Zinc he 2. Zinc (Zn): all about a chemical element and its role in human life

The element zinc (Zn) in the periodic table has serial number 30. It is in the fourth period of the second group. The atomic weight is 65.37. Distribution of electrons by layers 2-8-18-2

The origin of the element's name is unclear, but it seems plausible that it is derived from Zinke (German for "point" or "tooth"), thanks to appearance metal.

Zinc is a bluish-white metal that melts at 419 C and turns into vapor at 913 C; its density is 7.14 g / cm3. At ordinary temperatures zinc is quite fragile, but at 100-110 C it bends well and rolls into sheets. In air, zinc is covered with a thin layer of oxide or basic carbonate, which protects it from further oxidation.

Water has almost no effect on zinc, although it is much more to the left of hydrogen in the series of voltages. This is due to the fact that the hydroxide formed on the surface of zinc when it interacts with water is practically insoluble and prevents the further course of the reaction. In dilute acids, zinc dissolves easily with the formation of the corresponding salts.

In addition, zinc, like beryllium and other metals that form amphoteric hydroxides, dissolves in alkalis. If zinc is heated in air to the boiling point, then its vapors ignite and burn with a greenish-white flame, forming zinc oxide

When heated, zinc interact with non-metals (except hydrogen, carbon and nitrogen). Reacts actively with acids:

Zn + H2SO4 (dil.) \u003d ZnSO4 + H2

Zinc is the only element of the group that dissolves in aqueous solutions of alkalis with the formation of ions (hydroxozincates):

Zn + 2OH + 2H2O \u003d + H2

Physical properties of zinc. Zinc is a medium hard metal. In the cold state, it is brittle, and at 100-150 ° C it is very plastic and easily rolled into sheets and foil about hundredths of a millimeter thick. At 250 ° C, it becomes brittle again. It has no polymorphic modifications. It crystallizes in a hexagonal lattice with parameters a \u003d 2.6594 Å, c \u003d 4.9370 Å. Atomic radius 1.37Å; ionic Zn2 + -0.83 Å. The density of solid zinc is 7.133 g / cm3 (20 ° C), liquid zinc is 6.66 g / cm3 (419.5 ° C); m.p. 419.5 ° C; tboil 906 ° C. Temperature coefficient of linear expansion 39.7 10-3 (20-250 ° C), thermal conductivity coefficient 110.950 W / (m K) 0.265 cal / cm sec ° C (20 ° C), electrical resistivity 5.9 10-6 ohm cm (20 ° C), specific heat of Zinc 25.433 kJ / (kg K). Tensile strength 200-250 MN / m2 (2000-2500 kgf / cm2), elongation 40-50%, Brinell hardness 400-500 MN / m2 (4000-5000 kgf / cm2). Zinc is diamagnetic, its specific magnetic susceptibility is -0.175 · 10-6.

Chemical properties of zinc. The outer electronic configuration of the Zn atom is 3d104s2. The oxidation state in compounds is +2. The standard electrode potential of -0.76 V characterizes Zinc as an active metal and an energetic reducing agent. In air at temperatures up to 100 ° C, Zinc quickly tarnishes, becoming covered with a surface film of basic carbonates. In humid air, especially in the presence of CO2, metal is destroyed even at normal temperatures. When heated strongly in air or oxygen, Zinc burns intensely with a bluish flame to form white smoke of zinc oxide ZnO. Dry fluorine, chlorine and bromine do not interact with zinc in the cold, but in the presence of water vapor, the metal can ignite, forming, for example, ZnCl2. A heated mixture of zinc powder with sulfur gives zinc sulfide ZnS. Zinc sulfide is precipitated by the action of hydrogen sulfide on weakly acidic or ammoniacal aqueous solutions of Zn salts. ZnH2 hydride is obtained by the interaction of LiAlH4 with Zn (CH3) 2 and other zinc compounds; a metal-like substance that decomposes into elements when heated. Zn3N2 nitride is a black powder, formed when heated to 600 ° C in a stream of ammonia; stable in air up to 750 ° C, water decomposes it. Zinc carbide ZnC2 was obtained by heating zinc in a stream of acetylene. Strong mineral acids dissolve Zinc vigorously, especially when heated, to form the corresponding salts. When interacting with dilute HCl and H2SO4, H2 is released, and with HNO3, in addition, NO, NO2, NH3. Zinc reacts with concentrated HCl, H2SO4 and HNO3, releasing H2, SO2, NO and NO2, respectively. Alkali solutions and melts oxidize zinc with the release of H2 and the formation of water-soluble zincites. The intensity of the action of acids and alkalis on Zinc depends on the presence of impurities in it. Pure Zinc is less reactive towards these reagents because of the high overvoltage of hydrogen on it. In water, zinc salts hydrolyze when heated, giving off a white hydroxide precipitate

a) interaction of zinc with dilute acids

Zn (OH) 2. H2SO4 + Zn \u003d Zn SO4 + H2

Zinc, as an active metal, can form sulfur dioxide, elemental sulfur, and even hydrogen sulfide with concentrated sulfuric acid.

2H2SO4 + Zn \u003d SO2 + ZnSO4 + 2H2O

When zinc reacts with very dilute nitric acid, ammonia is released, which reacts with excess acid to form ammonium nitrate.

