Nitrogen content in the earth's crust. Nitrogen in nature

Nitrogen (general information)

Nitrogen

brief information

Nitrogen is an element of the 15th group of the second period of the periodic table of chemical elements of Mendeleev D.I., with atomic number 7.

General information about nitrogen

Nitrogen is the most common gas in the Earth's atmosphere. In other words, three-quarters of the air around us consists of nitrogen, not oxygen. In Mendeleev's periodic table of chemical elements, nitrogen is designated by the symbol N (from the Latin Nitrogenium), has atomic number 7 and occupies a place in the 15th group. Under normal conditions, nitrogen is a diatomic and highly inert gas. It has no color, taste or smell, therefore, it is not perceptible to humans. Nitrogen gas formula N2; It is in this molecular state that it fills three-quarters of the atmosphere of our planet.

History of discovery

At the end of the 18th century, several scientists came close to the discovery of a new chemical element, the properties of which had not yet been studied by science. Thus, Henry Cavendish in 1772 carried out the following experiment: he repeatedly passed air over hot coal, treated the coal with an alkaline solution, and ultimately obtained the remainder of the new substance. The chemist called this residue “suffocating air.” Cavendish actually received nitrogen, a new chemical element, but he could not guess about it. In the same year, Cavendish’s friend Professor Priestley continued experiments to produce “suffocating air”. He also repeatedly obtained nitrogen during his experiments, but mistakenly assumed that this gas was oxygen. Therefore, neither of the two scientists are considered the discoverers of nitrogen.

In parallel with these experiments, Daniel Rutherford conducted his own experiments in the same 1772. It was he who correctly described the basic properties of nitrogen in his master's thesis. In particular, the fact that it is not suitable for breathing, does not react with alkalis and does not support the combustion process. Most often, Rutherford is called the discoverer of nitrogen.

Properties of nitrogen

The physical properties of nitrogen under normal conditions characterize it as a colorless gas, odorless and not perceptible to the human senses. Nitrogen is slightly soluble in water and has a density of 1.2506 kg/m 3 . In the liquid state, nitrogen is a colorless and mobile liquid, visually similar to water. It boils at a temperature of −195.8 °C. The density of liquid nitrogen is reduced to 808 kg/m3. At −209.86 °C, nitrogen enters a solid state of aggregation, taking the form of bright white crystals of large sizes.

The free state of nitrogen is a diatomic N2 molecule with a triple bond between the molecules. This bond makes the nitrogen molecule extremely strong, and under normal conditions there is practically no dissociation of molecules. As a result, nitrogen is a very inert gas: it practically does not enter into chemical reactions with other substances and under normal conditions is in a free state. The forces of intermolecular interaction are extremely weak, which is why under normal conditions nitrogen is a gas and not a liquid or solid.

Interesting facts about nitrogen

The name nitrogen, which means “deprived of life,” appeared with the light hand of Antoine Lavoisier at the end of the 18th century, when it was experimentally established that nitrogen cannot support respiration and combustion. Now we know that, although "lifeless" in name, nitrogen is extremely important for maintaining the life of all creatures. The Latin name for nitrogen “nitrogenium” is translated as “saltpeter-giving” and recalls the critical importance of this element for industry.

All living organisms cannot absorb nitrogen in its pure form. We absorb the required amount through protein foods. When a person breathes, he inhales nitrogen contained in the air. It is not absorbed by the lungs in any way (unlike oxygen), so our exhalation mainly contains nitrogen. Surprisingly, it is precisely the abundance of nitrogen in the atmosphere that helps us not consume oxygen in quantities that are fatal to the human body.

A common story in science fiction is about freezing living things with nitrogen in order to preserve them for future generations. In reality, modern scientists cannot do this, since freezing with liquid nitrogen occurs slowly, and the body dies before it has time to freeze “correctly.”

Application of nitrogen

The use of nitrogen in industrial production is determined by its high inert properties. Liquid nitrogen is used as an industrial refrigerant. Nitrogen in the gaseous state is used as an antioxidant. Since pure gaseous nitrogen can replace air (which contains oxygen as an oxidizing agent), cavities are purged with nitrogen in the electrical industry and in mechanical engineering as such. It is used to purge tanks and pipelines and control their operation at high pressure inside the tank.

Nitrogen is the raw material for the synthesis of important nitrogen-containing compounds. These include nitrogen fertilizers, which, together with phosphorus and potassium fertilizers, are indispensable in crop production. Nitrogen is a component of ammonia, which is used in refrigeration equipment, as an industrial solvent, in medicine, and in general is an important chemical raw material. The production of most explosives on the planet is based on the chemical properties of oxygen and nitrogen.

Nitrogen can also be found in the food industry as food additive E941. Nitrogen gas is needed to fill tire tubes for aircraft landing gear. It has now become fashionable to fill tires with nitrogen among car enthusiasts, although scientific evidence of the effectiveness of such use has not yet been provided. Nitrogen and other gases have found wide application in medicine: both in the creation of new drugs and techniques, and in the manufacture of high-precision medical equipment.

The leading supplier of gases in Ukraine today is the company DP Air Gas.

Nitrogen is a chemical element, atomic number 7, atomic mass 14.0067. In the air, free nitrogen (in the form of N 2 molecules) is 78.09%. Nitrogen is slightly lighter than air, density 1.2506 kg/m 3 at zero temperature and normal pressure. Boiling point -195.8°C. The critical temperature is -147°C and the critical pressure is 3.39 MPa. Nitrogen is a colorless, odorless, tasteless, non-toxic, non-flammable, non-explosive and non-combustible gas in the gaseous state at ordinary temperatures and is highly inert. Chemical formula - N. Under normal conditions, the nitrogen molecule is diatomic - N 2.

The production of nitrogen on an industrial scale is based on obtaining it from the air (see).

There is still debate about who was the discoverer of nitrogen. In 1772, a Scottish doctor Daniel Rutherford(Daniel Rutherford) passing air through hot coal, and then through an aqueous solution of alkali, produced a gas that he called “poisonous gas.” It turned out that a burning splinter brought into a vessel filled with nitrogen goes out, and a living creature quickly dies in the atmosphere of this gas.

