Platinum
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2008-07-17T06:06:03Z
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:''This page is about the [[chemical element]]. For other uses, see [[Platinum (disambiguation)]]''.
{{Elementbox_header | number=78 | symbol=Pt | name=platinum | left=[[iridium]] | right=[[gold]] | above=[[palladium|Pd]] | below=[[darmstadtium|Ds]] | color1=#ffc0c0 | color2=black }}
{{Elementbox_series | [[transition metal]]s }}
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{{Elementbox_heatfusion_kjpmol | 22.17 }}
{{Elementbox_heatvaporiz_kjpmol | 469 }}
{{Elementbox_heatcapacity_jpmolkat25 | 25.86 }}
{{Elementbox_vaporpressure_katpa | 2330 | (2550) | 2815 | 3143 | 3556 | 4094 | comment= }}
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{{Elementbox_oxistates | 1, 2, 3, '''4''', 5, 6<br />(mildly [[base (chemistry)|basic]] oxide) }}
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{{Elementbox_ionizationenergies2 | 870 | 1791 }}
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{{Elementbox_magnetic | [[paramagnetism|paramagnetic]] }}
{{Elementbox_eresist_ohmmat20 | 105 n}}
{{Elementbox_thermalcond_wpmkat300k | 71.6 }}
{{Elementbox_thermalexpansion_umpmkat25 | 8.8 }}
{{Elementbox_speedofsound_rodmpsatrt | 2800 }}
{{Elementbox_youngsmodulus_gpa | 168 }}
{{Elementbox_shearmodulus_gpa | 61 }}
{{Elementbox_bulkmodulus_gpa | 230 }}
{{Elementbox_poissonratio | 0.38 }}
{{Elementbox_mohshardness | 4–4.5 }}
{{Elementbox_vickershardness_mpa | 549 }}
{{Elementbox_brinellhardness_mpa | 392 }}
{{Elementbox_cas_number | 7440-06-4 }}
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{{Elementbox_isotopes_decay | mn=190 | sym=Pt
| na=0.014% | hl=6.5×10<sup>11</sup> [[year|y]]
| dm=[[alpha decay|α]] | de=3.18 | pn=186 | ps=[[osmium|Os]] }}
{{Elementbox_isotopes_decay | mn=191 | sym=Pt
| na=[[synthetic radioisotope|syn]] | hl=2.76 d
| dm=[[electron capture|ε]] | de=? | pn=191 | ps=[[iridium|Ir]] }}
{{Elementbox_isotopes_stable | mn=192 | sym=Pt | na=0.782% | n=114 }}
{{Elementbox_isotopes_decay | mn=190 | sym=Pt
| na=[[synthetic radioisotope|syn]] | hl=50 [[year|y]]
| dm=[[electron capture|ε]] | de=? | pn=193 | ps=[[iridium|Ir]] }}
{{Elementbox_isotopes_decay | mn=181[[nuclear isomer|m]] | sym=Pt
| na=[[synthetic radioisotope|syn]] | hl=4.33 d
| dm=[[Internal conversion|IT]] | de=0.1355[[Conversion electron|e]] | pn=193 | ps=Pt }}
{{Elementbox_isotopes_stable | mn=194 | sym=Pt | na=32.967% | n=116 }}
{{Elementbox_isotopes_stable | mn=195 | sym=Pt | na=33.832% | n=117 }}
{{Elementbox_isotopes_decay | mn=195[[nuclear isomer|m]] | sym=Pt
| na=[[synthetic radioisotope|syn]] | hl=4.02 d
| dm=[[Internal conversion|IT]] | de=0.1297[[Conversion electron|e]] | pn=195 | ps=Pt }}
{{Elementbox_isotopes_stable | mn=196 | sym=Pt | na=25.242% | n=118 }}
{{Elementbox_isotopes_decay | mn=197 | sym=Pt
| na=[[synthetic radioisotope|syn]] | hl=19.8913 h
| dm=[[beta emission|β]]<sup>-</sup> | de=0.719 | pn=197 | ps=[[gold|Au]] }}
{{Elementbox_isotopes_decay | mn=197[[nuclear isomer|m]] | sym=Pt
| na=[[synthetic radioisotope|syn]] | hl=1.59 h
| dm=[[Internal conversion|IT]] | de=0.3465 | pn=197 | ps=Pt }}
{{Elementbox_isotopes_stable | mn=198 | sym=Pt | na=7.163% | n=120 }}
{{Elementbox_isotopes_end}}
{{Elementbox_footer | color1=#ffc0c0 | color2=black }}
