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
The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of an atomic nucleus. For ordinary nuclei, this is equal to the proton number (''n''p) or the number of protons found in the nucleus of every ...
78. It is a
dense
Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematically ...
, malleable,
ductile
Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stres ...
, 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 can ...
. Its name originates from
Spanish
Spanish might refer to:
* Items from or related to Spain:
**Spaniards are a nation and ethnic group indigenous to Spain
**Spanish language, spoken in Spain and many Latin American countries
**Spanish cuisine
Other places
* Spanish, Ontario, Cana ...
, 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
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 ...
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
Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbers) ...
. It is one of the
rarer elements in Earth's crust, with an average abundance of approximately 5
μg/kg. It occurs in some
nickel
Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...
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 pinkis ...
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
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 countri ...
, 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 engine ...
, even at high temperatures, and is therefore considered a
noble metal
A noble metal is ordinarily regarded as a metallic chemical element that is generally resistant to corrosion and is usually found in nature in its raw form. Gold, platinum, and the other platinum group metals (ruthenium, rhodium, palladium, o ...
. 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
In the history of the Americas, the pre-Columbian era spans from the original settlement of North and South America in the Upper Paleolithic period through European colonization, which began with Christopher Columbus's voyage of 1492. Usually, th ...
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 converter
A catalytic converter is an exhaust emission control device that converts toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalyzing a redox reaction. Catalytic converters are usually ...
s, laboratory equipment,
electric
Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by ...
al contacts and
electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials de ...
s,
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
In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively cha ...
; but due to its corrosion resistance, metallic platinum has not been linked to adverse health effects. Compounds containing platinum, such as
cisplatin
Cisplatin is a chemotherapy medication used to treat a number of cancers. These include testicular cancer, ovarian cancer, cervical cancer, breast cancer, bladder cancer, head and neck cancer, esophageal cancer, lung cancer, mesothelioma, br ...
,
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
Carboplatin, sold under the trade name Paraplatin among others, is a chemotherapy medication used to treat a number of forms of cancer. This includes ovarian cancer, lung cancer, head and neck cancer, brain cancer, and neuroblastoma. It is used b ...
, are applied in
chemotherapy
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. Chemotherap ...
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 met ...
, 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 the ...
.
Characteristics
Physical
Pure platinum is a lustrous,
ductile
Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stres ...
, and
malleable
Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stres ...
, 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 met ...
,
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 pinkis ...
, 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
Jewellery ( UK) or jewelry (U.S.) consists of decorative items worn for personal adornment, such as brooches, rings, necklaces, earrings, pendants, bracelets, and cufflinks. Jewellery may be attached to the body or the clothes. From a wester ...
.
Chemical
![Platin löst sich in heißem Königswasser](https://upload.wikimedia.org/wikipedia/commons/f/fc/Platin_l%C3%B6st_sich_in_hei%C3%9Fem_K%C3%B6nigswasser.jpg)
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 engine ...
. 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 state
In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...
s 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
Chlorine is a chemical element with the Symbol (chemistry), 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 betwee ...
,
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 simila ...
,
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 tetrafluoride is the inorganic compound with the chemical formula . In the solid state, the compound features platinum(IV) in octahedral coordination geometry.
Preparation
The compound was first reported by Henri Moissan by the fluorinat ...
.
Platinum is insoluble in
hydrochloric
Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid. It is a component of the gastric acid in the digestiv ...
and
nitric acid
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...
, 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 complexes have been reported and care is taken in the choosing of reaction solvents.
In 2007, the German scientist
Gerhard Ertl
Gerhard Ertl (; born 10 October 1936) is a German physicist and a Professor emeritus at the Department of Physical Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft in Berlin, Germany. Ertl's research laid the foundation of modern su ...
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 simple ...
over platinum (
catalytic converter
A catalytic converter is an exhaust emission control device that converts toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalyzing a redox reaction. Catalytic converters are usually ...
).
