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

[p244]

The higher sulphides of the arsenic group, and arsenious and antimonious sulphides among the lower ones, combine with the alkali sulphides to form soluble alkali salts of sulpho-acids, in the same way as carbon bisulphide does. In the case of arsenious sulphide, for instance, we have the action

As₂S₃ + (NH₄)₂S ⇄ 2 NH₄AsS₂.

(4)

The salt, ammonium sulpharsenite, is ionized as follows:

NH₄AsS₂ ⇄ NH₄⁺ + AsS₂⁻.

Sulpho-Acids.

2 HAsS₂ ⥂ As₂ S₃ ↓ + H₂S ↑.

This instability of the sulpho-acids is entirely analogous to the instability of the metal hydrosulphides (p. [203]) and to the instability of certain oxygen acids, notably of carbonic acid. Sulpho-carbonic acid, H₂CS₃, is the best-known free acid of this type. It may be precipitated, undecomposed, as an oil, and its gradual decomposition into hydrogen sulphide and carbon disulphide may be observed.

Sulpho-Bases.