Tetrachlorferrates, MFeCl₄

Ammonium tetrachlorferrate, NH₄FeCl₄, or FeCl₃.NH₄Cl, obtained by heating the two substances together, is interesting as possessing a definite boiling-point, namely 386° C. A salt of similar empirical composition has been obtained by crystallisation from mixed solutions of ferric chloride and ammonium chloride in the form of olive-brown needles, which, however, are unstable.

Caesium tetrachlorferrate, 2CsFeCl₄.H₂O, or possibly anhydrous, is extremely hygroscopic.

Cuprous tetrachlorferrate, CuFeCl₄, melts at 320° C. If crystallised from an aqueous solution, the tetrahydrate, CuFeCl₄.4H₂O, is obtained.