(J /T^^tU_>U / con , f TRY A SHORT MANUAL OF ANALYTICAL CHEMISTRY. A SHORT MANUAL OF ANALYTICAL CHEMISTRY <$aaliiaUbe mitt <$uanpftfaititt Jnorpuic antr BY JOHN MUTER, Ph.D., F.R.S.E., F.I.C., F.C.S. ANALYST TO THE METROPOLITAN ASYLUMS BOARD ; PUBLIC ANALYST FOR THE METROPOLITAN BOROUGHS OF LAMBETH AND WANDSWORTH, AND THE ADMINISTRATIVE COUNTY OF LINDSEY, LINCOLNSHIRE; PAST PRESIDENT OF THE SOCIETY OF PUBLIC ANALYSTS; LATE EDITOR OF "THE ANALYST," ETC., ETC. FOURTH AMERICAN EDITION ILLUSTRATED. THE CHAPTERS RELATING TO THE ANALYSIS OF DRUGS BEING BASED UPON THE EIGHTH REVISION (1905) OF THE UNITED STATES PH ARM ACOPCE I A PHILADELPHIA: P. BLAKISTON'S SON & CO., 1012, WALNUT STREET, 1906. * Authority to use for comment the ' Pharmacopoeia of the United States of America,' Eighth Decennial Revision, in this volume, has been granted by the Board of Trustees of the United States Pharmacopoeia! Convention, which Board of Trustees is in noway responsible for the accuracy of any translation of the official weights and measures or for any statements as to strength of official preparations." M39 !90& PREFACE TO THE FOURTH AMERICAN EDITION. THE continued favour with which the book has been received has encouraged me to persevere in offering to students a concise, and consequently low- priced, manual, designed to introduce them to the chief developments of analytical chemistry, from the simplest operations upwards, and including many organic questions generally overlooked in initiatory books. By working through it, a student will become familiar with a great variety of processes, and will then be in a position to use, with satisfaction, the more exhaustive treatises dealing with any special branch he may desire to follow. Originally written for the use of pharmaceutical students, it has, I hope, far passed its primary limits, while at the same time not losing its value to them.' In the chapters on Volumetric and Drug Analysis, wherever British processes are different from those of the U.S. P., they have been altered to suit that excellent and carefully compiled authority. Certain comparatively unim- portant matters contained in the ninth British edition have been dropped out to make room for the greatly extended chapter on Drug Analysis, necessitated to meet American requirements as contained in the revised U.S. P. of September ist, 1905, but even then it has been found imperative to increase the size of the book. J.U. SOUTH LONDON SCHOOL OF PHARMACY, 325, KENNIXGTON ROAD, LONDON, S.E. DECEMBER 1905. TABLE OF CONTENTS. PART I. QUALITATIVE ANALYSIS. CHAPTER I. The Processes Employed by Practical Chemists. 8. Solution 2. Lixiviati 3. Precipitation 4. Decantation 5. Filtration 6. Distillation 7. Sublimation PACE . I and Extraction i a . 2 1 . . . 3 L 4 8. Fusion ..... 4 9. Evaporation ... 5 10. Crystallisation and Dialysis . 5 n. Electrolysis .... 6 12. Pyrology .... 7 13. Preparation of sulphuretted by drogen ... 9 CHAPTER II. Detection of the Metals. Group Reagents . . 10-11 Division A. * . 18-21 I. Iron . . 18 GROUP I. . . 11-13 2. Cerium . 20 I. Silver . 2. Mercurosum ii 12 3. Aluminium . 4. Chromium 2O 21 3. Lead 12 Division B. . 21-24 GROUP II. . 13-18 i. Manganese 21 Division A. . I 3~ I 5 2. Zinc 22 AT T ") 2'2 i. Aiercuncum 4. Cobalt . 23 14 GROUP IV. . 24-26 4. Cadmium I C 24 Division B. . * J . 15-18 2. Strontium 3. Calcium 25 25 15 _/ _o 2. Antimony 3. Tin 16 I? i. Magnesium . 26 4. Gold 5. Platinum . 17 18 2. Lithium . . 3. Potassium 4. Sodium . . 26 27 27 <;. Ammonium . 27 Vlll TABLE OF CONTENTS. CHAPTER III. Detection and Separation of Acid Radicals. 1. Hydrofluoric Acid and Fluorides 2. Chlorine, Hydrochloric Acid, and Chlorides .... 3. Hypochlorites .... 4. Chlorates 5. Perchlorates .... 6. Bromine, Hydrobromic Acid, and Bromides .... 7. Hypobromites .... 8. Bromates 9. Iodine, Hydriodic Acid, and Io- dides 10. lodates 11. Periodates 12. Water and Hydrates . 13. Oxides ...*.. 14. Sulphur, Hydrosulphuric Acid, and Sulphides 15. Thiosulphates (Hyposulphites) . 16. Sulphurous Acid and Sulphites . 17. Sulphuric Acid and Sulphates 1 8. Carbon, Carbonic Acid, and Car- bonates .... 19. Boric Acid and Borates ; 20. Silicic Acid and Silicates . . 21. Hydrofluosilicic Acid . 22. Nitrous Acid and Nitrites . 23. Nitric Acid and Nitrates 24. Cyanogen, Hydrocyanic Acid, and Cyanides 25. Cyanic Acid and Cyanates, Cyan- uric Acid, and Fulminic Acid 26. Thiocyanates (Sulphocyanates) . 27. Ferrocyanides .... 28. Ferricyanides .... 29. Hypophosphites .... 30. Phosphorous Acid and Phosphites 31. Meta- and Pyro-Phosphoric Acids 32. Orthophosphoric Acid (B.P.) and Orthophosphates . 33. Arsenious Acid and Arsenites 34. Arsenic Acid and Arseniates 35. Manganates .... 36. Permanganates 37. Chromic Acid and Chromates 38. Stannic Acid and Stannates 39. Antimonic Acid .... 40. Formic Acid and Formates 41. Acetic Acid and Acetates . 42. Valerianic Acid and Valerianates 43. Sulphovinates (Ethyl Sulphates) . 44. Stearic Acid and Stearates . 45. Oleic Acid and Oleates 46. Lactic Acid and Lactates . 47. Oxalic Acid and Oxalates . 48. Succinic Acid and Succinates 49. Malic Acid and Malates 50. Tartaric Acid and Tartrates . 51. Citric Acid and Citrates 52. Meconic Acid and Meconates 53. Carbolic Acid and Carbolates PAGE 2 9 54- 55- 29 56. 30 57- 3 30 58. 59- 3 60. 61. 31 62. 31 63- 32 32 64. 3 2 33 65. 33 66. 34 35 67. 35 68. 36 69. 37 37 70. 38 71. 39 72. 40 4i 73- JJ 74- 42 42 43 43 75- 43 76. 44 45 77- 45 45 78. 45 46 79- 46 46 80. 47 47 81. 47 48 82. 48 48 83 48 84. 49 49 85. 49 5 86. Benzoic Acid and Benzoates . 51 Salicylic Acids .... 52 Tannic, Gallic, & Pyrogallic Acids 52 Separation of Chlorates and Chlorides 53 Detection of Chlorides in Bromides 53 Detection of Bromides in Iodides 53 Detection of Chlorides in Iodides 53 Separation of Iodide from a Bro- mide and Chloride . . 53 Detection of lodate in Iodide . 54 Detection of Sulphide in presence of Sulphite and Sulphate . 54. Separation of Thiosulphates from Sulphides .... 54 Separation of Sulphides, Sul- phites, and Sulphates . . 54 Separation of Silica from all other Acids .... 54 Detection of Nitrites in Nitrates . 55 Detection of free Nitric Acid in the presence of a Nitrate . 55 Detection of a Nitrate in the presence of an Iodide . 55 Separation of Chlorides, Bromides, and Iodides from Nitrates . 55 Separation of Cyanides from Chlorides 55 Separation of Ferro- from Ferri- Cyanides .... 56 Detection of Cyanides in the presence of Ferro- and Ferri- Cyanides .... 56 Detection of a Phosphate in the presence of Calcium, Barium, Strontium, Manganese, and Magnesium .... 56 Detection of a Phosphate in the presence of Iron . . 56 Separation of an Arseniate from a Phosphate ... 56 Detection of Formates in the pre- sence of other Organic Acids 56 Separation of Oxalates, Tartrates, Citrates, and Malates . . 57 Detection of Carbolic Acid in the presence of Salicylic Acid . 57 Test for Cinnamic Acid in Ben- zoates 57 Test for Chlorobenzoic Acid in Benzoic Acid 57 Test for Ilippuric Acid in Benzoic Acid 57 Test for Cresol in Phenol . . 57 Special Tests for Tartaric Acid in Citric Acid . . . . 57 Distinction of Salicylates from Carbolates and Sulphocar- bolates .... 57 Test for Selenium in Sulphuric Acid . ... 57 TABLE OF CONTEN1S. IX CHAPTER IV. Qualitative Analysis, as applied to the Detection of Unknown Salts. PAGE I. General Preliminary Exami- nation . . . . $&-6o II. Detection of the Metal present in any Simple Salt (with Tables for same) .... 61-64 III. Detection of the Metals in Complex Mixtures of two or more Salts (with Tables for same) .... 65-74 IV. Detection of Radicals . the Acid . 75-80 Div. A. Preliminary Examina- tion ... 75 ,, B. Preparation of Solution 77 C. Course for Inorganic Acids ... 78 D. Course for Organic Acids ... 80 Solubility Tables . 82. 83 TABLES. PAGE Full table for the Detection of the Metal in a Solution containing one Base only 62 Table for the Detection of the Me'al in a Simple Salt, limited to Salts included in the Pharmacopoeia . 64 Table for the Detection of Metals in mixtures of Pharmacopoeia Salts Jacing p. 74 Table for the Separation of Metals into Groups 66 Table A. Separation of Metals of Group 1 67 Table B. Separation of Metals of Group II., Div. (a) . . 68 Table C. Separation of Metals of Group II., Div. (b) . . 69 Table D. Separation of Metals of Group III., Div. (a) . . 70 Table E. Separation of Metals of Group III., Div. (a), in pre- sence of Phosphoric Acid . 71 Table F. Separation of Metals of Group III., Div. (b} . . 72 Table G. Separation of Metals of Group IV 73 Table H. Separation of Metals of Group V 74 CHAPTER V. Qualitative Detection of Alkaloids and Certain Organic Bodies used in Medicine, with a General Sketch of Toxicological Procedure. Division A. Course for the Detection of the Alkaloids and Alkaloid Salts used in Medicine, together with a general Resume of the Tests for all the chief Alkaloids (as under) ........ 84-87 Aconitine. Apomorphine. Atropine. Beberine. Berberine. Brucine. Caffeine. Calabarine. Chelidonine. Cinchonine. Cinchonidine. Cocaine. Codeine. Colchicine. Colchice'ine. Coniine. Curarine. Delphinine. Delphinoidine. Emetine. Gelsemine. Homatropine. Hydrastinine. Hyoscine. Hyoscyamine. Jervine. Morphine. Narceine. Narcotine. Nepaline. Nicotine. Papaverine. Physostigmine. Pilocarpine. Piperine. Quinamine. Quinidine. Quinine. Sabadilline. Sabatrine. Solanine. Sparteine. Staphysagrine. Strychnine. Taxine. Thalictrine. Thebaine. Theobromine. Veratrine. Veratroidine. TABLE OF CONTENTS. Division B. Qualitative Detection of certain Organic Bodies commonly employed Acetanilide. Chloral. Guaiacum Resin. Acetic Ether. Chloroform. lodoform. Adeps Lanae. Chrysarobin. Jalap Resin. Aloin. Creasote. Methyl Alcohol. Amyl Alcohol. Elaterin. Naphthol. Amyl Nitrite. Ethyl Alcohol. Nitrobenzene. Antipyrin. Fel Bovinum. Paraldehyd. Benzin (petroleum). Gelatine. Phenacetin. Benzol (benzene). Glycerine. Picrotoxin. Division C. Qualitative Analysis of Scale Preparations . D. General Sketch of the Method of Testing for Poisons in Podophyllin Resin. Resin. Resorcin. Saccharine. Salol. Santonin. Scammony Resin. Sugars. Sulphonal. . 91-92 Mixtures . 92-93 PART If. QUANTITATIVE ANALYSIS. CHAPTER VI. Weighing, Measuring, and Specific Gravity, 1. Weighing and Measuring 2. Specific Gravity (a) Of Liquids . (6) Of Solids . 94-95 96-103 96-98 98-99 of (r) Practical Applications Specific Gravity . . 99-100 (4 slightly soluble in water, but rendered entirely insoluble by the addition of a little alcohol. It is decomposed by boiling strong hydrochloric acid, and is also freely soluble in solutions of ammonium acetate or tartrate, containing an excess of ammonium hydrate. 4. K 2 Cr0 4 gives a yellow precipitate of plumbic chromate PbCrO 4 insoluble in acetic and very dilute nitric acids, but soluble in strong boiling nitric acid. 5. KI gives a yellow precipitate of plumbic iodide PbI 2 soluble in 33 parts of boiling water, and crystallising out on cooling in golden scales. 6. KHO and NaHO both cause white precipitates of plumbic oxy-hydrate (PbO) 2 Pb(HO) 2 soluble in excess, forming potassium or sodium plumbates K 2 PbO 2 and Na 2 PbO 2 . 7. NH,HO causes a white precipitate of a white basic nitrate Pb(NO 3 HO) insoluble in excess. 8. KCN produces a white precipitate of plumbic cyanide Pb(CN) 2 insoluble in excess, but soluble in dilute nitric acid. MERCURICUM. 13 9. Alkaline Carbonates cause a precipitate of (PbCOa^PMHO), " white lead " insoluble in excess, and also in potassium cyanide. 10. Fragments of zinc or iron in the presence of a little acetic acid cause the separation of metallic lead in crystalline laminae. (b) DRY REACTION. (To be practised on red lead Pb 3 O 4 , or litharge PbO.) Heated on charcoal in the inner blowpipe flame, a bead of metallic lead is formed, which is soft and malleable, and soluble in dilute nitric acid. The solution thus obtained gives the wet tests for lead. GROUP II. Metals which are not affected by acidulation with hydrochloric acid, but are precipitated by passing sulphuretted hydrogen through the acidulated solution. DIVISION A. Metals which, when precipitated by sulphuretted hydrogen as above, yield sulphides insoluble in ammonium sulphide. I. MERCURICUM (Hg)." (a] WET REACTIONS. (To be practised on a solution of mercuric chloride HgCl 2 .) 1. H 2 S after acidulation by HC1 (2nd group reagent) gives a black precipitate of mercuric sulphide HgS insoluble in ammonium sulphide and nitric acid, and only soluble in nitro-hydrochloric acid. Care must be taken that the sulphuretted hydrogen is passed really in excess, and that the whole is warmed gently, as unless this be done, the precipitate is not the true sulphide, but a yellowish-brown dimercuric sulpho- dichloride Hg 2 SCl 2 . Although insoluble in any single acid, mercuric sulphide may be caused to dissolve in hydrochloric acid by the addition of a crystal of potassium chlorate. 2. KHO or NaHO both give a yellow precipitate of mercuric oxide HgO insoluble in excess. 3. NH 4 HO produces a white precipitate of an insoluble mercuric-ammonium chloride (NH 2 Hg)Cl also insoluble in excess. 4. KI yields a red precipitate of mercuric iodide, soluble in excess both of the precipitant and the mercuric salt. 5. SnCl 2 , boiled with a mercuric solution, first precipitates mercurous chloride, and then forms metallic mercury, as in the case of mercurosum compounds. 6. Alkaline Carbonates (except ammonium carbonate) produce an immediate reddish-brown precipitate of mercuric oxy-carbonate. 7. Fragments of Cu, Zn, or Fe precipitate metallic mercury in the presence of dilute hydrochloric acid. (V) DR Y REACTION. (To be tried on mercuric oxide HgO and on " Ethiops mineral " HgS. ) All compounds of mercury are volatile by heat ; the oxide breaking up into oxygen and mercury, which sublimes, while the sulphide sublimes unaltered unless previously mixed with sodium carbonate or some reducing agent. 1 4 DETECTION OF 7 HE METALS. II. BISMUTH (Bi). (a) WET REACTIONS. (To be practised upon bismuth subnitrate^ dissolved in water by the aid of the smallest possible quantity of nitric acid, and any excess of the latter carefully boiled off. This solution will then contain bismuth nitrate Bi(N0 3 ) 3 . 1. H 2 S after addulation by HC1 (znd group reagent) gives a black precipitate of bismuth sulphide Bi 2 S 3 insoluble in ammonium sulphide, but soluble in boiling nitric acid. 2. H 2 S0 4 gives no precipitate (distinction from lead). 3. NH 4 HO, KHO, and NaHO, all give precipitates of white bismuthous hydrate Bi(HO) 3 insoluble in excess, and becoming converted into the yellow oxide Bi 2 O 3 on boiling. 4. Water H 2 in excess to a solution in which the free acid has been as much as possible driven off by boiling, gives a white precipitate of a basic salt of bismuth. This reaction is more delicate in the presence of hydrochloric than of nitric acid ; and the precipitate, which is in this case bismuth oxy-chloride BiOCl is insoluble in tartaric acid (dis- tinction from antimonious oxy-chloride). 5. K 2 Cr0 4 yields a yellow precipitate of bismuth oxy-chromate Bi 2 O 2 CrO 4 soluble in dilute nitric acid, but not in potassium hydrate (distinction from plumbic chromate). 6. KI gives brown bismuthous iodide, soluble in excess. 7. Alkaline Carbonates give white precipitates of bismuth oxy-carbonate, insoluble in excess. 8. Fragments of zinc added to a solution of bismuth, cause a deposit of the metal as a dark grey powder. (If) DRY REACTION. (To be practised upon bismuth sub nit rate.) Mixed with sodium carbonate Na 2 CO 3 and heated on charcoal before the blowpipe, a hard bead of metallic bismuth is produced, and the surrounding charcoal is incrusted with a coating of oxide, deep orange-yellow while hot and pale yellow on cooling. III. COPPER (Cu.) (a) WET REACTIONS. (To be practised with a solution of cupric sulphate CuSO 4 .) 1. H 2 S after addulation with HC1 (2nd group reagent) forms a precipitate of brownish-black cupric sulphide CuS which is nearly insoluble in ammonium sulphide, but soluble in nitric acid. Its precipitation is prevented by the presence of potassium cyanide (distinction from cadmium). When long exposed to the air in a moist state, it oxidises to cupric sulphate and dissolves spontaneously. 2. NH 4 HO causes a pale blue precipitate instantly soluble in excess, forming a deep blue solution of tetrammonio-cupric sulphate (NH^CuSO^H^O. 3. Potassium ferrocyanide K 4 Fe(CN) 6 yields a chocolate-brown precipitate of cupric ferrocyanide Cu 2 Fe(CN) 6 . This test is very delicate, and is not affected by the presence of a dilute acid, but does not take place in an alkaline liquid. 4. KHO or NaHO precipitates light-blue cupric hydrate Cu(HO) 2 insoluble in excess, but turning to black cupric oxy-hydrate (CuO)2Cu(HO) 2 on boiling. CA DMIUMA RSENIC. 15 5. Potassium sodium tartrate (Rochelle salt} KNaC 4 H 4 6 and NaHO added successively, the latter in excess, produce a deep blue liquid (Fehling's solution), which, when boiled with a solution of glucose (grape sugar) deposits brick-red cuprous oxide Cu 2 O. 6. The Alkaline Carbonates precipitate Cu(HO) 2 CuCO 3 . 7. Fragments of zinc or iron precipitate metallic copper from solutions acidulated with HC1. (b) DRY REACTIONS. (To be practised upon cupric oxide CuO or verdigris Cu 2 O(C 2 H 3 O 2 )2.) 1. Heated with Na 2 CO 3 and KCN on charcoal, in the inner blowpipe flame, red scales of copper are formed. 2. Heated in the borax bead before the outer blowpipe flame, colours it green while hot and blue on cooling. By carefully moistening the bead with SnCl 2 and again heating, this time in the inner flame, a red colour is produced. IV. CADMIUM (Cd). (a) WET REACTIONS. (To be practised with a solution of cadmium iodide CdI 2 .) 1. H 2 S after aridulation with HC1 (2nd group reagent] gives a yellow precipi- tate of cadmium sulphide CdS insoluble in ammonium sulphide, but soluble in boiling nitric acid. This precipitate does not form readily in presence of much acid ; but its production is not hindered by the addition of potassium cyanide (distinction from copper). 2. NH 4 HO produces a white precipitate of cadmium hydrate Cd(HO) 2 soluble in excess. 3. KHO or NaHO both give precipitates of cadmium hydrate Cd(HO) 2 insoluble in excess (distinction from zinc). 4. Alkaline Carbonates precipitate cadmium carbonate CdCOs insoluble in excess. (b) DRY REACTION. (To be practised on cadmium carbonate CdCO 3 .) Heated on charcoal before the blowpipe, a brownish incrustation of oxide is produced, owing to reduction of the metal and its subsequent volatilisation and oxidation by the outer flame. DIVISION B. Metals which are precipitated by sulphuretted hydrogen in the presence of hydrochloric acid, but yield sulphides which are soluble in ammonium sulphide. I. ARSENIC (As). (a) WET REACTIONS. (To be practised with a solution of arsenious anhydride in boiling water slightly acidulated by hydrochloric acid.) i. HjS, after addulation with HC1, causes- a yellow precipitate of arsenious sulphide As 2 Ss soluble in ammonium sulphide, forming ammonium sulpharsenite (NH 4 ) 3 AsS 3 but insoluble j n strong boiling hydro- chloric acid (distinction from the sulphid es of Sb and Sn). This precipitate is also soluble in cold solution O f commercial carbonate of ammonia (distinction from the sulphides of Sb, Sn, Au, and Pt). Dried 16 DETECTION OF THE METALS. and heated in a small tube with a mixture of Na,CO 3 and KCN, it yields a mirror of arsenic. (Detects i part of As in 8000.) 2. Boiled with KH and a fragment of Zinc, arseniuretted hydrogen AsH 3 is evolved, which stains black a paper moistened with solution of argentic nitrate and held over the mouth of the tube during the ebul- lition (Fleitmanris test). 3. Boiled with ^ of its bulk of HC1 and a slip of Copper, a grey coating is deposited on the copper of cupric arsenide. On drying the copper carefully, cutting it into fragments, and heating in a wide tube, a crystalline sublimate of arsenious anhydride As 2 O 3 is obtained, which, when examined by a lens, is seen to be in octohedral crystals, and, when dissolved in water, gives a yellow precipitate of argentic arsenite Ag 3 As0 3 with solution of ammonio-nitrate of silver (Reinch's test). (Detects i part As in 40,000.) 4. Placed in a gas bottle furnished with a jet (illustrated in the margin), together with dilute sulphuric or hydro- chloric acid and a few fragments of zinc, arseniuretted hydrogen AsH 3 is evolved, which may be lighted Flg " l6< at the jet, and burns with a lambent flame, producing As 2 O 3 . If a piece of cold porcelain be held in the flame, dark spots of arsenic are obtained, readily volatile by heat and soluble in solution of chlorinated lime (Marsh's test). (Detects i part As in 200,000,000.) Note. For reactions of arsenites and arseniates, see Acid Radicals. (V) DRY REACTION. (To be practised on arsenious anhydride As 2 O 3 .) Heated in a small tube with Na 2 COs and KCN, a mirror of arsenic is pro- duced, accompanied by a garlic-like odour. The same effect may be produced with black flux. II. ANTIMONY (Sb). (a) WET REACTIONS. (To be practised with a solution of tartar emetic (K(SbO)C 4 H 4 O 6 ) 2 .H,O.) 1. H ; S, after acidulation by HC1, causes an orange precipitate of antimonious sulphide Sb^Ss soluble in ammonium sulphide, forming ammonium sulphantimonite (NH 4 )J5bS 3 also soluble in strong boiling hydro- chloric acid, forming antimonious chloride SbCl 3 but insoluble in cold solution of commercial carbonate of ammonia. 2. KHO and NaHO produce precipitates of antimonious oxide readily soluble in excess to form antimonites (K 3 SbO 3 or NagSbOa). 3. Acidulated with HC1 and introduced into a platinum dish with a rod of zinc so held that it touches the platinum outside the liquid, a black stain of metallic antimony is produced closely adherent to the platinum. This stain is not dissolved by HC1 (tin reduced in the same manne is granular and soluble in boiling HC1). 4. Reinch's test (see Arsenic) produces a black coating on the copper, which, when heated, forms an amorphous sublimate of Sb 2 O 3 dose to the copper^ and insoluble in water, but dissolved by a solution of cream of tartar in which H 2 S then produces the characteristic orange sulphide. 5. Marsh's test (see Arsenic) yields stains of antimony on the porcelain, not nearly so readily volatile by heat as in the case of arsenic, and not discharged by solution of chlorinated Hm?. TIN GOLD. , 7 6. Fleitmann's test will not act with antimony at all (distinction from arsenic). (b) DRY REACTION. (To be practised on antimonious oxide Sb 2 O 3 .) Heated on charcoal with Na 2 CO 3 and KCN before the blowpipe, a bead of metallic antimony is formed and copious white fumes of the oxide are produced. III. TIN (Sn or Sn"). (a) WET REACTIONS. (To be practised with a solution of stannous chloride SnCl 2 and one of stannic chloride SnCU prepared by warming the stannous solution with a little nitric acid.) 1. H 2 S, after addulation with HC1, produces a brown or yellow precipitate of SnS or SnS 2 respectively, both soluble in ammonium sulphide and in boiling hydrochloric acid. 2. KHO or NaHO both produce white precipitates of Sn(HO). 2 or Sn(HO) 4 , soluble in excess, the former to produce stannites and the latter stan- nates. The stannous solution is, however, reprecipitable on boiling, while the stannic is not. 3. NH 4 HO produces similar precipitates, very difficultly soluble in excess. 4. Acidulated by HC1, and introduced into a platinum dish with a rod of zinc, so held in the fluid that it touches the platinum outside the liquid, granules of metallic tin are deposited, soluble in boiling HC1, to form stannous chloride. 5. HgCl 2 boiled with stannous salts deposits a grey precipitate of metallic mercury. (b) DRY REACTION. (To be practised on putty powder SnOj.) Heated on charcoal with Na 2 CO 3 before the blowpipe, a bead of metallic tin is produced, and a white incrustation of oxide is formed on the charcoal. IV. GOLD (Au). (a) WET REACTIONS. (To be practised with a solution of auric chloride AuCl 3 .) 1. H L ,S (group reagent) in the presence of HC1 gives black auric sulphide Au 2 S 3 . If the solution be hot, aurous sulphide Au 2 S falls. Both are only soluble in nitro-hydrochloric acid, but they are soluble in ammonium sulphide when it is yellow. 2. NH 4 HO precipitates reddish ammonium aurate, or fulminating gold Au 2 (NH 3 )A, but KHO gives no result. 3. Hydrogen oxalate (oxalic acid} H 2 C 2 4 (or Ferrous sulphate FeS0 4 ) when boiled with an acid solution throws down Au. Reducing agents generally act thus. The liquid containing the metal may exhibit a blue, green, purple, or brown colour. 4. SnCl 2 throws down a brownish or purplish precipitate known as " purple of Cassius," consisting of the mixed oxides of gold and tin. 5. Zn, Cu, Fe, Pt, or almost any metal, gives a precipitate of metallic Au in a finely divided state. f8 DETECTION OF THE METALS. (b) DRY REACTION. (To be practised on any gold salt.) Heated on charcoal with Na 2 CO 3 , the metal is produced V. PLATINUM (Pt). (a) WET REACTIONS. (To be tested with a solution of platinic chloride PtCl 4 .) t. H 2 S (2 nd group reagent) in presence of HC1 gives a brown precipitate of platinic sulphide PtSo. This precipitate forms slowly, and is readily dissolved by yellow ammonium sulphide. 2. Potassium chloride KC1 in presence of HC1, especially after addition of alcohol, produces a yellow crystalline precipitate of potassium platinic chloride PtCl 4 (KCl) 2 soluble to a moderate extent in water, but not in alcohol. Decomposition takes place when this is strongly heated, metallic Pt and KC1 remaining. 3. Ammonium chloride NH 4 C1 gives a precipitate of ammonium platinic chloride PtCl 4 (NH 4 Cl) 2 which is almost identical in properties, but is more readily decomposed by heat, pure platinum remaining. 4. In, Fe, and several other metals decompose platinic salts with the produc- tion of the metal. (b) DRY REACTIOA. (To be practised upon potassium platinic chloride PtCl 4 (KCl) 2 .) Heat on charcoal, with or without Na 2 CO3, before the blowpipe. The ietal is produced by reduction. GROUP III. Metals which escape precipitation by sulphuretted hydrogen in presence of hydrochloric acid, but which are precipitated by ammonium sulphide in the presence of ammonium hydrate, ammonium chloride having been previously added to prevent the precipitation of magnesium. DIVISION A. Metals which, in the insured absence of organic matter, are precipitated as hydrates by the addition of the ammonium chloride and ammonium hydrate only. I. IRON (Ferrous, Fe ; and Ferric, Fe 2 ). (a) WET REACTIONS. instead of HC1, when nickelic hydrate Ni(HO) 6 is slowly precipitated (separation from Co, which gives no precipitate). 5. Alkaline Carbonates behave, so far as colour and solubility in excess are concerned, like their respective hydrates. (b) DR Y REACTIONS. 1. Heated on charcoal with Na 2 CO 3 in the inner blowpipe flame, a grey- metallic and magnetic powder is produced. 2. Heated in the borax bead in the outer blowpipe flame, red to violet-brown is produced while hot, and a yellowish to sherry-red when cold. These colours might be mistaken for those of iron ; but on fusing a< small fragment of potassium nitrate with the bead, its colour at once.- changes to blue or dark purple (distinction from Fe). IV. COBALT (Co). (a) WET REACTIONS. (To be practised on a solution of cobaltous nitrate Co(NO 3 ) 2 .) 1. NH 4 HS in the presence of NH 4 C1 and NH t HO (group reagent] gives a black precipitate of cobaltous sulphide CoS insoluble in acetic and cold dilute hydrochloric acid, and requiring to be boiled with the strongest HC1, often with the addition of a drop or two of nitric acid before solution is effected. 2. KHO, or NaHO, gives a blue precipitate, which rapidly changes on boiling; to pink cobaltous hydrate Co(HO) 2 (distinction from nickel). 3. KCN gives a light brown precipitate of cobaltous cvanide, raoidlv soluWc DETECTION OF THE METALS. in excess, but reprecipitated by excess of dilute hydrochloric acid. If, however, the HC1 be added drop by drop just so long as it causes the evolution of hydrocyanic acid fumes on boiling,* soluble potassium cobalticyanide K 6 CCX(CN) 12 results, which is not decomposed by hydrochloric acid; nor is any precipitate produced on adding excess of sodium hydrate or chlorinated soda (separation from nickel). 4. Alkaline Carbonates throw down basic carbonates, behaving like the respective hydrates. (b) DRY REACTIONS, 1. Heated on charcoal with Na 2 COs in the inner blowpipe flame, the cobalt separates as a grey magnetic powder. 2. Heated in the borax bead, first in the outer and then in the inner flame, a fine blue colour is produced. It is an important distinction of cobalt from copper, manganese, etc., that prolonged heating in the inner flatne does not affect this blue. GROUP IV. Metals the hydrates and sulphides of which, being soluble, are not precipi- tated by the addition of NH 4 HO and NH 4 HS in the presence of NH 4 C1, but separate as insoluble carbonates on the addition of ammonium carbonate to the same solution. I. BARIUM (Ba). (a) WET REACTIONS. (To be practised on a solution of barium chloride BaClj.) 1. Ammonium carbonate (NH 4 ) 2 C0 3 in the presence ^NH^Cl (group reagent) produces a white precipitate of barium carbonate BaCO 3 soluble with effervescence in dilute acetic acid. 2. H 2 S0 4 and all soluble Sulphates give a white precipitate of barium sul- phate BaSO 4 insoluble in ammonium acetate or tartrate (distinction from PbSO 4 ) and also in boiling nitric acid. 3. K 1 Cr0 4 gives a yellow precipitate of barium chfomate BaCrO 4 insoluble in water and in dilute acetic acid, but soluble in hydrochloric acid (distinction from Sr and Ca). 4. (NH 4 ) 2 C 2 4 gives a white precipitate of barium oxalate BaC 2 O 4 not readily formed in the presence of much acetic acid. 5. Na i HP0 4 gives a white precipitate of barium hydrogen phosphate BaHPO 4 soluble in acetic acid, and to some extent in ammonium chloride. (b) DRY REACTION. (To be practised also on barium chloride.) If a platinum wire be dipped first in hydrochloric acid and then in the salt, and held in the inner blowpipe or Bunsen flame, the outer flame is coloured yellowish-green. * This must be done in a fume chamber, as it is a highly poisonous operation if the fumes nhould happen to escape into the room. STRONTIUM CALCIUM. 25 II. STRONTIUM (Sr). (a) WET REACTIONS. (To be practised on strontium nitrate Sr(NO 3 ) 2 -) 1 (NH 4 ) 2 C0 3 (group reagent] in the presence of NH 4 C1 and NH 4 HO gives a white precipitate of strontium carbonate SrCO 3 soluble in dilute acetic acid. 2 H 2 S0 4 , or a soluble sulphate (preferably calcium sulphate), yields a white precipitate of strontium sulphate SrSO 4 which only separates com- pletely from dilute solutions on allowing them to stand in a warm place for some hours. It is insoluble in a boiling strong solution of ammonium sulphate rendered alkaline by ammonium hydrate (distinc- tion from calcium sulphate). \. The other reactions are similar to those of calcium. ($) DRY REACTION. (To be also practised on Sr(NO 3 ) 2 .) A platinum wire moistened with hydrochloric acid, dipped in the substance and introduced into the inner blowpipe or Bunsen flame, colours the outer flame crimson. III. CALCIUM (Ca). .(a) WET REACTION'S. (To be practised on a solution of calcium chloride CaCI 2 .) I. (NH 4 ) 2 C0 3 in presence of NH 4 C1 and NH 4 HO (group reagent) produces a white precipitate of calcium carbonate CaCO 3 soluble in acetic acid and settling best on warming. a. (NH 4 ) 2 C 2 4 precipitates white calcium oxalate CaC 2 O 4 insoluble in acetic or oxalic acids, but soluble in hydrochloric acid. 3. H 2 S0 4 in strong solutions produces a precipitate of calcium sulphate CaSO 4 . Being slightly soluble in water, it does not form in dilute solutions, nor is it precipitated by a saturated solution of calcium sulphate (distinction from Ba and Sr). It is soluble in a boiling saturated solution of ammonium sulphate containing excess of ammo- nium hydrate, but quite insoluble in a mixture of two parts alcohol and one part water. 4. Na 2 HP0 4 produces a white precipitate of dicalcium phosphate CaHPO* soluble in acetic acid. (b) DRY REACTION. (To be practised on calcium carbonate CaCO 3 .) A platinum wire moistened with hydrochloric acid, dipped in the substance and held in the inner blowpipe or Bunsen flame, colours the outer flame yellowish-red. This reaction is masked by the presence of barium or strontium. 26 DETECT JON OF THE MEIALS GROUP V. Metals not precipitable either as sulphide, hydrate, or carbonate, including magnesium, the precipitation of which as hydrate or carbonate has been prevented by the presence of ammonium chloride. I. MAGNESIUM (Mg). (a) WET REACTIONS. (To be practised on a solution of magnesium sulphate MgSO 4 .) 1. Na 2 HP0 4 in the presence ofNHf.1 tf^NH 4 HO produces a white crystalline precipitate of ammonium magnesium phosphate MgNH 4 PO 4 . It is slightly soluble in water, and scarcely at all in water containing ammonium hydrate, but entirely soluble in all acids. In very dilute solutions it only forms on cooling and shaking violently, or on rubbing the inside of the tube with a glass rod. 2. (NH 4 ) 2 HAs0 4 produces a similar precipitate of ammonium magnesium arseniate MgNH 4 AsO 4 possessing like features. 3. KHO, NaHO, and NH 4 HO give precipitates of magnesium hydrate Mg(HO) 2 insoluble in excess, but soluble in the presence of ammonium salts. The alkaline carbonates (except ammonium car- bonate) precipitate magnesium carbonate, also soluble in ammonium salts. 4. Calcium hydrate (lime water) C&(H.Q) 2 and Barium hydrate (baryta water} Ba(HO) 2 produce a similar effect. Either of these reagents is useful for the separation of magnesium from all the alkalies except ammonium. The solution, which must contain no ammonium salts, is treated with excess of either lime or baryta water. The precipitated magnesium hydrate is then filtered out and excess of ammonium carbonate added, which precipitates in turn the excess of Ca or Ba employed, and leaves K, Na, or Li in solution. (l>) DRY REACTION. (To be practised on magnesium oxide.) Heated on charcoal before the blowpipe, it becomes strongly incandescent, and leaves a white residue, which when moistened with a drop of solution of cobaltous nitrate Co(NOs) 2 and again heated, becomes rose-coloured. This test is not, however, infallible. II. LITHIUM (Li). (a) WET REACTIONS. (To be practised on a solution of lithium chloride, prepared by dissolving lithium carbonate in dilute hydrochloric acid.) 1. Na 2 HP0 4 in strong solutions produces a white precipitate of lithium phos- phate (Li 3 PO 4 )^H 2 O on boiling only (distinction from Mg). It is soluble in hydrochloric acid, and reprecipitated by boiling with ammonium hydrate. 2. Na 2 C0 3 and even NaHO, in very strong solutions, yield the carbonate and hydrate respectively. 3. Platinic chloride PtCl 4 gives no precipitate (distinction from potassium). POT A SSIUM SODIUM A MMONIUM. b DRY REACTION. (To be practised with lithium carbonate.) A platinum wire, moistened with hydrochloric acid, dipped in the substance and held in the inner blowpipe or Bunsen flame, colours the outer flame carmine red. The presence of sodium disguises this reaction. III. POTASSIUM (K). WET REACTIONS. (To be practised on solution of potassium carbonate treated with dilute HC1 till effervescence ceases, forming potassium chloride KC1.) 1. PtCl 4 , in strong solutions, gives a yellow crystalline precipitate of potassium platino-chloride PtCI 4 (KCl) 2 soluble on great dilution, especially on warming, but insoluble in acids, alcohol, and ether. 2. Hydrogen tartrate (tar tar ic tf<^) H 2 C 4 H 4 6 throws down, from strong solutions only, a white crystalline precipitate of potassium hydrogen tartrate KHC 4 H 4 O 6 soluble in much cold water, rather freely in hot water, readily in acids and in KHO or NaHO, and not formed unless the original solution be nearly neutral. Its separation is facili- tated by stirring and shaking violently, in which case it settles quickly. 3. Hydrogen silicofluoride (hydrofluosilidc acid) H 2 SiF 6 yields white gela- tinous potassium fluosilicate K 2 SiF 6 sparingly soluble in water. DRY REACTION. (To be practised on potassium carbonate K 2 CO 3 .) Dip a platinum wire, moistened with HCl, in the salt. Held in a Bunsen flame a violet colour is imparted. The masking effect of Na (yellow) is obviated by viewing the flame through cobalt glass. IV. SODIUM (Na). WET REACTIONS. (To be tested with solution of sodium chloride NaCl.) 1. K 2 H.,Sb^0 7 (potassium pyroantimoniate, generally called metantimomate) gives a white granular precipitate of sodium pyroantimoniate Na 2 H 2 Sb 2 O 7 6H 2 O from strong solutions only, which must be neutral or alkaline. This precipitate is insoluble in alcohol. 2. H 2 SiF 6 gives a similar precipitate to that obtained with K salts in concen- trated solutions only. Sodium salts are, practically, all soluble in water, and there is no thoroughly trustworthy wet reaction which can be applied to detect small quantities. If we have a solution which gives no precipitate with any of the group reagenrs, but leaves, on evaporating, a non-volatile residue, capable of imparting a strong yellow colour to the Bunsen flame (dry reaction) we may infer with certainty the presence of sodium. V. AMMONIUM (NH 4 ). WET REACTIONS. (To be tested with solution of ammonium chloride NH 4 C1.) i. PtCl 4 produces a heavy yellow precipitate of ammonium platino-chloride PtCl 4 (NH 4 Cl) 2 which, being rather soluble in water, is not formed in 28 DETECTION OF THE METALS dilute solutions, unless alcohol, in which it is insoluble, be added in considerable quantity. When ignited, pure spongy platinum is left This precipitate may be distinguished from that with K salts by adding, after ignition, a little water and AgNO 3 , when no white precipitate of AgCl is formed (the K salt leaves KC1 on being strongly heated). 2. H 2 C 4 H 4 6 yields ammonium hydrogen tartrate (NH 4 )HC 4 H 4 O 6 almost identical with KHC 4 H 4 O 6 in its properties. On ignition, however, the latter gives a black residue, which turns moistened red litmus paper blue (KoCOs and C), the former leaving pure C without reaction. 3. NaHO or Ca(HO) 2 boiled with the solution causes the evolution of ammonia gas NH 3 . A glass rod dipped in HC1 or HC 2 H 3 O 2 produces, when held over a mixture evolving NH 3 , white clouds (solid NH 4 salts), and moist red litmus paper is turned blue. 4. Nessler's Solution (HgI 2 dissolved in KI and KHO added) gives a yellow or brown colour, or a brown precipitate, of dimercuric ammonium iodide NHg 2 IH 2 O with all NH 4 salts. This reaction is extremely delicate, and the estimation of NH 4 in water is founded upon it. DR Y RE A CTIONS. Ammonium salts volatilise (i) with decomposition, leaving a fixed acid {e-g-1 phosphate) ; (2) with decomposition, leaving no residue whatever (e.g., sulphate, nitrate) ; (3) without decomposition, when they are said to sublime (t.g; chloride, bromide, etc.). CHAPTER III. DETECTION AND SEPARATION OF ACID RADICALS. I. HYDROFLUORIC ACID and FLUORIDES, (The test for fluorides undernoted may be practised on fluor spar CaFj.) Hydrofluoric Acid, or Fluoric Acid, is known 1. By its strongly acid reaction and corrosive power. a. By its action upon glass, from which it dissolves out silicic acid SiO 2 thus roughening the surface and rendering it semi-opaque or translucent, and white ; a colourless gas, silicic fluoride SiF 4 passing off. Fluorides are detected as follows : The mineral or salt is finely powdered, and introduced into a leaden dish with a little sulphuric acid. A piece of glass, previously prepared by coating its surface with wax, and etching a few letters on the waxed side with the point of a pin, is placed over the dish, waxed side down. A gentle heat is then applied, but not sufficient to melt the wax, and the operation continued for some time. The glass is then taken off, and the wax removed from it ; when, if fluorine were present, the letters written on the waxed surface will be found engraved upon it by the action of the hydrofluoric acid. 2. CHLORINE, HYDROCHLORIC ACID, and CHLORIDES. 'Free Chlorine C1 2 may be detected 1. By its odour. 2. By turning paper dipped in solution of potassium iodide brown. 3. By bleaching a solution of indigo or litmus. Hydrochloric Acid HC1 may be recognised 1. By its acidity and its giving off C1 2 when heated with MnCX. 2. By producing dense white fumes when a rod dipped in ammonium hydrate is held over the mouth of the bottle. 3. By giving a curdy white precipitate of argentic chloride with argentic nitrate, instantly soluble in ammonium hydrate. Chlorides give the following reactions (to be practised with any soluble chloride, say NaCl) : 1. Heated with sulphuric acid they evolve white fumes of HC1. 2. Heated with H_,S0 4 and MnO, they evolve chlorine. 3. AgN0 3 in the presence 0/HN0 3 gives a white precipitate of argentic chloride AgCl insoluble in boiling nitric acid, but instantly soluble in dilute ammonium hydrate of a strength of i in 20. 30 DETECTION, ETC., OF ACID RADICALS. 4. The solid substance mixed with K 2 Cr.,0 7 , and distilled with H 2 S0 4 , yields chloro-chromic oxide- CiCl 2 O 2 in red fumes which, when passed into dilute ammonium hydrate, colour it yellow, owing to the formation of ammonium chromate (NH 4 ) 2 CrO 4 . The yellow should change readily to green on the addition of a few drops of sulphurous acid. Insoluble Chlorides should be first boiled with strong sodium hydrate and the whole diluted and filtered. The chloride is then transferred to the sodium, and is to be searched for in the filtrate by acidulating with nitric acid and adding argentic nitrate, as above described. 3. HYPOCHLORITES. (Practise on a solution of chlorinated lime Ca(ClO) 2 CaCl2.) Hypochlorites are all readily soluble in water, are contained in the so-called chlorinated compounds, and are recognised 1. By having an odour of chlorine. 2. By giving a blue with potassium iodide, starch paste, and acetic acid, due to liberation of chlorine. 4. CHLORATES. (To be practised on potassium chlorate KC1O 3 .) 1. Heated on charcoal, they deflagrate. 2. Heated with strong sulphuric acid, they evolve chlorine peroxide ClaO 4 which is yellow and explosive. 3. Their solutions yield no precipitate with argentic nitrate ; but if a little of the solid be heated to redness, and the residue dissolved in water, a precipitate of argentic chloride may be obtained. The same reduction from chlorate to chloride may also be effected by adding zinc and dilute sulphuric acid to the solution. 4. Mixed with KI and starch paste, and acidulated with acetic acid, they give no blue (distinction from hypochlorites), but on adding HC1 a blue is developed. 5. PERCHLORATES. These are distinguished from chlorates 1. By giving off perchloric acid HC1O 4 when heated with sulphuric acid, without explosion or evolution of chlorine peroxide. 2. Like chlorates, they require reduction to chlorides before giving a precipitate with argentic nitrate. 6. BROMINE, HYDROBROMIC ACID, and BROMIDES. Bromine Br 2 is distinguished 1. By its appearance heavy, reddish-brown liquid, giving off reddish fumes of a very penetrating, unpleasant odour. 2. By turning starch paste orange. 3. When present in small quantity in solution, on adding a few drops of chloroform and shaking, an orange colour is imparted to that liquid, which sinks to the bottom of the aqueous solution. Hydrobromic Acid HBr is known By its acid reaction and the production of fumes of bromine when heated with strong sulphuric acid. BROMIDES IODIDES. 31 Bromides are all soluble in water, except the silver, mercurous, and lead salts ; they are detected by the following characters (to be practised on potassium bromide KBr) : 1. Heated with strong sulphuric acid, they evolve red vapours of bromine. 2. A similar effect is produced by sulphuric acid and metallic dioxides, such as PbO 2 , MnO 2 . 3. Mixed with starch paste, and a few drops of chlorine water care- fully added, they give an orange colour (starch bromide). 4. Mixed in a long tube with chloroform, and a few drops of chlorine water added, the whole, when shaken well together, leaves, on settling, a characteristic reddish-brown stratum at the bottom of the liquid in the tube, due to free bromine in the chloroform. 5. With argentic nitrate they give a dirty-white precipitate of argentic bromide, insoluble in nitric acid, slowly soluble in ammonium hydrate, but insoluble in dilute NH 4 HO, of a strength of i in 20 (argentic chloride dissolves). 6. Distilled with potassium dichromate and sulphuric acid, red fumes are evolved, which give no colour when passed into ammonium hydrate (distinction from chlorides). Insoluble Bromides should be first boiled with NaHO, as described under insoluble chlorides. 7. HYPOBROMITES. These are very similar to hypochlorites, and react as follows: 1. They decompose by heat, leaving a bromide ; 2. On boiling with an alkali, a mixture of bromide and bromate results. 8. BROMATES. These are recognised 1. By deflagrating on charcoal, leaving the corresponding bromide. 2. By liberating bromine on the addition of dilute sulphurous acid. 9. IODINE, HYDRIODIC ACID, and IODIDES. Iodine 1 2 may be recognised by its glistening black scales, its odour, the violet vapour on heating, and the production of blue iodide of starch on adding a solution to starch paste. Hydriodic Acid HI in the gaseous state, is detected by the formation of a brown colour on paper moistened with chlorine water (blue if also dipped in starch paste) held over a tube from which it is being evolved. Iodides are readily known by the following reactions (which may be practised on a solution of potassium iodide, KI) : 1. Heated with strong sulphuric acid they give a liberation of iodine with violet fumes. 2. Mucilage of starch and chlorine water or strong nitric acid (if not added too plentifully) produces blue iodide of starch, decom- posed by heat, but re-formed on cooling ; also bleached by excess of Cl. 3. AgN0 3 gives a light yellow precipitate of argentic iodide Agl. The precipitate, when freed from the supernatant liquid, does not dissolve in hot HNO 3 , and is practically insoluble in ammonium hydrate, being thus distinguished from a chloride 32 DETECTION, ETC., OF ACID RADICALS. 4. A neutral solution gives with one part of cupric sulphate CuSO 4 and three parts of ferrous sulphate FeSO 4 dissolved in a little water, a greyish precipitate of cuprous iodide Cu. 2 I 2 . The same precipitate is produced if sulphurous acid H^SOa be used with the cupric sulphate instead of ferrous sulphate. 5. Palladious Chloride PdCl, or palladious nitrate Pd(N0 3 ) 2 gives a black precipitate of palladious iodide PdI 2 decom- posed somewhat below the temperature of boiling mercury, iodine being evolved, and the metal left. This is a very expensive but efficient separation. 6. Mercuric chloride and plumbic nitrate give respectively red and yellow precipitates with soluble iodides. 10, IODATES. (Practise on solution of potassium iodate KIO 3 .) lodates are known 1. By giving, when heated with strong sulphuric acid, similar reactions to those obtained with chlorates. 2. By giving a blue colour with starch paste on the addition of sulphurous acid. 3. By giving a blue colour with starch paste on the addition of potassium iodide and tartaric acid. 4. By yielding a precipitate of ferric oxy-iodate on adding ferric chloride. 11. PERIODATES. Periodates are distinguished I. By giving a precipitate with BaCL, in a neutral solution, which is not decomposed by digesting with ammonium carbonate and a little NH 4 HO. lodates leave barium carbonate, which when washed dissolves in acid with effervescence. I. By adding Hg(NO 3 ) 2 and treating the yellowish precipitate with SnCl,. It turns green, HgI 2 being produced. 12. WATER and HYDRATES. Water is recognised 1. By its absolute neutrality to test-paper. 2. By its evaporating without residue, fumes, or odour of any kind. 3. By its turning white anhydrous cupric sulphate blue. 4. By yielding pure hydrogen when it is boiled and the steam passed slowly over copper turnings heated to bright redness in an iron tube. 5. By its undergoing electrolysis when acidified, yielding hydrogen at the negative and oxygen at the positive electrode. The soluble Hydrates, viz., KHO, NaHO, LiHO, Ba(HO) 2 , Sr(HO) 2 , and Ca(HO). 2 are known 1. By being more or less soluble in cold water, yielding solutions which are strongly alkaline to test-paper. 2. By dissolving in hydrochloric acid without effervescence and without smell. 3. By giving a brownish-black precipitate of argentic oxide Ag 2 O with argentic nitrate. The insoluble Hydrates are recognised By giving off steam when heated in a dry test-tube, and leaving a residue which behaves like the corresponding oxide. OXIDES-SULPHIDES. 33 13. OXIDES. All oxides are insoluble in water. Oxides of K, Na, Li, Ba, Sr, and Ca unite with water to form hydroxides, which dissolve with a greater or less degree of readiness and give the characters of the soluble hydrates already mentioned. Normal Oxides can only be recognised by negative results, such as : 1. Heated alone, they are not changed; except argentic oxide, which leaves the metal, and mercuric oxide, which volatilises and breaks up into the metal and oxygen. 2. They are insoluble in water (exceptions K, Na, etc., as above), hut soluble in hydrochloric or nitric acid without effervescence and without smell. 3. After dissolving and removing the metal by H 2 S or Na 2 ( J0 3 as most convenient, no acid radical is found, other than that of the acid used to dissolve. 4. Boiled with strong NaHO and filtered, or fused with KNaC0 3 and digested with water, the solution gives no reaction for any acid radical except the soluble hydrate or carbonate employed. Peroxides, on account of their containing an excess of oxygen, differ from normal oxides (practise on MnO 2 ), 1. By giving off oxygen when strongly heated. 2. By evolving chlorine when heated with hydrochloric acid. 14. SULPHITE, HYDROSULPHURIC ACID, and SULPHIDES. Ordinary Sulphur S 2 or S 6 is recognised 1. By its burning entirely away with a pale blue flame, and evolving sulphurous anhydride. 2. By its insolubility in all ordinary menstrua, such as water, alcohol, and ether, but dissolving readily in carbon disulphide. 3. When slowly heated in a tube, it first melts, then thickens, then liquefies again, and finally boils, the vapour taking fire and forming sulphurous anhydride. Precipitated Sulphur possesses the above characters, and is specially distin- guished from ordinary sulphur by being quite amorphous under the microscope, while the latter is crystalline. Hydrosulphuric Acid H 2 S (sulphuretted hydrogen) is known 1. By being a colourless gas with a disgusting odour of rotten eggs. It is inflammable, burning in the air to produce sulphurous acid. 2. By turning a piece of paper black, which has been moistened with solution of plumbic acetate and held over the mouth of the tube or jet from which it issues. Normal Sulphides are divisible into five classes : 1. Soluble in water, including the sulphides of K, Na, NH 4 , Ca, sr, Ba, and Mg. 2. Insoluble in water, but readily soluble in dilute hydrochloric acid including those of Fe, Mn, Zn. 3. Insoluble in dilute, but soluble in strong boiling hydrochloric acid, including the sulphides of Ni, Co, Sb, and Sn (PbS is also slightly affected, but separates on cooling, as chloride). 4. Insoluble in hydrochloric acid, but attacked by strong heated nitric acid, being converted wholly or partially into su'phates. These include the sulphides of Pb, Ag, Bi, Cu (arsenious sulphide is slowly affected). 34 DETECTION, ETC., OF ACID RADICALS. 5. Not dissolved by any single acid, but converted into a soluble sulphate by the action of nitre-hydrochloric acid, or hydro- chloric acid and potassium chlorate; including those of Hg, As, Au, and Pt. Sulphides soluble in water or in hydrochloric acid are recognised (practise on soluiion of NagS) 1. By giving off sulphuretted hydrogen when heated with HC1. 2. Soluble sulphides give black and yellow precipitates, with solutions of lead and cadmium respectively. 3. Alkaline sulphides give a purple colour with sodium nitroprusside -Na,Fe(NO)C 6 N 6 . Sulphides insoluble in hydrochloric acid are best detected (practise on vermilion) 1. Mix a little with sodium carbonate and borax, and heat on charcoal before the blowpipe. Remove the mass thus obtained, place it on a clean silver coin, and moisten with a drop of distilled water ; when, owing to the formation during ignition of sodium sulphide Na_S, a black stain of argentic sulphide Ag^S will be produced. 2. By heating with strong nitric or nitro-hydrochloric acid, diluting the solution, and testing for a sulphate with barium chloride (see page 36). 3. By fusion with KNaC0 3 and KNOs, digesting the residue in water, filtering and testing the solution for a sulphate* formed by the oxidising action of the potassium nitrate. Polysulphides as commonly met with are those of the alkalies, and are soluble in water. They are known (practise on sulphuretted potash K 2 Ss) 1. By the deep yellow or orange colour of their solutions. 2. By evolving sulphuretted hydrogen accompanied by a deposit oj sulphur when treated with hydrochloric or dilute sulphuric acids. The polysulphides which are insoluble in hydrochloric acid, such as iron pyrites, copper pyrites, etc., are best proved by fusion with potassium nitrate and carbonate and conversion into sulphate. They may, however, be recog- nised by heating with hydrochloric acid and zinc, when the excess of sulphur will pass off as H 2 S, leaving the normal sulphide. 15 THIOSULPHATES (Hyposulphites). (Practise on solution of sodium thiosulphate Na^S-XXjS H 2 O.) These salts, commonly known as hyposulphites, are usually soluble in water, and exhibit the following characters : i. With either dilute or strong HC1 and H.,S0 4 , they give off SO, and form a yellow deposit of S (distinction from sulphides, polysulphi.tes, and sulphites], i. AgNO^ gives no precipitate at first, owing to excess of a hypo- sulphite dissolving argentic hyposulphite Ag.,S 2 O 3 but on continuing the addition, this Ag 2 S 2 Os is precipitated of a white colour. The salt splits up spontaneously, becoming yellow, brown, and lastly black, and being changed completely into argentic sulphide Ag 2 S. The same decomposition of the precipitate occurs on substituting HgNO^ or Pb(NO 3 ). 2 for AgNO,; and in all three cases heat accelerates the action, and HJ5O 4 is the by-product. SULPHITES AND SULPHATES. 35 3. Fe.,Cl 6 produces a reddish-violet colour, gradually disappearing as FeCL, is formed. (This colour is not produced by sulphites^ and a somewhat similar tint produced by Fe 2 Cl 6 in thiocyanatss does not disappear.} 4. Na.,OCl 2 or C1 2 water converts hyposulphites into sulphates, even without applying heat. 16. SULPHUROUS ACID and SULPHITES. Sulphurous Acid H 2 S0 3 is recognised in solution 1. By its pungent odour of burning sulphur, due to evolution of SO^. It combines directly with peroxides to form sulphates. Foi instance : PbO, + SO 2 = PbSO 4 . (This reaction is utilised in gas analysis, to separate SO 2 from a mixture.) 2. By adding barium chloride in excess, filtering out any precipitate of barium sulphate which may form (owing to the fact that all samples of the ordinary acid contain sulphuric acid), and then adding chlorine water and getting another copious white precipitate of barium sulphate, owing to the conversion of the sulphurous into sulphuric acid by the oxidising action of the chlorine water, thus : H 2 S0 3 + BaCl 2 + Cl, + H 2 p = BaSO 4 + 4HC1. 3. Treated with zinc and hydrochloric acid, it evolves sulphuretted- hydrogen, thus : 3 Zn + 6HC1 + H,S0 3 = 3 ZnCl ? + H 2 S + 3 H 2 a 4. When a solution of iodine is dropped into the liquid, its colour is- discharged, owing to its conversion into hydriodic acid by the hydrogen of the water, the oxygen of which passes at the same time to the sulphurous acid, forming sulphuric acid. H.S0 3 + I 2 + H 2 = H 2 S0 4 + 2HI. Sulphites are known by the following characteristics (practise on solution of sodium sulphite Na 2 SO 3 ) : 1 . All except the alkaline sulphites are sparingly soluble in water. 2. When heated with sulphuric acid they evolve sulphurous anhydride,. witnbut deposit of sulphur. 3. Acted on with zinc and hydrochloric acid, they evolve sulphuretted hydrogen, which blackens a piece of paper moistened with. plumbic acetate and held over the mouth of the test-tube. 4. A salt of silver, mercury, or lead produces a precipitate which on. heating turns dark, owing to the formation of a sulphide and free sulphuric acid. 5. By boiling with barium chloride and chlorine water or nitric acid, barium sulphate is produced, and precipitates. 6. K 2 Cr.,0 7 and HC1 give a green coloration of chromic sulphate 01 chloride. This test is very delicate, but by itself is not con- clusive, as any reducing agent acts similarly. 17. SULPHURIC ACID and SULPHATES. Sulphuric Acid H,S0 4 is detected 1. By its appearance. A heavy, oily, odourless, and nearly colourless liquid, powerfully acid and corrosive. 2. By its charring effect. This is made evident when the strong acid is dropped upon white paper, wood, etc., or when the dilute 3 DETECTION,. El C., OF ACID RADICALS. acid is evaporated in a basin containing a little white sugar. The carbonisation is due to the power the acid has of abstract- ing the elements of water from organic bodies. 3. By liberating an explosive gas when dropped on a small fragment of KC10 3 . Sulphates are soluble in water, with the exception of basic sulphates (soluble in acids) and BaSO^, SrSO 4) CaSO 4 , and PbSO 4 . (Ag 2 S0 4 is only slightly soluble.) When it is necessary to analyse such sulphates as are insoluble in dilute acids, they are decomposed, either by boiling with potassium or sodium hydrates or by fusion with KNaCOg (the latter being preferable), and extracting the fused mass with water when the sulphate passes into solu- tion. Sulphates are recognised by the following characters (practise on solution of magnesium sulphate) : 1. BaCl 2 or Ba(NO a ) 2 produces a white precipitate of barium sulphate BaSO 4 insoluble in boiling water and boiling nitric acid. The addition of barium chloride to a strongly acid solution often causes the reagent to crystallise out, and this is then mistaken by the student for a true precipitate of sulphate ; therefore the boiling water should always be employed. 2. The addition of a soluble salt of lead or strontium also causes the formation of insoluble sulphates ; but these reactions are never used in practice, the barium chloride being at once the most delicate and serviceable reagent. 3 Heated with a little Na 2 C0 3 on charcoal in the inner blowpipe flame, sulphates are reduced to sulphides; and the residue, placed on a clean silver coin and moistened with water, leaves a black stain. 18. CARBON, CARBONIC ACID, and CARBONATES. Carbon C 2 is known 1. By its black colour and by burning in the air and producing a gas which is odourless, so heavy that it can be poured from one vessel to another, and causes a white precipitate when passed into solution of calcium hydrate. 2. By its capability of removing many vegetable colouring matters from their solutions. Carbonic Acid H 2 C0 3 is not known in the free state, as it splits up into carbonic anhydride CO 2 and water on isolation. CO 2 is recognised 1. By being odourless and giving white insoluble CaCO^ (or BaCO 3 ) when passed into a solution of Ca(HO) 2 (or Ba(HO).,). 2. By turning blue litmus purple or wine-red, the original tint being restored by heat, the CO 2 escaping. Carbonates are mostly insoluble in water, the alkaline carbonates alone dissolving. All carbonates give off CO 2 on ignition, except K. 2 CO 3 and Na 2 CO 3 . A white heat is needed to decompose BaCO 3 and SrCO 3 . Most carbonates on heating to redness leave the oxide. Their recognition depends upon the following reactions (practise upon calcium carbonate) 1. Effervescence with a solution of almost any acid (H 2 S and HCN excepted), organic or inorganic, and giving off an odourless gas CO 2 . 2. When the gas given off is poured or passed into a solution of calcium hydrate, a white precipitate of CaCO 3 falls, soluble in excess of CO 2 . When CO 2 is given off along with H 2 S or SOg, BORATES, AND SILICATES. either of these may be removed by passing through K 2 CrO 4 and HC1, which is rendered green, and the unacted-upon CO 2 is allowed to pass into calcium hydrate solution as before, thus enabling us to detect a carbonate in the presence of a sulphide or sulphite. 3 HgCLj gives a reddish-brown precipitate with the carbonates of of K, Na, and Li, and a white one with bicarbonatcs of the same metals. 4. Soluble carbonates give a white precipitate with cold solution of MgSO 4 , while bicarbonates do not. 19. BORIC ACID and BORATES. Boric (or Boracic) Acid H 3 BO ? is distinguished as under : 1. It is a white crystalline solid, giving off water on being heated, and leaving the anhydride B 2 O 3 . 2. A solution in alcohol burns with a green flame. 3. When dissolved in hot water, and a piece of turmeric paper dipped in the solution, the yellow colour is unaffected ; but upon drying the paper it becomes brownish-red, turned green on moistening with KHO. All borates dissolve in dilute acids, but few in water, and when decomposed by hot acids, let fall crystalline boric acid on> cooling, which answers to the above characters. The presence of soluble borates is detected by the following tests (practise upon borax Na 2 B 4 O 7 ioH,O : 1. They give, on heating with calcium chloride, rendered slightly alkaline with ammonium hydrate, a white precipitate of calcium borate, soluble in acetic acid, and so distinguished from oxalate. 2. On rendering the solution just acid with hydrochloric acid, it reacts with turmeric paper as does H 3 BO 3 . 3. Besides these two tests, which are in themselves, taken together, quite conclusive, borates give a white precipitate with argentic nitrate soluble in nitric acid. 4. When a little of the solid borate is moistened with a drop of sulphuric acid, and alcohol is added, the green flame of H o BO 3 is obtained on applying a light. 20. SILICIC ACID and SILICATES. The acid H 4 Si0 4 is scarcely ever met with, and we have practically to deal with the anhydride SiC>2 which is totally insoluble in water and dilute" acids, the acid dissolving slightly in both. SiO 2 is characterised 1. By its infusibility when heated. 2. By its insolubility in water, and all acids except HF. 3. By forming when heated with H 2 S0 4 and CaF., in a leaden vessel. gaseous silicic fluoride SiF 4 which deposits the acid H 4 SiO 4 and forms hydro-fluosilicic acid H SiF 6 in contact with moisture. Silicates are insoluble in water, except the alkaline silicates. Many of them do not dissolve in strong acids (a few are decomposed by hot H 2 SO 4 , but by no other acid), but all are split up by the action of gaseous hydrofluoric acid or a mixture of CaF 2 and H L SO 4 . i. On adding HC1 to an alkaline silicate, H 4 SiO4 falls as a gelatinous $8 DETECTION, ETC., OF ACID RADICALS. scarcely visible precipitate, slightly soluble in water. On evaporating to dryness and heating to 140 or 150 C., the addition to the residue of a little HC1 and water leaves the SiO 8 as a white gritty powder. 2. NH 4 C1 precipitates H 4 SiO 4 from an alkaline silicate. 3. Silicic anhydride is separated from all acid and basic radicals by fusing the finely powdered silicate with KNaCO 3 (fusion mix- ture], in a platinum crucible; adding dilute HC1 to the residue till effervescence ceases, evaporating, and, when dry, heating to 140 or 150 C. On again treating this residue with water and HC1, SiO 2 alone remains insoluble. 21. HYDROFLTJOSILICIC ACID (H 2 SiF 6 ). This acid is only known in solution. I. It is very acid, and dissolves metals with the evolution of hydrogen, forming silico fluorides which decompose by heat, leaving fluorides, and giving off silicon fluoride SiF 4 . ~*. It gives off hydrofluoric acid when evaporated, and should not, therefore, be heated in glass vessels, as they would be etched. .J. The majority of silico-fluorides are soluble, the exceptions being K 3 SiFg, BaSiF 6 , and Na 2 SiF 6 , which are insoluble, especially in presence of a little alcohol. '4. It does not precipitate strontium salts, even from strong solutions, but throws down BaSiF 6 on adding BaCl 2 and alcohol, as a white translucent crystalline precipitate. $. Potassium salts throw down gelatinous K 2 SiF 6 . 22. NITROUS ACID AND NITRITES. 'Nitrons Acid (so called commercially) is nitric acid containing nitrous anhydride. It is yellowish in colour, and evolves reddish fumes. ~ Nitrites are all soluble in water, the least so being argentic nitrite. They are known as follows (practise upon potassium nitrate which has been heated vto dull redness or upon sodium nitrite NaNO 2 ) : j. They give red fumes when treated with strong sulphuric acid. 2. They give an instantaneous blue colour with potassium iodide and starch paste on the addition of a few drops of dilute sulphuric .acid. The sulphuric acid liberates hydriodic acid from the iodide, and nitrous acid from the nitrite ; the hydriodic acid is decomposed by the nitrous acid into iodine, water, and nitric oxide : 2 HNO 2 + 2HI = I, + 2H,0 f 2 NO. [Nitrates, it must be remembered, would give frequently a similar reaction after starding, through the possible reduction of some portion of their nitric acid to nitrous acid ; so that unless the reaction appears instantly, and is confirmed by others, it is not safe to rely upon it as a test.] 3. -They give a dark brown colour with ferrous sulphate without the previous addition of sulphuric acid, as required by nitrates. 4. Potassium dichromate in solution is converted into a green liquid by the. addition of a nitrite and an acid. These two latter substances also reduce solution of auric chloride, forming a precipitate of the metal, possessing a dark colour. NITRIC ACID AND NITRATES. 39 23. NITRIC ACID and NITRATES. Nitric Acid HN0 3 is strongly acid and corrosive, fumes in tne air, and readily dissolves most metals. It may be at once recognised by the following characters : 1. When poured on a piece of copper foil, and a piece of white paper held behind the test-tube, orange-red fumes of nitric peroxide NgO* are observed. 2. When dropped on a piece of quill in a basin, or evaporated in contact therewith, the quill is stained yellow, intensified to orange on adding an alkali, and not discharged by warming (distinction from the corresponding stains produced by iodine and bromine). 3. Dropped on a few crystals of brucine, a deep red colour is produced. Nitrates are characterised by the following properties (practise upon solution of potassium nitrate KNCK) : 1. All nitrates are soluble in water, especially when slightly acidulated with nitric acid. The nitrates of the alkalies are only decom- posed by a very high temperature, but nitrates of the heavy metals, such as copper, mercury, and lead, are readily decom- posed by heat, leaving a residue of oxide. (Argentic nitrate leaves metallic silver.) 2. When heated with sulphuric acid, they evolve pungent fumes of nitric acid. 3. When heated with sulphuric acid and a piece of copper wire, red fumes of nitric peroxide are formed in the tube. 4. When mixed with a solution of ferrous sulphate in the presence of sulphuric acid, a black coloration is produced, due to the formation of nitrosyl ferrous sulphate. On heating, the colour disappears, and the ferrous is changed to \kzferric sulphate. Note. There are two ways of applying this test : (a) Place a drop or two of the solution on a white porcelain slab or crucible lid, and having added a drop of strong sulphuric acid, put a small and clean crystal of the ferrous sulphate in the liquid, when a black ring will gradually form round the crystal. () Place the solution in a tube, and having added some strong solution of ferrous sulphate, cautiously pour some strong sulphuric acid down the side of the tube, so that it sinks to the bottom by reason of its great gravity without mixing with the fluid. If nitric acid be present, a dark line will be formed at the junction of the two liquids. 5. Treated with sulphuric acid, and a few drops of indigo sulphate added, the blue colour of the latter is destroyed, being changed to yellow (not characteristic). 3C ]6 Hi N 2 O 2 (!NDIGOTIN) + 4 HNO 3 = 6C 8 H 5 NO 2 (ISATIN) + 4NO + 2H 2 O. 6. The most delicate test for nitrates is, however, phenol -sulphonio (sulpho-carbolic] acid. This reagent is prepared by dissolving one part of carbolic acid in four parts of strong sulphuric acid, and then diluting with two parts of water. A few drops of the solution to be tested are evaporated to dryness on a porcelain crucible lid over the water bath, and while still over the bath a drop of the reagent is added, when a reddish colour is im- mediately produced, owing to the formation of nitro- phenol. 40 DETECTION, ETC., OF ACID RADICALS. 21 CYANOGEN, HYDROCYANIC ACID, and CYANIDES. Cyanogen (C 2 N 2 ) or (Cy 2 ) is a colourless gas, which is recognised 1. By its odour of bitter almonds. 2. By its burning in the air with a peach-blossom-coloured flame, pro- ducing carbonic anhydride and nitrogen. 3. By forming ammonium oxalate when passed into water. Hydrocyanic Acid HCN is volatile, soluble in water, and possesses a characteristic faint sickly odour of almonds. Its reddening action on litmus paper is very transient. Its tests are four in number, as follows : 1. The Silver Test. Argentic nitrate gives a curdy white precipitate of argentic cyanide. The precipitate is soluble in ammonium hydrate and in strong boiling nitric acid, but not in dilute nitric acid ; nor does it blacken on exposure to the light. 2. Scheetes Iron Test. An excess of solution of potassium hydrate is mixed with the solution. To this a mixture of a ferrous and a ferric salt is added, and the whole acidulated with hydrochloric acid. If hydrocyanic acid be present, Prussian blue will be formed. The explanation of the test is as follows (according to Gerhardt's view) : (1) The hydrocyanic acid and the potassium hydrate form potassium cyanide. (2) The addition of the ferrous salt produces ferrous cyanide. (3) This reacting with the excess of alkali forms potassium ferrocyanide. (4) On the addition of the ferric salt, it is at first precipitated by the excess of alkali, as ferric hydrate, which on acidulation dissolves to ferric chloride, forming ferric ferrocyanide (Prussian blue). (i.) 6HCN + 6KHO = 6KCN -f 6H 2 O. (ii.) 6KCN -f 3FeCl, = 3Fe(CN) + 6KC1. (iii.) 3Fe(CN), + 4KHO = K 4 Fe(CN) 6 + 2Fe(HO),. (iv.) 3K 4 Fe(CN) 6 +2Fe,C] 6 =(Fe 2 ) 2 (Fe(CN) 6 ) 3 + "i2KCl. Or the whole may be shown in one equation, thus : iSKCN + 3FeCl 2 + 2Fe 2 Cl 6 = (Fe a ) 2 (Fe(CN) 6 ) 3 + 18 KC1. 3. The Sulphur Test. A few drops of yellow ammonium sulphydrate is added, and the whole is evaporated to dryness at a very gentle heat, with the addition of a drop of ammonium hydrate. A residue is thus obtained which (when cold) strikes a blood- red colour with ferric chloride, not dischargeable by hydro- chloric acid, but at once bleached by solution of mercuric chloride. fhis colour is due to the formation of ammonium thiocyanate (which takes place when an alkaline sulphide, containing excess of sulphur, is brought into contact with cyanogen) 2HCN + (NH 4 ),S + S 2 = 2NH 4 CNS + H ? S, and subsequent production of red ferric sulphocyanide. 4 ScKSribMs Test. Filtering paper is soaked first in a 3 per cent, alcoholic solution of guaiacum resin, and then in a 2 per cent, solution of cupric sulphate, and exposed to the air. When this paper is either moistened with the suspected solution or exposed to its vapour, a blue colour is produced. Cyanides are known (practise upon solution of potassium cyanide KCN) i. By effervescing and giving off the odour of hydrocyanic acid when heated with sulphuric acid. * By answering to all the tests for hydrocyanic acid above mentioned. . In applying the silver test to a soluble cyanide, the reagent must be adde<) in excess, as argentic cyanide is soluble in alkaline cyanides to form double CYANATES AND FERROCYANIDES. 41 cyanides of silver and the alkali used. Excess of argentic nitrate, however, decomposes these compounds, and forms insoluble argentic cyanide. The previous addition of a slight excess of dilute nitric acid ensures the immediate separation of the argentic cyanide, by preventing the reaction just referred to. 3. Insoluble cyanides yield cyanogen when heated per se in a small dry test-tube, the open end of which has been drawn out into a jet after the introduction of the cyanide. The application of a light to the jet gives the characteristic flame of cyanogen. 25. CYANIC ACID and CYANATES, CYANTJRIC ACID and FULMINIC ACID. Cyanic Acid HCNO is characterised 1. By being a colourless liquid, having a strong pungent odour, greatly resembling acetic acid, or very weak sulphurous acid, and forming ammonium bicar- bonate on adding water. 2. By changing into a white solid isomer on keeping, heat being evolved, but no decomposition occurring. Cyanates are known 1. By giving, when moistened, a bicarbonate. (The potassium salt KCNO foi instance forms potassium bicarbonate KHCO 3 .) 2. By producing urea when evaporated with an ammonium salt. Cyanuric Acid is a polymeric modification of cyanic acid, which is recognised 1. By being a crystalline solid, yielding cyanic acid on applying heat. 2. By not being decomposed by strong hot HNO 3 or H 2 SO 4 . Fulminic Acid (intermediate between the two above acids) differs from both by the fearful explosibility of its salts. 26. THIOCYANATES (Snlphocyanates). (Practise upon solution of potassium thiocyanate KCNS). Snlphocyanates are recognised 1. By evolving hydrocyanic acid and depositing sulphur on heating with sulphuric acid. 2. By producing with Fe 2 Cl 6 , or any ferric salt, a blood-red solution of ferric thiocyanate Fe 2 (CNS) 6 not destroyed by HC1 (dis- tinction from acetate), but bleached by mercuric chloride (distinction from meconate). 27. FERROCYANIDES (Practise upon solution of potassium ferrocyanide K 4 Fe(CN) 6 .) Ferrocyanides are mostly insoluble in water, except those of the metals of the first and second groups. They are characterised 1. By giving off hydrocyanic acid and forming a deposit on heating with diluted sulphuric acid. 2. By giving with FeS0 4 or any ferrous salt a white precipitate of potassium ferrous. ferrocyanide K 2 Fe(Fe(CN) 6 ) changing quickly to blue. 3. By yielding with Fe Cl r> or any ferric salt a dark blue precipitate of ferric ferrocyanide (^^(^^(C^}^ insoluble in HC1, but turned reddish-brown by KHO, which decomposes it into ferric hydrate and potassium ferrocyanide. The original blue is restored by adding HC1. 4. Cupric salts produce a reddish-brown precipitate of cupric ferro- cyanide Cu 2 Fe(CN) 6 insoluble in acids, dissolved by NH 4 HO but left unaltered on evaporating off the ammonia. 42 DETECTION, ETC., OF ACID RADICALS. 5. By precipitating white plumbic ferrocyanide from solutions of lead salts. 6. By yielding white mercuric ferrocyanide with a mercuric salt. 7. By giving a white gelatinous precipitate of zinc ferrocyanide on the addition of solutions of zinc salts. 8. By producing with argentic nitrate AgN0 3 white gelatinous silver ferrrocyanide, dissolved by NH 4 HO on heating. None of these precipitates can be produced in alkaline solutions ; and they form best in slightly acid solutions. 28. FERRICYANIDES. (Practise upon solution of potassium ferricyanide K 6 Fe 2 (CN) 12 .) Most ferricyanides are insoluble, those of the alkalies and of the barium group being exceptions. They are recognised 1. By yielding an odour of hydrocyanic acid, and a deposit on heating with diluted sulphuric acid. 2. By producing with FeS0 4 or any ferrous salt dark-tinted Turn- bults blue Fe 3 Fe 2 (CN) 12 insoluble in acids, but forming K 6 Fe 2 (CN)i2 when boiled with KHO, and depositing dirty green Fe (HO) 2 . 3. By producing no precipitate but a brownish coloration when added to Fe 2 Cl 6 or any feme salt in solution (distinction from ferrocyanide). 4. By giving no precipitate in a lead solution (another distinction from ferrocyanide). 5. By throwing down mercurous ferricyanide of a brownish-red colour from a mercurous solution. 6. By yielding with argentic nitrate solution an orange precipitate of argentic ferricyanide (another distinction from ferrocyanide}. 9. HYPOPHOSPHITES. (Practise upon solution of calcium hypophosphite Ca(PH 2 O 2 ) 2 .) All soluble except the silver salt. The following reactions serve for their detection : 1. When heated in a solid state, they take fire, evolving phosphuretted hydrogen, and leaving a residue of pyrophosphate. Note. This must be done on porcelain, as they destroy platinum foil. 2. With argentic nitrate they give a white precipitate, which turns brown owing to its reduction to metallic silver. 