The Elements of Qualitative Chemical Analysis, vol. 1, parts 1 and 2. / With Special Consideration of the Application of the Laws of Equilibrium and of the Modern Theories of Solution.

by Julius Stieglitz

[498] See the discussion on p. [177]. See also the discussion by Remsen on acidic and basic halides, Am. Chem. J., 11, 300 (1889) Stud.

[499] In both cases acid salts, KHCO₃ and KHCS₃, are also formed.

[500] McCay, Z. anorg. Chem., 29, 36 (1901).

[501] On p. [238] the analogous equation for the condition of equilibrium of the anion of an oxygen acid with its components was developed. Applying the result to the ion SnO₃²⁻ of stannic acid, H₂SnO₃, we have:

[Sn⁴⁺] × [O²⁻]³ / [SnO₃²⁻] = K.

It is evident, from the form of the equation, that for the stronger oxygen acids, which are most stable as acids and ionize as bases at most in traces, the value of the constant must be extremely small.

[502] Mercuric sulphide is somewhat soluble in potassium and sodium sulphides, forming the salts Me₂HgS₂, and the complex ion HgS₂²⁻. A liter of 0.1 molar Na₂S dissolves, at 25°, 1.9 grams (0.0082 mole) of HgS [Knox, Trans. Faraday Society, 4, 36 (1908)]. While the oxide (hydroxide) shows no perceptible tendency toward acid ionization, mercuric salts, it will be recalled, show in many cases an abnormally small tendency to form the mercuric-ion (see p. [115]), and the latter also shows a particularly great tendency towards forming very stable complex ions of all kinds (e.g. HgI₄²⁻, in K₂HgI₄, HgCl₄²⁻ in K₂HgCl₄, Hg(CN)₄²⁻, etc.). Knox found for [Hg²⁺] × [S²⁻]² / [HgS₂²⁻] = k, the approximate value of k to be 1 / 10⁵³. Bismuth sulphide is also very sparingly soluble in sodium or potassium sulphide, but not in ammonium sulphide. Solid salts, KBiS₂ and NaBiS₂ are known [Knox, J. Chem. Soc. (London), 95, 1760 (1909)].

[503] See the table, p. [104].

[504] See the discussion of the reaction, given below.

[505] See Chap. XVI, for the interpretation of the reduction as an ionic reaction.