkalies; insoluble in acetic acid. The chloride of gold gives a somewhat similar amorphous precipitate; sparingly soluble in acetic acid. Caustic alkalies blacken it. 5. When mixed with sulphuric acid and bichromate of potash, orange, green, and yellow tints are produced in turn, due to the reduction of the chromium. 6. If, to a solution of brucine in strong alcohol, a little methyl iodide is added, in a few minutes circular rosettes of methyl brucine iodide, C23H25(CH3)N204HI, form. 319. Igasurine is an alkaloid as yet but little studied. It is said to be poisonous, its action being similar to that of strych- nine and brucine, in activity standing midway between the two. It is obtained from the boiling-hot watery extract of nux-vomica seeds after precipitating the strychnine and brucine by lime and then evaporating the filtrate. 320. Morphine (Ci7H19N03) was discovered by Serturner in 1816. It is one of the poisonous alkaloids of opium, good opium yielding from six to fifteen per cent, of the alkaloid. Hesse (1872) presented a division of the opium alkaloids by treating them with pure sulphuric acid: 1. Morphine, pseudomorphine, codeine, gave dirty dark green. 2. Laudanine, codamine, laudanosine, gave dirty red violet. 3. Thebaine (?), cryptopine, protopine, gave dirty green to brown green. 4. Papaverine gave dark violet. 5. Narceine, lanthopine, gave black brown to dark brown. 6. Narcotine, hydrocotarnine gave dirty red violet of a dif- ferent shade from (2) above. The salts of morphine are, for the most part, crystalline, and are all bitter, neutral, and poisonous. They are insoluble in ether, chloroform, benzene, or petroleum ether. It is a decided POISONS. 197 base, and neutralizes strong acids. The medicinal dose is one- fifth of a grain. The smallest fatal dose is one grain. It is about six times as strong as good opium. Drowsiness and stupor are the first symptoms; pulse, weak; breathing, slow and almost imperceptible; the pupils, in most cases, contracted. When large doses (poisonous) are given, these symptoms are some- times attended with convulsions. The post mortem appearances have nothing characteristic, except, in some cases, the peculiar odor of opium. During treatment, keep the patient constantly aroused by any means. The poison should be eliminated by emetics and the stomach pump. In some cases the magneto- electricity is used with good effect to prevent insensibility; solu- tions of iodine, bromine, and tannic acid have been recom- mended. Strong tea or coffee is the best drink. Ammonia can be applied to the nostrils in case of a collapse. The existence of opium is determined by the presence of morphine and meconic acid. The aqueous solutions of morphine can be concentrated on the water bath, better under diminished pressure, at 75° C. The residue is treated with hot alcohol. The acidified aqueous solu- tion may be purified from other alkaloids by being treated with benzene, ether, and chloroform. The liquid is made alkaline with ammonia and treated with amyl alcohol to dissolve out the morphine. 321. Tests:— 1. Nitric acid gives, at first, a bright red, then an orange red color. Chloride of tin does not decrease the color, differing from brucine. 2. Dissolve ammonium molybdate in strong sulphuric acid (and it should be made as required for use). It gives with mor- phine, or its salts, a reddish purple or crimson red color. This changes to a green, and ultimately to a sapphire blue (Frcehde's reagent). 3. If iodic acid and bisulphide of carbon are mixed together no change occurs; if morphine (solid or solution) is added, 198 LABORATORY GUIDE. iodine is separated from the iodic acid, and dissolves in the bisul- phide, coloring it pink or red. Of course, a solution of starch will do as well, giving a blue color. 4. The reducing power of morphine is also shown by treat- ing a drop of neutral ferric chloride with a drop of a dilute solu- tion of potassium ferricyanide; a blue color indicates morphine. Narcotine, brucine, and the ptomaines, give this reduction. 5. Morphine, treated with concentrated sulphuric acid and potassium chromate, gives a green color, due to the reduction of the chromium. 6. Neutral ferric chloride gives a blue color with morphine or its salts. 7. The general qualitative reagents for alkaloids all give tests with morphine. 8. Add a drop of pure sulphuric acid to the dry residue of morphine; with a glass rod, moistened with nitric acid (sp. gr. 1.42), touch the moistened residue, when a red to violet color indicates morphine. Potassium nitrate can take the place of nitric acid above. 322. MeCOniC acid (H8C7H07). Found only in opium (three to four per cent.) It crystallizes in white, shining scales or small rhombic prisms. It is soluble in 115 parts of water, freely soluble in alcohol, slightly soluble in ether. It has a marked acid reaction, and an astringent taste. The meconates are nearly all insoluble in alcohol. It gives, with a solution of ferric chloride, red color; with acetate of lead, yellowish-white color. Nitrate of silver precipitates yellovo amorphous meconate of silver; barium hydroxide precipitates yellow meconate of barium. The physiological action is thought to be similar to lactic acid. There is slight narcotic action on man. The alcoholic extract from organic fluids is made feebly acid with HN03 ; on filtration, the alcohol, after the addition of a little water, is distilled off, and to the remaining fluid a solution of lead acetate is added, and the whole filtered. The filtrate will contain any alkaloids; whilst meconic acid, if present, is with the lead on the filter. It is POISONS. 199 washed with acetic acid to purify it. The lead salt is decom- posed by II2S, and the filtrate is tested with ferric chloride, or evaporated to dryness and weighed. 323. Codeine (C18H21N03) was discovered by Robiquet in 1832. Opium contains from one-tenth to one per cent. It is separated from morphine and narcotine by its solubility in water (eighty parts cold, seventeen parts hot), benzene, and ether. The anhydrous alkaloid melts at 150° C, and solidifies to a crystalline mass on cooling. It has a strong alkaline reaction. It is odor- less, somewhat bitter, and resembles morphine in its physiologi- cal action. The dose is from five-tenths to one grain (.032 to .065 grams). It is readily soluble in alcohol, ether, and chloro- form (seven parts amyl alcohol, ten parts benzene); almost insoluble in petroleum benzin. Chloroform extracts it from alkaline solutions most readily. 324. Tests: — 1. Ammonia precipitates it after standing (not completely), potassium hydroxide, iodine in potassium iodide (brown), potas- sium mercuric iodide (white), potassium cadmium iodide (white), phosphomolybdic acid (yellow brown), tannic acid (white), mer- curic chloride (crystalline), platinum chloride (yellow), gold chloride (brown). 2. Concentrated sulphuric acid dissolves it without color, becoming blue on warming. If a trace of nitric acid or ferric salt be added, the blue color is hastened. 3. Nitric acid (sp. gr. 1.2) dissolves it to a yellow liquid, which should not become red (difference from, and absence of, morphine). 4. It is distinguished from morphine by (1) the different form of its crystals (which are octohedral); (2) its solubility in boiling ether; (3) its insolubility in alkaline solutions; (4) not assuming a red color with nitric acid, (5) or a blue with ferric salts. Morphine is artificially converted into codeine (Grimaux, 1881) by treatment with methyl iodide and fixed alkali. 200 LABORATORY GUIDE. 