Use of nitric acid. Nitric acid: chemical formula, properties, preparation and application. Physical and physico-chemical properties

The areas of application of nitric acid are very diverse. At present, nitrogen is widely used.

Due to its low boiling point (-196 °C), liquid nitrogen is used as a refrigerant. Industrial applications of nitrogen gas are due to its inert properties. If oxidation or decay are negative factors in a process traditionally using air, nitrogen can successfully replace air.

Most of it (up to 75 - 80%) is spent on the production of nitrogen and complex mineral fertilizers and various nitrates, 10 - 15% is used to produce explosives and rocket fuel. The rest is consumed by the production of dyes, organic synthesis and non-ferrous metallurgy (metal pickling). On fig. No. 4 presents the use of nitric acid in various areas of the national economy.

Rice.

In organic synthesis, a mixture of concentrated nitric and sulfuric acid is widely used - the "nitrating mixture".

Nitric acid is widely used for the production of many products used in industry and agriculture:

• · about 40% of it is spent on obtaining complex and nitrogen mineral fertilizers;
• nitric acid is used to produce
• synthetic dyes,
• explosives,
• nitro-varnishes,
• plastics,
• Medicinal synthetic substances, etc.;

in the production of mineral fertilizers;

in the military industry (fuming - in the production of explosives, as an oxidizer for rocket fuel, diluted - in the synthesis of various substances, including poisonous ones);

extremely rare in photography - diluted - acidification of some tinting solutions;

in easel graphics - for etching printing forms (etching boards, zincographic printing forms and magnesium clichés).

in the production of dyes and drugs (nitroglycerin)

in jewelry - the main way to determine gold in a gold alloy.

iron dissolves well in dilute nitric acid.

Concentrated nitric acid forms a thin but dense layer of oxide insoluble in concentrated acid on the surface of iron, which protects the metal from further corrosion. This ability of iron to be passivated is used to protect it from corrosion.

Concentrated nitric acid (especially with the addition of 10% H 2 SO 4) is usually transported in steel tanks. Many organic substances (in particular, animal and plant tissues) are destroyed by the action of HNO 3, and some of them can ignite on contact with a very concentrated acid. In laboratory practice, nitric acid is usually used, containing about 65% HNO 3 (pl. 1.40). In industry, two grades of nitric acid are used: dilute with a content of 50-60% HNO 3 and concentrated, containing 96-98% HNO 3 .

Other applications: for the production of ammonia, an inert medium in chemical and metallurgical processes, in metal welding, in vacuum installations, electric lamps, gas thermometers.

Liquid nitrogen is used as a refrigerant and for cryotherapy.

Industrial applications of nitrogen gas are due to its inert properties. Gaseous nitrogen is fire and explosion-proof, prevents oxidation, decay. In the petrochemical industry, nitrogen is used to purge tanks and pipelines, test the operation of pipelines under pressure, and increase the production of deposits. In mining, nitrogen can be used to create an explosion-proof environment in mines, to burst rock layers. In electronics manufacturing, nitrogen is used to purge areas where oxidizing oxygen cannot be present. If oxidation or decay are negative factors in a process traditionally using air, nitrogen can successfully replace air.

An important field of application of nitrogen is its use for the further synthesis of a wide variety of compounds containing nitrogen, such as ammonia, nitrogen fertilizers, explosives, dyes, etc. Large amounts of nitrogen are used in coke production (“dry coke quenching”) during unloading coke from coke oven batteries, as well as for "squeezing" fuel in rockets from tanks to pumps or engines.

: monohydrate (HNO 3 ·H 2 O) and trihydrate (HNO 3 ·3H 2 O).

Physical and physico-chemical properties

Phase diagram of an aqueous solution of nitric acid.

Nitrogen in nitric acid is tetravalent, oxidation state +5. Nitric acid is a colorless liquid fuming in air, melting point −41.59 °C, boiling point +82.6 °C with partial decomposition. The solubility of nitric acid in water is not limited. Aqueous solutions of HNO 3 with a mass fraction of 0.95-0.98 are called "fuming nitric acid", with a mass fraction of 0.6-0.7 - concentrated nitric acid. Forms an azeotropic mixture with water (mass fraction 68.4%, d 20 = 1.41 g/cm, T bp = 120.7 °C)

When crystallized from aqueous solutions, nitric acid forms crystalline hydrates:

• monohydrate HNO 3 H 2 O, T pl \u003d -37.62 ° C
• trihydrate HNO 3 3H 2 O, T pl \u003d -18.47 ° C

Solid nitric acid forms two crystalline modifications:

• monoclinic, space group P 2 1/a, a= 1.623 nm, b= 0.857 nm, c= 0.631, β = 90°, Z = 16;

Monohydrate forms orthorhombic crystals, space group P na2, a= 0.631 nm, b= 0.869 nm, c= 0.544, Z = 4;

The density of aqueous solutions of nitric acid as a function of its concentration is described by the equation

where d is the density in g/cm³, c is the mass fraction of the acid. This formula poorly describes the behavior of density at a concentration of more than 97%.