Isotopes
Platinum has six naturally occurring
isotopes
Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbers) ...
: , , , , , 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
Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and thereby transforms or 'decays' into a different atomic nucleus, with a mass number that is reduced by four and an atom ...
, but its decay has never been observed (the
half-life
Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ato ...
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
In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta particle (fast energetic electron or positron) is emitted from an atomic nucleus, transforming the original nuclide to an isobar of that nuclide. For ...
and alpha decay. , , and decay primarily by
electron capture
Electron capture (K-electron capture, also K-capture, or L-electron capture, L-capture) is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shells. Thi ...
. and are predicted to have energetically favorable
double beta decay
In nuclear physics, double beta decay is a type of radioactive decay in which two neutrons are simultaneously transformed into two protons, or vice versa, inside an atomic nucleus. As in single beta decay, this process allows the atom to move clos ...
paths.
Occurrence
![Platinum-palladium ore, Stillwater mine MT](https://upload.wikimedia.org/wikipedia/commons/0/05/Platinum-palladium_ore%2C_Stillwater_mine_MT.JPG)
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, ductility, ...
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 f ...
mostly. Most often the native platinum is found in secondary deposits in
alluvial
Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluv ...
deposits. The alluvial deposits used by
pre-Columbian
In the history of the Americas, the pre-Columbian era spans from the original settlement of North and South America in the Upper Paleolithic period through European colonization, which began with Christopher Columbus's voyage of 1492. Usually, th ...
people in the
Chocó Department
Choco Department is a department of Western Colombia known for its large Afro-Colombian population. It is in the west of the country, and is the only Colombian department to have coastlines on both the Pacific Ocean and the Atlantic Ocean. It ...
,
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
The Ural Mountains ( ; rus, Ура́льские го́ры, r=Uralskiye gory, p=ʊˈralʲskʲɪjə ˈɡorɨ; ba, Урал тауҙары) or simply the Urals, are a mountain range that runs approximately from north to south through western ...
, Russia, and it is still mined.
In
nickel
Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...
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 pinkis ...
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., ),
antimonide Antimonides (sometimes called stibnides) are compounds of antimony with more electropositive elements. The antimonide ion
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative b ...
s (PdSb), and
arsenide
In chemistry, an arsenide is a compound of arsenic with a less electronegative element or elements. Many metals form binary compounds containing arsenic, and these are called arsenides. They exist with many stoichiometries, and in this respect ars ...
s (e.g. ), and as end alloys with nickel or copper. Platinum arsenide,
sperrylite
Sperrylite is a platinum arsenide mineral with the chemical formula and is an opaque metallic tin white mineral which crystallizes in the isometric system with the pyrite group structure. It forms cubic, octahedral or pyritohedral crystals in a ...
(), 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
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 Ca ...
,
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 tot ...
. 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
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, the ...
cooperite, , contains platinum along with
palladium
Palladium is a chemical element with the symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal discovered in 1803 by the English chemist William Hyde Wollaston. He named it after the asteroid Pallas, which was itself na ...
and nickel. Cooperite occurs in the
Merensky Reef
The Merensky Reef is a layer of igneous rock in the Bushveld Igneous Complex (BIC) in the North West, Limpopo, Gauteng and Mpumalanga provinces of South Africa which together with an underlying layer, the Upper Group 2 Reef (UG2), contains most of ...
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
Gauteng ( ) is one of the nine provinces of South Africa. The name in Sotho-Tswana languages means 'place of gold'.
Situated on the Highveld, Gauteng is the smallest province by land area in South Africa. Although Gauteng accounts for only ...
,
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 countri ...
.
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
Hans Merensky (16 March 1871 – 21 October 1952) was a South African geologist, prospector, scientist, conservationist and philanthropist. He discovered the rich deposit of alluvial diamonds at Alexander Bay in Namaqualand, vast platinum ...
discovered a large supply of platinum in the
Bushveld Igneous 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 is ...
in South Africa. The specific layer he found, named the
Merensky Reef
The Merensky Reef is a layer of igneous rock in the Bushveld Igneous Complex (BIC) in the North West, Limpopo, Gauteng and Mpumalanga provinces of South Africa which together with an underlying layer, the Upper Group 2 Reef (UG2), contains most of ...
