Iridium

Have paleontologists, Jurassic Park fans or Ross Geller from Friends made you curious about dinosaurs? Have you always wondered why they are no longer on the planet? There are many theories about the cause of the dinosaurs’ extinction and one of them is linked to our metal of the month! 

Only a very thin layer of iridium exists in the Earth’s crust, although meteors and asteroids contain high levels of the metal. A large meteorite impact would have caused a huge dust cloud, depositing iridium across the globe. Some scientists think that 66 million years ago, a meteor or asteroid impact like this wiped out the dinosaurs. Iridium from the object is key evidence for this theory.

Applications

Because of the difficulties involved in preparation and fabrication/production, the pure metal has few applications.

Though brittle, iridium can be worked if brought to a white heat of 1,200°C to 1,500°C (2,200 to 2,700 degrees Fahrenheit). Its main application is therefore to harden platinum by producing a platinum alloy, usually used in pacemakers, medical probes and other applications of this type.

Platinum-iridium alloys are found in jewelry, pen points, surgical pins and pivots, as well as electrical contacts and sparking points. Because of its corrosion-resistant property, it is used to set standards in weights and measures. The international prototype standard meter kept at the “Pavillon de Sèvres” in France is made from a 90% Pt–10% Ir alloy.

Iridium has catalytic properties which make it suitable for hydrogenation. It is widely used in anode catalysts for PEM electrolyzers, which are needed to produce green hydrogen. The demand for this kind of application is certain to increase in the years to come.

Over the past couple of decades, iridium’s main application has been in the production of synthetic sapphire and other crystals which are vital for LED and OLED lighting and flat screen panels, as well as other crystals used in mobile electronic devices.

Iridium linings and fabrications are also suitable for glass production because the metal is inert in contact with molten glass. 

Iridium is not affected by acids, bases or most other strong chemicals. This property makes it suitable for producing objects that are exposed to such materials.

Other applications include crucibles in which synthetic single crystals for LED and data-storage technologies can be grown.

Recycling

Recycling accounts for a small proportion of the metal produced globally each year. It is usually commercially recovered as a by-product of nickel or copper refining.

Properties

Iridium is one of the rarest elements on Earth. It is found uncombined in nature in sediments deposited by rivers.

Iridium is a very hard, brittle and dense metal that belongs to the platinum group. Like platinum, it is a white metal, though with a glint of yellow.

It has the highest density of all the elements and a high melting point (2.454°C), and its volume mass (22,420 kg/m3) is only slightly less than that of osmium (22,570 kg/m3). Iridium is also the most corrosion-resistant material known.

History

Smithson Tennant discovered iridium in London in 1804 while examining the black residue obtained when attacking impure platinum with aqua regia. This residue was thought to be graphite, but Tennant believed otherwise and was able to separate it into two new elements: iridium and osmium.

The name iridium is derived from the Greek goddess of the rainbow ιρις (Iris) and reflects the various colors of its salts.