Appearance and Characteristics
Harmful effects:
Iridium is considered to be of low toxicity. Iridium in powder form is a known irritant and is a fire hazard.
Characteristics:
Iridium is a rare, hard, lustrous, brittle, very dense platinum-like metal. Chemically it is very unreactive. It is the most corrosion-resistant metal known and it resists attack by any acid. Iridium is attacked by molten salts such as sodium chloride (NaCl) and sodium cyanide (NaCN). Iridium is generally credited with being the second densest element (after osmium) based on measured density, although calculations involving the space lattices of the elements show that iridium is denser.
Uses of Iridium
The main use of iridium is as a hardening agent for platinum alloys. With osmium, it forms an alloy that is used for tipping pens, and compass bearings. Iridium is used in making crucibles and other equipment that is used at high temperatures. It is also used to make heavy-duty electrical contacts. Iridium was used in making the international standard kilogram, which is an alloy of 90% platinum and 10% iridium. Radioactive isotopes of iridium are used in radiation therapy for the treatment of cancer.