325. Narcotine (Desrone, 1803). Opium contains from 1.3 to 10.9 %. It acts as a narcotic poison only in large doses (from 1.5 to 3 grams). It is distinguished and separated from mor- phine by its solubility in ether. It is soluble in 7,000 parts of boiling water; in 24 parts of boiling alcohol (96%); in 48 parts of boiling ether (sp. gr. .735); in 60 parts of acetic ether; in 2.7 parts of chloroform; in 300 parts of amylic alcohol; in 22 parts of benzene. Chloroform removes it from acid solutions. It can be obtained from the residue after treating opium with water, by treating with dilute HCl, precipitating with NaHC03, extracting the precipitate with boiling 80% alcohol, and crystallizing. It is estimated gravimetrically or by Mayer's solution. 326. Tests: — 1. It gives precipitates with alkaline hydroxides, carbo- nates and acid carbonates, iodine in potassium iodide (brown), potassio-mercuric iodide (white), potassium sulphocyanate (amorphous). Other reagents not characteristic precipitates. 2. Concentrated sulphuric acid dissolves first colorless, then yellow. On heating, it becomes orange red, violet, dark blue, finally violet red. If a drop of HN03 is added to H2S04 solu- tion of narcotine, a red color is produced. 327. Quinine (C20H24N2O2). (Pelletier and Caventou, 1820.) It has a bitter taste. It is poisonous to the lower forms of animal life. It is excreted in the urine to the extent of seventy to ninety-six per cent, of the amount taken. It sometimes appears in one hour after being taken, and disappears in about forty-eight hours. It is found in the liver. The bisulphate is more soluble than the sulphate. It has a decided alkaline reac- tion. The normal salts are neutral. The sulphate [(C20H22N2O2)2H2SO4.7H2O] is soluble in thirty parts of boiling water, in three parts of boil- ing alcohol, in forty parts of glycerin, in one thousand parts of chloroform, and slightly in ether. Quinine salts, with mineral acids containing oxygen, exhibit blue fluorescence in their aqueous solutions. The bisulphate POISONS. 201 shows this better than the sulphate. Other alkaloids of cin- chona show this reaction. Quinine is very nearly separated from strychnine and morphine by its solubility in ether, partially separated by its solubility in ammonia. The sulphate of quinine is approximately separated from atropine and morphine by the difference of solubility in water. Kerner's method of identifica- tion is as follows: A certain quantity of the sulphate of the alkaloid is dissolved in a certain quantity of water, and then the water of ammonia is added gradually until the precipitated alka- loid is redissolved. The quantity of the ammoniacal liquid nec- essary to produce this effect, indicates inversely the solubility of the alkaloid. Quinidine requires from ten to eleven times more of the ammoniacal liquid than quinine; cinchonidine from twelve to thirteen times more; while cincohonine is not dissolved by a much larger proportion than is required by either of the others, and, though when mixed in very small proportion with quinine it is dissolved at first, yet it afterwards separates on standing. This test is now officinal. 328. Tests: — 1. Treated with fresh chlorine water or bromine water, not in excess, or well diluted, and then with ammonia to alkaline reac- tion, green precipitate, dilute solutions, green solution (Thalleio- quin test). If ferricyanide of potassium be added after the Cl or Br, and then ammonia, a red color is obtained. Quinidine, diqui- nicine, quinicine, hydroquinine, and hydroquinidine give the above reaction, while cinchonidine and cinchonine do not give it. 2. Alkaline hydroxides and carbonates precipitate quinine. 3. The general reagents give precipitates with quinine. 329. Veratrine (C^HggNOu) was discovered by Meiss- ner in 1819. It is an alkaloid, or mixture of alkaloids, prepared from the seeds of Asagrxa officinalis. The seeds are treated with alcohol, and the alcohol recovered by distillation. The residuary liquid contains veratrine with veratric acid. The resins are pre- cipitated with water, and filtered; ammonia is added to the 202 LABORATORY GUIDE. filtrate. Veratrine is precipitated. It is purified by recrystalli- zation. It is a white or grayish-white amorphous powder with an acrid taste. It leaves a numbness on the tongue, and is highly irritant to the nostrils. It has a feebly alkaline reaction. It i.s soluble in three parts of alcohol, six parts of ether, two parts of chloroform, ninety-six parts of glycerin. When heated, it melts ; at higher temperatures it chars and is wholly volatilized. It is given (one-twelfth of a grain) in gout, rheumatism, and neural- gia. It is sometimes employed in dysmenorrhcea, paralysis, hysteria, and disorders dependent upon spinal irritation. 330. Tests: — 1. The general reagents give precipitates with veratrine. 2. "With nitric acid, veratrine forms a yellow solution, and, by contact with sulphuric acid, it first assumes a yellow color, which soon passes to reddish yellow, then to an intense scarlet, and after a while, to violet red. On triturating veratrine with sulphuric acid in a glass mortar, the yellow or yellowish-red solution exhibits, by reflected light, a strong, greenish-yellow fluorescence, which becomes more intense on adding more sul- phuric acid. Heated with concentrated hydrochloric acid, it dis- solves with a blood-red color."—U. S. Selmi has found in the viscera ptomaines that act like this poison. 331. Aconitine (C33H43N012). It was discovered by Geiger and Hesse in 1832. From Aconitum Napellus. It exists in an amorphous and crystalline form, is inodorous, and has a bitter and acrid taste. It is used in the form of an ointment for neuralgia. It is, possibly, the most powerful poison known. The medicinal dose is T^7 of a grain. It is doubtful if the alkaloid can be administered internally with safety; one-tenth grain can be regarded as a fatal dose. When taken in poisonous doses, the symptoms come on rapidly. There is diminished sensibility; the skin loses its sensation, whilst there is deafness and ringing in the ears, dimness and loss of sight; the pulse is low, feeble, and irregular, becoming at last almost imperceptible, with clammy, POISONS. 203 cold sweats; finally, after a few convulsive gasps, the patient expires. In treating, evacuate the contents of the- stomach. Brandy and ammonia may be used as stimulants. The following substances are recommended: Vegetable infusions containing tannic acid, iodine in iodide of potassium, also a dilute solution of nux-vomica; strong tea and coffee can be given. The post mortem appearances are characterized by general venous conges- tion, the brain, liver, and lungs being more or less engorged, and usually accompanied by signs of gastro-intestinal irritation. It is separated from the plant (roots) or from animal tissues by extracting with alcohol feebly acidulated with tartaric acid, evaporating the extract at a low temperature, 60° C.; redissolve in water, treat with ether to remove impurities, and precipitate with sodium bicarbonate, and recrystallize. The physiological action of aconitine is excessively ener- getic— so much so as to render working with it a matter of con- siderable pain and difficulty. It is soluble in 726 parts of cold water (more soluble in hot water), twenty-four parts of ninety per cent, alcohol, benzene (sparingly when cold), freely soluble in chloroform, soluble in amyl alcohol; does not dissolve in petroleum benzin or carbon disulphide. 332. Tests: — 1. The general reagents give precipitates with aconitine. 2. The physiological action is its chief test. If it is rubbed on the inside of the gums (dilute solution), it produces a sense of tickling and numbness. Note.