Magnesium compounds have been known to man for a very long time. Magnesite (in Greek Magnhsia oliqV) was a soft, white, soapy mineral (soapstone, or talc) found in the Magnesia region of Thessaly. When this mineral was calcined, a white powder was obtained, which became known as white magnesia.

In 1695, N. Gro, evaporating the mineral water of the Epsom spring (England), obtained salt that had a bitter taste and a laxative effect (MgSO 4 · 7H 2 O). A few years later it turned out that when interacting with soda or potash, this salt forms a white, loose powder, the same as that formed when magnesite is calcined.

In 1808, the English chemist and physicist Humphry Davy, by electrolysis of slightly moistened white magnesia with mercury oxide as a cathode, obtained an amalgam of a new metal capable of forming white magnesia. It was called magnesium. Davy obtained the contaminated metal, and pure magnesium was isolated only in 1829 by the French chemist Antoine Bussy (1794–1882).

Distribution of magnesium in nature and its industrial extraction.

Magnesium is found in crystalline rocks in the form of insoluble carbonates or sulfates, and also (in a less accessible form) in the form of silicates. The estimate of its total content depends significantly on the geochemical model used, in particular, on the weight ratios of volcanic and sedimentary rocks. Currently, values ​​from 2 to 13.3% are used. Perhaps the most reasonable value is 2.76%, which ranks magnesium sixth in abundance after calcium (4.66%) and ahead of sodium (2.27%) and potassium (1.84%).

Large land areas such as the Dolomites in Italy are composed predominantly of the mineral dolomite MgCa(CO 3) 2 . There are also sedimentary minerals magnesite MgCO 3, epsomite MgSO 4 · 7H 2 O, carnallite K 2 MgCl 4 · 6H 2 O, langbeinite K 2 Mg 2 (SO 4) 3.

There are dolomite deposits in many other areas, including the Moscow and Leningrad regions. Rich deposits of magnesite were found in the Middle Urals and in the Orenburg region. The largest carnallite deposit is being developed in the Solikamsk region. Magnesium silicates are represented by the basalt mineral olivine (Mg,Fe) 2 (SiO 4), soapstone (talc) Mg 3 Si 4 O 10 (OH) 2, asbestos (chrysotile) Mg 3 Si 2 O 5 (OH) 4 and mica. Spinel MgAl 2 O 4 belongs to precious stones.

A large amount of magnesium is found in the waters of the seas and oceans and in natural brines ( cm. CHEMISTRY OF HYDROSPHERE). In some countries, they are the raw materials for the production of magnesium. In terms of metallic element content in seawater, it is second only to sodium. Each cubic meter of sea water contains about 4 kg of magnesium. Magnesium is also found in fresh water, which, along with calcium, determines its hardness.

Magnesium is always found in plants, as it is part of chlorophylls.

Characteristics of simple substances and industrial production of metallic magnesium.

Magnesium is a silvery-white shiny metal, relatively soft, ductile and malleable. Its strength and hardness are minimal in prevalence for cast samples, higher for pressed ones.

Under normal conditions, magnesium is resistant to oxidation due to the formation of a strong oxide film. However, it reacts actively with most non-metals, especially when heated. Magnesium ignites in the presence of halogens (in the presence of moisture), forming the corresponding halides, and burns with a blindingly bright flame in air, turning into MgO oxide and Mg 3 N 2 nitride:

2Mg (k) + O 2 (g) = 2MgO (k) ; DG° = –1128 kJ/mol

3Mg (k) + N 2 (t) = Mg 3 N 2 (k); DG° = –401 kJ/mol

Despite the low melting point (650° C), it is impossible to melt magnesium in air.

When exposed to hydrogen under a pressure of 200 atm at 150° C, magnesium forms the hydride MgH 2 . Magnesium does not react with cold water, but displaces hydrogen from boiling water and forms hydroxide Mg(OH) 2:

Mg + 2H 2 O = Mg(OH) 2 + H 2

At the end of the reaction, the pH value (10.3) of the resulting saturated solution of magnesium hydroxide corresponds to equilibrium:

In the latter case, the resulting mixture of carbon monoxide and magnesium vapor must be quickly cooled with an inert gas to prevent a reverse reaction.

World magnesium production is approaching 400 thousand tons per year. The main producers are the USA (43%), CIS countries (26%) and Norway (17%). In recent years, China has been sharply increasing its magnesium exports. In Russia, one of the largest producers of magnesium is the titanium-magnesium plant in Berezniki (Perm region) and the Solikamsk magnesium plant. Magnesium production is also taking place in the city of Asbest.

Magnesium is the lightest structural material used on an industrial scale. Its density (1.7 g cm–3) is less than two-thirds that of aluminum. Magnesium alloys weigh four times less than steel. In addition, magnesium is highly machinable and can be cast and reworked using any standard metalworking methods (rolling, stamping, drawing, forging, welding, soldering, riveting). Therefore, its main application is as a lightweight structural metal.

