
Thulium(III) oxide

Thulium(III) oxide is a pale green solid compound, with the formula Tm2O3. It was first isolated in 1879 from an impure sample of erbia by Per Teodor Cleve, who named it "thulia".
It can be prepared in the laboratory by burning thulium metal in air, or by decomposition of their oxoacid salts, such as thulium nitrate.