Iridium is a chemical element with a symbol of Ir. It is very hard and has a silvery-white colour being part of the platinum transition metal group. It is one of the rarest metals in the Earth's crust and the most corrosion-resistant metal (resistant to air, acid, water, and salts). This element is used as a hardening agent in platinum alloys. The alloy formed with osmium is used in tipping pens, and compass bearings.
Iridium is mined as a by-product of nickel. In South Africa and Russia, the deposits are maximum. First, the metals- gold, silver, palladium, and platinum are removed from the ore. The residue is melted with sodium bisulfate to remove rhodium. The part containing iridium is melted with sodium peroxide, which leaves iridium oxide.
Then iridium oxide is dissolved in aqua regia and then evaporated to get the final product pure iridium. Pure iridium is not present in abundance in the earth's crust, but it is found a lot as natural alloys with other noble metals.
Credits: Harini
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