— The small quantity required to produce death, the sj'mptoms, and the physiological action, are indications of as much importance as the chemical tests for this poison. 333. Atropine (C17H24N03) was first announced by Brandes in 1819, and in 1833 by Mein, a German pharmaceutist, who obtained it pure. It is found in the roots, leaves, and berries of the atropa belladonna or deadly nightshade, in about .5 per cent. The fatal dose is two grains; the medicinal dose for hypo- dermic injection should not exceed ^T grain. Symptoms : The 204 LABORATORY GUIDE. patient is drowsy and giddy; the pulse is strong and rapid, the action,of the heart being increased; the eyes are prominent and sparkling, and the pupils always dilated. There is often a desire to micturate or walk, and an inability to do either. As it approaches fatal termination there is delirium and sometimes convulsions; these may alternate, and either may end in death. The post mortem appearances are not well marked. Treatment is by emetics; morphine is sometimes administered. Atropine forms colorless crystals, having a bitter and acrid taste and an alkaline reaction. It is soluble in six hundred parts of cold water, thirty-five parts of boiling water, in three parts of chloroform, in sixty parts of ether, very soluble in alcohol, in amyl alcohol, and benzene forty-two parts, scarcely soluble in petroleum benzin or carbon disulphide. Fixed oils dissolve it. It may be separated from the contents of the stomach by acidulating with twenty per cent, of sulphuric acid, digesting for some time at a temperature not exceeding 70° C, and then reducing any solid matter by fric- tion, and filtering with a Bunsen pump. The acid liquid thus obtained is shaken up with amyl alcohol (to remove the impuri- ties), and after the separation of the amyl alcohol, it is agitated with chloroform, which serves to purify it further; the fluid is now made alkaline and shaken up with ether, and the ether is allowed to evaporate spontaneously. The residue contains the atropine, and in some cases, sulphate of ammonia. If treated with absolute alcohol, the alkaloid is dissolved; the sulphate of ammonia is insoluble. 334. Tests: — 1. The general reagents give precipitates with atropine. 2. "With sulphuric acid, atropine gives a colorless solution, which is neither colored by nitric acid (absence of, and difference from, morphine) nor at once by solution of bichromate of potas- sium (absence of, and difference from, strychnine), though tl.c latter reagent, by prolonged contact, becomes green. The aqu - ous solution of atropine, or of any of its salts, is not precipitated by test solution of platinic chloride (difference from most other alkaloids)." —U.S. POISONS. 205 3. Vitali's test: The dry residue is treated with a little fuming nitric acid, then dried on the water bath, and, when cold, touched with a drop of a solution of potassium hydroxide in absolute alcohol, when, in evidence of atropine, or of its isomers, a violet color will be produced, slowly changing to a dark red. Strychnine gives a red, brucine a greenish color. The violet color is distinctive for atropine among all the important alka- loids, and gives this test with .000001 of a gram of the alkaloid. 4. The physiological test for the presence of atropine is best tried on the eye of a cat. The pupil-dilating alkaloids are chiefly atropine and its isomers, but it must be noticed that other bodies besides the solanaceous alkaloids dilate the pupil — cocaine, digi- talis and its active principle, and conine. 335. Nicotine (C10H14N2) is found in the common tobacco plant, which contains from four to eight per cent, of it. It was discovered by Posselt and Reimann in 1828. It is a trans- parent, colorless, oily, liquid (sp. gr. 1.027), boiling at 247° C. It has an exceedingly acrid taste, even when largely diluted. It is volatile, and when in the state of vapor, very irritating to the nos- trils ; the odor resembles that of tobacco. It is one of the most active poisons known. It is soluble in water, alcohol, ether, chloroform, turpentine, and the fixed oils. It is strongly alkaline in its reactions, and forms crystallizable salts with the acids. It has the remarkable property of resisting decomposition amid the decaying tissues of the body. Both chloroform and ether extract it from aqueous solutions. The characteristic symptoms of poisoning by it are vertigo, nausea, vomiting, extreme prostration, trembling of the limbs, etc.; respiration is difficult, the skin cold and clammy. The poison Is very rapid in its action, and when taken in poisonous doses (one drop usually fatal), death occurs in a few minutes, even equaling hydrocyanic acid in the rapidity of its action. In treating, remove the poison by emetics, etc. Allay pain with opium, or its equivalent, and preserve power with stimulants. The post mortem appearances are not very characteristic. The poison should be boked for in the lungs^ liver, and stomach. 206 LABORATORY GUIDE. Nicotine and conine are separated in the same manner from organic matters. The substances are digested with water, acidu- lated with H2S04, at a temperature not exceeding 40° C, and filtered. To the filtrate concentrated alcohol is added, the liquid refiltered, and from the filtrate the alcohol is separated by distil- lation. On cooling, the acid liquid is agitated with benzene, and the latter separated. The fluid is now rendered alkaline with ammonia, and shaken up once or twice with its own volume of petroleum ether; the latter is separated and washed with dis- tilled water, and the alkaloid is obtained almost pure. If the petroleum ether leaves no residue, it is certain that the alkaloid was not present in the part examined. The oxalate of nicotine is the best salt from which to regen- erate nicotine in a pure state. 336. Tests: — 1. Nicotine is precipitated by alkalies, and by many oxyhy- drates — lead, copper, etc. Light changes it to a yellow or brown color, and it becomes thick; in which state it leaves, on evapo- ration, a brown resinous substance, partly soluble in petroleum ether. 2. It gives, from etherial solution, needle-like crystals when treated with a solution of iodine in ether. The crystals form in a few hours. 3. Chlorine gas colors nicotine blood red or brown; the product is soluble in alcohol, and on evaporation separates in crystals. 4. A drop of nicotine poured on dry chromic acid blazes up and gives the odor of tobacco. The general reagents give precipitates. NICOTINE. CONINE. Tobacco odor. "Mousy" odor. Freely soluble in water. Sparingly soluble in water. No crystals with HCl fumes. Crystals with IICI fumes. AgN03 gives a white precipitate. AgN03 gives a dark-brown precipitate. Docs not coagulate albumin. Coagulates albumin. Gives crystalline precipitates with aque- Similar precipitates with HgCl2 are ous solution of HgCl2. amorphous. POISONS. 207 337. Conine (C8H15N) is an alkaloid from the poison hemlock. The death of Socrates is generally believed to have been due to this poison. The alkaloid is most abundant in the fruit of the plant, containing about one per cent. It was first obtained as an impure sulphate by Giseke in 1827. One drop may be regarded as a fatal dose. The symptoms are a gradual and complete paralysis of the extremities, enlargement of the pupils, and loss of power. The paralysis gradually extends to the muscles of respiration, and the patient dies of apnoea. The characteristic post mortem appearances are congestion of the stomach and lungs, and more or less congestion of the brain. The blood remains fluid, and there is little evidence of poison in the intestines. In treating, remove the poison by emetics and the stomach pump; then give stimulants. Nicotine and conine are volatile alkaloids, and are liquids at ordinary temperatures. They are colorless, oily, and volatile. Conine boils at 163° C. One part is soluble in one hundred parts of water, six parts of ether, and in almost all proportions of amyl alcohol, chloroform, and benzene. It ignites easily, and burns with a smoky flame. It acts as a strong base, precipitating the oxides of metals and alkaline earths from their solutions. It coagulates albumin. (It is written coniine, conia, conicine.) 