, contains around 75% of the world's known platinum.
The large copper–nickel deposits near
Norilsk
Norilsk ( rus, Нори́льск, p=nɐˈrʲilʲsk, ''Norílʹsk'') is a closed city in Krasnoyarsk Krai, Russia, located south of the western Taymyr Peninsula, around 90 km east of the Yenisey River and 1,500 km north of Krasnoyarsk. Norilsk i ...
in
Russia
Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...
, 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
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 tot ...
, 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
The Absaroka Range ( or ) is a sub-range of the Rocky Mountains in the United States. The range stretches about across the Montana–Wyoming border, and at its widest, forming the eastern boundary of Yellowstone National Park along Paradise Va ...
in
Montana
Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columbi ...
.
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 States and union territories of India, state in southern India. It is the List of states and union territories of India by area, tenth largest Indian state by area and the List of states and union territories of India ...
,
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 so ...
.
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 of ...
and in meteorites. Correspondingly, platinum is found in slightly higher abundances at sites of
bolide
A bolide is normally taken to mean an exceptionally bright meteor, but the term is subject to more than one definition, according to context. It may refer to any large crater-forming body, or to one that explodes in the atmosphere. It can be a ...
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
Ammonium hexachloroplatinate, also known as ammonium chloroplatinate, is the inorganic compound with the formula (NH4)2 tCl6 It is a rare example of a soluble platinum(IV) salt that is not hygroscopic. It forms intensely yellow solutions in water. ...
,
which is relatively insoluble in ammonium solutions. Heating this ammonium salt in the presence of hydrogen reduces it to elemental platinum.
Potassium hexachloroplatinate
Potassium hexachloroplatinate is the inorganic compound with the formula K2PtCl6. It is a yellow solid that is an example of a comparatively insoluble potassium salt. The salt features the hexachloroplatinate(IV) dianion, which has octahedral coor ...
is similarly insoluble, and hexachloroplatinic acid has been used in the determination of potassium ions by
gravimetry
Gravimetry is the measurement of the strength of a gravitational field. Gravimetry may be used when either the magnitude of a gravitational field or the properties of matter responsible for its creation are of interest.
Units of measurement
Gr ...
.
When hexachloroplatinic acid is heated, it decomposes through
platinum(IV) chloride
Platinum(IV) chloride is the inorganic compound of platinum and chlorine with the empirical formula PtCl4. This brown solid features platinum in the 4+ oxidation state.
Structure
Typical of Pt(IV), the metal centers adopt an octahedral coordinati ...
and
platinum(II) chloride
Platinum(II) chloride is the chemical compound Pt Cl2. It is an important precursor used in the preparation of other platinum compounds. It exists in two crystalline forms, but the main properties are somewhat similar: dark brown, insoluble in wa ...
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
Platinum hexafluoride is the chemical compound with the formula Pt F6, and is one of seventeen known binary hexafluorides. It is a dark-red volatile solid that forms a red gas. The compound is a unique example of platinum in the +6 oxidation stat ...
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
Adams' catalyst, also known as platinum dioxide, is usually represented as platinum(IV) oxide hydrate, PtO2•H2O. It is a catalyst for hydrogenation and hydrogenolysis in organic synthesis. This dark brown powder is commercially available. The ox ...
", is a black powder that is soluble in
potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash.
Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...
(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
Palladium(II) acetate is a chemical compound of palladium described by the formula d(O2CCH3)2sub>n, abbreviated d(OAc)2sub>n. It is more reactive than the analogous platinum compound. Depending on the value of n, the compound is soluble in man ...
