Dependence of kinetics of copper sulfate pentahydrate dehydration on water vapor pressure

The dependence of the growth rate v_g of nuclei during CuSO ₄·5H ₂O dehydration upon water vapor pressure P_{H 2O} has been investigated. At small P_{H 2O} (less than 1 Torr at 50°C), v_g falls rapidly with decreasing P_{H 2O} , and simultaneously v_g anisotropy disappears. At P_{H 2O} = 1-9 Torr, v_g for elliptic and round nuclei is constant and independent of P_{H 2O} . The influence of initially keeping the samples in water vapor upon the kinetics of the following dehydration has been studied. Treatment by water vapor leads to slowing of dehydration and increasing its degree of transformation. On the basis of data obtained a kinetic interpretation of the Topley-Smith effect has been proposed.