Magnesium Metaphosphate, Mg(PO₃)₂

Magnesium Metaphosphate, Mg(PO₃)₂, is obtained, by heating magnesium carbonate at 316° C. with excess of phosphoric acid, as an anhydrous powder which is insoluble in water, little soluble in dilute acids, and soluble in concentrated sulphuric acid. The tetrahydrate was obtained by adding alcohol to a solution of a magnesium salt and ammonium metaphosphate.