'''Platinum''' ({{pronEng|ˈplæt<s>ɪ</s>nəm}}) is a [[chemical element]] with the [[atomic symbol]] '''Pt''' and an [[atomic number]] of 78. It is in group 10 of the Periodic Table of Elements. A heavy, [[malleability|malleable]], [[ductility|ductile]], [[precious metal|precious]], gray-white [[transition metal]], platinum is resistant to corrosion and occurs in some [[nickel]] and [[copper]] ores along with some native deposits. Platinum is used in [[jewellery|jewelry]], laboratory equipment, [[electric]]al contacts, dentistry, and [[automobile emissions control]] devices. Platinum [[bullion]] has the [[ISO 4217|ISO currency code]] of XPT. As of June 24, 2008, Platinum was worth $2,032 per ounce (approximately $71.676 per gram).<ref name=Kitco>{{cite web |title=Live Market Quotes |publisher=Kitco |url=http://www.kitco.com/market/ |accessdate=2008-06-24 }}</ref>
== Characteristics ==
When pure, the [[metal]] appears greyish-white and firm. The metal is [[corrosion]]-resistant. The [[catalyst|catalytic]] properties of the six [[platinum family]] metals are outstanding. For this catalytic property, platinum is used in [[catalytic converter]]s, incorporated in [[automobile]] exhaust systems, as well as tips of [[spark plugs]]. Platinum has a cubic crystal structure.
Platinum's wear- and tarnish-resistance characteristics are well suited for making fine [[jewelry]]. Platinum is more precious than [[gold]]. The price of platinum changes along with its availability, but its price is normally more than twice the price of gold. In the 18th century, platinum's rarity made King [[Louis XV of France]] declare it the only metal fit for a king.<ref name=mineralszone>{{cite web |title=Platinum |publisher=Minerals Zone |url=http://www.mineralszone.com/minerals/platinum.html |accessdate=2007-04-05 }}</ref>
Platinum possesses high resistance to chemical attack, excellent high-temperature characteristics, and stable electrical properties. All these properties have been exploited for industrial applications. Platinum does not generally [[oxidation|oxidize]] in air at any temperature, but can be corroded by [[cyanide]]s, [[halogen]]s, [[sulfur]], and caustic [[alkali]]s. This metal is insoluble in [[hydrochloric acid|hydrochloric]] and [[nitric acid]], but does dissolve in the mixture known as [[aqua regia]] (forming [[chloroplatinic acid]]). When crude platinum is dissolved in aqua regia, gold is removed from the solution as a precipitate by treatment with iron(II) chloride (FeCl<sub>2</sub>). The platinum is precipitated out as impure (NH<sub>4</sub>)<sub>2</sub>PtCl<sub>6</sub> on treatment with ammonium chloride (NH<sub>4</sub>Cl), leaving H<sub>2</sub>PdCl<sub>4</sub> in solution.
Common [[oxidation state]]s of platinum include +2, and +4. The +1 and +3 oxidation states are less common, and are often stabilized by metal bonding in bimetallic (or polymetallic) species.
== Applications ==
* As a catalyst in the [[catalytic converter]], an optional (though often mandatory by law) component of the gasoline-fueled automobile exhaust system (see "Notable characteristics" in this article).
* As a catalyst in [[fuel cell]]s. Reducing the amount of platinum required (and thus cost) is a major focus of fuel cell research.
* Certain platinum-containing compounds are capable of crosslinking [[DNA]] and kill cells by similar pathways to alkylating [[chemotherapy|chemotherapeutic agents]]. [[Cisplatin]], [[carboplatin]] and [[oxaliplatin]] are licensed examples of this class of drugs.<ref>Richards, A.D. & Rodger, A. (2007). [http://www.rsc.org/publishing/journals/CS/article.asp?doi=b609495c Synthetic metallomolecules as agents for the control of DNA structure] ''Chem. Soc. Rev.'' '''36''' 471–483.</ref>
* [[Resistance thermometer|Platinum resistance thermometer]]s.
* [[Electrode]]s for use in [[electrolysis]] and electrochemical measurements (e.g., the [[standard hydrogen electrode]]).