3. With mercuric chloride they yield, when slightly acidulated with HC1, a precipitate of calomel, which, on heating, turns dark, owing to a reduction to the metallic state. 4. After removal of the base, the free hypophosphorous acid, when boiled with solution of cupric sulphate, will give a deposit of metallic copper. 5. Treated with ammonium molyldate (NH 4 )_Mo0 4 they give a fine blue precipitate. As afterwards mentioned, phosphates give a yellow, and consequently when the solution contains both classes of salts the precipitate is green. This forms an excellent and rapid method of checking any commercial sample of hypophosphites. PHOSPHITES AND ORTHOPHOSPHATES. 43 They are distinguished from phosphites by not giving precipitates with neutral barium, or calcium chloride, or with plumbic acetate. In performing the 4th reaction, the base, if calcium, is removed by oxalic acid, if barium, by sulphuric acid, and if a heavy metal, by sulphuretted hydrogen. 30. PHOSPHOROUS ACID H 3 P0 3 and PHOSPHITES are distinguished as follows : 1. Heated on platinum foil, they burn. They are powerful reducing agents. 2. The only phosphites soluble in water are those of K, Na, and NH 4 , but acetic acid dissolves all, except plumbic phosphite. 3. With zinc and sulphuric acid (nascent hydrogen) they yield phosphuretted hydro- gen, burning with an emerald-green colour, and throwing down Ag 3 P, as well as Ag from AgNO 3 in solution. 4. They give precipitates with neutral barium, and calcium chlorides, and also with plumbic acetate, which hypophosphites do not. 5. Heated with mercuric chloride or argentic nitrate, they yield a precipitate of metallic mercury or silver. 2HgCl 2 + 2H 3 PO 3 -I- 2H 2 O = 2H 3 PO 4 + Hg 2 + 4HC1. 31. META- AND PYRO-PHOSPHORIC ACIDS AND THEIR SALTS. Metaphosphoric Acid HP0 3 is a glassy solid, not volatile by heat. It is freely soluble in cold water, and is converted by boiling into orthophosphoric acid. It is known by giving a white precipitate with ammonio-argentic nitrate, and by its power of coagulating albumen. Metaphosphates are known by 1. Giving no precipitate with ammonium chloride, ammonium hydrate, and mag- nesium sulphate, added successively. 2. Giving a white precipitate of argentic metaphosphate AgPO 3 with argentic nitrate only in neutral solutions, and soluble both in nitric acid and am- monium hydrate. Pyrophosphoric Acid H 4 P 2 7 is also soluble in water and convertible by boiling into orthophosphoric acid. It gives a white precipitate with ammonio-argentic nitrate, but does not coagulate albumen. Pyrophosphates are insoluble in water, except those of the alkalies. Their tests are not very well defined, but they give 1. A white precipitate of argentic pyrophosphate Ag 4 P 2 O 7 with argentic nitrate in a neutral solution only, and soluble both in nitric acid and ammonium hydrate. 2. (NH 4 ) 2 MoO 4 does not produce an immediate precipitate. 32. ORTHOPHOSPHORIC ACID and ORTHOPHOSPHATES. Orthophosphoric acid H 3 P0 4 is a liquid with a strongly acid reaction, converted by heat first into pyro- and finally into meta-phosphoric acid, which remains as a glassy residue. It is 1. Not volatile by a red heat. 2. It gives a yellow precipitate of argentic phosphate AgsPO* when treated with ammonio-argentic nitrate, soluble both in nitric acid and ammonium hydrate. Phosphates are as a rule insoluble in water, except the alkaline ones. They are readily soluble in dilute acids, and entirely reprecipitated on neutral- ising by an alkali or an alkaline carbonate. Calcium, strontium, and barium phosphates are only partly soluble in dilute sulphuric acid, being converted into a soluble phosphate and an insoluble sulphate of the metal. If the insoluble sulphate be filtered out, the addition of an alkali causes only a slight precipitate of a dimetallic phosphate, and a phosphate of the alkali used is left in solution ; but it is only after the use of sulphuric acid that any phosphate thus remains dissolved. Phosphates are detected as follows (practise on solution of disodium-phos- phate Na 2 HPO 4 ) 44 DETECTION, ETC., OF ACID RADICALS. 1. With barium or calcium chloride white precipitates are produced, soluble in acetic acid (distinction from oxalates] and all stronger acids. 2. With argentic nitrate a lemon-yellow precipitate of anrentic phos- phate forms, soluble both in nitric acid and ammonium hydrate. 3. With ferric chloride in the presence of ammonium acetate a white precipitate of ferric phosphate appears, insoluble in acetic acid. 4. With magnesia mixture phosphates yield a white crystalline pre- cipitate, forming slowly in dilute solutions, consisting of ammo- nium-magnesium phosphate Mg(NH 4 )PO 4 + 6H 2 O soluble in acetic and all acids. 5. With solution of ammonium molybdate in nitric acid a yellow precipitate is produced, insoluble in nitric acid, but soluble in ammonium hydrate. 6. With uranic nitrate UrO.(NO 3 ) 2 phosphates yield a yellow precipitate of uranic phosphate ', also insoluble in acetic acid. 7. With mercurous and bismuthous nitrates white precipitates are formed, the former soluble and the latter insoluble in nitric acid. 8. With any soluble salt of lead a white precipitate of plumbic phos- phate is produced, soluble in nitric acid, but insoluble in acetic acid or ammonium hydrate. Note. Magnesia mixture is made by dissolving ordinary magnesium carbonate in a slight excess of dilute HC1, then adding to this solution g of its bulk of strong NH 4 HO, and finally stirring in solid NH 4 C1 until the precipitate is dissolved. 33. ARSENIOUS ACID and ARSENITES. Arsenious Acid JLAs0 3 is not known in the free state; but its anhydride As 2 O 3 is commonly sold as arsenious acid, and when T. Dropped upon red-hot charcoal or coal, or heated in a dry tube with black flux (or a mixture of dry sodium carbonate and potassium cyanide), arsenic As 4 is set free, and volatilises with an odour of garlic, producing a steel-grey mirror on the sides of the tube. 2. Dissolved in water only, and ammonio-argentic nitrate added, a canary-yellow precipitate of argentic arsenite Ag^AsO 3 is produced, soluble in excess of either NH 4 HO or HNO 3 . 3. A pure aqueous solution, mixed with ammonio-cupric sulphate, gives a bright-green cupric arsenite Scheele's green CuHAsO 3 also soluble in NH 4 HO or in HNO 3 . 4. Any solution yields all the reactions for arsenic (see page 15). Arsenites behave peculiarly in many respects. Ammonium arsenite leaves arsenious acid on evaporating a solution, while potassium and sodium arsenites possess a degree of alkalinity which no excess of arsenious acid will disturb. Ba, Sr, and Ca form soluble hydrogen salts. All other arsenites are insoluble. Neutral solutions of arsenites are possessed of the undermentioned distinctive peculiarities : 1. CuSO } throws down greenish cupric-hydrogen arsenite. 2. AgN0 3 is transformed into yellow insoluble argentic arsenite. 3. H S, in the presence of hydrochloric acid, gives a yellow precipitate of arsenious sulphide. 4. The solution gives the usual reactions for arsenic (see page 15). ARSENIA1ES, PERMANGANATES AND CHROMATES. 45 34. ARSENIC ACID and ARSENIATES. Arsenic Acid H 3 As0 4 is known by the following characters : 1. The crystals are deliquescent, white, and strongly acid. Heated, they leave a residue, which, on moistening with water, is also acid. 2. It is strongly corrosive and blisters the skin. It gives brick red Ag 3 AsO 4 on adding ammanio-argentic nitrate. Arseniates behave in every respect exactly like phosphates, except that they give a brick-red precipitate with argentic nitrate, instead of a yellow. Insoluble arseniates are best treated by boiling with NaHO, filtering, exactly neutralising the filtrate with dilute HNO 3 , and then getting the brick-red precipitate with AgNO 3 . 35. MANGANATES, Manganates are unstable compounds, and only the alkaline salts dissolve in water, forming green solutions. 1. Soluble manganates decompose spontaneously, depositing MnO^ the green colour changing to purple or reddish violet, owing to the formation of a perman- ganate, 3K,MnO 4 + 2H a O = 2KMnO 4 + 4KHO + MnO 2 . 2. Dilute acids effect this change more rapidly, and the reaction is very delicate. The free hydrate is then replaced by a salt of the acid used. 3. Strong, heated H.,SO 4 acts as represented in this equation : K.,MnO 4 + 2H,SO 4 = K ? SO 4 + MnSO 4 + 2H 2 O + O 2 . 4. Strong HC1 causes the evolution of CL. The other actions are similar to those of permanganates, but less energetic. 36. PERMANGANATES. (Practise on solution of potassium permanganate KMnO 4 .) Permanganates are known 1. By the violet colour of their solutions, which is entirely bleached by oxalic acid or by heating with hydrochloric acid and dropping in rectified spirit. 2KMnO 4 + 5 H 2 C 2 O 4 + 3H 2 SO 4 =K 2 SO 4 + 2MnSO 4 + loCO^ + 8H 2 O. 2. By giving off oxygen on heating. 3. By giving off oxygen when heated with sulphuric acid, often with explosive violence. 4. By evolving chlorine when simply mixed with hydrochloric acid. 5. By getting the reactions for manganese after reducing with HC1 and a few drops of alcohol. 37. CHROMIC ACID and CHROMATES. Chromic Acid H.,Cr0 4 not being capable of isolation, is represented by its anhydride -CrO 3 . This is a dark red crystalline solid, giving off oxygen when heated, and when mixed with an aqueous solution of hydrogen peroxide (H 2 O 2 ) in ether a deep blue liquid results. This test, for either CrO 3 or H 2 O 2 , is exceedingly delicate, the ethereal solution of perchromic acid separating from the water and thus concentrating the colour into a small bulk of ether 46 DETECTION, ETC., OF ACID RADICALS. Chromates of the alkalies are soluble, while those of the other metals are chiefly insoluble, but have brilliant yellow or red colours. They are very poisonous, and are detected as follows (practise on solution of K i CrO 4 and K 2 Cr 2 O 7 respectively) : 1. Soluble chromates give a yellow precipitate with plumbic acetate or barium chloride, soluble in nitric acid, insoluble in acetic acid. The lead salt is darkened in colour by alkalies, and is freely soluble in excess of hot KHO. 2. With argentic nitrate a dark red precipitate, also soluble in nitric acid, and in NH 4 HO, but not in acetic acid. 3. Boiled with hydrochloric acid and alcohol, or any reducing agent, they turn green, owing to the production of chromic chloride. 4. Treated with sulphuretted hydrogen, in the presence of hydrochloric acid, they turn green, and a deposit of sulphur takes place : 2K 2 Cr 2 O 7 + I6HC1 + 6H,S = 2Cr 2 Cl + 4KC1 + 382 + i 4 H 2 O. 5. Soluble chromates treated with an acid turn orange ; and soluble dichromates, when treated with potassium hydrate, turn yellow. In this way they are mutually distinguished. 6. Heated with strong H 2 S0 4 they give off oxygen. 7. Treated with an excess of sulphuric acid, and shaken up with solution of hydrogen peroxide in ether, they give a gorgeous blue colour. 38. STANNIC ACID and STANNATES (Stannites ?). This is thrown down by an alkaline hydrate from a stannic salt, and is aho produced by the action of nitric acid upon tin. Stannates are formed by the solution of the acid in an alkaline hydrate, and are detected in the examination for metals. Stannites are said to be formed by the solution of stannous hydrates in an alkaline hydrate. They decompose on boiling with KHO, forming stannates and throwing down metallic tin. 39. ANTIMONIC ACID Is produced by the action of nitric acid upon antimony as a white powder. Its presence is delected during the examination for metals. 40. FORMIC ACID and FORMATES. Formic Acid HCH0 2 is the organic acid which contains the highest percentage of oxygen, and approaches most nearly in composition to the supposititious carbonic acid H 2 CO 3 . It is a tolerably stable liquid, boiling at the same temperature as water. Formates are all soluble in water, and behave as follows : 1. Heated to redness they decompose without blackening. 2. Heated with H.,S0 4 they evolve CO, which, being free from CO^, gives no effect when passed through lime-water t but burns with the usual pale blue flame. The reaction is HCHO 2 = CO + H.O. 3. They readily reduce argentic nitrate, when boiled, metallic silver separating as a mirror on the tube. A CRT A TES- VA LERIA NA TESS ULPHO VINA TES. 47 41. ACETIC ACID and ACETATES. Practise on sodium acetate NaC 2 H 3 O 2 .) This acid is characterised by its odour of vinegar. The strong acid chars when heated with strong H 2 SO 4 . Acetates are all soluble in water. They decompose at a red heat if the heat rise gently and the mass be not alkaline yielding acetone, and leaving a carbonate, oxide, or metal, according to the nature of the basic radical. When heated with alkalies marsh gas CH 4 is evolved. The reaction is of this type : NaC 2 H 3 2 + NaHO - Na 2 CO 3 +CH 4 . In the case of no alkaline hydrate or carbonate being present, the following is an example of the effect of heat on acetates : Ba(C 2 H 3 O 2 ) 2 = BaCO 3 + C 3 H 6 O (Acetone). Acetates of easily reducible metals, such as copper, yield, when heated, a distillate of acetic acid, leaving a residue of the metal, or in some cases of oxide. The presence of acetates is analytically determined as follows : 1. By evolving an odour of acetic acid when heated with sulphuric acid. 2. By a characteristic apple-like odour of acetic ether C 2 H 5 (C 2 H 3 O 2 ) which they evolve when heated with sulphuric acid and alcohol. 3. By the deep red colour which they reduce with neutral ferric chloride ferric acetate, Fe 2 (C 2 H P 2 ) 6 dis. hargeable by both hydrochloric acid and mercuric chloride. 42. VALERIANIC ACID and VALERIANATES. Valerianic Acid HC 5 H 9 2 is a liquid, which is Volatile, malodorous, colourless, and oily. It reddens test-paper, and dissolves in most menstrua. The general characters of Valerianates are : 1. A more or less strong odour of valerian root when warmed or moistened. 2. They give, when heated with sulphuric acid, an odour of valerian and a distillate which, on the addition of solution of cupric acetate, forms, after the lapse of some time, an oily precipitate ; gradually solidifying, by the absorption of water, into a greenish- blue crystalline solid. 43. SULPHOVINATES (Ethyl sulphates). These salts, derived from ethyl hydrogen sulphate C 2 H 5 HS0 4 behave as follows : 1. Heated with strong sulphuric acid, they evolve a faint ethereal odour. 2. They give no precipitate in the cold with barium chloride; but on boiling, a white precipitate of barium sulphate falls, and a smell of alcohol is perceived. The addition of a little solution of barium hydrate after the chloride and before boiling, facilitates the reaction ; but in this case all metals precipitable by a fixed alkali must first, of course, be removed. 3. Heated to redness, they leave a sulphate of the metal. DETECTION, ETC., OF ACID RADICALS. 4. Heated with sulphuric acid and an acetate, or with strong acetic acid, they evolve acetic ether with its characteristic odour of apples. 44. STEARIC ACID HC 18 H 35 2 -and STEARATES. This acid is distinguished by the following characters : 1. A white, odourless, fatty solid, melting by heat and soluble in absolute alcohol, the solution having an acid reaction. 2. Giving, when dissolved in KHO and the solution as nearly neutral- ised as possible, a white insoluble precipitate of plumbic stearate Pb(C 18 H 35 O 2 ) 2 on the addition of plumbic acetate, which is insoluble in ether (distinction from plumbic oleate). Stearates of the alkalies are alone soluble in water. Any stearate heated with dilute HC1 gives the free acid, which floats as an oily liquid, solidifying on cooling to a white mass. This test is applicable to the analysis of soap (hard, containing Na, or soft, in which K is present). 45. OLEIC ACID and OLEATES. Oleic Acid HC ]8 H3 3 2 is usually an oily liquid, but remains solid below 15 C. when crystallised from alcohol. It does not dissolve in water, but is taken up by ether and by strong alcohol, the latter solution being acid in reaction. Oleates of K and Na alone dissolve in water. Acid oleates are all liquid and soluble in cold absolute alcohol and ether. 1. They do not separate out from either of these solvents when a hot solution is cooled (distinction from stearates and palmitates}. 2. Plumbic oleate is precipitable like plumbic stearate, but is separated and distinguished from it by dissolving in ether. 46. LACTIC ACID HC 3 H 5 3 and LACTATES. The pure strong acid resembles glycerine in appearance, liberates hydrogen on adding zinc, and on heating takes fire and burns away with a pale flame, gradually becoming luminous. It dissolves in ether. It gives pure CO when heated with sulphuric acid. Boiled with solution of potassium permanganate it gives the odour of aldehyd. Lactates are not very soluble in water. They 1. Are insoluble in ether. 2. Argentic lactate AgC 3 H 5 O 3 when boiled gives a dark precipitate, which on subsidence leaves a blue liquid. 3. Strong solution of an alkaline lactate, when boiled with HgNO 3 , deposits crimson or pink mercurous lactate Hg 2 (C 3 H 5 O 3 ) 2 . 47. OXALIC ACID and OXALATES. (Practise on oxalic acid H.,C 2 O 4 and on " salts of sorrel.") The acid is recognised 1. By its colourless prismatic crystals, which are strongly acid, effloresce when exposed to dry air, and volatilise on heating with partial decomposition. 2. Ey the complete discharge it effects of the colour of a solution of potassium permanganate acidulated with dilute H 2 S0 4 . SUCCINA TESMALA TESTARTRA TES 40 3. By producing free H 2 S0 4 when added to solution of CuS0 4 . (Thi. is one of the very rare instances in which SOi is replaced by another acid radical and HJSO 4 liberated.) 4. By giving the reactions of an oxalate. Oxalates of the alkalies are soluble, the others insoluble, in water. Insoluble oxalates dissolve in hydrochloric, but not in acetic acid. They are known by 1. Not charring when heated, but only turning faintly grey ; followed by a sudden glow of incandescence, which runs through the mass. 2. Not charring when heated with sulphuric acid, but yielding CO and CO 2 with effervescence. 3. Not effervescing with cold dilute sulphuric acid; but at once liberating CO 2 with effervescence on the additon of a pinch of manganese peroxide. 4. With calcium chloride or barium chloride in a neutral or alkaline solution, they give a white precipitate of calcium or barium, oxalate, insoluble in acetic acid, but soluble in hydrochloric add. (For separation of oxalates from tartrates, etc., see No. 78.) 48. SUCCINIC ACID H 2 C 4 H 4 4 and SUCCINATES. This acid is a white crystalline solid. It is known 1. By not charring with strong hot sulphuric acid. 2. By subliming in a tube open at both ends, in silky needles, without giving off an irritating vapour (distinction from benzoic acid). 3. By burning, when heated on platinum, with a blue smokeless flame. Succinates are recognised as follows : 1. With ferric chloride, a brownish-red precipitate Q{ ferric succinate Fe 2 (C 4 H 4 O 4 ) 3 is formed. 2. With hydrochloric and sulphuric acids no precipitate is produced (distinction from benzoates}. With plumbic acetate, a white precipitate of plumbic succinate, soluble in succinic acid, succinates, and plumbic acetate. 3. Barium succinate is soluble in hydrochloric acid, hence no effect results from the addition of succinic acid to barium chloride ; but on the further addition of alcohol and ammonium hydrate, a white precipitate is formed (another point 0^ distinction from benzoates}. 49. MALIC ACID and MALATES. Malic Acid H^C 4 H 4 5 is a colourless, crystalline, very deliquescent acid, freely soluble in water and alcohol. Acid malates are most stable. The characters are : 1. Calcium chloride, added to a neutral solution of a malate, gives no precipitate. Alcohol, however, even if added in small quantity, throws down a white precipitate ; and boiling aids the effect. If boiled with lime water, calcium malate dissolves. Calcium citrate is insoluble. 2. Strong I1 2 SO 4 gives no charring for some time (a tartrate is carbonised in a few minutes]. 3. Amorphous plumbic malate fuses below 100 C. in water, but not in an air-bath. 50. TARTARIC ACID and TARTRATES. (Practise upon the free acid and also upon " Rochelle salt.") Tartaric Acid H 2 C 4 H 4 6 is a strong acid, soluble in water and spirit. 1. It forms usually oblique rhombic prismatic crystals, of an acid taste. 2. Heated to redness, it chars and finally burns away. 3. Heated with strong H 2 S0 4 , it blackens, and gives the odour of burnt sugar. 4. KC 2 H 3 2 gives a white precipitate of potassium hydrogen tartrate KHC 4 H 4 O C increased by the addition of 90 per cent, alcohol. 5. One drop of solution of FeS0 4 , followed by a few drops of solution of hydrogen peroxide and an excess of KHO, gives a purple or violet colour. 5C DETECTION, ETC., OF ACID RADICALS. The same compound is produced on adding any potassium salt, provided the liquid contain excess of free tartaric acid only. Tail-rates of the alkalies are mostly soluble ; but the others are insoluble. The acid tartrates of K and (NH 4 ) are nearly insoluble. Tartrates are recognised by the following characters : 1. Heated to dull redness they char rapidly and give off a smell of burnt sugar. The black residue contains the metal as car- bonate if it be K, Na, Li, Ba, Sr, or Ca ; but the tartrates cf other metals usually leave the oxides, or more rarely (as in th^ case of Ag 2 C 4 H 4 O 6 ) the metal. 2. Heated with strong sulphuric acid, they blacken rapidly, and give first a smell of burnt sugar, and afterwards evolve S0 2 . 3. Neutral solutions (free from more than a trace of ammonium salts) give, on adding calcium chloride, a white precipitate of calcium tartrate^ which, when freed from other salts by washing, dissolves readily in cold solution of potassium hydrate, but is again pre- cipitated on boiling. The precipitate is somewhat soluble in NH 4 C1, but not in NH 4 HO. 4. AgN0 3 yields a white precipitate, soluble in solution of ammonia and in nitric acid. The ammoniacal solution is reduced on heating, and deposits metallic silver as a mirror on the sides of the test tube. 5. KC 2 H-0 2 gives a white precipitate in moderately concentrated solu- tions when acidulated with acetic acid and well stirred, and especially on the addition of 90 per cent, alcohol. 6. If to the solution of a tartrate acidulated with acetic acid be added a drop of solution of ferrous sulphate, then a few drops of solution of hydrogen peroxide, and finally an excess of KIIO, a purple or violet colour will be produced. 51. CITRIC ACID and CITRATES. (Practise upon the free acid and upon potassium citrate.) t^itric Acid H3C 6 H 5 7 is soluble in water and alcohol, but insoluble in pure ether. It entirely burns away when heated to redness in the air ; blackens slowly when heated with strong sulphuric acid; and when neutralised by ammonium hydrate, and cooled, the solution gives no precipitate with calcium chloride until it has been boiled. Added to ferric, chromic, or aluminic salts in solution, it prevents their precipitation by ammonium hydrate. titrates exhibit the following characters : i. Heated alone, they char slowly, and evolve an odour of burnt sugar, but not so intense as that of a tartrate. At a dull red heat, the citrates of K, Na, Li, Ba, Sr, and Ca leave their carbonates ; but those of most other metals leave the oxides. Argentic citrate leaves the metal. s. Heated with strong sulphuric acid, they slowlv blacken, and evolve a slight odour of burnt sugar. 3. Mixed in the cold with calcium chloride, in the presence of a slight excess of ammonium hydrate, they give no precipitate ; but on boiling, calcium citrate Ca^(C 6 H 5 O 7 ) 2 separates as a white precipitate. If this precipitate be filtered hot, and washed with a little boiling water, it is found to be quite insoluble in cold solution of potassium hydrate, but readily soluble in neutral solution of cupric chloride. 4. Mixed with argentic nitrate and boiled, no mirror of metallic silver is produced. MECONA TES CA RB OLA TESBENZOA TES. 5 1 52. MECONIC ACID and MECONATES. Meeonic Acid H 2 C 7 H 2 073H 2 is a white powder, with a strongly acid reaction, soluble in water, alcohol, and ether, and giving the reaction for meconates. Meconates communicate a red colour to ferric chloride solution. This colour is not discharged by HgCl^ but is bleached by dilute HCl (distinction from a sulpho-cyanaie). 53. CARBOLIC ACID (or Phenol) C 6 H 5 HO and CARBOLATES (Phenates). The qualities of this body are very distinctive. 1. It is a colourless, crystalline solid, melting at not lower than 33 C., and not volatile at 100 C., having the odour and taste of creasote, being very poisonous, and not reddening blue litmus paper. 2. The crystals deliquesce readily, forming a liquid which does not mix freely with water, but is soluble in all proportions in alcohol, ether, and glycerine. 3. Mixed with HCl and exposed to the air on a strip of deal, it becomes greenish blue. 4. It coagulates albumen. It does not rotate polarised light. 5. Saturated with ammonia gas NH 3 and heated in a closed tube, aniline is formed : C 6 H 5 HO + NH 3 = C 6 H 5 H 2 N + H 2 O. 6. It does not decompose carbonates. 7. NH 4 HO and CaOCL,, or Na 2 OCl 2 , produce a blue liquid, turned red by acids. 8. It unites directly with strong H 2 S0 4 to form phenol-sulphonic (or sulpho-carbolic] acid. 9. With bromine water it gives a white precipitate of tribromophenol C 6 H 3 Br 3 0. Carlolates give the following reactions : 1. When heated alone, they evolve the odour of carbolic acid and decompose. 2. Heated with strong sulphuric acid they also smell of carbolic acid. 3. Ferric chloride causes a reddish-violet colour. Sulpho-Carbolates behave similarly, but, after fusion with KN0 3 and redis- solving the residue in diluted HCl, they also give the reactions of a sulphate with barium chloride. 54. BENZOIC ACID and BENZOATES. Benzoic Acid HC 7 H 5 0., is of characteristic appearance, being usually seen in light, feathery, flexible, nearly colourless crystalline plates or needles, and containing a trace of an agreeable volatile oil, unless it is the artificial acid prepared from naphthalene, when it is odourless. 1. It is only slightly soluble in water, but dissolves in three parts of alcohol, and in solutions of soluble hydrates. 2. Heated in the air, it burns with a luminous smoky flame ; and when made hot in a tube open at both ends, sublimes in needles, giving off an irritating vapour. Benzoates possess the following general qualities : r. Heated with sulphuric acid they evolve the odour of benzoic acid, and darken. 2. Ferric chloride, in a solution made slightly alkaline by ammonium hydrate, gives a reddish-white precipitate ferric benzoate DETECTION, ETC., OF ACID RADICALS. Fej(C 7 H 5 O 2 ) 6 soluble in acids (benzole included) If this pre- cipitate be now filtered out and digested in ammonium hydrate, it is decomposed into a precipitate of ferric hydrate, and a solution of ammonium benzoate, which is separated by filtration and treated as in 3. 3. Strong hot solutions of benzoates yield crystals of benzole add when hydrochloric acid is added and the solution allowed to cool. 55. SALICYLIC ACID (HC 7 H 5 3 ). This acid occurs in prisms, when crystallised from a solution in alcohol in which it is readily soluble. It is freely dissolved by hot water, but not readily by cold, requiring 1,800 parts of the latter to completely dissolve it. 1. Its aqueous solution gives with ferric chloride a deep violet coloration. The compounds with methyl, ethyl, etc., give this reaction, as well as the ordinary salts. 2. Its methyl ether, formed by warming a salicylate with sulphuric acid and wood spirit has the odour of oil of wintergreen. From most other solid bodies it may be separated by taking advantage of its exceptionally great solubility in ether. In the event of its presence in an organic liquid (such as milk), it or its salts may be procured in a pure condition by dialysis. 56. TANNIC, GALLIC, and PYROGALLIC ACIDS. Tannic Acid C 27 H 22 17 is soluble in water and alcohol, and very soluble in glycerine. It is insoluble in pure dry ether, but dissolves readily in ether containing a little water. Gallic Acid H^C-H^OgHcjO is slightly soluble in cold water, but readily in boiling ; it is also freely soluble in glycerine, and slightly in alcohol and ether. Pyrogallic Acid C 6 H 6 O a is very soluble in water, the solution rapidly absorbing oxygen from the air and becoming brown. It also dissolves in alcohol and ether. DISTINCTION BETWEEN GALLIC, TANNIC, AND PYROGALLIC ACIDS. BEHAVIOUR OF THE ACID WITH GALLIC. TANNIC. PYROGALLIC. Ferrous salts A dark solution The same effect A blue solution. FeS0 4 . is formed, as Gallic. gradually de- positing a precipitate. Ferric salts Purplish pre- Same as pre- A red solution. Fe 2 Cl fl . cipitate im- ceding. mediately formed. Calcium hydrate A brownish pre- A white preci- Instantaneous Ca(OH) 2 cipitate, be- pitate slowly production of in the form of coming deep changing. a purple solu- Milk of Lime. brown in a tion becoming few seconds. brown by oxi- dation. Gelatine . . . No precipitate Immediate No precipitate. (except in the brownish presence of precipitate. \ gum). 1 CHL ORIDESBR OMIDES IODIDES. 53 57. SEPARATION OF CHLORATES AND CHLORIDES. Note. The tests which follow are applicable to tests for adulterations, where, for obvious reasons, the confirmatory test for a suspected adulterant would not apply. (Practise on mixed solutions of KC1 and KC1O E .) Add excess of argentic nitrate, filter out the argentic chloride formed, and then acidulate with sulphuric acid, and drop in a fragment of zinc, when, if a chlorate be present, a second precipitate of argentic chloride will form. 58. DETECTION OF CHLORIDES IN THE PRESENCE OF BROMIDES. (To be practised on a mixture of KC1 and KBr.) The solution is divided into two parts, in one of which the bromide is proved by the addition of chlorine water, and shaking up with chloroform. The second portion is either (i) Evaporated to dryness, the residue placed in a tube retort with a little potassium dichromate and sulphuric acid, while into the receiver is placed a little dilute ammonium hydrate, and distillation is proceeded with, when, if a chloride be present, the liquid in the receiver will be coloured yellow ; or (2) Precipitated with excess of AgNO 3 , washed on a filter, percolated with dilute NH 4 HO (i in 20) and nitric acid added to the percolate, when a distinctly curdy white precipitate proves the presence of chlorides. This latter method is simple, and rarely fails if, on adding the acid, a mere cloud be disregarded. 59. DETECTION OF BROMIDES IN THE PRESENCE OF IODIDES. (Practise on a mixture of KBr and KI.) Add to the solution a very small quantity of starch paste and then a drop or two of chlorine water, when a blue colour will be produced, proving the iodide. Continue to add more chlorine water until this blue is entirely dis- charged, and then shake up with chloroform, when, if a bromide be present, the characteristic golden colour will be communicated to the chloroform. 60. DETECTION OF CHLORIDES IN THE PRESENCE OF IODIDES. (Practise on a mixture of KC1 and KI.) Add excess of argentic nitrate, warm, pour off the supernatant liquid, wash with warm water, and shake up the precipitate in dilute solution of ammonium hydrate (i in 3). The argentic iodide will remain insoluble, while the chloride will dissolve and may be detected in the solution, after filtration, by reprecipita- tion with excess of nitric acid. As argentic iodide is not absolutely insoluble in ammonium hydrate, a mere cloud on adding the nitric acid is to be dis- regarded. This test is only accurate in the insured absence of a bromide, proved as above directed (see 59). 61. SEPARATION OF AN IODIDE FROM A BROMIDE AND CHLORIDE. (Practise on a mixture of KC1, KBr, and KI.) 1. Add to the solution a mixture of one part cupric sulphate and three parts ferrous sulphate, or mix the solution with excess of cupric sulphate and drop in sulphurous acid till precipitation ceases. The io.lide will separate as cuprous iodide CuJ., leaving the bromide and chloride in solution. Unless carefully done, this separation is not absolutely accurate, or 2, Add to the solution palladious nitrate until precipitation ceases. Filter out the palladious iodide which separates, and pass sulphuretted hydrogen through the liquid to remove excess of palladium, and again filter. Boil to expel t^ excess of H 2 S, and the bromide and chloride remain in solution. 54 DETECTION, ETC., OF ACID RADICALS. 62. DETECTION OF AN IODATE IN AN IODIDE. (Practise on a solution of iodine in heated potassium hydrate KI -f KIO 3 .) When excess of tartaric acid is added to potassium iodate, iodic acid is set free; and when the same acid is added to potassium iodide, hydriodic acid is set free, and potassium hydro-tartrate formed. Thus : 5KI + KIO 3 + 6H,C 4 H 4 O 6 = sHI + HIO 3 -f 6KHC 4 H 4 O 6 . If these acids be thus liberated together, they immediately decompose, forming water and free iodine : 5 HI + HI0 3 = 3 I 2 + 3 H 2 0. If therefore starch paste and tartaric acid be added to pure potassium iodide no coloration takes place, because only hydriodic acid is liberated; but if the sample contains potassium iodate, an immediate production of free iodine ensues, which turns the starch blue. 63. DETECTION OF A SOLUBLE SULPHIDE IN PRESENCE OF A SULPHITE AND A SULPHATE. (Practise on mixed solutions of Na 2 S, Na 2 SO 3 , and Na 2 SO 4 .) Pour the solution on a little cadmium carbonate CdCO 3 filter, and treat the insoluble matter with acetic acid to remove any unacted-upon cadmium carbonate. If a sulphide has been present, a yellow residue of cadmium sulphide will remain insoluble in the acetic acid, while cadmium sulphite and sulphate will be found in the first filtrate, if these two radicals were present. 61 SEPARATION OF THIOSULPHATES FROM SULPHIDES. (Practise on solution of commercial hyposulphite of soda, to which a drop of NH 4 HS has been added.) Having obtained a good preliminary idea by heating with H 2 SO 4 , add to a portion of the original solution ZnSO 4 in excess, and filter. (a) Precipitate white, and soluble in HC1, with smell of H 2 S. = Sulphides. b) A portion of filtrate heated with H 2 SO 4 deposits S and smells of SO-2 ; and another portion added to a drop or two of ammonio- cupric sulphate instantly causes decolorisation. = Hyposulphites. 65. SEPARATION OF SULPHIDES, SULPHITES, and SULPHATES. (Practise on mixed solutions of sodium sulphite and sulphate, to which a drop of NH 4 HS has been added.) Pour the solution on an excess of cadmium carbonate, digest at a gentle heat, filter, and examine the precipitate for a sulphide as already directed (63). The filtrate, which may contain the sulphite and sulphate, is precipitated by barium chloride, the insoluble precipitate filtered out and boiled with a little hydrochloric acid, which will dissolve the barium sulphite with evolution of sulphurous anhydride SO 2 and leave the barium sulphate insoluble. 66. SEPARATION OF SILICIC ANHYDRIDE (SILICA) FROM ALL OTHER ACIDS. (Practise upon powdered glass.) Fuse the substance with a large excess of KNaCO 3 in a platinum crucible, and when all action has ceased, cool, and boil the residue with water. The QUALITATIVE SEPARATION OF NITRITES, IODIDES, ETC. 55 silica passes into solution with the other acid radicals, and the metals are left as oxides. Acidulate the solution with hydrochloric acid, evaporate to dry- ness, and heat the residue to 140 C., and maintain the heat for some time. Drench the residue with strong hydrochloric acid, then add water, and boil, when the silica will alone remain insoluble. 67. DETECTION OF A NITRITE IN THE PRESENCE OF A NITRATE, Add a little potassium iodide and starch paste, and acidulate with acetic acid, when, if a nitrite be present, a blue colour will be produced, due to the liberation of iodine. 68. DETECTION OF FREE NITRIC ACID IN THE PRESENCE OF A NITRATE. Digest with excess of barium carbonate ; filter, and add to the filtrate some dilute sulphuric acid, when, if the free acid is present, a precipitate of barium sulphate will be produced. This test is only good in the insured absence of any other acid capable of dissolving barium carbonate. It will also serve for detecting free hydrochloric and acetic acids in presence of- their salts. 69. DETECTION OF A NITRATE IN THE PRESENCE OF AN IODIDE. The fact that the addition of strong sulphuric acid liberates iodine renders the proof of a nitrate by the ordinary iron process doubtful in the presence of iodides and bromides. In this case boil with excess of KHO until any ammonium salts are decomposed, then add a fragment of zinc and again boil. Any nitrate present will be converted into ammonia, which may be recognised in the steam with moistened red litmus paper. 70. SEPARATION OF CHLORIDES, IODIDES, and BROMIDES FROML NITRATES. Digest with argentic sulphate, which will precipitate the halogens as silver salts and leave the nitrate in solution. 71. SEPARATION OF CYANIDES FROM CHLORIDES. Acidulate slightly with HNOs, add excess of AgNO 3 , wash the precipitate with boiling water, and boil it with strong nitric acid, when the AgCN is decomposed, leaving the chloride insoluble. The solution is diluted and HCL added, when a white precipitate indicates dissolved cyanide. 72. SEPARATION OF FERRO- FROM FERRI-CYANIDES. Acidulate with HC1, add excess of Fe 2 Cl6, warm gently ; the ferrocyanide- will be precipitated. Pour off some of the brownish liquid and heat with a little zinc amalgam, when a blue precipitate indicates ferricyanide. 73. DETECTION OF CYANIDES IN THE PRESENCE OF FERRO- AND FERRI-CYANIDES. Acidulate slightly with HNOs, and add an excess of a mixture of ferrous and ferric sulphates, and warm gently. Pour off a little of the supernatant liquid, add excess of KHO, and then acidulate with HC1, when the production of another blue precipitate proves cyanide. 5 6 DETECTION, ETC., OF ACID RADICALS. 74. DETECTION OF A PHOSPHATE IN THE PRESENCE OF CALCIUM, BARIUM, STRONTIUM, MANGANESE, AND MAGNESIUM. Dissolve in water by the aid of the smallest quantity of nitric acid, then add excess of ammonium acetate ; then add Fe2Cl and warm, when a white pre- cipitate of ferric phosphate Fe.,(PO 4 )2 will form, insoluble in the acetic acid liberated. 75. DETECTION OF A PHOSPHATE IN THE PRESENCE OF IRON. Dissolve in the smallest possible quantity of hydrochloric acid, add some citric acid, followed by excess of ammonium hydrate, and lastly cool and add magnesia mixture, when a white precipitate proves phosphate. 76. SEPARATION OF AN ARSENIATE FROM A PHOSPHATE. Acidulate with HC1, and pass a slow stream of H 2 S for several hours, until the whole of the arsenic is removed. 77. DETECTION OF A FORMATE IN THE PRESENCE OF FIXED ORGANIC ACIDS WHICH REDUCE SILVER SALTS. Distil with dilute H 2 SO 4 , neutralise the distillate with Na. 2 CO 3 , add a slight excess of acetic acid, and boil with AgNO 3 , when a dark deposit of metallic silver will form. 78. SEPARATION OF OXALATES, TARTRATES, CITRATES, AND MALATES. If the solution be acid, neutralise it with sodium hydrate ; but if neutral or alkaline it is ready for use, and is treated as follows : A. Acidulate slightly with acetic acid, boil and add CaCl 2 till precipi- tation ceases. Keep warm till the precipitate aggregates, and filter. This precipitate is calcium oxalate, and it should be quite insoluble in cold solution of KHO. B. To filtrate from A, mixed with some more CaCl 2 , ammonia is added in slight excess, and the whole thoroughly cooled. Calcium tartrate precipitates and the liquid is poured off and preserved for C. This precipitate, after washing, should be soluble in cold KHO, and reprecipitable by boiling. C. The liquid is slowly boiled for some time ; and if a precipitate does not form readily, a little more CaCl 2 and NH 4 HO is added, and the boiling resumed. The precipitate is filtered out whilst still hot. It should be (after washing) quite insoluble in cold KHO, but soluble in neutral solution of CuCl 2 . D. To the filtrate add alcohol, when calcium malate will separate ; but this portion of the separation is not infallible, and the precipitate must be carefully examined to see that it really is malate. 79. DETECTION OF PHENOL IN SALICYLIC ACID. Dissolve i gram in excess of a cold solution of Na 2 COs ; then shake up with ether, separate the latter and allow it to evaporate, when any phenol will be left as a residue from the ether. QUALITATIVE SEPARATION OF ORGANIC ACIDS, ETC. 57 80. TEST FOR CINNAMIC ACID IN PRESENCE OF BENZOATES. The mixture warmed with its own weight of K 2 Mn 2 O8 and excess of diluted H 2 SO 4 gives the odour of benzaldehyd (oil of bitter almonds) if a cinnamate be present. 81. TEST FOR CHLOROBENZOIC ACID IN THE PRESENCE OF BENZOIC ACID. 5 grm. is heated in a closed crucible with its own weight of CaCOa, and the resulting mass having been dissolved in diluted nitric acid, a white pre- cipitate will be produced on adding AgNOs if the chloro-acid be present, A mere cloud must be disregarded. 82. TEST FOR HIPPURIC ACID IN BENZOIC ACID. 2 grm. suspended in 10 c.c. of water will immediately discharge the colour of 2 drops of a i per cent, solution of K 2 Mn 2 Os when this impurity is present. A similar effect is produced by cinnamic acid. 83. TEST FOR CRESOL IN PHENOL. One volume of phenol (carbolic add), liquefied by the addition of 10 per cent, of water, should form a perfectly clear solution with an equal volume of glycerine ; if not, then cresol (cresylic acid) is present. 84. SPECIAL TESTS FOR THE PRESENCE OF TARTARIC ACID IN CITRIC ACID. (1) One drop of solution of FeSOi with a few drops of H 2 O 2 and an excess of KHO added to a solution of citric acid gives a violet or purple colour if tartaric acid be also present. (2) One gram of citric acid shaken with 5 c.c. solution of ammonium molybdate and 3 drops H2O 2 and placed in boiling water for 10 minutes becomes bluish if tartaric acid be present. This test can also be simulated by the presence of any metallic particles in the sample. 85. DISTINCTION OF SALICYLATES FROM CARBOLATES AND SULPHOCARBOLATES. Any solution of a salicylate if not weaker than i per cent, gives a yellowish- brown precipitate with uranic nitrate, while carbolates and sulph* carbolates do not. In testing salicylic acid it should be first dissolved in solution of ammonium citrate, acetate, or borax. 86. TESTS FOR SELENIUM IN SULPHURIC ACID. If a solution of Na^SOs in HC1 be gently poured on the surface of FLSO4 a red colour will be produced at the junction of the two liquids in presence of selenium. CHAPTER IV. QUALITATIVE ANALYSIS, AS APPLIED TO THE DETECTION OF UNKNOWN SALTS. I. GENERAL PRELIMINARY EXAMINATION. UNDER this head are included 1. The observation of the physical properties of the substance sub- mitted for analysis. 2. Its behaviour when heated, either alone or in the presence of reducing agents or fluxes. 3. Its reaction with test-papers ; the colour it communicates to flame, etc. So particular and minute may this examination be, that in the larger works on chemical analysis many pages will be found devoted to it ; but for the purposes of the analysis likely to come before the ordinary chemical student, it is sufficient only to carry it the length of a few readily obtainable and unmistakable inferences. It should also be remembered that in many cases these inferences require subsequent confirmation, and therefore a student should be taught not to jump too readily at conclusions from the preliminary investigation. Step 1. If the substance be a liquid, carefully mark its reaction with blue and red litmus paper, evaporate a little to dryness at a gentle heat on a clean porcelain crucible lid, observing the nature of the residue left, if any ; and finally raise this residue to a red heat, carefully noting whether it is volatilised, blackened, or altered in colour any way. If a solid, heat it directly to redness on a crucible lid (or in a dry test tube), and note effect ; then shake a little up with distilled water, and note its reaction with blue and red litmus paper. From a careful study of these points, the following simple inferences may safely be drawn ; any appearance not herein referred to being neglected as not affording a really distinctive indication. A. Neutral, no odour, and leaving no residue whatever. Probably water. L. Strongly acid, leaving no residue. Probably an ordinary volatile acid, such as HC1, HNO 3 , HC 2 H,O.,, etc. C Strongly acid, leaving a residue, fusible by heat and also strongly acid. Probably a non-volatile mineral acid, such as H a PO 4 . D Strongly acid, leaving a residue, which on heating chars, and entirely burns away. Probably free organic acid, such as H 2 C 4 H 4 6 , H 3 C 6 H 5 7 , HC 7 H 5 0,, etc. Note Oxalic and formic acids do not char. E. Neutral or slightly acid, leaving a residue, which volatilises in fumes, but without blackening. Probably an ordinary salt of a volatile metal, such as NH 4 , Hg, As, Sb, etc. f. Nautral or slightly acid, leaving a residue which on heating blackens and volatilises in fumes. Probably an organic salt of NH 4 , Hg, or other volatile metal. Note. In this case it is best at once to test the original for NH 4 or Hg by boiling with KHO and SnCl 2 respectively. 55 GENERAL PRELIMINARY EXAMINATION. 59 G. Neutral or slightly acid, leaving a residue, which on heating changes colour as follows : Yellow while hot, white on cooling. Probably salt of Zn. Deep yellow while hot, yellow on cooling. Probably salt of Pb. Yellowish-brown while hot, dirty light-yellow on cooling. Pro- bably salt of Sn iv . Orange or red while hot, dull yellow on cooling. Probably salt of Bi. Red while hot, reddish brown on cooling. Probably salt of Fe or Ce. Permanent brownish-black. Certain salts of Mn. H. Neutral or slightly acid, leaving a white residue, which blackens on heating, burns, and -leaves a black or greyish mass. Pro- bably an organic salt of a fixed metal. In this special cast, proceed as follows: Moisten the residue with a little water, and touch it with reddened litmus paper. If alkaline, the original substance was an organic salt of K, Na, or Li, in which case proceed by (a). If not alkaline, proceed by (b\ (a) Boil the ash with the smallest possible quantity of water, filter, acidulate with HC1 till effervescence ceases ; dip a perfectly clean platinum wire in the solu- tion and try the flame test. If crimson, Li. Bright yellow, Na. Violet, K. Note. The latter flame not being very easily seen in the daylight, it is advisable to add to the solution PtCl 4 and C 2 H 6 O. Shake well and cool. Yellow crystal- line precipitate of potassium platinochloride PtCl 4 2KCl. When potassium is found with a tartrate it is always necessary to test also with H 2 S for antimony as the salt might be tartar emetic. (V) The ash is covered with water and treated with HC 2 H 3 O ? . If effervescence takes place, the original substance was probably an organic salt of Ba, Sr, or Ca ; and these metals may at once be tested for in the acetic acid solution. Note. Oxalates, although organic, do not blacken to any extent. If carefully observed, however, a slight greyish tint, followed by a distinct glow running through the mass, will be noticed at the moment of decomposition. To make certain it is well to place a little of the original powder in one tube, and the residue, after ignition, in another ; cover them both with water, and add a drop of acetic acid to each. If the residue effervesce, and the original powder does not, strong presumptive evidence is obtained of the presence of an oxalate of the alkaline or earthy metals. /. Neutral or slightly acid, leaving a residue, which takes fire and continues to burn even after removal from the flame, giving off clouds of white fumes and leaving a fixed white or pinkish residue. Probably a hypophosphite ; which fact should be noted as an aid to future information as to acid radicals. K. Strongly alkaline, leaving a fixed white residue, also alkaline. A hydrate, carbonate, bicarbonate, phosphate, arseniate, borate, sulphite, or sulphide of a fixed alkaline metal, or a hydrate or oxide of Ba, Sr, or Ca. In this case proceed as follows : Acidulate a portion of the original solution with HC1. (a) If it effervesces without odour, and is therefore a carbonate or bicarbonate, test at once by the flame for K, Li, Na, and also another portion of the original solution with HgCl 2 . If red, a carbonate : if not, a bicarbonate. () Effervesces with odour of II 2 S. In this case it is a sulphide ; and if a deposit of S also takes place, a polysulphide. Add to a fresh portion of the original solution excess of HC1, boil till H 2 S is expelled, filter, if necessary, and test the solution for all metals of fourth and fifth groups. (c) Effervesces with odour of HCN. Probably an alkal ne cyanide, such as KCN. (d) Effervescence with odour of SO,,, an alkaline sulphite. (e) It does not effervesce. In this case add to a fresh portion of the original solution, AgNO 3 . If a brownish-black precipitate be formed, it is a soluKe hydrate. A portion of the original solution should be neutralised with HC1, and then examined for all metals of fourth and fifth groups. Note. If AgNO 3 with original solution gives a yellow, a white, or k brick-red precipitate, the presence of a phosphate, borate, or arseniate of K or Na may 6o QUALITATIVE ANALYSIS. be suspected. In the case of a complex solution in which a salt of some other metal is given dissolved in excess of an alkali, an intimation of the fact will be obtained on cautiously adding the HC1, as, at the moment of neu- tralisation, the dissolved substance appears as a precipitate before again dissolv- ing in the excess of HCl. Basic plumbic acetate has an alkaline reaction. Step 2. Dip a clean platinum wire in the solution, or, if a solid, moisten the wire with HCl, dip it in the powdered substance, and heat in the inner Bunsen or blowpipe flame. The outer flame is coloured as under : Violet . . . Potassium. Golden-yellow . . Sodium. Yellowish-green . . Barium. Crimson . . . Strontium or Lithium. Orange-red . . Calcium. Green . . . Copper or Boracic acid. Blue .... Lead, Arsenic, Bismuth ; also Copper as chloride. Step 3. Heat a little of the solid substance (or the residue left on evapora- tion if in solution) on charcoal before the blowpipe. Ordinary alkaline salts fuse and sink into the charcoal ; some decre- pitating (example Nad, etc.). others deflagrating (as KNO 3 , KC1O 3 , etc.), but no sufficiently characteristic indications are usually obtained, except in one of the following cases : A. A white luminous residue is left. Moisten it when cold with a drop or two of cobaltous nitrate, and again apply the blowpipe, observing any change of colour as follows : The residue becomes blue, indicating Al, Silicates, Phosphates, or Borates. green, Zn. ,, pink or flesh-coloured, indicating Mg. B. A coloured residue is left. Prepare a borax bead, and heat a little of the substance in it, both in the reducing and oxidising flame, and note any colours corresponding with the following list : METAL. IN OXIDISING FLAME. IN REDUCING FLAME. I Cu Co Green (hot). Blue (cold). Blue. Red (cold). Blue. Cr Green. Green. Fe Mn Ni Red (hot). Yellowish (cold). Amethyst. Reddish-brown (hot). Yellow (cold). Bottle-green. Colourless. Same as oxidising flame. C. A metallic residue is left, with or without incrustation surrounding it. Mix a little of the substance with KCN and Na 2 COs, and expose on charcoal to the reducing flame. (a) Metallic globules are produced without any surrounding incrusta- tion of oxide. This occurs with Ag, Au, Cu, Fe, Co, and Ni, all easily recognisable. (b) Metallic globules are produced with a surrounding incrustation of oxide. This occurs with Sn, Bi, Pb, and Sb ; the incrustation having the characteristic colours already described in Case I., Step i, G. Nole. Sb often forms a white and distinctly crystalline crust. (f) The metal volatilises, and only leaves an incrustation of oxide. This occurs with As (odour of garlic, and white incrustation), Zn (yellow [hot], white [cold]), and Cd (reddish-brown). DETECTION OF METALS IN SALTS. 61 II. DETECTION OF THE METAL PRESENT IN ANY SIMPLE SALT. Step 1. Preparation of the solution for analysis for the metal, if the substance be not already dissolved. 1. Take a minute portion of the substance and boil it with water in a test-tube; should it dissolve, then take a large portion and dissolve for testing. 2. Should the salt prove insoluble, take another small portion and heat with HC1, and add a little water and again heat. If it now dissolves, prepare a larger quantity of the solution for use in the same manner. 3. Should it resist HC1, try another small portion with HN0 3 by heating and then adding water. If this dissolves it, make up a larger quantity of a similar solution for testing. 4. Should HNO 3 also fail, try another small portion with two parts HC1 and one part HN0 3 , warming and diluting as before; and if it suc- ceeds, make up a larger amount of solution in the same manner. 5. If all acids fail, then take another portion of the substance, mix it with several times its bulk of a perfectly dry mixture of sodium and potassium carbonates (prepared by heating Rochelle salt in an open crucible until the residue thoroughly ceases to evolve any gases, then extracting with distilled water, filtering, evapo- rating to dryness, heating the residue to redness, and preserving for use in a stoppered bottle. This reagent will hereafter be shortly described as fusion mixture). Place the whole in a platinum crucible, and fuse at a bfright-red heat; when cold, boil with water and save the solution thus obtained for acid radicals. The insoluble matter is then to be drenched with strong HC1, slightly diluted and boiled, and the solution used for testing for the metal. Any insoluble white gritty matter still remaining is put down as silica. Step 2. Detection of the metal. The processes to be applied vary according to the limitation of the possible substances under examination, and the following tables are to be used accord- ingly, using the solution obtained in Step i. Remember that even when we have apparently found out the metal by the table, we should always proceed to perfect confirmation by applying (to fresh portions of the solution each time) all the tests for the metal given in Chapter II. Unless otherwise directed, all confirmations referred to in the tables are intended to be tried upon fresh portions of the original solution. For brevity the said solution is in the tables indicated by a capital in thick type, and the word precipitate is contracted to ppt. In simple salts we go through the groups until we get a result, and as soon as we do we stop and go no farther with the groups, but simply confirm the result obtained by special tests. The following brief instructions may aid the student to find readily the pages required foi the full analysis of a simple salt : 1. Find whether soluble in H 2 O or in acids, or neither. ( acid = free acid or acid salt. 2. Take the reaction < alkaline = complete the analysis by " K," p. 59. ( neutral. 3. Heat *, . tube {< tt^SS? See - H," p. 59- 4. Find the metal by p. 64. ( solubility table, p. 82. 5. Find the acid radical by \ If K, Na,^ tables pp. 76 to 80, if inorganic. ( Li, or NHJ ,, p. 80 if organic. 6. Name the salt and write its chemical formula. " .- 00 i O 2-S Ml Sv S>lr siififc ^ * - x 25.=:^ . . ^fc -S *t3 ^ 42 ** 5 -< .52 ^.JZ O "3 >,*& v. >-> > Ct $ Q~ clC^ RQ * 1) C rt If 1 I .s 3 oo I 3 1 origi M .S i. . -*-S a ill 11 alJ I 1 ' 1 ex, 'o 5- C3 I 1 cl 1 u S rt On3 ^ a^ < ffect GR an o *-~ C T3 ^ >s l ** '. T5 ft. o> c E>^S > rt sa'?-s -55^0,0 -a Soc J HH ?l 211 SSI ' " CS O -r IS ii DETECTION OF UNKNOWN SALTS. 05 in. DETECTION OF THE METALS IN COMPLEX MIXTURES OF TWO OR MORE SALTS. Step I. Preparation of the solution for analysis in cases where the substance for analysis is not given in solution. Note. By carefully applying this step and intelligently judging the results, we can often reduce a separation of two salts to the performance of two separate simple analyses, and so save much time and trouble. 1. Boil some of the powdered substance with distilled water, and filter off from any insoluble matter. Evaporate a drop or two of the filtrate to dryness, at a gentle heat, on a slip of clean platinum foil, and if any residue be left, then save the balance of the filtrate for analysis as representing the portion of the original (if any) that is soluble in water. 2. If anything remains insoluble in water, then wash it on the filter with boiling water until a drop of the washings leaves no marked residue on evaporation. Rinse the insoluble portion off the paper into a tube, and add hydrochloric acid drop by drop (noting carefully any effervescence or odour as indicating the presence of certain acid radicals, such as carbonates, sulphides, sulphites, cyanides, etc.), and warm. If it now all dissolves, save the fluid for anajysis. If not, then separate the insoluble part, test the filtrate by evaporation of a drop or two, to see whether anything has dissolved, and if so, save the fluid for analysis as repre- senting the metals present in the form of salts insoluble in water, but soluble in HC1. Note. This division of any mixture into salts soluble and insoluble in water gives the greatest assistance in the subsequent testing for the acid radicals. For example, if a metal of the 5th group be found in the portion soluble in water ? then any acid radical almost may be present ; while if a metal of one of the other groups be found, then generally speaking only a nitrate, sulphate, chloride, or acetate need be first searched for. If, on the other hand, the substance resists the action of water and only goes into solution with HC1, then as a rule no metal of the ^th group is present, and we might consider that we were probably dealing with a carbonate, oxide, phosphate, arseniate, oxalate, sulphide, sulphite, cyanide, ferro- or ferri-cyanide, or borate of a metal, not in the 5th group. Certain tartrates and citrates, chiefly of the 4th group, would also come in this category. j. If the substance is insoluble in both water and HC1, try nitric acid, first alone, and then with the addition of hydrochloric acid. This treatment dissolves certain metals in the free state, such as Ag, Pb, Bi, Hg, and Cu, and also acts upon Hg 2 Cl 2 , HgS and other insoluule sul- phides, and on Fe 2 O 3 and some refractory oxides. Gold and platinum dis- solve only ii nitre-hydrochloric acid. Note. When H \ T O 3 has been used as a solvent, the liquid should always be evaporated A.ith HC1 till all the HNO 3 has been displaced, then allowed to get quite cold and any precipitate filtered out and treated as belonging to the 1st group, vhile the filtrate is directly treated with H^S. 4. If anything still remains insoluble, it must be fused with fusion mixture (KNaCO 3 ) at a bright red heat till action ceases, and the residue so obtained boiled with water and filtered. The filtrate is used for the detection of acid radicals ; while the insoluble matter is dissolved (after washing) in nitric acid and used for finding the metals. The usual run of articles requiring this treatment are sand, clay, and other silicates, sulphates of Ba, Sr, Ca (latter not always), and Pb, the haloid salts of silver, SnO 2 and Sb 2 O 5 . Step II. Proceed to apply the following tables to the prepared solution from Step I. Note. The whole of the first table for "separation into groups" must be gone through, but if no effect be obtained in Groups I. or II.. a fresh portion of the prepared solution should be taken for Group III., etc., so saving the time required for evaporating to a considerable extent. 5 66 QUALITATIVE ANALYSIS. 1 at 1 5> Q C ^ III ** * iaf --' -0 1 8 i s " ^ o >> w ^ >-, o T ~ ^ rt T3 i 2gc'^ M -^ &-S, 2j II! m\ rt r r \ ^4 9\. y ^ y? X r ^4 r x T *\ *J\ _^? r \ ^? ^? fl -" v "^ ;2 " "3 " 5 12 "==S | ^s ~2 ^HB.-l> *S 05^2- 8. : cxo^^i^aK. =- M-^S 1 . H \% o laJb* Is -, DETECTION OF UNKNOWN SALTS. ,0 G u PH JG 5 !Q' VM O * : l 'a. 8 o G *\ 1 ti 1 T3 g *o "o ^ ^ tuo a s ^ 13 O ^ r s r ^ ^^ fl> ^ I a "2 i r o D .*"! ^ 9 *l | S a o ." tc 111. [a, >_, ^H 'o T3 r 3 rt .0 t5 .9 ^ fc : 'g, a 1 3 C!J ,fi 1 1 "rrt . ^^ QJ is '-C o ft I ! 1 S "8 fi o3 O OH -c ^ c -o ^ri O C 3 S f W tH t-3 W w c^ FT-I "^ c2 bJO | | .g- o ^ ^ 1 H o S-j Mjifsjl t 1 i U 1 -g I .a 2 *s I-H k^ >^ (*S . O o 1 1 S 5 1 Igls 1 * 1 S ; U3 ^tS Jjj; O O ^ ^ dn - ~ 4-> -H '*" >' fi 1 ; ' B 3 * 1 S3 3*5 ui | , C^ s H H ^ 2 68 QUALITATIVE ANALYSIS. Ill 1 | I T3 a C D S g I 3 i s a J9 O S lag 8 =3 i; 1 00 * a B 2 W - == y u -5 O fc Hi 5 W w c c -J 1 c a m s > 3 a S o * fi -5 1 C | '1 o II SI a a> bo 3 rt 'o C -I |S 8S S s >> g 1 1 DETECTION OF UNKNOWN SALTS. ft! ill a. ^ M i .2 5 slie isi .ti co a, a o .a co I -o W W2 O C r T ' bc ,. . n C r- < ^ i-C ^J C boo O 5l! .2 . CJ a ' s grg c/f - o u T3 ^ W5 > g '^ 5 S e s 2 S 3 , Au in a tu sent. bonate ontain A by fusion tainly p ium ca may c he A are f on cer amm cipitate confirm Au or Pt solution o .S s g 03 ,_ 1 82 S -w . QUALITATIVE ANALYSIS. g s r p fri S g o > i H S w CA: -r C rt 1 o K + O rt add sodium peroxide (which if yell and boiled. The soluti HC 2 H PQ T3 ^i r *a =2| !I II P< O H c U JC ^1^ S " ^J JK - .2 u g * O ^ - *j S C! 2*3-1 ^ < Jgfll .G 0 ^ l' s o g I uW^ r ug 1 ' s ".-" fc ** SIS i & :ci ill i m sril-! 5 8 Is QUALITATIVE ANALYSIS. g - w s -5 J rt ^3 3 li Ml . C N < d preci ecipitation po ofe.) The sup Fe escaping p SI 2 K C CJ *> % X SJ *5 oo a; 3 ^C 3 ' *- O b^ :^o ft ^ > W3 >^ 3 Cu g x - ^ - .2 w CU fcJO P 'o .a s o rt Pd ^ S < 'o i- > -Q 1=0 " S C^ ^ ^3 O _T > ^ U "3 V*H HH t^ 7 -c ^ .2 J, ^ H CO S3 a 'O 2 bO _C S I by 6 S -6 || r: fi -3 bC S g * ' 'g o rt DETECTION OF UNKNOWN SALTS. 73 d 1 g -S H 2i s ^ M> 'O ^^ Cj d" ffi o w c 3 igf ^ X g -2 8 R o > ^.^-irtw tllt-f 1 tf g S. 1 1 . lo s- M ^ s a s & - w t!'o HT ? lc ' 5 o .a ^ a ^ S I a o 5P ^ S 3 flit I s ! "S so a S c 5 .9 'S -S -e 5 S w U ( QUALITATIVE ANALYSIS. c & , o> o bo - 1 g 1 1 i *O "^ " g ... X * 4) O J3 ,c .C S 2 .t: rt O 1 2 O M ^ g 5 i .2 50 3 :s rt ^ ^ O " S c - , tn rt C -5 -d s g S 2 - - -S rt -o i its 2- & > u ? r >% > ^_. O 1 1 TJ 3 ' ^ 13 "*"* S "o 'Sb 'C co O 2^ w ^c .S A O 9 c .? "S 'C ^ ."2 O rt rt OT o ' ^ i U H DETECTION OF UNKNOWN SALTS. 75 IV. DEIECTION OF THE ACID RADICALS. Division A. Preliminary Examination. IMPORTANT NOTE. We must always decide what metals or bases are present before we proceed to test for acid radicals. We must then note which bases are present as soluble and which as insoluble salts (in H 2 O). Lastly, we must consider what acids might be present in each case, and only test for such possible acids, because nothing leads to so many errors as testing for acids which could not possibly exist. We must also carefully note the information received in the former preliminary exami- nation, especially as regards the presence of organic matter, and remember that, if the original substance does not char on heating we must never enter into the testing for organic acids, because none can possibly be present except oxalate, which is provided for in the inorganic portion of the course with this very object, together with a few others included for convenience. We must also remember to note what happens when we dissolve the original substance in HC1, provided such a step is necessary, and if any effervescence occurs we must be sure to smell the gas given off, because we may then at once detect the following : *Carbonate . . effervescence without odour, and the evolved gas poured into lime-water renders it milky. *Sulphide . . odour of H. S (with deposit of S polysulphide). *Sulphite . . SO 2 ( hyposulphite). *Cyanide . . HCN. Peroxide . . chlorine. Fe, Zn, or Sn (as metals) Hydrogen evolved ; without odour. We must also remember that organic bodies, such as alkaloids or sugar, other than organic salts, might be contained in a mixture which would cause charring on heating, and so lead us to test for what was not there. It will be useful at this point to see how we can guard against two of the more commonly occurring of such cases. (1) Sugar. This will cause the soluble portion to be syrupy, and when warmed with dilute H 2 SO 4 it will rapidly darken, whereas organic salts, as a rule, require fairly strong H 2 SO4 to char them. The solution will have a sweet taste, and after boiling with a drop or two of very dilute H 2 SO 4 it will reduce Fehling's solution. (2) Alkaloids (nitrogenous organic bases). These will cause an odour like burning hair on heating to redness. The soluble portion of the mixture carefully treated with very dilute NH 4 HO will usually give a cloud (which may or may not dissolve in excess), and then the same liquid shaken up with chloroform, and the chloroform evaporated at a gentle heat, will leave the alkaloid as a residue. If no residue be thus obtained, then no alkaloid can be present except morphia, and this latter would never be put in a mixture unless specially intended for toxicological inves- * In soluble salts these effects will come on adding HC1 in Group I. QUALITATIVE ANALYSIS. tigation, because its detection requires altogether special work, which will be afterwards detailed. Having well considered all this, we now proceed to the actual work, carefully remembering that all the indications are merely preliminary, and that we are not to take notice unless we really get a distinct result. If we really do get one, then it may save us going so far through our actual acid course, but if we are not certain, then it is no use attempting to persuade ourselves and wasting time, but we should just note the probability and then at once pass on to confirm by the actual course hereafter detailed. No attempt is made to describe odours, because the student should simply put himself through a course of training for this preliminary examination on known salts, and learn to recognise all the odours, etc. This is a most important study, and should be carefully stuck to, until the nose and eyes have been quite trained to recognise the individual effects to be expected from each acid. Step I. Put a portion of the original solution in a tube, or if it be a solid cover it with some water, just acidulate with dilute H 2 S0 4 , and look for any effervescence or odour, then boil and smell. The following radicals may be thus recognised : Effervescence without odour . . Carbonate. ^Sulphide. Effervescence with characteristic odours . ) Sulphite. ) Cyanide. (Hypochlorite. Red fumes Nitrite. Step II. Add another drop of H 2 S0 4 , and again warm. Odour of vinegar Acetate. SO 2 with deposit of S . . Hyposulphite. HCN ,, . Sulphocyanate. HCN crystalline deposit, f Ferro- or often bluish ( J*erri-cyanide. Valerian or sharp odour 1 v ^rianate, Ben- ( zoate, buccmate. Carbolic acid . . Carbolate. Note. The effects of Step II. will often come perfectly in Step I., ana than Step II. may be considered as part of Step I. Step in. Put a little of the original solid (or the residue left on evapo- ration if the original was a liquid) into a dry tube, cover it with strong H S0 4 , and warm, but not sufficiently to cause the H 2 SO 4 itself to fume. (See note, important to prevent accidents.) Thus we get : Chloride. /Iodide NitmtP Change of colour (f Jf- White fumes (characteristic of) Nitrate. " lodate Flimrirlff and coloured Bat fume, (char- }* Succinate. actenstic of) Sulpho-carbolate. DETECTION OF UNKNOWN SALTS. 77 Effervescence on warming only, which persists after withdraw- ing from flame, but with no darkening in colour and no odour. Effervescence on warming, but the liquid darkens in colour * to a greater or less extent. Formates give off CO only, and con- sequently the gas does not affect lime-water. Oxalatesg\\e both CO and CO 2 , and the gas therefore renders lime-water milky. Tartrates rapid charring and smell of burnt sugar. Lactates not so dark, and peculiar odour. Citrates slow darkening and peculiar sharp odour. Oleates char and give odour of acrolein. Meconate. Darkening in colour without any I , very marked effervescence. 1 p yroga j late . { Salicylate (very slow darkening). No fumes gelatinous deposit (or flaky) Silicate. scaly crystals with pearly lustre Borate (best seen on cooling). No change takes place at all with Sulphate, phosphate, and arseniate. Chromates turn orange and then green Bichromates turn green straight off. NOTE, IMPORTANT. On adding strong sulphuric acid to any solid, one drop only should be first carefully applied, because chlorates, iodates, etc., are apt to explode on the first touch of the acid. If we get a decided indication of the presence of any acid radical as above, we may at once apply confirmatory tests for the radical found to onr original substance, and so save going through the course, especially if the substance be soluble in water ; but if insoluble, a solution must always be specially prepared for acid testing. Division B. Preparation of a Solution for Testing for Acid Radical, The success of the course for the detection of acids depends in the highest degree upon the care with which the solution is first prepared. It may be taken as a general rule that no testing for acids is reliable unless they are present in the form of salts of alkaline metals. It is therefore necessary to transform our acids into such salts ; and, to do this successfully, the following rules must be closely adhered to : I. If the original is soluble in water, and absolutely neutral to test- paper, you may venture as a rule to use it as it is, and this will also apply, if it be alkaline, to test-paper. II. If the original be soluble in water, but in the least acid, we must drop in NaHO till it is rendered just alkaline, boil, and, if any precipitate should form, filter and use the filtrate for the acid course. III. The portion insoluble in water (or the whole of the original if all insoluble) must be boiled with a little NaHO, then diluted, filtered, and the filtrate orrly used for the acid course. QUALITATIVE ANALYSIS. tfotc.lt Al, Zn, Sb,Sn, Cr, Pb, or any metal whose hydrate is soluble in excess of NaHO has been found, then we must use a solution of Na 2 CO 3 instead of NaHO in both Cases II. and III. We" must also take care to prepare plenty of our solution, because if the full acid course has to be gone through, we shall require possibly to employ eight to ten different portions before we have finished. This course now about to be explained is so devised that by working upon the prepared solution, in the presence successively of HC1, HN(X, HQjH/),, H 2 SO 4 and absolute neutrality, we can insure the precipitation in each stage of certain given acid radicals only by reagents, which, if used without such precautions, w r ould precipitate many more than they do when so employed. Division C. Course for the Detection of Inorganic Acids together with a few Organic included for certain reasons, Step I. Acidulate a portion of the prepared solution with HC1, and then to successive portions thereof apply the following tests : REAGENT. EFFECT. ACID PRESENT. (a) BaCl 2 FeCl (c) FeSO, (d) Turmeric paper . (White ppt. insoluble in| 1 boiling HNO 3 . . j" 'Dark blue ppt Blood red colour dis- charged by HgCl 2 . Blood red colour not dis- charged by HgCl 2 . . Dark blue Dip in and dry over the gas when the paper turns pink, changed/ to green by KHO. . j Sulphate. Ferrocyanide. Sulphocyanate. Meconate. Ferricyanide. B orate. Step II. Acidulate a portion of the prepared solution with HNO , add excess of AgNO , warm and shake, disregarding any precipi- tate that is not white or yellow and distinctly curdy. Thus we get the following : (a) Cyanide Curdy white ; soluble in very dilute NH 4 HO, and also in boiling HNOs. () Chloride Curdy white : soluble in very dilute NH 4 HO, but in- soluble in boiling IIXOs. to Bromide Curdy dirty white; slowly soluble in fairly strong XHjIK), but not in very dilute; insoluble in HNO 3 . (d) Iodide Curdy pale yellow; insoluble even in strong NH.HO and also in I IN' Note. Many other acids, such as ferrocyanidc, oxalate, eliminate, etc., are apt to come down with AgXO 3 in presence even of HNO 3 , but the precipitates are (if white) uotairdy, or they are coloured red and so will be disregarded ; and we therefore deal only with the four acids mentioned giving curdy precipitates. DETECTION OF UNKNOWN SALTS. 79 To distinguish between these four acids we (1) Filter out the precipitate with AgNO 3 , wash it, and then percolate it several times with very dilute NH 4 HO (i in 20), when AgCl and AgCN will dissolve, and can be reprecipitated from the filtrate by HNOs, while any AgBr or Agl will be left on the filter. Note. It is very important to have the dilute NH 4 HO exactly I in 20, because, if stronger, then AgBr will also dissolve, and in any case a mere cloud on adding the HNO$ is to b^ disregarded, because if AgCl or AgCN be really present, they will reprecipitate in distinct curds, on adding HNO 3 , warming and shaking. (2) If by (i) evidence of the presence of Cl or CN be obtained, then test a portion of the original prepared solution for CN by Scheele's test, and if not present then the precipitate was all due to Cl. If CN be found, then another precipitate must be obtained by excess of AgNO 3 , filtered, washed, drained, and transferred to a tube with strong HNO 3 and boiled, when any AgCl will remain insoluble. Note. As HCN is so easily smelt in the preliminary examination, we should always know before we begin the group whether it is there, and then if it be present the boiling with HNO 3 will be required, but if not, then we put it down at once as chloride if the NH 4 HO dissolves anything. (3) If, after treating with NH 4 HO (i in 20), any residue be left on the filter, leading to the idea that AgBr or Agl may be present, we proceed as follows : To a small portion of our prepared solution a drop of mucilage of starch is added, and then one or two drops of chlorine water. If iodide be present we shall get a blue. Now we go on adding fresh chlorine water till all the blue has been bleached, and if the whole is now perfectly white only iodide is present ; but if it remain at all yellow, then we add some chloroform and shake up, when an orange colour in the chloroform will indicate bromide. This depends on the fact that free iodine combines with chlorine more readily than with bromine. Step III. Acidulate a portion of the prepared solution with acetic acid, bring it to the boil, and then test successive portions while boiling as follows : REAGENT. EFFECT. ACID PRESENT. (a) CaCl 2 .... (It) Fe 2 Cl 6 (0/irn White ppt. soluble in HC1 . White ppt Oxalate. j Phosphate or excess) ) ' M Pb(C 2 H A) 2 - - Yellow ppt ( Arseniate. Cbromate. To distinguish between phosphate and arseniate exactly neutralise a portion of the prepared solution with dilute HNO.J and add AgN0 3 . Yellow precipitate soluble in NH 4 HO == Phosphate Red = Arseniate QUALITATIVE ANALYSIS. Step IV. Just acidulate a portion of the prepared solution with dilute H,S0 4 , then add a strong and fresh solution of FeS0 4 , and run some strong H 2 S0 4 down the side of the tube so that it collects at the bottom. A dark ring where the liquids meet proves Nitrate. Kate. If ro//V&has been previously found, this test fails to be conclusive, and in such case we must take advantage of the power of nascent hydrogen to reduce nitrates to ammonia. If no salt of NH 4 has been found in metal testing, we add to some of the prepared solution a fragment of zinc and sufficient HC1 to cause a brisk effervescence. After ten minutes we add excess of KHO and boil, when an odour of NH 3 proves Nitrate. If NH 4 salts be present we add a little KHO to the prepared solution, evaporate to dryness, heat the residue till no more fumes are evolved, and then dissolve in water and apply the zinc, etc., as above described. Extra Step. lodates being very difficult to detect in the preliminary, it is well to test for them specially (if they can possibly be present) by adding to the .prepared solution KI and starch , paste, and acidulating with tartaric acid. This is not reliable in presence of nitrites. Division D. Course for the Detection of Organic Acids. (Only to be entered upon in the event of the original substance being proved to contain organic matter by charring on heating in the preliminary examination.