Zinc or Zincum is the 30th element of Mendeleev's Periodic Table of Chemical Elements and is denoted by the symbol Zn. It is mainly used in the creation of deformed semi-finished products and as part of various kinds of mixtures. In its pure form, it looks like a brittle metal of a bluish-silver color, quickly oxidizes and becomes covered with a protective film (oxide), due to which it noticeably tarnishes.
It is mined in Kazakhstan, Australia, Iran and Bolivia. Due to the difficulties in determining the metal of its often referred to as "cheating".
History reference
The name "zinc" itself was first mentioned in the book "Liber Mineralium" by Paracelsus. According to some sources, it meant "tooth". An alloy of zinc with copper or brass has long been known. It was used in ancient Greece, India and ancient Egypt, later the material became known in China.
In its pure form, the metal was obtained only in the first half of the 18th century in 1738 in Great Britain using the distillation method. William Champion became its discoverer. Industrial production began after 5 years, and in 1746 in Germany, the chemist Andreas Sigismund Marggraf developed and described in detail his own method for obtaining zinc. He suggested using the method of calcining a mixture of metal oxide with coal in refractory clay retorts without air access. The subsequent condensation of the vapors had to take place in a refrigerator. Because of his detailed description and painstaking development, Marggraf is often credited as the discoverer of the substance.
At the beginning of the 19th century, a method was found to isolate the metal by rolling at 100 C o -150 C o. At the beginning of the next century, they learned how to extract zinc by the electrolytic method. In Russia, the first metal was received only in 1905.
Physical properties
- Atomic number: 30.
- Atomic mass: 65.37.
- Atomic Volume: 9.15
- Density: 7.133 g/cm3.
- Temperature required for melting: 419.5 C about.
- Boiling point: 906 C about.
- Surface energy: 105 mJ/m 2 .
- Specific electrical conductivity: 16.2 * 10 -6 Sm / m.
- Molar heat capacity: 25.4 J / (K * mol).
- Molar volume: 9.2 cm 3 /mol.
Zinc has weak mechanical properties, easily breaks and crumbles at normal temperatures, but at a temperature of 100 C o -150 C o becomes quite malleable and easily deformed: it is forged, rolled into sheets. Plain water is safe for metal, while acids and alkalis corrode easily. Because of this, zinc in its pure form is not used for the manufacture of parts, only alloys.
Chemical properties
The external electronic configuration of one zinc atom can be written as 3 d 10 4 s 2 . The metal is active and is an energetic reducing agent. At a temperature of 100 ° C in the open air, it becomes covered with a film consisting of basic carbonates and becomes very dull. When exposed to carbon dioxide and high humidity, the element begins to break down. In an oxygen or normal environment, when strongly heated, zinc burns, forming a bluish flame and white smoke, which consists of zinc oxide. The dry elements of fluorine, bromine and chlorine have a flammable effect on zinc, but only with the participation of water vapor.
When a metal and strong mineral acids are combined, the former dissolves, especially if the mixture is heated, as a result corresponding salts are formed. Alkalis, melts and solutions oxidize the substance, resulting in the formation of zincites, soluble in water, and hydrogen is released. The intensity of exposure to acids and alkalis depends on the presence of impurities in zinc. The more "pure" the metal, the weaker it interacts due to hydrogen overvoltage.
As an independent element, zinc is not found in nature. It can be mined from 66 minerals, including sphalerite, calamine, franklinite, zincite, willemite, smithsonite. The former is the most common source of the metal and is often referred to as "zinc blende". It consists of zinc sulfide and impurities that give the mineral a variety of colors. This complicates its search and correct identification.
You can find zinc in acidic and igneous rocks - in the latter there is a little more of it. Often metal in the form of sulfide along with lead found in thermal waters, migrates in surface and underground sources.
The temperature required to melt zinc must be less than 419 C o, but not more than 480 C o. Otherwise, the waste of metal will grow and the wear of the walls of the bath, which is usually made from iron, will increase. In the molten state, no more than 0.05% iron impurities are allowed, otherwise the temperature required for melting will begin to rise. If the percentage of iron content exceeds 0.2%, the zinc cannot be rolled.
Zinc is obtained from polymetallic ores, in which can contain up to 4% element. If the ores have been enriched by selective flotation, up to 60% of zinc concentrates can be obtained from them, the rest will be occupied by concentrates of other metals. Zinc concentrates are calcined in fluidized bed furnaces, after which zinc sulfide turns into oxide, and sulfur dioxide is released. The latter goes to waste: sulfuric acid is obtained from it.
To convert zinc oxide into the metal itself, two methods are used.
- Distillation or pyrometallurgical. The concentrate is fired, then sintered to impart gas permeability and granularity, and reduced with coke or coal at a temperature of 1200-1300°C. During the reaction, metal vapors are formed, which are condensed and poured into molds. The purity of zinc reaches 98.7%, after which it can be increased to 99.995% using rectification, but the latter method is quite expensive and complicated.
- Electrolytic or hydrometallurgical. The calcined concentrates are treated with sulfuric acid, the solution is cleaned of impurities with zinc dust and subjected to electrolysis in baths lined with lead or vinyl plastic. Zinc is deposited on aluminum cathodes, from where it is collected and melted in induction furnaces. The purity of the metal obtained by this method reaches 99.95%.
To enhance strength and increase the melting point, the metal is mixed with copper, aluminum, tin, magnesium and lead.
The most famous and sought after alloy is brass. This is a mixture of copper with the addition of zinc, sometimes tin, nickel, manganese, iron, and lead are also found. The density of brass reaches 8700 kg / m 3. The temperature required for melting is kept at around 880 C o - 950 C o: the more zinc it contains, the lower it is. The alloy perfectly resists the unfavorable external environment, although it turns black in the air, if not varnished, it is perfectly polished and welded by contact welding.
There are two types of brass:
- Alpha brass: more ductile, bends well in any condition, but wears out more.
- Alpha + beta brass: only deforms when heated, more wear resistant. Often alloyed with magnesium, aluminium, lead and iron. This increases strength but reduces ductility.
Alloy Zamak or Zamac consists from zinc, aluminium, copper and magnesium. The name itself is formed from the first letters of the Latin names: Zink - Aluminum - Magnesium - Kupfer / Cuprum (Zinc-Aluminum-Magnesium-Copper). In the USSR, the alloy was known as TsAM: Zinc-Aluminum-Copper. Actively used in injection molding, melting starts at a low temperature (381 C o - 387 C o) and has a low coefficient of friction (0.07). It has increased strength, which makes it possible to obtain products of complex shape that are not afraid to break: door handles, golf clubs, firearm bolts, construction fittings, fasteners of various types and fishing tackle.