338. Tests: 1. The general reagents give precipitates with conine. 2. A crystal of K2Cr207 is put at the bottom of a test tube, and some dilute sulphuric acid with a drop of the supposed conine added. On heating, the butyric acid reveals itself by its odor. Butyric acid is formed by heating K2Cr207 with dilute H2S04 and conine. 3. When dropped into a solution of alloxan, the latter is colored, after a few minutes, an intense purple red, and white needle-shaped crystals are separated, which dissolve in cold potash-lyo into a beautiful purple blue, and emit an odor of the base. 208 LABORATORY GUIDE. 339. Caffeine (C8H10N4O2) was first discovered by Runge in 1821. Oudry found it (theine) in tea in 1827. Mulder Jobest, in 1838, showed that caffeine and theine were identical. The average percentage is as follows : In tea (prepared leaf of Camellia Thea), two to three per cent. In coffee (dried seed of Coffea arabica), one per cent. In guarana (crushed seed of Paulinia sorbilis), four per cent. In mate (leaf of Ilex paraguayensis), one-half per cent. In cola nut (seed of Sterculia acuminata), two per cent. Caffeine is a strong base. It is without odor, and has a bitter taste. The medicinal dose is three grains. Caffeine is remarkable for containing a larger proportion of nitrogen than almost any other proximate vegetable principle, in this respect equaling some of the most highly animalized products. It dissolves in 68 parts of cold water, 10 parts of boiling water, in 35 parts of ordi- nary alcohol, in 476 parts of ether, in 8 parts of chloroform, in 4,000 parts of petroleum benzin. Exhaust the substance with boiling water, evaporate the filtrate with one-half its weight of magnesia and about its weight of ground glass. The residue is pulverized, and treated with eight times its weight of ether for twenty-four hours, filtered, and the residue again treated with ether; the ether is evaporated and the residue weighed. A smaller quantity of chloroform will do; but the product is not so pure an alkaloid. Or this method can be used: Exhaust the bruised coffee by successive portions of boiling water, unite the infusion, add acetate of lead, filter, decompose the lead with H2S, filter, concentrate by evaporation, neutralize with ammonia; the caffeine is precipitated. 340. Tests: — 1. A portion of the solid in a white porcelain dish is heated on the water bath with a few drops of HCl, a minute fragment of KC10S is added, the mixture evaporated to dryness, and well dried on the water bath. When cold, the residue is slightly POISONS. 209 moistened with ammonia water, applied by the point of a glass rod : a purple color is obtained. It has a reddish-yellow to pink- ish color before the action of ammonia. .00005 gram gives this test. 2. It crystallizes in long, slender, flexible, white crystals of silky lustre. It requires a magnifying power of three hundred diameters to bring these out nicely. 3. It is distinguished from most other alkaloids by non- precipitation with potassium mercuric iodide, by yielding cyanide when heated with soda-lime, by dissolving in* water, and from acidulous mixture by dissolving in chloroform. 4. Contact with H2S04 should not cause coloration, and on heating at 100° C, it should darken but slowly. Contact with cold (colorless) nitric acid should not give immediate coloration. When heated in a test tube, it sublimes, leaving no residue. 341. Cocaine (C17H21N04) was discovered by Lossen in 1865. It is the chief alkaloid of the Erythroxylon coca leaf. The hydrochlorate is the chief form of the alkaloid in general use. Cocaine melts at 98° C. It has a bitter taste, and is with- out odor. It is very slightly soluble in water, soluble in alcohol, ether, chloroform, benzene, petroleum benzin, disulphide of car- bon, and in fixed and volatile oils. The cocaine solutions have a strongly alkaline reaction. It is removed from aqueous solution of its salts by adding ammonia to liberate the alkaloid, avoiding an excess, and shaking out with ether, chloroform, benzene, or petroleum benzin. From etherial solutions the alkaloid is taken up by slightly acidulated water, upon agitation. 342. Tests:— 1. It has an intense local anaesthetic and blanching effect upon the mucous membrane. A valuable reagent in minor surgi- cal operations. 2, Mayer's solution, iodine in iodide of potassium, phospho- molybdate, tannin, mercuric chloride (in concentrated solutions), with red color. Caustic alkalies, platinum chloride, gold chlo- ride, alkaline carbonates, cause precipitates. When paper is wet « 210 LABORATORY GUIDE. with a drop of ferricyanide and a drop of ferric chloride, on adding a drop or two of the alkaloid, a reduction takes place, and Prussian blue is formed in this order: morphine, in one-half a minute; cocaine, one and one-half minutes ; brucine, six minutes; quinine, seven minutes; cinchonine, ten minutes; strychnine, veratrine, each fifteen minutes (Curtman). 343. The Salts of the alkaloids are more soluble in H20 than the alkaloids, and are generally used for the solutions to be tested. After the alkaloids and volatile bodies are removed by the treatment before described in No. 302, the organic matter is removed, in order to dissolve out the metals more completely. From one hundred to five hundred grams of the contents of the stomach or other organ are mixed in a large retort (it should only fill one-third of the retort), with twenty-five per cent, of KHS04 and a quantity of fuming HN03, equal in weight to the organic matter taken, is added. The reaction is at first violent, but must afterwards be assisted by gentle heat. Any thing that may come over is caught in a receiver and saved. H2S04 is added in large excess, and the mixture heated to near the boiling point of the acid. This may have to be repeated. When the liquid has cooled, add a few crystals of KN03, and again heat until white fumes are given off: a clear liquid, which solidifies on cooling, contains, in the form of sulphate, all the metals as bases. Now dissolve in boiling H20, and add what is in the receiver, if any, and dilute the whole to one liter. The solution, without previous filtration, is then electrolyzed by means of a battery. If Hg is present, or sought, use gold electrode; otherwise platinum will do. From this solution the bases can be separated and identified by the group reagents. If the solution is too acid, it can be removed by evaporation at a gentle heat. The tests for the inorganic poisons are sufficiently described where they occur in the body of the book. 344. Antimony. The most important compound to the toxicologist is tartar emetic (KSbOC4H406). Discovered in 1831 POISONS. 