} The solution to be used is that prepared for acid testing, as already described. Step I. Place a minute fragment of litmus paper in a little of the pre- pared solution and add acetic acid drop by drop with agitation until the paper /w/ turns red, then take out the paper and add AgN0 3 in excess, lastly add a drop or two of very dilute NH 4 HO till the precipitate/*^ 1 / 1 commences to redissolve. Now warm the tube in the Bunsen flame, when a reduction to metallic silver, forming a mirror on the tube = Tartrate. Note. The tube used must first be rendered chemically clean by boiling in it successively some dilute HNO 3 and then some dilute NaHO, and rinsing with distilled water. Formates produce the same effect, but do not char on heating. Step II. Place a minute fragment of test-paper into a portion of the prepared solution, and drop in dilute HC1 till it just turns red, then dilute NH 4 HO till \\.just turns blue again, cool thoroughly, add some CaCl., and shake well. If a precipitate forms (oxalate, tartrate, etc.), add excess of CaCl.,, shake, and let it stand in cold water for ten minutes and filter. Now add to the filtrate a little more NH 4 HO and boil gently for some time, when a white precipitate = Citrate. Kote. If CaClj gives nothing in the cold, of course we simply warm for the citrate straight off. As oxalate, tartrate, etc., have all been previously tested for, we shall know, before commencing to test for a citrate, whether we need to separate them in the cold or simply to add the NH 4 HO and CaCl 2 and boil straight away. The addition of rectified spirit to the solution in which boiling has failed to indicate citrate will bring down a Malatc on cooling, but unless specially ctcd this reaction is not a very certain one. Step III. Place a fragment of test-paper into a portion of the prepared solution, and if alkaline, make it exactly neutral by carefully DETECTION OF UNKNOWN SALTS. dropping in dilute HC1. Then apply the following tests to portions of the neutralised liquid : (a) Prepare some neutral ferric chloride, by adding very dilute NH 4 HO to a solution of Fe 2 Cl 6 until a permanent cloud just forms, and filtering. Now add some of this reagent, and observe effect as follows: Acetate (Carbolate (i) Red colour . Sulphocyanate ( 2 ) Purple colour 1 Sulphocarbolate (3) Blue-black Pi " kish Notes. (1) Acetate, red, is instantly discharged by a drop of HC1 ; pyrogallate is turned black by excess of KHO and exposure to air. Sulphocyanate and meconate have been already proved in the inorganic acid course, but distinguished by action of HgCl 2 if desired. (2) Acidulate a portion of prepared solution with HC1 and shake up with ether. Remove the ether by a pipette and evaporate it on a watch-glass at a very gentle heat. Carbolic acid is left, an oily liquid readily recognised, while salicylic acid is left in characteristic crystals, as giving a beautiful violet with Fe.;Cl 6 . (Also see page 57 for another separation.) Sulphocarbolic acid gives no immediate precipitate with BaCl 2 , but on evaporating with a little Na 2 CO 3 and KNO 3 , and fusing, then the residue dissolved in H 2 O shows a sulphate with Bad,. (3) With excess of KHO a solution of gallic acid rapidly becomes dark on exposure to the air, while tannic acid gives a flocculent liquid not so rapidly changing. Tannic acid also precipitates solution of gelatine, and gallic does not. (4) Take a good quantity of the neutralised and prepared solution, add excess of Fe 2 Cl 6 , filter out the precipitate and wash it. Now percolate it with some dilute NH 4 HO, evaporate the liquid so obtained to a low bulk, cool thoroughly, and acidulate with HC1. Benzoic aoid will separate in silky crystals, and succinic acid will not. Step IV. If oleic, lactic, or sulphovinic (ethyl-sulphuric) acids be suspected, specially test for them as follows: Oleic acid will have shown its presence by always floating to the surface as an oily liquid whenever the prepared solution is acidulated with any acid. To confirm and distinguish it from the other fatty acids (stearic, etc.), take some of the prepared solution and acidulate with HC1, warm, and set aside till the oily layer floats up. Now remove the liquid beneath, as far as possible, with a pipette, add some water, boil, and drop in small fragments of K^COg, until the oily layer is saponified and dissolves. Now put in a piece of test-paper and carefully add acetic acid to exact neutrality, then cool and precipitate with excess of Pb(C 2 H 3 O 2 )2. Filter out the oleate of lead, wash it with boiling water, let it thoroughly drain, and then prove that it is soluble in ether (stearate and palmitate of lead are insoluble). Lactic acid. Acidulate the prepared solution with HC1 and shake up with ether. Pipette off the ether into a porcelain capsule and let it evaporate at a gentle heat, when the acid will be left and may be recognised as follows : (a) A portion heated burns at first with a blue flame, and then the flame becomes luminous as the temperature rises. (^) Another portion warmed with K 2 Mn i; O 8 gives the odour of aldehyd. Sulphovinates do not precipitate BaCl 2 in the cold, but, on boiling, give a precipitate of BaSO4 and an odour of spirit. 6 QUALITATIVE ANALYSIS. s-g |l 2- .i: rt e ^ ? 3 w 3 III S S| water but soluble in following radicals. -. S? ji it 9 q mi! 5 CJ <-cT .- . J3 o 1 < 5 g S o s u o" u A A a 000 M S5 o s 2 o s M U rS ^^i 8U TOO 00 (^c^i 00 I ^i ^ 's O o C/3(^ CJ rd iQ s oio-i is UU ^ - M. a DETECTION OF UNKNOWN SALTS. ss* -S-S s- -3 00 s 2 C/2 72 (^ oTU .0 , ^ r? r5 acetate. Amyl Alcohol (fousel oil). Miscible with alcohol, but sparingly soluble in water, on which it floats. Does not volatilise under 128 C. Gently warmed with sodium acetate and diluted H 2 SO4 it gives the odour of pears. Distilled with K 2 Cr 2 O7 + H 2 SO 4 , and the distillate boiled with KHO, potassium valerianate is formed, giving the tests for valerianates. Amyl Nitrite. Miscible with alcohol but not with water, on which it floats. Dropped into fused KHO it forms potassium valerianate. Shaken up with a solution of KI, acidulated with diluted H 2 SO 4 , iodine is liberated and NO is evolved. Benzol (benzene). Miscible with alcohol but not with water, upon which latter it floats. Dropped into HNOs it yields nitro- benzene, having an odour of bitter almonds. Dropped into' H 2 SO 4 and the solution boiled with KHO a carbolate is* obtained and may be tested for. Benzinum (petroleum spirit). Miscible with alcohol, but insoluble in y and lighter than, water. Does not give reactions with HNOs, H 2 SO4, and KHO (distinction from benzene]. Chloroform. Miscible with alcohol. Very slightly soluble in, and heavier than, water. Reduces Fehling's solution. Boiled with 88 QUALITATIVE DETECTION OF ALKALOIDS, ETC. KHO and a fragment of resorcin gives an intense red (rosolic add] ; add a drop of aniline to 'Some alcoholic solution of KHO, then add a drop or two of the suspected liquid and boil, when a fearfully offensive odour of phenyl-isocyanide is produced. Creasote (chiefly guaiacol and creasol). Very slightly soluble in water, in which it sinks. The aqueous solution gives a green colour with ferric chloride, rapidly changing to a reddish-brown precipitate. Creasote is miscible with collodion without pro- ducing any turbidity, and it is insoluble in cojnmercial glycerine. (distinction from liquid carbolic acid}. Ethyl Alcohol. Add K 2 Cr 2 O: and H 2 SO 4 and boil, and get a green colour and odour of aldehyd ; heat with NaC2H 3 O2 and H 2 SO 4 , and get odour of apples ; warm with KHO and iodine, and get yellow precipitate of iodoform (Leiberis test best done on a portion that has been distilled off from the original liquid). Glycerine. Colourless and odourless syrupy liquid, volatilising on heating with very irritating vapours. A borax bead dipped in glycerine and held in the Bunsen flame colours it green (if the original liquid be acid it must be first neutralised and ammonium salts must be absent). Two drops of concentrated glycerine heated to 125 C, with two drops each of phenol and H 2 SO 4 , yield a semi-solid mass which dissolves in dilute ammonia solution, giving a carmine colour. Before these tests are used for any mixture, it should be evaporated to dryness with excess of slaked lime at a temperature under 1 00 C., and the residue having been extracted with a mixture of equal volumes of absolute alcohol and ether, the resulting solution should be evaporated on a water-bath, and the tests applied to the residue. Jlfethyl Alcohol. To 5 c.c. of the liquid add 2 grammes of K 2 Cr 2 O7, and 20 c.c. of dilute H 2 SO 4 (i in 4); let the whole stand for twenty minutes, and then distil off 10 c.c. Neutralise this dis- tillate with Na 2 COs, evaporate to a low bulk, acidulate with acetic acid, and apply the tests for formate (page 46). Nitrobenzene (oil of mirbane). Yellowish oily liquid having an odour of bitter almonds. Placed in contact with zinc dust and diluted H 2 SO 4 , it is reduced to aniline. If a crystal of KC1O 3 be dropped in and H 2 SO 4 run down the tube (as in testing for nitrates) a violet colour is produced round the crystal. Paraldehydum (paraldehyd). Soluble in water (i in 10); miscible with ether; no colour with KHO after standing (dist.from aldehyd}. Mirror on warming with ammonio-argentic nitrate. II. The substance is a solid which chars on heating and entirely burns away. Observe the colour of the substance, try its solubility, first in cold water and then in cold chloroform, and apply the following : Case (A). Substance white, difficultly soluble (or insoluble) in cold water, but readily in chloroform. Suspect and test for : Acetanilide (antifebrin). Slightly soluble in cold water (neutral reaction); freely soluble in chloroform, ether, benzol, and rectified spirit. Heated with solution of KHO and a drop of chloroform, the odour of phenyl-isonitrile is developed. Aqueous solution gives yellowish-white precipitate with bromine water (distinctions from fihe.nacetin). DETECTION OF CERTAIN ORGANIC BODIES. 89 A cold solution gives no colour with Fe 2 Cl 6 (distinction from antipyrin, acetone, and aniline salts). No colour with H 2 SO 4 . Elaterin. In greenish-white friable masses. Insoluble in water, but soluble in chloroform. With a drop of liquefied carbolic acid and two drops of H2SO4 gives first crimson and then scarlet. Naphtol (beta-naphthol). Often buff or yellow when old stock. Slightly soluble in water, freely in chloroform, and has a slight odour of phenol. Hot saturated solution with i drop of solution of NH 3 has a pale blue fluorescence. OT grm. added to 5 c.c. aqueous KHO (i in 4) with i c.c. chloroform, and gently warmed, the aqueous layer goes first blue, then green, and finally brown. o'i grm. in 10 c.c. boiling H 2 O, mixed with 10 c.c. of 3 per cent, solution of Fe^Cle, gives a precipitate becoming brown, but not violet (absence of alpha-naphthol). Picrotoxinum (picrotoxin). Slightly soluble in water, freely in chloro- form ; soluble in 10 parts of a solution of KHO, and the liquid reduces Fehling's solution ; H 2 SO4 gives a saffron-yellow ; its solution is not precipitated by HgCl 2 , by bismuth potassium iodide, PtCl 4 , or by tannic acid (showing that it is not an alkaloid). Salol (phenol salicylate). White crystalline powder. Almost insoluble in water, but freely in chloroform. On melting together salol and NaHO, and then rendering acid with HC1, crystals of salicylic acid separate, and the odour of phenol is obtained. If a few drops of very dilute Fe 2 Cle be added to 10 c.c. alcoholic solution of salol a violet is produced. Water that has been shaken with salol gives no colour with Fe 2 Cl6 (absence of free salicylic acid}. Sa?itonin. White when fresh, pale yellow when old ; nearly insoluble in water, soluble in alkali ; added to a warm alcoholic solution of KHO gives a violet-red colour, gradually fading away; added to i c.c. of H 2 SO4 and a few drops of Fe 2 Cl6 and heated gives a red colour changing to brown. (These will detect santonin in urine.) Heated on a porcelain dish and H 2 SO 4 added gives a purple. Sulphcnal. Slightly soluble in cold water and in chloroform ; fused with an equal weight of KCN the odour of mercaptan is evolved, and the residue dissolved in water, acidulated with HC1 and FesCle added, a red colour is produced ; a solution mixed with 4 drops of carbolic acid, and strong H 2 SO 4 added till the liquid boils, a green colour is obtained. Heated in air gives off S0 2 , or with dried NaC 2 H 3 O 2 gives H 2 S. Case (B). Substance white, not readily soluble in cold water or cold chloroform. Suspect and test for : Glusidum (saccharine or benzoyl-sulphonic imide). Not readily soluble in cold water or in chloroform ; heated to redness with Na 2 COa it chars and gives off an odour of benzene ; not blackened by H 2 SO 4 ; on fusing with NaHO, cooling, dissolving in water, faintly acidulating with HC1, and adding Fe 2 Cl 6 , a reddish purple is obtained. Phenacetinum (phenacetin). Only slightly soluble in cold water, and not freely in chloroform. A hot solution gives a violet with chlorine water, fading to red ; boiled with HC1 and Fe 2 Cle added gives a red ; mixed with four drops of carbolic acid, and H2SO 4 added till the liquid boils, gives a purplish-brown colour and odour of acetone; o'i grm. boiled with 2 c.c. of HC1 for 90 QUALITATIVE DETECTION OF ALKALOIDS, ETC. \ minute, and the liquid diluted with 10 volumes of water, cooled and filtered, gives a deep red with solution of chromic acid ; does not give precipitate with bromine water, nor does it give the isonitrile test (dist. from acetanilide). 0*3 grm. in i c.c. 90 per cent, alcohol, diluted with 3 c.c. water and boiled with i drop yjj- iodine solution, gives no red (absence of paraphenetidin). Case (C). Substance white (crystalline), and readily soluble in cold water. Suspect and test for : Chloral (hydrous). Soluble in water. Heated with solution of KHO gives odour of chloroform, and the contents of the tube give the reactions of a formate (page 46). Gives the same test with resorcin as chloroform. Mixed with a 5 per cent, solution of carbolic acid, and an equal bulk of H 2 SO 4 added, gives a pink. Phenazonum (antipyrin or phenyl-methyl-pyrazolone). Freely soluble both in water and chloroform ; with NaNC>2 and diluted sul- phuric acid gives a green ; an aqueous solution with an equal volume of HNOs is yellow, passing to crimson on warming; Fe 2 Cle gives a deep red, discharged by dilute H 2 SO 4 . 2 c.c. of a i per cent, aqueous solution with 2 drops of HNOs goes green, changed to red by adding 3 drops more and boiling. Resorcin. Freely soluble in water ; Fe 2 Cl6 added to an aqueous solution gives violet, discharged by NH 4 HO ; Na 2 OCl 2 gives a violet, fading to yellow; NH 4 HO and CaOCl 2 gives a red violet, turning yellow. Soluble Saccharine. Tests as for glusidum, but when heated to redness leaves a residue giving the tests for sodium. Sugars. (a) Sucrose (cane sugar). A solution boiled with dilute H 2 SO 4 darkens markedly, but not when boiled with liquor potasses. Trommer's test (a few drops of solution of CuSO 4 with an excess of KHO and boiled) gives no red. Fehling's solution (see p. 129) gives no red. (b) Glucose (grape sugar). A solution gives no darkening when boiled with dilute H 2 SO 4 , but darkens when boiled with liquor potasses. Trommer's and Fehling's tests both give a red precipitate. (c) Lactose (milk sugar). A solution is only slightly affected either by boiling with dilute H 2 SO 4 or with liquor potassce. Fehling's and Trommer's tests both give a red precipitate. Case (>). The substance is coloured. Suspect and test for : Adeps Lance (cholesterin-fat). Insoluble in water, soluble in chloro- form and ether, sparingly in rectified spirit. The chloroformic solution poured gently over the surface of strong H 2 SO 4 gives a purple ; five grammes in ethereal solution mixed with phenol- phthalein give a red on the addition of '2 c.c. of normal sodium hydrate (distinction from ordinary fatty acids, which would saponify and absorb much more soda). Soluble in boiling alcohol, and crystallises out on cooling. Aloin. Yellow and slightly soluble in cold water, freely in hot ; insoluble in ether. HNOs gives a red (except with socaloin, which goes brownish). Dissolve in strong H 2 SO 4 and a few drops HNOs, dilute with water, and get a yellow, turned deep claret by excess of NH 4 HO. H 2 SO 4 on a fragment of aloin, and a rod moistened with HNOs held near, gives a blue with nataloin only. Chrysarobin. A brownish-yellow powder, partly volatile by heat with QUALITATIVE ANALYSIS OF SCALE PREPARATIONS. 91 yellow vapours; insoluble in water, but soluble in KHO, gradu- ally producing a brilliant red. H 2 SO 4 on the fragment gives a reddish brown. Fel Bovinum (ox bile). Yellowish-green substance, soluble in water and spirit. A solution mixed with a drop of syrup and then H 2 SO4 cautiously added becomes cherry-red, changing suc- cessively to carmine, purple, and violet. Gelatinum (gelatine). Swells up in water, soluble on boiling. Tannic acid gives a flocculent precipitate ; HgCl2 gives a white ; not precipitated by dilute acids, alum, plumbic acetate, or ferric chloride. Guaiacum Resin. In powder yellowish green. Insoluble in H 2 O, but soluble in alcohol, and this solution becomes blue with Fe 2 Cl6 or solution of H 2 O 2 . The H 2 SO 4 + H 2 O test (see Jalap Resin) gives a characteristic odour somewhat balsamic. lodoform. Yellow, insoluble in water, and characteristic odour ; warmed with alcoholic solution of KHO, and then mixed with starch paste and excess of HNOs, gives a blue. (May be detected in urine by adding alcohol and pouring upon phenol-potassium contained in a test-tube, when the red colour will cover the bottom of the tube ; soluble in alcohol.) Jalap Resin. Dark brown in fragments, paler in powder. Insoluble in water, but soluble in alcohol ; insoluble in turpentine. H 2 SO 4 dropped on a fragment turns ij; reddish, and on adding a few drops of water, so as to cause evolution of steam, the charac- teristic odour of jalap is observed. Only 10 per cent, should be soluble in ether (absence of scammony or Tampico jalap resins). Podophyllin. Pale yellow to orange-brown. Insoluble in water, but soluble in spirit ; soluble in NH 4 HO ; H 2 SO 4 on a fragment slightly colours it, and on adding a drop or two of water no characteristic odour is evolved. Partly soluble in ether. Resin. Insoluble in water, soluble in alcohol and in turpentine ; H 2 SO 4 on a fragment gives a strong red, and on adding a few drops of water, so as to cause evolution of steam, the character- istic odour is observed. Scammony Resin. Brownish translucent fragments. Insoluble in H 2 O, but soluble in alcohol, and completely in ether (distinction from ialap resin). Alcoholic solution gives no colour with Fe 2 Cle or H 2 Oa (absence of guaiacum resin). The H 2 SO 4 + H 2 O test gives the odour of scammony. DIVISION C. QUALITATIVE ANALYSIS OF SCALE PREPARATIONS. Step I. Heat a little to redness on platinum foil, and observe the following possible cases : (a) If it entirely burns suspect Beberine sulphate. Confirm by testing for sulphate by BaQ 2 ; and for beberine with KHO, getting a yellowish- white precipitate entirely dissolved by agitating the liquid with twice its volume of ether. This ethereal liquid evaporated leaves a yellow residue entirely insoluble in dilute HC1. (b) An ash is left : (a) Put a small fragment of the ash upon a piece of red litmus paper, moisten it with a drop of water, and, if it turns the paper blue, suspect potassium; (b) Dissolve the remainder of the ash in nitric acid, dilute and test with excess of ammonium molybdate for phosphoric acid. Note. If K be suspected, prove it by igniting some more of the scale, extracting the ash with very little boiling water, filtering, cooling, and adding PtCl 4 . 9 2 QUALITATIVE DETECTION OF ALKALOIDS, ETC. Step II. Make a weak solution of the scale, acidulate it with a drop of HC1, and test for ferrous iron with K 6 Fe 2 Ci 2 Ni 2 , and for ferric with K^FeCeNg. Also test another portion by adding excess of AgNO 3 , and heating, when reduction to black or a mirror tartrate. Step III. To a strong solution add excess of NaHO, boil, and smell for ammonia. If neither phosphoric nor tartaric acid has been already found, filter out the precipitated ferric hydrate and use the filtrate for testing for acids as follows : (a) Test a portion for citric acid exactly as directed in the organic acid course (page 80). (b) Test another portion by exactly neutralising with HNOs, and adding AgNOs, when a white precipitate = pyrophosphate, and the same turning black = hypophosphite, Of course this step is never to be taken unless an indication of P be got in the ash with molybdate in Step I. Step IV. Make a solution of a fair amount of the scale, add a drop or two of very dilute NH 4 HO, and then add some strong NH 4 HO. Case (A). There is either no precipitate, or it dissolves in strong NH 4 HO : Add some chloroform and shake up. Separate the chloroform by a pipette, and evaporate it to dryness in two portions on separate white dishes. Test the one residue for strychnine, and the other for quinine. Case (j9). The NH 4 HO causes a permanent white precipitate : Filter out precipitate, and dissolve it off the filter with a little warm water containing a few drops of acetic acid. Boil the solution down to a low bulk, cool, neutralise if necessary with very dilute NaHO, and then add a few drops of saturated solution of Rochelle salts and shake, when a white precipitate = cinchonidine. If not that, then add NH 4 HO, when a white precipitate insoluble on shaking with ether = cinchonine. DIVISION D. GENERAL SKETCH OF THE METHOD OF TESTING FOR POISONS IN MIXTURES. This course is only carried down to the best method of preliminary procedure for the isolation of the poison, all the individual tests to be after- wards applied having been already fully described in this or former chapters. Note. Students desiring to study the subject more deeply are referred to Dr. Leyda's articles on detection of poisons in the Analyst for 1890. Step I. If the liquid be very strongly acid, and effervesces violently with NaHCOs, test for poisonous acids, specially for Nitric and Oxalic. Note. Oxalic acid is best separated from a mixture by precipitation with plumbic acetate, filtering, suspending the precipitate in water, and passing H..S This removes the lead, and, after again filtering out the PuS, the liquid is evaporated to a suitable bulk and tested for oxalic acid. Step II. Acidulate with | of its bulk of HC1 (filter, if necessary), and apply Reinch's test for As, Sb, Hg. Step III. Burn to ash, dissolve this in HC1 or HNOs, and test by ordinary course for poisonous metals, especially Pb, Cu, and Zn. Step IV. If the original, either alone or when heated with dilute H 2 SO4, gives the odour of HCN, of carbolic acid, or of phosphorus, test specially for them. METHOD OF TESTING FOR POISONS IN MIXTURES. 93 The reactions of HCN have been given at page 40, while those of carbolic acid are found at page 51. If a piece of filter paper, moistened with solution of AgNOs, and suspended in the neck of the flask or bottle containing the suspected matter, be not darkened after warming the whole to 50 C. for a short time, no phosphorus is there. If darkening should occur, the suspected matter is to be acidulated with H 2 SO4, and distilled in a dark room, using a glass Liebig's condenser, when a luminous ring will be observed to form in the upper part of the condenser tube. If the suspected matter should contain spirit or certain other volatile bodies, the ring will not appear till they have passed over. Step V. If the original has no odour of opium we proceed to apply Stas's process for the detection of alkaloids as follows : If the original be a solid, it is operated upon directly, but, if a fluid, it is first evaporated to dryness on a water- bath. Add some strong alcohol and a small crystal of tartaric acid, boil, and filter. Evaporate the filtrate to dryness O on the water-bath, and take up with warm water slightly /~\ acidified with acetic acid, then cool and filter (if neces- / J sary), taking care that the liquid just remains acid. Put V I this acid liquid into a separator (fig. 17), and shake it \ / up with ether or benzene, and carefully separate the * ' ether. (This ether may contain fat, certain bitter prin- ciples, and glucosides, and therefore, in a general in- vestigation of a drug, it should not be rejected, but evaporated, and the residue examined.) Now make Flgl I7- the liquid distinctly alkaline by the careful addition of Na 2 COs or NaHO, and again shake up in the separator with chloroform, which will take up all the alkaloids except morphine. The chloroform is separated, evaporated at a very gentle heat, and the residue tested for alkaloids by the course given in Division A by the table facing page 87 of this chapter. Lastly, the alkaline liquid is shaken up with warm amylic alcohol, which extracts morphine and leaves it upon evaporation. Note. It is often better to get the alkaloids out from the chloroform or amylic alcohol by shaking the separated solvent up with water acidulated with acetic acid or HC1, thus getting an aqueous solution of the alkaloid and leaving any resinous matters in the chloroform. The re-treatment of this solution with alkali and chloroform, etc., will then enable us to get the alkaloid in a state of purity. Step VI. When opium is suspected. Acidulate with acetic acid and filter, if necessary (any alcohol present being got rid of by boiling it off). Precipitate when cold with solution of plumbic acetate, filter, and preserve the precipitate (A) for examination for meconic acid and the filtrate (B) for morphine. (a] Precipitate (A) is suspended in water and treated with H 2 S till per- fectly decomposed ; the PbS filtered out, and the filtrate, after evaporation to drive off H 2 S, tested for meconic acid. If this be found, it is held to be sufficient proof of presence of opium taken in connection with the odour of the original. (l>) Filtrate freed from Pb by H 2 S and filtering is evaporated to dryness with a slight excess of NaHCOs on a water-bath. The residue will yield its morphine to alcohol, generally in a state suffi- ciently pure to evaporate a drop, and test. If not, then am.ylic alcohol must be used. PART II. QUANTITATIVE ANALYSIS. CHAPTER VI. WEIGHING, MEASURING, AND SPECIFIC GRAVITY. I. WEIGHING AND MEASURING. ALL bodies mutually attract each other. As the earth is the largest body within our atmosphere, it follows that its attraction is always greater than that of any surrounding matter. The force thus developed is called the attraction of gravitation, and its exercise is the cause of weight. Weighing is performed by means of the well-known appliance called the balance. Figure 18 illustrates a chemical balance of the modern short-beam type. H is the handle by which the balance is put into action, and R is the appliance for Fig. 18. placing rider weights upon the graduated beam. Weights are made either according to the metrical or the English system, as follows : (a) The Metrical system. The metrical weights of precision above one irramme are in brass ; and then we have '5, '2, *i, -i, and following them .05, '02, 'oi, 'oi, all in platinum or aluminium foil. The quantities below 'ci (one centigramme) are weighed by a rider on the beam. The combination of 5, 2, i, and i has been chosen because they have been found to give the greatest number of possible combinations with the fewest weights. Figure 19 shows such a box ri e- 9- of metrical weights as usually employed in quantita- tive analysis. The metrical system is founded upon the metre. The metre is multiplied and divided entirely by ro, thus : WEIGHING AND MEASURING. 95 Kilo-metre IODQ- Hecto-metre 100- Deca-metre ...... io Metre ....... 1 Deci-metre .... *l Centi-metre *oi Milli-metre 'OO* The metre taking the practical place of the English yard, the decimetre consequently takes the place of the foot, and the centimetre of the inch ; and just as weight is got in our system from the cubic inch, so it is got metrically from the cubic centimetre, only much more simply, because i cubic centimetre of distilled water ; measured at 4 C. and 760 millimetres bar., weighs one gramme. The gramme is multiplied and divided exactly as the metre, thus : Kilo-gramme ..'... iooo - Hecto-gramme 100- Deca-gramme ..... icr Gramme ...... ! Deci-gramme ..... 'I Centi-gramme -OI Milli-gramme 'ooi One kilogramme (1000 grammes) of water at the standard temperature and pressure measures one litre (or 1000 cubic centimetres), and we have therefore the following simple relation of weights and measures of water : Weight. Measure. 1000 grammes . . . . I litre or looo cubic centimetres. 100 .... I deci-litre or 100 ,, 10 .... I centi-litre or 10 I gramme i milli-litre or I cubic centimetre. So we see that using water at 4 C, a gramme by weight and a cubic centi- metre by measure amount to the same thing ; as likewise do a kilogramme by weight and a cubic decimetre (or litre) by measure. The relation between the two systems is easily calculated from the following standards : Metrical. English. I Gramme =- 15-432 grains. I Kilogramme 2-205 Ib. (or 15.432 grains). I l/tre = 1-76 pints (or 35 fl. oz., 2 drachms, II minims). I Metre = 39-37 inches. So that i decimetre is, as nearly as possible, 4 inches ; and i decilitre, a trifle under 4 fluid ounces. (b) The English system. In weights of precision, any amount above 10 grains is usually represented by a series of small brass cylinders, from 10 to j ceo grains ; then follow 6, 3, 3, 2, and t grain in platinum wire, and afterwards '6, '3, '3, *2, and 'i of a grain in platinum, or, more frequently, in aluminium wire. Quantities of less than ^ grain are weighed by a small rider of gold wire placed on the beam of the balance. The foundation of the English system is the inch. One cubic inch of distilled water, measured at 60 F. and 30 inches barometrical pressure, weighs 252-45 grains, or 252^ grains nearly. There are 437*5 grains in an ounce, and 16 ounces (or 7000 grains) in a pound. Measure of capacity is obtained by weighing out 10 Ib. of water at 60 F. and 30 inches bar., when the whole measures one gallon. The gallon is in turn divided into 8 pints (= 20 ounces, or 8750 grains of water, per pint); the pint into 20 fluid ounces (= 437*5 grains of water per fluid ounce) ; the fluid ounce is divided into 8 fluid drachms (= 54'68 grains of water per fluid drachm) ; and, lastly, the fluid drachm is divided into 60 minims ('91 grain of water in each minim). 96 WEIGHING, MEASURING, AND SPECIFIC GRA VITY. II. SPECIFIC GRAVITY may be generally explained to be the ratio of the weight of one thing to the weight of an equal volume of something else taken as a standard. For liquids and solids the standard is distilled water at a temperature of 60 F. An acquaint- ance with the various cases which may occur in the taking of specific gravity is of great importance, as it forms an exceedingly ready method of testing the purity and strength of many substances. A knowledge of the specific gravity of the various bodies also enables the chemist to tell at once what any given volume of a liquid ought to weigh, or conversely, what size of vessel will be required to contain any given weight. The following are the chief varieties of cases which may occur in taking : (A) Specific Gravity of Liquids. CASE i. To take the specific gravity of a fluid. A small bottle of thin glass is procured, and counterpoised upon a balance. It is then filled with distilled water at 15-5 C. (60 F.), and the weight of the water thus introduced noted. The bottle, having been emptied and dried, is filled with the liquid to be tested, also at 15*5 C. (60 F.), and the whole is again weighed. By this means, having ascertained the weight of equal bulks of water and fluid, it only remains to divide the weight of the fluid by the weight of the water, and the quotient will be the specific gravity required. To make the calculation clear, observe the following examples : A counterpoised bottle filled with distilled water weighs 100 grammes ; the same bottle filled with sulphuric acid weighs 184*3 grammes, then : 'i-3=- 1*843, the specific gravity of the acid. Again, the same bottle, carefully washed, and filled with rectified spirit, weighs 83*8 grammes, then : 8v8 _2_ ='838, the specific gravity of rectified spirit. 100 In practice, bottles are sold with perforated stoppers, which, when entirely filled with the liquid, and the stopper dropped in, so that no bubbles of air are allowed to remain between the stopper and the liquid, exactly hold a given weight of water. A counterpoising weight for the empty bottle is also provided ; so that there is nothing further to be done but simply to place the counterpoise in one scale, and the bottle, filled with the liquid under examination, in the other ; and having ascertained the weight, to divide by the known weight of water for which the bottle was constructed. Fig. 20 shows an ordinary specific-gravity bottle. Fig. 21 shows a specific-gravity bottle the stopper of which is a thermometer, thus enabling us to observe the exact temperature of the liquid at the moment of weighing. CASE 2. To take the specific gravity of a liquid by means of the hydrometer. The hydrometer depends for its action on the theorem of Archimedes. If a solid body be immersed in a liquid specifically heavier than ^ itself, it continues to sink until it has displaced a bulk l& of fluid equal to its own weight, and then it becomes K stationary. Suppose an elongated body with a weight ^^ at its base to cause it to float upright, which has a specific weight exactly half that of water, be immersed in that fluid, it will sink to exactly half its length, because its whole weight is counterpoised by a bulk of fluid equal to half its size. A hydrometer is a long narrow glass or metal tube with a bulb near the bottom filled with air, and another smaller bulb beneath containing a sufficient quantity of mercury to SPECIFIC GRAVITY. 97 weight it and cause it to float upright. There are two kinds of hydrometers : (i) for fluids heavier than water, and (2) for fluids lighter than water. The graduation of the former is performed by immersing the instrument in water and introducing such a quantity of mercury as will cause it to sink, so that only about one inch remains unsubmerged, and marking this point i. The instrument is then plunged successively into several liquids heavier than water, the specific gravities of which are known, and the points to which it rises are marked and numbered. By this means a scale can be made between those points indicating any gravity from i upwards. In hydro- meters for fluids lighter than water, the first sinking in that liquid is continued by weighing until only the upper bulb is immersed ; and this point having been marked i, the instrument is placed successively in known fluids lighter than water, the points to which it sinks marked, and by this means a whole scale is obtained. The method of using the hydrometer is readily Q seen from the illustration (fig. 22), in which A is the hydrometer, and B is a thermometer also placed in the liquid to show the temperature. Most hydrometers being made to indicate specific gravity at 15-5 C. (60 F.), it follows that the liquid must either be first brought to that temperature before using the instrument, or else the temperature employed must be noted, and a calculation made, based upon the coefficient of expansion of the liquid in question. Syke's hydrometer is used in England by the officers of excise, to indicate the strength of spirituous liquors, and thus facilitate the collection of the revenue. It is a short brass instrument with the stem graduated from o to 10, and a series of nine weights to place beneath the bulb. By observing (i) the temperature, (2) the wefght put on, and (3) the point to which it sinks on the stem, and referring to a book of tables which is sold with the hydrometer, the strength of the spirit is ascertained. Another modification of the instrument is found in TwaddelFs hydrometer, which is used in chemical works for testing the density of liquids having a greater specific gravity than water. It is so graduated that the reading of any indi- cated degree, multiplied by 5 and added to 1000, gives the specific gravity as compared with water. Specific gravity beads form the only other variation of the hydrometric idea. These are small loaded bulbs of known specific gravities, which are thrown into the liquid to be tested, when the number marked upon the bead, which just floats underneath the surface and shows no tendency to sink or rise, gives the specific gravity required. Hydrometers in any form must in accuracy rank considerably beneath that of the specific gravity bottle ; but in commercial operations, where an approximation only to correctness is required, these little instruments are invaluable CASE 3. To take the specific gravity of a liquid by weighing a solid body in it. Take the weight of a glass stopper, or other suitable plummet, by suspending it from the hook provided for the purpose in all balances of modern type (see fig. 18, page 94). Put a wooden stool (also provided with all modern balances) over the pan, and upon this place a beaker containing distilled water at 15-5 C. (60 F.). Let the plummet hang beneath the surface of the water and again weigh, and then empty out the water, substitute the fluid (also at 15*5 C. (60 F.) ), immerse the plummet as before, and once more weigh. By deducting respectively the weights in water and in fluid from the weight in air, we get the loss of weight sustained by the plummet in each case. It is evident that the lighter the liquid, the more the plummet will weigh ; therefore we divide the loss of weight in the fluid by the loss of weight in water, which will give the specific gravity of the liquid. This rule is now practically applied in all modern laboratories by means of the Westphal 98 WEIGHING, MEASURING, AND SPECIFIC GRA VITY. balance (fig. 23). By this a small thermometer (A), adjusted to a counter- balancing weight (B), is placed in the liquid, and the loss of weight is restored by little rider weights placed on the beam, which are so contrived as to readily indicate the specific gravity without calculation. (B} Specific Gravity of Solids. CASE i. To take the specific gravity of a solid body in mass which is insoluble in and heavier than water. The method by which this process is conducted was suggested by a theorem attributed to Archimedes, which may be thus expressed: A solid on being immersed in a liquid is buoyed up in proportion to the weight of the fluid which it displaces, and the weight it thus apparently loses is equal to that of its own bulk of the liquid. A piece of the solid substance to be tested is weighed, and is suspended by means of a fine thread from one arm of a balance so that it dips under the surface of a vessel containing distilled water so > if we multiply the former figures by the latter, we obtain 806 '31 grains, which is the weight of a fluid ounce of this acid. EXAMPLE ii. How much should a litre of chloroform weigh? The weight of a litre of water is 1000 grammes ; and by multiplying 1000 by i -49, the specific gravity of the chloroform, we obtain 1490 grammes, as an answer to the question. EXAMPLE iii. How much should a fluid ounce of pure ether weigh? The specific gravity is 72, and a fluid ounce of distilled water weighs 437*5 grains ; multiplying the one number by the other gives 315 grains. ioo WEIGHING, MEASURING, AND SPECIFIC GRA VITY. CASE 2. Given the weight of any known bulk of a liquid, to find its specific gravity. Divide the weight by that of the given bulk considered as distilled water. EXAMPLE. A pint of spirit weighs 16} ounces. Is it rectified or proof spirit ? By dividing this weight by 20 ounces, the ascertained weight of a pint of distilled water, we obtain as an answer '838. We know, therefore, that the spirit thus tested must have been rectified. CASE 3. To find the amount of solid matter, in grammes, present in 100 c.c. of a solution of given specific gravity. So far as any ordinary rule can be laid down, especially with regard to saccharine liquids, for which this calcula- tion is generally used, we multiply the gravity by 1000, and then, having deducted 1000 from the product, we divide by 3 '85. EXAMPLE. A saccharine solution has a gravity of i'OU4 : how much solid matter in grammes does it contain in each c.c. ? i'oii4X looo = 1011*4 IODO = ii'4 .*. ^= 2*961 grammes per loo c.c. 3 "o5 (D) Specific Gravity of Gases. Taking the density of gases and vapours involves many more complicated considerations than are required in the methods applicable to the specific gravity of liquids and solids. The standard adopted for such bodies is hydrogen, measured at a temperature of o C. and a barometrical pressure of 760 millimetres (N.T.P.). When taking the specific gravity of liquids or solids, it is easy to obtain the water or other fluid required at the exact temperature necessary, by the use of cooling or heating appliances. With a gas we need exercise no such manipu- lation, because the coefficient of expansion of all vapours and gases is alike and well ascertained. The measurement of gases is therefore conducted without any attempt to modify these conditions ; but the indication of the thermometer and barometer being carefully noted at the time of the experi- ment, a simple series of calculations enables us to ascertain how much the volume of gas would have measured had the test been conducted at a standard of temperature and pressure. The following are specimens of such calcu- lations : Correction of the volume of a gas for changes of temperature. This is based on Charles' law, which states that " the volume occupied by any given weight of a gas is directly proportional to its absolute temperature." Absolute temperature means degrees above 273 C., which is the absolute zero of tem- perature. To convert degrees of ordinary temperature into absolute degrees, it is therefore necessary to add 273 to all degrees above zero, while degrees below o are to be deducted from 273. From this law, given v, the volume ; v, the required volume ; /, the given absolute temperature ; and /*, the required absolute temperature ; we employ the following calculations : Correction of the volume of a gas for changes of pressure. The law of Boyle states that "the volume occupied by any given weight of a gas is inversely proportional to the pressure." Therefore, / being the given pressure, and/' the required pressure, we have When a gas is measured it is generally necessary to correct for both con- ditions, and then we employ double proportion. Vhe following formulae will be found useful as meeting all ordinary cases : SPECIFIC GRAVITY. 101 (1) Wanted the change of volume resulting from a given alteration of temperature and pressure : p x f x v _ , p'xt (2) Wanted the change of temperature resulting from a given alteration of volume and pressure : / x if x / _ f px v (3) Wanted the change of pressure resulting from a given alteration of volume and temperature : x f x = / v* x / (4) To find the volume at N.T.P. of any gas measured at a given temperature and pressure (the temperature being above o) : / x 273 x v _, P X (273 + given temp.) Or, in a decimal fraction (dt = difference between o and given temperature) : / x (i + -003665 dt) ~ The manner in which the specific gravity of a permanent gas was formerly obtained was by exhausting a thin glass globe by means of the air-pump and weighing it ; then filling it with air at known temperature and pressure, and weighing ; and lastly, pumping out the air, filling the globe with the gas at a similar temperature and pressure, and again weighing. After deducting the weight of the empty globe from each of the two latter weights, the weight of the gas was divided by that of the air. Now, however, in modern laboratories all that is practically done away with, and the standard taken for the density of gases and vapours is hydrogen ; because (i) it is the lightest known gas, and (2) we know the weight of any given volume of it without the necessity of weighing each time. Therefore, to take the density of a gas or vapour we weigh a given number of cubic centimetres of the gas, noting the temperature and pressure at the moment of weighing, and having corrected the volume so obtained to N.T.P., we divide this by the weight of the same number of c.c. of hydrogen. A litre of hydrogen at o C. and 760 mm. bar. weighs "0896 gramme; therefore each c.c. of H will weigh "0000896 gramme. (E) Vapour Density. After finding the percentage composition of substances by analysis, and from that calculating an empirical formula (which is done by dividing the percentage of each element by its own atomic weight, then, taking the lowest of these answers as unity, dividing all the others by it and expressing the mutual ratios in the simplest full numbers), it is necessary to prove whether the sum of such formula is the true molecular weight. Upon the theory that all molecules occupy a space double that of an atom of hydrogen, we can prove our case by taking the hydrogen density of the substance in vapour (if volatile), and then such vapour density x 2 = the true molecular weight. This research acts as a check upon our formula obtained by analysis, and may or may not lead to our having to multiply it until its sum equals th required weight thus found. 102 WEIGHING, MEASURING, AND SPECIFIC GRA VITY. (a) Meyer's Method. This is the simplest and most rapid process. The apparatus used is illustrated in fig 24. The inner tube (A) is closed with a cork and arranged so that its bent delivery tube just dips under the surface of mercury contained in a trough. Any suitable liquid, boiling at a higher temperature than the body of which the density is to be taken, is placed in the outer tube (B), and heat being applied so as to boil the fluid, the air in the inner tube expands and passes off through the mercury. When bubbles of air cease to pass, some water is poured upon the surface of the mercury, and a graduated gas collecting tube, filled with water, is inverted over the delivery tube. A known weight of the substance, enclosed in a specially made minute stoppered bottle, is then introduced into the inner tube (A) by rapidly raising the cork, dropping the bottle in, and instantly closing. The vapour produced now displaces an equivalent volume of air, which passes into the measuring tube. When action ceases, the cork is opened to prevent back suction, and the air in the tube is measured, noting tempera- ture and pressure. This volume in c.c. when corrected to N.T.P., and multiplied by '0000896, gives the weight of a volume of hydrogen equal to that of the vapour, and lastly, by dividing the weight of the substance taken, by this calculated weight, we obtain the vapour density. The coefficient of expansion of all gases being practically Fig. 24. equal, it is evidently the same thing whether we measure a volume of actual vapour at a given temperature, or that of an equivalent volume of air displaced by it at the same temperature. Such a minute quantity of the substance must be taken as shall not, when in vapour, more than displace the air contained in the inner tube of the apparatus (which should hold about 100 c.c.), otherwise the whole process manifestly fails. As the gas is collected over water it is necessary to refer to a table of the tension of aqueous vapour at the temperature of measuring, and to deduct it from the observed height of the barometer, before correcting to N.T.P. (b) Dumas' Process. A thin, clean, dry glass globe, about three inches in diameter, is employed. Its neck having been drawn out to a fine tube in the blowpipe flame, it is weighed, and the temperature and pressure noted. By gently heating the bulb and dipping the open end into the volatile liquid, a suitable quantity is drawn into the globe by the contraction of the air. Attaching a handle by means of wire, the sphere is plunged into an oil bath furnished with a thermometer, and is then heated somewhat above the volati- lising point of the contained liquid. When all vapour has ceased to issue from the globe, the orifice is hermetically sealed, and the temperature and pressure again noted. The apparatus is allowed to cool, separated from the handle, cleansed, weighed, and the weight noted. The last step is to break off a fragment of the neck beneath the surface of a sufficiency of mercury, when, should the experiment have been carefully performed, the liquid enters the globe, completely filling it, and the capacity is ascertained by emptying its contents into a graduated glass measure. Supposing the experiment to have been perfectly successful, we have the following five data : 1. Weight of globe filled with air. 2. Temperature and pressure at the time of weighing. 3. \Veight of globe plus vapour. 4. Temperature and pressure at sealing. 5. Capacity of the globe. Proceeding from these data, the first point is to find the actual weight of the globe. This is done by calculating the capacity of the globe from the SPECIFIC GRAVITY. 103 temperature and pressure at the time of weighing to o C. and 760 mm. bar., and then multiplying the true volume thus found by '001295, which is the weight of a cubic centimeter of air (i litre at o C. and 760 mm. bar. = 1*295 gramme). Having thus obtained the weight of the air, it is deducted from the weight of globe and air, and the difference gives the true weight of the globe ; and by deducting this latter from the weight of the globe plus vapour, we obtain the actual weight of the vapour. But as this weight is that of the volume of vapour at the temperature and pressure at the moment of sealing, it must be corrected to standard temperature and pressure, and the weight of an equal volume of hydrogen ascertained. To do this, the capacity of the globe is once more put down, and reduced from the temperature and pressure at sealing to o C. and 760 mm. bar., and the resulting volume is multiplied by "0000896, which is the weight of i cubic centimeter of hydrogen. The product, which gives the actual weight of an equivalent volume of hydrogen, is then taken, and divided into the weight of the vapour already found, and the answer is the density. (F) Note on TJ.S.P, "Weights, Measures, and Specific Gravities, The American Pharmacopoeia has entirely discontinued the use of any weights and measures except those of the metrical system, viz : gramme to gram, abbreviated to Gm. litre to liter ,, ,, lit. or 1000 Cc. cubic centimetre to cubic centimeter, abbreviated to Cc. These abbreviations, being very convenient, will be employed in the following chapter on Volumetric Analysis. Owing to the fact that the average temperature of laboratories in the U.S.A. is nearer 25 C. (77 F.) than 15-5 C. (60 F.), the Committee of Revision of the U.S. P. have decided upon the former temperature as the working standard. All the specific gravities given in Chapter XL of this book have been revised in accordance with this decision, and are all supposed to be taken at 25 C. as against an equal volume of water also at 25 C. CHAPTER VII. VOLUMETRIC QUANTITATIVE ANALYSIS. I. INTRODUCTORY REMARKS. VOLUMETRIC analysis is that in which the quantity of any reagent required to perform a given reaction is ascertained, and the amount of the substance acted upon is found by calculation. The process of adding the reagent from a graduated measure is called titration. (A) Volumetric or standard solution is a solution of definite strength, made by dissolving a given weight of a reagent in grams in a definite volume of water in cubic centimeters. Such solutions are usually made on the following principles : The theoretical normal solution is an imaginary one, containing i Gm. of hydrogen in i liter (1000 Cc.) of water, and a normal solution of any reagent is such a weight of the substance in Gm. (also i liter of water) as is capable of combining with, displacing, or otherwise performing a chemical function equal to that of i Gm. of hydrogen. This weight is termed the equivalent of the reagent, and it is ascertained as follows : (a) Trie reagent is an element. We divide the atomic weight of the element by its valency. Thus H' = i, Cl' = 35-5, Br' = 80, I' - 127, O" - 8, etc. (^) The reagent is an acid or an alkali. We divide the molecular weight by the active combining power, as shown by the number of atoms of displaceable hydrogen in acids, and by the valency of the base in alkalies : Name. Formula. Equivalent. Hydrogen . H = i Hydrochloric acid HC1 = 36 -37 Sulphuric acid . H 2 SO 4 H-2 =48-91 Citric acid Sodium hydroxide Calcium hydroxide Potassium carbonate Potassium bicarbonate H,C 6 H 4 0,H 2 0-r3 - 69-83 NallO = 39-96 Ca(HO) 2 -r-2 = 56-87 K,CO 3 2 - 68-95 KHCO 3 = 99-88 (c] The reaction is a special one, depending on a particular action. We divide the molecular (or atomic) weight of the reagent by its combining power, as shown in the equation. For example, taking the case of the action between iodine and arsenious acid, we find the equation : As 2 O 3 + 2l 2 + 2H 2 O = As 2 O 5 + 4HI. Each atom of iodine being equivalent of one of hydrogen, it follows that each H would equal \ of As 2 Os ; therefore a normal solution of that body would be 198 -f- 4 = 49-5 Gm. per liter, and would exactly decolorize i atomic weight (=127 Gm.) of iodine. 104 INTRODUCTORY REMARKS. 105 The following abbreviations are used to express the strength of standard solutions : N = a normal solution having I equivalent weight in Gm. per 1000 Cc. ^ = a half-normal solution having ^ equivalent weight in Gm. per 1000 Cc. yjj- = a tenth-normal solution having ^ equivalent weight in Gm. per 1000 Cc. Q = a fiftieth-normal -fa ,, ,, (^) An indicator is a substance added to enable us to ascertain, by a change of color (or other equally marked effect), the exact point at which a given reaction is complete. The principal indicators employed are prepared as follows : (1) Indicators for estimating acids or alkalies. (a) Litmus indicator. Boil powdered litmus in alcohol of '82 sp. gr. repeatedly till no more red color is extracted, and then digest the residue in an equal weight of cold distilled water. Pour or filter off, and then boil the blue powder remaining in 5 times its weight of distilled water ; filter and preserve the filtrate in a bottle stoppered with a loose plug of cotton, so that air is admitted, but dust excluded. This indicator is blue with alkalies and red with acids, and is affected by all acids, includ- ing CO 2 . It therefore does not give a reliable indication with alkaline carbonates unless the CO 2 is expelled by boiling. (b} Phenol-phthalein indicator. Make a i per cent, solution of phenol- phthalein in diluted alcohol of '937 sp. gr., i.e. i Gm. in 100 Cc. This solution is red with alkalies, and colorless with acids. It is not suitable as an indicator with ammonia or alkaline bicarbonates. (c) Methyl-orange indicator. Dissolve i Gm. of methyl orange (or the commercial dyes known as helianthin, Palmer's orange jP or tropceolin D) in 1000 Cc. of distilled water. Into this carefully drop diluted sulphuric acid till the liquid turns red and just ceases to be transparent, and then filter. This solution is yellow with alkalies and red with mineral acids, but is not affected by CO 2 or boric acid, so that it is the best indicator for the analysis of alkaline carbonates and borax. It cannot, however, be used with oxalic acid or organic acids generally. (d} Cochineal, Hematoxylin and lodeosin indicators. These solutions are specially employed as indicators for the titration of alka- loids. Full instructions for their preparation will be found in Chapter XL when treating of the assay of alkaloidal drugs. Note. The U.S. P. gives a very suitable warning as to the above indicators, which is worthy of being quoted in full. It says: " Each test-solution used as indicator should be examined as soon as prepared, and afterwards from time to time, as to its neutrality. If necessary, it should be brought, by the cautious addition of diluted sulphuric acid, or of a dilute solution of an alkali, to such a point that, when a few drops of it are added to 25 Cc. of water, a single drop of a centinormal acid or alkali, respectively, will distinctly develop the corresponding tints. Since many of the colored test-solutions are injured by exposure to light, it is best to preserve them in dark amber-colored vials." (2) Indicators for special purposes (a) Starch mucilage. Mix i Gm. of starch (arrowroot is preferable) with 10 Cc. of cold water, and then add enough boiling water, with constant stirring, to make about 200 Cc. of a thin, io6 VOLUMETRIC QUANTITATIVE ANALYSIS. transparent jelly. To preserve this solution for any length of time, 10 Gm. of zinc chloride should be added to it, and the solution transferred to small bottles, which should be well stoppered. It is used for the detection of free iodine, with which it strikes a dark blue. (b] Potassium chromate solution. Dissolve 10 Gm. of pure K 2 CrO4 in TOO Cc. of water, then carefully drop in dilute solution of argentic nitrate till a slight red turbidity is produced, let settle, and pour off into a stoppered bottle. This solution gives a red precipitate with AgNOs, but not until any chloride, bromide, iodide, or cyanide present has entirely combined with the silver. (c) Potassium ferricyanide solution. Dissolve i part of potassium ferricyanide in about 10 parts of water. This solution must be made freshly when required, as it is rapidly decomposed by light. The freshly prepared aqueous solution, when mixed with some ferric chloride solution and diluted with water, must show a brown tint, free from turbidity or any shade of green. (C) The apparatus specially employed in volumetric analysis. i. The measuring flask, so constructed as to hold a definite amount of fluid (say 1000 or 100 Cc.) when filled up to the mark on the neck (fig. 25). -I Fig. 25. Fig. 26. Fig. 27. Fig. 28. 2. The test mixer, a cylindrical vessel, to hold i liter of fluid graduated in measures of 10 Cc. each (fig. 26). 3. The burette, a graduated tube, usually containing 100 Cc. and graduated in divisions of i Cc. (or 50 Cc. in -^ Cc.), for con- taining and delivering the standard solution. This is fitted with a clamp or stopcock at the bottom, which, when pressed or turned, allows the contained liquid to run out at any regulated speed desired. It should also be furnished with an appliance called " Erdmann's float," which enables us to read the quantity of fluid delivered more accurately. (Fig. 27 shows two burettes in their stand as usually employed.) 4. The pipette is an instrument graduated to deliver a fixed volume of liquid (say 10, 20, 50, or 100 Cc.). Fig. 28 shows a set of such instruments arranged in a convenient stand. INTRODUCTORY REMARKS. 107 (D) Weighing operations. The student should have a tared watch-glass for weighing out solids and a small stoppered bottle for weighing volatile liquids. By carefully keeping these much trouble is saved. (1) To weigh a solid. Place the tared glass on the scale, and put on it what is judged to be a sufficient quantity of the article to be weighed, then weigh the whole and note the weight thus : Glass + substance 5*632 Gm. Known tare of glass .... 5-132 ,, Weight taken for analysis . . . -500 ,, (2) To weigh a volatile liquid. Fill the small stoppered bottle with the liquid and weigh ; pour out what is judged to be sufficient into the flask containing the indicator, replace the stopper and again weigh, noting each weight at the time thus : Total weight of bottle + fluid . . . 20-982 Gm. Weight of bottle + fluid after pouring out 15-482 ,, Weight of fluid taken .... 5'5oo ,, Note. It is most important always to take the weights directly down in a note-book from the balance, and to cultivate the habit of always replacing the weights in tJieir proper holes in the weight box when finished. This enables us to have a double check (i) from the weights in the pans, and (2) from looking at the empty holes in the weight box, In weighing brass weights are used from 50 to I Gm. ; flat platinum weights from "5 to "Oi Gm. ; and the rider on the beam is used for milligrams (i.e. -009 to -ooi). Before weighing, see that all the weights are in their right places in the box. At the conclu- sion of the weighing, read off the weights and put them down in a note-book, and then check that reading by putting them back into the box, looking, as you do so, at the note already made. Always close the case of the balance before using the rider, so as to prevent currents of air affecting the weight. (E) General modus operandi. A known weight of the substance to be analyzed is accurately weighed, and, having been placed in a flask, and dissolved in, or diluted with, water (if necessary), the indicator is added, and the standard solution of the reagent is dropped in from a burette until the desired effect is produced. The number of Cc. of standard solution used having been noted, it is multiplied by the " Cc. equivalent " of the substance analyzed. Suppose, for example, we desire to ascertain the purity of a sample of sodium hydroxide, and, having weighed out i Gm., we find that 24 Cc. of standard normal oxalic acid were required for exact neutralization. Normal oxalic acid is 62*85 Gm. per liter, or '06285 in each Cc., and by the equation we find H 2 C 2 O 4 . 2H 2 O + 2NaHO - Na,C 2 O 4 + 4H 2 O. 2)1257 2)79-92 62-85 39'9^ - 39-96 Gm. of NaHO, equivalent to 62-85 Gm. acid. The normal liter equivalent of NaHO is therefore 39*96, and the normal Cc. equivalent is 39*96 -*- 1000 = '03996 ; therefore each Cc. of acid used will represent '03996 Gm. of soda. Then 24 X -03996 = -95904 Gm. of real NaHO in the I Gm. weighed out for analysis. Lastly = 95 '94 P er cent - rea l soda in sample. Expressing the above in rules to commit to memory, we have the follow- ing steps : I. Write out the equation and reduce the first side of it to normal equivalent weights. io8 VOLUMETRIC QUANTITATIVE ANALYSIS. II. According to the strength of the standard solution employed, divide the normal equivalent of the substance under analysis by 1000 (for normal solution), 10,000 (for decinormal), etc., thus getting the " Cc. equivalent." III. Multiply the number of Cc. of standard solution used from the burette by the Cc. equivalent of the substance analyzed, thus getting the actual amount of such substance in the quantity weighed out for analysis. IV. If percentage be required, multiply the last result by 100, and divide by the weight taken for analysis. (F) The quantity of the substance to be weighed out for analysis. Two considerations are to be kept in view, viz, : (a) The smaller the weight operated on, the greater will be the multiplication of any error in the final result. (b) On the other hand, the weighing out of an amount of substance that will take more than one buretteful of the standard solution is to be deprecated as a source of error. The point is to steer a judicious middle course, and this can always be done by considering the equation, reducing it to normal or decinormal, etc., equivalents, as the case may be, and then seeing how much will be required to take a reasonable number of Cc. of the standard solution, supposing the substance to be pure. Thus taking the equation already considered, H,C 2 O 4 . 2H 2 O + 2NaHO = Na 2 C 2 O 4 2)1257 2)79-92 62-85 3996 it is evident that (roughly speaking) 40 Gm. of soda would take 1000 Cc. of normal acid, and vice versa. If therefore we are using a 50 Cc. burette, we evidently must weigh out somewhat less than 63-7-20 = 3-15 oxalic acid 40-7-20 = 2'OO sodium hydrate for titration by 50 Cc of a normal solution. In many cases the after-calculation may be altogether saved by weighing out a previously determined quantity, so that the number of Cc. of standard solution used will at once give the percentage. This idea is conveniently exemplified in the determination of iron in salts thereof. The normal equiva- lent of iron is (roughly speaking) 56, and the solutions employed in its esti- mation are usually decinormal, thus giving a liter equivalent of 5*6, and a Cc. equivalent of '0056. If therefore we were to weigh out "56 of iron, it is evident that each Cc. of a decinormal solution of a reagent for estimating it would represent yj^ of "56 or i per cent. Similarly, if we take "56 of any ferrous salt (containing one atom of iron in each molecule), each Cc. of the volumetric solution will represent i per cent, of iron present. Supposing the percentage of iron to be small (as in Liq. ferri perchlor.}, we would take double the quantity or 1*12 Gm., and then each Cc. would equal -5 per cent. of iron. The rule may be thus stated for all titration : Calculate the Cc. equivalent of the substance you desire to estimate, taking into consideration the standard of the solution you are using (i.e. normal, decinormal, etc.), and, having multiplied by 100, weigh out this quantity for analysis. Then each Cc. of your solution used from the burette will = i per cent, of real substance in the quantity weighed out, and fractions of a Cc. = similar fractions of i per cent. When it is not desired to use a larger burette than 50 Cc., only 50 STANDARD ACID SOLUTIONS. 109 times the equivalent should be weighed, and then every -5 Cc. = i per cent. With very accurate 10 Cc. burettes graduated in -^ Cc. only 10 times the equivalent may be weighed, and then each ^ Cc. = i per cent. ; but, as before stated, the delicate work in this respect leads frequently to error. (G) Precautions in direct titration. The standard solution may be added at first from the burette to the liquid analyzed at the rate of about '5 Cc. at a time, and the liquid should be stirred or agitated after each addition. When it is seen, by the effect on the indicator, that the desired point is approaching, the standard solution should be added more carefully, and finally, at the rate of a single drop at one time, till the effect is obtained. The placing of a white porcelain slab, or a sheet of white paper, under the vessel containing the solution to be analyzed, helps us to see the changes in color more accurately. All titrations are better done in flasks, the contents of which can be readily agitated by holding the neck, and giving a circular movement from the wrist between each addition of the standard solution from the burette. (H) Residual titration. This method is employed when the indication of the completion of a reaction is not easily seen. It consists in adding a definite excess of the reagent, and then, by means of another volumetric solution which gives a precise indication, ascertaining the amount of the reagent remaining uncombined. This residue, deducted from the total amount of original reagent added, will manifestly leave a difference due to the actual amount of that body taken up in performing the reaction. Sup- posing, for example, we are analyzing a body (W) by finding how many Ccs. of a volumetric solution (S) would be required to be added until no more precipitate forms, but that this exact point is difficult to see. We therefore choose another volumetric solution (S 2 ), that will exactly neutralize S in presence of an indicator giving a definite change of color when the reaction is complete. To W we add, say, 50 Cc. of S (taking care that this amount is more than sufficient to entirely precipitate W), and, having added our indicator, we titrate with S 2 , of which we will suppose we used 10 Cc, Then 508 ioS 2 40 Cc. S, required for the original precipitation. And lastly 40 X the "Cc. equivalent" of W the weight of real article present in the amount thereof weighed out for analysis. Having thus given a general idea of the mode of working, we now com- mence to practise with the chief standard solutions as follows. n, STANDARD ACID SOLUTIONS (Alkalimetry). The standard acids usually employed in volumetric analysis are thus prepared and used : (A) Preparation. (I.) NORMAL OXALIC ACID. Strength: H^C^O^. zH^O 125-10 -4- 2 = 62-55 Gm. per 1000 Cc. This is made by powdering some pure oxalic acid, pressing it between the folds of blotting-paper (to remove any chance moisture), and weighing out exactly 62-55 Gm. in a tared beaker. The powder is then washed out with distilled water from the beaker into the 1000 Cc. measuring flask, which is nearly filled with water and slightly warmed to aid solution. When all is dissolved, no VOLUMETRIC QUANTITATIVE ANALYSIS. more water is poured in till the solution arrives at the mark in the neck of the flnsk, and finally the whole is cooled down to 25 C., and is once more exactly made up to the line with water. (II.) TENTH-NORMAL OXALIC ACID. Strength: 6*255 Gm. per 1000 Cc. Take 100 Cc. of the normal acid, wash into a 1000 Cc. flask, and make up to the mark with distilled water at 25 C. (III.) NORMAL SULPHURIC ACID. Strength: H^SO^ = 97*35 -4- 2 = 48^675 Gm per 1000 Cc. Mix 30 Cc. ordinary strong sulphuric acid (98 per cent.) with 900 Cc. of distilled water, let it cool to 15 C., and then make up to 1050 Cc. This rough acid is then to be standardized as follows : (a) With normal alkali. Put 10 Cc, of the rough acid in a flask, add a few drops of phenol-phthalein, and run in normal solution of KHO or NaHO until a faint permanent pink is produced. Note the number of Cc. of normal alkali used, multiply by 100, and dilute 1000 Cc. of rough acid to this amount. Example loCc. rough acid took 11*2 Cc. alkali ; then 1000 Cc. acid are to be diluted to 1120 Cc., and 50 Cc. of this should exactly neutralize 50 Cc. of normal alkali. (b) With pure anhydrous sodium carbonate (in the absence of reliable normal alkali). Weigh out 2*6327 Gm. pure sodium carbonate, and dissolve in water in a flask ; add a few drops of methyl orange, and run in the rough acid from a burette till the yellow changes to pink. Note the number of Cc. used, and then put 20 times this amount into the test mixer, and make up to 1000 Cc. with water. Note. Pure Na 2 CO 3 is best made by packing a percolator with good sodium bicarbonate, and percolating with distilled water until the fluid, passing through, gives no reaction with AgNO., or BaCl 2 , after acidulating with HNO 3 and HC1 respectively. The contents of the percolator are then dried and heated to redness, and the residue saved as " chemically pure Na.,CO 3 for standardizing acids." (IV.) HALF-NORMAL SULPHURIC ACID. Strength: 24*3375 Gm. per 1000 Cc. Put 500 Cc. normal sulphuric acid into a 1000 Cc. flask, and make it up to the mark with distilled water at 25 C. (V.) TENTH-NORMAL SULPHURIC ACID. Strength: 4*8675 Gm. per 1000 Cc. Put TOO Cc. normal sulphuric acid into a 1000 Cc. flask, and make it up to the mark with distilled water at 25 C. (VI.) NORMAL HYDROCHLORIC ACID. Strength : HCl 36*18 Gm. per 1000 Cc. Make up 130 Cc. of ordinary 32 per cent, acid to 1000 Cc. with distilled water. This makes a rough acid rather too strong, which is standardized as follows : (a) With normal alkali. Put 10 Cc. rough acid into a flask, and titrate STANDARD ACID SOLUTIONS. m with normal alkali as above directed for sulphuric acid. Note number of Cc. alkali used, multiply by 100, and make 1000 Cc. of acid of equal strength. Supposing 10 Cc. rough acid took n Cc. normal alkali, then IOOO X IO = 909*1 Cc. rough acid to be made to 1000 Cc. 50 Cc. of this acid should then exactly neutralize 50 Cc. of normal alkali. (b) With crystallized calcium carbonate (in the absence of reliable normal alkali). CaCO 3 + 2HC1 = CaCl 2 -f CO 2 + H 2 O. 2)99*35 2)72-36 49-675 36-18 Therefore 1000 Cc. of normal acid should dissolve 49*675 Gm. of CaCOs, and 50 Cc. would therefore dissolve 2-4832 Gm. Weigh out 3 Gm. of broken (but not powdered) calc-spar in a small tared beaker, and run on 50 Cc. of rough acid. When all action has ceased, pour off, wash by decantation with cold water, and then pour off close, and dry the beaker and contents by spontaneous evaporation in a warm place. Weigh and deduct from original weight ; difference equals CaCO 3 dissolved. Sup- posing that this difference be 2*75, then: 2731 - 2-483 = -248; therefore the acid was ^ too strong, and requires diluting accordingly. (VII.) HALF-NORMAL HYDROCHLORIC ACID. Strength: iS'oQ Gm. per 1000 Cc. Dilute 500 Cc. normal acid to 1000 Cc. with distilled water at 25 C. (B) Estimation of fixed Alkaline Hydroxides and Borax. Any of the standard acids may be used for this purpose, but, if normal acid be employed, sulphuric is preferable, especially in winter, because normal oxalic tends to crystallize in cold weather. A proper weight of the alkali having been taken and dissolved, or if in solution diluted, a few drops of solution of methyl-orange or litmus are added, and the acid is run in from the burette until the color changes. The addition of the acid is made at the rate of about | Cc. at a time (with constant agitation after each addition) until the color shows signs of turning, then the acid is added in -^ of a Cc. until it changes. In dealing with solid KHO or NaHO, put about i Gm. into a stoppered weighing bottle and weigh accurately. Then dissolve in 50 Cc. water and titrate. For Aq. Ammon. and Sp. Ammon. put about 3 Cc. in a weighing bottle and weigh accurately. Then dilute with 50 Cc. water and titrate, using litmus indicator. The following table shows the convenient quantities to weigh, and the equivalent weight of the substance for each Cc. of normal acid used : Name and formula. Gm. to weigh. Equivalent. Aqua ammonise NH 3 3 Cc. '01693 fort. NH 3 Spiritus ,, NH 3 Liquor potassae KHO ,, sodse NaHO Potassium hydroxide KHO Sodium NaHO 3Cc. 2 Cc. 27-87 I9-90 I -oo (about) I'OO 01693 01693 05574 03976 05574 03976 Liquor calcis is titrated with ^ acid and phenol-phthalein indicator. 50 Cc. is taken for analysis, and it should use 19 Cc. acid, each Cc. of which = -003678 Ca(HO) 2 . 112 VOLUMETRIC QUANTITATIVE ANALYSIS. The following are typical equations of the chief reactions : (a) Potassium hydroxide or sodium hydroxide or their solutions. H 2 SO 4 + 2NaHO = Na 2 SO 4 + 2H 2 O. HjSO, + 2KHO = K 2 S0 4 + 2H 2 0. (b) Liquor ammonite fort, and liquor ammonia. H 2 S0 4 + 2NH, . H 2 = (NH 4 ) 2 S0 4 + 2 H 2 O. (f) Borax (with methyl orange). + NA^Oy . ioH 2 O = N^SC^ + H 2 B 4 O 7 + ioH,O. Equivalent of N acid. 068635 08343 of acid. 049705 (C) Estimation of Alkaline Carbonates. By titration with normal sulphuric acid, with methyl orange as the indicator, because the CO 2 given off does not affect this indicator. The acid is added till the color just changes from yellow to pink. The change is better seen when a very small quantity of the methyl orange is used, just sufficient to tinge the liquid pale yellow. For KHCO 3 and Na 2 CO 3 the U.S.P. employs acid. The following table shows the convenient quantities to weigh, and the equivalent of the substance for each Cc. of normal acid or half-normal expended : Gm. to Equivalent Equivalent Name and formula. weigh. Potassium bicarbonate KHCO 3 .... I'OOO ,, carbonate K 2 CO 8 I'ooo Sodium bicarbonate NaHCO, .... 2*000 ,, carbonate Na 2 CO 3 rooo . . -026327 ,, ,, monohydrated Na 2 CO 3 . H 2 O . rooo . . '030797 The following are typical equations for the chief reactions involved : {a) Sodium carbonate monohydrated. H 2 SO 4 + Na^CO, . H 2 O = Na 2 SO 4 + CO 2 + 2H 2 O. (b) Sodium bicarbonate. H 2 S0 4 + 2NaHCO s = Na 2 SO 4 + 2CO 2 + 2H 2 O. (D) Estimation of Organic Salts of the Alkalies. Organic salts of potassium, sodium, or lithium are examined by weighing out the salt in a platinum or porcelain crucible, and then heating to redness in contact with the air until all is perfectly charred. The crucible is then cooled, and its contents dissolved in boiling water and filtered into a flask, and the filter washed with boiling water until the washings do not affect red litmus paper. The contents of the flask are then colored by methyl orange and titrated with standard sulphuric acid, in the manner described above for alkaline carbonates. The ignition causes the conversion of the organic salt into an alkaline carbonate. The U.S.P. employs sulphuric acid for the titration of organic salts, but it prefers to use HC1 for Rochelle salts and sodium benzoate. The following table shows the best quantities to weigh out, and the equivalent weight of the substance for each Cc. of half-normal acid used : Name and formula. Potassium acetate KC 2 H,O, bitartrate KHC 4 H 4 O 8 . ,, citrate K 3 C a H 5 O 7 . ,, sodium tartrate KNaC 4 H 4 O 6 Sodium acetate NaC 2 H 3 O 2 . 3H 2 O ,, benzoate NaC 7 H 6 O 2 ,, citrate 2Na.,C 6 H 5 O 7 ~+ II H 2 O salicylate NaC 7 H 6 O, 4H 2 Gm. to acid weigh. 2 equivalent. I '000 04872 I'OOO 09339 I -000 0507 rooo 070045 I'OOO 06755 rooo 07150 I'OOO 0591 I'OOO 07944 <; STANDARD ACID SOLUTIONS. 113 The following are specimens of typical equations for some of the above reactions, on the model of which the rest can easily be constructed : (a) Cream of tartar. 2KHC 4 H 4 O 6 + 50, = K,CO 3 + 7CO, + sH 2 O ; then K,CO 3 + H.,SO 4 = K..SO. + CO 2 + H,O ; therefore H 2 SO 4 ~=2KHC 4 H 4 O 6 . (b) Neutral potassium tartrate. 2(K 2 C 4 H 4 O (i . H 2 O) + sO 2 = 2^003 + 6CO 2 + 6H.,O ; then 2H 2 SO 4 + 2K 2 CO 3 = 2K 2 SO 4 + 2CO 2 + 2H 2 O~; therefore 2lI,SO 4 = 2K 2 C 2 H 4 O 6 . H 2 O. (c) Rochelle salt. 2(KNaC 4 H 4 O fi . 4H.,O) + 5O 2 = 2KNaCO 3 + 6CO 2 + I2H 2 O ; then 2KNaCO 3 + 2H.,SO 4 = 2KNaSO 4 + 2CO 2 + 2H 2 O ; therefore 2H 2 SO 4 = 2KNaC 4 H 4 O 6 . 4H 2 O ; (d) Potassium citrate. 2K 3 C 6 H 5 7 + 9 2 = 3K 8 CO, + 9 C0 2 + sH 2 O ; then 3 K.,CO, + 3 H 2 SO 4 = 3 K 2 SO, + 3 CO 2 + 3 H 2 O ; therefore 3 H 2 SO 4 = 2K 3 C 6 H 5 O 7 . (E) Estimation of Lead Salts. (a) Plumbic acetate. Weigh i Gm., dissolve in plenty of water (the flask \ full), with a drop or two of acetic acid to clarify, and then carefully drop in normal sulphuric acid till precipitation ceases. The following is the equation : H 2 SO 4 + Pb(C 2 H 3 O 2 ) 2 . 