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Cornell University Library 
 Brief course In qualitative analysis. 
 
 ,. 3 1924 031 284 148 
 olin,anx 
 
The original of tliis bool< is in 
 tine Cornell University Library. 
 
 There are no known copyright restrictions in 
 the United States on the use of the text. 
 
 http://www.archive.org/cletails/cu31924031284148 
 
A BRIEF COURSE 
 
 IN ■ I (^ ,' ,, 
 
 QUALITATIVE ANALYSIS 
 
 ERNEST A. CpNGDON, Ph.B., F.CS. 
 
 Professor of Chemistry in the Drexel institute, 
 Philadelphia, Pa. 
 
 NEW YORK 
 
 HENRY HOLT AND COMPANY 
 
 i8q8 
 
Copyright, 1898, 
 
 BY 
 
 HENRY HOLT & CO. 
 
 ■ DEUMMOND, PKINTER, NEW YORK. 
 
PREFACE. 
 
 It has been the aim in the preparation of this manual 
 to render it as concise as possible with the least sacrifice 
 of a study of reactions and solubilities of chemical im- 
 portance. For this reason, many of the reactions found 
 in larger books have been omitted. 
 
 The following are the points covered in the manual : 
 Preliminary Reactions on Bases and Acids; Schemes of 
 Analysis for Bases and Acids ; Brief Explanatory Notes on 
 the Analyses ; Treatment of Solid Substances (Powders, 
 Alloys or Metals); Table of Solubilities of salts of the 
 Bases studied. A comprehensive list of questions on 
 Qualitative Analysis, that will force the student to think, 
 completes the Manual. These questions, together with 
 the explanatory notes on the schemes of analysis, it is 
 hoped will excite the student's interest and prove a source 
 of anspiration as well as an incentive to intelligent work. 
 
 The book is intended merely as a laboratory guide, and 
 should be supplemented by frequent " Quiz Classes " and 
 by constant personal attention. The educational value of 
 such instruction cannot be overestimated. 
 
 It is through personal contact with the teacher that the 
 rationale of scientific work is understood, and without the 
 requisite amount of this personal instruction Qualitative 
 Analysis becomes ■ mere " test-tubing " and an arbitrary 
 and perfunctory thing, instead of the branch of logical 
 Science which it is. 
 
 This Brief Course has been satisfactorily given in the 
 Drexel Institute within the allotted time of one laboratory 
 
 iii 
 
IV 
 
 period (four hours) and one hour for a lecture or quiz per 
 week, during the school year of thirty-two weeks. 
 
 I take pleasure in acknowledging the advice and assist- 
 ance received from Mr. Abraham Henwood, Instructor in 
 Chemistry in the Drexel Institute, in the preparation of 
 this manual. 
 
 E. A. C. 
 Philadelphia, Pa., 
 May I, 1898. 
 
LABORATORY INSTRUCTIONS. 
 Qualitative Analysis. 
 
 Classification of the Metals for Use in 
 Chemical Analyis. 
 
 GROUP I. 
 
 Silver, lead, mercury (mercnrous). 
 
 Precipitated by the group reagent, hydrochloric acid, HCl, 
 as: — 
 
 AgCl, 
 PbCl„ 
 Hg.Cl,. 
 
 GROUP II. 
 
 Lead (imperfectly removed by reagent of Group I.), mer- 
 cury (meTcnrt'c), bismuth, copper, cadmium, arseuic (arseni- 
 ous and arsenic), tin (sta.nnous and stannzV:), antimony. 
 
 Precipitated by the group reagent, hydrogen sulphide, 
 HjS, as:— 
 
 PbS, 
 
 HgS, 
 
 BijSs, 
 
 CuS, 
 
 CdS, 
 
 ASjSj, 
 
 ASjSs+S,, 
 
 SnS, 
 
 SnSj, 
 
 SbjS,- 
 (3) 
 
4 
 
 GROUP III. 
 
 Iron ({exrous and ferrzc), aluminium, chromium, nickel, 
 cobalt, manganese, zinc. 
 
 Precipitated by the group reagent, ammonium sulphide, 
 (NH,),S, as:— 
 
 FeS (from both fenous and ferric compounds), 
 
 Al,(OH)„ 
 
 Cr,(OH)„ 
 
 NiS, 
 
 CoS, 
 
 MnS, 
 
 ZnS. 
 
 GROUP IV. 
 
 Barium, strontium, and calcium. 
 
 Precipitated by the group reagent, ammonium oxalate, 
 as: — 
 
 BaC,0„ 
 
 SrC,0„ 
 
 CaCjO,. 
 
 GROUP V. 
 
 Magnesium, potassium, sodium (ammonium). 
 Not precipitated by a group reagent. 
 
5 
 
 A. — Reactions of the Metals. 
 
 GROUP 1. 
 
 SiLVBR. Ag. Valence = I. 
 
 Use preferably AgNOg. 
 
 1. HCl precipitates AgCl. 
 
 White, curdy, darkens on exposure to light. 
 Soluble in NH^OH, KCN. 
 
 Insoluble in HNO3 and other dilute mineral acids; sol- 
 uble in concentrated HCl. 
 
 2. HjS or alkaline sulphides precipitate AgjS. 
 Black. 
 
 Insoluble in alkaline sulphides. 
 Insoluble in dilute mineral acids. 
 Soluble in boiling HNOg. 
 
 3. NH^OH, NaOH, or KOH precipitates Agp. 
 Brown. 
 
 Insoluble in excess of NaOH or KOH; soluble in ex- 
 cess of NH,OH. 
 Soluble in HNO,. 
 
 4. KCN precipitates AgCN. 
 White, curdy.' 
 
 Soluble in excess of KCN. 
 Soluble in NH.OH. 
 Insoluble in HNO3. 
 
 5. Heated with the blowpipe on charcoal, + NajCOj, silver 
 
 is reduced from all its compounds and forms bright 
 malleable globules which are soluble in HNO3. 
 
 IvBAD. Pb. Valence = II. 
 
 Use preferably PbCNOj),. 
 
 6. HCl precipitates PbCl,. 
 White, pulverulent. 
 
Insoluble in alcohol. 
 
 Decidedly soluble in cold water. 
 
 Completely soluble in boiling water. 
 
 Soluble in sodium acetate and salts of organic acids. 
 
 Soluble in concentrated HCl. 
 
 7. H2S or alkaline sulphides precipitate PbS. 
 
 Black. (All lead compounds are blackened by HjS.) 
 Insoluble in excess of alkaline sulphides. 
 Insoluble in quite dilute mineral acids. 
 Soluble in hot, moderately concentrated HNO3. 
 Converted to PbSO, by concentrated HNO3. 
 
 8. NH4OH, NaOH, or KOH precipitates Pb(OH),. 
 White. 
 
 Insoluble in excess of NH^OH. 
 Soluble in excess of NaOH and KOH. 
 
 9. KCN precipitates PbCCN^. 
 White, pulverulent. 
 Insoluble in excess of KCN. 
 Soluble in HNO3. 
 
 10. HjSOi precipitates PbSO^. 
 White, pulverulent. 
 Insoluble in dilute mineral acids. 
 Insoluble in alcohol. 
 
 Soluble in excess of concentrated H^SO^. 
 Soluble in alkaline solutions of salts of organic acids, 
 especially acetic and tartaric. 
 
 1 1 . K2Cr04 or KjCrjO, precipitates PbCrO^. 
 Yellow. 
 
 Soluble in HNO3 with difficulty. 
 Soluble in NaOH or KOH. 
 
 12. Heated with the blowpipe on charcoal, + Na^CO,, lead 
 
 is reduced from all its compounds and forms soft, 
 malleable, easily fusible globules which yield a yel- 
 low incrustation of PbO. 
 
Mbrcury (Mercurous). Hg. Valence = I. 
 Use preferably Hgj (NOa)^. 
 
 13. HCl precipitates HgjCla. 
 White, pulverulent. 
 
 Converted by NH^OH into NH^Hg^Cl, black. 
 Oxidizing agents convert HgjClj into the soluble chlo- 
 ride, HgCl,. 
 
 14. NH4OH precipitates NH^Hg^NOs. 
 Black. 
 
 15. NaOH or KOH precipitates Hg^O. 
 
 Black. (Readily decomposes into HgO + Hg.) 
 
 16. SnClj precipitates Hg^Clj and finally metallic Hg, grey. 
 
 17. Heated in a glass tube with dry Na^COs, mercury is 
 
 reduced from all its compounds. It is vaporized 
 and condenses in the cooler part of the tube, forming 
 globules. 
 
Scheme of Analysis of Group I. 
 
 + dilute HCl. 
 
 Ppt = AgCl. 
 Treat + hot water. 
 
 PbCL. 
 
 Hg,Cl„ 
 
 Residue = AgCl, Hg^Cl,. 
 Treat + NH^OH. 
 
 Residue NH,Hg,Cl. 
 Confirm Hg by 17. 
 
 Solution NHjAgCl. 
 Confirm Ag by i. 
 
 Solution PbClj. 
 Confirm Pb by 7, 
 10 or II. 
 
 Alternative Scheme. 
 
 + HCl, dilute. Filter and treat precipitate. 
 + KOH in excess. 
 
 Residue = AgCl. Hg^Cl^ or Hg^O. 
 
 Mix + dry Na^COa. 
 
 Heat in glass tube to completely 
 expel Hg. Forms mirror. Col- 
 lect globules of Hg. Dissolve in 
 HNO3. Confirm Hg by 21. 
 
 Residue AgjO.NaCl, excess NajCOj. 
 
 Treat with hot water. 
 
 Dissolve residue in dilute HNO,. 
 
 Confirm by i. 
 
 Solution KjPbOj. 
 Confirm Pb by 7. 
 
 iVo^i?.— Examine filtrate from precipitation + HCl, for 
 remaining groups. 
 
Notes on Analysis of Qroup I. 
 
 I. lycad is not completely removed in the first group by 
 the reagent HCl, as the PbClj dissolves somewhat in water; 
 hence small amounts of Pb are always found in Group II. if 
 the metal has been found in Group I. 
 
 II. The action of NH^OH after the removal of the Pb is to 
 convert the AgCl and HgjClj into substituted ammonium 
 compounds. The first of these, being soluble, is found in the 
 filtrate, and the second, an insoluble compound, remains as 
 a black residue. 
 
 III. Compounds of metals of the first group are reduced 
 with particular ease when heated on charcoal with Na^COj, 
 giving metallic globules all of which are easily soluble in 
 HNOj. (For mercury a glass tube closed at one end is 
 used.) 
 
