Editing Indium

{{Distinguish|Iridium}}
{{good article}}
{{infobox indium}}
'''Indium''' is a [[chemical element]]; it has [[Symbol (chemistry)|symbol]] '''In''' and [[atomic number]] 49. It is a silvery-white [[post-transition metal]] and one of the softest elements. Chemically, indium is similar to [[gallium]] and [[thallium]], and its properties are largely intermediate between the two. It was discovered in 1863 by [[Ferdinand Reich]] and [[Hieronymous Theodor Richter]] by [[spectroscope|spectroscopic methods]] and named for the [[indigo]] blue line in its spectrum.

Indium is used primarily in the production of [[flat-panel display]]s as [[indium tin oxide]] (ITO), a transparent and conductive coating applied to glass. It is also used in the [[semiconductor industry]], in low-melting-point metal [[alloys]] such as [[Solder#Alloying element roles|solders]] and soft-metal high-vacuum seals. It is produced exclusively as a [[by-product]] during the processing of the ores of other metals, chiefly from [[sphalerite]] and other [[zinc]] [[Sulfide mineral|sulfide ores]].

Indium has no biological role and its compounds are toxic when inhaled or injected into the bloodstream, although they are poorly absorbed following ingestion.

==Etymology==
The name comes from the [[Latin]] word ''indicum'' meaning [[Violet (color)|violet]] or [[indigo]].<ref>Royal Society of Chemistry, https://www.rsc.org/ {{Webarchive|url=https://web.archive.org/web/20210420164549/https://www.rsc.org/ |date=2021-04-20 }}</ref> The word ''indicum'' means "Indian", as the naturally based dye [[Indigo dye|indigo]] was originally exported to Europe from [[India]].

==Properties==

===Physical===
[[File:Indium wetting glass.jpg|thumb|left|Indium wetting the glass surface of a test tube]]
Indium is a shiny silvery-white, highly [[ductile]] [[post-transition metal]] with a bright [[Lustre (mineralogy)|luster]].<ref name="InProcess">{{cite journal|last=Alfantazi|first=A. M.|date=2003|title=Processing of indium: a review|journal=Minerals Engineering|volume=16|issue=8|pages=687–694|doi=10.1016/S0892-6875(03)00168-7|author2=Moskalyk, R. R.|bibcode=2003MiEng..16..687A }}</ref> It is so soft ([[Mohs hardness]] 1.2) that it can be cut with a knife and leaves a visible line like a pencil when rubbed on paper.<ref name="Binder">{{cite book |last=Binder |first=Harry H. |date=1999 |title=Lexicon der chemischen Elemente |publisher=S. Hirzel Verlag |isbn=978-3-7776-0736-8 |language=de }}</ref> It is a member of [[boron group|group 13]] on the [[periodic table]] and its properties are mostly intermediate between its vertical neighbors [[gallium]] and [[thallium]]. As with [[tin]], a high-pitched [[tin cry|cry]] is heard when indium is bent – a crackling sound due to [[crystal twinning]].<ref name="InProcess" /> Like gallium, indium is able to [[wetting|wet]] glass. Like both, indium has a low [[melting point]], 156.60&nbsp;°C (313.88&nbsp;°F); higher than its lighter homologue, gallium, but lower than its heavier homologue, thallium, and lower than tin.<ref name="Lange">{{cite book |last=Dean |first=John A. |title=Lange's handbook of chemistry |publisher=McGraw-Hill, Inc.|date=523|isbn=978-0-07-016190-0|edition=Fifteenth }}</ref> The boiling point is 2072&nbsp;°C (3762&nbsp;°F), higher than that of thallium, but lower than gallium, conversely to the general trend of melting points, but similarly to the trends down the other post-transition metal groups because of the weakness of the metallic bonding with few [[Delocalized electron|electrons delocalized]].<ref name="Greenwood222">Greenwood and Earnshaw, p. 222</ref>

The density of indium, 7.31&nbsp;g/cm<sup>3</sup>, is also greater than gallium, but lower than thallium. Below the [[critical temperature]], 3.41&nbsp;[[kelvin|K]], indium becomes a [[superconductor]]. Indium crystallizes in the body-centered [[tetragonal crystal system]] in the [[space group]] ''I''4/''mmm'' ([[lattice parameter]]s:&nbsp;''a''&nbsp;=&nbsp;325&nbsp;[[picometer|pm]], ''c''&nbsp;=&nbsp;495&nbsp;pm):<ref name="Lange" /> this is a slightly distorted [[face-centered cubic]] structure, where each indium atom has four neighbours at 324&nbsp;pm distance and eight neighbours slightly further (336&nbsp;pm).<ref name="Greenwood252">Greenwood and Earnshaw, p. 252</ref> Indium has greater solubility in liquid mercury than any other metal (more than 50 mass percent of indium at 0&nbsp;°C).<ref>{{Cite journal|title=Hg-In phase diagram|journal=Journal of Phase Equilibria and Diffusion|volume=33|issue=2|pages=159–160|doi=10.1007/s11669-012-9993-3|year=2012|last1=Okamoto|first1=H.|s2cid=93043767}}</ref> Indium displays a ductile [[Viscoplasticity|viscoplastic]] response, found to be size-independent in tension and compression. However it does have a [[Size effect on structural strength|size effect]] in bending and indentation, associated to a length-scale of order 50–100&nbsp;μm,<ref>{{Cite journal|last1=Iliev|first1=S. P.|last2=Chen|first2=X.|last3=Pathan|first3=M. V.|last4=Tagarielli|first4=V. L.|date=2017-01-23|title=Measurements of the mechanical response of Indium and of its size dependence in bending and indentation|journal=Materials Science and Engineering: A|volume=683|pages=244–251|doi=10.1016/j.msea.2016.12.017|hdl=10044/1/43082|hdl-access=free}}</ref> significantly large when compared with other metals.

