Nickel Sulphite, NiSO₃

Nickel Sulphite, NiSO₃, may be prepared in two stages of hydration. The hexahydrate, NiSO₃.6H₂O, crystallises in tetrahedra on evaporating a solution of monoxide in aqueous sulphurous acid in the cold over sulphuric acid. If, on the other hand, the solution is concentrated on the water-bath, the tetrahydrate, NiSO₃.4H₂O, separates out as a green crystalline mass.

The salt readily oxidises in solution. It dissolves in ammonia, yielding a blue crystalline hydrated triammoniate, NiSO₃.3H₂O.3NH₃. A basic sulphite is obtained by addition of sodium sulphite to a solution of a nickel salt, and warming. With ammonium sulphite a green, crystalline precipitate of Nickel Ammonium Sulphite, (NH₄)₂SO₃.3NiSO₃.18H₂O, is obtained.