 .IV. Note that silver compounds are, as a rule, soluble in 
 NH4OH but not in NaOH or KOH; lead compounds are 
 insoluble in NH4OH but easily soluble in NaOH or KOH; 
 and mercurous compounds are insoluble in both. 
 
 QROUP II. 
 
 Mercury (MercurzV). Hg. Valence =: II. 
 
 Use preferably HgClj. 
 
 18. HjS or alkaline sulphides precipitate finally HgS. 
 Black. 
 
 Insoluble in HNO,. 
 Insoluble in (NH^jS. 
 i/Soluble in Na^S, K^S. 
 /Soluble in NaOH, KOH. 
 
 *^ Soluble in aqua regia (HCl + HNO3) or in other mix- 
 tures yielding CI. ■ %. 
 
V 19- NH^OH precipitates NH^HgCl. 
 
 White (distinction from Mercurous, see 14). 
 
 20. KOH or NaOH precipitates finally HgO. 
 v Yellow. 
 
 Insoluble in excess of reagent. 
 
 21. SnClj precipitates Hg^CIj and finally metallic Hg. 
 White at first and finally grey. 
 
 22. See 17. 
 
 ^ Bismuth. Bi. Valence =: III. 
 
 Use preferably BiCls- 
 
 23. HjS or alkaline sulphides precipitate BijS,. 
 \yery dark brown. 
 
 Ipsoluble in dilute acids. 
 
 I^oluble in alkaline hydroxides. 
 
 Insoluble in alkaline sulphides, 
 
 InsoM>le in KCN. 
 
 Soluble jn moderately concentrated HNO3. 
 
 24. NH.OH, NaOH, KOH precipitates Bi(OH),. 
 White, flocciilent. 
 
 Insoluble in excess of reagent. 
 
 25. HjO precipitates 3BiOCl. 
 White, pulverulent. 
 
 Insoluble in tartaric acid (distinction from antimony). 
 
 26. KjSnOa in ejccess, precipitates BijO^. 
 Black. 
 
 Copper. Cu. Valence = 11. 
 
 Use preferably CUSO4. 
 
 27. HjS or soluble sulphides precipitate CuS. 
 Brownish black. 
 
 Insoluble in Na^S and K^S. 
 Insoluble in KOH or NaOH. 
 
Insoluble in dilute acids, 
 ^g oluble in HNO ,. 
 
 Very slightly soluble in (NH.XS. 
 
 Soluble in KCN. 
 
 Oxidized, when moist, to CuSOj by O in the air. 
 
 zS^ NH4OH precipitates Cu(0H)2, immediately sohible in 
 excess forming a deep blue solution. '^^ r^ b)v( f"' ) l 
 
 29. KOH or NaOH precipitates CuCOH)^. 
 Light blue. 
 Insoluble in excess of reagent. 
 
 Converted by boiling into CuO, black. 
 6..Ji^ HC^+I j,Ot^ 
 /'30. KjFeCCNX precipitates Cu2Fe(CN)e, reddish brown. 
 This forms even in very dilute solutions. 
 
 31. Fe or Zn, in neutral or acid solutions, precipitates me- 
 
 tallic Cu. 
 
 32. Heated with the blowpipe on charcoal + NajCOj, cop- 
 
 per is reduced from all its compounds and forms red 
 malleable grains. 
 
 33. Copper compounds color beads of borax or microcos- 
 
 mic salt, blue in the oxidizing flame and opaque red 
 (due to CUjO) in the reducing flame. 
 
 34. Copper compounds acidified with HCl color the flame 
 
 blue or green. 
 
 Cadmium. Cd. Valence =: II. 
 
 Use preferably CdSO^. 
 
 35. HjS or alkaline sulphides precipitate CdS. 
 Yellow. 
 
 Insoluble in dilute HCl. 
 
 Insoluble in alkaline sulphides. 
 
 Insoluble in NaOH and KOH. 
 
 Insoluble in KCN. 
 
 Soluble in HNO3, and in boiling H^SOj and HCl. 
 
36. NH,OH precipitates Cd(OH),. 
 White. 
 
 Soluble in excess of reagent. 
 
 37. NaOH or KOH precipitates Cd(OH),. 
 White. 
 
 Insoluble in excess of reagent. 
 
 38. All compounds of Cd when heated on charcoal with 
 
 Na^COa, give CdO as a brown tarnish which exhibits 
 a play of colors. 
 
 Arsenic (Arsenious). As. Valence = III. 
 Use preferably NajAsOs. 
 
 39. HjS precipitates from acid solutions, AsjS,. 
 Yellow. 
 
 Insoluble in concentrated HCl. 
 
 Soluble in concentrated HNO3. 
 
 Soluble in alkaline sulphides. 
 
 Soluble in alkaline carbonates and hydroxides. 
 
 40. AgNOa added to neutral solutions precipitates AgjAsOj. 
 Yellow. (Easily soluble in HNO, and in NH^OH.) 
 
 41 . Nascent hydrogen acting on arsenic solutions produces 
 
 in all cases AsH, gas {highly poisonous /) ' ' Marsh 
 Test." Inflammable— burns to AS2O3+ HjO. 
 
 Arsenic, as a lustrous mirror, is separated if the flame 
 be chilled, e.g. by the introduction of cold porcelain. 
 Dissociated by heat with the separation of metallic 
 As. Soluble in HNO3 ; in NaClO. 
 
 Passed into a solution of AgNO, forms H^sOj. Neu- 
 tralized + dilute NHjOH forms AgjAsOj^^ Yellow 
 ring. 
 
 42. A strip of copper added to solutions of arsenic com- 
 
 pounds acidified with HCl, and heated, becomes 
 
13 
 
 coated with a gray deposit. (Reinseh Test.) On 
 heating this strip in an open tube with free access of 
 air, the white oxide As20s is formed. Crystalline and 
 easily volatilized. 
 
 43. All\arsenic compounds heated on charcoal + Na^COa 
 
 are reduced to arsenic which volatilizes with a char- 
 acteristic garlic-like odor. 
 
 44. Oxidizil^g agents, such as HNO3, CI, NaClO, Kfirfi,, 
 
 K2Mn208, convert arsenious into arsenzt compounds. 
 
 \^ Arsenic (Arsenic). As. Valence = V. 
 Use preferably^ NajAsO^. 
 
 45. HjS reduces arsenzV compounds to axsenious with the 
 
 separation of S. It then precipitates ASjSa. 
 Yellow. 
 See 39. 
 
 46. Alkaline sulphides precipitate ASjSj. 
 Yellow. 
 
 Insoluble in HCl. \ 
 
 Soluble in excess of reagents. 
 
 47. MgSOl in the presence ofXNH^Cl + NH^OH precipi- 
 
 tates MgNH^AsOj. \ 
 
 White, crystalline. 
 Insoluble in NH.OH. 
 Easily/ soluble in dilute acids. 
 ; 
 
 48. See 41. 
 
 49. See 42. 
 
 50. See 43. 
 
 51. Reducing agents, such as HjS, SO^, convert arsenzV into 
 
 axsenious compounds. 
 
14 
 Tin (Stannous). Sn. Valence =11. 
 Use preferably SnClj. 
 
 52. H^S precipitates SnS. 
 Brown. 
 
 Insoluble in alkaline mono-sulphides. 
 
 Insoluble in dilute acids, 
 t^luble in alkaline poly-sulphides. 
 (Soluble in alkaline hydroxides, 
 w^oluble in concentrated HCl. 
 
 53. Alkaline sulphides precipitate SnS. 
 Brown. 
 
 v^oluble in' excess of the" reagent, if poly-sulphides are 
 used. 
 
 54. Alkaline hydroxides? precipitate Sn(0H)2. 
 White. 
 
 Insoluble in excess of NH^OH. 
 Soluble in excess of NaOH and KOH. 
 
 55. HgCIj is reduced by stannous salts with the precipita- 
 
 tion of HgjClj; later Hg precipitates. 
 (See 21. Distinction from stannzc compounds.) 
 
 56. All tin compounds, when mixed with NajCOj and KCN 
 
 and heated on charcoal, are reduced to globules of 
 Sn, with an accompanying white incrustation of 
 SnOi,. 
 Moistened with CoCNOa)^ and heated with blowpipe, a 
 bluish green color results. 
 
 57. Oxidizing agents, such as HNO3, CI, FejClj, convert 
 
 Stannous compounds to sta.nnic. 
 
 Tin (StanmV-). Sn. Valence = IV. 
 
 Use preferably SnCl^. 
 
 58. HjS precipitates SuSj. 
 Yellow. 
 
 Insoluble in dilute acids. 
 
"^ 
 
15 
 
 Insoluble in (NKJ.CO,. 
 Soluble in concentrated HCl. 
 (.Soluble in alkaline sulphides. 
 Soluble in fixed alkaline hydroxides. 
 
 59. Alkaline sulphides precipitate SnS^. 
 Yellow. 
 
 i-'Soluble in excess of the reagent. 
 
 60. Alkaline hydroxides precipitate SnO(OH)j. 
 White. 
 
 Insoluble in excess of NH4OH. 
 i^bluble in excess of KOH and NaOH. 
 
 61. Neutral salts of the alkali metals, such as Na^SO^ and 
 
 NH4NQ3, give on boiling a precipitate of stannic or 
 meta-stannic acid, HjSnOs, or (HjSnOg)^. 
 
 62. See 56. 
 
 63. Reducing agents, such as nascent hydrogen and certain 
 
 metals (Sn, Cu), convert stanmc compounds first to 
 stannoM.? and finally, in some cases, to metallic Sn. 
 
 Antimony. Sb. Valence =111. 
 
 Use preferably SbClj. 
 
 64. HjS precipitates Sb^Sj. 
 Orange-red. 
 
 Insoluble in dilute acids. 
 Insoluble in (NHJ^COg. 
 Soluble in alkaline sulphides. 
 Soluble in alkaline hydroxides. 
 Soluble in concentrated HCl. 
 Soluble in hot concentrated HjCiHjOs. 
 
 65. Alkaline sulphides precipitate Sb^Sj. 
 Orange-red. 
 
 Soluble in excess of the reagent. 
 
l6 
 
 66. Alkaline hydroxides precipitate Sb(OH)j. 
 White. 
 
 Insoluble in excess of NH^OH. 
 Soluble in excess of KOH and NaOH. 
 
 67. HjO causes the precipitation of SbOCl. 
 White. 
 
 Easily soluble in HjCiH^Oe. (Distinction from Bi.) 
 
