抄録
Thermal decomposition of hydrous oxide and oxycarbonate of thorium has been studied by thermogravimetry (TG), differential thermal analysis (DTA) and Hahn's emanation technique. Hydrous oxide was precipitated from thorium salt solution by the addition of hydroxide ion. TG curves showed that hydrous oxide gradually lost water and did not suffer from a step-by-step dehydration. DTA curves showed an endothermic peak around 150°C followed by a small exothermic peak at 250°-300°C. In emanation curves two prominent peaks were observed, one corresponding to the 150°C peak in DTA, and the other centered at 400°-450°C. The endothermic peak in DTA and two emanation peaks were presumed to be due to the escape of adsorbed or occluded water, and the exothermic peak in DTA due to the crystallization of amorphous hydrous oxide. The hydrous oxide might be not hydroxide nor oxide hydrated but actuated oxide. Hydrous oxycarbonate lost water rapidly to about 200°C on heating, resulting in the formation of ThOCO3⋅H2O, and then followed by less rapid decomposition to the oxide.
In the electron microscope, the oxide particles prepared from hydrous oxide and oxycarbonate were in irregular shape of agglomerates of fine primary particles.
