AbstractThermal decompositions of the oxalates of the heavy rare earth metals and of yttrium were carried out on a Stanton thermobalance. These oxalates on precipitation and drying at 110° C for six hours, gave the trihydrates which were used in the decomposition studies. Dihydrates, stable in the temperature range 230 to 330° C were formed before complete dehydration. Maximum decomposition was found to take place between 400 and 460° C. Weight levels corresponding to oxide formation were obtained in the temperature range 680–700° C without any indication of formation of intermediate pro