Monomagnesium phosphate is one of the forms of magnesium phosphate. It is a magnesium acid salt of phosphoric acid with the chemical formula Mg(H2PO4)2.Di- and tetrahydrates are known also. It dissolves in water, forming phosphoric acid and depositing a solid precipitate of Mg(HPO4)·3H2O, dimagnesium phosphate.
As a food additive, it is used as an acidity regulator and has the E number E343.
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