Nitrogen is a large medical encyclopedia. Nitrogen use

Nitrogen is one of the most common elements on Earth - its content in the atmosphere exceeds 78%. The existence of such a large amount of nitrogen in a free state indicates its inertness and difficult interaction with other elements in normal conditions.

In a bound state, this substance can be found in organic and inorganic matter. Bound to carbon and oxygen, nitrogen is found in the proteins of animals and plants.

In itself, the name "nitrogen" was invented by Lavoisier, who, in the course of numerous experiments, established the presence of some inert substance in the atmosphere. The scientist considered this substance to be lifeless - in Greek "azote".

nitrogen cycle

Despite the inertness of nitrogen, in nature there are constant processes of its fixation or binding. So, for example, special bacteria accumulate in the roots of leguminous plants, which fix nitrogen, converting it into nitrates.

In the atmosphere, this gas is oxidized during lightning discharges. Then they dissolve in sediments, forming nitrogenous. With snow, rain, fog, nitrogen enters the soil, where it is converted into nitrites or nitrates. Then various plants use them to build proteins. Animals feed on plants, and are processed into animals. When plants and animals decompose after death, all nitrogen compounds in their bodies turn into ammonia. Bacteria break it down to its simplest elements, while again releasing pure nitrogen and hydrogen. This is how the nitrogen cycle or nitrogen cycle occurs in nature.

Chemical properties of nitrogen

Its main property under normal conditions is inertness, i.e. minimal chemical activity. A nitrogen atom can form a bond with another nitrogen atom, which is quite unusual for chemical elements (the only exceptions are silicon and carbon).

When heated, this element reacts with most metals. In this case, ionic, covalent or intermediate nitrides with a negatively charged nitrogen ion are formed.

In the reaction with hydrogen, nitrogen forms fairly stable compounds - nitric hydrogens, which vaguely resemble hydrocarbons. Such substances include ammonia, hydrazine and hydrazoic acid.

Obtaining and using nitrogen

The compounds of this substance play an important role in industry and agriculture. The method of obtaining nitrogen in the form of a chemical element depends on the required degree of its purity. Most nitrogen is necessary for, but at the same time, a slight content of noble gases in it is allowed.

Obtaining nitrogen from the atmosphere

This is one of the most economical methods, during which the purified air is successively liquefied by cooling and expansion. The resultant is distilled through fractions, while slowly raising the temperature. In this process, noble gases are released first, and then nitrogen. Remains only

Such production of nitrogen allows the production of many millions of tons of this substance every year. Nitrogen is used mainly for the subsequent production of ammonia, which, in turn, acts as a raw material for the production of industrial and agricultural nitrogen-containing compounds.

A pure nitrogen atmosphere may also be used when complete absence of oxygen is required.

Obtaining nitrogen in the laboratory

In not large quantities this gas is obtained by oxidizing ammonium ions or ammonia. In particular, the ammonium ion can be oxidized with the nitrite ion.

Obtaining nitrogen in the process of decomposition

When heated, azides decompose, ammonia decomposes, nitrites decompose from interaction with urea or sulfamic acid - as a result of all these reactions, nitrogen is formed.

Nitrogen is a gas, slightly soluble in water, tasteless, odorless and colorless. Despite the fact that the name of the element means "lifeless", it is necessary for life. The use of free nitrogen is widespread in many industries. The production of fixed nitrogen began to develop rapidly after the First World War and in our time has reached a very large scale. Let us consider in more detail the use of nitrogen by industry.

Gas, oil, chemistry

Use in gaseous form for the development of wells. This method of lowering the liquid level in wells is the most promising. It is characterized by reliability and ease of regulation and control of the process in a wide range of pressures and flow rates. Gaseous nitrogen helps to quickly empty deep wells, sharply and quickly or smoothly and slowly reduce the pressure in the well; can drain the formation with pressurized gas to create a flow.

Creation of an inert environment during loading and unloading operations in containers. Nitrogen is also used for fire extinguishing, testing and purging pipelines (this problem is especially relevant in the Far North, where gas and oil production is concentrated, due to the impossibility of using foaming agents and water during frosts).

Use in its pure form for the synthesis of ammonia and in the production of nitrogen fertilizers, for the processing of associated gases and the conversion of methane.

