Editing Thulium (section)

==History==
[[File:Per Teodor Cleve c1885.jpg|thumb|upright|Per Teodor Cleve, the scientist who discovered thulium as well as [[holmium]].]]
Thulium was [[discovery of the chemical elements|discovered]] by Swedish chemist [[Per Teodor Cleve]] in 1879 by looking for impurities in the [[oxide]]s of other rare earth elements. This was the same method [[Carl Gustaf Mosander]] earlier used to discover some other rare earth elements.<ref>See:
* {{cite journal|last1=Cleve|first1=P. T.|title=Sur deux nouveaux éléments dans l'erbine|journal=Comptes rendus|date=1879|volume=89|pages=478–480|url=https://babel.hathitrust.org/cgi/pt?id=umn.31951d00008409h;view=1up;seq=484|trans-title=Two new elements in the oxide of erbium|language=fr}} Cleve named thulium on p. 480: ''"Pour le radical de l'oxyde placé entre l'ytterbine et l'erbine, qui est caractérisé par la bande ''x'' dans la partie rouge du spectre, je propose la nom de ''thulium'', dérivé de Thulé, le plus ancien nom de la Scandinavie."'' (For the radical of the oxide located between the oxides of ytterbium and erbium, which is characterized by the ''x'' band in the red part of the spectrum, I propose the name of "thulium", [which is] derived from ''Thule'', the oldest name of Scandinavia.)
* {{cite journal|last1=Cleve|first1=P. T.|title=Sur l'erbine|journal=Comptes rendus|date=1879|volume=89|pages=708–709|url=https://babel.hathitrust.org/cgi/pt?id=umn.31951d00008409h;view=1up;seq=714|trans-title=On the oxide of erbium|language=fr}}
* {{cite journal|last1=Cleve|first1=P. T.|title=Sur le thulium|journal=Comptes rendus|date=1880|volume=91|pages=328–329|url=https://babel.hathitrust.org/cgi/pt?id=umn.31951d00008411u;view=1up;seq=332|trans-title=On thulium|language=fr}}</ref> Cleve started by removing all of the known contaminants of [[erbia]] ({{chem2|[[erbium|Er]]2[[oxygen|O]]3}}). Upon additional processing, he obtained two new substances; one brown and one green. The brown substance was the oxide of the element [[holmium]] and was named holmia by Cleve, and the green substance was the oxide of an unknown element. Cleve named the oxide [[thulia]] and its element thulium after [[Thule]], an [[Ancient Greek]] place name associated with Scandinavia or [[Iceland]]. Thulium's atomic symbol was initially Tu, but later{{when|date=April 2022}} changed to Tm.{{why|date=April 2022}}<ref name="history" /><ref>{{cite book |url=https://books.google.com/books?id=Owuv-c9L_IMC&pg=PA1061|page=1061 |title=Concise Encyclopedia Chemistry |isbn=978-3-11-011451-5 |last1=Eagleson |first1=Mary |date=1994|publisher=Walter de Gruyter}}</ref><ref name="Weeks">{{cite book |last1=Weeks |first1=Mary Elvira |title=The discovery of the elements |date=1956 |publisher=Journal of Chemical Education |location=Easton, PA |url=https://archive.org/details/discoveryoftheel002045mbp |edition=6th }}</ref><ref name="XVI">{{cite journal | author = Weeks, Mary Elvira |author-link=Mary Elvira Weeks| title = The discovery of the elements: XVI. The rare earth elements | journal = Journal of Chemical Education | year = 1932 | volume = 9 | issue = 10 | pages = 1751&ndash;1773 | doi = 10.1021/ed009p1751 | bibcode=1932JChEd...9.1751W}}</ref><ref name="Virginia">{{cite journal |last1=Marshall |first1=James L. Marshall |last2=Marshall |first2=Virginia R. Marshall |title=Rediscovery of the elements: The Rare Earths–The Confusing Years |journal=The Hexagon |date=2015 |pages=72–77 |url=http://www.chem.unt.edu/~jimm/REDISCOVERY%207-09-2018/Hexagon%20Articles/rare%20earths%20II.pdf |access-date=30 December 2019}}</ref><ref>{{Cite journal|last=Piguet|first=Claude|year=2014|title=Extricating erbium|journal=Nature Chemistry|volume=6|issue=4|page=370|doi=10.1038/nchem.1908|bibcode=2014NatCh...6..370P|pmid=24651207|doi-access=free}}</ref><ref name="RSThulium">{{cite web |title=Thulium |url=https://www.rsc.org/periodic-table/element/69/thulium |website=Royal Society of Chemistry|date= 2020 |access-date=4 January 2020}}</ref>

Thulium was so rare that none of the early workers had enough of it to purify sufficiently to actually see the green color; they had to be content with [[spectroscopy|spectroscopically]] observing the strengthening of the two characteristic absorption bands, as erbium was progressively removed. The first researcher to obtain nearly pure thulium was [[Charles James (chemist)|Charles James]], a British expatriate working on a large scale at [[University of New Hampshire|New Hampshire College]] in [[Durham, New Hampshire|Durham]], USA. In 1911 he reported his results, having used his discovered method of bromate fractional crystallization to do the purification. He famously needed 15,000 purification operations to establish that the material was homogeneous.<ref>{{cite journal|last=James|first=Charles|date=1911|title=Thulium I|journal=Journal of the American Chemical Society|volume=33|issue=8|pages=1332–1344|url=https://babel.hathitrust.org/cgi/pt?id=hvd.32044103069787;view=1up;seq=314|doi=10.1021/ja02221a007|bibcode=1911JAChS..33.1332J }}</ref>

High-purity thulium oxide was first offered commercially in the late 1950s, as a result of the adoption of [[ion exchange|ion-exchange]] separation technology. Lindsay Chemical Division of American Potash & Chemical Corporation offered it in grades of 99% and 99.9% purity. The price per kilogram oscillated between US$4,600 and $13,300 in the period from 1959 to 1998 for 99.9% purity, and it was the second highest for the lanthanides behind [[lutetium]].<ref>{{cite news |publisher= U.S. Geological Survey |title= Rare-Earth Metals |author= Hedrick, James B. |access-date= 2009-06-06 |url= https://minerals.usgs.gov/minerals/pubs/commodity/rare_earths/740798.pdf}}</ref><ref>{{cite news |title= Rare Earth Elements |author= Castor, Stephen B. |author2= Hedrick, James B. |name-list-style= amp |access-date= 2009-06-06 |url= http://www.rareelementresources.com/i/pdf/RareEarths-CastorHedrickIMAR7.pdf}}</ref>