3 H 2 O = PbSO 4 + 2HC 2 H 3 O 2 + 3 H 2 O. (b) Liquor plumbi subacetatis. The U.S. P. uses ^ oxalic acid to precipitate the lead as oxalate, and then estimates the uncombined acid by potassium permanganate, thus : If loGm. of the solution be diluted with distilled water, which has been previously boiled and cooled, to measure 100 Cc., and I 3 '6 Cc. of this be added to 3 5 Cc. of tenth-normal oxalic acid, contained in a graduated cylinder, and, after thoroughly shaking, the mixture be diluted with distilled water to measure 50 Cc., and again well shaken, then, after the precipitate has settled, 10 Cc. of the clear solution, after diluting with about 50 Cc. of water and adding 5 Cc. of sulphuric acid, should require not more than 2 Cc. of tenth-normal potassium permanganate to produce a permanent pink tint (each Cc. of tenth-normal oxalic acid required for the precipitation of the I 3 '6 Cc. of the diluted solution corresponding to I per cent, of lead subacetate). (f) Cases where residual titration is preferable to direct work. (a) Carbonate of ammonia. The action of indicators in the presence of ammonia not being, as a rule, well defined, the U.S.P. prefers to weigh out 2 Gm., dissolve in 50 Cc. each of N sulphuric acid and water, boiled to expel CO 2 , cool and titrate with N. KHO litmus indicator. The Cc. of KHO used deducted from 50 will leave the Cc. of N acid required to neutralize the 2 Gm. of ammon. carb. By the equation : 3 H 2 S0 4 + 2(N 3 H U C 2 5 ) = 3(N H 4 ) 8 SO 4 -f 4CO 2 + 2 H 2 O. each Cc. of normal acid neutralized = '052003 U.S.P. ammon. carb. (li) Insoluble carbonates and oxides. A weighed quantity is dissolved in a definite volume of normal acid and titrated back with normal alkali. The Cc. N. KHO used, deducted from the 8 1 1 4 VOLUMETRIC QUANTITATIVE ANALYSIS. acid started with, gives the Cc. of acid required to dissolve the substance. The U.S.P. applies this to : - Name. Gm. to weigh. Acid to start with Equivalent. Lithium carbonate '5 .20 Cc. Magnesium carbonate . '4 (freshly ignited) . 25 oxide '4 ,, - 2 5 Zinc oxide I 'O .30 036755 '048226 02003 04039 In dealing with ZnO it is best to use normal HC1. (c) Liquor formaldehydi. The U.S.P. process by oxidizing the formaldehyde to formic acid, and then ascertaining the amount formed by residual titration, is as follows : Transfer 3 Cc. of solution of formaldehyde to a well-stoppered Erlenmeyer flask, and weigh accurately. Add 50 Cc. of normal sodium hydroxide, and follow this immediately, but slowly, through a small funnel, with 50 Cc. of solution of hydrogen dioxide, to which a drop of litmus has been added, and which has been neutralized with normal sodium hydroxide. After the reaction has ceased and the foaming has subsided, rinse the funnel and sides of the vessel with distilled water, and, after allowing it to stand ten minutes, titrate back with normal sulphuric acid, using litmus as indicator. Subtract the number of Cc. of normal sulphuric acid consumed from 50 (the number of Cc. of normal sodium hydroxide employed), multiply the remainder by 2-979, and divide the product by the weight of the solution taken ; the quotient represents the percentage, by weight, of absolute formaldehyde in the liquid. Ill, STANDARD ALKALI SOLUTION. NORMAL ALKALI. Strength ; 5574 Gm. KHO in 1000 Cc. or 3976 Gm. NaHO. (A) Preparation of Normal Potassium Hydroxide. As the commercial alkalies are not pure, the U.S.P. standardized this solution against pure potassium bitartrate, which latter it orders to be obtained as follows : To 100 Gm. of potassii bilartras U.S.P. contained in a beaker is added a mixture of 85 Cc. of water and 25 Cc. of diluted hydrochloric acid ; the covered beaker is then placed upon a bath of boiling water and the mixture digested, with occasional stirring, for three hours. After quickly cooling, the solution is drained off from the precipitate, which is washed by affusion and decantation with two successive portions of 100 Cc. each of water j after collecting the precipitate upon a plain filter, the washing with cold water is continued until the nitrate, after adding a few drops of nitric acid, ceases to become opalescent upon the addition of silver nitrate. The precipitate of potassium bitartrate is then dissolved in the smallest possible volume of boiling water (about 1500 Cc. ), filtered, and the filtrate, while being rapidly cooled, is constantly stirred. When the mixture is cold, the crystalline precipitate is collected upon a plain filter, washed with 300 Cc. of cold water, and, after thoroughly draining, dried at 120 C. (248 F.) until of constant weight. It should be kept in dry, securely stoppered bottles. Having thus procured the pure standard, the normal alkali is made as follows : Dissolve 75 Gm. of potassium hydroxide {potassii hydroxidum, U.S.P.], in sufficient water to measure about 1050 Cc., and fill a burette with a portion of this liquid. Into a flask of the capacity of about 300 Cc. introduce 9*339 Gm. of the potassium bitartrate and 160 Cc. of distilled water. Boil the liquid until solution has taken place, add from 3 to 5 drops of phenol-phthalein indicator, followed by the cautious addition, from a burette, of the potassium hydroxide solution, frequently agitating the flask, boiling, and, toward the end of the operation, reducing the flow to drops until the red color produced by its influx no longer disappears on shaking, but is not deeper than pale pink. Note the number of Cc. of the potassium hydroxide solution consumed, and STANDARD ALKALI SOLUTION. 115 then dilute the remainder of the solution so that exactly 50 Cc. of the diluted liquid at 25 C. (77 F.) shall be required to neutralize the 9*339 Gm. of potassium bitartrate used. EXAMPLE. Assuming that 40 Cc. of the stronger solution of potassium hydroxide first prepared had been consumed in the trial, then each 40 Cc. must be diluted to 50 Cc., or the whole of the remaining solution in the same proportion at 25 C. (77 F.). Thus, if IOOO Cc. should be still remaining, this must be diluted with water to 1250 Cc. After the liquid is thus diluted, a new trial should be made in the manner above described, in which 50 Cc. of the diluted solution should exactly neutralize 9*339 Gm. of potassium bitartrate at 25 C. (77 F.). If necessary, a new adjustment should then be made to render the correspondence perfect. Standard alkali should be kept in bottles fitted with a rubber cork, through which passes a tube filled with soda-lime to prevent the entrance of CO 2 from the air. Normal alkali diluted at 25 C. from 100 Cc. to 1000 Cc. gives tenth- normal, and from 20 Cc. to 1000 Cc. yields fiftieth-normal, alkali, which latter is used in the titration of alkaloids (see Chapter XL). (B) Preparation and Check of Half-normal Alcoholic Alkali. Strength: 27*87 Gm. KHO in 1000 Cc. Dissolve about 40 Gm. of potassium hydroxide, which has been broken into small pieces, in about 20 Cc. of water, and add sufficient alcohol of '809 specific gravity at 25 C. to measure 1000 Cc. After setting aside in a well- stoppered bottle for one day, the clear supernatant solution should be quickly decanted into a bottle provided with a well-fitted rubber stopper. This rough solution is then to be standardized against 1-8678 Gm. of pure potassium bitartrate dissolved in 100 Cc. water, exactly as above described, but the dilution to strength being of course made with alcohol instead of water. Should it be found more convenient, it may also be standardized against half-normal HC1 with phenol-phthalein as indicator. alcoholic potash is used in the assay of certain organic substances, such as oils and fats (see Chapter XL). (C) Preparation and Check of Normal Sodium Hydroxide. Dissolve 54 Gm. of sodium hydroxide (Sodii hydroxidum^ U.S.?.) in sufficient water to measure 1050 Cc., and fill a burette with a portion of this liquid. Now proceed to standardize as above given for normal KHO. 50 Cc. of normal NaHO at 25 C. must exactly neutralize 9*339 Gm. pure KHC 4 H 4 Oc. (D) General Acidimetry. Standard alkali is used for taking the strength of acids by simply weighing out a quantity of the acid, and then running in the soda in presence of phenol-phthalein, with the precaution already described on page in. The following are some of the more important equations : O) KH O + HC1 = KC1 4- H,O. . (0 KHO + HC.,H a O, = KC,H 3 O + H..O. (V) 2KHO + H,S(J 4 = KL,S0 4 + 2 H 2 O. * (*)' 2KHO + H.C 4 H 4 O 6 =K,C 4 H 4 O, + 2H..O. (/) 3KHO + H 3 "C 6 M 5 O 7 . H 2 O = K^^O, + 4 H,O. The following table shows the convenient amount of each acid to weigh out, u6 VOLUMETRIC QUANTITATIVE ANALYSIS. the best indicator, and the equivalent weight of real acid for each Cc. of normal alkali used : Quantity taken. Indicator. Equivalent. . 5 '96 Gm. Phenol-phthalein '05958 . 23-80 3-0 Cc. J5 }> I'oo Gm. h 06154 1737 5, 06950 3-0 Cc. Methyl orange 03618 3 '62 Gm. 5 } } . 6-55 5, >5 06553 55 55 55 , , 4'47 ,5 Phenol-phthalein 08937 3-0 Cc. Methyl orange 06257 6'257 Gm. 5 ,, 3-0 Cc. 4-868 Gm. 55 55 3723 I'O Phenol-phthalein '048645 Methyl orange '048675 Phenol-phthalein '07446 16212 Name. Acidum aceticum HC a H 3 O 3 .... dilutum HC 2 H 3 O., glaciale HCJLA - ,, boricum H 3 BO S .... ,, citricum H ? C 6 H 5 O 7 . H,O ,, hydrochloricum HC1 ,, dilutum HC1 . ,, hypophosphorosum HPH 2 O 2 dilutum HPH 2 O 2 . lacticum HC 3 H 5 O 3 .... nitricum HNO 3 .... dilutum HNO 3 . phosphoricum H 3 PO 4 dilutum H 3 PO, . sulphuricum H 2 SO 4 .... ,, aromaticum H.,SO 4 dilutum H,SO 4 tartaricum H.,C 4 H 4 O 6 . trichloraceticum CC1 3 . COOH . The U.S.P. prefers to use normal NaHO for titrating boric and trichlor- acetic acids, for all the rest it uses normal KHO. Where Cc. are given in the above table instead of Gm., it means that this number of Cc. is to be put into a weighing bottle and then exactly weighed and calculated accordingly. The acidimetry of phosphoric acid is dependent on the indicator employed. If we use phenol-phthalein (as in U.S. P.), we complete the formation of the dibasic phosphate at the change of color thus : while with methyl orange the completion of the formation of the monobasic phosphate is indicated at the change thus : (6) H 3 PO 4 + KHO = KH 2 PO 4 +H 2 O. Note. Hydriodic, hydrobromic, hydrocyanic, and sulphurous acids are not valued by their acidity, but are titrated as shown on pp. 117 and 120. IV. STANDARD SOLUTION OF ARGENTIC NITRATE. Strength: Tenth-normal -^ = i6'869 Gm. per 1000 Cc. '(A) Preparation. Dissolve 16*869 Gm. of silver nitrate which, previous to weighing, has been pulverized and dried in a covered porcelain crucible in an air-bath at 130 C. (266 F.) for one hour, in sufficient water to measure, at 25 C. (77 F.), exactly 1000 Cc. Keep the solution in dark amber-colored, glass-stoppered vials, carefully protected from dust and sunlight. Check. As argentic nitrate is not always pure, this solution may be standardized by weighing out o'ii6 Gm. of pure powdered sodium chloride, dissolving it in water, adding sufficient potassium chromate indicator to color it yellow, and then running in the silver solution, with constant stirring, until the last drop just causes the color to change from yellow to pink. This should take 20 Cc. of silver solution. If the silver solution be too strong, it should be diluted by the rules already given (see ante) ; but if too weak, it must have more AgNO 3 added, and then again checked and diluted. Preparation of pure sodium chloride. Make a saturated solution of the best commercial salt, and pass in dry hydrochloric acid gas till precipitation ceases. Separate the crystalline precipitate, and dry at a temperature below redness, but sufficiently high to expel all traces of free acid. STANDARD SOLUTION OF ARGENTIC NITRATE. 117 (./>') Estimation of Halogens in Soluble and Neutral Salts. Tenth-normal silver solution is used for the estimation of haloid salts by weighing out any quantity ranging between *2 and '5 (2 or 5 Decigm.), dissolving and titrating, K 2 CrO4 being used as the indicator, exactly as above described. This process is only accurate in a perfectly neutral solution. If the solution be acid, then the estimation must be done by residual titration with KCNS (see p. 119). The following are some typical equations : (a) Potassium bromide AgNO 3 + KBr = AgBr + KNO 3 . (/;) Ammonium bromide. AgNO 3 + NH 4 Br = AgBr + NH,NO 3 . (c) Potassium iodide. KI + AgNO 3 = Agl + KNO 3 . Note. Bromides, if adulterated with iodides, will take less silver than they ought, but if the impurity be chloride, they will take more. Therefore they must neither take less nor more than the correct amount. The principle on which an excess of silver used can be calculated to per- centage of KC1 present in any sample of KBr is best explained by an example. 236 Gm. of impure KBr was found to take 21 Cc. of -^ AgNOs: what percentage of KBr did it contain? 236 KBr would require 20 Cc. ~-^ AgNO 3 . 236 KC1 3r87 Cc. T N g- AgN0 3 . Theoretical difference 11-87 due to KC1 ; but in this case the practical difference was 3187 21 = io - 87. Therefore 10^7x100 = 9r575 per cent> of KBr> leaving 8-425 KC1, 1 1 '87 or 21 20=1, and ^ = 8-425 per cent, of KC1 and 91 -575 KBr, 1 1 '87 which is as nearly correct as can be obtained arithmetically. The following table shows the salts thus estimated,' with the convenient quantities to weigh out and weight of each salt equivalent to i Cc. of tenth-normal silver nitrate : Name and formula. Hydrobromic acid (exactly neutralized) . Ammonium bromide NH 4 C1 chloride NH 4 C1 . Lithium bromide LiBr .... Potassium bromide KBr .... chloride KC1 . Gm. to weigh. . '804 . -30 'IO . "20 . -30 Equivalent. . '08036 '009729 . -005311 '008634 . '011822 'OO74O4. ,, iodide KI ... t;o '016476 Sodium bromide NaBr .... ,, chloride NaCl . -30 'IO . -010224 '005806 ,, iodide Nal . ro '014878 Strontium bromide SrBr., + 6H.,O Zinc bromide ZnBr. 2 .... ,, chloride ZnCl./ . . -30 '30 '3 . -017647 . -OIIl8l '006763 (C) Estimation of Hydrocyanic Acid. Silver solution is also used for taking the strength of hydrocyanic acid, which may be done by two methods as follows : (A) Half precipitation process. By this method the ~$ AgNOa is added in presence of excess of alkali with a little potassium iodide as indicator. The silver at first combines with the alkali and then forms a soluble double cyanide of silver and the alkali, and so soon as this reaction is complete a precipitate is produced with the indicator. Thus when this precipitate appears it shows that exactly half the cyanide present is combined with the n8 VOLUMETRIC QUANTITATIVE ANALYSIS. silver, therefore each Cc. of -^ silver solution used = '-{ ( ~ or '005368 HCN. The U.S. P. instructions are as follows : If 5 Gm. of diluted hydrocyanic acid be diluted with distilled water to measure 50 Cc., then 26-9 Cc. (26-84 Cc.) of this solution, after the addition of 5 Cc. of ammonia water and 3 drops of solution of potassium iodide (20 per cent, strength), should require for the production of a slight permanent precipitate the addition of not less than 10 Cc. of tenth-normal silver nitrate. If the dilution, etc., be calculated, it will be seen that 2 684 Gm. of U.S. P. acid are taken. This requires 10 Cc. yjj- AgNOj, therefore : 005368 x 10 --05368 and '05368 x loo = 2 ^ cem ^ RCN 2 '604 Potassium cvanide is done in the same way, using '647 Gm., and as AgNO 3 = 2KCN, each Cc. of T \ AgNO 3 = "012940 KCN. (B) Complete precipitation process. Put the hydrocyanic acid into a 100 Cc. flask with sufficient water and MgO to make an opaque mixture of about 10 Cc. Add 2 or 3 drops of solution of potassium chromate, and titrate as directed for haloid salts. The equation being HCN + AgNO s = AgCN + HNO :i , each Cc. of silver used will represent '002684 HCN. The U.S. P. employs this method for the assay of oil of bitter almond as follows : Mix, in a 100 Cc. flask, i Gm. of the oil of bitter almond to be tested, with sufficient water and freshly precipitated magnesium hydroxide (free from chlor- ides) to make an opaque mixture of about 50 Cc. Add to this 2 or 3 drops of potassium chromate, and then from a burette add tenth-normal silver nitrate until a red tint is produced which does not again disappear by shaking ; not less than 7-5 Cc. nor more than 14*9 Cc. of tenth-normal silver nitrate should be required, each Cc. corresponding to 0*002684 Gm. of hydrocyanic acid. V. STANDARD SOLUTION OF SODIUM CHLORIDE. Strength: Tenth-normal ~ = 5*837 (5*84) Gm. per 1000 Cc. (A) Preparation. Dissolve 5*837 Gm. pure NaCl in 900 Cc. of water, and when brought exactly to 15 C. make up 1000 Cc. Each Cc. = '005837 Gm. real NaCl. Pure sodium chloride is made as above described (p. r 16), or perfectly colorless and transparent crystals of rock salt may be employed. (B) Uses. For the estimation of silver in solutions of its salts, the titration being continued (with good stirring occasionally) until the last drop causes no further precipitate of AgCl. Insoluble salts, such as Ag 2 O, are dissolved in a sufficiency of dilute nitric acid, avoiding any great excess. Tenth-normal NaCl can also be employed to check the strength of tenth-normal AgNOs solution (which it should exactly equal Cc. to Cc.), as more convenient than weighing out NaCl every time. The following table gives the equivalent for each Cc. of tenth-normal NaCl : Name and formula. Gm. to weigh. Equivalent. Argentic nitrate AgNO. t ... '5 ... '016869 ,, oxide Ag./J .... '232 . . . '011506 Argenti nitras tlilufus . . . I 'oo . . . '016869 When the silver solution is neutral, it is often better to add a known volume of tenth-normal NaCl, more than sufficient to precipitate all the silver, and then having added potassium chromate as indicator, to proceed by residual titration with tenth-normal AgNOs. The U.S. P. applies this method to all forms of silver nitrate. STA NDA RD SOL UT1ON OF POT A SSIUM THIO C YA NA TE. \ \ g VI. STANDARD SOLUTION OF POTASSIUM THIOCYANATE (SULPHOCYANIDE). Strength: Tenth-normal -^ = 9*653 Gm. per 1000 Cc. (A) Preparation and Check. Dissolve 10 Gm. of potassium thiocyanate (sulphocyanide) in 1000 Cc. of water. This solution is a little too strong, and must then be standardized as follows: Take in a flask 10 Cc. of tenth-normal silver nitrate, acidulate with 3 Cc. of nitric acid, and then add as indicator 3 Cc. of a solution of ferric ammonium sulphate (10 per cent, strength). Now titrate with the crude thiocyanate solution by shaking constantly until a slight permanent reddish tint is produced. The thiocyanate will first precipitate the silver as thio- cyanate, and when that is finished will strike the well-known reddish color of ferric thiocyanate with the indicator. The red is always produced when the solution is dropped in, but it disappears on shaking so long as any silver remains unprecipitated. Note the number of Cc. of crude thiocyanate used, and make every 10 Cc. of that solution up to this number. Thus supposing that 10 Cc. tenth-normal silver nitrate took 10*5 Cc. crude sulphocyanate, and we had 980 Cc. left to make correct, then io-5* 980 = I029 cc. 10 So that 980 Cc. made up with distilled water to 1029 Cc. will give true tenth-normal thiocyanate, of which 50 Cc. should exactly balance 50 Cc. tenth-normal silver nitrate when tried again in a similar manner. Each Cc. of the perfected solution will then contain "09653 KCNS. () Estimation of Silver in Acid Solutions. This is done exactly as above described, and may be usefully applied to any compound of silver soluble in nitric acid. The equivalents for each Cc. are '010712 Ag and '016869 AgNOs- (C) Estimation of Haloid Salts in Acid Solutions. This is an application of residual titration, known as Volhard's method, and is, in certain cases, a much better idea for the estimation of haloid salts than the direct method with the chromate indicator, because it may be used in the presence of nitric acid, thus enabling a chloride, bromide, or iodide to be estimated in presence of a phosphate or other salt which precipitates silver in a neutral solution. It depends upon entirely pre- cipitating the chloride in the presence of nitric acid by a known volume of tenth-normal silver nitrate, and then estimating the excess thereof, left uncombined with the chloride, by standard solution of ammonium thiocyanate (sulphocyanate), using solution of ferric ammonium sulphate for the indicator as above described. The U.S.P. applies it to the estimation of the iodide in syr. acidi hydriodiri and in syr. ferri iodidi. It takes 3173 Gm. of syr. ac. hydriodici, makes it up to 50 Cc. with water, and then uses 10 Cc. of this solution for analysis with 10 Cc. water, 8 Cc. f^ AgNO 3 , 5 Cc. diluted nitric acid, and 3 Cc. ferric ammonium sulphate solution, and then titrates with y^ KCN as above. For syr. ferri iodidi it makes up 10 Cc. to 100 Cc. with water, and takes 15-4 Cc. for analysis, using 15 Cc. water, 6 Cc. of T N ^ AgNOs, 2 Cc. each diluted nitric acid and ferric ammonium sulphate, and finally titrating with -^ KCN as already described, and not more than 3 Cc. or r Cc. respectively of KCN should be required. Taking the case of syr. ferri iodidi, we have Tenth-normal silver added . . 6 Cc. ,, sulphocyanate taken I Cc. Difference . . 5 Cc., due to the silver precipitated as iodide. 120 VOLUMETRIC QUANTITATIVE ANALYSIS. Then 5 x '015365 = '076825 real FeI 2 present, or 5 per cent, of the i '54 Gm. syrup really started with. The process is also employed by the U.S. P. in the analysis of the following : Name and formula. Gra. to weigh. Equivalent. Hydiiodic acid (dil.) HI. . . . 2-54 . . '012690 Strontium iodide SrI 2 .... '50 . . '022301 Zinc iodide ZnL, ..... -50 .. '015835 VII. STANDARD SOLUTION OF IODINE. Strength: Tenth-normal^ 12 '59 Gm. per 1000 Cc. (A) Preparation and Check. Weigh out 1 2 '59 Gm. of pure iodine, and place it in a 1000 Cc. flask with 1 8 Gm. of potassium iodide and about 200 Cc. of water, agitate till dissolved, make up to 1000 Cc. with water, and preserve in small stoppered bottles in a dark place. Each Cc. = '01259 I. Preparation of pure iodine. Heat powdered iodine in a flat porcelain dish on a boiling-water bath, with constant stirring, for 20 minutes. Rub it up in a glass mortar with 5 per cent, of its weight of pure potassium iodide, and return to the dish. Place a clean, dry funnel over the dish and heat on a sand bath, when the pure iodine will sublime and collect on the funnel, from which it is detached, and kept in a well-stoppered bottle. Check. To standardize the strength of the solution (if desired), test it against '2 Gm. (2 Decigm.) of pure As 2 Os as hereafter described. (B) Estimation of Arsenious Acid. For arsenious acid, weigh out i Decigm. of the As 2 C>3, and dissolve it in boiling water by the aid of ten times its weight of NaHCO 3 . Let it cool, add some mucilage of starch, and titrate with the iodine solution until a faint permanent blue color is obtained. Then apply the equation : 2l, 4- As,O 3 + 5H,O - 2H 3 AsO, + 4HI. Each Cc. of y^ iodine used = '004911 A? 2 Os. For liquor acidi arseniosi or liquor potassii arsenitis use 24*6 Gm. in 100 Cc. water, adding 2 Gm. NaHCOs, and then titrating. (C) Estimation of Sulphurous Acid and Sulphites. For sulphurous acid weigh out 2 Gm. from a stoppered bottle, and dilute it with 25 Cc. of water. Add starch mucilage, and run in the iodine solution until the faintest possible per?nanent blue appears. Then apply the equation : I 2 + H,O + SO, . H,O = H,SO 4 + 2HI ; whereby each Cc. T N g- iodine used = '003180 SO 2 . For sulphites dissolve in 25 Cc. of water and proceed as above. The following table shows the convenient amounts to weigh, and the equivalent for i Cc. yjj- iodine of the salts named : Name and Formula. Gm. to weigh. Equivalent. Potassium sulphite K,SOj . 2H,O . . . -485 . . -009648 Sodium bisulphite NaHSO 3 .... '25 . -005168 ,, sulphite NaJ5O 3 . 7 H 2 O .... '63 . -012520 Sulphur dioxide (in sulphurous acid) SO 2 . . 2 - oo . . '003180 (D) Estimation of Antimony Potassium Tartrate. This salt absorbs iodine on a s'milar principle of indirect oxidation to that already shown for As 2 C>3. The reaction may be thus expressed : KSbOC 4 H 4 6 . H,0 + I, + 4 NaHC0 3 + H 2 O = KNaC ,H,O 6 + 2NaI + NaSbO 3 + 4 CO 2 + 4 H 2 O. Therefore each atom of iodine can oxidize | of the molecular weight of the STANDARD SOLUTION OF SODIUM THIOSULPHATE. 121 tartrate. In practice i Gm. of the salt is dissolved in sufficient water to measure 100 Cc., and of this 33 Cc. is taken for analysis. 20 Cc. of cold saturated solution of sodium bicarbonate is added, together with a little starch mucilage, and the whole is titrated with -^ iodine till a faint per- manent blue is produced. The number of Cc. of iodine used multiplied by 016495 gives the amount of real tartrate present, which should be 100 per cent. The NaHCOs is added to convert the insoluble potassium bitartrate shown in the equation into soluble KNaC^jOe, and to combine with the free antimonic and hydriodic acids also produced. VIII. STANDARD SOLUTION OF SODIUM THIOSULPHATE ("HYPO"), Strength: -^ = 24-646 Gm. Na^O^.^H^O per 1000 Cc. (A) Preparation and Check. Dissolve 30 Gm. of crystallized sodium thiosulphate (hyposulphite) in sufficient water to make 1100 Cc. at 15 C. Put 10 Cc. of this "crude hypo" into a flask, add a little starch mucilage, and titrate with tenth-normal iodine until a faint permanent blue is obtained. Note the number of Cc. of iodine used, and make every 10 Cc. of the "crude hypo" up to this bulk with distilled water. Suppose, for example, 10 Cc. of "crude hypo" took 10*8 Cc, ^ iodine, and we had 1080 Cc. of the crude solution left, then 1080 XI0 ' 8 = 1166-4 Cc. of correct ^ "hypo." 50 Cc. of the finished solution must be again titrated, and must take 50 Cc, of YJJ- iodine. It must be kept in dark amber-colored bottles and carefully protected from dust. Each Cc. will contain '024646 real Na 3 SsO 3 . 5H 2 O. Tenth-normal "hypo" deteriorates rapidly, even under the most favorable circumstances, and must therefore be checked against -^ iodine each day it is used, and any deficiency found allowed for in the calculations. Thus, suppose we checked our " hypo " as above explained, and found that 20 Cc. of it only took 19 Cc. of iodine, and then we used the same "hypo" in an analysis which absorbed 40 Cc., we would correct thus : 19x40^^ Cc rea] _ N _ hypo ,> actually absorbed ; and then 38 x Cc. equivalent of substance analyzed gives the amount thereof present. Practical analysts, knowing that they must always check in any case, always titrate with the "crude hypo," and do not trouble to make it exactly Tk, preferring simply to make a calculated correction on every analysis, as indicated by the check for the day previously done against $ iodine. Solution of sodium thiosulphate is used as follows : (B) Estimation of Free Iodine. Put about 5 Gm. in a weighing bottle, weigh accurately, and dissolve in 50 Cc. water by the aid of i Gm. potassium iodide, and then run in "hypo" till the color is reduced to that of a pale sherry ; lastly, add starch mucilage, and go on till the blue produced by the starch is just bleached. Then by the equation, 2(Na 2 S 2 O 3 - 5H,O) + I, = 2NaI 4- Na,S 4 O s + ioH 2 O, it is evident that each Cc. ~ "hypo " = '01259 iodine. (C) Estimation of Free Chlorine or Bromine. For chlorine water. Weigh 17-7 Gm. from a stoppered bottle, pouring it directly into a flask 122 VOLUMETRIC QUANTITATIVE ANALYSIS. containing 2 Gm. of potassium iodide previously dissolved in 50 Cc. of water, and then titrate with "hypo" as already described under (B). The Cl first liberates an equivalent quantity of iodine from the KI, and the " hypo " then acts upon the I 2 so set free, thus : , 2'Na,S,,O 3 . 5H..O) + I, = 2NaI + Na,S 4 O e + ioH,,O. Therefore each Cc. T N ^ "hypo" = '003518 chlorine. On the same principle we would titrate bromine wafer, but in that case each Cc. T N ^ "hypo" would = '007936 bromine. (D) Estimation of Available Chlorine. For chlorinated lime. Introduce into a stoppered weighing-bottle between 3 and 4 Gm. of chlorinated lime and weigh accurately ; triturate this thoroughly with 50 Cc. of water, transfer the mixture to a graduated vessel, together with the rinsings, and add sufficient water to make 1000 Cc. After thoroughly shaking, add to TOO Cc. of the mixture i Gm. of potassium iodide and 5 Cc. of diluted hydrochloric acid. Lastly, titrate with " hypo," adding starch mucilage towards the end of the titration as already described under (,#). Then by the equations O) CaOCl., + 2HC1 = CaCl, + H.,O + Cl,, (<*) CU + 2ia = 2KC1 + L, (0 2(Na,S,O 3 . 5H 2 O) + 1, = 2NaI + Na,S 4 O (i + ioH 2 O, we come to the result already shown for chlorine water namely, that 2(Na,S 2 O 3 . 5H,O) = I, = C1,. Therefore each Cc. ^ "hypo" = '003518 Gm. "available chlorine" in all chlorinated compounds. Liquor sodce chlorinates. Use 7 Gm., with 50 Cc. water, 2 Gm. KI., and 10 Cc. hydrochloric acid, and proceed as for chlorinated lime. The action and calculations are the same, only differing in the first equation, which is : Na 2 OCl, + 2HC1 = 2NaCl + H 2 O + C1 2 . (E) Estimation of Iron in Ferric Salts. When excess of potassium iodide is added to a ferric salt in solution in the presence of hydrochloric acid, and the whole is digested at 40 C. in a closely stoppered bottle for half an hour, the iron in the ferric salt is reduced to the ferrous state, and an equivalent quantity of iodine is liberated. Thus, taking ferric chloride, we would have : Fe,Cl G + 2KI = 2FeCl, + 2KC1 + I,. Therefore each atom of iron so reduced liberates i atom of iodine, and then the iodine so liberated is titrated with -^ "hypo"; and thus we see Na,S./) 3 . 5H,O = I,= Fe 2 . And so each Cc. of -^ "hypo" = '00555 iron in the ferric salt under analysis. In practice we usually weigh '555 Gm. of a solid ferric salt, or i'n Gm. of a ferric liquor, put it into a stoppered bottle of about 100 Cc. capacity, dissolve in or dilute with 15 Cc. of water, add 2 Cc. of hydrochloric acid and i Gm. of potassium iodide, and quickly close the bottle. The whole is then placed in a basin of water heated to 40 C. (104 F.), and maintained at that temperature for half an hour. At the expiration of that time the bottle and contents are cooled to 15 C., and starch mucilage having been added, the contents are titrated in the bottle with -^ " hypo." The number of Cc. of " hypo " used (after correction for check if fiecessary) are then multiplied by the Cc. equivalent of iron as above given. The point of the process is to get STANDARD SOLUTION OF BROMINE. 123 no loss of iodine vapour during the heating, and yet to take care that the bottle does not hurst by the expansion of the contained air by the heat. When -555 Gm. of a ferric salt is taken, each Cc. of T ^ "hypo" used = i per cent, of iron ; but when n i Gm. of a liquor is started with, then each Cc. = '5 per cent, of iron. (F) U.S. P. Assay of Reduced Iron (Ferrum redactuni). Introduce about 2*6 Gm. of iodine into a 100 Cc. flask and weigh accurately, then add 6 Cc. of water, 2 Gm. of potassium iodide, and 0*555 Gm. of reduced iron. Securely stopper the flask, and, after thoroughly mixing the contents by rotating the flask, set it aside for one hour. Then dilute the contents with sufficient distilled water to make the liquid measure exactly 100 Cc., mix well, and to 25 Cc. of this solution slowly add tenth-normal sodium thiosulphate with constant stirring, until the last trace of brown color has been discharged. Divide the weight of iodine taken, by 0*02518, and subtract from the quotient twice the number of Cc. of tenth-normal sodium thiosulphate used ; the remainder represents the percentage of metallic iron present in the reduced iron, and this should not be less than 90 per cent. Note. The percentage purity of the iodine employed should be accurately determined by a previous experiment, and in place of the 2'6 Gm. above directed, its equivalent in pure (100 per cent.) iodine may be taken (see p. 120). IX. STANDARD SOLUTION OF BROMINE. Strength: = 7*936 Gm. per 1000 Cc. (A) Preparation and Check. As it is impossible to keep an actual solution of bromine, we make and keep a mixed one of a bromide and bromate in such proportion that when acidulated with a fixed quantity of acid (5 Cc. HC1) shall give a definite amount of free bromine by the equation 5KBr + KBrOj + 6HC1 = 6KC1 + 3Br, + 3H,O. To do this we follow the procedure of the U.S. P. as follows : Dissolve 3 Gm. of sodium bromate and 50 Gm. of sodium bromide (or 3*2 Gm. of potassium bromate and 50 Gm. of potassium bromide) in enough water to make, at or near 15 C., 900 Cc. Of this solution transfer 20 Cc., by means of a pipette, into a bottle having a capacity of about 250 Cc., provided with a glass stopper ; add 75 Cc. of water, next 5 Cc. of pure hydro- chloric acid, and immediately insert the stopper. Shake the bottle a few times, then remove the stopper just sufficiently to quickly introduce 5 Cc. 20 per cent, solution of potassium iodide, taking care that no bromine vapour escapes, and immediately stopper the bottle. Agitate the bottle thoroughly, remove the stopper and rinse it and the neck of the bottle with a little water so that the washings flow into the bottle, and then add from a burette j^- sodium hyposulphite until the iodine tint is exactly discharged, using towards the end a few drops of starch indicator. Note the number of Cc. of the sodium hyposulphite thus consumed, and then dilute the bromine solution so that equal volumes of it and of T ^ sodium hyposulphite will exactly correspond to each other under the conditions mentioned above. EXAMPLE. Assuming that the 20 Cc. of the bromine solution have required 25*2 Cc. of the hyposulphite to completely discharge the iodine tint, the bromine solution must be diluted in the proportion of 20 to 25*2. Thus, if 850 Cc. of it are remaining, they must be diluted with water to measure 1071 Cc. After the solution is thus diluted, a new trial should be made in the manner above described, in which 25 Cc. of the ~ sodium hyposulphite I2 4 VOLUMETRIC QUANTITATIVE ANALYSIS. should exactly discharge the tint of the iodine liberated by the bromine set free from the 25 Cc. of bromine solution. Keep the solution in dark amber-colored glass-stoppered bottles. (} Estimation of Phenol (Carbolic Acid). The bromine solution is added in fixed excess, more than sufficient to convert all the phenol into insoluble tribromophenol C 6 H 2 Br 3 . OH and the bromine remaining undecomposed is titrated with KI, starch, and -*$ " hypo " as above described. The number of Cc. of " hypo " used having been deducted from the Cc. of -^ bromine started with, the difference x "001556 = real phenol present in the amount of sample weighed out for analysis. The following example is taken from the U.S. P. : Assay of Phenol. Dissolve 1*556 Gm. of the phenol to be valued in a sufficient quantity of water to make TOGO Cc. Transfer 25 Cc. of this solu- tion (containing 0*0389 Gm. of phenol) to a glass-stoppered bottle having a capacity of about 200 Cc., add 30 Cc. of tenth-normal bromine, than 5 Cc. of hydrochloric acid, and immediately insert the stopper. Shake the bottle repeatedly during half an hour, then remove the stopper just sufficiently to introduce quickly 5 Cc. of an aqueous solution of potassium iodide (i in 5), being careful that no bromine vapour escapes, and immediately stopper the bottle. Shake the latter thoroughly, remove the stopper and rinse it and the neck of the bottle with a little water, so that the washings may flow into the bottle, and then add i Cc. of chloroform and shake well. Add, from a burette, tenth-normal sodium thiosulphate until the iodine tint is exactly discharged, and does not reappear after thorough agitation. Note the number of Cc. of tenth-normal sodium thiosulphate consumed (which should not exceed 6 Cc.). The percentage of absolute phenol is found by subtracting the number of Cc. of tenth-normal sodium thiosulphate used, from 30 (the number of Cc. of bromine originally added), and multiplying the remainder by 4. X. ANALYSIS BY DIRECT OXIDATION. (A) General Principles. The two chief direct oxidizers employed in analysis are potassium per- manganate and potassium bichromate, both of which part with oxygen in presence of sulphuric acid, but in different proportions. These actions are represented by the following equations : With bichromate. K,Cr,O 7 + 4H,SO 4 = K, SO 4 + Cr,(SO 4 ) 3 + 4H,O + O 3 ; therefore each molecular weight of bichromate gives three atomic weights of oxygen. With permanganate. K,Mn,O 8 + 3H,SO 4 = K.SO 4 + 2MnSO 4 + O 5 + 3H 2 O ; therefore each molecular weight of permanganate gives five atomic weights of oxygen. We have already seen that the theoretical N solution of hydrogen is i Gm. per 1000 Cc., or 'coi in each Cc. ; and looking to the formula of the simplest compound of H and O, namely water, we notice that i atom O combines with 2 atoms H. It therefore follows that i Gm. of H would combine with 15-88 (T 6) H- 2 = 7-98 (8) Gm. of O. A theoretical N solution of O would thus be 7-94 Gm. per 1000 Cc., and a ~$ solution would be 794 Gm. O per 1000 Cc., and would contain '000794 oxygen in each Cc. In oxidation analysis, therefore, a -^ solution of any oxidant is that weight in Gm. per 1000 Cc. which will give off "794 Gm. oxygen under the conditions in which it is used. ANAL YSIS B Y DIRECT OXIDA T1ON. 1 2 5 Thus taking bichromate we have K 2 C r 2 O 7 = 292 -28 -r 6 = 4*8713 Gm. per 1000 as a yjj- oxidant ; and ion permanganate we have K 2 Mn 2 O 8 = 3i3'96 -7-10 = 3-1396 Gm. per 1000 as a y^ oxidant. Each Cc. of either of these solutions will give '000794 available oxygen, and will therefore produce exactly the same effect in the analysis of anything readily oxidized. Oxidants are never employed in stronger solution than y^, and frequently for delicate work they are made centinormal ( T 5nr)- There are almost unlimited cases in which such solutions may be applied to the various bodies capable of undergoing a definite change by oxidation, but the most common applications are : (i) For the estimation of ferrous salts. If we look at the simplest equation for the transference of iron from the ferrous to the ferric state, we find 2FeO + O = Fe 2 O 3 . So we observe that i atomic weight of O can oxidize 2 atomic weights of Fe, or that 2 7 - 94 = Fe 55-5; molecular weight tnerefore each Cc. of A- oxidant = '00555 metallic iron or 10,000 of any ferrous salt containing i atom of iron in its molecule. Either of the oxidants may be employed for the estimation of ferrous salts. Take, for example, crystallized ferrous sulphate. We have the equations : With bichromate. K,Cr 2 O 7 + 6FeSO 4 . 7H,O + 7H,SO 4 = 3Fe,(SO 4 ) 3 + K,,SO 4 + Cr 2 (SO 4 ) 3 + 49H 2 O. With permanganate. K 2 Mn 2 O 8 4- ioFeSO 4 . 7H 2 O + 8H 2 SO 4 = 5Fe,(SO 4 ) 3 + K 2 SO 4 + 2MnSO 4 + 78H 2 O. In certain ferrous salts, such as phosphate or arseniate^ the molecules of which contain Fes, it is evident that from the equation K,Cr 2 O 7 + 2Fe 3 (AsO 4 ), + 7H,SO 4 = Fe,(SO 4 ) 3 + 2Fe 2 (AsO 4 ) 2 + K 2 SO 4 + Cr 2 (SO 4 ) 3 + 7H 2 O. , ~ c N . , . molecular weight x 3 each Cc. ot YTT oxidant would equal of such salt. 10,000 Such salts are included in the B.P., but not in the U.S.P. The following table gives the equivalents of i Cc. of either oxidant for some of the more important ferrous salts : Name and formula. Gm. to weigh Equivalent. Iron (in ferrous salts) Fe Ferrous carbonate (in ferri carb. sacch.)FeCO 3 . sulphate (cryst.) FeSO 4 . 7H 2 O . anhydrous FeSO (dried U.S.P.) 2 FeSO 4 phosphate B. P. Fe 3 (PO 4 )., . 8H..O arseniateB.P. Fe 3 (AsO 4 ) 2 . 76 895 836 744 00555 "011505 '027601 015085 017767 016733 014867 (2) For the estimation of oxalic acid and oxalates. The following equation shows that to oxidize oxalic acid or an oxalate requires i atomic weight of oxygen for each molecule of oxalate : H 2 C,O 4 . 2H 2 O + O = 2CO 2 + 3H 2 O ; therefore each Cc, of a ^ oxidant will equal H 2C 2 O 4 2H 2 O Qr . Qo6 20,000 equivalent to each Cc. The only oxidant employed in this case is per- manganate. (3) For the estimation of hydrogen dioxides and peroxides. By the equations H,O,+ i 2 6 VOLUMETRIC QUANTITATIVE ANALYSIS. it is evident that i atomic weight of O acts with i molecular weight of the molecular weight r ,,, peroxide ; therefore i Cc. * oxidant = - 1 he only oxidant 20,000 available is permanganate, and the process is official in the U.S. P. : Name and formula. Equivalent. Hydrogen dioxide (in solution)H,O, ..... -001688 Barium dioxide BaO 2 ........ '008408 (4) For the estimation of hypophosphorous add and hypophosphites. The equation shows that each molecular weight of hypophosphorous acid requires 2 atomic t , r i molecular weight ,,. weights of oxygen ; therefore each Cc. TC7 oxidant = - 1 he 40,000 only oxidant used in this case is permanganate, and the table gives the usual information, but the U.S. P. does not employ this method : Name and formula. Gm. to weigh. Equivalent. Hypophosphorous acid HPH 2 O 2 . Sodium hypophosphite NaPH 2 O 2 Potassium ,, KPH 2 O 2 Calcium ,, Ca(PH.,O.,) 2 Ferric Fe,(PH 2 O 2 ) 6 001639 0021837 002588 0021108 002309 (5) For equivalent liberation of halogens from haloid salts. The equation 2KI -i- O + H 2 O = 2KHO + 1 2 shows that each atomic weight of nascent oxygen can liberate 2 atomic weights of a halogen from its salts; therefore each Cc. of ~ oxidant can atomic weight r t , , i i_ r- c \ liberate - - of the halogen. 1 nus each Cc. of y^ permanganate is 10,000 equivalent to '003518 Cl, '007936 Br, or '01259 I. The liberated halogen is then estimated by means of ^ sodium thio- sulphate ("hypo") as already described. (B] Preparation and Uses of Solution of Potassium Permanganate. Strength: f^ = 3*1396 Gm. K^Mn^O^, in icoo Cc. (1) Preparation and Check. (a) Solution for immediate use. Dissolve 3*5 Gm. K 2 Mn 2 O8 in 1000 Cc. of recently boiled and cooled distilled water. This is the crude solution, and must now be checked by placing 10 Cc. $ oxalic acid in a small flask, adding i Cc. of pure strong sulphuric acid, and titrating this liquid while hot with the crude solution (over a sheet of white paper) till a faint permanent pink is obtained. Note the number of Cc. of solution used, and dilute the remainder of the crude solution with similarly treated water until 50 Cc. exactly corre- spond to 50 Cc. T N ^ oxalic acid. Thus, if 10 Cc. -$ oxalic took 9-2 Cc. crude permanganate, we would have 920 Cc. up to 1000 Cc., and then we would (after confirmation of 50 Cc. against 50 Cc. acid) have true y\ permanganate. This solution cannot be depended on unless just made, and if a solution is to be made and stocked more precautions must be taken. These precautions are so well explained in U.S. P. that the directions therein given cannot be improved, and they are as follows : (b) Preparation of f^ permanganate for stock. Introduce about 3*3 Gm. of pure, crystallized potassium permanganate \potassii permanganas, U.S.P.] into a flask, add 1000 Cc. of distilled water, and boil for about five minutes. Close the flask with a plug of absorbent cotton, and set aside for at least two ANALYSIS BY DIRECT OXIDATION. 127 days, so that suspended matter may deposit. After the lapse of this time, pour off the clear portion of the solution into a glass-stoppered bottle. The water to be employed for diluting this solution (which is still too concentrated) should be prepared as directed under Distilled Water \aqua destillata, U.S. P.], adding, however, about i Gm. of potassium permanganate to the water in the retort before beginning the distillation. 1. Introduce into a flask 10 Cc. of an accurately standardized tenth-normal oxalic acid V.S., add i Cc. of pure, concentrated sulphuric acid, and before this mixture cools, gradually add, from a burette provided with a glass stop- cock, small quantities of the permanganate solution to be standardized, shaking the flask after each addition and reducing the flow to drops toward the end of the operation. When the last drop of the permanganate solution added is no longer decolorized but imparts a pinkish tint to the liquid, which remains permanent for one-half minute, note the number of Cc. consumed, and then dilute the trial permanganate solution with the specially prepared distilled water so that it will correspond, volume for volume, at 25 C. (77 F.), with the tenth-normal oxalic acid V.S. (note example under 2). 2. Tenth-normal potassium permanganate V.S. may also be standardized as follows : To a solution of about i Gm. of potassium iodide \J>otassii iodidum^ U.S.?.], in 10 Cc. of diluted sulphuric acid, contained in a flask, add, from a burette provided with a glass stop-cock, 20 Cc. of the potassium permanganate solution to be standardized ; then dilute the mixture at once with about 200 Cc. of distilled water. An accurately standardized tenth-normal sodium thiosulphate V.S. is then slowly added from a burette, while the mixture is vigorously shaken, until the color is discharged. Note the number of Cc. of the latter consumed, then dilute the permanganate solution so that equal volumes of the two solutions correspond to each other under the same conditions at 25 C. (77 F.). EXAMPLE. Assuming that 25 Cc. of the tenth-normal sodium thiosulphate V.S. were required to decolorize the liberated iodine of the mixture, then each 20 Cc. of the potassium permanganate solution must be diluted with the specially prepared distilled water to 25 Cc., or the whole of the remaining solution in the same proportion. Thus, if 920 Cc. remain, it should be diluted to measure 1150 Cc. at 25 C. (77 F.). After the potassium permanganate solution is thus diluted, a new trial should be made in the manner above described, in which 20 Cc. of this solution should require exactly 20 Cc. of the tenth-normal sodium thio- sulphate V.S. to decolorize the mixture. If necessary, a new adjustment should be made to render the correspondence perfect. Potassium permanganate V.S. should be kept in well-closed glass-stoppered bottles, and only burettes provided with glass stop-cocks should be employed in titrating with it. Even when properly prepared and preserved, this solution should be restandardized frequently. (c) Standardization of Crude permanganate solution by a ferrous salt. Many persons prefer this method to that already given above with oxalic acid. The salt employed is ferrous ammonium sulphate, FeSO 4 . (NH 4 ) 2 SO 4 . 6H 2 O, which contains practically \ of its weight of metallic iron. The process is performed by weighing out 7 Gm. of ammonia-ferrous sulphate ( = *i Gm. real Fe), dissolving it in 100 Cc. of distilled water, acidulating with 6 Cc. of dilute sulphuric acid (i to 5), and then titrating with the permanganate until a slight permanent pink is produced, not disappearing on shaking. To see the color, a sheet of white paper should be placed under the flask containing the iron solution, and, at the conclusion of the process, the number of Cc. having been noted, the solution is diluted, on the usual principles, until it takes exactly 18 Cc. to oxidize -i Gm. Fe. 128 VOLUMETRIC QUANTITATIVE ANALYSIS. (2) Estimation of Ferrous Salts. \Yeigh out a proper amount of the ferrous salt, dissolve in 2550 Cc. water, acidulate with 6 Cc. diluted sulphuric acid (i to 5), place the flask over a sheet of white paper, and titrate with y^ permanganate till a faint permanent pink is produced. Note the number of Cc. used, and multiply by the Cc. equivalent of the salt under analysis (see table, p. 125). (3) Estimation of Oxalic Acid and Oxalates. This is performed as already described under "preparation and check" of permanganate solution (see p. 126). The great point is that the solution to be analyzed should be sufficiently warm to give off visible steam. The equivalent of oxalic acid has been already given (see p. 125). (4) Estimation of Hydrogen Dioxide (Peroxide). The principle of this estimation has been already explained and the equiva- lents given on p. 126. The following would be the practical procedure : Assay of sohttion of hydrogen dioxide. Dilute 10 Cc. of the solution with water to make 100 Cc. Transfer 16*9 Cc. of this liquid (containing 1*69 Cc. of the solution) to a beaker, add 5 Cc. of diluted sulphuric acid, and then from a burette -^ potassium permanganate, until the liquid just retains a faint pink tint after being stirred. Each Cc. of the yrr potassium permanganate corresponds to *i of absolute hydrogen dioxide or 0*329 volumes of oxygen. (5) Estimation of Nitrites. This is best done by adding excess of -^ permanganate, and then perform- ing a residual titration with oxalic acid. The following is an example of this method as applied by the U.S. P. to the assay of sodium nitrite : If to 30 Cc. of tenth-normal potassium permanganate, diluted with about 150 Cc. of distilled water, 5 Cc. of sulphuric acid and 10 Cc. of a solution of i Gm. of sodium nitrite in sufficient distilled water to make 100 Cc. be successively added, the liquid brought to a temperature of 40 C. (104 F.) and allowed to stand for five minutes, not more than 375 Cc. of tenth-normal oxalic acid should be required to decolorize the solution (each Cc. of tenth- normal potassium permanganate consumed corresponding to 0*0034285 Gm. of pure sodium nitrite). (C) Preparation and Uses of Solution of Potassium Bichromate. Strength : ^ = 4-8713 Gm. K^Cr^Oi in 1000 Cc. (1) Preparation. Dissolve 4*8713 Gm. pure potassium bichromate in enough distilled water to make exactly 1000 Cc. at 15 C. (59 F.). Note. Pure K 2 Cr 2 O 7 , in addition to ordinary tests, should (according to the U.S. P.) conform to the following tests : In a solution of '5 Gm. of the salt in 10 Cc. of water rendered acid by "5 Cc. of nitric acid, no visible change should be produced either by barium chloride (absence of sulphate) or by silver nitrate (absence of chloride*). In a mixture of 10 Cc. of the aqueous solution (i in 20) with i Cc. of ammonia water, no precipitate should be produced by ammonium oxalate (absence of calcium}. (2) Uses. (a) For the estimation of ferrous salts. An appropriate quantity of the ferrous salt is weighed and dissolved in a flask in 50 Cc. of warm distilled water if soluble, or, if insoluble, dilute H 2 SO 4 is added till the salt dissolves. While this is proceeding a white porcelain slab is dotted over with drops (from a glass rod) of potassium ferricyanide indicator (see p. 106) ; the contents of the flask are then acidified with 10 Cc. of dilute H 2 SO 4 (i to 5), and titrated with the ^ bichromate till a drop taken from the flask on the end of a glass rod and touched on one of the spots of the indicator on the slab just ceases to give any blue, thus showing that all the iron has FEHLING'S STANDARD SOLUTION OF COPPER. 129 been oxidized from the ferrous to the ferric state. The number of Cc. ^ bichromate used x the Cc. equivalent of the salt under analysis (see table, p. 124) gives the weight thereof present in the amount taken for analysis. The process should be conducted rapidly to avoid spontaneous oxidation as far as possible. When applied to metallic iron or ferrum redactum, the metal should be dissolved in diluted HgSO* in a flask fitted with a cork, through which passes a narrow tube to admit the outward passage of the hydrogen evolved and to prevent ingress of air. With ferrous phosphate and sac- charated ferrous carbonate, it is better to replace sulphuric acid by hydrochloric acid and phosphoric acid respectively. (b} for alkalimetry. Solution of bichromate is sometimes employed to set the strength of volumetric solutions of alkalies. In this case the strength is not based upon the oxygen evolved with acid, but upon the following equation : K 2 Cr 2 7 + 2KHO = 2K 2 CrO 4 + H,O. Therefore \ molecular weight K 2 Cr 2 O7 = i molecular weight of KHO, i.e. K,CrX> 7 . 29378 (294) -f- 2 = 146-89 (147) = 55-99 (56) KHO. For alkalimetry, therefore, a decinormal bichromate solution would be made by dissolving 14*689 K 2 Cr 2 O7 in water at 15 C. to 1000 Cc., and each Cc. of such solution would neutralize '0056 KHO or '004 NaHO. If, therefore, we set 50 Cc. of this alkalimetric -~j bichromate against 50 Cc. of alkali, the latter will be correct -, and any acid in turn set against that would also be ~. The indicator used is phenol-phthalein, as in ordinary alkalimetry. This is a very useful method of standardizing volumetric alkali when we are not absolutely certain of the purity of our oxalic acid. The alkali, however, cannot be made stronger than y^, because 147 Gm. of K 2 Cr 2 O7 would not dissolve in 1000 Cc. of water, and therefore it is no use for normal alkalies. (<;) For equivalent liberation of halogens. The y^- bichromate (as oxidant) can do the same work in this respect as the -$ permanganate, and on the same principles. The process is done in presence of sulphuric acid, and the liberated iodine is titrated with $ " hypo." XI, FEHLING S STANDARD SOLUTION OF COPPER. (A) Manufacture and Check by the Ordinary Method. This solution is used for the estimation of sugars, and is made in two parts, as follows : No. I. Take of Sulphate of copper . .... 346*4 grains or 34*64 Gm. Distilled water ^ a sufficiency. Dissolve the sulphate of copper in a portion of the water, and dilute the solution with more of the water to the volume of 5000 grain-measures, or 500 Cc. No. 2. Take of Caustic soda ...... if ounce or 76^5 Gm. Tartarated soda 4 ounces or 1 75 'O Gm. Distilled water a sufficiency. Dissolve the caustic soda and tartarated soda in a portion of the water, and dilute the solution with more of the water to 5000 grain-measures, or 500 Cc. When required for use, mix equal volumes of the solutions No. i and a 9 1 30 VOLUMETRIC QUANTITATIVE ANALYSIS. No. 2. On heating the liquid in a test-tube to boiling, it should remain perfectly clear. Each 10 Cc. of this liquid will represent Glucose -oso Gm. Maltose "0807 Lactose '0678 Inveited cane sugar 'O475 > Inverted starch '045 To check Fehling's solution, weigh out "475 Gm. of pure sugar-candy and dissolve it in 100 Cc. of water in a small flask ; add 3 drops of strong HC1, and boil briskly for ten minutes to invert the cane sugar into glucose. Let it cool, neutralize with KHO, and then make up exactly to 100 Cc. with distilled water. Place this liquid in a burette arranged over a basin placed over the gas, and containing 10 Cc. of Fehling's solution and 50 Cc. of water. When the contents of the basin are boiling, run in the sugar solution until all blue color is destroyed. Then note the number of Cc. of sugar solution used, and whatever that number may be, it will contain the equivalent in sugar of 10 Cc. of " Fehling." If the "Fehling" be correct, 10 Cc. of the standard sugar will be used to entirely precipitate it. It is usually necessary to do the estimation twice, first roughly and then accurately, using the second time drops of K^FeCeNg acidulated with acetic acid on a slab, as an indicator for the disappearance of the last trace of Cu from solution. Another way of inverting a solution of cane sugar into glucose is to add one- tenth of its bulk of* fuming HC1, heat gradually up to 68 C., and then cool. This is the better method when the solution is to be used for the polariscopic estimation of sugar (see Chapter XII.). (} Manufacture and Check by Pavy's Method. Cuprous oxide dissolves in ammonia, forming a colorless liquid. Taking advantage of this point, Pavy treats an ammoniacal cupric solution at a boiling temperature with sufficient saccharine solution to exactly discharge the blue color. The advantage of this method over that above described lies simply in the fact that there is no bulky red precipitate to interfere with the ready observation of the end reaction. To prepare the test solution, dissolve 20*4 Gm. of Rochelle salt and the same weight of caustic potash in distilled water; dissolve separately 4*158 Gm. of pure cupric sulphate in more water with heat ; add the copper solution to that first prepared, and when cold add 300 Cc. of strong ammonia, and distilled water to i liter. The process is conducted as follows : TO Cc. of the ammoniated cupric solution (= 0-005 Gm. of glucose) are diluted with 20 Cc. of distilled water, and placed in a small flask. This is attached by means of a cork to the nozzle of a burette, fitted with a glass stopcock, and previously filled with the saccharine solution previously diluted to a fixed bulk. The cork of the flask should be traversed by a small bent tube, to permit steam to escape. Now heat the flask until the blue liquid boils. Turn the stopcock in order to allow the saccharine solution to flow into the hot solution which should be kept at the boiling-point at the rate of about 100 drops per minute (not more nor much less), until the azure tint is exactly discharged. Then stop the flow, and note the number of Cc. used. That amount of saccharine solution will contain 5 milligrams of glucose. To render the determination as accurate as possible, the solution for analysis should be diluted to such an extent that not less than 4 nor more than 7 Cc. are required to decolorize the solution. To find the total amount of sugar, multiply 0-005 DV tne original total ESTIMA TION OF PHOSPHORIC A CID. 13 1 bulk (in Cc.) of the sugar solution started with, and divide the product by the number of Cc. of solution used from the burette. To observe easily the exact end reaction, a piece of paper or other white body should be placed behind the flask. Mr. Stokes uses the half of an ordinary opal gas globe fixed in the proper position. If the operator objects to the escape of the waste ammoniacal fumes, they may be conducted by a suitable arrangement into water or dilute acid. For a special apparatus for this purpose see the Analyst, vol. xii. (C] Estimation of Sugar. The sugar weighed must not exceed '5 Gm., and must be dissolved in 100 Cc. of water. If the sugar be either glucose or maltose or lactose, it is titrated directly ; but if cane sugar, it is first inverted as above described. By always placing 10 Cc. of " Fehling " in the basin, then whatever number of Cc. of sugar solution we use, that number will contain the equivalent of 10 Cc., and we have only to calculate : As No. of Cc. used : Total volume of sugar solution : Equivalent of 10 Cc. *' Fehling " of the sugar in question : Real sugar present in the quantity weighed out for analysis. (D) Estimation of Starch. Starch is weighed and boiled in a flask with water containing dilute hydro- chloric acid, under an upright condenser, for some hours. It is then cooled, neutralized with potassium hydrate, diluted to a fixed volume (not stronger than i in 200), and then the solution so made is titrated into 10 Cc* of " Fehling." A much improved process will be found in Chapter X. XII. ESTIMATION OF PHOSPHORIC ACID is performed by means of a standard solution of uranic nitrate in the presence of sodium acetate. The necessary solutions are : 1. Standard solution of uranic nitrate, made by dissolving 70 Gm. in 900 Cc. of water, and then, after ascertaining its strength by performing an analysis of 50 Cc. of the standard phosphate solution, diluting with water so that 50 Cc. will correspond exactly to 50 Cc. of that solution. If absolutely pure uranic nitrate were obtainable, theory requires the solution of 71 Gm. in i liter of water to yield a solution which will balance the standard phos- phate (each i Cc. = '01 Gm. of P 2 Os). 2. Standard phosphate solution, made by dissolving 50*42 Gm. of perfectly pure disodium hydrogen phosphate in i liter of water, when each i Cc. will equal *oi Gm. of PgOs. 3. A solution of 100 Gm. of sodium acetate and 100 Gm. of acetic acid in water, and the whole diluted to i liter. 4. Finely powdered potassium ferrocyanide. To perform the process, the solution of the phosphate in about 50 Cc. of water is placed in a basin on the water bath, mixed with 5 Cc. of solution No. 3 (sodic acetate), and No. i (uranic nitrate) is run in from a burette, until a drop taken from the basin on to a white plate just gives a brown color, when a little powdered ferrocyanide is cautiously dropped into its center. The number of Cc. of uranic solution used having been noted, the usual calculations are to be applied. After repeated trials upon 50 Cc. of the standard phosphate solution, so as to thoroughly adjust the strength of the uranic solution, and at the same i 3 2 VOLUMETRIC QUANTITATIVE ANALYSIS. time accustom the eye to observe the exact moment of the appearance of the brown coloration, the process may be practically applied to Manures. The best method of preparing the solution of the manure is to heat 10 Gm. to dull redness for 15 minutes, and when cold to reduce it to a fine powder in a mortar, and add gradually 10 Gm. of sulphuric acid diluted to 200 Cc. with water. Rinse the whole into a stoppered bottle, and make up with water to i liter. Shake up occasionally for an hour, and having then let all settle for three hours, draw off 100 Cc. (= i Gm. manure) for analysis. To this add a little citric acid (10 drops of a cold saturated solution), followed by a slight excess of ammonium hydrate. Again acidify with acetic acid, add 10 Cc. sodium acetate solution, and then use the uranic solution as usual. If all these quantities be rigorously adhered to ; each Cc. of uranic solution used can without further calculation be taken as indicating i per cent, of tricalcium phosphate in the manure. This process is highly recommended by Mr. Sutton, of Norwich, and elaborate details will be found in his work on Volumetric Analysis. XIII. STANDARD SOLUTION OF BARIUM CHLORIDE. Normal 103 '82 Gm. per 1000 Cc. of BaCl^. This is used for taking the amount of a soluble sulphate, by adding it to a known weight of the sulphate dissolved in water acidulated with hydrochloric acid, until precipitation ceases. The process, however, is tedious, and the end of the reaction is not sharp, and it is therefore rarely employed. The following is a specimen of the reaction, using magnesium sulphate : MgSO 4 . 7H 2 O + BaCl 2 = BaSO 4 + MgCl 2 + 7H 2 O. Each Cc. of the standard solution equals '03993 SOs or '04791 SO 4 . The solution is made by dissolving 103*82 Gm. of pure barium chloride dried at 104 C. in i liter of water. XIV. STANDARD MAYER'S SOLUTION. Made by dissolving 13*546 Gm. of pure mercuric chloride and 49*8 Gm. of potassium iodide in water, and then making up to 1000 Cc. This solution is used for the estimation of alkaloids, which should be free from any mucilaginous matter and preferably dissolved in a little dilute sulphuric acid. The reagent is added till precipitation ceases, and the exact equivalent for each alkaloid should be practically checked by operating on a known weight of the pure alkaloid, and then always using the solution under exactly the same conditions in future analysis. In the author's hands the process has not worked very well, except for the amount of emetine in ipecacuanha, which may be rapidly ascertained as follows : 15 Gm. of ipecacuanha are treated -with 1-5 Cc. of dilute sulphuric acid, and sufficient alcohol of 80 per cent, added to make the whole bulk up to 150 Cc. The whole is allowed to stand for 24 hours, and 100 Cc. are decanted off for analysis. The liquid is evaporated until all the alcohol is driven off, and then brought under the burette containing the test solution, which is run in until it ceases to give a precipitate. The final point of the reaction is ascertained by filtering off a drop or two in a watch-glass placed on black paper, and adding a drop of the reagent, when, if no cloudiness appears, the precipitation of the alkaloid is complete. The number of Cc. of the test used multiplied by -0189 gives the amount of alkaloid in 10 Gm. of the sample, which again multiplied by 10 gives percentage. ANALYSIS BY THE NITROMETER. 133 XV. ANALYSIS BY THE NITROMETER. (A) General Remarks. This useful instrument is illustrated in fig. 29. It consists of a measuring tube (A) graduated in Cc., having a funnel-shaped cup (c) connected to it by means of the stopcock (D). This cock is a "three-way" one, and according to the direction in which it is turned, it can make connection and discharge the contents of the cup either into the tube A or out in the waste opening at E; or it can make, or quite shut off, all connection between A and the outer air through E. Connected to A by a piece of flexible indiarubber tube is the ungraduated control tube B. The object of the apparatus is the rapid and accurate measurement, at definite temperature and pressure, of gases evolved during any reaction; and it takes its name from the fact that it was first used to measure the nitric c oxide given off by the decomposition of nitric acid. If we fill the instrument with a fluid (say mercury) right up to the tap, and having closed the tap D, we lower the tube B and admit a little air through E (by opening and again closing the tap), we will have a volume of gas in the measuring tube which we desire to measure under definite conditions. Then (i) by allowing the instrument to stand until its contents must have assumed the temperature of the room, a thermometer suspended to the stand will give the temperature of the gas. (2) By then raising or lowering the control tube (B), so that the level of the liquid both in it and in the measuring tube is the same, it is evident that the pressure inside A is the same as in the room, and reference to a barometer standing near will give that pres- sure. It now only remains to read off the volume of the gas in the measuring tube, and having corrected it to N.T.P. (see page 101), to calculate its weight in Gm. from its volume in Cc., by multiplying the number of Cc. of volume at N.T.P. by the weight of i Cc. of the gas in Gm. This latter is obtained by multiplying '0896 Gm. by /iaJ/the molecular weight of the gas, and then dividing by 1000. Suppose, for example, that we have obtained 20 Cc. of nitric oxide at 15 C. and 750 Mm. barometer, and we require to know the weight of NO so got, we should say : 7 * 20 = IS'788 Co., corrected volume at N.T.P. Fig. 29. () - = '001344 Gm., weight of I Cc. NO. (c) 18788 X '001344 = -0253 Gm., weight of NO found. The various possible applications of this instrument are so numerous that exhaustive details would be impossible in the present work ; but the following should be practised as typical instances of its use : (B) Estimation of the Strength of Spirit of Nitrous Ether. The active principle of this drug is ethyl nitrite. Nitrites when mixed with excess of potassium iodide and acidulated with sulphuric acid cause a liberation of iodine, and evolve all their nitrogen in the form of nitric oxide, thus : C 2 H 5 .NO 2 + KI + H 2 SO 4 = C 2 H 5 .HO + KHSO 4 + I + NO. The process is thus conducted. The nitrometer is filled with saturated solution of sodium chloride, with which, owing to its density, a strong spirit 134 VOLUMETRIC QUANTITATIVE ANALYSIS. will not readily mix. We then put about 30 Gm. of the spirit of nitrous ether, which has been previously shaken with 0*5 Gm. of potassium bicar- bonate, into a tared 100 Cc. measuring flask, and weigh accurately. Add sufficient alcohol to bring the volume to exactly 100 Cc. Introduce into a nitrometer 10 Cc. of this alcoholic solution, followed by 10 Cc. of potassium iodide, and afterwards by 10 Cc. of normal sulphuric acid. When the volume of gas has become constant (within 30 to 60 minutes), read it off. Multiply this volume in Cc. by 0-307, and divide the product by the original weight of the spirit of nitrous ether. At standard temperature and pressure, the quotient will represent the percentage of ethyl nitrite in the liquid, which should not be less than 4 per cent. The temperature correction is one-third of i per cent, of the total percentage just found for each degree, additive if temperature is below, subtractive if above, 25 C. (77 F.). The barometric correction is four-thirtieths of i per cent, for each millimeter, additive if above, subtractive if below, 760. (C) Estimation of the Strength of Amyl Nitrite. Start with about 3 Cc. of amyl nitrite, and having proceeded exactly as for sp. cetheris nit., multiply the volume of gas obtained in Cc. by 4*8 and divide by the original weight of amyl nitrite taken. The sample should not show less than 80 per cent. (Z>) Estimation of Nitric Acid in Nitrates. This depends on the fact that when a nitrate is shaken up with excess of sulphuric acid and mercury the following reaction takes place : 2KN0 3 + 4H 2 S0 4 + 3 Hg = 3HgS0 4 + K 2 SO 4 + 2NO + 4 H 2 O- thus showing that each molecule of the nitrate radical gives off a molecule of NO. If any chlorides or other haloid salts be present, they are first removed by adding a slight excess of argentic sulphate to the solution and filtering. No quantity of A nitrate exceeding 2 Decigm. should be used, other- wise more gas may be evolved than the instrument will conveniently hold. The nitrometer is charged with mercury, and the nitrate solution, which should not exceed 5 Cc., is put into the cup and passed therefrom into the measuring tube, followed by excess of strong sulphuric acid. The instrument is well agitated for some time, and when action has ceased and the contents have cooled down to the temperature of the room, the level is adjusted and the volume of NO read off and calculated. All the precautions already mentioned must be observed. If any nitrites be present, they affect the accuracy of the estimation, being also decomposed to nitric oxide. (E) Estimation of Soluble Carbonate. It has been proposed to use the nitrometer for taking the strength of the medicinal solution of ammonium carbonate in the spirit known as spiritus ammonia aromaticus. A given volume of the spirit is placed in the cup and introduced into the nitrometer charged with mercury. This is followed by an excess of dilute hydrochloric acid, and the carbon dioxide evolved by the action of the acid upon the carbonate is measured. The percentage of ammonium carbonate may then be calculated, or an empirical comparison of volume on the principle of that already described for spirit of nitrous ether may be applied. According to Mr. Gravill, the originator of the test, good ANALYSIS BY THE NITROMETER. 135 aromatic spirit of ammonia should give off seven times its volume of carbon dioxide after allowing a correction for the slight solubility of the gas in the liquid with which it is inclosed. (F) Estimation of the Strength of Solutions of Hydrogen Peroxide. This depends upon the fact that, when hydrogen peroxide acts upore potassium permanganate, acidulated with sulphuric acid, oxygen is evolved* One half of this oxygen is due to the peroxide and the other to the perman- ganate. The nitrometer should be charged with concentrated solution of sodium sulphate (the B.P. uses brine), and i Cc. of the solution introduced from the cup, followed by 12 Cc. of a mixture of i Cc. H 2 SO 4 , 2 Cc. of 5 per cent, solution of K 2 Mn 2 O8 and 7 Cc. H 2 O. The contents of the measuring tube, after the reaction is complete, must remain colored violet, thus showing that sufficient permanganate has been employed. B.P. solution of hydrogen peroxide should, when thus treated, give not less than 18 and not more than. 22 times its volume of oxygen. (G) Estimation of Urea in TJrine. This process depends on the fact that when urea is decomposed by an alkaline hypobromite or hypochlorite, it gives off its nitrogen in the free state, the following reaction taking place : N 2 H 4 CO + sNaBrO = sNaBr + N 2 + CO 2 + 2H 2 O. A small flask is fitted with a tight cork, through which passes a funnel' tube closed by a clamp and reaching to the bottom of the flask, and also a bent delivery tube just passing through the cork. 5 Cc. of the urine is- placed in this flask, and the nitrometer having been filled with water the flask- is attached to the tap of the nitrometer at the end E (see fig. 29, page 133). 20 Cc. of a solution of bromine in sodium hydrate solution is then placed in the funnel and allowed to run into the urine, and the clamp immediately closed. At the same moment the tap of the nitrometer is so placed as to establish connection between E and the measuring tube. A little warm water in a basin is applied to the flask to hasten the reaction, and when no more gas is evolved, the tap is closed, the temperature and pressure adjusted, and the volume read off as usual. Each Cc. of gas at N.T.P. represents '0029 Gm. of urea present in the 5 Cc. of urine acted upon. Fig. 29*2 represents a very simple apparatus that can be improvised in a shop or dispensary. 5 Cc. of urine are placed in the test tube (A), and 20 Cc.. of hypobromite solution (or strong liquor sodcz chlorinate will do as well) into the bottle B. The bottle c is filled with water, and its delivery tube is suspended in a graduated Cc. measure. When all is tight the urine is caused to mix with the reagent by tipping up B, and the gas produced passing into c displaces water, which latter runs into the measure. The number of Cc. of water thus collected in the measure multiplied by '058 gives the percentage 01 urea in the urine. It is manifest that i fluid dram may be taken, and the measure used may be an ordinary 2 oz. dispensing one (where only English weights and measures are handy), when each fluid dram of water in the measure at the finish will equal 29 per cent, of urea. 136 VOLUMETRIC QUANTITATIVE ANALYSIS. XVI. COLORIMETRIC ANALYSIS. General Remarks. This is a variety of volumetric analysis in which the amount of a substance present in solution is found by adding, to a given volume, a fixed quantity of a reagent and observing the color produced. This color is then matched by adding, to an equal volume of distilled water, the same mixed quantity of reagent, and running in a volumetric solution of the pure substance until the same tint is produced. Evidently when this point is reached the amount of substance present in the solution under analysis equals that in the volumetric solution used for the comparative experiment. The applications commonly occurring of this method are : (A) Estimation of Ammonia by " Nesslerizing." For this process the following solutions and apparatus are required : (a) NessleSs solution. Dissolve 35 parts of potassium iodide in 100 parts of water. Dissolve 17 parts of mercuric chloride in 300 parts of water. The liquids may be heated to aid solution, but if so must be cooled. Add the latter solution to the former until a permanent precipitate is produced. Then dilute with a 20 per cent, solution of sodium hydrate to 1000 parts; add mercuric chloride solution until a permanent precipitate again forms ; allow to stand till settled, and decant off the clear solution. The bulk should be kept in an accurately stoppered bottle, and a quantity transferred from time to time to a small bottle for use. The solution improves by keeping. (b) Standard ammonia solution. Dissolve 3*15 Gm. pure ammonium chloride in 1000 Cc. of distilled water free from ammonia. For use, dilute 10 Cc. of this solution to 1000 Cc. with ammonia free distilled water. Each Cc. of the diluted solution will then contain *oi Milligm. of NHs (i.e. "ooooi Gm.). (c) Two narrow cylinders of colorless glass, of perfectly equal height and diameter, holding about 70 Cc., and graduated at 50 Cc. These should either have a milk glass foot or should stand upon a perfectly white paper. (d) A pipette to deliver 2 Cc. (e) A quantity of ammonia-free distilled water. This is obtained by placing a liter of ordinary distilled water in a retort, attaching a condenser and distilling until what passes over ceases to give any color with " Nessler's solution." The remaining water in the retort is then cooled and bottled for use. The liquid in which ammonia is to be estimated (usually a distillate obtained in water analysis) is first made up to a fixed bulk with ammonia-free distilled water, and the bulk noted. It must be so diluted that it only gives a color and not a precipitate with "Nessler." 50 Cc. of this solution are placed in a cylinder, and 2 Cc. of "Nessler" having been added by the pipette, and the whole stirred with a perfectly clean rod, the color produced is observed. A little experience soon teaches the operator to judge the probable amount of ammonia solution required to produce a similar tint. Let us suppose, for example, that the color is judged to be equal to 2 Cc. of ammonia, then we proceed to confirm our idea : 2 Cc. of the standard ammonia solution are run from a burette into the other cylinder, ammonia-free water is added to 50 Cc., COL ORIMETRIC ANAL YSIS. 137 then the 2 Cc. of " Nessler," and the whole stirred with the clean rod. If now, after a few minutes, the colors match, we are correct ; but if not, then we must try again and again with more or less standard ammonia until we get an exact match between the colors in the two cylinders. This having been attained, the calculation is very simple, and will be best explained by an example. Suppose that we start with a distillate containing ammonia and made up to 200 Cc., and that we employ 5 Cc. of standard ammonia solution in the comparison experiment, to match the color produced by " Nessler " in 50 Cc. of such distillate. Then '5 Cc. x '01 = "05, and -05 x 4 = *2 : there- fore the whole 200 Cc. of distillate contained "2 Milligm. of NH 3 . Beginners should train their eyes by observing the colors produced by adding various quantities of standard ammonia to 50 Cc. of ammonia-free water, and then introducing the " Nessler." T V of a Cc. of standard ammonia will produce a very faint yellow, while larger amounts will increase the color to orange, and finally to deep orange-red. We should always wait 3 minutes before observing, as the full color does not appear under that time, and the tem- perature of the room should not be below 12 C. (B) Estimation of Nitrites in Water. See Water Analysis, Chapter X. (C) Estimation of Minute Quantities of Copper or Iron. This has often^to be done in articles of food, such as preserved vegetables. After having been burned, and the ash dissolved in an appropriate acid, a solution is obtained, which is made up to a definite volume. 