Skip to main content
Select Source:

Platinum (revised)

PLATINUM (REVISED)

Note: This article, originally published in 1998, was updated in 2006 for the eBook edition.

Overview

Platinum is a transition metal in Group 10 (VIIIB) of the periodic table. The periodic table is a chart that shows how chemical elements are related to each other. Platinum is also a member of a group of metals named after itself. Other platinum metals include ruthenium, rhodium, palladium, osmium, and indium. They are found in Rows 5 and 6 of Groups 8 through 10 in the periodic table. Platinum is also considered to be a precious metal. A precious metal is one that is rare and desirable.

The platinum group metals are sometimes referred to as the noble metals. That term comes from the fact that they are all relatively inactive. They do not combine with or interact with most other elements or compounds. This chemical inactivity accounts for some of the uses of the platinum metals. For example, platinum is often used to make laboratory equipment because it will not react with materials that come into contact with the equipment.

SYMBOL
Pt

ATOMIC NUMBER
78

ATOMIC MASS
195.08

FAMILY
Group 10 (VIIIB)
Transition metal;
platinum group

PRONUNCIATIONY
PLAT-num

The primary use of platinum and other platinum metals is as catalysts. A catalyst is a substance used to speed up or slow down a chemical reaction without undergoing any change itself. For example, the catalytic converter in an automobile's exhaust system may contain a platinum metal.

Discovery and naming

The first known reference to platinum can be found in the writings of Italian physician, scholar, and poet Julius Caesar Scaliger (1484-1558). Scaliger apparently saw platinum while visiting Central America in 1557. He referred to a hard metal that the natives had learned to work with, but the Spanish had not. The metal had been called platina ("little silver") by the natives. The name was given to the material because it got in the way of mining silver and gold . Since the natives knew of no use for the platina, they thought of it as a nuisance.

The first complete description of platinum was given by the Spanish military leader Don Antonio de Ulloa (1716-95). While serving in South America from 1735 to 1746, de Ulloa collected samples of platinum. He later wrote a report about the metal, describing how it was mined and used. De Ulloa is often given credit for discovering platinum on the basis of the report he wrote.

Reports of the new element spread through Europe. Scientists were fascinated by its physical properties. It was not only beautiful to look at, but resistant to corrosion (rusting). Many people saw that it could be used in jewelry and art objects, as with gold and silver. Demand for the metal began to grow, leading to what was then called the "Platinum Age in Spain."

Physical properties

Platinum is a silver-gray, shiny metal that is both malleable and ductile. Malleable means capable of being hammered into thin sheets. Platinum can be hammered into a fine sheet no more than 100 atoms thick, thinner than aluminum foil.

Ductile means the metal can be drawn into thin wires. Platinum has a melting point of about 1,773°C (3,223°F) and a boiling point of about 3,827°C (6,921°F). Its density is 21.45 grams per cubic centimeter, making it one of the densest elements.

Chemical properties

Platinum is a relatively inactive metal. When exposed to air, it does not tarnish or corrode. It is not attacked by most acids, but will dissolve in aqua regia. Aqua regia is a mixture of hydrochloric and nitric acids. It often reacts with materials that do not react with either acid separately. Platinum also dissolves in very hot alkalis. An alkali is a chemical with properties opposite those of an acid. Sodium hydroxide ("common lye") and limewater are examples of alkalis.

An unusual property of platinum is that it will absorb large quantities of hydrogen gas at high temperatures. The platinum soaks up hydrogen the way a sponge soaks up water.

Occurrence in nature

The platinum metals are often found together in nature. In fact, one of the problems in producing platinum is finding a way of separating it from the other platinum metals. Unlike gold, however, these metals do not occur in masses large enough to mine. Instead, they are usually obtained as byproducts from mining other metals, such as copper and nickel.

Platinum is one of the rarest elements. Its abundance is estimated to be about 0.01 parts per million in the Earth's crust. The world's largest supplier of platinum by far is South Africa. In 1996, that nation produced 117,000 kilograms of platinum. The next largest producer was Canada, producing only 8,260 kilograms in 1996. The only other large producer of platinum is the United States. Most of the platinum in the United States comes from the Stillwater Mine in Montana.

Isotopes

Six naturally occurring isotopes of platinum exist: platinum-190, platinum-192, platinum-194, platinum-195, platinum-196, and platinum-198. Of these, only platinum-190 is radioactive. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element's name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. Each variation is an isotope.

Artificially radioactive isotopes of platinum have also been produced. These isotopes are produced when very small particles are fired at atoms. These particles stick in the atoms and make them radioactive.

