Liquid sodium chemical and physical properties. Sodium is a soft metal with interesting properties

Sodium in its pure form was obtained in 1807 by Humphry Davy, an English chemist who discovered sodium shortly before. Davy carried out the process of electrolysis of one of the sodium compounds - hydroxide, which melted and obtained sodium. Humanity has been using sodium compounds since ancient times; soda of natural origin was used back in Ancient Egypt (calorizator). Named the element sodium (sodium) , sometimes this very name can be found even now. The usual name is sodium (from the Latin sodium- soda) was proposed by the Swede Jens Berzelius.

Sodium is a group I element III third period of the periodic table of chemical elements D.I. Mendeleev, has an atomic number of 11 and an atomic mass of 22.99. Accepted notation - Na(from Latin sodium).

Being in nature

Sodium compounds are found in the earth's crust, sea water, as an impurity that tends to color rock salt Blue colour due to the effects of radiation.

Sodium is a soft, malleable alkali metal that is silvery-white in color and shiny when cut fresh (it is quite possible to cut sodium with a knife). When pressure is applied it turns into transparent substance red in color, crystallizes at ordinary temperatures. When interacting with air, it quickly oxidizes, so sodium must be stored under a layer of kerosene.

Daily sodium requirement

Sodium is an important trace element for the human body. daily requirement in it for adults it is 550 mg, for children and adolescents - 500-1300 mg. During pregnancy, the sodium norm per day is 500 mg, and in some cases ( profuse sweating, dehydration, taking diuretics) should be increased.

Sodium is found in almost all seafood (crayfish, crabs, octopus, squid, mussels, seaweed), fish (anchovies, sardines, flounder, smelt, etc.), chicken eggs, cereals (buckwheat, rice, pearl barley, oatmeal, millet), legumes (peas, beans), vegetables (tomatoes, celery, carrots, cabbage, beets), dairy products and meat by-products.

Beneficial properties of sodium and its effect on the body

The beneficial properties of sodium for the body are:

• Normalization of water-salt metabolism;
• Activation of enzymes of the salivary and pancreas;
• Participation in the production of gastric juice;
• Maintaining normal acid-base balance;
• Generating functions of the nervous and muscular system;
• Vasodilator effect;
• Maintaining blood osmotic concentration.

Sodium digestibility

Sodium is found in almost all foods, although the body receives most of it (about 80%) from. Absorption mainly occurs in the stomach and small intestine. improves the absorption of sodium, however, excessively salty foods and foods rich in proteins interfere with normal absorption.

Interaction with others

The use of sodium metal is in the chemical and metallurgical industries, where it acts as a powerful reducing agent. Sodium chloride (table salt) is used by all inhabitants of our planet without exception; it is the most famous flavoring agent and the oldest preservative.

Signs of sodium deficiency

Sodium deficiency usually occurs due to excessive sweating - in hot climates or during physical activity. A lack of sodium in the body is characterized by memory impairment and loss of appetite, dizziness, fatigue, dehydration, muscle weakness, and sometimes cramps, skin rashes, stomach cramps, nausea, and vomiting.

Signs of excess sodium

An excessive amount of sodium in the body makes itself felt by constant thirst, swelling and allergic reactions.

Position in the periodic table: sodium is in period 3, group I, main (A) subgroup.

Atomic number sodium 11, therefore, the charge of the sodium atom is + 11, the number of electrons is 11. Three electronic levels (equal to the period), 1 electron on the outer level (equal to the group number for the main subgroups).

Diagram of the arrangement of electrons by levels:
11 Na)))
2 8 1

The nucleus of the sodium atom 23 Na contains 11 protons (equal to the charge of the nucleus) and 12 neutrons ( atomic mass minus the number of protons: 23 − 11 = 12).

The simple substance sodium is a silvery-white metal, light (density 0.97 g/cm 3 - lighter than water), soft (easily cut with a knife), fusible (melting point 98° C).

Sodium, like all alkali metals, is a strong reducing agent. It reacts vigorously with non-metals:

1. When heated to 180° C in a moderate amount of oxygen, sodium oxide is formed:
   4Na + O 2 = 2Na 2 O
2. Sodium burns in air to form sodium peroxide:
   2Na + O 2 = Na 2 O 2
   Sodium is stored under a layer of kerosene.
3. Molten sodium in chlorine burns with a blinding flash (to put it simply - it reacts with chlorine when heated), A white coating of sodium chloride forms on the walls of the vessel:
   2Na + Cl 2 = 2NaCl

   Sodium may explode when triturated with sulfur powder (sodium sulfide is formed):
   2Na + S = Na 2 S

   When heated, sodium reduces hydrogen to form sodium hydride:
   2Na + H 2 = 2NaH

If a small piece of sodium is placed in water, it reacts violently with the water. The metal melts from the heat released and “runs” along the surface of the water. A sodium hydroxide solution is formed:
2Na + 2HOH = 2NaOH + H2

Sodium is found naturally in various minerals, as salt in seawater. In the human body, sodium salts are part of the blood plasma and lymph.