Zinc in nature as a native metal does not appear. Zinc is mined in two ways:

1) pyrometallurgical method

2) hydrometallurgical method from polymetallic ores containing 1-4% Zn in the form of sulfide, as well as Cu, Pb, Ag, Au, Cd, Bi. The ores are enriched by selective flotation, obtaining zinc concentrates (50-60% Zn) and simultaneously lead, copper, and sometimes also pyrite concentrates. Zinc concentrates are fired in fluidized bed furnaces, converting zinc sulfide into ZnO oxide; The resulting sulfur dioxide SO2 is used to produce sulfuric acid. There are two paths from ZnO to Zn.

1) According to the pyrometallurgical (distillation) method, which has existed for a long time, the fired concentrate is subjected to sintering to impart granularity and gas permeability, and then reduced with coal or coke at 1200 - 1300 ° C:

ZnO + C \u003d Zn + CO.

The resulting metal vapors are condensed and poured into molds. At first, restoration was carried out only in manually operated baked clay retorts; later, vertical mechanized carborundum retorts began to be used, then - shaft and electric arc furnaces; zinc is obtained from lead-zinc concentrates in blast shaft furnaces. The productivity increased gradually, but zinc contained up to 3% impurities, including valuable cadmium. Distillation zinc is purified by segregation (that is, by settling the liquid metal from iron and part of the lead at 500 ° C), reaching a purity of 98.7%. Sometimes used more complex and expensive cleaning rectification gives a metal with a purity of 99.995% and allows you to extract cadmium.

The main method for producing zinc is electrolytic (hydrometallurgical). The fired concentrates are treated with sulfuric acid; the resulting sulfate solution is purified from impurities (by precipitating them with zinc dust) and subjected to electrolysis in baths tightly lined with lead or vinyl plastic. Zinc is deposited on aluminum cathodes, from which it is removed (stripped) every day and melted in induction furnaces. Usually the purity of electrolyte zinc is 99.95%, the completeness of its extraction from the concentrate (taking into account waste processing) is 93-94%. Zinc sulfate, Pb, Cu, Cd, Au, Ag are obtained from production wastes; sometimes also In, Ga, Ge, Tl.

2) The hydrometallurgical method for processing roasted zinc concentrates consists in dissolving zinc oxide with an aqueous solution of sulfuric acid and subsequent zinc precipitation by electrolysis. Therefore, the hydrometallurgical method is sometimes called electrolytic. In the production of zinc by electrolysis, zinc concentrate is preliminarily subjected to oxidative roasting.

ZnSO4 → Zn 2+ + SO4 2-

2+ (-) cathode Zn, Н2О (+) anode: SO42–, Н2О

Zn + 2e Zn 2H2O - 4e O2 + 4H +

2H2O + 2e H2 + 2HO

Total Equation

ZnSO4 + 2H2O Zn + H2 + O2 + H2SO4.

The resulting cinder is leached with a spent electrolyte containing sulfuric acid. The resulting solution of zinc sulfate is purified from harmful impurities and sent to electrolysis. In this case, zinc is deposited on the cathode, and sulfuric acid is regenerated in the solution, which is returned again for leaching.

If the roasting of the zinc concentrate precedes the leaching, then its purpose is the fullest possible conversion of zinc sulfide into zinc oxide, which is soluble in dilute sulfuric acid solutions.

Leaching of cinder is carried out by spent electrolyte containing sulfuric acid and obtained by electrolysis of zinc solution. In the process of redistribution, losses of sulfuric acid are inevitable (both mechanical, occurring as a result of the loss of solution, and chemical, caused by the fact that sulfuric acid is wasted unproductively on dissolving impurities). These losses are supplemented by the fact that a certain amount of zinc sulfate is obtained in the cinder, which readily dissolves in water. For this purpose, it may be sufficient to have about 2-4% sulphate sulfur in the fired concentrate.

This method produces about 70% of the total world zinc production. This is explained by the fact that the electrolytic method, with good mechanization of labor-intensive processes and a high percentage of extraction, produces zinc that is more pure than distillation. In addition, the possibility of complex use of valuable components of the concentrate is facilitated. To extract zinc, the ZnS concentrate obtained after concentration is subjected to roasting:

2ZnS + 3O2 → 2ZnO + 2SO2

In general:

4Zn + 10HNO3 \u003d 4Zn (NO3) 2 + NH4NO3 + 3H2O

Zn + HNO3 \u003d Zn (NO3) 2 + NO + H2O

b) Interaction of soluble zinc salts with alkalis:

ZnCl2 + 2NaOH \u003d ZnOH2 ↓ + 2NaCl

Zn (NO3) 2 + 2KOH \u003d ZnOH2 ↓ + 2KNO3

Zinc is a typical representative of the group of metallic elements and has the entire spectrum of their characteristics: metallic luster, plasticity, electrical and thermal conductivity. However, the chemical properties of zinc are somewhat different from the basic reactions inherent in most metals. Under certain conditions, an element can behave like a non-metal, for example, react with alkalis. This phenomenon is called amphotericity. In this article, we will study the physical properties of zinc, and also consider the typical reactions characteristic of the metal and its compounds.

