PLATINUM GROUP METALS
Platinum (Pt) - chemical element, the best known and most widely used of the six platinum metals (ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), and platinum (Pt)). A very heavy, precious, silver-white metal, platinum is soft and ductile and has a high melting point and good resistance to corrosion and chemical attack.
Platinum, one of the most abundant platinum metals, and its alloys are indispensable in the chemical laboratory for electrodes and for crucibles and dishes in which materials can be heated to high temperatures. Platinum is used for electrical contacts and sparking points because it resists both the high temperatures and chemical attack of electric arcs. Jewelry and dental alloys account for much of its use; platinum-iridium is used for surgical pins. As a catalyst, platinum has many applications, notably in automotive catalytic converters and in petroleum refining.
Gold (Au) - a dense lustrous yellow precious metal. Gold has several qualities that have made it exceptionally valuable throughout history. It is attractive in colour and brightness, durable to the point of virtual indestructibility, highly malleable, and usually found in nature in a comparatively pure form. Gold is one of the densest of all metals. It is a good conductor of heat and electricity. It is also soft and the most malleable and ductile of the elements. Because gold is visually pleasing and workable and does not tarnish or corrode, it was one of the first metals to attract human attention. Examples of elaborate gold workmanship, many in nearly perfect condition, survive from ancient Egyptian, Minoan, Assyrian, and Etruscan artisans, and gold continues to be a highly favoured material out of which to craft jewelry and other decorative objects.
Silver (Ag) - a white lustrous metal valued for its decorative beauty and electrical conductivity.
Because of its comparative scarcity, brilliant white colour, malleability, ductility, and resistance to atmospheric oxidation, silver has long been used in the manufacture of coins, ornaments, and jewelry. Silver has the highest known electrical and thermal conductivity of all metals and is used in fabricating printed electrical circuits and as a vapour-deposited coating for electronic conductors; it is also alloyed with such elements as nickel or palladium for use in electrical contacts. Silver also finds use as a catalyst for its unique ability to convert ethylene to ethylene oxide, which is a precursor of many organic compounds. Silver is one of the noblest—that is, least chemically reactive—of the transition elements.