Editing Terbium (section)

== History ==
[[File:Mosander Carl Gustav bw.jpg|thumb|right|[[Carl Gustaf Mosander]], the scientist who discovered terbium, lanthanum and erbium]]
[[Sweden|Swedish]] [[chemist]] [[Carl Gustaf Mosander]] discovered terbium in 1843.<ref name="Beginnings">{{cite journal |last1=Marshall |first1=James L. Marshall |last2=Marshall |first2=Virginia R. Marshall |title=Rediscovery of the elements: The Rare Earths–The Beginnings |journal=The Hexagon |date=2015 |pages=41–45 |url=http://www.chem.unt.edu/~jimm/REDISCOVERY%207-09-2018/Hexagon%20Articles/rare%20earths%20I.pdf |access-date=30 December 2019}}</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> He detected it as an impurity in [[yttrium oxide]], {{chem2|Y2O3}}, then known as yttria. Yttrium, erbium, and terbium are all named after the village of [[Ytterby]] in [[Sweden]].<ref name="XVI">{{Unbulleted list citebundle|{{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}}|{{cite book |last1=Weeks |first1=Mary Elvira |url=https://archive.org/details/discoveryoftheel002045mbp |title=The discovery of the elements |date=1956 |publisher=Journal of Chemical Education |edition=6th |location=Easton, PA |pages=705–706}}}}</ref><ref name="James">{{cite book |last1=Marshall |first1=James L. |title=Science history: a traveler's guide |last2=Marshall |first2=Virginia R. |date=October 31, 2014 |publisher=ACS Symposium Series |isbn=978-0-8412-3020-0 |volume=1179 |pages=209–257 |chapter=Northern Scandinavia: An Elemental Treasure Trove |doi=10.1021/bk-2014-1179.ch011}}</ref> Terbium was not isolated in pure form until the advent of [[ion exchange]] techniques.<ref name="history">{{cite book |author=Gupta, C. K. |url=https://books.google.com/books?id=E1npz8pwmYwC&pg=PA5 |title=Extractive metallurgy of rare earths |author2=Krishnamurthy, Nagaiyar |date=2004 |publisher=CRC Press |isbn=978-0-415-33340-5 |page=5}}</ref>

Mosander first separated yttria into three fractions, all named for the ore: yttria, erbia, and terbia. "Terbia" was originally the fraction that contained the pink color, due to the element now known as [[erbium]]. "Erbia", the oxide containing what is now known as terbium, originally was the fraction that was yellow or dark orange in solution.<ref name="Beginnings" /><ref name="XVI" /> The insoluble oxide of this element was noted to be tinged brown,<ref>{{Cite journal|url=https://adsabs.harvard.edu/full/1906ApJ....24..309E |journal=Astrophysical Journal |volume=24 |page=309 |date=1906 |first1=G. |last1=Eberhard |title=A Spectroscopic Investigation of Dr. G. Urbain's Preparations of Terbium |issue=5|doi=10.1086/141398 |bibcode=1906ApJ....24..309E }}</ref><ref>{{Cite journal |last1=Stubblefield |first1=C. T. |last2=Eick |first2=H. |last3=Eyring |first3=L. |date=August 1956 |title=Terbium Oxides. II. The Heats of Formation of Several Oxides 1 |url=https://pubs.acs.org/doi/abs/10.1021/ja01597a005 |journal=Journal of the American Chemical Society |language=en |volume=78 |issue=16 |pages=3877–3879 |doi=10.1021/ja01597a005 |bibcode=1956JAChS..78.3877S |issn=0002-7863|url-access=subscription }}</ref><ref name=":02" /> and soluble oxides after combustion were noted to be colorless.<ref name=":0">{{Cite book |last=Watts |first=Henry |url=https://books.google.com/books?id=sYEPAQAAIAAJ&dq=terbium+sulfates+discovery&pg=PA2155 |title=A Dictionary of Chemistry and the Allied Branches of Other Sciences |date=1881 |publisher=Longmans, Green, and Company |pages=2155 |language=en}}</ref> Until the advent of spectral analysis, arguments went back and forth as to whether erbia even existed. Spectral analysis by [[Marc Delafontaine]] allowed the separate elements and their oxides to be identified,<ref name="history" /> but in his publications, the names of erbium and terbium were switched,{{Sfn|Voncken|2016|p=10-11}} following a brief period where terbium was renamed "mosandrum", after Mosander.<ref>{{Cite journal |last=Holden |first=Norman E. |date=March 12, 2004 |orig-date=July 8th, 2001 |title=History of the Origin of the Chemical Elements and Their Discoverers |url=https://www.nndc.bnl.gov/content/elements.html |journal=41st IUPAC General Assembly in Brisbane, Australia}}</ref> The names have remained switched ever since.<ref name="XVI" />

The early years of preparing terbium (as terbium oxide) were difficult. Metal oxides from [[gadolinite]] and [[Samarskite-(Y)|samarskite]] were dissolved in [[nitric acid]], and the solution was further separated using [[oxalic acid]] and [[potassium sulfate]]. There was great difficulty in separating erbia from terbia; in 1881, it was noted that there was no satisfactory method to separate the two.<ref name=":0" /> By 1914, different solvents had been used to separate terbium from its host minerals, but the process of separating terbium from its neighbor elements - [[gadolinium]] and [[dysprosium]] - was described as "tedious" but possible.<ref>{{Cite journal |last1=James |first1=C. |url=https://books.google.com/books?id=Yf_yAAAAMAAJ |journal=Journal of the American Chemical Society |last2=Bissel |first2=D. W. |date=June 4, 1914 |publisher=American Chemical Society |pages=2062 |language=en |title=Terbium}}</ref> Modern terbium extraction methods are based on the [[liquid–liquid extraction]] process developed by Werner Fischer et al., in 1937.<ref>{{Cite book |last1=Bünzli |first1=Jean-Claude G. |url=https://onlinelibrary.wiley.com/doi/book/10.1002/14356007 |title=Ullmann's Encyclopedia of Industrial Chemistry |last2=Mcgill |first2=Ian |date=2003-03-11 |publisher=Wiley |isbn=978-3-527-30385-4 |edition=1 |language=en |chapter=Rare Earth Elements |doi=10.1002/14356007.a22_607.pub2}}</ref>