Applicable in nuclear energy(as a coolant) and in the form of compounds ( table salt NaCl, soda Na 2 CO 3, etc.)

2. Experience. Carrying out the transformation: salt → insoluble base → metal oxide

To obtain an insoluble base, add sodium hydroxide to the salt solution. We heat the resulting precipitate in an alcohol lamp; it decomposes to form an oxide.

It is better to take copper (II) sulfate or chloride:

CuSO 4 + 2NaOH = Cu(OH) 2 ↓ + Na 2 SO 4

A blue precipitate of copper(II) hydroxide forms. When heated, the precipitate turns black due to the formation of black copper(II) oxide.

- an inorganic substance, a simple element of the periodic table, belongs to the group of alkali metals. It ranks sixth in abundance in the earth's crust; it is most abundant among metals dissolved in the waters of seas and oceans. It is found in the form of compounds in minerals such as halite, mirabilite, thenardite, sodium nitrate, trona, borax, etc. It is not found in its pure form.

Industrial production method: electrolysis of molten sodium chloride (table salt). Sodium and chlorine are produced at the same time.

Properties

Ductile metal silver color. In air it quickly oxidizes and fades. It is so soft that it can be cut with a scalpel, rolled, pressed. Lighter than water. Conducts current and heat well. The color of the flame is bright yellow. This reaction is typical for the detection of many sodium compounds.

Refers to chemically very active metals, has basic properties. Reacts with oxygen carbon dioxide, dilute and concentrated acids, alcohols, gaseous and liquid ammonia, oxides. Self-ignites when interacting with chlorine and fluorine, reacts violently with water (sometimes with an explosion), bromine, and sulfur. Reacts with almost all non-metals (sometimes this requires special conditions, electric discharge or heat). With water it forms a strong alkali - sodium hydroxide (caustic soda). Forms compounds with mercury and some other metals, with organic substances.

Sodium has a very significant difference between its melting and boiling points - almost 800 degrees. It melts at about +98 °C, boils at +883 °C. Thanks to this property, sodium makes a good coolant for powerful nuclear reactors, which does not boil to high temperatures.

Sodium plays an important role in the life of living organisms. It is necessary for normal metabolism, nervous and cardiovascular systems. Lack of sodium leads to disturbances in the gastrointestinal tract, convulsions, and neuralgia. Excess leads to edema, increased blood pressure, and kidney problems.

Precautionary measures

Sodium should not be handled by hand, as it immediately reacts with skin moisture and forms an alkali, causing severe chemical and thermal burns.

Store sodium under a layer of kerosene or mineral oil in sealed iron containers (the liquid should completely cover the reagent). If stored in a glass container, then it, in turn, must be placed in a fireproof metal cabinet.

After working with sodium metal, residues should be neutralized with alcohol, under no circumstances allowing sodium particles to enter the trash can or drain, as this can cause a fire and rapid destruction of sewer pipes.

Application

Reducing properties are used in the production of pure metals: potassium, zirconium, tantalum, etc.
. In gas discharge lamps.
. In metallurgy, sodium is added to lead alloys to give them strength. It makes alloys of other metals more refractory.
. In electrical engineering, sodium is used to make energy-intensive batteries, truck engine valves, and tires for very high currents.
. Since sodium does not absorb neutrons well, it is used as a coolant in nuclear reactors on fast neutrons.
. For drying organic solvents, for qualitative analysis in organic chemistry.
. Sodium isotopes are used in medicine and scientific research.
. Many salts are used in the food industry: glutamate, chloride, bicarbonate, benzoate, nitrite, sodium saccharinate.
. Table salt is used in water purification.
. Sodium hydroxide is in demand in the production of paper, soap, and synthetic fibers; as an electrolyte.
. Sodium carbonates and bicarbonates are used in fire fighting and pharmaceuticals.
. Sodium phosphate is necessary for the production of detergents, paints, in the glass industry, and photography.
. Sodium silicates are used in the production of fire- and acid-resistant concrete.
. Azide, cyanide, chlorate, peroxide, tetraborate, sulfate, sodium thiosulfate and many other of its compounds are used.

Sodium —element the main subgroup of the first group, the third period of the periodic system of chemical elements of D.I. Mendeleev, with atomic number 11. Denoted by the symbol Na (lat. Natrium). Simple substance sodium (CAS number: 7440-23-5) - soft alkali metal silver-white color.

In water, sodium behaves almost the same as lithium: the reaction proceeds with the rapid release of hydrogen, and sodium hydroxide is formed in the solution.