===Chemical===
Indium has 49 electrons, with an electronic configuration of &#91;[[krypton|Kr]]&#93;4d{{sup|10}}5s{{sup|2}}5p{{sup|1}}. In compounds, indium most commonly donates the three outermost electrons to become indium(III), In{{sup|3+}}. In some cases, the pair of 5s-electrons are not donated, resulting in indium(I), In{{sup|+}}. The stabilization of the [[valence (chemistry)|monovalent]] state is attributed to the [[inert pair effect]], in which [[relativistic quantum chemistry|relativistic effects]] stabilize the 5s-orbital, observed in heavier elements. Thallium (indium's heavier [[Homologous series|homolog]]) shows an even stronger effect, causing [[Redox|oxidation]] to thallium(I) to be more probable than to thallium(III),<ref>{{cite book|publisher = Walter de Gruyter|date = 1985|edition = 91–100|pages = 892–893|isbn = 978-3-11-007511-3|title = Lehrbuch der Anorganischen Chemie|first = Arnold F.|last = Holleman|author2 = Wiberg, Egon |author3 = Wiberg, Nils|chapter =Thallium|language=de}}</ref> whereas gallium (indium's lighter homolog) commonly shows only the +3 oxidation state. Thus, although thallium(III) is a moderately strong [[oxidizing agent]], indium(III) is not, and many indium(I) compounds are powerful [[reducing agent]]s.<ref name="G&E">{{Greenwood&Earnshaw2nd}}</ref> While the energy required to include the s-electrons in chemical bonding is lowest for indium among the group 13 metals, bond energies decrease down the group so that by indium, the energy released in forming two additional bonds and attaining the +3 state is not always enough to outweigh the energy needed to involve the 5s-electrons.<ref name="Greenwood256">Greenwood and Earnshaw, p. 256</ref> Indium(I) oxide and hydroxide are more basic and indium(III) oxide and hydroxide are more acidic.<ref name="Greenwood256" />

A number of standard electrode potentials, depending on the reaction under study,<ref>{{RubberBible92nd|page=8.20}}</ref> are reported for indium, reflecting the decreased stability of the +3 oxidation state:<ref name="Greenwood252" />
:{|
|-
| In<sup>2+</sup> + e<sup>−</sup>|| ⇌ In<sup>+</sup> || E<sup>0</sup> = −0.40 V
|-
| In<sup>3+</sup> + e<sup>−</sup>|| ⇌ In<sup>2+</sup> || E<sup>0</sup> = −0.49 V
|-
| In<sup>3+</sup> + 2 e<sup>−</sup>|| ⇌ In<sup>+</sup> || E<sup>0</sup> = −0.443 V
|-
| In<sup>3+</sup> + 3 e<sup>−</sup>|| ⇌ In || E<sup>0</sup> = −0.3382 V
|-
| In<sup>+</sup> + e<sup>−</sup>|| ⇌ In || E<sup>0</sup> = −0.14 V
|}

Indium metal does not react with water, but it is oxidized by stronger oxidizing agents such as [[halogen]]s to give indium(III) compounds. It does not form a [[boride]], [[silicide]], or [[carbide]], and the hydride [[Indium trihydride|InH<sub>3</sub>]] has at best a transitory existence in [[ether]]eal solutions at low temperatures, being unstable enough to spontaneously polymerize without coordination.<ref name="G&E" /> Indium is rather basic in aqueous solution, showing only slight [[amphoteric]] characteristics, and unlike its lighter homologs aluminium and gallium, it is insoluble in aqueous alkaline solutions.<ref name="Greenwood255">Greenwood and Earnshaw, p. 255</ref>

===Isotopes===
{{Main|Isotopes of indium}}
Indium has 39 known [[isotope]]s, ranging in [[mass number]] from 97 to 135. Only two isotopes occur naturally as [[primordial nuclide]]s: indium-113, the only [[stable isotope]], and indium-115, which has a [[half-life]] of 4.41{{e|14}} years, four orders of magnitude greater than the [[age of the Universe]] and nearly 30,000 times greater than half life of [[thorium-232]].<ref name="Audi">{{NUBASE 2003}}</ref> The half-life of <sup>115</sup>In is very long because the [[beta decay]] to <sup>115</sup>[[tin|Sn]] is [[selection rule|spin-forbidden]].<ref>{{cite journal |last1=Dvornický |first1=R. |last2=Šimkovic |first2=F. |date=13–16 June 2011 |title=Second unique forbidden β decay of <sup>115</sup>In and neutrino mass |journal=AIP Conf. Proc. |volume=1417 |issue=33 |page=33 |doi=10.1063/1.3671032|series=AIP Conference Proceedings |bibcode=2011AIPC.1417...33D }}</ref> Indium-115 makes up 95.7% of all indium. Indium is one of three known elements (the others being [[tellurium]] and [[rhenium]]) of which the stable isotope is less abundant in nature than the long-lived primordial radioisotopes.<ref>{{cite web |url=http://www.ciaaw.org/pubs/Periodic_Table_Isotopes.pdf |title=IUPAC Periodic Table of the Isotopes |date=1 October 2013 |website=ciaaw.org |publisher=[[IUPAC]] |access-date=21 June 2016 |archive-date=14 February 2019 |archive-url=https://web.archive.org/web/20190214115238/http://www.ciaaw.org/pubs/Periodic_Table_Isotopes.pdf |url-status=live }}</ref>

The stablest [[synthetic radioisotope|artificial]] isotope is [[indium-111]], with a half-life of approximately 2.8&nbsp;days. All other isotopes have half-lives shorter than 5 hours. Indium also has 47 meta states, among which indium-114m1 (half-life about 49.51&nbsp;days) is the most stable, more stable than the ground state of any indium isotope other than the primordial. All decay by [[isomeric transition]]. The indium isotopes lighter than <sup>113</sup>In predominantly decay through [[electron capture]] or [[positron emission]] to form [[cadmium]] isotopes, while the indium isotopes heavier than <sup>113</sup>In predominantly decay through beta-minus decay to form tin isotopes.<ref name="Audi" />

==Compounds==
{{See also|Indium chalcogenides|Category:Indium compounds}}

===Indium(III)===
[[File:Kristallstruktur Chrom(III)-chlorid.png|thumb|right|upright=1|[[Indium trichloride|InCl<sub>3</sub>]] ''(structure pictured)'' is a common compound of indium.]]
[[Indium(III) oxide]], In<sub>2</sub>O<sub>3</sub>, forms when indium metal is burned in air or when the hydroxide or nitrate is heated.<ref name="downs">{{Cite book| title = Chemistry of aluminium, gallium, indium, and thallium| author = Anthony John Downs| publisher = Springer| year = 1993| isbn = 978-0-7514-0103-5}}</ref> In<sub>2</sub>O<sub>3</sub> adopts a structure like [[alumina]] and is amphoteric, that is able to react with both acids and bases. Indium reacts with water to reproduce soluble [[indium(III) hydroxide]], which is also amphoteric; with alkalis to produce indates(III); and with acids to produce indium(III) salts:

:In(OH)<sub>3</sub> + 3&nbsp;HCl → InCl<sub>3</sub> + 3&nbsp;H<sub>2</sub>O

The analogous sesqui-chalcogenides with [[sulfur]], [[selenium]], and [[tellurium]] are also known.<ref name="Greenwood286">Greenwood and Earnshaw, p. 286</ref> Indium forms the expected [[indium halides|trihalides]]. Chlorination, bromination, and iodination of In produce colorless [[indium(III) chloride|InCl<sub>3</sub>]], [[indium(III) bromide|InBr<sub>3</sub>]], and yellow InI<sub>3</sub>. The compounds are [[Lewis acid]]s, somewhat akin to the better known aluminium trihalides. Again like the related aluminium compound, InF<sub>3</sub> is polymeric.<ref name="Greenwood263">Greenwood and Earnshaw, pp. 263–7</ref>

