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Platinum is a chemical element with the
symbol A symbol is a mark, sign, or word that indicates, signifies, or is understood as representing an idea, object, or relationship. Symbols allow people to go beyond what is known or seen by creating linkages between otherwise very different conc ...
Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish , a
diminutive A diminutive is a root word that has been modified to convey a slighter degree of its root meaning, either to convey the smallness of the object or quality named, or to convey a sense of intimacy or endearment. A (abbreviated ) is a word-formati ...
of "silver". Platinum is a member of the platinum group of elements and
group 10 Group 10, numbered by current IUPAC style, is the group of chemical elements in the periodic table that consists of nickel (Ni), palladium (Pd), platinum (Pt), and darmstadtium (Ds). All are d-block transition metals. All known isotopes of darm ...
of the
periodic table of elements The periodic table, also known as the periodic table of the (chemical) elements, is a rows and columns arrangement of the chemical elements. It is widely used in chemistry, physics, and other sciences, and is generally seen as an Cultural i ...
. It has six naturally occurring isotopes. It is one of the rarer elements in Earth's crust, with an average abundance of approximately 5 
μg In the metric system, a microgram or microgramme is a unit of mass equal to one millionth () of a gram. The unit symbol is μg according to the International System of Units (SI); the recommended symbol in the United States and United Kingdom whe ...
/kg. It occurs in some nickel and copper ores along with some
native Native may refer to: People * Jus soli, citizenship by right of birth * Indigenous peoples, peoples with a set of specific rights based on their historical ties to a particular territory ** Native Americans (disambiguation) In arts and entert ...
deposits, mostly in South Africa, which accounts for ~80% of the world production. Because of its scarcity in Earth's crust, only a few hundred tonnes are produced annually, and given its important uses, it is highly valuable and is a major precious metal commodity. Platinum is one of the least reactive metals. It has remarkable resistance to corrosion, even at high temperatures, and is therefore considered a noble metal. Consequently, platinum is often found chemically uncombined as native platinum. Because it occurs naturally in the alluvial sands of various rivers, it was first used by pre-Columbian South American natives to produce artifacts. It was referenced in European writings as early as the 16th century, but it was not until
Antonio de Ulloa Antonio de Ulloa y de la Torre-Giralt, FRS, FRSA, KOS (12 January 1716 – 3 July 1795) was a Spanish naval officer, scientist, and administrator. At the age of nineteen, he joined the French Geodesic Mission to what is now the country o ...
published a report on a new metal of
Colombia Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific Ocean. The Colombian mainland is bordered by the Car ...
n origin in 1748 that it began to be investigated by scientists. Platinum is used in catalytic converters, laboratory equipment, electrical contacts and electrodes,
platinum resistance thermometer Resistance thermometers, also called resistance temperature detectors (RTDs), are sensors used to measure temperature. Many RTD elements consist of a length of fine wire wrapped around a heat-resistant ceramic or glass core but other constructi ...
s,
dentistry Dentistry, also known as dental medicine and oral medicine, is the branch of medicine focused on the teeth, gums, and mouth. It consists of the study, diagnosis, prevention, management, and treatment of diseases, disorders, and conditions o ...
equipment, and jewelry. Platinum is used in the glass industry to manipulate molten glass which does not " wet" platinum. As a heavy metal, it leads to health problems upon exposure to its salts; but due to its corrosion resistance, metallic platinum has not been linked to adverse health effects. Compounds containing platinum, such as cisplatin,
oxaliplatin Oxaliplatin, sold under the brand name Eloxatin among others, is a cancer medication (platinum-based antineoplastic class) used to treat colorectal cancer. It is given by injection into a vein. Common side effects include numbness, feeling ti ...
and carboplatin, are applied in chemotherapy against certain types of cancer. Pure platinum is currently less expensive than pure gold, having been so continuously since 2015, but has been twice as expensive or more, mostly prior to 2008. In early 2021, the value of platinum ranged from US$1,055 to US$1,320 per troy ounce.


Characteristics


Physical

Pure platinum is a lustrous, ductile, and malleable, silver-white metal. Platinum is more ductile than gold, silver or copper, thus being the most ductile of pure metals, but it is less malleable than gold. Its physical characteristics and chemical stability make it useful for industrial applications. Its resistance to wear and tarnish is well suited to use in fine jewellery.