 68. Analogous to arsenic. See 41. The gas SbHj, passed 
 
 into a solution of AgNO,, precipitates AgjSb. (Dis- 
 tinction from As.) 
 Metallic Sb is converted into .SbjOj by means of HNO3; 
 insoluble in NaClO. (Distinctions from As.) 
 
 69. Zinc in the presence of HCl and Pt precipitates Sb as a 
 
 dull black adherent coating on the Pt. Insoluble in 
 HCl. Converted into oxide by HNO3. 
 
 70. Heated with NajCO, on charcoal in the reducing flame, 
 
 brittle beads of Sb are formed. These are easily 
 converted by oxidation into the volatile SbjOa which 
 coats the coal. Moistened with Co(NOs)j and ignited, 
 an olive green color is developed. 
 
17 
 
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19 
 
 Notes on Analysis of Group II. 
 
 I. At the time of the precipitation of the second group by 
 HjS, HNO3 and other oxidizing agents should be absent, or 
 present only in very small amounts. On boiling the solution 
 down to a small bulk with HCl, these oxidizing agents are 
 eliminated; HNO3, chlorine or chlorine oxides being vola- 
 tilized, whereas chromates and permanganates are reduced. 
 
 The presence of oxidizing agents is objectionable because 
 they oxidize the HjS, forming H^O, S, or even H2SO4; they 
 also have a solvent effect on the sulphides formed, and so 
 prevent a complete precipitation. 
 
 The best conditions for the precipitation of Group II. by 
 HjS are: — 
 
 Dilute solution. 
 Slightly acid +HC1. 
 Moderately warm. 
 
 II. Sulphides of the members of the second group are 
 somewhat soluble in mineral acids unless the acids are quite 
 dilute. CdS, SbjSj, and SnSj dissolve quite easily in HCl. 
 HgS is insoluble in HNO3 (concentrated HNOj may convert 
 HgS on boiling to white basic compounds). PbS dissolves 
 easily in HNO3 — a portion of it, however, being converted 
 into white insoluble PbSO^. Boiling saturated solution of 
 oxalic acid dissolves SnSj, but does not affect AsjSjOr Sb^Sj. 
 ('N'H.iXS^ dissolves easily SnS, SnSj, As^Sj, Sb2S3, and small 
 amounts of CuS. (NHJjS, colorless, dissolves these last 
 named, with the exception of SnS. Na2S or KjS dissolves 
 SnSa, SbjSs, ASjSj, and appreciable amounts of HgS. CuS, 
 CdS, Bi^Sj are insoluble in fixed alkaline sulphides. 
 
 Moist copper sulphide is easily oxidized by the oxygen of 
 the air, forming CuSO^; hence the sulphides of the second 
 group should not be allowed to stand. 
 
 All sulphides are dissolved by oxidizing agents. (Excep- 
 tion: HNO3 converts Sb2S3 and SnSj into the corresponding 
 oxides, and does not dissolve HgS.) 
 
III. NH.OH dissolves hydroxides of Cu and Cd. KOH 
 or NaOH dissolves hydroxides of Pb, Sn, and Sb. Neither 
 NHjOH nor KOH nor NaOH dissolves compounds of Hg 
 and Bi. 
 
 (Arsenic compounds are not precipitated by alkaline 
 hydroxides.) 
 
 IV. KCN precipitates solutions of Pb, Bi, Cu, and Cd. 
 Bismuth precipitates as hydroxide with the evolution of 
 HCN. The cyanides of Cu and Cd dissolve in excess, form- 
 ing Cu(CNX.2 KCN, Cd(CN),.2 KCN. 
 
 V. Cupric salts, when treated with NH4CNS and satu- 
 rated with SO2, give a precipitate of Cu2(CNS)2. White. 
 This distinguishes Cu from all metals but those of the first 
 group. 
 
 VI. Compounds of metals of the second group are easily 
 reduced to the metallic state when heated on charcoal with 
 NajCOj. Tin compounds req.uire the addition of KCN. 
 Bismuth easily oxidizes, yielding a yellow coat on the coal. 
 Cadmium forms a coat on the coal which has a characteristic 
 iridescence. Tin forms a white oxide that deposits near the 
 reduced metal. This oxide, on being moistened with 
 Co(N05)2, gives a blue-green mass. Antimony easily oxi- 
 dizes, forming a volatile white coat that collects on the coal 
 for some distance from the reduced metal. This oxide, on 
 being moistened with Co(N03)2 and heated with the blow- 
 pipe, gives an olive green mass. Arsenic compounds, on 
 being reduced on the coal, give off a characteristic garlic-like 
 odor. Copper compounds give no coat on the coal. For 
 behavior of mercury compounds, see Note III. on Group I., 
 and No. 17. 
 
 GROUP III. 
 
 Iron (Perrous). Fe. Valence = II. 
 Use preferably FeSO^. 
 71. (NHJjS and fixed alkaline sulphides precipitate FeS. 
 
Black. 
 
 Insoluble in excess of reagent. 
 Soluble in dilute mineral acids. 
 
 Oxidized by the air to FeSO^ and basic ferric com- 
 pounds. 
 
 72. Alkaline hydroxides precipitate Fe(0H)2. White, im- 
 
 mediately changing to dirty green and finally to red- 
 dish brown. Due to oxidation. 
 
 Insoluble in excess of NaOH or KOH. 
 
 Soluble in NH4OH in the presence of ammonium salts, 
 the solution precipitating on exposure to air, due to 
 formation of ferric compounds. 
 
 73. KsFe(CN), precipitates FeaFejCCN)^. 
 Blue. (Distinction from fernV.) 
 
 74. All compounds of iron fused in a bead of borax, give 
 
 in the reducing flame a pale green bead, and in the 
 oxidizing flame one which is brown or yellow when 
 hot, often colorless when cold. 
 
 75. Oxidizing agents, such as HNO3, CI, Br, KCIO3, 
 
 KjMUjOs, KjCr^O,, convert ienous into feme com- 
 pounds. 
 
 Ferric. Fe. Valence = III. 
 
 Use preferably FcjClj. 
 
 76. (NH4)2S and fixed alkaline sulphides precipitate FeS 
 
 + S. See 71. 
 
 77. Alkaline hydroxides precipitate Fe^COHX. 
 Reddish-brown. 
 
 Insoluble in excess of reagent. 
 
 Precipitation prevented by presence of organic sub- 
 stances, such as tartaric acid, citric acid, and sugar. 
 
 78. BaCOj suspended in water precipitates FeaCOH)^, with 
 
 the evolution of CO2 gas. (Distinction from ierrous 
 compounds.) 
 
All soluble carbonates precipitate FcjCOH), with evolu- 
 tions of COj. 
 
 79. KCNS or NH.CNS produces Fe^CCNSX- 
 Blood-red solution. 
 
 Not destroyed by HCl. 
 
 80. NaQHsO, in neutral solutions or those slightly acid 
 
 with HC^HjOj produces Fe2(C2H302)e, which is deep 
 red. On being boiled, reddish brown basic ferric 
 acetates are precipitated. 
 
 81. See 74. 
 
 82. Reducing agents, such as HjS, SOj and nascent hydro- 
 
 gen, convert ieritc into ferrous compounds. 
 
 Ai,UMiNiUM. Al. Valence = 111. 
 
 Use preferably Al^CSOJa. 
 
 83. (NHJjS and fixed alkaline sulphides precipitate 
 
 Al2(OH)8 with the evolution of H^S gas. 
 White, flocculent. 
 Insoluble in excess of reagent. 
 
 84. Alkaline hydroxides precipitate AljCOH)^. 
 White, flocculent. 
 
 Slightly soluble in excess of NH4OH (rendered less 
 soluble by the presence of ammonium salts). 
 
 Easily soluble in excess of NaOH and KOH; hot or 
 cold. 
 
 85. BaCOs suspended in water precipitates Ali(OH)e with 
 
 the evolution of COj. 
 
 86. Heated with blowpipe on charcoal, aluminium com- 
 
 pounds yield, when moistened with CoCNOa), and 
 again ignited, a sky-blue infusible mass. 
 
 87. NaCCjHaOj) analogous to ferric iron. See 80. 
 
23 
 
 Chromium. Cr. Valence = III. 
 
 Use preferably CrjCSOJj. 
 
 88 . (NHj^jS or fixed alkaline sulphides precipitate C|\[(0H)5. 
 Grayish green. 
 
 Insoluble in excess of reagents. 
 
 Insoluble in hot NaOH or KOH. 
 
 Soluble in excess of cold alkaline hydroxides. Repre- 
 
 cipitated by prolonged boiling. Slightly soluble in 
 
 large excess of NH^OH. 
 
 89. Alkaline hydroxides precipitate CrjCOH)^. See 88. 
 
 90. BaCOa suspended in water precipitates CrjCOH)^, with 
 
 the evolution of COj. 
 
 91. NaC^HjOj analogous to ferric iron. See 80. 
 
 92. Chromium compounds, heated on a loop of Pt wire 
 
 with borax or microcosmic salt, dissolve, giving a 
 clear emerald green bead. 
 
 93. Oxidizing agents, such as CI, Br, NaClO, convert solu- 
 
 tions of chromium salts to yellow alkaline chromates. 
 Solid chromium compounds, fused with NajCOj and 
 KNO3 or KCIO3, yield alkaline chromates, yellow, 
 soluble in water. 
 
 NiCKBi,. Ni. Valence = II. 
 
 Use preferably Ni(N03)2. 
 
 94. (NHJjS or fixed alkaline sulphides precipitate NiS. 
 Black. 
 
 Insoluble in cold dilute HCl (1—6). 
 
 Insoluble in acetic acid. 
 
 Slightly soluble in excess of (NHJ^S^, particularly in 
 
 the presence of NH^OH, giving inky brown solution. 
 
 Distinction from Co. (The presence of ammonium 
 
 salts hinders this solubility.) 
 Easily soluble in aqua regia. 
 
H 
 
 95. NHjOH precipitates Ni(OH)j, immediately soluble in 
 
 excess, particularly in presence of ammonium salts, 
 giving a blue solution. 
 
 96. NaOH or KOH precipitates Ni(OH),. 
 Light green. 
 
 Insoluble in excess of reagent. 
 Soluble in ammonium salts. 
 
 97. KCN precipitates Ni(CNX. 
 Yellowish green. 
 Insoluble in dilute HCl. 
 Soluble in excess of reagent. 
 
 This solution + excess NaOH or KOH, and treated 
 with oxidizing agents such as CI or Br or HgO, gives 
 a precipitate of Nij(OH \, black. (Distinction from 
 Co.) 
 