Direct reaction of indium with the [[pnictogen]]s produces the gray or semimetallic III–V [[semiconductor]]s. Many of them slowly decompose in moist air, necessitating careful storage of semiconductor compounds to prevent contact with the atmosphere. Indium nitride is readily attacked by acids and alkalis.<ref name="Greenwood288">Greenwood and Earnshaw, p. 288</ref>

===Indium(I)===
Indium(I) compounds are not common. The chloride, [[indium(I) bromide|bromide]], and iodide are deeply colored, unlike the parent trihalides from which they are prepared. The fluoride is known only as an unstable gas.<ref name="Greenwood270">Greenwood and Earnshaw, pp. 270–1</ref> Indium(I) oxide black powder is produced when indium(III) oxide decomposes upon heating to 700&nbsp;°C.<ref name="downs" />

===Other oxidation states===
Less frequently, indium forms compounds in oxidation state +2 and even fractional oxidation states. Usually such materials feature In–In bonding, most notably in the [[indium halides|halides]] In<sub>2</sub>X<sub>4</sub> and [In<sub>2</sub>X<sub>6</sub>]<sup>2−</sup>,<ref name="can82">{{cite journal| doi =10.1139/v82-102| title =Neutral complexes of the indium dihalides| date =1982| last1 =Sinclair| first1 =Ian| last2 =Worrall| first2 =Ian J.| journal =Canadian Journal of Chemistry| volume =60| issue =6| pages =695–698| doi-access =free}}</ref> and various subchalcogenides such as In<sub>4</sub>Se<sub>3</sub>.<ref name="Greenwood287">Greenwood and Earnshaw, p. 287</ref> Several other compounds are known to combine indium(I) and indium(III), such as In<sup>I</sup><sub>6</sub>(In<sup>III</sup>Cl<sub>6</sub>)Cl<sub>3</sub>,<ref>{{cite journal |doi = 10.1002/anie.199108241 |title = In7Cl9—A New"Old" Compound in the System In-Cl |date = 1991 |last1 = Beck |first1 = Horst Philipp |last2 = Wilhelm |first2 = Doris |journal = Angewandte Chemie International Edition in English |volume = 30 |issue = 7 |pages = 824–825}}</ref> In<sup>I</sup><sub>5</sub>(In<sup>III</sup>Br<sub>4</sub>)<sub>2</sub>(In<sup>III</sup>Br<sub>6</sub>),<ref>{{cite journal| doi =10.1002/anie.199511261| title =Synthesis, Structure, and Decay of In4Br7| date =1995| last1 =Dronskowski| first1 =Richard| journal =Angewandte Chemie International Edition in English| volume =34| issue =10| pages =1126–1128}}</ref> and In<sup>I</sup>In<sup>III</sup>Br<sub>4</sub>.<ref name="can82" />

===Organoindium compounds===
Organoindium compounds feature In–C bonds. Most are In(III) derivatives, but [[cyclopentadienylindium(I)]] is an exception. It was the first known organoindium(I) compound,<ref>{{cite journal| doi =10.1002/ange.19570692008| title =Metall-cyclopentadienyle des Indiums| date =1957| last1 =Fischer| first1 = E. O.| last2 =Hofmann| first2 = H. P.| journal =Angewandte Chemie| volume =69| issue =20| pages =639–640| bibcode =1957AngCh..69..639F| language =de}}</ref> and is polymeric, consisting of zigzag chains of alternating indium atoms and [[cyclopentadienyl complex]]es.<ref>{{cite journal | title = Synthesis, characterization and structural studies of In(C<sub>5</sub>H<sub>4</sub>Me) by x-ray diffraction and electron diffraction techniques and a reinvestigation of the crystalline state of In(C<sub>5</sub>H<sub>5</sub>) by x-ray diffraction studies |author1=Beachley O. T. |author2=Pazik J. C. |author3=Glassman T. E. |author4=Churchill M. R. |author5=Fettinger J.C. |author6=Blom R. | journal = Organometallics | year = 1988| volume = 7 | issue = 5 | pages = 1051–1059 | doi = 10.1021/om00095a007 }}</ref> Perhaps the best-known organoindium compound is [[trimethylindium]], In(CH<sub>3</sub>)<sub>3</sub>, used to prepare certain semiconducting materials.<ref>{{cite journal | doi = 10.1016/S0022-0248(02)01854-7 | title = Correlation of vapor pressure equation and film properties with trimethylindium purity for the MOVPE grown III–V compounds | year = 2003 | last1 = Shenai | first1 = Deo V. | last2 = Timmons | first2 = Michael L. | last3 = Dicarlo | first3 = Ronald L. | last4 = Lemnah | first4 = Gregory K. | last5 = Stennick | first5 = Robert S. | journal = Journal of Crystal Growth | volume = 248 | pages = 91–98 | bibcode=2003JCrGr.248...91S}}</ref><ref name="shenai2004">{{cite journal | doi = 10.1016/j.jcrysgro.2004.09.006 | title = Correlation of film properties and reduced impurity concentrations in sources for III/V-MOVPE using high-purity trimethylindium and tertiarybutylphosphine | last1 = Shenai | first1 = Deodatta V. | last2 = Timmons | first2 = Michael L. | last3 = Dicarlo | first3 = Ronald L. | last4 = Marsman | first4 = Charles J. | journal = Journal of Crystal Growth | volume = 272 | issue = 1–4 | pages = 603–608 | bibcode=2004JCrGr.272..603S | date= 2004}}</ref>

