Editing Rhodium (section)

==Applications==
The primary use of this element is in automobiles as a [[catalytic converter]], changing harmful unburned hydrocarbons, carbon monoxide, and nitrogen oxide exhaust emissions into less noxious gases. Of 30,000&nbsp;kg of rhodium consumed worldwide in 2012, 81% (24,300&nbsp;kg) went into this application, and 8,060&nbsp;kg was recovered from old converters. About 964&nbsp;kg of rhodium was used in the glass industry, mostly for production of fiberglass and flat-panel glass, and 2,520&nbsp;kg was used in the chemical industry.<ref name="USGSYB08">{{cite web|url = http://minerals.usgs.gov/minerals/pubs/commodity/platinum/myb1-2012-plati.pdf|publisher = United States Geological Survey|access-date = 2012-07-16|title = Commodity Report: Platinum-Group Metals|first = Patricia J.|last = Loferski|year = 2013|archive-date = 10 January 2019|archive-url = https://web.archive.org/web/20190110111705/https://minerals.usgs.gov/minerals/pubs/commodity/platinum/myb1-2012-plati.pdf|url-status = dead}}</ref><ref name="Whyrhodium">{{cite journal|last = Shelef|first =M.|author2=Graham, G. W. |year = 1994|title = Why Rhodium in Automotive Three-Way Catalysts?|journal = Catalysis Reviews|volume = 36|issue = 3|pages=433–457|doi = 10.1080/01614949408009468}}</ref>

In 2008, net demand (with the recycling accounted for) of rhodium for automotive converters made up 84% of the world usage,<ref>{{Cite thesis |last=Murray |first=Angela Janet |title=Recovery of Platinum Group Metals from Spent Furnace Linings and Used Automotive Catalysts |date=2012 |degree=PhD |publisher=University of Birmingham |url=https://etheses.bham.ac.uk/id/eprint/7210/1/Murray12PhD.pdf}}</ref> with the number fluctuating around 80% in 2015−2021.<ref>{{cite web | url=https://www.sfa-oxford.com/platinum-group-metals/rhodium-market-and-rhodium-price-drivers | title=The Rhodium Market and Rhodium Price }}</ref>

===Carbonylation===
[[image:HRh(CO)P3again.png|thumb|140px|[[Tris(triphenylphosphine)rhodium carbonyl hydride]], a widely used catalyst for hydroformylation (Ph = C<sub>6</sub>H<sub>5</sub>)]]

Rhodium [[catalyst]]s are used in some industrial processes, notably those involving [[carbon monoxide]].  In the [[Monsanto process]], rhodium iodides catalyze the [[carbonylation]] of [[methanol]] to produce [[acetic acid]].<ref>{{cite journal|title = Rhodium Catalysed Carbonylation of Methanol|first = James F.|last = Roth|journal = Platinum Metals Review|volume = 19|issue = 1 January|year = 1975|pages = 12–14|doi = 10.1595/003214075X1911214|url = http://www.platinummetalsreview.com/pdf/pmr-v19-i1-012-014.pdf|access-date = 5 February 2009|archive-date = 24 September 2015|archive-url = https://web.archive.org/web/20150924074253/http://www.platinummetalsreview.com/pdf/pmr-v19-i1-012-014.pdf|url-status = dead}}</ref> This technology has been significantly displaced by the [[iridium]]-based [[Cativa process]], which effects the same conversion but more efficiently.  Rhodium-based complexes are the dominant catalysts for [[hydroformylation]], which converts alkenes to [[aldehyde]]s according to the following equation:<ref>{{cite book | title=Organotransition Metal Chemistry: From Bonding to Catalysis | publisher=University Science Books | author=Hartwig, John | year=2010 | location=New York | pages=1160 | isbn=978-1-938787-15-7}}</ref><ref>{{cite book|title=Organometallics|author=C. Elschenbroich|publisher=VCH|year=2006|isbn=  978-3-527-29390-2}}</ref>

: {{chem2|RCH\dCH2  +  H2  +  CO  ->  RCH2\sCH2CHO}}

Rh-based hydroformylation underpins the industrial production of products as diverse as detergents, fragrances, and some drugs.  Originally hydroformylation relied on much cheaper cobalt carbonyl-based catalysts, but that technology has largely been eclipsed by rhodium-based catalysts despite the cost differential.

Rhodium is also known to catalyze many reactions involving hydrogen gas and [[hydrosilane]]s. These include hydrogenations and hydrosilylations of alkenes.<ref>{{cite journal|author=Heidingsfeldova, M.|author2=Capka, M.|name-list-style=amp |title=Rhodium complexes as catalysts for hydrosilylation crosslinking of silicone rubber|doi=10.1002/app.1985.070300505 |journal=Journal of Applied Polymer Science |volume=30|issue=5 |year=2003|pages=1837–1846}}</ref> Rhodium metal, but not rhodium complexes, catalyzes the hydrogenation of [[benzene]] to [[cyclohexane]].<ref>{{cite journal|author=Halligudi, S. B.|display-authors=etal |title=Hydrogenation of benzene to cyclohexane catalyzed by rhodium(I) complex supported on montmorillonite clay|doi=10.1007/BF02162706 |journal=Reaction Kinetics and Catalysis Letters|volume=48|issue=2|year=1992|pages= 547–552|bibcode=1992RKCL...48..505T |s2cid=97802315 }}</ref>