211 by Adrian de Mynsicht. It has small transparent crystals, which become opaque and white on exposure to air. It has a sweet, and, afterwards, metallic taste, and a feebly acid reaction. It is soluble in seventeen parts of cold water and three parts of boiling water; insoluble in alcohol, which precipitates it as a crystalline powder from its aqueous solution. Ten grains is the smallest dose reported to have proved fatal. The medicinal dose is from one-twelfth to one-sixth of a grain. The poisonous symptoms are metallic taste, nausea, vomiting, frequent hiccough, burning pain in the stomach, colic, frequent stools and tenesmus, small, contracted, and accelerated pulse, coldness of the skin, difficult and irregular respiration, painful cramps in the legs, prostration and death. It was formerly much used as a sedative, antiphlogistic, diaphoretic, and expectorant. It is sometimes used as a counter-irritant, mixed with lard. In some rare cases vomiting and purging do not take place, but the other symptoms are aggravated. The post mortem appearances are general congestion, a fluid condition of the blood, and intense vascularity of the digestive organs. Treatment: If the patient has not vomited, tickle the throat with a feather, or give emetics; tannic acid is given to form an inert tannate of antimony; if the vomiting is excessive, give an injection of laudanum or morphine. It can be known from most other metallic poisons from the fact that with ferrocyanide of potassium it does not give a pre- cipitate. It is easily identified by Marsh's test, Reinsch's test, or by sulphuretted hydrogen. It is well to dissolve out the poison by hydrochloric and tartaric acids, the latter to dissolve the anti- mony that may be there that is not combined already with tar- taric acid. For tests see No. 155. 345. Phosphorus was discovered in urine by Brandt in 1669. In 1769, Gahn discovered it in bones. It is always found' in combination, never free, its chief source being calcium phos- phate. It should be handled with care, and always cut under water. Its specific gravity is 1.83; its melting point is 44° C. It is insoluble in water, soluble in 350 parts of absolute alcohol, in 212 LABORATORY GUIDE. 80 parts of absolute ether, in 50 parts of any fatty oil. Bisul- phide of carbon will dissolve eighteen times its weight of phos- phorus without losing its fluidity (Vogel). (The red or amor- phous phosphorus has a specific gravity of 2.11, and is insoluble in bisulphide of carbon, alcohol, and ether. It is but little acted upon in the air, and is not poisonous.) It is given as a nutritive stimulant to the nervous system, in neuralgia, mania, chronic eczema, and other affections of the skin. The medicinal dose is T?ro" *o -fs of a grain. Poisoning by it has been confined mostly to the use of friction matches and the phosphorus paste used for rat poison. * When taken internally, it enters the circulation, imparts to the breath, urine, and sweat, a garlic odor, and makes the secretions luminous in the dark. The vapor of phosphorus causes a necrosis of the jaw bone. Symptoms: Besides those above described, there is a feeling of lassitude, nausea, and great thirst; cold perspiration, and feeble and irregular pulse; the abdomen becomes tender to the touch; the extremities, cold; pulse, imperceptible; and other symptoms of collapse. Death may take place in from one to three days. The smallest fatal dose was in the case of a child that died after sucking two matches, the estimated quantity being about ■£$ of a grain Treatment: Sulphate of zinc should be given in three-grain doses every five minutes until vomiting is induced; opium, to restrain the emesis, should be administered in such doses as the stomach will retain. Sulphate of magnesium should be used as a quickly acting purge, and symptoms treated upon general principles. The post mortem appearances are those of a corro- sive irritarit poison; blood is often found in the bladder, intes- tines, and pleural cavity. There is fatty change in the liver, kidneys, glands of the stomach, heart, and muscles. For tests see Nos. 107, 215, 216, 217, 218, 303. When it is tested by distilling it over in the dark, alcohol, ether, and oil of turpentine prevent the occurrence of the lumin- ous appearance until they have distilled over. 1. Hofmanrts test: Mix the viscera with water, and a little sulphuric acid. Now distill it until two d;:achms of liquid are POISONS. 213 obtained; to this add a few drops of sulphide of ammonium, and evaporate the liquid to dryness in a porcelain dish. If phos- phorus is present in minutest quantity, a drop of a solution of ferric chloride will produce a deep violet and brownish color that is evanescent. 2. Dusart's test: Consists in passing pure hydrogen gas, evolved in a separate vessel, through the solution supposed to contain phosphorus, which solution has been previously warmed to about 50° C. The gas then is allowed to issue from a fine jet, and is lighted. If phosphorus is present, the flame shows a green color in the center. 346. The mercury compound of most importance is cor- rosive sublimate (HgCl2). It is soluble in sixteen parts of cold water, two parts of boiling water, three parts of alcohol, four parts of ether. When heated to 265c C, the salt fuses;'at a higher temperature, it sublimes unchanged and without residue. Ether is capable of removing corrosive sublimate, to a consider- able extent, from its aqueous solution when agitated with it. Sulphuric, nitric, and hydrochloric acids dissolve it without alteration. Corrosive sublimate has the property of retarding putrefac- tion. Animal matters immersed in its solution shrink, acquire firmness, assume a white color, and become imputrescible. On account of this property it is usefully employed for preserving anatomical preparations. Corrosive sublimate is a very powerful poison, operating quickly and producing violent effects. It is less apt to salivate than most other mercurials. In minute doses, it produces a slight increase in the frequency of the pulse, and in the secretions from the skin and kidneys. It may purge, but this effect can be modified by combining it with a little opium. It is used in nearly all stages of syphilis, in chronic cutaneous affections, and in obstinate chronic rheumatism; externally it is used as a stimulant and escharotic. The medicinal dose is from one- twelfth to one-eighth grain. In poisonous doses, it produces heat 214 LABORATORY GUIDE. in the throat, pain in the stomach and bowels, thirst, vomiting of bloody mucous, diarrhoea, bloody stools, small rapid pulse. difficult respiration, fainting, convulsions, and death. Death may take place in half an hour, or it may be delayed for weeks. Treatment: White of egg in milk; albumin in some form, fol- lowed by emetics, with Peruvian bark, meconic acid, lime water, ferrocyanide of potassium. It is of the utmost importance in all poisons that whatever antidote is given it should be used without delay, and in this respect the one nearest at hand may be con- sidered the best. The pathological effects are too various to be distinctive. In acute poisoning the changes are great and strik- ing. After a violent death from corrosive sublimate, the eschar- otic whitening of the mouth, throat, and gullet will be seen. The mucous membrane from mouth to anus is more or less affected and destroyed, the stomach congested, may be destroyed; some- times the coats are black. The main channel by which the absorbed mercury passes out of the body is by the kidneys. If an insoluble compound is formed, it passes off by the bowels. For the tests see No. 139. Reinsch's test gives a stain that resembles As. A piece of polished gold immersed in a clear solution of cor- rosive sublimate and touched with the point of a pen knife (to make a battery) forms a white stain. 