CORNELL UNIVERSITY LIBRARY GIFT OF Professor CaldiArell QD 83.M48T894"'"""'''-'''"^ qualitative miimiiifi'iIII'S™"'''"" '° anal 3 1924 012 380 501 p^ Cornell University Library The original of tliis book is in tlie Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924012380501 BRIEF INTRODUCTION TO Qualitative Analysis: FOR USE IN INSTRUCTION IN CHEMICAL LABORATORIES. BY LUDWIG MEDICUS, PnOFESSOK OF CHEMISTRY IN THE UNIVERSITY AT WUEZBURG. TRANSLATED FROM THE FOURTH AND FIFTH GERMAN EDITIONS, WITH ADDITIONS, BY JOHN MAESHALL, ASSISTANT PBOFESSOR OF CHEMISTRY IN THE MEDICAL DEPARTMENT OF THE UNIVERSITY OP PENNSYLVANIA. THIRD EDITION. PHILADELPHIA: PRINTED BY J. B. LTPPINCOTT COMPANY. 1894. %t^S\ C s^ Copyright, 1891, by John Mabshali.. TRANSLATOR'S PREFACE, The merit of Medicus' " Qualitative Analysis," and its popularity, which is shown by its having already passed through five editions in the German language, led to this translation. The translator has taken the liberty of rearranging the elements in the first part of the book into groups, to corre- spond with their precipitation by group reagents, and also of adding two tables and amplifying the text to the extent of about forty pages. J. M. Philadelphia, 1892. PREFACE TO THE SECOND EDITION. In the second edition a number of additions and changes have been made in the parts treating of the methods of procedure in the separation of the bases into groups. A table showing the solubility of many of the salts of the commonly occurring metals has also been added. J. M. Philadelphia, 1892. ——— CONTENTS. PAGE Introduction 7 I. Properties of the Bases 9 I. Group : Silver, Mercurous Salts, and Lead 9 II. Group : Mercuric Salts, Copper, Bismuth, Cadmium, Arsenic, Antimony, Tin, Gold, and Platinum .... 15 III. Group: Iron, Chromium, Aluminium 38 IV. Group : Manganese, Zinc, Nicliel, and Cobalt 44 V. Group : Barium, Strontium, and Calcium 50 VI. Magnesium, Potassium, Sodium, Ammonium, and Lithium 53 II. Properties of the Acids 59 I. Group : Sulphuric Acid, Hydrofluosilicic Acid 59 II. Group : Sulphurous Acid, Hyposulphurous Acid, Phos- phoric Acid, Boric Acid, Hydrofluoric Acid, Carbonic Acid, Silicic Acid, Chromic Acid, Arsenic Acid, Arseni- ous Acid . 61 III. Group : Hydrochloric Acid, Hydrobromic Acid, Hydriodic Acid, Hydrocyanic Acid, Hydroferrocyanic Acid, Hydro- ferricyanic Acid, Sulphydric Acid, Nitrous Acid, Hypo- chlorous Acid 73 IV. Group : Nitric Acid, Chloric Acid 85 Appendix : Acetic Acid, Oxalic Acid, Tartaric Acid ... 87 III. Pkeliminaky Examination . .91 (a) Preliminary Tests in the Dry "Way ... 91 1. Examination in the Keduction-Tube . ... .91 2. Examination on Charcoal 94 3. Examination in the Flame . .98 4. Examination by means of Microcosmic Salt 98 (b) Preliminary Tests for Acids 100 1* 5 —— PAGE IV. —SOLUTIOK AND FuSlON 10-1 1. Dissolving Oxides and Salts 105 HI 2. Dissolving Metals and Alloys . .... 3. Sulphides of the Heavy Metals .... 112 4. Cyanides ... 112 5. Silicates 114 V. Detection of the Bases in the Wet Way . 117 Precipitation of the Different Groups 117 First Group 120 Second Group . .* 123 Third Group 125 Fourth Group 127 Fifth Group 128 Sixth Group . ... 129 Separation of the Bases contained in the Group Precipitates . 130 Separation of the First Group 130 Separation of the Second Group 132 Separation of the Third Group . 141 Separation of the Fourth Group . 149 Separation of the Fifth Group 150 Separation of the Sixth Group ... 154 VI.—Examination poe Acids 160 VII. Appendix. Behavior of the Compounds of the Eare Ele- ments .176 Examples for Practice in Testing for the Eare Elements . 181 INTRODUCTION. Qualitative analysis treats of the methods of ascertain- ing the composition of substances and the manner in which their constituents may be separated. Qualitative analysis determines what bodies are present, but does not refer to their quantity. The latter is the object of quantitative analysis. The following pages contain a systematic course for the detection of bases and acids, with the requisite preliminary tests, preceded by a brief description of the behavior of the more important bases and acids. The behavior of the rare elements is briefly considered and explained by examples in the Appendix. I. PROPERTIES OF THE BASES. FIRST GROUP. Metals precipitated as chlorides by HCl, hydrochloric acid : Silver, Mercurous Salts, and Lead. SILVER, Ag (ARGENTUM). Atomic weight, 107.66; valence, L White, glittering metal ; specific gravity, 10.57 ; melting- point, 954° C. AgNO^, argentic nitrate, may be employed in making the tests. 