* In the [[Clark electrode|Clark polarographic electrode]] for measuring oxygen tension.
* A wide range of [[jewellery|jewelry]].
* As a catalyst in the curing of [[silicone]] elastomers.
* As a catalyst in [[glow plug]]s in some model engines.
* In crucibles, alloyed with rhodium (10–40% of Rh), for high temperature melting (around 1500°C) of glass.
* In [[photography]], it is sometimes used for archival printmaking. Platinum prints display a greater range of tones than other Black and White printing methods. Additionally platinum's chemical stability makes for extremely long-lasting prints. The disadvantage of this method, in addition to the high cost, is that platinum is less light sensitive and prints must be contact printed at the same size as the negative. Therefore, enlargements can only be made by making an enlarged negative. Platinum salts alone generally create excessive contrast in prints; combined with salts from its sister metal, palladium, produce warmer and softer tones, without diminishing the tonal range platinum enables.
* In [[watchmaking]], [[Vacheron Constantin]], [[Patek Philippe]], [[Rolex]], [[Breitling]] and other companies use platinum for producing their limited edition watch series. Watchmakers highly appreciate the unique properties of platinum as it neither tarnishes nor wears out.<ref>[http://watches.infoniac.com/index.php?page=post&id=44 Unknown Facts about Platinum]</ref>
== History ==
Naturally-occurring platinum and platinum-rich alloys have been known for a long time. Though the metal was used by [[pre-Columbian]] Native Americans, the first European reference to platinum appears in 1557 in the writings of the [[Italy|Italian]] humanist [[Julius Caesar Scaliger]] (1484–1558) as a description of a mysterious metal found in Central American mines between Darién ([[Panama]]) and Mexico ("up until now impossible to melt by any of the Spanish arts"). The word ''platinum'' comes from the Spanish word ''platina'', meaning "little silver."
[[Image:platinum-symbol.png|thumb|left|75px|The [[alchemy|alchemical]] symbol for platinum (shown above) was made by joining the symbols of silver and gold.]]
Platinum was discussed by [[astronomer]] [[Antonio de Ulloa]] and Don [[Jorge Juan y Santacilia]] (1713–1773), both appointed by King [[Philip V of Spain|Philip V]] to join a [[French Geodesic Mission|geographical expedition]] in [[Peru]] that lasted from 1735 to 1745. Amongst other things, Ulloa observed the ''platina del pinto'', the unworkable metal found with gold in [[Viceroyalty of New Granada|New Granada]] ([[Colombia]]). British [[privateer]]s intercepted Ulloa's ship on the return voyage. Though he was well-treated in England, and even made a member of the [[Royal Society]] he was prevented from publishing a reference to the unknown metal until 1748. Before that could happen [[Charles Wood (scientist)|Charles Wood]] independently isolated the element in 1741. Major finds were discovered in Russia in 1819, which produced around 90% of the global Platinum production at the turn of the 20th century.<ref name=SmithJewelry>{{cite book | last = Smith | first = Marcell | title = Diamonds, Pearls and Precious Stones (for the trade) | publisher = Boston, Grifftih-Stillings Press | year = 1913}}, pages 39-40 </ref>
Due to its rarity, greater difficulty to work with and the need to alloy it with (at the time) an even more expensive metal [[iridium]], platinum was only used in a limited way in jewelry at the end of the 19th century. This changed at beginning of the 20th century when most diamond ring mountings and most exclusive jewelry were almost completely made of platinum.<ref name=SmithJewelry/>
From 1875 to 1960 the [[International System of Units|SI]] unit of length (the [[Metre#Prototype_metre_bar|standard metre]]) was defined as the distance between two lines on a standard bar of an alloy of ninety percent platinum and ten percent iridium, measured at 0 degrees [[Celsius]].