At the same time, while conducting a similar experiment, a British physicist obtained nitrogen Henry Cavendshin(Henry Cavendish) calling it "choking air", the British naturalist Joseph Priestley(Joseph Priestley) gave it the name "dephlogisticated air", a Swedish chemist Karl Wilhelm Scheele(Carl Wilhelm Scheele) - “spoiled air.”

The final name “nitrogen” was given to this gas by a French scientist Antoine Laurent Lavoisier(Antoine Laurent de Lavoisier). The word "nitrogen" is of Greek origin and means "lifeless".

A logical question arises: “If nitrogen forms, what is the point of using it for welding stainless steels that contain carbide-forming elements?”

The thing is that even a relatively small nitrogen content increases the thermal power of the arc. Because of this feature, nitrogen is most often used not for welding, but for plasma cutting.

Nitrogen is a non-toxic gas, but can act as a simple asphyxiant (asphyxiant gas). Asphyxiation occurs when nitrogen levels in the air reduce oxygen levels to 75% or below normal concentrations.

They release nitrogen in gaseous and liquid forms. For welding and plasma cutting use nitrogen gas 1st (99.6% nitrogen) and 2nd (99.0% nitrogen) grades.

It is stored and transported in a compressed state in steel cylinders. The cylinders are painted black with the inscription “NITROGEN” in yellow letters on the top cylindrical part.

Everyone knows: nitrogen is inert. We often complain about element No. 7 for this, which is natural: we have to pay too high a price for its relative inertia; too much energy, effort and money have to be spent on converting it into vital compounds.

But, on the other hand, if nitrogen were not so inert, reactions of nitrogen with oxygen would occur in the atmosphere, and life on our planet in the forms in which it exists would become impossible. Plants, animals, you and I would literally choke in streams of oxides and acids unacceptable to life. And “for all that,” we strive to convert as much of the atmospheric nitrogen as possible into oxides and nitric acid. This is one of the paradoxes of element No. 7. (Here the author risks being accused of triviality, because the paradoxical nature of nitrogen, or rather its properties, has become the talk of the town. And yet...)

Nitrogen is an extraordinary element. Sometimes it seems that the more we learn about him, the more incomprehensible he becomes. The contradictory properties of element No. 7 were reflected even in its name, because it misled even such a brilliant chemist as Antoine Laurent Lavoisier. It was Lavoisier who proposed calling nitrogen nitrogen after he was neither the first nor the last to obtain and study the part of the air that does not support respiration and combustion. According to Lavoisier, "nitrogen" means "lifeless", and this word is derived from the Greek "a" - negation and "zoe" - life.

The term “nitrogen” was still in use in the vocabulary of alchemists, from where the French scientist borrowed it. It meant a certain “philosophical principle,” a kind of cabalistic spell. Experts say that the key to deciphering the word “nitrogen” is the final phrase from the Apocalypse: “I am alpha and omega, the beginning and the end, the first and the last...” In the Middle Ages, three languages ​​were especially revered: Latin, Greek and Hebrew. And the alchemists made the word “nitrogen” from the first letter “a” (a, alpha, aleph) and the last letters: “zet”, “omega” and “tov” of these three alphabets. Thus, this mysterious synthetic word meant “the beginning and end of all beginnings.”

Lavoisier’s contemporary and compatriot J. Chaptal, without further ado, proposed calling element No. 7 with the hybrid Latin-Greek name “nitrogenium,” which means “saltpetre-bearing.” Nitrate is a nitrate salt, a substance known since ancient times. (We will talk about them later.) It must be said that the term “nitrogen” has taken root only in the Russian and French languages. In English, element No. 7 is “Nitrogen”, in German – “Stockton” (asphyxiant). The chemical symbol N is a tribute to Shaptal’s nitrogenium.

Who discovered nitrogen?

The discovery of nitrogen is attributed to the student of the remarkable Scottish scientist Joseph Black, Daniel Rutherford, who in 1772 published a dissertation “On the so-called fixed and mephitic air.” Black became famous for his experiments with “fixed air” - carbon dioxide. He discovered that after fixing carbon dioxide (binding it with alkali), some kind of “unfixed air” still remains, which was called “mephitic” - spoiled - because it did not support combustion and respiration. Black proposed the study of this “air” to Rutherford as a dissertation.

Around the same time, nitrogen was obtained by K. Scheele, J. Priestley, G. Cavendish, and the latter, as follows from his laboratory records, studied this gas before Rutherford, but, as always, was in no hurry to publish the results of his work. However, all these outstanding scientists had a very vague idea of ​​the nature of the substance they discovered. They were staunch supporters of the phlogiston theory and associated the properties of “mephic air” with this imaginary substance. Only Lavoisier, leading an attack on phlogiston, convinced himself and convinced others that the gas, which he called “lifeless,” was a simple substance, like oxygen...

Universal catalyst?

One can only guess what “the beginning and end of all beginnings” means in the alchemical “nitrogen”. But we can talk seriously about one of the “beginnings” associated with element No. 7. Nitrogen and life are inseparable concepts. At least, whenever biologists, chemists, and astrophysicists try to comprehend the “beginning of the beginnings” of life, they certainly encounter nitrogen.

Atoms of earthly chemical elements are born in the depths of stars. It is from there, from the night luminaries and the daylight, that the origins of our earthly life begin. This circumstance was what the English astrophysicist W. Fowler had in mind when he said that “we all... are a particle of stellar dust”...

Star “ashes” of nitrogen arise in a very complex chain of thermonuclear processes, the initial stage of which is the conversion of hydrogen into helium. This is a multi-step reaction, believed to occur in two ways. One of them, called the carbon-nitrogen cycle, is directly related to element No. 7. This cycle begins when stellar matter, in addition to hydrogen nuclei - protons, already contains carbon. The carbon-12 nucleus, adding another proton, turns into the unstable nitrogen-13 nucleus:

12 6 C + 1 1 H → 13 7 N + γ.

But, having emitted a positron, nitrogen again becomes carbon - a heavier isotope 13 C is formed:

13 7 N → 13 6 C + e + + γ.

Such a nucleus, having accepted an extra proton, turns into the nucleus of the most common isotope in the earth’s atmosphere - 14 N.

13 6 C + 1 1 H → 14 7 N + γ.