No radioactive isotope of platinum has any commercial application.

Extraction

The major challenge in obtaining pure platinum is separating it from other platinum metals. The first step in this process is to dissolve the mixture in aqua regia. Platinum dissolves in aqua regia, and other platinum metals do not. Platinum metal can then be removed from the aqua regia in a form known as platinum sponge. Platinum sponge is a sponge-like material of black platinum powder. Finally, the powder is heated to very high temperatures and melted to produce the pure metal.

Uses

If asked, most people would probably name jewelry as the most important use of platinum. And the metal is used for that purpose. It is hard, beautiful, corrosion-resistantideal for making bracelets, earrings, pins, watch bands, and other types of jewelry.

However, jewelry is not the most important use of platinum. The making of catalysts is. For example, platinum catalysts are widely used in the modern petroleum industry. Crude oil from the ground must be treated before it can be converted to gasoline, fuel oil, and other petroleum products. The molecules must be broken apart, rearranged, and put back together again in new patterns. Platinum is one of the most important catalysts in making these reactions happen.

Platinum catalysts are also used to make compounds that end up as fertilizers, plastics, synthetic fibers, drugs and pharmaceuticals, and dozens of other everyday products. For example, platinum is used in the manufacture of nitric acid (HNO3).

Nitric acid is used to produce ammonia, which, in turn, is used to make fertilizers.

Probably the best known use of platinum as a catalyst is in cars. All new automobiles have a catalytic convertor in the exhaust system. A catalytic converter is a device that helps gasoline burn more completely. It reduces the amount of pollutants released to the air. Most catalytic converters contain platinum or other platinum metals.

Platinum is used in other parts of a car or truck. Certain types of spark plugs, for example, may contain platinum. Overall, the greatest single use of platinum in the United States is in the manufacture of automobiles and trucks.

Many uses of platinum depend on its chemical inactivity. For example, some people have to have artificial heart pacemakers implanted into their chests. An artificial pacemaker is a device that makes sure the heart beats in a regular pattern. It usually replaces a body part that performs that function but has been damaged. Artificial pacemakers are usually made out of platinum. The platinum protects the pacemaker from corroding or being destroyed by adds inside the body.

Platinum is also used in small amounts in alloys. For example, cobalt alloyed with platinum makes a powerful magnet. An alloy is made by melting and mixing two or more metals. The mixture has properties different from those of the individual metals. The platinum-cobalt magnet is one of the strongest magnets known.

Compounds

Relatively few platinum compounds are commercially important.

Artificial pacemakers are usually made out of platinum. The platinum protects the pacemaker from corroding or being destroyed by acids inside the body.

Health effects

Platinum dust and some platinum compounds can have mild health effects. If inhaled, they can cause sneezing, irritation of the nose, and shortness of breath. If spilled on the skin, they can cause a rash and skin irritation.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Platinum (revised)." Chemical Elements: From Carbon to Krypton. . Encyclopedia.com. 23 Aug. 2017 <http://www.encyclopedia.com>.

"Platinum (revised)." Chemical Elements: From Carbon to Krypton. . Encyclopedia.com. (August 23, 2017). http://www.encyclopedia.com/science/news-wires-white-papers-and-books/platinum-revised

"Platinum (revised)." Chemical Elements: From Carbon to Krypton. . Retrieved August 23, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/news-wires-white-papers-and-books/platinum-revised

platinum

platinum (plăt´ənəm), metallic chemical element; symbol Pt; at. no. 78; at. wt. 195.084; m.p. 1,772°C; b.p. 3,827±100°C; sp. gr. 21.45 at 20°C; valence +2 or +4. Pure platinum is a malleable, ductile, lustrous, silver-white metal with a face-centered cubic crystalline structure. Chemically inactive, it is unaffected by common acids but dissolves in aqua regia, forming chloroplatinic acid (H2PtCl6). It is attacked by the halogens, sulfur, or caustic alkalies. It does not combine with oxygen even at high temperatures. Like palladium, it absorbs large quantities of hydrogen, which it releases at red heat.

Platinum is found in nature alloyed with the other metals of the so-called platinum group, found in Group 10 of the periodic table; the other five metals in this group are iridium, osmium, palladium, rhodium, and ruthenium. These metals are found in alluvial deposits in Russia, South Africa, Colombia, and Alaska. Platinum and the related metals are recovered commercially as a byproduct of the refining of nickel ores mined near Sudbury, Ont., Canada; from gold mines in South Africa; and from the alluvial deposits in Russia. There is no routine method for separating platinum from other metals; it is usually recovered by complex chemical methods.