A small percentage of zinc (not more than 0.01%) is contained in hardened alloys used in printing for casting typographic fonts and rulers, printing plates and machine typesetting. These are outdated mixtures, which were replaced by pure zinc with a small addition of impurities.
The low temperature required to melt zinc is often compensated by alloying with other metals, but the opposite is also true. If the temperature required to melt a "pure" metal is is 419.5 C about, then the alloy with tin is reduced to 199 C o, and with tin and lead - up to 150 C o. And although such alloys can be soldered and welded, most often mixtures with zinc are used only to repair existing defects due to their weak strength. For example, an alloy of tin, lead and zinc is recommended to be used only on nickel-plated products.
Most often, zinc alloys are used to create carburetors, speedometer frames, radiator grilles, hydraulic brakes, pumps and decorative elements, parts for washing machines, mixers and kitchen equipment, watch cases, typewriters, cash registers and household appliances. These parts cannot be used in industrial production: when the temperature rises to 100 C, the strength of the product decreases by a third, and the hardness - by almost 40%. When the temperature drops to 0 C, zinc becomes too brittle, which can lead to breakage.
Application
Zinc is one of the most sought-after metals in the world: it is the third largest mined non-ferrous metal, behind only copper and aluminium. This is facilitated by its low price. Most often it is used for corrosion protection and as part of an alloy such as brass.
in living organisms
The human body contains about 2 grams of zinc, about 400 enzymes contain it. The latter include enzymes that catalyze the hydrolysis of proteins, esters, and leptides, the polymerization of RNA and DNA, and the formation of aldehydes. The pure element is found in the muscles, pancreas and liver. Men need 11 mg of zinc per day, women need 8 mg.
Zinc in the body performs the following functions:
With a lack of an element in the body, there is fatigue, irritability, memory loss, decreased vision and weight without an objective reason, allergy attacks, depression. There is a decrease in the level of insulin and the accumulation in the body of certain elements: iron, lead, copper, cadmium.
In food
The element is found in meat, cheese, sesame, oysters, chocolate, legumes, oatmeal, sunflower and pumpkin seeds, and is often present in mineral water. The highest percentage of zinc found in the following products (per 100 grams):
- Oysters (up to 40 mg), anchovies (1.72 mg), octopus (1.68 mg), carp (1.48 mg), caviar (up to 1 mg), herring (about 1 mg).
- Pumpkin seeds (10 mg), sesame seeds (7 mg), sunflower seeds (5.3 mg), peanuts (4 mg), walnuts (3 mg), almonds (3 mg).
- Beef (up to 8.4 mg), lamb (up to 6 mg), beef liver (4 mg), pork (up to 3.5 mg), chicken (up to 3.5 mg).
- Cocoa powder without sugar and sweeteners (6.81 mg), pure dark chocolate (2.3 mg), chocolates (up to 2 mg depending on the amount and type of chocolate).
- Lentils (4.78 mg), oats (3.97 mg), wheat (3.46 mg), soybeans (3 mg), rye (2.65 mg), bread (up to 1.5 mg), green peas (1.24 mg), peas (1.2 mg), bamboo sprouts (1.1 mg), rice (1 mg), cereal biscuits (up to 1 mg).
- Hard cheese (up to 4 mg).
Human danger
Zinc poisoning usually occurs prolonged inhalation of its vapors. The first signs are intense thirst, loss of appetite, and a sweetish taste in the mouth. Often there is fatigue, drowsiness, dry cough, feeling of weakness, pressing pain in the chest. Prolonged exposure can lead to infertility, anemia, developmental delay. In everyday life, galvanized dishes, in which food is stored for a long time, are dangerous.
Zinc is a metal, standing in the periodic table, at number 30 and has the designation Zn. It melts at a temperature of 419 ° C degrees, but if the boiling point is 913 ° C, it begins to turn into steam. Under normal temperature conditions, the state is fragile, and at one hundred degrees it begins to bend.
The color of zinc is blue-white. When exposed to oxygen, oxidation appears, as well as a coating of carbonate that protects the metal from further oxidation reaction. The appearance of hydroxide on zinc means that water does not act on the chemical element.
Zinc is a chemical element that has its own distinctive properties, advantages and disadvantages. It is widely used in everyday life of a person, in pharmaceuticals and metallurgy.
Features of zinc
Metal is necessary and widely used in almost all areas of human daily life.
Mining is mainly carried out in Iran, Kazakhstan, Australia, Bolivia. In Russia, the manufacturer is OAO GMK Dalpolimetall.
It is a transition metal, has an oxidation state of +2, a radioactive isotope, a half-life of 244 days.
In its pure form, the element is not mined. Contained in ores and minerals: cleophane, marmatite, wurtzite, zincite. It is necessarily present in an alloy with aluminum, copper, tin, nickel.
Chemical, physical properties and characteristics of zinc
Zinc is a metal that has a number of properties and characteristics that distinguish it from other elements of the periodic table.
The physical properties of zinc include its state. Temperature is the main factor. If at room temperature it is a brittle material, the density of zinc is 7130 kg / m 3 (˃ the density of steel), which practically does not bend, then when it rises, it easily bends and rolls in sheets in factories. If we take a higher temperature regime, the material acquires a liquid state, and if we raise the temperature by 400-450 ° C, then it will simply evaporate. This is uniqueness - to change your state. If you act with acids and alkalis, it can crumble, explode, melt.
The formula of zinc Zn is zincum. The atomic mass of zinc is 65.382 a.m.u.
Electronic formula: the nucleus of a metal atom contains 30 protons, 35 neutrons. An atom has 4 energy levels - 30 electrons. (Fig. structure of the zinc atom) 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 .
The crystal lattice of zinc is a hexagonal crystal system with tightly pressed atoms. Lattice data: A=2.66U, C=4.94.
Structure and composition of zinc
The extracted and not processed material has isotopes 64, 66, 67, electrons 2-8-18-2.
In terms of application, among all the elements of the periodic table, the metal is in 23rd place. In nature, the element appears in the form of sulfide with impurities of lead Pb, cadmium Cd, iron Fe, copper Cu, silver Ag.
Depending on how many impurities, the metal is labeled.
Zinc production
As mentioned above, there is no pure form of this element in nature. It is extracted from other rocks, such as ore - cadmium, gallium, minerals - sphalerite.
The metal is received at the factory. Each plant has its own distinctive production features, so the equipment for obtaining pure material is different. It could be like this:
- The rotors, arranged vertically, are electrolytic.
- Special kilns with a sufficiently high temperature for firing, as well as special electric kilns.
- Conveyors and baths for electrolysis.
Depending on the method of metal extraction adopted, the appropriate equipment is involved.
