Properties of platinum group metals
The six platinum group metals (pgm) are chemically very similar. Platinum, iridium and osmium are the densest known metals, platinum being 11 per cent denser than gold and about twice the weight of the same volume of silver or lead. Palladium, rhodium and ruthenium are lighter, palladium having about the same density as silver.
Platinum and Palladium are soft, ductile and resistant to oxidation and high temperature corrosion. They have widespread catalytic uses. In industry they are often used with the addition of other metals, including other pgm.
Rhodium and Iridium are difficult to work, but are valuable alone as well as in alloys. Their chemical compounds have many uses, and rhodium is a particularly good catalyst.
Ruthenium and Osmium are hard, brittle and almost unworkable in the metallic state, with poor oxidation resistance, but are valuable as additions to other metals, usually other pgm, and as catalysts.