,
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
Sodium acetate, CH3COONa, also abbreviated Na O Ac, is the sodium salt of acetic acid. This colorless deliquescent salt has a wide range of uses.
Applications
Biotechnological
Sodium acetate is used as the carbon source for culturing bacteria ...
.
[ 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
Zeise's salt, potassium trichloro(ethylene)platinate(II), is the chemical compound with the formula K platinum">PtCl3(C2H4).html" ;"title="platinum.html" ;"title="/nowiki>PtCl3(C2H4)">platinum.html"_;"title="/nowiki>platinum">PtCl3(C2H4)H2O.__Th ...
, 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 compound
Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...
s 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
Cisplatin is a chemotherapy medication used to treat a number of cancers. These include testicular cancer, ovarian cancer, cervical cancer, breast cancer, bladder cancer, head and neck cancer, esophageal cancer, lung cancer, mesothelioma, br ...
, or is the first of a series of square planar platinum(II)-containing chemotherapy drugs. Others include carboplatin
Carboplatin, sold under the trade name Paraplatin among others, is a chemotherapy medication used to treat a number of forms of cancer. This includes ovarian cancer, lung cancer, head and neck cancer, brain cancer, and neuroblastoma. It is used b ...
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
Common Era (CE) and Before the Common Era (BCE) are year notations for the Gregorian calendar (and its predecessor, the Julian calendar), the world's most widely used calendar era. Common Era and Before the Common Era are alternatives to the or ...
. For example, a small box from burial of Shepenupet II
Shepenupet II (alt. Shepenwepet II, prenomen: ''Henutneferumut Irietre'') was an ancient Egyptian princess of the 25th Dynasty who served as the high priestess, the Divine Adoratrice of Amun, from around 700 BC to 650 BC. She was the daughter of ...
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
Esmeraldas () is a coastal city in northwestern Ecuador. It is the seat of the Esmeraldas Canton and capital of the Esmeraldas Province. It has an international sea port and a small airport ( IATA location identifier: ESM). Esmeraldas is the major ...
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
The antiquities trade is the exchange of antiquities and archaeological artifacts from around the world. This trade may be illicit or completely legal. The legal antiquities trade abides by national regulations, allowing for extraction of artifact ...
rather than obtained by direct archeological excavation. To work the metal, they would combine gold and platinum powders by sintering
Clinker nodules produced by sintering
Sintering or frittage is the process of compacting and forming a solid mass of material by pressure or heat without melting it to the point of liquefaction.
Sintering happens as part of a manufacturing ...
. 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
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 ...
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
Italian(s) may refer to:
* Anything of, from, or related to the people of Italy over the centuries
** Italians, an ethnic group or simply a citizen of the Italian Republic or Italian Kingdom
** Italian language, a Romance language
*** Regional Ita ...
humanist Julius Caesar Scaliger
Julius Caesar Scaliger (; April 23, 1484 – October 21, 1558), or Giulio Cesare della Scala, was an Italian scholar and physician, who spent a major part of his career in France. He employed the techniques and discoveries of Renaissance humanism ...
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
An adulterant is caused by the act of adulteration, a practice of secretly mixing a substance with another. Typical substances that are adulterated include but are not limited to food, cosmetics, pharmaceuticals, fuel, or other chemicals, that ...
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
Huancavelica () or Wankawillka in Quechua is a city in Peru. It is the capital of the department of Huancavelica and according to the 2017 census had a population of 49,570 people. The city was established on August 5, 1572 by the Viceroy ...
.
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
William Brownrigg ( – 6 January 1800) was a British doctor and scientist, who practised at Whitehaven in Cumberland. While there, Brownrigg carried out experiments that earned him the Copley Medal in 1766 for his work on carbonic acid gas. He ...
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, re ...
, 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 (ionic compound), a hydrated borate of sodium, with chemical formula often written . It is a colorless crystalline solid, that dissolves in water to make a basic solution. It is commonly available in powder or granular form, ...
