NITROGEN

From Big Medical Encyclopedia

NITROGEN (Nitrogenium, N) — chemical element V of group of a periodic system of elements of D. I. Mendeleyev, atom, number 7, at. weight 14,0067. It is opened by Rutherford (D. Rutherford) in 1772. The following isotopes A are known. (tab.).

In various connections A. has variable valency, edges it can be equal — 3, +1, +2, +3, +4 and +5.

Distribution in the nature. General contents And. in crust makes apprx. 0,016 weight. %. Its ground mass is airborne in a free, molecular look — N 2 . The dry air contains on average 78,09% on volume (or 75,6% on weight) free A. V rather trace amounts free And. is in the dissolved state in waters of oceans. And. in the form of connections with other elements (connected And.) is a part of all vegetable and animal organisms.

Life is inseparably linked with properties of easily changing complex nitrogenous substances — proteins. 15 — 17% on average are a part of proteins And. At dying off of organisms their difficult nitrogenous compounds in the course of circulation And. turn into simpler connections: ammonia, ammonium salts, nitrites and nitrates. All connections A., both organic, and inorganic, contained in the soil, combine under the name «nitrogen of the soil».

Receiving nitrogen

In laboratories pure And. receive usually heating of the concentrated aqueous solution of ammonium nitrite or solution of mix of ammonium muriate with sodium nitrite:

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

In the equipment of Ampere-second impurity to 3% of argon receive the fractioned distillation of a liquid air.

Properties of nitrogen

In a stand-at-ease And. represents the inodorous colorless gas and taste consisting of diatomic molecules — N 2 . Weight is 1 its l at t ° 0 ° and pressure of 760 mm of mercury. t ° is equal to 1,2506 g, kip - 195,8 °, t ° pl - 209,86 °; density liquid And. 0,808 (at t ° — 195,8 °), firm — 1,026 (at t ° — 255 °). In 1 ml of water at t ° 0 °, 20 ° both 38 ° and partial pressure And., the equal 760 mm, are dissolved respectively 0,0235, 0,0154 and 0,0122 ml of nitrogen.

Solubility And. in blood it is less; it makes at t ° 38 ° 0,0110 ml And. With small partial pressures And. its solubility in blood is slightly more, than in water.

In usual conditions And. it is physiologically inert, but at inhalation of the air compressed to 2 — 2,5 atm there comes the state called by a nitric anesthesia similar to intoxication alcohol. This phenomenon can take place at diving works (see) at a depth of several tens meters. For the prevention of emergence of a similar state sometimes use artificial gas mixtures in which And. it is replaced with helium or any other inert gas. At sharp and considerable decrease in partial pressure And. its solubility in blood and fabrics so decreases that a part it is allocated in the form of bubbles that is one of origins of the caisson disease which is observed at divers at their bystry rise on a surface and at pilots at big speeds of take-off of airplanes in an upper atmosphere (see. Compressed-air disease ).

Use of nitrogen

Free And. as chemically inactive gas is applied in laboratory practice p to the equipment in all cases when existence in the surrounding atmosphere of oxygen is inadmissible or it is undesirable, e.g. during the carrying out a biological experiment in anaerobic conditions, at transfusion of large numbers of combustible liquids (for prevention of the fires) etc. Main weight free And. it is used in the industry for synthesis of ammonia, calcium cyanamide and nitric to - you which are mother substances for receiving nitrogenous fertilizers, explosive substances, paints, varnishes, pharmaceuticals, etc.

Compounds of nitrogen

Free And. at usual temperatures it is chemically inert; at high temperature enters connection with many elements.

With hydrogen A. forms a series of compounds, the following is basic of which:

1. Ammonia (see). And., being a part of ammonia, it is accepted to call ammonia nitrogen. In a dignity. - a gigabyte. to practice definition ammoniac And. make at a research of drinking waters, during the studying of processes of rotting of proteic matters (in particular, meat and fish) etc.

