Potassium magnesium ferrocyanide, K₂MgFe(CN)₆

Potassium magnesium ferrocyanide, K₂MgFe(CN)₆, is obtained in the anhydrous condition by mixing cold concentrated solutions of potassium ferrocyanide and magnesium chloride. After a short time a white micro-crystalline precipitate is formed, which is not affected by heating to 120° C. When moist the salt soon becomes cream-coloured, owing to slight decomposition, possibly under the influence of atmospheric carbon dioxide.

A saturated aqueous solution of the salt contains 1.95 grams per litre.

The heptahydrate, 2K₂MgFe(CN)₆.7H₂O, is prepared by mixing dilute solutions of potassium ferrocyanide and magnesium chloride at the boiling-point.