. Other chemists across Europe soon began studying platinum, including Andreas Sigismund Marggraf
Andreas Sigismund Marggraf (; 3 March 1709 – 7 August 1782) was a German chemist from Berlin, then capital of the Margraviate of Brandenburg, and a pioneer of analytical chemistry. He isolated zinc in 1746 by heating Calamine (mineral), calamine ...
, Torbern Bergman
Torbern Olaf (Olof) Bergman (''KVO'') (20 March 17358 July 1784) was a Swedish chemist and mineralogist noted for his 1775 ''Dissertation on Elective Attractions'', containing the largest chemical affinity tables ever published. Bergman was the ...
, Jöns Jakob Berzelius
Jöns is a Swedish given name and a surname.
Notable people with the given name include:
* Jöns Jacob Berzelius (1779–1848), Swedish chemist
* Jöns Budde (1435–1495), Franciscan friar from the Brigittine monastery in NaantaliVallis Gratiae ...
, 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
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, but ...
. 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
Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stres ...
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, ductility, ...
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
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
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 f ...
—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
Iridium is a chemical element with the symbol Ir and atomic number 77. A very hard, brittle, silvery-white transition metal of the platinum group, it is considered the second-densest naturally occurring metal (after osmium) with a density of ...
, 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
A material is brittle if, when subjected to stress, it fractures with little elastic deformation and without significant plastic deformation. Brittle materials absorb relatively little energy prior to fracture, even those of high strength. Bre ...
. 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
Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...
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 pinkis ...
mining and processing. During electrorefining of copper, noble metals such as silver, gold and the platinum-group metals as well as selenium
Selenium is a chemical element with the symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, ...
and tellurium
Tellurium is a chemical element with the symbol Te and atomic number 52. It is a brittle, mildly toxic, rare, silver-white metalloid. Tellurium is chemically related to selenium and sulfur, all three of which are chalcogens. It is occasionally fou ...
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
Paramagnetism is a form of magnetism whereby some materials are weakly attracted by an externally applied magnetic field, and form internal, induced magnetic fields in the direction of the applied magnetic field. In contrast with this behavior, d ...
, 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
Iron(II) chloride, also known as ferrous chloride, is the chemical compound of formula FeCl2. It is a paramagnetic solid with a high melting point. The compound is white, but typical samples are often off-white. FeCl2 crystallizes from water as ...
and after filtering off the gold, the platinum is precipitated as ammonium chloroplatinate
Ammonium hexachloroplatinate, also known as ammonium chloroplatinate, is the inorganic compound with the formula (NH4)2 tCl6 It is a rare example of a soluble platinum(IV) salt that is not hygroscopic. It forms intensely yellow solutions in water ...
by the addition of ammonium chloride. Ammonium chloroplatinate can be converted to platinum by heating. Unprecipitated hexachloroplatinate(IV) may be reduced with elemental zinc
Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
, 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
Vehicle emissions control is the study of reducing the emissions produced by motor vehicles, especially internal combustion engines.
Types of emissions
Emissions of many air pollutants have been shown to have variety of negative effects on public ...
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
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
in chemical reactions, often as platinum black
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 ...
. 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
A catalytic converter is an exhaust emission control device that converts toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalyzing a redox reaction. Catalytic converters are usually ...
, 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
Catalytic reforming is a chemical process used to convert petroleum refinery naphthas distilled from crude oil (typically having low octane ratings) into high-octane liquid products called reformates, which are premium blending stocks for high-o ...
of straight-run naphthas into higher-octane gasoline that becomes rich in aromatic compounds. , also known as Adams' catalyst
Adams' catalyst, also known as platinum dioxide, is usually represented as platinum(IV) oxide hydrate, PtO2•H2O. It is a catalyst for hydrogenation and hydrogenolysis in organic synthesis. This dark brown powder is commercially available. The ox ...
