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Compounds of cobalt (name from the German Kobold or "goblin") were known in ancient times but the metal itself was isolated in 1739 by Georg Brandt.
Cobalt is closely associated with cobalt glass and its characteristic deep blue color. But the metal is silvery-white and brittle, with a slight bluish color when polished. Cobalt is typically found with iron and nickel deposits. Its chemistry is similar to that of these elements but it has notable magnetic properties and one-fourth of the worlds production of cobalt is used to make powerful "alnico" magnets (an alloy of Al, Ni, and Co). Although the metal can be obtained from cobaltite and erythrite ores (the arsenide and arsenate, respectively) it is often less expensive to recover it from the waste material obtained from refining other metal ores.
Cobalt(II) chloride is often used in humidity indicators because in dry form it is blue and when hydrated it is pink. The radioactive isotope of cobalt, Co-60, is used in portable "x-ray" devices. It actually produces gamma rays which can be used to detect internal flaws in metal in much the same way as x-rays by producing a shadowy image on film. Co-60 is also used in cancer treatment.
World production of rhodium (from the Greek rhodon, "rose") is about 10 tons. While the metal itself has few applications, it is an important alloying agent used as a hardener for platinum and palladium.
As one of the so-called "platinum" metals, rhodium is often found in association with these other elements. It shares the properties of these metals: high corrosion resistance, hardness and ductility. It is the rarest of the group, only occurring to the extent of about 1 part per 200 million in the earth's crust.
Rhodium was discovered in 1803 by William Hyde Wollaston who named it for the rose-red color of its salts.
Iridium has the reputation of being the most corrosion resistant of all metals. It was discovered in 1803 by Smithson Tennant in 1803 and named for the Latin iris, or "rainbow" because it forms a large number of very colorful compounds. The pure metal is very difficult to machine into useful shapes because of its hardness and its principal use is as a hardening agent for platinum. It will withstand attack by hot aqua regia (a mixture of concentrated hydrochloric and nitric acids---which dissolves even gold) and can be used routinely at temperatures up to 2000oC.
Element 109 was first synthesized by researchers at Darmstadt, (West) Germany in August of 1983. For 10 days they hurled a beam of iron-58 ions into a bismuth-209 target. They detected the formation of one nucleus of Mt-267 which rapidly "boiled off" a neutron, reverting to Mt-266. This decayed within milliseconds to give (element 107)-262, etc. A committee of the IUPAC suggested the name Meitnerium (Mt) after the German physicist Lise Meitner. Final approval of the name and symbol was given in August 1997.
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