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Chemical Fact Sheet

Gold

Chemical Abstract Number (CAS #) 7440-57-5
Synonyms BURNISH-GOLD-;CI-77480-;CI-PIGMENT-METAL-3-;COLLOIDAL-GOLD-;GOLD-FLAKE-; GOLD-LEAF-; GOLD-POWDER-;GOLD-197;MAGNESIUM-GOLD-PURPLE-;SHELL-GOLD-
Analytical Methods 200.7 - 200.8 - 6010 - 6020 - 231.1
Atomic Symbol Au

Synopsis from the CRC Handbook of Chemistry and Physics 92nd Edition 2011-2013

Gold (Sanskrit Jval; Anglo-Saxon gold), Au (L. aurum, gold); at. wt. 196.966569(4); at. no. 79; m.p. 1064.18 C; b.p. 2856 C; sp. gr. ~19.3 (20 C); valence 1 or 3. Known and highly valued from earliest times, gold is found in nature as the free metal and in tellurides; it is very widely distributed and is almost always associated with quartz or pyrite. It occurs in veins and alluvial deposits, and is often separated from rocks and other minerals by sluicing and panning operations. About 25% of the worlds gold output comes from South Africa, and about two thirds of the total U.S. production now comes from South Dakota and Nevada. The metal is recovered from its ores by cyaniding, amalgamating, and smelting processes. Refining is also frequently done by electrolysis. Gold occurs in sea water to the extent of 0.1 to 2 mg/ton, depending on the location where the sample is taken. As yet, no method has been found for recovering gold from sea water profitably. It is estimated that all the gold in the world, so far refined, could be placed in a single cube 60 ft on a side. Of all the elements, gold in its pure state is undoubtedly the most beautiful. It is metallic, having a yellow color when in a mass, but when finely divided it may be black, ruby, or purple. The Purple of Cassius is a delicate test for auric gold. It is the most malleable and ductile metal; 1 oz. of gold can be beaten out to 300 ft2. It is a soft metal and is usually alloyed to give it more strength. It is a good conductor of heat and electricity, and is unaffected by air and most reagents. It is used in coinage and is a standard for monetary systems in many countries. It is also extensively used for jewelry, decoration, dental work, and for plating. It is used for coating certain space satellites, as it is a good reflector of infrared and is inert. Gold, like other precious metals, is measured in troy weight; when alloyed with other metals, the term carat is used to express the amount of gold present, 24 carats being pure gold. For many years the value of gold was set by the U.S. at $20.67/troy ounce; in 1934 this value was fixed by law at $35.00/troy ounce, 9/10th fine. On March 17, 1968, because of a gold crisis, a two-tiered pricing system was established whereby gold was still used to settle international accounts at the old $35.00/troy ounce price while the price of gold on the private market would be allowed to fluctuate. Since this time, the price of gold on the free market has fluctuated widely. The price of gold on the free market reached a price of $620/troy oz. in January 1980. More recently, the U.K. and other nations, including the I.M.F. have sold or threatened to sell a sizeable portion of their gold reserves. This has caused wide fluctuations in the price of gold. Because this has damaged the economy of some countries, a moratorium for a few years has been declared. This has tended to stabilize temporarily the price of gold. The most common gold compounds are auric chloride (AuCl3) and chlorauric acid (HAuCl4), the latter being used in photography for toning the silver image. Gold has forty-eight recognized isotopes and isomers; 198Au, with a half-life of 2.7 days, is used for treating cancer and other diseases. Disodium aurothiomalate is administered intramuscularly as a treatment for arthritis. A mixture of one part nitric acid with three of hydrochloric acid is called aqua regia (because it dissolved gold, the King of Metals). Gold is available commercially with a purity of 99.999+%. For many years the temperature assigned to the freezing point of gold has been 1063.0 C; this has served as a calibration point for the International Temperature Scales (ITS-27 and ITS-48) and the International Practical Temperature Scale (IPTS-48). In 1968, a new International Practical Temperature Scale (IPTS- 68) was adopted, which demanded that the freezing point of gold be changed to 1064.43 C. In 1990 a new International Temperature Scale (ITS-90) was adopted bringing the t.p. The Elements 4-15 (triple point) of H2O (t90 (C)) to 0.01 C and the freezing point of gold to 1064.18 C. The specific gravity of gold has been found to vary considerably depending on temperature, how the metal is precipitated, and cold-worked. As of December 2001, gold was priced at about $275/troy oz. ($8.50/g).

Drinking Water

Impact

SEA WATER CONTAINS 3-4 MG/TON SEAWATER CONTAINS 0.004 PPB AU.


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