2. Hydrazine (N 2 H 4 ) — the colourless, smoking on air liquid. With acids forms salts of a hydrazine, napr, with salt to - that is chloride gidrazoniya (N 2 H 4 - HCl). It is applied as a strong reducer. Organic compounds of a hydrazine are important for the characteristic Sakharov (see. Carbohydrates ).

3. Azotistovodorodny acid (HN 3 ) — the colourless, boiling at t ° 37 ° liquid with a pungent smell. Blows up with a big force during the heating. In aqueous solutions it is steady and shows properties of weak acid. Its salts — azides — are unstable and explode during the heating or blow. Pb lead azide (N 3 ) 2 it is applied as a detonator. Steam inhalation of HN3 causes a severe headache and irritation of mucous membranes.

With oxygen A. forms five oxides.

1. Nitrous oxide, or laughing gas (N 2 O) — colorless gas, receive during the heating (higher than 190 °) ammonium nitrate:

NH 4 NO 3 = N 2 O + 2H 2 O. In mix with oxygen nitrous oxide is applied as the "soft drug " causing an ebrietas, euphoria, obtusion of painful sensitivity. It is applied for inhalation anesthesia (see).

2. Nitric oxide (NO) — colorless gas, low solubility in water; laboratories receive action nitric to - you average concentration on copper:

8HNO 3 + 3Cu = 2NO + 3Cu (NO 3 ) 2 + 4H 2 O, in the equipment — blowing off of air through a flame of an electric arch. On air instantly is oxidized, forming red-brown vapors of nitrogen dioxide; together with the last causes poisonings of an organism (see below — Professional harm of compounds of nitrogen).

3. Nitrogen dioxide (NO 2 ) — the red-brown gas having a characteristic smell and consisting of actually dioxide A. and its colourless polymer — nitrogen tetroxide (N 2 O 4 ) — nitrogen tetroxide. Nitrogen dioxide is easily condensed in the red-brown liquid boiling at t ° 22,4 ° and hardening at t ° — 11 ° in colourless crystals. It is dissolved in water with formation of nitrogenous and nitric acids:

2NO 2 + H 2 O = HNO 2 + HNO 3 .

Is a strong oxidizer and statutory poison. Nitrogen dioxide is formed during the receiving nitric acid, at reactions of nitration, pickling of metals, etc. and therefore represents professional poison.

4. Nitrogen trioxide, anhydride nitrogenous to - you (N 2 O 3 ) — the dark blue liquid hardening at t ° — 103 ° in blue crystals. It is steady only at low temperatures. With water forms weak and fragile nitrogenous to - that, with alkalis — salts nitrogenous to - you — nitrites.

5. Nitrogen pentoxide, anhydride nitric to - you (N 2 O 5 ) — the colourless prismatic crystals having density 1,63, melting at t ° 30 ° in the yellow, slightly decaying liquid; decomposition amplifies during the heating and at effect of light. Temperature of boiling apprx. 50 °. With water forms strong, quite steady nitric to - that, with alkalis — salts of this acid — nitrates.

During the heating And. directly Li3N, Mg connects to many metals, forming nitrides of metals, e.g. 3 N 2 , AlN, etc. Many of them decay water with formation of ammonia, e.g.

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

And. is a part of a large number of organic compounds among which alkaloids, amino acids, amines, nitro compounds, cyanic connections and the most difficult natural compounds — proteins have special value.

Fixing of atmospheric nitrogen. For a long time mother substances for receiving various connections A., necessary for agriculture, the industry and military science, natural nitratine and the ammonia received at dry distillation of black coal served. With exhaustion of deposits of nitratine the mankind was threatened by «nitric hunger». The problem of nitric hunger was resolved 19 at the end and the beginning of 20 century by development of a number of industrial methods of fixing atmospheric A. Naiboley of them synthesis of ammonia according to the scheme is important:

N 2 + 3H 2 <-> 2NH 3

(see. Ammonia ).

