Differential thermal analysis of bentonite clays

Differential thermal analysis was carried out on twelve Indian bentonite samples, sodium and calcium base, in the as received and gas condition with a view to examine the possible changes in structure and chemistry from treatment with different gases. Carbon dioxide, sulphur dioxide, nitrogen, ammonia, chlorine and their combinations were used as treatment gases. Gas treatment had practically no effect on differential thermograms. Treatment with combination of gases, however, resulted in minor changes in range and peak temperatures of some endothermic and exothermic reactions. The observed effects on differential thermograms due to gas treatment are considered insignificant so far as their effect on foundry bonding properties are concerned. (Dr. G.N. Rao, National Metallurgical Laboratory, Jamshedpur. Dr. M.Ram, Prof. of Metallurgy, Department of Metallurgy. Regional Institute of Technology, Jamshedpur)