The use of thermal analysis for the identification of clay minerals differsfrom its use for the determination of phase transitions in that the latterare, in theory at least, reversible and occur at definite temperatures whilethe dehydration reactions utilized in the identification of clays aremonotropic, irreversible decompositions proceeding at a velocity whichincreases continuously as the temperature is raised. There is, therefore, nodefinite transformation temperature and the temperature of the arrestregistered on a heating curve depends on the heating rate employed.

In view of the increasing importance of thermal analysis it was decided thatan attempt should be made to study the implications of this. Aninvestigation of the kinetics of the dehydration reaction seemed the mostobvious approach.