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Iridium - Properties and Applications

Chemical Formula



Iridium was first discovered by tenant in 1803 who found it in the residue left behind after the dissolution of crude platinum in aqua regia.

The name iridium was derived from the fact that its salts are highly coloured.


Iridium can be found uncombined in nature. Most commonly it is found associated with other platinum group metals in alluvial deposits.

It is also produced as a by-product of nickel and platinum refining.

Key Properties

Iridium is:

         Silvery-white in colour, with a yellowish cast

         It is very hard and brittle and hence difficult to machine and work

         It is the most corrosion resistant metal known and oxidises only slowly at high temperatures

         It is not attacked by any acids or aqua regia

         It is attacked by molten salts such as NaCl and NaCN

         It resists attacked by fused bases and molten metals

         Competes with Osmium for the mantle of the densest material known to man with a density of about 22.6g/cm3

         Fluorine and chlorine attack iridium at red heat

         Has a face centred cubic structure


Iridium’s main use is as a hardening agent for platinum.

It is also used for making:

         Crucibles and other equipment that operate at high temperatures

         Fountain pen nibs (alloyed with Osmium)

         Pivot bearings

         Scientific and other specialised equipment




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