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Chemical Reactions of the Elements

Chemical reactions of the elements

Reaction of gold with air

Gold metal is stable in air under normal conditions. However gold does dissolve in aqueous cyanide solutions in the presence of air.
Reaction of gold with water

Gold does not react with water.
Reaction of gold with the halogens

Gold metal reacts with chlorine, Cl2, or bromine, Br2, to form the trihalides gold(III) chloride, AuCl3, or gold(III) bromide, AuBr3, respectively. On the other hand, gold metal reacts with iodine, I2, to form the monohalide gold(I) chloride, AuI.
2Au(s) + 3Cl2(g) [IMG]file:///C:/DOCUME%7E1/Kim/LOCALS%7E1/Temp/msohtml1/01/clip_image001.gif[/IMG]2AuCl3(s)
2Au(s) + 3Br2(g) [IMG]file:///C:/DOCUME%7E1/Kim/LOCALS%7E1/Temp/msohtml1/01/clip_image001.gif[/IMG]2AuBr3(s)
2Au(s) + I2(g) [IMG]file:///C:/DOCUME%7E1/Kim/LOCALS%7E1/Temp/msohtml1/01/clip_image001.gif[/IMG]2AuI(s)
Reaction of gold with acids

Gold metal dissolves in aqua regia, a mixture of hydrochloric acid, HCl, and concentrated nitric acid, HNO3, in a 3:1 ratio. The name aqua regia was coined by alchemists because of its ability to dissolve gold - the "king of metals".
Reaction of gold with bases

Gold does not react with aqueous bases.
Binary Compounds

This section lists some compounds, largely binary, of gold. This section of WebElements will be expanded in the future. Select any formula given for further information on that compound
Hydrides

The term hydride is used to indicate compounds of the type MxHy and not necessarily to indicate that any compounds listed behave as hydrides chemically.
  • none listed
Fluorides

  • : gold (III) fluoride
  • : gold (V) fluoride
Chlorides

  • : gold (I) chloride
  • : gold (III) chloride
  • : gold (I, III) chloride
Bromides

  • : gold (I) bromide
  • : gold (III) bromide
Iodides

  • : gold (I) iodide
  • : gold (III) iodide
Oxides

  • : gold (III) oxide
Sulfides

  • : gold (I) sulphide
  • : gold (III) sulphide
Selenides

  • : gold (I, III) selenide
  • : gold (III) selenide
Tellurides

  • : gold ditelluride
Nitrides

  • none listed
Uses

The following for gold are gathered from a as well as from anecdotal comments. I'd be delighted to receive corrections as well as additional referenced uses (please use the feedback mechanism to add uses).
  • coinage metal, standard for monetary systems in many countries
  • jewellery, decoration
  • dentistry
  • plating. It is used for coating space satellites, as it is a good IR reflector and is inert.
  • chlorauric acid (HAuCl4) is used in photography for toning the silver image
  • Disodium aurothiomalate is administered (intramuscular) as a treatment for arthritis
  • electronics
  • photography for toning silver images
  • 198Au is used for treating cancer and other conditions
Gold was known and highly valued from earliest times. Egyption inscriptions dating back to 2600 B.C. describe gold and gold is mentioned several times in the Old Testament.
Gold is one of the elements which has an alchemical symbol, shown below (alchemy is an ancient pursuit concerned with, for instance, the transformation of other metals into gold).Sometime prior to the autumn of 1803, the Englishman John Dalton was able to explain the results of some of his studies by assuming that matter is composed of atoms and that all samples of any given compound consist of the same combination of these atoms. Dalton also noted that in series of compounds, the ratios of the masses of the second element that combine with a given weight of the first element can be reduced to small whole numbers (the law of multiple proportions). This was further evidence for atoms. Dalton's theory of atoms was published by Thomas Thomson in the 3rd edition of his System of Chemistry in 1807 and in a paper about strontium oxalates published in the Philosophical Transactions. Dalton published these ideas himself in the following year in the New System of Chemical Philosophy. The symbol used by Dalton for gold is shown below. [See History of Chemistry, Sir Edward Thorpe, volume 1, Watts & Co, London, 1914.]
Gold

For gold bars.
Atomic Number:
79
Atomic Symbol:
Au
Atomic Weight:
196.9665
Electron Configuration:
[Xe]6s14f145d10
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.
Sources

It 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 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.
Uses

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.
Cost

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. As of January 1990, gold was priced at about $410/troy oz.
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+%. For 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.

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