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

[281] J. für prakt. Chem., 25, 431 (1882).

[282] The suspension used is prepared by saturating, with hydrogen sulphide, an aqueous solution of arsenious oxide. The latter is saturated on a steam bath, cooled to 20°, filtered and diluted with an equal volume of water before it is used.

[283] Eight grams of NH₄NO₃ per 100 c.c.

[284] 0.6 c.c. of a tenth-normal solution is used, containing 1.28 gram Mg(NO₃)₂, 6 aq., in 100 c.c. Precipitation was found to be incomplete with 0.5 c.c.

[285] 0.15 c.c. of a tenth-normal solution is used, containing 1.2 gram Al(NO₃)₃, 4 aq., in 100 c.c. Precipitation was found to be incomplete with 0.1 c.c. of the solution.

[286] 3.3 grams (NH₄)₂SO₄ in 100 c.c.

[287] Freundlich found, for instance, that NaCl, KCl, BaCl₂, in equivalent concentrations, had practically the same effect on colloidal ferric hydroxide, but only one-fortieth as much of a sulphate (the precipitating ion is SO₄²⁻ versus Cl⁻) was required; Z. phys. Chem., 44, 129 (1903).

[288] For other reasons (e.g. to prevent oxidation of the sulphides), hydrogen sulphide is also used in the solution for washing the arsenic group, and ammonium sulphide in that for the zinc group (see Lab. Manual, pp. 101 and 110).

[289] Picton and Linder, loc. cit., and Whitney and Ober, loc. cit.

[290] A. A. Noyes describes a similar experiment with sodium chloride and silver nitrate, loc. cit.