Use to reduce sulfur deposits in refineries, for highly efficient processing of high-octane components, to increase the productivity of oil cracking enterprises.

Metallurgy

Nitrogen is used during annealing, neutral quenching, powder metal sintering, cyanidation, hard soldering, to protect non-ferrous and ferrous metals.

Nitrogen is needed for the operation of the boot device blast furnace, hydrogen sulfide compressors, machines for fire cleaning of metal in the blooming shop, coke production.

mining industry

Nitrogen is also used in fire fighting in coal mines.

Food industry.

Nitrogen is necessary for storage, transshipment and packaging of food products in order to increase the shelf life and preserve their taste.

The use of nitrogen is important to prevent bacterial growth by filling the package with a mixture of carbon dioxide and nitrogen.

Nitrogen is used to protect products from harmful insects, for which an inert atmosphere can be fatal.

pharmaceuticals

• Nitrogen is used in packaging, transportation and displacement of oxygen from product tanks.

The medicine

• The use of nitrogen is common in laboratory research, for hospital testing.

Pulp and paper industry

• Nitrogen is used to treat cardboard and paper, as well as wooden objects with a cathode ray or ultraviolet, in order to polymerize varnish coatings. This reduces the cost of photoinitiators, reduces the emission of volatile compounds, and improves the quality of processing.

Firefighting

• Being inert, nitrogen makes it possible to displace oxygen and prevent the oxidation reaction. Combustion is a rapid oxidation reaction that occurs due to the presence of oxygen and an ignition source (electric arc, spark, chemical reaction with a large release of heat) in the atmosphere. Nitrogen helps prevent this situation. At a nitrogen concentration of 90%, combustion does not occur. Mobile nitrogen stations and stationary plants for the production of nitrogen from 5 to 5000 Nm³ / h with a purity of 90% to 99.99%, effectively prevent fire or extinguish its source.

Part I

1. The structure of the atom -

2. The structure of the molecule.

3. Feature chemical bond in a molecule:
- according to EO covalent non-polar;
- by multiplicity triple.

4. Physical properties: gas, part of the air, colorless and odorless, inert.

5. Chemical properties.
1) Oxidative with respect to M and H2. Write down the reaction equations and consider them in terms of oxidation-reduction.

2) Restorative properties

6. Nitrogen in nature.

7. Getting in the industry: from liquid air.

Part II

1. Complete the Nitrogen Application Chart.

2. Give a complete classification characteristic of the ammonia synthesis reaction.

3. Give a complete classification characteristic of the reaction for the synthesis of nitric oxide (II).

4. Determine the formulas of unknown reagents and write down the reaction equations for the transitions:

5. What volume of nitrogen can be obtained from 540 m3 of air by fractional distillation?

6. Calculate the mass of the volume of nitrogen obtained in task 5.

7. What microorganisms solve the problem of bound nitrogen? What two groups of such microorganisms can be distinguished? (In case of difficulty, find additional information using the Internet.)
1) Nodule nitrogen-fixing bacteria that bind the free N2 atom into an assimilable form.
2) Soil algae, in particular blue-green ones, also bind atmospheric nitrogen.

8. Write a cinquain about the substance nitrogen.
1) nitrogen N2
2) colorless, odorless
3) inert, non-metal
4) obtained from liquid air
5) air

NITROGEN (Nitrogenium, N)- chemical element of group V periodic system elements of D. I. Mendeleev, atom, number 7, atomic mass 14.0067. Discovered by D. Rutherford in 1772. The following nitrogen isotopes are known (Table).

In various compounds, nitrogen has a variable valency, which can be equal to - 3, +1, +2, +3, +4 and +5.

distribution in nature. The total nitrogen content in earth crust is about 0.016 wt. %. Its main mass is in the air in a free, molecular form - N 2. Dry air contains on average 78.09% by volume (or 75.6% by weight) of free nitrogen. In relatively small quantities, free nitrogen is in a dissolved state in the waters of the oceans. Nitrogen in the form of compounds with other elements (bound nitrogen) is part of all plant and animal organisms.

Life is inextricably linked with the properties of easily changing complex nitrogenous substances - proteins. The composition of proteins on average includes 15-17% nitrogen. When organisms die, their complex nitrogenous compounds in the process of the nitrogen cycle turn into more simple connections: ammonia, ammonium salts, nitrites and nitrates. All nitrogen compounds, both organic and inorganic, found in the soil are collectively referred to as soil nitrogen.

