The topochemical transformations of Zn(H 2 PO 4 ) 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 temperature range of 0-40°C. It was established that under these conditions crystalline zinc hydrophosphate monohydrate (ZnHPO 4 ‚H 2 O) and going into a liquid phase phosphoric acid were formed. The influence of the chemical nature of the organic solvent, the residual quantities of water in it, the size of the initial crystals on localization particularities, and kinetics of the disproportionation process has been considered. The mechanism of the process which includes a solid-state proton transfer from one dihydrophosphate ion to another, the nucleation and growth of ZnHPO 4 ‚H 2 O crystals, the removal of phosphoric acid and of part of crystallization water from the reaction zone has been proposed. The experimentally found values of activation energy E ) 125-145 kJ/mol are related to the overall process, the limiting stage of which is crystallization.

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