The artificial radioisotope 192Ir was obtained by neutron radiation from the stable element 191Ir.
Decay gives off radioactivity, with a half-life of 74.2d, and is often used in industrial testing. (in normal circumstances, after 10 half-lives of radioactive materials, the radiation intensity is not strong enough to cause harm, and the use of iridium source for industrial detection is a relatively safe option.
Iridium was found in the insoluble impurities of platinum in 1803. The lead discoverer, Smithson Tennant, named it iridium, after Iris, for its many different colors of salt. Iridium is a rare element that produced and consumed three tons of iridium in the earth's crust last year. Iridium 191 and iridium 193 are the only two natural isotopes and the only stable isotopes. Iridium 193 is more abundant than iridium 191.
Iridium is chemically stable. Is the corrosion resistance of the metal, iridium for high chemical stability, acid insoluble in acid, only the spongy iridium will slowly dissolved in aqua regia, hot if it is the state of the dense iridium, even boiling aqua regia, nor corrosion [3]. However, in high temperature and pressure airtight reaction kettle, iridium above 250 ° C aqua regia was obvious corrosion; 1 by 20 strong hydrochloric acid and nitric acid configuration of mixed acid, under the temperature and pressure, corrosion of iridium is about 20 times of aqua regia, therefore in the chemical analysis commonly used for digestion reagent of metal iridium.
Iridium in the molten sodium hydroxide of 350 ° C (not pass into the air) are extremely resistant to corrosion, corrosion rate is less than 0.005 mm/year (about 3.5 MDD), but above 400 ° C molten sodium hydroxide of iridium corrosion is serious; Molten potassium hydroxide can also strongly corrode iridium.
At room temperature, the dense metal iridium has excellent corrosion resistance to dry fluorine gas, dry or wet chlorine, bromine, and iodine. No visible corrosion. No ordinary etchant can corrode iridium. There is a strong tendency to form coordination compounds. The main combination price is +2, +4, +6. Source of elements: only 9 x 10-9% in the earth's crust. It mainly exists in osmium iridium ore. The osmium iridium alloy can be separated from zinc in the process of refining platinum .
Element USES: a lot of high melting point oxide single crystal, it is to grow in the crucible made of pure iridium, pure iridium, platinum iridium alloy, iridium rhodium alloy used to make more scientific instruments, thermocouple, resistance wire, etc. To join in the platinum iridium, can improve the platinum in water, acid, corrosion resistance of halogen, and the mechanical strength under 500 ° C, but with the increase of the content of iridium above 900 ° C alloy in air oxidation weightless also increases. [3] platinum iridium alloy, containing 10% iridium and 90% platinum, is used to make international standard meter scale because of its small expansion coefficient. The world's original kilogram was also made of platinum iridium alloy.