, is used as a hydrogenation catalyst, specifically for vegetable oil
Vegetable oils, or vegetable fats, are oils extracted from seeds or from other parts of fruits. Like animal fats, vegetable fats are ''mixtures'' of triglycerides. Soybean oil, grape seed oil, and cocoa butter are examples of seed oils, or fat ...
s. Platinum also strongly catalyzes the decomposition of hydrogen peroxide
Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3% ...
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 a ...
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
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 wel ...
.
Standard
From 1889 to 1960, the meter
The metre (British spelling) or meter (American spelling; see spelling differences) (from the French unit , from the Greek noun , "measure"), symbol m, is the primary unit of length in the International System of Units (SI), though its prefi ...
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
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 constructio ...
(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
The standard hydrogen electrode (abbreviated SHE), is a redox electrode which forms the basis of the thermodynamic scale of oxidation-reduction potentials. Its absolute electrode potential is estimated to be at 25 °C, but to form a basis f ...
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
ISO 4217 is a Standardization, standard published by the International Organization for Standardization (ISO) that defines alpha codes and numeric codes for the representation of Currency, currencies and provides information about the relation ...
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
A watchmaker is an artisan who makes and repairs watches. Since a majority of watches are now factory-made, most modern watchmakers only repair watches. However, originally they were master craftsmen who built watches, including all their par ...
, 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
Rolex SA () is a British-founded Swiss watch designer and manufacturer based in Geneva, Switzerland. Founded in 1905 as ''Wilsdorf and Davis'' by Hans Wilsdorf and Alfred Davis in London, the company registered ''Rolex'' as the brand name of ...
, 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
Louis XV (15 February 1710 – 10 May 1774), known as Louis the Beloved (french: le Bien-Aimé), was King of France from 1 September 1715 until his death in 1774. He succeeded his great-grandfather Louis XIV at the age of five. Until he reached ...
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
Thermogravimetric analysis or thermal gravimetric analysis (TGA) is a method of thermal analysis in which the mass of a sample is measured over time as the temperature changes. This measurement provides information about physical phenomena, such ...
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 magnet
A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, ...
s. 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 met ...
" 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
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
Diamond is a Allotropes of carbon, 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 Chemical stability, chemically stable form of car ...
. 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
The Crown of Queen Elizabeth The Queen Mother, also known as The Queen Mother's Crown, is the crown made for Queen Elizabeth to wear at her coronation alongside her husband, King George VI, in 1937 and State Openings of Parliament during her h ...
, 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
The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georgi ...
, 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
OSHA or Osha may refer to:
Work
* Occupational Safety and Health Administration, a federal agency of the United States that regulates workplace safety and health
* Occupational Safety and Health Act (United States) of 1970, a federal law in the Un ...
standard is 2 micrograms per cubic meter of air averaged over an 8-hour work shift. The National Institute for Occupational Safety and Health
The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the C ...
has set a recommended exposure limit
A recommended exposure limit (REL) is an occupational exposure limit that has been recommended by the United States National Institute for Occupational Safety and Health. The REL is a level that NIOSH believes would be protective of worker safety ...
(REL) for platinum as 1 mg/m3 over an 8-hour workday.
As platinum is a catalyst
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
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
The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...
and other institutions have reviewed the issue and found no evidence to suggest toxicity in vivo
Studies that are ''in vivo'' (Latin for "within the living"; often not italicized in English) are those in which the effects of various biological entities are tested on whole, living organisms or cells, usually animals, including humans, and ...
. 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
* List of countries by platinum production
This is a list of countries by platinum production. It is based on information from the United States Geological Survey
The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of th ...
* 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
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 ...
* 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
Platinum prints, also called ''platinotypes'', are photographic prints made by a monochrome photographic printing, printing process involving platinum.
Platinum tones range from warm black, to reddish brown, to expanded mid-tone grays that are ...
* 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
''Periodic Videos'' (also known as ''The Periodic Table of Videos'') is a video project and YouTube channel on chemistry. It consists of a series of videos about chemical elements and the periodic table, with additional videos on other topics i ...
'' (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