==History==
In 1863, German chemists [[Ferdinand Reich]] and [[Hieronymous Theodor Richter|Hieronymus Theodor Richter]] were testing ores from the mines around [[Freiberg, Saxony]]. They dissolved the minerals [[pyrite]], [[arsenopyrite]], [[galena]] and [[sphalerite]] in [[hydrochloric acid]] and distilled raw [[zinc chloride]]. Reich, who was [[color-blind]], employed Richter as an assistant for detecting the colored spectral lines. Knowing that ores from that region sometimes contain [[thallium]], they searched for the green thallium emission spectrum lines. Instead, they found a bright blue line. Because that blue line did not match any known element, they hypothesized a new element was present in the minerals. They named the element indium, from the [[indigo]] color seen in its spectrum, after the Latin ''indicum'', meaning 'of [[India]]'.<ref>{{cite journal|title = Ueber das Indium|author = Reich, F.|author2 = Richter, T.|journal = Journal für Praktische Chemie|volume = 90|issue = 1|pages = 172–176|date = 1863|doi = 10.1002/prac.18630900122|s2cid = 94381243|language = de|url = https://zenodo.org/record/1427838|access-date = 2019-06-30|archive-date = 2020-02-02|archive-url = https://web.archive.org/web/20200202154729/https://zenodo.org/record/1427838|url-status = live}}</ref><ref name="Venetskii">{{cite journal|title = Indium|last = Venetskii|first = S.|journal = Metallurgist|volume = 15|issue = 2|pages = 148–150|date = 1971|doi = 10.1007/BF01088126}}</ref><ref name="Greenwood244">Greenwood and Earnshaw, p. 244</ref><ref name="Weeks">{{cite journal|author=Weeks, Mary Elvira |author-link=Mary Elvira Weeks |title=The Discovery of the Elements: XIII. Some Spectroscopic Studies |journal=Journal of Chemical Education |volume=9 |issue=8 |pages=1413–1434 |url=http://search.jce.divched.org/JCEIndex/FMPro?-db=jceindex.fp5&-lay=wwwform&combo=weeks&-find=&-format=detail.html&-skip=27&-max=1&-token.2=27&-token.3=10 |doi=10.1021/ed009p1413 |year=1932 |bibcode=1932JChEd...9.1413W }}{{dead link|date=April 2017 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

Richter went on to isolate the metal in 1864.<ref>{{cite journal|title = Ueber das Indium|author = Reich, F.|author2=Richter, T.|journal = Journal für Praktische Chemie|volume = 92 |issue = 1 |pages = 480–485 |date = 1864|doi = 10.1002/prac.18640920180|language=de}}</ref> An ingot of {{convert|0.5|kg|lb|abbr=on}} was presented at the [[Exposition Universelle (1867)|World Fair]] 1867.<ref name="SchSch">{{cite book|title = Indium: Geology, Mineralogy, and Economics|first = Ulrich|last = Schwarz-Schampera|author2=Herzig, Peter M.|publisher = Springer|date = 2002|isbn = 978-3-540-43135-0|url = https://books.google.com/books?id=k7x_2_KnupMC&pg=PA1}}</ref> <!-- Until 1924, only approximately a gram of indium constituted the world's supply.<ref name=g1>{{cite journal|doi =10.1063/1.1769802|title =New Materials|year =1941|last1 =Olpin|first1 = A. R.|journal =Review of Scientific Instruments|volume =12|page =560|issue =11|bibcode = 1941RScI...12..560O }}</ref><ref name=g2>{{cite book|url=https://books.google.com/books?id=QdU-lRMjOsgC&pg=PA24|title=Infectious diseases and pathology of reptiles: color atlas and text|author=Jacobson, E. R.|page=24|publisher=CRC Press|year=2007|isbn=0-8493-2321-5}}</ref> --> Reich and Richter later fell out when the latter claimed to be the sole discoverer.<ref name="Weeks" />

==Occurrence==
[[File:S-process-elem-Ag-to-Sb.svg|thumb|upright=1.4|alt=yellow squares with red and blue arrows|The s-process acting in the range from [[silver]] to [[antimony]]]]
Indium is created by the long-lasting (up to thousands of years) [[s-process]] (slow neutron capture) in low-to-medium-mass stars (range in mass between 0.6 and 10 [[solar mass]]es). When a silver-109 atom captures a neutron, it transmutes into silver-110, which then undergoes [[beta decay]] to become cadmium-110. Capturing further neutrons, it becomes cadmium-115, which decays to indium-115 by another [[beta decay]]. This explains why the radioactive isotope is more abundant than the stable one.<ref>{{cite journal|first=A. I. | last= Boothroyd| title = Heavy elements in stars| journal= Science| volume= 314 | issue= 5806| date= 2006 | pages= 1690–1691 | doi= 10.1126/science.1136842 | pmid = 17170281| s2cid= 116938510}}</ref> The stable indium isotope, indium-113, is one of the [[p-nuclei]], the origin of which is not fully understood; although indium-113 is known to be made directly in the s- and [[r-process]]es (rapid neutron capture), and also as the daughter of very long-lived cadmium-113, which has a half-life of about eight [[quadrillion]] years, this cannot account for all indium-113.<ref name="s-contrib">{{cite journal | last1 = Arlandini | first1 = C. | last2 = Käppeler | first2 = F. | last3 = Wisshak | first3 = K. | last4 = Gallino | first4 = R. | last5 = Lugaro | first5 = M. | last6 = Busso | first6 = M. | last7 = Straniero | first7 = O. | year = 1999| title = Neutron Capture in Low-Mass Asymptotic Giant Branch Stars: Cross Sections and Abundance Signatures. | journal = The Astrophysical Journal | volume = 525 | issue = 2 | pages = 886–900 | doi = 10.1086/307938 | arxiv = astro-ph/9906266 | bibcode = 1999ApJ...525..886A | s2cid = 10847307 }}</ref><ref name="r-contrib">{{cite journal | last1 = Zs | last2 = Käppeler | first2 = F. | last3 = Theis | first3 = C. | last4 = Belgya | first4 = T. | last5 = Yates | first5 = S. W. | year = 1994| title = Nucleosynthesis in the Cd-In-Sn region. | journal = The Astrophysical Journal | volume = 426 | pages = 357–365 | doi = 10.1086/174071 | bibcode = 1994ApJ...426..357N }}</ref>

