KINETIC STUDY OF THE THERMAL DEHYDRATION OF SYNGENITE K2CA(SO4)2.H2O UNDER NONISOTHERMAL CONDITIONS

Different calculation methods applied to TG, DTG and DTA curves obtained with a Mettler Thermoanalyzer at one or several heating rates have been tested. It has been shown that the dehydration of syngenite can best be described by the Avrami equation I [-1n(1-α)]1/2=3.46·1021exp (-2.73·104/T)·t where α is the degree of decomposition, T the absolute temperature, and t the time. The mean value of the activation energy is 54 kcal·mole-1. This is in good agreement with the results obtained under isothermal conditions. The method of Šatava and Škvára, supplemented by the numerical tables of Zsakó, is most useful in obtaining the kinetic equations describing the thermal decomposition of solids. © 1979 Wiley Heyden Ltd., Chichester and Akadémiai Kiadó, Budapest.