Nitrogen production

In laboratories, pure nitrogen is usually obtained by heating a concentrated aqueous solution of ammonium nitrate or a solution of a mixture of ammonium chloride and sodium nitrite:

NH 4 Cl + NaNO 2 = N 2 + NaCl + 2H 2 O.

In the technique of nitrogen with an admixture of up to 3% argon, it is obtained by fractionated distillation of liquid air.

Nitrogen Properties

In the free state, nitrogen is a colorless, odorless and tasteless gas, consisting of diatomic molecules - N 2 . The weight of 1 liter of it at t ° 0 ° and a pressure of 760 mm Hg. Art. equal to 1.2506 g, t° kip - 195.8°, t° pl - 209.86°; density of liquid A. 0.808 (at t ° - 195.8 °), solid - 1.026 (at t ° - 255 °). In 1 ml of water at t ° 0 °, 20 ° and 38 ° and a partial pressure of nitrogen equal to 760 mm, 0.0235, 0.0154 and 0.0122 ml of nitrogen are dissolved, respectively.

The solubility of nitrogen in the blood is less; it is at t ° 38 ° 0.0110 ml A. At low partial pressures of nitrogen, its solubility in the blood is somewhat greater than in water.

Under normal conditions, nitrogen is physiologically inert, but when air compressed to 2-2.5 atm is inhaled, a state occurs called nitrogen anesthesia, similar to alcohol intoxication. This phenomenon can take place during diving operations (see) at a depth of several tens of meters. To prevent the occurrence of such a state, artificial gas mixtures are sometimes used in which nitrogen is replaced by helium or some other inert gas. With a sharp and significant decrease in the partial pressure of nitrogen, its solubility in the blood and tissues is so reduced that part of it is released in the form of bubbles, which is one of the causes of decompression sickness observed in divers when they quickly rise to the surface and in pilots at high takeoff speeds aircraft into the upper atmosphere (see Decompression sickness).

Application of nitrogen

Free nitrogen as a chemically inactive gas is used in laboratory practice and technology in all cases where the presence of oxygen in the surrounding atmosphere is unacceptable or undesirable, for example, when conducting a biological experiment under anaerobic conditions, when pouring large amounts of flammable liquids (to prevent fires) and so on. The bulk of free nitrogen is used in industry for the synthesis of ammonia, calcium cyanamide and nitric acid, which are the starting materials for the production of nitrogen fertilizers, explosives, paints, varnishes, pharmaceuticals, and more.

Nitrogen compounds

Free nitrogen at ordinary temperatures is chemically inert; at high temperatures, it combines with many elements.

Nitrogen forms a number of compounds with hydrogen, the main of which are the following:

3. Nitrous acid (HN 3) - a colorless liquid boiling at t ° 37 ° with a pungent odor. Explodes with great force when heated. V aqueous solutions stable and exhibits the properties of a weak acid. Its salts - azides - are unstable and explode when heated or hit. Lead azide Pb (N 3) 2 is used as a detonator. Inhalation of HN3 vapors causes severe headache and irritation of the mucous membranes.

With oxygen, nitrogen forms five oxides.

1. Nitrous oxide, or laughing gas (N 2 O), is a colorless gas, obtained by heating (above 190 °) ammonium nitrate:

NH 4 NO 3 \u003d N 2 O + 2H 2 O. In a mixture with oxygen, nitrous oxide is used as a weak drug that causes a state of intoxication, euphoria, dulling pain sensitivity. It is used for inhalation anesthesia (see).

2. Nitric oxide (NO) - a colorless gas, poorly soluble in water; in laboratories it is obtained by the action of nitric acid of medium concentration on copper:

8HNO 3 + 3Cu \u003d 2NO + 3Cu (NO 3) 2 + 4H 2 O, in technology - by blowing air through an electric arc flame. In air, it instantly oxidizes, forming red-brown vapors of nitrogen dioxide; together with the latter causes poisoning of the body (see below - Occupational hazards of nitrogen compounds).

