Mosander, Carl Gustaf (1797-1858)

Swedish chemist

In a large part, credit for unraveling the complex nature of the rare Earth elements goes to Carl Gustaf Mosander. Mosander was born in Kalmar, Sweden, on September 10, 1797. He was educated as a physician and pharmacist and served as an army surgeon for many years.

Mossander's most important professional association was with the eminent Swedish chemist J. J. Berzelius. Mosander lived with Professor and Mrs. Berzelius for many years and worked as Berzelius' assistant at the Stockholm Academy of Sciences. Eventually, Mosander became curator of minerals at the Academy and, in 1832, succeeded Berzelius as Permanent Secretary of the Academy. Mosander was also Professor of Chemistry and Mineralogy at the Caroline Institute for many years.

Mosander became interested in the rare Earth elements in the late 1830s. Fifty years earlier, a Swedish army officer, Carl Axel Arrhenius, had discovered a new mineral near the small town of Ytterby that he named ytterite. Chemists spent much of the next century trying to separate the mineral into its many chemically-similar parts.

The first breakthrough in this effort occurred in 1794 when Johan Gadolin (1760–1852) showed that ytterite contained a large fraction of a new oxide, which he called yttria. A decade later, M. H. Klaproth, Berzelius, and Wilhelm Hisinger (1766–1852) showed that ytterite also contained a second oxide, which they termed ceria.

Mosander first concentrated his efforts on the ceria component of ytterite. In 1839, he found that the ceria contained a new element, which he named lanthanum (for hidden). Mosander did not publish his results immediately, however, because he was convinced that yet more discoveries were to be made. He was not disappointed in these hopes. In 1841, he identified a second new component of ceria. He named the component didymium, for twin, because it was so closely related to lanthanum. Later research showed that didymium was not itself an element, but a complex mixture of other rare earth elements.

In 1843, Mosander turned his attention to the yttria component of ytterite. He was able to show that the yttria consisted of at least three components. He kept the name yttria for one and called the other two erbia and terbia. The last two of these components are now known by their modern names of erbium and terbium. Mosander is acknowledged as the discoverer, then, of three elements: lanthanum, erbium, and terbium. Mosander died in Ångsholm, Sweden, on October 15, 1858.

See also Chemical elements

MOSANDER, CARL GUSTAF

(b. kalmar, Sweden, 10 September 1797; d. Angsholm, Sweden, 15 October 1858)

chemistry, mineralogy.

Mosander began his career as a pharmacist, at the age of fifteen becoming an apprentice at a Stockholm apothecary. Seven sears later he began medical studies and, after serving as an army surgeon, received the M.D. in 1825. In 1824 he was appointed teacher of chemistry at the Caroline Institute and shortly thereafter was put in charge of the chemistry laboratory. He succeeded Berzelius as professor of chemistry and pharmacy in 1832, when the latter retired. He held this position until his death. For a time Mosander and his wife lived with Berzelius, who had befriended the couple. Berezlius was taught Dutch by Mrs. Mosander. A close friendship also developed between Friedrich Wöhler and Mosander, who was affectionately referred to as “Father Moses” in correspondence between Wöhler and Berzelius.

Among Mosander’s responsibilities was the mineral collection at the Royal Swedish Academy of Sciences, which was helpful to his research on minerals containing rare earth elements. In 1839 he showed that ceria (isolated independently by Berzelius and by Martin Klaproth in 1803) was really a mixture of earths. When he treated the substance with dilute nitric acid, a yellow residue, true ceria (cerium oxide), remained; he named the dissolved component lanthana (from Greek lanthanein, “to escape notice”).

Two years later Mosander showed that lanthana was really a mixture of a white substance, lanthana, and a brown earth named didymia (Greek, “two”) because of its similarity to lanthana. Didymia was regarded as a pure earth until 1885, when Auer von Welsbach decomposed it into praseodymia and neodymia. Mosander also separated yttria (discovered by Gadolin in 1794) into yttria, erbia, and terbia (the oxides of yttrium, erbium, and terbium) in 1843. These names were derived from the Swedish town of Ytterby, where the mineral was discovered. In 1839 Axel Erdmann discovered lanthana in a new Norwegian mineral, which he named mosandrite.

BIBLIOGRAPHY

I. Original Works. Many of Mosander’s discoveries were communicated orally at meetings of chemists; Wöhler and Berzelius have commented on his reluctance to publish. A summary of his important work is his article, “On the New Metals, Lanthanum and Didymium, Which Are Associated With Cerium; and on Erbium and Terbium, New Metals Associated With Yttria,” in Philosophical Magazine, 23 (1843), 241–254. A short portion of this paper was published as “Lanthanum and Didymium, Erbium and Terbium: A Classic of Chemistry,” in Chemistry, 20 (Sept. 1946),53–59.

II. Secondary Literature. Biographical material on Mosander is rather scanty. A short article describing his work is J. Erik Jorpes, “Carl Gustaf Mosander,” in Acta chemica scandinavica, 14 (1960), 1681–1683. A more informal treatment and a photograph can be found in Mary Elvira Weeks and Henry M. Leicester, Discovery of the Elements, 7th ed. (Easton, Pa., 1968), 671–678.

Sheldon J. Kopperl