The untreated bentonite was separated into three fractions by subsequent precipitations from its suspension, during different periods. One fraction remained in suspension during infinite period. Hence, a total of four fractions were separated. Ure activation energies, and pre-exponential factors for the dehydration, dehydroxylation and calcination, of a total of five samples, comprising the untreated bentonite were determined by the Coats — Redfern procedure, using the thennogravimetric data, file decompositions were thought to obey a first order rate law. Their rate equations were written by usingthe determined quantities.