 98. All nickel compounds dissolve completely in borax and 
 
 microcosmic salt beads, imparting to them in the 
 oxidizing flame a brownish color; in the reducing, a 
 gray. (This color is obscured by the presence of Co 
 compounds.) 
 
 Cobalt. Co. Valence = II. 
 
 Use preferably CoCNO,),. 
 
 99. (NHJ2S or fixed alkaline sulphides precipitate CoS. 
 Insoluble in cold dilute HCl (1—6). 
 
 Insoluble in acetic acid. 
 Insoluble in excess of reagent. 
 Easily soluble in aqua regia. 
 
 100. NH4OH precipitates CoCOH)^ immediately soluble in 
 
 excess, giving a reddish-brown solution. 
 
 101. NaOH or KOH precipitates blue basic salts. 
 Converted by boiling into CoCOH)^. 
 
 Pink. 
 
 Insoluble in excess of reagents. 
 
25 
 
 102. KCN precipitates Co(CN)2. 
 Brownisli-wliite. 
 Insoluble in dilute HCl. 
 
 Soluble in excess of reagent. This solution on pro- 
 longed boiling with a few drops of HCl is oxidized by 
 the oxygen of the air to the soluble K3Co(CN)6. 
 (Distinction from Ni.) 
 
 103. KNOj in solutions, acid only with acetic acid, precipi- 
 
 tates KgCoCNOJe- 
 Yellow, crystalline. 
 Insoluble in acetic acid. 
 Soluble in HCl, 
 
 104. Cobalt compounds dissolve completely in borax and 
 
 microcosmic salt beads, giving an intensely deep blue 
 color, appearing black when large amounts of cobalt 
 are present. 
 
 Manganbsb. Mn. Valence = II. 
 
 Use preferably MnSOj. 
 
 105. (NHJjS or fixed alkaline sulphides precipitate MnS. 
 Flesh-tint. 
 
 Insoluble in excess of reagents. 
 
 Easily soluble in dilute mineral acids and in acetic acid 
 (this latter a distinction from ZnS). 
 
 106. NHPH precipitates Mn(OH)i,. 
 White. 
 
 Insoluble in excess of reagent. 
 
 Soluble in ammonium salts, hence precipitation does 
 not take place in their presence. But on standing 
 this solution becomes turbid and MnjOj(OH)„ brown, 
 separates because of atmospheric oxidation. 
 
 107. NaOH or KOH precipitates Mn(OH),. 
 White, turning brown on exposure to air. 
 Insoluble in excess of reagents. 
 
26 
 
 io8. Manganese compounds, fused in a bead of microcosmic 
 salt or borax, impart in the oxidizing flame an ame- 
 thyst red color, which becomes colorless in the re- 
 ducing flame. 
 If the hot microcosmic salt bead is laid on a crystal 
 of KNO3 or NaNOs, an intense violet coloration is 
 developed. 
 
 109. Oxidizing agents, such as HNOa+PbOj or PbjOi, CI or 
 Br in alkaline solutions, convert solutions of manga- 
 nous salts into permanganic acid or soluble perman- 
 ganates, purple. 
 
 Solid compounds fiised on Pt with NajCOa+KNOa or 
 KCIO3, form manganates, deep blue-green. Boiled 
 with water these dissolve, forming purple permanga- 
 nates and insoluble MnOj. 
 
 Bromine precipitates from acetic acid solutions, MnOj, 
 brown. 
 
 Zinc. Zn. Valence := II. 
 
 Use preferably ZnSO,. 
 
 no. (NHJjS or fixed alkaline sulphides precipitate ZnS. 
 White. 
 
 Insoluble in excess of reagents. 
 Insoluble in acetic acid. 
 (Distinction from MnS.) 
 Easily soluble in dilute min. acids. 
 
 111. NH4OH or fixed alkaUne hydroxides precipitate 
 
 Zn(OH),. 
 "White. 
 Readily soluble in excess of reagents. 
 
 112. Heated on charcoal with NajCOj, ZnO is produced, yel- 
 
 low while hot, white when cold; moistened with 
 Co(N03)3 and heated again, it gives a green infusible 
 mass. 
 
27 
 
 
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29 
 
 Scheme for Analysis of Third Group in Presence of 
 (a) Oxalic Acid, (b) Phosphoric Acid. 
 
 + NH4OH until alkaline (NHJjS in slight excess. Warm 
 and allow to settle. Filter and wasli with water containing 
 a little (NH,),S. 
 
 Precipitate: 
 Treat + cold, 
 
 dilute HCl (1—6). 
 
 Residue: 
 
 NiS, CoS. 
 
 Examine ac- 
 cording to 
 methods 
 previously 
 given. 
 
 Filtrate: 
 Examine small portion, 
 after boiling out H^S, for 
 (a) oxalic acid by adding 
 a slight excess of NH,OH 
 and then acidifying with 
 acetic acid-|-CaClj,awhite 
 precipitate = CaC^O,. 
 
 Filtrate: 
 
 Reserve for 
 
 examination 
 
 of Groups 
 
 IV. and V. 
 
 If oxalic acid is found to be present, evaporate entire fil- 
 trate to dryness and ignite gently to decompose oxalates. 
 Allow dish to become cold; dissolve in dilute HCl and 
 proceed, using either of the previous schemes of analysis. 
 
 (b) Kxamine a small portion of filtrate according to 191. 
 If phosphoric acid is found to be present, use the following 
 scheme of analysis. 
 
 {Note. — If oxalic acid and phosphoric acid are both present, 
 destroy the oxalic acid according to method given above 
 and then analyze the solution according to the method 
 following.) 
 
 Boil the filtrate with a few drops of HNO3, and examine a 
 small portion for Fe according to 79. 
 
 Add to remainder of filtrate FcjClj, neutralize with Na^COj, 
 acidify slightly with acetic acid, add NaC^HsOj and boil. 
 
 Precipitate: Examine for Al, Cr. 
 
 Filtrate: 
 
 Heat with excess of NaOH -|- 
 
 Examine for Mn, Zn, 
 
 NaClO. 
 
 Ba, Sr, Ca, Mg, 
 
 Filter and reject the precipitate. 
 
 according to 
 
 To filtrate, add NH^Cl, in excess. 
 
 methods used in the 
 
 boil and filter. 
 
 regular systematic 
 
 Precipitate: 
 
 Filtrate: 
 
 grouping. 
 
 White, floccu- 
 
 Na,CrO,. 
 
 
 lent, shows 
 
 Acidify with 
 
 
 presence of Al. 
 
 HC^HaO^and 
 examine for 
 Cr, according 
 to II. 
 
 
30 
 
 Alternative Method for Use in Presence of Oxalates and 
 Phosphates. 
 
 Treat the filtrate from Group II. with Sn and HNO,. 
 Evaporate to dryness and gently ignite. The oxalic acid 
 will be decomposed and the phosphoric acid removed as 
 phosphate of tin. Take up with dilute HNO3 and examine 
 the filtrate according to the regular systematic grouping. 
 
 Notes on Analysis of Group HI. 
 
 I. — For action of (NHJjS on the members of this group, 
 compare Nos. 71, 76, 83, 88, 94, 99, 105, no. 
 
 Tartaric acid, citric acid, and other organic matter, such as 
 sugar, prevent the precipitation of hydroxides but not of 
 sulphides, therefore Al and Cr are not precipitated by the 
 group reagent in the presence of these matters. 
 
 If any of the above are found to be present, evaporate to 
 dryness and destroy by ignition. Take up with dilute HCl 
 and proceed with the regular scheme. 
 
 II. — If phosphates or oxalates be present, the fourth group 
 will be precipitated on the addition of NH^OH, and thus 
 will be found with the third group. (See Nos. 116, 117, 121, 
 122, 126, 127.) Magnesium compounds are also similarly 
 precipitated in the presence of phosphates. (See 131.) 
 
 In this case analyze the precipitate formed by the addition 
 of third group reagents, according to the schemes given for 
 use when phosphates or oxalates are present. 
 
 III. — BaCOj suspended in water precipitates, as hydroxides, 
 salts derived from oxides of the type RjOj, (Fe, Al, Cr); but 
 not salts derived from oxides of the type RO. 
 
 IV. — When compounds of this group are fused with a mix- 
 ture of alkaline carbonate and nitrate, two of them give rise 
 to combinations which dissolve in water, viz. , Mn and Cr, 
 which form respectively Na^MnO^ and Na^CrOi. The former 
 
31 
 
 dissolves in water, giving a purple solution of NajMn^Oa, 
 with the simultaneous precipitation of MnOj. The NajCrO^ 
 dissolves in water giving a yellow solution. The other 
 members of this group are converted by this treatment into 
 oxides, insoluble in water. 
 
 V. — All of the members of this group give colored char- 
 acteristic beads with the exception of Al and Zn. See Nos. 
 74, 92, 98, 104, 108. 
 
 GROUP IV. 
 
 Barium. Ba. Valence = II. 
 
 Use preferably BaClj. 
 
 113. (NH4)2C03 or fixed alkaline carbonates precipitate 
 
 BaCO,. 
 
 White, pulverulent. 
 
 Insoluble in excess of reagents. 
 
 Insoluble in alkaline hydroxides. 
 
 Soluble in acids. 
 
 Soluble in solutions containing CO2, with the formation 
 of Ba(HC03)2. This is decomposed by boiling or by 
 the addition of soluble hydroxides with the re-pre- 
 cipitation of BaCOj. 
 
 Slightly soluble in NH^Cl. 
 
 1 14. H2SO4 precipitates BaSOj. 
 White, pulverulent. 
 
 Insoluble in acids (with the exception of concentrated 
 H,SOJ. 
 
 115. KjCrOi precipitates BaCrOj, distinction from Sr and Ca. ,_ 
 
 116. (NHJjCjO^ precipitates BaC^O,. 
 White, pulverulent. 
 
 Soluble in HCl; solution hastened by warming. 
 Insoluble in NH4OH. 
 
32 
 
 117. Na^HPOi precipitates BaHPOj. 
 White, flocculent. 
 
 Soluble in acids. 
 Insoluble in NH^OH. 
 
 1 1 8. Ba compounds moistened with HCl on the loop of a 
 
 clean platinum wire, impart to the flame a yellowish- 
 green color. 
 
 Strontium. Sr. Valence = II. 
 
 Use preferably SrClj. 
 
 119. (NH4)2C03 or fixed alkaline carbonates. 
 (Analogous to Ba. See 113.) 
 
 120. H2SO4 precipitates SrSO^. 
 White, pulverulent. 
 
 Very slightly soluble in water. 
 
 Strontium compounds are immediately precipitated by 
 a solution of CaSO,. 
 
