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Gold is a rich yellow noble metal with a characteristic luster. It occupies 79th place in the periodic table. In chemistry, it is designated as Au (Aurum). About all languages of the world the name "gold" is translated as "yellow". The Latin word aurum refers us to the goddess of the morning dawn, Aurora. People have been mining for gold since time immemorial. The name of this metal is repeatedly found in the Bible, including in the listing of the gifts brought by the wise men. The first gold coin appeared in Ancient Lydia in 560 BC.

Characteristics and types of gold Gold in its pure form is a very soft metal. It can be easily scratched with a fingernail, so silver, copper and platinum are added to gold coins to give strength when making jewelry. Gold has a high density coefficient. That is why it is easy to get it. In terms of its weight, gold ranks 6th, second only to platinum, osmium, iridium, rhenium and plutonium. Gold is very plastic. You can hammer this metal into sheets only ~ 0.1 microns thick - the so-called "gold leaf". Gold conducts electricity and heat well. This metal does not oxidize under normal conditions, it is not afraid of acid. It dissolves only in "aqua regia" and solutions of potassium or sodium cyanide. The most common classification of gold is by color. Moreover, the color of gold depends on the ligature (added metals).

Traditionally, yellow gold in jewelry is an alloy of gold and silver or copper. If the metal is yellow with a reddish tint, then more copper has been added. Lemon yellow gold, typical of jewelry from Europe, contains more silver. White gold is obtained by alloying this metal with platinum, nickel or palladium. Moreover, the presence of nickel in the alloy makes gold a strong allergen. Red gold has long been known in Russia. It is obtained by fusion with copper. And for shine, add a little silver. There is also blue, green, purple and even black gold.

Depending on the composition of the ligature, the sample of gold is determined. Russia has its own sample scale: 375 standard - 38% gold plus copper and silver. Such gold tarnishes quickly but is easy to polish. 500 fineness - 50.5% gold plus copper and silver. This gold does not melt well and loses its luster over time. 585 standard - 59% gold plus copper, nickel, palladium and silver. Metals added percentages may vary. 750 standard - 75.5% gold plus the same ingredients as in 585 gold. This gold perfectly retains its luster and has a rich color palette. 999 standard - pure gold, no impurities. 999 gold items are the most expensive. In other countries, there is a slightly different scale for determining the ligature.

Deposits and mining Gold is the most ancient metal. People began to mine gold almost simultaneously with copper, back in the Neolithic era. But at the same time, gold is a rather rare metal. So, according to rough estimates, 165 thousand tons of gold were mined in the entire history of mankind (as of 2009). If you cast all this gold into one ingot, you get a cube with a side of 20 meters. For comparison, the same amount of iron in the world is mined in 45 minutes. The richest gold deposits are in South Africa. This is followed by China, USA, Australia and Peru. Russia is only in 6th place in this list. This is due to the fact that at one time Russia sold Alaska to America. The price (in terms of current tariffs) was $ 100 million. A few years later, the richest placers of gold were discovered in Alaska. The "gold rush" began, enriching the American economy by billions of dollars.

The richest gold deposits in Russia are found in Chukotka, in the Krasnoyarsk Territory and in the Amur Region. The method of gold mining depends on the types of deposits. For the extraction of nuggets, the flushing method is used. At deposits with scattered gold, the amalgamation method is used. If the ore containing gold contains a large amount of impurities, then gold is mined by cyanidation or regeneration. At the same time, multi-stage complex technologies are used. This work is carried out in refineries.

Use of gold Statistics states that 90 percent of mined gold is stored either in banks as the country's gold reserves, or by individuals in the form of jewelry, coins and other items. Only 10% of the mined gold is used in the industry. In electrical engineering, the surface of contacts, connectors, and also as a solder is coated with gold. Gilding of metals is used to protect them from corrosion. Gold is contained in the shell of the neutron bomb. In the food industry, gold is registered as a food additive E175.

Gold is used for glass casting. A thin gold film in the glass protects against infrared radiation. And the current passed through such a layer gives the glass anti-fog properties. This is how glass is made for ships, ships, steam locomotives, aircraft. In medicine, for the manufacture of crowns and dentures, for the manufacture of medicines. In cosmetology - for skin rejuvenation. But most of all, gold is used for making jewelry.

Gold(lat. Aurum), Au, chemical element of group 1 of the periodic system of Mendeleev; atomic number 79, atomic mass 196.9665; heavy yellow metal. Consists of one stable isotope 197 Au.

History reference. Z. was the first metal known to man. Articles made of gold have been found in the cultural layers of the Neolithic period (5th – 4th millennia BC). In the ancient states — Egypt, Mesopotamia, India, and China — mining of gold and the manufacture of jewelry and other items from it existed for 3–2 thousand BC. e. Z. is often mentioned in the Bible, the Iliad, the Odyssey, and other monuments of ancient literature. Alchemists called Z. "the king of metals" and designated him as the symbol of the sun; the discovery of methods for converting base metals into gold was the main goal alchemy.

On the development of gold mining, see Noble metals.

Prevalence in nature. The average gold content in the lithosphere is 4.3 · 10 -7% by weight. Gold is dispersed in magma and igneous rocks, but hydrothermal deposits of gold are formed from hot waters in the earth's crust, which are of great industrial importance (quartz gold-bearing veins, etc.). In ores gold is mainly found in a free (native) state (see Fig. Native gold) and only very rarely forms minerals with selenium, tellurium, antimony, bismuth. Pyrite and other sulfides often contain an admixture of gold, which is extracted during the processing of copper, polymetallic, and other ores.

In the biosphere, gold migrates in combination with organic compounds and mechanically in river suspensions. 1 liter of sea and river water contains about 4 · 10 -9 G H. In areas of gold ore deposits, groundwater contains gold approximately 10 -6 g / l. It migrates in soils and from there enters the plants; some of them concentrate gold, for example, horsetails and corn. The destruction of endogenous gold deposits leads to the formation of industrial gold placers. Gold is mined in 41 countries; its main reserves are concentrated in the USSR, South Africa and Canada.

