Carl Gustaf Mosander (10 September 1797 – 15 October 1858) was a
Swedish
Swedish or ' may refer to:
Anything from or related to Sweden, a country in Northern Europe. Or, specifically:
* Swedish language, a North Germanic language spoken primarily in Sweden and Finland
** Swedish alphabet, the official alphabet used by ...
chemist
A chemist (from Greek ''chēm(ía)'' alchemy; replacing ''chymist'' from Medieval Latin ''alchemist'') is a scientist trained in the study of chemistry. Chemists study the composition of matter and its properties. Chemists carefully describe ...
. He discovered the
rare earth elements
The rare-earth elements (REE), also called the rare-earth metals or (in context) rare-earth oxides or sometimes the lanthanides (yttrium and scandium are usually included as rare earths), are a set of 17 nearly-indistinguishable lustrous silve ...
lanthanum
Lanthanum is a chemical element with the symbol La and atomic number 57. It is a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air. It is the eponym of the lanthanide series, a group of 15 similar elements between lantha ...
,
erbium
Erbium is a chemical element with the symbol Er and atomic number 68. A silvery-white solid metal when artificially isolated, natural erbium is always found in chemical combination with other elements. It is a lanthanide, a rare-earth element, orig ...
and
terbium
Terbium is a chemical element with the symbol Tb and atomic number 65. It is a silvery-white, rare earth metal that is malleable, and ductile. The ninth member of the lanthanide series, terbium is a fairly electropositive metal that reacts with w ...
.
Early life and education
Born in
Kalmar
Kalmar (, , ) is a city in the southeast of Sweden, situated by the Baltic Sea. It had 36,392 inhabitants in 2010 and is the seat of Kalmar Municipality. It is also the capital of Kalmar County, which comprises 12 municipalities with a total o ...
, Mosander attended school there until he moved to
Stockholm with his mother in 1809. In Stockholm, he became an apprentice at the ''Ugglan'' pharmacy. He took his pharmacy examination in 1817, but had an interest in medicine and joined the
Karolinska Institute
The Karolinska Institute (KI; sv, Karolinska Institutet; sometimes known as the (Royal) Caroline Institute in English) is a research-led medical university in Solna within the Stockholm urban area of Sweden. The Karolinska Institute is consis ...
in 1820. He passed his medical examination in 1825.
He worked in the laboratory of
Jöns Jakob Berzelius
Jöns is a Swedish given name and a surname.
Notable people with the given name include:
* Jöns Jacob Berzelius
Baron Jöns Jacob Berzelius (; by himself and his contemporaries named only Jacob Berzelius, 20 August 1779 – 7 August 1848) ...
and became a close friend of fellow student
Friedrich Wöhler
Friedrich Wöhler () FRS(For) HonFRSE (31 July 180023 September 1882) was a German chemist known for his work in inorganic chemistry, being the first to isolate the chemical elements beryllium and yttrium in pure metallic form. He was the first ...
.
Career
In 1832 Jöns Jakob Berzelius retired in favor of his student Carl Gustaf Mosander who succeeded him as professor of chemistry and pharmacy in the Karolinska Institute.
From 1845 Mosander was also a professor at and inspector for the Pharmaceutical Institute.
Mosander was an assistant curator of the mineralogical collections of the
Swedish Museum of Natural History,
founded by the
Swedish Academy of Sciences
The Royal Swedish Academy of Sciences ( sv, Kungliga Vetenskapsakademien) is one of the royal academies of Sweden. Founded on 2 June 1739, it is an independent, non-governmental scientific organization that takes special responsibility for prom ...
in 1819.
From 1825 he was the owner of a spa in Stockholm where people could go to drink the waters.

Mosander discovered
lanthanum
Lanthanum is a chemical element with the symbol La and atomic number 57. It is a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air. It is the eponym of the lanthanide series, a group of 15 similar elements between lantha ...
in 1838. 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. At that time, one of the two known components of the mineral ytterbite (later named
gadolinite
Gadolinite, sometimes known as ytterbite, is a silicate mineral consisting principally of the silicates of cerium, lanthanum, neodymium, yttrium, beryllium, and iron with the formula . It is called gadolinite-(Ce) or gadolinite-(Y), depending ...
) was a white oxide called
ceria. Mosander partially decomposed ceria by heating it and treating the resulting salt with dilute
nitric acid
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available ni ...
.
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" for this new discovery.
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
Dmitri Ivanovich Mendeleev (sometimes transliterated as Mendeleyev or Mendeleef) ( ; russian: links=no, Дмитрий Иванович Менделеев, tr. , ; 8 February O.S. 27 January">Old_Style_and_New_Style_dates.html" ;"title="no ...
's periodic system as number 95, with the symbol Di. In 1874,
Per Teodor Cleve
Per Teodor Cleve (10 February 1840 – 18 June 1905) was a Swedish chemist, biologist, mineralogist and oceanographer. He is best known for his discovery of the chemical elements holmium and thulium.
Born in Stockholm in 1840, Cleve earned his ...
predicted that didymium contained at least two elements.
In 1879, Lecoq de Boisbaudran isolated samarium,
while in 1885
Carl Auer von Welsbach
Carl Auer von Welsbach (1 September 1858 – 4 August 1929), who received the Austrian noble title of Freiherr Auer von Welsbach in 1901, was an Austrian scientist and inventor, who separated didymium into the elements neodymium and praseo ...
separated the two remaining elements through repeated fractional crystallizations. Welsbach named them praseodidymium (green didymium) and neodidymium (new didymium). They came to be known as praseodymium and neodymium.

In 1843 Mosander discovered
terbium
Terbium is a chemical element with the symbol Tb and atomic number 65. It is a silvery-white, rare earth metal that is malleable, and ductile. The ninth member of the lanthanide series, terbium is a fairly electropositive metal that reacts with w ...
and
erbium
Erbium is a chemical element with the symbol Er and atomic number 68. A silvery-white solid metal when artificially isolated, natural erbium is always found in chemical combination with other elements. It is a lanthanide, a rare-earth element, orig ...
as components of
yttria
Yttrium oxide, also known as yttria, is Y2 O3. It is an air-stable, white solid substance.
The thermal conductivity of yttrium oxide is 27 W/(m·K).
Uses Phosphors
Yttria is widely used to make Eu:YVO4 and Eu:Y2O3 phosphors that give the red ...
.
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.
Mosander was elected a member of the
Royal Swedish Academy of Sciences in 1833.
Personal life and final years
Mosander married Hulda Philippina Forsström on 20 December 1832. They had four children, two sets of twins.
Mosander suffered from
cataracts
A cataract is a cloudy area in the lens of the eye that leads to a decrease in vision. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colors, blurry or double vision, halos around light, trouble w ...
in later life. He died in 1858, at his summer house on the island of
Lovön,
Stockholm County
Stockholm County ( sv, Stockholms län, link=no ) is a county or '' län'' (in Swedish) on the Baltic Sea coast of Sweden. It borders Uppsala County and Södermanland County. It also borders Mälaren and the Baltic Sea. The city of Stoc ...
.
References
{{DEFAULTSORT:Mosander, Carl Gustaf
1797 births
1858 deaths
People from Kalmar
Swedish chemists
Discoverers of chemical elements
Karolinska Institute faculty
Members of the Royal Swedish Academy of Sciences
19th-century Swedish scientists
19th-century chemists
Lanthanum
Erbium
Terbium
Rare earth scientists