The position of the element in the periodic table and distribution in nature

The metal is located in a side subgroup of the second group of the periodic system. In addition to zinc, it contains cadmium and mercury. Zinc belongs to d-elements and is in the fourth period. IN chemical reactions its atoms always donate electrons of the last energy level, therefore, in such compounds of the element as oxide, medium salts and hydroxide, the metal exhibits an oxidation state of +2. The structure of the atom explains all the physicochemical properties of zinc and its compounds. The total metal content in the soil is approximately 0.01 wt. %. It is found in minerals such as galmey and zinc blende. Since the zinc content in them is low, at first the rocks undergo enrichment, which is carried out in shaft furnaces. Most of the zinc-bearing minerals are sulfides, carbonates, and sulfates. These are zinc salts, the chemical properties of which underlie their processing processes, such as roasting.

Getting metal

The violent oxidation reaction of zinc carbonate or zinc sulfide results in the production of zinc oxide. The process takes place in a fluidized bed. it special method, based on close contact of finely ground mineral and a jet of hot air moving at high speed. Next, zinc oxide ZnO is reduced with coke and the formed metal vapors are removed from the reaction sphere. Another method of metal production, based on the chemical properties of zinc and its compounds, is the electrolysis of zinc sulfate solution. It is a redox reaction under the action of electric current... The high-purity metal is then deposited on the electrode.

Physical characteristic

Bluish-silver, brittle metal under normal conditions. In the temperature range from 100 ° to 150 °, zinc becomes flexible and can be rolled into sheets. When heated above 200 °, the metal becomes unusually brittle. Under the influence of atmospheric oxygen, pieces of zinc are covered with a thin layer of oxide, and upon further oxidation, it turns into hydroxycarbonate, which plays the role of a protector and prevents further interaction of the metal with atmospheric oxygen. The physical and chemical properties of zinc are interrelated. Let us consider this using the example of the interaction of a metal with water and oxygen.

Severe oxidation and reaction with water

When heated strongly in air, zinc chips burn with a blue flame, and zinc oxide is formed.

It exhibits amphoteric properties. In water vapor heated to a red-hot temperature, the metal displaces hydrogen from the Н 2 О molecules; in addition, zinc oxide is formed. The chemical properties of the substance prove its ability to interact with both acids and alkalis.

Redox reactions involving zinc

Since an element in the row of metal activity stands before hydrogen, it is able to displace it from acid molecules.

The reaction products between zinc and acids will depend on two factors:

• type of acid
• her concentration

Zinc oxide

A white, porous powder that turns yellow when heated and returns to its original color when cooled is a metal oxide. The chemical properties of zinc oxide, the equations for the reactions of its interaction with acids and alkalis confirm the amphoteric nature of the compound. So, the substance cannot react with water, but interacts with both acids and alkalis. The reaction products will be medium salts (in the case of interaction with acids) or complex compounds - tetrahydroxozincates.

Zinc oxide is used in the production of a white paint called zinc white. In dermatology, the substance is included in ointments, powders and pastes that have an anti-inflammatory and drying effect on the skin. Most of the zinc oxide produced is used as a filler for rubber. Continuing to study the chemical properties of zinc and its compounds, consider the hydroxide Zn (OH) 2.

Amphoteric nature of zinc hydroxide

The white precipitate that precipitates under the action of alkali on solutions of metal salts is a zinc base. The compound dissolves quickly under the action of acids or alkalis. The first type of reaction ends with the formation of medium salts, the second - zincates. Complex salts - hydroxyzincates - were isolated in solid form. A feature of zinc hydroxide is its ability to dissolve in an aqueous solution of ammonia to form tetraamminezinc hydroxide and water. Zinc base is a weak electrolyte, therefore, both its medium salts and zincates in aqueous solutions are hydrolyzable, that is, their ions interact with water and form zinc hydroxide molecules. Solutions of metal salts such as chloride or nitrate will react acidic due to the accumulation of excess hydrogen ions.

Characterization of zinc sulfate

The previously considered chemical properties of zinc, in particular, its reactions with dilute sulfate acid, confirm the formation of an average salt - zinc sulfate. These are colorless crystals, heating them up to 600 ° and above, you can get oxosulfates and sulfur trioxide. Upon further heating, zinc sulfate is converted to zinc oxide. The salt is soluble in water and glycerin. The substance is isolated from solution at temperatures up to 39 ° C in the form of crystalline hydrate, the formula of which is ZnSO 4 × 7H 2 O. In this form, it is called zinc sulfate.

In the temperature range 39 ° -70 °, a hexahydrate salt is obtained, and above 70 °, only one water molecule remains in the crystalline hydrate. The physicochemical properties of zinc sulfate make it possible to use it as a bleach in the manufacture of paper, in the form of a mineral fertilizer in plant growing, as a top dressing in the diet of domestic animals and poultry. In the textile industry, the compound is used in the production of viscose fabric, in dyeing chintz.

Zinc sulphate is also included in the composition of the electrolyte solution used in the process of galvanic coating with a zinc layer of iron or steel products by the diffuse method or by hot-dip galvanizing. The zinc layer protects such structures from corrosion for a long time. Considering the chemical properties of zinc, it should be noted that in conditions of high salinity of water, significant fluctuations in temperature and air humidity, galvanizing does not give the desired effect. Therefore, metal alloys with copper, magnesium and aluminum are widely used in industry.