Physical and chemical properties. Z. - soft, very ductile, ductile metal (can be forged into sheets up to 8 10 -5 mm, stretched into the wire, 2 km which weigh 1 G), conducts heat and electricity well, very resistant to chemical influences. The crystal lattice of the gold is face-centered cubic. a = 4.704 Å. The atomic radius is 1.44 Å, the ionic radius of Au 1+ is 1.37 Å. Density (at 20 ° C) 19.32 g / cm 3, t pl 1064.43 ° C, t kip 2947 ° C; thermal coefficient of linear expansion 14.2 · 10 -6 (0-100 ° C); specific thermal conductivity 311.48 tue/(m·TO) ; specific heat 132.3 j/(kg K) (at 0 -100 ° C); specific electrical resistance 2.25 · 10 -8 ohm(m(2.25 10 -6 ohm(cm) (at 20 ° C); temperature coefficient of electrical resistance 0.00396 (0-100 ° C). Elastic modulus 79 103 Mn / m 2(79 10 2 kgf / mm 2), for annealed gold. ultimate tensile strength 100-140 Mn / m 2(10-14 kgf / mm 2), elongation 30-50%, cross-sectional narrowing 90%. After plastic deformation in the cold, the tensile strength increases to 270-340 Mn / m 2 (27-34 kgf / mm 2). Brinell hardness 180 Mn / m 2 (18 kgf / mm 2) (for gold annealed at about 400 ° C).

The configuration of the outer electrons of the atom Z. 5d 10 6s 1. In compounds, gold has valences of 1 and 3 (complex compounds are known in which gold is 2-valent). Gold does not interact with non-metals (except for halogens). With halogens Z. forms halides, for example 2Au + 3Cl 2 = 2AuC13. Gold dissolves in a mixture of hydrochloric and nitric acids, forming hydrochloric acid H. In solutions of sodium cyanide NaCN (or potassium KCN), with the simultaneous access of oxygen, gold is converted into sodium cyanoaurate (I) 2Na. This reaction, discovered in 1843 by P.R. Bagration, received practical application only at the end of the 19th century. (cm. Cyanide). Gold is characterized by its easy reducibility from compounds to metal and the ability to form complexes. The existence of zinc oxide, that is, zinc oxide (I) Au 2 O, is doubtful. Gold chloride (I) AuCl is obtained by heating gold chloride (III): AuC1 3 = AuCl + C1 2.

Chloride gold (III) AuC1 3 is obtained by the action of chlorine on powder or thin sheets of gold at 200 ° C. Red needles AuC1 3 give a brown-red solution of a complex acid with water: AuC1 3 + Н 2 О = Н 2.

When the AuC1 3 solution is precipitated with a caustic alkali, the amphoteric yellow-brown hydroxide Z. (III) Au (OH) 3 with a predominance of acidic properties is precipitated; therefore it is called golden acid, and its salts are called aurat (III). When heated, gold hydroxide (III) is converted into gold oxide Au 2 O 3, which decomposes above 220 according to the reaction:

2Au 2 O 3 = 4Au + 3O 2.

In the reduction of gold salts with tin (II) chloride 2AuC1 3 + 3SnCl 2 = 3SnCl 4 + 2Au

a very stable purple colloidal solution of gold is formed (cassian purple); this is used in analysis for the detection of gold. The quantitative determination of gold is based on its precipitation from aqueous solutions by reducing agents (FeSO 4, H 2 SO 3, H 2 C 2 O 4, etc.) or on the use of assay analysis.

Getting Z. and its refining. Gold can be extracted from placer deposits by elutriation, based on the large difference in the densities of gold and waste rock. This method, which was already used in ancient times, is associated with great losses. He made way amalgamation(known already in the 1st century BC and used in America from the 16th century) and cyanidation, which became widespread in America, Africa and Australia in the 1890s. In the late 19th - early 20th centuries. Primary deposits became the main source of gold. Gold-bearing rock is first subjected to crushing and beneficiation. Gold is extracted from the resulting concentrate with a solution of potassium or sodium cyanide. Zinc is precipitated from the complex cyanide solution; in this case, impurities also fall out. For purification (refining) of gold by electrolysis (E. Wolville's method, 1896), anodes cast from unclean gold are suspended in a bath containing a hydrochloric acid solution of AuCl 3; a sheet of pure gold serves as the cathode.When current flows, impurities precipitate (anode sludge , sludge), and gold is deposited on the cathode with a purity of at least 99.99%.

Application. Z. in the conditions of commodity production performs the function money(see section Economic significance). In technology, gold is used in the form of alloys with other metals, which increases the strength and hardness of gold and makes it possible to save it. Gold alloys The gold content in alloys used for the manufacture of jewelry, coins, medals, semi-finished products of denture production, etc., is expressed by the breakdown (see. Try precious metals, Jewelry alloys); usually the additive is copper (the so-called ligature). Alloyed with platinum, gold is used in the manufacture of chemically resistant equipment, and alloys with platinum and silver in electrical engineering. Gold compounds are used in photography (toning).

S. A. Pogodin.

Z . in art. Z. has been used since ancient times in jewelry art(decorations, cult and palace utensils, etc.), as well as for gilding... Due to its softness, malleability, and its ability to stretch, gold lends itself to particularly fine processing by chasing, casting, and engraving. Z. is used to create a variety of decorative effects (from the smooth surface of a yellow polished surface with smooth tints of light reflections to complex textured comparisons with a rich light and shadow play), as well as to perform the finest filigree... Z., often colored with impurities of other metals in various colors, is used in combination with precious and semi-precious stones, pearls, enamel, rabble.

