Finally, it was washed with ethanol and reacted with zinc, forming the precious metal that it is known today. Since rhodium occurs in ores mixed with other metals (examples: silver, gold, and platinum), its extraction is complex. For example, it is obtained as a white inert metal from platinum ores, which is quite difficult to fuse. In order of increasing mass abundance (parts per billion), the precious metals are rhenium, rhodium, iridium, ruthenium, osmium, gold, platinum, palladium, and silver. These metals are not radioactive and are mostly used for industrial purposes and for jewelry. 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 extreme toxicity and volatility of osmium's oxide makes it nearly impossible for this element to be used in its pure state. For this reason, it is often necessary to alloy osmium with other elements for use in high-wear applications. For example, osmiridium (a natural alloy of osmium and iridium) is alloyed with the other metals in the platinum group and used in instrument pivots and phonograph needles (apart from electrical contacts and fountain pen tips as mentioned earlier). Electrical contacts for spark plugs (due to its resistance to arc erosion); 2. Computer memory devices; 3. Direct-ignition engine (as a catalyst); 4. 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). They named it after the Latin word "rhenus", for "Rhine", one of Europe's longest and most important rivers. As for the precious metals gold and silver, both are known to be already in use since ancient times (gold was in use probably as early as before 6000 BC, while silver probably as early as before 5000 BC). Like rhodium, palladium is largely used as a catalytic converter. As of January 2010, the price of this metal is estimated to be approximately USD424 per troy ounce (USD13,632 per kilogram). 4. Osmium - This element is represented by the symbol Os. Its atomic number is 76. It is found in nature as an alloy in platinum ores.