Magnesium alloys typically contain more than 90% magnesium, as well as 2–9% aluminum, 1–3% zinc, and 0.2–1% manganese. Strength retention at high temperatures (up to 450° C) is noticeably improved when alloyed with rare earth metals (for example, praseodymium and neodymium) or thorium. These alloys can be used for automobile engine housings, as well as aircraft fuselages and landing gear. Magnesium is used not only in aviation, but also in the manufacture of stairs, dock walkways, cargo platforms, conveyors and lifts, as well as in the production of photographic and optical equipment.

Up to 5% magnesium is added to industrial aluminum to improve mechanical properties, weldability and corrosion resistance. Magnesium is also used for cathodic protection of other metals against corrosion, as an oxygen scavenger and reducing agent in the production of beryllium, titanium, zirconium, hafnium and uranium. Mixtures of magnesium powder with oxidizing agents are used in pyrotechnics for the preparation of lighting and incendiary compositions.

Magnesium compounds.

The predominant oxidation state (+2) for magnesium is determined by its electronic configuration, ionization energies and atomic sizes. The oxidation state (+3) is impossible, since the third ionization energy for magnesium is 7733 kJ mol –1. This energy is much higher than can be compensated for by the formation of additional bonds, even if they are predominantly covalent. The reasons for the instability of magnesium compounds in the oxidation state (+1) are less obvious. An assessment of the enthalpy of formation of such compounds shows that they must be stable with respect to their constituent elements. The reason that magnesium(I) compounds are not stable is the much higher enthalpy of formation of magnesium(II) compounds, which should lead to rapid and complete disproportionation:

Mg(k) + Cl 2 (g) = MgCl 2 (k);

D N° arr = –642 kJ/(mol MgCl 2)

2Mg(k) + Cl 2 (g) = 2MgCl(k);

D N° arr = –250 kJ/(2 mol MgCl)

2MgCl(k) = Mg(k) + MgCl 2 (k);

D N° disprop = –392 kJ/(2 mol MgCl)

If a synthetic route can be found that makes disproportionation difficult, such compounds may be obtained. There is some evidence for the formation of magnesium(I) particles during electrolysis on magnesium electrodes. Thus, during the electrolysis of NaCl on a magnesium anode, hydrogen is released, and the amount of magnesium lost by the anode corresponds to a charge of +1.3. Similarly, during the electrolysis of an aqueous solution of Na 2 SO 4, the amount of hydrogen released corresponds to the oxidation of water by magnesium ions, the charge of which corresponds to +1.4.

Most magnesium salts are highly soluble in water. The dissolution process is accompanied by slight hydrolysis. The resulting solutions have a weakly acidic environment:

2+ + H 2 O + + H 3 O +

Compounds of magnesium with many non-metals, including carbon, nitrogen, phosphorus, and sulfur are irreversibly hydrolyzed by water.

Magnesium hydride composition MgH 2 is a polymer with bridging hydrogen atoms. The coordination number of magnesium in it is 4. This structure leads to a sharp decrease in the thermal stability of the compound. Magnesium hydride is easily oxidized by atmospheric oxygen and water. These reactions are accompanied by a large release of energy.

Magnesium nitride Mg 3 N 2. Forms yellowish crystals. The hydrolysis of magnesium nitride produces ammonia hydrate:

Mg 3 N 2 + 8H 2 O = 3Mg(OH) 2 + 2NH 3 H 2 O

If the hydrolysis of magnesium nitride is carried out in an alkaline medium, ammonia hydrate is not formed, but ammonia gas is released. Hydrolysis in an acidic environment leads to the formation of magnesium and ammonium cations:

Mg 3 N 2 + 8H 3 O + = 3Mg 2+ + 2NH 4 + + 8H 2 O

Magnesium oxide MgO is called burnt magnesia. It is obtained by firing magnesite, dolomite, basic magnesium carbonate, magnesium hydroxide, as well as calcining bischofite MgCl 2 ·6H 2 O in an atmosphere of water vapor.

The reactivity of magnesium oxide depends on the temperature at which it is produced. Magnesium oxide prepared at 500–700°C is called light magnesia. It reacts easily with dilute acids and water to form the corresponding salts or magnesium hydroxide, and absorbs carbon dioxide and moisture from the air. Magnesium oxide obtained at 1200–1600° C is called heavy magnesia. It is characterized by acid resistance and water resistance.

Magnesium oxide is widely used as a heat-resistant material. It is characterized by both high thermal conductivity and good electrical insulating properties. Therefore, this compound is used in insulating radiators for local heating.

Lighter grades of magnesia are used for the preparation of magnesia cement and building materials based on it, and also as a vulcanizing agent in the rubber industry.

Magnesium hydroxide Mg(OH) 2 forms colorless crystals. The solubility of this compound is low (2·10 –4 mol/l at 20° C). It can be converted into solution by the action of ammonium salts:

Mg(OH) 2 + 2NH 4 Cl = MgCl 2 + 2NH 3 H 2 O

Magnesium hydroxide is thermally unstable and decomposes when heated:

Mg(OH) 2 = MgO + H 2 O

On an industrial scale, magnesium hydroxide is produced by precipitation with lime from sea water and natural brines.

