Carl Gustaf Mosander
Swedish chemist who discovered three rare earth elements.
Carl Gustaf Mosander, a Swedish chemist born in Kalmar on 10 September 1797, is credited with isolating the rare earth elements lanthanum, erbium, and terbium. After moving to Stockholm with his mother in 1809, he apprenticed at the Ugglan pharmacy, passed his pharmacy exam in 1817, and then pursued medicine at the Karolinska Institute, earning his medical qualification in 1825. He trained in the lab of Jöns Jakob Berzelius and became close with fellow student Friedrich Wöhler. When Berzelius stepped down in 1832, Mosander took over as professor of chemistry and pharmacy at the Karolinska Institute.
In 1838, Mosander discovered lanthanum by working with cerite from Bastnäs, Sweden—then the main source of what was thought to be the element cerium, first identified by Berzelius and Hisinger (and independently by Klaproth) in 1803. At the time, a white oxide called ceria was one of two known components in the mineral ytterbite (later gadolinite). Mosander partially broke down ceria by heating it and treating the salt with dilute nitric acid. He hesitated to publish, worried about embarrassing his mentor Berzelius by showing that cerium wasn’t a pure element, and unsure he had fully separated it. Berzelius suggested the name “lanthan,” meaning “hidden.” By 1840, Mosander had split cerium oxide into three parts: yellow cerium oxide, white lanthanum oxide, and a pinkish third component he named “didymium” (meaning “twin”). Didymium was long accepted as an element, even appearing as number 95 in Mendeleev’s periodic table with the symbol Di. In 1874, Per Teodor Cleve predicted didymium contained multiple elements; Lecoq de Boisbaudran isolated samarium from it in 1879, and in 1885 Carl Auer von Welsbach separated the remaining two via fractional crystallization, naming them praseodidymium and neodidymium—later shortened to praseodymium and neodymium.
In 1843, Mosander identified terbium and erbium as components of yttria, but this discovery faced strong opposition. Spectroscopist Nils Johan Berlin denied the existence of two elements, failing to confirm “erbia” and suggesting that name be given to “terbia.” In 1864, Marc Delafontaine used optical spectroscopy to prove that yttrium, terbium, and erbium were distinct. Ironically, the earlier name confusion persisted: Mosander’s original labels were swapped, so the amethyst compound became known as erbium oxide and the yellow one as terbium oxide, the reverse of his proposal.
Mosander married Hulda Philippina Forsström on 20 December 1832; they had four children, two sets of twins. From 1845, he also served as professor and inspector at the Pharmaceutical Institute, and he was assistant curator of the mineralogical collections at the Swedish Museum of Natural History. In 1825, he owned a Stockholm spa where people could drink the waters. Elected to the Royal Swedish Academy of Sciences in 1833, he suffered from cataracts in later life and died on 15 October 1858 at his summer house on Lovön, Stockholm County.
- born
- 10 September 1797
- died
- 15 October 1858
- field
- Chemistry
- nationality
- Swedish
- known_for
- Discovery of lanthanum, erbium, and terbium
Verified Timeline
Quick Facts
- Birth Date
- df=yes · 1797 · 9 · 10
- Birth Place
- Kalmar
- Death Date
- df=yes · 1858 · 10 · 15 · 1797 · 9 · 10
- Death Place
- Lovö, Stockholm County
- Field
- chemistry
- Workplaces
- Karolinska Institute
- Known For
- lanthanum / erbium / terbium
Facts from the source article.
Lore & Background
Mosander discovered lanthanum in 1838 from the Cerite-(Ce) from Bastnaes, Sweden, which at the time was the only abundant source for 'Cerium.' He partially decomposed ceria by heating it and treating the resulting salt with dilute nitric acid. He was hesitant to report his results, both for fear of embarrassing his mentor Berzelius, by showing that his discovery cerium was not an element; and because he was uncertain that he himself had reduced cerium to all of its components. Berzelius eventually suggested the name 'lanthan,' for 'hidden.' By 1840, Mosander had separated cerium oxide into yellow cerium oxide, white lanthanum oxide and a pinkish third component which he called 'didymium' meaning 'twin.' In 1843 Mosander discovered terbium and erbium as components of yttria. However, this discovery was hotly contested. Spectroscopist Nils Johan Berlin denied that two elements existed, failing to confirm the existence of 'erbia' and suggesting that its name be applied to 'terbia.' In 1864, Marc Delafontaine used optical spectroscopy to conclusively prove that yttrium, terbium and erbium were separate elements. Ironically, however, the confusion that had been introduced between the names continued. Mosander's proposed names were switched, giving the amethyst compound the name 'erbium' oxide and the yellow substance the name 'terbium' oxide, instead of the other way around as originally proposed.
Reader's Guide
Mosander's significance lies in his pioneering work on rare earth elements, which revealed that previously accepted 'elements' were mixtures. In 1838, he discovered lanthanum by partially decomposing ceria from the mineral cerite, a finding that initially embarrassed his mentor Berzelius because it showed that cerium was not a pure element. Mosander also isolated didymium, later shown to be a mixture of praseodymium and neodymium. In 1843, he discovered terbium and erbium in yttria, though his findings were contested by spectroscopist Nils Johan Berlin. The confusion over names was eventually resolved by Marc Delafontaine in 1864, but the names were swapped from Mosander's original proposal. His work laid the groundwork for later rare earth separations by scientists such as Carl Auer von Welsbach. Mosander was elected to the Royal Swedish Academy of Sciences in 1833. He married Hulda Philippina Forsström on 20 December 1832. They had four children, two sets of twins. Mosander suffered from cataracts in later life. He died in 1858, at his summer house on the island of Lovön, Stockholm County.
Did You Know?
- Mosander discovered lanthanum in 1838 from the Cerite-(Ce) from Bastnaes, Sweden, which at the time was the only abundant source for 'Cerium.'
- Berzelius suggested the name 'lanthan' for 'hidden' for Mosander's new discovery.
- Mosander isolated a pinkish third component from cerium oxide which he called 'didymium' meaning 'twin.'
- In 1843 Mosander discovered terbium and erbium as components of yttria, but his proposed names were later switched.
- Mosander married Hulda Philippina Forsström on 20 December 1832 and they had four children, two sets of twins.
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