Chemical properties

Highly concentrated HNO 3 usually has a brown color due to the decomposition process taking place in the light:

When heated, nitric acid decomposes according to the same reaction. Nitric acid can only be distilled (without decomposition) under reduced pressure (the indicated boiling point at atmospheric pressure is found by extrapolation).

c) displaces weak acids from their salts:

When boiling or exposed to light, nitric acid partially decomposes:

Nitric acid in any concentration exhibits the properties of an oxidizing acid, while nitrogen is reduced to an oxidation state of +4 to -3. The depth of reduction depends primarily on the nature of the reducing agent and on the concentration of nitric acid. As an oxidizing acid, HNO 3 interacts:

Nitrates

Nitric acid is a strong acid. Its salts - nitrates - are obtained by the action of HNO 3 on metals, oxides, hydroxides or carbonates. All nitrates are highly soluble in water. The nitrate ion does not hydrolyze in water.

Salts of nitric acid decompose irreversibly when heated, and the composition of the decomposition products is determined by the cation:

a) nitrates of metals standing in the series of voltages to the left of magnesium:

b) nitrates of metals located in a series of voltages between magnesium and copper:

c) nitrates of metals located in a row of voltages to the right:

Nitrates in aqueous solutions practically do not show oxidizing properties, but at high temperatures in the solid state they are strong oxidizing agents, for example, when solids are fused:

Historical information

The technique for obtaining dilute nitric acid by dry distillation of saltpeter with alum and copper sulfate was apparently first described in the treatises of Jabir (Geber in Latinized translations) in the 8th century. This method, with various modifications, the most significant of which was the replacement of copper sulfate with iron sulfate, was used in European and Arabic alchemy until the 17th century.

In the 17th century, Glauber proposed a method for obtaining volatile acids by the reaction of their salts with concentrated sulfuric acid, including nitric acid from potassium nitrate, which made it possible to introduce concentrated nitric acid into chemical practice and study its properties. Method

Nitric acid- a colorless liquid with a pungent odor, density 1.52 g/cm3, boiling point 84°C, at a temperature of -41°C it solidifies into a colorless crystalline substance. Commonly used in practice, concentrated nitric acid contains 65 - 70% HNO3 (maximum density 1.4 g/cm3); acid is miscible with water in any ratio. There is also fuming nitric acid with a concentration of 97 - 99%.

Nitric acid in high concentrations, it releases gases in air, which in a closed bottle are found in the form of brown fumes (nitrogen oxides). These gases are highly toxic, so be careful not to inhale them. Nitric acid oxidizes many organic substances. Paper and fabrics are destroyed due to the oxidation of the substances that form these materials. Concentrated nitric acid causes severe burns on prolonged contact and yellowing of the skin for several days on brief contact. Yellowing of the skin indicates the destruction of the protein and the release of sulfur (a qualitative reaction to concentrated nitric acid is a yellow color due to the release of elemental sulfur when the acid acts on the protein - a xantoprotein reaction). That is, it is a skin burn.

Wear rubber gloves when handling concentrated nitric acid to prevent burns. At the same time, the handling of nitric acid is less dangerous than, for example, sulfuric acid, it evaporates quickly and does not remain in unexpected places. Sprays of nitric acid should be washed off with plenty of water, and even better moistened with a solution of soda.

Fuming nitric acid partially decomposes during storage under the action of heat and in the light:

4HNO3 = 2H2O + 4NO2 + O2.

The higher the temperature and the more concentrated the acid, the faster the decomposition. Therefore, store it in a cool and dark place. The released nitrogen dioxide dissolves in the acid and gives it a brown color.

Dilute acid is easily prepared by pouring concentrated acid into water.

Diluted nitric acid is stored and transported in chromium steel containers, concentrated - in aluminum containers, because. concentrated acid passivates aluminum, iron and chromium due to the formation of insoluble oxide films:

2Al + 6HNO3 = Al2O3 + 6NO2 + 3H2O.