1. HCl, hydrochloric acid, or a soluble chloride precipitates white, curdy AgCl, argentic chloride. At first the liquid becomes milky in appearance, due to the finely-divided par- ticles of precipitate in suspension, but on shaking or heating the liquid the precipitate collects in curdy masses and the liquid becomes clear. On exposui'e to sunlight the precipitate turns violet and finally black, due to the liberation of a slight quantity of chlorine. The precipitate is insoluble in HNO3, nitric acid, but dissolves on agitation in NH4OH, ammonium hydroxide, with the formation of argent-ammonium chloride : AgCl + NH.OH = AgNHsCl + Ufi, from which solution it may be reprecipitated by the addition of nitric acid : AgNHsCl + HNO3 = AgCl + NH.NOj. It is also dissolved by KCN, potassium cyanide, and, in 9 : 10 the absence of free acid, by NajSPj, sodium hyposulphite (thiosulphate). 2. NaOH, sodium hydroxide, as well as KOH, potassium hydroxide, precipitates brownish-gray AgjO, argentic oxide, insoluble in excess of either reagent. 3. NH4OH, ammonium hydroxide (very dilute), added in small quantity, precipitates brownish-gray AgjO, argentic oxide, readily soluble in a slight excess of the reagent, form- ing AgNHjOH, argent-ammonium hydroxide AgijO + 2NHPH = 2AgNH30H + Hfi. 4. HjS, hydrogen sulphide, precipitates black AgjS, argen- tic sulphide, insoluble in dilute acids and in (NH4)2S, ammo- nium sulphide. Boiling nitric acid dissolves it, with the formation of AgNOj, argentic nitrate. 5. (NH4)2S, ammonium sulphide, precipitates black AgjS, argentic sulphide, insoluble in dilute acids. 6. K2Cr04, potassium chromate, produces a purplish-red precipitate of Ag2Cr04, argentic chromate, soluble in am- monium hydroxide and in nitric acid. 7. NajHPO^, sodium hydrogen phosphate, precipitates yellowish, flocculent Ag3P04, argentic phosphate, soluble in ammonium hydroxide and in nitric acid. 8. KI, potassium iodide, precipitates yellowish, curdy Agl, argentic iodide, insoluble in dilute nitric acid, and almost insoluble in ammonium hydroxide. 9. KCN, potassium cyanide, precipitates white, curdy AgCN, argentic cyanide, soluble in excess of the reagent and in ammonium hydroxide, insoluble in dilute nitric acid. 10. Compounds of silver fused with Na2C03, sodium car- bonate, iu the reducing blowpipe flame on charcoal yield a white, ductile globule of metallic silver, usually without an incrustation. Occasionally a slight reddish-brown incrusta- tion of oxide is produced. : : 11 MERCURY. Hg (HYDRARGYRUM). Atomic weight, 199.8; valence, II. Silver-white metal ; specific gravity, 13.59 ; solidifies at —39.4° C. and boils at 357.2° C. Mercury forms two series of compounds, named respec- tively mercurous and mercuric compounds. HgjO, mercu- rous oxide, may be taken as the type of the mercurous, and HgO, mercuric oxide, as the type of the mercuric compounds. BEHAVIOR OF MEECUEY IN THE MEECUEOUS CONDITION. IIgJ^N0^2) inercurovs nitrate, may be employed in making the tests. 1. HCI, hydrochloric acid, or a soluble chloride precipi- tates from solutions of mercurous salts white, pulverulent HgjClj, mercurous chloride (calomel), insoluble in water and in cold dilute acids, easily soluble in nitro-hydrochloric acid (aqua regia), with the" formation of HgClj, mercuric chloride (corrosive sublimate) SUgfil^ + 2HNO3 4- 6HC1 = GHgClj + 2N0 + iUjO. Ammonium hydroxide converts the HgjClj, mercurous chlo- ride, into black NHjHgjCl, dimercurous ammonium chlo- ride, insoluble in excess of the reagent HgjCl^ + 2NHPH = NH^Hg^Cl + NH.Cl + 2}I,0. 2. NaOH, sodium hydroxide, or KOH, potassium hy- droxide, precipitates black HgjO, mercurous oxide, insoluble in excess of the reagent. 3. NH^OH, ammonium hydroxide, produces in solutions of mercurous salts a black precipitate containing nitrogen, depending in composition upon the mercurous salt employed and the conditions under which precipitation has occurred. For example, on adding ammonium hydroxide to a solution of Hg2(N03)2, mercurous nitrate, black NHaHgjNOs, dimer- : 12 curous ammonium nitrate (mercurius solubilis Hahnemanni), is formed Hg^CNOj), + 2NHPH = NH,Hg,N63 + NH,N03 + 2H,0. The precipitate is insoluble in excess of the reagent. 4. HjS, hydrogen sulphide, as well as (NH^^S, ammonium sulphide, produces a black precipitate, consisting of a mix- ture of HgS, mercuric sulphide, and metallic mercury (not HgaS, mercurous sulphide). On boiling this precipitate with concentrated nitric acid, a white compound composed of HgS, mercuric sulphide, and Hg(N03)2, mercuric nitrate [Hg3S2(N03)J,(" insoluble in nitric acid, is formed, while the liquid (filtrate) contains Hg(N03)2, mercuric nitrate. Yellow ammonium sulphide, (NH^)2S^, converts the mixture of HgS and metallic mercury wholly into HgS, mercuric sulphide. Yellow sodium sulphide, NajS^;, as well as yellow potassium sulphide, KjSj;, converts the mixture into HgS, mercuric