Thermolyse de melanges de chromates et d'oxalates de metaux alcalino-terreux I. Composes du baryum et du strontium

Abstract The thermolysis of mixtures of chromates and oxalates of Ba and Sr has been studied using a combination of techniques, among which thermal analysis and EPR. It is shown that relatively dispersed Cr(III) species can be obtained by thermal treatment in the temperature range 450–500°C. No dispersed Cr(V) has been observed while the end product of the thermolysis, at 850°C, has been identified to be M 3 (CrO 4 2 (M = Ba or Sr). The alkaline earth carbonate, produced by decomposition of the corresponding oxalate, is found to play a major role in the reduction of Cr(VI) to Cr(V) which occurs above 60°C.