3. Nitrogen dioxide (NO 2) - a red-brown gas that has a characteristic odor and consists of A. dioxide itself and its colorless polymer - nitrogen tetroxide (N 2 O 4) - nitrous anhydride. Nitrogen dioxide easily condenses into a red-brown liquid, boiling at t° 22.4° and solidifying at t° - 11° into colorless crystals. It dissolves in water to form nitrous and nitric acids:

2NO 2 + H 2 O \u003d HNO 2 + HNO 3.

Is an strong oxidizing agent and dangerous poison. Nitrogen dioxide is formed during the production of nitric acid, during nitration reactions, pickling of metals, and the like, and therefore is an occupational poison.

4. Nitrogen trioxide, nitrous anhydride (N 2 O 3), is a dark blue liquid that hardens at t ° - 103 ° into blue crystals. Stable only at low temperatures. With water it forms a weak and fragile nitrous acid, with alkalis - salts of nitrous acid - nitrites.

5. Nitrogen pentoxide, nitric anhydride to-you (N 2 O 5), - colorless prismatic crystals having a density of 1.63, melting at t ° 30 ° into a yellow, slightly decomposing liquid; decomposition is enhanced by heating and exposure to light. The boiling point is about 50°. With water it forms a strong, fairly stable nitric acid, with alkalis - salts of this acid - nitrates.

When heated, nitrogen combines directly with many metals, forming metal nitrides, for example, Li3N, Mg 3 N 2, AlN, etc. Many of them decompose with water to form ammonia, for example

Mg 3 N 2 + 6H 2 O \u003d 2NH 3 + 3Mg (OH) 2.

Nitrogen is part of a large number of organic compounds, among which alkaloids, amino acids, amines, nitro compounds, cyanide compounds, and the most complex natural compounds- proteins.

Atmospheric nitrogen fixation. For a long time, the starting materials for obtaining a variety of nitrogen compounds necessary for Agriculture, industry and military affairs, served as natural Chilean nitrate and ammonia obtained by dry distillation hard coal. With the depletion of the deposits of Chilean saltpeter, "nitrogen starvation" threatened humanity. The problem of nitrogen starvation was resolved in the late 19th and early 20th century by the development of a number of industrial methods for fixing atmospheric nitrogen. The most important of them is the synthesis of ammonia according to the scheme:

Determination of nitrogen

To determine free nitrogen, the gas to be analyzed is brought into contact with heated magnesium; in the presence of nitrogen, magnesium nitride is formed, which with water gives ammonia.

nitrogen cycle

Nitrogen is the most important biogenic element necessary for the construction of proteins and nucleic acids. However, atmospheric nitrogen is not available to animals and most plants. Therefore, in the nitrogen cycle, the process of its biological fixation (fixation of atmospheric molecular nitrogen) is of paramount importance. Nitrogen fixation is carried out by nitrogen-fixing microorganisms, such as bacteria from the genus Rhizobium, or nodule bacteria living in symbiosis (see) with legumes (peas, alfalfa, soybeans, lupins and others), on the roots of which nodules are formed containing bacteria that can absorb molecular nitrogen . Symbiotic nitrogen fixers also include some actinomycetes living in the root nodules of alder, sucker, sea buckthorn, and so on. Active nitrogen fixers are also some free-living microorganisms living in the soil, fresh and salt water bodies. This is an anaerobic spore-bearing bacterium Clostridium (Clostridium pasteurianum), discovered by S. N. Vinogradsky, an aerobic bacterium - Azotobacter (see Azotobacter). In addition, mycobacteria, some types of blue-green algae (Nostoc, Anabaena, etc.), as well as photosynthetic bacteria, have the ability to assimilate molecular nitrogen.

Nodule bacteria are of the greatest importance in soil enrichment with nitrogen. As a result of the activity of these bacteria, 100-250 kg/ha per season is introduced into the soil; blue-green algae in rice fields fix up to 200 kg/ha of nitrogen per year. Free-living nitrogen-fixing bacteria bind several tens of kilograms of nitrogen per hectare of soil.