Alas, only part of this nitrogen travels around the Universe. Under the influence of protons, nitrogen-14 turns into oxygen-15, which, in turn, emitting a positron and a gamma quantum, turns into another terrestrial isotope of nitrogen - 15 N:

14 7 N + 1 1 H → 15 8 O + γ;

15 8 O → 15 7 N + e + + γ.

Terrestrial nitrogen-15 is stable, but it is also subject to nuclear decay in the interior of a star; after the 15 N nucleus accepts another proton, not only the formation of oxygen 16 O will occur, but also another nuclear reaction:

15 7 N + 1 1 H → 12 6 C + 4 2 He.

In this chain of transformations, nitrogen is one of the intermediate products. The famous English astrophysicist R.J. Theiler writes: “14 N is an isotope that is not easy to construct. Nitrogen is formed in the carbon-nitrogen cycle, and although it subsequently turns back into carbon, if the process proceeds stationary, then there is more nitrogen in the substance than carbon. This appears to be the main source of 14 N"...

The moderately complex carbon-nitrogen cycle exhibits interesting patterns. Carbon 12C plays the role of a kind of catalyst in it. Judge for yourself, ultimately there is no change in the number of 12 C nuclei. Nitrogen, appearing at the beginning of the process, disappears at the end... And if carbon in this cycle is a catalyst, then nitrogen is clearly an autocatalyst, i.e. the product of a reaction that catalyzes its further intermediate steps.

It is not by chance that we started talking here about the catalytic properties of element No. 7. But has stellar nitrogen retained this feature in living matter? Catalysts of life processes are enzymes, and all of them, as well as most hormones and vitamins, contain nitrogen.

Nitrogen in the Earth's atmosphere

Life owes a lot to nitrogen, but nitrogen, at least atmospheric nitrogen, owes its origin not so much to the Sun as to life processes. The discrepancy between the content of element No. 7 in the lithosphere (0.01%) and in the atmosphere (75.6% by mass or 78.09% by volume) is striking. In general, we live in a nitrogen atmosphere moderately enriched with oxygen.

Meanwhile, free nitrogen has not been found either on other planets of the solar system, or in comets or any other cold space objects. There are its compounds and radicals - CN *, NH *, NH * 2, NH * 3, but there is no nitrogen. True, about 2% nitrogen was recorded in the atmosphere of Venus, but this figure still requires confirmation. It is believed that element No. 7 was not present in the primary atmosphere of the Earth. Where then does it come from in the air?

Apparently, the atmosphere of our planet initially consisted of volatile substances formed in the bowels of the earth: H 2, H 2 O, CO 2, CH 4, NH 3. Free nitrogen, if it came out as a product of volcanic activity, turned into ammonia. The conditions for this were the most suitable: excess hydrogen, elevated temperatures - the Earth’s surface had not yet cooled. So what does it mean that nitrogen was first present in the atmosphere in the form of ammonia? Apparently so. Let's remember this circumstance.

But then life arose... Vladimir Ivanovich Vernadsky argued that “the earth’s gas shell, our air, is the creation of life.” It was life that launched the most amazing mechanism of photosynthesis. One of the end products of this process, free oxygen, began to actively combine with ammonia, releasing molecular nitrogen:

CO 2 + 2H 2 O → photosynthesis→ HSON + H 2 O + O 2;

4NH 3 + 3O 2 → 2N 2 + 6H 2 O.

Oxygen and nitrogen, as is known, do not react with each other under normal conditions, which allowed the earth’s air to maintain the “status quo” composition. Note that a significant part of the ammonia could have dissolved in water during the formation of the hydrosphere.

Nowadays, the main source of N2 entering the atmosphere is volcanic gases.

If you break the triple bond...

Having destroyed the inexhaustible reserves of bound active nitrogen, living nature has confronted itself with the problem of how to bind nitrogen. In a free, molecular state, as we know, it turned out to be very inert. The reason for this is the triple chemical bond of its molecule: N≡N.

Typically, bonds of this multiplicity are unstable. Let's remember the classic example of acetylene: HC = CH. The triple bond of its molecule is very fragile, which explains the incredible chemical activity of this gas. But nitrogen has a clear anomaly here: its triple bond forms the most stable of all known diatomic molecules. It takes enormous effort to destroy this connection. For example, the industrial synthesis of ammonia requires a pressure of more than 200 atm. and temperatures above 500°C, and even the obligatory presence of catalysts... Solving the problem of nitrogen fixation, nature had to establish a continuous production of nitrogen compounds using the thunderstorm method.

Statistics say that more than three billion lightning strikes in the atmosphere of our planet every year. The power of individual discharges reaches 200 million kilowatts, and the air is heated (locally, of course) to 20 thousand degrees. At such a monstrous temperature, oxygen and nitrogen molecules disintegrate into atoms, which, easily reacting with each other, form fragile nitric oxide:

N 2 + O 2 → 2NO.

Thanks to rapid cooling (a lightning strike lasts a ten-thousandth of a second), nitrogen oxide does not disintegrate and is freely oxidized by atmospheric oxygen to a more stable dioxide:

2NO + O 2 → 2NO 2.

In the presence of atmospheric moisture and raindrops, nitrogen dioxide is converted to nitric acid:

3NO 2 + H 2 O → 2HNO 3 + NO.

So, caught in a fresh thunderstorm, we get the opportunity to swim in a weak solution of nitric acid. Penetrating into the soil, atmospheric nitric acid forms various natural fertilizers with its substances. Nitrogen is also fixed in the atmosphere by photochemical means: having absorbed a quantum of light, the N2 molecule goes into an excited, activated state and becomes capable of combining with oxygen...

Bacteria and nitrogen

From the soil, nitrogen compounds enter plants. Further: “horses eat oats,” and predators eat herbivores. The cycle of matter, including element No. 7, occurs along the food chain. At the same time, the form of existence of nitrogen changes; it becomes part of increasingly complex and often very active compounds. But not only “thunderstorm-generated” nitrogen travels through food chains.

Even in ancient times, it was noticed that some plants, in particular legumes, are capable of increasing soil fertility.

“...Or, as the year changes, sow the golden grains
Where I gathered the harvest from the field, the pods rustling,
Or where small-fruited vetch grew with bitter lupine..."

