Ferroso-ferric chloride, Fe₃Cl₈

Ferroso-ferric chloride, Fe₃Cl₈.18H₂O, or FeCl₂.2FeCl₃.18H₂O, results when the corresponding oxide, Fe₃O₄, is dissolved in concentrated aqueous hydrogen chloride and evaporated over sulphuric acid. The salt separates out as a yellow crystalline mass, which readily deliquesces.