Platinum

The name platinum is derived from the Spanish "platina", meaning "little silver".

Platinum is a lustrous silvery-white, malleable, ductile metal and a member of group 10 of the periodic table of the elements. It has the third highest density, behind osmium and iridium. Platinum is unaffected by air and water, but will dissolve in hot aqua regia, in hot concentrated phosphoric and sulphuric acids, and in molten alkali. It is as resistant as gold to corrosion and tarnishing. Indeed, platinum will not oxidize in air no matter how strongly it is heated.

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. Hydrogen and oxygen gas mixtures explode in the presence of platinum wire.

There are six naturally occurring isotopes : the most abundant are platinum-194, which accounts for 33%, platinum-195 (34%) and platinum-196 (25%). The others are platinum-198 (7%), platinum-192 (1%) and platinum-190 (0.01%). The latter is weakly radioactive, with a half life of 700 billion years, while the other five are non-radioactive.

Applications

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. It is used (30%) as a catalyst in the catalytic converter, an optional component of the gasoline-fuelled automobile exhaust system. The largest use (50%) of platinum is for jewellery, another 20% is used in industry: platinum is used in the chemical, electrical, glass and aircraft industries, each accounting for about 10 tonnes of the metal per year. The glass industry uses platinum for optical fibers and liquid crystal display glass, especially for laptops.