Read this: this is a grass farming system! These lines are taken from a poem by Virgil, written about two thousand years ago.

Perhaps the first person to think about why legumes increase grain yields was the French agrochemist J. Boussingault. In 1838, he established that legumes enrich the soil with nitrogen. Grains (and many other plants) deplete the earth, taking, in particular, the same nitrogen. Boussingault suggested that legume leaves absorbed nitrogen from the air, but this was misleading. At that time, it was unthinkable to assume that the problem was not in the plants themselves, but in special microorganisms that caused the formation of nodules on their roots. In symbiosis with legumes, these organisms fix atmospheric nitrogen. Now this is a common truth...

Nowadays, quite a few different nitrogen fixers are known: bacteria, actinomycetes, yeasts and molds, blue-green algae. And they all supply nitrogen to plants. But here’s the question: how do microorganisms break down the inert N2 molecule without much energy expenditure? And why do some of them have this most useful ability for all living things, while others do not? For a long time this remained a mystery. The quiet mechanism of biological fixation of element No. 7, without thunder and lightning, was discovered only recently. It has been proven that the path of elemental nitrogen into living matter became possible thanks to reduction processes during which nitrogen is converted into ammonia. The enzyme nitrogenase plays a decisive role in this process. Its centers containing iron and molybdenum compounds activate nitrogen to “docking” with hydrogen, which is previously activated by another enzyme. Thus, very active ammonia is obtained from inert nitrogen - the first stable product of biological nitrogen fixation.

That's how it works! First, life processes converted the ammonia of the primordial atmosphere into nitrogen, and then life converted the nitrogen back into ammonia. Was it worth nature to “break its spears” on this? Of course, because this is exactly how the cycle of element No. 7 arose.

Saltpeter deposits and population growth

Natural nitrogen fixation by lightning and soil bacteria annually produces about 150 million tons of compounds of this element. However, not all fixed nitrogen participates in the cycle. Some of it is removed from the process and deposited in the form of saltpeter deposits. The richest such storehouse turned out to be the Chilean Atacama Desert in the foothills of the Cordillera. It hasn't rained here for years. But occasionally heavy rains fall on the mountain slopes, washing away soil compounds. Over the course of thousands of years, water flows carried down dissolved salts, among which most of all was nitrate. The water evaporated, the salts remained... This is how the world's largest deposit of nitrogen compounds arose.

The famous German chemist Johann Rudolf Glauber, who lived in the 17th century, noted the exceptional importance of nitrogen salts for the development of plants. In his writings, reflecting on the cycle of nitrogenous substances in nature, he used expressions such as “nitrous juices of the soil” and “saltpeter is the salt of fertility.”

But natural saltpeter began to be used as a fertilizer only at the beginning of the last century, when Chilean deposits began to be developed. At that time it was the only significant source of fixed nitrogen on which the well-being of mankind seemed to depend. The nitrogen industry was out of the question then.

In 1824, the English clergyman Thomas Malthus proclaimed his infamous doctrine that population was growing much faster than food production. At this time, the export of Chilean saltpeter was only about 1000 tons per year. In 1887, Malthus’s compatriot, the famous scientist Thomas Huxley, predicted the imminent end of civilization due to the “nitrogen famine” that should occur after the development of Chilean saltpeter deposits (its production by this time was already more than 500 thousand tons per year).

Eleven years later, another famous scientist, Sir William Crookes, declared at the British Society for the Advancement of Science that within half a century there would be a food crisis if the population did not decline. He also argued his sad forecast by the fact that “the Chilean saltpeter deposits will soon be completely depleted” with all the ensuing consequences.

These prophecies did not come true - humanity did not die, but mastered the artificial fixation of element No. 7. Moreover, today the share of natural nitrate is only 1.5% of the world production of nitrogen-containing substances.

How nitrogen was fixed

People have been able to obtain nitrogen compounds for a long time. The same saltpeter was prepared in special sheds - saltpeter, but this method was very primitive. “They make saltpeter from heaps of manure, ash, droppings, skin scrapings, blood, and potato tops. During these two years, the heaps are watered with urine and turned over, after which a coating of saltpeter forms on them,” this is a description of saltpeter production in one old book.

Coal, which contains up to 3% nitrogen, can also serve as a source of nitrogen compounds. Bound nitrogen! This nitrogen began to be released during the coking of coals, trapping the ammonia fraction and passing it through sulfuric acid.

The final product is ammonium sulfate. But even this, in general, is crumbs. It is difficult to even imagine in what ways our civilization would have developed if it had not solved in time the problem of industrially acceptable fixation of atmospheric nitrogen.

Scheele was the first to bind atmospheric nitrogen. In 1775, he obtained sodium cyanide by heating soda and coal in a nitrogen atmosphere:

Na 2 CO 3 + 4C + N 2 → 2NaCN + 3CO.

In 1780, Priestley discovered that the volume of air contained in a vessel inverted over water decreases if an electric spark is passed through it, and water acquires the properties of a weak acid. This experiment was, as we know (Priestley did not know it), a model of the natural mechanism of nitrogen fixation. Four years later, Cavendish, passing an electric discharge through air enclosed in a glass tube with alkali, discovered saltpeter there.

And although all these experiments could not go beyond the laboratory at that time, they show the prototype of industrial methods of nitrogen fixation - cyanamide and arc, which appeared at the turn of the 19th...20th centuries.

The cyanamide method was patented in 1895 by German researchers A. Frank and N. Caro. Using this method, nitrogen, when heated with calcium carbide, was bound into calcium cyanamide:

CaC 2 + N 2 → Ca(CN) 2.

In 1901, Frank's son, with the idea that calcium cyanamide could serve as a good fertilizer, essentially began the production of this substance. The growth of the fixed nitrogen industry has been fueled by the availability of cheap electricity. The most promising method of fixing atmospheric nitrogen at the end of the 19th century. was considered an arc, using an electric discharge. Soon after the construction of the Niagara Power Plant, the Americans launched the first arc plant nearby (in 1902). Three years later, an arc installation developed by the theorist and specialist in the study of the northern lights H. Birkeland and practical engineer S. Eide came into operation in Norway. Plants of this type have become widespread; The saltpeter they produced was called Norwegian. However, the energy consumption during this process was extremely high and amounted to up to 70 thousand kilowatt/hour per ton of bound nitrogen, and only 3% of this energy was used directly for fixation.