Definition of nitrogen

For definition free And. the analyzed gas is brought into contact with heated magnesium; in the presence And. magnesium nitride which with water gives ammonia is formed.

Contents And. in its oxygen connections define, transferring these connections to an oxide And., e.g. in Lunge's nitrometra. In organic compounds A. usually determine by Kyeldal's method (see. Kyeldalya method ).

Nitrogen cycle

And. is the major biogenic element necessary for creation of proteins and nucleic acids. However And. the atmospheres it is unavailable to animals and the most part of plants. Therefore in circulation And. paramount value has process of its biological fixing (molecular A.atmosfera's fixing). Azotfixation is carried out by nitrogen-fixing microorganisms, e.g. bacteria from the sort Rhizobium, or the nodule bacteriums living in symbiosis (see) with bean plants (peas, a lucerne, soy, a lupine, etc.) on which roots the nodules containing bacteria capable to acquire molecular A. K to symbiotic nitrogen fixers are formed also some actinomycetes living in root nodules of an alder, the sucker, a sea-buckthorn etc. belong. Active nitrogen fixers are also some free living microorganisms living in the soil, fresh and salty reservoirs. It is an anaerobic sporiferous bacterium klostridium (Clostridium pasteurianum), the opened by S. N. Vinogradsky, aerobic bacterium — azotobacter (see. Azotobacter ). Ability to acquire molecular And. mycobacteria, some species of blue-green seaweed (Nostoc, Anabaena, etc.), and also photosynthesizing bacteria possess, besides.

The greatest value in enrichment of the soil And. have nodule bacteriums. As a result of activity of these bacteria 100 — 250 kg/hectare during the season are brought in the soil; blue-green seaweed on rice fields fix up to 200 kg/hectare And. in a year. Free living nitrogen-fixing bacteriums connect several tens of kilograms And. on one hectare of the soil.

S. N. Vinogradsky for the first time (1894) suggested that an initial product of process of biological azotfixation is ammonia. In a crust, time it is the assumption it is completely confirmed. It is proved that transformation of N 2 in NH 3 represents enzymatic process. The enzyme which is carrying out this process (nitrogenaza) consists of two proteinaceous components, is active only for lack of oxygen, and process happens due to energy adenosine triphosphoric to - you are (ATP). Plants, and also microorganisms then turn inorganic ammonium And. in its organic compounds (amino acids, proteins, nucleic acids etc.), and in such look it becomes available to animals and the person, joining in the exchange processes proceeding in their organisms. Organic And. animals and plants gets to the soil (with allocations of animals or products of their decomposition) and it is processed by various worms living there, mollusks, nematodes, insects, and also microorganisms. Microorganisms of the soil — ammonifiers (putrefactive bacteria, some actinomycetes and mushrooms) — mineralize in turn organic And. soils (bodies of animals and plants, organic fertilizers, a humus) to ammonium. Ammonification — a complex of the enzymatic processes proceeding generally in two stages: hydrolysis of proteins and nucleic acids to amino acids and nitrogen bases and the subsequent decomposition of these connections to ammonia. The formed ammonia is neutralized, reacting with the organic and inorganic acids which are contained in the soil. At the same time there is a formation of ammonium salts. Ammonium salts and ammonia in turn are exposed to a nitrification under the influence of the nitrifying bacteriums (opened in 1890 by S. N. Vinogradsky) with formation of nitrates and nitrites.

the Scheme of a nitrogen cycle in the nature

Processes of a nitrification and ammonification provide plants with easily acquired connections A. Ammonium salts and nitrates are acquired by plants and microorganisms, turning in And. organic compounds. However part A. turns in the soil in molecular And. as a result of the process of a denitrification which is carried out by the microorganisms living in the soil — denitrifiers (fig). Denitrifying bacteria are eurysynusic in the nature, meeting in a large number in the soil, manure and in smaller — in water of the rivers, lakes and seas. The most typical denitrifiers — mobile, gram-negative sticks. Bacterium fluorescens, V. of denitrificans, V. of pyocyaneum, etc. treat them.