History and origin of the name

Sodium (or rather, its compounds) has been used since ancient times. For example, soda (natron), found naturally in the waters of soda lakes in Egypt. The ancient Egyptians used natural soda for embalming, bleaching canvas, cooking food, and making paints and glazes. Pliny the Elder writes that in the Nile Delta, soda (it contained a sufficient proportion of impurities) was isolated from river water. It went on sale in the form of large pieces, colored gray or even black due to the admixture of coal.

Sodium was first obtained by the English chemist Humphry Davy in 1807 by electrolysis of solid NaOH.

The name "sodium" comes from the Arabic natrun in Greek - nitron and originally it referred to natural soda. The element itself was previously called Sodium.

Receipt

The first way to produce sodium was the reduction reaction sodium carbonate coal when heating a close mixture of these substances in an iron container to 1000°C:

Na 2 CO 3 +2C=2Na+3CO

Then another method of producing sodium appeared - electrolysis of molten sodium hydroxide or sodium chloride.

Physical properties

Metallic sodium stored in kerosene

Qualitative determination of sodium using a flame - bright yellow color of the emission spectrum of the “sodium D-line”, doublet 588.9950 and 589.5924 nm.

Sodium is a silvery-white metal, in thin layers with purple tint, plastic, even soft (easily cut with a knife), a fresh cut of sodium shines. The electrical and thermal conductivity values ​​of sodium are quite high, the density is 0.96842 g/cm³ (at 19.7° C), the melting point is 97.86° C, and the boiling point is 883.15° C.

Chemical properties

An alkali metal that oxidizes easily in air. To protect against atmospheric oxygen, metallic sodium is stored under a layer kerosene. Sodium is less active than lithium, therefore with nitrogen reacts only when heated:

2Na + 3N 2 = 2NaN 3

When there is a large excess of oxygen, sodium peroxide is formed

2Na + O 2 = Na 2 O 2

Application

Sodium metal is widely used in preparative chemistry and industry as a strong reducing agent, including in metallurgy. Sodium is used in the production of highly energy-intensive sodium-sulfur batteries. It is also used in truck exhaust valves as a heat sink. Occasionally, sodium metal is used as a material for electrical wires intended to carry very high currents.

In an alloy with potassium, as well as with rubidium and cesium used as a highly efficient coolant. In particular, the alloy composition is sodium 12%, potassium 47 %, cesium 41% has a record low melting point of −78 °C and was proposed as a working fluid for ionic rocket engines and coolant for nuclear power plants.

Sodium is also used in high- and high-gas discharge lamps. low pressure(NLVD and NLND). NLVD lamps of the DNaT (Arc Sodium Tubular) type are very widely used in street lighting. They give off a bright yellow light. The service life of HPS lamps is 12-24 thousand hours. Therefore, gas-discharge lamps of the HPS type are indispensable for urban, architectural and industrial lighting. There are also lamps DNaS, DNaMT (Arc Sodium Matte), DNaZ (Arc Sodium Mirror) and DNaTBR (Arc Sodium Tubular Without Mercury).

Sodium metal is used in qualitative analysis organic matter. The alloy of sodium and the test substance is neutralized ethanol, add a few milliliters of distilled water and divide into 3 parts, J. Lassaigne's test (1843), aimed at determining nitrogen, sulfur and halogens (Beilstein test)

— Sodium chloride (table salt) is the oldest used flavoring and preservative.
— Sodium azide (Na 3 N) is used as a nitriding agent in metallurgy and in the production of lead azide.
— Sodium cyanide (NaCN) is used in the hydrometallurgical method of leaching gold from rocks, as well as in the nitrocarburization of steel and in electroplating (silvering, gilding).
— Sodium chlorate (NaClO 3) is used to destroy unwanted vegetation on railway tracks.

Biological role

In the body, sodium is found mostly outside the cells (about 15 times more than in the cytoplasm). This difference is maintained by the sodium-potassium pump, which pumps out sodium trapped inside the cell.

Together withpotassiumsodium performs the following functions:
Creating conditions for the occurrence of membrane potential and muscle contractions.
Maintaining blood osmotic concentration.
Maintaining acid-base balance.
Normalization of water balance.
Ensuring membrane transport.
Activation of many enzymes.

Sodium is found in almost all foods, although the body gets most of it from table salt. Absorption mainly occurs in the stomach and small intestine. Vitamin D improves the absorption of sodium, however, excessively salty foods and foods rich in protein interfere with normal absorption. The amount of sodium taken in from food shows the sodium content in the urine. Sodium-rich foods are characterized by accelerated excretion.

Sodium deficiency in the dieter balanced food does not occur in humans, however, some problems can arise with vegetarian diets. Temporary deficiency may be caused by diuretic use, diarrhea, excessive sweating, or excess water intake. Symptoms of sodium deficiency include weight loss, vomiting, gas in the gastrointestinal tract, and impaired absorption amino acids and monosaccharides. Long-term deficiency causes muscle cramps and neuralgia.