Application of zinc alloys

The transportation of many chemicals, such as ammonia, through pipelines requires special requirements for the composition of the metal from which the pipes are made. They are made on the basis of alloys of iron with magnesium, aluminum and zinc and have a high corrosion resistance to aggressive chemical environment. In addition, zinc improves the mechanical properties of alloys and neutralizes the harmful effects of impurities such as nickel and copper. Alloys of copper and zinc are widely used in industrial electrolysis processes. Tankers are used to transport refined products. They are constructed from aluminum alloys containing, in addition to magnesium, chromium and manganese, a large proportion of zinc. Materials of this composition have not only high anti-corrosion properties and increased strength, but also cryogenic resistance.

The role of zinc in the human body

The Zn content in cells is 0.0003%, therefore it is referred to as trace elements. The chemical properties, reactions of zinc and its compounds play an important role in the metabolism and maintenance of a normal level of homeostasis, both at the level of the cell and the whole organism as a whole. Metal ions are part of important enzymes and other biologically active substances... For example, it is known about the serious effect of zinc on the formation and function of the male reproductive system. It is part of the coenzyme of the hormone testosterone, which is responsible for the fertility of the seminal fluid and the formation of secondary sexual characteristics. The non-protein part of another important hormone, insulin, produced by the beta cells of the islets of Langerhans in the pancreas, also contains a trace element. The immune status of the body is also directly related to the concentration of Zn +2 ions in the cells, which are found in the thymus hormone - thymulin and thymopoietin. A high concentration of zinc is recorded in the structures of the nucleus - chromosomes containing deoxyribonucleic acid and participating in the transmission of hereditary information of the cell.

In our article, we studied the chemical functions of zinc and its compounds, and also determined its role in the life of the human body.

Zinc (lat. Zincum), Zn, chemical element of group II of Mendeleev's periodic system; atomic number 30, atomic mass 65.38, bluish white metal. There are 5 known stable isotopes with mass numbers 64, 66, 67, 68 and 70; the most common is 64 Zn (48.89%). A number of radioactive isotopes were artificially obtained, among which the most long-lived 65 Zn with a half-life of T ½ \u003d 245 days; used as an isotope indicator.

History reference. Zinc alloy with copper - brass - was known to the ancient Greeks and Egyptians. Pure Zinc could not be isolated for a long time. In 1746, A.S. Marggraf developed a method for producing metal by calcining a mixture of its oxide with coal without air access in clay refractory retorts, followed by condensation of zinc vapor in refrigerators. Zinc smelting began on an industrial scale in the 17th century.

Distribution of Zinc in nature. Average Zinc content in earth crust (clarke) - 8.3 · 10 -3% by weight, in the basic igneous rocks it is somewhat higher (1.3 · 10 -2%) than in acidic rocks (6 · 10 -3%). There are 66 known zinc minerals, the most important of which are zincite, sphalerite, willemite, calamine, smithsonite, frank-linite ZnFe 2 O 4. Zinc is an energetic water migrant; its migration in thermal waters together with Pb is especially characteristic; Zinc sulfides, which are of great industrial importance, are precipitated from these waters. Zinc also vigorously migrates to surface and groundwater; the main precipitant for it is H 2 S, a lesser role is played by clay sorption and other processes. Zinc is an important nutrient; living matter contains on average 5 · 10 -4% Zinc, but there are also concentrating organisms (for example, some violets).

Physical properties of zinc. Zinc is a medium hard metal. In the cold state, it is brittle, and at 100-150 ° C it is very plastic and easily rolled into sheets and foil about hundredths of a millimeter thick. At 250 ° C, it becomes brittle again. It has no polymorphic modifications. It crystallizes in a hexagonal lattice with parameters a \u003d 2.6594 Å, c \u003d 4.9370 Å. Atomic radius 1.37Å; ionic Zn 2+ -0.83 Å. The density of solid zinc is 7.133 g / cm 3 (20 ° C), liquid zinc is 6.66 g / cm 3 (419.5 ° C); t pl 419.5 ° C; bale t 906 ° C. Temperature coefficient of linear expansion 39.7 · 10 -3 (20-250 ° С), thermal conductivity coefficient 110.950 W / (m · K) 0.265 cal / cm · sec · ° С (20 ° С), electrical resistivity 5.9 · 10 -6 ohm · cm (20 ° C), specific heat of Zinc 25.433 kJ / (kg · K). Tensile strength 200-250 MN / m 2 (2000-2500 kgf / cm 2), elongation 40-50%, Brinell hardness 400-500 MN / m 2 (4000-5000 kgf / cm 2). Zinc is diamagnetic, its specific magnetic susceptibility is -0.175 · 10 -6.

