Barium potassium ferricyanide, BaKFe(CN)₆

Barium potassium ferricyanide, BaKFe(CN)₆.4H₂O, first isolated by Bette, who regarded it as a trihydrate, is conveniently prepared by addition of the requisite quantity of potassium sulphate to a solution of barium ferricyanide and allowing the filtered liquid to evaporate.