Indium is the [[Abundance of elements in Earth's crust|68th most abundant element in Earth's crust]] at approximately 50 [[parts per billion|ppb]]. This is similar to the crustal abundance of [[silver]], [[bismuth]] and [[Mercury (element)|mercury]]. It very rarely forms its own minerals, or occurs in elemental form. Fewer than 10 indium minerals such as [[roquesite]] (CuInS<sub>2</sub>) are known, and none occur at sufficient concentrations for economic extraction.<ref name="Frenzel-2016">{{Cite journal|url=https://www.researchgate.net/publication/309583931|title=The distribution of gallium, germanium and indium in conventional and non-conventional resources - Implications for global availability (PDF Download Available)|website=ResearchGate|doi=10.13140/rg.2.2.20956.18564|access-date=2017-06-02|year=2016|last1=Frenzel|first1=Max|archive-date=2018-10-06|archive-url=https://web.archive.org/web/20181006235214/https://www.researchgate.net/publication/309583931|url-status=live}}</ref> Instead, indium is usually a trace constituent of more common ore minerals, such as [[sphalerite]] and [[chalcopyrite]].<ref>{{Cite journal|last1=Frenzel|first1=Max|last2=Hirsch|first2=Tamino|last3=Gutzmer|first3=Jens|date=July 2016|title=Gallium, germanium, indium, and other trace and minor elements in sphalerite as a function of deposit type — A meta-analysis|journal=Ore Geology Reviews|volume=76|pages=52–78|doi=10.1016/j.oregeorev.2015.12.017|bibcode=2016OGRv...76...52F }}</ref><ref>{{Cite journal|last1=Bachmann|first1=Kai|last2=Frenzel|first2=Max|last3=Krause|first3=Joachim|last4=Gutzmer|first4=Jens|date=June 2017|title=Advanced Identification and Quantification of In-Bearing Minerals by Scanning Electron Microscope-Based Image Analysis|journal=Microscopy and Microanalysis|volume=23|issue=3|pages=527–537|doi=10.1017/S1431927617000460|pmid=28464970|issn=1431-9276|bibcode=2017MiMic..23..527B|s2cid=6751828}}</ref> From these, it can be extracted as a [[by-product]] during smelting.<ref name="Frenzel-2017">{{Cite journal|last1=Frenzel|first1=Max|last2=Mikolajczak|first2=Claire|last3=Reuter|first3=Markus A.|last4=Gutzmer|first4=Jens|date=June 2017|title=Quantifying the relative availability of high-tech by-product metals – The cases of gallium, germanium and indium|journal=Resources Policy|volume=52|pages=327–335|doi=10.1016/j.resourpol.2017.04.008|bibcode=2017RePol..52..327F |doi-access=free}}</ref> While the enrichment of indium in these deposits is high relative to its crustal abundance, it is insufficient, at current prices, to support extraction of indium as the main product.<ref name="Frenzel-2016" />

Different estimates exist of the amounts of indium contained within the ores of other metals.<ref name="USGSCS2007">{{cite web|url=http://minerals.usgs.gov/minerals/pubs/commodity/indium/indiumcs07.pdf|title=Mineral Commodities Summary 2007: Indium|publisher=United States Geological Survey|access-date=2007-12-26|archive-date=2008-05-09|archive-url=https://web.archive.org/web/20080509184325/http://minerals.usgs.gov/minerals/pubs/commodity/indium/indiumcs07.pdf|url-status=live}}</ref><ref>{{Cite journal|last1=Werner|first1=T. T.|last2=Mudd|first2=G. M.|last3=Jowitt|first3=S. M.|date=2015-10-02|title=Indium: key issues in assessing mineral resources and long-term supply from recycling|journal=Applied Earth Science|volume=124|issue=4|pages=213–226|doi=10.1179/1743275815Y.0000000007|bibcode=2015ApEaS.124..213W |s2cid=128555024|issn=0371-7453}}</ref> However, these amounts are not extractable without mining of the host materials (see Production and availability). Thus, the availability of indium is fundamentally determined by the ''rate'' at which these ores are extracted, and not their absolute amount. This is an aspect that is often forgotten in the current debate, e.g. by the Graedel group at Yale in their criticality assessments,<ref>{{Cite journal|last1=Graedel|first1=T. E.|last2=Barr|first2=Rachel|last3=Chandler|first3=Chelsea|last4=Chase|first4=Thomas|last5=Choi|first5=Joanne|last6=Christoffersen|first6=Lee|last7=Friedlander|first7=Elizabeth|last8=Henly|first8=Claire|last9=Jun|first9=Christine|date=2012-01-17|title=Methodology of Metal Criticality Determination|journal=Environmental Science & Technology|volume=46|issue=2|pages=1063–1070|doi=10.1021/es203534z|pmid=22191617|issn=0013-936X|bibcode=2012EnST...46.1063G}}</ref> explaining the paradoxically low depletion times some studies cite.<ref>{{Cite journal|last1=Harper|first1=E. M.|last2=Kavlak|first2=Goksin|last3=Burmeister|first3=Lara|last4=Eckelman|first4=Matthew J.|last5=Erbis|first5=Serkan|last6=Sebastian Espinoza|first6=Vicente|last7=Nuss|first7=Philip|last8=Graedel|first8=T. E.|date=2015-08-01|title=Criticality of the Geological Zinc, Tin, and Lead Family|journal=Journal of Industrial Ecology|volume=19|issue=4|pages=628–644|doi=10.1111/jiec.12213|bibcode=2015JInEc..19..628H |s2cid=153380535|issn=1530-9290|url=http://hdl.handle.net/10.1111/jiec.2015.19.issue-4}}{{Dead link|date=October 2022 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref name="Frenzel-2017" />

==Production and availability==
[[File:Indium world production.svg|thumb|World production trend<ref>[http://minerals.usgs.gov/minerals/pubs/historical-statistics/ U.S. Geological Survey – Historical Statistics for Mineral and Material Commodities in the United States]; [http://minerals.usgs.gov/minerals/pubs/historical-statistics/ds140-indiu.pdf INDIUM STATISTICS] // USGS, April 1, 2014</ref>]]
Indium is produced exclusively as a [[by-product]] during the processing of the ores of other metals. Its main source material are sulfidic zinc ores, where it is mostly hosted by sphalerite.<ref name="Frenzel-2017" /> Minor amounts are also extracted from sulfidic copper ores. During the [[Zinc smelting|roast-leach-electrowinning process of zinc smelting]], indium accumulates in the iron-rich residues. From these, it can be extracted in different ways. It may also be recovered directly from the process solutions. Further purification is done by [[electrolysis]].<ref name="Greenwood247">Greenwood and Earnshaw, p. 247</ref> The exact process varies with the mode of operation of the smelter.<ref name="InProcess" /><ref name="Frenzel-2017" />

