среда, 13 июля 2011 г.

Much of the gold

Gold - 79th element of the periodic table of elements, the noble metal of yellow color.

Origin of name

Proto-Slavic * zolto (русск. gold, Ukr. Gold, Art-Slav. Gold, Pol. Zloto) cognate literature. geltonas «yellow», ltsh. zelts «gold, gold", with another vocalism: Gotha. gul?, it. Gold, Eng. gold; further Skt. hira?yam, Zend. zaranya «gold», as Skt. hari «yellow, golden, green," from the root praindoevropeyskogo * ? ? el-«yellow, green, bright." Hence, also the names of colors: yellow, green.

Relationshipwith the root for "sun" (Latin sol, etc., Greek. ?????) is questionable.

Physical properties

Pure gold - a soft yellow metal. 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 electrical resistance.

Gold - a very heavy metal: a ball of pure gold, 46 mm in diameter has a mass of 1 kg. Liter bottle filled with golden sand weighs about 16 kg. The severity of gold - a plus for its production. The most common processes, such as, for example, flushing at the gateway, can provide a very high degree of extraction of gold from the rock flushed.

Gold is very ductile and forging. From a piece of gold weighing one gram can be stretched wire length of three kilometers, or make a gold foil is 500 times thinner than a human hair (0.0001 mm). Through a sheet of foil, a beam of light shines green in color. The softness of pure gold is so high that it can be scratched with a fingernail. Therefore, the gold jewelry is always fused with copper or silver. The composition of these alloys is expressed in the sample, which indicates the number of parts by weight of gold in 1000 parts of alloy (in Russian practice). A sample of chemically pure gold 999.9 corresponds to the sample - it is called "bank" in gold, because of such gold and ingots are made.

Chemical properties

Gold - the most inert metal, standing in a row stresses the right of all other metals 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. Then there was the ability to open aqua regia to dissolve gold, which shook the confidence of its inertia.

The most stable oxidation state of gold in three compounds in this oxidation state is easily formed with singly charged anions (F-, Cl-. CN-) stable square-planar complexes [AuX4] -. Also relatively stable compound with a degree of oxidation, giving the linear complexes [AuX2] -. It was long thought that the three - the highest possible oxidation states of gold, however, using krypton difluoride, yielded compound Au +5 (fluoride AuF5, salt complex [AuF6] -). Gold compounds (V) are stable only with fluorine and is a strong oxidant.

The oxidation state of +2 for gold is unusual, in materials in which it is formally equal to 2 and half gold, usually oxidized to a and a half - up to 3, for example, the correct formula of ionic sulfate, gold (II) AuSO4 will not Au2 + (SO4) 2 -, and Au1 + Au3 + (SO4) 2-2. Recently discovered systems in which the gold still has a degree of oxidation of 2.

Of pure gold acid dissolves only in hot concentrated acid, selenium:
2Au + 6H2SeO4 = Au2 (SeO4) 3 + 3H2SeO3 + 3H2O

Gold is relatively easy to react with oxygen and other oxidants, with the participation kompleksobrazovateley. Thus, in aqueous solutions of cyanide in gold supply of oxygen is dissolved, forming tsianoauraty:
4Au + 8CN-+ 2H2O + O2 > 4 [Au (CN) 2] - + 4 OH-

In the case of reaction with chlorine to the possibility of complexation also greatly facilitates the reaction course, if the dry chlorine reacts with gold ~ 200 ° C to form gold chloride (III), in aqueous solution (aqua regia) dissolves with the formation of gold hloraurat ion at room Temperature:
2Au + 3Cl2 + 2Cl-> 2 [AuCl4] -

Gold readily reacts with liquid bromine and its solutions in water and organic solvents, giving tribromide AuBr3.

Gold reacts with fluorine in the temperature range 300-400 ° C, at lower reaction does not occur, and at higher gold fluorides decompose.

Gold dissolves in mercury and, in fact, forming a low melting alloy (amalgam).

Geochemistry of gold

The gold content in the crust is very low - 3 mg / kg, but the field and areas, dramatically enriched metal, are very numerous. Gold contained in the water. 1 with sea and river water is about 4 * 10-9 g of gold.

For gold is characteristic of native form. Among its other forms it is worth noting electrum, an alloy of gold and silver, which has a greenish hue and relatively easily destroyed by water transport. In the rocks of gold is usually dispersed at the atomic level. In the fields it is often enclosed in sulfides and arsenides.

Differ in the primary gold deposits, deposits in which it falls as a result of the destruction of ore deposits and deposits with complex ores in which gold is extracted as the associated component.

Obtaining

Golden Nugget

To get the gold used his basic physical and chemical properties: the presence of nature in the native state, the ability to react with only a few substances (mercury, cyanide). C development of modern technologies increasingly popular chemical methods.

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. Schliches received, except for gold, contain a number of 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. Unfortunately, the washing is lost not only a fine gold, which is easily washed off with washing the deck, but also large nuggets, hydraulic size does not allow them to settle down quietly in the cell mat. Therefore, on dredges and Prompribor necessarily follow the large rolling debris - it may well be the nuggets!

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 more than 0.1 grams per 1 cubic meter of loose rock (sand, loam, etc.).

