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For gold bars. | Atomic Number: | 79 | Atomic Symbol: | Au | | Atomic Weight: | 196.9665 | Electron Configuration: | 2-8-18-32-18-1 | | Shells: | 2,8,18,32,18,1 | Filling Orbital: | 5d10 | | Melting Point: | 1064.43oC | Boiling Point: | 2807oC | | Description: | Soft bright yellow transition metal. | | Uses: | Very malleable. Used in electronics and jewlery |
History(Sanskrit Jval; Anglo-Saxon gold; L. aurum, gold) 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.
OccurenceIt occurs in veins and alluvial deposits, and is often
separated from rocks and other minerals by mining 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.
Properties- 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 ft^2.
- It is a soft metal and is usually alloyed to give it more strength.
Uses- 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.
Compounds and Isotopes- The most common gold compounds are auric chloride and chlorauric acid, the
latter being used in photography for toning the silver image.
- Gold has 18 isotopes; 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+%.
TemperatureFor many years the temperature assigned to the freezing
point of gold has been 1063.0C; 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 demands that the freezing point
of gold be changed to 1064.43C. The specific gravity of gold has been found to
vary considerably depending on temperature, how the metal is precipitated, and
cold-worked.
CostsFor 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. As of now ,The price is $4400 per 100g.
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