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Metal Profile: Platinum

What is Platinum?

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Metal Profile: Platinum

Platinum coated hard disks

Image © Johnson Matthey
Metal Profile: Platinum

Platinum grain produced by Anglo American.

Image c/o Vismedia

Platinum is a dense, stable and rare metal that is often used in jewelry for its attractive, silver-like appearance, as well as in medical, electronic and chemical applications due to its various and unique chemical and physical properties.

Properties:

  • Atomic Symbol: Pt
  • Atomic Number: 78
  • Element Category: Transition metal
  • Density: 21.45 g/cm3
  • Melting Point: 3214.9 °F (1768.3 °C)
  • Boiling Point: 6917 °F (3825 °C)
  • Moh's Hardness: 4-4.5

Characteristics:
Platinum metal has a number of useful properties, which explains its application in a wide-range of industries. It is one of the densest metal elements - almost twice as dense as lead - and very stable, giving the metal excellent corrosion resistant properties. A good conductor of electricity, platinum is also malleable and ductile.

Platinum is considered a biologically compatible metal because it is non-toxic and stable, so it does not react with, or negatively affect, body tissues. Recent research has also shown platinum to inhibit the growth of certain cancerous cells.

History:
An alloy of the platinum group metals (PGMs), which includes platinum, was used to decorate the Casket of Thebes, an Egyptian tomb that dates back to about 700BC. This is the earliest known use of platinum, although pre-Columbian South Americans also made ornaments from gold and platinum alloys.

Spanish conquistadors were the first Europeans to encounter the metal, although they found it a nuisance in their pursuit of silver because of its similar appearance. They referred to the metal as Platina - a version of Plata, the Spanish word for silver - or Platina del Pinto because of its discovery in the sands along the banks of the Pinto river in modern day Columbia.

Although studied by a number of English, French and Spanish chemists in the mid-18th century, Francois Chabaneau was the first to produce a pure sample of platinum metal in 1783. In 1801, Englishman William Wollaston discovered a method for effectively extracting the metal from ore, which is very similar to the process used today.

Platinum metal's silver-like appearance quickly made it a valued commodity amongst royalty and the wealthy who sought jewelry made from the latest precious metal.

Growing demand led to the discovery of large deposits in the Ural Mountains in 1824 and Canada in 1888, but the finding that would fundamentally change platinum's future did not come until 1924 when a farmer in South Africa stumbled across a platinum nugget in a riverbed. This ultimately led to geologist Hans Merensky's discovery of the Bushveld igneous complex, the largest platinum deposit on earth.

Although some industrial applications for platinum (e.g. spark plug coatings) were in use by the mid-20th century, most of the current electronic, medical and automotive applications have only been developed since 1974 when air quality regulations in the US initiated the autocatalyst era.

Since that time, platinum has also become an investment instrument, and is traded on the New York Mercantile Exchange and the London Platinum and Palladium Market.

Production:
Like the platinum along the banks of the Pinto river, the metal is most often naturally occurs in placer deposits. Platinum and PGMs miners, however, usually extract the metal from sperrylite and cooperite; two platinum containing ores.

Platinum is always found alongside other PGMs. In South Africa's Bushveld complex and a limited number of other ore bodies, PGMs occur in sufficient quantities so as to make it economical to exclusively extract these metals; whereas, at Russia's Norilsk and Canada's Sudbury deposits platinum and other PGMs are extracted as by-products of nickel and copper.

Extracting platinum from ore is both capital and labor intensive. More...

Applications:
For a metal whose annual global production is a mere 192 tonnes, platinum is found in, and critical to the production of, many everyday items.

The largest use, accounting for about 40% of demand, is the jewelry industry where it is primarily used in the alloy that makes white gold. It is estimated that over 40% of wedding rings sold in the US contain some platinum. The USA, China, Japan and India are the largest markets for platinum jewelry.

Platinum's corrosion resistance and high temperature stability make it ideal as a catalyst in chemical reactions. Catalysts speed up chemical reactions without themselves being chemically altered in the process.

Platinum's main application in this sector, accounting for about 37% of total demand for the metal, is in catalytic converters for automobiles. Catalytic converters reduce harmful chemicals from exhaust emissions by initiating reactions that turn over 90% of hydrocarbons (carbon monoxide and oxides of nitrogen) into other, less harmful, compounds.

Platinum is also used to catalyze nitric acid and gasoline; increasing the octane levels in fuel.

In the electronics industry, platinum crucibles are used to make semiconductor crystals for lasers, while alloys are used to make magnetic disks for computer hard drives and switch contacts in automotive controls.

Demand from the medical industry is growing as platinum can be used for both its conductive properties in pace-makers electrodes, as well as aural and retinal implants, and for its anti-cancer properties in drugs (e.g. carboplatin and cisplatin).

Below is a list of some of the many other applications for platinum:

  • With rhodium, used to make high temperature thermocouples
  • To make optically pure, flat glass for TVs, LCDs and monitors
  • To make threads of glass for fiber optics
  • In alloys used to form the tips of automotive and aeronautic spark plugs
  • As a substitute for gold in electronic connections
  • In coatings for ceramic capacitors in electronic devices
  • In high temperature alloys for jet fuel nozzles and missile nose cones
  • In dental implants
  • To make high quality flutes
  • In smoke and carbon monoxide detectors
  • To manufacture silicones
  • In coatings for razors

Sources:
Wood, Ian. 2004. Platinum. Benchmark Books (New York).
The International Platinum Group Metals Association (IPA).
Source: http://www.ipa-news.com/
USGS: Platinum Group Metals.
Source: http://minerals.usgs.gov/minerals/pubs/commodity/platinum/

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