Obtaining Pure Zinc
As mentioned above, there is no pure species in nature. Basically, mining is done from ores, in which it comes with various elements.
To obtain pure material, a special flotation process with selectivity (selectivity) is involved. After the process, the ore breaks down into elements: zinc, lead, copper, and so on.
The pure metal extracted by this method is fired in a special furnace. There, at certain temperatures, the sulfide state of the material becomes oxide. During roasting, sulfur-containing gas is released, which is sent to produce sulfuric acid.
There are 2 ways to get metal:
- Pyrometallurgical - the process of roasting is underway, after - the resulting mass is restored using black coal and coke. The final process is settling.
- Electrolytic - the extracted mass is treated with sulfuric acid. The resulting solution is subjected to electrolysis, while the metal settles, it is melted in furnaces.
Smelting zinc in a furnace
The melting temperature of zinc in a furnace is 419-480 ° C degrees. If the temperature regime is exceeded, then the material begins to evaporate. At this temperature, an admixture of iron of 0.05% is allowed.
With an interest rate of 0.2 iron, the sheet cannot be rolled.
Various methods are used to smelt pure metal, up to the production of zinc vapors, which are sent to special tanks and there the substance falls down.
metal application
The properties of zinc allow its use in many areas. As a percentage:
- Galvanizing - up to 60%.
- Medicine - 10%.
- Various alloys containing this metal 10%.
- Tire output 10%.
- Production of paints - 10%.
And also the use of zinc is necessary for the recovery of metals such as gold, silver, platinum.
Zinc in metallurgy
The metallurgical industry uses this element of the periodic table as the main one to achieve certain goals. The smelting of pig iron and steel is the main one in the entire metallurgy of the country. But, these metals are subject to negative environmental influences. Without a certain treatment, there is a rapid oxidation of metals, which leads to their deterioration. The best protection is galvanizing.
The application of a protective film on cast iron and steel is the best remedy for corrosion. Galvanizing takes about 40% of the total production of pure material.
Galvanizing methods
Metallurgical plants are distinguished not only by their equipment, but also by the methods of production used. It depends on the pricing policy, and the location (natural resources used for the metallurgical industry). There are several galvanizing methods which are discussed below.
Hot dip galvanizing
This method consists in dipping a metal part in a liquid solution. It happens like this:
- The part or product is degreased, cleaned, washed and dried.
- Further, zinc is melted to a liquid state at temperatures up to 480 ° C.
- The prepared product is lowered into the liquid solution. At the same time, it is well wetted in solution and a coating up to 450 μm thick is formed. This is 100% protection against external factors on the product (moisture, direct sunlight, water with chemical impurities).
However, this method has a number of disadvantages:
- The zinc film on the product turns out to be an uneven layer.
- You cannot use this method for parts that meet exact GOST standards. Where every millimeter is considered a marriage.
- After hot-dip galvanizing, not every part will remain strong and wear-resistant, because brittleness appears after passing through high temperatures.
And also this method is not suitable for products coated with paints and varnishes.
Cold galvanizing
This method has 2 names: galvanic and electrolytic. The procedure for coating the product with corrosion protection is as follows:
- A metal part, the product is being prepared (degreased, cleaned).
- After that, the “staining method” is carried out - a special composition is used that has the main component - zinc.
- The part is covered with this composition by spraying.
Thanks to this method, parts with an exact tolerance, products coated with paints and varnishes are covered with protection. Increases resistance to external factors leading to corrosion.
Disadvantages of this method: thin protective layer - up to 35 microns. This results in less protection and shorter protection times.
Thermal diffusion method
This method makes a coating that is an electrode with positive polarity, while the metal of the product (steel) becomes negative polarity. An electrochemical protective layer appears.
The method is applicable only if the parts are made of carbon steel, cast iron, steel with impurities. Zinc is used in this way:
- At temperatures from 290 °C to 450 °C in a powder medium, the surface of the part is saturated with Zn. Here, the marking of steel, as well as the type of product, matter - the appropriate temperature is selected.
- The thickness of the protective layer reaches 110 microns.
- A product made of steel, cast iron is placed in a closed tank.
- A special mixture is added there.
- The last step is a special treatment of the product from the appearance of white efflorescence from salt water.
Basically, this method is used if it is required to cover parts that have a complex shape: carving, small strokes. The formation of a uniform protective layer is important because these parts are exposed to multiple external aggressive environments (constant moisture).
This method gives the highest percentage of product protection against corrosion. Galvanized coating is wear-resistant and practically indelible, which is very important for parts that rotate and disassemble from time to time.
Other applications of zinc
In addition to galvanizing, the metal is also used in other industries.
- Zinc sheets. For the production of sheet, rolling is carried out, in which ductility is important. It depends on the temperature regime. A temperature of 25 ° C gives plasticity only in one plane, which creates certain properties of the metal. The main thing here is what the sheet is made for. The higher the temperature, the thinner the metal is. Depending on this, the product is labeled C1, C2, C3. After that, various products for cars, profiles for construction and repair, for printing, and so on are created from the sheets.
- zinc alloys. For improved properties of metal products, zinc is added. These alloys are created at high temperatures in special furnaces. Most often, alloys are made from copper, aluminum. These alloys are used for the production of bearings, various bushings, which are applicable in mechanical engineering, shipbuilding and aviation.
In household use, a galvanized bucket, a trough, sheets on the roof are the norm. Zinc is used, not chrome or nickel. And it's not just that galvanizing is cheaper than coating with other materials. This is the most reliable and durable protective material than chrome or other materials used.
As a result, zinc is the most common metal widely used in metallurgy. In mechanical engineering, construction, medicine - the material is applicable not only as protection against corrosion, but also to increase strength, long service life. In private houses, galvanized sheets protect the roof from precipitation; in buildings, walls and ceilings are leveled with plasterboard sheets based on galvanized profiles.
Almost every housewife in the house has a galvanized bucket, a trough, which she uses for a long time.
) refers to the metals of antiquity, the date of discovery of which is lost for centuries.
The reduction of zinc oxide with charcoal requires a temperature of at least 1000 ° C. Since the metal at this temperature is in a vapor state and is easily oxidized, the release of zinc requires the ability to condense the metal vapor, and this must be done in the absence of air, otherwise the metal will turn into an oxide.
The production of zinc alloys from mixed ores does not require the isolation of zinc itself and is easier to achieve. Small amounts of zinc present in samples of ancient Egyptian copper reflect the composition of local ores; and containing about 23% zinc, copper ore should have been deliberately mixed with zinc ore. Brass was also obtained in Cyprus and, later, in the Cologne region (Germany). Chinese craftsmen mastered the art of zinc smelting in the Middle Ages. Zinc coins were used during the Ming Dynasty (1368–1644).
