Carl Gustaf Mosander
Swedish chemist who discovered three rare earth elements.
Carl Gustaf Mosander was a Swedish chemist who discovered the rare earth elements lanthanum, erbium and terbium. Born in Kalmar on 10 September 1797, he moved to Stockholm in 1809 and became an apprentice at the Ugglan pharmacy. After passing his pharmacy examination in 1817, he pursued medicine at the Karolinska Institute, passing his medical examination in 1825. He worked in the laboratory of Jöns Jakob Berzelius and became a close friend of fellow student Friedrich Wöhler. In 1832 Berzelius retired in favor of Mosander, who succeeded him as professor of chemistry and pharmacy at the Karolinska Institute. Mosander was also an assistant curator of the mineralogical collections of the Swedish Museum of Natural History and owned a spa in Stockholm from 1825.
- born
- 10 September 1797
- died
- 15 October 1858
- field
- Chemistry
- nationality
- Swedish
- known_for
- Discovery of lanthanum, erbium, and terbium
Verified Timeline
Lore & Background
Mosander discovered lanthanum in 1838 from the mineral Cerite-(Ce) from Bastnaes, Sweden. At that time, ceria was thought to be a single oxide. Mosander 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.' Didymium was accepted as an element for many years, appearing in Dmitri Mendeleev's periodic system as number 95, with the symbol Di. In 1874, Per Teodor Cleve predicted that didymium contained at least two elements. In 1879, Lecoq de Boisbaudran isolated samarium, while in 1885 Carl Auer von Welsbach separated the two remaining elements through repeated fractional crystallizations, naming them praseodidymium and neodidymium—later praseodymium and neodymium. In 1843 Mosander discovered terbium and erbium as components of yttria. 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, the confusion 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 work was foundational to the discovery of rare earth elements, a group that proved chemically complex and difficult to separate. His discovery of lanthanum in 1838 revealed that the mineral ceria contained more than one component, challenging the earlier assumption that cerium was a pure element. His subsequent identification of didymium, later shown to be a mixture of praseodymium and neodymium, and his separation of yttria into terbium and erbium, opened the door to the modern understanding of the lanthanide series. The controversy over the naming of terbium and erbium, resolved by spectroscopy, illustrates the evolving nature of chemical identification in the 19th century. Mosander's legacy lies in his careful experimental work and his role in expanding the periodic table, even as some of his discoveries were later refined by others.
Did You Know?
- Mosander discovered lanthanum in 1838 from the mineral Cerite-(Ce) from Bastnaes, Sweden.
- Berzelius suggested the name 'lanthan' for 'hidden' for Mosander's new element.
- Mosander's pinkish third component 'didymium' (meaning 'twin') was later split into praseodymium and neodymium by Carl Auer von Welsbach in 1885.
- Mosander's proposed names for terbium and erbium were switched after confusion introduced by Nils Johan Berlin and resolved by Marc Delafontaine in 1864.
- Mosander was elected a member of the Royal Swedish Academy of Sciences in 1833.
Frequently Asked Questions
Who is Carl Gustaf Mosander?
Carl Gustaf Mosander (1797–1858) was a Swedish chemist best remembered for identifying three rare earth elements. He spent most of his career at the Karolinska Institute in Stockholm, where he held the chair in chemistry and pharmacy.
What elements did Carl Gustaf Mosander discover?
Mosander is credited with isolating lanthanum, erbium, and terbium, all rare earth elements. His work in the 1830s and 1840s expanded the known set of elements considerably.
How is Carl Gustaf Mosander connected to Jöns Jacob Berzelius?
Mosander trained as a student and laboratory assistant under Berzelius, the preeminent Swedish chemist of the era. After Berzelius died, Mosander inherited his professorship at the Karolinska Institute and continued much of his mentor's research direction.
What other positions did Carl Gustaf Mosander hold?
Beyond his teaching role, Mosander served as an assistant curator of mineralogical collections at the Swedish Museum of Natural History. Access to those mineral specimens was essential to the analytical work that led to his elemental discoveries.
When and where did Carl Gustaf Mosander die?
Mosander died on 15 October 1858 in Stockholm, Sweden, at the age of 61. He had been active in Swedish academic chemistry for roughly three decades before his passing.
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