Its by-product status means that indium production is constrained by the amount of sulfidic zinc (and copper) ores extracted each year. Therefore, its availability needs to be discussed in terms of supply potential. The supply potential of a by-product is defined as that amount which is economically extractable from its host materials ''per year'' under current market conditions (i.e. technology and price).<ref>{{Cite journal|last1=Frenzel|first1=Max|last2=Tolosana-Delgado|first2=Raimon|last3=Gutzmer|first3=Jens|date=December 2015|title=Assessing the supply potential of high-tech metals – A general method|journal=Resources Policy|volume=46, Part 2|pages=45–58|doi=10.1016/j.resourpol.2015.08.002|bibcode=2015RePol..46...45F }}</ref> Reserves and resources are not relevant for by-products, since they ''cannot'' be extracted independently from the main-products.<ref name="Frenzel-2017" /> Recent estimates put the supply potential of indium at a minimum of 1,300 t/yr from sulfidic zinc ores and 20 t/yr from sulfidic copper ores.<ref name="Frenzel-2017" /> These figures are significantly greater than current production (655 t in 2016).<ref name="USGS-2017">{{Cite book|url=https://minerals.usgs.gov/minerals/pubs/commodity/indium/mcs-2017-indiu.pdf|title=Indium - in: USGS Mineral Commodity Summaries|publisher=United States Geological Survey|year=2017|access-date=2017-06-02|archive-date=2019-01-11|archive-url=https://web.archive.org/web/20190111092318/https://minerals.usgs.gov/minerals/pubs/commodity/indium/mcs-2017-indiu.pdf|url-status=live}}</ref> Thus, major future increases in the by-product production of indium will be possible without significant increases in production costs or price. The average indium price in 2016 was {{US$}}240/kg, down from {{US$}}705/kg in 2014.<ref>{{Cite web|url=https://minerals.usgs.gov/minerals/pubs/historical-statistics/index.html|title=Historical Statistics for Mineral and Material Commodities in the United States|last1=Kelly|first1=TD|last2=Matos|first2=GR|date=2015|access-date=2017-06-02|archive-date=2017-05-11|archive-url=https://web.archive.org/web/20170511080923/https://minerals.usgs.gov/minerals/pubs/historical-statistics/index.html|url-status=live}}</ref>

China is a leading producer of indium (290 tonnes in 2016), followed by South Korea (195 t), Japan (70 t) and Canada (65 t).<ref name="USGS-2017" /> The [[Teck Resources]] refinery in [[Trail, British Columbia]], is a large single-source indium producer, with an output of 32.5&nbsp;tonnes in 2005, 41.8&nbsp;tonnes in 2004 and 36.1&nbsp;tonnes in 2003.

The primary consumption of indium worldwide is [[Liquid crystal display|LCD]] production. Demand rose rapidly from the late 1990s to 2010 with the popularity of LCD computer monitors and television sets, which now account for 50% of indium consumption.<ref name=":0">{{cite web|title = Indium Price Supported by LCD Demand and New Uses for the Metal|work = Geology.com|format = PDF|url = http://geology.com/articles/indium.shtml|access-date = 2007-12-26|archive-url = https://web.archive.org/web/20071221130320/http://geology.com/articles/indium.shtml|archive-date = 2007-12-21}}</ref> Increased manufacturing efficiency and recycling (especially in Japan) maintain a balance between demand and supply. According to the [[UNEP]], indium's end-of-life recycling rate is less than 1%.<ref name="USGS2011">{{cite web|title=USGS Mineral Commodity Summaries 2011|url=http://minerals.usgs.gov/minerals/pubs/mcs/2011/mcs2011.pdf|publisher=USGS and USDI|access-date=August 2, 2011|archive-date=January 11, 2019|archive-url=https://web.archive.org/web/20190111211631/https://minerals.usgs.gov/minerals/pubs/mcs/2011/mcs2011.pdf|url-status=live}}</ref>

==Applications==
===Industrial uses===
[[File:Dell axim LCD under microscope.jpg|thumb|right|A magnified image of an [[TFT LCD|LCD]] screen showing RGB pixels. Individual transistors are seen as white dots in the bottom part.]]
In 1924, indium was found to have a valued property of stabilizing [[non-ferrous metals]], and that became the first significant use for the element.<ref name="dd">{{cite journal |doi = 10.1021/ed011p270 |title = A story of indium |date = 1934 |last1 = French |first1 = Sidney J. |journal = Journal of Chemical Education |volume = 11 |issue = 5 |page = 270|bibcode = 1934JChEd..11..270F }}</ref> The first large-scale application for indium was coating [[bearing (mechanical)|bearings]] in high-performance [[aircraft]] engines during [[World War II]], to protect against damage and [[corrosion]]; this is no longer a major use of the element.<ref name="Greenwood247" /> New uses were found in [[fusible alloy]]s, [[solder]]s, and [[electronics]]. In the 1950s, tiny beads of indium were used for the emitters and collectors of PNP [[alloy-junction transistor]]s. In the middle and late 1980s, the development of [[indium phosphide]] [[semiconductor]]s and [[indium tin oxide]] thin films for [[liquid-crystal display]]s (LCD) aroused much interest. By 1992, the thin-film application had become the largest end use.<ref name="USGSYB2007">{{cite web|title = Mineral Yearbook 2007: Indium|publisher = United States Geological Survey|first = Amy C.|last = Tolcin|url = http://minerals.usgs.gov/mineralofthemonth/indium.pdf|access-date = 2009-12-03|archive-date = 2016-12-31|archive-url = https://web.archive.org/web/20161231013853/https://minerals.usgs.gov/mineralofthemonth/indium.pdf|url-status = live}}</ref><ref name="Downs">{{cite book|title = Chemistry of Aluminium, Gallium, Indium, and Thallium |first =Anthony John|last = Downs|publisher = Springer|date = 1993|isbn = 978-0-7514-0103-5|pages = 89 and 106|url = https://books.google.com/books?id=v-04Kn758yIC}}</ref>

Indium(III) oxide and [[indium tin oxide]] (ITO) are used as a [[transparency (optics)|transparent]] [[electrical conductor|conductive]] coating on [[glass]] substrates in [[electroluminescent]] panels.<ref>{{cite web|title=The Electroluminescent Light Sabre |work=Nanotechnology News Archive |publisher=Azonano |date=June 2, 2005 |url=http://azonano.com/news.asp?newsID=1007 |access-date=2007-08-29  |archive-url=https://web.archive.org/web/20071012003936/http://azonano.com/news.asp?newsID=1007 |archive-date=October 12, 2007 }}</ref> Indium tin oxide is used as a light filter in [[sodium-vapor lamp#Low-pressure sodium|low-pressure sodium-vapor lamps]]. The [[infrared radiation]] is reflected back into the lamp, which increases the temperature within the tube and improves the performance of the lamp.<ref name="Downs" />