There was no special production of zinc in medieval Europe, although small amounts were obtained from the production of lead, silver, and brass. Starting around 1605, it was imported from China by the East India Company. The English zinc industry appeared in the Bristol region at the beginning of the 18th century, and its products quickly penetrated into Silesia and Belgium.
The origin of the element's name is unclear, but it seems plausible that it is derived from Zinke (German for "point" or "tooth"), due to the appearance of the metal.
Distribution of zinc in nature and its industrial extraction. The content of zinc in the earth's crust is 7.6 10 -3%, it is distributed approximately the same as rubidium (7.8 10 -3%), and slightly more than copper (6.8 10 -3%) .
The main zinc minerals are zinc sulfide ZnS (known as zincblende or sphalerite) and zinc carbonate ZnCO 3 (calamine in Europe, smithsonite in the USA). This mineral got its name in honor of James Smithson, the founder of the Smithsonian Institution in Washington. Less important minerals are hemimorphite Zn 4 Si 2 O 7 (OH) 2 ·H 2 O and franklinite (Zn,Fe)O·Fe 2 O 3 .
Canada occupies the first place in the world in terms of production (16.5% of world production, 1113 thousand tons, 1995) and zinc reserves. In addition, rich zinc deposits are concentrated in China (13.5%), Australia (13%), Peru (10%), USA (10%), Ireland (about 3%).
Zinc is mined in 50 countries. In Russia, zinc is extracted from copper pyrite deposits in the Urals, as well as from polymetallic deposits in the mountains of Southern Siberia and Primorye. Large reserves of zinc are concentrated in Rudny Altai (Eastern Kazakhstan), which accounts for more than 50% of zinc production in the CIS countries. Zinc is also mined in Azerbaijan, Uzbekistan (Almalyk deposit) and Tajikistan.
Characterization of a simple substance and industrial production of metallic zinc. Metallic zinc has a characteristic bluish luster on a fresh surface, which it quickly loses in moist air. Melting point 419.58 ° C, boiling point 906.2 ° C, density 7.133 g / cm 3. At room temperature, zinc is brittle, at 100–150°C it becomes ductile and can be easily rolled into thin sheets and wire, and at 200–250°C it again becomes very brittle and can be ground into powder.
When heated, zinc interacts with non-metals (except hydrogen, carbon and nitrogen). Actively reacts with acids:
Zn + H 2 SO 4 (razb.) \u003d ZnSO 4 + H 2
Zinc is the only element of the group that dissolves in aqueous solutions of alkalis with the formation of 2– ions (hydroxozincates):
Zn + 2OH - + 2H 2 O \u003d 2- + H 2
When metallic zinc is dissolved in an ammonia solution, an ammonia complex is formed:
Zn + 4NH 3 H 2 O \u003d (OH) 2 + 2H 2 O + H 2
The feedstock for the production of metallic zinc is zinc sulfide and polymetallic ores. The extraction of zinc begins with the concentration of the ore by sedimentation or flotation methods, then it is burned to form oxides:
2ZnS + 3O 2 = 2ZnO + SO 2
The resulting sulfur dioxide is used in the production of sulfuric acid, and zinc oxide is processed by the electrolytic method or smelted with coke.
In the first case, zinc is leached from the crude oxide with a dilute solution of sulfuric acid. In this case, cadmium is precipitated with zinc dust:
Zn + Cd 2+ = Zn 2+ + Cd
The zinc sulfate solution is then subjected to electrolysis. Metal of 99.95% purity is deposited on aluminum cathodes.
Recovery of zinc oxide with coke is described by the equation:
2ZnO + C \u003d 2Zn + CO 2
For the smelting of zinc, rows of highly heated intermittent horizontal retorts were previously used, then they were replaced by continuously operating vertical retorts (in some cases, electrically heated). These processes were not as thermally efficient as the blast furnace process, in which the heating fuel is burned in the same chamber as the oxide reduction, however, an inevitable problem in the case of zinc is that the reduction of zinc oxide with carbon does not proceed below the boiling point of zinc ( this problem does not exist for iron, copper or lead), so subsequent cooling is necessary to condense the vapors. In addition, in the presence of combustion products, the metal is re-oxidized.
This problem can be solved by spraying the zinc vapors coming out of the furnace with molten lead. This results in rapid cooling and dissolution of the zinc so that re-oxidation of the zinc is minimized. Nearly 99% pure zinc is then isolated as a liquid and further purified by vacuum distillation to a purity of 99.99%. All cadmium present is recovered during distillation. The advantage of a blast furnace is that the composition of the charge is not critical, so mixed ores of zinc and lead (ZnS and PbS are often found together) can be used to continuously produce both metals. Lead is released from the bottom of the furnace.
According to experts, in 2004 zinc production amounted to 9.9 million tons, and its consumption - about 10.2 million tons. Thus, the shortage of zinc in the world market is 250-300 thousand tons.
In 2004, the output of refined zinc in China reached 2.46 million tons. Canada and Australia each produce approximately 1 million tons. The price of zinc at the end of 2004 was over $1,100 per ton.
Demand for metal remains strong, thanks to the rapid growth in the production of anti-corrosion coatings. To obtain such coatings, various methods are used: immersion in molten zinc (hot zinc plating), electroplating, spraying with liquid metal, heating with zinc powder, and using paints containing zinc powder. Galvanized sheet is widely used as a roofing material. Metal zinc in the form of bars is used to protect against corrosion of steel products in contact with sea water. Zinc-brass alloys (copper plus 20-50% zinc) are of great practical importance. For injection molding, in addition to brass, a rapidly growing number of special zinc alloys are used. Another area of application is the production of dry cell batteries, although this has declined significantly in recent years.
Approximately half of all zinc produced is used for the production of galvanized steel, one third for hot dip galvanizing of finished products, and the rest for strip and wire. Over the past 20 years, the world market for these products has more than doubled, adding an average of 3.7% per year, and in Western countries, metal production is increasing annually by 4.8%. Currently, galvanizing 1 ton of steel sheet requires an average of 35 kg of zinc.
According to preliminary estimates, in 2005 zinc consumption in Russia may amount to about 168.5 thousand tons per year, including 90 thousand tons for galvanizing, 24 thousand tons for semi-finished products (brass, zinc rolled products, etc.), 29 thousand tons - in the chemical industry (paints and varnishes, rubber products), 24.2 thousand tons - for foundry zinc alloys.
Zinc compounds.
Zinc forms numerous binary compounds with non-metals, some of which have semiconductor properties.