Magnesium hydroxide is a mild base that, in the form of an aqueous solution (milk of magnesia), is widely used to reduce the acidity of gastric juice. Moreover, despite its softness, Mg(OH) 2 neutralizes acids 1.37 times more than sodium hydroxide NaOH and 2.85 times more than sodium bicarbonate NaHCO 3.

It is also used to produce magnesium oxide, sugar refining, water purification in boiler plants, and as a component of toothpastes.

Magnesium carbonate MgCO 3 forms colorless crystals. It occurs naturally in anhydrous form (magnesite). In addition, penta-, tri- and monohydrates of magnesium carbonate are known.

The solubility of magnesium carbonate in the absence of carbon dioxide is about 0.5 mg/l. In the presence of excess carbon dioxide and water, magnesium carbonate transforms into soluble bicarbonate, and when boiling, the reverse process occurs. Carbonate and bicarbonate react with acids to release carbon dioxide and form the corresponding salts. When heated, magnesium carbonate, without melting, decomposes:

MgCO 3 = MgO + CO 2

This process is used to produce magnesium oxide. In addition, natural magnesium carbonate is the starting material for the production of metallic magnesium and its compounds. It is also used as fertilizer and to reduce soil acidity.

Loose magnesium carbonate powder is poured between the double walls of liquid oxygen storage tanks. This thermal insulation is cheap and reliable.

Magnesium sulfate MgSO 4 is known in the anhydrous state, as well as in the form of various hydrates. Kieserite MgSO 4 ·H 2 O, epsomite MgSO 4 ·7H 2 O and hexahydrate MgSO 4 ·6H 2 O are found in nature.

In medicine, magnesium sulfate heptahydrate MgSO 4 ·7H 2 O is used, commonly known as Epsom or bitter salt. This compound has a laxative effect. With intramuscular or intravenous infusions, magnesium sulfate relieves convulsive conditions and reduces vascular spasms.

Magnesium sulfate is used in the textile and paper industries as a dyeing mordant, as a weighting agent for cotton and silk, and as a paper filler. It serves as a raw material for the production of magnesium oxide.

Magnesium nitrate Mg(NO 3) 2 are colorless hygroscopic crystals. Solubility in water at 20° C is 73.3 g per 100 g. The hexahydrate crystallizes from aqueous solutions. Above 90°C it dehydrates to monohydrate. Then water is separated with partial hydrolysis and decomposition to magnesium oxide. This process is used in the synthesis of high purity magnesium oxide. From magnesium nitrate, nitrates of other metals are obtained, as well as various magnesium compounds. In addition, magnesium nitrate is part of complex fertilizers and pyrotechnic mixtures.

Magnesium perchlorate Mg(ClO 4) 2 forms very hygroscopic colorless crystals. It is highly soluble in water (99.6 g per 100 g) and organic solvents. The hexahydrate crystallizes from aqueous solutions. Concentrated solutions of magnesium perchlorate in organic solvents and its solvates with reducing agent molecules are explosive.

Partially hydrated magnesium perchlorate, containing 2–2.5 molecules of water, is produced under the commercial name “anhydrone”. To obtain anhydrous magnesium perchlorate, it is dried in a vacuum at 200–300 ° C. It is used as a gas desiccant. It absorbs not only water vapor, but also ammonia, alcohol vapor, acetone and other polar substances.

Magnesium perchlorate is used as an acylation catalyst in the Friedel–Crafts reaction, and also as an oxidizing agent in microanalysis.

Magnesium fluoride MgF 2 is slightly soluble in water (0.013 g per 100 g at 25 ° C). It occurs naturally as the mineral selaite. Magnesium fluoride is obtained by reacting magnesium sulfate or oxide with hydrofluoric acid or magnesium chloride with potassium or ammonium fluoride.

Magnesium fluoride is part of fluxes, glasses, ceramics, enamels, catalysts, mixtures for producing artificial mica and asbestos. In addition, it is an optical and laser material.

Magnesium chloride MgCl 2 is one of the most industrially important magnesium salts. Its solubility is 54.5 g per 100 g of water at 20 ° C. Concentrated aqueous solutions of magnesium chloride dissolve magnesium oxide. MgCl 2 mMg(OH) 2 nH 2 O crystallizes from the resulting solutions. These compounds are part of magnesia cements.

Magnesium chloride forms crystalline hydrates with 1, 2, 4, 6, 8 and 12 water molecules. As the temperature increases, the number of molecules of water of crystallization decreases.

In nature, magnesium chloride is found in the form of the minerals bischofite MgCl 2 ·6H 2 O, magnesite chloride MgCl 2, and carnallite. It is found in sea water, brine from salt lakes, and some underground brines.

Anhydrous magnesium chloride is used in the production of metallic magnesium and magnesium oxide, and hexahydrate is used to produce magnesium cements. An aqueous solution of magnesium chloride is used as a coolant and antifreeze. It serves as a de-icing agent on airfields, railway tracks and switches, as well as against freezing of coal and ores. The wood is impregnated with a solution of magnesium chloride to make it fire resistant.

