Pentachlorferrates, M₂FeCl₅

Ammonium pentachlorferrate, (NH₄)₂FeCl₅.H₂O, associated with varying quantities of ammonium chloride, is known popularly as ammonio-chloride of iron. It is used medicinally, and is obtained as garnet cubes by crystallising from a solution of the mixed chlorides.

Caesium pentachlorferrate, Cs₂FeCl₅.H₂O, has been obtained as a red salt.

Potassium pentachlorferrate, K₂FeCl₅.H₂O, is obtained by dissolving ferric chloride in concentrated hydrochloric acid, adding potassium chloride, and allowing to crystallise. It is a red, deliquescent salt, decomposed by water.

Apparently no double salts with sodium exist, at any rate between 0° and 60° C.