Tri-nickel Tetrasulphide, Ni₃S₄

Tri-nickel Tetrasulphide, Ni₃S₄, results when metallic nickel is heated either with sulphurous acid or a solution of nickel sulphite to 200° C. under pressure. Its existence as a separate chemical entity is indicated by the shape of the freezing-point curves of nickel sulphides.