Platinum has many uses. Its wear- and tarnish-resistance characteristics are well-suited for making fine jewelry. Platinum and its alloys are used in surgical tools, laboratory utensils, electrical resistance wires, and electrical contact points. The most important of the alloys are those with iridium. The International Prototype Kilogram, kept at Sèvres, France, is a cylinder of platinum-iridium alloy, and the standard definition of a meter for a long time was based on the distance between two marks on a bar of platinum-iridium. Platinum is also used in the definition of the Standard Hydrogen Electrode (a reference for determining cell voltages). Because its thermal coefficient of expansion is nearly equal to that of glass, platinum is used to make electrodes sealed in glass. It is used extensively in dentistry and a platinum-osmium alloy is used in implants such as pacemakers and replacement valves. A platinum-cobalt alloy is used to make very powerful magnets.

Platinum is specially prepared for use as a catalyst. Finely divided, the metal is platinum black, a powder. It also may be used as platinum sponge, formed when platinic ammonium chloride, (NH4)2PtCl6, is ignited, or as platinized asbestos, prepared by heating asbestos after dipping it in chloroplatinic acid. Platinum catalysts are used in the contact process for producing sulfuric acid, in the Ostwald process for the production of nitric acid, and in petroleum cracking, as well as in a variety of other reactions. Platinum is also used as a catalyst in fuel cells and in catalytic converters for automobiles.

Naturally-occurring platinum and platinum-rich alloys have been known since antiquity. Although there is evidence that the metal was used in the Americas in pre-Columbian times, the first European reference to platinum appears in 1557 as a description of a mysterious metal found in Central American mines. When the Spanish first encountered the metal, they regarded it as an undesirable impurity in the silver they were mining and often discarded it.

Modern knowledge of the metal dates from about 1736, when its existence in South America was reported by A. de Ulloa. Some of this platina [little silver], was taken to England, and soon thereafter many leading chemists published reports on it. A process discovered about 1803 by W. H. Wollaston for making the metal malleable made possible its commercial use for laboratory apparatus and other purposes. Although platinum was used as an adulterant for gold over a century ago, it is now considered the more valuable of the two.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"platinum." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 23 Aug. 2017 <http://www.encyclopedia.com>.

"platinum." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (August 23, 2017). http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/platinum

"platinum." The Columbia Encyclopedia, 6th ed.. . Retrieved August 23, 2017 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/platinum

Platinum

Platinum


melting point: 1,739°C
boiling point: 4,170°C
density: 21.45 g/cm
3
most common ions: Pt 2+, Pt(Cl) 62, Pt(CN) 42, Pt(CN) 62

The first reports of the discovery of platinum were the papers of Antonio de Ulloa, who found an unworkable metal , platina (Spanish for "little silver"), in the gold mines of Colombia in 1736. Charles Wood provided the first samples in 1741. Platinum has a concentration of approximately 106 percent in Earth's crust. Platinum crystallizes in the face-centered cubic structure. The pure metal is malleable and ductile , and lustrous and silvery in appearance. It is capable of absorbing gaseous hydrogen. Platinum is found in nature in alluvial deposits and in association with copper, iron, and nickel sulfide ores. The metal is soluble in aqua regia, isolated as (NH4)2PtCl6 from aqua regia, and obtained as a sponge or powder by ignition of (NH4)2PtCl6.

Platinum is used as a catalyst in a wide variety of chemical reactions. Some of the more common catalytic uses are the oxidation of organic vapors in automobile exhaust, the oxidation of ammonia in the production of nitric acid, and the rearrangement of atoms in petroleum reforming. Most of the halides are formed by direct combination of the halogen elements with platinum, resulting in PtF6, [PtF5]4, PtX4 (where X = F, Cl, Br, or I), and PtX3 and PtX2 (where X = Cl, Br, or I). The two oxides, PtO and PtO2, are unstable and decompose upon heating. In the +2 and +3 oxidation states, platinum forms coordination complexes bonded to carbon, nitrogen, phosphorous, oxygen, and sulfur donor atoms. Perhaps the most well known coordination complex is cis -platin, Pt(NH3)2Cl2, used in chemotherapy treatments of cancer.

D. Paul Rillema

Bibliography

Cotton, F. Albert, and Wilkinson, Geoffrey (1988). Advanced Inorganic Chemistry, 5th edition. New York: Wiley.