== Occurrence ==
[[Image:PlatinumOreUSGOV.jpg|thumb|left|Platinum ore]]
[[Image:2005platinum (mined).PNG|thumb|right|Platinum output in 2005]]
Platinum is an extremely rare metal, occurring as only 0.003 [[Parts-per notation#Types of Parts-per Notations|ppb]] in the [[Earth]]'s [[crust (geology)|crust]], and is 30 times rarer than gold. If all the world's platinum reserves were poured into one Olympic-size swimming pool, it would be just deep enough to cover one's ankles. Gold would fill more than three such pools.<ref name="RJI">{{cite web |url=http://www.rji.ie/didyouknow_platinum.html |title=Platinum: Pure, Rare, Eternal. |accessdate=2007-10-27}}</ref>
In 2005, South Africa was the top producer of platinum with an almost 80% share followed by Russia and Canada, reports the [[British Geological Survey]].<ref name="Platinum-Geological_Survey">{{cite web |url=http://minerals.usgs.gov/minerals/pubs/commodity/platinum/platimcs07.pdf |format=PDF |title=PLATINUM-GROUP METALS |publisher=U.S. Geological Survey, Mineral Commodity Summaries |date=January 2007 |accessdate=2007-08-19}}</ref>
Platinum is often found chemically uncombined as native platinum and [[alloy]]ed with [[iridium]] as [[platiniridium]]. The platinum [[arsenide]], [[sperrylite]] (PtAs<sub>2</sub>), is a major source of platinum associated with [[nickel]] ores in the [[Sudbury Basin]] deposit in [[Ontario]], [[Canada]]. The rare [[sulfide]] mineral [[cooperite]], (Pt,Pd,Ni)S, contains platinum along with [[palladium]] and nickel. Cooperite occurs in the [[Merensky Reef]] within the [[Bushveld complex]], [[Gauteng]], [[South Africa]].
Platinum, often accompanied by small amounts of other [[platinum family]] metals, occurs in [[alluvium|alluvial]] [[Placer mining|placer]] deposits in the [[Witwatersrand]] of South Africa, the [[Ural Mountains]], and in the [[Absaroka Range]] in the [[United States|American]] state of [[Montana]].<ref name=NewYorkTimes>{{cite web |url=http://query.nytimes.com/gst/fullpage.html?res=9802E3D6153AF930A2575BC0A96E958260 |title=Mining Platinum in Montana |accessdate=December 2007}}</ref>
Platinum is produced commercially as a by-product of [[nickel]] ore processing in the Sudbury deposit. The huge quantities of nickel ore processed makes up for the fact that platinum is present as only 0.5 [[parts per million|ppm]] in the ore.
Platinum exists in relatively higher abundances on the [[Moon]] and in meteorites. Correspondingly, platinum is found in slightly higher abundances at sites of [[bolide]] impact on the Earth that are associated with resulting post-impact volcanism, and can be mined economically; the [[Sudbury Basin]] is one such example.
== Production and price ==
[[Image:One litre of Platinum.jpg|thumb|250px|right|1000 cubic centimetres of 99.9% pure platinum]]
[[Image:platinum prices 91-07.JPG|thumb|250px|right|Average price of platinum from 1991 to 2007 in US$ per [[troy ounce]] (~$40/g).<ref>[http://www.lppm.org.uk/statistics_cover.html] London Platinum and Palladium Market</ref>]]
In order to obtain pure platinum, the ore is crushed, made into a [[slurry]] with water, and then mixed with a [[detergent]] containing "collector" molecules. Air is then blown through the mixture, enabling the grains of metal minerals to be separated from the rest of the mixture. This process is called "[[Froth flotation|flotation]]." The next step is smelting.
In 2007, global supplies of 6.55 million [[ounce]]s were more than matched by demand of 7.03 million ounces.<ref>[http://www.platinum.matthey.com/media_room/platinum_market_in_0000_oz_deficit_18599215.html Platinum Today]</ref>
In 2006, world supply of platinum was of about 217,700 kg or 7 million troy ounces.<ref>[http://www.platinum.matthey.com/publications/pgmreview.html Johnson Matthey] 2006 supply and demand charts</ref><ref>{{cite news |url=http://news.bbc.co.uk/1/hi/business/1998102.stm |title=Green curbs hit platinum supply |publisher=BBC News |date=[[May 20]] [[2002]] |accessdate=2007-08-19}}</ref>
== Precautions ==
According to the Centers for Disease Control and Prevention, short-term exposure to platinum salts "may cause irritation of the eyes, nose, and throat" and long-term exposure "may cause both respiratory and skin allergies." The current OSHA standard is 0.002 milligram per cubic meter of air averaged over an 8-hour work shift.<ref>{{cite web |url=http://www.cdc.gov/niosh/pdfs/0520.pdf |format=PDF |title=Occupational Health Guideline for Soluble Platinum Salts (as Platinum) |publisher=Centers for Disease Control and Prevention |accessdate=2007-08-19}}</ref>
Certain platinum complexes are used in chemotherapy and show good anti-tumor activity for some tumours. [[Cisplatin]] is particularly effective against testicular cancer; cure rate was improved from 10% to 85%.<ref>{{cite journal |author=Einhorn LH. |url=http://jco.ascopubs.org/cgi/content/abstract/8/11/1777 |title=Treatment of testicular cancer: a new and improved model |journal=J. Clin. Oncol. |year=1990 |volume=8 |issue=11 |pages=1777–81 |pmid=1700077}}</ref> However, the side effects are severe. Cisplatin causes cumulative, irreversible kidney damage and deafness.<ref>{{cite journal |author=Von Hoff DD, ''et al'' |url=http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=387223&dopt=Citation |title=Toxic effects of cis-dichlorodiammineplatinum(II) in man |journal=Cancer Treat. Rep. |date=1979 |volume=63 |issue=9–10 |pages=1527–31}}</ref>. As with other ototoxic agents, deafness may be secondary to interactions with [[melanin]] in the [[stria vascularis]].