Chemical

Platinum has excellent resistance to corrosion. Bulk platinum does not oxidize in air at any temperature, but it forms a thin surface film of that can be easily removed by heating to about 400 °C. The most common oxidation states of platinum are +2 and +4. The +1 and +3 oxidation states are less common, and are often stabilized by metal bonding in bimetallic (or polymetallic) species. Tetracoordinate platinum(II) compounds tend to adopt 16-electron
square planar The square planar molecular geometry in chemistry describes the stereochemistry (spatial arrangement of atoms) that is adopted by certain chemical compounds. As the name suggests, molecules of this geometry have their atoms positioned at the corne ...
geometries. Although elemental platinum is generally unreactive, it is attacked by chlorine, bromine,
iodine Iodine is a chemical element with the symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a semi-lustrous, non-metallic solid at standard conditions that melts to form a deep violet liquid at , and boils to a vi ...
, and
sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
. It reacts vigorously with fluorine at to form platinum tetrafluoride. Platinum is insoluble in hydrochloric and nitric acid, but dissolves in hot '' aqua regia'' (a mixture of nitric and hydrochloric acids), to form aqueous
chloroplatinic acid Chloroplatinic acid (also known as hexachloroplatinic acid) is an inorganic compound with the formula 3Osub>2 tCl6H2O)''x'' (0 ≤ ''x'' ≤ 6). A red solid, it is an important commercial source of platinum, usually as an aqueous solution. Alth ...
, : : As a soft acid, the ion has a great affinity for sulfide and sulfur ligands. Numerous
DMSO complex Dimethyl sulfoxide (DMSO) is an organosulfur compound with the formula ( CH3)2. This colorless liquid is the sulfoxide most widely used commercially. It is an important polar aprotic solvent that dissolves both polar and nonpolar compounds and ...
es have been reported and care is taken in the choosing of reaction solvents. In 2007, the German scientist Gerhard Ertl won the Nobel Prize in Chemistry for determining the detailed molecular mechanisms of the catalytic oxidation of carbon monoxide over platinum ( catalytic converter).


Isotopes

Platinum has six naturally occurring isotopes: , , , , , and . The most abundant of these is , comprising 33.83% of all platinum. It is the only stable isotope with a non-zero
spin Spin or spinning most often refers to: * Spinning (textiles), the creation of yarn or thread by twisting fibers together, traditionally by hand spinning * Spin, the rotation of an object around a central axis * Spin (propaganda), an intentionally b ...
. The spin of 1/2 and other favourable magnetic properties of the nucleus are utilised in NMR. Due to its spin and large abundance, satellite peaks are also often observed in and NMR spectroscopy (''e.g.,'' for Pt-phosphine and Pt-alkyl complexes). is the least abundant at only 0.01%. Of the naturally occurring isotopes, only is unstable, though it decays with a half-life of 6.5 years, causing an activity of 15 Bq/kg of natural platinum. can undergo alpha decay, but its decay has never been observed (the half-life is known to be longer than 3.2 years); therefore, it is considered stable. Platinum also has 34 synthetic isotopes ranging in atomic mass from 165 to 204, making the total number of known isotopes 40. The least stable of these are and , with half-lives of 260 µs, whereas the most stable is with a half-life of 50 years. Most platinum isotopes decay by some combination of beta decay and alpha decay. , , and decay primarily by electron capture. and are predicted to have energetically favorable double beta decay paths.