Excess sodium causes swelling of the legs and face, as well as increased excretion of potassium in the urine. The maximum amount of salt that can be processed by the kidneys is approximately 20-30 grams, large quantity already life-threatening.

Sodium compounds

Sodium, Natrium, Na (11)
The name sodium - sodium, natrium comes from an ancient word common in Egypt, among the ancient Greeks (vixpov) and Romans. It is found in Pliny (Nitron) and other ancient authors and corresponds to the Hebrew neter. In ancient Egypt, natron, or nitron, was generally called an alkali obtained not only from natural soda lakes, but also from plant ash. It was used for washing, making glazes, and mummifying corpses. In the Middle Ages, the name nitron (nitron, natron, nataron), as well as boron (baurach), also applied to saltpeter (Nitrum). Arab alchemists called alkali alkali. With the discovery of gunpowder in Europe, saltpeter (Sal Petrae) began to be strictly distinguished from alkalis, and in the 17th century. already distinguished between non-volatile, or fixed alkalis, and volatile alkali (Alkali volatile). At the same time, a difference was established between vegetable (Alkali fixum vegetabile - potash) and mineral alkali (Alkali fixum minerale - soda).

IN late XVIII V. Klaproth introduced the name natron, or soda, for the mineral alkali and Kali for the vegetable alkali; Lavoisier did not place the alkali in the “Table simple bodies", indicating in a note to it that this is probably complex substances, which will someday be decomposed. Indeed, in 1807 Davy, by electrolysis of slightly moistened solid alkalis, obtained free metals - potassium and sodium, calling them potassium and sodium. IN next year Gilbert, publisher of the famous Annals of Physics, proposed calling the new metals potassium and sodium (Natronium); Berzelius shortened last name to “sodium” (Natrium). At the beginning of the 19th century. in Russia sodium was called sodia (Dvigubsky, 182i; Solovyov, 1824); Strakhov proposed the name sod (1825). Sodium salts were called, for example, soda sulfate, hydrochloric soda, and at the same time acetic soda (Dvigubsky, 1828). Hess, following the example of Berzelius, introduced the name sodium.

The content of the article

SODIUM– (Natrium)Na, chemical element 1st (Ia) group of the Periodic table, refers to the alkaline elements. Atomic number 11, relative atomic mass 22.98977. In nature there is one stable isotope 23 Na. Six known radioactive isotopes this element, and two of them are of interest to science and medicine. Sodium-22, with a half-life of 2.58 years, is used as a source of positrons. Sodium-24 (its half-life is about 15 hours) is used in medicine for the diagnosis and treatment of some forms of leukemia.

Oxidation state +1.

Sodium compounds have been known since ancient times. Sodium chloride - essential component human food. It is believed that people began to use it in the Neolithic, i.e. about 5–7 thousand years ago.

IN Old Testament a certain substance “neter” is mentioned. This substance was used as a detergent. Most likely, neter is soda, a sodium carbonate that formed in the salty Egyptian lakes with calcareous shores. The Greek authors Aristotle and Dioscorides later wrote about the same substance, but under the name “nitron,” and the ancient Roman historian Pliny the Elder, mentioning the same substance, called it “nitrum.”

In the 18th century Chemists already knew a lot of different sodium compounds. Sodium salts were widely used in medicine, in tanning leather, and in dyeing fabrics.

Metallic sodium was first obtained by the English chemist and physicist Humphry Davy by electrolysis of molten sodium hydroxide (using a voltaic column of 250 pairs of copper and zinc plates). The name "sodium" chosen by Davy for this element reflects its origin from the soda Na 2 CO 3 . The Latin and Russian names of the element are derived from the Arabic “natrun” (natural soda).

Distribution of sodium in nature and its industrial extraction.

Sodium is the seventh most abundant element and the fifth most abundant metal (after aluminum, iron, calcium and magnesium). Its content in the earth's crust is 2.27%. Most of the sodium is found in various aluminosilicates.

Huge deposits of sodium salts in relatively pure form exist on all continents. They are the result of the evaporation of ancient seas. This process is still ongoing in Salt Lake (Utah), the Dead Sea and other places. Sodium occurs as NaCl chloride(halite, rock salt), as well as carbonate Na 2 CO 3 NaHCO 3 2H 2 O (trona), nitrate NaNO 3 (saltpeter), sulfate Na 2 SO 4 10H 2 O (mirabilite), tetraborate Na 2 B 4 O 7 ·10 H 2 O (borax) and Na 2 B 4 O 7 ·4H 2 O (kernite) and other salts.