Magnesium bromide MgBr 2 is highly soluble in water (101.5 g per 100 g at 20° C). From aqueous solutions it crystallizes from –42.7 to 0.83 ° C in the form of decahydrate, at higher temperatures - in the form of hexahydrate. It forms numerous crystal solvates, such as MgB 2 6ROH (R = Me, Et, Pr), MgBr 2 6Me 2 CO, MgBr 2 3Et 2 O, as well as amines MgBr 2 n NH 3 ( n = 2–6).

Complex magnesium compounds. In aqueous solutions, magnesium ion exists in the form of an aqua complex 2+. In non-aqueous solvents, such as liquid ammonia, the magnesium ion forms complexes with solvent molecules. Solvates of magnesium salts usually crystallize from such solutions. Several halide complexes of the MX 4 2– type are known, where X is the halide anion.

Among complex magnesium compounds, chlorophylls, which are modified porphyrin complexes of magnesium, are of particular importance. They are vital for photosynthesis in green plants.

Organomagnesium compounds. Numerous compounds containing metal–carbon bonds have been obtained for magnesium. Especially a lot of research is devoted to Grignard reagents RMgX (X = Cl, Br, I).

Grignard reagents are the most important organometallic magnesium compounds and probably the most used organometallic reagents. This is due to their ease of production and synthetic versatility. It has been established that in solution these compounds can contain a variety of chemical particles that are in mobile equilibrium.

Grignard reagents are usually prepared by slowly adding an organic halide to a suspension of magnesium turnings in an appropriate solvent under vigorous stirring and in the complete absence of air and moisture. The reaction usually starts slowly. It can be initiated by a small crystal of iodine, which destroys the protective layer on the metal surface.

Grignard reagents are widely used for the synthesis of alcohols, aldehydes, ketones, carboxylic acids, esters and amides and are probably the most important reagents for creating carbon-carbon bonds, as well as bonds between carbon atoms and other elements (nitrogen, oxygen, sulfur, etc.) .d.).

R2Mg compounds usually decompose when heated. In the crystalline state, they have the structure of linear polymers with bridging alkyl groups. The MgMe 2 compound is a non-volatile polymer, stable up to ~250° C, insoluble in hydrocarbons and only slightly soluble in ether. The compound MgEt 2 and higher homologues are very similar to MgMe 2, but they decompose at lower temperatures (175–200 ° C), forming the corresponding alkene and MgH 2 in the opposite reaction to their formation. MgPh 2 is also similar to them; it is insoluble in benzene, dissolves in ether to form the monomeric complex MgPh 2 · 2Et 2 O and decomposes at 280 ° C to form Ph 2 and metallic magnesium.

Biological role of magnesium.

Green plant leaves contain chlorophylls, which are magnesium-containing porphyrin complexes involved in photosynthesis.

Magnesium is also closely involved in biochemical processes in animal bodies. Magnesium ions are necessary for the initiation of enzymes responsible for the conversion of phosphates, for the transfer of nerve impulses and for the metabolism of carbohydrates. They are also involved in muscle contraction, which is initiated by calcium ions.

Several years ago, scientists at the University of Minnesota in the USA found that eggshells are stronger the more magnesium they contain.

The body of an adult weighing 65 kg contains about 20 g of magnesium (mainly in the form of ions). Most of it is concentrated in the bones. Magnesium complexes with ATP and ADP are present in the intracellular fluid.

The daily requirement for this element is 0.35 g. With a monotonous diet, a lack of green vegetables and fruits, as well as with alcoholism, magnesium deficiency often occurs. Apricots, peaches and cauliflower are especially rich in magnesium. It is also found in regular cabbage, potatoes, and tomatoes.

Statistics show that residents of areas with warmer climates experience spasms of blood vessels less frequently than northerners. It is believed that the reason for this is the dietary habits in cold regions. They eat less fruits and vegetables, which means they get less magnesium.

Research by French biologists has shown that the blood of tired people contains less magnesium than that of rested people. It is believed that a diet rich in magnesium should help doctors in the fight against such a serious illness as overwork.

Elena Savinkina

Magnesium is a metal widespread in nature and of great biogenic importance for humans. It is a component of a large number of different minerals, sea water, and hydrothermal waters.

Properties

Silvery shiny metal, very light and ductile. Non-magnetic, has high thermal conductivity. Under normal conditions in air it becomes covered with an oxide film. When heated above 600 °C, the metal burns, releasing a large amount of heat and light. It burns in carbon dioxide and reacts actively with water, so it is useless to extinguish it using traditional methods.

Magnesium does not interact with alkalis; it reacts with acids to release hydrogen. Resistant to halogens and their compounds; for example, does not interact with fluorine, hydrofluoric acid, dry chlorine, iodine, bromine. It is not destroyed under the influence of petroleum products. Magnesium is poorly resistant to corrosion; this deficiency is corrected by adding small amounts of titanium, manganese, zinc, and zirconium to the alloy.

