Biography & contributions
Smithson Tennant was born on November 30, 1761 – died on February 22, 1815. Tennant is best known for his discovery of the elements iridium and osmium. He also contributed to the proof of the identity of diamond and charcoal. The mineral tennantite is named after him.
Following research work done by tenant which leads to the discovery of osmium and iridium elements.
Tennant fused the insoluble residue with alkali at high temperature and dissolved the resulting cooled solid in water, producing a further black solid and a yellow solution. The yellow solution was probably a basic form of osmium tetroxide, OsO4. The black solid was further treated with hydrochloric acid, the solid produced was fused with caustic soda and further treatment with acid obtained red crystals. These are most likely to have been Na2[IrCl6].nH2O. On heating these, a white powder of an unknown element was obtained, which was later identified as iridium element.
Facts about Osmium element
Osmium is a hard, brittle, bluish-white transition metal in the platinum group. Its alloys with platinum, iridium and other platinum group metals are employed in fountain pen nibs, electrical contacts, and other applications. Osmium is a hard but brittle metal that remains lustrous even at high temperatures. It has a very low compressibility. The most common oxidation states of osmium element include +2, +3, +4, and +8. It can be dissolved by fused alkalies, especially if an oxidizing agent such as sodium chlorate is present. Osmium will react at 200° C with air or oxygen to form OsO4. Osmium has high reflectivity in the ultraviolet range of the electromagnetic spectrum.
Facts about iridium element
Iridium is a very hard, brittle, silvery-white transition metal of the platinum family. It is the only metal to maintain good mechanical properties in air at temperatures above 1600 °C. The most important iridium compounds in use are the salts and acids it forms with chlorine, though iridium also forms a number of organometallic compounds used in industrial catalysis, and in research. Iridium metal is employed when high corrosion resistance at high temperatures is needed, as in high-performance spark plugs, crucibles for recrystallization of semiconductors at high temperatures, and electrodes for the production of chlorine in the chloralkali process. Iridium radioisotopes are used in some radioisotope thermoelectric generators.
Iridium forms compounds in oxidation states between −3 and +9. Iridium has two naturally occurring, stable isotopes, 191Ir and 193Ir, with natural abundances of 37.3% and 62.7%, respectively. Iridium is one of the nine least abundant stable elements in Earth's crust, having an average mass fraction of 0.001 ppm in crustal rock. Iridium is obtained commercially as a by-product from nickel and copper mining and processing.
Read full article online - http://www.worldofchemicals.com/462/che ... ments.html