In medicine, Z. preparations are used in the form of a suspension in oil (the domestic drug Krizanil, the foreign one, myocrizin) or water-soluble drugs (foreign ones, Sankrizin and Solganal) for injection in the treatment of chronic rheumatic arthritis, erythematous lupus erythematosus, often in combination with hormonal drugs, etc. drugs. Z. preparations often cause side effects (an increase in body temperature, irritation of the intestines, kidneys, etc.). Contraindications to the use of medicinal products: severe forms of tuberculosis, diabetes mellitus, diseases of the cardiovascular system, liver, kidneys, and blood.

Radioactive gold (most often 198 Au) is injected into tissues in the form of pins, granules, and the like. - for gamma therapy and in the form of colloidal solutions - for beta therapy... It is used in the treatment of tumors, usually in combination with surgical and drug treatment, as well as for diagnostic purposes - in the form of colloidal solutions in the study of the reticuloendothelial system, liver, spleen, and other organs.

Lit .: Plaksin IN, Gold, in the book: Brief chemical encyclopedia, vol. 2, M., 1966; Remy G., Course in inorganic chemistry, trans. from it., t. 2, M., 1966, p. 439-451; Ullmanns Enzykiopädie dertechnischen Chemie, 3 Aufl., Bd 8, Münch. - B., 1957, S. 253-307; Magakyan I.G., Ore Deposits, 2nd ed., Er., 1961; Russian gold and silver business of the 15-20 centuries, M., 1967 (bibl. Pp. 289-93); Rosenberg M., Geschichte der Goldschmiedekunst auf technischer Grundlage, Fr./M., 1918.

Economic significance. Under conditions of commodity production, gold performs the function of a universal equivalent. "The first function of gold is to provide the commodity world with material for expressing value, that is, in order to express the value of goods as quantities of the same name, qualitatively the same and quantitatively comparable" (K. Marx, in the book: K. and F. Engels, Soch., 2nd ed., vol. 23, p. 104). Expressing the value of all other commodities, gold as a universal equivalent acquires a special use value, becomes money. "Gold and silver by their nature are not money, but money by their nature - gold and silver" (K. Marx, ibid., Vol. 13, p. 137). The world of commodities singled out gold as money because it possesses the best physical and chemical properties for a money commodity: homogeneity, divisibility, preservation, portability (high value for a small volume and weight), and can be easily processed. A significant amount of gold is used for the manufacture of coins or in the form of ingots is stored as a gold reserve of central banks (states). Gold is widely used for industrial consumption (in radio electronics, instrument making, and other progressive industries) and also as a material for making jewelry.

Initially, gold was used exclusively for making ornaments; later, it began to serve as a means of saving and accumulating wealth, as well as exchange (first in the form of ingots). Gold was used as money as early as 1500 BC. e. in China, India, Egypt and the states of Mesopotamia, and in Ancient Greece - in the 8-7 centuries. BC e. In Lydia, rich in gold deposits, in the 7th century. BC e. the minting of the first coins in history began. The name of the Lydian king Croesus (reigned about 560-546 BC) has become synonymous with untold wealth. On the territory of the USSR (in Armenia) coins from Z. were minted in the 1st century. BC e. But in antiquity and in the Middle Ages, gold was not the main currency metal. Along with it, the functions of money were performed by copper and silver.

The pursuit of Z. and a passion for enrichment were the reasons for numerous colonial and trade wars, and during the era of the great geographical discoveries they were pushed to search for new lands. The flow of precious metals to Europe after the discovery of America was one of the sources initial capital accumulation... Until the middle of the 16th century. From the New World, gold was imported to Europe mainly (97-100% of the imported metal), and from the second third of the 16th century, after the discovery of the richest silver deposits in Mexico and Peru, it was mainly silver (85-99%). In Russia at the beginning of the 19th century. new deposits of gold began to be developed in the Urals and Siberia, and for three decades the country occupied the first place in the world in its production. In the middle of the 19th century. rich gold deposits were discovered in the USA (California) and Australia; in the 1880s. - in the Transvaal (South Africa). The development of capitalism and the expansion of intercontinental trade increased the demand for money metals, and although gold production increased, in all countries, along with gold, silver continued to be widely used as money. At the end of the 19th century. there was a sharp decline in the cost of silver due to the improvement of methods for its extraction from polymetallic ores. The growth of world gold production, and especially its influx into Europe and the United States from Australia and Africa, hastened the ousting of depreciated silver and created the conditions for the transition of most countries to monometallism (gold) in its classic form of the gold coin standard (see Fig. gold standard). The first to go over to gold monometallism at the end of the 18th century. Great Britain. Head of the 20th century the gold currency has established itself in most countries of the world.

Reflecting the relations of people in the conditions of spontaneous commodity production, the power of wealth appears on the surface of phenomena as a relation of things, seems to be a natural intrinsic property of wealth and gives rise to gold and money fetishism (see Sect. Money, Commodity fetishism). The passion for the accumulation of gold wealth grows endlessly, pushes one to monstrous crimes. The power of the land increases especially under capitalism, when labor power becomes a commodity. Education under capitalism of the world market expanded the sphere of circulation of gold and made it world money.