S. N. Vinogradsky for the first time (1894) suggested that the initial product of the process of biological nitrogen fixation is ammonia. This assumption has now been fully confirmed. It has been proven that the conversion of N 2 to NH 3 is an enzymatic process. The enzyme that carries out this process (nitrogenase) consists of two protein components, is active only in the absence of oxygen, and the process itself occurs due to the energy of adenosine triphosphoric acid (ATP). Plants, as well as microorganisms, then convert inorganic ammonium nitrogen into its organic compounds (amino acids, proteins, nucleic acids, and so on), and in this form it becomes available to animals and humans, being included in the metabolic processes occurring in their organisms. Organic nitrogen of animals and plants enters the soil (with animal secretions or their decomposition products) and is processed by various worms, mollusks, nematodes, insects, and microorganisms living there. Soil microorganisms - ammonifiers (putrefactive bacteria, some actinomycetes and fungi) - in turn mineralize the organic nitrogen of the soil (bodies of animals and plants, organic fertilizers, humus) to ammonium. Ammonification is a complex of enzymatic processes occurring mainly in two stages: the hydrolysis of proteins and nucleic acids to amino acids and nitrogenous bases and the subsequent decomposition of these compounds to ammonia. The resulting ammonia is neutralized by reacting with the organic and inorganic acids contained in the soil. This results in the formation of ammonium salts. Ammonium salts and ammonia, in turn, undergo nitrification under the influence of nitrifying bacteria (discovered in 1890 by S. N. Vinogradsky) with the formation of nitrates and nitrites.

The processes of nitrification and ammonification provide plants with easily digestible nitrogen compounds. Ammonium salts and nitrates are absorbed by plants and microorganisms, turning into nitrogen organic compounds. However, part of the nitrogen is converted in the soil into molecular nitrogen as a result of the denitrification process carried out by microorganisms living in the soil - denitrifiers (Fig.). Denitrifying bacteria are widely distributed in nature, found in large numbers in soil, manure and in smaller numbers in the water of rivers, lakes and seas. The most typical denitrifiers are mobile, Gram-negative rods. These include Bacterium fluorescens, B. denitrificans, B. pyocyaneum and more.

The process of denitrification leads to the loss of nitrogen available to plants, however, the constantly ongoing process of nitrogen fixation to some extent compensates for these losses, and under certain conditions (in particular, when the soil is rich in nitrogen-free organic matter) and significantly enriches the soil with bound nitrogen.

In general, the combined effect of the processes of nitrogen fixation, nitrification and denitrification is of great biogeochemical importance, contributing to the maintenance of a dynamic balance between the content of molecular nitrogen in the atmosphere and the bound nitrogen of the soil, flora and fauna.

The nitrogen cycle thus plays a critical role in sustaining life on Earth.

Occupational hazards of nitrogen compounds

Nitric acid (see), ammonia (see), amino compounds (see Amines) and amido compounds (see Amides), as well as mixtures of nitrogen oxides, or nitrogases (N 2 O, NO, NO 2 , N 2 O 4 and N 2 O 5). The latter are formed during the production and use of nitric acid (in the process of its interaction with various metals or organic substances), in the process of thermal oxidation of air nitrogen during electric and gas welding, operation of diesel and carburetor engines, fuel combustion in powerful boiler houses, as well as during blasting, and so on. The general nature of the action of nitrogases on the body depends on the content of various nitrogen oxides in the gas mixture. Basically, poisoning proceeds by an irritating, or nitrite, type of action. When nitrogen oxides come into contact with the moist surface of the lungs, nitric and nitrous acids are formed, which affect the lung tissue, causing pulmonary edema. At the same time, nitrates (see) and nitrites (see) are formed in the blood, directly acting on the blood vessels, expanding them and causing a decrease in blood pressure. Nitrites, interacting with oxyhemoglobin, turn it into methemoglobin, causing methemoglobinemia (see). A common consequence of the action of nitrogen oxides is oxygen deficiency.

Under production conditions, there may be cases of exposure to individual oxides of nitrogen (see below).

Nitrous oxide. Its large concentrations cause tinnitus, asphyxia, loss of consciousness. Death occurs from paralysis of the respiratory center.

Nitric oxide acts on the central nervous system, affects hemoglobin (converts oxyhemoglobin to methemoglobin).

With mild nitric oxide poisoning, general weakness, drowsiness, dizziness are observed (symptoms are reversible).

