Platinum is a
chemical element
A chemical element is a species of atoms that have a given number of protons in their nuclei, including the pure substance consisting only of that species. Unlike chemical compounds, chemical elements cannot be broken down into simpler sub ...
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
In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. They are the elements that c ...
. Its name originates from
Spanish , a
diminutive of "silver".
Platinum is a member of the
platinum group of elements and
group 10 of the
periodic table of elements. 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
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish ...
ores along with some
native deposits, mostly in
South Africa
South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring count ...
, which accounts for ~80% of the world production. Because of its scarcity in Earth's crust, only a few hundred
tonne
The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...
s 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
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engi ...
, 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 published a report on a new metal of
Colombian 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 thermometers,
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 ...
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 and
carboplatin, are applied in
chemotherapy against certain types of cancer.
Pure platinum is currently less expensive than pure
gold
Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile ...
, 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
Troy weight is a system of units of mass that originated in 15th-century England, and is primarily used in the precious metals industry. The troy weight units are the grain, the pennyweight (24 grains), the troy ounce (20 pennyweights), and ...
.
Characteristics
Physical
Pure platinum is a lustrous,
ductile, and
malleable, silver-white metal.
Platinum is more ductile than
gold
Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile ...
,
silver
Silver is a chemical element with the Symbol (chemistry), symbol Ag (from the Latin ', derived from the Proto-Indo-European wikt:Reconstruction:Proto-Indo-European/h₂erǵ-, ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, whi ...
or
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish ...
, 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
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engi ...
. 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 geometries. Although elemental platinum is generally unreactive, it is attacked by
chlorine
Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is ...
,
bromine
Bromine is a chemical element with the symbol Br and atomic number 35. It is the third-lightest element in group 17 of the periodic table (halogens) and is a volatile red-brown liquid at room temperature that evaporates readily to form a simil ...
,
iodine
Iodine is a chemical element with the Symbol (chemistry), 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
sulfur. 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, :
:
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
)
, image = Nobel Prize.png
, alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then "M ...
for determining the detailed molecular mechanisms of the catalytic oxidation of
carbon monoxide
Carbon monoxide ( chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...
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. 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
An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductilit ...
with the other platinum-group metals and
iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in ...
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 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
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish ...
deposits, platinum-group metals occur as
sulfides (e.g., ,
tellurides (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 deposit in
Ontario
Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central C ...
,
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tota ...
. At
Platinum, Alaska, about was mined between 1927 and 1975. The mine ceased operations in 1990. The rare
sulfide mineral
The sulfide minerals are a class of minerals containing sulfide (S2−) or disulfide (S22−) as the major anion. Some sulfide minerals are economically important as metal ores. The sulfide class also includes the selenides, the tellurides ...
cooperite, , contains platinum along with
palladium and nickel. Cooperite occurs in the
Merensky Reef within the
Bushveld complex,
Gauteng,
South Africa
South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring count ...
.
In 1865,
chromites 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
Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-eigh ...
, and the
Sudbury Basin,
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tota ...
, 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
Montana () is a U.S. state, state in the Mountain states, Mountain West List of regions of the United States#Census Bureau-designated regions and divisions, division of the Western United States. It is bordered by Idaho to the west, North ...
.
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
Tamil Nadu (; , TN) is a state in southern India. It is the tenth largest Indian state by area and the sixth largest by population. Its capital and largest city is Chennai. Tamil Nadu is the home of the Tamil people, whose Tamil languag ...
,
India
India, officially the Republic of India ( Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the ...
.
Platinum exists in higher abundances on the
Moon
The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width ...
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 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, 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) bromides are known as well.
Platinum hexafluoride is a strong oxidizer capable of
oxidizing oxygen.
Oxides
Platinum(IV) oxide, , 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 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 ligand, was one of the first organometallic compounds discovered. is a commercially available olefin 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. These compounds are capable of crosslinking 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. Chemoth ...
. (Side effects of cisplatin include nausea and vomiting, hair loss, tinnitus, hearing loss, and nephrotoxicity.)
Organoplatinum 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 and Jorge Juan y Santacilia 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, 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
The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, r ...
, 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
Borax is a salt (chemistry), salt (ionic compound), a hydration (chemistry), hydrated borate of sodium, with chemical formula often written . It is a colorless crystalline solid, that dissolves in water to make a base (chemistry), basic aqueo ...
. 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. 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
Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, bu ...
. 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 alloy
An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductilit ...
ing 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 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
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in ...
—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 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 provided a library and laboratory to Pierre-François Chabaneau
Pierre-François Chabaneau (27 June 1754 – 18 February 1842) was a 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 Dordogne, France, ...
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, is obtained commercially as a by-product from nickel and copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish ...
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. 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 sensors, spark plugs 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
Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...
and oxygen and it is used in fuel cells as a catalyst for the reduction of oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as we ...
.
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 previous bar was made of platinum in 1799. Until May 2019, the kilogram was defined as the mass of the international prototype of the kilogram, 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 (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 electrode due to its corrosion resistance, and other attributes.
As an investment
Platinum is a precious metal commodity; its bullion 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) as a desirable feature in an attempt to enhance value of platinum products.
In watchmaking, Vacheron Constantin, 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 compan ...
, 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
Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile ...
" cards. " Platinum awards" are the second highest possible, ranking above "gold", "silver
Silver is a chemical element with the Symbol (chemistry), symbol Ag (from the Latin ', derived from the Proto-Indo-European wikt:Reconstruction:Proto-Indo-European/h₂erǵ-, ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, whi ...
" and " bronze", but below diamond
Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the chemically stable form of carbon at room temperature and pressure, ...
. 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 Death and state funeral of George VI, his death in 1952. ...
, 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 and gel components of several types of medical implants (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
The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...
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
* Platinum group
* Platinum in Africa
* Platinum nanoparticle
* 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
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External links
Platinum
at '' The Periodic Table of Videos'' (University of Nottingham)
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Nuclides and Isotopes
Fourteenth Edition: Chart of the Nuclides'', General Electric Company, 1989.
Centers for Disease Control and Prevention
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{{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