Chemical properties of zinc. The outer electron configuration of the Zn atom is 3d 10 4s 2. The oxidation state in compounds is +2. The normal redox potential of 0.76 volts characterizes Zinc as an active metal and an energetic reducing agent. In air at temperatures up to 100 ° C, Zinc quickly tarnishes, becoming covered with a surface film of basic carbonates. In humid air, especially in the presence of CO 2, metal is destroyed even at normal temperatures. When heated strongly in air or oxygen, Zinc burns intensely with a bluish flame to form white smoke of zinc oxide ZnO. Dry fluorine, chlorine and bromine do not interact with zinc in the cold, but in the presence of water vapor, the metal can ignite, forming, for example, ZnCl 2. A heated mixture of zinc powder with sulfur gives zinc sulfide ZnS. Zinc sulphide precipitates when hydrogen sulphide acts on weakly acidic or ammoniacal aqueous solutions salts of Zn. ZnH 2 hydride is obtained by the interaction of LiAlH 4 with Zn (CH 3) 2 and other zinc compounds; a metal-like substance that decomposes into elements when heated. Nitride Zn 3 N 2 - black powder, formed when heated to 600 ° C in a stream of ammonia; stable in air up to 750 ° C, water decomposes it. Zinc carbide ZnC 2 was obtained by heating zinc in a stream of acetylene. Strong mineral acids dissolve Zinc vigorously, especially when heated, to form the corresponding salts. When interacting with diluted HCl and H 2 SO 4, H 2 is released, and with HNO 3, in addition, NO, NO 2, NH 3. Zinc reacts with concentrated HCl, H 2 SO 4 and HNO 3, releasing H 2, SO 2, NO and NO 2, respectively. Solutions and melts of alkalis oxidize zinc with the release of Н 2 and the formation of water-soluble zincites. The intensity of the action of acids and alkalis on Zinc depends on the presence of impurities in it. Pure Zinc is less reactive with respect to these reagents due to the high overvoltage of hydrogen on it. In water, zinc salts are hydrolyzed upon heating, giving off a white precipitate of Zn (OH) 2 hydroxide. Known complex compounds containing Zinc, for example SO 4 and others.

Getting Zinc. Zinc is mined from polymetallic ores containing 1-4% Zn in the form of sulfide, as well as Cu, Pb, Ag, Au, Cd, Bi. The ores are enriched by selective flotation, obtaining zinc concentrates (50-60% Zn) and simultaneously lead, copper, and sometimes also pyrite concentrates. Zinc concentrates are fired in fluidized bed furnaces, converting zinc sulfide to ZnO oxide; The resulting sulfur dioxide SO 2 is consumed in the production of sulfuric acid. There are two paths from ZnO to Zn. According to the pyrometallurgical (distillation) method, which has existed for a long time, the fired concentrate is subjected to sintering to impart granularity and gas permeability, and then reduced with coal or coke at 1200-1300 ° C: ZnO + C \u003d Zn + CO. The resulting metal vapors are condensed and poured into molds. At first, restoration was carried out only in manually operated baked clay retorts; later, vertical mechanized carborundum retorts began to be used, then - shaft and electric arc furnaces; Zinc is obtained from lead-zinc concentrates in blast shaft furnaces. The productivity gradually increased, but Zinc contained up to 3% impurities, including valuable cadmium. Distillation zinc is purified by segregation (i.e., by settling the liquid metal from iron and part of the lead at 500 ° C), reaching a purity of 98.7%. The sometimes more complicated and expensive purification by rectification, which is sometimes used, gives the metal with a purity of 99.995% and allows the recovery of cadmium.

The main method for producing zinc is electrolytic (hydrometallurgical). The fired concentrates are treated with sulfuric acid; the resulting sulfate solution is purified from impurities (by precipitating them with zinc dust) and subjected to electrolysis in baths tightly lined with lead or vinyl plastic. Zinc is deposited on aluminum cathodes, from which it is removed (stripped) daily and melted in induction furnaces. Usually, the purity of electrolyte zinc is 99.95%, the completeness of its extraction from the concentrate (taking into account waste processing) is 93-94%. Zinc sulfate, Pb, Cu, Cd, Au, Ag are obtained from production wastes; sometimes also In, Ga, Ge, Tl.

Application of Zinc. About half of the Zinc produced is used to protect steel against corrosion (Zinc plating). Since Zinc in the series of stresses is up to iron, then when galvanized iron gets into a corrosive environment, Zinc is destroyed. Due to its good casting properties and low melting point, various small parts of aircraft and other machines are injection molded from Zinc. Alloys of copper with zinc - brass, nickel silver, as well as zinc with lead and other metals are widely used in technology. Zinc gives intermetallic compounds with gold and silver (insoluble in liquid lead), and therefore Zinc is used for refining lead from precious metals. In the form of a powder, Zinc serves as a reducing agent in a number of chemical and technological processes: in the production of hydrosulfite, in the precipitation of gold from industrial cyanide solutions, copper and cadmium in the purification of solutions of zinc sulfate, and others. Many Zinc compounds are phosphors, for example, the three primary colors on the CRT screen depend on ZnS · Ag (blue), ZnSe · Ag (green) and Zn 3 (PO 4) 2 · Mn (red). Zinc compounds of the type A II B VI - ZnS, ZnSe, ZnTe, ZnO - are important semiconductor materials. The most common chemical current sources have Zinc as a negative electrode.

Zinc in the body. Zinc as one of the biogenic elements is constantly present in the tissues of plants and animals. The average zinc content in most terrestrial and marine organisms is thousandths of a percent. Fungi are rich in zinc, especially poisonous ones, lichens, conifers and some marine invertebrates, for example, oysters (0.4% dry weight). In zones of high zinc content in rocks, there are so-called galmein plants concentrating zinc. Zinc enters the organism of plants from soil and water, animals - from food. The daily human need for zinc (5-20 mg) is covered by bakery products, meat, milk, vegetables; in infants, the need for zinc (4-6 mg) is satisfied by breast milk.

The biological role of zinc is associated with its participation in enzymatic reactions in cells. It is part of the most important enzymes: carbonic anhydrase, various dehydrogenases, phosphatases associated with respiration and others. physiological processes, proteinases and peptidases involved in protein metabolism, nucleic acid metabolism enzymes (RNA and DNA polymerases), and others. Zinc plays an essential role in the synthesis of messenger RNA molecules at the corresponding DNA sites (transcription), in the stabilization of ribosomes and biopolymers (RNA, DNA, some proteins).

