Chemical Fact Sheet
Gold
| Chemical Abstract Number (CAS #) | 7440-57-5 |
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| 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 |
| Molecular Formula | Au |
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Synopsis
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Gold - (Sanskrit Jval; Anglo-Saxon gold), Au (L. aurum, gold);at.wt. 196.96654(3); at.no. 79; m.p. 1064.18 deg C; b.p. 2856 deg C; sp.gr. ~19.3 (20 deg 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 two thirds of the world's gold output comes from South Africa, and about two thirds of the total U.S. production 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 sq ft. It's 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 c@rood 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. 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 six 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 deg 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 deg C. In 1990 a new International Temperature Scale (ITS-90) was adopted bringing the t.p. (triple point) of H2O (t90 (deg C)) to 0.01 deg C and the freezing point of gold to 1064.18 deg 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 January 1996, gold was priced at about $390/troy oz. ($12.50/g). |
| Use | IN MFR OF JEWELRY; IN GOLD PLATING OTHER METALS; MOST FREQUENTLY ALLOYED WITH SILVER AND COPPER; AS STD OF CURRENCY ANTINEOPLASTIC AGENT USED IN ALLOY WITH PLATINUM, IN PHOTOGRAPHY, IN DENTISTRY INFRARED REFLECTORS; ELECTRICAL CONTACT ALLOYS; BRAZING ALLOYS; POLAROGRAPHIC ELECTRODES; SPINNERETS; LABORATORY WARE; IN ELECTRONICS; COLLOIDAL DISPERSIONS USED IN COLORING GLASS, AS NUCLEATING AGENT, & FOR SPECIALIZED MEDICAL TREATMENTS; GOLD LEAF IS USED IN SURGERY COMPONENT OF JEWELRY & ART PRODUCTS; DENTAL AGENT FOR INLAYS; ALLOYING AGENT WITH OTHER METALS; PLATING AGENT IN ELECTRON TUBES & OTHER METALS; COMPONENT OF ELECTRICAL CONTACTS & FABRICATED BARS FOR INVESTMENT |
| Consumption Patterns | APPROX 52% IN JEWELRY & ARTS, 25% IN INDUSTRIAL APPLICATIONS, 15% IN DENTAL APPLICATIONS, & 6% FOR INVESTMENT PRODUCTS +Jewelry and Arts, 52%; Industrial (mainly electronic), 35%; Dental, 12%;and small bars, etc, mainly for investment, about 1% (1985) |
| Apparent Color | YELLOW, SOFT METAL; FACE-CENTERED CUBIC STRUCTURE;CUBIC YELLOW, METALLIC CRYSTALS;WHEN FINELY DIVIDED IT MAY BE BLACK, RUBY, OR PURPLE; *WHEN PREPD BY VOLATILIZATION OR PPTN METHODS, DEEP VIOLET, PURPLE, OR RUBY POWDER;SOFT, DUCTILE, MALLEABLE |
| Boiling Point | 2700 DEG C |
| Melting Point | 1064.76 DEG C |
| Molecular Weight | 196.9665 |
| Density | 19.3 |
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Chemical and Physical Properties |
HARDNESS (MOHS') 2.5-3.0; (BRINELL'S) 18.5; ONE NATURAL ISOTOPE: 197; ARTIFICIAL ISOTOPES (MASS NUMBER): 177-179, 181, 183, 185-196, 198-203; ATOMIC NUMBER: 79; VALENCES 1, 3 GOOD CONDUCTOR OF HEAT AND ELECTRICITY GOLD EASILY FORMS COMPLEX COMPD IN WHICH IT IS MONOVALENT OR TRIVALENT METAL IN ITS LOWER OXIDATION STATE, GOLD YIELDS AUROUS COMPD SUCH AS AUCL; IN THE TRIPOSITIVE STATE, IT YIELDS AURIC COMPD SUCH AS AUCL3; GOLD SHOWS A DECIDED TENDENCY TO ENTER INTO COMPLEXES IN WHICH IT FUNCTIONS ANIONICALLY IT FORMS ALLOYS WITH A NUMBER OF METALS INCLUDING SILVER, COPPER, PLATINUM, PALLADIUM, MANGANESE, ZINC & MAGNESIUM MONOVALENT GOLD HAS A RELATIVELY STRONG AFFINITY FOR SULFUR, WEAK AFFINITIES FOR CARBON & NITROGEN |
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Environmental Impact |
CASES OF ARSINE POISONING OCCURRED IN MEN EMPLOYED IN EXTRACTION OF GOLD BY CYANIDE PROCESS. |
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Environmental Fate |
OCCURRENCE IN EARTH'S CRUST: 0.005 PPM GOLD GENERALLY OCCURS IN THE FREE STATE AS VEINS IN QUARTZ, & IN RIVER SANDS WHICH HAVE RESULTED FROM DISINTEGRATION OF GOLD-BEARING ROCK. IT IS ALSO FOUND IN SMALL AMT OF MANY PYRITIC & OTHER SULFIDE & TELLURIDE ORES. OCCURS IN NATURE IN ITS NATIVE FORM & IN MINUTE QUANTITIES IN ALMOST ALL ROCKS & IN SEAWATER. GOLD ORES INCL CALAVARITE (AUTE2), SYLVANITE [(AG,AU)TE2], PETZITE [(AG,AU)2TE]. SOUTH AFRICA, USSR, NORTHWEST CANADA, US (SOUTH DAKOTA, NEVADA, UTAH, ALASKA, CALIFORNIA), AUSTRALIA. OCEANS ARE ESTIMATED TO CONTAIN 70 MILLION TONS IN SOLN, WITH 10 BILLION ADDNL TONS ON OCEAN FLOOR. THERE IS NO PRESENT METHOD OF EXPLOITING THESE RESOURCES. SMALL AMT, 0.03-1 MG%, HAVE BEEN REPORTED IN MANY FOODS. GOLD IS NOT NORMALLY PRESENT IN PLANT TISSUES, & IT IS NOT ESSENTIAL NUTRIENT. |
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Drinking Water Impact |
SEA WATER CONTAINS 3-4 MG/TON SEAWATER CONTAINS 0.004 PPB AU. |
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