50 Cc. is treated with a fixed excess of ammonium hydrate in a " Nessler " glass. The same amount of ammonia is added to 50 Cc. of water in another glass, and a very weak standard solution of cupric sulphate is dropped in from a burette until the colors match, and the amount of copper solution used is noted and calculated. Small quantities of ferric iron may also be estimated in the same way by the use of potassium ferrocyanide in the presence of a fixed amount of acidulation with hydrochloric acid, and matching the color by a weak stan- dard solution of ferric chloride. This is often useful in analyzing bread for the presence of alum, when we first weigh the precipitate of aluminium phosphate containing some ferric phosphate, then dissolve it in HC1, find the amount of iron present in this manner, and deduct it, so saving a long separation. CHAPTER VIII. GRAVIMETRIC QUANTITATIVE ANALYSIS OF METALS AND ACIDS. DIVISION I. PRELIMINARY REMARKS. GRAVIMETRIC quantitative analysis is that method by which the substance to be estimated is converted into some chemically definite compound, weighed as such, and the amount of the original substance obtained from this weight by calculation. The same definite compound will answer both for the estimation of its metal and of its acid. For example, if we precipitate a known weight of argentic nitrate with hydrochloric acid we obtain insoluble argentic chloride, which may be filtered out and weighed, and the amount (x) of Ag in the quantity started with calculated therefrom, because AgCl : Ag :: weight of AgCl found : x. 142-3 : 107-11 :: : x. If, on the other hand, we start with a known weight of hydrochloric acid, precipitate it with argentic nitrate, and collect and weigh the argentic chloride formed, we can find the amount (x) of real HC1 actually present in quantity- started with, because AgCl : HC1 : : weight of AgCl found : x. 142-3:36-19:: :x. Before giving individual processes for quantitative analysis, we must first say something about the usual manipulation involved, which will serve as general directions, so saving continual repetition of details. (A) The Preparation of Filters. Ready-cut filters may be procured from the dealers in chemical apparatus. The kind known as Swedish is the best for all cases where the precipitate is finely divided or pulverulent. For gelatinous precipitates, such as ferric hydrate and calcium phosphate, the white English or German filters work more rapidly ; but they should never be used, say, for barium sulphate, or calcium oxalate, as those bodies would very likely pass through the pores of the filter, and so cause a loss in the analysis. Whatever paper be employed, the size for quantitative operations is, for the larger sort six inches in diameter, for the smaller, about two inches. The latter size is used where we have to deal with traces of precipitate only, or when a small quantity of fluid has to be filtered. The paper should yield nothing to dilute acids, and if the ash exceed one milligramme per large filter it should be reduced by placing, say, 138 PRELIMINARY REMARKS. 139 100 cut filters for some hours in a basin filled with a mixture of one volume of HC1 and eight volumes of water. They must be then repeatedly washed with distilled water till quite free from acidity, otherwise they woul J crumble to pieces when being folded. The washing is a very tedious operation indeed, and having been completed, the basin is put on to a water bath till the filters are perfectly dry. (B) Estimation of the Ash of Filters. This is most conveniently done by folding ten filters in a small compass, twisting a long platinum wire round the packet so as to form a cage, holding the free end in the hand and the paper over a previously weighed platinum crucible, while touching it with the flame of a Bunsen burner. The paper burns and the ash drops into the crucible, while any particles of carbon which have escaped combustion are quite consumed by exposing the crucible foi some time to a red heat till the ash gets perfectly white. The crucible after cooling is reweighed, and its increase is the ash of ten filters. Divided by 10, we get the ash of one filter ; and in every case where both filter and precipitate are burned, the ash of the filter thus found must always be deducted from their total weight, and the difference is then the actual weight of the precipitate. Filter papers ready cut and freed, as far as possible, from mineral matter by the action of hydrochloric and hydrofluoric acids can now be purchased. By the use of such papers the filter ash is so reduced that it need not be considered, except in the most delicate investigations. (Q The CoUection and Washing of Precipitates. When the precipitate has been fully formed and the supernatant fluid has become quite clear, the latter is poured on the filter (which is either previously tared or not, according to circumstances), care being taken not to disturb the precipitate. This is done by holding a glass rod in a perpendicular position over the filter, placing the lip of the beaker against it, and causing the liquid to flow steadily down the rod into the filter. When the latter is three-fourths full, the beaker is turned into an erect position and the rod drained against the inside of the lip, and then laid across the top of the beaker until it is time to refill the filter. After thus pouring off as much as practicable, the precipitate remaining in the beaker is treated with water and well stirred. When the whole has once more settled, the clear fluid is again passed through the filter. This operation having been repeated three or four times, the Fi s- 30. precipitate is allowed to pass on to the filter, any particles which stick to the sides of the beaker being removed with a feather or a rod tipped with a small piece of black india-rubber tubing ; and the whole having been thus collected, the washing is continued by means of a washing-bottle (fig. 30), till the precipitate is quite freed from its soluble impurities. For instance, in estimating sulphuric acid, the barium sulphate is washed till the filtrate no longer gives a turbidity with argentic nitrate. Many bodies, as ferric and aluminic hydrate, most phosphates, barium sul- phate, and some of the carbonates, are best washed with boiling water. Others, on the contrary, must be washed with cold water, while a few require washing with special mixtures such as plumbic sulphate, for which we use cold water acidified with some H. 2 SO4 ; magnesium ammonium phosphate, for which cold dilute ammonium hydrate is used, etc. 140 -RA VI METRIC ANALYSIS OF METALS. (D) Drying of Precipitates. After the precipitate has been thoroughly washed and perfectly drained, the funnel containing it is loosely covered over with filter paper and then put into the water oven or air bath till dry. Most precipitates are dried at a temperature of 100 C. (2i2F.), but some of them require a heat of 105 C. (220 F.) before becoming constant in weight. Prolonged and repeated drying is only necessary when, the precipitate is weighed on the filter, as described below. Fig. 31 shows a water oven for drying at 100 C., while fig. 32 shows an air bath for drying at higher temperatures. This bath is fitted with an apparatus (called a thermostat) for automatically controlling the gas supply, and consequently the temperature. Fig. 3*. (E) Igniting and Weighing Precipitates. Miny precipitates must first be ignited before they can be weighed. This is to drive off water, which they may still retain after drying at 100 C., or to reduce them to a more definite condition. For instance, zinc is best weighed as oxide, and therefore the precipitate, consisting of oxycarbonate, is first ignited. Iron is precipitated as hydrate, but the composition of that body not being constant, it is ignited and so made into pure oxide before weighing. As soon, therefore, as the precipitate appears dry, it is carefully detached from the filter and put into a previously ignited and weighed crucible, the filter is burned on the lid (which has been weighed together with the crucible), the ash is thrown into the crucible, and the latter covered with the lid. The Fig. 33- Fig. 34- crucible is now supported by a pipe-clay triangle, and gently ignited at first, to prevent spurting from the sudden evolution of steam or other gases. The lid is now taken off, and the crucible inclined a little, so as to give a free access of air. The ignition is continued for some minutes, and the crucible, having been again covered with a lid, is allowed to cool in a desiccator and weighed. A desiccator is shown in fig. 33, and will be seen to consist of a glass shada PRELIMINA R Y REMA RKS. , ^ , in which is a vessel containing strong sulphuric acid to keep the air under the glass shade always free from moisture. The heat of an ordinary Bunsen burner is generally sufficient for all pur- poses ; but the conversion of calcium carbonate into oxide requires the aid of a gas blowpipe ; while argentic chloride must only be heated over a rose Bunsen or spirit lamp until it just begins to fuse. The filters are, as already shown, burned separately, to prevent any reduction of the precipitate by the carbon of the filter. Some precipitates are not ignited, but weighed on a previously tared filter. Before weighing the filter for which purpose a weighing tube (fig. 34) is used, or the filter is placed between two closely-fitting watch-glasses provided with a clamp to hold them together it must first be dried for fifteen minutes at 100 C. After drying the precipitate, the filter is again placed in the tube or between the glasses and reweighed : the increase shows, of course, the weight of the substance. It is well to re-place the filter in the bath for, say, half an hour, and to weigh again. Should the weight be considerably less, it must be once more put into the bath and reweighed. Another method of weighing precipitates on a filter is to prepare two filters of equal size, A and B. Cut off the bottom point of B, so that A will go inside it with its point projecting through the opening. Now put B on the weight scale of the balance, and cut off minute slices from the top of A until the two are exactly counterbalanced. Place A inside B, and then, having put both in the funnel, collect the preci- pitate, wash and dry as usual, and cool under the desiccator. Lastly, detach B, and use it for a tare, putting it into the weight pan, and then the weights required to balance A and its contents will be the weight of the precipitate, because, both filters having been exposed to the same conditions, the tare is accurate. (F} Estimation of Moisture. A watch-glass is exactly tared on the balance, and then 2 grammes of the substance (in powder, if possible) are carefully weighed upon the glass, and the total weight noted. The glass, with contents, is then placed in the drying oven and heated therein for an hour, at the expiration of which it is removed to the desiccator, and, when cold, is weighed and the weight noted. It is then replaced in the oven for half-an-hour, and the cooling and weighing repeated. If the two weights do not agree within, say, 2 milligrammes, the process is repeated until two concordant weighings are obtained. The weight after drying, deducted from the total weight of glass + substance started with, gives the moisture, which figure multiplied by 50 gives percentage. (G) Estimation of the Ash of Organic Bodies. This determination is necessary in every analysis of a vegetable or animal substance. A platinum dish is heated to redness, cooled under the desiccator, weighed, and the weight noted. A suitable quantity, say 5 to 10 grammes of the substance, is weighed into the dish, which is then arranged on a triangle support over a Bunsen burner and heated to dull redness. If after fumes cease the substance is seen to have assumed a coke-like form, it is removed from the dish into a small, dry mortar, and having been carefully powdered, the powder is replaced in the dish and maintained at a dull red heat until it has become perfectly white, or at least until all carbon has been burned off. If the burning proves very tedious and the last traces of carbon are very difficult to burn, the addition of a light sprinkling of ammonium nitrate will cause the process to complete itself more rapidly. The dish is now cooled under the desiccator and weighed, and the weight of the empty dish having 142 GRAVIMETRIC ANALYSIS OF METALS. been deducted, the difference gives the weight of the ash, which is then cal- culated to percentage. The heat should not be allowed to rise to bright redness, because potassium and sodium chlorides, which are very common constituents of the ash, would be thereby volatilised to some extent and so lost. The estimation of ash soluble in water is frequently of great importance as showing, when too low, that the article has been tampered with so as to remove its active properties. For example, tea which has been used and redried, or ginger, that has been employed to make ginger essence and then redried and sold would both show great deficiency in this respect. To ascertain the amount of soluble ash, the total ash is extracted with boiling distilled water, filtered, washed, and the filter and contents having been dried are ignited and weighed ; lastly, this weight deducted from that of the total ash, gives the soluble ash. (ff) Analytical Factors for Calculating the Results of Analyses. To save the working out of a rule-of-three sum on the result of each analysis it is customary to employ factors. These are obtained by dividing the weight of the required body by the equivalent weight of the body in the form in which it is precipitated. Thus, supposing we are estimating the amount of argentic nitrate present in a solution containing -6 gramme of the salt, and have precipitated and weighed the same in the form of argentic cnloride, we have : Molecular weight of AgNOs i68'6Q Equivalent weight of AgCl l^J : = l ' lS ^> analytical factor. It now only remains to multiply this factor by the weight of the precipitat- to obtain the answer. Let us further suppose that the weight of the precipie tate was -5 gramme, then 1-1854 x -5 = -59270 real AgNO 3 present in the 6 gramme taken ; then 59 2 7 x ^> _ ^.^ per cent real ^gNO 3 present in the sample. DIVISION II. GRAVIMETRIC ESTIMATION OF METALS. I. ESTIMATION OF SILVER. (A) As Argentic Chloride. (Practise upon -5 gramme pure AgNO 3 dissolved in 100 c.c. H 2 O.) Silver is most conveniently weighed as chloride. The silver solution to be estimated is acidified with nitric acid, and hydrochloric acid is dropped in until no more precipitate forms. It is best to have the solution warm, and to stir till the supernatant liquid has got perfectly clear. The clear fluid is now poured off through a filter, and the chloride is washed by decantation with boiling water (always pouring the washings through the filter) till every trace of acid is removed, and subsequently the whole precipitate is brought upon the filter. The filter and contents are then dried in the water oven, and the chloride transferred into a weighed porcelain crucible, and heated over a low flame till it just commences to fuse. The filter is burned on the crucible lid, and the ash treated with a drop of aqua regia, the resulting chloride dried, the lid placed on the crucible, and the whole weighed. The tare of the crucible, lid and filter ash having been deducted, the balance is AgCl, from the quantity weighed out for analysis. ESTIMATION OF LEAD AND MERCURY. 143 (ff) As Metal. (a) In organic salts, by igniting a weighed quantity of the salt in a tared porcelain crucible, and weighing the ash, which will consist of pure metallic silver. (b) In alloys, by cupellation, as follows : The weighed alloy is wrapped in lead foil, placed on a little cup or cupel made of bone ash, and heated to bright redness in a muffle furnace. The lead oxidises and sinks into the cupel, carrying the impurities with it, and leaving a button of pure silver, which is cooled and weighed. 8. ESTIMATION OF LEAD. (A) As Plumbic Oxide. (Practise upon '5 gramme pure plumbic acetate.) The solution containing the substance to be analysed is precipitated with ammonium carbonate in the presence of a little ammonium hydrate. The precipitated plumbic carbonate is then collected on a small filter, washed, and dried. The dry precipitate is removed as completely as possible from the filter-paper, and introduced into a weighed porcelain crucible. The filter having been burned on the lid, and its ash added to the contents of the crucible, the whole is ignited, cooled, and weighed. By ignition the oxide is formed ; and after deducting the weight of the crucible and filter ash, the balance is PbO, from the quantity weighed out for analysis. Organic salts of lead require simply to be ignited in a tared porcelain crucible, with free access of air, adding a sprinkling of ammonium nitrate (to prevent reduction to the metallic state), and weighing the resulting PbO. (B} As Plumbic Chromate. (Practise upon "5 gramme of plumbic nitrate.) The solution is mixed with excess of sodium acetate and precipitated with potassium chromate. The precipitate is collected, washed with water acidu- lated with acetic acid, dried, and ignited in a platinum crucible with the usual precautions. The filter is burned on the lid, treated with a drop or two of nitric acid, dried, and again ignited. The crucible and contents are weighed, and the tare of the crucible having been deducted, the balance is PbCrO 4 , from the quantity weighed out for analysis. Lead may also be precipitated as PbSO*, washed with cold and very dilutf sulphuric acid, dried, ignited, and weighed as such. 3. ESTIMATION OF MERCURY. (A) As Metal. (Practise upon i gramme of " white precipitate," which should yield 77*5% Hg.) Take a combustion tube of hard glass, closed at one end, and put in : (i) a little magnesite MgCO 3 ; (2) the weighed quantity of the mercury salt, mixed with excess of quicklime ; (3) a few inches of quicklime ; (4) a loose plug of asbestos. Draw out the open end of the tube before the blowpipe and bend it down at a right angle. Give the tube a tap or two on the table to insure I44 GRAVIMETRIC ANALYSIS OF METALS. a free passage along the upper part for gases, and place it in a combustion furnace, with its open end dipping under the surface of some water in a small flask. Heat the front of the tube, and go gradually backwards until the whole is red hot, and the CO 2 , given off by the MgCO 3 , has swept all the mercury vapour out of the tube. The mercury collects as a globule, and is transferred to a tared watch-glass, perfectly dried by pressure with blotting-papar, and weighed. A similar globule may be obtained by prolonged boiling of the mercury salt with excess of-stannous chloride strongly acidulated with HC1> the flask used being connected to an upright condenser to save fumes. With HgI 2 granulated copper must be used instead of lime. (B] As Mercuric Sulphide. (Practise upon '5 gramme of mercuric chloride.) Through the solution of the mercuric salt the current of H 2 S is passed till the liquid is saturated. The precipitate is collected on a weighed filter, washed first with water, then with absolute alcohol, and finally, to remove any free sulphur, with a mixture of equal parts of ether and carbon disulphide. After drying at 100 C. and weighing, the balance, after deducting the tare of the filter, is HgS from the quantity weighed out for analysis. 4. ESTIMATION OF CADMIUM. As Sulphide. (Practise upon -5 gramme of CdCO 3 dissolved in diluted HC1.) The solution is precipitated with ammonium hydrate and ammonium sul- phide. The cadmium sulphide is collected in a weighed filter, washed, dried at 100 C., and weighed as CdS. In the presence of metals of the fourth group the solution must be slightly acidified with hydrochloric acid and precipitated by a current of sulphuretted hydrogen. 5. ESTIMATION OF COPPER. (A) As Cupric Oxide. (Practise upon -5 gramme of pure CuSO* . 5H 2 O.) The solution is boiled with a slight excess of sodium hydrate. The precipitate is filtered out, washed, and dried. It is then carefully removed from the paper to a weighed crucible, and the filter having been burned on the lid and the ash added to the contents of the crucible, the whole is well ignited, cooled in a desiccator, and weighed rapidly, because cupric oxide is very hygroscopic. To make sure that the oxide contains no cuprous oxide, it is moistened with a little fuming nitric acid, dried with the lid on, ignited for ten minutes, and then weighed as CuO. This operation requires care, being liable to involve loss by spurting. () As Metallic Copper. The solution, which must be free from other metals precipitable by electro- lysis, is introduced into a weighed and very clean platinum basin. It must contain a slight excess of sulphuric acid, but on no account nitric acid. The dish is then attached to the wire from the zinc plate of a galvanic cell, thus becoming the cathode. The other wire is connected to a piece of platinum ESTIMATION OF BISMUTH, GOLD, PLATINUM, AND TIN. 1^5 wire to form an anode, and this latter is then immersed in the liquid. After a short time the fluid will become quite colourless, and the basin will be coated with metallic copper. The fluid is now poured off, and the copper repeatedly washed with boiling water till all acidity is removed. The basin is finally rinsed with absolute alcohol, quickly dried, weighed, and the tare of the basin having been deducted, the difference is metallic copper in the quantity weighed out for analysis. The use of a battery may be dispensed with, and a fragment of pure zinc used to precipitate the copper, with sufficient acid to dissolve all the zinc before pouring off. 6. ESTIMATION OF BISMUTH. (A) As Bismuth Sulphide. (Practise upon 75 gramme of bismuthi et ammonia citras B.P.) This process (although employed in the B.P.) cannot be much recom- mended, as the sulphide is apt to increase in weight on drying, owing to the absorption of oxygen. A current of sulphuretted hydrogen is passed through the acid bismuth solution ; the resulting sulphide is collected on a tared filter, dried at 100 C., and weighed as BigSg. (B) As Bismuth Oxide. The solution for analysis is diluted with water, and precipitated with a slight excess of ammonium carbonate. The precipitated bismuthous oxy- carbonate is collected, washed, and dried. It is then separated from the filter paper, and the latter having been burned on the lid of a weighed crucible, the whole is introduced into the crucible, and ignited, cooled, and weighed as Bi 2 8 . 7. ESTIMATION OF GOLD. As Metallic Gold, by Cupellation. The alloy containing the gold is treated exactly as described under silver. The resulting metallic button is rolled out into a flat foil, and is then digested with nitric acid, which dissolves any silver, and the resulting gold is re-fused into a button and weighed. 8. ESTIMATION OF PLATINUM. As Metallic Platinum. The solution, which must contain the platinum as chloride, is concentrated and precipitated with excess of ammonium chloride. The precipitate is well washed with rectified spirit, dried, ignited, and weighed as metallic platinum. 9. ESTIMATION OF TIN. (A) As Stannic Oxide. Alloys containing tin, but free from antimony or arsenic, are treated with nitric acid, which converts the tin into oxide and other metals into nitrates. The acid fluid is evaporated nearly to dryness, the residue taken up with 10 146 GRAVIMETRIC ANALYSIS OF METALS. water and a little nitric acid ; the oxide is washed by decantation, collected on a filter, completely washed and dried. It is then as completely as possible detached from the filter, the latter is burned on a lid, the ash added to the contents of the crucible, and the whole ignited. After cooling, the oxide is moistened with a little nitric acid, dried (with the lid on), again ignited, and weighed as SnO 2 . Where we have to deal with tin in solution, the following method is applied : The solution, which must be free from other metals of the first three groups, is precipitated with sulphuretted hydrogen, the resulting sulphide is washed with solution of ammonium acetate, which will prevent the stannic sulphide from passing through the filter. The sulphide is transferred to a weighed crucible, and the whole ignited, at first very gently, until fumes of sulphurous anhydride cease, and then at a very high temperature, with the addition of a fragment of ammonium carbonate. This process depends on the conversion of the sulphide into SnO2 by ignition ; but it must be conducted with care, as a too rapid application of heat would cause the change to take place suddenly, and some of the sulphide wouM be lost. (B) As Metallic Tin. This process, which is only applicable to tin stone, consists in fusing a known quantity of the pulverised ore with potassium cyanide in a porcelain crucible, when a small button or granules of metallic tin will be obtained on treating the mass with water. The tin is washed, dried, and weighed. 10. ESTIMATION OF ANTIMONY. As Antimonious Sulphide, with or without Subsequent Conversion into Antimonious Antimonic Oxide. (Practise upon '5 gramme of " tartar emetic.") The acid solution is mixed with tartaric acid, to prevent the precipitation of an oxysalt, diluted with water, and precipitated with sulphuretted hydrogen, the sulphide collected on a weighed filter, dried at 105 C., and weighed. The conversion of the sulphide into oxide is best done by igniting an aliquot part in a porcelain crucible, with excess of mercuric oxide, and finally igniting very strongly. The remaining Sb 2 O 4 is then weighed. The B.P. simply moistens and warms the sulphide with nitric acid till red fumes cease, and then dries, ignites, and weighs as Sb 2 O 4 . 11. ESTIMATION OF ARSENIC. (A) As Arsenious Sulphide. (Practise upon '5 gramme As 2 O 3 .) The folution must contain the arsenic as arsenious acid. After adding some HO, a current of sulphuretted hydrogen is passed through the liquid, till the latter acquires a strong smell. The excess of gas is now removed by warming the fluid and passing a current of carbonic anhydride through it. The sulphide is collected on a weighed filter, washed, dried at 100 C., and weighed as As 2 S 3 . ESTIMATION OF COBALT, NICKEL, AND MANGANESE, 147 (B) As Magnesium Ammonium Arseniate. If the substance be arsenious acid it is dissolved in some hot solution of sodium carbonate, excess of hydrochloric acid is added, and the fluid mixed with excess of bromine water. Arsenic and sulphur compounds, on the other hand, are dissolved in hot potassium hydrate and treated with excess of chlorine gas to convert them into arsenic acid. The solution of arsenic acid thus obtained by either of the foregoing methods is mixed with large excess of ammonium hydrate, and, after being allowed to cool, precipitated with magnesia mixture. After standing for at least twelve hours, the precipitate is collected on a weighed filter, washed with a mixture of one volume of ammonium hydrate and three volumes of water till free from chlorine, dried for three hours at 105 C., and weighed as (MgNH 4 AsO 4 ) 2 H 2 O. 12. ESTIMATION OF COBALT. As Potassium Cobaltous Nitrite. The solution is concentrated to a small bulk, the excess of acid is neutralised with potash, and excess of potassium nitrite and a little acetic acid (to keep the solution slightly acid to test-paper) are then added. After the lapse of twenty-four hours all the cobalt will have crystallised out as potassium cobaltous nitrite. This salt is quite insoluble in the mother liquor, but slightly so in pure water. For the washing a 10% solution of potassium acetate is used, wherein the salt is also insoluble, and the acetate is afterwards removed by washing with alcohol. A weighed filter is used and the precipitate dried at 100 C. 13. ESTIMATION OF NICKEL. As Metal. The solution is precipitated with excess of sodium hydrate and boiled. The precipitate is washed with boiling water, dried, ignited, and weighed. The ignited residue, or a known portion of it, is now introduced into a weighed porcelain boat, and reduced at red heat by a current of hydrogen. The reduced metallic nickel is afterwards weighed. 14. ESTIMATION OF MANGANESE, As Manganese-manganic Oxide. (Practise upon 75 gramme of pure MnS04 7H<,O.) The solution for analysis, if strongly acid, is neutralised with ammonium hydrate and precipitated by ammonium sulphide. The precipitated manganous sulphide is washed with water containing ammonium sulphide, and dissolved in hydrochloric acid. Excess of sodium acetate is then added, and chlorine gas is passed through the liquid until all the manganese precipitates as manganic peroxide, which is then collected, washed, and calcined in a weighed crucible to bright redness. This forms Mn 3 O 4 ; the crucible with the contents is then cooled and weighed. 148 GRAVIMETRIC ANALYSIS OF METALS. 15. ESTIMATION OF ZINC. As Zinc Oxide. (Practise upon 75 gramme of pure ZnSC>4 7H 2 O.) The solution of the zinc salt is precipitated, while boiling, with sodium carbonate, and the whole is well boiled. The precipitate is allowed to settle, washed by decantation wi h boiling water, filtered out, and dried. It is then introduced into a weighed crucible, ignited for some time at a bright red heat, cooled, and weighed. The ignition changes the precipitated zinc carbonate to oxide, and it is weighed as ZnO. Or the solution is precipitated with ammonium sulphide, the zinc sulphide collected on a filter, washed with dilute ammonium sulphide, dried, ignited, and finally weighed as oxide. This latter method is useful when only small quantities of zinc are present. 16. ESTIMATION OF IRON. As Ferric Oxide. (Practise upon "75 gramme of pure FeSC>4 7H 2 O.) The solution is boiled with a nitro-hydrochloric acid, to ensure that the whole of the iron is in the ferric state. Excess of ammonium hydrate is added, the whole boiled and rapidly filtered. The precipitated ferric hydrate is washed with boiling water, dried, and ignited in a weighed crucible for some time. In the presence of organic matter, such as citric or tartaric acid, the iron must first be separated by precipitation with ammonium sulphide, the precipi- tate washed with dilute ammonium sulphide, redissolved in hydrochloric acid, boiled, oxidised by potassium chlorate, and then precipitated with ammonium hydrate, as directed. In the presence of manganese the solution should be nearly neutralised by ammonium hydrate and then boiled with excess of ammonium acetate, and the resulting ferric oxy-acetate collected, washed, dried, and ignited to Fe 2 Os. 17. ESTIMATION OF ALUMINIUM. As Aluminic Oxide. (Practise upon i gramme of pure alum.) The solution is precipitated with a slight excess of ammonium hydrate, and boiled until it only smells very faintly of ammonia. The precipitated aluminic hydrate thus obtained is filtered out, washed with boiling water, and dried. The dry filter and its contents are transferred to a weighed platinum crucible, and ignited to bright redness for some time, allowed to cool, and weighed as A1 2 O 3 . 18. ESTIMATION OF CHROMIUM. As Chromic Oxide. Salts of chromium are at once precipitated with ammonium hydrate, and the precipitate washed, dried, ignited, and weighed as Cr^C^. Soluble chromates are first reduced by means of hydrochloric and sulphurous acids (or, instead of the latter, spirit of wine may be used), and the chromium precipitated as hydrate by ammonium hydrate, ignited and weighed as CrgO^ all as described above for aluminium. ESTIMATION OF BARIUM, CALCIUM, ETC. 149 19. ESTIMATION OF BARIUM. As Barium Sulphate. (Practise upon "5 gramme of BaClj . 2H 2 O.) To a solution in boiling water add excess of sulphuric acid, boil rapidly foi a few minutes, and set aside to settle. The clear liquor is poured off as closely as possible, and the precipitate collected on a filter of Swedish paper, and washed with boiling water. The filter and precipitate are next dried and ignited in a weighed platinum crucible (the precipitate being removed as perfectly as possible from the paper, and the latter first burned separately on the crucible lid, and the ash added to the contents of the crucible, to avoid the reduction of BaSO 4 to BaS by the carbon of the paper). The crucible and its contents having been weighed, and the weight of the crucible and filter ash deducted, the difference equals the BaSO 4 . 20 ESTIMATION OF CALCIUM. As Calcium CarbDnate. (Practise upon "5 gramme of powdered calc-spar dissolved in dilute HC1.) The solution of the lime salt is mixed with ammonium chloride, and is then; made alkaline by ammonium hydrate. Ammonium oxalate is now added in excess. The whole is kept just below the boiling-point until the precipitate aggregates, then filtered and the precipitate washed with hot distilled water until free from chlorides. The filter and contents having been dried at 100 C., the precipitate is carefully transferred to a tared platinum crucible and gently ignited. It is then moistened with a solution of pure ammonium carbonate, evaporated to dryness, heated until no more fumes are evolved, and then weighed as CaCOs. 21. ESTIMATION OF MAGNESIUM, As Magnesium Pyrophosphate. (Practise upon '5 gramme of pure MgSO 4 . 7H 2 O.) The solution (which should be strong) is mixed with some ammonium chloride, and then with one-third of its bulk of ammonium hydrate, welt cooled, excess of disodium hydrogen phosphate added, and the whole set aside for some hours. Care must be taken not to touch the sides of the beaker with the stirring rod, as otherwise particles of the precipitate will adhere to them so tenaciously as to be only removable with great difficulty. The precipitate is collected on the filter, washed with a mixture of one volume of ammonium hydrate and three volumes of water, till the washings are free from chlorine, and dried. The precipitate is now detached from the filter and put into a weighed platinum crucible, the filter is burned in the lid, the ash added to the contents of the crucible, and the whole strongly ignited and weighed as Mg 2 P 2 O 7 . It sometimes happens that the phosphate, even after prolonged ignition, is very black. In that case it is, after cooling, thoroughly moistened with nitric acid, carefully dried, and re-ignited, when it will be found to be perfectly white. The B.P. estimates magnesium in MgSO 4 by simply precipitating a boiling solution with Na 2 CO3, and collecting, drying, igniting, and weighing as MgO. 150 GRAVIMETRIC ANALYSIS OF METALS. 22. ESTIMATION OF POTASSIUM. As Potassium Platino-Chloride, (To be practised upon "2 gramme of pure KC1.) The solution is placed in a small porcelain basin, and mixed with a good excess of solution of platinic chloride. The whole is evaporated to dryness on a water bath kept at a temperature of about 94 C. When quite dry it is again digested with a few drops of platinic chloride solution, and taken up with alcohol. The precipitate is collected on a weighed filter, washed with alcohol till the washings appear quite colourless, dried at 100 C., and weighed as PtCU 2KC1. 23. ESTIMATION OF SODIUM. As Sodium Sulphate. (Practise upon '5 gramme of pure NaCl.) This method is only applicable where we have to deal with a sodium salt 'containing a volatile acid. The solution is mixed with excess of sulphuric acid and evaporated in a weighed platinum basin. When fumes of sulphuric acid become visible, the basin is covered over with a lid (which has been weighed together with the crucible) and gradually heated till fumes cease. While red-hot the lid is lifted up a little, and a small lump of ammonium carbonate put in the crucible, which operation is repeated after a few minutes, and the residual NagSO* is cooled and weighed. The object of introducing the ammonium carbonate is to remove the last traces of free sulphuric acid. 24. ESTIMATION OF POTASSIUM AND SODIUM IN PRESENCE OF METALS OF FOURTH GROUP. (Practise upon the residue left on evaporating i litre of ordinary drinking- water, and redissolving in a little dilute HC1.) The solution is first of all precipitated with excess of barium chloride, which throws down sulphuric, phosphoric, etc., acids. Barium hydrate (or some milk of lime) is now added in slight excess, when any magnesia will also be thrown down. To the filtered liquid excess of ammonium carbonate is added, the precipitate is filtered out, and the fluid evaporated to dryness in a platinum crucible on the water bath. When quite dry, it is gently heated as long as white ammoniacal fumes are visible. The residue, which will now consist of alkaline chlorides, is, however, not quite fit for weighing, and must be purified. This is done by redissolving in water, and adding a little ammonium carbonate, when a slight precipitate will form. After filtering, the fluid is evaporated (this time in a tared platinum basin) on the water bath, and when dry the residue is gently heated to faint redness for a minute, cooled, and weighed. When no sodium is present it will now be pure potassium chloride ; but should it also contain sodium chloride, it must be redissolved, the potassium estimated by PtCl 4 , and the sodium obtained by difference. This process is one of the most commonly occurring operations, because it is required in every full analysis of water, and also of the ash of all vegetable and animal substances, where potassium and sodium have always to be estimated in presence of Ca, Mg, phosphates, etc. It is therefore a very important one to thoroughly master. ESTIMATION OF CHLORIDES, IODIDES, ETC. 25. INDIRECT ESTIMATION OF POTASSIUM AND SODIUM. The weighed mixture of KC1 + Nad obtained as in 24 is redissolved in distilled water and titrated with ^ solution of argentic nitrate (see p. 116). The number of c.c. having been noted and multiplied by "003519, we obtain the amount of Cl present in the mixed chlorides. If now all this Cl had been present as KC1, every 35*19 Cl would represent 74/02 KC1, but if present as NaCl, then 35*19 Cl would equal 58-07 NaCl, thus showing a theoretical difference of 15^95, which we will call d. We therefore first calculate : 74*02 x Cl found ... .. T ^ _, = x grammes, if all KC1. 35'I9 From this we deduct the actual weight of the mixed chlorides found, and obtain a practical difference, which we will call d'. Then : d' x 58-07 _ t | ie we igh t of NaCl present in the mixed chlorides. d and by deducting this from the total mixed chlorides the balance is KC1. 26. ESTIMATION OF AMMONIUM. As Ammonium Platino-Chloride. If the solution contains other basylous radicals, a known quantity of it is distilled with some slaked lime in a suitable apparatus, and the distillate received into dilute hydrochloric acid. About three-fourths is distilled over. The distillate is then evaporated to dryness with excess of pure platinic chloride (free from nitre-hydrochloric acid). The dry residue is now treated with a mixture of two volumes of absolute alcohol and one of ether, collected on a weighed filter, washed with the said ether mixture, dried at 100 C., and weighed as PtCl 4 . 2NH 4 C1. A less expensive method is to distil the ammonia into a known bulk of volumetric acid, and then check back with volumetric soda, so finding the amount of acid neutralised by the ammonia. DIVISION III. GRAVIMETRIC ESTIMATION OF ACID RADICALS. 1. ESTIMATION OF CHLORIDES. As Argentic Chloride. (Practise upon '5 gramme pure NaCl.) The solution containing the chloride is precipitated with argentic nitrate. Nitric acid is then added, and the whole stirred till the liquid is perfectly clear. The precipitate is now treated as directed (see Silver, p. 142). After weighing the chloride it is calculated to Cl. 2. ESTIMATION OF IODIDES. 3. ESTIMATION OF BROMIDES. 4. ESTIMATION OF CYANIDES. The process for each of these is practically the same as for chloride. The argentic cyanide is, however, collected and weighed upon a weighed filter. The argentic iodide and bromide are treated like the chloride ; but // a filter is used, it must be a weighed one. The filter is afterwards reweighed, and the increase in weight is the amount of argentic iodide or bromide carried on to the filter during the washing by decantation. 1 52 GRA VI METRIC ANALYSIS OF ACIDS. 5. ESTIMATION OF AN IODIDE IN THE PRESENCE OF A CHLORIDE AND A BROMIDE. By Palladium. The solution, slightly acidified, is precipitated with excess of palladious chloride. The whole is then allowed to stand in a warm place for twenty-four hours, so that the precipitate may thoroughly settle. The supernatant liquor is poured off, and the precipitate having been collected on a filter, and washed, is placed in a weighed platinum crucible and ignited. The whole is then again weighed, and the weight, less that of the crucible and filter ash, equals the amount of metallic palladium left after ignition, which x 2-396 =- the amount of iodine in the weight of the sample taken for analysis. Note. A method for estimating chloride in the presence of bromide will be found on page 116. 6. ESTIMATION OF SULPHIDES. By Conversion into Sulphate. (Practise upon '5 gramme of purified "black antimony.") Fuse with a large excess of a mixture of potassium nitrate and carbonate, extract the fused mass with water, filter, acidulate with hydrochloric acid, add excess of barium chloride, and proceed as for a sulphate ; but calculate at the last to sulphur instead of sulphuric acid. Some sulphides can be attacked by dissolving in nitric acid with the addition of successive small crystals of potassium chlorate. Excess of hydrochloric acid is added, and the whole having been evaporated to dryness, the residue is then boiled with dilute hydrochloric acid, filtered, and the filtrate precipitated with barium chloride. 7. ESTIMATION OF SULPHATES. As Barium Sulphate. (Practise upon '5 gramme of MgSC>4 7H 2 O.) The solution is acidulated with hydrochloric acid, excess of barium chloride is added, and the whole boiled. When quite clear a little more barium chloride is added, to ascertain whether all the sulphate has precipitated. The precipitate is now treated precisely as in the barium estimation (page 149) and the resulting BaSO 4 is calculated to sulphate. 8. ESTIMATION OF NITRATES. (A) In Alkaline Nitrates. If nitric acid be required to be estimated in, say, ordinary nitre, the sample must first be heated to fusion to remove moisture, and then be quickly powdered. A weighed quantity of it is now mixed in a platinum crucible with (exactly) four times its weight of plumbic sulpha:e. The mixture is ignited till it ceases to lose weight, when the loss will just represent the amount of nitric anhydride in the sample taken for analysis. The reaction is represented by the following equation : PbSO 4 + 2 KNO 3 = PbO + K 2 SO 4 + 2NO 2 + O. ESTIMATION OF PHOSPHATES. I53 (B) By Conversion into Nitric Oxide. Already described at page 133. (C) By Conversion into Ammonia, The nitrate is converted into ammonia by the action of nascent hydrogen> thus : HN0 3 + 4 H 2 = NH 3 + 3 H 2 0. The nascent hydrogen may be applied in various ways, as follows : .1. By distillation with sodium hydrate and metallic aluminium, and receiving the evolved ammonia into a known volume of normal standard acid. 2. By acting on the nitrate for 12 hours with zinc or iron and dilute sulphuric acid, and then adding excess of sodium hydrate, and distilling off the ammonia into a known volume of normal standard acid. The standard acid used is then titrated by normal standard sodium hydrate, and the excess of acid started with, over that of alkali now used, gives the number of c.c. of standard acid neutralised by the ammonia. This number multiplied by '06258 = HNO 3 present, or by '05364 = N 2 O 5 - 9. ESTIMATION OF PHOSPHATES. (A) Estimation of the Strength of Free Phosphoric Acid. i grm. of strong B.P. acid is evaporated in a weighed dish with 2 '5 grms. of- PbO ; the dry residue is ignited, and should weigh 2*98 grms. i grm. dilute acid similarly treated with -5 grm. PbO should yield '6 grm. (B) As Magnesium Pyrophosphate in Alkaline Phosphates. (Practise upon 75 gramme of pure Na 2 HPO 4 . i2H 2 O.) Ammonium hydrate and magnesia mixture are added in excess, and the precipitate is treated as directed under Magnesium (page 149). Should the solution contain meta- or pyro-phosphates it must either be previously boiled with strong nitric acid for one hour, or be fused with potassium sodium car- bonate. (C) As Magnesium Pyrophosphate in the Presence of Calcium and Magnesium. (Practise upon -5 gramme of pure Ca3(PO 4 ) 2 dissolved in dilute HC1.) The solution (which must contain orthophosphoric acid, or, failing that, should be boiled with HNO 3 as above) is precipitated with ammonium hydrate, and the precipitate is redissolved m the smallest amount of acetic acid. The. calcium is then removed by adding excess of ammonium oxalate, and the nitrate having been evaporated to a bulk not exceeding 3 ounces is cooled, treated with excess of ammonium hydrate and magnesia mixture, and the precipitate is collected as already described for magnesium (page 149). This process is suitable for determining the " soluble phosphates " in an artificial manure. 154 GRAVIMETRIC ANALYSIS OF ACIDS. (D) As Magnesium Pyrophosphate in the Presence of Iron and Aluminium, (Practise upon 75 gramme of B.P. Ferri phosphas dissolved in dilute HC1.) The solution is mixed with excess of ammonium acetate, boiled, and ferric chloride added till a dark-brown precipitate forms. This is washed with boiling water and redissolved in a small quantity of dilute HC1. About five grammes (or more) of citric acid are now introduced, and ammonium hydrate is added to the whole in large excess, and, after cooling, magnesia mixture, the precipitate being treated as for magnesium. If the addition of excess of NH 4 HO does not produce a clear lemon-yellow solution, then enough citric acid has not been added. (E) Estimation as Phosphomolybdate. If necessary, the acid solution is heated and precipitated with H 2 S to remove arsenic. The excess of B^S is boiled off, and large excess of nitric acid is added. An excess of ammonium molybdate and ammonium nitrate dissolved in nitric acid is now poured in,* the liquid boiled, and finally allowed to stand for some hours in a warm place. The precipitate is filtered off, washed with dilute alcohol until free from acidity, redissolved in dilute ammonium hydrate, the solution evaporated in a weighed dish on the water bath and the residue dried in the water oven. Its weight -^ 28-5 =P2O 5 present. This process is the best for determining small amounts of total phosphates in cast iron, waters, and soils. 10. ESTIMATION OF TOTAL AND SOLUBLE PHOSPHATES IN AN ARTIFICIAL MANURE OR OF TOTAL ONLY IN SOIL. (A) Total Phosphates. About 2 grammes of the finely powdered substance are weighed accurately, transferred to a beaker and decomposed with HC1, and where necessary with the addition of a drop or two of HNOs. The solution is then evaporated to dryness in a water bath, taken up with HC1, and after digestion the insoluble silicious matter is separated by filtration ; a weighed quantity of citric acid is added, the solution heated up nearly to boiling point, and a weighed quantity of ammonium oxalate added. The quantities used must vary with the substance under examination, the knowledge only being acquired by experience ; but it is seldom necessary to add more than 2 grammes citric acid or 2:5 grammes ammonium oxalate. The free acid is then just neutralised with dilute ammonia, and acetic acid added, to decidedly acid reaction. The liquid is kept simmering for a few minutes with constant stirring, and after standing a short time the calcium oxalate is filtered out. Great care must be observed not to have too large an excess of ammonium oxalate present, as magnesium oxalate in an ammoniacal solution is somewhat easily precipitated. To the filtrate ammonia of '880 sp. gr. is added to about one-fourth of the bulk ; and to the liquid, which must remain clear, or only slowly throw down a small precipitate, due to the magnesia present, magnesia mixture is added in moderate excess. The liquid must be set aside, with occasional stirring for the precipitate to form the time required being principally determined by the quantity of alumina present. It is best, however, to allow it to stand over night, although in cases where the alumina is absent, or small, the prc- * This solution is prepared by dissolving 10 grammes of molybdic acid in 417 c.c. of ammonia solution (-96 sp. gr.), and then adding to 125 c.c. of nitric acid, sp. gr. r2O. ESTIMATION OF ARSENIATES AND CARBONATES. 15^ cipitation will be found to be complete in two hours. The precipitate is then separated from the liquid by filtration, dissolved in as little HC1 as possible, and reprecipitated with one-third of its bulk of ammonia. After allowing to stand for two hours with occasional stirring, it may be filtered, and after drying converted, by ignition in a weighed platinum crucible, into Mg 2 P 2 O 7 , and weighed as such. The calcium oxalate is converted into CaCO 3 by gentle ignition, weighed, dissolved in HC1, and tested for P 2 O 5 , which may be present in small quantities, and if so it should be determined. The Mg 2 P 2 O 7 is calculated to Ca 3 (PO 4 ) 2 unless a full analysis is being made, when it is calculated to P 2 O 5 , and divided pro rata among the bases actually found to be in combination with it. Note. Recent researches have sho\vn that by the addition of a sufficiently large amount of citric acid, all the intermediate steps of the process are saved, it being only necessary to afterwards add the _excess of ammonia and magnesia mixture. By this method, a large excess of citric acid having been first introduced, ammonia is added, and should no precipitate occur, it is followed by the magnesia mixture ; but if even a cloud should appear, more citric acid must go in, until sufficient has been added to cause a perfectly clear solution on the subsequent addition of ammonia. The whole must stand in the cold for at least twenty-four hours before filtering off the precipitate of ammonium magnesium phosphate, so that, after all, no time is saved by the new method, but the risk of loss is less, because the intermediate filtration (to remove calcium) is avoided. (B] Soluble Phosphates. Five grammes of the manure are well triturated in a mortar with distilled water, washed into a stoppered 250 c.c. flask, and made up to the mark with water. After standing with occasional shaking for two hours, 100 c.c. ( = 2 grammes of sample) is drawn off by a pipette into a beaker, 2 grammes of citric acid and 2^5 grammes of ammonium oxalate are dissolved in the liquid, which is then treated with ammonia, acetic acid, etc., as above described. If the amount of soluble calcium comes out low, the process should be repeated, using such a weighed quantity of ammonium oxalate as will just remove it from solution. This is because the great source of error in phosphate estimations is the use of excess of oxalate, causing the precipitation of magnesium oxalate with the magnesium ammonium phosphate. The adoption of the direct citric acid and ammonia method (given above) of course avoids any difficulty in this respect. The Mg 2 P 2 O 7 is calculated to Ca 3 (PO 4 ) 2 , and reported as " phosphate made soluble." 11. ESTIMATION OF ARSENIATES. Arseniates are estimated precisely like phosphates ; but the precipitate of ammonium magnesium arseniate is dried at 105 C. on a weighed filter, as already directed under Arsenic. The precipitate thus dried is (MgNH 4 AsO 4 ) 2 . H 2 O; or, for simplicity of calculation, MgNH 4 AsC>4 . |H 2 O. 12. ESTIMATION OF CARBONATES. A carbonate is estimated by the loss of weight it undergoes by the dis- placement of its carbonic anhydride by an acid. A small and light flask is procured and fitted with a cork through which passes a tube (c) containing fragments of calcium chloride (see fig. 35). A weighed quantity of the carbonate is introduced into the flask with a little water, and a small test-tube about two inches long is filled with sulphuric acid and dropped into the flask, so that, being supported in an upright position, none of the acid shall mix with the carbonate. The cork is put in, and the weight of the whole , 5 6 GRA VI METRIC ANALYSIS OF ACIDS. apparatus having been carefully noted, it is inclined so as to allow the acid to run from the small tube into the body of the flask. Effervescence sets in, the carbonate is dis- solved, and the COs, escaping through the calcium chloride tube, is deprived of any moisture it might carry with it. When all action has ceased, and the whole has cooled, air is drawn through the apparatus to displace the remaining CO 2 and it is once more weighed. The difference between the two weights gives the amount of CO 2 evolved. A better apparatus is that figured (No. 36), in which c is the flask, A the tube to contain HC1 to decompose the carbonate, Fig. 36 and B a tube containing strong H 2 SO 4 , through which the evolved CO^ must pass, and so be perfectly deprived of moisture. 13. ESTIMATION OF BORIC ACID IN EQUATES. This is best done by distilling off the boron in the form of methyl borate, and finally estimating it as calcium borate. The apparatus required is a distilling flask heated by a water-bath and fitted with a tap-funnel, the tube of which reaches nearly to the bottom of the flask. The side delivery-tube is attached to an upright condenser having a spiral worm and ending in a receiver standing in a dish of cold water and furnished with a set of bulbs containing dilute ammonia, to ensure against the escape of any methyl borate. The weighed quantity of the boric acid (or borate) is put into the flask with as little liquid as possible, and i c.c. of nitric acid having been added, the whole is distilled to dryness. 10 c.c. of methyl alcohol are then introduced by the funnel and entirely distilled off, which operation is repeated four times. 2 c.c. of an equal mixture of nitric acid and water are again added, distilled off, and the treatment with methyl alcohol is continued until a drop of the distillate, absorbed into filter-paper, ceases to burn with a green flame. While this distillation is proceeding, some pure lime (10 grammes for every '5 gramme of borate taken) is put into a platinum dish, heated for some time over the blow-pipe, cooled under the desiccator and weighed. The weighed dish and lime having been placed on ice, the contents of the receiver and bulbs are added to it and, after standing for twenty minutes, the whole is very cautiously evaporated at a temperature below 59 C. The heat is then gradually increased until the mass is quite dry and the whole is finally ignited over the blow-pipe and weighed. The increase in weight is the B 2 O 3 from the weight of sample started with. 14. ESTIMATION OF OXALIC ACID. As Calcium Carbonate. The solution is made alkaline with ammonium hydrate and precipitated with calcium chloride. The precipitate is washed till free from chlorides, dried, ignited, and finally weighed as carbonate, as directed under Calcium (page 149). 15. ESTIMATION OF TARTARIC ACID. As Calcium Oxide. The solution (which must contain no other bases than K, Na, or NH 4 ) is made faintly alkaline by sodium hydrate, and precipitated by excess of calcic chloride. The precipitate is washed with cold water, dried, ignited (with the blowpipe), and weighed as calcic oxide. FULL MINERAL ANALYSIS OF POTABLE WATER. 157 16. ESTIMATION OF SILICIC ACID. (A) In Soluble Silicates. By soluble silicates are meant those which are either soluble in water of in hydrochloric acid. The solution (which must contain some free HC1) is evaporated to dryness on the water bath, and the residue dried for an hour at 120 C. (248 F.). After cooling, the mass is moistened with strong hydro- chloric acid, and then boiled with water, thus leaving an insoluble residue of pure silica SiO 2 which is collected on a filter, washed, dried, ignited, and weighed. (J3) In Insoluble Silicates. These bodies must be decomposed by mixing a weighed quantity of the finely powdered substance with four times its weight of sodium potassium carbonate, and fusing the whole for about half an hour. ( When alkalies have to be estimated, a separate special fusion must be made with barium hydrate, or pure lime mixed with ammonium chloride, instead of the double carbonate.} The crucible must be well covered during fusion. After cooling, the residue is treated with dilute and warm HC1 until effervescence ceases, evaporated to dryness, and treated as above described at 120 C. (248 F.), etc. DIVISION IV. GRAVIMETRIC SEPARATIONS. This department is beyond the scope of the present edition. When the student has practised all the contents of the book up to this point, he will already have a sufficiently general idea of chemical analysis to enable him to fix the line of work he desires to make his speciality. If this be mineral analysis, he must pass to a larger book, such as " Fresenius," to complete his knowledge. So as to give, however, some idea of how the preceding processes may be joined in performing the full analysis of a mixture, we take the following example, because it is a standard one, and give a sketch of the manner of working in performing : The Full Analysis of the Mineral Contents of a Sample of Ordinary Potable Water. Step I. Take the total solid residue of 100 c c. (calculated in grains per gallon) as directed in Chapter X., to serve as a check on the results ; then ignite and again weigh : loss = organic and volatile matter. Step II. Evaporate 2000 c.c. of the water to dryness in a large porcelain dish. Moisten the residue with 10 c.c. of distilled water, and then add 200 c.c. of dilute alcohol '92 sp. gr. : having gently detached it all from the dish, filter and wash with similarly diluted alcohol till practically nothing more dissolves. This procedure is useful because it separates the salts present thus : (a) The filtrate may contain all salts of K and Na, chlorides and nitrates of Ca and Mg, and the sulphate of Mg. (b] The insoluble residue may contain the sulphate and carbonate of Ca and the carbonate of Mg, together with any iron and silicious matter present. (l) Analysis of the filtrate. (a) Evaporate till the spirit is driven off, cool, transfer to a 200 c.c. flask, and make up to the mark with distilled water. Divide into two portions of loo c.c. respectively, marking them A and B. (6) To A add NH 4 C1, NH 4 HO and (NHJ 2 C,O 4 , to precipitate the Ca, and estimate ai usual as CaCO 3 . Calculate to CaO, and then x 2 = CaO present as Cl or NO,, in the original 2000 c.c. of water taken. (c) To filtrate and washings from (3), concentrated to 50 c.c. and cooled, add Na 2 HPO 4 , to precipitate Mg, treat as usual, and weigh as Mg 2 P 2 O 7 . Calculate to MgO, and then X 2 = MgO present as Cl, SO 4 , or NO 3 in the original 2000 c.c. of water. (d] To B acidulate with HC1 and add BaCl 2 to precipitate sulphate. Treat as usual and weigh as BaSO 4 . Calculate to SO,, and then X 2 = total SO S present in the original 2000 E.C. of water taken in combination with K or Na. I 5 8 GRAVIMETRIC SEPARATIONS. (e) The filtrate and washings from (,/) are evaporated to a low bulk rendered alkaline with pureCa(HO)2, the separation for alkalies given at page 150 gone through, and the K and Na present both estimated as chlorides. Results X 2 = total K and Na present in the 2000 c.c. of water started with. (f) The residue from (e) is dissolved in a little water, and the K estimated thereon by PtCl 4 in the usual manner and calculated to K 2 O (see page 150). An equivalent amount of KC1 (calculated from this ICO) is then deducted from residue (e), and the balance is NaCl, which is calculated to Na 2 O. (2) Analysis of the insoluble portion. (a) This is washed from the filter with distilled water and then boiled with 100 c.c. of II .AD and HC1 added till effervescence ceases. Any insoluble is filtered out, washed with boiling H,O, dried, ignited, and weighed = silicious matter in the 2000 c.c. of water started with. (3) The filtrate and washings are warmed with a drop or two of HNO 3 and mixed with NH 4 C1 + NH 4 HO, and the iron estimated if present as Fe 2 O 3 , and result calculated to Fe = total Fe in the 2000 c.c. of water taken. (c) Divide filtrate and washings into two equal parts, A and B. (d) The portion A is precipitated with (NH 4 ) a C a O 4 , and the calcium estimated as CaCO 3 and calculated to CaO. Result X 2 = total CaO as carbonate or sulphate in the original 2000 c.c. of water taken. ( and. calculated to MgO. Result X 2 = total MgO present as carbonate in the original 2000 c.c. of water. (/") The portion K is acidulated with HC1, and the sulphate estimated by BaCl 2 , weighed as BaSO 4 , and calculated to SO 3 . Result X 2 = total SO 3 in combination with Ca in the original 2000 c.c. of water. Step III. Evaporate 250 c.c. of the water to a bulk of 2 c.c., and treat in the nitrometer to estimate the nitric acid (see page 134)- Resulting NO calculated to N 2 O 5 and x 8 = total N,O 5 present in 2000 c.c. of water. Step IV. Take the amount of chlorides volumetrically (page 116) in 100 c.c. of the water. Result X 20 = Cl in 2000 c.c. of water. Step V. Calculation of results. (a) All our results being in grammes or fractions of the same from 2000 c.c. of water, each must be multiplied by 35, which will bring them all to grains per imperial gallon (parts in 70,000). The analysis is then stated as follows (example taken from actual practice) : A sample of water yielding 20 -I grains of total solids per gallon, of which '45 grain was " organic and volatile matter," and the balance (19*65 grains) was-mineral matter, showed on analysis : ) In the portion soluble in spirit : grains per gallon. Potassium oxide . . . '2704 Sodium oxide . . 1*4097 Chlorine . . .1-2133 Sulphuric anhydride . '6803 Calcium oxide . . none. Magnesium oxide . . none. Nitric anhydride . . . none. (b) In the portion insoluble in spirit : grains per gallon. Calcium oxide . . . 7'3953 Magnesium oxide . . I 'oooo Sulphuric anhydride . 17647 Silicious matter . '2000 Ferric oxide . '0500 Total found . 13-9837 From this residue is now to be always deducted an amount of oxygen equivalent to the chlorine found, because all the bases have been calculated to oxides, while haloid salts contain no oxygen. The chlorine found is 1-2133, and = * 2 737 xv g en equivalent to Cl found. Performing the deduction, we have I 3'9^37 '2737 == 137100 grains of solid matter actually found. The total residue, after driving off organic matter, was 19 '65 grains per gallon, and the difference is due to CO;, unestimated, thus : "19-65 13-71 = 5-94 grains of CO., per gallon. Adding now this CO 2 to the substances actually estimated, we get Total substances found + CO 2 = 19 65, Actual residue found = 19^65, which proves our analysis to be correct. It now remains to calculate how these bases and acids are probably combined as salts actually present, by the following general rules of affinity, thus : (a) In the portion soluble in spirit. (l) Any sulphuric anhydride will prefer the bases in the following order : K, Na, Mg. (2) Chlorine will prefer the bases in the same order after the SO 3 is satisfied. Therefore we first calculate our K 2 O to K 2 SO 4 , which gives -50 and uses up '2296 of our SO 3 , and the balance of SO 3 ( '4507) we calculate to Na.,SO 4 This gives 80 Na^SO^ and leaves 1*0604 NajO not as sulphate and therefore existing as chloride. FULL MINERAL ANALYSIS OF POTABLE WATER. 159 Calculating accordingly, we get 2 - oo of NaCl, which just uses up all our chlorine. There- fore this portion contained altogether Potassium sulphate ..... -50 Sodium sulphate ...... -80 Sodium chloride ...... 2 - oo () /;/ the portion insoluble in spirit, (i) The SO 3 found will all be present as CaSO 4 , and the balance of CaO and all the MgO will be as carbonates. Therefore 17647 SO 3 calculated to CaSO 4 becomes 3-00 and uses up 1-2353 f ^ a O leaving 6*16 to be calculated to CaCO 3 . This yields iroo CaCO 3 , and the roo of MgO found, calculated to MgCO, gives 2-10. Thus this portion contains Calcium sulphate ...... 3-00 Calcium carbonate ..... iroo Magnesium carbonate ..... 2 g io Putting now the whole analysis together, we have Potassium sulphate .... -50 Sodium sulphate . . . -80 Sodium chloride ...... 2 - oo Calcium sulphate ... . . 3-00 Calcium carbonate , iroo Magnesium carbonate . 2 10 Ferric oxide . . -05 Silica ..... -20 Organic and volatile matter .... -45 Total residue 20' IO CHAPTER IX. ULTIMATE ORGANIC ANALYSIS. THIS process consists in estimating the amount of each element present in any organic compound, as distinguished from proximate analysis, which estimates the amounts of the compounds themselves. I. LIST OF APPARATUS REQUIRED. 1. A combustion furnace, which is a series of Bunsen burners arranged in a frame so as to gradually raise a tube placed over them to a red heat. The tube lies in a bed made of a series of firebricks, which confine the heat and make it play all round the tube (see fig. 37). 2. Combustion tubes made of hard glass, not softening at a red heat. These tubes are closed at one end by drawing out before the blowpipe and turning up. The mode of doing this is illustrated in fig. 38. Fig. 39- Fig. 37. 01 ft c d ^-- Fig. 38. Fig. 40. 3. U tubes packed with perfectly dry calcium chloride in small fragments, so as to allow the free passage of gases (illustrated in fig. 39), and hereafter referred to for brevity as " CaCL tubes." 4. Bulbs charged with strong solution of potassium hydrate (i in i), hereafter for brevity referred to as ' KHO bulbs." Two common forms of such bulbs are illustrated in fig. 40. 5. Bulbs for absorbing ammonia and intended to be charged with dilute acid of known strength, and hereafter referred to as "nitrogen bulbs" for brevity. Two common forms of such bulbs are illustrated in fig. 41. 6. Graduated tubes closed at one end, to hold 50 c.c., and graduated from the closed end downwards in ^ of a c.c., used for collecting gases and measuring them after collection, hereafter referrred to as "gas-collecting tubes" for brevity (fig. 42). 7- A deep cylindrical vessel of glass filled with water and furnished with a thermo- meter dipping in the water ; the whole sufficiently deep to permit of the entire immersion of the gas-measuring tubes, and wide enough at the top to admit the hand, as shown in fig. 43. This is hereafter called the " measuring trough " for brevity. 160 ESTIMATION OF CARBON AND HYDROGEN. 161 3 Glass towers, filled in one limb with fragments of CaCl 2 to absorb moisture, and in the other with fragments of soda-lime to absorb carbon dioxide. These are illustrated in fig. 44, and are used for freeing any air which may be caused to pass through them from moisture and CO 3 ; hereafter called "air-purifying towers " for brevity. II. ESTIMATION OF CARBON AND HYDROGEN. I. Liebig's Process. This process is performed by heating a weighed quantity of the substance in a tube with some body readily parting with oxygen at a red heat, such as cupric oxide or plumbic chromate, by which the hydrogen and carbon of the organic body are respectively oxidised into water and carbonic anhydride. These products are passed first through a weighed tube containing calcium chloride, which retains the water, and then through a weighed bulb apparatus containing potassium hydrate, which absorbs the carbonic anhydride. After the experiment is finished, the increase in weight of the tubes is calculated thus : As H..O : H 2 : : increase in CaCl 2 tube : x. As CO., : C : : increase in KHO bulbs : x. Fig. 41. Fig. 43- Fig. 43- Fig. 44. The details of the actual process are as follows : (i) Preliminary steps. (a) Choose a combustion tube, drawn out and sealed at one end (fig. 38), about eighteen inches long and \ to f inch in bore, and fit two corks to it, one whole and the other bored so as to be all ready to take the bulb end of the CaCl 2 tube (fig. 39), which must fit air-tight when pushed through the cork. () Measure out sufficient CuO (powdered) to fill the combustion tube, and put it into a small pear-shaped hard glass flask over a good il Bunsen " to heat to dull redness and drive off all moisture. Then remove the source of heat, cork it up, and let it cool. (f) While the CuO is cooling weigh your CaCL tube and your KIIO bulbs (fig. 40), and, having noted their respective weights, close the open ends by means of short pieces of black rubber tubing, having bits of glass rod put in to act as stoppers. (of) '4 gramme of KC1O 3 is then to be weighed out, powdered and heated gently in a porcelain capsule until it just fuses. The fused mass is crushed to powder by a glass rod and the capsule put under the desiccator. (0 '3 to '4 gramme of the substance is (if solid) weighed on a watch glass and put Binder the desiccator. If liquid, a very minute stoppered tube (to be obtained at any apparatus shop) is weighed, and having been filled with the liquid it is closed and again weighed, the difference being the weight of liquid taken. (/) Sufficient asbestos fibre to make a plug that will occupy about \ inch of the combustion tube is heated to redness and cooled under the desiccator. (,;,') A long wire with a curled end is got ready* II 1 62 ULTIMATE ORGANIC ANALYSIS. (2) Charging the combustion tube. When the CuO has cooled suf- ficiently so that it can be handled, the KClOs is first dropped into the combustion tube and is followed by four inches of CuO (rapidly transferred from the flask with as little exposure to the air as possible). The weighed substance, if solid, is then dropped in, and immediately followed by another three inches of CuO. The long wire is then used to mix the sub- stance through the upper six inches of CuO, taking care not to disturb the lower inch or the KC1O 3 (if a liquid only two inches of CuO are put in, and then the bottle is dropped in, and followed by five inches cf CuO). The tube is now filled with CuO to within two and a half inches of its end ; the asbestos is introduced so as to form a loose plug, leaving a space of an inch between it and the charge, and the tube is securely corked. It is then laid flat upon the table and tapped thereon until its contents settle down, so leaving a clear passage for any gases along the upper part of the tube, which is then placed in the furnace (fig. 37) with the corked end just pro- truding. The cork is removed and the CaCl2 tube is attached by means of the perforated cork (taking care to put the "bulbed" limb next the tube), and to the other end of that the KHO bulbs are attached by means of a piece of black rubber tubing, seeing that the larger side of the bulbs is next the CaCls tube. The whole apparatus is now complete, and after testing it for air tightness of the cork and joints (by gently warming the inner side of the KHO bulbs so as to expel some of the air, and seeing that on cooling the, liquid stands at a higher level in the inner bulb than before), we are ready to perform : (3) The Combustion. We first light the first six burners next the bulbs, and when the front part of the tube is red-hot we carefully light the other burners one at a time, so as to cause the heat to travel gradually backwards. The art is to so regulate our heat as never to produce bubbles of gas passing through the bulbs at a more rapid rate than can be distinctly counted. When the whole tube is red-hot, all except the last inch, and the evolution of gas has practically ceased, we light the last burner and cause an evolution of oxygen from the KC1O 3 which clears the tube of any residual gases and carries them through the bulbs. The gas is then turned off, and when cooled the CaGl* tube and KHO bulbs are detached and reweighed, and the increase noted in each case. (4) Calculation of results. The following is an example of the method of calculating ; the substance under analysis being sugar- candy. Weight of sugar taken ..... '475 gramme. Potash bulbs after combustion weighed . . . 79-113 grammes, before ,, 7^32 Difference, due to CO 2 . . . 731 ,, Calcium chloride tube after combustion weighed . 23*605 grammes. before ,, . 23-330 Difference, due to 1I V O . . . '275 , ESTIMATION OF CARBON AND HYDROGEN. 163 (C) 12 x 7^1 (H,) 2 X '271; ) Alkaline potassium permanganate solution. Dissolve 200 parts of potassium hydrate and 8 parts of pure potassium per- manganate in I2OO parts of distilled water, and boil the solution rapidly till concentrated to 1000 parts, cool, and keep in a well-stoppered bottle. (c) Distilled water "which is f fee from ammonia. Distilled water which gives no reaction with Nessler test is pure enough. But, if this is not available, take the purest distilled water procurable, add pre ignited sodium carbonate in the proportion of I part per 1000, and boil briskly until at least one-fourth has been evaporated. (d) A 4O-ounce stoppered retort, with a neck small enough to pass loosely into the internal tube of a Liebig's condenser to the extent of 6 inches (see illustration, Chap. I., page 4). The joint between the retort and condenser is made by an ordinary india-rubber ring such as those used for the tops of umbrellas which has been previously soaked in a dilute solution of soda or potash, being stretched over the retort tube in such a position that when the retort tube is inserted in the condenser it shall fit fairly tightly within the mouth of the tube about half an inch from the end. (f) All the materials for " Nesslerising" (see Chap. VII., page 136). The process is as follows : (a) For ammonia. First test a little of the waiter with tincture of cochineal, to see if it shows an alkaline reaction. Put 500 c.c. of distilled water into the retort, and distil until 50 c.c. of the distillate gives no colour with ik c.c. of Nessler, thus rendering the whole apparatus " ammonia-free." Let the whole cool, pour out the distilled water (which may be saved for .ammonia-free water), put in 500 c.c. of the water to be analysed, and, if it has not an alkaline reaction, make it alkaline with a drop or two of the sodium car- bonate solution. The distillation should then be commenced, and not less than 100 c.c. distilled over. The receiver should fit closely, but not air-tight, into the condenser. The distillation should be conducted as rapidly as is compatible with a certainty that no spurting takes place. After 100 c.c. have been distilled over, the receiver should be changed, that containing the distil- late being stoppered to preserve it from access of ammoniacal fumes. 100 c.c. measuring-flasks make convenient receivers. The distillation must be con- tinued until 50 c.c. more are distilled over ; and this second portion of the distillate must be tested with Nessler's re-agent to ascertain if it contains any ammonia. If it does not, the distillation for free ammonia may be discon- tinued, and this last distillate rejected ; but, if it does contain any, the distilla- tion must be continued still longer, until a portion of 50 c.c., when collected, shows no coloration with the Nessler test. The whole of the distillates must be mixed together and " Nesslerised " in the usual manner, and the total number of milligrammes of ammonia found are multiplied by 2, which gives milligrammes per litre (parts per million). This number in turn multiplied by 7 and divided by 100 gives grains per gallon of ammonia. THE SANITARY ANALYSIS OF WATER. 