DISPROPORTIONATION OF ZN(H2PO4)(2)CENTER-DOT-2H2O CRYSTALS (TOPOCHEMICAL PARTICULARITIES)

The topochemical transformations of Zn(H2PO4)(2) . 2H(2)O crystals in the medium of acetone, ethanol, and diethyl ether have been studied by chemical analysis and X-ray powder diffraction methods in the tempera ture range of 0-40 degrees C. It was established that under these cond itions crystalline zinc hydrophosphate monohydrate (ZnHPO4 . H2O) and going into a liquid phase phosphoric acid were formed, The influence o f the chemical nature of the organic solvent, the residual quantities of water in it, the size of the initial crystals on localization parti cularities, and kinetics of the disproportionation process has been co nsidered. The mechanism of the process which includes a solid-state pr oton transfer from one dihydrophosphate ion to another, the nucleation and growth of ZnHPO4 . H2O crystals, the removal of phosphoric acid a nd of part of crystallization water from the reaction zone has been pr oposed. The experimentally found values of activation energy E = 125-1 45 kJ/mol are related to the overall process, the limiting stage of wh ich is crystallization.