 121. CNHJ^CjOj precipitates SrCjO^. 
 (Analogous to Ba. See 116.) 
 
 122. Na^HPOj precipitates SrHPO^. 
 (Analogous to Ba. See 117.) 
 
 123. Sr(N03)2 is insoluble in alcohol. 
 (Distinction from calcium.) 
 
 124. Strontium compounds moistened with HCl, and heated 
 
 on a Pt wire, impart a crimson color to the flame. 
 
 Cai<cium. Ca. Valence = II. 
 
 Use preferably CaClj. 
 
 125. (NHJjCOj or fixed alkaline carbonates precipitate 
 
 CaCOj. 
 (Analogous to Ba and Sr. See 113.) 
 
 126. (NHJjCPj precipitates CaCjO^. 
 (Analogous to Ba and Sr. See 116.) 
 Insoluble in acetic acid. 
 
33 
 
 127. Na^HPO^ precipitates CaHPOi. 
 (Analogous to Ba and Sr. See 117.) 
 
 128. Ca(NOs)2 is soluble in alcohol. (Distinction from stron- 
 
 tium.) 
 
 129. HjSOj precipitates CaSO^ only from concentrated solu- 
 
 tions on addition of rather strong HjSOj. 
 Decidedly soluble in water. 
 
 130. Calcium compounds moistened with HCl, and heated 
 
 on a Pt wire, impart a brick-red color to the Bunsen 
 flame. 
 
34 
 
 Analysis of Fourth Group. 
 
 + HCl to slightly acid reaction. 
 
 Boil to separate sulphur. 
 
 Filter. Render alkaline with NH^OH. 
 
 Filtrate BaCli,, SrCl^, CaCl^ and Group V. 
 + (NHJjCjOj and warm gently. 
 
 Precipitate BaC^Ot, SrC^Oi, CaQO,. 
 Ignite in a porcelain dish. 
 Dissolve in HCjHjOj. 
 
 Filtrate. 
 Fxamine for 
 Group V. 
 
 + K,CrO. 
 
 Precipitate: 
 BaCrOi. 
 See 115. 
 
 Filtrate 
 SrCrO^, CaCrO,. 
 
 + NH4OH to alkaline reaction. 
 + (NH,),C,0,. 
 
 Precipitate SrCA> CaCjO^. 
 Dissolve in dilute HNO3. 
 
 Evaporate to dryness on steam-bath. 
 
 Digest + C2H5OH absolute. 
 
 Residue: 
 SrCNO,),. 
 Confirm by 120 or 
 
 Filtrate: 
 
 CaCNO,),, H,0. ater. 
 Confirm by 126 or 
 130- 
 
35 
 
 Notes. 
 
 I. — In the scheme of analysis given for the fourth group, 
 (NHJjCjO^is used in preference to (NHJ2CO3, chiefly on 
 account of the greater insolubility of the oxalates. 
 
 II. — ^The fact of the different solubilities of the chlorides 
 and nitrates of the members of this group in absolute alcohol 
 is conveniently taken advantage of in methods of analysis 
 of this group. Thus: — 
 
 BaCla, insoluble in alcohol. 
 
 ^"^SV I soluble in alcohol. 
 CaClj, i 
 
 Sr(N03)2, insoluble in alcohol. 
 
 CaCNOs)^, soluble in alcohol. 
 
 III. — ^The colors imparted to the Bunsen flame are charac- 
 teristic and are specially important as confirmatory tests. 
 (See Nos. 118, 124, 130.) 
 
 GROUP V. 
 
 Magnesium. Mg. Valence = II. 
 
 Use preferably MgSO^. 
 
 131. Na^HPOi in the presence NH^OH and NH^Cl precipi- 
 
 tates MgNHjPOi. White, crystalline. Converted 
 by heat into Mg^PjO,. 
 
 132. Alkaline carbonates, oxalates or hydroxides fail to 
 
 precipitate Mg solutions in the presence of salts of 
 ammonium. 
 
 133. Solutions of Mg compounds containing an excess of 
 
 (NHJjCjOi, leave on evaporation to dryness and 
 ignition of the residue, white MgO, practically in- 
 soluble in water. 
 
 134. Compounds of magnesium ignited with CoCNOJ, on 
 
 charcoal yield a rose pink infusible mass. 
 
36 
 Potassium. K. Valence ;= I. 
 
 Use preferably KCl. 
 
 135. PtCli precipitates K^PtCls. Yellow, heavy. 
 Insoluble in alcohol. (Distinction from Na.) Slightly 
 
 soluble in cold water. Readily soluble in hot water, 
 from which solution it crystallizes in yellow octa- 
 hedra. (Similar compound with similar properties 
 formed with NH^Cl.) 
 
 136. Potassium compounds moistened with HCl give, when 
 
 heated in the Bunsen flame on a Pt wire, a lilac 
 coloration. 
 
 Sodium. Na. Valence = I. 
 
 Use preferably NaCl. 
 
 137. PtClj forms Na^PtCle, which, on evaporation, crystal- 
 
 lizes in needle-shaped prisms. 
 Aurora-red. 
 
 Readily soluble in water and in alcohol. 
 (Distinction from K. See 135.) 
 
 138. Sodium compounds moistened with HCl, and heated on 
 
 a Pt wire in the Bunsen flame, impart a strong dafib- 
 dil yellow color. 
 
 Ammonium. NH^. Valence = I. 
 
 Use preferably NH^Cl. 
 
 139. PtClj forms (NHJ2 PtCle similar to K compound. 
 
 140. All NH4 salts on being boiled -f excess KOH or NaOH, 
 
 yield NH3 gas, recognized by its characteristic odor, 
 turning red litmus blue, or paper moistened with 
 CuSOi deep blue, or with mercurous nitrate black. 
 With HCl, white fumes of NH^Cl are formed. 
 
37 
 
 Analysis of Group V. 
 
 + (NHJjCjO^ in excess. 
 
 Evaporate to dryness. Ignite to expel ammonium salts. 
 
 Extract with water. 
 
 Residue: MgO. 
 Confirm by 134, 
 
 or dissolve in 
 
 HCl. 
 Add NH^OH 
 
 and confirm 
 
 by 131. 
 
 Filtrate Na^COj, K^COs- 
 
 + HCl to acid reaction. 
 
 Evaporate to dryness on water-bath + 
 
 PtCl,. 
 Add CH.OH to residue. 
 
 Precipitate KjPtCls' 
 See No. 135. 
 
 Filtrate Na^PtCle- 
 Evaporate sponta- 
 neously. 
 See 137. 
 
 Note. — Examine for ammonium compounds in the original 
 solution. (See 140.) 
 
38 
 
 Notes. 
 
 I. — Dry oxalates decompose on ignition with the evolution 
 of CO and the production of carbonates. In most cases 
 these carbonates are decomposed with the evolution of CO, 
 and production of oxides. (See analyses given for Group V. 
 Also compare analysis of Groups III., IV., V., in presence 
 of oxalates.) 
 
 II. — NH4CI must be removed by ignition before testing for 
 K and Na, as it forms a similar compound with PtCl,. 
 
 III. — All ammonium salts are volatile on ignition. 
 
 IV. — Nessler's solution (Hglj.2 KI + excess KOH) pro- 
 duces a brown precipitate of NHgJ with ammonium com- 
 pounds. 
 
 An extremely delicate test. Traces of NH, give a yellow 
 or brown coloration. 
 
 V. — The colors imparted to the Bunsen flame are charac- 
 teristic and are of special importance as confirmatory tests. 
 (See 136 and 138.) 
 
B. — Reactions of the Acids. 
 
 AcBTic Acid. HCjHjOj. 
 
 Use preferably NaCjHjOj. 
 
 141. H2SO4 + CjHjOH form, on gently warming, ethyl ace- 
 
 tate, C2H5C2H3O2, possessing a characteristic, fragrant 
 odor. 
 
 142. Fe^Clg forms Fe^CCjHsOjX, a deep red solution, which 
 
 on boiling is converted into basic ferric acetate. 
 (See 80.) 
 
 143. AgNOj, in rather concentrated solutions, precipitates' 
 
 AgC,H30,. 
 White, crystalline. 
 Easily soluble in HNO3. 
 
 144. Acetates yield on ignition either carbonates or oxides, 
 
 without blackening. 
 
 Arsenic Acid. HjAsO,. 
 
 Use preferably NajAsO^. 
 
 145. HjS in acid solutions first effects a reduction with sepa- 
 
 ration of sulphur, and subsequently precipitates AsjSj. 
 (See 45.) 
 
 146. MgSOt in presence of NH^OH and NH^Cl precipitates 
 
 MgNH.AsOi. 
 (See 47.) 
 
 (Distinction from arsenious acid.) 
 This precipitate ignited forms MgjASjO,. Heated on 
 
 charcoal it is decomposed with the production of a 
 
 characteristic garlic-like odor. 
 
 147. AgNOj precipitates AgjAsOi. 
 Reddish brown. 
 
 Easily soluble in HNO3. 
 
 (39) 
 
4° 
 
 Easily soluble in NH.OH. 
 Slightly soluble in NH.NOs. 
 
 148. Arsenic acid is converted into arsenious acid by reduc- 
 
 ing agents, such as HjS, SOj, FeSOj. 
 For other reactions, see As, page 13. 
 
 Arsenious Acid. HjAsOs. 
 
 Use preferably NajAsOj. 
 
 149. HjS in acid solutions immediately precipitates ASjSj. 
 
 (Distinction from arsenzV acid. See 39.) 
 
 150. AgNOa precipitates AgjAsO,. 
 Yellow. 
 
 Easily soluble in HNO3. 
 Easily soluble in NH^OH. 
 Slightly soluble in NH^NOs. 
 
 151. Oxidizing agents, such as FcjClj, KjMnjOg, or KjCfjO, 
 
 in acid solutions, also CI, Br, I and NaClO in acid 
 or alkaline solutions, convert arsenious acid into 
 arsenic acid. 
 For other reactions, see As, pages 12 and 13. 
 
 Boric Acid. H3BO3. 
 
 Use preferably NajB^Oj. 
 
 152. AgNOa in moderately concentrated solutions precipi- 
 
 tates AgBOj. 
 White. 
 Soluble in HNO3. • 
 
 153. BaCLj in moderately concentrated solutions precipitates 
 
 Ba(BO,),. 
 White. 
 Soluble in HCl or HNO3. 
 
 154. Turmeric paper moistened with solutions slightly acid 
 
 with HCl, develops, on drying at a gentle heat, a fine 
 rose-red color. 
 
