среда, 13 июля 2011 г.

Gold

History

Gold - the first metal, whom he met humanity. Native gold and silver known to mankind for thousands of years, evidenced by articles found in ancient tombs, and primitive mining, preserved to this day. In ancient times, the main centers for production of precious metals were Upper Egypt, Nubia, Spain, Colchis (the Caucasus), there is evidence of mining in Central, South America, Asia (India, the Altai, Kazakhstan, China). Metals extracted from alluvial deposits of sand washing animal skinswith fur trimmed (to capture the grains of gold) as well as with primitive trenches, trays and buckets. Metals from ore mined by heating the rock to crack, followed by crushing lumps of stone mortars, abrasion and washing millstones. Separation by size was carried out on sieves. In ancient Egypt was known method of separating gold and silver alloys, acids, recovery of gold and silver from lead alloy cupellation, extracting gold by amalgamation with mercury, or collection of particles by means of surface fat (Ancient Greece). Cupellation carried out in clay crucibles, where lead is added, table salt, tin, and bran.

In the XI-VI centuries BC. Oe. Gold was mined in Spain in the valleys of the Tagus, Douro, Minho and Guadyaro. In the VI-IV centuries BC. Oe. began developing and placer gold deposits in the Western Carpathians and Transylvania.

Origin of name

Since gold was known, probably, before the advent of writing, trace the history of its name, most likely, impossible. It is known, however, that in the Slavic languages ??the word was gold in ancient times a common root with the word "yellow", the original version of the word is written as zolto. Some attributed the origin of the word "gold" with the word "sun" (the root of the sol). However, sufficiently reliable versions of the origin of the name there.

Physical properties

Pure gold - a soft metal pure yellow. Some reddish tint of gold, such as coins, give any admixture of other metals, particularly copper. In thin films of gold shines green. Gold has exceptionally high thermal conductivity and low resistance.

Chemical properties

Gold metal relatively inert under normal conditions it does not react with most acids and does not form oxides, so that was attributed to noble metals, in contrast to conventional metals, is easily destroyed by the environment.


Obtaining

To get the gold used its basic chemical properties: the presence of nature in the native state, the ability to react with only a few substances (mercury, cyanide).

Flushing

The method of cleaning based on the high density of gold, through which a flow of water, minerals with a density of less than gold (which is almost all the minerals the earth's crust) are washed away and the metal is concentrated in the heavy fraction, sand, consisting of minerals of higher density, which is called schliches. This process is called washing schliches or shlihovaniem. In small amounts it can be done manually, using the washing tray. This method is used since ancient times, and still to work out of small alluvial deposits by prospectors, but its main use - search for gold, diamonds and other precious metals.

Flushing is used to develop large-scale alluvial deposits, but are subject to special technical device: the drag and flushing device. Obtained schliches than gold contain many other solid minerals, and metals are extracted, for example, by amalgamation.

Method developed by washing all the placer deposits of gold, it is limited to use in primary deposits. To do this, rock is crushed and then subjected to washing. This method can be applied to deposits with gold, where it is dispersed in the rock so that after cleavage is not segregated into individual grains and washed off by washing with other minerals.

This method of gold mining has historically been the first, and it is very cheap, because it does not require construction of expensive plants, and in case of river sediments do not have to break up the rock. Cost-effective testing of placer gold content of 0.5 g / t.

Application

Gold in Industry

According to its chemical resistance and mechanical strength of gold is inferior to most platinum, but indispensable as a material for electrical contacts. Therefore, the gold wires and Microelectronics electroplating gold contact surfaces, connectors, printed circuit boards are used very widely.

Gold is used as a target in nuclear research, as a coating of mirrors, working in the far infrared range, as a special envelope in the neutron bomb. Gold alloys are well moistened with a variety of metal surfaces and are used for soldering metals. Thin pads are made of soft alloy of gold used in the technique of ultra-high vacuum.

Gilding metal (in ancient times - only amalgam method, at present - mainly electroplating) has been widely used as a method of corrosion protection. Although such a precious metal coating has significant shortcomings (soft cover, high potential for pitting corrosion), it is also commonly due to the fact that the final product becomes very expensive, "gold".

