Still, precious metals have some safety issues attached to them: Rhenium: Since rhenium is used in very small amounts, its toxicity is virtually unknown. The hazardous property of rhenium halide, for example, may be attributed either to rhenium itself or to the other elements that make up the compound. Radiotherapy (as a source of radiation); 5. X-ray telescopes. In 2007, worldwide demand for iridium reached 3,701 kilograms (119,000 troy ounces). Distribution of these were as follows: electrochemical uses (1,100 kilograms); electrical uses (780 kilograms); for catalysis (750 kilograms); and other applications (1,100 kilograms). The ranking appears different when the estimated world market prices, per troy ounce, of these nine precious metals are considered (estimates as of January 2010): 1st: Rhodium - USD2,750 2nd: Platinum - USD1,555 3rd: Gold - USD1,131 4th: Palladium - USD424 5th: Iridium - USD408 6th: Osmium - USD380 7th: Rhenium - USD194 8th: Ruthenium - USD173 9th: Silver - USD18 Of the nine precious metals, gold and silver are the best known. mol-1 Atomic: Oxidation States: -1, 1, 2, 3, 4, 5 Electronegativity: 2.54 (Pauling scale) Atomic Radius: 144 picometre Covalent Radius: 136 6 picometre Van der Waals Radius: 166 picometre Ionization Energies: 890.1 kJ.mol-1 (first), 1980 kJ.mol-1 (second) The term "gold" was derived from "geolu", an Old English Anglo-Saxon word which means "yellow". Silver bullion bars can be bought or sold over the counter in most banks in Switzerland. They may be stored in safe deposit boxes in banks or placed in non-fungible (allocated) or pooled (unallocated) storage with a silver dealer. Opening a silver account: An investor may open a silver account with one of the major banks in Switzerland. Osmium's characteristic of having a bad smell led to its naming as such, which was derived from the Greek word "osme", meaning "smell". 4. Iridium - Smithson Tennant discovered iridium in 1803, at the same time of his discovery of osmium from the same solution of platinum ores. Iridium is named after the Latin word "iris", which means "rainbow".