Through ammonia

The methods of nitrogen fixation listed above were only approaches to a method that appeared shortly before the First World War. It was about him that the American popularizer of science E. Slosson very wittily remarked: “It has always been said that the British dominate the sea, and the French dominate the land, while the Germans have only air left. The Germans seemed to take this joke seriously and began to use the kingdom of air to attack the British and French... The Kaiser... had a whole fleet of Zeppelins and a method of nitrogen fixation that was not known to any other nation. The Zeppelins burst like bags of air, but the nitrogen-fixing plants continued to operate and made Germany independent of Chile not only during the war, but also in peacetime. "... We are talking about the synthesis of ammonia - the main process of the modern industry of fixed nitrogen.

Slosson was not entirely right when he said that the method of fixing nitrogen into ammonia was not known anywhere except Germany. The theoretical foundations of this process were laid by French and English scientists. Back in 1784, the famous C. Berthollet established the composition of ammonia and expressed the idea of ​​​​the chemical equilibrium of the reactions of synthesis and decomposition of this substance. Five years later, the Englishman W. Austin made the first attempt to synthesize NH 3 from nitrogen and hydrogen. And finally, the French chemist A. Le Chatelier, having clearly formulated the principle of mobile equilibrium, was the first to synthesize ammonia. At the same time, he used high pressure and catalysts - sponge platinum and iron. In 1901, Le Chatelier patented this method.

Research on the synthesis of ammonia at the beginning of the century was also carried out by E. Perman and G. Atkins in England. In their experiments, these researchers used various metals as catalysts, in particular copper, nickel and cobalt...

But it was indeed possible for the first time to establish the synthesis of ammonia from hydrogen and nitrogen on an industrial scale in Germany. This is due to the famous chemist Fritz Haber. In 1918 he was awarded the Nobel Prize in Chemistry.

The NH 3 production technology developed by the German scientist was very different from other industries of that time. Here, for the first time, the principle of a closed cycle with continuously operating equipment and energy recovery was applied. The final development of ammonia synthesis technology was completed by Haber's colleague and friend K. Bosch, who in 1931 was also awarded the Nobel Prize for the development of methods of chemical synthesis at high pressures.

Along the path of nature

Ammonia synthesis has become another model for the natural fixation of element No. 7. Let us recall that microorganisms bind nitrogen precisely in NH 3 . With all the advantages of the Haber-Bosch process, it looks imperfect and cumbersome compared to the natural one!

“The biological fixation of atmospheric nitrogen... was a kind of paradox, a constant challenge for chemists, a kind of demonstration of the insufficiency of our knowledge.” These words belong to Soviet chemists M.E. Volpin and A.E. Shilov, who attempted to fix molecular nitrogen under mild conditions.

At first there were failures. But in 1964, at the Institute of Organoelement Compounds of the USSR Academy of Sciences, in Volpin’s laboratory, a discovery was made: in the presence of transition metal compounds - titanium, vanadium, chromium, molybdenum and iron - element No. 7 is activated and under normal conditions forms complex compounds that are decomposed by water to ammonia. It is these metals that serve as centers for nitrogen fixation in nitrogen-fixing enzymes and as excellent catalysts in the production of ammonia.

Soon after this, Canadian scientists A. Allen and K. Zenof, studying the reaction of hydrazine N 2 H 2 with ruthenium trichloride, obtained a chemical complex in which, again under mild conditions, nitrogen was bound. This result was so contrary to usual ideas that the editors of the journal, where the researchers sent their article with a sensational message, refused to publish it. Subsequently, Soviet scientists managed to obtain nitrogen-containing organic substances under mild conditions. It is still too early to talk about industrial methods for the mild chemical fixation of atmospheric nitrogen, however, the successes achieved make it possible to foresee an impending revolution in the technology for binding element No. 7.

Modern science has not forgotten the old methods of producing nitrogen compounds through oxides. Here, the main efforts are aimed at developing technological processes that accelerate the splitting of the N 2 molecule into atoms. The most promising areas of nitrogen oxidation are considered to be the combustion of air in special furnaces, the use of plasma torches, and the use of a beam of accelerated electrons for these purposes.

What to be afraid of?

Today there is no reason to fear that humanity will ever lack nitrogen compounds. Industrial fixation of element No. 7 is progressing at an incredible pace. If at the end of the 60s the world production of fixed nitrogen was 30 million tons, then by the beginning of the next century it will, in all likelihood, reach a billion tons!

Such successes are not only encouraging, but also cause concern. The fact is that the artificial fixation of N2 and the introduction of huge amounts of nitrogen-containing substances into the soil is the most gross and significant human intervention in the natural cycle of substances. Nowadays, nitrogen fertilizers are not only fertility substances, but also environmental pollutants. They are washed out of the soil into rivers and lakes, cause harmful blooms in water bodies, and are carried over long distances by air currents...

Up to 13% of the nitrogen contained in mineral fertilizers goes into groundwater. Nitrogen compounds, especially nitrates, are harmful to people and can cause poisoning. Here's nitrogen as your breadwinner!

The World Health Organization (WHO) has adopted a maximum permissible concentration of nitrates in drinking water: 22 mg/l for temperate latitudes and 10 mg/l for the tropics. In the USSR, sanitary standards regulate the content of nitrates in the water of reservoirs by “tropical” standards - no more than 10 mg/l. It turns out that nitrates are a “double-edged sword”...

On October 4, 1957, humanity once again intervened in the cycle of element No. 7, launching a “ball” filled with nitrogen into space - the first artificial satellite...

Mendeleev about nitrogen

“Although the most active, i.e. the most easily and often chemically active part of the air around us is oxygen, but the largest mass of it, judging by both volume and weight, is formed by nitrogen; namely, nitrogen gas constitutes more than 3/4, although less than 4/5, of the volume of air. And since nitrogen is only slightly lighter than oxygen, the weight content of nitrogen in the air is about 3/4 of its total mass. Being part of the air in such a significant amount, nitrogen apparently does not play a particularly prominent role in the atmosphere, the chemical action of which is determined primarily by the oxygen content in it. But a correct understanding of nitrogen is obtained only when we learn that in pure oxygen animals cannot live long, and even die, and that the nitrogen of the air, although only slowly and little by little, forms various compounds, some of which play a very important role in nature, especially in the life of organisms."

