The oxalate precipitate was ignited at 950 °C and the
analysis of the final product revealed that the recovery
of rare earths as oxide was 89.9% with 96% RE2O3, the
major impurities were Ca and Ti with traces of U and
Th. Chi and Xu (1999) found that the purity of the rare
earth oxalates decreased with increasing pH, probably
due to coprecipitation of non-rare earth species.