Copper ferricyanide, Cu₃[Fe(CN)₆]₂

Copper ferricyanide, Cu₃[Fe(CN)₆]₂, is a greenish brown precipitate obtained on mixing solutions of copper sulphate and potassium ferricyanide. The precipitate has a constant composition, no matter what relative proportions of the two salts are used.

If ammoniacal cupric hydroxide is added to potassium ferricyanide the pent-ammoniate, Cu₃[Fe(CN)₆]₂.5NH₃, is obtained as black, stable crystals. The salt Cu₃[Fe(CN)₆]₂.16NH₃ has also been obtained.