Where is nitrogen used?

Nitrogen is the cheapest of all gases, chemically inert under normal conditions. It is widely used in chemical technology to create non-oxidizing environments. In laboratories, compounds that are easily oxidized are stored in a nitrogen atmosphere. Outstanding works of painting are sometimes (in storage or during transportation) placed in sealed cases filled with nitrogen to protect the paints from moisture and chemically active components of the air.

The role of nitrogen in metallurgy and metalworking is significant. Different metals in the molten state react to the presence of nitrogen in different ways. Copper, for example, is absolutely inert towards nitrogen, so copper products are often welded in a stream of this gas. Magnesium, on the contrary, when burned in air produces compounds not only with oxygen, but also with nitrogen. So, a nitrogen environment is not applicable for working with magnesium products at high temperatures. Saturation of the titanium surface with nitrogen gives the metal greater strength and wear resistance - a very strong and chemically inert titanium nitride is formed on it. This reaction occurs only at high temperatures.

At ordinary temperatures, nitrogen reacts actively with only one metal – lithium.

The largest amount of nitrogen is used to produce ammonia.

Nitrogen narcosis

The widespread opinion about the physiological inertness of nitrogen is not entirely correct. Nitrogen is physiologically inert under normal conditions.

With increased pressure, for example when divers dive, the concentration of dissolved nitrogen in the protein and especially fatty tissues of the body increases. This leads to so-called nitrogen narcosis. The diver seems to be getting drunk: coordination of movements is disturbed, consciousness is clouded. Scientists were finally convinced that the reason for this was nitrogen after conducting experiments in which, instead of ordinary air, a helio-oxygen mixture was supplied to the diver’s spacesuit. At the same time, the symptoms of anesthesia disappeared.

Space ammonia

The large planets of the solar system, Saturn and Jupiter, are believed by astronomers to be partly made of solid ammonia. Ammonia freezes at –78°C, and on the surface of Jupiter, for example, the average temperature is 138°C.

Ammonia and ammonium

In the large family of nitrogen there is a strange compound - ammonium NH 4. It is not found anywhere in its free form, but in salts it plays the role of an alkali metal. The name “ammonium” was proposed in 1808 by the famous English chemist Humphry Davy. The Latin word ammonium once meant: salt from Ammonium. Ammonia is a region in Libya. There was a temple of the Egyptian god Ammon, after whom the entire region was called. In Ammonia, ammonium salts (primarily ammonia) have long been obtained by burning camel dung. When the salts decomposed, a gas was produced, which is now called ammonia.

Since 1787 (the same year that the term “nitrogen” was adopted), the commission on chemical nomenclature gave this gas the name ammoniaque (ammonia). Russian chemist Ya.D. Zakharov thought this name was too long, and in 1801 he excluded two letters from it. This is how ammonia was created.

Laughing gas

Of the five nitrogen oxides, two - oxide (NO) and dioxide (NO 2) - have found wide industrial use. The other two - nitrous anhydride (N 2 O 3) and nitric anhydride (N 2 O 5) - are not often found in laboratories. The fifth is nitrous oxide (N 2 O). It has a very unique physiological effect, for which it is often called laughing gas.

The outstanding English chemist Humphry Davy used this gas to organize special sessions. This is how one of Davy’s contemporaries described the effects of nitrous oxide: “Some gentlemen jumped on tables and chairs, others had their tongues loosened, and others showed an extreme tendency to brawl.”

Swift laughed in vain

The outstanding satirist Jonathan Swift willingly mocked the sterility of contemporary science. In Gulliver's Travels, in the description of the Lagado Academy, there is the following passage: “He had at his disposal two large rooms, cluttered with the most amazing curiosities; fifty assistants worked under his direction. Some condensed the air into a dry, dense substance, extracting saltpeter from it...”

Now saltpeter from the air is an absolutely real thing. Ammonium nitrate NH 4 NO 3 is actually made from air and water.

Bacteria fix nitrogen

The idea that some microorganisms can bind nitrogen from the air was first expressed by the Russian physicist P. Kossovich. Russian biochemist S.N. Winogradsky was the first to succeed in isolating from the soil one type of bacteria that fixes nitrogen.

Plants are picky

Dmitry Nikolaevich Pryanishnikov found that a plant, if given the opportunity to choose, prefers ammonia nitrogen to nitrate nitrogen. (Nitrates are salts of nitric acid).

Important oxidizing agent

Nitric acid HNO 3 is one of the most important oxidizing agents used in the chemical industry. One of the greatest chemists of the 17th century was the first to prepare it by acting sulfuric acid on saltpeter. Johann Rudolf Glauber.

Among the compounds now produced with the help of nitric acid, many are absolutely necessary substances: fertilizers, dyes, polymeric materials, explosives.

Dual Role

Some nitrogen-containing compounds used in agrochemistry perform dual functions. For example, calcium cyanamide is used by cotton growers as a defoliant - a substance that causes leaves to fall before harvesting. But this compound also serves as a fertilizer.

Nitrogen in pesticides

Not all substances that contain nitrogen contribute to the development of any plant. Amine salts of phenoxyacetic and trichlorophenoxyacetic acids are herbicides. The first suppresses the growth of weeds in fields of cereal crops, the second is used to clear land for arable land - it destroys small trees and shrubs.

Polymers: from biological to inorganic

Nitrogen atoms are part of many natural and synthetic polymers - from protein to nylon. In addition, nitrogen is the most important element of carbon-free, inorganic polymers. The molecules of inorganic rubber - polyphosphonitrile chloride - are closed cycles composed of alternating nitrogen and phosphorus atoms, surrounded by chlorine ions. Inorganic polymers also include nitrides of some metals, including the hardest of all substances, borazone.