In plants, along with participation in respiration, protein and nucleic acid metabolism, zinc regulates growth, affects the formation of the amino acid tryptophan, and increases the content of gibberellins. Zinc stabilizes macromolecules of various biological membranes and can be an integral part of them, affects the transport of ions, and participates in the supramolecular organization of cell organelles. In the presence of Zinc in the culture of Ustilago sphaerogena, a greater number of mitochondria are formed; with a lack of Zinc in Euglena gracilis, ribosomes disappear. Zinc is necessary for the development of the egg and the embryo (in its absence, no seeds are formed). It increases drought, heat and cold resistance of plants. Zinc deficiency leads to impaired cell division, various functional diseases - whitening of the tops of corn, rosette plants and others. In animals, in addition to participating in respiration and nucleic acid metabolism, zinc increases the activity of the sex glands, affects the formation of the fetal skeleton. It has been shown that zinc deficiency in nursing rats reduces the RNA content and protein synthesis in the brain, and slows down the development of the brain. A zinc-containing protein has been isolated from the saliva of the human parotid gland; it is assumed that it stimulates the regeneration of the cells of the taste buds of the tongue and maintains their gustatory function. Zinc plays a protective role in the body against environmental pollution with cadmium.

Zinc deficiency in the body leads to dwarfism, delayed sexual development; in case of its excessive intake into the body, it is possible (according to experimental data) a carcinogenic effect and toxic effect on the heart, blood, gonads, etc. Industrial hazards may be associated with the adverse effects on the body of both metallic zinc and its compounds. Casting fever is possible when smelting zinc-containing alloys. Zinc preparations in the form of solutions (Zinc sulfate) and as part of powders, pastes, ointments, suppositories (Zinc oxide) are used in medicine as astringents and disinfectants.

Zinc is the number 30 metal in the periodic table 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 a hundred degrees it begins to bend.

Zinc color is blue-white. When exposed to oxygen, oxidation appears, as well as a carbonate coating, which protects the metal from further oxidation reaction. The appearance of hydroxide on zinc means that water does not act on a chemical element.

Zinc is a chemical element that has its own distinctive properties, advantages and disadvantages. It is widely used in everyday life human, in pharmaceuticals and metallurgy.

Features of zinc

Metal is essential and widely used in almost all areas of human daily life.

The production is mainly carried out in Iran, Kazakhstan, Australia, Bolivia. In Russia, the manufacturer is OJSC MMC Dalpolymetal.

It is a transition metal, has an oxidation state of +2, a radioactive isotope, and a half-life of 244 days.

The element is not mined in its pure form. Contained in ores and minerals: kleiophane, marmatite, wurtzite, zincite. 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.

TO physical properties zinc refers to its condition. The main factor is the temperature regime. 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 rolled in sheets at factories. If you take a higher temperature regime, the material acquires a liquid state, and if you raise the temperature by 400-450 ° C degrees, then it will simply evaporate. This is the uniqueness - to change your state. If acted with acids and alkalis, it can crumble, explode, melt.

Zn formula Zn - zincum. The atomic mass of zinc is 65.382 amu.

Electronic formula: the nucleus of a metal atom contains 30 protons, 35 neutrons. An atom has 4 energy levels - 30 electrons. (Fig. structure of zinc atom) 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2.

Crystal cell zinc is a hexagonal crystalline system with tightly pressed atoms. Lattice data: A \u003d 2.66Y, C \u003d 4.94.

Zinc structure and composition

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, metal is in 23 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 the amount of impurities, the metal is marked.

Zinc production

As mentioned above, there is no pure form of this element in nature. It is mined from other rocks, such as ore - cadmium, gallium, minerals - sphalerite.

The metal is obtained at the plant. Each plant has its own distinctive features production, so the equipment for obtaining pure material is different. It can be like this:

• The rotors are vertical electrolytic.
• Special furnaces with a sufficiently high temperature for firing, as well as special electric furnaces.
• Conveyors and baths for electrolysis.

Depending on the accepted method of metal mining, the appropriate equipment is involved.

Obtaining pure zinc

As mentioned above, there is no pure species in nature. It is mainly mined from ores in which it comes with various elements.

To obtain a clean 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 turns into an oxide state. During the roasting, a gas with a sulfur content is released, which is directed to the production of sulfuric acid.

There are 2 ways to get metal:

1. Pyrometallurgical - the process of burning is in progress, after - the resulting mass is restored with the help of black coal and coke. The final process is settling.
2. 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 the furnace is 419-480 ° C degrees. If the temperature regime is exceeded, then the material begins to evaporate. At this temperature, an iron impurity of 0.05% is allowed.

At an interest rate of 0.2 iron, the sheet cannot be rolled.

Are applied different ways smelting of pure metal, up to obtaining 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. Percentage:

1. Zinc plating - up to 60%.
2. Medicine - 10%.
3. Various alloys containing this metal 10%.
4. Tire production 10%.
5. Paint production - 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. Smelting of pig iron and steel is the main one in the entire metallurgy of the country. But, these metals are susceptible to negative effects. environment... Without specific treatment, metals are rapidly oxidized, which leads to their deterioration. The best protection is galvanized.

