THE SYSTEM MGO-P2O5-H2O AT 25-DEGREES-C

The phase diagram for the ternary system MgO-P2O5-H2O at 25-degrees-C has been constructed. The magnesium phosphates represented are Mg(H2PO 4)2.nH2O (n = 4, 2, 0), MgHPO4.3H2O, and Mg3(PO4)2.mH2O (m = 8, 22). B ecause of the large differences in the solubilities of these compounds , the technique which involves plotting the mole fractions of MgO and P2O5 as their 10th roots has been employed. With the exception of MgHP O4.3H2O, the magnesium phosphates are incongruently soluble. Because i ncongruency is associated with a peritectic-like reaction, the phase M g2(PO4)3.8H2O persists metastably for an extended period.