Gold in the economy

Gold is an essential element of the global financial system and, therefore, an interesting financial instrument, since the metal does not corrode, is attractive in appearance and its reserves are low. World bank gold reserves are estimated at 32 tons (if all this gold to float together, get a cube with sides of only 12 m).

Gold has long been used by many people as money. Gold Coins - the most well-conserved ancient monument. However, as a monopoly money commodity is approved only to the XIX century. Up until World War I gold was the measure of all world currencies (the period of 1870-1914 is called the "golden age"). Paper money at that time acted as identification of the presence of gold. They are freely exchanged for gold.

In 1792, the United States found that 1 ounce of gold contained in 19.3 $. In 1834 an ounce already given $ 20.67 as the U.S. did not have enough gold reserves to provide the entire amount of issued money, and the exchange rate had reduced.

After World War I continued devaluation. In 1934, for an ounce of gold was given $ 35. Despite the economic crisis, the U.S. tried to maintain a fixed peg to the dollar to gold, for it raised the discount rate, but to no avail. However, due to have followed the wars gold from the Old World has moved into new, restored at that time, bind the dollar to gold.

1944 was made of the Bretton Woods agreement. Gold exchange standard was introduced, based on gold and two currencies - the U.S. dollar and British pound sterling, thus ending the monopoly of the gold standard. Under the new rules, the dollar became the only currency is directly pegged to gold. U.S. Treasury pledged to exchange dollars for gold to foreign government agencies and central banks in the ratio of $ 35 per troy ounce. In fact, gold has turned out in the main reserve currency.

In the late 1960s, high inflation in the U.S. again made it impossible to maintain a gold anchor on the same level, complicating the situation and the U.S. trade deficit. The market price of gold was significantly higher than officially established. In 1971 the gold content in the dollar has been reduced to $ 38 per ounce, and in 1973 - up to $ 42.22 an ounce. In 1971, U.S. President Richard Nixon bind the dollar to gold, although this step was officially confirmed until 1976, when it created the so-called Jamaican monetary system of floating exchange rates. This meant that gold is no longer a general currency and the dollar became the reserve currency.

After that, gold has become a particular investment product. Investors over the years to trust only the gold. By the end of 1974, gold prices jumped to $ 195 per ounce, and by 1978 - up to $ 200 per ounce. By the beginning of 1980 the gold price reached a record high - $ 850 per ounce, after which she began to fall slowly. In late 1987, it was about $ 500 per ounce. The most rapid decline occurred in 1996-1999. When the price of gold fell from 420 to $ 260 per ounce. Among analysts, there is no consensus about the reasons for this rapid decline in the price of gold: some attribute this to the objective economic factors, others are talking about a global conspiracy of the largest countries, led by the United States.

Whatever it was, the decline has stopped and again began to increase the price of gold in connection with the agreement of major central banks to limit gold sales in 1999. By the end of 2006 the price of gold reached $ 620. Analysts predict that, due to instability of the U.S. economy and global financial climate in general the price of gold could rise to $ 1,000 per ounce. Gold for investment appears in two forms - gold bullion and gold coins.

Measures the purity of gold

British carat system

Traditionally, the purity of gold is measured in British carats. 1 British carat equals one twenty-fourth of the weight of the alloy. 24-karat gold (24K) is clean and free of any impurities.


To change the qualitative characteristics of gold for various purposes (for example, to increase hardness) are made from alloys with different impurities. For example, 18-karat gold (18K) means the content in the alloy is 18 parts gold and 6 parts of impurities.


The Russian system of trial

The adopted system in Russia is different from the world. In Russia, the purity of gold is measured breakdown. The sample ranges from 0 to 1000 and shows the content of gold in thousandths. Thus, the 18-carat gold of 750 corresponds to the sample. Gold 996-th sample is considered "almost clear" and is used in jewelry. Gold higher samples are extremely expensive to acquire and is only used in chemistry.

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