During the general crisis of capitalism, the gold standard is undermined. In the internal circulation of the capitalist countries, paper money and banknotes irredeemable for gold are becoming dominant. The export of gold and its purchase and sale are limited or prohibited altogether. In this regard, gold ceases to perform the functions of a medium of circulation and a means of payment, but, acting ideally as a measure of value, and also retaining the value of a means of forming treasures and world money, it remains the basis of monetary systems and the main means of final settlement of mutual monetary claims and obligations of capitalist countries. ... The size of gold reserves is an important indicator of the stability of capitalist currencies and the economic potential of individual countries (see also gold reserve, Gold reserves). The purchase and sale of gold for industrial consumption, as well as for private saving (accumulation), is carried out in special gold markets (see. Gold Markets). The loss of gold from the free interstate market circulation caused a reduction in its share in the currency system of the capitalist world and, above all, in the foreign exchange reserves of the capitalist countries (from 89% in 1913 to 71% in 1928, 69% in 1958, and 55% in 1969). An increasingly significant part of the newly mined gold is supplied for tezavration and industrial use (in the modern chemical industry, for rocketry, and space technology). For example, in 1960-70 the private use of gold increased 3.3 times, its industrial and jewelry use almost 2.3 times, the gold reserves of the capitalist countries remained practically at the same level ($ 41 billion). (On gold mining in capitalist countries, see Art. Gold mining industry.)

Under the conditions of a socialist economy, gold is also a universal equivalent, acting as a measure of value and a scale of prices. Since January 1, 1961, the gold content of the Soviet ruble is set at 0.987412 G net gold. The same amount of gold is the basis of the transferable ruble, the international socialist currency of the CMEA member countries. In the world socialist market, gold performs the function of world money.

Lit .: Mikhalevsky F. I., Gold during the World Wars, [M.], 1945; his, Gold in the system of capitalism after the Second World War, M., 1952; Borisov S.M., Gold in the economy of modern capitalism, M., 1968.

A.I. Stadnichenko.

Hello! Gold is a chemical element that has claimed many lives. During the construction of St. Isaac's Cathedral in St. Petersburg, the domes were gilded with gold amalgam. Architect Auguste Montferrand took measures to protect workers from mercury fumes, but realized that they were doomed. But the domes will never have to be gilded again.

And so it happened: all 60 people died from poisoning, and since then the cathedral has never been gilded.

A cubic kilometer of sea water contains 5 kg of the desired element, and if you prick your finger and squeeze out a drop of blood, it will contain 0.00025 mg of gold. 10 mg is contained in the human skeleton: if you set out to melt a ring out of humans, you only need 300 people. But this gold is in the environment in such a scattered form that it is unprofitable and often impossible to extract it from there.

Deposits suitable for gold mining are primary (postmagmatic) and secondary (alluvial).

Primary deposits

The chemical element Au is rich in magma - the melt inside the globe. Gold is found in the upper layers of the mantle and partially in the earth's crust (however, it contains almost the entire periodic table). Magma comes out to the surface of the planet, cools down and turns into solid rock. The places where it contains so much of a precious element that industrial development will pay off, and there are primary deposits.

Natural gold is found in the form of nuggets - whole grains of a chemically pure substance. It is often combined with other elements (magma contains almost everything):

silver;
copper;
metals of the platinum group;
bismuth and others.

Secondary deposits

Secondary deposits are the result of the destruction of primary deposits, the so-called weathering, which happens:

physical (the reason is wind, water, temperature fluctuations);
chemical (chemical reactions);
biological (bacteria and other organisms).

A placer of pure gold looks like sand and is sometimes treated by waters for many kilometers from the primary deposit.

Item discovery history

In its pure form, gold fell into the hands of man in the 6th century BC. Massive development of African deposits began earlier - around 2000 BC. e., but there were no methods of getting rid of impurities, and gold items of that time have a low standard.

In late antiquity (the beginning of our era), alchemy began to spread around the world with its desire to convert non-precious chemical elements into noble ones. She did not succeed, but thanks to her modern civilization owns many wonders - for example, the technique of extracting chemically pure gold from ore.

The Latin name for gold is Aurum (read as aurum) - "yellow". It is accepted as international. The symbol of the sun in alchemists looked like a circle with a dot inside, and in modern chemistry it is denoted by the abbreviation Au.

How do you get

The main methods for producing gold on an industrial scale complement each other - for example, the concentrate can be cleaned of dense impurities by amalgamation.

Flushing

Flushing (dressing) is an ancient method of extraction from secondary deposits. The sand is washed out due to its density: less dense minerals are washed out with water, and the concentrate settles.

Large-scale gold mining is automated: washing devices and excavators work instead of people. However, their principle of operation has hardly changed over the past 2000 years.

Schlich is not pure gold. There are elements that are denser - they settle with sand at the bottom of the wash tank. For final cleaning, other, in particular chemical, methods are used.

Amalgamation

This method has also been known since antiquity, but was described in the 16th century. It is possible due to the property of mercury to form alloys (amalgams) with other metals without additional thermal or chemical effects. After getting rid of the waste rock fragments, the chemical elements are mechanically separated.

Expert opinion

Vsevolod Kozlovsky

6 years in jewelry. Knows everything about samples and can identify a fake in 12 seconds

Amalgamation is not used everywhere: in a number of countries (since 1988 - in Russia) it is forbidden to use mercury because of the mortal danger of this element to humans.

Cyanide

The method of extracting a precious element from ore by cyanidation is based on the ability of gold to dissolve in hydrocyanic acid (hydrogen cyanide, HCN) and its salts. The ore is processed with a weak (0.03–0.3%) cyanide solution. The noble metal reacts earlier than other chemical elements, and after a chemical reaction it precipitates out of solution.

Physical and chemical properties

: in its pure form does not form oxides, does not corrode. He also has:

high density - 19.32 g / cm³;
medium melting point (melting temperature in the range 600–1600 ° С - 1064.43 ° С);
low hardness - 2.5 points on the Mohs scale;
high malleability (thanks to it, gilding is created);
high plasticity, ductility.

Place of gold in the periodic table

The element is located in the XI group (copper subgroup), the VI period of the periodic table of chemical elements.

The atomic number (charge number) of gold is 79. This is the number of protons in the nucleus of an atom, equal to the number of electrons revolving around the nucleus. The atomic mass - the total mass of protons and neutrons (atomic nuclei) - for gold is equal to 196.9665 amu. (atomic mass units). Natural gold exists as a chemically stable isotope 197 Au. All others are unstable and possible only in a nuclear reactor.

