Question

What are the main properties of iridium?

Answer 1

Iridium was discovered together with osmium in1803 by Smithson Tennant in London. When crude platinum was dissolved in dilute aqua regia, which is a mixture of nitric and hydrochloric acids, it left behind a black residue thought to be graphite. Tennant thought otherwise, and by treating it alternately with alkalis and acids he was able to separate it into two new elements. These he announced at the Royal Institution in London, naming one iridium, because its salts were so colourful and the other osmium because it had a curious odour (see osmium).

Despite its seeming intractability, a group of chemists, including the great Humphry Davy, demonstrated in 1813 that iridium would indeed melt like other metals. To achieve this they exposed it to the powerful current generated by a large array of batteries.

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Answer 2

It has a very high density and melting point. Iridium is the most corrosion-resistant material known. It is used in special alloys and forms an alloy with osmium, which is used for pen tips and compass bearings. It was used in making the standard metre bar, which is an alloy of 90% platinum and 10% iridium.

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