Zinc salts are colorless (if they do not contain colored anions), their solutions have an acidic environment due to hydrolysis. Under the action of alkali and ammonia solutions (starting from pH ~ 5), basic salts precipitate and turn into hydroxide, which dissolves in excess of the precipitant.
zinc oxide ZnO is the most important industrial zinc compound. As a by-product of brass production, it was known before the metal itself. Zinc oxide is obtained by burning in air the vapors of zinc formed during the smelting of ore. A cleaner and whiter product is produced by burning vapors obtained from pre-purified zinc.
Zinc oxide is usually a white fine powder. When heated, its color changes to yellow as a result of the removal of oxygen from the crystal lattice and the formation of a nonstoichiometric phase Zn 1+ x O( x£7.10–5). An excess of zinc atoms leads to the appearance of lattice defects that capture electrons, which are subsequently excited by the absorption of visible light. By adding a 0.02–0.03% excess of metallic zinc to zinc oxide, a whole range of colors can be obtained - yellow, green, brown, red, however, reddish shades of the natural form of zinc oxide - zincite - appear for a different reason: due to the presence manganese or iron. Zinc oxide ZnO is amphoteric; it dissolves in acids to form zinc salts and in alkalis to form hydroxozincates such as - and 2-:
ZnO + 2OH – + H 2 O = 2–
The main industrial application of zinc oxide is in the production of rubber, in which it reduces the curing time of the original rubber.
As a pigment in the production of paints, zinc oxide has advantages over traditional lead white (basic lead carbonate), due to the absence of toxicity and darkening under the action of sulfur compounds, but is inferior to titanium oxide in terms of refractive index and hiding power.
Zinc oxide increases the life of glass and is therefore used in the production of special glasses, enamels and glazes. Another important area of application is in the composition of neutralizing cosmetic pastes and pharmaceutical preparations.
In the chemical industry, zinc oxide is usually the starting material for the production of other zinc compounds, of which soaps (ie fatty acid compounds such as stearate, palmitate and other zinc salts) are the most important. They are used as paint hardeners, plastic stabilizers and fungicides.
A small but important application of zinc oxide is the production of zinc ferrites. These are spinels of the Zn II type. x M II 1– x Fe III 2 O 4 containing another doubly charged cation (usually Mn II or Ni II). At x = 0, they have the structure of an inverted spinel. If x = 1, then the structure corresponds to a normal spinel. A decrease in the number of Fe III ions in tetrahedral sites leads to a decrease in the Curie temperature. Thus, by changing the zinc content, it is possible to influence the magnetic properties of ferrites.
Zinc hydroxide Zn(OH) 2 is formed as a gelatinous white precipitate when alkali is added to aqueous solutions of zinc salts. Zinc hydroxide, like oxide, is amphoteric:
Zn(OH) 2 + 2OH – = 2–
It is used for the synthesis of various zinc compounds.
zinc sulfide ZnS is released in the form of a white precipitate during the interaction of soluble sulfides and zinc salts in an aqueous solution. In an acidic environment, zinc sulfide does not precipitate in an acidic environment. Hydrogen sulfide water precipitates zinc sulfide only in the presence of anions of weak acids, such as acetate ions, which reduce the acidity of the medium, which leads to an increase in the concentration of sulfide ions in the solution.
Sphalerite ZnS is the most common zinc mineral and the main source of the metal, but a second natural, although much rarer, form of wurtzite is also known, which is more stable at high temperatures. The names of these minerals are used to designate crystal structures, which are important structure types found in many other AB compounds. In both structures, the zinc atom is tetrahedrally coordinated by four sulfur atoms, and each sulfur atom is tetrahedrally coordinated by four zinc atoms. The structures differ significantly only in the type of closest packing: in wurtzite it is cubic, while in sphalerite it is hexagonal.
Pure zinc sulfide is white and, like zinc oxide, is used as a pigment, for this it is often obtained (as lithopone) together with barium sulfate by reacting aqueous solutions of zinc sulfate and barium sulfide.
Freshly precipitated zinc sulfide readily dissolves in mineral acids with the release of hydrogen sulfide:
ZnS + 2H 3 O + = Zn 2+ + H 2 S + 2H 2 O
However, baking makes it less reactive, and therefore it is a suitable pigment in children's toy paints, as it is harmless if swallowed. In addition, zinc sulfide has interesting optical properties. It turns gray when exposed to ultraviolet radiation (perhaps due to dissociation). However, this process can be slowed down, for example, by adding traces of cobalt salts. Cathodic, X-ray and radioactive radiation causes the appearance of fluorescence or luminescence of various colors, which can be enhanced by the addition of traces of various metals or by replacing zinc with cadmium and sulfur with selenium. It is widely used for the production of cathode ray tubes and radar screens.
zinc selenide ZnSe may precipitate out of solution as a lemon-yellow, poorly filterable precipitate. Wet zinc selenide is very sensitive to air. Dried or obtained by dry method, it is stable in air.
Single crystals of zinc selenide are grown by directional crystallization of the melt under pressure or by deposition from the gas phase. Zinc sulfide is used as a laser material and a component of phosphors (together with zinc sulfide).
Zinc telluride ZnTe, depending on the method of preparation, is a gray powder that turns red when rubbed, or red crystals, is used as a material for photoresistors, infrared receivers, dosimeters and counters of radioactive radiation. In addition, it serves as a phosphor and semiconductor material, including in lasers.
zinc chloride ZnCl 2 is one of the important zinc compounds in industry. It is obtained by the action of hydrochloric acid on secondary raw materials or burnt ore.
Concentrated aqueous solutions of zinc chloride dissolve starch, cellulose (so they cannot be filtered through paper) and silk. It is used in the production of textiles, in addition, it is used as a wood preservative and in the manufacture of parchment.
Since zinc chloride easily dissolves oxides of other metals in the melt, it is used in a number of metallurgical fluxes. Using a zinc chloride solution, metals are cleaned before soldering.
Zinc chloride is also used in magnesian cement for dental fillings, as a component of electrolytes for electroplating and in dry cells.
zinc acetate Zn(CH 3 COO) 2 is highly soluble in water (28.5% by weight at 20°C) and many organic solvents. It is used as a fixative in dyeing fabrics, a wood preservative, an antifungal agent in medicine, and a catalyst in organic synthesis. Zinc acetate is an ingredient in dental cements and is used in the manufacture of glazes and porcelain.
Distillation of zinc acetate under reduced pressure produces basic acetate, its molecular structure includes an oxygen atom surrounded by a tetrahedron of zinc atoms bound along the edges by acetate bridges. It is isomorphic to basic beryllium acetate, but unlike it, it rapidly hydrolyzes in water, this is due to the ability of the zinc cation to have a coordination number higher than four.