Amalgamation

Amalgamation method based on the ability of mercury to form alloys - an amalgam of various metals, including gold. In this method, the wetted crushed rock mixed with mercury and subjected to additional grinding in the mills - the runners bowls. Amalgam of gold (and associated metals) were recovered from the resulting slurry wash, followed by mercury amalgam is distilled from the collected and reused. Amalgamation method is known from the I century BC. e. the greatest extent in the American colonies gained from Spain of the XVI century: it has become possible due to the presence in Spain, a huge deposit of mercury - Almaden. More recently, we used the method of external amalgamation, when the crushed gold-bearing rock in the wash was passed through a gateway concentrating lined with copper plates coated with a thin layer of mercury. Amalgamation method applies only to deposits with high content of gold or even for his enrichment. Now it is used very rarely, mostly miners in Africa and South America.

Cyanidation

Gold dissolves in cyanide solutions, acid and its salts, and that his property has given rise to a number of methods for extraction by cyanide leaching of ores.

Cyanide method based on the reaction of gold with cyanide in the presence of atmospheric oxygen: crushed gold-bearing rock is treated with dilute (0,3-0,03%) solution of sodium cyanide, gold produced from a solution of sodium tsianoaurata Na [Au (CN) 2] precipitate or zinc dust or ion exchange resins for the special.

Cyanide method was originally used for large factories, where the breed is fragmented and cyanidation was carried out in special tanks. However, advances in technology led to a heap leaching method, which consists of the following: preparing waterproof floor, it poured and it poured ore cyanide solution, which, seeping through the thick rock, dissolve the gold. After that they go on special columns, in which gold is deposited, and the regenerated solution was again sent to the heap.

Cyanide method is limited to the mineral composition of ores, it does not apply if the ore contains a large amount of sulfides and arsenides as cyanides react with these minerals. Therefore, low-sulphide ore cyanidation or processed ore from the oxidation zone, in which sulfides and arsenides are oxidized by atmospheric oxygen.

To extract the gold from sulfide ores using complex multi-stage technology. Gold, mined from deposits contain various impurities, so it is subjected to special processes of high purity, which are produced at refineries.

Regeneration

Implemented a 10% solution of alkali salt solutions on gold, followed by precipitation of gold refining aluminum hydroxide from the hot solution.

Application

Available now in the world, gold is distributed as follows: 10% - in industrial products, the rest is divided about equally between the centralized inventory (mostly in the form of standard ingots of pure gold), owned by private individuals in the form of ingots and jewelry.

As an investment object

Gold is an essential element of the global financial system, since the metal does not corrode, has many areas of technical applications, and its reserves are low. Gold almost lost in the process of historical cataclysms, but only accumulated and melted. Currently, the 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 all world currencies were based on the gold standard (the period 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.

The 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 is registered as a food additive E175.

In Jewelry

Gold Jewellery. Gold Medal received by the artist GN Gorelov in 1909 at the International Exhibition in Munich for the painting "Mockery heretics" and gold wedding rings and spouses Gorelova G.N Gorelova TN

The traditional and the largest consumer of gold is the jewelry industry. Jewelry is made not of gold, and of its alloys with other metals, gold is vastly superior mechanical strength and durability. At the present time for this are alloys Au-Ag-Cu, which may contain additives zinc, nickel, cobalt, and palladium. Corrosion resistance of these alloys are determined primarily, their content of gold, and shades of color and mechanical properties - the ratio of silver and copper.

The most important characteristic is the jewelry of their sample, characterizing the content of gold.

In dentistry

Significant quantities of gold consumption dentistry: crowns and dentures made of gold alloys with silver, copper, nickel, platinum, zinc. These alloys combine corrosion resistance with good mechanical properties.

In pharmacology

Gold compounds are part of some medicines used to treat several diseases (tuberculosis, rheumatoid arthritis, etc.). Radioactive gold is used in the treatment of malignant tumors

Gold prices

The price of gold after a default on U.S. gold

In 1792, the United States found that 1 ounce of gold will be worth $ 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.

In 1944 it was decided 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 the dollar was no longer secured by nothing but debt U.S..

The price of gold adjusted for inflation

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 (over 2000 in 2008 prices), 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.

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 per ounce of gold reached $ 620 by the end of 2007 for about $ 800. In early 2008 the price of gold exceeded the threshold of $ 1,000 per ounce. Nevertheless, at comparable prices, gold has not reached the peak of 80 - above $ 2,000. Gold stands for investment in several forms - gold bars, gold coins, gold dust. Bullion coins are the best way to invest in Russia: the buyer does not pay VAT. However, the price for 1 gram of gold in coins in Russia exceeds the price of 1 gram of bullion, even with VAT and interest on the spread of the latter (for example, the Savings Bank of Russia). Unlike auction E-bay, where the cost of strongly correlated with world prices. Gold coin minting in Uncirculated (name of issue for investment coins) can cost 20-30% more expensive than gold bullion 50 or 100 grams, even taking into account the fact that for the gold in the ingot is paid 18% tax and interest of so-called "spread" to the bank (about 2% to buy gold and 2% of the bank to sell it to you, that is, a total of about 4% in addition to VAT).

In addition, the dynamics of the price of gold is the most important economic indicator, allowing to assess risk appetite. Often one can observe that the price of gold and stock indices move in opposite phase, since in times of unstable economic situation, conservative investors prefer assets that are protected from the full depreciation. Conversely, when expectations of economic growth become more optimistic appetite for higher yields rise, causing the yellow metal to fall quotes.

Комментариев нет:

Отправить комментарий