Kinetics of the Thermal Dehydration of Potassium Copper(II) Chloride Dihydrate

Article abstract of DOI:10.1021/j100335a036

Thermogravimetry (TG) complemented by differential scanning calorimetry (DSC) has been used to study the kinetics of the dehydration of powered and single-crystal samples of K2CuCl4*2H2O.The dehydration of single crystals was followed by observing, microscopically in polarized light, thin sections of the sample dehydrated to different fractions reacted, α.The mass-change traces for the isothermal dehydration of the powdered material were recorded at different temperatures.Nonisothermal dehydration of single crystals proceeds in three stages: (1) surface nucleation and growth of nuclei, followed by the advancement of reaction fronts inward, (2) random nucleation and growth near the reaction front as well as in the bulk, and (3) the rapid escape of water vapor through the cracks formed by crystallization of the solid product in the bulk.The isothermal dehydration of the powdered material, which proceeded in a single step, was described by a contracting geometry law, 1-(1-α)^1/n=kt, with 1a contracting geometry model with the exponent n being slightly different from that in the isothermal analysis.This was substantiated by a comparison of the rate constants, k, derived isothermally with those caolculated in terms of the kinetic compensation effect for nonisothermal dehydration at various heating rates.