Magnesium is necessary for the health of the cardiovascular and nervous systems, for the synthesis of proteins and the body's absorption of glucose, fats and amino acids. Magnesium orotate (vitamin B13) plays an important role in metabolism, normalizes cardiac activity, prevents the deposition of cholesterol on the walls of blood vessels, increases the performance of athletes, being as effective as steroid drugs.

Magnesium is obtained in various ways, from natural minerals and sea water.

Application

Most of the mined magnesium is used for the production of magnesium structural alloys, which are in demand in the aviation, automotive, nuclear, chemical, oil refining industries, and instrument making. Magnesium alloys are distinguished by lightness, strength, high specific rigidity, and good machinability. They are non-magnetic, excellent heat dissipation, and 20 times more resistant to vibration than alloy steel. Magnesium alloys are used for the manufacture of tanks for storing gasoline and petroleum products, parts of nuclear reactors, jackhammers, pneumatic pipes, cars; tanks and pumps for working with hydrofluoric acid, for storing bromine and iodine; laptop and camera cases.
- Magnesium is widely used to obtain some metals by reduction (vanadium, zirconium, titanium, beryllium, chromium, etc.); for giving steel and cast iron better mechanical characteristics, for cleaning aluminum.
- In its pure form, it is part of many semiconductors.
- In the chemical industry, powdered magnesium is used for drying organic substances, for example, alcohol, aniline. Organomagnesium compounds are used in complex chemical synthesis (for example, to obtain vitamin A).
- Magnesium powder is in demand in rocket technology as a high-calorie fuel. In military affairs - in the production of flares, tracer ammunition, incendiary bombs.
- Pure magnesium and its compounds are used to make powerful chemical current sources.
- Magnesium oxide is used for the manufacture of crucibles and metallurgical furnaces, refractory bricks, and in the manufacture of synthetic rubber.
- Magnesium fluoride crystals are in demand in optics.
- Magnesium hydride is a solid powder containing a large percentage of hydrogen, which is easily obtained by heating. The substance is used as a “storage” for hydrogen.
- Less common now, but previously magnesium powder was widely used in chemical flashes.
- Magnesium compounds are used for bleaching and etching fabrics, for the manufacture of thermal insulation materials, and special types of bricks.
- Magnesium is included in many medicines, both internal and external (bischofite) use. It is used as an anticonvulsant, laxative, sedative, cardiac, antispasmodic, to regulate the acidity of gastric juice, as an antidote for acid poisoning, as a gastric disinfectant, to treat injuries and joints.
- Magnesium stearate is used in the pharmaceutical and cosmetic industries as a filler for tablets, powders, creams, eye shadows; in the food industry it is used as a food additive E470, which prevents caking of products.

In the Prime Chemicals Group chemical store you can buy chemical magnesium and its various compounds - magnesium stearate, bischofite magnesium chloride, magnesium carbonate and others, as well as a wide range of chemical reagents, laboratory glassware and other goods for laboratories and production. You will like the prices and level of service!

MAGNESIUM

Plan:

1. Characteristics of the element.

2. Obtaining magnesium.

3. Properties of magnesium.

3.1. Physical properties of magnesium.

3.2. Chemical properties of magnesium.

4. Magnesium compounds.

4.1. Inorganic compounds

4.2. Organomagnesium compounds

5. Natural magnesium compounds

6. Determination of magnesium in soils and water

7. Biological significance of magnesium

8. Applications of magnesium

9. Water hardness

10. Practical work “Determination of water hardness”

1. Characteristics of the element

Name "magnesia" found already in the 3rd century AD, although it is not entirely clear what substance it means. For a long time, magnesite - magnesium carbonate - was mistakenly identified with limestone - calcium carbonate. The word magnesia comes from the name of one of the Greek cities - Magnesia. Until the 18th century, magnesium compounds were considered varieties of calcium or sodium salts. The discovery of magnesium was facilitated by the study of the composition of mineral waters. In 1695, the English physician Crewe reported that he had isolated salt with medicinal properties from the water of the Epsom mineral spring, and its individual nature was soon proven. Then other magnesium compounds became known. Magnesium carbonate is called “white magnesia”, in contrast to “black magnesia” - manganese oxide. Hence the consonance of the names of the metals subsequently isolated from these compounds.

Magnesium was first obtained by Devi (19th century) from magnesium oxide. Bussy, Liebig, Devils, Caron and others obtained magnesium by the action of potassium or sodium vapor on magnesium chloride.

In 1808, the English chemist G. Devi, by electrolysis of a moistened mixture of magnesia and mercury oxide, obtained an amalgam of an unknown metal, to which he gave the name “magnesia,” which is still preserved in many countries. In Russia, the name “magnesium” has been adopted since 1831. In 1829, the French chemist A. Bussy obtained magnesium by reducing its molten chloride with potassium. The next step towards industrial production was made by M. Faraday. In 1830, he first obtained magnesium by electrolysis of molten magnesium chloride.

