Aluminium ammonium ferrocyanide, Al(NH₄)Fe(CN)₆

Aluminium ammonium ferrocyanide, Al(NH₄)Fe(CN)₆.4H₂O, is formed as a jelly on mixing equivalent solutions of aluminium chloride and ammonium ferrocyanide. The salt is difficult to isolate, but is obtained as a precipitate by centrifugating at 3000 revolutions per minute. The precipitate is washed with acetone and ether and dried in vacuo. It resembles the potassium salt in appearance, being dark green and transparent in lumps, but a light bluish green when powdered. At 100° C. it becomes anhydrous and assumes a deep blue colour.