347. Arsenic is. found combined with many of the metals; as, Ag, Cu, Fe, etc. Its principal source is the arsenical pyrites. The substance used in the arts under the name of arsenic is really the oxide of arsenic (arsenious anhydride As203). It is entirely volatilized by heat at 204° C. The specific gravity is 3.7. It has little, if any, taste. It is soluble in from thirty to eighty parts of water, the solubility varying with its physical condition; it is slowly but completely soluble in fifteen parts of boiling water, sparingly soluble in alcohol. It is freely soluble in HCl, the alkalies, and their carbonates, and moderately soluble in glycerin. The transparent form is more soluble than the opaque. POISONS. 215 When taken in large doses, all the compounds of arsenic are violent irritants or escharotics. Medicinal doses are alteratives affecting the nutrition of the nervous system, and are given in nervous debility, chorea, and chronic malaria. It is the chief ingredient in nearly all the empirical remedies for the cure of cancer by external application. It has a wide application in skin diseases. It is used in many paints, bug and rat poisons, pyro- techny, medicines, and in making aniline dyes. It is no longer considered a cumulative poison; that is, the continued use of frequent small doses is not believed to possess the power of grad- ually and silently accumulating in the body, and then suddenly breaking out with dangerous or fatal violence. The poisonous symptoms are bad taste, fetid state of the mouth, often ptyalism, continued hawking, a feeling of contraction in the oesophagus and pharynx, hiccough, nausea, burning pain at praecordia; inflammation of the mouth, throat, and oesophagus; irritable stomach, vomiting; black, fetid stools ; small, frequent, irregular pulse; great thirst, difficult respiration, cold sweats, suppression of urine (it may be scanty, or bloody, or contain albumin) ; the mind is generally clear. The symptoms may terminate in many ways: (1) Convulsions, in fits of an epileptic nature; (2) col- lapse, with or without pain, and vomiting or diarrhoea; (3) intense coma; (4) immediate death, as if by shock; (5) it may act like cholera, and deceive the practitioner. Treatment: Give emetics of sulphate of zinc or sulphate of copper; afterwards give milk and white of eggs. The chemical antidote, due to Bunsen and Berthold, is the hydrated sesquioxide of iron. The chemistry of the operation is thought to be as follows: The arsenious acid is oxidized to arsenic acid by the oxygen of the iron, while the iron is reduced to the protoxide (2Fe203 + As203 = 4(FeO) + As205); now this protoxide of iron combines with acid to form an insolu- ble or difficultly soluble arsenate of iron, about fourteen parts of the moist, recently precipitated iron being used to one of arsenic. The hydrated sesquioxide is made by precipitating a ferric salt of iron by an excess of ammonia, filtering through muslin, pocket 216 LABORATORY GUIDE. handkerchief, or anything handy, and washing out the ammonia. If the arsenic is not in solution, the hydrated oxide of iron or magnesia is of no use. Arsenic has the power of preserving the body from decay. The blood is usually fluid, but this is the case with most animals that die a violent death; the organs have the appearance usually produced by irritant poisons. For tests see No. 153. Christison, on poisons, regards the confirmation by the following reagents as unimpeachable evidence of the presence of arsenic. While there are fallacies in any one test taken alone, there is "no other substance in nature (but arsenic) which pro- duces the same effects as it with the whole three tests in succes sion." These are : (1) With H2S. (2) Hume's test — ammonia nitrate of silver. It should be made fresh each time it is required. Add to a solution of nitrate of silver a weak solution of ammonia, drop by drop, until the brown precipitate first produced is nearly dissolved, and pour off the clear solution ; this gives, with a solu- tion of arsenious acid, a bright yellow precipitate of arsenite of silver. Some trouble is often experienced in getting this pre- cipitate, as the reagent is decomposed by organic matter. (3) Scheele's test — the ammonia sulphate of copper. It is made by adding to a weak solution of copper, ammonia, drop by drop, until the precipitate first formed is nearly dissolved; the clear liquid is now decanted and used. It gives, with arsenious acid, a light apple-green precipitate of arsenite of copper (Scheele's green). It can be also determined by Bloxam's, Marsh's, Reinsch's, and Fleitman's tests, or those given under No. 153. 348. Lead. The effects of lead in its various combinations are those of a sedative and astringent. It is used internally for reducing the action of the heart and arteries, and for restraining inordinate discharges ;m externally, as an abater of inflammation When taken in small quantities often repeated, it acts injuriously on the nervous system, producing pain with sinking about the navel, the seat of the colon ; constipation, loss of appetite, thirst POISONS. 217 fetid odor of the breath, and general emaciation, especially of the muscles of the arms, and a blueness of the edges of the gums. The effect on the nervous system is numbness of feeling in the Bkin, trembling of the arms and legs, paralysis of the extensor muscles so that the hand drops; the body becomes emaciated, the legs oedematous, and the person dies exhausted. In acute poisoning these symptoms come on rapidly, and with greater intensity. There is, invariably, constipation from paralysis of the intestinal muscular coat; the urine is scanty and red; violent cramps, cold sweats, paralysis of the lower extremities, and often convulsions and tetanic spasms come on; the mind is usually clear to the last. The time death takes place and the dose to produce it are quite variable. Treatment: Cause vomiting by sulphate of zinc, warm water, or the stomach pump. Give any soluble alkaline or earthy sulphate. Sulphate of magnesia is one of the best; it can be given in milk mixed with white of eggs. In chronic cases, iodide of potassium is given three times a day in from five to ten grain doses; also, sweetened dilute sulphuric acid. But first and last, great cleanliness is of more importance to the workman than all the doctor's medicine, and at the first indication of lead poisoning, the work must be discontinued, and proper treatment at once adopted. Many of the hair washes or hair restorers are solutions of lead acetate mixed with sulphur. The acetate and carbonate are the most important salts to the toxicologist. All the soluble salts of lead are poisonous. For tests see No. 137. 349. Zinc. The acetate of zinc is used almost exclusively as a local remedy, as an astringent collyrium in ophthalmia, and as injections in gonorrhoea after the acute stage has passed. The chloride is used mostly as an escharotic; internally, as an altera- tive and antispasmodic. The oxide of zinc is used as a cosmetic, tonic, antispasmodic, and astringent. The sulphate is soluble in less than one part of water. This salt is used as a tonic, astrin- gent, and in large doses as an emetic. It is used in dyspepsia, in night sweats of consumption, with extract of belladonna or of 218 LABORATORY GUIDE. hyoscyamus; sometimes in cholera. The acetate and sulphate are, as a general rule, used in the same class of diseases. The sulphate, in over doses, acts as an irritant poison. It rapidly coagulates albumin and the delicate tissues of the body. The pulse and breathing are accelerated, the voluntary muscles are paralyzed, pupils dilated, coma supervenes, and death comes without a struggle. Treatment: Carbonate of soda with milk, white of egg,'tea, etc. Opium is given to relieve pain. The post mortem appearances are inflammation of the intestinal tract; the brain and lungs are generally congested. In toxicology, the chloride, the acetate, and the sulphate are the most important. Sulphate of zinc has been very frequently taken by accident or design, but death from it is rare. The infrequency of fatal result is due, not to any inactivity of the salt, but rather to its being almost always expelled by vomiting; so much so that it is often relied upon in poisoning from other substances. It is found in the stomach, liver, and intestines; in some cases in the spleen. The tests are sufficiently described in No. 175. 