41 
 
 155- Solid borates moistened with concentrated HjSO^ and 
 mixed with, a little glycerine or alcohol and set on 
 fire, give a flame which is greenish on the edges. 
 
 156. A bead of a mixture of KHSO^ and CaF^ (4 — i) dipped 
 
 into a solid borate and then heated in a Bunsen flame, 
 gives a greenish color which is instantly developed on 
 the edges. 
 
 Carbonic Acid. H2CO3. 
 Use preferably Na^COa. 
 
 157. AgNOj precipitates AgjCOj. 
 White. 
 
 Soluble in HNO,. 
 Soluble in NH^OH. 
 
 158. BaClj precipitates BaCOa. 
 White, pulverulent. 
 (See 113.) 
 
 159. Carbonates give with dilute acids an evolution of CO2 
 
 gas, which passed into CaCOH)^ gives a precipitate of 
 CaCOs. 
 (See 125.) 
 
 Chromic Acid. H^CrO,. 
 Use preferably K^CrOi. 
 
 160. AgNOg precipitates dark red AgjCrO^. 
 
 161. BaClj precipitates BaCrOj. (See 115.) 
 
 162. Pb(C2H302)j precipitates PbCrO^. 
 Yellow. 
 
 Insoluble in dilute acids. 
 Soluble in KOH or NaOH. 
 
 163. Reducing agents, such as HjS, SO^, H3ASO3, nascent 
 
 hydrogen, in acid solutions, convert chromates 
 (yellow or red) to chromium salts (green or violet). 
 
42 
 
 Hydrobromic Acid. HBr. 
 Use preferably NaBr. 
 
 164. AgNOs precipitates AgBr. 
 Pale yellow. 
 
 Insoluble in HNO3. 
 
 Soluble with difficulty in NH^OH. 
 
 165. Chlorine or chlorine oxides (acid solutions of hypo- 
 
 chlorites or chlorates) liberate bromine which dis- 
 solves in CS2 or CHCI3, coloring it a reddish brown. 
 
 166. Concentrated HjSO^ decomposes solid bromides, giving 
 
 reddish brown vapors of bromine. 
 Passed into dilute NH^OH forms NH^Br. 
 Colorless. (See i68.) 
 
 Hydrochloric Acid. HCl. 
 Use prefeiSbly NaCl. 
 
 167. AgNOj precipitates AgCl. (See i.) 
 
 168. Solid chlorides mixed with solid KjCr^O, and covered 
 
 with concentrated HjSOi, yield, on gently warming, 
 
 CrOjClj. 
 Blood-red gas. 
 
 Passed into dilute NH^OH forms (NHJjCrOj. 
 Yellow solution. (See 162.) 
 
 169. Concentrated H2SO4 decomposes solid chlorides, giving 
 
 off fumes of HCl gas. 
 
 Hydrocyanic Acid. HCN. 
 
 Use preferably KCN. 
 
 170. AgNOj precipitates AgCN. (See 4.) 
 
 171. FeSO^ and Fe^Clj added to a solution of a cyanide, 
 
 alkaline with KOH or NaOH, and then acidified with 
 HCl, form Fe,(FeCeN,\, "Prussian Blue." 
 
 172. Alkaline cyanides mixed with (NHJ^S and evaporated 
 
 to dryness on the water-bath produce NH^CNS. 
 (See 79.) 
 
43 
 
 173- HjSO^ decomposes solid cyanides, giving off HCN gas. 
 (Danger! Highly poisonous ! I") 
 
 Hydrofi,uoric Acid. HF. 
 Use preferably CaF;,. 
 
 174. Solid fluorides mixed with concentrated H^SO^ in a 
 
 lead dish yield, on gently warming, HF, hydrofluoric 
 acid gas, which etches glass. 
 
 175. (See 156.) 
 
 Hydriodic Acid. HI. 
 Use preferably Nal. 
 
 176. AgNOa precipitates Agl. 
 Straw yellow. 
 Insoluble in HNO3. 
 
 Very slightly soluble in NH^OH. 
 
 177. Chlorine or chlorine oxides (see 165) liberate iodine 
 
 which dissolves in CSj or CHCI3, coloring it violet or 
 purple. The color is destroyed by excess of CI, ICl, 
 being formed. These decompositions take place 
 before the similar reactions with bromides. 
 
 178. Starch made into a thin paste with water, boiled and 
 
 then cooled, is colored an intense indigo blue by 
 free iodine. 
 
 179. Concentrated H^SOj decomposes solid iodides, giving 
 
 violet vapors of iodine, which soon condense as a 
 dark colored solid. 
 
 Hydrosulphuric Acid. H^S. 
 
 Use preferably FeS. 
 
 180. Sulphides warmed with concentrated HCl give off" H^S 
 
 gas. 
 Characteristic odor. 
 Papers moistened with Pb(C2H302)2 are blackened by 
 
 the gas. 
 
44 
 
 i8i. Solid sulphides fused + Na^COj in a porcelain dish 
 yield NajS. Fused mass placfed on Ag and moistened 
 gives black stain of AgjS. 
 
 Nitric Acid. HNO3. 
 
 Use preferably KNO3. 
 
 182. On adding a few drops of a solution of a nitrate 
 
 to concentrated H^SO,, containing a clear crystal of 
 FeSOj.yHjO, a brown ring around the crystal is 
 developed, due to the formation of FeS04(NO)2 — an 
 exceedingly unstable compound easily decomposed 
 by heat, setting free NO, which on contact with the 
 oxygen of the air forms brown fumes of NOj. 
 
 OxAivic Acid. HjCjO^. 
 
 Use preferably (NHJ^CjOj. 
 
 183. BaClj precipitates BaCjO^. 
 White, pulverulent. 
 
 Easily soluble in HCl and HNO,. 
 
 184. AgNOa precipitates AgjCjO^. 
 White. 
 
 Easily soluble in HNO,. 
 Easily soluble in NH^OH. 
 
 185. CaClj precipitates CaCjOi. 
 Insoluble in HC^HgOj. 
 Insoluble in NH^OH. 
 Soluble in HCl and HNO3. 
 
 186. Solid oxalates warmed with concentrated HjSO^ are 
 
 broken up, yielding CO2 and CO gases. If MnOj is 
 mixed with the powder, COj only is produced. 
 
 187. Oxalates and oxalic acid ignited decompose without 
 
 separation of carbon. 
 
45 
 Phosphoric Acid. H3PO4. 
 
 Use preferably Na^HPOi. 
 
 188. BaClj precipitates BaHPO,. 
 White, pulverulent. 
 Easily soluble in acids. 
 
 189. AgNOa precipitates AggPO^. 
 Yellow. 
 
 Easily soluble in NH4OH and in acids. 
 
 igo. Mg salts in the presence of NH4OH and NH^Cl precipi- 
 tate MgNH^PO^. 
 
 White, crystalline. 
 
 Insoluble in NH.OH. 
 
 Soluble in acids. 
 
 Ignited, forms Mg^PjO,, which, moistened with CoCNOs), 
 and heated on charcoal, gives a blue mass. (Distinc- 
 tion from As. See 146.) 
 
 191. (NHJjMoO^in HNO3 solution precipitates, on warm- 
 
 ing, (NHj3PO,.iiMo03. 
 Yellow, pulverulent. 
 Insoluble in HNO3. 
 
 Soluble in NH^OH and in fixed alkalis. 
 HjAsO^ gives similar results. 
 
 Siwcic Acid. HjSiOa. 
 
 Use preferably NajSiOa. 
 
 192. BaClj precipitates BaSiOa. 
 White. 
 
 193. HCl decomposes moderately concentrated solutions, 
 
 silicates forming H^SiOj. 
 White, gelatinous. On evaporation to dryness, SiO, 
 remains as a white insoluble powder. Heat on char- 
 coal with Co(NOs)2, SiOa, or any silicate, gives a blue 
 mass. 
 
46 
 
 194- Silicates heated in a bead of microcosmic salt are decom- 
 posed with the separation of SiOj, which floats about 
 in the hot bead, unaffected. 
 
 Sulphuric Acid. H2SO4. 
 
 Use preferably Na^SOj. 
 
 195. BaClj precipitates BaSOi. 
 (See 114.) 
 
 196. Sulphates fused with Na^COj on charcoal are reduced 
 
 to sulphides. 
 (See 181.) 
 The fused mass placed on silver coin and moistened 
 
 with water, produces a black stain of AgjS. 
 
 Tartaric Acid. HjCiH^Oj. 
 
 Use preferably NajC^HjO,. 
 
 197. BaClj precipitates BaCjHiOj. 
 White. 
 
 Soluble in HCl and HNO,. 
 
 198. AgNOs precipitates from neutral tartrates AgjC^HjOj. 
 White. 
 
 Easily soluble in HNO3 and in NHiOH. 
 
 The ammoniacal solution of this precipitate on being 
 gently warmed forms on the side of the containing 
 vessel an adherent brilliant coating of metallic silver. 
 
 If boiled, metallic silver is precipitated in the form of 
 a black powder. 
 
 199. KCl precipitates white, crystalline KHC,HjOj. 
 
 200. HjCjHjOg, or solid tartrates, yield on ignition a black 
 
 residue and give off a characteristic odor of burnt 
 sugar, accompanied by much intumescence. 
 
47 
 
 Analysis of the Acids. 
 
 (a) Arsenic Acid. 
 Boil a portion of the original solution with an excess of 
 Na,COs. To the filtrate add NH.OH, NH.Cl, MgSO,. Test 
 the precipitate formed for MgNH^AsO^. (See No. 146.) 
 This precipitate may also contain MgNH^PO^. 
 
 ((5) Arsenious Acid. 
 Acidify the filtrate from the precipitate caused by the ad- 
 dition of MgSO^.with HCl, warm and pass HjS; a yellow 
 precipitate is AsjSg. Confirm by 149. 
 
 (c) Chromic Acid. 
 To the filtrate from the As^S, in (5), add NH^OH till 
 alkaline. (See 163 and 89, 88, 92.) 
 
 (^) Carbonic Acid. 
 Add dilute HCl to a portion of the original solution and 
 pass the gas evolved through a solution of Ca(OH)2. (See 
 I59-) 
 
 {e) Hydrofluoric Acid. 
 Evaporate a portion of the original solution to dryness 
 and examine the powder obtained by 174. 
 
 (/) Hydrosulphuric Acid. 
 (See 180.) 
 
 (g) Nitric Acid. 
 To a portion of the original solution, add a slight excess 
 of Pb(C2H302)2. Filter and remove the excess of Pb from the 
 filtrate with dilute HjSOi. Concentrate the filtrate and 
 examine according to 182. 
 