With more severe poisoning, the initial symptoms intensify, they are joined by nausea, sometimes vomiting, and a fainting state occurs. With moderate poisoning, severe weakness and dizziness last for many hours, cyanosis of the mucous membranes and skin, and increased heart rate are often observed. In severe poisoning, the initial symptoms often subside, but after a 1-3-day remission, weakness and dizziness appear, a decrease in blood pressure, a gray-blue color of the mucous membranes and skin, an increase and soreness of the liver are observed; the borders of the heart are expanded, the tones are deaf, the pulse is slow. There are polyneuritis, polyneuralgia. Chocolate-brown blood, high viscosity. The consequences of severe poisoning can last more than a year: impaired associative abilities, weakening of memory and muscle strength, general weakness, headache, dizziness, fatigue.

Nitrogen dioxide. Acute poisoning begins with a mild cough, severe cases- with a strong cough, chest tightness, headache, sometimes vomiting, salivation. The period of relatively satisfactory condition lasts 2-18 hours. Then there are signs of increasing pulmonary edema: severe weakness, increasing cough, chest pain, cyanosis, many wet rales in the lungs, rapid heartbeat, sometimes chills, fever. Frequent significant disturbances gastrointestinal tract: nausea, vomiting, diarrhea, severe pain in the upper abdomen. Pulmonary edema is characterized by a serious condition (severe cyanosis, severe shortness of breath, rapid pulse, cough with frothy sputum, sometimes with blood). Blood pressure is normal, in the blood - an increase in the number of erythrocytes and hemoglobin, leukocytosis, delayed ESR. X-ray - reduced transparency of the lung fields, in both lungs a large number of flaky blackouts of various sizes. Toxic pulmonary edema is accompanied by a "blue" type of hypoxemia, with a complication of collapse, a "gray" type is observed (see Hypoxia). Frequent complications of pneumonia. Possible fatal outcome. On the section - pulmonary edema, hemorrhages in them, dark liquid blood in the heart and blood vessels. The condition of the poisoned and the prognosis worsens if the victims suffered from heart or lung diseases before the poisoning.

In chronic poisoning - chronic inflammatory diseases of the upper respiratory tract, chronic bronchitis, emphysema, low blood pressure, greenish plaque on the teeth, destruction of the crowns of the incisors.

Nitrous anhydride acts on the body in a similar way to nitric oxide and its other lower oxides.

First aid for poisoning with nitrogen compounds- transfer the victim to Fresh air; ensure complete rest, inhalation of oxygen. According to indications - cardiac drugs, when breathing stops - lobelin. Then the mandatory transportation of the victim in the supine position to the hospital. With signs of incipient pulmonary edema - intravenously 10-20 ml of a 10% solution of calcium chloride, 20 ml of a 40% glucose solution with ascorbic acid (500 mg), oxygen therapy.

Treatment of developed pulmonary edema depends on the type of hypoxemia. With the "blue" type - intermittent administration of oxygen (carbogen is contraindicated), bloodletting (200-300 ml), if necessary - repeating it after 6-8 hours; blood pressure lowering agents, cardiac agents are recommended. With the "gray" type of anoxemia - stimulation of the respiratory and vasomotor center by intermittent inhalation of carbogen, caffeine, ephedrine, intravenously 50-100 ml of 40% glucose solution. Bloodletting is contraindicated.

In order to prevent and treat pneumonia - early appointment of sulfonamides and antibiotics.

Prevention: personal protection - filtering gas masks of grades B, M, KB, acid-proof gloves and boots, sealed goggles, special clothing. Complete seal required production equipment where nitrogases can form and be released, shelter of fixed sources of these gases, local ventilation system.

The maximum permissible concentration for nitrogen oxides in the air of working premises is 5 mg / m 3 (in terms of NO 2), in atmospheric air settlements 0.085 mg / m 3 or 0.4 mg / m 3 (for nitric acid).

The determination of nitrogen oxides in the air is based on the absorption of nitrogen dioxide and nitrogen tetroxide by a solution of potassium iodide and the colorimetric determination of the formed nitrous acid with the Griess-Iloshvai reagent.

Bibliography: Nekrasov B.V. Fundamentals of General Chemistry, t. 1, p. 377, M., 1969; Remy G. Course of inorganic chemistry, trans. from German, vol. 1, p. 560, M., 1972.

The circle A.- Vinogradsky S. N. Soil microbiology, M., 1952; Kretovich V. L. Exchange of nitrogen in plants, M., 1972, bibliogr.; Mishustin E. N. and Shilnikova V. K. Biological fixation of atmospheric nitrogen, M., 1968, bibliogr.