There are inexhaustible reserves of sodium chloride in natural brines and ocean waters(about 30 kg m–3). It is estimated that rock salt in an amount equivalent to the sodium chloride content in the World Ocean would occupy a volume of 19 million cubic meters. km (50% more than the total volume of the North American continent above sea level). A prism of this volume with a base area of ​​1 sq. km can reach the Moon 47 times.

Currently, the total production of sodium chloride from sea ​​water reached 6–7 million tons per year, which is about a third of total world production.

Living matter contains an average of 0.02% sodium; There is more of it in animals than in plants.

Characteristics of a simple substance and industrial production of sodium metal.

Sodium is a silvery-white metal, in thin layers with a purple tint, plastic, even soft (easily cut with a knife), a fresh cut of sodium is shiny. The values ​​of electrical conductivity and thermal conductivity of sodium are quite high, the density is 0.96842 g/cm 3 (at 19.7 ° C), the melting point is 97.86 ° C, the boiling point is 883.15 ° C.

The ternary alloy, containing 12% sodium, 47% potassium and 41% cesium, has the lowest melting point for metal systems, equal to –78 ° C.

Sodium and its compounds color the flame bright yellow. The double line in the sodium spectrum corresponds to transition 3 s 1–3p 1 in the atoms of the element.

The chemical activity of sodium is high. In air, it quickly becomes covered with a film of a mixture of peroxide, hydroxide and carbonate. Sodium burns in oxygen, fluorine and chlorine. When a metal is burned in air, Na 2 O 2 peroxide is formed (with an admixture of Na 2 O oxide).

Sodium reacts with sulfur when ground in a mortar, sulfuric acid reduces to sulfur or even sulfide. Solid dioxide carbon (“dry ice”) explodes on contact with sodium (carbon dioxide fire extinguishers cannot be used to extinguish burning sodium!). With nitrogen reaction is underway only in electrical discharge. Sodium does not interact only with inert gases.

Sodium reacts actively with water:

2Na + 2H 2 O = 2NaOH + H 2

The heat released during the reaction is enough to melt the metal. Therefore, if a small piece of sodium is thrown into water, it will thermal effect reaction melts and a drop of metal, which is lighter than water, “runs” along the surface of the water, driven reactive force released hydrogen. Sodium reacts much more calmly with alcohols than with water:

2Na + 2C 2 H 5 OH = 2C 2 H 5 ONa + H 2

Sodium readily dissolves in liquid ammonia to form bright blue metastable solutions with unusual properties. At –33.8° C, up to 246 g of sodium metal dissolves in 1000 g of ammonia. Dilute solutions are blue, concentrated solutions are bronze. They can be stored for about a week. It has been established that in liquid ammonia, sodium ionizes:

Na Na + + e –

The equilibrium constant of this reaction is 9.9·10 –3. The leaving electron is solvated by ammonia molecules and forms a complex -. The resulting solutions have metallic electrical conductivity. When ammonia evaporates, the original metal remains. When the solution is stored for a long time, it gradually becomes discolored due to the reaction of the metal with ammonia to form the amide NaNH 2 or imide Na 2 NH and the release of hydrogen.

Sodium is stored under a layer of dehydrated liquid (kerosene, mineral oil) and transported only in sealed metal containers.

The electrolytic method for the industrial production of sodium was developed in 1890. Electrolysis was carried out on molten sodium hydroxide, as in Davy's experiments, but using more advanced energy sources than the voltaic column. In this process, along with sodium, oxygen is released:

anode (nickel): 4OH – – 4e – = O 2 + 2H 2 O.

During the electrolysis of pure sodium chloride, serious problems arise, associated, firstly, with the close melting point of sodium chloride and the boiling point of sodium and, secondly, with the high solubility of sodium in liquid sodium chloride. Adding potassium chloride, sodium fluoride, calcium chloride to sodium chloride allows you to reduce the melt temperature to 600° C. Production of sodium by electrolysis of a molten eutectic mixture (an alloy of two substances with the lowest melting point) 40% NaCl and 60% CaCl 2 at ~580° C in a cell developed by the American engineer G. Downs, it was started in 1921 by DuPont near the power plant at Niagara Falls.

The following processes occur on the electrodes:

cathode (iron): Na + + e – = Na

Ca 2+ + 2e – = Ca

anode (graphite): 2Cl – – 2e – = Cl 2.

Sodium and calcium metals form on a cylindrical steel cathode and are lifted up by a cooled tube in which the calcium solidifies and falls back into the melt. Chlorine generated at the central graphite anode is collected under the nickel roof and then purified.

Currently, the production volume of sodium metal is several thousand tons per year.

The industrial use of sodium metal is due to its strong restorative properties. For a long time most of the produced metal was used to produce tetraethyl lead PbEt 4 and tetramethyl lead PbMe 4 (anti-knock agents for gasoline) by the reaction of alkyl chlorides with an alloy of sodium and lead at high blood pressure. Now this production is rapidly declining due to environmental pollution.