Industrial production of magnesium by electrolytic method was undertaken in Germany at the end of the 19th century. Before the Second World War, the development of thermal methods for producing magnesium began.

Currently, along with the development of the electrolytic method, silicothermic and carbothermic methods for producing magnesium are being improved. At the first stage of development of the magnesium industry, carnallite chloride salts, natural brines, and magnesium chloride alkalis of the potassium industry were used as raw materials.

Nowadays, along with chloride salts, dolomite and magnesite are widely used. Of great interest is the use as a raw material for the production of magnesium from sea water. In Russia, the electrolytic method for producing magnesium was first developed by P.P. Fedotiev in 1914 at the Petrograd Polytechnic Institute. In 1931, the first pilot magnesium plant came into operation in Leningrad. Industrial production of magnesium in the USSR began in 1935.

+12 Mg))) 1S 2 2S 2 2P 6 3S 2 3P 0 – electron formula of a normal atom 282

When the required energy is expended, one of the electrons goes into the P-state, i.e. both electrons become unpaired. Therefore, magnesium exhibits an oxidation state of +2.

3S 2 -valence electrons

1S 2 2S 2 2P 6 3S 1 3P 1

- electronic formula of an excited atom+12 Mg +P 12 ,n 0 12 e12

The structure of the outer electron shell of magnesium, which has a 3S 2 structure, with two weakly bound electrons explains the reductive nature of typical reactions in which magnesium transforms into the divalent cation Mg 2+. Due to its high chemical affinity for oxygen, magnesium is capable of removing oxygen from many oxides and chlorine from chlorides. This property has recently been used in the magnesium-thermal production of titanium, zirconium, and uranium. At room temperature in air, compact magnesium is chemically stable. An oxide film forms on its surface, protecting it from oxidation. When heated, the chemical activity of magnesium increases. It is believed that the upper temperature limit of magnesium stability in oxygen is in the range of 350-400 o C. Magnesium decomposes boiling water with the release of hydrogen.

Distilled water, hydrofluoric acid of any concentration, chromic acid, aqueous solutions of fluoride salts, etc. have no noticeable effect on magnesium.

Sea and mineral water, aqueous solutions of hydrochloric, sulfuric, nitric, phosphoric, hydrofluorosilicic acids, aqueous solutions of halide salts, sulfur compounds, ammonia and its aqueous solutions, organic acids, glycols and glycol mixtures, and many aldehydes have a destructive effect on magnesium.

Magnesium is one of the most common elements in the earth's crust, ranking sixth in abundance after oxygen, silicon, aluminum, iron and calcium. Magnesium content in the lithosphere, according to A.P. Vinogradov, is 2.10%. In nature, magnesium is found exclusively in the form of compounds and is part of many minerals: carbonates, silicates, etc. The most important of them are: magnesite MgCO 3, dolomite MgCO 3 *CaCO 3, carnallite MgCl 2 *KCL*6H 2 O, brucite Mg (OH) 2, kieserite MgSO 4, epsonite MgSO 4 *7H 2 O, kainite MgSO 4 *KCl*3H 2 O, olivine (Mg,Fe) 2, serpentine H 4 Mg 3 Si 2 O 9.

Natural or natural magnesium is a mixture of three stable isotopes 24 Mg -78.6%, 25 Mg -10.1%, 26 Mg -11.3%.

In reactions, magnesium almost always exhibits an oxidation state of +2 (valency II). In order to transfer a magnesium atom from the 3S 2 state to the reactive 3S 1 3P 1 state, it is necessary to spend 259 KJ/mol, and with the sequential removal of electrons, i.e. ionization of Mg to Mg + and Mg +2, 737 KJ/mol and 1450 KJ/mol are required, respectively. Magnesium crystallizes into a hexagonal close-packed lattice.

2. OBTAINING MAGNESIUM.

The predominant industrial method for producing magnesium is electrolysis of a melt mixture of MgCl 2

MgCl 2 Mg 2+ 2Cl - K -) A +)
Mg 2+ +2 e Mg 0 2Cl - -2 e Cl 2 0

Magnesium
Atomic number	12
Appearance of a simple substance	light, malleable, silvery-white metal
Properties of the atom
Atomic mass (molar mass)	24.305 a. e.m. (/mol)
Atomic radius	160 pm
Ionization energy (first electron)	737.3 (7.64) kJ/mol (eV)
Electronic configuration	3s 2
Chemical properties
Covalent radius	136 pm
Ion radius	66 (+2e) pm
Electronegativity (according to Pauling)	1,31
Electrode potential	−2.37 V
Oxidation states	2
Thermodynamic properties of a simple substance
Density	1.738 g/cm³
Molar heat capacity	24.90 J/(K mol)
Thermal conductivity	156 W/(m K)
Melting temperature	922 K
Heat of Melting	9.20 kJ/mol
Boiling temperature	1 363 K
Heat of vaporization	131.8 kJ/mol
Molar volume	14.0 cm³/mol
Crystal lattice of a simple substance
Lattice structure	hexagonal
Lattice parameters	a=3.210 c=5.21 Å
c/a ratio	1,624
Debye temperature	318 K

Mg	12
24,305
3s 2
Magnesium

Magnesium- an element of the main subgroup of the second group, the third period of the periodic table of chemical elements, with atomic number 12. Denoted by the symbol Mg Magnesium. The simple substance magnesium (CAS number: 7439-95-4) is a light, malleable metal of a silvery-white color.