===Ornamental uses===
Rhodium finds use in [[jewelry]] and for decorations. It is [[electroplated]] on [[white gold]] and platinum to give it a reflective white surface at time of sale, after which the thin layer wears away with use. This is known as rhodium flashing in the jewelry business. It may also be used in coating [[sterling silver]] to protect against tarnish ([[silver sulfide]], Ag<sub>2</sub>S, produced from atmospheric [[hydrogen sulfide]], H<sub>2</sub>S). Solid (pure) rhodium jewelry is very rare, more because of the difficulty of fabrication (high melting point and poor malleability) than because of the high price.<ref>{{cite journal|doi = 10.1111/j.1600-0536.1984.tb00056.x|title = Contact sensitivity to nickel in white gold|year = 1984|last1 = Fischer|first1 = Torkel|journal = Contact Dermatitis|volume = 10|pages = 23–24|pmid = 6705515|last2 = Fregert|first2 = S.|last3 = Gruvberger|first3 = B.|last4 = Rystedt|first4 = I.|issue = 1|s2cid = 46626556}}</ref> The high cost ensures that rhodium is applied only as an [[electroplating|electroplate]].<!--, Text seems to add nothing, left for second opinion: "...where tiny amounts of powder, commonly called rhodium sponge,&nbsp;[clarification needed] are in solution." --> Rhodium has also been used for honors or to signify elite status, when more commonly used metals such as silver, gold or platinum were deemed insufficient. In 1979 the ''[[Guinness Book of World Records]]'' gave [[Paul McCartney]] a rhodium-plated disc for being history's all-time best-selling songwriter and recording artist.<ref>{{cite news| url = https://www.independent.co.uk/news/people/hit-and-run/hit--run-ring-the-changes-1044166.html| work= [[The Independent]] |access-date=2009-06-06| title= Hit & Run: Ring the changes |location=London|date=2008-12-02}}</ref>

===Other uses===
Rhodium is used as an alloying agent for hardening and improving the corrosion resistance<ref name="ASM13B" /> of [[platinum]] and [[palladium]]. These alloys are used in furnace windings, bushings for glass fiber production, [[thermocouple]] elements, [[electrode]]s for aircraft [[spark plug]]s, and laboratory crucibles.<ref>{{Cite book|author= Lide, David R|title= CRC handbook of chemistry and physics 2004–2005: a ready-reference book of chemical and physical data|year=2004|publisher=CRC Press|location=Boca Raton|isbn=978-0-8493-0485-9 |edition=85th |pages=4–26|url=https://books.google.com/books?id=WDll8hA006AC}}</ref> Other uses include:

* [[Switch#Contacts|Electrical contacts]], where it is valued for small [[electrical resistance]], small and stable [[contact resistance]], and great [[corrosion]] resistance.<ref>{{cite journal|journal = Metal Finishing|volume = 97|issue = 1|year = 1999|pages =296–299| title = Rhodium plating|doi = 10.1016/S0026-0576(00)83088-3|first = Alfred M.|last = Weisberg}}</ref>
* Rhodium plated by either [[electroplating]] or evaporation is extremely hard and useful for optical instruments.<ref>{{cite book|title = Modern optical engineering: the design of optical systems|first = Warren J.|last = Smith|publisher = McGraw-Hill|year = 2007|isbn = 978-0-07-147687-4|chapter-url = https://books.google.com/books?id=DrtM_bAnf_YC|pages = 247–248|chapter = Reflectors}}</ref>
* Filters in [[mammography]] systems for the characteristic X-rays it produces.<!--produces or filters/transmits?--><ref>{{cite journal|author=McDonagh, C P|display-authors=etal|title=Optimum x-ray spectra for mammography: choice of K-edge filters for tungsten anode tubes|doi=10.1088/0031-9155/29/3/004 |pmid=6709704|journal=Phys. Med. Biol. |volume=29|issue=3 |pages=249–52|year=1984|bibcode = 1984PMB....29..249M |s2cid=250873106 }}</ref>
* Rhodium neutron detectors are used in nuclear reactors to measure neutron flux levels—this method requires a digital filter to determine the current neutron flux level, generating three separate signals: immediate, a few seconds delay, and a minute delay, each with its own signal level; all three are combined in the rhodium detector signal. The three [[Palo Verde Nuclear Generating Station|Palo Verde]] nuclear reactors each have 305 rhodium neutron detectors, 61 detectors on each of five vertical levels, providing an accurate 3D "picture" of reactivity and allowing fine tuning to consume the nuclear fuel most economically.<ref>{{cite journal
|first1 = A. P. |last1 = Sokolov
|last2 = Pochivalin|first2 = G. P.
|last3 = Shipovskikh|first3 = Yu. M.
|last4 = Garusov|first4 = Yu. V.
|last5 = Chernikov|first5 = O. G.
|last6 = Shevchenko|first6 = V. G.
|title = Rhodium self-powered detector for monitoring neutron fluence, energy production, and isotopic composition of fuel|doi = 10.1007/BF00844622|journal = Atomic Energy|volume = 74|year = 1993|issue = 5 |pages = 365–367 |s2cid = 96175609
}}</ref>

In automobile manufacturing, rhodium is also used in the construction of headlight reflectors.<ref name="Stwertka">Stwertka, Albert. ''A Guide to the Elements'', Oxford University Press, 1996, p. 125. {{ISBN|0-19-508083-1}}</ref>

<gallery widths="200px" heights="180px">
File:Rhodium 78g sample.jpg|A 78&nbsp;g sample of rhodium
Image:Aufgeschnittener Metall Katalysator für ein Auto.jpg|Cut-away of a metal-core catalytic converter
Image:White-gold--rhodium-plated.jpg|Rhodium-plated white gold wedding ring
Image:Rhodium foil and wire.jpg|Rhodium foil and wire
</gallery>