Thermal Decomposition of Cerous Oxalate

Abstract

Thermal decomposition of cerous oxalate decahydrate, Ce₂(C₂O₄)₃⋅10H₂O, has been studied by thermogravimetry (TG) and differential thermal analysis (DTA) in air and nitrogen. TG curves suggested that the decahydrate decomposed to the dihydrate and successively to the monohydrate giving an endothermic peak in DTA. The monohydrate decomposed to the oxide. In nitrogen the dehydration process to the monohydrate was the same as that in air, but the decomposition of the monohydrate to the oxide was sluggish and shifted to higher temperature. The decomposition products in nitrogen and in vacuum were black in color, owing to the deposition of the finely divided carbon particles formed by the disproportionation of CO.
The infra-red absorption spectra of the decomposition products indicated that the oxalate partially decomposed to the oxide through the formation of an intermediate carbonate. Surface area showed a maximum value at about 350°C due to the decomposition of the oxalate, and it was followed by a decrease with increasing heating temperature, which corresponded to the decrease in X-ray diffraction line broadening.
In electron microscopy, the oxalate particles were rectangular platelet and the oxide appeared as the skeleton particles of the original oxalate.