Another area of ​​application is the production of titanium, zirconium and other metals by reducing their chlorides. Smaller amounts of sodium are used to produce compounds such as hydride, peroxide and alcoholates.

Dispersed sodium is a valuable catalyst in the production of rubber and elastomers.

There is increasing use of molten sodium as a heat exchange fluid in fast neutron nuclear reactors. Low temperature sodium melting, low viscosity, small neutron absorption cross section, combined with extremely high heat capacity and thermal conductivity, make it (and its alloys with potassium) an indispensable material for these purposes.

Sodium reliably cleans transformer oils, ethers and other organic substances from traces of water, and with the help of sodium amalgam you can quickly determine the moisture content in many compounds.

Sodium compounds.

Sodium forms a complete set of compounds with all the usual anions. It is believed that in such compounds there is almost complete separation of charge between the cationic and anionic parts of the crystal lattice.

Sodium oxide Na 2 O is synthesized by the reaction of Na 2 O 2, NaOH, and most preferably NaNO 2, with sodium metal:

Na 2 O 2 + 2Na = 2Na 2 O

2NaOH + 2Na = 2Na2O + H2

2NaNO 2 + 6Na = 4Na 2 O + N 2

In the last reaction, sodium can be replaced with sodium azide NaN 3:

5NaN 3 + NaNO 2 = 3Na 2 O + 8N 2

It is best to store sodium oxide in anhydrous gasoline. It serves as a reagent for various syntheses.

Sodium peroxide Na 2 O 2 in the form of a pale yellow powder is formed during the oxidation of sodium. In this case, under conditions of limited supply of dry oxygen (air), Na 2 O oxide is first formed, which then turns into Na 2 O 2 peroxide. In the absence of oxygen, sodium peroxide is thermally stable up to ~675°C.

Sodium peroxide is widely used in industry as a bleaching agent for fibers, paper pulp, wool, etc. It is a strong oxidizing agent: it explodes when mixed with aluminum powder or charcoal, reacts with sulfur (and becomes hot), and ignites many organic liquids. Sodium peroxide reacts with carbon monoxide to form carbonate. The reaction of sodium peroxide with carbon dioxide releases oxygen:

2Na 2 O 2 + 2CO 2 = 2Na 2 CO 3 + O 2

This reaction is important practical use in breathing apparatus for submariners and firefighters.

Sodium superoxide NaO 2 is obtained by slowly heating sodium peroxide at 200–450° C under an oxygen pressure of 10–15 MPa. Evidence of the formation of NaO 2 was first obtained in the reaction of oxygen with sodium dissolved in liquid ammonia.

The action of water on sodium superoxide leads to the release of oxygen even in the cold:

2NaO 2 + H 2 O = NaOH + NaHO 2 + O 2

As the temperature rises, the amount of oxygen released increases as the resulting sodium hydroperoxide decomposes:

4NaO 2 + 2H 2 O = 4NaOH + 3O 2

Sodium superoxide is a component of systems for air regeneration in confined spaces.

Sodium ozonide NaO 3 is formed by the action of ozone on anhydrous sodium hydroxide powder at low temperature, followed by extraction of red NaO 3 with liquid ammonia.

Sodium hydroxide NaOH is often called caustic soda or caustic soda. This strong foundation, it is classified as a typical alkali. Numerous NaOH hydrates have been obtained from aqueous solutions of sodium hydroxide n H 2 O, where n= 1, 2, 2.5, 3.5, 4, 5.25 and 7.

Sodium hydroxide is very aggressive. It destroys glass and porcelain by interacting with the silicon dioxide they contain:

2NaOH + SiO 2 = Na 2 SiO 3 + H 2 O

The name "caustic soda" reflects the corrosive effect of sodium hydroxide on living tissue. Getting this substance into the eyes is especially dangerous.

The Duke of Orleans' physician, Nicolas Leblanc (1742–1806), developed a convenient process for producing sodium hydroxide from NaCl in 1787 (patent 1791). This first large-scale industrial chemical process became a major technological achievement in Europe in the 19th century. The Leblanc process was later replaced by the electrolytic process. In 1874, world production of sodium hydroxide amounted to 525 thousand tons, of which 495 thousand tons were obtained by the Leblanc method; by 1902, the production of sodium hydroxide reached 1800 thousand tons, but only 150 thousand tons were obtained using the Leblanc method.

