Method of Comparing Solid‐State Kinetic Data and Its Application to the Decomposition of Kaolinite, Brucite, and BaCO ₃

A method of comparing the kinetics of isothermal solid‐state reactions based on the classical equation for analysis of nucleation‐and‐growth processes is described. In this method, plots of In In (1‐α) vs In (time), where α is the fraction reacted, are used to distinguish reaction mechanisms. Even nonintegral slopes obtained for values of the fraction reacted from 0.15 to 0.50 may indicate whether the reaction rate is diffusion‐ or phase‐boundary‐controlled. The problems of ascertaining zero time and self‐cooling (or heating) of the reacting sample can be observed in the analysis but do not cause severe difficulties in interpretation, as they can for analyses based on reduced‐time plots. The analysis is applied to the dehydroxylation of kaolinite and of brucite and the decomposition of BaCO 3 .