Occurrence

Platinum is an extremely rare metal, occurring at a concentration of only 0.005 ppm in
Earth's crust Earth's crust is Earth's thin outer shell of rock, referring to less than 1% of Earth's radius and volume. It is the top component of the lithosphere, a division of Earth's layers that includes the crust and the upper part of the mantle. The ...
. It is sometimes mistaken for silver. Platinum is often found chemically uncombined as native platinum and as alloy with the other platinum-group metals and iron mostly. Most often the native platinum is found in secondary deposits in alluvial deposits. The alluvial deposits used by pre-Columbian people in the Chocó Department,
Colombia Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific Ocean. The Colombian mainland is bordered by the Car ...
are still a source for platinum-group metals. Another large alluvial deposit is in the Ural Mountains, Russia, and it is still mined. In nickel and copper deposits, platinum-group metals occur as
sulfide Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to chemical compounds lar ...
s (e.g., ,
tellurides The telluride ion is the anion Te2− and its derivatives. It is analogous to the other chalcogenide anions, the lighter O2−, S2−, and Se2−, and the heavier Po2−. In principle, Te2− is formed by the two-e− reduction of telluri ...
(e.g., ), antimonides (PdSb), and arsenides (e.g. ), and as end alloys with nickel or copper. Platinum arsenide, sperrylite (), is a major source of platinum associated with nickel ores in the
Sudbury Basin The Sudbury Basin (), also known as Sudbury Structure or the Sudbury Nickel Irruptive, is a major geological structure in Ontario, Canada. It is the third-largest known impact crater or astrobleme on Earth, as well as one of the oldest. The cra ...
deposit in Ontario, Canada. At
Platinum, Alaska Platinum ( esu, Arviiq) is a city in Bethel Census Area, Alaska, United States. The population was 61 at the 2010 census, up from 41 in 2000. Geography Platinum is located at . It is located on Goodnews Bay adjacent to the mouth of the Small R ...
, about was mined between 1927 and 1975. The mine ceased operations in 1990. The rare sulfide mineral cooperite, , contains platinum along with palladium and nickel. Cooperite occurs in the Merensky Reef within the
Bushveld complex The Bushveld Igneous Complex (BIC) is the largest layered igneous intrusion within the Earth's crust. It has been tilted and eroded forming the outcrops around what appears to be the edge of a great geological basin: the Transvaal Basin. It i ...
, Gauteng, South Africa. In 1865,
chromite Chromite is a crystalline mineral composed primarily of iron(II) oxide and chromium(III) oxide compounds. It can be represented by the chemical formula of FeCr2O4. It is an oxide mineral belonging to the spinel group. The element magnesium can s ...
s were identified in the Bushveld region of South Africa, followed by the discovery of platinum in 1906. In 1924, the geologist Hans Merensky discovered a large supply of platinum in the Bushveld Igneous Complex in South Africa. The specific layer he found, named the Merensky Reef, contains around 75% of the world's known platinum. The large copper–nickel deposits near Norilsk in Russia, and the
Sudbury Basin The Sudbury Basin (), also known as Sudbury Structure or the Sudbury Nickel Irruptive, is a major geological structure in Ontario, Canada. It is the third-largest known impact crater or astrobleme on Earth, as well as one of the oldest. The cra ...
, Canada, are the two other large deposits. In the Sudbury Basin, the huge quantities of nickel ore processed make up for the fact platinum is present as only 0.5 ppm in the ore. Smaller reserves can be found in the United States, for example in the Absaroka Range in Montana. In 2010, South Africa was the top producer of platinum, with an almost 77% share, followed by Russia at 13%; world production in 2010 was . Large platinum deposits are present in the state of Tamil Nadu, India. Platinum exists in higher abundances on the Moon and in meteorites. Correspondingly, platinum is found in slightly higher abundances at sites of bolide impact on Earth that are associated with resulting post-impact volcanism, and can be mined economically; the
Sudbury Basin The Sudbury Basin (), also known as Sudbury Structure or the Sudbury Nickel Irruptive, is a major geological structure in Ontario, Canada. It is the third-largest known impact crater or astrobleme on Earth, as well as one of the oldest. The cra ...
is one such example.


Compounds


Halides

Hexachloroplatinic acid mentioned above is probably the most important platinum compound, as it serves as the precursor for many other platinum compounds. By itself, it has various applications in photography, zinc etchings,
indelible ink ''Indelible'' is the fourth book in the Grant County series by author Karin Slaughter. It was originally released in hardback in 2004. Previous books in the series are '' Blindsighted'', ''Kisscut'', and ''A Faint Cold Fear''. These books star Sar ...
, plating, mirrors, porcelain coloring, and as a catalyst. Treatment of hexachloroplatinic acid with an ammonium salt, such as ammonium chloride, gives ammonium hexachloroplatinate, which is relatively insoluble in ammonium solutions. Heating this ammonium salt in the presence of hydrogen reduces it to elemental platinum. Potassium hexachloroplatinate is similarly insoluble, and hexachloroplatinic acid has been used in the determination of potassium ions by gravimetry. When hexachloroplatinic acid is heated, it decomposes through platinum(IV) chloride and platinum(II) chloride to elemental platinum, although the reactions do not occur stepwise: : : : All three reactions are reversible. Platinum(II) and
platinum(IV) bromide Platinum(IV) bromide is the inorganic compound with the formula PtBr4. It is a brown solid. It is a little-used compound mainly of interest for academic research. It is a component of a reagent used in qualitative inorganic analysis Classical ...
s are known as well. Platinum hexafluoride is a strong oxidizer capable of oxidizing oxygen.


Oxides

Platinum(IV) oxide Platinum is a chemical element with the Symbol (chemistry), symbol Pt and atomic number 78. It is a density, dense, malleable, ductility, ductile, highly unreactive, precious metal, precious, silverish-white transition metal. Its name origina ...
, , also known as " Adams' catalyst", is a black powder that is soluble in potassium hydroxide (KOH) solutions and concentrated acids. and the less common both decompose upon heating. Platinum(II,IV) oxide, , is formed in the following reaction: :