350. Copper. The common salts are acetate and sulphate. The local and general action of verdigris (acetate) upon the animal economy and the treatment of its poisoning are the same as those of the sulphate of copper. It is never used internally in modern practice. The sulphate is soluble in 2.6 parts of cold water, in one-half part of boiling water; insoluble in alcohol. At a temperature of 230° C, it becomes anhydrous; at a high tem- perature, it loses its acid and becomes cupric oxide. The sul- phate is an irritant or mildly escharotic; when in dilute solution, stimulant and astringent. It is not used internally, except for its influence upon the gastro-intestinal mucous membrane. In chronic diarrhoea with ulceration, it is often a useful remedy. In five grain doses, it is used as an emetic in narcotic poisoning and to dislodge false membrane or foreign bodies from the larynx and oesophagus. Externally it is used in solution as a stimulant to ulcers; as an escharotic for warts, fungus granulations, and POISONS. 219 callous edges; and as a styptic to bleeding surfaces. The medici- nal dose is one-fourth of a grain, gradually increased; as an emetic, five grains every fifteen minutes. When taken in poison- ous doses, it produces a coppery taste in the mouth, nausea, and vomiting; violent pain in the stomach and bowels; frequent black and bloody stools; small, irregular, and frequent pulse; fainting, burning thirst, scanty urine, pain in voiding it, violent headache, cramps, convulsions, and finally death. The best anti- dote is ferrocyanide of potassium; soap and alkalies are also given; milk and white of eggs. Vessels of copper which are not coated with tin should not be used in pharmacy nor in the house- hold. The post mortem appearances are fatty liver, swollen kid- neys, and the mucous membrane of the stomach excoriated. The post mortem appearances are usually confined to the alimentary canal. The tests are sufficiently described in No. 149. Of the acids, oxalic and hydrocyanic are the most important, The tests are described in Nos. 222 and 242. 351. We trace the poisons to the circulation, and observe that death is the result; but there is at present no satisfactory theory to account for the fatal effects, or explain how they oper- ated. The blood seems to be so changed by the poison as to ren- der it unfitted to perform its proper functions, but the modus operandi is as yet a perfect mystery. Neither the chemist, micro- scopist, nor physiologist has been able to throw any light upon the changes produced by the poison in the blood or in the organs necessary to life. It has been clearly shown that no substance act?; as a poison until it has been absorbed and passed through the arterial capillary system. The sooner the poison reaches the blood the more rapidly does it act, and it depends not so much upon the quantity as the amount absorbed in a given time. The time for this absorption, under favorable circumstances, is only a few seconds. The fatal effects are produced when the absorption takes place more rapidly than the elimination. The fatal propor- tion of poison present in the blood at any one time is infihitesi- mally small (one-sixteenth grain of strychnine has caused the 220 LABORATORY GUIDE. death of a child in four hours). The blood is about one-thirteenth of the body by weight, and the proportion of the poison by weight, compared with the blood, would be only one part in millions. The poison of a cobra is yet in a smaller proportion; but this is not all. The blood, urine, saliva, or milk of an animal poisoned by the cobra, when injected into another animal, will produce death As to the intent, poisons are divided into criminal, accidental, and suicidal. The general arrangement of nearly all toxicologists has been based upon the physiological effects of poisons. Some' authors, however, adopt the more simple plan of arranging them according to their origin or natural source, viz.: (1) Mineral, (2) vegetable, (3) animal, (4) gaseous. CHAPTER VIII. GENERAL STOICHIOMETRY. USEFUL CONSTANTS. micromillimeter.........= ^Joo °f an mc^1 (microscopic unit). I 1 1 1 29.57 1 1 1 29.92 33.81 81.1 28.349 grams............. 480 grains............. 437.5 grains............ 455.7 grains............. 46.73 C. c. of hydrogen. 100 cubic inches of air. gram...... .............= 15.4 kilogram................= 2.2 cubic centimeters........= 1 liter.....................-= 61 meter......:............= S9.3", inch.....................= 2.5 inches...................= 760 fluid ounces.............= grams...................= = 3 grains. pounds. fluid ounce. cubic inches or 2.1 pints. inches or 100 centimeters. centimeters or 25 millimeters. millimeters. liter. Troy ounce. Avoirdupois ounce. Troy ounce. Avoirdupois ounce. fluid ounce. grain. grains in weight. Water at 0° C. is 11,160 times heavier than hydrogen. The " crith " is the weight of one liter of hydrogen at 0° C, and 760 millimeters pressure = .0896 grams. The mechanical equivalent of heat is 772 foot pounds for 1° F., or 1,390 foot pounds for 1° C, or 423.6 kilogram meters. The U. S. gallon is to the Imperial gallon as 61,440:76,800, or as 1 is to 1.2. II. Conversion of thermometric scales (C, Centigrade; F., Fahrenheit; R., Reaumur). p c R 212 100 80 180 100 80 32 0 0 A glance at these figures will show that 180° F. = 100° C. = 80° R., or dividing by 20, 9° F. = 5° C. = 4° R. 222 LABORATORY GUIDE. To convert— C.° to F.°, multiply by 9, divide by 5, and add 32. C.° to R.°, multiply by 4 and divide by 5. F.° to C.°, subtract 32, multiply by 5, and divide by 9. F.° to R.°, subtract 32, multiply by 4, and divide by 9. • R.° to C.°, multiply by 5 and divide by 4. R.° to F.°, multiply by 9, divide by 4, and add 32. 1. Express 40° F. in degrees C.: 40 _ 32 = 8; 8X5-^9 = V= 4.4° C. 2. Express — 10° F. in degrees C.: — 10 — 32----42; — 42 X 5 -^- 9 = — 23.3° C. 3. At what point, below zero, are the numbers on the scales of Fahrenheit and Celsius identical? Let x = the number; 32° + | of x° C. = x° F. 160° + 9x = hx. — Ax = 160°. x = — 40°. (The Nos. will agree with unlike signs between 11° and 12°). III. Gases expand -%{-$ part of their volume at 0° C. for every increase in temperature beyond 1° C.; the contraction follows the same law. Expressed decimally, ■$-$ = .003663, and is called the coefficient of expansion of gases. The volume of a gas varies directly as its absolute temperature, and inversely as the pressure to which it is subjected. Rule — As 273 plus given temperature is to 273 plus required temperature, so is given volume to required volume. 1. Five hundred C. c. of a gas at 5° C. are heated until they become 700 C. c. Through what number of degrees C. has the gas been heated? y 500 : 700 :: 273 -f 5 :273 + x. 500 (273 + x) = 700 X 278. 500 x — 700 X 278 — 273 X 500. x = 116.2° C. — 5° C. = 111.2° C. GENERAL STOICHIOMETRY. 223 2. Fifty C. c. of air is measured at 12° C. and 750 m. m. Required, volume of the air at 20° C. and 800 m. m. 800:750 : 50: x. 273 + 12 :273 -f 20 50 X 750 X 293 p x" 800X285 =48-19C'c- 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).. Solve for x. 720:700 )" 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. W equals weight in air; w equals loss of weight in water. .