Platinum

UsesJewelry; oxygen sensor in internal combustion engines; chemical and electrical industries; dentistry; windings of hightemperature furnaces; electroplating; photography; cancer chemotherapeutic agents

UsesCatalysis:Platinum is found in the environment naturally and from anthropogenic sources. Platinum is primarily used in industry as a catalyst, predominately for the production of vehicle catalytic converters. Platinum is also used in the chemical, electrical, glass, dental, healthcare, pharmaceutical, petroleum, and jewelry fields. In addition to its catalytic properties, platinum, in combination with cobalt, has powerful magnetic properties.Platinum metal and its alloys have numerous applications. As a precious metal it is used extensively in jewelry. Other important applications include construction of laboratory crucibles and high temperature electric furnaces; in instruments as thermocouple elements; as wire; for electrical contacts; as electrodes; in dentistry; in cigarette lighters; and for coating missile and jet engine parts.Platinum also is used extensively as a catalyst in hydrogenation, dehydrogenation, oxidation, isomerization, carbonylation, and hydrocracking. Also, it is used in organic synthesis and petroleum refining. Like palladium, platinum also exhibits remarkable ability to absorb hydrogen. An important application of platinum is in the catalytic oxidation of ammonia in Ostwald's process in the manufacture of nitric acid. Platinum is installed in the catalytic converters in automobile engines for pollution control.

DescriptionPlatinum was discovered in Colombia, South America by Ulloa in 1735 and six years later in 1741 by Wood. The metal was isolated from native platinum by Delisle in 1775 and produced in malleable form by Chabaneau in 1786. Wollaston in 1803 developed a method of obtaining pure malleable platinum from crude platinum by extraction with aqua regia. The process led to the discovery of two other platinum group metals, palladium and rhodium, that were found in the aqua regia extract after platinum precipitated. Platinum derived its name from platina originating from the Spanish word plata for silver, because it was thought to be a trivial unwanted material associated with gold in gold mines of Central America. Platinum occurs in nature as a bright-white cubic crystalline solid with metallic luster associated with other noble metals of its group. Platinum also occurs as the mineral sperrylite, PtAs2, found as tin-white brittle cubic crystals containing 52−57% platinum in certain nickel-bearing deposits. Some other minerals of platinum are cooperite PtS (Pt 80-86%); and braggite(Pt, Pd, Ni)S (Pt 58-60%). The abundance of platinum in the earth’s crust is estimated to be 0.005 mg/kg.

OccurrencePlatinum is the 75th most abundant element and, unlike many elements, is found in itspure elemental form in nature, as are deposits of silver and gold. Platinum is widely distributedover the Earth and is mined mainly in the Ural Mountains in Russia and in South Africa,Alaska, the western United States, Columbia in South America, and Ontario in Canada.When found in the mineral sperrylite (PtAs2), it is dissolved with aqua regia to form a precipitatecalled “sponge” that is then converted into platinum metal. It is also recovered as aby-product of nickel mining, mainly in Ontario, Canada.

HistoryDiscovered in South America by Ulloa in 1735 and by Wood in 1741. Platinum was used by pre-Columbian Indians. Platinum occurs native, accompanied by small quantities of iridium, osmium, palladium, ruthenium, and rhodium, all belonging to the same group of metals. These are found in the alluvial deposits of the Ural mountains and in Columbia. Sperrylite (PtAs2), occurring with the nickel-bearing deposits of Sudbury, Ontario, is a source of a considerable amount of metal. The large production of nickel offsets there being only one part of the platinum metals in two million parts of ore. The largest supplier of the platinum group of metals is now South Africa, followed by Russia and Canada. Platinum is a beautiful silvery-white metal, when pure, and is malleable and ductile. It has a coefficient of expansion almost equal to that of soda–lime–silica glass, and is therefore used to make sealed electrodes in glass systems. The metal does not oxidize in air at any temperature, but is corroded by halogens, cyanides, sulfur, and caustic alkalis. It is insoluble in hydrochloric and nitric acid, but dissolves when they are mixed as aqua regia, forming chloroplatinic acid (H2PtCl6), an important compound. Natural platinum contains six isotopes, one of which, 190Pt, is radioactive with a long half-life. Thirtyseven other radioactive isotopes and isomers are recognized. The metal is used extensively in jewelry, wire, and vessels for laboratory use, and in many valuable instruments including thermocouple elements. It is also used for electrical contacts, corrosion-resistant apparatus, and in dentistry. Platinum–cobalt alloys have magnetic properties. One such alloy made of 76.7% Pt and 23.3% Co, by weight, is an extremely powerful magnet that offers a B-H (max) almost twice that of Alnico V. Platinum resistance wires are used for constructing hightemperature electric furnaces. The metal is used for coating missile nose cones, jet engine fuel nozzles, etc., which must perform reliably for long periods of time at high temperatures. The metal, like palladium, absorbs large volumes of hydrogen, retaining it at ordinary temperatures but giving it up at red heat. In the finely divided state platinum is an excellent catalyst, having long been used in the contact process for producing sulfuric acid. It is also used as a catalyst in cracking petroleum products. There is also much current interest in the use of platinum as a catalyst in fuel cells and in its use as antipollution devices for automobiles. Platinum anodes are extensively used in cathodic protection systems for large ships and ocean-going vessels, pipelines, steel piers, etc. Pure platinum wire will glow red hot when placed in the vapor of methyl alcohol. It acts here as a catalyst, converting the alcohol to formaldehyde. This phenomenon has been used commercially to produce cigarette lighters and hand warmers. Hydrogen and oxygen explode in