Other compounds

Unlike palladium acetate,
platinum(II) acetate Platinum(II) acetate is a purple-colored coordination complex. The complex adopts an unusual structure consisting of a square array of Pt atoms. Preparation Several syntheses of platinum(II) acetate have been reported. Geoffrey Wilkinson ''et al. ...
is not commercially available. Where a base is desired, the halides have been used in conjunction with sodium acetate. The use of platinum(II) acetylacetonate has also been reported. Several barium platinides have been synthesized in which platinum exhibits negative oxidation states ranging from −1 to −2. These include BaPt, , and . Caesium platinide, , a dark-red transparent crystalline compound has been shown to contain Pt anions. Platinum also exhibits negative oxidation states at surfaces reduced electrochemically. The negative oxidation states exhibited by platinum are unusual for metallic elements, and they are attributed to the relativistic stabilization of the 6s orbitals. It is predicted that even the cation in which platinum exists in +10 oxidation state may be achievable. Zeise's salt, containing an
ethylene Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon-carbon double bonds). Ethylene i ...
ligand, was one of the first organometallic compounds discovered. is a commercially available
olefin In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond. Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, an ...
complex, which contains easily displaceable cod ligands ("cod" being an abbreviation of 1,5-cyclooctadiene). The cod complex and the halides are convenient starting points to platinum chemistry. Cisplatin, or is the first of a series of square planar platinum(II)-containing chemotherapy drugs. Others include carboplatin and
oxaliplatin Oxaliplatin, sold under the brand name Eloxatin among others, is a cancer medication (platinum-based antineoplastic class) used to treat colorectal cancer. It is given by injection into a vein. Common side effects include numbness, feeling ti ...
. These compounds are capable of
crosslinking Cross-linking may refer to *Cross-link In chemistry and biology a cross-link is a bond or a short sequence of bonds that links one polymer chain to another. These links may take the form of covalent bonds or ionic bonds and the polymers ca ...
DNA, and kill cells by similar pathways to alkylating
chemotherapeutic agents Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs ( chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemothera ...
. (Side effects of cisplatin include nausea and vomiting, hair loss, tinnitus, hearing loss, and nephrotoxicity.)
Organoplatinum Organoplatinum chemistry is the chemistry of organometallic compounds containing a carbon to platinum chemical bond, and the study of platinum as a catalyst in organic reactions. Organoplatinum compounds exist in oxidation state 0 to IV, with oxida ...
compounds such as the above antitumour agents, as well as soluble inorganic platinum complexes, are routinely characterised using nuclear magnetic resonance spectroscopy. File:Hexachloridoplatinat-Ion.svg, The hexachloroplatinate ion File:Zeise's-salt-anion-3D-balls.png, The anion of Zeise's salt File:Dichloro(cycloocta-1,5-diene)platinum(II)-from-xtal-3D-balls-E.png, File:Cisplatin-3D-balls.png, Cisplatin


History


Early uses

Archaeologists have discovered traces of platinum in the gold used in ancient Egyptian burials as early as 1200 BCE. For example, a small box from burial of Shepenupet II was found to be decorated with gold-platinum hieroglyphics. However, the extent of early Egyptians' knowledge of the metal is unclear. It is quite possible they did not recognize there was platinum in their gold. The metal was used by Native Americans near modern-day Esmeraldas, Ecuador to produce artifacts of a white gold-platinum alloy. Archeologists usually associate the tradition of platinum-working in South America with the La Tolita Culture ( BCE – 200 CE), but precise dates and location is difficult, as most platinum artifacts from the area were bought secondhand through the antiquities trade rather than obtained by direct archeological excavation. To work the metal, they would combine gold and platinum powders by sintering. The resulting gold–platinum alloy would then be soft enough to shape with tools. The platinum used in such objects was not the pure element, but rather a naturally occurring mixture of the platinum group metals, with small amounts of palladium, rhodium, and iridium.


