Orthophosphates. Part VIII. The transformation of newberryite into bobierrite in aqueous alkaline solutions

Abstract

Newberryite, MgHPO4,3H2O, was transformed in aqueous solutions of NaOH into bobierrite, Mg3(PO4)2,8H2O. A competing transformation in a solution which was 10–1M in both NaOH and NaF is the formation of magnesium fluoroapatite Mg5F(PO4)3. The nature of the reactions are discussed and ΔG°f values for Mg3(PO4)3,8H2O. MgHPO4,3H2O, Mg5F(PO4)3, Mg5OH(PO4)3, Mg(H2PO4)2, Mg(H2PO4)2,2H2O, Mg(H2PO4)2,4H2O, Mg4O(PO4)2, and Mg2F(PO4)2 have been calculated as –1302·7, –549·0, –1399·2. –1376·2, –652·5, –764·9, –878·2, –997·3 and –551·0 kcal mol–1 respectively. The nature of the stability relationships existing between the orthophosphate phases has been determined.