 (Ji) Acetic Acid. 
 To a portion of the original solution, add a slight excess 
 of Pb(N03)j. Filter and examine the filtrate by 141 or 
 142. 
 
48 
 
 Treat the remainder of the original solution in the following 
 manner; — 
 
 Dilute the solution, warm and saturate -witli HjS. Reject 
 the precipitate, and to the filtrate add an excess of NajCOj. 
 Boil and filter. Reject the precipitate as before, neutral- 
 ize the filtrate with HNO3, and examine the solution for the 
 remaining acids as indicated below. 
 
 (?) Boric Acid. 
 
 Examine a portion of the solution according to 154, or 
 evaporate a portion to dryness and examine according to 155 
 or 156. 
 
 (7) Hydriodic Acid. — {k) Hydrobromic Acid. 
 
 Examine a portion of the solution according to 177 and 
 165. 
 
 (/) Hydrochloric Acid. 
 
 Examine a portion of the solution according to 167, or, 
 preferably, 
 
 Evaporate a portion of the solution and examine according 
 to 168. 
 
 (»«) Hydrocyanic Acid. 
 
 To a portion of the solution add concentrated HjSO^, warm 
 gently and pass the gas evolved into KOH. Examine this 
 solution according to 171 or 172. 
 
 (w) Oxalic Acid. 
 
 Acidify a portion of the solution with acetic acid and add 
 CaCl^. (See 185.; 
 
 This precipitate on ignition forms CaCOj, which effervesces 
 with acid. 
 
 Evaporate a portion of the solution and examine accord- 
 ing to 186. 
 
 ((?) Phosphoric Acid. 
 Examine a portion according to 190 or 191 (in absence of 
 silicic acid). 
 
49 
 
 (/) Siwcrc Acir. 
 Evaporate a portion of the solution to dryness and examine 
 according to 194. 
 
 {q) SutPHURic Acid. 
 Examine a portion of the solution according to 195, or 
 evaporate to dryness and examine according to 196. 
 
 (r) Tartaric Acid. 
 Evaporate a portion of the solution to dryness and examine 
 according to 200. 
 
 Notes on Analysis of the Acids. 
 
 I. NajCOj is used to precipitate the bases before the 
 examination for certain acids. Arsenic and arsenious com- 
 pounds are not removed by this treatment. In the presence 
 of organic acids or ammonium salts, certain metals, such as 
 Cu, Hg, Fe, etc. , are not removed by this treatment; hence 
 the first treatment with HjS, by means of which the above 
 are removed as sulphides. 
 
 II. Chromic acid compounds are reduced by H^S to 
 chromium salts. The change in color from yellow or red of 
 the chromate to green or purple of the chromium salt is 
 characteristic, and the resultant solution answers to any of 
 the regular tests for chromium salts. 
 
 III. HCN produces a turbidity in lime water similar to that 
 produced by COj. (See CI.) In case this acid is present, add 
 an excess of AgNOj, whereby both the AgCN and AgjCOj 
 are precipitated. Shake and allow precipitate to settle. 
 Decant the clear liquid. On adding HNO3 dilute to the pre- 
 cipitate, the carbonate dissolves with effervescence, setting 
 free CO,. The cyanide is unaffected. 
 
 IV. Before testing for HNO3, the addition of PbCC^HsOj), 
 
 effects the removal of chromates, bromides, and iodides. 
 4 
 
so 
 
 The first of these would be reduced by the FeSO^+HjSO, 
 to a dark-colored solution, while the bromides and iodides 
 would yield bromine and iodine, which would give mis- 
 leading indications. Before examining for HC2H3O2, 
 Pb(N0s)2 is added to effect the removal of the same sub- 
 stances which also interfere with the examination for this 
 acid. Chromic acid, bromine, and iodine, being oxidizing 
 agents, prevent the formation of the ethyl acetate, and are 
 therefore removed. 
 
 V. When a dry chloride mixed with dry K^CrjO, is 
 moistened with concentrated HjSOj, CrOjClj, a blood-red 
 gas is given off. Bromides and iodides do not form 
 analogous compounds. They are decomposed by concen- 
 trated HjSO,, setting free bromine and iodine respectively. 
 These colored vapors might easily be mistaken for the gas 
 CrOjCla, hence the subsequent treatment with ammonia, 
 the formation of a chromate with its characteristic yellow 
 color, and precipitations yielded by such metals as Pb. The 
 bromine and iodine dissolve in the NH^OH with the forma- 
 tion of colorless compounds. 
 
 VI. In examining for phosphoric acid with (NHj^HMoOj, 
 silicic acid should be absent, as it forms a similar yellow 
 precipitate. If silicic acid is present, it should be removed 
 by 193. 
 
 VII. Tartaric acid is decomposed on ignition with black- 
 ening; acetic and oxalic acids decompose without blackening. 
 Organic matter, such as dust accumulated from the air, or 
 filter paper, decomposes with blackening, but without the 
 characteristic odor of " burnt sugar." 
 
 VIII. All solid sulphides heated in air or oxygen yield 
 SO,. 
 
51 
 Solubility of the Metals in the Common Mineral Acids. 
 
 HCl, HNO,, H,SO,. . 
 
 1. HNO3 is the general solvent for the metals. All the 
 metals dissolve in this acid, with evolution of nitrogen 
 oxides, with the exception of Sn and Sb, which form 
 insoluble oxides, and Au and Pt, which are unaffected. 
 
 2. HCl is not so general a solvent for the metals. 
 
 Cd, As, Sn, Fe, Al, Cu, Mn, Zn and fourth and fifth 
 group metals dissolve in HCl. 
 Ni and Co are slowly attacked. 
 Sb is dissolved with difficulty in concentrated HCl. 
 
 3. H2SO4, dilute, dissolves the same metals given above 
 (excepting Sn), with the evolution of Hydrogen gas. 
 
 H2SO4, concentrated, hot, dissolves Ag, Cu, Bi, Hg and 
 heavy metals generally with the evolution of SOj gas. 
 
 The metals easily dissolved by dilute HjSO^ are, as a rule, 
 unaffected by cold concentrated HjSOj. Boiled with con- 
 centrated H2SO4, they are dissolved with the evolution of 
 SO2 gas. 
 
 4. A mixture of concentrated HCl and concentrated HNO3, 
 termed aqua regia, is the solvent for gold and platinum. 
 They dissolve forming chlorides. 
 
52 
 
 
 a = soluble in water. 
 
 b = soluble in acids. 
 
 c = insoluble in acids. 
 
 ab = sparingly soluble in 
 water. 
 
 be = sparingly soluble in 
 acids. 
 
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S3 
 A. Treatment of a Solid {not a Metal or Alloy) . 
 
 (a) Kxtract all substances soluble in boiling water. 
 
 Ascertain the reaction of this solution with litmus paper. 
 Analyze a portion of the solution for the bases, in the usual 
 manner. 
 
 According to the bases found to be present, examine the 
 remainder of the solution for the acids which can be present. 
 (See Table of Solubilities.) 
 
 {S) From the residue from (a), extract all substances 
 soluble in HCl, dilute and concentrated, hot and cold. 
 
 Analyze a portion of this solution for the bases in the 
 usual manner. 
 
 Ascertain what acids can be present (see Table of Solu- 
 bilities) and examine the remainder of the solution for these. 
 
 (c) From the residue from {b), extract all substances 
 soluble in HNO3, dilute and concentrated, hot and cold. 
 
 Analyze a portion of this solution for the bases in the 
 usual manner. 
 
 Ascertain what acids can be present (see Table of Solu- 
 bilities) and examine the remainder of the solution for these. 
 
 (d) From the residue from (c), extract all substances 
 soluble in aqua regia (3 parts concentrated HCl, -|- i part 
 concentrated HNO3). Proceed as before. 
 
 (e) From the residue from (d), extract all substances 
 soluble in NH4OH. Examine for silver salts. 
 
 (/) From the residue from (e), extract all substances 
 soluble in KOH or NaOH. 
 Examine for Pb or Sn compounds. 
 
 {g) Fuse residue from (/) + NaKCOs in iron crucible. 
 Extract with water and examine solution for silicates and 
 sulphate. Residue heat -1- HC^HjOj. Solution. Examine for 
 Ba -f- Sr. Residue fuse -\- KHSO^ on Pt. Dissolve in water 
 and examine solution for Fe, Al, Cr. 
 
54 
 B. Treatment of a Solid (a Metal or Alloy) . 
 
 Reduce the alloy to small fragments. 
 
 Place in a porcelain dish and warm + concentrated HNOj 
 (use not more than i gram of the" alloy). 
 
 Repeat the treatment with acid, if necessary, until no 
 metallic particles remain. Evaporate to dryness. Add 
 water containing a little HNO,, filter, wash. 
 
 Residue: Oxides of Sb and Sn heat + hot concentrated 
 HjC^HiOg. Solution. Examine for Sb by 64. If residue 
 remains, examine for Sn by fusing + NajCO, + S, extract- 
 ing Na^SuSs with water, and examining solution for Sn by 
 58. 
 
 Examine the HNO3 solution from the residue of Sb and 
 Sn oxides for first, second, and third groups. (Fourth and 
 fifth group metals are rarely found in alloys.) 
 
 Note (i). — If Au and Pt are present, they will be found 
 with the residue of Sb and Sn oxides, as they are insoluble 
 in HNO3. Suspend the residue in a little water, add bromine 
 water, and warm gently. When the Au and Pt are dissolved, 
 filter. Examine the residue for Sb and Sn as before. Divide 
 the filtrate into two portions. Boil out excess of bromine. 
 Examine one portion for Au by precipitation with FeSOj or 
 oxalic acid. Examine the other portion for Pt by addition 
 KBr. Evaporate and add alcohol. Precipitate = KjPtBrj. 
 
 Note (2). — If the alloy contains phosphorus, it will be 
 found in the residue from the HNO3 treatment, combined as 
 stannic phosphate. The fusion with the NajCOj + S will 
 give NajSnSs and NajPO^. On acidifying this with acid, 
 SnSj will be precipitated and the solution will contain HaPO^. 
 Examine this solution for phosphoric acid. (See 191.) 
 
Questions in Qualitative Analysis. 
 
 1. A solution having an alkaline reaction is precipitated 
 
 ■with dilute HCl. What may the precipitate con- 
 tain ? How would the ordinary course of analysis 
 be modified ? 
 
 2. What would be the effect of precipitating the metals 
 
 with HjS, without removal of the first group with 
 HCl ? Give a scheme for the separation of the pre- 
 cipitate obtained. 
 
