Cobaltic Sulphite, Co₂(SO₃)₃

Cobaltic Sulphite, Co₂(SO₃)₃, has not been isolated, but apparently it can exist momentarily in solution. This was indicated by Meyer, who dissolved cobaltic hydroxide in sulphurous acid. At first a brown colour was produced, rapidly giving place to a rose-red tint which remained permanent even on boiling. The colour change is attributable to the formation of the unstable cobaltic sulphite which decomposes into cobaltous sulphite and dithionate respectively. Thus:

Co₂(SO₃)₃ = CoSO₃ + CoS₂O₆.

Stable double and complex cobaltic salts are known.