6. Scandinavian purification (Sc2O3)

Concentrated scandin contains numerous impurities: lanthanides, Th, Fe, Mn, Al, Mg, Ca, Ba, etc. . The major difficulty is to remove the rare earths. They can be precipitated as double fluorides with potassium; or, by acidification, rare-earth oxalates can be formed in the presence of a complexing agent (EDTA) for scandium, which keeps it in solution. These operations then lead to a Sc ₂ O ₃ oxide of fairly good quality. Nevertheless, differential precipitation is difficult to achieve on an industrial scale.