Trommel: This method involves the use of a screened cylinder to separate materials by size (trommel is Dutch word for "drum"). A trommel specifically consists of a rotating metal tube that is slightly tilted, with a screen at the discharge end. Attached to the inside part of the metal tube are lifter bars. mol-1 * Electron Configuration: [Xe] 4f14 5d9 6s1 Physical: * Density (near room temperature): 21.45 g.cm-3 * Liquid Density (at melting point): 19.77 g.cm-3 * Melting Point: 1768.3 C, 3214.9 F, 2041.4 K * Boiling Point: 3825 C, 6917 F, 4098 K * Heat of Fusion: 22.17 kJ.mol-1 * Heat of Vaporization: 469 kJ. These are, in no particular order, gold, palladium, silver, rhodium, iridium, ruthenium, platinum, osmium, and rhenium. So that while the chemical element tellurium is considered one of the rarest element in the Earth's crust (its mass abundance being the same as that of rhodium, iridium, and ruthenium), its estimated price is only less than 5 U. mol-1 (second) The name "osmium" was derived from the Greek word "osme", which means "smell". It was discovered by the English chemists William Hyde Wollaston and Smithson Tennant in London, England in 1803. Wollaston's and Tennant's discovery of the element involved the discovery as well of the other elements in the platinum group. As to its main property, this is best expressed in its being considered the most corrosive resistant of all the precious metals. In fact, this is shown even in temperatures of as high as 2000 C (3632 F or 2273.15 K). Iridium was discovered in 1803 by the English chemist Smithson Tennant. It was identified from the residue of platinum ore which was dissolved in nitro-hydrochloric acid (also known as aqua regia). mol-1 Atomic: Oxidation States: 7, 6, 5, 4, 3, 2, 1, 0, -1 Electronegativity: 1.9 (Pauling scale) Atomic Radius: 137 picometre Covalent Radius: 151 7 picometre Ionization Energies: 760 kJ.mol-1 (first), 1260 kJ.mol-1 (second), 2510 kJ.mol-1 (third) Rhenium is silvery-white in appearance. It is the third element (after tungsten and carbon) with the highest melting point and the fourth densest (after platinum, iridium, and osmium).