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| | Men have been fascinated by gold more than any other precious metals. Since it
was discovered in about 5000 B.C., gold was used in jewelry, and later
in decorations on glasses and dishes and well as in furniture for centuries. The whole branch of chemistry - alchemy was dedicated
to one primary goal of finding a cornerstone chemical element that
would turn other elements into gold when mixed with it. While such
element was never found, we have to thank alchemy for many scientific discoveries
that helped the development of chemistry, physics and other sciences. Perhaps the most eloquent example of people's
obsession with gold is the gold rush period in America, when thousands of
people sold their possessions, to buy a ticket to California and try
their luck digging the gold nuggets and becoming rich through gold mining. Many of them
ended up with nothing, but some made their fortunes, and returned
home as rich people. This was the greatest adventure the world have
ever seen. Today, hundreds of years later, gold is still as precious
to our society as before. Gold is used as means of investment, also in
electronics for its high conductor properties, and last but not least
golden jewelry is beautiful and is a sign of style and prosperity.
After diamonds, gold is definitely girl's second best friend.
Gold - This precious yellow metal is the 79th element of the periodic table.
Perhaps gold is the first metal known to mankind (for details refer precious metals).
Pure gold is very soft metal of yellow color. Mixtures of other metals, particularly copper, are added to some items made of gold, for example coins, to give it a reddish tone. Fine films of gold glow in green color. Gold is highly heat conductive and possesses low resistance. Gold is very heavy metal: a ball made of pure gold in diameter 46mm weighs 1kg. One liter bottle filled with gold dust weighs approximately 16kg. Density of gold is an advantage for its mining (extraction). The most simple technological processes like washing on sluices, can ensure high level of extraction of gold from the rock being washed. Gold is very malleable and ductile. Piece of one gram gold can be drawn into a wire of three kilometer or it can be used to make golden foil 500 times thinner than human hair (0.0001mm). When light is transmitted through such sheet it glows in green color. Gold is so soft that it can be scratched by human nail. That is why, gold is always mixed with copper or silver while making jewelery items. Composition of such alloys is expressed in grades, which indicates the number of weight portions of precious metal in 1000 parts of alloy.
For obtaining gold, its two main chemical properties are considered: it is found in nature in native state, reacts with only a few substances (mercury, cyanides).
Chemical stability and mechanical strength of gold are inferior than most of the platinum, but gold is not replaceable, as a material for electrical contacts.
Therefore gold conductors and galvanic gold plating of contact surfaces, connectors, PCB’s are widely used in microelectronics.
Gold is used as a target in atomic research, as a coating of mirrors, working in far infra-red range, as special shell in neutron bomb.
Gold solders very well bind to different metallic surfaces and are used for soldering of metals. Fine packings, made from soft alloys of gold, are used in ultrahigh-vacuum technology.
Gold plating (in ancient times – exclusively amalgam method, nowadays – mainly the galvanic method) is widely used for protection from corrosion. Although, gold plating of base metals has considerable drawbacks (softness of coating, high potential at point corrosion), it is prevalent because the items made from it look very precious as if they are made from gold. |
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