Organozinc compounds. The discovery in 1849 by the English organic chemist Frankland Edward (1825–1899) of zinc alkyls, although not the first of the synthesized organometallic compounds (the Zeise salt was obtained in 1827), can be considered the beginning of organometallic chemistry. Frankland's research initiated the use of organozinc compounds as intermediates in organic synthesis, and measurements of vapor density led him to the proposition (critical in the development of valence theory) that each element has a limited but definite strength of affinity. Grignard reagents, discovered in 1900, greatly supplanted zinc alkyls in organic synthesis, but many of the reactions in which they are now used were first developed for zinc compounds.
Alkyls like RZnX and ZnR 2 (where X is halogen, R is alkyl) can be obtained by heating zinc in boiling RX in an inert atmosphere (carbon dioxide or nitrogen). Covalent ZnR 2 are non-polar liquids or low melting solids. They are always monomeric in solution and are characterized by the linear coordination of the zinc atom
C–Zn–C. Organozinc compounds are very sensitive to the action of air. Compounds with low molecular weight self-ignite, producing zinc oxide smoke. Their reactions with water, alcohols, ammonia and other substances proceed similarly to Grignard reactions, but less vigorously. An important difference is that they do not interact with carbon dioxide.
The biological role of zinc.
Zinc is one of the most important biologically active elements and is essential for all forms of life.
The body of an adult contains about 2 g of zinc. Although zinc-containing enzymes are present in most cells, its concentration is very low, and therefore it became quite late to understand how important this element is. The necessity and indispensability of zinc for humans was established 100 years ago.
The role of zinc in the vital activity of the body is mainly due to the fact that it is part of more than 40 important enzymes. They catalyze the hydrolysis of peptides, proteins, some esters and aldehydes. Two zinc-containing enzymes attract the most attention: carboxypeptidase A and carbonic anhydrase.
Carboxypeptidase A catalyzes the hydrolysis of the terminal peptide bond in proteins during digestion. It has a relative molecular weight of about 34,000 and contains a zinc atom tetrahedrally coordinated to two histidine nitrogen atoms, the carboxyl oxygen atom of the glutamate residue ( cm. PROTEINS) and a water molecule. The exact mechanism of its action is not completely clear, despite the intensive study of model systems; however, it is generally accepted that the first stage is the coordination of the terminal peptide to the zinc atom.
Carbonic anhydrase was the first of the discovered zinc-containing enzymes (1940), it catalyzes the reversible reaction of the conversion of carbon dioxide into carbonic acid. In mammalian erythrocytes, the forward reaction (hydration) occurs when carbon dioxide is taken up by the blood in the tissues, and the reverse reaction (dehydration) occurs when carbon dioxide is then released in the lungs. The enzyme increases the rates of these reactions by about a million times.
The relative molecular weight of the enzyme is about 30,000. The almost spherical molecule contains one zinc atom located in a deep pocket of the protein, where there are also several water molecules arranged in the same order as in ice. The zinc atom is tetrahedrally coordinated with three imidazole nitrogen atoms and a water molecule. The exact details of the enzyme's action have not been established, but it seems likely that the coordinated H 2 O molecule ionizes to form Zn–OH - and the OH nucleophile then reacts with the carbon atom in CO 2 (which can be held in the correct position by hydrogen bonds between its two oxygen atoms ) with the formation of HCO 3 - .
In the absence of the enzyme, this reaction requires a high pH. The role of the enzyme is to create a suitable environment within the protein "pocket" that facilitates the dissociation of the coordinated water molecule at pH 7.
Later, the function of zinc in proteins responsible for DNA base sequence recognition and, therefore, regulating the transfer of genetic information during DNA replication was established. These so-called "zinc finger" proteins contain 9 or 10 Zn 2+ ions, each of which, coordinating with 4 amino acids, stabilizes the protruding fold ("finger") of the protein. The protein wraps around the DNA double helix, with each of the "fingers" binding to the DNA. Their location coincides with the base sequence in DNA, which ensures accurate recognition.
Zinc is involved in carbohydrate metabolism with the help of a zinc-containing hormone - insulin. Only in the presence of zinc does vitamin A work. This element is necessary for the formation of bones. In addition, it exhibits antiviral and antitoxic effects.
Zinc affects taste and smell. Due to the lack of zinc, necessary for the full development of the fetus, many women in the first 3 months of pregnancy complain about the vagaries of taste and smell.
It is believed that there is a certain relationship between the mental and physical abilities of a person and the content of zinc in his body. So, well-performing students have more zinc in their hair than students who are lagging behind. In patients with rheumatism and arthritis, there is a decrease in the level of zinc in the blood.
Zinc deficiency can be caused by thyroid disorders, liver disease, poor absorption, lack of zinc in water and food, and too much phytin in food (phytin binds zinc, making it difficult to absorb). Alcohol also lowers the level of zinc in the body, especially in muscle and blood plasma.
Zinc is needed by the body in the amount of 10–20 mg per day, but it is very difficult to compensate for the lack of zinc with drugs. In natural combinations, zinc is found only in food, which determines its absorption. The most zinc-rich meat, liver, milk, eggs.
In the body there is competition between zinc and copper, as well as iron. Therefore, when eating foods rich in zinc, one should supplement the diet with foods rich in copper and iron. You can not use zinc together with selenium, since these two elements interact with each other and are excreted from the body.
Elena Savinkina
Zinc is a silvery-white metal that has been widely used in an alloy with copper (brass) since ancient times in Egypt, China, Greece and India. In the middle of the 18th century, the substance was isolated in its pure form. Zinc received its modern name only in the 1920s. In nature, it is represented by salts that are part of minerals. In this article, you will learn more about what zinc is and how it can be used.
general characteristics
Zinc is an element of a side subgroup of the 2nd group of the 4th period of the periodic table, with serial number 30. The atomic mass of zinc is 65.39. It owes its name to Paracelsus, in whose writings there are the words zinken and zincum, apparently derived from the word zinke, meaning a tooth. From here came the chemical formula of zinc - Zn. Being a very common element, zinc is found in the earth's crust in almost all water resources of the planet and in the lion's share of living organisms. To date, more than six dozen minerals of this substance are known. The bulk of zinc is mined in Bolivia, Australia, Kazakhstan and Iran.
Physical and chemical properties
Let's find out what zinc is in terms of science. This element is a brittle and ductile transition metal. When exposed to air, the silvery-white substance tarnishes. Zinc burns to form a white oxide. When a plate of this material is bent, a crackling sound can be heard due to the friction of the crystals. Zinc heated to 100-150 °C becomes very ductile.
Industrial use
Metallic zinc has found wide application in industry. With its help, gold and silver are mined by underground leaching. Zinc is also used to protect steel from corrosion (galvanizing and plating). In batteries and accumulators, this substance acts as a material for the negative electrodes.
