Mosander

Carl Gustaf Mosander (1797–1858) was a Swedish chemist known for his work on rare earth elements. He conducted most of his notable research in the laboratory of Jöns Jacob Berzelius and contributed to the understanding of the complex mixtures found in yttria and ceria, minerals rich in rare earth elements.

In 1839 Mosander obtained lanthanum from cerium oxide by separating it from other components, establishing lanthanum as a distinct element. He named the new element lanthanum, from the Greek lanthanein, meaning to lie hidden, reflecting its position among the rare earths. His method showed that what had been considered a single substance could be divided into multiple elemental components.

Mosander continued his investigations of the yttrium group and, in 1843 and 1844, reported the discovery of two additional elements within yttria. He produced terbia (terbium oxide) and erbia (erbium oxide), from which the elements terbium and erbium were later isolated. These discoveries expanded the known set of rare earth elements and highlighted the complexity of the yttrium-cerium family.

Mosander’s work helped establish the concept that certain minerals contained multiple elements that were chemically related, laying groundwork for the later classification of the lanthanide series. His contributions are regarded as foundational in the study of rare earth chemistry, and the elements lanthanum, terbium, and erbium are commonly associated with his name in historical accounts.