Sodium hydroxide is the most important alkali in industry today. Annual production in the USA alone exceeds 10 million tons. It is obtained in huge quantities electrolysis of brines. Electrolysis of a sodium chloride solution produces sodium hydroxide and releases chlorine:

cathode (iron) 2H 2 O + 2 e– = H 2 + 2OH –

anode (graphite) 2Cl – – 2 e– = Cl 2

Electrolysis is accompanied by the concentration of alkali in huge evaporators. The largest in the world (at the PPG Inductries "Lake Charles plant) has a height of 41 m and a diameter of 12 m. About half of the sodium hydroxide produced is used directly in the chemical industry to produce various organic and inorganic substances: phenol, resorcinol, b-naphthol, sodium salts (hypochlorite, phosphate, sulfide, aluminates). In addition, sodium hydroxide is used in the production of paper and pulp, soap and detergents, oils, textiles. An important area of ​​application of sodium hydroxide is the neutralization of acids.

Sodium chloride NaCl is known as table salt and rock salt. It forms colorless, slightly hygroscopic crystals cubic shape. Sodium chloride melts at 801° C, boils at 1413° C. Its solubility in water depends little on temperature: 35.87 g of NaCl dissolves in 100 g of water at 20° C, and 38.12 g at 80° C.

Sodium chloride is a necessary and indispensable seasoning for food. In the distant past, salt was equal in price to gold. IN ancient Rome Legionnaires were often paid not in money, but in salt, hence the word soldier.

In Kievan Rus they used salt from the Carpathian region, from salt lakes and estuaries on the Black and Seas of Azov. It was so expensive that at ceremonial feasts it was served on the tables of noble guests, while others went away “slurping.”

After the annexation of the Astrakhan region to the Moscow state, the Caspian lakes became important sources of salt, and still there was not enough of it, it was expensive, so there was discontent among the poorest segments of the population, which grew into an uprising known as Salt Riot (1648)

In 1711 Peter I issued a decree introducing a salt monopoly. Trade in salt became the exclusive right of the state. The salt monopoly lasted for more than a hundred and fifty years and was abolished in 1862.

Nowadays sodium chloride is a cheap product. Together with coal, limestone and sulfur, it is one of the so-called “big four” mineral raw materials, the most essential for the chemical industry.

Most sodium chloride is produced in Europe (39%), North America(34%) and Asia (20%), while in South America and Oceania account for only 3% each, and Africa – 1%. Rock salt forms extensive underground deposits (often hundreds of meters thick) that contain more than 90% NaCl. A typical Cheshire salt deposit ( main source sodium chloride in Great Britain) covers an area of ​​60 - 24 km and has a salt layer thickness of about 400 m. This deposit alone is estimated at more than 10 11 tons.

World salt production by the beginning of the 21st century. reached 200 million tons, 60% of which is consumed chemical industry(for the production of chlorine and sodium hydroxide, as well as paper pulp, textiles, metals, rubbers and oils), 30% - food, 10% falls on other areas of activity. Sodium chloride is used, for example, as a cheap deicing agent.

Sodium carbonate Na 2 CO 3 is often called soda ash or simply soda. It is found in nature in the form of ground brines, brine in lakes and the minerals natron Na 2 CO 3 ·10H 2 O, thermonatrite Na 2 CO 3 ·H 2 O, trona Na 2 CO 3 ·NaHCO 3 ·2H 2 O. Sodium forms and other various hydrated carbonates, bicarbonates, mixed and double carbonates, for example Na 2 CO 3 7H 2 O, Na 2 CO 3 3NaHCO 3, aKCO 3 n H 2 O, K 2 CO 3 NaHCO 3 2H 2 O.

Among the salts of alkali elements obtained industrially, sodium carbonate has highest value. Most often, the method developed by the Belgian chemist-technologist Ernst Solvay in 1863 is used for its production.

A concentrated aqueous solution of sodium chloride and ammonia is saturated with carbon dioxide under slight pressure. In this case, a precipitate of relatively poorly soluble sodium bicarbonate is formed (the solubility of NaHCO 3 is 9.6 g per 100 g of water at 20 ° C):

NaCl + NH 3 + H 2 O + CO 2 = NaHCO 3 Ї + NH 4 Cl

To obtain soda, sodium bicarbonate is calcined:

The carbon dioxide released is returned to the first process. Additional quantity Carbon dioxide is produced by calcining calcium carbonate (limestone):

The second product of this reaction, calcium oxide (lime), is used to regenerate ammonia from ammonium chloride:

Thus, the only by-product of soda production using the Solvay method is calcium chloride.

The overall process equation is:

2NaCl + CaCO 3 = Na 2 CO 3 + CaCl 2

Obviously, under normal conditions in an aqueous solution the reverse reaction occurs, since the equilibrium in this system is completely shifted from right to left due to the insolubility of calcium carbonate.

Soda ash obtained from natural raw materials (natural soda ash) is of better quality compared to soda produced by the ammonia method (chloride content less than 0.2%). In addition, specific capital investments and the cost of soda from natural raw materials are 40–45% lower than those obtained synthetically. About a third of the world's soda production now comes from natural deposits.