Formula

Gold does not have its own chemical formula, since it exists in the form of monoatomic molecules. The electronic configuration of the Au atom is written as 4f14 5d10 6s1 and denotes the exact distribution of electrons in orbitals.

5interaction with acids

Due to its inertness (not absolute, but significant), gold does not dissolve in acids. This allows them to be used for refining (chemical purification of an element from impurities): the alloy is treated with an acid, for example, nitric acid, and thus gets rid of the ligature.

But there are exceptions. Pure gold is dissolved by acids:

selenium;
hydrocyanic acid and its salts (cyanides);
nitrogen mixed with hydrochloric acid (aqua regia).

Oxidation states and bond with halogens

Under natural conditions, Au does not oxidize when exposed to oxygen - this is one of the properties that make the element precious. When heated, gold interacts with halogens (elements of group XVII): iodine, fluorine, bromine and chlorine, forming iodide, fluoride, bromide and chloride, respectively.

The standard oxidation states are 1 and 3. In laboratory conditions, fluoride with an oxidation state of +5 was removed.

Gold purity measures

States control the turnover of precious metals. A century ago, almost every country had its own probing system, but now the majority has been brought to a common denominator.

British carat system

In the carat system (USA, Canada, Switzerland), the number 24 is taken as 100%. The 18 K stigma indicates that the jewelry consists of 75% of precious metal, and 25% of something else - for example, copper and palladium ...

Metric system

In Russia, the CIS, Germany, the number on the stamp is the number of ppm (thousandths) of gold in the alloy. 500 ‰ - fineness 500, 375 ‰ -375. There is only a sample of 1000 - instead of it 999.9. It contains a microscopic amount of impurities and is conventionally considered pure.

Spool system

The spool-type sampling system operated in the Russian Empire, the RSFSR and the USSR in 1798–1927. It is based on the Russian pound, which is equal to 96 spools, is similar to the carat mathematically, but divides the whole not into 24, but into 96 parts.

Sample correspondence table

Let's look at three systems in comparison. There is also a lot test - it essentially repeats the carat test, but takes 16 units (lot) for one hundred percent. The lot test was used for silver assaying in Europe before the introduction of the metric system and is not related to gold.

Alloys with other metals

In industry, they are used in silver, platinum, palladium, nickel and other metals. The master alloy changes the properties of the alloy. Platinum and palladium give it a white color, zinc and cadmium lower the melting point (but zinc makes the alloy brittle, but cadmium does not), copper turns red and makes it harder.

Application

You cannot imagine without gold:

jewelry making;
Information Technology;
petrochemical production;
production of measuring instruments;
electronics and microelectronics;
pharmacology;
nuclear research.

Until now, gold has not lost its original purpose - it is used to save and increase funds.

How to distinguish a fake

In order to weld, presenting products from base alloys as valuable, fraudsters resort to tricks: they burn silver on a fire, combine copper with zinc and tin. Pay attention to:

Brand - it must comply with the standard.
Price - if it's incredibly low, it's a red flag.
Country of origin - check the jewelry once again if it is Turkey, China or the United Arab Emirates.

There are advice to try a thing on a tooth with a seller or test it chemically by dropping iodine on it. These are effective methods for determining the authenticity of high samples, but they are not always acceptable in society. If the seller raises doubts in you so much that you are ready to bite his product, you should refuse to buy.

Conclusion

Do not put gold in mercury or spill hydrocyanic acid on it - it will last longer. And also subscribe to my articles and share them with your friends!

Gold(lat. aurum), au, chemical element of group 1 of Mendeleev's periodic system; atomic number 79, atomic mass 196.9665; heavy yellow metal. Consists of one stable isotope 197 au.

History reference. Z. was the first metal known to man. Articles made of gold have been found in the cultural layers of the Neolithic period (5th – 4th millennia BC). In the ancient states — Egypt, Mesopotamia, India, and China — mining of gold and the manufacture of jewelry and other items from it existed for 3–2 thousand BC. e. Z. is often mentioned in the Bible, the Iliad, the Odyssey, and other monuments of ancient literature. Alchemists called Z. "the king of metals" and designated him as the symbol of the sun; the discovery of methods for converting base metals into gold was the main goal alchemy.

Prevalence in nature. The average gold content in the lithosphere is 4.3 · 10 -7% by weight. Gold is dispersed in magma and igneous rocks, but hydrothermal deposits of gold are formed from hot waters in the earth's crust, which are of great industrial importance (quartz gold-bearing veins, etc.). In ores gold is mainly found in a free (native) state and only very rarely forms minerals with selenium, tellurium, antimony, and bismuth. Pyrite and other sulfides often contain an admixture of gold, which is extracted during the processing of copper, polymetallic, and other ores.

In the biosphere, gold migrates in combination with organic compounds and mechanically in river suspensions. one l sea and river water contains about 4 · 10 -9 G H. In areas of gold ore deposits, groundwater contains gold approximately 10 -6 g / l. It migrates in soils and from there enters the plants; some of them concentrate gold, for example, horsetails and corn. The destruction of endogenous gold deposits leads to the formation of industrial gold placers. Gold is mined in 41 countries; its main reserves are concentrated in the USSR, South Africa and Canada.

