Platinum Pt

Discovery

Long before Columbus, Indigenous metalworkers in South America made objects from mixtures of gold and platinum grains. After the Spanish conquest, the silvery grains found with alluvial gold in what is now Colombia were often treated as an annoying impurity.

Platinum was described systematically for European scientists in the mid-eighteenth century. The Spanish naval officer and scientist Antonio de Ulloa, who joined an expedition to South America beginning in 1735, observed the metal and published an account in 1748; around the same time Charles Wood brought samples to England. Because platinum melts at such a high temperature, it was hard to work until William Hyde Wollaston developed a powder-metallurgy process in the early nineteenth century and profited handsomely from it.

Origin of the name

The name comes from the Spanish platina, "little silver", a slightly dismissive name for a metal that looked like silver but was considered inferior. The symbol Pt comes from the Latinised name platinum.

Main uses

• Catalytic converters: with palladium and rhodium, platinum converts carbon monoxide, hydrocarbons and nitrogen oxides in exhaust into less harmful gases; this is one of its largest uses.
• Industrial catalysis: the Ostwald process for nitric acid, petroleum refining and fuel-cell electrodes.
• Jewellery and investment: its untarnishing white lustre suits rings and fine jewellery, and it is traded as an investment metal.
• Medicine: platinum drugs such as cisplatin are standard treatments for testicular, ovarian and several other cancers; platinum is also used in pacemaker electrodes.
• Measurement: platinum resistance thermometers are a standard for precise temperature measurement.

Isotopes

Natural platinum has six isotopes, the most abundant being platinum-195 at about 34%. Platinum-190, present in tiny amounts, is radioactive with a half-life of hundreds of billions of years. Platinum-195 can be observed by nuclear magnetic resonance, a useful tool for studying platinum compounds.

In everyday life

In the 1960s Barnett Rosenberg's team in the United States passed a current through a bacterial culture using platinum electrodes and noticed that the bacteria stopped dividing. The cause was a platinum compound formed from the electrodes, and the discovery led to the cancer drug cisplatin. Platinum jewellery rarely causes allergies, although certain platinum salts can sensitise the airways of workers who are exposed to them repeatedly.