Chemical and physical properties of rhodium:
Crystal system: face- centered cubic
Color: silver white
Mohs scale hardeness: 6,0
Specific gravity: 12,41 g/cm³
Melting point: 1964 °C
Silver white hard metal. It belongs to the transition metal series and the platinum family. Rhodium is an allergy-free metal. Rhodium is a relatively good electrical conductor. A metal used in the precious metal industry mainly for plating silverware and rhodium plating. It is also sometimes used for the surface plating of more valuable jewellery.
It occurs in platinum ores, which often contain up to 4.6% rhodium.
Its production from the residue obtained in the manufacture of platinum is laborious, because it requires lengthy operations to separate the rhodium from the metals in the residue.
Pure rhodium is very difficult to melt. When heated to higher temperatures in air, it oxidises on the surface but is not attacked by acids. It forms alloys with most metals, most readily with zinc.
Rhodium is capable of absorbing more hydrogen than palladium and is very notable for its ability to decompose formic acid into hydrogen and carbon dioxide, and to oxidise alcohol to acetic acid in the presence of potassium hydroxide during hydrogen evolution.