Thermal stability of zinc pyrophosphate and potassium zinc pyrophosphates

Abstract

The behavior during heating of Zn2P2O7.5H2O (I), K2Zn3(P2O7)2.3H2O (II), K2ZnP2O7.2H2O (III), and K6Zn(P2O7)2.10H2O (IV) was studied by chem. and thermal anal. methods, chromatog., IR spectra, and x-ray phase anal. The dehydration of I occurs in 2 steps with the loss of 2 and 3 mols. H2O at 85 and 137°. Amorphous Zn2P2O7 is converted to cryst. Zn2P2O7 at 480° which melts at 980°. Dehydration of II occurs in one step at 280° with the transformation of amorphous to cryst. K2Zn3(P2O7)2 at 450° which melts at 780°. Dehydration of III occurs at 138° and cryst. K2ZnP2O7 undergoes a polymorphic conversion at 240°, a substance which melts at 640°. Dehydration of IV occurs in 4 steps at 105, 160, 220, and 260° and cryst. K6Zn(P2O7)2 melts at 585°.