Greenwood, Norman N., and Earnshaw, A. (1984). Chemistry of the Elements. New York: Pergamon Press.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Platinum." Chemistry: Foundations and Applications. . Encyclopedia.com. 23 Aug. 2017 <http://www.encyclopedia.com>.

"Platinum." Chemistry: Foundations and Applications. . Encyclopedia.com. (August 23, 2017). http://www.encyclopedia.com/science/news-wires-white-papers-and-books/platinum

"Platinum." Chemistry: Foundations and Applications. . Retrieved August 23, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/news-wires-white-papers-and-books/platinum

platinum

platinum (symbol Pt) Lustrous, silver-white metal, the first of the six metallic transition elements. Platinum was used for decorations by pre-Columbian South Americans. It was discovered in 1557 in Central America by the Italian-born French scientist Julius Scaliger (1484–1558) with the Spanish conquistadors and named ‘little silver’ in Spanish (platina). it is chiefly found in certain ores of nickel. Malleable and ductile, it is used in jewellery, dentistry, electrical-resistance wire, magnets, thermocouples, surgical tools, electrodes and other laboratory apparatus, and as a catalyst in catalytic converters for car exhausts. It is chemically unreactive and resists tarnishing and corrosion. Properties: at.no. 78; r.a.m. 195.09; r.d. 21.45; m.p. 1772°C (3222°F); b.p. 3800°C (6872°F); most common isotope Pt195 (33.8%).

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"platinum." World Encyclopedia. . Encyclopedia.com. 23 Aug. 2017 <http://www.encyclopedia.com>.

"platinum." World Encyclopedia. . Encyclopedia.com. (August 23, 2017). http://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/platinum

"platinum." World Encyclopedia. . Retrieved August 23, 2017 from Encyclopedia.com: http://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/platinum

platinum

plat·i·num / ˈplatn-əm/ • n. a precious silvery-white metal, the chemical element of atomic number 78. It was first encountered by the Spanish in South America in the 16th century and is used in jewelry, electrical contacts, laboratory equipment, and industrial catalysts. (Symbol: Pt) ∎  the grayish-white or silvery color of platinum. • adj. 1. of a platinum color: a platinum wig. 2. (of a recording) having sold enough copies to merit a platinum disk. PHRASES: go platinum (of a recording) achieve sales meriting a platinum disk.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"platinum." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. 23 Aug. 2017 <http://www.encyclopedia.com>.

"platinum." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. (August 23, 2017). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/platinum-0

"platinum." The Oxford Pocket Dictionary of Current English. . Retrieved August 23, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/platinum-0

platinum

platinum XIX. alt., in conformity with metalnames in -um, of †platina (XVIII) — Sp., dim. of plata silver.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"platinum." The Concise Oxford Dictionary of English Etymology. . Encyclopedia.com. 23 Aug. 2017 <http://www.encyclopedia.com>.

"platinum." The Concise Oxford Dictionary of English Etymology. . Encyclopedia.com. (August 23, 2017). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/platinum-1

"platinum." The Concise Oxford Dictionary of English Etymology. . Retrieved August 23, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/platinum-1

platinum

platinum •minimum • maximum • optimum •chrysanthemum, helianthemum •cardamom • Pergamum • sesamum •per annum • magnum • damnum •Arnhem, Barnum •envenom, venom •interregnum • Cheltenham • arcanum •duodenum, plenum •platinum • antirrhinum • Bonham •summum bonum • Puttnam •ladanum • molybdenum • laudanum •origanum, polygonum •organum • tympanum •laburnum, sternum •gingham • Gillingham • Birmingham •Cunningham • Walsingham •Nottingham • wampum • carom •Abram • panjandrum • tantrum •angstrom • alarum • candelabrum •plectrum, spectrum •arum, harem, harum-scarum, Sarum •sacrum, simulacrum •maelstrom • cerebrum • pyrethrum •Ingram •sistrum, Tristram •Hiram •grogram, pogrom •nostrum, rostrum •cockalorum, decorum, forum, jorum, Karakoram, Karakorum, Mizoram, pons asinorum, quorum •wolfram • fulcrum • Durham •conundrum • buckram • lustrum •serum, theorem •labarum • marjoram • pittosporum •Rotherham • Bertram

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"platinum." Oxford Dictionary of Rhymes. . Encyclopedia.com. 23 Aug. 2017 <http://www.encyclopedia.com>.

"platinum." Oxford Dictionary of Rhymes. . Encyclopedia.com. (August 23, 2017). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/platinum

"platinum." Oxford Dictionary of Rhymes. . Retrieved August 23, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/platinum