171 (b) For albuminoid ammonia. As soon as the distillation above referred to has been started, 50 c.c. of the alkaline potassium permanganate solution are placed in a basin with 150 c.c. of distilled water, and boiled gently during the whole time that the free ammonia is distilling, adding some ammonia-free water if necessary, to prevent too much concentration. [The object of this is' to ensure the entire evolution of any trace of ammonia present in the alkaline permanganate, thus avoiding a check analysis, as usually recommended.] At the same time a few fragments of clay tobacco-pipe are put into a platinum dish, heated to redness, and then kept warm till required for use. When the distillation of the ammonia is complete, take out the stopper of the retort and pour in the boiled alkaline permanganate by means of a perfectly clean funnel with a long limb ; then remove the funnel and drop in the fragments of clay pipe. Now replace the stopper and continue the distillation, when the albuminoid ammonia will begin to come over. After 200 c.c. have been distilled, change the receiver and take off 50 c.c. at a time, as already described, until the last 50 comes over ammonia-free. Mix the distillates, " Nesslerise " -and calculate as for the ammonia, noting the total result as albuminoid ammonia in parts per million or grains per gallon. Great care must be taken that no ammonia is kept in the room devoted to water analysis, and that all /receivers used are first insured to be perfectly ammonia-free by proper rinsing with ammonia-free water and testing with Nessler. 10. Oxygen required to oxidise the Organic Matter. Solutions required : (a) Standard solution of potassium permanganate. Dissolve 395 parts of pure potassium permanganate in 1000 of water. Each c.c. contains - oooi gramme available oxygen. (b~) Potassium iodide solution. One part of the pure salt recrystallised from alcohol, dissolved in 10 parts distilled water. (c) Dilute sulphuric acid. One part by volume of pure sulphuric acid is mixed with three parts by volume of distilled water, and solution of potassium permanganate dropped in until the whole retains a very faint pink tint, after warming to 27 C. for four hours. (^/) Sodium hyposulphite. One part of crystallised sodium hyposulphite dissolved in 1000 parts of water. (.') Starch water. One part of starch to be intimately mixed with 500 parts of cold water, and the whole briskly boiled for five minutes, and filtered, or allowed to settle. The Process. Two separate determinations have to be made : ris. t the .amount of oxygen absorbed during 15 minutes, and that absorbed during four 'hours ; both are to be made at a temperature of 27 C. It is most convenient ito make these determinations in i2-oz. stoppered bottles, which have been irinsed with sulphuric acid and then with water. Put 250 c.c. of the water linto each bottle, which must be stoppered and immersed in a water-bath until the temperature rises to 27 C. Now add to each bottle 10 c.c. of the dilute sulphuric acid, and then 10 c.c. of the standard potassium permangan- .ate solution. Fifteen minutes after the addition of the potassium perman- ganate, one of the bottles must be taken from the bath, and two or three drops of the solution of potassium iodide added to remove the pink colour. After thorough admixture add from a burette the standard solution of sodium hyposulphite, until the yellow colour is nearly destroyed, then introduce a few drops of starch water, and continue the addition of the hyposulphite until the blue colour is just discharged. If the titration has been properly con- -ducted, the addition of one drop of potassium permanganate solution will restore the blue colour. At the end of four hours remove the other bottle, THE ANALYSIS OF WATER, AIR, AND FOOD. add potassium iodide, and titrate with sodium hyposulphite, as just described. Should the pink colour of the water in the bottle diminish rapidly during the four hours, further measured quantities of the standard solution of potassium permanganate must be added from time to time, so as to keep it markedly pink. The hyposulphite solution must be standardised, not only at first, but (since it is liable to change) from time to time in the following way : To 250 c.c. of pure redistilled water, acidulated with 10 c.c. acid as before, add two or three drops of the solution of potassium iodide, and then 10 c.c. of the standard solution of potassium permanganate. Titrate with the hypo- sulphite solution, as above described. The quantity used will be the amount of hyposulphite solution, corresponding to 10 c.c. of the standard potassium permanganate solution, and therefore representing i milligramme of oxygen consumed. The difference between the number of c.c. of hyposulphite used in the blank experiment and that used in the titration of the samples of water multiplied by the amount of available oxygen contained in the perman- ganate added (= i milligramme if 10 c.c. have been used), and the product divided by the number of c.c. of hyposulphite corresponding to the latter as found by the check experiment, is equal to the amount of oxygen absorbed by the water. Finally, the amount in milligrammes of oxygen absorbed, thus found, is multiplied by 4 for parts per million, and that result x 7 and -f- 100 = grains per gallon. 11. Clark's Process for Hardness. Total before boiling and permanent after boiling. Solutions, etc., required : (a) Standard solution of calcium chloride. Made by dissolving i gramme of pure calcium carbonate in the smallest excess of hydrochloric acid, then carefully neutralising with dilute ammonia, and making the solution up to a litre with distilled water. (b) Standard saap soJu'ion. Dissolve 10 grammes of air-dried white Castile soap, cut into thin shavings, in a litre of dilute alcohol (sp. gr. o 949). To determine whether this solution contains the proper amount of soap, 10 c.c. of the solution of CaCl 2 are diluted with 60 c.c. of water, and the soap solution added till a persistent lather forms on agitation. If n c.c. of the soap solution have been used, it has the proper strength. If a greater or less quantity, it must be concentrated or diluted to proper strength. The soap solution, if turbid, must be shaken before using, but not filtered. The Process. (a) For total hardness. Put 70 c.c. of the water into the bottle, of 250 c.c. capacity, and add the soap solution gradually from a burette. After each addition of soap solution, the bottle is shaken and allowed to lie upon its side five minutes. This is continued until, at the end of five minutes, a lather remains upon the surface of the liquid in the bottle. At this time the hardness is indicated by the number of c.c. of soap solution added, minus one. If magnesium salts are present in the water the character of the lather will be very much modified, and a kind of scum (simulating a lather) will be seen in the water before the reaction is completed. The character of this scum must be carefully watched, and the soap test added more carefully, with an increased amount of shaking between each addition. With this precaution it will be comparatively easy to distinguish the point when the false lather due to the magnesium salt ceases, and the true persistent lather is produced. If the water is of more than 16 of hardness, mix 35 c.c. of the sample with an equal volume of recently boiled distilled water, which has been cooled in a closed vessel, and make the determination on this mixture of the sample and distilled water. THE SANITARY ANALYSIS OF WATER. 573 (b] For permanent hardness. To determine the hardness after boiling, boil a measured quantity of the water in a flask briskly for half an hour, adding distilled water from time to time to make up for loss by evaporation. It is not desirable to boil the water under a vertical condenser, as the dissolved carbonic acid is not so freely liberated. At the end of half an hour, allow the water to cool, the mcuth of the flask being closed ; make the water up to its original volume with recently boiled distilled water, and, if possible, decant the quantity necessary for testing. If this cannot be done quite clear, it must be filtered. Conduct the test in the same manner as described above. The hardness is to be returned in each case to the nearest half-degree. 12. Judging the Results. No definite rule can be laid down for judging all the results on one uniform scale, because the analyst ought to have special information as to the locality, nature of the soil, or depth of the well, before giving an opinion. For example, nitrates, which have in river and shallow surface waters the highest significance, as indicating the presence of previous sewage contamina- tion, entirely lose such force in waters from deep artesian wells, because these are naturally rich in such salts. The same thing may be said of ammonia, which, although highly unfavourable in shallow waters, is yet always found in artesian wells, most probably from the metal pipes acting as reducing agents upon the nitrates. Again, with upland peaty waters we always find a large reduction of permanganate, and consequently an excess of "oxygen consumed," although the organic matter so acting cannot be viewed as dangerous. Setting aside, however, all questions of mineral constituents and only looking at the indications of the presence or absence of organic matter, the author has devised a valuation scale, originally presented by him in a paper read before the Society of Public Analysts, and which has proved since that time as nearly correct as any general scale can be. The principle is to divide the amount of each figure found in the analysis by a fixed divisor, and where the quotient exceeds 10 to double all figures over that number. Let us suppose that, for example, a water yielded '012 grain of albuminoid ammonia per gallon, and that the divisor fixed for this indication is '0007 ; then we have then 17*1 10 7'i, and 7*1x2= 14*2 ; therefore 14*2 -f 10 = 24*2, indicated degree of impurity. To prevent the production of enormous figures, likely to startle non-pro- fessional persons, the indicated degree of impurity is expressed as a decimal by dividing it by 100. Thus, it is only when the article is very bad indeed that the indication comes into full numbers. Taking, then, the whole scale, it stands as follows : GRAINS PER GALLON. Ammonia each '0015 = I. Albuminoid Ammonia ,, -0007 =-= I. Oxygen consumed in 15 minutes . . ,, '004 = I. Oxygen consumed in 4 hours ,, 'oio = i. PARTS PER MILLION. Ammonia each *O2 Albuminoid Ammonia ... ,, - oi Oxygen in 15 minutes . . . . . ,, '057 Oxygen in 4 hours . . . . ,, '143 When any number exceeds 10, then all over 10 is to be doubled and added to the original number, and the total valuation is to be divided by 100 and noted as "comparative degree of organic impurity." Then, supposing w, 174 THE ANALYSIS OF WATER, AIR, AND FOOD. other consideration intervenes to modify the analyst's opinion of the sample, the following limits should be observed : 1st Class Water up to '25 degree. 2nd ,, ,, (more or less questionable) . up to '50 ,, Undrinkable Water over '40 DIVISION II. THE SANITARY ANALYSIS OF AIR. For definite sanitary purposes it is really necessary to make a bacteriological as well as a chemical examination, but the former being outside the scope of this book, only the latter is considered. The chief points are : 1. Testing for Gaseous Impurities. The odour will call attention to these when present in notable proportions. Blotting paper dipped : (a) in tincture of turmeric, and introduced into the bottle containing the suspected air, turns red-brown in presence of ammonia; (1}) in solution of subacetate of lead black with sulphuretted hydrogen, or the vapour of ammonium sulphide ; (c) in solution of sodium nitroprusside purple with the vapour of ammonium sulphide, but no colour with H 2 S ; (d} in solution of potassium iodide mixed with starch paste blue with chlorine or ozone or nitrous acid ; (e) red litmus paper dipped in solution of potassium iodide blue with ozone, but not with chlorine or nitrous fumes. A few drops of: (a) weak solution of indigo introduced into the bottle is decolourised by chlorine and sulphurous acid ; (b) solution of barium chloride containing nitric acid is rendered turbid by sulphurous acid; (c) solution of argentic nitrate is rendered turbid by chlorine and not by nitrous fumes ; (d) lime water is rendered slightly turbid by ordinary air, but becomes strongly milky with air containing an excess of carbonic acid. Air which is simply " foul " from sewage impurities or overcrowding will have a very characteristic <; heavy" smell, and will decolourise a few drops of a weak solution of potas- sium permanganate, and will also show an excess of carbonic acid. 2. Estimation of Carbon Dioxide. This is done by the method of Pettenkofer, which consists in standardising 100 c.c. of lime (or baryta) water with standard oxalic acid 2-25 grammes per litre, of which i c.c. = 'ooi (i milligramme of CaO). The air to be examined having been collected in a large bottle of known capacity, 100 c.c. of the same lime water are added, the bottle is closed, and well shaken for some time. The CC>2 is absorbed, forming CaCOs. The resulting milky liquid is allowed to settle, and 50 c.c. are drawn off clear and immediately titrated with the same acid. The indicator is turmeric paper, or phenol- phthalein, and the number of c.c. of acid used is multiplied by 2. The difference between the two titrations gives the amount of CaO precipitated as carbonate by the CC>2 in the air, and this is then calculated thus : c.c. used x 'ooi x 44 = co nt in the volume of air taken . 56 In strict analyses, the volume of air taken must be corrected for observed temperature and pressure to its volume at N.T.P. Normal air contains about 04 per cent, of COs- 3. Estimation of Organic Matter. A known volume of air is sucked by an aspirator through a specially arranged apparatus containing ammonia-free distilled water, and the resulting liquid is analysed for "free " and " albuminoid " ammonia like a water. THE ANALYSIS OF FOOD. 175 DIVISION III. FOOD ANALYSIS. Here we will only attempt to consider a few of the more commonly occur- ring cases, always choosing the simplest and most rapid process. 1. Milk. (1) Specific Gravity. Take the specific gravity at 60 F. If not at 6o r take the temperature and refer to the annexed table to get the true gravity at 60, which will be found in the column opposite the observed gravity and under the observed temperature. (2) Total Solids. Heat a small flat platinum dish about i| inch in diameter to redness, cool it under the desiccator, and weigh. Put in 5 c.c. of the milk and again weigh. The difference = milk taken. Now transfer to the drying oven at 100 C. for 6 hours, cool under the desiccator and weigh. Put it back in the oven for an hour, repeat the cooling and weighing, and if the difference does not exceed a milligramme or two it is dry; if it does,, then repeat the drying. The weight of the dish and dry residue minus the tare of the dish equals the total solids, which x TOO and -f- by weight of milk taken = per cent, of total solids. (3) Fat. Is got by using " Richmond's milk slide rule/' an instrument constructed to automatically calculate by the following formula thus (T~ total solids : G specific gravity : F fat) : T = -2$G + 1-2 F + -14. Deducting the fat thus found from the total solids, we get the "solids not fat? In event of the sample being the least sour, or when we are dealing with absolutely skimmed or " separated ?J milk, the rapid process above given fails. It is then necessary to extract the fat as follows : 10 grammes of the milk are weighed in a porcelain dish, 30 grammes of plaster of Paris are stirred in, and the whole is placed upon the top of the water bath and stirred occasionally till it appears dry. (When the sample is sour 2 drops of strong liquor ammonia are to be added to the milk in the dish before stirring in the plaster.) The mass is well powdered and introduced into a narrow-mouthed 8-ounce bottle with a well-fitting stopper, and 140 c.c. of pure ether having been rapidly poured in, the bottle is closed, shaken at intervals during two hours, and finally set aside in a cool place to settle during the night. In the morning, if the plastered milk was not over-dried, it will be found quite easy to pour off 70 c.c. of the ether perfectly clear into a weighed flask, from which the ether may then be distilled off, and the residual fat dried at 100 C. and weighed. The weight of fat found x 20 = percentage of fat in sample. Some analysts prefer to place the plastered milk in a paper cartridge and exhaust it with ether in the " Soxhlet's tube " (see Chap. I., p. 2), while others cause the milk to be soaked up into a roll of blotting paper, dried thereon, and then extracted in the " Soxhlet " with ether. This latter is the official process of the British Society of Public Analysts, but with ordinary milk nothing is so. simple and good as the gravity, solids, and formula. (4) Added Water. The limit for the strength of milk is at present based upon that of the poorest possible natural milk. Average milk will show : Fat ... 3-00 Solids not fat ... 9'co Total 12-00 176 THE ANALYSIS OF WATER, AIR, AND FOOD. 2 a > c as RAVITY. g p CM O CM O CO CM O I o p CM O p 00 p Oi P O CO o co o 1 CO s p p OT O g P N i? jf r? 1 b CO ro Vt ^0 vb ON g fl S ro S VO CO 1 M M i j? CO 00 00 CO M ON N ON O N ro O ro p vo i v * ^ vO i K. N 00 oo b CO ON ON ON ON vo ** c? 10 CO if !? vo S Tl- r? 1 1 1 f^ S" CO CO op ' s b ri S i | M X? -8 M CO N ON i M to vp "S vo ro CO CO b N S (S N i M M i7 oo ON Cl 1 M i to ro VO H CO b M N | r 1 Vj- VO N M S % 1? to b L p M P to Vj- P vo rH CO i N M M M o? i i: | s- | ^ ro r^ ro vo ro O -> o O O o PH w CO o CM CM O CO CM O i ib CM O 1 00 CM CD o CO o rH CO O CM 2 CO s i X rH rH rH rH rH CT> iO ON ON ON b ON ON N ON M ON ON ON ON ON cb ON ON ro ON ? ON ro 1 00 10 ON ON ON ON N op M op CO M 00 co cb M op CO j> to r^ 5 C/J w 10 00 2" CO b M CO op PO M i r? M N 00 ON b S ro "to vp ro w CO IO S b M ri N vp '-3- CJ 1 Pj 1 vp b ;? v vo to ro VO w 10 iO "bN o "2 M i? 1 O ri O CO p ON N ON ON ON CO M ro vp I'M RV1D PEC1FIC KAVITY. P O p rH CM O CO CM O p o Co CM O p CD CM O O a o 05 CM O O P rH S o CM CO o o CO CO o P CO o p CO O o w THE ANALYSIS OF FOOD. 177 If, however, a milk has only Fat ... 30 Solids not fat . . . 8-5 Total 1 1 -5, it will not be considered as definitely proved to be adulterated. In calculating the amount of water added the " solids not fat " are used for the basis of calculation because they are a fairly constant quantity, the fat being variable. The amount of pure standard milk present in any sample may be calculated thus : Solids not fat x 100 0/ f . TT = % of pure milk present, and the difference between this result and 100 is, of course, added water. (5) Ash. The total solids in the platinum dish are burned over a low flame at dull redness till quite white, and the ash is weighed. The ash should be about 70 %, and it will never, as a rule, fall below '67 in an unwatered milk. (6) Preservatives are frequently added to milk, the favourite ones being boric acid and formalin, which can be detected as follows : (a) Formalin (formic aldehyd, 40 %) is detected by diluting the sample in a test tube with an equal volume of water, and then carefully running strong sulphuric acid down one side of the tube, so that about an inch layer of it forms at the bottom. On now gently agitating a violet shade will appear at the point of contact of the two liquids if formalin be present. (b} Boric acid is detected in the ash of the milk by moistening with a drop or two of strong sulphuric acid, then adding alcohol and setting it on fire, when it will burn with a green flame in presence of boric preservative. To estimate the quantity we evaporate 100 grammes of milk to dryness, in a platinum dish, with 2 grammes of sodium hydroxide, and having thoroughly charred the residue we treat it with 20 c.c. of water and add HC1 drop by drop till nothing more dissolves. We then wash from the dish into a 100 c.c. flask, taking care not to use more than 30 c.c. of water, and we then add *5 gramme solid CaClg. To this we then add a few drops of phenol-phthalein, and drop in 10 per cent, solution of sodium hydroxide until a slight pink is produced, and then having added 25 c.c. of lime water, we make the whole up to the 100 c.c. mark and filter through a dry filter. To 50 c.c. of this filtrate (= 50 grammes milk) we add N sulphuric acid till the colour is dis- charged, then add methyl-orange indicator, and continue to add the acid till a faint pink is produced, and lastly we drop in 4' alkali till the liquid assumes the yellow tinge. At this stage all acids other than boric likely to be present are in a state neutral to phenol-phthalein. The solution having been cooled, is mixed with some phenol-phthalein and 33 % of glycerine (to set free boric acid), and is titrated with ^ alkali, each c.c. of which consumed = "0124 crystallised boric acid in 50 grammes of milk, and this x 2 = per cent. (7) Sour Milks that will not readily become homogeneous should have one drop of liquor ammon. fort, added to each ounce, before shaking, when a sufficiently fair sample will be generally obtainable for analysis. Sour milks are generally from -2 to '3 too low in the " solids not fat," and the results are not really properly comparable with those from fresh milk, so caution is necessary in forming opinions on sour samples, unless the departure from the standard is very marked. a 12 178 THE ANALYSIS OF WATER, AIR, AND FOOD. 2. Butter. The only really serious adulteration of butter consists in mixing it with other fats of lower commercial value. Such a mixture may be legally sold if labelled " margarine." The butter is to be first melted in a beaker on the top of the water bath, when it will gradually separate with a top layer of clear butter-fat, and a bottom one of water and curd. If the top layer of fat does not become quite clear it must be filtered through a dry filter placed over a beaker inside the water oven, but it will often clear sufficiently to enable enough to be poured off without filtering, and, speaking generally, the better the butter the more easily the fat will clarify. Having thus got the actual fat ready for analysis we counterbalance a small flask of about 250 c.c. capacity, and having a mark at 150 c.c., and weigh into it 5 grammes of the clarified fat and then add 50 c.c. of a solution of potassium hydrate in alcohol (S.V.R.) having a strength of 30 grammes per litre (3 per cent.). The flask having been closed by a cork through which passes a piece of narrow glass tube, its contents are heated on the water bath, with constant agitation, until the fat is entirely dissolved. The flask is then attached to a condenser, and the alcohol entirely distilled off. The residual soap thus left in the flask is dissolved in a little hot water, and 25 c.c. of diluted sulphuric acid of 5 per cent, strength having been added, the whole is made up by distilled water to the 150 c.c. mark. A few fragments of recently ignited pipe-clay having been dropped in, the flask is connected to a short condenser and the contents distilled until the distillate measures ico c.c. This distillate is then filtered, and a few drops of solution of phenol-phthalein having been added the whole is titrated with decinormal solution of sodium hydrate or with vigintinormal baryta water, which latter is preferred by some analysts ; 5 grammes of pure butter-fat thus treated yields a distillate requiring not less thah 25 c.c. of decinormal soda, while lard, tallow, and the other solid animal fats do not take more than 1-5 c.c. The only fat coming anywhere near butter is cocoa-nut fat, which takes about 7 c.c., because it also contains fatty acids, volatile at the heat of boiling water. To calculate the amount of butter present in any mixture we multiply the number of c.c. of soda used by 100 and divide by 25. Certain excep- tional butters having been met with, during the winter months, which only consumed 21 c.c., no definite expression of opinion can safely be given unless the article takes less than that number of c.c. of decinormal soda. 3. Taking the Alcoholic Strength of Spirits, Tinctures, Wines, Beer, and all Alcoholic Liquids. If the sample is simply one of pure diluted alcohol we ascertain its specific gravity, taking care that the temperature of the liquid is exactly 60 F. We then look at the annexed table and find the strength of the spirit. It, how- ever, frequently happens that it is not possible to get the sample exactly to 60 F., and in such a case we must carefully note the temperature at which ;ve worked and make a calculated correction for the expansion of the spirit, based on the following data : If the spirii be above 70 per cent, of apparent strength, then we must add 0005 to the specific gravity for each degree F. that the spirit was above (3) Table for ascertaining the percentages respectively of Alcohol by Weight, by Volume, and as Proof Spirit, from the Specific Gravity. Specific K'F'. Absolute Alcohol :>y Wght Per cent. Absolut Alcoho by vol'm Per cen Proof Spirit. Per cent Specific gravity, at 60 F. Absolute Alcohol by w'ght Per cent Absolute Alcohol by vol'mc Per cent Procf Spirit. Per ctn. Specific gravity, at 60 F. Absolute Alcohol >.y w'ght Per cent Absolut Alcohol by vol'm Per cen Proof Spirit. Per cent. I '000 000 O'OO OO 928 45-50 53-I5 93'2 859 75-50 8l70 I43-2 999 0'55 0-65 O'l 927 45-95 53-65 94-1 858 75^0 81-95 143-8 998 1-05 I-30 2'4 926 46-40 54'10 94-8 857 76-30 82-40 144-4 997 1-60 2'OO 3'5 925 46-90 54'60 95-6 856 76-70 8275 M50 996 2T5 2-70 4'9 924 47-30 55'10 96*5 855 77-15 83-I5 145-6 995 275 3'5o 6-1 923 47-80 55-55 97-4 854 77-55 83-45 I46-2 994 3'3Q 4-i5 7-2 922 48-25 56-05 98-2 853 78-00 83-80 146*7 993 3-90 4-90 8-6 921 48-65 56-50 99-o 8 5 2 78-40 84-I5 147-4- 992 4-50 5-65 9'9 920 49-I5 56-95 99-8 8 5 I 78-80 84-45 I48-0 'GOT p-ie 6'jd.o 1 1"2 "850 7Q'2O 84-84 i/iS-f> yy i 99 J 1 J 575 7-15 12-6 9198 ! 49-25 57-05 loo-oPS 849 /y ^u 79-60 85-I5 1 40 t> 149-1 oSo f\" A d X-nn _ 1 1 II .0.0 8o-oc 8c-cn yoy 988 U a^\J 7-10 o OO 8-80 14 1 iS'S 919 49'65 57-40 ioG-6 *-7^'SS 18-4 917 50-55 58-40 102-3 845 81-20 86-50 I S 1 '5 985 9-20 11-40 20 -o 9l6 5I-OO 58-8 5 103-1 844 81-65 86-80 152-1 984 9-90 !2'35 21-5 915 5^45 59-30 103-9 843 82-00 87-10 1527 983 10-65 13-20 23-1 914 5I-90 59-75 104-7 8 4 2 82-45 87-45 153-2 982 1 1 '45 14-10 247 913 52-35 60-15 105-5 8 4 I 82-80 87-75 I53-8 9 8l 12-25 15-10 26-5 912 52-80 60'6S 106-5 840 83-20 88-05 I54-3 980 13-00 16-00 28-0 911 53-25 5I-05 107-0 839 83-60 88*35 I54-9 '979 13-80 17-00 29-8 -9IO 53-65 6r50 107-8 838 8400 88-65 !55'4 978 H'SS 18-00 31-6 909 54'10 6l'95 108-5 837 84-40 89-00 156-0 '977 I5-45 19-00 33-3 9 08 54-55 62*40 109*3 836 84-80 89-30 156*5 976 16-30 20-00 35 -i 907 54^5 62-80 IIO'O 835 85-20 89-60 157-1 '975 17-10 21-00 36-8 906 55-45 63-30 110-9 834 85-60 8995 I57-6 "974 17-90 21-95 38-5 905 55-90 63-70 ni'6 833 85-95 90-25 158*1 '973 18-80 23-05 40-5 904 56-35 64-10 112-3 8 3 2 86-35 90-55 158-6 972 I9-55 23-90 42-0 903 56-75 64-55 113-1 831 86-75 90-85 i59-i 971 20-35 24-90 43'6 902 57-20 65-00 113-9 830 87-15 91-10 I59-7 970 2TIO 2575 45'2 9OI 57^0 65-35 114-6 829 87-50 91-40 160-2 969 21-95 26-85 46-9 900 58-05 65-80 II5-4 828 8790 91-70 160-7 968 2275 27-75 48-6 8 99 58*55 66-30 Il6'2 827 88-30 92-00 161-2 967 23-5 28-65 50-2 898 58-95 66-65 116-8 826 88-65 92-30 161-7 966 24-25 29-55 51-8 8 97 59-35 67-05 117-5 825 8905 92*55 162-2 965 25-00 30-40 53-3 8 9 6 59-85 67-55 1184 824 89-50 92-90 162-8 964 25-70 31-20 54-7 8 95 60-30 68-00 119*2 823 89-90 93-25 163-4 963 26-45 32-05 56-2 894 60-70 68-35 119-8 822 90-25 93-50 163-9 962 27-I5 3290 57-6 893 6rio 68-75 120-5 821 9065 93-75 164-3 961 27-80 3360 59'0 892 6i-55 69-15 I2I'I 820 9095 94-00 164-7 960 28-45 34'40 60-3 8 9 I 62-00 69-96 I21'9 8l 9 9I-35 94-25 165-1 959 29-10 35-10 6r6 8 9 62-45 69-95 I22'6 8l8 9170 94-5 165-6 958 2970 35-8o 62-8 889 62-85 70-35 123*3 *8l 7 9205 94-75 1 66- 1 '957 30-35 36-55 64-1 -888 63-25 70*75 124-0 816 92*45 95-00 166-5 956 31-00 37'35 65-4 887 63-70 71-20 124-7 815 92-80 95-25 167 o '955 31-55 37'95 66-5 386 64-15 71-60 I25-4 814 93-20 95-50 167-4 '954 32-I5 38-60 67-6 885 64-55 71-90 126-0 813 93-55 95*80 167-9 '953 3270 39'2o 68-7 884 65-00 72-35 126-3 812 93-95 96-10 168-4 952 33-30 39-90 700 883 65-40 72*75 127-5 811 94-3 96*35 168-8 95i 33'SO 40-55 71-0 882 65-80 73-I5 128-2 810 94-60 9655 169-2 950 34-40 41-20 72-2 881 66-25 73-50 I28-9 809 94-95 96-80 169-6 949 35-00 41-85 73-3 880 66-65 73-90 129-6 *3o8 95-3 97-05 170-0 948 35-50 42-40 74-3 879 67-05 74-3 I30-2 807 95-70 97-25 170-4 '947 36-05 43-00 75-4 878 67-55 74-70 130-9 806 96-00 97-50 170-8 946 36-55 43-60 76-4 877 67-95 75-10 I3r6 805 96-35 97-70 171-2 '945 37-10 44 -I 5 77-4 .876 68-40 75-45 I32-2 804 96-70 97-95 171-6 '944 37-65 44-75 78-4 875 68-80 75-8o 132-9 803 97-03 98-15 172-0 943 38-20 45-40 79-5 874 69-20 76-15 I33-5 802 97-35 98-40 172-4 942 38-65 45^5 80-4 873 69-65 76-60 I34'3 801 97-70 98-55 172-7 941 39-I5 46-40 81-4 872 70-05 76*95 I34-9 800 98*00 98*75 173-i 940 39-70 47-00 82-4 871 70-50 7735 1 35 '6 "799 98-35 99-00 I73-5 939 40-15 47-50 83-3 870 70-85 77-65 136-1 798 98-65 99-20 173-8 938 40-65 48-05 84-1 869 71-30 78-10 136-6 797 98-95 99-40 174*1 937 4I-I5 4860 85-1 868 71-75 78-45 I37-4 796 9930 99-55 174-4 936 41-65 49-10 86-1 867 72-20 78-75 138*1 "795 99-60 99-75 1748 935 42-15 49'65 87-0 866 72-55 79-I5 138-8 794 99'95 99-95 175-2 '934 4265 5' 1 5 87-9 865 73-00 79-55 I39-4 '933 43-I5 50-70 889 864 73-45 7995 140-1 932 43-6o 51-20 89-8 863 73-80 80-25 140-7 Absolute Alcohol. 93i 44-10 51-70 90-6 862 74-25 80-60 141-3 020 A A ' C C rii 'A 86 1 *7 A ' 7O S i *oo T A T Tl yj u 929 44 33 45-00 5 2-I 5 5270 yi 4 92-3 860 /4 / u 75-10 81*35 141 y I42-6 7938 roo-oo lOO'OO I75-2S i8o THE ANALYSIS OF WATER, AIR, AND FOOD. 60 F., or we must deduct the same amount for each degree that the spirit- was below 60. This will now give the real gravity at 60 F., and a reference to the table will show the true strength. If the spirit is below 70 per cent., we must then use smaller amounts to add or deduct as follows :- Under 70 but over 40 add or deduct '0004 for each degree F. ,, 40 25 -0003 ,, 25 ,, 15 ,, -0002 15 t ' C001 When we are operating on a wine, tincture, or other complex alcoholic liquor, the spirit it contains must be distilled off and the specific gravity of the distillate ascertained. To do this we take 50 c.c. of the sample, and having carefully taken its temperature and noted the same, we transfer it to a. small retort attached to a condenser, rinsing out the measuring flask with two successive quantities of 5 c.c. each of distilled water. We then place the same measuring flask at the end of the condenser and distil until 40 c.c. have passed over. 10 c.c. of distilled water are now to be added to the contents of the retort, and the distillation is to be continued until very nearly 50 c.c. have been distilled over. The temperature of this distillate having been brought to the same degree as that at which the sample was measured, distilled water is to be added exactly up to the 50 c.c. mark. By this means it is possible to obtain a volume of pure spirit of precisely the same strength as the sample, and we finally take the specific gravity of the same and apply the tables as above directed. Some chemists prefer to distil off three-fourths of the sample, and having taken the specific gravity of the distillate, to add some water and distil off the remaining fourth, taking its gravity separately, and finally adding the results both together. 4. Bread and Flour. Take 10 grammes of the bread in a weighed platinum dish, and dry it in the water oven for 3 hours at a temperature of 100 C. Good bread should not lose more than 44 per cent, of its weight. Now place the dish over the Bunsen burner and heat it to redness until it is reduced to a uniformly greyish-white ash and again weigh. This ash should not weigh more than 1*5 per cent, of the original bread. Note. Both bread and flour are very difficult to burn, and it is better to first char them to a mass of coke, then to remove this mass to a glass mortar and powder it, and finally to return the powder to the platinum dish to finish. Acidity. Put 20 grammes of bread (or 10 grammes of flour) into an 8-oz. wide-mouthed stoppered bottle, and pour in 200 c.c. of rectified spirit ; close the bottle and let it stand some hours. Then pour off 100 c.c. of the clear liquor, add a drop of solution of phenol-phthalein and run in decinormal solution of soda until a pink tint is produced. Good fresh bread or flour should not require more than i c.c. of the soda solution to render it alkaline. Alum. Mix together 5 c.c. of freshly prepared tincture of logwood with 5 c.c. of a saturated solution of official carbonate of ammonia .ind 50 c.c. of water, and at once pour it on to a mass of the bread taken from the inner portion of the loaf. If a fair adulteration of alum be present a slate-blue colour will be produced, but if the amount of alum be small (say less than 10 grains per 4-lb. loaf) then the colour will only appear after gently warming on the top of the water oven for some time. If the presence of alum be shown by this test, its amount must be estimated as follows : 100 grammes of the bread are burned to ash in a platinum dish, and when cold 5 c.c. of fuming hydrochloric acid are added, and the dish having at once been covered by a glass plate the whole is allowed to stand for 15 minutes; 25 c.c. of water are THE ANALYSIS OF FOOD. 181 then added to the dish and its contents are gently boiled for five minutes and filtered. The insoluble matter (chiefly silicious matter and clay) having been washed and the washings added to the filtrate, the latter is mixed with 5 c.c. of strong liquor ammonias and 40 c.c. of acetic acid. The ash of bread being rich in phosphoric acid, the precipitate thus produced will consist of aluminium phosphate with some ferric phosphate; and such precipitate must then be filtered off, washed, dried, ignited, and weighed. If this precipitate does not exceed 5 milligrammes it is not worth going farther, but if it does, we must then proceed to estimate the iron present in it by the colouri metric, method given at page 126. The ferric chloride solution used should contain an amount of iron equivalent to one-tenth of a milligramme of ferric phosphate in each c.c. After the iron has been estimated and deducted from the original weight of the precipitate, each milligramme remaining may be taken, as representing one grain of alum per 4-lb. loaf. Alum and other mineral impurities added to flour are best detected by shaking up some of the sample with chloroform in a separatory funnel, and then letting it stand, when the flour will float on the top, and the sand, alum,, and other mineral matters will sink to the bottom. 5, Mustard. This is chiefly a microscopical matter for the exact identification of impuri- ties, but the following chemical operations may be performed : (1) Test a cooled decoction for starch with solution of iodine. (2) If starch be found, extract a weighed portion in the " Soxhlet " with petroleum spirit or ether. Distil off the spirit, dry and weigh the oil. Mustard contains as an ordinary minimum 33 % of oil, and the amount of genuine mustard in the sample, will then be found thus : % of oil found x 100 33 ~~ % genuine mustard J by deducting this from 100 the difference is added starch or flour. (3) Moisten the mustard with a little ammonia, when the turmeric broy'Li will be developed if that colouring agent be present. 6. Pepper. Mineral Impurities. Weigh out 10 grammes of the sample in 'a tared platinum dish and ignite it to a perfect ash, as already described under bread, and weigh. If the ash does not much exceed 2 per cent, in white, or 5 per cent, in black pepper, it may be passed, but if it does, the contents of the dish must be boiled with diluted hydrochloric acid, and the insoluble matter having been collected on a filter, and washed until free from acidity, is to be dried, ignited, and weighed. Any insoluble matter thus found over 4-5 per cent, may be considered to represent adulteration with sand. Vegetable Impurities. These are rendered visible under the microscope by mounting some of the sample with a drop of an acid solution of aniline acetate, which stains poivrette (ground olive stones) and other woody im- purities yellow, without affecting the detection of any rice flour or other cereal that may be present. If they be found we can get a fair idea of their amount by estimating the amount of matter soluble in alcohol (resin, piperine, etc.),, present in the sample as follows : 2 grammes of the pepper are boiled in a long- 182 THE ANALYSIS OF WATER, AIR, AND FOOD. necked flask with 40 c.c. of absolute alcohol for ten minutes and the solution passed through a filter placed over a large platinum dish, the insoluble matter on the filter being washed with another 25 c.c. of alcohol. The dish is placed on the water bath until the spirit has passed off, and the residue is dried for half an hour at 100 C. and weighed. Lastly, it is placed over the " Bunsen " and ignited, cooled, and again weighed, and the weight deducted from the former one. The difference is the weight of the extract, which should not be less than 8 per cent, in white, or 10 per cent, in black pepper. If, for example, the extract of a sample of white pepper, in which rice starch had been found by the microscope, only amounted to 4 per cent., we should then charge it with being adulterated to the extent of 50 per cent. In the case of poivrette or excessive bleached pepper husk being found in a sample, we boil one gramme for an hour with 100 c.c. of water, and 2 c.c. of sulphuric acid under an upright condenser for an hour, cool and filter through a pair of counterbalanced filters, wash till every trace of acidity has been removed, and dry the filters and their contents to constant weight in the water oven. Pure pepper thus treated yields not more than 35 per cent, of insoluble matter, while husks and poivrette yield 70 and 75 per cent, respec- tively. The calculation is manifest thus, suppose a sample (in which much husk was seen under the microscope) to show 52-5 per cent, of insoluble matter, it would contain 50 per cent, of added husks. A not uncommon recent adulteration of pepper consists in adding ground ginger which has been already exhausted by spirit to make the essence of ginger. 7. Coffee, If chicory be found by a microscopic examination of the sample best done after boiling with dilute NaHO 10 grammes of the coffee are placed in a flask with 100 c.c. of distilled water. The flask is counterbalanced, and then boiled for a quarter of an hour. It is then placed on the scales, and the original balance is restored by adding water. Finally the decoction is filtered, cooled to 1 5 '5 C., and its specific gravity is taken. The gravity of pure coffee does not exceed 1009-5, while that of chicory solution is 10217. Supposing, therefore, that a decoction showed a gravity of 1015 '5, then 10217 I oo9'5 = I2'2, and ioi5'5 1009*5 = 6*0 therefore I2'2 : 6 :: 100 = 49 per cent, of chicory. 8. Colored Sweets. The poisonous colors are nearly all mineral and insoluble. They may be scraped off, washed with water, and identified by the ordinary methods given in Chapter IV. As a rule, at present, only aniline colors are used, and they are added in such minute proportions as not to be considered dangerous. 9. Free Sulphuric Acid in Vinegar. To a dilute solution of methyl violet add a drop of vinegar. A blue colour shows the presence of a mineral acid in the sample. Mix 50 c.c. of the vinegar with 25 c.c. of volumetric solution of sodium hydrate, made decinormal by diluting the normal volumetric solution to ten times its bulk with water. The whole is evaporated to dryness, and incinerated at the lowest possible' temperature. 25 c.c. of decinormal solution of oxalic acid (made to exactly balance the sodium hydrate solution) are THE ANALYSIS OF FOOD. 183 now added to the ash, the liquid heated to expel CO 2 , and filtered. The filter is washed with hot water, and the washings having been added to the filtrate, phenol-phthalein solution is added, and the amount of free acid ascer- tained by running in decinormal soda from a burette. The number of c.c. of soda thus used multiplied by '0049 gi yes tne amount of free sulphuric acid in the vinegar. This process depends on the fact that whenever the ash of vinegar has an alkaline react ion, free mineral acid was undoubtedly absent. CHAPTER XL ANALYSIS OF DRUGS, FIXED AND ESSENTIAL OILS, FATS, WAXES, SOAPS, DISINFECTANTS, URINE, AND URINARY CALCULI. DIVISION I. ANALYSIS OF DRUGS, I. GENERAL SCHEME. THE analysis of drugs is so large a subject that only a few of the more commonly occurring problems can be discussed in the present volume. It will, however, be interesting, before proceeding to the consideration of special matters, to give a sketch of the general method of analysing a vegetable sub- stance used in medicine, following the lines laid down by Dragendorff. Step I, Dry a weighed portion of the substance in the water oven until it ceases to lose weight. Step II, Pack the dried and powdered substance, mixed with a little sand, in a " Soxhlet " apparatus, thoroughly exhaust it with petroleum spirit, and cork up and save the fluid extract so obtained, marking it A. Step III. Spread the solid left from Step II. out to dry on a plate of glass on the top of the water oven, and when all odour of petroleum has passed off, replace it in the Soxhlet, and exhaust it this time with perfectly anhydrous ether. Cork up the ethereal extract obtained and mark it B. Step IV. Spread out as before, and when all odour of ether is gone re-pack and extract with purified commercial methyl alcohol, as sold for making methylated spirit. This is more volatile than common alcohol, and is as a rule a better solvent of the articles required in this group, while it does not so readily extract glucose, etc. It is an article of commerce, and can be specially ordered through a purveyor of chemicals as " commercial methol, highest strength." Save this alcoholic extract and mark it c. Step V. Extract the insoluble matter from Step IV. with distilled water at a temperature not. exceeding 120 Fahr., and filter. Wash with cold water and save the filtrate (D). Step VI. Wash the insoluble matter off the filter into a large flask, with plenty of water, acidulated with i per cent, of hydrochloric acid, and boil it for an hour under an upright condenser. Let it settle, pour off the liquid as close as possible (saving it), and then collect the insoluble matter on a filter and wash with boiling water, adding the washings to what was poured off. This extract is marked E. 184 GENERAL SCHEME. 185 Step VII. Once more wash the insoluble matter from the filter into a beaker and boil it up for an hour with plenty of water rendered distinctly alkaline with sodium hydrate. Collect on a weighed filter, wash first with boiling water, acidulated with hydrochloric acid, and then with plain boiling water, till no trace of a chloride remains ; dry in the water oven and weigh, deducting the tare of the filter. Lastly, ignite the filter and its contents in a weighed platinum basin, and deduct the ash so found from the first weight, and the difference will be a woody fibre in the drug. Step VIII. Make a nitrogen determination by KjeldahPs method (page 166) on a fresh portion, and the nitrogen found (after deducting any due to alkaloids present) multiplied by 6^33 will give the amount of albuminous bodies present. Treatment of the Separate Solutions. Each liquid is made to a definite number of c.c. with the same solvent, and then an aliquot part, say 10 c.c., is taken and evaporated, and the residue weighed, to find the total matter soluble in each solvent. The remainders of the liquids are then treated as follows : Liquid A. This will contain chiefly fixed and volatile oils. The spirit is allowed to evaporate spontaneously, or in a current of cold dry air, and the residue is distilled with water, when the volatile oil passes over, leaving the fixed oil in the retort. Liquid B. This chiefly contains resins, together with some bitters, alkaloids, and organic acids. The solution is evaporated to dryness on the water bath with sand, and the residue, having been powdered, is boiled with water slightly acidulated with HC1. A portion of this watery solution is tested for benzoic, cinnamic, salicylic, gallic, and other free organic acids, and the remainder is saved for subsequent use in Group C. The portion insoluble in water now chiefly represents any resins present in the drug, which are soluble in ether. These may be further divided and examined by the action of alcohol. Resins are recognised by their behaviour with solvents, their odour on warming, and by the action of H 2 SO 4 , HNOs, HC1, etc., on spots of the solid resin left by evaporating the solutions. This matter requires special experience ; but a description of the nature and reactions of all the principal resins will be found in any large book on Materia Medica. Liquid C. Is evaporated to a low bulk, and then poured into water faintly acidulated with hydrochloric acid. Any insoluble matter is probably a resinous body insoluble in ether, and is to be filtered out and examined as a resin. A portion of the aqueous solution is to be tested for tannin, and the remainder is to be mixed with the reserved liquid from B, the whole gently evaporated to a convenient bulk, and treated by immiscible solvents as follows : Step I. The liquid (which must still retain a slightly acid reaction) is shaken up successively with chloroform and ether in a separator (see fig. 17, page 93). The solvents are drawn off and evapo- rated, and the residues so obtained tested for glucosides and bitter principles. 1 86 ANALYSIS OF DRUGS, ETC. Step II. The liquid remaining in the separator is now rendered alkaline with sodium hydrate and again shaken up with chloroform. This extracts nearly all the alkaloids. The chloroform is evaporated and the residue tested for alkaloids (see Chap. V.). Step III. The liquid still remaining in the separator is shaken up with warm amylic alcohol, which takes out morphine and leaves it on evaporation, when any residue is tested for its presence. Liquid D, Is evaporated to a low bulk and then mixed with twice its volume of rectified spirit, when gums precipitate insoluble and may be examined, and sugars dissolve and may be estimated by " Fehling." Saponin also may be found with the sugars. II, ALKALOIDAL ASSAY BY IMMISCIBLE SOLVENTS. The immiscible solvents usually employed in the assay of alkaloids are chloroform, ether, benzin (petroleum spirit), benzol (benzene), and amylic alcohol, or a mixture of the latter two called benzolated amylic alcohol. The liquids are not miscible with water, but can be diffused through it by shaking, and then separate from it when set at rest. It is a general property of alkaloids that they themselves are as a rule soluble in all the above solvents, while their salts are insoluble. If, therefore, we start with an acid aqueous solution of, say, quinine sulphate, and, having added sufficient alkali to set free the quinine, we shake up with chloroform, and then leave the latter to settle, the chloroformic layer will contain all the alkaloid. If we then run off this layer and shake it up with diluted sulphuric acid, the quinine will become quinine sulphate, and, being insoluble in the chloroform, will then leave that solvent, and pass to the aqueous layer once more in its original form. The main exception to these rules is morphine, which only comes out satisfactorily from its alkalised salts to warm amylic alcohol. If a drug should also contain resinous or other matters soluble in the chloroform, they will come into it with the free alkaloids, but will remain behind when the chloroformic solution is acted upon by acidulated water. The process is done in a separator (see fig. 17, p. 93), and the following precautions are so lucidly described by the U.S. P. that they cannot be improved upon : When the solution of an alkaloid, suitably prepared, is introduced into a separator, and chloroform subsequently added, the latter, owing to its higher specific gravity, will form the lower layer. If the two layers are violently shaken together, there will often result an emulsion, which will separate only slowly, and often imperfectly. This is particularly liable to happen when the aqueous liquid containing the alkaloid either in suspension or in solution is strongly alkaline, and when it has a high specific gravity. To avoid the formation of an emulsion, the extraction should be accomplished rather by rapid rotation and frequent inversion of the separator than by violent shaking. When an emulsion has formed, its separation may be promoted by the addition of more of the solvent, preferably somewhat heated, aided, if necessary, by the external application of a gentle heat (the stopper being removed for the time being), or by the introduction of a small quantity of alcohol or of hot water. The separation of the two layers may also be promoted by stirring the lower, chloroformic layer with a glass rod, and detaching from the walls of the separator the. adhering drops of emulsion. On withdrawing the chloroform solution of an alkaloid from the separator, a small amount of the solution will generally be retained in the outlet tube by U.S. P. ASSAYS OF DRUGS. 18; capillary attraction. If this were lost, the results of the assay would be seriously vitiated. To avoid this loss, several successive, small portions of chloroform should be poured into the separator without agitation, and drawn off through the stopcock to wash out the outlet tube. Another source of loss is the pressure sometimes generated in the separator by the rise of temperature caused when an alkaline and an acid liquid are shaken together. On loosening the stopper, the liquid which adheres to the juncture of the latter with the neck is liable to be ejected. This is best avoided by mixing the liquids at first by rotation (avoiding contact of the contents with the stopper), and allowing them to become cold before stoppering the separator. The same precautions should be observed when an alkali carbonate has been used, in place of a caustic alkali, for setting free the alkaloid. In this case the liquids should be cautiously and gradually mixed by rotation, and the separator should be left unstoppered until gas is no longer given off. If a regular glass separator is not available, and the quantity of liquid is small, an ordinary burette, stoppered with a sound cork, may be employed in its place. III. U.S.P. ASSAYS OF DRUGS WHERE THE ALKALOIDAL RESIDUE IS WEIGHED. (1) Alkaloidal Scale Preparations. (a) Ferri et quinines citrus. Introduce i'n Gm. of iron and quinine citrate in a dish, and, with the aid of a gentle heat, dissolve it in 20 Cc. of water. Transfer the solution, together with the rinsings of the dish, to a separator, allow the liquid to become cold, then add 5 Cc. of ammonia water and 10 Cc. of chloroform, and shake the separator for one minute. Allow the liquids to separate, draw off the chloroformic layer, and shake the residuary liquid a second and a third time with portions of 10 Cc. each of chloroform. Allow the combined chloroformic solutions to evaporate spontaneously in a tared dish, and dry the residue at 100 C. (212 F.) to a constant weight. This residue should weigh not less than 0*1276 Gm. (corresponding to at least 1 1 -5 per cent, of dried quinine).* (b} Ferri et strychnines citras. Dissolve 4*44 Gm. of iron and strychnine citrate, in a separator, in 15 Cc. of water, add 5 Cc. of ammonia water and jo Cc. of chloroform, and shake the separator for one minute. Allow the liquids to separate, draw off the chloroformic layer, and shake the residuary liquid a second and a third time with portions of 10 Cc. each of chloroform. Allow the combined chloroformic liquids to evaporate spontaneously in a tared dish, and dry the residue at ico C. (212 F.) to a constant weight. This residue should weigh not less than 0*04 (0-0399) Gm. nor more than 0-0444 Gm. (corresponding to not less than 0*9 nor more than i per cent, of strychnine). (2) Colchicum and its Preparations. (a) Assay of colchicum corm. Introduce 10 Gm. of colchicum corm (in No. 60 powder) into a 200 Cc. Erlenmeyer flask, and add to it 100 Cc. of a mixture of 77 Cc. of ether, 25 Cc. of chloroform, 8 Cc. of alcohol, and 3 Cc. of ammonia water, insert the stopper securely, and macerate, with frequent shaking, for twelve hours (or preferably for four hours in a mechanical shaker). Filter off 50 Cc. of the liquid (representing 5 Gm. of colchicum corm), transfer this to a beaker, and evaporate it nearly to dryness at a gentle heat. Dissolve the residue in 10 Cc. of ether, add 5 Cc. of water, stir well, and heat gently * The U.S.P. uses the aqueous liquids left in the separator after extraction of the alkaloids for the volumetric estimation of the iron by the " hypo " process (see p. 122). 1 88 ANALYSIS OF DRUGS, ETC. until the ether has evaporated. After cooling, filter the aqueous solution inta a small separator, retaining the insoluble matter as much as possible in the beaker or dish. Redissolve the residue in a little ether, add 5 Cc. of water, and proceed as before. Wash the container and filter with a little water, and shake the combined aqueous solutions well for one minute with 15 Cc. of chloroform. Draw off the chloroform, after separation, into a beaker, and again shake out the aqueous liquid successively with three portions of 10 Cc. each of chloroform, collecting these solutions in the beaker. Evaporate the chloroform completely ; dissolve the residue in a little alcohol, evaporate the latter, redissolve the residue in 5 Cc. of ether, add 5 Cc. of water, and stir the liquid for a few seconds. Then evaporate the ether on a water-bath con- taining warm water, and filter the remaining aqueous liquid through a small wetted filter into a separator, washing the dish and filter with 5 Cc. of water, and adding the washings to the separator. Shake out the aqueous liquid with 15 Cc. of chloroform, and draw off the separated chloroform into a tared flask. Repeat the shaking out successively with three portions of 10 Cc. of chloroform and add each to the tared flask. Evaporate the chloroform, dissolve the residue in a little alcohol, evaporate the latter, redissolve the residue in alcohol, evaporate the alcohol as before, and dry the residue at 100 C. (212 F.) until the weight, after cooling, remains constant. The weight of the residue multiplied by 20 gives the percentage of colchicine in the colchicum corm. (b) Assay of extract of colchicum corm. Dissolve 4 Gm. of the extract of colchicum corm in 20 Cc. of distilled water, transfer the solution to a graduated flask, and add sufficient alcohol to make the liquid measure 100 Cc. Shake the flask well, allow it to stand for five minutes, filter, and collect 50 Cc. of the filtrate (representing 2 Gm. of the extract), and evaporate it to dryness in a porcelain dish by means of a water- bath. Add to the residue 10 Cc. of ether and 5 Cc. of distilled water, stir the mixture well and heat it gently until the ether is evaporated. After cooling, pour off the aqueous solution, filtering it into a separator, retaining as much of the insoluble matter in the dish as possible. Again treat the residue with 10 Cc. of ether, and 5 Cc. of water, and proceed as before ; rinse the dish and filter with a little water and collect all of the aqueous liquids in the separator. Introduce a small piece of red litmus paper into the separator, add enough ammonia water to render the liquid alkaline, and then shake it out with three successive portions of chloro- form, of 20, 15, and 10 Cc. respectively. Collect the combined chloroformic solutions in an Erlenmeyer flask, evaporate the chloroform, and add to the alkaloidal residue two successive small portions of alcohol, evaporating the alcohol each time. Now add' to the residue a mixture of 5 Cc. of distilled water and 10 Cc. of ether, agitate the liquid gently and evaporate the ether ; after cooling filter the aqueous liquid into a separator. Rinse the flask with distilled water, pass the rinsings through the filter into the separator, and shake out the aqueous solutions with three successive portions of chloroform, 20, 15, and 10 Cc. respectively. Collect the combined chloroformic solutions in a tared Erlenmeyer flask, evaporate the chloroform, and treat the alkaloidal residue with two successive small portions of alcohol, evaporating the alcohol each time, and dry the residue, at 100 C. (212 F.), to a constant weight. The weight multiplied by 50 will give the percentage of colchicine in the extract of colchicum conn. (c) Assay of colchicum seed. Introduce 10 Gm. of colchicum seed into a 200 Cc. Erlenmeyer flask, and add to it 100 Cc. of a mixture of 77 Cc. of ether, 25 Cc. of chloroform, 8 Cc. of alcohol, and 3 Cc. of ammonia water, insert the stopper securely, and macerate, with frequent shaking, for twelve hours (or preferably for four hours in a mechanical shaker). Filter the liquid into a U.S.P. ASSAYS OF DRUGS. 189 measuring cylinder until 50 Cc. of filtrate (representing 5 Gm. of colchicum -seed) have been obtained; then transfer this to a beaker or dish, and evaporate it nearly to dryness by applying a very gentle heat. Dissolve the residue in 10 Cc. of ether, add 5 Cc. of water, stir well, and heat gently until the ether has evaporated. After cooling filter the aqueous solution into a small separator, retaining the insoluble matter as much as possible in the beaker or dish. Redissolve the residue in a little ether, add 5 Cc. of water, and proceed as before. Wash the container and filter with a little water, and shake the combined aqueous solutions well for one minute with 15 Cc. of chloroform. Draw off the separated chloroform into a tared flask, and again shake out the aqueous liquid successively with three portions of 10 Cc. each of chloroform, collecting these solutions in the tared flask. Evaporate the chloroform ; dissolve the residue in a little alcohol, evaporate the latter, redissolve the residue in alcohol, evaporate the alcohol as before, and dry the residue at 100 C. (212 F.) until the weight, after cooling, remains constant. The weight of the residue multiplied by 20 gives the percentage of colchicine in the colchicum seed. (d) Assay of fluidextract of colchicum seed. Measure into a separator 10 Cc. of fluidextract of colchicum seed, add i Cc. of ammonia water, and shake out the alkaloid with three successive portions, 15, 15, and 10 Cc., of chloroform. Collect the chloroformic solution in a beaker or dish, and evaporate it nearly to dryness by applying a very gentle heat. Dissolve the residue in 10 Cc. of ether, add 5 Cc. of water, stir well, and heat gently until the ether is evaporated. From this point the process goes on as for colchicum seed, and the weighed residue so obtained is multiplied by 10, which gives Cms. of colchicine in 100 Cc. of the extract analyzed. (e) Assay of tincture of colchicum seed. Transfer TOO Cc. of tincture of colchicum seed to an evaporating dish, and evaporate it on a water-bath until it measures about 10 Cc. Add, if necessary, sufficient alcohol to dissolve any separated substance, and then assay the resulting liquid by the method above given for the fluidextract, with the exception that the multiplication of the product by 10 be omitted; the result will represent the weight in Gms. of colchicine contained in one hundred cubic centimeters of tincture of colchicum seed. (3) Conium and its Preparations. (a) Assay of conium. Place 10 Gm. of conium in a 200 Cc. Erlenmeyer flask, add 100 Cc. of a mixture of ether 98 parts, alcohol 8 parts, and ammonia water 3 parts (by volume), insert the stopper securely, and shake the flask at intervals during four hours. After the powder has settled, decant 50 Cc. of the clear liquid into a beaker (representing 5 Gm. of conium), and add sufficient N. H 2 SO 4 to produce a distinctly acid reaction. Evaporate the ether at a gentle heat by the aid of a water-bath ; then add 15 Cc. of alcohol, and set the beaker aside in a cool place for two hours to allow the ammonium sulphate to deposit. Filter; wash the residue and filter with a little alcohol, and add the washings to the filtrate ; neutralize any excessive amount of acid with sodium carbonate, being careful to retain a slight acidity. Concentrate the liquid to 3 Cc. by the aid of a gentle heat on a water-bath, add 3 Cc. of distilled water and 2 drops of N. H 2 SO 4 . Add 15 Cc. of ether to remove traces of fatty matter, pour off the ether-solution and repeat the washing with 15 Cc. of ether. Then transfer the acid liquid to a separator, introduce a small piece of red litmus paper, and add sufficient sodium carbonate to render the liquid slightly alkaline ; then shake out with successive portions f T 5> J 5 an< 3 I0 Cc. f ether. To the combined ether-solutions, in a tared 1 9 o ANALYSIS OF DRUGS, ETC. beaker, add, drop by drop, sufficient hydrochloric acid solution (5 per cent.) to insure an excess of acid, and then evaporate the ether by a gentle heat on a water-bath. Remove the excess of hydrochloric acid by adding to the residue 3 Cc. of alcohol and heating gently to evaporate the liquid ; repeat this operation once, and dry the residue at a temperature not exceeding 60 C. (140 F.) until the weight, after cooling in a desiccator, remains constant. The weight of the residue multiplied by 0*777, and this product by 20, gives the percentage of coniine contained in the conium. (b) Assay of fluidextract of conium. Transfer 10 Cc. of fluidextract of conium by means of a graduated pipette to an evaporating dish containing a little clean sand, and evaporate it to dryness at a gentle heat. Mix the sand uniformly with the extract and transfer it to an Erlcnmeyer flask of about 200 Cc. capacity, rinse the dish with 100 Cc. of a mixture of ether 100 Cc., alcohol 7 Cc., and ammonia water 3 Cc., added in portions, and transfer the rinsings to the flask. Insert the stopper securely and shake the flask at intervals during one hour. Decant 50 Cc. of the liquid (representing 5 Cc. of the fluidextract of conium) into a beaker, and add sufficient N. H 2 SO 4 to produce a distinctly acid reaction. Evaporate the ether at a gentle heat by the aid of a water-bath; then add 15 Cc. of absolute alcohol, and set the beaker aside in a cool place for two hours to allow the ammonium sulphate to deposit. Filter the liquid and proceed as above directed for the assay of conium. The weighed residue multiplied by 0777 x 20 = Cms. of coniine in 100 Cc. of fluidextract. (4) Cinchona and its Preparations. (a) Assay of cinchona. Introduce 15 Gm. of cinchona (in No. 80 powder or finer) into an Erlenmeyer flask or bottle of about 200 Cc. capacity, and add a mixture of 125 Cc. of ether and 25 Cc. of chloroform; then insert the stopper securely, shake vigorously, and set aside for ten minutes. Then add 10 Cc. of ammonia water, and set aside for five hours, shaking at frequent intervals (or continuously with the aid of a mechanical shaker). Next add 15 Cc. of distilled water, shake vigorously, and allow it to stand for a few minutes, to cause the powder to settle. Measure off 100 Cc. of the clear supernatant fluid (representing 10 Gm. of cinchona), transfer this to a separator and add 15 Cc. of N. H 2 SO4 or sufficient to make the liquid distinctly acid. Shake the separator vigorously for one minute, and allow the two layers of liquid to separate completely. Draw off the lower aqueous layer into the flask. Then add 5 Cc. of N. H 2 SO 4 and 5 Cc. of distilled water to the separator and shake it vigorously for about one minute, allow the liquids to separate as before, and again draw off the lower aqueous layer into the flask. Repeat the operation, using 5 Cc. of distilled water in the separator (without acid), drawing off the aqueous liquid into the flask. Filter the combined acid liquids into a measuring cylinder, and wash the filter and flask with enough distilled water to make the contents of the cylinder measure exactly 50 Cc. Pour half (25 Cc.) of the acid liquid into a separator marked No. i, and the remaining half (25 Cc.) into another separator marked No. 2, which set aside. i. for anhydrous cinchona alkaloids. To separator No. i (see above) add 25 Cc. of a mixture of chloroform 3 volumes and ether i volume, also 5 Cc. of ammonia water, or sufficient to render the liquid alkaline. Insert the stopper, shake for one minute, and then draw off the lower layer into a tared flask. Add 20 Cc. more of the chloroform-ether mixture to the separator, insert the stopper, and shake for one minute, again drawing off the lower layer into the tared flask. Repeat the operation with 10 Cc. of chloroform, and draw this off into the tared flask. Evaporate the chloroform-ether solutions U.S.P. ASSAYS OF DRUGS. 191 in the tared flask slowly and carefully to dryness on a water-bath. Add 3 Cc. of ether to the dry residue, and again evaporate to dryness. Then place the flask in an air-bath and heat at 110 C. (230 F.) until the weight after cooling remains constant. This weight in Gms. multiplied by 20 will give the per- centage of anhydrous cinchona alkaloids (total alkaloids) in the cinchona. 2. For ether-soluble alkaloids. To separator No. 2 (see above), containing the other 25 Cc. of acid liquid, add 25 Cc. of ether and 5 Cc. of ammonia water, or sufficient to render the liquid alkaline. The temperature of the liquid should be kept below 20 C. (68 F.), by cooling it, if necessary. Shake the separator moderately for two minutes, and allow the liquid to stand for ten minutes at 15 C. (59 F.) ; after the liquids have separated, draw off and reject the lower aqueous layer and transfer the ethereal liquid to a tared beaker. Add 5 Cc. more of ether to the separator, rinse carefully, and add the rinsings to the tared beaker. Evaporate the ether carefully by the aid of a water-bath, dry the beaker and contents in an air-bath at 110 C. (230 F.) for two hours, cool, and weigh. This weight in Gms. multiplied by 20 gives the percentage of the anhydrous ether-soluble alkaloids contained in the cinchona. Note. Ether-soluble alkaloids include quinine, quinidine, and cinchonidine. (&) Assay of fluidextract of cinchona. Transfer 10 Cc. of fluidextract of cinchona by means of a graduated pipette to an Erlenmeyer flask of 200 Cc. capacity, and add a mixture of 100 Cc. of ether, 25 Cc. of chloroform, and 10 Cc. of ammonia water. Insert the stopper, and shake the flask, at intervals, during 10 minutes. Allow the liquids to separate, decant exactly 66 Cc. of the supernatant liquid (representing 5 Cc. of the fluidextract), and transfer this to a separator, rinsing the measure with 5 Cc. of ether and adding this to the separator. Add to the latter about 10 Cc. of N. H 2 SO 4 , or enough to make the solution distinctly acid, and shake the separator vigorously for several minutes, and when the liquids have completely separated, draw off the lower layer into a second separator. To the first separator add 5 Cc. more of N. H 2 SO4, and 5 Cc. of distilled water, shake it for several minutes, and when the liquids have separated, draw off the lower layer into the second separator. Now add 5 Cc. of distilled water to the first separator, shake it, separate as before, and then draw off the lower aqueous layer into the second separator. To the second separator add 25 Cc. of ether, a small piece of red litmus paper, and then, gradually, ammonia water, keeping the temperature of the liquids below 25 C. (77 F.), until the reaction is alkaline. Then shake the separator for two minutes, and allow the liquids to stand for ten minutes at a tempera- ture below 15 C. (59 F.). Draw off and reject the lower aqueous layer, and then transfer the ether-layer into a tared beaker. Add 5 Cc. more of ether to the separator, rinse carefully, and add the rinsings to the tared beaker, and entirely evaporate the ether at a moderate heat on a water-bath. Then dry the beaker in an air-bath at 120 C. (248 F.) for half an hour, cool, and weigh. Replace the beaker in the air-bath, and heat again at the same temperature for half an hour, cool, and weigh, repeating until the weight is constant. Multiply the weight of the residue by 20 to obtain the weight in Gms. of anhydrous ether-soluble alkaloids contained in 100 Cc. of the fluid- extract of cinchona. (c) Assay of tincture of cinchona. Transfer 50 Cc. of tincture of cinchona to an evaporating dish, and evaporate it on a water-bath until it measures about 10 Cc., transfer the liquid to a bottle having the capacity of about 1 80 Cc., rinsing the dish with 10 Cc. of diluted alcohol, then assay the resulting liquid by the method above given for the fluidextract, with the exception that the multiplication of the product should be by 4 instead of 20 ; i 9 2 ANALYSIS OF DRUGS, ETC. the result will represent the weight in Gms. of anhydrous ether-soluble alka- loids contained in one hundred cubic centimeters of tincture of cinchona. (5) Guarana and its Preparations. (a) Assay of gnat-ana. Introduce 6 Gm. of guarana (in No. 60 powder) into an Erlenmeyer flask, and pour upon it 120 Cc. of chloroform and 6 Cc. of ammonia water, and insert the stopper securely. Shake the flask at intervals of half an hour, and allow it to stand for four hours. Filter off 100 Cc. of the liquid (representing 5 Gm. of guarana), then transfer the filtrate to a flask, and distil off all of the chloroform by means of a water-bath. Dissolve the alkaloid.il residue in a mixture of 2 Cc. of N. H 2 SO4 and 20 Cc. of warm distilled water. Allow the liquid to cool, and filter it into a separator, rinse the flask and filter with several small portions of distilled water, add 20 Cc. of chloroform and 2 Cc. of ammonia water to the separator, and shake it for one minute. Draw off the chloroform into a tared flask and repeat the extraction with two portions of 10 Cc. each of chloroform. Distil off the chloroform from the combined liquids, and when the residue is dry, add 2 Cc. of ether and evaporate on a water-bath very carefully to avoid decrepitation ; continue the heating until the weight of the residue after cooling remains constant. This weight multiplied by 20 will give the per- centage of the alkaloidal principles contained in the guarana, (/>) Assay of flnidextract of guarana. Transfer to a separator 5 Cc. of fluidextract of guarana, add 15 Cc. of chloroform and i Cc. of ammonia water. Shake well and allow the liquid to separate completely. Draw oft' the chloroform into a beaker. Shake out the fluid remaining in the separator with two additional portions of chloroform of 10 Cc. each ; evaporate the combined chloroformic solutions carefully to dry ness. From this point proceed as above given for the assay of guarana, when the result will be the weight in Gms. of alkaloids in 100 Cc. of the fluidextract. (6) Hydrastis and its Preparations. (a) Assay oj hydrastis. Introduce 15 Gm. of hydrastis (in No. 60 powder) into an Erlenmeyer flask of 250 Cc. capacity, add 150 Cc. of ether, shake the flask during ten minutes, and add 5 Cc. of ammonia water, again shaking the flask at intervals during half an hour. Then add 15 Cc. of distilled water to the mixture in the flask and shake it until the drug collects in masses, and at once pour off 100 Cc. of the supernatant ether-solution and transfer it to a separator. Add 15 Cc. of N. H 2 SO 4 to the separator, and shake during one minute. Allow the liquids to separate, and draw off the lower acid liquid into a second separator. Again shake out the ether-solution with 5 Cc. of N. H 2 SO 4 and 5 Cc. of distilled water, and shake for one minute. After separation, draw off the acid solution as before into the second separator. Repeat process with 5 Cc. of distilled water, drawing this also into the second separator. Introduce a small piece of red litmus paper into the second sepa- rator, add enough ammonia water to render the liquid alkaline, and then 25 Cc. of ether, and shake the separator during one minute, and when the liquids have separated draw off the lower alkaline liquid into another separator, and the ether-solution into a tared beaker. Again shake out the alkaline liquid, using 20 Cc. of ether, shake the separator for one minute, and, after separation, draw off the alkaline liquid into the other separator, and the ether-solution into the tared beaker. Finally, again shake out the alkaline liquid, using 15 Cc. of ether, proceeding as before, and adding the ether-solution to the liquid in the tared beaker. Evaporate the ether carefully with the aid of a water-bath, and dry the alkaloidal residue in the beaker to a constant weight U.S.P. ASSAYS OF DRUGS. 193 at 100 C. (212 K). The weight found, multiplied by 10, will give the percentage of hydrastine in the hydrastis. (b) Assay of fluidextract of hydrastis. Transfer 10 Cc. of fluidextract of hydrastis by means of a graduated pipette to a 100 Cc. measuring flask, add 85 Cc. of distilled water in which 2 Gm. of potassium iodide have been previously dissolved, and sufficient water to make 100 Cc., and shake the liquid for several minutes. Then filter off 50 Cc. of the liquid and transfer it to a separator. Render the liquid alkaline with ammonia water, add 30 Cc. of ether, and shake the separator at intervals during several minutes. When separated, draw off the aqueous layer into a beaker, and the ether-solution into a tared beaker. Return the aqueous solution to the separator, and shake it with 20 Cc. more of ether for one minute. Draw off and reject the aqueous layer, and run the ether-solution into the tared beaker. Allow the combined ether-solutions to evaporate at a gentle heat, and dry the residue in the beaker to a constant weight on a water-bath. Multiply the weight by 20, which will give the weight in Gms. of hydrastine contained in one hundred cubic centimeters of fluidextract of hydrastis. (f) Assay of tincture of hydrastis. Transfer 100 Cc. of tincture of hydrastis to an evaporating dish, and evaporate it on a water-bath until the liquid measures about 10 Cc. If any insoluble matter has separated, add sufficient alcohol to dissolve it, and then assay the resulting liquid by the method given above for the fluidextract, with the exception that the weight of the residual alkaloids must be multiplied by 2 instead of by 20 as there directed, to give the weight in Gms. of hydrastine contained in one hundred cubic centimeters of tincture of hydrastis. (7) Opium and its Preparations. (a) Assay of opiiim. Introduce 10 Gm. of opium (which, if fresh, should be in very small pieces, and if dry, in very fine powder) into an Erlenmeyer flask having a capacity of about 300 Cc., add 100 Cc. of distilled water, stopper the flask, and agitate it every ten minutes (or continuously in a mechanical shaker) during three hours. Then pour the contents as evenly as possible upon a wetted filter having a diameter of 12 Cm., and, when the liquid has drained off, wash the residue with distilled water, dropped upon the edges of the filter and its contents, until 150 Cc. of filtrate have been obtained. Then transfer the moist opium back to the flask, add 50 Cc. of distilled water, agitate it thoroughly during fifteen minutes, and return the whole to the filter. When the liquid has drained off, wash the residue, as before, until the second filtrate measures 150 Cc., and finally collect about 20 Cc. more of a third filtrate. Evaporate carefully in a tared dish, first, the second filtrate to a small volume, then add the first filtrate, rinsing the vessels with the third filtrate, and continue the evaporation until the residue weighs 14 Gm. Rotate the concentrated solution about in the dish until the rings of extract are redissolved, pour the liquid into a tared Elenmeyer flask having a capacity of about 100 Cc., and rinse the dish with a few drops of water at a time, until the entire solution, after the rinsings have been added to the flask, weighs 20 Gm. Then add 10 Gm. (or 12-2 Cc.) of alcohol, shake the flask well, add 25 Cc. of ether, and repeat the shaking. Now 3*5 Cc. ammonia water (10 per cent, strength), stopper the flask with a sound cork, shake it thoroughly during ten minutes, and then set it aside, in a moderately cool place, for at least six hours, or over night. Remove the stopper carefully, and should any crystals adhere to it, brush them into the flask. Place in a small funnel two rapidly acting filters, of a diameter of 7 Cm., plainly folded, one within the other (the triple fold of the 13 i 94 ANALYSIS OF DRUGS, ETC. inner filter being laid against the single side of the outer filter), wet them well with ether, and derant the ethereal solution as completely as possible upon the inner filter. Add 10 Cc. of ether to the contents of the flask, rotate it, and again decant the ethereal layer upon the inner filter. Repeat this operation with another portion of 10 Cc. of ether. Then pour the liquid in the flask into the filter, in portions, in such a way as to transfer the greater portion of the crystals to the filter, and, when the liquid has passed through, transfer the remaining crystals to the filter by washing the flask with several portions of water, using not more than 15 Cc. in all. Use a feather or rubber-tipped glass rod to remove the crystals that adhere to the flask. Allow the double filter to drain, then apply water to the crystals, drop by drop, until they are practically free from mother-liquor, and afterwards wash them drop by drop, from a pipette, with alcohol previously saturated with powdered morphine. When this has passed through, displace the remaining alcohol by ether, using about 10 Cc. or more, if necessary. Allow the filter to dry in a moderately warm place, at a temperature not exceeding 60 C. (140 F.) until its weight remains constant, then carefully transfer the crystals to a tared watch-glass and weigh them. Place the crystals (which are not quite pure) in an Elenmeyer flask, add lime water (10 Cc. for each o'i Gm. of morphine) and shake the flask at intervals during half an hour. Pass the liquid through two counterpoised rapidly acting, plainly folded filters, one within the other (the triple fold of the inner filter being laid against the single fold of the outer filter), rinse the flask with more lime water and pass the washings through the filter until the filtrate, after acidulating, no longer yields a precipitate with mercuric potassium iodide. Press the filters until nearly dry between bibulous paper and dry them to a constant weight, then weigh the contents, using the outer filter as a counterpoise. Deduct the weight of the insoluble matter on the filter from the weight of the impure morphine previously found. The difference, multiplied by 10, represents the percentage of crystallized morphine contained in the opium. (b) Assay of extract of opium. Dissolve 4 Gm. of extract of opium in 30 Cc. of water, filter the solution through a small filter, and wash the filter and residue with water, until all soluble matters are extracted, collecting the *,vashings separately. Evaporate, in a tared dish, on a water-bath, first, the washings to a small volume, then add the first filtrate, and evaporate the whole to a weight of 10 Gm. Determine the morphine in this extract by the method above given for opium (beginning with the word " Rotate "), but use 2*2 Cc. of ammonia water instead of 3*5 Cc., and finally multiply by 25 instead of by ic. (c) Assay of tincture of opium. Transfer 100 Cc. of tincture of opium to an evaporating dish and evaporate it on a water-bath to about 20 Cc., add 40 Cc. of water, mix thoroughly and set the liquid aside for one hour, occasionally stirring to disintegrate the resinous flakes adhering to the dish. Then filter the liquid and wash the filter and residue with water, until all soluble matter is extracted (indicated by an almost colorless filtrate), and collect the washings separately. First evaporate the washings in a tared dish, to a small volume, then add the first filtrate and evaporate the whole to a weight of 14 Gm. Determine the morphine in this extract by the method given under opium assay (l>eginning with the word " Rotate "), using the same details as there directed for 10 Gm. of opium, with the exception that the final multiplication by 10 be omitted. The result will represent the weight in Cms. of crystallized morphine yielded by one hundred cubic centimeters of tincture of opium. TITRATION OF ALKALOIDAL RESIDUES. 