Process of a denitrification leads to loss available to plants And., however constantly going process of azotfixation to some extent offsets these losses, and in the known conditions (in particular, at richness of the soil nitrogen-free organic matters) and considerably enriches the soil connected And.

In general cumulative action of processes of azotfixation, a nitrification and denitrification has great biogeochemical value, promoting preservation of a dynamic equilibrium between contents molecular And. in the atmosphere and connected And. soils, plant and animal life.

Circulation And., thus, plays an important role in maintenance of life on Earth.

Professional harm of compounds of nitrogen

To number of connections A most harmful professionally. belong nitric acid (see), ammonia (see), amino compounds (see. Amines ) and amidoconnections (see. Amides ), and also mixes of oxides A., or nitrogases (N 2 O, NO, NO 2 , N 2 O 4 and N 2 O 5 ). The last are formed by production and use nitric to - you (in the course of its interaction with various metals or organic matters), in the course of thermal oxidation And. air at electro-and gas welding, operation of diesel and carburetor engines, fuel burning in powerful boiler rooms, and also during the blasting etc. The general nature of effect of nitrogases on an organism depends on the content in gas mixture of various oxides A. Generally poisoning proceeds on irritating, or nitrite, to type of action. At contact of oxides of Ampere-second the wet surface of lungs forms nitric and nitrogenous acids which strike pulmonary fabric, causing a fluid lungs. At the same time in blood are formed nitrates (see) and nitrites (see), directly acting on blood vessels, expanding them and causing lowering of blood pressure. Nitrites, interacting with oxyhemoglobin, turn it into a methemoglobin, causing methemoglobinemia (see). General consequence of effect of oxides A. oxygen insufficiency is.

Under production conditions chances of influence of separate oxides A. (see below).

Nitrous oxide. Its big concentration cause a sonitus, asphyxia, a loss of consciousness. Death comes from paralysis of a respiratory center.

Nitric oxide acts on c. the N of page, influences hemoglobin (transfers oxyhemoglobin to a methemoglobin).

At slight poisoning with an oxide And. the general weakness, drowsiness, dizziness is observed (symptoms are reversible).

At more serious poisoning initial symptoms amplify, nausea, sometimes vomiting joins them, there comes subconscious state. At moderately severe poisonings sharp weakness and dizziness proceed many hours, cyanosis of mucous membranes and skin, increase of pulse is quite often observed. At a serious poisoning the initial phenomena quite often abate, but after 1 — 3-day remission there are a weakness and dizziness, lowering of blood pressure, gray-blue coloring of mucous membranes and skin, increase and morbidity of a liver are observed; borders of heart are expanded, tones deaf, pulse is slowed down. There are polyneurites, polyneuralgias. Blood of chocolate-brown color, the increased viscosity. Effects of a serious poisoning can last over a year: disturbance of associative abilities, easing of memory and muscle strength, general weakness, headache, dizziness, bystry fatigue.

Nitrogen dioxide. Acute poisoning begins with slight cough, in more hard cases — with a severe cough, feeling of constraint in a breast, a headache, sometimes vomitings, sialoses. The period of rather satisfactory condition lasts 2 — 18 hour. Then there are signs of the accruing fluid lungs: strong weakness, the increasing cough, stethalgias, cyanosis, in lungs is a lot of wet rattles, a cardiopalmus, sometimes a fever, temperature increase. Considerable frustration from outside are frequent went. - kish. path: nausea, vomiting, a diarrhea, severe pains in an upper part of a stomach. The fluid lungs is characterized by serious condition (sharp cyanosis, severe short wind, the speeded-up pulse, cough with a foamy phlegm, sometimes with blood). Blood pressure is normal, in blood — increase in quantity of erythrocytes and hemoglobin, a leukocytosis, the slowed-down ROE. Radiological — the lowered transparency of pulmonary fields, in both lungs a large number of flocculent blackouts of various size. The toxic fluid lungs is followed by «blue» type of an anoxemia, at a complication the collapse observes «gray» type (see. Hypoxia ). Complications pneumonia are frequent. Death is possible. On section — a fluid lungs, hemorrhages in them, dark liquid blood in heart and vessels. The state poisoned and the forecast worsens if victims to poisoning had heart diseases or lungs.

