Potassium aluminium ferrocyanide, KAlFe(CN)₆

Considerable difficulty attends the preparation of Potassium aluminium ferrocyanide, KAlFe(CN)₆.4H₂O, which forms a jelly on mixing equivalent solutions of aluminium chloride and potassium ferrocyanide. By centrifugating at 3000 revolutions per minute it may be isolated as a precipitate, washed with acetone and ether, and dried in vacuo. The salt is dark green, and transparent when in bulk, but when powdered is light bluish green. At 100° C. it becomes anhydrous and assumes a deep blue colour.