Sodium cuproferrocyanide, Na₂Cu₂Fe(CN)₆

Sodium cuproferrocyanide, Na₂Cu₂Fe(CN)₆, results on adding a cold, saturated solution of sodium copper cyanide to a hot solution of sodium ferrocyanide; or by boiling a solution of sodium ferrocyanide with cuprous cyanide in the presence of a little sodium sulphite, and cooling in an atmosphere of hydrogen. It crystallises in minute, colourless hexagonal prisms, which are conveniently dried over sulphuric acid in a vacuum.

It retains 27.5 per cent, of water. In air it slowly oxidises, turning brown. It is insoluble in water, alcohol, and ether.