NITROGEN, N (lat. Nitrogenium * a. nitrogen; n. Stickstoff; f. azote, nitrogene; i. nitrogeno), is a chemical element of group V of the Mendeleev periodic system, atomic number 7, atomic mass 14.0067. Discovered in 1772 by the English explorer D. Rutherford.

Properties of nitrogen

Under normal conditions, nitrogen is a colorless and odorless gas. Natural nitrogen consists of two stable isotopes: 14 N (99.635%) and 15 N (0.365%). The nitrogen molecule is diatomic; the atoms are connected by a covalent triple bond NN. The diameter of the nitrogen molecule, determined by various methods, is 3.15-3.53 A. The nitrogen molecule is very stable - the dissociation energy is 942.9 kJ/mol.

Molecular nitrogen

Molecular nitrogen constants: f melting - 209.86°C, f boiling - 195.8°C; The density of gaseous nitrogen is 1.25 kg/m3, liquid nitrogen - 808 kg/m3.

Characteristics of nitrogen

In the solid state, nitrogen exists in two modifications: cubic a-form with a density of 1026.5 kg/m3 and hexagonal b-form with a density of 879.2 kg/m3. Heat of fusion 25.5 kJ/kg, heat of evaporation 200 kJ/kg. Surface tension of liquid nitrogen in contact with air 8.5.10 -3 N/m; dielectric constant 1.000538. Solubility of nitrogen in water (cm 3 per 100 ml of H 2 O): 2.33 (0°C), 1.42 (25°C) and 1.32 (60°C). The outer electron shell of the nitrogen atom consists of 5 electrons. The oxidation states of nitrogen vary from 5 (in N 2 O 5) to -3 (in NH 3).

Nitrogen compound

Under normal conditions, nitrogen can react with transition metal compounds (Ti, V, Mo, etc.), forming complexes or being reduced to form ammonia and hydrazine. Nitrogen interacts with active metals such as when heated to relatively low temperatures. Nitrogen reacts with most other elements at high temperatures and in the presence of catalysts. Nitrogen compounds with: N 2 O, NO, N 2 O 5 have been well studied. Nitrogen combines with C only at high temperatures and in the presence of catalysts; this produces ammonia NH 3 . Nitrogen does not directly interact with halogens; therefore, all nitrogen halides are obtained only indirectly, for example, nitrogen fluoride NF 3 - by interaction with ammonia. Nitrogen does not combine directly with sulfur either. When hot water reacts with nitrogen, cyanogen (CN) 2 is formed. When ordinary nitrogen is exposed to electric discharges, as well as during electric discharges in the air, active nitrogen can be formed, which is a mixture of nitrogen molecules and atoms with an increased energy reserve. Active nitrogen interacts very energetically with oxygen, hydrogen, vapor, and some metals.

Nitrogen is one of the most common elements on Earth, and the bulk of it (about 4.10 15 tons) is concentrated in a free state in. Every year, volcanic activity releases 2.10 6 tons of nitrogen into the atmosphere. A small part of nitrogen is concentrated in (average content in the lithosphere 1.9.10 -3%). Natural nitrogen compounds are ammonium chloride and various nitrates (saltpeter). Nitrogen nitrides can only form at high temperatures and pressures, which appears to have been the case in the earliest stages of Earth's development. Large accumulations of saltpeter are found only in dry desert climates (, etc.). Small amounts of fixed nitrogen are found in (1-2.5%) and (0.02-1.5%), as well as in the waters of rivers, seas and oceans. Nitrogen accumulates in soils (0.1%) and living organisms (0.3%). Nitrogen is part of protein molecules and many natural organic compounds.

Nitrogen cycle in nature

In nature, there is a nitrogen cycle, which includes a cycle of molecular atmospheric nitrogen in the biosphere, a cycle in the atmosphere of chemically bound nitrogen, a cycle of surface nitrogen buried with organic matter in the lithosphere with its return back to the atmosphere. Nitrogen for industry was previously extracted entirely from natural saltpeter deposits, the number of which is very limited in the world. Particularly large deposits of nitrogen in the form of sodium nitrate are found in Chile; saltpeter production in some years amounted to more than 3 million tons.

Nitrogen

Nitrogen- an element of the main subgroup of the fifth group of the second period of the periodic system of chemical elements of D.I. Mendeleev, with atomic number 7. Denoted by the symbol N (lat. Nitrogenium). Simple substance nitrogen - a diatomic gas, quite inert under normal conditions, without color, taste and smell (formula N2), of which three-quarters of the earth’s atmosphere consists.

It was “discovered” several times by different people. It was called differently, attributing almost mystical properties - “phlogisticated air”, and “mephitic air”, and “atmospheric mofett”, and simply “asphyxiating substance”. Until now, it has several names: English Nitrogen, French Azote, German Stickstoff, Russian “nitrogen”...

The history of “spoiled air”

Nitrogen(from the Greek word azoos - lifeless, in Latin Nitrogenium) - the fourth most common element in the solar system (after hydrogen , helium And oxygen ). Nitrogen compounds - saltpeter, nitric acid, ammonia - were known long before nitrogen was obtained in a free state.

In 1777, Henry Cavendish repeatedly passed air over hot coal and then treated it with lye. The result was a residue that Cavendish called suffocating (or mephitic) air. From the standpoint of modern chemistry, it is clear that in the reaction with hot coal, atmospheric oxygen was bound into carbon dioxide, which then reacted with alkali. The remainder of the gas was mostly nitrogen. Thus, Cavendish isolated nitrogen, but failed to understand that it was a new simple substance (chemical element).

That same year, Cavendish reported this experience to Joseph Priestley. Priestley at this time conducted a series of experiments in which he also bound atmospheric oxygen and removed the resulting carbon dioxide, that is, he also received nitrogen, however, being a supporter of the phlogiston theory that was dominant at that time, he completely misinterpreted the results obtained (in his opinion, the process was the opposite - it was not oxygen that was removed from the gas mixture, but on the contrary, as a result of firing, the air was saturated with phlogiston; he called the remaining air (nitrogen) saturated phlogiston, that is, phlogisticated).

It is obvious that Priestley, although he was able to isolate nitrogen, failed to understand the essence of his discovery, and therefore is not considered the discoverer of nitrogen. At the same time, similar experiments with the same result were carried out by Karl Scheele.

