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Iridium is a member of the platinum group metals (PGM). It is famous as a the element that revealed that the dinosaurs were killed by an asteroid 65 million years ago. Iridium is the second densest element, second to osmium. Iridium is also very chemical resistent and is used in high temperature crucibles used for high purity crystal production.
It is a hard, brittle silver white metal with a melting point of 2446 °C (4435 °F) and density of 22.56 g/cm3.
- High temperature crucibles
- Alloyed with osmium in pen nibs
- In Industrial catalysts
- In spintronics, for example in some hard disk read heads
- 90% Pt 10% Ir is used as a jewellery alloy
Iridium is extremely inert when it comes to chemical reactions. It is not attacked by most acids, aqua regia, by most molten metals or even molten silicates. Below 2000 °C oxygen doesn't affect solid pieces of iridium.
Catalysts based on iridium instead of platinum can sometimes boost production in chemical plants.
Iridium can be oxidized by a peroxide fusion into IrO2.
( Main article List of iridium compounds )
Iridium can take oxidation states between -3 and +9 so there are a lot of possible compounds that can be formed with iridium. Most commonly is +3 and +4 compounds.
Some compounds :
- Hexachloroiridic acid, (H2IrCl6) is a common iridium compound, used both in iridium refining and as a precursor to other iridium compounds.
- Iridium trichloride, (IrCl3) is formed by reacting iridium with chlorine at 650 °C or by dissolving Ir2O3 in hydrochloric acid.
- Iridium dioxide, (IrO2) is formed by reacting finely divided iridium powder with air at red hot temperature.
- Iridium oxide, (Ir2O3) an oxide formed by mixing IrCl3 with KOH, it might over time react with O2 to form IrO2
An iridium based organic LED material has been discovered and could provide a scrap source of iridium in the future.
The easiest way to melt iridium is to use induction melting. The high melting point of iridium makes it just barely possible to melt with an oxygen hydrogen torch.
(Main article iridium refining)
- PeriodicVideos : Iridium
- GRF : How to refine iridium
- GRF : Refining rhodium and iridium mix
- GRF : Publications of Gilchrist
- GRF : Separation and Purification Au,Pt,Pd,Ag,Rh,Os,Ir,Ru
- Wikipedia : Iridium
- Webelements : Iridium
- Hoke : Hoke page 179 : PART V. REPURIFYING IRIDIUM
- Ullmann's Encyclopedia of Industrial Chemistry : Platinum Group Metals and Compounds
- HARFIR : Heusler Alloy Replacement for Iridium, spintronics research.
- IBM : The application of spintronics
- Journal of The Minerals, Metals & Materials Society (TMS) : Articles related to iridium
- JOM : Refining of the platinum-group metals
- Science Madness : Iridium
- The Japan Institute of Metals : Chemical Dissolution of Iridium Powder Using Alkali Fusion Followed by High-Temperature Leaching (pdf)