European discovery

The first European reference to platinum appears in 1557 in the writings of the Italian humanist Julius Caesar Scaliger as a description of an unknown noble metal found between Darién and Mexico, "which no fire nor any Spanish artifice has yet been able to liquefy". From their first encounters with platinum, the Spanish generally saw the metal as a kind of impurity in gold, and it was treated as such. It was often simply thrown away, and there was an official decree forbidding the adulteration of gold with platinum impurities. In 1735,
Antonio de Ulloa Antonio de Ulloa y de la Torre-Giralt, FRS, FRSA, KOS (12 January 1716 – 3 July 1795) was a Spanish naval officer, scientist, and administrator. At the age of nineteen, he joined the French Geodesic Mission to what is now the country o ...
and
Jorge Juan y Santacilia Jorge Juan y Santacilia (Novelda, Alicante, 5 January 1713 – Madrid, 21 June 1773) was a Spanish mathematician, scientist, naval officer, and mariner. He determined that the Earth is not perfectly spherical but is oblate, i.e. flattened at the ...
saw Native Americans mining platinum while the Spaniards were travelling through Colombia and Peru for eight years. Ulloa and Juan found mines with the whitish metal nuggets and took them home to Spain. Antonio de Ulloa returned to Spain and established the first mineralogy lab in Spain and was the first to systematically study platinum, which was in 1748. His historical account of the expedition included a description of platinum as being neither separable nor calcinable. Ulloa also anticipated the discovery of platinum mines. After publishing the report in 1748, Ulloa did not continue to investigate the new metal. In 1758, he was sent to superintend mercury mining operations in Huancavelica. In 1741, Charles Wood, a British
metallurgist Metallurgy is a domain of materials science and engineering that studies the physical and chemical behavior of metallic elements, their inter-metallic compounds, and their mixtures, which are known as alloys. Metallurgy encompasses both the sc ...
, found various samples of Colombian platinum in Jamaica, which he sent to William Brownrigg for further investigation. In 1750, after studying the platinum sent to him by Wood, Brownrigg presented a detailed account of the metal to the Royal Society, stating that he had seen no mention of it in any previous accounts of known minerals. Brownrigg also made note of platinum's extremely high melting point and refractoriness toward borax. Other chemists across Europe soon began studying platinum, including Andreas Sigismund Marggraf, Torbern Bergman, Jöns Jakob Berzelius,
William Lewis William or Willie Lewis may refer to: Politicians * William Lewis (MP for Anglesey) (by 1526–1601 or later), MP for Anglesey in 1553 and 1555 * William Lewis (MP for Helston), MP for Helston in 1584 * William Lewis (MP for King's Lynn) (died 15 ...
, and
Pierre Macquer Pierre-Joseph Macquer (9 October 1718 – 15 February 1784) was an influential French chemist. He is known for his ''Dictionnaire de chymie'' (1766). He was also involved in practical applications, to medicine and industry, such as the French de ...
. In 1752, Henrik Scheffer published a detailed scientific description of the metal, which he referred to as "white gold", including an account of how he succeeded in fusing platinum ore with the aid of arsenic. Scheffer described platinum as being less pliable than gold, but with similar resistance to corrosion.


Means of malleability

Karl von Sickingen Karl Heinrich Joseph Reichsgraf von Sickingen was a German academic who is known for his work on platinum. Biography von Sickingen was born in 1737. He died on July 13, 1791 in Vienna en, Viennese , iso_code = AT-9 , reg ...
researched platinum extensively in 1772. He succeeded in making malleable platinum by alloying it with gold, dissolving the alloy in hot '' aqua regia'', precipitating the platinum with ammonium chloride, igniting the ammonium chloroplatinate, and hammering the resulting finely divided platinum to make it cohere.
Franz Karl Achard Franz Karl Achard (28 April 1753 – 20 April 1821) was a German (Prussian) chemist, geoscientist, physicist, and biologist. His principal discovery was the production of sugar from sugar beets. Life and work Achard was born in Berlin, the so ...
made the first platinum crucible in 1784. He worked with the platinum by fusing it with arsenic, then later volatilizing the arsenic. Because the other platinum-family members were not discovered yet (platinum was the first in the list), Scheffer and Sickingen made the false assumption that due to its hardness—which is slightly more than for pure iron—platinum would be a relatively non-pliable material, even brittle at times, when in fact its ductility and malleability are close to that of gold. Their assumptions could not be avoided because the platinum they experimented with was highly contaminated with minute amounts of platinum-family elements such as
osmium Osmium (from Greek grc, ὀσμή, osme, smell, label=none) is a chemical element with the symbol Os and atomic number 76. It is a hard, brittle, bluish-white transition metal in the platinum group that is found as a trace element in alloys, mos ...
and iridium, amongst others, which embrittled the platinum alloy. Alloying this impure platinum residue called "plyoxen" with gold was the only solution at the time to obtain a pliable compound, but nowadays, very pure platinum is available and extremely long wires can be drawn from pure platinum, very easily, due to its crystalline structure, which is similar to that of many soft metals. In 1786,
Charles III of Spain it, Carlo Sebastiano di Borbone e Farnese , house = Bourbon-Anjou , father = Philip V of Spain , mother = Elisabeth Farnese , birth_date = 20 January 1716 , birth_place = Royal Alcazar of Madrid, Spain , death_d ...
provided a library and laboratory to
Pierre-François Chabaneau Pierre-François Chabaneau (27 June 1754 – 18 February 1842) was a French people, French chemist who spent much of his life working in Spain. He was one of the first chemists to succeed in producing malleable platinum. Chabaneau was born in Dor ...
to aid in his research of platinum. Chabaneau succeeded in removing various impurities from the ore, including gold, mercury, lead, copper, and iron. This led him to believe he was working with a single metal, but in truth the ore still contained the yet-undiscovered platinum-group metals. This led to inconsistent results in his experiments. At times, the platinum seemed malleable, but when it was alloyed with iridium, it would be much more brittle. Sometimes the metal was entirely incombustible, but when alloyed with osmium, it would volatilize. After several months, Chabaneau succeeded in producing 23 kilograms of pure, malleable platinum by hammering and compressing the sponge form while white-hot. Chabeneau realized the infusibility of platinum would lend value to objects made of it, and so started a business with Joaquín Cabezas producing platinum ingots and utensils. This started what is known as the "platinum age" in Spain.


