DEHYDRATIONS OF CA(H2PO4)2-H2O AND MG(H2PO4)2-2H2O AND THEIR REACTIONS WITH KCL, EXAMINED WITH SIMULTANEOUS TG, DTG, DTA AND EGA

The dehydrations of Ca(H2PO4)2·H2O and Mg(H2PO4)2 H2O were examined with a simultaneous TG, DTG, DTA and EGA method, partly under conventional, and partly under quasi-isothermal and quasi-isobaric conditions. It was found among others that the dehydrations of the examined compounds took place gradually between 100 and 500°, a series of intermediates being formed. The end-products were [Ca(PO3)2]3 and Mg(PO3)2. The reactions of these hydrates with KCl were also examined. The many subsequent part reactions could be described by the following overall equation: 3 Ca(H2PO4)2 + 2 KCl=Ca2P2O7 + Ca(PO3)2 + 2 KPO3 + 2 HCl + 5 H2O It is noteworthy that the reactions do not lead to the formation of orthophosphates, but stop after the liberation of 2 moles of HCl. © 1979 Wiley Heyden Ltd., Chichester and Akadémiai Kiadó, Budapest.