Per Teodor Cleve

Per Teodor Cleve
Per Teodor Cleve, c. 1880–1890
Born	10 February 1840 Stockholm, Sweden
Died	18 June 1905(1905-06-18) (aged 65) Uppsala, Sweden
Nationality	Swedish
Alma mater	Stockholms Lyceum (1858) Uppsala University (1863)
Known for	discovery of holmium and thulium
Spouse	Carolina Alma Öhbom ​ (m. 1874)​
Children	Astrid Cleve Agnes Cleve-Jonand Célie Brunius
Awards	Davy Medal (1894)
Scientific career
Fields	Chemistry, geology

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.^[1][2]

Born in Stockholm in 1840, Cleve earned his BSc and PhD from Uppsala University in 1863 and 1868, respectively. After receiving his PhD, he became an assistant professor of chemistry at the university. He later became professor of general and agricultural chemistry. In 1874 he theorised that didymium was in fact two elements; this theory was confirmed in 1885 when Carl Auer von Welsbach discovered neodymium and praseodymium.

In 1879 Cleve discovered holmium and thulium.^[3] His other contributions to chemistry include the discovery of aminonaphthalenesulfonic acids, also known as Cleve's acids. From 1890 on he focused on biological studies. He developed a method of determining the age and order of late glacial and postglacial deposits from the types of diatom fossils in the deposits, and wrote a seminal text in the field of oceanography. He died in 1905 at age 65.