Topochemical transformations of Co(H2PO4)(2)center dot 2H(2)O in humid air

Topochemical transformations of Co(H2PO4)(2) . 2H(2)O in humid air were inv estigated by chemical analysis, x-ray diffraction, gravimetry, and optical microscopy. Isothermal holding at temperatures between 35 and 95 degrees C is accompanied by the formation of crystalline CoHPO4 . 3H(2)O, acid libera tion, and water uptake. The temperature and humidity ranges are determined in which the process takes place in the solid phase. The proton conductivit y of the product thus obtained is three orders of magnitude higher than tha t of the parent cobalt dihydrogen phosphate.