Even before that time, in 1772, Daniel Rutherford, burning phosphorus and other substances in a glass bell, saw that the gas remaining after combustion, which he called “suffocating air,” did not support respiration and combustion. Only in 1787 did Antoine Lavoisier establish that the “vital” and “asphyxiating” gases that make up the air are simple substances, and proposed the name “nitrogen”.

Earlier, in 1784, G. Cavendish showed that nitrogen is part of nitrate; This is where the Latin name for nitrogen comes from (from the Late Latin nitrum - saltpeter and the Greek genna - I give birth, I produce). By the beginning of the 19th century. The chemical inertness of nitrogen in the free state and its exclusive role in compounds with other elements as bound nitrogen were clarified.

"Non-life-sustaining" is vital

Although the title " nitrogen " means "non-life-sustaining", in fact it is an element necessary for life. Animal and human protein contains 16-17% nitrogen. In the organisms of carnivorous animals, protein is formed due to the consumed protein substances present in the organisms of herbivorous animals and in plants. Plants synthesize protein by assimilating nitrogenous substances contained in the soil, mainly inorganic. Significant amounts of nitrogen enter the soil thanks to nitrogen-fixing microorganisms that are capable of converting free nitrogen from the air into nitrogen compounds. As a result of the extraction of huge amounts of fixed nitrogen from the soil by plants (especially during intensive farming), the soils become depleted.

Nitrogen deficiency is typical for agriculture in almost all countries. Nitrogen deficiency is also observed in animal husbandry (“protein starvation”). On soils poor in available nitrogen, plants develop poorly. In the last century, a fairly rich source of fixed nitrogen was discovered in nature. This is Chilean nitrate, the sodium salt of nitric acid. For a long time, nitrate was the main supplier of nitrogen for industry. Its deposit in South America is unique, practically the only one in the world. And it is not surprising that in 1879, a war broke out between Peru, Bolivia and Chile over the possession of the rich saltpeter border province of Tarapaca. The winner was Chile. However, the Chilean deposit, of course, could not satisfy the world demand for nitrogen fertilizers.

“Nitrogen starvation” of the planet

The Earth's atmosphere contains almost 80% nitrogen, while the earth's crust contains only 0.04%. The problem of “how to fix nitrogen” is old, it is the same age as agrochemistry. The possibility of binding nitrogen in the air with oxygen in an electric discharge was first seen by the Englishman Henry Cavendish. This was back in the 18th century. But the process of controlled synthesis of nitrogen oxides was carried out only in 1904. In 1913, the Germans Fritz Haber and Carl Bosch proposed the ammonia method for nitrogen fixation. Now, using this principle, hundreds of factories on all continents produce more than 20 million tons of fixed nitrogen per year from the air. Three quarters of it goes to the production of nitrogen fertilizers. However, the nitrogen deficiency in the cultivated areas of the globe is more than 80 million tons per year. The Earth clearly does not have enough nitrogen. The bulk of the free nitrogen produced is used for the industrial production of ammonia, which is then processed in significant quantities into nitric acid, fertilizers, explosives, etc.

Application of nitrogen

Free nitrogen used in many industries: as an inert medium in various chemical and metallurgical processes, for filling free space in mercury thermometers, when pumping flammable liquids, etc.

A liquid nitrogen used as a coolant and for cryotherapy. Industrial applications of nitrogen gas are due to its inert properties. Gaseous nitrogen is fire and explosion-proof, prevents oxidation and rotting.

IN petrochemicals nitrogen used for purging tanks and pipelines, checking the operation of pipelines under pressure, increasing the production of fields. In mining nitrogen can be used to create an explosion-proof environment in mines and to expand rock layers.

IN electronics production nitrogen used for purging areas that do not allow the presence of oxidizing oxygen. If in a process traditionally carried out using air, oxidation or putrefaction are negative factors - nitrogen can successfully replace air.

Important area of ​​application nitrogen is his use for further synthesis a wide variety of compounds containing nitrogen , such as ammonia, nitrogen fertilizers, explosives, dyes, etc. Large quantities nitrogen used in coke production (“dry quenching of coke”) when unloading coke from coke batteries, as well as for “pressing” fuel in rockets from tanks to pumps or engines.

Misconceptions: nitrogen is not Santa Claus

IN Food Industry nitrogen registered as a food additive E941, as a gaseous medium for packaging and storage, refrigerant. Liquid nitrogen It is often demonstrated in films as a substance that can instantly freeze fairly large objects. This is a common mistake. Even freezing a flower requires quite a long time, which is partly due to the very low heat capacity nitrogen .

For the same reason, it is very difficult to cool, say, locks to −180 °C and split them with one blow. Liter of liquid nitrogen , evaporating and heating up to 20 °C, forms approximately 700 liters of gas. For this reason, you should not store nitrogen in closed vessels not suitable for high pressures. The principle of extinguishing fires with liquid is based on the same fact. nitrogen . Evaporating nitrogen displaces the air needed for combustion and the fire stops.

Because nitrogen , unlike water, foam or powder, simply evaporates and disappears, nitrogen fire extinguishing is the most effective fire extinguishing mechanism from the point of view of preserving valuables. Freezing liquid nitrogen living creatures with the possibility of their subsequent defrosting is problematic. The problem is the inability to freeze (and unfreeze) a creature quickly enough so that the inhomogeneity of freezing does not affect its vital functions. Stanislav Lem, fantasizing about this topic in the book “Fiasco,” came up with an emergency freezing system nitrogen , in which a hose with nitrogen, knocking out teeth, was thrust into the astronaut’s mouth and a copious stream was supplied inside him nitrogen .

As mentioned above, nitrogen liquid and gaseous are obtained from atmospheric air by deep cooling.

Quality indicators of gaseous nitrogen GOST 9293-74

Indicator name	Special	Increased	Increased
	2nd grade	1st grade	2nd grade
Volume fraction of nitrogen, not less	99,996	99,99	99,95
Oxygen, no more	0,001	0,001	0,05
Water vapor in nitrogen gas, no more	0,0007	0,0015	0,004
Hydrogen, no more	0,001	Not standardized	Not standardized
Sum of carbon-containing compounds in terms of CH 4, no more	0,001	Not standardized