World production of Na 2 CO 3 in 1999 was distributed as follows:

The world's largest producer of natural soda ash is the USA, where the largest explored reserves of trona and brine of soda lakes are concentrated. The deposit in Wyoming forms a layer 3 m thick and an area of ​​2300 km 2. Its reserves exceed 10 10 tons. In the USA, the soda industry is focused on natural raw materials; the last soda synthesis plant was closed in 1985. Soda ash production in the United States has stabilized at 10.3–10.7 million tons in recent years.

Unlike the United States, most countries in the world depend almost entirely on the production of synthetic soda ash. China ranks second in the world in soda ash production after the United States. The production of this chemical in China in 1999 reached approximately 7.2 million tons. The production of soda ash in Russia in the same year amounted to about 1.9 million tons.

In many cases, sodium carbonate is interchangeable with sodium hydroxide (for example, in the production of paper pulp, soap, cleaning products). About half of the sodium carbonate is used in the glass industry. One of developing areas Applications – removal of sulfur contaminants in gas emissions energy enterprises and high-power furnaces. Sodium carbonate powder is added to the fuel, which reacts with sulfur dioxide to form solid products, particularly sodium sulfite, which can be filtered or precipitated.

Sodium carbonate was previously widely used as "washing soda", but this application has now disappeared due to the use of other household detergents.

Sodium bicarbonate NaHCO 3 (baking soda), is used mainly as a source of carbon dioxide in the baking of bread, the manufacture of confectionery, the production of carbonated drinks and artificial mineral waters, as a component of fire extinguishing compositions and a medicine. This is due to the ease of its decomposition at 50–100° C.

Sodium sulfate Na 2 SO 4 occurs in nature in anhydrous form (thenardite) and in the form of decahydrate (mirabilite, Glauber's salt). It is part of astrachonite Na 2 Mg(SO 4) 2 4H 2 O, vanthoffite Na 2 Mg(SO 4) 2, glauberite Na 2 Ca(SO 4) 2. Most large reserves sodium sulfate - in the CIS countries, as well as in the USA, Chile, Spain. Mirabilite, isolated from natural deposits or brine of salt lakes, is dehydrated at 100 ° C. Sodium sulfate is also a by-product of the production of hydrogen chloride using sulfuric acid, as well as the end product of hundreds of industrial processes that use neutralization of sulfuric acid with sodium hydroxide.

Data on the production of sodium sulfate are not published, but global production of the natural raw material is estimated to be about 4 million tons per year. The recovery of sodium sulfate as a by-product is estimated globally at 1.5–2.0 million tons.

For a long time, sodium sulfate was little used. Now this substance is the basis paper industry, since Na 2 SO 4 is the main reagent in kraft pulping for the preparation of brown wrapping paper and corrugated cardboard. Wood shavings or sawdust are processed in a hot alkaline solution of sodium sulfate. It dissolves lignin (the component of wood that holds the fibers together) and releases the cellulose fibers, which are then sent to paper making machines. The remaining solution is evaporated until it is capable of burning, providing steam for the plant and heat for evaporation. Molten sodium sulfate and hydroxide are flame resistant and can be reused.

A smaller portion of sodium sulfate is used in the production of glass and detergents. The hydrated form of Na 2 SO 4 ·10H 2 O (Glauber's salt) is a laxative. It is used less now than before.

Sodium nitrate NaNO 3 is called sodium or Chilean nitrate. The large deposits of sodium nitrate found in Chile appear to have been formed by the biochemical decomposition of organic remains. The ammonia released initially was probably oxidized to nitrous and nitric acids, which then reacted with dissolved sodium chloride.

Sodium nitrate is obtained by the absorption of nitrous gases (a mixture of nitrogen oxides) with a solution of sodium carbonate or hydroxide, or by the exchange interaction of calcium nitrate with sodium sulfate.

Sodium nitrate is used as a fertilizer. It is a component of liquid salt refrigerants, quenching baths in the metalworking industry, and heat-storing compositions. A ternary mixture of 40% NaNO 2, 7% NaNO 3 and 53% KNO 3 can be used from the melting point (142° C) to ~600° C. Sodium nitrate is used as an oxidizing agent in explosives, rocket fuels, pyrotechnic compositions. It is used in the production of glass and sodium salts, including nitrite, which serves as a food preservative.

Sodium nitrite NaNO 2 can be obtained by thermal decomposition of sodium nitrate or its reduction:

NaNO 3 + Pb = NaNO 2 + PbO

For industrial production sodium nitrite absorb nitrogen oxides aqueous solution sodium carbonate.

Sodium nitrite NaNO 2, in addition to being used with nitrates as heat-conducting melts, is widely used in the production of azo dyes, for corrosion inhibition and meat preservation.

Elena Savinkina