At hron. poisonings — hron. inflammatory diseases of upper respiratory tracts, hron. bronchitis, emphysema, lowering of blood pressure, a greenish plaque on teeth, destruction of crowns of cutters.

Nitrous anhydride affects an organism similar to nitric oxide and other its lowest oxides.

First aid at poisonings with compounds of nitrogen — to transfer the victim to fresh air; to provide absolute rest, inhalation of oxygen. According to indications — cardiacs, at an apnoea — lobeline. Then obligatory transportation of the victim in lying situation in a hospital. At signs of the beginning fluid lungs — intravenously 10 — 20 ml of 10% of solution of calcium chloride, 20 ml of 40% of solution of glucose with ascorbic to - that (500 mg), oxygen therapy.

Treatment of the developed fluid lungs depends on type of an anoxemia. At «blue» type — discontinuous administration of oxygen (Carbogenum is contraindicated), bloodletting (200 — 300 ml), if necessary — its repetition in 6 — 8 hours; the means lowering the blood pressure, cardiacs are recommended. At «gray» type of an anoxemia — stimulation of the respiratory and vasculomotor center by discontinuous inhalation of Carbogenum, caffeine, ephedrine, intravenously 50 — 100 ml of 40% of solution of glucose. Bloodletting is contraindicated.

For prevention and treatment of pneumonia — early purpose of streptocides and antibiotics.

Prevention: individual protection — the filtering gas masks of brands B, M, KB, acid protective gloves and boots, tight glasses, special clothes. Full sealing of the production equipment where nitrogases, the shelter of the fixed sources of release of these gases, the local vent system can be formed and be emitted is necessary.

Maximum allowable concentration for oxides A. in air of workrooms of 5 mg/m 3 (in terms of NO 2 ), in free air of settlements of 0,085 mg/m 3 or 0,4 mg/m 3 (for nitric to - you).

Definition in air of nitric oxides is based on absorption of dioxide and nitrogen tetroxide by solution of potassium iodide and colorimetric definition formed nitrogenous to - you with Gris's reactant — Iloshvai.


Bibliography: Nekrasov B. V. Fundamentals of the general chemistry, t. 1, page 377, M., 1969; Remy G. Kurs of inorganic chemistry, the lane with it., t. 1, page 560, M., 1972.

Circulation And. - Vinogradsky S. N. Microbiology of the soil, M., 1952; Kretovich V. L. Exchange of nitrogen in plants, M., 1972, bibliogr.; Mishustin E. N. and Shilnikova V. K. Biological fixing of atmospheric nitrogen, M., 1968, bibliogr.

Professional harm of connections And. — Harmful substances in the industry, under the editorship of N. V. Lazarev, the p. 2, page 136, L., 1971; Occupational health in chemical industry, under the editorship of Z. A. Volkova, etc., page 373, M., 1967; Gurtova Yu. A. Poisoning with vapors of nitric acid, Court. - medical examination, t. 12, No. 3, page 45, 1969; Neymark E. Z. and Zinger F. X. Professional poisonings of working coal mines, their treatment and prevention, page 34, M., 1961; A rebuzzing E. A., Bykhovskaya M. S. and Gernet E. V. Bystrye methods of definition of harmful substances in air, page 67, M., 1970; Safronov V. A. Features of a clinical current of a fluid lungs at the combined defeats by nitric acid, Voyen. - medical zhurn., No. 7, page 32, 1966; Air quality criteria for nitrogen oxides, Washington, 1971, bibliogr.

V. P. Mishin; Z. G. Yevstigneyeva, V. L. Kretovich (circulation And.); E. N. Marchenko (prof).

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