Cadmium Sulphite, CdSO₃

When cadmium dissolves in aqueous sulphurous acid, cadmium sulphite and a yellow precipitate of cadmium sulphide are formed.

Crystals of anhydrous sulphite, CdSO₃, are obtained by dissolving cadmium carbonate in aqueous sulphurous acid and evaporating on the water-bath, or from hot mixed solutions of a cadmium salt and sodium sulphite.

A gelatinous dihydrate, CdSO₃.2H₂O, precipitates when alcohol is added to a solution of cadmium carbonate in aqueous sulphurous acid. It becomes crystalline on standing. The same hydrate is precipitated from mixed solutions of a cadmium salt and sodium sulphite at ordinary temperatures. Deniges said that he thus obtained crystals of a trihydrate.

Cadmium sulphite, anhydrous or hydrated, is difficultly soluble in water and readily in dilute acids.

Muspratt could not confirm the CdSO₃.NH₄ mentioned by Rammelsberg.