Abstract
The thermal decomposition of chromic anhydride supported on gamma-alumina at 300°, 350° and 450°C was examined by chemical analysis and by magnetic susceptibility measurements. The stabilization of the plus-six oxidation state of chromium in a highly dispersed state was confirmed by the present experiments. In addition, by comparing the oxidation number and the magnetic susceptibility of chromium, it was found that the behavior of supported chromic anhydride in large aggregates is also anomalous. Contrary to the case of the thermal decomposition of massive chromic anhydride, the intermediate oxides CrO2.6 and CrO2.4∼5 were not found. The large aggregates of chromic anhydride on alumina lose the greater part of their active oxygen at relatively low temperatures and crystallize continuously into chromia with further loss of oxygen.

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