Physical and chemical properties. Z. - soft, very ductile, ductile metal (can be forged into sheets up to 8 10 -5 mm, stretched into the wire, 2 km which weigh 1 G), conducts heat and electricity well, very resistant to chemical influences. The crystal lattice of the gold is face-centered cubic. a = 4.704 a. Atomic radius 1.44 a, ionic radius au 1+ 1.37 a. Density (at 20 ° C) 19.32 g / cm 3, t pl 1064.43 ° C, t kip 2947 ° C; thermal coefficient of linear expansion 14.2 · 10 -6 (0-100 ° C); specific thermal conductivity 311.48 tue/(m· TO) ; specific heat 132.3 j/(kg K) (at 0 ° -100 ° C); specific electrical resistance 2.25 · 10 -8 ohm(m(2.25 10 -6 ohm(cm) (at 20 ° C); temperature coefficient of electrical resistance 0.00396 (0-100 ° С). Elastic modulus 79 103 Mn / m 2(79 10 2 kgf / mm 2), for annealed gold. tensile strength 100-140 Mn / m 2(10-14 kgf / mm 2), elongation 30-50%, cross-sectional narrowing 90%. After plastic deformation in the cold, the tensile strength increases to 270-340 Mn / m 2 (27-34 kgf / mm 2) . Brinell hardness 180 Mn / m 2 (18 kgf / mm 2) (for gold annealed at about 400 ° C).

The configuration of the outer electrons of the atom Z. 5d 10 6s 1. In compounds, gold has valences of 1 and 3 (complex compounds are known in which gold is 2-valent). Gold does not interact with non-metals (except for halogens). With halogens Z. forms halides, for example 2au + 3cl 2 = 2auc13. Gold dissolves in a mixture of hydrochloric and nitric acids, forming hydrochloric acid h. In solutions of sodium cyanide nacn (or potassium kcn), with the simultaneous access of oxygen, gold is converted into sodium cyanoaurate (i) 2na. This reaction, discovered in 1843 by P.R. Bagration, received practical application only at the end of the 19th century. Gold is characterized by its easy reducibility from compounds to metal and the ability to form complexes. The existence of gold oxide, that is, gold oxide (i) au 2 o, is doubtful. Z. chloride (i) aucl is obtained by heating Z. chloride (iii): auc1 3 = aucl + c1 2.

Chloride Z. (iii) auc1 3 is obtained by the action of chlorine on powder or thin leaves of Z. at 200 ° C. Red needles auc1 3 give a brown-red solution of complex acid with water: auc1 3 + Н 2 О = Н 2.

When the solution of auc1 3 precipitates with a caustic alkali, the amphoteric yellow-brown hydroxide Z. (iii) au (oh) 3 with a predominance of acidic properties is precipitated; therefore it is called golden acid, and its salts are called aurat (iii). When heated, gold hydroxide (iii) is converted to gold oxide au 2 o 3, which decomposes above 220 ° by the reaction:

2au 2 o 3 = 4au + 3o 2.

In the reduction of gold salts with tin (ii) chloride 2auc1 3 + 3sncl 2 = 3sncl 4 + 2au

a very stable purple colloidal solution of gold is formed (cassian purple); this is used in analysis for the detection of gold. The quantitative determination of gold is based on its precipitation from aqueous solutions by reducing agents (feso 4, h 2 so 3, h 2 c 2 o 4, etc.) or on the use of assay analysis.

Getting Z. and its refining. Gold can be extracted from placer deposits by elutriation, based on the large difference in the densities of gold and waste rock. This method, which was already used in ancient times, is associated with great losses. He made way amalgamation(known already in the 1st century BC and used in America from the 16th century) and cyanidation, which became widespread in America, Africa and Australia in the 1890s. In the late 19th - early 20th centuries. Primary deposits became the main source of gold. Gold-bearing rock is first subjected to crushing and beneficiation. Gold is extracted from the resulting concentrate with a solution of potassium or sodium cyanide. Zinc is precipitated from the complex cyanide solution; in this case, impurities also fall out. For purification (refining) of gold by electrolysis (E. Wolville's method, 1896), anodes cast from unclean gold are suspended in a bath containing a hydrochloric acid solution of auc1 3; a sheet of pure gold serves as the cathode.When current flows, impurities precipitate (anode sludge , sludge), and gold is deposited on the cathode with a purity of at least 99.99%.

Application ... Z. in the conditions of commodity production performs the function money... In technology, gold is used in the form of alloys with other metals, which increases the strength and hardness of gold and makes it possible to save it. The gold content in alloys used for the manufacture of jewelry, coins, medals, semi-finished products of denture production, etc., is expressed by breakdown; usually the additive is copper (the so-called ligature). Alloyed with platinum, gold is used in the manufacture of chemically resistant equipment, and alloys with platinum and silver in electrical engineering. Gold compounds are used in photography (toning).

S. A. Pogodin.

Z. in art. Z. has been used since ancient times in jewelry art(decorations, cult and palace utensils, etc.), as well as for gilding. Due to its softness, malleability, and its ability to stretch, gold lends itself to particularly fine processing by chasing, casting, and engraving. Z. is used to create a variety of decorative effects (from the smooth surface of a yellow polished surface with smooth tints of light reflections to complex textured comparisons with a rich light and shadow play), as well as to perform the finest filigree. Z., often colored with impurities of other metals in various colors, is used in combination with precious and ornamental stones, pearls enamel, niello.

Radioactive gold (usually 198 au) is injected into tissues in the form of pins, granules, and the like. - for gamma therapy and in the form of colloidal solutions - for beta therapy. It is used in the treatment of tumors, usually in combination with surgical and drug treatment, as well as for diagnostic purposes - in the form of colloidal solutions in the study of the reticuloendothelial system, liver, spleen, and other organs.

Lit .: Plaksin IN, Gold, in the book: Brief chemical encyclopedia, t. 2, M., 1966; Remy G., Course in inorganic chemistry, trans. from it., t. 2, M., 1966, p. 439-451; ullmanns enzykiop a die dertechnischen chemie, 3 aufl., bd 8, m u nch. - b., 1957, s. 253-307; Magakyan I.G., Ore Deposits, 2nd ed., Er., 1961; Russian gold and silver business of the 15-20 centuries, M., 1967 (bibl. Pp. 289-93); rosenberg M., geschichte der goldschmiedekunst auf technischer grundlage, fr./m., 1918.