195 IV. TITRATION OF ALKALOIDAL RESIDUES. When, by the evaporation of the immiscible solvent containing it, we can obtain the alkaloid in a sufficient state of purity, it may be directly weighed, but in most cases it is more convenient to be satisfied with a residue not absolutely pure and to ascertain the amount of real alkaloid contained therein by volumetric analysis. Alkaloids behave towards acids in a similar manner to ammonia, which we have already seen (Chap. VII.) to be best estimated by residual titration i.e. by first adding excess of standard acid and then titrating back with.standard alkali to ascertain the amount of acid remaining uncombined with the alkaloid, and thus obtaining the amount of the alkaloid by difference. The standard acid is usually employed of ^ strength, and the alkali of ^. The following table shows the equivalent amount of alkaloid in Gms. for each Cc. of ~^ acid : Alkaloid. i Cc. ^ acid = i Cc. -^ acid = Aconitine, C 3I H 47 NO U 0-06406 . . 0-012811 Atropine, C, 7 H., 3 NO 3 0-02870 . . 0*005741 Brucine, C. a H. >(j N.,O 4 0*03913 . . 0*007826 Cephaeline, C," 4 H, 9 NO 2 0*02314 . . 0-004628 Cinchonicline, C, 9 H 22 N 2 O .... 0*02920 . . 0*005841 Cinchonine, C 19 H 2 ,N 2 O . . . . 0^02920 . . 0*005841 Combined alkaloids of cinchona . . . 0-03069 . . O '006139 ,, ,, of ipecac. . . . 0-02384 . . 0*004768 Cocaine, C |7 H 21 NO 4 0*03009 . . 0*006018 Coniine, C 8 H, 7 N ...... 0-01262 . 0*002524 Emetine, C 15 H,,NO 2 0*02453 . . 0*004906 Hydrastine, C 2 JH 21 NO 8 0*03803 . . 0-007606 Morphine, crystallized, C 17 H 19 NO 3 + H 2 O . 0*03009 . . O'oo6oi8 anhydrous, C, 7 H 19 NO 3 . . . 0*02830 . . 0*005661 Physostigmine, C 15 H 21 N 3 O 2 .... 0*02732 . . 0*005464 Pilocarpine, C U HJ 6 N 2 O 2 . 0*02066 . . 0*004133 Quinine, C. H 24 N 2 O 2 " 0*03218 . . 0*006436 Strychnine," C 2I H 22 NvO 2 0-03317 . . 0*006635 It is manifest that each Cc. of f$ alkali would also correspond to the same amount of alkaloid as i Cc. of ^j acid. The indicators employed in these titrations are : (a) Cochineal. Macerate i Gm. of unbroken cochineal during four days with 20 Cc. of alcohol and 60 Cc. of water. Then filter. The color of this test solution is turned violet by alkalies, and yellowish-red by acids. (b) Hematoxylin. Dissolve 0*2 Gm. of hematoxylin in 100 Cc. of alcohol. Use about 5 drops for each titration. This indicator assumes a yellow to orange color in acid solutions, and a violet to purple color in alkaline solutions. The titration is complete when the change in color remains permanent upon the addition of one drop of the volumetric solution after stirring the liquid. (c) lodeosin. Dissolve OT Gm. of iodeosin, C 2 oH8l4O5, in 100 Cc. of alcohol. This indicator becomes colorless in acid solutions, changing to pink in alkaline solutions. For assaying alkaloidal residues dissolve the latter in a measured excess of volumetric acid solution, and transfer the acid solution to a 200 Cc. flask, washing the container well with water until the contents of the flask measure about 100 Cc. Add 20 Cc. of ether and 5 drops of the iodeosin solution, cork, and shake well. Then add the volumetric alkali solution gradually, shaking well after each addition. The titration is complete when the lower aqueous solution retains a faint pink color after shaking thoroughly. I 9 8 ANALYSIS OF DRUGS, ETC. chloroformic layer, rejecting the same, and then run the acid aqueous layer into the beaker. Pass the combined acid aqueous solutions through a pledget of purified cotton into the first separator, after cleaning it thoroughly, rinsing the second separator, the beaker, and the funnel with about TO Cc. of distilled water. To the first separator, add 15 Cc. of chloroform, a small piece of red litmus paper, and enough ammonia water to produce a distinctly alkaline reaction. Shake the separator for half a minute, and when the liquids have separated draw off the chloroformic layer into a beaker. Repeat this process with two portions of 10 Cc. each of chloroform, and evaporate thj combined chloroformic liquids in the beaker to dryness on a water-bath containing warm water ; dissolve the residue in 3 Cc. of ether, and allow the latter to evaporate completely. To the alkaloidal residue add 5 Cc. of T ^ H 2 SO 4 and 5 drops of hematoxylin (or iodeosin), then titrate the excess of acid with ~ KHO. Divide the number of cubic centimeters of -$ KHO used, by 5, subtract the quotient from 5 (the 5 Cc. ofy^HjSO* taken), and multiply the remainder by 0-0287, and this product by 20, to obtain the percentage of mydriatic alkaloids contained in the extract of belladonna leaves. The figure 0^0287 represents the weight in Cms. of mydriatic alkaloids (mainly atropine) required to neutralize i Cc. of -f^ H, 2 SO 4 - (/) Assay of fluidextract of belladonna root. Transfer 10 Cc. of fluid- extract of belladonna root by means of a graduated pipette to a separator, add 10 Cc. of distilled water, 20 Cc. of chloroform, and 2 Cc. of ammonia water. Shake the separator well for one minute, and draw off the lower chloroformic layer into a second separator. Repeat the extraction with two portions of 10 Cc. each of chloroform, and draw the chloroformic solution into the second separator. To the latter add 8 Cc. of N. H 2 SO 4 and 20 Cc. of distilled water, shaking well for one minute. When perfectly separated draw off and reject the lower chloroformic layer, and filter the acid aqueous layer into a clean separator. Wash the separator and filter with 10 Cc. of distilled water, adding this to the clean separator. To the latter add 20 Cc. of chloroform and 4 Cc. of ammonia water, and shake well for several minutes. Draw off the lower chloroformic layer into a beaker, and repeat the extraction with two portions of 10 Cc. each of chloroform, adding the chloroformic solution to the beaker. Allow the chloroform in the beaker to evaporate on a water-bath, containing warm water, until the residue is perfectly dry. To the alkaloidal residue add 5 Cc. of -$ H 2 SO 4 , and when the residual alkaloids have all dissolved, titrate the solution with -^ KHO, using 5 drops of hematoxylin or iodeosin as an indicator. Divide the number of cubic centimeters of -^ KHO used, by 5, subtract the quotient from 5 (the 5 Cc. of y^ H 2 SO 4 ), and multiply the remainder by o'o287, an d this product by 10, to obtain the weight in Cms. of mydriatic alkaloids contained in one hundred cubic centimeters of the fluid- extract of belladonna root. (g) Assay of fluidextract of hyoscyamus. Use 50 Cc. of the fluidextract and proceed as above shown for fluidextract of belladonna root, but finally multiplying the product by 2 instead of 10. (h) Assay of fluidextract of stramonium. The method to be employed is identical with that above given for fluidextract of belladonna root, using ten cubic centimeters of fluidextract of stramonium. (/) Assay of tincture of belladonna leaves. Transfer 100 Cc. of tincture of belladonna leaves to an evaporating dish and evaporate it on a water-bath until it measures about 10 Cc. Add, if necessary, sufficient alcohol to dis- solve any separated substance, and then assay the resulting liquid by the method above given for fluidextract of belladonna root, using the same details as there directed for 10 Cc. of fluidextract of belladonna root, with the exception that the multiplication of the product by 10 be omitted ; the result U.S.P. ASSAYS OF DRUGS. 199 will represent the weight in Gms. of alkaloids contained in one hundred cubic centimeters of tincture of belladonna leaves. (k) Assay of tincture of hyoscyamus. Transfer 100 Cc. of tincture of hyoscyamus to an evaporating dish, and evaporate it on a water-bath until it measures about 10 Cc. Add, if necessary, sufficient alcohol to dissolve any separated substance, and then assay the resulting liquid by the method above given for fluidextract of belladonna root, using the same details as there directed for 10 Cc. of fluidextract of belladonna root, with the exception that the multiplication by 10 be omitted ; the result will represent the weight in Gms. of alkaloids contained in one hundred cubic centimeters of tincture of hyoscyamus. (/) Assay of tincture of stramonium. Transfer 100 Cc. of tincture of stramonium to an evaporating dish, and evaporate it on a water-bath until it measures about 10 Cc. Add, if necessary, sufficient alcohol to dissolve any separated substance, and then assay the resulting liquid by the method above given for fluidextract of belladonna root, using the same details as there directed for 10 Cc. of fluidextract of belladonna root, with the exception that the multiplication by 10, as there directed, be omitted ; the result will represent the weight in Gms. of alkaloids contained in one hundred cubic centimeters of tincture of stramonium. (m) Assay of belladonna plaster (rubber base}. Into a suitable beaker containing 50 Cc. of chloroform and 3 Cc. of ammonia water, introduce 10 Gm. of belladonna plaster cut into strips. Stir until the plaster is entirely removed from the cloth ; then pour off the chloroform into another beaker r .. wash the cloth with 25 Cc. of chloroform and i Cc. of ammonia water carefully, and add the washings to the chloroformic solution first obtained. If necessary, repeat the washing with 25 Cc. of chloroform, and add this also to the chloroformic solution. Then dry the cloth at a low temperature ; cooB and weigh it, and subtract its weight from the original weight of the plaster. To the chloroformic solution, add four-fifths of its volume of alcohol, stir gently, and allow the liquid to stand until all of the rubber has separated in a compact mass. Then pour off the supernatant liquid into a separator of 250 Cc. capacity, and, having prepared a solution of sulphuric acid by diluting, 40 Cc. of N. H 2 SO 4 with 60 Cc. of distilled water, add 20 Cc. of the soluiior^ to the separator, and agitate for two minutes, rotating gently. Draw off the chloroformic solution into another separator, shake this with 10 Cc. of the sulphuric acid solution, and add the acid solution to that in the first separator.. Repeat until the acid washings cease to give a reaction with mercuric potassium* iodide T.S. ; combine the acid liquids, and, having rendered this solution, alkaline with ammonia water, shake out the alkaloids with three successive- portions of 25, 15, and 10 Cc. of chloroform. Collect these in a flask, distill off all of the chloroform with the aid of a water-bath. To the alkaloidal/ residue add a slight excess of j H 2 SO 4 , noting the quantity used, and then, add 10 drops of chloroform and, after rotating, evaporate the latter by means of a water-bath, Then add 5 drops of hematoxylin, and, rotating, titrate the excess of acid with ~~ KHO. Divide the number of cubic centimeters of -^ KHO used, by 5, subtract the quotient from the number of cubic centi- meters of ^ H 2 SO 4 first added, and divide the difference by the number of Gms. of belladonna plaster separated from the cloth ; multiply the quotient by 0*0287, and this product by 100, which will give the percentage of mydriatic alkaloids in the belladonna plaster. (3) Coca and its Preparations. (a) Assay of coca. Place 10 Gm. of coca in an Erlenmeyer flask, add 50 Cc. of a mixture of chloroform i volume and ether 4 volumes, and insert 196 ANALYSIS OF DRUGS, ETC. V. TT.S.P. ASSAYS OF DRUGS WHERE THE RESIDUE IS TITRATED. (1) Aconite and its Preparations. (a) Assay of aconite. Introduce 10 Gm. of aconite (in No. 40 powder) into a 200 Cc. Erlenmeyer flask, add 75 Cc. of a mixture of alcohol 7 parts, and distilled water 3 parts (by volume), stopper the flask securely, and agitate it at intervals during four hours. After placing a pledget of cotton in the bottom of a small cylindrical glass percolator (25 Mm. in diameter), carefully transfer the contents of the flask to the percolator. When the liquid has all passed through, continue the percolation with more of the same mixture until 150 Cc. of percolate have been obtained. Pour the percolate into a shallow porcelain evaporating dish, and evaporate it to dryness at a temperature not exceeding 60 C. (140 F.). Add 5 Cc. of ^ H 2 SO 4 and 10 Cc. of distilled water. When the extract is dissolved, filter the liquid into a separator, washing the dish and filter with about 40 Cc. of distilled water, and add the washings to the separator. Add 25 Cc. of ether and 2 Cc. of ammonia water to the separator, and agitate it for one minute. Draw off the lower layer into a flask, and filter the ether-solution into a beaker. Return the contents of the flask to the separator, add 15 Cc. of ether, and again agitate it for one minute. Draw off the lower layer into the flask, and filter the ether-solution into the beaker. Repeat the shaking out with two other portions of 10 Cc. each of ether. Evaporate the combined ether-solutions to dryness, and dissolve the residue in 3 Cc. of ^ H 2 SO 4 , diluted with 20 Cc. of distilled water. Add to the solution 5 drops of hematoxylin indicator, and then carefully run in -~$ KHO until a violet color is produced, the transition stages being as follows : first yellow, then green, finally passing into violet. Divide the number of Cc. of -$ KHO used, by 5, subtract this number from 3 (the 3 Cc. of j^ H 2 SO 4 taken), multiply the remainder by 0*064, and this product by 10, which will give the percentage of aconitine in the aconite. (b) Assay of fluidextract of aconite. Transfer TO Cc. of fluidextract of aconite by means of a graduated pipette to a porcelain dish, and evaporate it carefully to dryness on a water-bath at a temperature not exceeding 60 C. (140 F.). Add 5 Cc. of > H 2 SO 4 and 10 Cc. of distilled water. When the extract is dissolved, filter the liquid into a separator, washing the dish and filter with about 40 Cc. of distilled water and adding the washings to the separator. From this point proceed as instructed for the assay of aconite until the titration is complete. Finally divide the number of Cc. of ^ KHO used, by 5, subtract this number from 3 (the 3 Cc. of T N ^ H 2 SO 4 taken), multiply the remainder by 0-064, an d this product by 10, which will give the weight in Gms. of aconitine contained in one hundred cubic centimeters of the fluidextract of aconite. (c) Assay of tincture of aconite. Transfer 100 Cc. of tincture of aconite to an evaporating dish and evaporate it carefully to dryness at a temperature not exceeding 60 C. (140 F.), and assay the resulting extract by the method above given for the fluidextract, using the same details as there directed for 10 Cc. of fluidextract of aconite, with the exception that the multiplication of the product by 10 must be omitted; the result will represent the weight in Gms. of aconitine contained in one hundred, cubic centimeters of tincture of aconite. (2) Assays of Drugs containing Mydriatic Alkaloids. (a) Assay of belladonna leaves. Place 10 Gm. of belladonna leaves (in No. 60 powder) in an Erlenmeyer flask, and add 50 Cc. of a mixture of chloroform i part and ether 4 parts (both by volume). After inserting the U.S.P. ASSAYS OF DRUGS. iq; stopper securely, allow the flask to stand ten minutes, then add 2 Cc. of ammonia water mixed with 3 Cc. of distilled water, and shake the flask well at frequent intervals during one hour. Then transfer as much as possible of the contents of the flask to a small percolator which has been provided with a pledget of cotton packed firmly in the neck and inserted in a separator containing 6 Cc. of N. H,SO 4 diluted: with 20 Cc. of distilled water. When the liquid has passed through the cotton, pack the belladonna leaves firmly in the percolator with the aid of a glass rod, and having rinsed the flask with 10 Cc. of the chloroform-ether mixture, transfer the remaining contents of the flask to the percolator, by the aid of several small portions (5 Cc.) of the chloroform-ether mixture, and continue the percolation with successive small portions of the same liquid (using in all 50 Cc.). Next, shake the separator well for one minute, after securely inserting the stopper, and when the liquids have completely separated, draw off the acid solution into another separator. Add to the chloroform-ether mixture 10 Cc. of sulphuric acid mixture of the same strength as that previously used, agitate well, and again draw off the acid solution into the second separator ; repeat this operation once more, drawing off the acid solution as before ; introduce into the acid solutions contained in the second separator a small piece of red litmus paper, then add ammonia water until the liquid is distinctly alkaline, and shake out with three successive portions of chloroform 15, 15, and 5 Cc.; collect the chloroform solutions in a beaker, place it on a water-bath containing warm water, and allow the chloroform to entirely evaporate. Dissolve the residue in 3 Cc. of ether, and let this also evaporate completely. To the alkaloidal residue add 3 Cc. of T N F H 2 SO 4 and 5 drops of hematoxylin (or iodeosin), then titrate the excess of acid with -/u KHO potassium hydroxide. Divide the number of cubic centimeters of T N g- KHO used, by 5, subtract the quotient from 3 (the 3 Cc.. of y^ H 2 SO 4 taken), and multiply the remainder by 0*0287 and this product by 10; the result will be the percentage of total mydriatic alkaloids contained in the belladonna leaves. (b) Assay ofscopola. The method to be employed is identical with that given above for belladonna leaves, using ten Gins, of scopola, in No. 60 powder. (f) Assay of hyoscyamus. The method to be employed is identical with that given above for belladonna leaves, with the exception that tiventy-five Gms. of hyoscyamus, in No. 60 powder, are to be used, the quantity of chloroform-ether mixture which is added at first increased from 50 Cc. to TOO Cc., and the product at the end of the assay multiplied by 4 instead of TO. (d) Assay of stramonium. The method to be employed is identical with that given above for belladonna leaves, using ten Gms. of stramonium, in No. 60 powder. (e) Assay of extract of belladonna leaves. Introduce 5 Gm. extract of belladonna leaves into a small beaker and dissolve it in a mixture consisting of alcohol 5 Cc., distilled water 10 Cc., ammonia water 2 Cc., and chloroform 20 Cc. When dissolved, transfer it to a separator, rinsing the beaker with a little alcohol and adding the rinsings to the separator. Insert the stopper securely, and shake the separator for half a minute. Draw off the chloroformic layer into a second separator, and add to the first separator ro Cc. more of chloroform. Shake it for half a minute, allow to separate, and again draw off the chloroformic layer into the second separator. Repeat this with 10 Cc. more of chloroform. To the united chloroformic liquids in the second separator, add 5 Cc. of N. H 2 SO 4 and 10 Cc. of distilled water, and shake it for half a minute. Draw off the chloroformic layer, after the liquids have separated, into the first separator, after cleaning it thoroughly, and the aqueous layer into a beaker, and repeat the process by adding to the first separator 10 Cc. of distilled water and i Cc. of N. H 2 SO 4 . Draw off the I 9 8 ANALYSIS OF DRUGS, ETC. chloroformic layer, rejecting the same, and then run the acid aqueous layer into the beaker. Pass the combined acid aqueous solutions through a pledget of purified cotton into the first separator, after cleaning it thoroughly, rinsing the second separator, the beaker, and the funnel with about TO Cc. of distilled water. To the first separator, add 15 Cc. of chloroform, a small piece of red litmus paper, and enough ammonia water to produce a distinctly alkaline reaction. Shake the separator for half a minute, and when the liquids have separated draw off the chloroformic layer into a beaker. Repeat this process with two portions of 10 Cc. each of chloroform, and evaporate the combined chloroformic liquids in the beaker to dry ness on a water-bath containing warm water ; dissolve the residue in 3 Cc. of ether, and allow the latter to evaporate completely. To the alkaloidal residue add 5 Cc. of $ H 2 SO 4 and 5 drops of hematoxylin (or iodeosin), then titrate the excess of acid with -^ KHO. Divide the number of cubic centimeters of ^j KHO used, by 5, subtract the quotient from 5 (the 5 Cc. of ^ H 2 SO 4 taken), and multiply the remainder by 0-0287, and this product by 20, to obtain the percentage of mydriatic alkaloids contained in the extract of belladonna leaves. The figure 0-0287 represents the weight in Cms. of mydriatic alkaloids (mainly atropine) required to neutralize i Cc. of T ^ H,,SO 4 . (f) Assay of fluidextract of belladonna roof. Transfer 10 Cc. of fluid- extract of belladonna root by means of a graduated pipette to a separator, add 10 Cc. of distilled water, 20 Cc. of chloroform, and 2 Cc. of ammonia water. Shake the separator well for one minute, and draw off the lower chloroformic layer into a second separator. Repeat the extraction with two portions of 10 Cc. each of chloroform, and draw the chloroformic solution into the second separator. To the latter add 8 Cc. of N. H 2 SO 4 and 20 Cc. of distilled water, shaking well for one minute. When perfectly separated draw off and reject the lower chloroformic layer, and filter the acid aqueous layer into a clean separator. Wash the separator and filter with 10 Cc. of distilled water, adding this to the clean separator. To the latter add 20 Cc. of chloroform and 4 Cc. of ammonia water, and shake well for several minutes. Draw off the lower chloroformic layer into a beaker, and repeat the extraction with two portions of 10 Cc. each of chloroform, adding the chloroformic solution to the beaker. Allow the chloroform in the beaker to evaporate on a water-bath, containing warm water, until the residue is perfectly dry. To the alkaloidal residue add 5 Cc. of ~Q H 2 SO 4 , and when the residual alkaloids have all dissolved, titrate the solution with -$ KHO, using 5 drops of hematoxylin or iodeosin as an indicator. Divide the number of cubic centimeters of -$ KHO used, by 5, subtract the quotient from 5 (the 5 Cc. of ~$ H 2 SO 4 ), and multiply the remainder by 0*0287, an d this product by 10, to obtain the weight in Cms. of mydriatic alkaloids contained in one hundred cubic centimeters of the fluid- extract of belladonna root. (g) Assay of fluidextract of hyoscyamus. Use 50 Cc. of the fluidextract and proceed as above shown for fluidextract of belladonna root, but finally multiplying the product by 2 instead of 10. (h) Assay of fluidextract of stramonium. The method to be employed is identical with that above given for fluidextract of belladonna root, using ten cubic centimeters of fluidextract of stramonium. (j) Assay of tincture of belladonna leaves. Transfer 100 Cc. of tincture of belladonna leaves to an evaporating dish and evaporate it on a water-bath until it measures about 10 Cc. Add, if necessary, sufficient alcohol to dis- solve any separated substance, and then assay the resulting liquid by the method above given for fluidextract of belladonna root, using the same details as there directed for 10 Cc. of fluidextract of belladonna root, with the exception that the multiplication of the product by 10 be omitted ; the result U.S.P. ASSAYS OF DRUGS. 199 will represent the weight in Gms. of alkaloids contained in one hundred cubic centimeters of tincture of belladonna leaves. (k) Assay of tincture of hyoscyamus. Transfer 100 Cc. of tincture of hyoscyamus to an evaporating dish, and evaporate it on a water-bath until it measures about 10 Cc. Add, if necessary, sufficient alcohol to dissolve any separated substance, and then assay the resulting liquid by the method above: given for fluidextract of belladonna root, using the same details as there directed for 10 Cc. of fluidextract of belladonna root, with the exception that the multiplication by 10 be omitted ; the result will represent the weight ira Gms. of alkaloids contained in one hundred cubic centimeters of tincture of hyoscyamus. (/) Assay of tincture of stramonium. Transfer 100 Cc. of tincture of stramonium to an evaporating dish, and evaporate it on a water-bath until it measures about 10 Cc. Add, if necessary, sufficient alcohol to dissolve any separated substance, and then assay the resulting liquid by the method above given for fluidextract of belladonna root, using the same details as there directed for 10 Cc. of fluidextract of belladonna root, with the exception that the multiplication by 10, as there directed, be omitted ; the result will represent the weight in Gms. of alkaloids contained in one hundred cubic centimeters of tincture of stramonium. (m) Assay of belladonna plaster (rubber base). Into a suitable beaker containing 50 Cc. of chloroform and 3 Cc. of ammonia water, introduce 10 Gm. of belladonna plaster cut into strips. Stir until the plaster is entirely" removed from the cloth ; then pour off the chloroform into another beaker y . wash the cloth with 25 Cc. of chloroform and i Cc. of ammonia water carefully, and add the washings to the chloroformic solution first obtained.. If necessary, repeat the washing with 25 Cc. of chloroform, and add this also to the chloroformic solution. Then dry the cloth at a low temperature; cooli and weigh it, and subtract its weight from the original weight of the plaster. To the chloroformic solution, add four-fifths of its volume of alcohol, stir gently, and allow the liquid to stand until all of the rubber has separated in a compact mass. Then pour off the supernatant liquid into a separator of 250 Cc. capacity, and, having prepared a solution of sulphuric acid by diluting; 40 Cc. of N. H 2 SO 4 with 60 Cc. of distilled water, add 20 Cc. of the solution* to the separator, and agitate for two minutes, rotating gently. Draw off the chloroformic solution into another separator, shake this with 10 Cc. of the sulphuric acid solution, and add the acid solution to that in the first separator.. Repeat until the acid washings cease to give a reaction with mercuric potassium - iodide T.S. ; combine the acid liquids, and, having rendered this solution, alkaline with ammonia water, shake out the alkaloids with three successive- portions of 25, 15, and 10 Cc. of chloroform. Collect these in a flask, distil off all of the chloroform with the aid of a water-bath. To the alkaloida^ residue add a slight excess of ~ H 2 SO 4 , noting the quantity used, and then, add 10 drops of chloroform and, after rotating, evaporate the latter by means of a water-bath. Then add 5 drops of hematoxylin, and, rotating, titrate the excess of acid with -^ KHO. Divide the number of cubic centimeters of -J-Q KHO used, by 5, subtract the quotient from the number of cubic centi- meters of j H 2 SO 4 first added, and divide the difference by the number of Gms. of belladonna plaster separated from the cloth ; multiply the quotient by o'028y, and this product by 100, which will give the percentage of mydriatic alkaloids in the belladonna plaster. (3) Coca and its Preparations. (a) Assay of coca. Place 10 Gm. of coca in an Erlenmeyer flask, ado! 50 Cc. of a mixture of chloroform i volume and ether 4 volumes, and insert 200 ANALYSIS OF DRUGS, ETC. the stopper securely. Allow the flask to stand ten minutes, then add 2 Cc. of ammonia water mixed with 3 Cc. of distilled water, and shake the flask well, at frequent intervals, during one hour. Then transfer as much as possible of the contents of the flask to a small percolator which has been provided with a pledget of cotton packed firmly in the neck, and inserted in a separator containing 6 Cc. of N. H 2 SO 4 diluted with 20 Cc. of distilled water. When the liquid has passed through the cotton, pack the coca firmly in the perco- lator with the aid of a glass rod, and, having rinsed the flask with 10 Cc. of chloroform-ether mixture, transfer the remaining contents of the flask to the percolator by the aid of several small portions (5 Cc.) of a chloroform-ether mixture, using the same proportions as before, and continue the percolation with successive small portions of the same liquid (in all 50 Cc). Next, shake the separator well for one minute, after securely inserting the stopper, and when the liquids have completely separated, draw off the acid liquid into another separator. Add to the chloroform-ether mixture 10 Cc. of a sulphuric acid mixture, using the same proportions as before, agitate well and again draw off the acid liquid. Repeat this operation once more, drawing off the acid solution as before into the second separator, introduce a small piece of red litmus paper, add ammonia water until the liquid is distinctly alkaline, and shake out with 3 successive portions of ether (25, 20, and 15 Cc.). Collect the ether-solutions in a beaker, place it on a water-bath filled with warm water, and allow the ether to evaporate entirely. Dissolve the residue in 3 Cc. of ether, and let this also evaporate. To the alkaloidal residue add 4 Cc. of YQ- H 2 SO4 and 5 drops of hematoxylin or iodeosin, then titrate the excess of acid with -^j- KHO. Divide the number of cubic centi- meters of -2$ KHO used, by 5, subtract this number from 4 (the 4 Cc. of Y0- H 2 SO 4 taken), and multiply the remainder by 0*03 and this product by 10, to obtain the percentage of ether-soluble alkaloids contained in the coca. (b) Assay of fluidextract of coca. Transfer 10 Cc. of fluidextract of coca foy means of a graduated pipette to a separator, add 25 Cc. of ether, and then 2 Cc. of ammonia water, shaking together for one minute. When the liquids have completely separated, draw off the lower aqueous layer into a second separator, and to this add 20 Cc. more of ether, and repeat the shaking for one minute. Draw off and reject the lower aqueous layer from the second separator, and add the ether-layer to the first separator. To this separator now add 5 Cc. of N. H 2 SO 4 and 5 Cc. of distilled water, and shake it well for one or two minutes. After the liquids have separated, draw off the lower aqueous layer into the other separator, and repeat the extraction in the first separator with 9 Cc. of distilled water and i Cc. of N. H 2 SO 4 , shaking the liquids for one minute, and separating as before. Add the aqueous solution to the other separator, and reject the ether. Now add to the combined acid liquids 20 Cc. of ether, a small piece of red litmus paper, and sufficient ammonia water to render the mixture distinctly alkaline, and shake the liquids for one or two minutes. Draw off the separated aqueous layer into the other separator and the ether-layer into a beaker. Repeat the extraction of the aqueous layer in the other separator with two portions (15 Cc. each) of ether, and add the resulting ether-solutions to the beaker. Now evaporate the ether from the beaker, and, when dry, add to it 5 Cc. of ~$ H 2 SO 4 , and stir until the alkaloidal residue is dissolved. Then add 5 drops of hematoxylin or iodeosin, and titrate the excess of acid with ^ KHO. Divide the number of cubic centimeters of ~$ KHO used, by 5, subtract this number from 5 (the 5 Cc. of Yff H 2 SO 4 taken), and multiply the remainder by 0^03, and this product by 10, to obtain the weight in Gins, of ether-soluble alkaloids contained in one hundred cubic centimeters of the fluidextract of coca. U.S. P. ASSAYS OF DRUGS. 201 (4) Ipecac and its Preparations. (a) Assay of ipecac. Introduce 15 Gm. of ipecac (in No. 80 powder) into an Erlenmeyer flask of 250 Cc. capacity, add 115 Cc. of ether and 35 Cc. of chloroform, shake the flask during five minutes, and then add 3 Cc. of ammonia water and again shake the flask at intervals during half an hour. Now add 10 Cc. of distilled water, shake the liquid until the powder collects in masses, and pour off 100 Cc. of the clear ethereal solution into a measuring cylinder. Transfer the latter to a separator, add 10 Cc. of N. H 2 SO 4 and 10 Cc. of distilled water. Shake the separator moderately during two minutes, and when the liquids have separated, draw off the lower acid solution into a second separator. Repeat the shaking out of the ether- solution with 3 Cc. of N. H 2 SO 4 and 5 Cc. of distilled water, drawing the acid solution into the second separator. Repeat the shaking out again, using 10 Cc. of distilled water, and add the aqueous solution to the second separator. Reject the ether in the first separator, introduce a small piece of red litmus paper into the second separator, add enough ammonia water to render the liquid alkaline, and 25 Cc. of ether, and then shake the separator vigorously during one minute ; draw off the alkaline aqueous liquid into another separator, and transfer the ether-solution to a flask. Add 20 Cc. of ether to the alkaline liquid in the separator, shake it for one minute, and, having allowed the liquids to separate, draw off the alkaline liquid into the other separator, and transfer the ether-solution to the flask. Again shake out the alkaline liquid with 10 Cc. of ether, and, when the fluids have separated, reject the alkaline liquid and add the ether-solution to the liquid in the flask. Distil the ether from the flask with the aid of a water- bath, and dissolve the alkaloidal residue in 12 Cc. of ^y H 2 SO 4 , warming it gently on a water- bath if necessary. Then add five drops of hematoxylin and titrate with TTQ KHO. Divide the number of cubic centimeters of T N ^KHO used, by 5, subtract the quotient from 12 (the 12 Cc. of ^5- H 2 SO 4 taken), and multiply the remainder by 0*0238, and this product by 10, which will give the per- centage of alkaloids in the ipecac. (b) Assay of fluidextract of ipecac. Transfer 10 Cc. of fluidextract of ipecac by means of a graduated pipette to a porcelain evaporating dish. Evaporate off the alcohol with the aid of a water-bath, and, when almost cool, add 5 Cc. N. H 2 SO 4 , and stir the liquid at intervals for three minutes. Filter the liquid into a separator, rinse the dish, and wash the filter successively with 10 Cc. and 5 Cc. of distilled water, and add these liquids to the separator. To the separator add 20 Cc. of ether and a small piece of red litmus paper ; render the liquid alkaline with ammonia water and shake the separator for one minute. Draw off the aqueous layer into a beaker, and the ether-layer into another beaker. Return the aqueous solution to the separator, add 10 Cc. more of ether, and shake the liquid, adding the ether-solution to that already in the beaker, and returning the aqueous solution to the separator ; repeat the extraction with 10 Cc. more of ether, and then add the ether-layer to that already in the beaker. Allow the combined ether-solutions to evaporate, either spontaneously or with the aid of a water-bath containing warm water, and then add 10 Cc. of H 2 SO 4 . Stir the liquid carefully with a glass rod to facilitate the solution of the alkaloids, and when these have all dissolved, add 5 drops of hematoxylin. From a graduated burette, add sufficient ^ KHO to just cause the yellow color of the solution to turn purple. Divide the number of cubic centimeters of -j^ KHO used, by 5, subtract the quotient from 10 (the 10 Cc. of yjy H^SO 4 taken), and multiply the remainder by o'o238, and this product by TO, which will give the weight in Gms. of alkaloids contained in each one hundred cubic centimeters of fluidextract of ipecac. 202 ANALYSIS OF DRUGS, ETC. (5) Nux Vomica and its Preparations. (a) Assay of nnx vomica. Introduce 20 Gm. of nux vomica (in No. 60 powder) into a 250 Cc. Erlenmeyer flask and add to it 200 Cc. of a mixture of 137-5 Cc. of ether, 44 Cc. of chloroform, i3'5 Cc. of alcohol, and 5 Cc. of ammonia water ; insert the stopper securely and macerate with frequent shaking during one hour and allow it to stand in a cool place for twelve hours. Decant into a measuring cylinder 100 Cc. of the liquid (representing 10 Gm. of nux vomica), and pour this into a separator, preferably of a globular shape. Rinse the cylinder with a little chloroform, add this to the separator, and then add 15 Cc. of N. H 2 SO 4 ; shake the mixture moderately during one minute, being careful to avoid emulsification ; when the liquids have separated completely, draw off the acid liquid into a beaker. Repeat the shaking out with successive portions of 5 and 3 Cc. of N. H 2 SO 4 ; collect the acid solu- tions and pour them into a separator. If a drop of the last acid solution yields a precipitate with mercuric potassium iodide, repeat the shaking out of the ether solution with 5 Cc. of N. H 2 SO 4 . To the combined acid solu- tions in the separator add a small piece of red litmus paper, 25 Cc. of chloroform, and then sufficient ammonia water to render the liquid alkaline, and shake the separator thoroughly. When the liquids have separated draw off the chloroform into a flask of 100 Cc. capacity, and repeat the shaking out of the alkaline liquid with two successive portions of 15 Cc. each of chloro- form, adding the latter to that already in the flask. Evaporate the combined chloroformic solutions in the flask until the alkaloidal residue is dry, then dissolve in it 15 Cc. of sulphuric acid (3 per cent.), warming it on a water-bath. When the solution has cooled, add 3 Cc. of a cooled mixture of equal volumes of nitric acid (specific gravity 1*40) and distilled water, and after rotating the liquid a few times, set it aside for exactly ten minutes, shaking it gently three times during this interval. Transfer the resulting red liquid to a separator containing 25 Cc. of an aqueous solution of sodium hydroxide (i in 10) and wash the flask three times with very small amounts of distilled water, and add the washings to the separator. If the liquid is not turbid add 2 Cc. more of the solution of sodium hydroxide. Now add 20 Cc. of chloroform to the separator, and shake it well by a rotating motion for a few minutes, allow the liquids to separate, and draw off the chloroform, through a small filter wetted with chloroform, into a flask. Repeat this twice, using 10 Cc. of chloroform each time, and draw off both portions into the flask, using the same filter. Finally, wash the filter and funnel with 5 Cc. of chloroform, and then evaporate all the chloroform by means of a water-bath very carefully, to avoid decrepitation. To the alkaloidal residue add 6 Cc. of -$ H 2 SO 4 , 5 drops of iodeosin, about 80 Cc. of distilled water, and 20 Cc. of ether. When all the alkaloid is dissolved, titrate the excess of acid with -^j KHO until the aqueous liquid just turns pink. Divide the number of cubic centimeters of J^ KHO used, by 5, subtract this number from 6 (the 6 Cc. of T ^H 2 SO 4 taken), multiply the remainder by 0*0332, and this product by TO, which will give the percentage of strychnine in the nux vomica. (b) Assay of extract of ?iux vomica. Introduce 2 Gm. of extract of nux vomica into a beaker, and dissolve it in 25 Cc. of a mixture of 16 Cc. of ether, 5 Cc. of chloroform, and 4 Cc. of ammonia water. When dissolved, transfer it to a separator, rinsing the beaker with a little chloroform, and adding the rinsings to the separator. Insert the stopper securely and shake the separator carefully for a few minutes. Draw off the aqueous layer into another separator, washing the ether-solution and separator with a little water, and adding this to the second separator. Then shake out the aqueous liquid with two portions of 15 and 10 Cc., respectively, of chloroform, and add these to the first separator. If a few drops of the liquid left in the second separator U.S. P. ASSAYS OF DRUGS. 203 still give a reaction with mercuric potassium iodide after acidulating, repeat the shaking out with 10 Cc. more of chloroform. Now shake out the chloro- formic solution in the first separator with three portions of 15, 10, and 10 Cc. of sulphuric acid solution (3 per cent.), and collect the combined acid solu- tions in another separator. Introduce a small piece of red litmus paper, add enough ammonia water to render the liquid alkaline, and extract the mixture with three portions, respectively, of 15, 10, and 10 Cc. of chloroform. Draw off the chloroformic solutions into a beaker, and evaporate the chloroform with the aid of a water-bath. Dissolve the alkaloidal residue in the beaker in 15 Cc. of 3 per cent, sulphuric acid solution by the aid of a water-bath. From this point proceed by adding HNO 3 and extracting the alkaloid by CHCl a in the presence of NaHO, as directed above in the assay of nux vomica, until the alkaloidal residue is obtained. To the alkaloidal residue add 10 Cc. of i N Jy H.;SO4, 5 drops of iodeosin, about 90 Cc. of distilled water, and 20 Cc. of ether. When all the alkaloid is dissolved, titrate the excess of acid with ^ KHO until the aqueous liquid just turns pink. Divide the number of cubic centimeters of yjj- KHO used, by 5, subtract this number from 10 (the 10 Cc. of T N ff H 2 SO 4 taken), multiply the remainder by 0*0332, and this product by 50, which will give the percentage of strychnine contained in the extract of nux vomica. (c] Assay of fluidextract of nux vomica. Transfer 10 Cc. of fluidextract of nux vomica by means of a graduated pipette to a porcelain dish, evaporate it to dryness with the aid of a water-bath, and dissolve the residue, while warm, in a mixture of 16 Cc. of ether, 5 Cc. of chloroform, and 4 Cc. of ammonia water, and transfer the solution to a separator, rinsing the dish with a little chloroform, which is to be added to the separator, and shake the separator carefully for a few minutes. When the fluids have separated, draw off the aqueous layer into another separator, wash the chloroform-ether liquid and separator with a little water, and add this to the second separator. Then shake the aqueous liquid with two successive portions of 15 and 10 Cc. respec- tively of chloroform, and add these to the first separator. If a small portion of the liquid left in the second separator still shows, after acidifying, a reaction with mercuric potassium iodide, repeat the shaking out with 10 Cc. more of chloroform. Now shake the combined liquids in the first separator with three successive portions, respectively, of 15, 10, and 10 Cc. ol N. H 2 SO 4 , and collect the combined acid solutions in another separator. To this acid solution add a small piece of red litmus paper, and sufficient ammonia water to render it alkaline, then shake out successively with three portions, respectively, of 25, 10, and 10 Cc. of chloroform, and collect the chloroform- solutions in a beaker. Evaporate the chloroform with the aid of a water- bath, dissolve the alkaloidal residue in 15 Cc. of 3 per cent, sulphuric acid solution, by the aid of a water-bath, and allow the liquid to cool. From this point proceed by adding HNOs and extracting the alkaloid by CHC1 3 in the presence of NaHO, as directed above in the assay of nux vomica, until the alka- loidal residue is obtained. To the alkaloidal residue add loCc. of ^ H 2 SO 4 , 5 drops of iodeosin, about 80 Cc. of distilled water, and 20 Cc. of ether. When all the alkaloid is dissolved, titrate the excess of acid with -^ KHO, until the aqueous liquid just turns pink. Divide the number of cubic centi- meters of ^ KHO taken, by 5, subtract this number from 10 (the 10 Cc. of j^ H 2 SO 4 taken), multiply the remainder by 0^0332, and this product by 10, which will give the weight in Cms. of strychnine in 100 Cc. of the fluidextract. (d) Assay of tincture of nux vomica. Transfer 100 Cc. of tincture of nux vomica to a porcelain dish, evaporate it to dryness on a water-bath, and assay the resulting extract by the method above given for extract of nux vomica, using the same details as there directed for 2 Gm. of extract of nux vomica, with the exception that the multiplication by 50 be omitted ; the result will 204 ANALYSIS OF DRUGS, ETC. represent the weight in Cms. of strychnine contained in one hundred cubic centimeters of tincture of nux vomica. (6) Pilocarpus and its Preparations. (a) Assay of pilocarpus. Moisten 10 Gin. of pilocarpus with 2 Cc. of ammonia water and 3 Cc. of chloroform, and at once pack it firmly in a small cylindrical percolator, which has been provided with a pledget of cotton packed firmly in the neck. Percolate the powder slowly with chloroform containing about 2 per cent, of ammonia water, until it is exhausted, about TOO Cc. of menstruum usually being sufficient. Pour into a separator the percolate, and shake it out with 15 Cc. of N. H 2 SO4, transferring the acid aqueous layer to another separator, and repeating the shaking out of the chloroform-solution with 2 Cc. of N. H 2 SO 4 , mixed with 8 Cc. of distilled water. Add the acid layer to the second separator, and again repeat the shaking out with 10 Cc. of distilled water, and add the aqueous liquid to the second separator. Introduce into the second separator a small piece of red litmus paper, add enough ammonia water to render the liquid alkaline, and shake out the liquid with 20 Cc. of chloroform, drawing off the chloroformic solution into a beaker. Repeat the shaking out with two portions of 15 and 10 Cc. each of chloroform, and add the chloroformic solutions to the beaker. Evaporate the chloroform by means of a water-bath, and dissolve the alkaloidal residue in 7 Cc. of y^ H 2 SO 4 . Add 5 drops of cochineal or iodeosin, and titrate the excess of acid with ~ KHO. Divide the number of cubic centimeters of ^ KHO used, by 5, subtract the quotient from 7 (the 7 Cc. of ^ H 9 SO 4 taken), and multiply the remainder by o'02, and this product by 10; the result will be the percentage of alkaloids contained in the pilocarpus. The figure 0*02 represents the weight in Gms. of alkaloids (mainly pilocarpine) required to neutralize i Cc. of $ H 2 SO 4 . (b) Assay of fluidextract of pilocarpus. Transfer TO Cc. of fluidextract of pilocarpus by means of a graduated pipette to a porcelain dish containing a little clean sand, and evaporate it to dryness with the aid of a water-bath. Mix the sand uniformly with the extract and transfer the mixture to an Erlenmeyer flask of about 100 Cc. capacity, rinsing the dish with a mixture of 25 Cc. of chloroform and 2-5 Cc. of ammonia water. Transfer the rinsings to the flask, cork it securely, and shake it well at intervals during one hour. Decant the liquid, transfer to a separator, wash the sand with several portions of chloroform, draw off and filter the chloroformic liquid into another separ- ator. Then shake out the chloroform-solution with 15 Cc. of N. H 2 SO 4 , transferring the acid aqueous solution to another separator. Repeat the shaking out with a mixture of 5 Cc. of N. H 2 SO 4 and 5 Cc. of distilled water, collecting the acid solutions in the second separator. Again repeat the shaking out with 10 Cc. of distilled water, and add the aqueous liquid to the second separator. Introduce into the second separator a piece of red litmus paper, and proceed to shake out with ammonia water and CHCls, all as above directed to obtain the alkaloidal residue. Dissolve the alkaloidal residue in 8 Cc. of f\ H 2 SO 4 . Add 5 drops of cochineal or iodeosin, and titrate the excess of acid with -^ KHO. Divide the number of cubic centimeters of / F KHO used, by 5,' subtract the quotient from 8 (the 8 Cc. of -^ H,SO 4 taken), and multiply the remainder by 0*02, and this product by 10, to obtain the weight in Gms. of alkaloids contained in one hundred cubic centimeters of the fluidextract of pilocarpus. (7) Physostigma and its Preparations. (a) Assay of physostigma. Introduce 20 Gm. of physostigma into an Erlenmeyer flask of about 250 Cc. capacity, add 200 Cc. of ether, and shake the flask well during ten minutes. Then add 10 Cc. of an aqueous solution of sodium bicarbonate (i in 20), and shake the mixture vigorously at intervals U.S.P. ASSAYS OF DRUGS 205 during four hours. Allow the powder to settle, and decant 100 Cc. of the ether-solution (representing 10 Gm. of physostigma) into a measuring cylinder ; then transfer it to a separator, introduce a small piece of blue litmus paper, and add sufficient N. H 2 SO 4 to render the liquid acid, and then 10 Cc. of distilled water. Shake the liquid well for several minutes, and draw off the aqueous layer into another separator. Repeat the extraction, using 2 Cc. of N. H 2 SO 4 and 8 Cc. of distilled water, add the acid aqueous layer to the second separator, and finally again shake out the ether-solution, using i Cc. of N. H 2 SO 4 and 9 Cc. of distilled water, adding this also to the second separator. To the combined acid liquids in the second separator, add 25 Cc. of ether, a small piece of red litmus paper, and sufficient sodium bicarbonate solution (i in 20) to render it alkaline. Shake the separator for one minute, allow the liquids to separate, and draw off the ether into a beaker. Repeat the shaking out process with 20 Cc. and again with 15 Cc. of ether added to the separator, shake each time for one minute, allow the liquids to separate, and draw off the ether into the beaker. Carefully evaporate the ether from the combined solutions by means of a water-bath, and when dry, dissolve the residue in 5 Cc. of ~ H 2 SO 4 and 20 Cc. of ether, which must be strictly neutral, and transfer this solution to a bottle, rinsing with 80 Cc. of water; add 5 drops of iodeosin, and titrate the excess of acid with ~ KHO, until, after shaking, the aqueous liquid just acquires a pink color. Divide the number of cubic centimeters of -$ KHO used, by 5, subtract the quotient from 5 (the 5 Cc. of j^j H 2 SO 4 taken), and multiply the remainder by 0*0273, and this- product by 10; the result will be the percentage of alkaloids soluble in ether contained in the physostigma. The figure 0*0273 represents the weight in Gins, of alkaloids (mainly physostigmine) required to neutralize i Cc. of ^ H 2 SO 4 . (b) Assay of extract of physostigma. Transfer i Gm. of extract of physos- tigma to a small porcelain dish, add 5 Cc. of diluted alcohol, and digest for five minutes in a water-bath below boiling temperature ; then add about 5 Gm. of very clean, fine quartz sand, and evaporate to dryness on a water-bath,, triturating thoroughly with a pestle to secure uniform admixture. When dry, carefully transfer the contents of the dish to an Erlenmeyer flask, add 100 Cc. of ether, and shake the flask. Then add 10 Cc. of an aqueous solution of sodium bicarbonate (i in 20), and shake the contents vigorously at intervals for one hour. Allow the mixture to stand, and, when settled, decant 50 Cc. of the ether-solution into a separator, to which add a small piece of blue litmus paper, sufficient N. H 2 SO 4 to render the liquid acid, and 10 Cc. of distilled water. From this point proceed as for physostigma (commencing from " shake the liquid well ") until the alkaloidal residue is obtained. Dissolve this residue in 2 Cc. of y^ H 2 SO 4 ; rinse the solution carefully into a 200 Cc. flask with distilled water, add enough distilled water to bring the volume to about 90 Cc., add 25 Cc. of ether, and, having shaken the flask, add 5 drops- of iodeosin, then titrate the excess of acid with -$ KHO, until, after shaking,, the aqueous liquid just acquires a pink color. Divide the number of cubic centimeters of -^ KHO used, by 5, subtract the quotient from 2 (the 2 Cc. of yjj- H 2 SO 4 taken), and multiply the remainder by 0*0273, an( ^ tms product by 200 ; the result will be the percentage of ether-soluble alkaloids contained in the extract of physostigma. (c) Assay of tincture of physostigma. Transfer 100 Cc. of tincture of physostigma to a porcelain dish, evaporate it to dryness on a water-bath, and assay the resulting extract by the method given above, using the same details as there directed for i Gm. of extract of physostigma, with the exception that the product must be multiplied by 2 instead of 200 ; the result will represent the weight in Gms. of ether-soluble alkaloids from physostigma contained in one hundred cubic centimeters of tincture of physostigma. 208 ANALYSIS OF DRUGS, ETC. distilled water added to make the liquid measure 10 Cc. If the alcohol be already diluted, a correspondingly larger volume of it should be taken and diluted to 10 Cc., so that the pro- portion of alcohol in the liquid shall not be more than about 10 per cent., by volume. A copper wire spiral (made by winding I meter of No. 18 clean copper wire closely around a glass rod 7 millimeters thick, making a coil about 3 centimeters long, the end of the wire being formed into a handle) should be heated to redness in a flame free from soot, and plunged steadily quite to the bottom of the liquid in the test-tube and held there for a second or two, then withdrawn and dipped into water to cool. This treatment with red-hot copper should be repeated five or six times, immersing the test-tube in cold water to keep down the temperature of the liquid. The contents of the test-tube should now be filtered into a wide test-tube and boiled very gently. If the odor of acetaldehyde be perceptible, the boiling is to be continued until the odor ceases to be distinguished clearly. The liquid is now cooled, and to it should be added I drop of a solution containing I part of resorcinol in 200 parts of water. A portion of this liquid is then poured cautiously into a second tube containing pure sulphuric acid, in such a way that the two liquids shall not mix, the tube being held in an inclined position ; this tube is allowed to stand for three minutes, and then slowly rotated. No rose-red ring should show at the line of contact of the two layers (absence of more than 2 per cent, of methyl alcohoi). X. ANALYSIS OF FIXED OILS AND FATS. This is a matter requiring the greatest practice and experience, and, unfortunately, it is still possible so to sophisticate dearer with cheaper oils as to practically defy definite analysis. If, however, we confine our attention to the ordinary fixed oils of the U.S. P., we can get a very fair idea of their purity, or otherwise, by applying the following methods : (i) Specific Gravity, (a) In the case of oils, this is taken at 25 C. gravities of the U.S. P. oils are The Almond Castor . Cod liver Cotton seed Croton Lard oil Linseed Olive . 90510-915 '945 '905 918 915 '935 '90S 925 910 922 921 950 915 '935 915 (b) In the case of solid fats we melt them, and take their gravity either at 40 C. or at the boiling point of water. The U.S. P. uses the former standard, but for a person not continually operating with oils, the latter is more likely to give good results, and may be worked in the following manner : Take an ordinary specific-gravity bottle with a well-fitting perforated stopper, and also a deep basin capable of holding a good deal more water than will quite cover the bottle. Charge the basin with distilled water, and put it over a good gas flame, so that it is rapidly heated to boiling point. Melt the fat, and charge the specific-gravity bottle with it in the usual way, and then, holding it with a pair of wooden tongs, plunge it into the water so that it lies on its side, entirely immersed, with its neck pointing downwards. The melted fat expands, and, passing through the hole in the stopper, absolutely prevents the entrance of any of the water, which must be kept briskly boiling for twenty minutes. The bottle is then fished out, rapidly wij,ed dry, cooled, and weighed. The weight of the empty bottle having been deducted, the balance gives the weight of fat it holds at the temperature of boiling water, which, divided by the weight of water that the bottle holds under the same conditions, gives a sufficiently accurate gravity for all ordinary purposes. Thus treated the following solid fats give ANALYSIS OF FIXED OILS AND FATS. 209 Butter -867 to '870 Lard -860 ,, -861 Cacao butter '857 ,, '858 Beef fat -857 ,, '859 (2) Hubl's Method of Iodine Absorption. The iodine value or number of a fat or an oil is a figure which indicates the percentage of iodine absorbed under certain conditions. It is determined as follows : To a solution of 0*3 Gm. of oil in 10 Cc. of chloroform contained in a glass-stoppered bottle of 250 Cc. capacity, add 25 Cc. of a mixture of equal volumes of alcoholic iodine (25 Gm. I in 500 Cc. alcohol), and alcoholic mercuric chloride (30 Gm. HgCl2 in 500 Cc. alcohol), both of which have been measured from a burette. After having been securely stoppered, the bottle is set aside in a cool place, protected from the light, for a period of four hours. After this time, the mixture must still possess a brown color; if it does not, a further measured portion of the mixture of the two reagents should be added, and the mixture be again set aside. Finally, 20 Cc. of a 20 per cent, solution of potassium iodide are added, followed by 50 Cc. of water, and -^ Na 2 S 2 O 3 is then added in small successive portions, shaking thoroughly after each addition until the color of the mixture is discharged. The number of Cc. of -^ Na 2 S 2 Os con- sumed is noted. At the same time that this test is carried out, a blank experiment is made in which exactly the same quantities of chloroform, iodine, and mercuric chloride are mixed, and, after standing for four or more hours, the free iodine is estimated by titration as directed above. The number of Cc. of ^ Na 2 S 2 O 3 consumed is noted, and from this is deducted the number of Cc. which was consumed in the test; the difference multiplied by 1 2 -5 9, and this product divided by 3, gives the iodine value of the fat or oil. In dealing with linseed oil only '15 Gm. should be taken, the bottle should be allowed to stand for sixteen hours, and the product divided by 1-5 instead of by 3. With solid fats, such as Ol. Theobroma, *8 Gm. is to be taken and the product divided by 8. Thus treated, the following oils and fats show : Per cent, of iodine absorbed. Almond 95 to 100 Castor 86 89 Cod liver 140 Cotton ...... 102 Croton ....'.. 100 Lard oil . . . . . 56 Linseed 170 Olive 80 Cacao butter . . . 33 (3) Saponification Equivalent. The determination of the saponification value is conducted as follows : Weigh out accurately, in a flask holding 150 to 200 Cc., 1-5 to 2 Gm. of the purified and filtered fat. Next run into the flask, with a burette, 25 Cc. of alcoholic potassium hydroxide (28 Gm. KHO in 1000 Cc. alcohol). While exactly 25 Cc. is not indispensable, in com- parative tests precisely the same amount must be used, allowing the burette to drain in exactly the same way in each test. Then place a small funnel in the flask and heat it on a water-bath containing boiling water, for half an hour, so that the alcohol is simmering, frequently imparting a rotatory motion to the contents of the flask. Then add i Cc. of phenol-phthalein, and titrate back the excess of KHO with HC1. A blank test is made at the -same time, using the 25 Cc. of alcoholic KHO alone; the difference in the number of Cc. of J HC1 c'onsumed by the blank test and the real test, multiplied by 27-87, and divided by the weight in grammes of the fat or oil taken, will give the saponification equivalent of the sample tested. 150 1 08 105 74 187 88 38 210 ANALYSIS OF DRUGS, ETC, The following are the saponification equivalents of the oils referred to : Per cent, of KHO neutralized. Almond . . . . . 191 to 200 Castor ...... 179 ,, 180 Cod liver 175 , 18' Cotton ...... 191 Croton ...... 212 Linseed 187 Olive ...... 191 Lard oil ...... 195 Cacao butter 188 190 218 195 195 197 195 (4) Specific Heating Power. The process consists in placing 50 Gm. of the oil or melted fat in a glass cylinder, immersing a thermometer, noting the temperature, and then causing 10 Cc. of strong sulphuric acid, brought to exactly the same temperature as that of the oil, to flow slowly in from a stoppered burette, stirring with the thermometer all the time, and noting the extreme point to which the mercury rises. The experiment is then repeated under exactly the same conditions, using 50 Cc. of distilled water instead of oil, and the rise is again noted. Lastly, the rise in temperature observed with the oil is divided by that shown with the water. The stopper of the burette should be so set that it takes exactly one minute to deliver 10 Cc. of acid. The following are some characteristic results : Water . I -oo Castor Cod liver Cotton Linseed Olive 0'89 to 0-92 2-46 272 1-63 ,, 170 3'2o 3-49 o 89 0-94 The rise is so great with linseed oil, that it is best to work upon it after diluting it one half with a mineral oil, previously found to give only a slight definite rise, and to make a correction. (5) Qualitative Tests for TT.S.P. Fixed Oils and Fats. (a) Almond oil. (i) Remains clear at IOC., and does not congeal until cooled to nearly 20 C. (absence of olive oil or lard oil}. (2) 2 Cc. vigorously shaken with i Cc. of fuming nitric acid and i Cc. of water forms a whitish mixture, which, after standing for some hours at about 10 C. (50 F.), separates into a solid, white mass and a slightly colored liquid (distinction from oils of peach and apricot kernels , which give a red color, and sesame and cotton seed oils, which are colored brown). (3) 10 Cc. mixed with 15 Cc. of solution of sodium hydroxide (i in 6) and 10 Cc. of alcohol, and the mixture allowed to stand at a temperature of 35 to 40 C., with occasional agitation, until it becomes clear, and then diluted with 100 Cc. of water, yields a clear solution which, on adding an excess of hydrochloric acid, will throw up a layer of oleic acid. This, when separated from the aqueous liquid, washed with warm water, and clarified by heating on a water-bath, will remain -liquid if cooled to 15 C. This acid, when mixed with an equal volume of alcohol, should yield a clear solution, which at 15 C. should not deposit any fatty acids, nor become turbid upon the further addition of I volume of alcohol (dis- tinction from olive, arachis, cotton seed, sesame, and other fixed oils}. (b} Castor oil. (i) Soluble in all proportions in absolute alcohol, and in glacial acetic acid, and in 3 times its volume of 92*5 per cent, alcohol. (2) 3 Cc. shaken for a few minutes with 3 Cc. of carbon disulphide and I Cc. of sulphuric acid, should not acquire a blackish-brown color (absence oft. foreign oils}. (c} Cod liver oil. (i) Very slightly soluble in alcohol, but readily soluble in ether, chloroform, or carbon disulphide ; also in 2-5 parts of acetic ether. (2) I drop of the oil dissolved in 20 drops of chloroform and shaken with I drop of sulphuric acid, will give a violet-red tint, rapidly changing to rose-red and, finally, brownish-yellow. (3) If a glass rod moistened with sulphuric acid be drawn through a few drops of the oil, on a porcelain plate, a violet color will be produced. (4) If two or 3 drops of fuming nitric acid be allowed to flow alongside of 10 or 15 drops of the oil, contained in a watch-glass, a red color will be produced at the point of contact. On Stirling the mixture with a glass rod, this color becomes bright rose-red, soon changing to lemon-yellow (distinction from seal oil, which shows at first no change of color, and from other fish oils, which become at first blue and afterwards brown and yellow). ANALYSIS OF FIXED OILS AND FATS. 211 (d) Cotton seed oil. (i) On cooling the oil to a temperature below 12 C., particles of solid fat will separate. At about o to 5 C. , the oil becomes nearly or quite Solid. (2) 6 Cc. of the oil thoroughly shaken for ten minutes with a mixture of I '5 Cc. of nitric- acid and o'5 Cc. of water, then heated in a bath of boiling water for not more than fifteen minutes, will assume an orange or reddish-brown color, and will form a semi-solid mass in twelve hours at ordinary temperature. (3) 5 Cc. thoroughly shaken in a test-tube with 5 Cc. of an alcoholic solution of silver nitrate (o - i Gm. of silver nitrate in 10 Cc. of alcohol and 2 drops of nitric acid), and then heated for about five minutes on a water-bath, will assume a red or reddish-brown color. (4) If 2 Cc. be mixed in a test-tube with I Cc. each of amyl alcohol and carbon disulphide containing I per cent, of sulphur in solution, and the test-tube be immersed to one-third or one-half its depth in boiling salt water, a red color will develop in from ten to fifteen minutes. (e) Croton oil. (i) When gently heated with twice its volume of absolute alcohol, it forms a clear solution from which the croton oil should separate on cooling. (2) If 2 Cc. be mixed with i Cc. of fuming nitric acid and i Cc. of water and then vigorously shaken, it should not solidify, even partially, after standing two days (absence of other non-drying oils). (/) Lard oil. (i) At a temperature a little below 10 C. (50 F.), it usually commences to deposit a white, granular fat, and at or near o C. (32 F.), it forms a solid white mass. (2) Tested for the presence of cotton seed oil, as above directed by tests (3) and (4), none should be found. (3) Should be completely saponifiable with alcoholic potassium hydroxide and the resulting soap entirely soluble in water, without separation of an oily layer (absence of mineral oils). (g) Linseed oil. (i) It does not congeal at temperatures above 20 C., and is soluble in about 10 parts of absolute alcohol, and in all proportions in ether, chloroform, petroleum benzin, carbon disulphide, and oil of turpentine. (2) Should be completely saponifiable with alcoholic potassium hydroxide, and the resulting soap entirely soluble in water without leaving an oily residue (absence of mineral oils and rosin oil). (3) If 2 Cc. of the oil be warmed and shaken in a test-tube with an equal volume of glacial acetic acid, and if to this mixture, after cooling, i drop of sulphuric acid be added, a greenish color should be produced (a violet color under these circumstances indicates the presence of rosin or rosin oils). (h) Olive oil. (i) When cooled to from 8 to 10 C., the oil becomes somewhat cloudy from the separation of crystalline particles, and at o C. it forms a whitish granular mass. (2) If 2 Cc. of olive oil be shaken vigorously with an equal volume of nitric acid (sp. gr. I '37)> tne oil should retain a light yellow color, not becoming orange or reddish-brown, and after standing for six hours should change into a yellowish-white solid mass and an almost colorless liquid (absence of appreciable quantities of cotton seed oil and most other seed oils). (3) Tested for the presence of cotton seed oil by the tests (3) and (4) above given, none should be found. (4) If 2 Cc. of the oil be mixed with i Cc. of hydrochloric acid (sp. gr. ri8) containing I per cent, of sugar, and the mixture be shaken for half a minute and allowed to stand for five minutes, and then 3 Cc. of water added and the whole again shaken, the acid layer shou'd not show a pink color (absence of sesame oil). (z) Cacao butter (theobroma). (i) Is brittle at temperatures below 15 C., and melts at 30 to 35 C. It is readily soluble in ether, chloroform, or benzene ; also soluble in 100 parts of cold absolute alcohol, and in 20 parts of boiling absolute alcohol ; the solutions should be neutral to test paper. (2) If i Gm. of oil of theobroma be dissolved in 3 Cc. of ether in a test-tube at a tem- perature of 17 C., and the tube frequently plunged into water at o C., the liquid should not become turbid nor deposit white flakes in less than three minutes ; and if the mixture after congealing be again brought to 15 C., it should gradually form a perfectly clear liquid (absence of wax, stearin, tallow, etc.). (/6) Q Lard, (i) Specific gravity : about 0*917 at 25 C., and about 0*904 at 40 C., water at 25 C. taken as the standard. It melts at 38 to 40 C. to a perfectly clear liquid, which is colorless in thin layers and from which an aqueous layer should not separate. (2) Tested for the presence of cotton s^ed oil as above (employing tests (3) and (4), and applying them to 5 Cc. of melted and filtered lard while still warm), none should be found. (1) Wool-fat, (i) Melts at about 40 C., and at a higher temperature vaporizes, the vapor igniting and burning with a luminous, sooty flame. (2) The solution of wool-fat in chloroform (i in 50), when poured upon the surface of concentrated sulphuric acid, gradually develops a deep brownish-red color at the line of contact of the layers. (3) Should show no free fatty acids, alkalies, or chlorides when tested by the ordinary methods. (4) If 10 Gm. of wool-fat be heated with 50 Cc. of water on a bath of boiling water until 210 ANALYSIS OF DRUGS, ETC. The following are the saponification equivalents of the oils referred to : Per cent, of KHO neutralized. Almond ...... 191 to 200 Castor ...... 179 ,, 180 Cod liver 175 ,, 185 Cotton ...... 191 196 Croton 212 ,, 218 Linseed ...... 187 ,, 195 Olive 191 195 Lard oil ...... 195 ,, 197 Cacao butter ..... 188 ,, 195 (4) Specific Heating Power. The process consists in placing 50 Gm. of the oil or melted fat in a glass cylinder, immersing a thermometer, noting the temperature, and then causing 10 Cc. of strong sulphuric acid, brought to exactly the same temperature as that of the oil, to flow slowly in from a stoppered burette, stirring with the thermometer all the time, and noting the extreme point to which the mercury rises. The experiment is then repeated under exactly the same conditions, using 50 Cc. of distilled water instead of oil, and the rise is again noted. Lastly, the rise in temperature observed with the oil is divided by that shown with the water. The stopper of the burette should be so set that it takes exactly one minute to deliver 10 Cc. of acid. The following are some characteristic results : Water roo Castor 0-89 to 0-92 Cod liver 2-46 ,, 272 Cotton '. 1-63 ,, 170 Linseed 3-20 ,, 3-49 Olive o 89 ,, 0-94 The rise is so great with linseed oil, that it is best to work upon it after diluting it one half with a mineral oil, previously found to give only a slight definite rise, and to make a correction. (5) Qualitative Tests for U.S.P. Fixed Oils and Fats. (a) Almond oil. (i) Remains clear at IOC., and does not congeal until cooled to nearly 20 C. (absence of olive oil or lard oil}. (2) 2 Cc. vigorously shaken with I Cc. of fuming nitric acid and I Cc. of water forms a whitish mixture, which, after standing for some hours at about 10 C. (50 F.), separates into a solid, white mass and a slightly colored liquid (distinction from oils of peach and apricot kernels, which give a red color, and sesame and cotton seed oils, which are colored brown). (3) 10 Cc. mixed with 15 Cc. of solution of sodium hydroxide (i in 6) and 10 Cc. of alcohol, and the mixture allowed to stand at a temperature of 35 to 40 C., with occasional agitation, until it becomes clear, and then diluted with 100 Cc. of water, yields a clear solution which, on adding an excess of hydrochloric acid, will throw up a layer of oleic acid. This, when separated from the aqueous liquid, washed with warm water, and clarified by heating on a water-bath, will remain -liquid if cooled to 15 C. This acid, when mixed with an equal volume of alcohol, should yield a clear solution, which at 15 C. should not deposit any fatty acids, nor become turbid upon the further addition of I volume of alcohol (dis- tinction from olive, arachis, cotton seed, sesame, and other fixed oils). (U) Castor oil. (i) Soluble in all proportions in absolute alcohol, and in glacial acetic acid, and in 3 times its volume of 92*5 per cent, alcohol. (2) 3 Cc. shaken for a few minutes with 3 Cc. of carbon disulphide and I Cc. of sulphuric acid, should not acquire a blackish-brown color (absence Q{ foreign oils). (c) Cod liver oil. (i) Very slightly soluble in alcohol, but readily soluble in ether, chloroform, or carbon di^ulphide ; also in 2-5 parts of acetic ether. (2) I drop of the oil dissolved in 20 drops of chloroform and shaken with I drop of sulphuric acid, will give a violet-red tint, rapidly changing to rose-red and, finally, brownish-yellow. (3) If a glass rod moistened with sulphuric acid be drawn through a few drops of the oil, on a porcelain plate, a violet color will be produced. (4) If two or 3 drops of fuming nitric acid be allowed to flow alongside of 10 or 15 drops of the oil, contained in a watch-glass, a red color will be produced at the point of contact. On stining the mixture with a glass rod, this color becomes bright rose-red, soon changing to lemon-yellow (distinction from seal oil, which shows at first no change of color, and from other fish oils, which become at first blue and afterwards brown and yellow). ANALYSIS OF FIXED OILS AND FATS. 211 (d) Cotton seed oil. (i) On cooling the oil to a temperature below 12 C., particles of solid fat will separate. At about o to 5 C. , the oil becomes nearly or quite solid. (2) 6 Cc. of the oil thoroughly shaken for ten minutes with a mixture of I '5 Cc. of nitric acid and 0*5 Cc. of water, then heated in a bath of boiling water for not more than fifteen minutes, will assume an orange or reddish-brown color, and will form a semi-solid mass in twelve hours at ordinary temperature. (3) 5 Cc. thoroughly shaken in a test-tube with 5 Cc. of an alcoholic solution of silver nitrate (cri Gm. of silver nitrate in 10 Cc. of alcohol and 2 drops of nitric acid), and then heated for about five minutes on a water-bath, will assume a red or reddish-brown color. (4) If 2 Cc. be mixed in a test-tube with I Cc. each of amyl alcohol and carbon disulphide containing i per cent, of sulphur in solution, and the test-tube be immersed to one-third or one-half its depth in boiling salt water, a red color will develop in from ten to fifteen minutes. ( ,, viridis. * -914 '934 - 35 to - 48. Myristicae . -862 -910 . + 14 to + 28. t Pimentse . i '033 1-048 . not constant, gener; ( Rosse . -855 865 . 5> >t ! Rosmarini '894 912 . + 15 (not more). > Sabinae -903 923 . + 40 to + 60. Santali . -965 '975 - 1 6 (not less). J Sassafras . . 1-065 1-075 + 4 (not more). > Sinapis . . . 