Dimagnesium phosphate

Dimagnesium phosphate is a compound with formula MgHPO4. It is a Mg2+ salt of monohydrogen phosphate. The trihydrate is well known, occurring as a mineral.

It can be formed by reaction of stoichiometric quantities of magnesium oxide with phosphoric acid.
 * MgO + H3PO4 → MgHPO4 + H2O

Dissolving monomagnesium phosphate in water, forms phosphoric acid and depositing a solid precipitate of dimagnesium phosphate trihydrate:
 * Mg(H2PO4)2 +  3 H2O  →   Mg(HPO4).3H2O  +  H3PO4

The compound is used as a nutritional supplement, especially for infants and athletes. Its E number is E343.