Applying a protective film to cast iron and steel is the best anti-corrosion agent. Galvanizing takes about 40% of the total production of clean material.

Galvanizing methods

Metallurgical plants are distinguished not only by their equipment, but also by their production methods. It depends on the pricing policy, and the location ( natural resourcesused for the metallurgical industry). There are several methods of galvanizing, which are discussed below.

Hot dip galvanizing

This method consists in dipping a metal part in a liquid solution. It happens like this:

1. The part or product is degreased, cleaned, washed and dried.
2. Next, the zinc is melted to liquid state at temperatures up to 480 ° C.
3. The prepared product is dipped into the liquid solution. At the same time, it is well wetted in solution and a coating with a thickness of up to 450 microns is formed. This is 100% protection from external factors on the product (moisture, direct sunlight, water with chemical impurities).

But, this method has several disadvantages:

• The zinc film on the product is an uneven layer.
• You cannot use this method for parts that meet the exact standards of GOST. 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 a high temperature.

Also, this method is not suitable for products coated with paints and varnishes.

Cold galvanized

This method has two names: galvanic and electrolytic. The procedure for coating a product with corrosion protection is as follows:

1. A metal part, the product is prepared (degreased, cleaned).
2. After that, the "dyeing method" is carried out - a special composition is used, which has the main component - zinc.
3. The part is coated with this compound by spraying.

Thanks to this method, parts with exact tolerances, products coated with paints and varnishes are covered with protection. Increases resistance to external factors leading to corrosion.

Disadvantages of this method: a 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 a positive polarity, while the metal of the workpiece (steel) becomes negative. 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:

1. 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 the steel, as well as the type of product, matters - the appropriate temperature is selected.
2. The thickness of the protective layer reaches 110 microns.
3. A product made of steel, cast iron is placed in a closed tank.
4. A special mixture is added there.
5. The last step is a special treatment of the product from the appearance of white efflorescence from salt water.

Basically, this method is used when it is required to cover parts that have a complex shape: threads, small strokes. The formation of a uniform protective layer is important, since these parts undergo multiple effects of an external aggressive environment (constant moisture).

This method provides the highest percentage of product corrosion protection. Galvanized spraying is wear-resistant and practically indelible, which is very important for parts that rotate and disassemble from time to time.

Other uses of zinc

In addition to galvanizing, metal is also used in other industries.

1. Zinc sheets. For sheet production, rolling is performed, in which plasticity is important. It depends on the temperature regime. A temperature of 25 ° C gives plasticity in only 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 Ts1, Ts2, Ts3. After that, various products for cars, profiles for construction and repair, for printing, and so on are created from the sheets.
2. 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 and 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, trough, sheets on the roof are the norm. Zinc is used, not chromium or nickel. And it's not just that galvanizing is cheaper than coating with other materials. This is the most reliable and long-lasting protective material than chrome or other materials used.

As a result, zinc is the most widespread 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 has a galvanized bucket in the house, a trough, which she uses for a long time.

Zinc is one of the metals that were discovered a long time ago, but to this day have not lost their relevance in use due to their remarkable properties. Its physical and chemical properties allow the material to be used in a wide variety of industries and households. It also has a significant impact on human health.

Brief history of element discovery

What is zinc, people knew before our era. After all, it was then that they learned to use alloys containing this metal. The Egyptians used ores containing copper and zinc, alloyed them and obtained a very strong, oxidation-resistant material. Household items, dishes made of this material were found.

The name zinc is found in the writings of the physician Paracelsus in the 16th century AD. In the same period, the Chinese began to actively use the metal, casting coins from it. Gradually, knowledge about this substance and its good technical properties is transferred to Europe. Then in Germany and England they also learned what zinc is and where it can be used.

Brass was one of the first and most famous alloys used since ancient times in Cyprus and later in Germany and other countries.

The name comes from the Latin zincum, but the etymology is not entirely clear. There are several versions.

1. From the German zinke, which translates as "edge".
2. From the Latin zincum, which means "white bloom".
3. Persian "cheng", that is, stone.
4. Ancient Germanic zinco, which translates as "plaque", "eyesore".

The element received its current name only at the beginning of the 20th century. The value of zinc ions in the human body also became known only relatively recently (XX century). Prior to that, no ailments were associated with this element.

However, it is known that already in ancient times many peoples used lamb meat soups as a means of recovering from an illness and for a speedy recovery. Today we can say that the effect was achieved due to zinc ions, which are quite a lot in this dish. He helped restore blood circulation, relieve fatigue and stimulate brain activity.

Zinc element: characteristic

This element is located in the periodic table in the second group, a side subgroup. The serial number is 30, the mass of Zinc is 65.37. The only and constant oxidation state is +2. The electronic configuration of the outer layer of the atom is 4s 2.

In the table, Zinc, Copper, Cadmium, Chromium, Manganese and many others are transition metals. These include all those in which electrons fill the outer and pre-outer d and f energy sublevels.

Zinc salts

Almost all salts that are not double and complex, that is, do not contain foreign colored ions, are colorless. The most popular in terms of human use are the following.

