Ferrous dihydrogen orthophosphate, Fe(H₂PO₄)₂

Ferrous dihydrogen orthophosphate, Fe(H₂PO₄)₂.2H₂O. is obtained by dissolving iron in excess of phosphoric acid solution in a current of hydrogen gas. Excess of acid is removed by washing with ether, and the substance dried in hydrogen. Obtained in this way the salt is a white, crystalline powder, which readily oxidises in air, yielding a ferric salt. It is insoluble in alcohol, but readily dissolves in water.