Economic significance. Under conditions of commodity production, gold performs the function of a universal equivalent. "The first function of gold is to deliver to the commodity world material for expressing value, that is, in order to express the value of goods as quantities of the same name, qualitatively identical and quantitatively comparable" (K. Marx, in the book: K. and F. Engels, Soch., 2nd ed., vol. 23, p. 104). Expressing the value of all other commodities, gold as a universal equivalent acquires a special use value, becomes money. "Gold and silver by their nature are not money, but money by their nature - gold and silver" (K. Marx, ibid., Vol. 13, p. 137). The world of commodities singled out gold as money because it possesses the best physical and chemical properties for a money commodity: homogeneity, divisibility, preservation, portability (high value for a small volume and weight), and can be easily processed. A significant amount of gold is used for the manufacture of coins or in the form of ingots is stored as a gold reserve of central banks (states). Gold is widely used for industrial consumption (in radio electronics, instrument making, and other progressive industries) and also as a material for making jewelry.

The pursuit of Z. and a passion for enrichment were the reasons for numerous colonial and trade wars, and during the era of the great geographical discoveries they were pushed to search for new lands. The flow of precious metals to Europe after the discovery of America was one of the sources initial capital accumulation. Until the middle of the 16th century. From the New World, gold was imported to Europe mainly (97-100% of the imported metal), and from the second third of the 16th century, after the discovery of the richest silver deposits in Mexico and Peru, it was mainly silver (85-99%). In Russia at the beginning of the 19th century. new deposits of gold began to be developed in the Urals and Siberia, and for three decades the country occupied the first place in the world in its production. In the middle of the 19th century. rich gold deposits were discovered in the USA (California) and Australia; in the 1880s. - in the Transvaal (South Africa). The development of capitalism and the expansion of intercontinental trade increased the demand for money metals, and although gold production increased, in all countries, along with gold, silver continued to be widely used as money. At the end of the 19th century. there was a sharp decline in the cost of silver due to the improvement of methods for its extraction from polymetallic ores. The growth of world gold production, and especially its influx into Europe and the United States from Australia and Africa, hastened the ousting of depreciated silver and created the conditions for the transition of most countries to monometallism (gold) in its classical form of the gold coin standard. The first to go over to gold monometallism at the end of the 18th century. Great Britain. Head of the 20th century the gold currency has established itself in most countries of the world.

Reflecting the relations of people in the conditions of spontaneous commodity production, the power of wealth appears on the surface of phenomena as the relation of things, seems to be a natural intrinsic property of wealth and gives rise to gold and money fetishism. . The passion for the accumulation of gold wealth grows endlessly, pushes one to monstrous crimes. The power of the land increases especially under capitalism, when labor power becomes a commodity. Education under capitalism of the world market expanded the sphere of circulation of gold and made it world money.

During the general crisis of capitalism, the gold standard is undermined. In the internal circulation of the capitalist countries, paper money and banknotes irredeemable for gold are becoming dominant. The export of gold and its purchase and sale are limited or prohibited altogether. In this regard, gold ceases to perform the functions of a medium of circulation and a means of payment, but, acting ideally as a measure of value, and also retaining the value of a means of forming treasures and world money, it remains the basis of monetary systems and the main means of final settlement of mutual monetary claims and obligations of capitalist countries. ... The size of gold reserves is an important indicator of the stability of capitalist currencies and the economic potential of individual countries. . The purchase and sale of gold for industrial consumption, as well as for private collection (accumulation), is carried out in special gold markets. The loss of gold from the free interstate market circulation caused a reduction in its share in the currency system of the capitalist world and, above all, in the foreign exchange reserves of the capitalist countries (from 89% in 1913 to 71% in 1928, 69% in 1958, and 55% in 1969). An increasingly significant part of the newly mined gold is supplied for tezavration and industrial use (in the modern chemical industry, for rocketry, and space technology). For example, in 1960-70 the private use of gold increased 3.3 times, its industrial and jewelry use almost 2.3 times, the gold reserves of the capitalist countries remained practically at the same level ($ 41 billion). (On gold mining in capitalist countries, see Art. Gold mining industry.)

GOLD (chemical element) GOLD (chemical element)