Story

origin of name

In 1695, from the mineral water of Epsom Spring in England isolated salt, which had a bitter taste and a laxative effect. Pharmacists called it bitter salt, as well as Epsom or Epsom salt. The mineral epsomite has the composition MgSO 4 7H 2 O.

It was first isolated in its pure form by Sir Humphry Davy in 1808.

Receipt

The usual industrial method for producing magnesium metal is the electrolysis of a melt of a mixture of anhydrous magnesium chlorides MgCl 2 (bischofite), sodium NaCl and potassium KCl. In this melt, magnesium chloride undergoes electrochemical reduction:

MgCl 2 (electrolysis) = Mg + Cl 2.

The molten metal is periodically removed from the electrolysis bath, and new portions of magnesium-containing raw materials are added to it. Since the magnesium obtained in this way contains relatively a lot of impurities - about 0.1%, if necessary, “raw” magnesium is subjected to additional purification. For this purpose, electrolytic refining is used, melting in a vacuum using special additives - fluxes, which “remove” impurities from magnesium, or distillation (sublimation) of the metal in a vacuum. The purity of refined magnesium reaches 99.999% and higher.

Another method for obtaining magnesium has been developed - thermal. In this case, coke is used to reduce magnesium oxide at high temperature:

or silicon. The use of silicon makes it possible to obtain magnesium from raw materials such as dolomite CaCO 3 ·MgCO 3 without preliminary separation of magnesium and calcium. The following reactions occur with the participation of dolomite:

CaCO 3 MgCO 3 = CaO + MgO + 2CO 2,

2MgO + CaO + Si = Ca 2 SiO 4 + 2Mg.

The advantage of the thermal method is that it allows one to obtain magnesium of higher purity. To obtain magnesium, not only mineral raw materials are used, but also sea water.

Physical properties

Magnesium is a very light, rather brittle metal that gradually oxidizes in air, turning into white magnesium oxide. The crystal lattice of the α-form Ca (stable at ordinary temperatures) is face-centered cubic, a = 5.56 Å. Atomic radius 1.97Å, ionic radius Ca2+, 1.04Å. Density 1.74 g/cm³ (20 °C). Above 464 °C, the hexagonal β-form is stable. t melt = 650 °C, t boil = 1105 °C; temperature coefficient of linear expansion 22.10-6 (0-300 °C); thermal conductivity at 20 °C 125.6 W/(m.K) or 0.3 cal/(cm.sec.°C); specific heat capacity (0-100 °C) 623.9 J/(kg.K) or 0.149 cal/(g.°C); electrical resistivity at 20 °C 4.6.10-8 ohm.m or 4.6.10-6 ohm.cm; temperature coefficient of electrical resistance 4.57.10-3 (20 °C). Elastic modulus 26 Gn/m² (2600 kgf/mm²); tensile strength 60 MN/m² (6 kgf/mm²); elastic limit 4 MN/m² (0.4 kgf/mm²), yield strength 38 MN/m² (3.8 kgf/mm²); relative elongation 50%; Brinell hardness 200-300 MN/m² (20-30 kgf/mm²). Magnesium of sufficiently high purity is plastic, easily pressed, rolled and amenable to cutting.

Chemical properties

A mixture of powdered magnesium with potassium permanganate KMnO 4 is an explosive! Hot magnesium reacts with water:
Mg (declared) + H 2 O = MgO + H 2;
Alkalis do not affect magnesium; it dissolves easily in acids, releasing hydrogen:
Mg + 2HCl = MgCl 2 + H 2;
When heated in air, magnesium burns to form an oxide; a small amount of nitride can also form with nitrogen:
2Mg + O 2 = 2MgO;
3Mg + N 2 = Mg 3 N 2

Definition

Silvery-white, medium-hard metal. Moderately widespread in nature. When burning, a large amount of light and heat is released.

Application

Alloys

Magnesium-based alloys are an important structural material in the aircraft and automotive industries due to their lightness and strength. Prices for magnesium bullion in 2006 averaged $3/kg.

Chemical current sources

Magnesium in the form of pure metal, as well as its chemical compounds (bromide, perchlorate) are used for the production of very powerful backup electric batteries (for example, magnesium-perchlorate cell, sulfur-magnesium cell, lead chloride-magnesium cell, silver-magnesium chloride cell, copper-magnesium chloride cell element, magnesium-vanadium element, etc.), and dry elements (manganese-magnesium element, bismuth-magnesium element, magnesium-m-DNB element, etc.). Magnesium-based CCDs are distinguished by very high specific energy characteristics and high discharge voltage. In recent years, the problem of developing a battery with a long service life has become more acute in a number of countries, since theoretical data suggest very great prospects for its widespread use (high energy, environmental friendliness, availability of raw materials).