Production

Platinum, along with the rest of the
platinum-group metals The platinum-group metals (abbreviated as the PGMs; alternatively, the platinoids, platinides, platidises, platinum group, platinum metals, platinum family or platinum-group elements (PGEs)) are six noble, precious metallic elements clustered to ...
, is obtained commercially as a by-product from nickel and copper mining and processing. During electrorefining of copper, noble metals such as silver, gold and the platinum-group metals as well as selenium and tellurium settle to the bottom of the cell as "anode mud", which forms the starting point for the extraction of the platinum-group metals. If pure platinum is found in
placer deposits In geology, a placer deposit or placer is an accumulation of valuable minerals formed by gravity separation from a specific source rock during sedimentary processes. The name is from the Spanish word ''placer'', meaning "alluvial sand". Placer min ...
or other ores, it is isolated from them by various methods of subtracting impurities. Because platinum is significantly denser than many of its impurities, the lighter impurities can be removed by simply floating them away in a liquid. Platinum is paramagnetic, whereas nickel and iron are both
ferromagnetic Ferromagnetism is a property of certain materials (such as iron) which results in a large observed magnetic permeability, and in many cases a large magnetic coercivity allowing the material to form a permanent magnet. Ferromagnetic materials ...
. These two impurities are thus removed by running an electromagnet over the mixture. Because platinum has a higher melting point than most other substances, many impurities can be burned or melted away without melting the platinum. Finally, platinum is resistant to hydrochloric and sulfuric acids, whereas other substances are readily attacked by them. Metal impurities can be removed by stirring the mixture in either of the two acids and recovering the remaining platinum. One suitable method for purification for the raw platinum, which contains platinum, gold, and the other platinum-group metals, is to process it with ''aqua regia'', in which palladium, gold and platinum are dissolved, whereas osmium, iridium, ruthenium and rhodium stay unreacted. The gold is precipitated by the addition of iron(II) chloride and after filtering off the gold, the platinum is precipitated as ammonium chloroplatinate by the addition of ammonium chloride. Ammonium chloroplatinate can be converted to platinum by heating. Unprecipitated hexachloroplatinate(IV) may be reduced with elemental zinc, and a similar method is suitable for small scale recovery of platinum from laboratory residues. Mining and refining platinum has environmental impacts.


Applications

Of the 218 tonnes of platinum sold in 2014, 98 tonnes were used for vehicle emissions control devices (45%), 74.7 tonnes for jewelry (34%), 20.0 tonnes for chemical production and petroleum refining (9.2%), and 5.85 tonnes for electrical applications such as hard disk drives (2.7%). The remaining 28.9 tonnes went to various other minor applications, such as medicine and biomedicine, glassmaking equipment, investment, electrodes, anticancer drugs,
oxygen sensor An oxygen sensor (or lambda sensor, where lambda refers to air–fuel equivalence ratio, usually denoted by λ) or probe or sond, is an electronic device that measures the proportion of oxygen (O2) in the gas or liquid being analysed. It was ...
s,
spark plug A spark plug (sometimes, in British English, a sparking plug, and, colloquially, a plug) is a device for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel/air ...
s and turbine engines.


Catalyst

The most common use of platinum is as a catalyst in chemical reactions, often as platinum black. It has been employed as a catalyst since the early 19th century, when platinum powder was used to catalyze the ignition of hydrogen. Its most important application is in automobiles as a catalytic converter, which allows the complete combustion of low concentrations of unburned hydrocarbons from the exhaust into carbon dioxide and water vapor. Platinum is also used in the petroleum industry as a catalyst in a number of separate processes, but especially in catalytic reforming of straight-run naphthas into higher-octane gasoline that becomes rich in aromatic compounds. , also known as Adams' catalyst, is used as a hydrogenation catalyst, specifically for vegetable oils. Platinum also strongly catalyzes the decomposition of hydrogen peroxide into water and oxygen and it is used in
fuel cell A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Fuel cells are different from most batteries in requ ...
s as a catalyst for the reduction of oxygen.