1. Zinc chloride - ZnCL 2. Another name for the compound is soldering acid. Outwardly, it is white crystals that absorb moisture well. It is used for cleaning the surface of metals before soldering, obtaining fiber, in batteries, for impregnating wood before processing as a disinfectant.
2. Zinc sulphide. A white powder that turns yellow quickly when heated. Has a high melting point, unlike pure metal. It is used in the production of luminescent compounds applied to screens, panels and other items. It is a semiconductor.
3. - a common poison used to get rid of gnawing animals (mice, rats).
4. Smithsonite, or zinc carbonate - ZnCO 3. Colorless crystalline compound, insoluble in water. It is used in petrochemical production, as well as in silk-making reactions. It is a catalyst in organic synthesis, used as a fertilizer for soils.
5. Zinc acetate - (CH 3 COO) 2 Zn. Colorless crystals, readily soluble in all solvents of any nature. It is widely used in both chemical and medical and food Industry... Used to treat nosapharyngitis. It is used as a food additive E650 - it freshens breath, prevents the appearance of plaque on the teeth when it is part of the gum. It is also used for etching dyes, wood preservation, plastics production and other organic syntheses. It plays the role of an inhibitor almost everywhere.
6. Zinc iodide - white crystals used in X-ray photography, as an electrolyte in batteries, as a dye for electronic micro-studies.
7. Black or dark green crystals, which cannot be obtained by direct synthesis, since zinc does not react with nitrogen. Formed from metal ammonia. At high temperatures, it decomposes with the release of zinc, therefore it is used to obtain it.
8. Zinc nitrate. Colorless hygroscopic crystals. The use of zinc in this form is carried out in the textile and leather industries for etching fabrics.

Zinc alloys

As mentioned above, the most common zinc alloy is brass. It is he who has been known since ancient times and is still actively used by people. What is he like?

Brass is a combination of copper and zinc, which work harmoniously with several other metals to add extra shine, strength and refractoriness to the alloy. Zinc in the composition as an alloying element, copper as the main one. The color of the material is yellow, shiny, but in the open air in a humid environment it can turn black. The melting point is about 950 o C, it can vary depending on the zinc content (the more it, the lower the temperature).

The material is well rolled into sheets, pipes, and welded by a contact method. Has good specifications, therefore, the following elements are made from it:

1. Machine parts and various technical devices.
2. Liners and stampings.
3. Nuts, bolts, pipes.
4. Fittings, bushings, anti-corrosion parts different types transport.
5. Watch details.

Most of the metal that we are mining in the world goes to the manufacture of this alloy.

Another type of intermetallic compound is zinc antimonide. Its formula is Zn 4 Sb 3. It is also an alloy that is used as a semiconductor in transistors, thermal imagers, and magnetoresistive devices.

It is obvious that the use of zinc and its compounds is very widespread and almost ubiquitous. This metal is as popular as copper and aluminum, silver and gold, manganese and iron. It is especially important for technical purposes as an anti-corrosion material. After all, it is zinc that covers various alloys and products to protect against this destructive natural process.

Biological role

What is zinc from a medical and biological point of view? Does it matter for the life of organisms and how great is it? It turns out that zinc ions must be present in living things. Otherwise, the deficit will lead to the following consequences:

• anemia;
• decrease in insulin;
• allergies;
• loss of weight and memory;
• fatigue;
• depression;
• deterioration of vision;
• irritability and others.

The main places of concentration of zinc ions in the human body are the liver and muscles. Also, it is this metal that is part of most enzymes (for example, carbonic anhydrase). Therefore, most catalysis reactions take place with the participation of zinc.

What exactly do ions do?

1. Participate in the synthesis of male hormones and seminal fluid.
2. Promote the absorption of vitamin E.
3. Participate in the breakdown of alcohol molecules in the body.
4. They are direct participants in the synthesis of many hormones (insulin, growth hormone, testosterone, and others).
5. Takes part in hematopoiesis and healing of damaged tissues.
6. Regulates the secretion of the sebaceous glands, maintains normal hair and nail growth, and promotes regeneration processes in the skin.
7. It has the ability to eliminate toxins from the body and strengthen the immune system.
8. Influences the formation of taste, as well as the sense of smell.
9. Takes part in the processes of transcription, the exchange of vitamin A, nucleic acid synthesis and decay.
10. It is a participant in all stages of cell growth and development, and also accompanies the process of gene expression.

All this proves once again how much important element is this metal. Its role in biological systems was clarified only in the XX century. Many troubles and ailments in the past could have been avoided if people knew about the treatment with zinc-based preparations.

How can you maintain the required amount of this element in the body? The answer is obvious. You must eat foods containing zinc. The list can be long, so we will indicate only those in which the maximum number of the element in question:

• nuts and seeds;
• legumes;
• meat;
• seafood, especially oysters;
• cereals and bread;
• milk products;
• greens, vegetables and fruits.

Human use

We have already generally indicated in which industries and areas of industry zinc is used. The price for this metal and its alloys is quite high. For example, a brass sheet measuring 0.6 x 1.5 is approximately estimated at 260 rubles. And this is quite justified, because the quality of the material is quite high.

So, metallic zinc, that is, as a simple substance, is used:

• for coating against corrosion on iron and steel products;
• in batteries;
• typography;
• as a reducing agent and catalyst in organic syntheses;
• in metallurgy for the separation of other metals from their solutions.

It is used not only for cosmetic purposes, which we have already mentioned, but also as a filler in the production of rubber, as a white pigment in paints.

We talked about where the various zinc salts are used when considering these compounds. It is obvious that, in general, zinc and its substances are important and significant components in industry, medicine and other industries, without which many processes would be impossible or very difficult.