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.

    40/180 (page 24)
    6. Repeat reactions 5 and 6 for Hg\ Similar results will be obtained. Mercuric chloride, HgCl2 (corrosive siAlimate) is the most important •soluble mercuric salt. Mercuric nitrate, Hg(N03)2, is also soluble, but the salt is unstable, and when in solution tends to form insoluble basic salts. LEAD, Pb. Unless the solution be very dilute, lead is usually detected in Group I. If not so detected, a black precipitate of lead sulphide, PbS, will be obtained on addition of H2S in Group II., if the solution be not too acid. For this reason, if there is a doubtful indication of a precipitate in Group I., and lead is suspected from preliminary exami¬ nation (see Chap, iv.), H2S should be passed through the original solution if that be acid, and not through the portion to which HC1 has been added. [This point is of importance in systematic analysis. On account of the slight solubility of PbCl2 in cold water, Pb is not completely precipitated in Group I. ; and if the solution be too acid, or too con¬ centrated, it is not precipitated at all in Group II., and therefore appears in Group III., where it is often mistaken for some other metal.] For other reactions of Lead, see Group I. BISMUTH, Bi. Solution—Bismuth Nitrate, Bi(N03)3, dissolved in dilute nitric acid. 1. Sulphuretted hydrogen gives a brownish-black preci¬ pitate of bismuth sulphide, Bi2S3. 3 H2S + 2 Bi(N03)3 = Bi2S3 + 6 HN03. The precipitate is soluble in hot dilute nitric acid, but insoluble in ammonium sulphide and in caustic alkalies. 2. Water added in large quantity to a solution of bismuth, to which ammonium chloride, NH4C1, has first been added, produces a white precipitate of a basic chloride, BiOCl, which is insoluble in tartaric acid. [Distinction from the basic chloride of antimony, Sb OCl, which is soluble in tartaric acid.] BiClg + HoO = BiOCl + 2 HC1.