However, the international prototype kilogram , which defines a kilogram, also made of a platinum and platinum-iridium alloy, is still in use around the world. Today, iridium is commercially recovered as a byproduct of copper or nickel mining. Pure iridium is so rare on the Earth's crust that there is only about 2 parts per billion located in the crust, according to Chemistry Explained. It is so dense that it mainly exists in the Earth's core, rather than crust," said Amanda Simson, an assistant professor of chemical engineering at the University of New Haven.
But some iridium exists in the crust. In scientist Luis Alvarez and his son Water Alvarez found significant amounts of iridium in a certain part of the Earth's crust, spread out all over the Earth's surface. Though brittle, iridium can be worked if heated to a white heat of 2, to 2, degrees Fahrenheit 1, to 1, degrees Celsius , according to Encyclopedia Britannica. Iridium's principal use is to harden platinum by making a platinum alloy. It is also used to make devices needed for high temperatures and in electrical contacts.
It's a rare material that makes platinum seem commonplace. There are only about 3 tonnes of iridium produced each year. These days it is more likely to turn up in the central electrode of spark plugs, where its resistance to corrosion and hardness are equally valuable.
You'll also find it in specialist parts of industrial machinery. Iridium, with atomic number 77 and two stable isotopes, and , turns up in an alloy with platinum in the standard bar and weight used for many years to define the metre and the kilogramme. Now, though, the distance is defined from the speed of light, permanently fixed in as ,, metres per second. As the second is accurately defined by an atomic clock, the metre falls out of the calculation.
Iridium has also found its way into space, both as a secure container for the plutonium fuel of the nuclear electric generators on long range probes and as a coating on the X-ray mirrors of telescopes like the Chandra X-ray Observatory.
But perhaps iridium's best-known claim to fame is as a clue in a piece of 65 million-year-old Crime Scene Investigation. The concentration of iridium in meteorites is considerably higher than in rocks on the Earth, as most of the Earth's iridium is in the molten core. One class of meteorite, called chondritic meaning they have a granular structure still has the original levels of iridium that were present when the solar system was formed. This layer contains considerably more iridium that would normally be expected, suggesting that there may have been a large meteor or asteroid strike on the Earth at this time.
There is so much iridium present that the asteroid would have to have been around 10 kilometres across - sizeable enough to devastate global weather patterns, bringing about changes in climate that could have wiped out the dinosaurs. It was iridium that provides the principle clue as to why we now believe that so many species were wiped out, leaving the way clear for mammals to take the fore. In one small way, iridium disappoints. Unlike its oxides, the element itself doesn't display the rainbow hues that its name suggests.
But that apart, this is a true superhero of an element: tough, practically incorruptible and, yes, extremely dense. So, a rare metal that not only has uses varying from fountain pens to telescopes but also helped us understand the extinction of the dinosaurs.
Now next week a colourful element that likes to shed a tear. Indium is a soft, malleable metal with a brilliant lustre. The name indium originates from the indigo blue it shows in a spectroscope. Indium has a low melting point for metals and above its melting point it ignites burning with a violet flame. Bizarrely, the pure metal of indium is described as giving a high-pitched "cry" when bent.
This is similar to the sound made by tin or the "tin cry", however, neither of them is really much like a cry! And join UCL's Claire Carmalt to find out what tricks, other than crying, indium has up its sleeve in next week's Chemistry in its element. Until then I'm Meera Senthilingam from the nakedscientists.
Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by thenakedscientists. There's more information and other episodes of Chemistry in its element on our website at chemistryworld. Click here to view videos about Iridium. View videos about. Help Text. Learn Chemistry : Your single route to hundreds of free-to-access chemistry teaching resources.
We hope that you enjoy your visit to this Site. We welcome your feedback. Data W. Haynes, ed. Version 1. Coursey, D. Schwab, J. Tsai, and R. Dragoset, Atomic Weights and Isotopic Compositions version 4. Periodic Table of Videos , accessed December Podcasts Produced by The Naked Scientists. Download our free Periodic Table app for mobile phones and tablets. Explore all elements. D Dysprosium Dubnium Darmstadtium. E Europium Erbium Einsteinium. F Fluorine Francium Fermium Flerovium. G Gallium Germanium Gadolinium Gold.
I Iron Indium Iodine Iridium. K Krypton. O Oxygen Osmium Oganesson. U Uranium. V Vanadium. X Xenon. Y Yttrium Ytterbium. Z Zinc Zirconium. Membership Become a member Connect with others Supporting individuals Supporting organisations Manage my membership. Facebook Twitter LinkedIn Youtube. Discovery date. Privacy Policy. All rights reserved. Atomic number. Iridium Iridium is a hard, brittle, lustrous, dense, transition metal of the platinum family.
Applications Nowadays demand for iridium comes mainly from the electronic industry, the automotive industry and from the chemical industry, where it is used to coat the electrodes in the chlor-alkali process, and in catalyst.
Iridium in the environment The level of iridium in land plants is below 20 ppb. We continue to review some of the most important materials in heat treatment and metallurgy.
Iridium chemical symbol: Ir. David Pye - Metallurgy. Dan Kay - Brazing. Debbie Aliya - Failure Analysis. George Vander Voort - Metallography. Thomas Joseph - Intellectual Property.
Omar Nashashibi — Government. Reed Miller — Thermal Processing. Recent Comments Safety for eyes. Vacuum brazing.
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