Connections

Magnesium hydride is one of the most capacious hydrogen batteries used for hydrogen storage.

Fireproof materials

Magnesium oxide MgO is used as a refractory material for the production of crucibles and special linings of metallurgical furnaces.

Magnesium perchlorate, Mg(ClO 4) 2 - (anhydrone) is used for deep drying of gases in laboratories, and as an electrolyte for chemical current sources involving magnesium.

Magnesium fluoride MgF 2 - in the form of synthetic single crystals is used in optics (lenses, prisms).

Magnesium bromide MgBr 2 - as an electrolyte for chemical backup current sources.

Medicine

Magnesium oxide and salts are used in medicine (asparkam, magnesium sulfate, magnesium citrate, bischofite mineral). Bischophytotherapy uses the biological effects of natural magnesium in the treatment and rehabilitation of a wide range of diseases, primarily the musculoskeletal system, nervous and cardiovascular systems.

Photo

Magnesium powder with oxidizing additives (barium nitrate, ammonium nitrate, potassium permanganate, sodium hypochlorite, potassium chlorate, etc.) was used (and is now used in rare cases) in photography in chemical flashes (magnesium flash).

Biological role and toxicology

Magnesium is one of the important biogenic elements; it is found in significant quantities in the tissues of animals and plants. Magnesium is a cofactor in many enzymatic reactions. Magnesium is necessary for the conversion of creatine phosphate into ATP, a nucleotide that is a universal supplier of energy in living cells of the body. Therefore, magnesium is the element that controls the energy of the body. Magnesium is necessary at all stages of protein synthesis. It has also been established that 80-90% of modern people suffer from magnesium deficiency. This can manifest itself in different ways: insomnia, chronic fatigue, osteoporosis, arthritis, fibromyalgia, migraines, muscle cramps and spasms, cardiac arrhythmia, constipation, premenstrual syndrome (PMS) and other symptoms and illnesses. And with frequent use of laxatives, alcohol, great mental and physical stress, the need for magnesium increases.

Foods rich in magnesium include: sesame, bran, nuts. There is very little magnesium in bread, dairy, meat and other everyday food products of modern people. To obtain the daily requirement of magnesium, about 300 mg for women and 400 mg for men, you need to drink 2-3 liters of milk or eat 1.5-2 kg of meat.

According to the results of recent studies, it has been found that magnesium citrate is the most absorbable magnesium-containing product.

It has been established that in order to absorb calcium, the body needs magnesium. One of the most biologically appropriate sources of magnesium for transcutaneous (percutaneous) absorption is the mineral bischofite, which is widely used for the purposes of medical rehabilitation, physiotherapy and spa treatment.

Magnesium, Magnesium, Mg (12)
The name magnesia is found already in the Leiden papyrus X (third century). It probably comes from the name of a city in the mountainous region of Thessaly - Magnesia. Magnesian stone in ancient times was called magnetic iron oxide, and magnes was a magnet. These names passed into Latin and other languages.

The external similarity of magnetic iron oxide with pyrolysis (manganese dioxide) led to the fact that minerals and ores of dark and dark brown color, and later other minerals, began to be called magnesia stone, magnetis and magne. In alchemical literature, the word Magnes meant many substances, such as mercury, Ethiopian stone, Heraclian stone. Minerals containing magnesium have also been known since ancient times (dolomite, talc, asbestos, jade, etc.) and were already widely used. However, they were not considered individual substances, but modifications of other, more well-known minerals, most often lime.

The fact that a special metallic base is present in magnesium-containing minerals and salts was helped by studies of the mineral water of the Epsom spring in England, discovered in 1618. Solid salt from bitter Epsom water was isolated in 1695 by Grew, pointing out that by its nature This salt is noticeably different from all other salts. In the 18th century Many prominent analytical chemists studied Epsom salt - Bergman, Neumann, Black and others. When sources of water similar to Epsom were discovered in continental Europe, these studies expanded even more. Apparently, Neumann was the first to suggest that Epsom salt (magnesium carbonate) be called white magnesia in contrast to black magnesia (pyrolusite). The land of white magnesia (Magnesia alba) called magnesia appears in Lavoisier's list of simple bodies, and Lavoisier considers the “base of Epsom salt” (base de sel d"Epsom) to be synonymous with this land.

In Russian literature of the early 19th century. magnesia was sometimes called bitter earth. In 1808, Davy, by subjecting white magnesia to electrolysis, obtained some impure metallic magnesium; this metal was obtained in its pure form by Bussy in 1829. At first, Davy proposed calling the new metal magnesium (Magnium) in contrast to magnesia, which at that time denoted the metal base of pyrolusite (Magnesium). However, when the name of black magnesia was changed, Davy preferred to call the metal magnesium. Interestingly, the original name magnesium survived only in Russian thanks to Hess’s textbook. At the beginning of the 19th century. Other names were also proposed - magnesium (Strakhov), magnesium, bitter earth (Shcheglov).