Standard

From 1889 to 1960, the meter was defined as the length of a platinum-iridium (90:10) alloy bar, known as the
international prototype meter The history of the metre starts with the Scientific Revolution that is considered to have begun with Nicolaus Copernicus's publication of ''De revolutionibus orbium coelestium'' in 1543. Increasingly accurate measurements were required, and sc ...
. The previous bar was made of platinum in 1799. Until May 2019, the
kilogram The kilogram (also kilogramme) is the unit of mass in the International System of Units (SI), having the unit symbol kg. It is a widely used measure in science, engineering and commerce worldwide, and is often simply called a kilo colloquially ...
was defined as the mass of the
international prototype of the kilogram The International Prototype of the Kilogram (referred to by metrologists as the IPK or Le Grand K; sometimes called the '' ur-kilogram,'' or ''urkilogram,'' particularly by German-language authors writing in English) is an object that was used t ...
, a cylinder of the same platinum-iridium alloy made in 1879. The Standard Platinum Resistance Thermometer (SPRT) is one of the four types of thermometers used to define the
International Temperature Scale of 1990 The International Temperature Scale of 1990 (ITS-90) is an equipment calibration standard specified by the International Committee of Weights and Measures (CIPM) for making measurements on the Kelvin and Celsius temperature scales. It is an appro ...
(ITS-90), the international calibration standard for temperature measurements. The resistance wire in the thermometer is made of pure platinum (NIST manufactured the wires from platinum bar stock with a chemical purity of 99.999% by weight). In addition to laboratory uses, Platinum Resistance Thermometry (PRT) also has many industrial applications, industrial standards include ASTM E1137 and IEC 60751. The standard hydrogen electrode also uses a
platinized Platinum black (Pt black) is a fine powder of platinum with good catalytic properties. The name of platinum black is due to its black color. It is used in many ways; as a thin film electrode, a fuel cell membrane catalyst, or as a catalytic igniti ...
platinum electrode due to its corrosion resistance, and other attributes.


As an investment

Platinum is a
precious metal Precious metals are rare, naturally occurring metallic chemical elements of high economic value. Chemically, the precious metals tend to be less reactive than most elements (see noble metal). They are usually ductile and have a high lustre. ...
commodity In economics, a commodity is an economic good, usually a resource, that has full or substantial fungibility: that is, the market treats instances of the good as equivalent or nearly so with no regard to who produced them. The price of a comm ...
; its
bullion Bullion is non-ferrous metal that has been refined to a high standard of elemental purity. The term is ordinarily applied to bulk metal used in the production of coins and especially to precious metals such as gold and silver. It comes from t ...
has the ISO currency code of XPT. Coins, bars, and ingots are traded or collected. Platinum finds use in jewellery, usually as a 90–95% alloy, due to its inertness. It is used for this purpose for its prestige and inherent bullion value. Jewellery trade publications advise jewellers to present minute surface scratches (which they term
patina Patina ( or ) is a thin layer that variously forms on the surface of copper, brass, bronze and similar metals and metal alloys (tarnish produced by oxidation or other chemical processes) or certain stones and wooden furniture (sheen produced b ...
) as a desirable feature in an attempt to enhance value of platinum products. In watchmaking,
Vacheron Constantin Vacheron Constantin SA () is a Swiss luxury watch and clock manufacturer founded in 1755. Since 1996, it has been a subsidiary of the Swiss Richemont Group. Vacheron Constantin is the second oldest Swiss manufacturer and one of the oldest watch ...
,
Patek Philippe Patek Philippe SA is a Swiss luxury watch and clock manufacturer, located in the Canton of Geneva and the Vallée de Joux. Established in 1839, it is named after two of its founders, Antoni Patek and Adrien Philippe. Since 1932, the company ha ...
, Rolex, Breitling, and other companies use platinum for producing their limited edition watch series. Watchmakers appreciate the unique properties of platinum, as it neither tarnishes nor wears out (the latter quality relative to gold). During periods of sustained economic stability and growth, the price of platinum tends to be as much as twice the price of gold, whereas during periods of economic uncertainty, the price of platinum tends to decrease due to reduced industrial demand, falling below the price of gold. Gold prices are more stable in slow economic times, as gold is considered a safe haven. Although gold is also used in industrial applications, especially in electronics due to its use as a conductor, its demand is not so driven by industrial uses. In the 18th century, platinum's rarity made King Louis XV of France declare it the only metal fit for a king. File:One litre of Platinum.jpg, 1,000 cubic centimeters of 99.9% pure platinum, worth about US$696,000 at 29 Jun 2016 prices File:Platinum price.webp, Platinum price 1970-2022


Other uses

In the laboratory, platinum wire is used for electrodes; platinum pans and supports are used in thermogravimetric analysis because of the stringent requirements of chemical inertness upon heating to high temperatures (~1000 °C). Platinum is used as an alloying agent for various metal products, including fine wires, noncorrosive laboratory containers, medical instruments, dental prostheses, electrical contacts, and thermocouples. Platinum-cobalt, an alloy of roughly three parts platinum and one part cobalt, is used to make relatively strong permanent magnets. Platinum-based anodes are used in ships, pipelines, and steel piers. Platinum drugs are used to treat a wide variety of cancers, including testicular and ovarian carcinomas, melanoma, small-cell and non-small-cell lung cancer, myelomas and lymphomas.