Zinc plates are widely used in printing, mainly for printing illustrations. Brass is made from copper and zinc. Alloys of this substance with magnesium and aluminum are widely used in mechanical engineering. Zinc is introduced into the composition of solid solders to reduce their melting point. Its oxide is an antiseptic and anti-inflammatory agent, therefore it is popular in medicine. It is also used to produce paints - the so-called zinc white.
Zinc selenide, phosphide, sulfide and telluride are widely used semiconductors. In addition, phosphide is used as a poison for rodents, sulfide is used as a part of phosphors, and selenide is used in the manufacture of optical glasses.
Zinc in the body
The action of the macronutrient is due to the fact that it is part of a large number of enzymes. Thus, zinc plays an important role in the human body. Even in ancient Egypt, it was used to heal wounds. To date, scientists have proven that this macronutrient is directly involved in strengthening the immune system and maintaining normal hormonal levels, and also stabilizes growth.
In the human body, this chemical can be found in: muscle tissues, bones, kidneys, liver, blood cells, and even the retina of the eye. Zinc not only contributes to longevity, but also helps to maintain youth and get rid of signs of fatigue.
Today, even young people suffer from a lack of antioxidants, one of which is zinc. This has an extremely negative effect on female reproduction and the endocrine system. Girls who are deficient in zinc suffer from insufficient production of sex hormones and grow more than they should. They have excessively long limbs, a violation of the deposition of fat cells and the menstrual cycle, and external infantilism.
For men, zinc is also very important. It regulates the growth of the prostate gland, and is also responsible for the prevention of male infertility and prostate adenoma. In addition, this microelement activates the activity of sex hormones and spermatozoa.
In old age, a lack of zinc leads to hearing loss, the development of atherosclerosis and frequent infectious diseases. With sufficient use of this substance, memory, attention and other brain functions improve.
A huge amount of zinc is found in our hair. Therefore, problems with the hairline (brittleness, dullness, loss) are the first signal of its deficiency. Many people know that vitamin A is a guarantee of healthy nails, skin and hair. However, even its enhanced intake may be ineffective if you do not take zinc, which acts as an activator of vitamins E and A.
In addition, it allows you to get rid of acne, rheumatism, and infectious diseases of the oral cavity. Studies have shown that the high mortality of newborn boys may be caused by maternal zinc deficiency during pregnancy. This problem is exacerbated by the fact that women's need for this substance is much less than men's. For the same reason, preeclampsia and miscarriages are possible.
Due to its antioxidant and regenerative properties, this macronutrient has been used for over 5000 years to heal wounds and burns. It is still added to ointments, lotions and creams to this day.
Daily rate
The norm of zinc consumption was determined only in 1970. In men, it is 15 mg per day, and in women - 12 mg. However, many experts insist that these figures should be at least doubled. Statistics show that the majority of the world's population does not receive even the indicated amounts of macronutrients. In some cases, the dose of zinc is definitely worth increasing. These are: psychological stress, pregnancy and feeding, physical activity, vegetarianism.
It must also be borne in mind that with cortisone treatment, the use of contraceptives, and the abuse of too sweet and salty foods, the absorption of zinc decreases. But the use of magnesium and vitamin B6, on the contrary, increases the activity of this macronutrient. Therefore, magnesium and zinc are often presented in tandem in medicines.
Signs of deficiency
The lack of zinc in the body can be due to a number of reasons: insufficient intake from food, poor absorption, disorders in the thyroid gland, liver disease. In addition, the reason for the deficiency of this macronutrient may be an excess of proteins, phytin and selenium consumed with food. The cause of this problem and a decrease in the quality of life in general can also be moral and physical stress, an unstable lifestyle, stressful situations, and bad habits.
Overconsumption of zinc in the body occurs during inflammation and oncology. The reason is that in the treatment of these diseases, cell growth is activated, in which zinc plays an important role.
The lack of this macronutrient in the body is a rather serious problem. It can lead to problems like this:
- Pathology of the gastrointestinal tract.
- Sleep disturbances, fatigue, nervousness.
- Tendency to alcohol dependence, depressive states.
- Hyperactivity.
- Loss of smell, appetite and taste sensations.
- Decreased visual acuity.
- Anemia.
- Acne, dermatitis, eczema, psoriasis and other skin diseases.
- Hair and nail damage.
- The development of diabetes.
- Delayed puberty, which can lead to prostate adenoma and impotence.
- Pathologies during pregnancy or even infertility.
- Weakened immunity and, as a result, allergic and respiratory diseases.
- Premature aging.
As recent studies have shown, if there is a lack of zinc and taurine in the human body, then epilepsy may begin to develop.
Zinc is especially important for children, as a lack of it can lead to stunted growth. In some eastern countries, because of this reason, there are many people of dwarf growth.
Excess zinc
An overabundance of a macronutrient occurs when using more than two grams per day. If you take more than 200 g of zinc, it will cause vomiting. Long-term use of the substance in an amount of more than 100 grams per day leads to a deterioration in immunity and contributes to the development of stomach ulcers. Acute poisoning is accompanied by gag reflexes, diarrhea and the appearance of a specific taste in the mouth.
The cause of an excess of zinc can be taking medications that are not agreed with the doctor, metabolic disorders at the cellular level, working in hazardous industries, and even improper use of galvanized dishes.
Symptoms of the initial stages of poisoning with this macroelement are: pathologies of the skin, nails and hair, weakening of the immune system, stomach pain, disorders in the liver, pancreas and prostate. With more severe poisoning, pain in the lumbar region, increased heart rate and pain when urinating can occur. There is also a high probability of increasing the level of cholesterol in the vessels.
Positive is the fact that, according to many scientists, an overdose of zinc is practically impossible, since it does not have toxicity and cannot accumulate in tissues in the form of excess. This is especially true of the macronutrient contained in its natural form in food. But the lack of a substance in the diet of many people is indeed a serious problem.
Sources in food
It would seem that if zinc is found in foods almost everywhere, why do people have problems with a deficiency of this macronutrient. There are a number of nuances here. First, the amount of zinc in plant sources is extremely small. Secondly, macronutrients that enter the body with food are not always absorbed in full. And thirdly, culinary processing and cultivation on depleted soils (as applied to plants) can affect the decrease in the nutritional value of products. Therefore, before compiling a comprehensive diet, it is worth understanding what zinc is and how much it is in a particular product. Vegetarians should be especially careful.
By the way, in folk medicine there is a simple but effective remedy for replenishing zinc deficiency - an infusion of birch leaves.
