[1]: 38 He worked in the laboratory of Jöns Jakob Berzelius and became a close friend of fellow student Friedrich Wöhler.
[1]: 38 In 1832 Jöns Jakob Berzelius retired in favor of Mosander, his student, who succeeded him as professor of chemistry and pharmacy in the Karolinska Institute.
This came from the Cerite-(Ce) from Bastnaes, Sweden, which at the time was the only abundant source for "Cerium", which had been discovered therein by Berzelius and Hisinger, and independently by Klaproth, in 1803.
Mosander partially decomposed ceria by heating it and treating the resulting salt with dilute nitric acid.
[8][7] Didymium was accepted as an element for many years, appearing in Dmitri Mendeleev's periodic system as number 95, with the symbol Di.
[9] In 1879, Lecoq de Boisbaudran isolated samarium,[9] while in 1885 Carl Auer von Welsbach separated the two remaining elements through repeated fractional crystallizations.
In 1864, Marc Delafontaine used optical spectroscopy to conclusively prove that yttrium, terbium and erbium were separate elements.