Editing Per Teodor Cleve (section)

{{Short description|Swedish chemist who discovered holmium and thulium (1840–1905)}}
{{Use dmy dates|date=March 2014}}
{{Infobox scientist
| name              = 
| image             = Per Teodor Cleve c1885.jpg
| caption           = Per Teodor Cleve, c. 1880–1890
| image_size        = 
| alt               = 
| birth_name        = 
| birth_date        = 10 February 1840
| birth_place       = [[Stockholm]], Sweden
| death_date        = {{death date and age|1905|6|18|1840|2|10|df=y}}
| death_place       = [[Uppsala]], Sweden
| residence         = 
| citizenship       = 
| nationality       = Swedish
| ethnicity         = 
| fields            = [[Chemistry]], [[geology]]
| workplaces        = 
| alma_mater        = [[Stockholms Lyceum]] (1858)<br>[[Uppsala University]] (1863)
| doctoral_advisor  = 
| academic_advisors = 
| doctoral_students = 
| notable_students  = 
| known_for         = discovery of [[holmium]] and [[thulium]]
| author_abbrev_bot = 
| author_abbrev_zoo = 
| influences        = 
| influenced        = 
| awards            = [[Davy Medal]] <small>(1894)</small>
| religion          = 
| signature         = <!--(filename only)-->
| signature_alt     = 
| footnotes         = 
| spouse            = {{marriage|[[: se : Alma Cleve|Carolina Alma Öhbom]]|1874|<!-- Omission per Template:Marriage instructions -->}}
| children          = [[Astrid Cleve]]<br/>[[: se : Agnes Cleve-Jonand|Agnes Cleve-Jonand]]<br/>[[: se : Célie Brunius|Célie Brunius]]
}}

'''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]].<ref name = "britannica">{{Cite encyclopedia | encyclopedia=Encyclopædia Britannica |url = http://www.britannica.com/EBchecked/topic/121389/Per-Teodor-Cleve|title = Per Teodor Cleve|accessdate = 13 March 2014}}</ref><ref name = "encyclopedia"/>

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.<ref name="Virginia"/> 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 [[Till|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.