-. 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 4 HCl occupies 1J35 ==-6U6 °f a ^ ""* 2° ^^ °CCUPy .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 -t-tjt> == ^-^ times heavier than air. (b) The density of a compound gas is £ its molecular weight. 12 -4- 32 The molecular weight of C02 =—-~— = 22; i. e., 22 times A 22 heavier than hydrogen, or ^tt-tk =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 = ——----= ---—- = .16. a + 6 — c 82 + /85 — 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 X 100; M 14 X 100. „ 39 X 100 T, . . .. , /01 IN =---rjyj---; K. =---r^r-j---. lhe 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; Cl = 3rVrof 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 = 232 of 93-75; s = ~mof 93-75- 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 + (Lj. The molecular weight of KC103 is (K = 39, Cl = 35.5, O, =48) 48 122.5; 0==J225' 48:122,5: :50:x'> 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? 2AgNQ3 + Zn = Zn(NQ3)2 + Ag2. The molecular weight of AgNO3 = 170. .-. 340 parts of AgN03 require 65.2 parts of zinc. 65.2 One gram of AgN03 requires —rr grams of zinc. 65 2 One hundred grams of AgN03 require -^ttt 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^. 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 + Na. Sixteen volumes of NH3 require 6 volumes of Cl; 1 volume of NH3 requires % volume of Cl.; x volumes of NH3 require f x volumes of Cl. 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 2| 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. 227 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 formulas 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 = 10.50055, the amount of silver used. At. wt. Ag : at. wt. Cl :: wt. Ag : wt. Cl. 108 : 35.5 :: 10.50055 : x, or 3.45157. 7.25682 — 3.45157 = wt. of K, or 3.80525. Wt. Cl : wt. K :: at. wt, of Cl : 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. silver chloride. Calculate from this the atomic weight of chlo- rine. 121.4993 — 91.462 = 30.0373 the amount of Cl. Wt. of Ag : at. wt. Ag :: wt. Cl : at. wt. Cl. 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-^- 1 = 2] Sulphur................ 32.65 -f 32 = 1 I 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 1 Hydrogen ." .............73 -j- 1 = .73 = 1 Sulphur "............ 23.52 -i- 32 = .73 = 1 Oxygen " ............ 47.02 -f 16 = 2.93 = 4 KHS04. 100.00 I 3. Iron equals............ 70.01 -^ 56 = 1.25 -|- 62 = 2 , Oxygen equals......... 29.99 ^ 16 = 1.87 rr 62 = 3 j Fe2°a 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. (6) 2KNQ3 + H2S04 = K2S04 + 2HN03. (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 (KHS04) is formed. i 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. XL 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. XL) 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, a; = 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.................................... 34 432 "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 = T\ O = -If, 8 times as much oxygen 232 LABORATORY GUIDE. as hydrogen); 6.2 -f- 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 -7- 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 power 8,020.8 by this number (8,020.8 -i- 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 Hydrosulphuric......------........ 19 Hypochlorous........—......---47, 139 Hyposulphurous.................... 135 Iodic___................----------135 Lactic......---.....---........----151 Malic___.......-..........-.........146 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........______......______147 Sulphocyanic_________.....___21, 150 Sulphuric______.......---.....21, 128 Sulphur.............................128 Sulphurous.........—.......___22, 134 Sulphanilic___________........... 182 Tantalic................._________128 Acids — 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 —....................... 184 Quinine______.........______.....200 Reagents............................ 190 Strychnine..................______193 Tyrotoxicon_______........_______185 Veratrine ...___.....____________201 Zinc........1........................217 Aluminum, tests........______....... 97 Ammonium — Carbonate.......______........___ 24 Chloride............................ 24 Hydroxide..............___........ 26 ITerrous sulphate__________....... 25 Fluoride..................... _.. __ 25 Molybdate.................._______ 27 Nitrate__________.................. 27 Nitrate of silver_________________ 28 Oxalate__________.....______..... 27 INDEX. 235 Ammonium —Continued. page Succinate.......................___ 2^ 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___.........__________ 36 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__________.........._____'.... 118 Litmus paper______....._____........ 38 Magnesium wire........................ 55 Tests______,_______..............112 Mixture____,__________........... 39 236 LABORATORY GUIDE. PAGE Manganese______......_____________102 ic —........____________......... 103 ous..........._._.................... 102 Mercury...............................39, 80 Tests for..........................77, 80 Mercuric chloride....................39, 8U " 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 Fe " ............ 94 Fe " __________ 106 alkaline earths......114 alkalies.............. 119 Organic acids.......................... 144 Acetic...............................150 Benzoic........____................148 Butyric............................. 153 Citric....................—........145 Ferricyanic__________............. 149 Ferrocyanic____________________149 Formic.........................----151 Lactic_____.........................151 Malic................................146 Oxalic-.........................-- 132 Proprionic........____............. 152 Succinic..............______...... 147 Sulphocyanic______............... 150 Tartaric..........___........______144 Oxygen .............................--- 41 Platinum vessels, care of______....... 41 " chloride..................___ 42 Potassium tests..............___........ 116 " bisulphate______.......... 42 " chlorate............_........ 42 PAGE 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 Cl, Br, I.............______ 137 Silver chloride.......................... 74 " chromate......................... 75 " nitrate___............._______45, 74 Sodium........................._____55, 117 " acetate..............._.......... 45 " carbonate........____________ 46 " chloride.........____........... 46 " hypochlorite___................ 47 11 lime___......................... 47 " nitrate..................______ 47 " nitroprusside..........___..... 47 " palladio-chloride............... 48 " phosphates (arnmonium)...... 48 " sulphite........___........____ 48 " thiosulphate.................... 49 Solution of indigo.....____.......___142 Stannous chloride______.............. 49 Strontium...............................Ill Starch solution......................... 49 Thallium....................._......... 74 Tin...................................... 90 ic..................................... 91 ous................................... 91 Tungsten___........................... 74 Turmeric paper.................______ 49 Venadium.........................____ 94 INDEX. 237 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 > -*;Xi ■■^v'y .■■■■; ,':<-.;;:-* *-.■ ■ t..- »<. j■ .■&%'■ ^< Ki $ mmm **:-£K MWl m v-fc'il- •■VJ *■■.•*' -.*viir-'*»*. •' -n- + ♦ ' 'V* >>■•. 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