Occupational hazards of compounds A. - Harmful substances in industry, ed. N. V. Lazareva, part 2, p. 136, L., 1971; Occupational health in chemical industry, ed. Z. A. Volkova and others, p. 373, M., 1967; Yu. A. Gurtovoy. Poisoning with vapors of nitric acid, Sud.-med. examination, vol. 12, no. 3, p. 45, 1969; Neimark E. Z. and Singer F. X. Occupational poisoning of coal mine workers, their treatment and prevention, p. 34, Moscow, 1961; Peregud E. A., Bykhovskaya M. S. and Gernet E. V. Rapid methods for determining harmful substances in the air, p. 67, M., 1970; Safronov V. A. Features of the clinical course of pulmonary edema in combined lesions with nitric acid, Voyen.-med. journal, no. 7, p. 32, 1966; Air quality criteria for nitrogen oxides, Washington, 1971, bibliogr.

V. P. Mishin; Z. G. Evstigneeva, V. L. Kretovich (circulation of A.); E. N. Marchenko (prof.).

Nitrogen is a chemical element that is known to everyone. It is denoted by the letter N. It can be said to be the basis of inorganic chemistry, and therefore they begin to study it as early as the eighth grade. In this article, we will take a detailed look at nitrogen, as well as its characteristics and properties.

Element Discovery History

Compounds such as ammonia, nitrate, and nitric acid were known and used in practice long before the production of pure nitrogen in the free state.

During an experiment conducted in 1772, Daniel Rutherford burned phosphorus and other substances in a glass bell. He found that the gas remaining after the combustion of the compounds does not support combustion and respiration, and called it "suffocating air."

In 1787, Antoine Lavoisier established that the gases that make up ordinary air are simple chemical elements, and proposed the name "Nitrogen". A little later (in 1784), physicist Henry Cavendish proved that this substance is part of saltpeter (a group of nitrates). From here comes Latin name nitrogen (from late Latin nitrum and Greek gennao), proposed by J. A. Chaptal in 1790.

TO early XIX centuries, scientists have found chemical inertness element in the free state and its exclusive role in compounds with other substances. Since that moment, the "binding" of nitrogen in the air has become the most important technical problem in chemistry.

Physical properties

Nitrogen is slightly lighter than air. Its density is 1.2506 kg / m³ (0 ° C, 760 mm Hg), melting point - -209.86 ° C, boiling point - -195.8 ° C. Nitrogen is difficult to liquefy. Its critical temperature is relatively low (-147.1 °C), while the critical pressure is quite high - 3.39 MN/m². Density in the liquid state - 808 kg / m³. In water, this element is less soluble than oxygen: 23.3 g of N can dissolve in 1 m³ (at 0 ° C) of H₂O. This figure is higher when working with some hydrocarbons.

When heated to low temperatures, this element interacts only with active metals. For example, with lithium, calcium, magnesium. With most other substances, nitrogen reacts in the presence of catalysts and/or at high temperatures.

Compounds of N with O₂ (oxygen) N₂O₅, NO, N₂O₃, N₂O, NO₂ have been well studied. Of these, during the interaction of elements (t - 4000 ° C), oxide NO is formed. Further, in the process of cooling, it is oxidized to NO₂. Nitrogen oxides are formed in the air during the passage of atmospheric discharges. They can be obtained with an action. ionizing radiation to a mixture of N and O₂.

When N₂O₃ and N₂O₅ are dissolved in water, respectively, the acids HNO₂ and HNO₂ are obtained, which form salts - nitrates and nitrites. Nitrogen combines with hydrogen exclusively in the presence of catalysts and at high temperatures, forming NH₃ (ammonia). In addition, other (they are quite numerous) compounds of N with H₂ are known, for example, diimide HN = NH, hydrazine H₂N-NH₂, octazone N₈H₁₄, acid HN₃ and others.

It is worth saying that most hydrogen + nitrogen compounds have been isolated exclusively in the form of organic derivatives. This element does not interact (directly) with halogens, so all its halides are obtained only indirectly. For example, NF₃ is formed when ammonia reacts with fluorine.