 3. Agl and AgjPO^ are both yellow. How would you dis- 
 
 tinguish between them ? Pblj and PbCrOi ? 
 
 4. A precipitate consisting of a mixture of AgCl, PbClj 
 
 and HgjCla is exhausted with NH^OH. The insolu- 
 ble residue is treated with boiling HjO, but no lead 
 can be detected in the solution. Why ? 
 
 5. Given a solution containing arsenious and arsenic com- 
 
 pounds, how would you detect each ? likewise in a 
 solution containing stannous and stannic compounds, 
 how would each be detected ? 
 
 6. Explain the action of the following reducing agents: 
 
 Nascent hydrogen, hydrogen gas + heat, H^S, SO2, 
 C, Fe. Give examples. 
 
 7. Explain the action of the following oxidizing agents, 
 
 stating the conditions under which they are used: 
 HNO3, CI, Br, I, KNO3, KCIO3, KCIO, K^MnA. 
 KjCr^O,. Give examples. 
 
 8. Convert a stannous into a stannic salt, by the use 
 
 of yellow ammonium sulphide, and explain the 
 action. 
 
 (55) 
 
56 
 
 g. Two yellow solutions which contain no HNOg are 
 treated with HjS, sulphur separates in each case. 
 («) The solution becomes colorless. 
 {S) The solution becomes green. 
 What are your inferences ? Proofs ? 
 
 ID. A solution has not been made acid with HCl before the 
 precipitation by HjS. At the moment of the intro- 
 duction of the HjS, a white precipitate appears. 
 What may it be ? 
 
 11. What would be the effect of an excessive amount of 
 
 HCl, HNO3 or HjSOi before the addition of H^S? 
 How could these undesirable conditions be rectified ? 
 
 12. What would be the effect of allowing the precipitated 
 
 sulphides of the second group to stand some time 
 before analysis; of washing them with pure water ? 
 
 13. A solution made by mixing aqueous solutions of the 
 
 chlorides of the metals, contains a white precipitate. 
 What may it be ? Prove it. 
 
 14. A mixture of the sulphides of the second group is 
 
 treated with concentrated HNO3. An insoluble resi- 
 due remains. What may it contain? Analyze it. 
 
 15. After Pb had been removed in the second group with 
 
 H,SO« NH^OH was added. The white flocculent 
 precipitate obtained was dissolved in HCl and water 
 added. No precipitate was obtained. Why? 
 
 16. In the separation of As^Sg, Sb^Sj, SnSj, with concen- 
 
 trated HCl, why cannot a portion of the solution be 
 examined directly for Sn by adding HgCl^ instead of 
 using the method given ? 
 
 17. Account for the occurrence of Pb in different parts of 
 
 the scheme of analysis. 
 
57 
 
 i8. If Cd is not completely removed in the second group, 
 where will it be found? Why? How can its pres- 
 ence be proved ? Under what conditions is Cd not 
 removed in the second group ? 
 
 19. A solution containing Fe (ferric), Al, Cr, Mn, Zn, Ni, 
 
 Co salts, is treated with NH^OH + NH.Cl. What is 
 the precipitate obtained? Analyze it. Use KOH 
 instead of NH.OH + NH.Cl. What is the re- 
 sult? 
 If an insufficient quantity of NH4CI were added, what 
 would be the result ? 
 
 What would be the effect if, after the addition of the 
 NH4OH and NH^Cl, the whole were allowed to stand 
 before analysis ? 
 
 20. The third group precipitate is washed with pure water; 
 
 what is the effect ? 
 
 21. What would be the effect of allowing the precipitated 
 
 sulphides of the third group to stand some time 
 before analysis ? 
 
 22. Which is preferable for the precipitation of the third 
 
 group, colorless or yellow ammonium sulphide ? 
 Why? 
 
 23. In separating the precipitate containing the third group, 
 
 with HCl, what would be the effect if the filtrate were 
 not boiled to expel the H^S ? 
 
 24. When the residue consisting of FejCOH)^ and 
 
 MnjO,(OH)3 is dissolved in HCl, why is CI given 
 off, and why is it boiled out ? What would be the 
 effect if it were not boiled out ? 
 
 25. What would be the result if a solution containing 
 
 phosphates and oxalates were analyzed by the regular 
 scheme of analysis instead of by the special scheme ? 
 Do these acids interfere with the analysis of the first 
 and second groups ? 
 
58 
 
 26. Take a solution containing the members of the first, 
 
 second and third groups. First add NH^OH to alka- 
 line reaction. Second, add it in excess. State the 
 effect in each case. Use KOH similarly. What is 
 the effect in each case ? 
 
 27. "Why is the precipitation of the fourth group with 
 
 (NHJ2C2O4 to be preferred to that by (NHJjCO,? 
 
 28. Why must this precipitate be ignited before proceeding 
 
 with the analysis? 
 
 29. What would be the effect of a solution of CaSOi on a 
 
 solution of BaClj ? 
 SrCl,? 
 CaCl,? 
 
 30. Given a solution containing BaClj, SrClj, CaClj. Analyze 
 
 it with the use of CJIfiK. 
 
 31. Why is magnesium found in the fifth group and not in 
 
 the fourth ? 
 
 32. Why are NH^ compounds tested for in the original 
 
 solution and not in the fifth group ? 
 
 33. An acid solution containing ammonium salts was treated 
 
 with NaOH and boiled, but no odor of NH3 was 
 developed. Why ? 
 
 34. What would be the effect of incomplete precipitation and 
 
 incomplete washing of precipitates ? 
 
 35. If the members of the various groups are incompletely 
 
 precipitated by the group reagents, state where each 
 member, so lost, will be found in the course of the 
 regular scheme of analysis used. 
 
 36. What is the action of HNO3 on metals generally? 
 
 What is the action of aqua regia? How do the 
 products resulting from the action of HNO3 differ 
 
59 
 
 from those resulting from the action of aqua regia? 
 Why does aqua regia dissolve Au and Pt while HCl 
 or HNO3 does not ? 
 
 37. Red oxide of lead is not dissolved by water nor HNO3, 
 
 but on the addition of a small quantity of solution of 
 KNOj or HjCjOj to the HNO3 it is dissolved. Ex- 
 plain the action. 
 
 38. Fe^Oj, Cr^Og, Al^Os, after ignition at a high heat, are 
 
 practically insoluble in acids. Given the following 
 
 fluxes: 
 Na,COs, KNO3, KHSO,, NaBO,, 
 How could these oxides be brought into solution ? State 
 
 reasons. 
 
 39. Describe several ways of proving whether a powder 
 
 under examination is an oxide. 
 State in what cases each method can be used. Give 
 examples. 
 
 40. A powder given for analysis evolves oxygen on being 
 
 heated. Does this fact necessarily demonstrate the 
 presence of certain oxides ? Draw up a list of the 
 substances that yield oxygen on being heated. 
 
 41. On treating a powder with HCl and heating, CI is 
 
 evolved. Give a list of the substances which would 
 cause this. 
 
 42. A dry substance is heated in a glass tube closed at one 
 
 end. 
 (a) I^iquid condenses in the cool part. 
 
 1. It is neutral. 
 
 2. It is alkaline. 
 
 3. It is acid. 
 
 (i) Gases or fumes are given off. 
 
 1. O is evolved. 
 
 2. CO2 is evolved. 
 
 3. NOj is evolved. 
 
6o 
 
 (c) Sublimate is formed. 
 
 1. Hg. 
 
 2. S. 
 
 (d) Residue blackens. 
 
 State what substances are indicated by each result. 
 
 43. A powder submitted for analysis was: — 
 
 1. Heated on charcoal with NajCO., in reducing and 
 
 oxidizing flames. 
 
 2. Heated on charcoal with Co(N03)2. 
 
 3. Borax and microcosmic salt beads were made 
 
 with it. 
 
 4. HCl and Pt wire (flame test). 
 Give all deductions. 
 
 44. A solution containing no acetic acid, but a quantity of 
 
 KjCrjO,, or some other oxidizing agent, gives, on 
 testing for acetic acid by means CjHjOH and HjSOj, 
 a peculiar odor. To what is it due ? 
 
 45. In examining for HjAsOj by (a), analysis of the acids, 
 
 why is the precipitate obtained still further tested for 
 arsenic ? Why is not the formation of this precipi- 
 tate sufficient evidence ? 
 
 46. Could a yellow precipitate formed in testing for HjAsOj 
 
 in (^) be sulphur ? Why not ? 
 
 47. A solution containing Cu was tested for boric acid by 
 
 155. Was the test conclusive ? Would you suggest 
 a modification ? 
 
 48. Under what conditions is it necessary to test a solution 
 
 having an acid reaction for carbonates ? 
 
 49. A solution was found to contain sulphides. It was sub- 
 
 sequently tested for chromic acid. Was it found ? 
 State reasons. 
 
6i 
 
 50. Under what conditions does silver nitrate fail to preci- 
 
 pitate CI, Br, and I from compounds containing 
 them? 
 
 51. How would you determine the presence of HCl, HBr, 
 
 and HI in the cases of one, two, or all three of these 
 acids being present ? State reasons. 
 
 52. Given a solution containing free bromine and iodine, 
 
 how could this solution be examined for HBr and 
 HI? 
 
 53. Explain how the formation of Prussian blue in 171 is 
 
 an evidence of HCN. 
 
 54. Is it rational to examine for HF, in solutions kept in 
 
 glass vessels ? Why ? 
 
 55. Under what conditions may a solution contain sul- 
 
 phides ? What would be the reaction of this solution 
 toward litmus paper ? 
 What metals could be found in a solution containing 
 sulphides ? 
 
 56. How could a solution or a substance containing sul- 
 
 phides and sulphates be examined for each ? 
 
 57. Is it necessary to examine a substance which is insoluble 
 
 in water for the presence of nitrates ? 
 
 58. Oxalates and carbonates when treated with concentra- 
 
 ted H2SO4 both yield COj. How can you distinguish 
 between these acids by this test ? 
 
 59. Under what conditions would you examine a neutral 
 
 aqueous solution for phosphates ? 
 
 60. An insoluble silicate is fused with KHSO4 and the fused 
 
 mass is extracted with water. Where will the silica 
 be found? Why? 
 
62 
 
 6i, A solution which is acid with HCl, is treated with 
 BaClj. Is the white precipitate produced necessarily 
 a sure indication of H^SO^ ? 
 
 62. In what case may BaSO^ be found in a solution ? 
 
 63. The residue left on the evaporation of a solution con- 
 
 taining no carbonates, shows carbonates after igni- 
 tion. To what may this be due ?