Dehydration of Crystallization Water in Salts Using a New Designed Controlled-Water Vapor Micro DTA
The effects of water vapor pressure on the equilibria and kinetics for the dehydration of crystallization water in salts have been studied using a new designed controlled-water vapor micro sample DTA instrument. The dehydrations of CuSO4·H2O, CaC2O·H2O, ZnC2O4 · 2H2O and CaSO4 · 1/2H2O have been examined respectively. The partial pressures of H20(g) in N2 carrier gas flowing through the DTA chamber were kept constant within ±0.001atm over the wide pressure range from 0.01atm to 0.7atm. A dumbbel type Pt detector and Pt pan were used. For the comparison of data, the usual Ni block cell was also used. The van’t Hoff plots by using the initiation temperatures of DTA peaks and the fixed pH2O values gave the reasonable enthalpy changes for the dehydration reactions. The activation energies were obtained by introducing the correction term (1-P/Pe) in the kinetic equation.
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