Qualitative analysis / by William Briggs and R.W. Stewart.

  • William Briggs
Date:
1913
Catalogue details

Licence: Public Domain Mark

Credit: Qualitative analysis / by William Briggs and R.W. Stewart. Source: Wellcome Collection.

    112/180 (page 96)
    NOTES ON THE SEPAKATION OF THE METALS INTO GKOUPS. The separation of the metals into groups depends upon the following facts :— Group I.—The insolubility of AgCl, PbCl2, Hg2Cl2, all other chlorides being soluble. Group II.—The insolubility of the following sulphides in dilute hydrochloric acid:—HgS, PbS, Bi2S3, CuS, CdS, As2S3, Sb2S3, Sb2S3, SnS2, SnS. Group II. (b).—The solubility of As2S3, Sb2S3, SnS2> SnS, in yellow ammonium sulphide or in caustic alkalies -f Na202. Group III.—The precipitation of Fe(OH)3, Al(OH)3, Cr(OH)3, on the addition of NH4C1 and NH4OH. Group IV.—The insolubility of CoS, NiS, ZnS, MnS in an alkaline (or neutral) solution. Group Y.—The insolubility of CaC03, SrC03, I>aC03, in an alkaline (or neutral) solution. The following points should be carefully noted:— Group I.—The hydrochloric acid must not be too strong, or barium chloride (BaCl2), which is insoluble in strong HC1, may be precipitated. The precipitate in this case dissolves readily on adding water. Group II.—It is well to dilute considerably before passing II2S; mineral acids, especially nitric, unless greatly, diluted, are likely to interfere. Cadmium, in particular, is difficult to precipitate in a strongly acid solution, and might pass forward to Group III., where it would be thrown down as a yellow sulphide on the addition of ammonium hydroxide. Antimony also is often kept in solution by hot moderately strong HC1; addition of water brings about precipitation. On passing sulphuretted hydrogen through the solution