1-013 i -020 . inactive. Terebinthinae . . -860 , -870 . not constant, but dextrogyrate. ), Thymi . . -900 , . '930 - 3 (not more). of oil obtained by fractional dis- tillation should not differ more than 2 from the original. American oil is The boiling point is scarcely ever constant, as these oils are always mixtures, and therefore require fractional distillation in a proper dephlegmator. The results depend so much on the apparatus employed, that it is hopeless to get any agreement in this respect between different operators, until an official method is definitely laid down. If, however, 50 Cc. of the oil be distilled from a long-necked Erlenmeyer flask of 100 Cc. capacity, with a thermometer in the neck, and placed on a piece of wire gauze, to which heat is directly applied by a Bunsen burner, fairly concordant estimations may be made on successive quantities. Treated in this way Oleum Terebinthince, U.S. P. should practically entirely distil over between 155 and 162 C. The combination of fractional distillation and specific gravity or optical rotation is often very useful in detecting mixtures of essential oils with turpentine, etc. This method is employed by the U.S. P. in the examination of certain oils as follows : Oleum Limonis and Oleum Rosmarini should respectively rotate the plane of a ray of polarized light not les? than 60 and not more than 15 to the right in a tube 100 millimeters long; and if 100 volumes be fractionally distilled, the 10 volumes first collected should not produce a rotation differing by more than 2 from that produced by the original oil in the former case, and should also be dextrogyrate in the latter. Oleum Sinapis Volatile should distil between 148 C. and 152 C., and the first and last portions of the distillate should have the same specific gravity as the original oil (absence of ethylic alcohol and petroleum). In the case of Oleum Aurantii Cortex fractional distillation is resorted to, and any oil passing over under 170 C. may be limonene, but, should the oil be adulterated with turpentine, pinene may also come over, and therefore the U.S. P. applies the following test to this fraction : Dissolve 5 Cc. of the fraction to be tested in half its volume of glacial acetic acid, add 5 Cc. of amyl nitrite, cool thoroughly in a freezing mixture, and add, very gradually, 5 Cc. of a mixture of equal volumes of hydrochloric acid and glacial acetic acid. Collect any crystals which separate upon standing, on a force filter, and wash them with a little alcohol. Transfer the crystals to a flask, add 5 Cc. of alcoholic KHO, and heat on a water-bath fifteen minutes. Pour into cold water, collect the precipitate, and wash it with cold water. Recrystallize the dried precipitate from alcohol, and determine the melting point of the crystals. Nitrosopinene melts at 132 C., whereas nitrosolimonene melts at 72 C. The determination of the congealing or crystallizing point of an oil is also occasionally of value. This method is applied to the following oils by the U.S. P. as under : Oleum Anisi. Transfer 10 Cc. of the oil to a test-tube placed in water cooled by ice ; insert a thermometer at once into the oil, and allow it to remain undisturbed until its ANALYSIS OF ESSENTIAL OILS. 217 temperature has fallen to about 6 C. Induce crystallization either by rubbing the inner wall of the test-tube with the thermometer or by the addition of a particle of solid anethol, and stir continuously during the solidification of the oil. The highest temperature reached during the crystallization is regarded as the congealing point, and this should not be below 15 C. Oleum Fceniculi. Is similarly done, but a freezing mixture must be used to bring the temperature down to 5 C., and the congealing point should not be below 5 C. Oleum Rosa should congeal between 18 and 22 C. when tested as follows : Introduce about 10 Cc. of oil into a test-tube of about 15 Mm. diameter; insert a thermometer so that it touches neither the bottom nor the sides of the tube. Raise the temperature of the oil in the tube from 4 to 5 above the saturation point by grasping it in the hand, and shake the tube gently. Allow the oil to cool, and when the first crystals appear, note the temperature. This is regarded as the congealing point ; a second test should be made for confirmation. 2. Solubility. The presence of turpentine and various adulterants is frequently made manifest by the use of a definite volume of alcohol, and on this point the U.S.P. lays down the following standards : Name. Standard of Solubility. Oleum Amygd. Amane equal vols. of 70 per cent, alcohol. Anisi 5 ,,9 Cajuputi I ,, 80 Cari equal ,, 92*3 Caryophylli . . . . .2 ,, 70 Chenopodii . . . . .5 ,,70 Cinnamoni 2 7 Copaike ...... 2 ,, 92-3 Coriandri 3 ,,70 Eucalypti 3 ,,70 Fceniculi . . . . . . 10 (or less) ,, 80 Hedeomae 2 ,,70 Juniperi ...... 10 , } 90 Lavandulse. ..... 3 7 Menthae piperitse . . . .4 ,,70 ,, viridis ..... equal ,, 80 Myristicse , . . . . .3 ,, 90 3. Chemical Analysis. Qualitative tests are, as a rule, unnecessary, because each oil has a perfectly characteristic odor, but some are useful to detect impurities, such as : (a) Alcohol in essential oils may be detected by shaking up a measured quantity with water in a burette, when the bulk will diminish owing to the alcohol dissolving out. (b) Metals (chiefly copper and lead) are detected by shaking up the oil with a little very dilute acid, and then applying the usual tests to the acid liquid. (c) Petroleum products are detected by the action of sulphuric acid, which will combine with the oil, but not with paraffins. The U.S.P. applies this method to the detection of petroleum in oil of turpentine as follows : If 5 Cc. of oil of turpentine be placed in a small beaker, and 20 Cc. of sulphuric acid be gradually added, with agitation, while the beaker is cooled by immersion in cold water, and the contents, after cooling and renewed agitation, be transferred to a burette, graduated in tenths, the clear layer which forms after the dark mass has settled should not measure more than o - 35 Cc. (absence of petroleum, benzzn, kerosene, or similar hydrocarbons). Quantitative Analysis to ascertain the amount of the active odoriferous principle is now being more and more applied to essential oils. When these active constituents are not simple mixtures of terpenes, they are capable of chemical determination, and may be divided into six classes as follows : (a) Esters (compound ethers) ; (b) Phenols or phenolic ethers ; (c) Aldehyds ; (d) Ketones; (e) Alcohols; (/) Isothiocyanates. They may be respectively tested for and estimated as follows : (a) Estimation of Esters (compound ethers). These bodies are capable of sapomncation by boiling with alcoholic KHO, and the amount of alkali unconsumed having been ascertained by residual titration with acid, the 2i 8 ANALYSIS OF DRUGS, ETC. difference gives the means of calculating the amount of ester. Taking, for example, bornyl acetate (existing in OL Ros?narini\ the equation would be : C 10 H J7 O . C 2 H 3 O + KHO = C 10 H 17 . HO + KC.H 3 O,, and therefore each Cc. of \ KHO consumed would equal '09734 bornyl acetate. For the menthyl acetate (in Ol. Menth. pip.) the similar equivalent would be '09834. The U.S. P. directions are : Introduce 10 Cc. of oil into a tared flask, and note the exact weight ; add 25 Cc. of alcoholic KHO, connect with a reflux condenser, and boil the mixture during one hour. After cooling titrate the residual alkali with HJ5O 4 , using phenol-phthalein as indicator. Subtract the number of Cc. of H 2 SO 4 required from the 25 Cc. of KHO taken, multiply the difference by 9734 (or 9*834), and divide the product by the weight of the oil taken to find the percentage. Ol. Rosmarini should contain not less than 5 per cent., and OL Menth. pip. not less than 8 per cent., of their respective esters. The esters in Ol. Roses not having as yet been properly studied, the U.S. P. takes an empirical saponification factor founded on experience, thus : Place about 2 Cc. of the oil in a weighing-bottle, and weigh accurately. Transfer it, with the aid of a little alcohol, to a 100 Cc. flask, and add 20 Cc. of alcoholic KHO. Connect the flask with a reflux condenser, and boil the mixture during thirty minutes on a water-bath. When cool, add 50 Cc. of distilled water and a few drops of phenol-phthalein, and titrate with H 2 SO 4 . Subtract the number of Cc. of H 2 SO 4 required, from 20, multiply the difference by 27^87, and divide by the weight of the oil to obtain the saponification value, which should be between 10 and 17. (b) Estimation of Phenols and Phenolic Ethers. Such bodies are met with in anethol CsH 5 . CeH 4 . OCH 3 (in oil of anise) and eugenol C 6 H 3 . OCH 3 . OH . C 3 H 5 (in oils of clove, pimento, etc.). The U.S.P. does not make any estimation of the former, relying on the other constants for OL Anisi, especially the congealing point (see supra), but it assays the oils of clove, pimento, and thyme for the latter by taking advantage of the fact that such bodies combine with and dissolve in solutions of alkaline hydroxides, and can be so extracted from a bulk of oil, and the unacted-upon portion read off thus : Introduce into a flask with a long neck (graduated in tenths) 10 Cc. of the oil of pimenta and loo Cc. of 5 per cent, solution of KHO, and shake the mixture for five minutes. When the liquids have separated completely, add sufficient KHO solution to raise the lower limit of the oily layer to the zero mark of the scale, and note the volume of residual liquid. This should not exceed 2 Cc., 3*5 Cc., and 8 Cc. respectively in oils of clove, pimento, and thyme, thus proving them to contain respectively 80, 65, and 20 per cent, of phenolic bodies. (c) Estimation of Aldehyds. Such bodies are met with as cinnamic aldehyd C6H 5 .C2H 2 . CHO (in oils of cinnamon and cassia), benzoic aldehyd (in oil of bitter almonds), citral CioHi 6 O (in oil of lemon), etc., and to estimate them advantage is taken of the well-known reaction of aldehyds with sodium or potassium bisulphite, whereby a crystalline compound is produced which is soluble in water, and thus the aldehyd can be removed and the rest of the oil left and measured. The U.S.P. directs for OL Cinnamoni : Introduce into a flask with a long graduated neck (in 5 V Cc.), by means of a measuring- pipette, 10 Cc. of the oil of cinnamon, add IO Cc. of a 30 per cent, solution of sodium Bisulphite, shake the flask, and heat it in a water-bath containing boiling water until the contents are liquefied; add successive portions (10 Cc. each) of the bisulphite solution, shaking and heating as before, after each addition, until the flask is three-fourths filled. Continue to heat it in the water-bath until the odor of cinnamic aldehyd is no longer per- ceptible, cool the flask to about 25 C., and add enough of the bisulphite solution to raise the lower limit of the oily layer to the zero mark of the scale. The residual liquid should not measure more than 2 '5 Cc., corresponding to at least 75 per cent., by volume, of cinnamic aldehyd. For the estimation of benzaldehyd in OL Amygd. Amarcz, and of citral in ANALYSIS OF ESSENTIAL OILS. 219 OL Limonis, this rough process is not sufficiently delicate, therefore the U.S. P. directs as follows : (1) Benzaldehyd. Introduce into a tared 150 Cc. flask 10 Cc. of purified kerosene, note the exact weight, add 12 drops of the oil, and again note the weight; add 20 Cc. of dis- tilled water with 6 drops of phenol-phthalein, and then neutralize the solution exactly by the addition of ^ NaHO, agitating the flask thoroughly. Add from a burette, gradually, a solution of sodium sulphite (i in 5), alternating with HC1 from ^ second burette, until 10 Cc. of the sodium sulphite solution have been added, and enough HC1 to maintain the neutrality of the mixture ; after adding a few drops of phenol-phthalein, and agitating the flask frequently, allow it to stand two hours to insure a permanent condition of neutrality, and then note the number of Cc. of the HC1 used. Carry out a blank test, identical with the foregoing, without the oil, and note the amount of ^ HC1 consumed. Subtract the number of Cc. required in the blank test from the number required in the original test ; each Cc. of this difference corresponds to 0-0526 Gm. of benzaldehyd. To find the percentage, multiply the above difference by 0-0526, and this product by 100, and divide by the weight of the oil taken. This process is also applicable to the assay of artificial benzaldehyd, which should show 84 per cent., while the natural Ol. Amygd. Am. should contain 85 per cent. The same process is also applicable to artificial cinnamic aldehyd, except that the equivalent for each Cc. ^ HC1 is 0*033, an d the article should show 95 per cent. (2) Citral. Introduce about 15 Cc. of oil of lemon into a counterpoised 150 Cc. flask, and note the exact weight ; add 5 Cc. of distilled water and a few drops of phenol-phthalein, and then neutralize the liquid exactly by the cautious addition of ^ NaHO. Add 25 Cc. of a neutral solution of sodium sulphite (i in 5), and immerse the flask in a water-bath containing boiling water. From a burette add, as needed, just sufficient HC1 to maintain the neutrality of the mixture, keeping the flask continuously heated and frequently agitated, and adding a drop or two of phenol-phthaleiri. When a permanent condition of neutrality is reached, note the number of Cc. of the HC1 consumed. Carry out a blank test, identical with the tore- going, without the oil, and note the amount of HC1 consumed. Subtract the number of Cc. required in the blank test from the number required in the original test ; each Cc. of this difference corresponds to 0-03802 Gm. of citral. To find the percentage, multiply the above difference by 0*03802, and this product by 100, and divide by the weight of the oil of lemon taken. The oil should not show less than 4 per cent. (d) Estimation of Ketones or organic oxides. These bodies, such as carvol (in oils of carraway, dill, and green mint) and cineol (in oils of cajuput and eucalyptus), combine with phosphoric acid to form a precipitate which is insoluble, but is decomposed by the action of warm water. The U.S. P. only employs the process for cineol, and directs as follows : Introduce into a beaker a solution prepared by dissolving 10 Cc. of oil in 50 Cc. of purified petroleum benzin ; immerse the beaker in a freezing mixture and add phosphoric acid, drop by drop, with constant stirring, until the white magma of cineol phosphate formed begins to assume a yellowish or pinkish tint ; then transfer the magma to a force filter, wash it with cold purified petroleum benzin, and then dry it by pressure between two porous plates. Transfer the precipitate to a narrow graduated cylinder, and add warm water, which will cause separation of the cineol. The volume, in Cc., of the separated oil, multiplied by 10, represents the volume per cent, of cineol. Thus tested, 01. Cajuputi should show 55 per cent., and Ol. Eucalypti 50 per cent. (e) Estimation of alcoholic bodies. These bodies, such as borneol CioHigO (in oil of rosemary), menthol CioH 2 oO (in oil of peppermint), and santalol CisHgcO (in santal oil), may all be estimated by first converting them into their acetic ester, and then titrating that as already directed under Esters (see (a) supra). The following is the method of acetylization : Introduce 10 Cc. of the oil into a flask provided with a ground-glass tube-condenser (acetylization flask), add 10 Cc. of acetic acid anhydride and about I Gm. of anhydrous sodium acetate, and boil gently during one hour. Allow it to cool, wash the acetylized oil with distilled water, and afterwards with 5 per cent, solution of NaHO. until the mixture is slightly- alkaline to phenol-phthalein, and then dry it with the aid of fused calcium chloride, and filler. In dealing with Ol. Santali this process is applied directly, but in the oils of rosemary and peppermint it is performed on the residual oil left after esti- mation of the respective esters in 10 Cc. of the original oil (see (a) supra). 220 ANALYSIS OF DRUGS, E1C. Having thus obtained the acetic ester, we then proceed to estimate it by residual titration. For santal oil the U.S.P. instructs as follows : Transfer to a tared 100 Cc. flask 3 Cc. of the dry acetylized oil, note the exact weight, add 50 Cc. of alcoholic KHO, connect with a reflux condenser, and boil gently during one hour. After cooling, titrate the residual alkali with H 2 SO 4 , using phenol-phthalein as indicator. Subtract the number of Cc. of H 2 SO, required from the 50 Cc. of alcoholic KHO taken, multiply the difference by 1 1 -026, and divide by the weight of the dry acetylized oil taken, less the above difference multiplied by 0*021 ; the quotient will represent the percentage of santalol in the oil of santal, which should amount to 90 per cent. ANALYSIS OF ESSENTIAL OILS. 221 /4 2&r*f, 2 -. &^) If the deposit be not dissolved by heating, let it settle, wash once by decantation with cold water, and warm with acetic acid. Phosphates will dissolve, and may be reprecipitatecl from the solution by excess of NII 4 HO filtered out, well washed with boiling H 2 O, dissolved in HC 2 H 3 O.>, and examined for Ca or Mg by the usual course for these metals in presence of PO 4 . (c) If the deposit be insoluble in acetic acid, warm it with HC1. Any soluble portion is calcium oxalate, which may be precipitated by NH 4 HO. (d) If the deposit be insoluble in HC1, it is probably uric acid. In this case apply the murexid test as follows : Place it in a small white dish, remove moi ture by means of a piece of bibulous paper, add a drop or two of strong HNO 3 , and evaporate to dry ness at a gentle heat. When cold add a drop of NH 4 HO, which will produce a purple colour, deepened to violet by a drop of KHO. 4. Test for albumin, as follows : (a) Boiling test. Filter the urine, place 10 c.c. in a narrow test tube, and add one drop of acetic or nitric acid. Heat the tube ANALYSIS OF URINE. 221 over a small flame in such a way that the upper portion of the liquid only shall be heated. Coagulation will take place, and the presence of albumin will be evident from the formation of a turbidity ranging from a faint cloud to a dense coagulum, but always strongly contrasted with the clear liquid beneath, which was not heated. Mucin also precipitates with this test. () Nifric test. To five volumes of cold saturated solution of magnesium sulphate add one volume of nitric acid (sp. gr. 1*42), and pre- serve this reagent for use. Pour some perfectly clear filtered urine into a tube, and carefully add an equal volume of the reagent, delivered gently from a pipette, so that the liquids shall not mix. An opalescent zone will form at the point of contact either immediately or within twenty minutes, according to the quantity of albumin present. This zone should not dissolve on gently warming, but should be a distinct ring at the bottom of the urine, and not a general haze near the top, which latter indicates mutin. If the zone of contact has a pink colour, indican or other colouring matter is excessive. Indican may be further confirmed by mixing equal volumes of urine, strong HC1, and chlorine water, which pro- duces a violet colour, and may be estimated by colour titration with chloroformic solution of indigo of known strength. (c] Picric acid test. Dissolve 7*5 grms. of pure crys- tallised trinitro-phenol (picric acid) in 500 c.c. of water, let it stand for some days to perfectly clarify, pour oft", and preserve the reagent for use. Mix some of the filtered urine in a tube with an equal volume of this reagent, look for any cloud or precipitate, and then heat to boiling. The true albumin cloud will remain permanent, while that due to peptones or alkaloids accidentally present will be dissolved. Picric acid does not precipi- tate mucin, and is therefore a valuable con- firmatory test. (d] Bodeker's method. Take a drachm of the urine, acidulate it with acetic acid, and add some potas- sium ferrocyanide drop by drop till a clear excess has been added. If during the addition a pre- cipitate forms, albumin is to be suspected. Mere traces require some time to cause the cloud. (e] To estimate the albumin. This may be done empirically by means of an albumino meter (fig. 48). Fill to u with the urine and R with the precipitant (picric acid 10 grms., citric acid 20 grms., and water to make 1000 c.c.). Mix by inverting the tube several times, not by agitation, and set aside for 24 hours. The height of the precipitate, as indicated by the graduations, represents the grains of albumin per thousand c.c. of urine. Be careful to read the height of the precipitate from the middle of the albuminous surface. If the urine is alkaline, make it acid with acetic acid. In the absence of such a convenient appliance \ve may take a weighed quantity of the urine, and allow it to 1. Fig 4 8. 224 ANALYSIS OF DRUGS, ETC. drop into boiling water acidulated with acetic acid. Collect the precipitate on a tared filter, wash with boiling water, dry at 100 C., weigh, and deduct the weight of the filter, when the balance = albumin in the weight of urine operated upon. 5. Test for grape sugar, as follows: (a) Moore's test. Acidulate with acetic acid, boil, and filter out any albumin if necessary. Then mix the filtrate with equal parts of liquor potasses and heat to boiling, when ordinary urine will turn brownish red, but saccharine urine will become dark brown or black. (b) B.cttger's test (modified by Nylander). Dissolve 2*5 grms. of pure bismuth oxynitrate (free especially from silver) and 4 grms. of Rochelle salt in 100 grins, of 8 per cent, solution of sodium hydrate, and preserve for use. To use this reagent i c.c. of urine is added to jo c.c., and the whole boiled gently for some time, when if even only traces of sugar be present the mixture becomes black. (c) Failing's test. Render the urine alkaline with potassium hydrate, and filter to remove any phosphates, etc., which may pre- cipitate. Boil the filtrate with Fehling's solution of copper (see page 130), and if a precipitate should form sugar is present. (d) To estimate the sugar. This is best done by taking 10 grms. of the urine and diluting it with water to 100 c.c. Place this solution in a burette, and run it gradually into 10 c.c. of Pavy's or Fehling's solution, kept boiling in a flask as directed under the Volumetric Analysis of Sugar, page 130. The number of c.c. of urine used will contain '005 grm. of grape sugar if Pavy's solution, or '05 grm. if Fehling's, was used, and then 100 x '005 /T1 x 100 x 'ex; /T , , ,. x ^- (Pavy). or ^(tehling) sugar in the 10 c.c. used c.c. used grms. of urine taken. () Estimation of sugar by fermentation. Take I grm. of com- mercial compressed yeast; shake thoroughly in the graduated test tube with 10 c.c. of the urine to be examined. Then pour the mixture into the bulb of the saccharometer (shown in fig. 49, page 218). By inclining the apparatus the mixture will easily flow into the cylinder, thereby forcing out the air. Owing to the atmospheric pressure the fluid does not flow back, but remains there. The apparatus is to be left undisturbed for 20 to 24 hours in a room of ordinary temperature. If the urine contains sugar, alcoholic fermentation begins in about 20 to 30 minutes. The evolved carbonic acid gas gathers at the top of the cylinder, forcing the fluid back into the bulb. On the following day the upper part of the cylinder is filled with carbonic acid gas. The changed level of the fluid in the cylinder shows that the reaction has taken place, and indicates by the numbers to which it corresponds the approximate quantity of sugar present. If the urine contains more than I per cent, of sugar, then it must be diluted with water before being tested. Diabetic urines of straw colour and a specific fravity of 1018 1022 may be diluted twice; of 1022 1028, ve times ; 1028 1038, ten times. The original (not diluted) urine contains, in proportion to the dilution, two, five, or ten times more sugar than the diluted urine. ANALYSIS OF URINE. 22$ Fig. 49. 6. Test for bile, as follows : (a) Oliver's test. Dissolve 2 grms. of flesh peptone, '25 grm. of salicylic acid, and 2 c.c. of 33 per cent, acetic acid in enough water to yield 200 c.c. of pro- duct. The solution should be rendered perfectly brilliant by passing it through frozen filtering paper. The urine, which should be very clear, is diluted to a specific gravity of roo8. One cubic centimetre of this is added to 3 c.c. of Oliver's reagent. An opalescence at once appears, which will be found to be more or less distinct according to the quantity of bile salts present. Keller's contact method can be advantageously employed for applying the test. (b) Gmeliris test for bile pigments. Place a drachm of nitric acid in a test tube, and cautiously pour upon it an equal volume of the urine. In the presence of bile a play of colours from green to violet, blue, and red will be observed where the liquids touch. (c) Pettenkofer 's test for biliary acids. Mix equal parts of urine and sulphuric acid, add one drop of saturated syrup, and apply a gentle heat. If biliary acids be present, the colour will change from cherry-red to deep purple. Note. Bilious urine is usually of a brownish-green colour. 7. Test for urea, as follows : (a) Separate any albumin (as directed in Moore's test) if necessary, and evaporate an ounce of the urine to a syrupy consistence on the water bath. When cold add nitric acid, drop by drop, till crystals of nitrate of urea cease to deposit. (b) Estimation of urea. This is performed by the hypobromite process already given at page 135. Normal urine contains 2 to 3 per cent. 8. Test for uric acid by mixing one ounce of the urine with one drachm of hydrochloric acid in a beaker, and set aside for some hours. The uric acid will be de- posited in reddish-brown crystals, which may, if desired, be weighed and proved by the murexid test. Normal urine contains 3 to 7 parts per thousand. A volumetric method is also used which is based on the known fact that argentic urate is insoluble in ammonia, but dissolves in nitric acid. The solutions required are: i. " T ^j- ammonium thiocyanate " ; dissolve about 8 grms. of ammonium thiocyanate in a litre of water, and check with y argentic nitrate solution; dilute it for use with nine volumes of water. 2. Dissolve 5 grms. of argentic nitrate in 100 c.c. of distilled water, and add ammonia until the solution becomes clear. 3. Dilute 70 per cent, nitric acid with two volumes of distilled water, boil, to destroy Fig. P, linen . 50.- Extraneous Matters often seen in the lower Oxides of nitrogen^ and preSCFVC Urine. A, silk ; B, cotton ; c, wool ; f , r T i A en; E, feather; F, mycelium; c, cork from the action of light. 4. A saturated IS 226 ANALYSIS OF DRUGS, ETC. solution of ferric alum. 5. Strong solution of ammonia. The following is a description of the process : Place 25 c.c. of urine in a beaker with i grm. of sodium bicarbonate. Add 2 or 3 c.c. of strong ammonia, and then i or 2 c.c. (or an excess) of the ammoniated silver solution. A special procedure is necessary in order to collect the precipitate, as follows : Fill a glass funnel to about one third with broken glass, and cover this with a bed of good asbestos to about a quarter of an inch deep. This is best done by shaking the latter in a flask with water until the fibres are thoroughly separated, and then pouring .the emulsion so prepared in separate portions on to the broken glass. On account of the nature of the precipitate and of the filter, it is necessary to use a Bunsen water pump in order to suck the liquid through. Having thus collected the precipitate, wash it with distilled water until the filtrate ceases to become opalescent with a solution of NaCl. Now dissolve the precipitate by washing it through the filter into a beaker, with a few cubic centimetres of the special nitric acid. Estimate the silver by Volhard's method thus : Add to the liquid in the beaker a few drops of the ferric alum solution to act as an indicator, and from a burette carefully drop in y^- ammonium thiocyanate solution until a permanent red colour appears. The number of c.c. used, multiplied by "00168, gives the amount of uric acid in the 25 c.c. of urine. One milligramme may be added to this amount as an allowance for average loss, and the whole multiplied by 4 gives the percentage of uric acid in the urine. The sodium bicarbonate is added in the early part of the process, to prevent decomposition of the argentic urate, which would other- wise occur. This method has, however, been lately stated to be unreliable. 9. Test for phosphates, as follows : (a) Add to one ounce of the urine a slight excess of ammonium hydrate, and boil. Ca 3 (PO 4 ) 2 and MgNH 4 PO 4 will both be precipitated, and the precipitate, if more than a distinct cloud, should be filtered out, dissolved in HC1, and analysed by the ordinary process already given for phosphates. (J?) After filtering out the earthy phosphates as above, alkaline phos- phates may be tested for by adding magnesia mixture to the filtrate, and getting the usual precipitate of MgNH 4 PO 4 after standing some hours in a cold place. (c) Estimation of phosphates. This is done by the volumetric process with uranic nitrate, already described at page 131. Normal urine contains 2 to 3 parts P 2 O5 per thousand. 10. Test for sulphates, as follows : Acidulate a little of the urine with HC1, warm, and add excess of BaCl 2 . If the precipitate appear too copious, estimate as usual, using 50 c.c. urine (see page 132). Normal urine contains 1*5 to 3 parts SOs per thousand. 11. Test for chlorides, as follows : Acidulate a little of the urine with HNOs, and add excess of argentic nitrate. If the precipitate thus produced looks very large, a weighed quantity of the urine should be taken, and the chlorides estimated by Volhard's method (see page 118). Normal urine contains 5 to 10 parts sodium chloride per thousand. 12. Blood is best seen under the microscope; but urine containing it has always a very characteristic smoky appearance. A test for blood is "to add tincture of guaiacum and ethereal solution of hydrogen peroxide, which pro- duce a sapphire blue ; but such colour of itself should not be taken as positive proof without the blood discs beings also visible under the microscope, ANALYSTS OF URINARY CALCULI. 227 DIVISION III, ANALYSIS OF URINARY CALCULI, The following table will show at a glance the compositions and methods of proving the various calculi. 1. Calculi, fragments of which, heated to redness on platinum, entirely burn away. NAME. PHYSICAL CHARACTERS. CHEMICAL CHARACTERS. Urid acid, C 5 N 4 H,O 3 . Ammonium urate. Cystine, Xanthin, C 3 II 4 N 4 O 2 . Brownish-red ; smooth or tuberculated ; concentric laminae (common). Clay-coloured ; usually smooth, and rarely with fine concentric laminae (uncommon). Brownish-yellow, semi-transparent and crystalline (very un- common). Pale polished brown surface (very un- common). Insoluble in water ; soluble in KHO by heat, but evolves no NH 3 ; dis- solves with effervescence in HNO V and the residue on evaporating the solution is red and gives the murexid test. Soluble in hot water ; soluble in heated KHO, evolving NH 3 . Be- haves with HNO 3 like uric acid. Insoluble in H 2 O, alcohol, and ether. Soluble in NH 4 HO, and depositing, when allowed to evaporate spon- taneously, hexagonal plates. When heated, gives off odour of CS 2 . Soluble in KHO ; soluble in HNO 3 without effervescence, and the solu- tion leaves on evaporation a deep yellow residue. 2. Calculi, fragments of which, heated to redness on platinum, do not burn away, NAME. PHYSICAL CHARACTERS. CHEMICAL CHARACTERS. Calcium oxalate, mulberry calculus, CaCA- Tricalcium phosphate, bone-earth calculus, Ca 3 (P0 4 ) 2 . Magnesium ammonium phosphate, triple phosphate calculus, MgNH,PO 4 . Mixed phosphates of Ca, Mg, and NII 4 , fusible calculus. Deep brown, hard, and rough ; thick layers (common). Pale brown, with regu- lar laminae (uncom- mon). White, brittle, crys- talline, with an un- even and not usually laminated surface (uncommon). White, and rarely laminated. Insoluble in acetic acid, but soluble, without effervescence, in HC1 ; heated to redness, it is converted into CaCO 3 , which dissolves with effervescence in acetic acid, and the solution gives a white precipitate with (NH 4 ) 2 C.,O 4 . Heated strongly before the blow-pipe, CaO remains, which, when moistened, is alkaline to test-paper. Infusible before the blow-pipe, and residue, when moistened, is not al- kaline. Soluble in HC1, and the solution gives a gelatinous precipi- tate with excess of NH 4 HO. Fusible with difficulty before the blow-pipe, evolving NH 3 , and re- sidue not alkaline. Soluble in HC1, and solution gives white crystalline precipitate with NH 4 HO. Readily fusible before the blow-pipe. Soluble in acetic acid, and solution gives a white precipitate with (NH 4 ) 2 C 2 O 4 , and the filtrate from that precipitate gives a white pre- cipitate with excess of NH 4 HO. CHAPTER XII. THE TAKING OF MELTING, SOLIDIFYING, AND BOIL- ING POINTS, POLARISATION ANALYSIS, SPECTRUM ANAL YSIS, AND THE ANAL YSIS OF GASES. DIVISION I. THE TAKING OF MELTING, SOLIDIFYING, AND BOILING POINTS, (1) Melting Points, Many methods have been from time to time proposed, but the following will be found to be sufficiently good for all ordinary purposes, and is, moreover, the method officially adopted in the Pharmacopoeia. A piece of narrow glass tube is softened in the gas flame and drawn out, so as to give it a long thin end with a capillary bore of about i millimetre. The substance is melted, and a little of it is sucked up into this capillary tube and allowed to solidify therein. The tube, having been sealed at the lower end, is then tied to a delicate thermometer so that the substance is near the middle of the bulb, and the thermometer with the attached tube should be immersed in a suitable liquid, contained in a beaker placed over a small lamp flame. Water is suitable for substances melting below 212 F. (100 C), sulphuric acid, hard paraffin, or glycerine for substances melting at higher temperatures. The liquid should be continually stirred by means of a glass ring moved up and down till the substance is seen to melt. The temperature is noted, the tube cooled till the substance solidifies, and the operation then repeated. The latter reading of the thermometer should be taken as the melting point. To obtain accurate results, the whole of the mercury column of the thermometer should be immersed in the heated liquid ; but as this is seldom practicable, the mean temperature of the emergent column that is, of that portion above the surface of the heated liquid should be ascertained and the necessary correction applied. To obtain the mean temperature of the emergent column, a small thermometer is fixed by india-rubber bands in such a position that its bulb is about the middle of the emergent column. The corrected temperature may be calculated with approximate accuracy from the formula : Corrected Temperature = T -f '000143 (T t) N, in which T = observed, i.e. uncorrected, temperature ; t = mean temperature of the emergent column ; N = the length of the emergent column in scale degrees. (2) Solidifying Points. It frequently happens, especially in solid fats, that this is a more constant factor than the melting point. We heat the substance to a temperature of about ten degrees above its melting point, and place it in a glass cylinder surrounded by cotton-wool. We then stir slowly with a delicate thermometer, and, as the liquid cools, the temperature regularly falls, until a moment arrives when, after a slight pause, the thermometer shows a ANALYSIS BY CIRCULAR POLARISATION. 229 sudden rise of a fraction of a degree. This is then the solidifying point of the fat. (3) Boiling Points. To determine the boiling point of a substance, the liquid under examination should be placed in a distilling flask having a side tube for conveying the vapour to a condenser, while the thermometer passes through a cork inserted in the neck. The bulb of the thermometer should be near to, but not immersed in, the liquid, and the whole of the thread of mercury should be surrounded by the vapour ; the temperature is read off as soon as the liquid is distilling freely. With certain substances (such as melted hydrous chloral) which do not boil without "bumping," it is necessary to introduce a few fragments of broken glass or recently ignited clay tobacco pipe. All boiling points are supposed to be taken under a normal barometric pressure (760 mm., or 29^ inches), therefore we must always read the pressure for the day, and either add to or deduct from the observed boiling point f i C. for every 27 mm. of barometric variation. DIVISION II. ANALYSIS BY CIRCULAR POLARISATION. THE SACCHAROMETER. Crystals which do not belong to the regular system (notably calc-spar) possess the power of double refraction. That is to say, when a ray of light falls upon them, it is divided into two rays, one of which follows the ordinary rule of refraction, while the other takes a totally different course ; and the two rays are called respectively the " ordinary " and the " extraordinary " ray. The most convenient polarising medium is what is called a " Nicol's prism." It is composed of a crystal of calc-spar cut into two portions in the direction of its axis, and the two parts thus obtained cemented together with Canada balsam. When a beam of light enters the prism, it is doubly refracted by the first portion of the crystal, and the extraordinary ray only passes through the second portion to the eye of the observer ; while the ordinary ray is com- pletely reflected away by the layer of Canada balsam, and so lost to view. When this extraordinary ray is examined, it is found to possess peculiar properties, such as showing colour in transparent bodies which are usually colourless. This is accounted for by believing that it has become polarised i.e., that all its vibrations have been reduced to the same plane. If the polarised light thus obtained be examined by means of another Nicol's prism, it will be found that, when the two prisms are placed with the principal sections parallel to each other, the ray will pass freely ; but if the second prism, called the analyser, be then turned round, so that its chief section is at right angles to that of the first, the polarised ray will in turn be entirely reflected from the layer of balsam, and no light will now reach the observer's eye. This holds good so long as nothing intervenes between the two prisms ; but it has been found that certain bodies, such as quartz, possess the power, when interposed between the prisms, of giving a colour instead of darkness, owing to their possessing the power of twisting the polarised ray from its original plane. Such substances are said to possess the power of circular polarisation, either in a "right-handed" or "left-handed" direction, accord- ing as it is necessary to turn the prism either to the right or left from its proper position, to once more produce complete passage of the colourless polarised ray. The direction of the rotation is indicated by the use of arrows, thus : c?*o. Cane sugar, grape sugar, dextrin, maltose, creasote, camphor, turpentine (American), cinchonine, castor oil, croton oil, and lemon oil, rotate the plane of the polarised ray to the right ; while fruit or (invert) sugar, quinine, cinchonidine, turpentine (French), and many essential oils, morphine, etc., have a left-handed rotation. There are two varieties of quartz, known as right-handed and left-handed, 2 3 o MELTING, ETC., POINTS; ANALYSIS OF GASES, ETC. one of which rotates the plane of polarisation to the right, and the other to the left. If a plate of quartz i millimetre thick be placed between the two " Nicol's/'the ray of polarised light is rotated, and, instead of being colourless, is coloured, changing to all the colours of the spectrum as the analyser is turned, until it once more becomes colourless, and the amount that the analyser has to be turned (registered by a pointer on the degrees of the circle) is the index of rotary polarisation possessed by the quartz either in a right or left-handed direction. If the turning of the analyser be now con- tinued, colour will again show itself, but this time it will be the colour complementary to that at first produced. Thus, if we start with a plate of quartz showing red between the uncrossed prisms, and rotate, we shall find that, when we have turned through an angle of 45, we get no colour, but after that we begin to get the complementary colour green, which becomes most intense at the right angle of 90, when the prisms are crossed. The polariscope as used for analysis is therefore essentially (a) a Nicol's prism acting as a polariser, (b] a plate of quartz usually divided down the centre, the one side being right-handed and the other left, (c) a tube to contain the solution, (d) another " Nicol " capable of being rotated, and having a pointer acting on degrees of the circle on a scale, (e) a telescope to focus the line between the two sides of the quartz. When the pointer is placed at zero, the tube filled with water, and the line focussed, no colour is seen on either side of it ; but if a solution, say of sugar, be introduced, colour appears on one side of the line according to the nature of the sugar, and then the distance through which the pointer has to be moved round the graduated circle to get both sides of the quartz colourless is the degree of rotary polarisation. In practice, monochromatic light from a sodium flame is employed, which causes a dark shadow, instead of a colour, to appear when the instrument is used, so enabling colour-blind persons to employ it without difficulty. Another reason for the employment of a definite monochromatic light lies in the fact that the rotating power of bodies alters according to the ray of the spectrum used, being least for the red rays, and increasing till it reaches its highest point at the violet end of the spectrum. Optical deter- minations are made in a dark room, and the instrument is illuminated by a bead of fused sodium chloride held by a platinum support in a "Bunsen" flame. Light thus obtained corresponds to that emitted at the D line of the solar spectrum. Since the deviation of the plane of polarisation either to the right or to the left of the zero point is directly proportional to the length of the column of liquid, it is important that the observations should be made with tubes of a definite length, such as 100, 50, or 25 mm. The selection of the length of the tube to be employee! is, however, usually dependent upon the depth of colour of the liquid and the extent of its optical rotation. The rotatory power of an optically active, liquid substance, observed with sodium light, and referred to the ideal density i, and in a tube having a length of i deci- metre (100 mm.), is designated as its specific rotatory poiver. This is usually expressed by the term [a] D . Since, however, not only the density of an optically active liquid, but also its rotation, is influenced by the temperature, the specific rotation varies with the latter. In stating the specific rotation, it is therefore necessary to indicate at what temperature the rotation and the density of the liquid have been determined. But for the same temperature the specific rotation of a pure, optically active liquid is always a constant number. To use the instrument we make a solution of the body to be examined of a definite percentage strength by dissolving a certain number of grammes in 100 c.c. of a solvent. We then fill the tube, observe the degree of rotation produced, and from that we calculate the absolute angle SPECTR UM ANAL YSIS. 231 of rotation for the sodium light (always expressed as [a] D ) by the following formula and factors : I. For liquid substances [a] D =-^ L X d TT T- i i.- r i'j / r i IOOOO X d II. r or solutions or solids | [ajn = or I [>] D = L X p X d 10000 X a L x c a = the angle of rotation of the liquid or solid observed with sodium light L = the length of the tube in millimetres, d = the density or specific gravity of the active liquid, p = the amount of active substance in 100 parts by weight of the solution, c = the number of grammes of active substance in 100 c.c. of the solution. If the absolute angle thus found coincides with that obtained from the same substance in a state of purity, then the article under examination is pure ; but if not, then a simple percentage calculation gives the impurity. Thus the [a] D of pure cane sugar = 66*5 . A sample examined as above gave an [a]o = 65-5, Then : 5 ^ * IO = per cent, of real sugar present in the sample. UO '^ DIVISION III. SPECTRUM ANALYSIS When a ray of sunlight is allowed to pass through a prism, it is deflected and dispersed into a number of rays differing in their degree of refrangibility. When these rays, as they pass from the prism, are caused to fall upon a white surface, they are observed to have a marked difference in colour. The image so produced is called a spectrum ; and when sunlight is thus treated it is found to give a spectrum consisting of the following colours viz., violet, indigo, blue, green, yellow, orange, and red. The violet end of the spectrum, owing to its greater refrangibility, is always the nearer to the base or broad end of the prism. By this means of separating the rays of light we are able to ascertain the peculiar properties of each of the colours which go to compose it, and we find that the chemical activity of light resides chiefly in the most highly refrangible rays just outside the violet end of the visible spectrum, which are called the actinic rays ; while, on the other hand, the heat transmitted by the sun is most felt at the opposite or red end of the spectrum. Further research has demonstrated that, if we substituted the light emitted fiom various bodies in a state of incandescence to the action of a prism, the image or spectrum produced varied in each case, and was, moreover, almost characteristic of the particular bodies employed. This discovery led to the invention of the spectroscope, which, in its simplest form, consists of a metallic diaphragm with a narrow slit, through which a lay of light from the burning body is allowed to pass and is condensed by a lens upon a prism of glass, or, better still, a triangular bottle of thin glass filled with disulphide of carbon. At the opposite side of the prism is a short telescope, so arranged that an observer, looking through it, sees the spectrum or image produced by the light after passing through the prism. This telescope works upon a graduated scale, by which its position for viewing any particular line observed can be noted. When ordinary solar light is examined through the spectroscope, a number of dark lines are found crossing the image at certain fixed points. They are called " Fraunhofer's lines," and their position is characteristic of sunlight It has been proved that such lines are only formed when the source of light contains volatile substances, as we find that the light emitted by a non-volatile heated body gives a continuous image, devoid of lines. If, for example, a platinum wire be heated to a high temperature in a Bunsen burner, and tne light thus produced be examined, no lines will be visible ; but if the wire be 232 MELTING, ETC., POINTS; ANALYSIS Of GASES, ETC. now tipped with a fragment of sodium chloride, and once more ignited, a bright line will suddenly appear in the yellow of the spectrum, and in so dazzling a manner as to render the whole of the rest of the image almost invisible. In carrying out this system of analysis, therefore, it is only necessary to procure a perfectly clean piece of platinum wire, with one end bent into the form of a loop, and place a Bunsen gas burner in such a position that the rays from anything heated in it will pass into the spectroscope. The wire is then to be moistened with a little hydrochloric acid, and, having been dipped in the substance to be examined, is to be held in the hottest portion of the Bunsen flame, and its spectrum simultaneously observed through the spectro- scope, noting carefully the colour, number, and position on the scale, of the bright lines produced. When thus examined we find that potassium exhibits one bright line in the red, and one in the blue ; lithium, one bright line in the yellow, and one more brilliant in the red; strontium, one blue, one orange, and six red lines ; barium, a number of lines chiefly green and yellow ; calcium, three distinct bright yellow lines, one within green, and some broad but indistinct ones in the orange and red; and lastly, sodium, the single bright yellow line already mentioned. The student must commence with the examination of pure salts, carefully noting for reference the position of the index of the telescope on the scale where each characteristic line is found. When it is desired to examine any mixture, the telescope index is brought to the required position and the substance is examined : if the proper line is seen, then the element searched for is present ; if not, it is absent. If we examine ordinary light which has been made to pass through solutions of various coloured bodies, we obtain dark bands analogous to the lines of Fraunhofer. These are called absorption spectra, and are very useful in the detection of soluble colouring-matters. A solution of blood, for example, shows characteristic bands in the green of the spectrum. All this is a matter of special study, and to go farther into it would be beyond the scope of this volume. DIVISION IV. THE ANALYSIS OF GASES. This operation is conducted by measuring a volume of the mixed gas under definite conditions of temperature and pressure, then exposing it to the action of some substance having the power of absorbing some one con- stituent of the mixture, and again measuring the gas left. By seeing that the inside of the measuring tube is always kept moist the question of tension of aqueous vapour is equalised all through the experiment, and as many ab- sorbents as may be necessary are employed in turn Many of the gas-measuring appliances are large, costly, and require to be kept in special rooms devoted to the purpose. Hempel has, however, devised a gas-measuring apparatus which is reasonable in price, and yet is capable of measuring gas volumes with very fair accuracy. It consists essentially of a vessel for measuring volumes of gas known as a Gas Burette and a number of other vessels called Gas Pipettes in which the necessary absorptions are carried out. The Gas Burette (fig. 51) is an arrangement similar to the Nitrometer already fully described at page 133, and is composed of two tubes, A and u. The tube B is THE ANALYSIS OF GASES. 233 graduated in cubic centimetres, and has a capacity of 100 c.c. It is closed at c by a piece of india-rubber tube and a pinch-cock, and at d is connected by a long flexible tube with A. To measure off a volume of gas insoluble in water, the two tubes are completely filled with water, c is closed and A is partially emptied. Connection is now made at c with the vessel containing the gas, c is opened, the gas flows into B and an equal volume of water runs Fig. Fig. 53- into A (which is placed on a lower level if necessary), aad after adjusting the level of the water in the two tubes the volume is read off. Of the Gas Pipettes there are three forms. Fig. 52 is a single pipette, and has two bulbs, E and F, connected by a tube, t. The bulb E terminates in a capillary tube /, by which connection is made with the gas burette. In using the pipette E is completely filled with the reagent intended to act on the gas. The gas burette is closely connected with k by means of a small black rubber tube, and by raising A and opening c the gas is forced into E, part of the reagent into F. After the absorption which may be quickened by shaking is completed, the gas is again allowed to flow back into B, c is closed, the water levels are adjusted, and the volume is read off as before. Fig. 53 is a modification with an opening at / closed by a cork. It is adapted for use with solid reagents, e.g., moist phosphorus for the absorption of oxygen. 234 MELTING, ETC., POINTS; ANALYSIS OF GASES, ETC. Fig. 54 is a compound absorption pipette, and is for use with solutions which require to be preserved from the action of the oxygen of the air, such as alkaline solution of potassium pyrogallate for absorbing oxygen, or ammoniacal cuprous chloride for absorbing CO. The bulb E is filled with the solution, the bulb G with distilled water. By means of the water in G the solution is exposed to the action of only a small quantity of air in F, which is quickly deprived of its oxygen, and thus the absorbing power of the solution remains unimpaired. To perform an analysis 100 c.c. of gas are measured off in the burette, this volume being chosen so that the result of each absorption may represent, without calculation, the percentage of volume of the absorbed gas contained in the mixture. As many pipettes are prepared and furnished with the necessary reagents as there are constituents in the gas. The gas is then passed into each of these, allowed to remain a sufficient time for the absorption to take place, again collected in the burette, and the change of volume noted. 55. The chief absorbents employed in gas analysis are as follows, it being understood that it is necessary to employ them in such an order as shall be suitable to the particular mixture of gases under analysis : A. Strong solution of potassium hydrate absorbs CO 2 . J?. i vol. of 25 per cent, solution of pyrogallic acid + 6 vols. 60 pei cent, solution of KHO absorbs O 2 (after removal of any gas absorbed by KHO alone). C. Moist phosphorus absorbs oxygen, but not CO 2 . D. Concentrated solution of cuprous chloride in dilute hydrochloric acid absorbs CO (after removal of CO and O 2 with alkaline pyrogallate). E. Ammoniacal solution of cuprous chloride absorbs C 2 H 2 , after removal of CO, CO. 2 , and O. fr. Palladium black absorbs hydrogen, but not CH 4 . The palladium black is contained in a (J tube, one limb of which is connected to the burette, the other to a simple absorption pipette filled with water. The gas is passed backwards and forwards over the palladium several times, and complete absorption takes place. G. A solution of sulphuric anhydride in strong sulphuric acid, or solution of bromine, absorbs C 2 H 4 , and the other gaseous hydrocarbons of the series CJi^, and of C n H 2n . 2 . THE ANALYSIS OF GASES. 235 H. The addition of an excess of pure oxygen, and absorption with alkaline pyrogallate, will remove NO, together with the excess of oxygen used. NO is also readily absorbed by solution of FeSO 4 . /. Marsh gas and nitrogen are left to be estimated by difference. They may be separated by adding more than double the volume of pure oxygen, measuring the total volume, and passing the mixture into an explosion pipette (fig. 55), where it is ignited by an electric spark between two platinum terminals fused into the upper part of E. The marsh gas then forms CO 2 and H 2 O, and the resulting gas having been treated in the KHO pipette to Fig. 56- remove the CO 2 , and then remeasured, \ of the total loss in volume represents the CH 4 present. Lastly, the excess of O 2 having been removed by alkaline pyrogallate, the remainder isN 2 . /. If the mixture should contain HC1, HBr, HI, SO 2 , H 2 S, and NH 3 , all of which are soluble in water, they are previously dissolved out thereby in a special apparatus (fig. 56), and the solution so obtained is treated by methods of gravimetric and ordinary volumetric analysis. Full details of the analysis of gases, beyond the scope of the present work, will be found in Button's " Volumetric Analysis." APPENDIX. LIST OF THE ATOMIC WEIGHTS OF THE CHIEF ELEMENTS REFERRED TO IN THIS MANUAL. NAME. ATOMIC WEIGHT. Aluminium . . . . . . . . . 26*90 Antimony 119*00 Arsenium ......... 74'4O Barium .......... 136*40 Bismuth .......... 206*90 Boron 10*90 Bromine 79'36 Calcium .......... 39'8o Carbon .......... 11*91 Cerium I39'2O Chlorine . . . . . . . . . 35' 18 Chromium ......... 51*70 Copper 63*10 Gold I957o Hydrogen . . . . 1*00 Iodine 125*90 Iron 55'5o Lead 205*35 Lithium .......... 6*98 Magnesium ......... 24*18 Manganese ......... 54'6o Mercury 198*50 Nitrogen I3'93 Oxygen 15*88 Phosphorus 30*77 Platinum 193'3O Potassium 38*86 Silver 107*12 Sodium 22*88 Sulphur 31*83 Tin , 118*10 Zinc 64*90 236 INDEX. Absorbents in gas analysis, 234. Absorption, pipettes, 233. Spectra, 232. Acetanilide, 84, 88. Acetates, 47. Acetic acid, 47. Acetic ether, 87. Acidimetry, 115. Acid radicals, detection of, 29, 75- Gravimetric estimation of, I 5 I Aconite and preps., assay of, 196. Adeps lanae, 90. Air bath, 140 Air, sanitary analysis of, 174. Albumin, 222. Albuminoid ammonia, 171. Alcohol, estimationof, inspirits, etc., 178. Table of percentages of , 179. Tests for Amyl, 87. Ethyl, 88. Methyl, 88. Alcoholic bodies Assay of, 219. Estimation of, 219. Aldehyds Estimation of, 114, 218. Alkalies, organic salts of, esti- mation of, 112. Alkalimetry, 109. Alkaline course, 59. Carbonates, estimation of, 112. Hydroxides and borax, estimation of, in. Alkaloidal residues, titration of, 195- Alkaloidal strength of scale pre- parations, 187. Alkaloids Cinchona, separation of, 86. Detection of, 84 to 87. Estimation of, 186. Mydriatic, 196. Table of reactions of, facing p. 87. Tests for, 84. Allyl-isothiocyanate, assay of, 222. Almond oil testing, 210. Aloin, 90. Aluminium, 20. Gravimetric estimation of, 148. Ammonia, 135. Albuminoid, 171. 1'Ytv, 170. Ammoniacum, 194. Ammonium, 27. Gravimetric estimation of, IS 1 - Amyl alcohol, 87. Amyl nitrite, 87, 134. Analysis Air, sanitary analysis of, 174. Balsams, 196. Bread, 180. Butter, 178. By direct oxidation, 124. By immiscible sol vents, 1 86. Coffee, 182. Colorimetric, 136. Colored sweets, 182. Drugs, 184. Essential oils, 215. Flour, 1 80. Food, 175. Gases , H em pel" s a ppar atus, 232. Gravimetric, 142. Gum resins, 206. Milk, 175. Mineral, of water, 157. Mustard, 181. Nitrometer, by the, 133. Oils and fats, 208. Organic, ultimate, 160. Pepper, 181. Polariscopic, 229. Qualitative, i to 93. Quantitative, 94 to end. Scale preparations, 91. Soap, 215. Spectrum, 231. Starch, 131. Urine, 222. Urinary calculi, 227. Vinegar, 182. Volumetric, 104. Water, 167. Waxes, 212. Analytical factors, use of, 142. Anion, 7. Anode, 6. Antifebrin, tests for, 88. Antimonic acid, 46. Antimony, 16. Estimation of, 146. Antipyrin, tests for, 90. Apomorphine, 85. Apparatus, 106, 160. Argentic nitrate, standard solu- tion of, 116. Arseniates, 45. Estimation of, 155. Arsenic, 15. Estimation of, 146. Arsenic acid, 45. Arsenious acid, 44. Estimation of, 120, Arsenites, 44. Asafetida, 206. Ash of Filters, 139. Organic bodies, 141. Assay, alkaloidal of Aconite and preps. , 196. Belladonna and preps. , 196 to 199. Cinchona, 190. Coca and preps. , 199. Colchicum, 187. Conium and preps. , 189. Guarana and preps. , 192. Hydrastis and preps. , 192. Hyoscyamus and preps., 197 to 199. Ipecac and preps. , 201. Nux vomica and preps., 201. Physostigma and preps., 204. Pilocarpus and preps. , 204. Opium and preps., 193. Scopola and preps. , 197 to 199. Stramonium and preps. , 197 to 199. Scale preparations, 187. Atropine, 85. Balance, 94. Balsams, analysis of, 207. Peru, 207. Tolu, 207. Storax, 207. Barium, 24. Chloride, standard solution of, 132. Estimation of, 149. Barks, cinchona, assay of, 190. Beer, alcoholic strength of, 178. Bees' wax, analysis of, 212. Belladonna and preps., assay of, 196 to 199. Benzoates, 51. Benzoic acid, 51. Benzoin, 207. Benzin (petroleum), 87. Benzol, 87. Bichromate of potassium, stan- dard solution of, 128. Bile (urine), 225. Ox, 91. Bismuth, 14. Estimation of, 145. Blood (urine), 226. Bodeker'smethod, 223. 238 INDEX. Boettger's test, 224. Boiling-point, 5. Taking the, 229. Borntes, 37. Borax beads, 60. Boric acid, 37. Estimation of, 156. Boyle's law, 100. Bread, analysis of, 180. Bromates, 31. Bromides, 30. Estimation of, 117, 151, 154. Estimation of, in presence of chlorides, 117. Separation of, 53. Bromine, 30. Estimation of, 121. Standard solution of, 123. Brucine, 85. Bunsen burner, 9. Bunsen's battery, 6. Butter, analysis of, 178. Cacao butter testing, 211. Cadmium, 15. Estimation of, 144. Caffeine, 85. Calcium, 25. Estimation of, 149. Calculi, urinary, analysis of, 227. Cane sugar, 90. Carbolates, 51. Carbolic acid, 51, 57. Carbon, 36. Dioxide in air, 175. Estimation of, 161. Carbonates, 36. Estimation of (gravi- metric), 155 Estimation of (volu- metric), 112. Estimation of soluble, 134. Carbonic acid, 36. Castor oil testing, 210. Cerium, 20. Charcoal, use of, 8. Charles's law, 100. Chemical processes, i. Chloral hydrate, tests for, 90. Chlorates, 30. Chlorides, 29, 53. Gravimetric estimation of, I 5 I - Volumetric estimation of, 117. Volumetric estimation of, with bromides, 117. With bromides, detection o f . 53- With iodides, detection of, Chlorine, 29. Available, estimation of, 122. Estimation of, in solution, 122. In organic analysis, 166. Chloroform, tests for, 87. Chromates, 45. Chromic acid, 45. Chromium, ai. Estimation of, 148. Chrysarobin, tests for, 90. Cinchona and preps. , assay of, 190. Cinchonidine, 86. Cinchonine, 86. Citrates, 50. Citric acid, 50. Clark's process, 172. Coca and preps. , assay of, 199, 200. Cobalt, 23. Estimation of, 147. Cocaine, 85. Codeine, 85. Cod liver oil testing, 210. Coefficients for analysis, 137. Coffee, analysis, 182. Colchicum and preps., assay of, 187, 189. Colloids, 6. Colorimetric analysis, 136. Conium and preps., assay of, 189. Copper, 14. Estimation of, 144. Fehling's standard solution of, 129. Cotton oil testing, 211. Creasote, 88. Croton oil testing, 211. Crucible, Rose's, 5. Crum process, 168. Crystallisation, 5. Cupellation, 4. Cyanates, 41. Cyanic acid, 41. Cyanides, 40. Estimation of, gravimetric, I S I - Volumetric, 116. Cyanogen, 40. Cyanuric acid, 41. Decantation, 3. Density, vapour, 101. Detection of Alkaloids, 84. Bromine, hydrobromic acid and bromides, 30. Bromides in presence of iodides, 53. Carbolic acid in presence of salicylic acid, 57. Chlorides in presence of bromides, 53. Chlorides in presence of iodides, 53. Chlorine, hydrochloric acid, and chlorides, 29. Cyanides in presence of ferro- and ferri-cyanides, 56. Formate in presence of fixed organic acids, 56. Inorganic acids, 78. lodate in an iodide, 54. Metals, 10. In any simple salt, 61. In complex mixtures, 65. Detection of (contd.} Nitrate in presence of iodide, 55. Nitric acid (free) in pre- sence of nitrate, 55. Nitrite in presence of a nitrate, 55. Organic acids, 80. Organic bodies used in medicine, 87. Phosphate in presence of calcium, barium, stron- tium, manganese, mag- nesium, or iron, 56. Soluble sulphide in pre- sence of sulphite and sulphate, 54. Sugar, 75. Dialysis, 5. Digestive ferments, analysis of, T 93- Distillation, 4. Dragendorff s tables, 86. Drugs, analysis, 184. Dumas' process, 165. Ebullition, 5. Elaterin, tests for, 98. Electrolysis, 6. Electrolyte, 7. Essential oils, analysis of, 215 to 222. Esters, assay of, 217. Estimation of Acids, 114. Albumin, 222. Alcoholic bodies in essen- tial oils, 219. Aldehyds in essential oils, 218. Alkaline carbonates, 112. ,, hydroxides, in. Alkaloids, 186 et seg. Allyl-isothiocyanate, 222. Aluminium, 148. Ammonia (Nesslerising), 136. Ammonium, 151. Antimony, 120, 146. Arseniates, 155. Arsenic, 146. Arsenious acid, 120. Ash of filters, 139. ,, of organic bodies, 141. Barium, 149. Bismuth, 145. Borax, in. Boric acid in borates, 156. Bromides, 117, 154. Bromine, 121. Cadmium, 144. Calcium, 149. Carbon and hydrogen, 161. Carbonates, 155. Carbon dioxide in air, 174. Chlorides, 116, 151. , , in the presence of bromides, 117. Chlorine, available, 122. ,, free, 121. ,, in organic bodies, 166. INDEX. 239 Estimation ot(contd.) Chlorine in water analysis, 168. Chromium, 148. Cobalt, 147. Copper, 144. ,, and iron, minute traces of, 136. Esters in essential oils, 217. Extracts, alkaloidal strength of, 187 et scq. Fatty acids in soap, 215. Ferric and ferrous salts, 122, 128. Gold, 145. Gravimetric (of metals), 138. Haloid salts, 116, 119. Hydrocyanic acid, 117. Hydrogen peroxide, 128, I35- Hypophosphites, 126. Iodides, 116, 151. ,, in presence of bromide and chloride, 117. Iodine, free, 121. Iron, 125, 127, 148. Ketones, in essential oils, 219. Lead, 113, 143. Magnesium, 149. Manganese, 149. Mercury, 143. Metals as oxalates, 128. Mineral oil in fats, 212. Moisture, 141. Morphine in opium, 194. Nickel, 147. Nitric acid in nitrates, 134. Nitrites, 152. ,, m water analysis, 137. Nitrogen, 164. ,, in water analysis, 1 68. Nitrous ether, 133. Olcic acid, 210. Organic matter in air, 174 salts of alkalies, 112. Oxalic acid and oxalates, 109, 128, 156. Peroxides, 128. Pepsin, 206. Phenol, 124. Phenols in essential oils, 218. Phosphates, 153. In artificial manures, 154. Phosphoric acid, 116, 131, *S3- Phosphorus in organic bodies, 166. Platinum, 145. Potassium, 150. ,, andsodium,i5i. Resin in soap, 215. Rosin oil in fats, 212. Scale preparations, 182. Silicic acid, 157. Silver, 142. Sodium, 150. ,, nitrite, 137. Estimation of (contd.) Soluble carbonates, 112, 134- Soluble haloid salts, 116. Sugar, estimation of, 131. ,, in urine, 224. Starch, 131. Sulphates, 131, 152. Sulphides, 152. Sulphites, 1 20. Sulphur in organic bodies, 166. Sulphurous acid, 120. Tartaric acid, 156. Thiosulphates, 121. Tin, 145. Urea in urine, 135. Zinc, 148. Ether, acetic, 87. Nitrous (estimation), 133. Ethyl alcohol, test for, 88. Nitrite, 134. Ethylsulphates, 47. Evaporation, 5. Examination, preliminary, 58 Extraction, 2. Extracts, estimation of, alka- loidal strength of, 187 etseq. Factors, analytical (use of), 142. Fats, analysis of, 208. Fatty acids, estimation of, 215. Fehling's solution, 129. Test in urine, 224. Fel Bovinum, 91. Ferments, digestive, 206. Ferric and ferrous salts (estima- tion), 122, 128. Ferricyanides, 42. Ferro- from ferri-cyanides, separation, 56. Ferrocyanides, 41. Filters, preparation of, 138. Ash, estimation of weight of, 139- Filtration, 3. Flame, oxidising, 7. Reducing, 7. Tests, 60. Flour, 170. Fluorides, 29. Food analysis, 175. Formic acid and formates, 46 Fraunhofer's lines, 223. Free acids in oils, 212. Fulminic acid, 41. Fusion, 4. G Gallic acid, 52. Gas burette, 232. Gaseous impurities (testing for, in air), 174. Gases, sp. gr. , 100. Analysis of, 232. Correction of volume of, for temperature and pres- sure, 100. Gelatine, tests for, 91. Glucose, 89. Glusidum, tests for, 89. Glycerine, 88. Gmelin's test, 225. Gold, 17. Estimation of, 145. Grape sugar, 90. Gravill's test, 134. Gravimetric estimations, 138. Acid radicals, 151. Metals, 142. Gravity, specific, of Essential oils, 215. Gases, 100. Liquids, 96. Milk, 175. Oil and fats, 208. Solids, 98. Waxes, 212. Group reagents, 10. Guaiacum, 206. Guarana and preps. , assay of, 192. Gum resins, 206. H Haloid salts, estimation of, 119, IS 2 - Hardness, Clark's process, 172. Hempel's apparatus, 232. Homatropine, 85. Hubl's method, 209. Hydrastinine, 85. Hydrastis and preps. , assay of, 192. Hydriodic acid, 31. Hydrobromic acid, 30. Hydrochloric acid, 29. Standard solution of, no. Hydrocyanic acid, 40, 117. Hydrofluoric acid, 29. Hydrofluosilicic acid, 38. Hydrogen, estimation of, in organic analysis, 161. Peroxide, estimation of, 128, 135. Hydrosulphuric acid, 33. Hydroxides, 32. Alkaline, estimation of, 1 1 1. Hyoscine, 85. Hyoscyamine, 85. Hyoscyamus and preps. , assay of, 197 to 19*9. Hypobromites, 31. Hypochlorites, 30. Hypophosphites, 42. Hyposulphites, 34. Igniting precipitates, 140. Indicators, 105. Inorganic acid course, 78. lodates, 32. lodate with iodide, detection of, 54- Iodides, 31, 35. Estimation of, 117, 151. Estimation of, in presence of a chloride and a bro- mide, 152. 2 4 INDEX. Iodine, 31. Estimation of, 121. Standard solution of, 120. lodoform, tests for, 91. Iron, 18. Gravimetric estimation of, 148. Volumetric estimation of, by bichromate, 128. Volumetric estimation of, by permanganate, 127. Ipecac and preps., assay of, 201. Jalap, assay of, 206. Jalapin, tests for, 91. K Kathion, 7. Kathode, 6. Ketones, assay of, 219. Kipp's apparatus, 9. Kjeldahl's process, 166. Lactates, 48. Lactic acid, 48. Lactose, 90. Lard testing, 211. ,, oil testing, 211. Laws Boyle's, 100. Charles's, 100. Lead, 12. Estimation of, 113, 143. Liebig's condenser, 4. Linseed oil testing, 211. Lithium, 26. Lixiviation, 2. M Magnesium, 26. Estimation of, 149. Malates, 49, 57. Malic acid, 49. Manganates, 45. Manganese, 21. Estimation of, 147. Manures, estimation of phos- phates in, 154. Mayer's standard solution, 132. Measuring and weighing, 94. Meconates, 51. Meconic acid, 51. Melting points, 228. Mercuricum, 13. Mercurosum, 12. Mercury, estimation of, 143. Metals, detection of, 10. Gravimetric estimation of, 142. In complex mixtures, 65. Present in a simple salt, 61. Separation of, into groups. 10, 64, 66; Hamilton's table, 74. Tables for detection of, 62. Metaphosphoric acid and salts, 43- Method, Meyer's, 102. Pavy's, 130. Varrentrapp, 164. Vol hard's, 119. Methyl alcohol, 88. Methylated spirit, in tinctures, 207. Milk, analysis of, 175. Sour, analysis of, 177. Sugar, detection of, 90. Mineral contents of water, analysis of, 157. Mineral oil in oils, 212. Moisture, estimation of, 141. Moore's test, 224. Morphine, 85. Murexid test, 222. Mustard analysis, 181. Myrrh, 207. N Naphtol, 89. Nesslerising, 136. Nickel, 23. Estimation of, 147. Nitrates, 39, 55. Estimation of, by nitro- meter, 134. Estimation of, gravimetric, 152. Nitric acid, 39. Nitrite with nitrate, detection of. 55- Nitrites, 38. Estimation of, in water analysis, 169. Nitrobenzene, 88. Nitrogen, estimation of, 164. Estimation of, in water analysis, 168. Nitrometer, use of, 133. Analysis by, 133. Nitrous acid, 38. Nitrous ether, estimation of, 133. Nux vomica and preps., assay of, 201-203. Oils, analysis of, 208. Essential, 215. Free acids in, 212. Mineral oils in, 212. Qualitative tests for, 210. Rosin oil in, 212. Specific heating power of, 210. Oleates, 48. Oleic acid, 48, 210. Olive oil testing, 211. Oliver's test, 216. Opium and preps. , assay of, 193. Organic acid course, 80. Analysis, ultimate, 160. Matter in air, 175. Matter in water, 171. Organic bodies used in medicine, detection of, 87. Orthophosphates, 43. Orthophosphoric acid, 43. Oxalates, 48. Estimation of metals as, 1 19. Oxalic acid, 48. Gravimetric estimation of, 156. Standard solution of, 109. Ox bile, 91. Oxidation, 7. Oxides, 33. Oxygen consumed in water analysis, 171. Pancreatin, 206. Paraldehyd, tests for, 88. Pavy's method, 130. Pepper analysis, 181. Pepsin, 206. Perchlorates, 30. Periodates, 32. Permanganate of potassium, standard solution of, 126. Permanganates, 45. Pettenkofer's test, 225. , Phenacetin, tests for, 89. Phenazone, tests for, 90. Phenol and phenates, 51, 124. Phenolic ethers, assay of, 218. Phenols, assay of, 218. Phosphates Detection of, 43, 56, 226. Estimation of, as magne- sium pyrophosphate and phosphomolybdate, 153, 154. Estimation of soluble, in a manure, 155. Estimation of total, in a manure or soil, 154. Volumetric estimation of, *3*. Phosphites, 43. Phosphoric acid, 43. Gravimetric estimation of, free, 153. Volumetric estimation of, 116. Phosphorous acid, 43. Phosphorus, estimation of, in organic analysis, 166. Physical constants of essential oils, 215. Physostigma and preps., assay of, 204, 205. Physostigmine, 85. Picrotoxin, tests for, 89. Pilocarpus and preps., assay of, 204. Pilocarpine, 85. Platinum, 18. Estimation of, 145. Podophyllin, tests for, 91. Podophyllum resin, 207. Poisons in mixtures, testing for, 92. Polarisation, analysis by, 229. Potassium, 27. Bichromate, standard so- lution of, 128. Estimation of, 150. Estimation of, with sodium, INDEX. 241 Potassium (cont.} Hydroxide, standard solu- | tion of, 114. Permanganate, standard solution of, 126. Thiocyanate, standard so- lution of, 119. Precipitates, drying, etc., 140. Precipitation, 2. Preliminary examination, 58. Process, Clark's, 172. Crum's, 168. Dumas', 103, 165. Kjeldahl's, 166. Liebig's, 161. Reichert's, 178. Processes, chemical, i. Pyrogallic acid, 52. Pyrology, 7. Pyrophosphoric acid and salts, 43- Qualitative analysis- Detection and separation of acid radicals, 29. Detection of alkaloids, 84. Detection of certain organic bodies used in medicine, 87. Detection of metals, 10. "Scale" medicinal pre- parations, 91. Detection of unknown salts, 58. Processes, r. Quantitative analysis- Separations, 157. Specific gravity, 96. Standard solutions, 104. Vapour density, 101. Weighing and measuring, 94- Quinidine, 86. Quinine, 86. ,, tests for purity, 191. Radicals, acid, 29, 75. Gravimetric estimation of, IS 1 - Reagents, 10. Group I., IT. Group II. Div. A, 13. Group II. Div. B, 15. Group III. Div. A, 18. Group III. Div. B, 21. Group IV., 24. Group V. , 26. Reduction, 7, 8. Reichert's process, 168. Resin, tests for, 91. Resina, 207. Resorcin, tests for, 90. Rosin oil in fats, 212. Saccharimeter, 229. Saccharine, tests for, 89. Soluble, tests for, 89. Salicine, 84. Salicylic acid, 52. Salol, 89. Salts Detection of alkaloid, 84, 86. Detection of unknown, 58- 83- Used in pharmacopceia, table for detection of, 64. Volumetric estimation of various, 104-129. Sanitary analysis of air, 174. ,, ,, water, 167. Santonin, tests for, 89. Saponification equivalent, 209. Scale preparations, qualitative analysis of, 91. Alkaloidal strength of, 187. Scammony resin, 207. Scopola and preps., assay of, 197 to 199. Separation Arseniate from phosphate, 56. Chlorates from chlorides, Chlorides, iodides, bro- mides from nitrates, 55. Cinchona alkaloids, 86. Cyanides from chlorides, 55. Ferro- from ferri-cyanides, 56. Group metals, 66, 74. Iodide from bromide and chloride, 53. Metals in groups, 66. Oxalates, tartrates.citrates, malates, 57. Quantitative, 157. Silica from all other acids, 54- . Sulphides, sulphites, and sulphates, 54. Thiosulphates from sul- phides, 54. Silica, 37, 54. Silicates, 37. Silicic acid, 37. Anhydride, separation of, 54- Estimation of, 157. Silver, n. Estimation of, 142. Soap, analysis of, 215. Resin in, 215. Sodium, 27. Estimation of, 150. Estimation of, with potas- sium, 151. Chloride, standard solution of, 1 1 8. Hydroxide, standard solu- tion of, 115. Nitrite, estimation of, 134. Thiosulphate, standard solution of, 121. Soil, estimation of phosphates in, 154. Solubility tables, 82. Solution, T. Solutions Preparation of, to test for acids, 77. Solutions (contd.} Preparation of, to test for metals, 6r, 65. Standard, 104. Soxhlet's apparatus, 2. Specific gravity, 96-103. Specific gravity of Alcoholic bodies, 178. Essential oils, 215. Gases, 100. Liquids, 96. Milk, 175. Oils and fats, 208. Solid bodies, 98. Urine, 222. Specific gravity, practical appli- cations of, 99. Specific heating power of oils, 210. Spectrum analysis, 231. Spermatozoa, 220. Spirits, alcoholic strength of, 178. Table for percentages, 178. Standard solutions Argentic nitrate, 116. Barium chloride, 132. Bromine, 123. Copper, Fehling's, 129. Hydrochloric acid, no. Iodine, 120. Mayer's, for alkaloids, 132. Oxalic acid, 109. Phosphate, 131. Potassium bichromate, 128. Potassium hydroxide, 114. Potassium permanganate, 126. Soap, 172. Sodium chloride, 118. Sodium hydroxide, 115. Sulphuric acid, no. Thiocyanate, 119. Thiosulphate, 121. Uranic nitrate, 131. ' Stannates, 46. Stannic acid, 46. Starch estimation, 131. Stearates, 48. Stearic acid, 48. Stramoniun and preps., assay of, 197 to 199. Strength of alkaloidal extracts, 187. Strontium, 25. Strychnine, 85. Sublimation, 4. Succi nates, 49. Succinic acid, 49. Sucrose, 89. Sugar estimation, 131. In urine, 224. Sugars, tests for, 90. Sulphates, 35. Estimation of, 132, 152, 212. Sulphides, 33, 54. Estimation of, 152. Sulphides, sulphites, and sul phates, separation of, 54. Sulphites, 35. Sulphocyanates, 41. Sul phonal, 89. Sulphovinates, 47. 16 2 4 2 INDEX. Sulphur, 33. Estimation of, in organic analysis, 166. Sulphuretted hydrogen, pre- paration of, 9. Sulphuric acid, 35. Standard solution of, no. Sulphurous acid, 35. Estimation of, 120. Sweets, analysis of, 182. Sykes's hydrometer, 97. Tables- Detection of the metal in a simple salt, the metals as in pharmacopoeia, 64. Detection of the metal in a solution containing one base only, 62. Distinction between gallic, tannic, and pyrogallic acids, 52. General reactions of alka- loids, 86. Percentages of alcohol, 169. Separation of metals into groups, 66. Solubility of salts, 82. Specific gravity of milk, temperature corrections for, 176 Tannic acid, 52. 1'artaric acid, 49, 156. Tartrates, 49. Testing for poisons, 92. Thiocyanates, 41. Thiosulphates, 34. Estimation of, 121. Tin, 17. Estimation of, 145. Tinctures Methyl alcohol in, 207. Toxicological analysis, 92. U Ultimate organic analysis, 160. Uranic nitrate, standard solu- tion of, 131. Urea, estimation of, 134. Test for, 225 Uric acid, 222. Urinary calculi, analysis of, 227. Urine Analysis of, 222. Estimation of urea in, 135. Valerianates, 47. Valerianic acid, 47. Valuation of ferments, 206. Van Babo's apparatus, 9. Vaporisation, 5. Vapour, specific gravity of, 101. Vapours, density of, 101, Varrentrapp's method, 165. Ditto modified, 164. Veratrine, 84. Vinegar, sulphuric acid in, 182. Volhard's method, 119. Volumetric analysis, 104. W Washing precipitates, 139. Water, 32. Mineral analysis of, 157. Oven, 140. Sanitary analysis of, 167. Waxes, analysis of, 212. Tests for the chief un- official, 214. Weighing, 94, 106. Precipitates, 140. Westphal balance, 97. Wines, alcoholic strength of, 178. Wool-fat testing, 211. Zinc, 22. Estimation of, 148. Printed by Hasell, Watson Viney, Ld, t London and Aylesbury, England Date Due 1 . NQV 2 4 1930 ^LP 4 1931 APR 18 932 $33 , i D2840 * analyti f h . ed. w 24 i:- 5 ^ y OL LIBRARY m