Symbol of prestige in marketing

Platinum's rarity as a metal has caused advertisers to associate it with exclusivity and wealth. "Platinum" debit and credit cards have greater privileges than " gold" cards. " Platinum awards" are the second highest possible, ranking above "gold", " silver" and "
bronze Bronze is an alloy consisting primarily of copper, commonly with about 12–12.5% tin and often with the addition of other metals (including aluminium, manganese, nickel, or zinc) and sometimes non-metals, such as phosphorus, or metalloids such ...
", but below diamond. For example, in the United States, a musical album that has sold more than 1 million copies will be credited as "platinum", whereas an album that has sold more than 10 million copies will be certified as "diamond". 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 The Queen Mother, manufactured for her coronation as Consort of
King George VI George VI (Albert Frederick Arthur George; 14 December 1895 – 6 February 1952) was King of the United Kingdom and the Dominions of the British Commonwealth from 11 December 1936 until his death in 1952. He was also the last Emperor of Ind ...
, is made of platinum. It was the first British crown to be made of this particular metal.


Health problems

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 2 micrograms per cubic meter of air averaged over an 8-hour work shift. The National Institute for Occupational Safety and Health has set a recommended exposure limit (REL) for platinum as 1 mg/m3 over an 8-hour workday. As platinum is a catalyst in the manufacture of the
silicone rubber Silicone rubber is an elastomer (rubber-like material) composed of silicone—itself a polymer—containing silicon together with carbon, hydrogen, and oxygen. Silicone rubbers are widely used in industry, and there are multiple formulations ...
and gel components of several types of
medical implants An implant is a medical device manufactured to replace a missing biological structure, support a damaged biological structure, or enhance an existing biological structure. Medical implants are man-made devices, in contrast to a transplant, whi ...
(breast implants, joint replacement prosthetics, artificial lumbar discs, vascular access ports, etc.), the possibility that platinum could enter the body and cause adverse effects has merited study. The Food and Drug Administration and other institutions have reviewed the issue and found no evidence to suggest toxicity in vivo. Chemically unbounded platinum has been identified by the FDA as a "fake cancer 'cure'". The misunderstanding is created by healthcare workers who are using inappropriately the name of the metal as a slang term for platinum-based chemotherapy medications like cisplatin. They are platinum compounds, not the metal itself.


See also

*
Chelated platinum Chelated platinum is an ionized form of platinum that forms two or more bonds with a counter ion. Some platinum chelates are claimed to have antimicrobial activity. Synthesis Although the concept and practical use of metal chelation is common, c ...
*
Iron–platinum nanoparticle Iron–platinum nanoparticles (FePt NPs) are 3D superlattices composed of an approximately equal atomic ratio of Fe and Pt. Under standard conditions, FePt NPs exist in the face-centered cubic phase but can change to a chemically ordered face-cen ...
* List of countries by platinum production *
Mixed metal oxide electrode Mixed metal oxide (MMO) electrodes, also called Dimensionally Stable Anodes (DSA), are devices with high conductivity and corrosion resistance for use as anodes in electrolysis. They are made by coating a substrate, such as pure titanium plate or ...
* Platinum group *
Platinum in Africa Platinum and platinum group metals are produced in Zimbabwe and South Africa. Of the multitudes of companies involved in producing platinum group metals in these two countries, these are the principal operators: South Africa World's leading pl ...
*
Platinum nanoparticle Platinum nanoparticles are usually in the form of a suspension or colloid of nanoparticles of platinum in a fluid, usually water. A colloid is technically defined as a stable dispersion of particles in a fluid medium (liquid or gas). Spherical ...
* Platinum print *
2000s commodities boom The 2000s commodities boom or the commodities super cycle was the rise of many physical commodity prices (such as those of food, oil, metals, chemicals and fuels) during the early 21st century (2000–2014), following the Great Commodities Depress ...


References


Further reading

*


External links


Platinum
at '' The Periodic Table of Videos'' (University of Nottingham) *
Nuclides and Isotopes
Fourteenth Edition: Chart of the Nuclides'', General Electric Company, 1989.

Centers for Disease Control and Prevention * * * * * {{Authority control Chemical elements Transition metals Cubic minerals Minerals in space group 225 Noble metals Precious metals Native element minerals Catalysts Chemical elements with face-centered cubic structure