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. |