UsesPlatinum is a white noble metal that looks very much like metallic silver found in copper ore. The name platinum comes from the Spanish word plata, meaning silver. Platinum compounds were used in the platinum printing process and for toning silver images.

Usesmanufacture of apparatus for laboratory and industrial use, thermocouples, platinum resistance thermometers, acidproof containers, electrodes, etc. In dentistry; jewelry; electroplating. As oxidation catalyst in manufacture of acetic acid, nitric acid from ammonia, manufacture of sulfuric acid; control of automotive emissions.

UsesBecause of its chemical and physical properties, platinum has many uses. It is used widelyin jewelry making and is often mixed with gold to improve gold’s strength and durability.In the early 1800s it was known that when hydrogen is passed over powdered platinum, thehydrogen ignites without being heated and without consuming the platinum. This propertyled to a major use of platinum as a catalyst to speed up chemical reactions. An example is presentin the internal combustion engine that produces harmful gases. Gasoline fuel burns insidethe engine, as compared to the steam engine, where the fuel is burned outside the engine. Thecatalytic converter in automobiles uses a platinum-coated ceramic grid in the exhaust systemto convert unburned fuel to carbon dioxide and water. The platinum in the converter will lastas long as the car since a catalyst is not consumed by the chemical reaction.Fuel Cells: As a catalyst, platinum is used for hydrogenation of liquid vegetable oils to produce solidforms of the oil, such as margarine. It is also used in the cracking process that breaks downlarge crude oil molecules into smaller, more useful molecules, such as gasoline. The catalyticproperties of platinum make it useful in the production of sulfuric acid (H2SO4) and in fuelcells that unite hydrogen and oxygen to produce electricity.

General DescriptionSilvery, whitish-gray, malleable, ductile metal. Mp: 1772°C; bp: 2187°C. Density: 21.45 g cm-3 at room conditions (very dense). Also shipped as a finely divided powder (Platinum black), as a sponge, and as particles deposited on a supporting material such as alumina. Has strong catalytic activity in these forms; finely divided Platinum can be dangerous to handle in the vicinity of other chemicals on this account. Used Platinum catalysts are particularly dangerous and can be explosive.

DefinitionA silvery-white malleable ductile transition metal. It occurs naturally in Australia and Canada, either free or in association with other platinum metals. It is resistant to oxidation and is not attacked by acids (except aqua regia) or alkalis. Platinum is used as a catalyst for ammonia oxidation (to make nitric acid) and in catalytic converters. It is also used in jewelry. Symbol: Pt; m.p. 1772°C; b.p. 3830 ± 100°C; r.d. 21.45 (20°C); p.n. 78; r.a.m. 195.08.

Definitionplatinum: Symbol Pt. A silverywhite metallic transition element(see also platinum metals); a.n. 78;r.a.m. 195.09; r.d. 21.45; m.p. 1772°C;b.p. 3827±100°C. It occurs in somenickel and copper ores and is alsofound native in some deposits. Themain source is the anode sludge obtainedin copper–nickel refining. Theelement is used in jewellery, laboratoryapparatus (e.g. thermocouples,electrodes, etc.), electrical contacts,and in certain alloys (e.g. with iridium or rhodium). It is also a hydrogenationcatalyst. The elementdoes not oxidize nor dissolve inhydrochloric acid. Most of its compoundsare platinum(II) orplatinum(IV) complexes.