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Key Data and Description

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Crystallography

Reactions of Platinum

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Description

• Standard state: Solid at 298K

• Colour: Greyish white

• Classification: Metallic

Platinum jewellery

Platinum, when pure, is a beautiful silvery-white metal and is malleable and ductile.  It has a expansion coefficient almost equal to that of soda-lime-silica glass and is therefore used to make sealed electrodes in glass systems.

Isolation

The metal occurs in ores mixed with other metals such as palladium and gold and its extraction is complex.

Preliminary treatment of the ore or base metal byproduct with aqua regia (a mixture of hydrochloric acid, HCl, and nitric acid, HNO₃), gives a solution containing complexes of gold and palladium as well as H₂PtCl₆.  The gold is removed from this solution as a precipitate by treatment with iron chloride, FeCl₂.  The platinum is them precipitated as impure (NH₄)₂PtCl₆ on treatment with NH₄Cl, leaving H₂PdCl₄ in solution.  The (NH₄)₂PtCl₆ is burned leaving an impure platinum sponge.  This can be purified by redissolving in aqua regia, and removal of rhodium and iridium impurities by treatment of the solution with sodium bromate, and them precipitation of pure (NH₄)₂PtCl₆ by treatment with ammonium hydroxide, NH₄OH.  This yields platinum metal by burning.