As platinum is a [[catalyst]] in the manufacture of the [[silicone rubber]] and gel components of several types of [[implant (medicine)|medical implants]] (breast implants, joint replacement prosthetics, artificial lumbar discs, vascular access ports), the possibility that platinum free radicals could enter the body and cause adverse effects has merited study. The FDA and other countries have reviewed the issue and found no evidence to suggest toxicity in vivo.<ref>{{cite web |url=http://www.fda.gov/cdrh/breastimplants/platinum.html |title=FDA Backgrounder on Platinum in Silicone Breast Implants |publisher=U.S. Food and Drug Administration |accessdate=2007-08-19}}</ref>
== Symbol of prestige ==
[[Image:Platinum nuggets.jpg|thumb|An assortment of native platinum nuggets]]
Platinum's rarity as a metal has caused advertisers to associate it with exclusivity and wealth. "Platinum" credit cards have greater privileges than do "[[gold]]" ones. "Platinum awards" are the second highest possible, ranking above gold, [[silver]] and [[bronze]], but below "[[Diamond]]". For example, in the United States a musical album that has sold more than 1,000,000 copies, will be credited as "platinum", whereas an album that sold more than 10,000,000 copies will be certified as “diamond”. And some products, such as blenders and vehicles, with a silvery-white color are identified as "platinum". Platinum is considered a precious metal, although its use is not as common as the use of gold or silver. The frame of the [[Crown of Queen Elizabeth|Crown of Queen Elizabeth the Queen Mother]], manufactured for her Coronation as Consort of King George VI, is made of platinum. It was the first British crown to be made of this particular metal.
==See also==
* [[Platinum black]]
* [[Platinum coin]]
* [[:Category:Platinum compounds|Platinum compounds]]
* [[Platinum group]]
* [[Platinum in Africa]]
* [[Merensky Reef]]
* [[Precious metal]]
* [[Palladium]]
== References ==
{{reflist}}
* [http://periodic.lanl.gov/elements/78.html Los Alamos National Laboratory — Platinum]
* ''[http://chartofthenuclides.com/default.html Nuclides and Isotopes] Fourteenth Edition: Chart of the Nuclides'', General Electric Company, 1989.
* [http://education.jlab.org/itselemental/ele078.html Jefferson Lab — The Element Platinum]
== External links ==
{{Commons|Platinum}}
{{wiktionary|platinum}}
*[http://www.platinummetalsreview.com/jmpgm/index.jsp The Platinum Group Metals Database]
*[http://www.vanderkrogt.net/elements/elem/pt.html A balanced historical account of the sequence of discoveries of platinum; illustrated.]
*[http://www.webelements.com/webelements/elements/text/Pt/index.html WebElements.com — Platinum]
*[http://www.platinummetalsreview.com/ Platinum Metals Review E-Journal]
*[http://www.platinumguild.com/ Platinum Guild International]
*[http://minerals.usgs.gov/minerals/pubs/commodity/platinum/ United States Geological Survey Platinum-Group Metals Statistics and Information]
*[http://www.pse-mendelejew.de/bilder/pt.jpg picture of a 999.5 fine platinum ingot in the element collection from Heinrich Pniok]
{{Jewellery Materials}}
{{Compact periodic table}}
[[Category:Platinum| ]]
[[Category:Chemical elements]]
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