Most nitrogen halides are low-resistant compounds, oxyhalides are more stable: NOBr, NO₂F, NOF, NOCl, NO₂Cl. Direct connection of N with sulfur also does not occur, N₄S₄ is obtained during the reaction of ammonia + liquid sulfur. During the interaction of red-hot coke with N, cyanogen (CN)₂ is formed. In the process of heating C₂H₂ acetylene with nitrogen to 1500 °C, hydrogen cyanide HCN can be obtained. When N interacts with metals at relatively high temperatures, nitrides are formed (for example, Mg₃N₂).

When ordinary nitrogen is exposed to electric discharges [at a pressure of 130–270 N/m² (corresponds to 1–2 mmHg)] and during the decomposition of Mg₃N₂, BN, TiNx and Ca₃N₂, as well as during electric discharges in air, active nitrogen can be formed, with increased energy reserves. It, unlike the molecular one, interacts very vigorously with hydrogen, sulfur vapor, oxygen, some metals and phosphorus.

Nitrogen is part of quite a few important organic compounds, including amino acids, amines, nitro compounds, and others.

Nitrogen production

In the laboratory, this element can be easily obtained by heating a concentrated solution of ammonium nitrite (formula: NH₄NO₂ = N₂ + 2H₂O). The technical method for obtaining N is based on the separation of preliminarily liquefied air, which is subsequently distilled.

Application area

The main part of the free nitrogen obtained is used in the industrial production of ammonia, which is then processed in fairly large quantities into fertilizers, explosives, etc.

In addition to the direct synthesis of NH₃ from elements, the cyanamide method developed at the beginning of the last century is used. It is based on the fact that at t = 1000 °C calcium carbide (formed by heating a mixture of coal and lime in an electric furnace) reacts with free nitrogen (formula: CaC₂ + N₂ = CaCN₂ + C). The resulting calcium cyanamide decomposes into CaCO₃ and 2NH₃ under the action of heated water vapor.

In its free form, this element is used in many industries: as an inert medium in various metallurgical and chemical processes, when pumping flammable liquids, to fill the space in mercury thermometers etc. In the liquid state, it is used in various refrigeration units. It is transported and stored in steel Dewar vessels, and compressed gas - in cylinders.

Many nitrogen compounds are also widely used. Their production began to develop intensively after the First World War and this moment reached truly enormous proportions.

This substance is one of the main biogenic elements and is part of essential elements living cells - nucleic acids and proteins. However, the amount of nitrogen in living organisms is small (approximately 1–3% by dry weight). The molecular material present in the atmosphere is assimilated only by blue-green algae and some microorganisms.

Quite large reserves of this substance are concentrated in the soil in the form of various mineral (nitrates, ammonium salts) and organic compounds (in the composition of nucleic acids, proteins and their decay products, including not yet completely decomposed remains of flora and fauna).

Plants perfectly absorb nitrogen from the soil in the form of organic and inorganic compounds. V natural conditions Of great importance are special soil microorganisms (ammonifiers), which are able to mineralize soil organic N to ammonium salts.

The nitrate nitrogen of the soil is formed during the vital activity of nitrifying bacteria, discovered by S. Vinogradsky in 1890. They oxidize ammonium salts and ammonia to nitrates. Part of the material assimilated by flora and fauna is lost due to the action of denitrifying bacteria.

Microorganisms and plants perfectly assimilate both nitrate and ammonium N. They actively convert inorganic material into various organic compounds - amino acids and amides (glutamine and asparagine). The latter are part of many proteins of microorganisms, plants and animals. Synthesis of asparagine and glutamine by amidation (enzymatic) of aspartic and glutamic acids is carried out by many representatives of flora and fauna.

The production of amino acids occurs through the reductive amination of a number of keto acids and aldehyde acids, which arise through enzymatic transamination, as well as as a result of the oxidation of various carbohydrates. The end products of the assimilation of ammonia (NH₃) by plants and microorganisms are proteins that are part of the cell nucleus, protoplasm, and are also deposited in the form of so-called storage proteins.

Man and most animals can synthesize amino acids only to a fairly limited extent. They are not able to produce eight essential compounds (lysine, valine, phenylalanine, tryptophan, isoleucine, leucine, methionine, threonine), and therefore the main source of nitrogen for them is the proteins consumed with food, that is, ultimately, the own proteins of microorganisms and plants.