Indium has many [[semiconductor]]-related applications. Some indium compounds, such as [[indium antimonide]] and [[indium phosphide]],<ref>{{cite journal|title = Properties, Preparation, and Device Applications of Indium Phosphide|journal = [[Annual Review of Materials Science]]|volume = 11|pages = 441–484|date = 1981|doi = 10.1146/annurev.ms.11.080181.002301|first = K. J.|last = Bachmann|bibcode = 1981AnRMS..11..441B }}</ref> are [[semiconductor]]s with useful properties: one precursor is usually [[trimethylindium]] (TMI), which is also used as the [[semiconductor]] [[dopant]] in II–VI [[compound semiconductor]]s.<ref name="shenai2004" /> InAs and InSb are used for low-temperature transistors and InP for high-temperature transistors.<ref name="Greenwood247" /> The [[compound semiconductor]]s [[InGaN]] and [[InGaP]] are used in [[light-emitting diode]]s (LEDs) and laser diodes.<ref>{{cite book|isbn=978-0-521-53351-5|title=Light-Emitting Diodes|author=Schubert, E. Fred |date=2003|page=16|publisher=Cambridge University Press}}</ref> Indium is used in [[photovoltaics]] as the semiconductor [[copper indium gallium selenide]] (CIGS), also called [[CIGS solar cell]]s, a type of second-generation [[thin-film solar cell]].<ref>{{cite journal|title = Scaling up issues of CIGS solar cells
| volume = 361–362| issue = 1–2|date = 2000| pages = 540–546|doi = 10.1016/S0040-6090(99)00849-4|first = M.|last = Powalla|author2=Dimmler, B.|journal = Thin Solid Films|bibcode=2000TSF...361..540P}}</ref> Indium is used in PNP [[bipolar junction transistor]]s with [[germanium]]: when soldered at low temperature, indium does not stress the germanium.<ref name="Greenwood247" />

[[File:Indium wire.jpg|thumb|left|Ductile indium wire]]
[[File:Indium Lung Disease.webm|thumb|left|A video on [[indium lung]], an illness caused by indium exposure]]
Indium wire is used as a [[cryogenic seal|vacuum seal]] and a thermal conductor in [[cryogenics]] and [[ultra-high vacuum|ultra-high-vacuum]] applications, in such manufacturing applications as [[gasket]]s that deform to fill gaps.<ref>{{Cite book|url = https://books.google.com/books?id=tfLWfAx1ZWQC&pg=PA296|page = 296|isbn = 978-0-12-475914-5|editor= Weissler, G. L. |date = 1990|publisher = Acad. Press|location = San Diego|title = Vacuum physics and technology}}</ref> Owing to its great plasticity and adhesion to metals, Indium sheets are sometimes used for cold-soldering in [[Microwave engineering|microwave]] circuits and [[waveguide]] joints, where direct soldering is complicated. Indium is an ingredient in the gallium–indium–tin alloy [[galinstan]], which is liquid at room temperature and replaces [[mercury (element)|mercury]] in some [[thermometer]]s.<ref>{{cite journal|doi=10.1007/s00216-005-0069-7|date=Nov 2005|author=Surmann, P|author2=Zeyat, H| title=Voltammetric analysis using a self-renewable non-mercury electrode| volume=383|issue=6|pages=1009–13| pmid=16228199|journal= Analytical and Bioanalytical Chemistry|s2cid=22732411}}</ref> Other alloys of indium with [[bismuth]], [[cadmium]], [[lead]], and [[tin]], which have higher but still low melting points (between 50 and 100&nbsp;°C), are used in [[fire sprinkler system]]s and heat regulators.<ref name="Greenwood247" />

Indium is one of many substitutes for mercury in [[alkaline batteries]] to prevent the [[zinc]] from corroding and releasing [[hydrogen]] gas.<ref>{{cite book|title=Minerals Yearbook, 2008, V. 1, Metals and Minerals|author=Geological Survey (U.S.)|date=2010|pages=35–2|publisher=Government Printing Office|isbn=978-1-4113-3015-3}}</ref> Indium is added to some [[dental amalgam]] alloys to decrease the [[surface tension]] of the mercury and allow for less mercury and easier amalgamation.<ref>{{cite journal|author=Powell L. V. |author2=Johnson G. H. |author3=Bales D. J. |title=Effect of Admixed Indium on Mercury Vapor Release from Dental Amalgam|journal=Journal of Dental Research|volume=68|issue=8|pages=1231–3|doi=10.1177/00220345890680080301|pmid=2632609|year=1989|citeseerx=10.1.1.576.2654|s2cid=28342583}}</ref>

Indium's high neutron-capture cross-section for thermal neutrons makes it suitable for use in [[control rod]]s for [[nuclear reactors]], typically in an alloy of 80% [[silver]], 15% indium, and 5% [[cadmium]].<ref>{{cite book | chapter-url = https://books.google.com/books?id=9yzN-QGag_8C&pg=PA222 | page = 222 | chapter= Other types of cadmium alloys | title = Mercury, cadmium, lead: handbook for sustainable heavy metals policy and regulation | isbn = 978-1-4020-0224-3 | author1 = Scoullos, Michael J. | date = 2001-12-31| publisher = Springer }}</ref> In nuclear engineering, the (n,n') reactions of <sup>113</sup>In and <sup>115</sup>In are used to determine magnitudes of neutron fluxes.<ref>{{cite book | chapter-url = https://books.google.com/books?id=b1ZwQXdxAtUC&pg=PA50 | pages = 50–51 | chapter = Image Detectors for Other Neutron Energies | title = Practical applications of neutron radiography and gaging: a symposium | author1 = Berger, Harold | author2 = National Bureau Of Standards, United States | author3 = Committee E-7 On Nondestructive Testing, American Society for Testing and Materials | date = 1976}}</ref>

In 2009, Professor [[Mas Subramanian]] and former graduate student Andrew Smith at [[Oregon State University]] discovered that indium can be combined with [[yttrium]] and [[manganese]] to form an intensely [[blue]], non-toxic, inert, fade-resistant [[pigment]], [[YInMn blue]], the first new inorganic blue pigment discovered in 200 years.<ref name="Kupferschmidt pp. 424–429">{{cite journal | last=Kupferschmidt | first=Kai | title=In search of blue | journal=Science | publisher=American Association for the Advancement of Science (AAAS) | volume=364 | issue=6439 | date=2019-05-02 | issn=0036-8075 | doi=10.1126/science.364.6439.424 | pages=424–429| pmid=31048474 | bibcode=2019Sci...364..424K | s2cid=143434096 }}</ref>