GOLD (lat.Aurum ) , Au (read "aurum"), a chemical element with atomic number 79, atomic mass 196.9665. It has been known since ancient times. In nature, there is one stable isotope, 197 Au. Configuration of outer and pre-outer electronic enclosures 5 s 2 p 6 d 10 6s one . Located in group IВ and in the 6th period of the periodic table, it belongs to the noble metals. Oxidation states 0, +1, +3, +5 (valencies from I, III, V).
The metal radius of the gold atom is 0.137 nm, the radius of the Au + ion is 0.151 nm for the coordination number 6, the Au 3+ ion is 0.084 nm and 0.099 nm for the coordination numbers 4 and 6. Ionization energies Au 0 - Au + - Au 2+ - Au 3 + are respectively equal to 9.23, 20.5 and 30.47 eV. Pauling electronegativity (cm. POLING Linus) 2,4.
Being in nature
The content in the earth's crust is 4.3 · 10 -7% by weight, in the water of the seas and oceans less than 5 · 10 -6% mg / l. Refers to scattered elements. More than 20 minerals are known, of which the main one is native gold (electrum, cuprous, palladium, bismuth gold). Large nuggets are extremely rare and usually have personal names. Chemical compounds of gold are rare in nature, mainly tellurides - kaleverite AuTe 2, krennerite (Au, Ag) Te 2, and others. Gold can be present as an impurity in various sulfide minerals: pyrite (cm. PYRITE), chalcopyrite (cm. HALCOPIRITE), sphalerite (cm. SPHALERITE) and others.
Modern methods of chemical analysis make it possible to detect the presence of trace amounts of Au in the organisms of plants and animals, in wines and cognacs, in mineral waters and in sea water.
Discovery history
Gold has been known to mankind since ancient times. Perhaps it was the first metal that a person met. There is data on the extraction of gold and the manufacture of products from it in Ancient Egypt (4100-3900 BC), India and Indochina (2000-1500 BC), where money, expensive jewelry, works were made from it. cult and art.
Receiving
Sources of gold in its industrial production are ores and sands of gold placer and primary deposits, the gold content of which is 5-15 g per ton of starting material, as well as intermediate products (0.5-3 g / t) of lead-zinc, copper, uranium and some other industries.
The process of obtaining gold from placers is based on the difference in density between gold and sand. With the help of powerful jets of water, the crushed gold-bearing rock is transferred to a suspended state in water. The resulting pulp flows down an inclined plane in a dredge. In this case, heavy particles of gold settle, and grains of sand are carried away by the water.
In another way, gold is extracted from ore by treating it with liquid mercury and obtaining a liquid alloy - amalgam. Then the amalgam is heated, the mercury evaporates, and the gold remains. The cyanide method for extracting gold from ores is also used. In this case, gold-bearing ore is treated with sodium cyanide NaCN solution. In the presence of atmospheric oxygen, gold goes into solution:
4Au + O 2 + 8NaCN + 2H 2 O = 4Na + 4NaOH
Next, the resulting solution of the gold complex is treated with zinc dust:
2Na + Zn = Na 2 + NO + H 2 O
followed by selective precipitation of gold from solution, for example, using FeSO 4.
Physical and chemical properties
Gold is a yellow metal with a cubic face-centered lattice ( a= 0.40786 nm). Melting point 1064.4 ° C, boiling point 2880 ° C, density 19.32 kg / dm 3. Possesses exceptional plasticity, thermal conductivity and electrical conductivity. A ball of gold with a diameter of 1 mm can be flattened into the thinnest sheet, translucent bluish-green, with an area of 50 m 2. The thickness of the thinnest gold leaves is 0.1 microns. The finest threads can be drawn out of gold.
Gold is stable in air and water. With oxygen (cm. OXYGEN), nitrogen (cm. NITROGEN), hydrogen (cm. HYDROGEN), phosphorus (cm. PHOSPHORUS), antimony (cm. ANTIMONY) and carbon (cm. CARBON) does not directly interact. Antimonide AuSb 2 and gold phosphide Au 2 P 3 are obtained indirectly.
In the series of standard potentials, gold is located to the right of hydrogen; therefore, it does not react with non-oxidizing acids. Dissolves in hot selenic acid:
2Au + 6H 2 SeO 4 = Au 2 (SeO 4) 3 + 3H 2 SeO 3 + 3H 2 O,
in concentrated hydrochloric acid when passing through a chlorine solution:
2Au + 3Cl 2 + 2HCl = 2H
Upon careful evaporation of the resulting solution, yellow crystals of hydrochloric acid HAuCl 4 3H 2 O can be obtained.
With halogens (cm. HALOGENS) without heating, in the absence of moisture, gold does not react. When gold powder is heated with halogens or with xenon difluoride, gold halides are formed:
2Au + 3Cl 2 = 2AuCl 3,
2Au + 3XeF 2 = 2AuF 3 + 3Xe
Only AuCl 3 and AuBr 3 are soluble in water, consisting of dimeric molecules:
Thermal decomposition of hexafluoroaurates (V), for example, O 2 + - obtained gold fluorides AuF 5 and AuF 7. They can also be obtained by oxidizing gold or its trifluoride with KrF 2 and XeF 6.
Gold monohalides AuCl, AuBr, and AuI are formed when the corresponding higher halides are heated in vacuum. When heated, they either decompose:
2AuCl = 2Au + Cl 2
or disproportionate:
3AuBr = AuBr 3 + 2Au.
Gold compounds are unstable and hydrolyze in aqueous solutions, easily reducing to metal.
Gold (III) hydroxide Au (OH) 3 is formed by adding alkali or Mg (OH) 2 to a solution of H:
H + 2Mg (OH) 2 = Au (OH) 3 Ї + 2MgCl 2 + H 2 O
When heated, Au (OH) 3 readily dehydrates, forming gold (III) oxide:
2Au (OH) 3 = Au 2 O 3 + 3H 2 O
Gold (III) hydroxide exhibits amphoteric properties by reacting with solutions of acids and alkalis:
Au (OH) 3 + 4HCl = H + 3H 2 O,
Au (OH) 3 + NaOH = Na
Other oxygen compounds of gold are unstable and easily form explosive mixtures. The compound of gold (III) oxide with ammonia Au 2 O 3 · 4NH 3 - "explosive gold", explodes when heated.
When gold is reduced from dilute solutions of its salts, as well as when gold is electrically sprayed in water, a stable colloidal solution of gold is formed:
2AuCl 3 + 3SnCl 2 = 3SnCl 4 + 2Au
The color of colloidal solutions of gold depends on the degree of dispersion of gold particles, and the intensity on their concentration. Gold particles in solution are always negatively charged.
Application
Gold and its alloys are used for the manufacture of jewelry, coins, medals, dentures, parts of chemical equipment, electrical contacts and wires, microelectronic products, for cladding pipes in the chemical industry, in the production of solders, catalysts, watches, for dyeing glasses, making feathers for fountain pens, coating on metal surfaces. Usually, gold is used in an alloy with silver or palladium (white gold; also called an alloy of gold with platinum and other metals). The gold content in the alloy is designated by the state mark. Gold 583 assay value is an alloy with 58.3% gold by weight. See also Gold (in economics) (cm. GOLD (in economy)).
Physiological action
Some gold compounds are toxic, accumulate in the kidneys, liver, spleen and hypothalamus, which can lead to organic diseases and dermatitis, stomatitis, thrombocytopenia.

encyclopedic Dictionary. 2009 .

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