Interaction of zinc with other substances
Zinc has both "enemies" and "helpers". The first category of substances includes: copper, iron, mercury and calcium. Zinc is poorly absorbed under the influence of: tannin, alcohol, anabolics, diuretics and contraceptives. Such an important substance for the body as fiber can reduce the effectiveness of zinc up to 80%. Here, again, it is worth being attentive to vegetarians who consume a lot of vegetables and fruits that contain fiber.
Zinc assistants include: vitamins of groups A, E, C and B6, fluorine and picolinic acid. By the way, a complex of zinc, manganese and vitamin B6 is used to prevent certain types of schizophrenia.
Zinc-based preparations
Having figured out what zinc is and how it is used, we will briefly consider in which medical preparations it is presented. Here it is immediately worth mentioning that it is highly undesirable to use medicines without consulting a doctor. Most often, patients are prescribed zinc solutions, powders, ointments (for example, Bureau Plus, Desitin, Glutamol, zinc ointment), as well as oxides and sulfates in the form of drops. Zinc-containing vitamins are also popular (Centrum, Selinitsink Plus, Zincteral, Zinkit). In addition, zinc suppositories are used to treat hemorrhoids, and tablets are used to combat baldness.
Zinc- a brittle transition metal of a bluish-white color (tarnishes in air, becoming covered with a thin layer of zinc oxide). Essential (irreplaceable) trace element of human tissues. According to the quantitative ratio in the body, it occupies the second place after iron. It plays a key role in the regeneration of damaged tissues, since without zinc, the synthesis of nucleic acids and protein is disrupted.
See also:
STRUCTURE
Zinc crystals have hexagonal atomic packing. But unlike the densest hexagonal packing of spherical atoms, zinc lattices are elongated in one direction. Each atom is surrounded by six other atoms lying in the same plane or layer. The distance between the centers of neighboring atoms in this flat layer a is equal to 0.26649 nm. The external electronic configuration of the atom is 3d 10 4s 2 . Not polymorphic. PROPERTIES
It is brittle at room temperature; when the plate is bent, a crackling sound is heard from the friction of crystallites (usually stronger than the “tin cry”). Has a low melting point. The volume of the metal during melting increases in accordance with the decrease in density. With an increase in temperature, the kinetic viscosity and electrical conductivity of zinc decrease and its electrical resistivity increases. At 100-150 °C zinc is plastic. Impurities, even minor ones, sharply increase the fragility of zinc. It is diamagnetic.
RESERVES AND PRODUCTION
The average content of zinc in the earth's crust is 8.3·10 -3%, in the main igneous rocks it is slightly higher (1.3·10 -2%) than in acidic (6·10 -3%). Zinc is an energetic water migrant; its migration in thermal waters along with lead is especially characteristic. Zinc sulfides, which are of great industrial importance, precipitate from these waters. Zinc also migrates vigorously in surface and underground waters, the main precipitant for it is hydrogen sulfide, sorption by clays and other processes play a lesser role.
Zinc deposits are known in Iran, Australia, Bolivia, Kazakhstan. In Russia, the largest producer of lead-zinc concentrates is OJSC MMC Dalpolimetall
Zinc is mined from polymetallic ores containing 1-4% Zn in the form of sulfide, as well as Cu, Pb, Ag, Au, Cd, Bi. Ores are enriched by selective flotation, obtaining zinc concentrates (50-60% Zn) and simultaneously lead, copper, and sometimes also pyrite concentrates.
The main method of obtaining zinc is electrolytic (hydrometallurgical). Calcined concentrates are treated with sulfuric acid; the resulting sulfate solution is purified from impurities (by deposition with zinc dust) and subjected to electrolysis in baths tightly lined inside with lead or vinyl plastic. Zinc is deposited on aluminum cathodes, from which it is daily removed (stripped off) and melted in induction furnaces.
ORIGIN
Zinc is not found in nature as a native metal. 66 zinc minerals are known, in particular zincite, sphalerite, willemite, calamine, smithsonite, and franklinite. The most common mineral is sphalerite, or zinc blende. The main component of the mineral is zinc sulfide ZnS, and various impurities give this substance all kinds of colors. Due to the difficulty of identifying this mineral, it is called blende (ancient Greek σφαλερός - deceptive). Zinc blende is considered the primary mineral from which other minerals of element No. 30 were formed: smithsonite ZnCO 3, zincite ZnO, calamine 2ZnO SiO 2 H 2 O. In Altai, you can often find striped "chipmunk" ore - a mixture of zinc blende and brown spar. A piece of such ore from a distance really looks like a hidden striped animal.
APPLICATION
Pure metallic zinc is used to recover precious metals mined by underground leaching (gold, silver). In addition, zinc is used to extract silver, gold (and other metals) from crude lead in the form of zinc-silver-gold intermetallic compounds (the so-called “silver foam”), which are then processed by conventional refining methods.
It is used to protect steel from corrosion (zinc coating of surfaces not subject to mechanical stress, or metallization - for bridges, tanks, metal structures).
Zinc is used as a material for the negative electrode in chemical current sources, that is, in batteries and accumulators.
Zinc plates are widely used in printing, in particular, for printing illustrations in large-circulation publications. For this, zincography has been used since the 19th century - the manufacture of clichés on a zinc plate by acid etching a pattern in it. Impurities, with the exception of a small amount of lead, impair the etching process. Before pickling, the zinc plate is annealed and hot rolled.
Zinc is added to many brazing alloys to lower their melting point.
Zinc oxide is widely used in medicine as an antiseptic and anti-inflammatory agent. Also, zinc oxide is used for the production of paint - zinc white. 
Zinc is an important component of brass. Zinc alloys with aluminum and magnesium (ZAMAK, ZAMAK), due to their relatively high mechanical and very high casting qualities, are very widely used in engineering for precision casting. In particular, in the weapons business, the bolts of pistols are sometimes cast from the ZAMAK (-3, -5) alloy, especially those designed for the use of weak or traumatic cartridges. Also, all kinds of technical fittings are cast from zinc alloys, such as car handles, carburetor bodies, scale models and all kinds of miniatures, as well as any other products that require precision casting with acceptable strength.
Zinc chloride is an important flux for soldering metals and a component in fiber production.
Telluride, selenide, phosphide, zinc sulfide are widely used semiconductors. Zinc sulfide is an integral part of many phosphors. Zinc phosphide is used as a rodent poison.
Zinc selenide is used to make optical glasses with very low absorption in the mid-infrared range, such as in carbon dioxide lasers.
Zinc (English Zinc) - Zn
CLASSIFICATION
| Strunz (8th edition) | 1/A.04-10 |
| Nickel-Strunz (10th edition) | 1.AB.05 |
| Dana (7th edition) | 1.1.8.1 |
| Dana (8th edition) | 1.1.5.1 | Hey's CIM Ref | 1.8 |