Before the turn of the 20th century, countries that were still on silver standard started pegging their monetary units to the gold standard of either the United States or the United Kingdom. For example, Mexico, the Philippines, and Japan pegged their respective silver units to the U.S. dollar at fifty cents. mol-1 Electron Configuration: [Xe] 4f14 5d7 6s2 Physical: Density (near room temperature): 22.56 g.cm-3 Liquid Density (at melting point): 19 g.cm-3 Melting Point: 2466 C, 4471 F, 2739 K Boiling Point: 4428 C, 8002 F, 4701 K Heat of Fusion: 41.12 kJ.mol-1 Heat of Vaporization: 563 kJ.mol-1 Atomic: Oxidation States: -3, -1, 0, 1, 2, 3, 4, 5, 6 Electronegativity: 2.20 (Pauling scale) Atomic Radius: 136 picometre Covalent Radius: 141 6 picometre Because of its characteristic of being very brittle, pure iridium is quite difficult - almost impossible, in fact - to machine. Osmium - Smithson Tennant, an English chemist, discovered osmium in 1803 from the residues of platinum ores that were dissolved in nitro-hydrochloric acid. Osmium's characteristic of having a bad smell led to its naming as such, which was derived from the Greek word "osme", meaning "smell". Bullion is traded on commodity markets in two forms: bulk ingots or coins, the latter minted by the government of a country. At least ten countries are known to mint gold and silver bullion coins. These are Australia, Austria, Canada, China, Mexico, Poland, South Africa, Switzerland, the United Kingdom, and the United States. Along with the five other precious metals in the platinum group, ruthenium is generally found in ores in North America, South America, and the Ural Mountains in Russia. Small quantities of this element also occur in pentlandite (an iron-nickel sulfide) obtained from Sudbury in Ontario, Canada, and in South Africa's pyroxenite (an ultrabasic igneous rock) deposits. Palladium - VIIIb/5; Pd -> Pd2+ + 2 e-; 0.987 V 4. Silver - Ib/5; Ag -> Ag+ + e-; 0.7996 V 5. Osmium - VIIIb/6; Os + 4 H2O -> OsO4 + 8 H+ + 8 e-; 0.838 V 6. Iridium - VIIIb/6; Ir -> Ir3+ + 3 e-; 1.156 V 7. Platinum - VIIIb/6; Pt -> Pt2+ + 2 e-; 1.18 V 8. Gold - Ib/6; Au -> Au3+ + 3 e-; 1.498 V The second item appearing after the name of the metal (the three items are separated by semi-colons) represents the metal's reaction in water.