===Medical applications===
Radioactive indium-111 (in very small amounts) is used in [[nuclear medicine]] tests, as a [[radiotracer]] to follow the movement of labeled proteins and [[indium leukocyte imaging|white blood cells]] to diagnose different types of infection.<ref name="Indium-111 Radiochemical Indium Chloride Solution">{{cite web|title=IN-111 FACT SHEET|url=http://www.nordion.com/documents/products/In-111_Can.pdf|publisher=Nordion(Canada), Inc.|access-date=23 September 2012|archive-url=https://web.archive.org/web/20111203082605/http://www.nordion.com/documents/products/In-111_Can.pdf|archive-date=3 December 2011}}</ref><ref>{{cite journal |last1=Van Nostrand |first1=D. |last2=Abreu |first2=S. H. |last3=Callaghan |first3=J. J. |last4=Atkins |first4=F. B. |last5=Stoops |first5=H. C. |last6=Savory |first6=C. G. |date=May 1988 |title=In-111-labeled white blood cell uptake in noninfected closed fracture in humans: prospective study |journal=Radiology |volume=167 |issue= 2|pages=495–498 |pmid=3357961 | doi = 10.1148/radiology.167.2.3357961}}</ref> Indium compounds are mostly not absorbed upon ingestion and are only moderately absorbed on inhalation; they tend to be stored temporarily in the [[muscle]]s, [[skin]], and [[bone]]s before being excreted, and the [[biological half-life]] of indium is about two weeks in humans.<ref>{{cite book |first1=Gunnar F. |last1=Nordberg |first2=Bruce A. |last2=Fowler |first3=Monica |last3=Nordberg |title=Handbook on the Toxicology of Metals |publisher=Academic Press |page=845 |edition=4th |date=7 August 2014 |isbn=978-0-12-397339-9}}</ref> It is also tagged to [[growth hormone]] analogues like [[octreotide]] to find [[growth hormone]] receptors in [[neuroendocrine tumors]].<ref>{{cite journal |pmid=1349039 |date=1992 |last1=Krenning |first1=E. P. |last2=Bakker |first2=W. H. |last3=Kooij |first3=P. P. |last4=Breeman |first4=W. A. |last5=Oei |first5=H. Y. |last6=De Jong |first6=M. |last7=Reubi |first7=J. C. |last8=Visser |first8=T. J. |last9=Bruns |first9=C. |last10=Kwekkeboom |first10=D. J. |title=Somatostatin receptor scintigraphy with indium-111-DTPA-D-Phe-1-octreotide in man: Metabolism, dosimetry and comparison with iodine-123-Tyr-3-octreotide |journal=Journal of Nuclear Medicine |volume=33 |issue=5 |pages=652–658 }}</ref>

==Biological role and precautions==
{{Chembox
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|Section7={{Chembox Hazards
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| GHSSignalWord = Warning
| HPhrases = {{H-phrases|302|312|332|315|319|335}}
| PPhrases = {{P-phrases|261|280|305+351+338}}<ref>{{cite web | url=https://www.sigmaaldrich.com/catalog/product/aldrich/57083?lang=en&region=US | title=Indium 57083 | access-date=2018-10-02 | archive-date=2018-10-02 | archive-url=https://web.archive.org/web/20181002172504/https://www.sigmaaldrich.com/catalog/product/aldrich/57083?lang=en&region=US | url-status=live }}</ref>
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Indium has no [[Dietary element|metabolic]] role in any organism. In a similar way to aluminium salts, indium(III) ions can be toxic to the kidney when given by injection.<ref name="toxic">{{cite journal |last1=Castronovo |first1=F. P. |last2=Wagner |first2=H. N. |date=October 1971 |title=Factors Affecting the Toxicity of the Element Indium |pmc=2072430 |journal=British Journal of Experimental Pathology |volume=52 |issue=5 |pages=543–559 |pmid=5125268}}</ref> Indium tin oxide and indium phosphide harm the pulmonary and immune systems, predominantly through ionic indium,<ref>{{Cite journal
 | pmid = 25527823
| pmc = 4349143
| year = 2014
| last1 = Gwinn
| first1 = W. M.
| title = Macrophage Solubilization and Cytotoxicity of Indium-Containing Particles as in vitro Correlates to Pulmonary Toxicity in vivo
| journal = Toxicological Sciences
| last2 = Qu
| first2 = W.
| last3 = Bousquet
| first3 = R. W.
| last4 = Price
| first4 = H.
| last5 = Shines
| first5 = C. J.
| last6 = Taylor
| first6 = G. J.
| last7 = Waalkes
| first7 = M. P.
| last8 = Morgan
| first8 = D. L.
| doi = 10.1093/toxsci/kfu273
 | volume=144
 | issue = 1
| pages=17–26
}}</ref> though hydrated indium oxide is more than forty times as toxic when injected, measured by the quantity of indium introduced.<ref name="toxic" />

People can be exposed to indium in the workplace by inhalation, ingestion, skin contact, and eye contact. [[Indium lung]] is a lung disease characterized by pulmonary alveolar proteinosis and pulmonary fibrosis, first described by Japanese researchers in 2003. {{As of|2010}}, 10 cases had been described, though more than 100 indium workers had documented respiratory abnormalities.<ref name="Sauler">{{cite journal|last1=Sauler|first1=Maor|last2=Gulati|first2=Mridu|title=Newly Recognized Occupational and Environmental Causes of Chronic Terminal Airways and Parenchymal Lung Disease|journal=Clinics in Chest Medicine|date=December 2012|volume=33|issue=4|pages=667–680|doi=10.1016/j.ccm.2012.09.002|pmid=23153608|pmc=3515663}}</ref> The [[National Institute for Occupational Safety and Health]] has set a [[recommended exposure limit]] (REL) of 0.1&nbsp;mg/m{{sup|3}} over an eight-hour workday.<ref>{{Cite web|title = CDC – NIOSH Pocket Guide to Chemical Hazards – Indium|url = https://www.cdc.gov/niosh/npg/npgd0341.html|website = www.cdc.gov|access-date = 2015-11-06|archive-date = 2015-12-08|archive-url = https://web.archive.org/web/20151208163910/http://www.cdc.gov/niosh/npg/npgd0341.html|url-status = live}}</ref>

==Notes==
{{notelist}}

==References==
{{Reflist|30em}}

==Sources==
*{{Greenwood&Earnshaw1st}}

==External links==
* [http://www.periodicvideos.com/videos/049.htm Indium] {{Webarchive|url=https://web.archive.org/web/20230313152040/http://www.periodicvideos.com/videos/049.htm |date=2023-03-13 }} at ''[[The Periodic Table of Videos]]'' (University of Nottingham)
* [https://www.organic-chemistry.org/chemicals/reductions/indiumlowvalent.shtm Reducing Agents > Indium low valent] {{Webarchive|url=https://web.archive.org/web/20230709174439/https://www.organic-chemistry.org/chemicals/reductions/indiumlowvalent.shtm |date=2023-07-09 }}
* [https://www.cdc.gov/niosh/npg/npgd0341.html NIOSH Pocket Guide to Chemical Hazards] {{Webarchive|url=https://web.archive.org/web/20151208163910/http://www.cdc.gov/niosh/npg/npgd0341.html |date=2015-12-08 }} (Centers for Disease Control and Prevention)

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[[Category:Indium| ]]
[[Category:Chemical elements]]
[[Category:Post-transition metals]]
[[Category:Native element minerals]]
[[Category:Chemical elements with body-centered tetragonal structure]]