Mechanism of dehydration of Zn 0.5Mg 0.5(H 2PO 4) 2 · 2H 2O

Abstract

Thermal analyses under non-isothermal and under quasi-isothermal-isobaric conditions were used to follow the condensation reactions proceeding during the calcination of Zn 0.5Mg 0.5 (H 2PO 4) 2 · 2H 2O. Calcination in an electric oven under isothermal conditions was adopted for preparation of the intermediates and the main product, which were analysed by chromatography, IR spectroscopy, NMR spectroscopy, X-ray analysis, electron microscopy, and extraction experiments with solutions of water, acetone and 0.3 M HCl. The effect of water vapour pressure on the course of calcination has been monitored, in terms of the rate and yield of the condensation reactions and the formation of the main product and other products such as the new compound binary cyclotetraphosphate (tetrametaphosphate) ZnMgP 4O 12.