Small quantities are stored in glass bottles. Nitric acid is highly corrosive to rubber. Therefore, bottles must be with ground-in or polyethylene stoppers.

Nitric acid is used mainly in the form of aqueous solutions, it is one of the components of aqua regia, and is contained in assay acids. In industry, they are used to obtain combined nitrogen fertilizers, to dissolve ores and concentrates, in the production of sulfuric acid, various organic nitro products, in rocket technology as a fuel oxidizer, etc.

Industrial production of nitric acid

Modern industrial methods for producing nitric acid are based on the catalytic oxidation of ammonia with atmospheric oxygen. When describing the properties of ammonia, it was indicated that it burns in oxygen, and the reaction products are water and free nitrogen. But in the presence of catalysts, the oxidation of ammonia with oxygen can proceed differently.

If you pass a mixture of ammonia with air over the catalyst, then at 750 ° C and a certain composition of the mixture, an almost complete transformation occurs

The formed NO easily passes into NO2, which with water in the presence of atmospheric oxygen gives nitric acid.

Platinum-based alloys are used as catalysts in the oxidation of ammonia.
Nitric acid obtained by oxidation of ammonia has a concentration not exceeding 60%. If necessary, it is concentrated,
The industry produces dilute nitric acid with a concentration of 55, 47 and 45%, and concentrated - 98 and 97%,

The use of nitric acid

Nitric acid is used in the production of nitrogen and combined fertilizers (sodium, ammonium, calcium and potassium nitrate, nitrophos, nitrophoska), various sulfate salts, explosives (trinitrotoluene, etc.), organic dyes.

In organic synthesis, a mixture of concentrated nitric acid and sulfuric acid is widely used - the "nitrating mixture".

In metallurgy, nitric acid is used to dissolve and pickle metals, as well as to separate gold and silver. Also, nitric acid is used in the chemical industry, in the production of explosives, in the production of intermediates for the production of synthetic dyes and other chemicals.

Technical nitric acid is used in nickel plating, galvanization and chrome plating of parts, as well as in the printing industry. Nitric acid is widely used in the dairy and electrical industries.

Density of solutions of various concentrations of nitric acid

Density, g/cm 3	Concentration		Density, g/cm 3	Concentration
		g/l.			g/l.
1, 000	0, 3296	3, 295	1, 285	46, 06	591, 9
1, 005	1, 255	12, 61	1, 290	46, 85	604, 3
1, 010	2, 164	21, 85	1, 295	47, 63	616, 8
1, 015	3, 073	31, 19	1, 300	48, 42	629, 5
1, 020	3, 982	40, 61	1, 305	49, 21	642, 1
1, 025	4, 883	50, 05	1, 310	50, 00	644, 7
1, 030	5, 784	59, 57	1, 315	50, 85	668, 5
1, 035	6, 661	68, 93	1, 320	51, 71	682, 4
1, 040	7, 530	78, 32	1, 325	52, 56	696, 3
1, 045	8, 398	87, 77	1, 330	53, 41	710, 1
1, 050	9, 259	97, 22	1, 335	54, 27	724, 0
1, 055	10, 12	106, 7	1, 340	55, 13	738, 5
1, 060	10, 97	116, 3	1, 345	56, 04	753, 6
1, 065	11, 81	125, 8	1, 350	56, 95	768, 7
1, 070	12, 65	135, 3	1, 355	57, 87	783, 8
1, 075	13, 48	145, 0	1, 360	58, 78	799, 0
1, 080	14, 31	154, 6	1, 365	59, 69	814, 7
1, 085	15, 13	164, 1	1, 370	60, 67	831, 1
1, 090	15, 95	173, 8	1, 375	61, 69	848, 1
1, 095	16, 76	183, 5	1, 380	62, 70	865, 1
1, 100	17, 58	193, 3	1, 385	63, 72	882, 8
1, 105	18, 39	203, 1	1, 390	64, 74	900, 4
1, 110	19, 19	213, 0	1, 395	65, 84	918, 1
1, 115	20, 00	223, 0	1, 400	66, 97	937, 6
1, 120	20, 79	232, 9	1, 405	68, 10	956, 6
1, 125	21, 59	242, 8	1, 410	69, 23	976, 0
1, 130	22, 38	252, 8	1, 415	70, 34	996, 2
1, 135	23, 16	262, 8	1, 420	71, 63	1017
1, 140	23, 94	272, 8	1, 425	72, 86	1038
1, 145	24, 71	282, 9	1, 430	74, 09	1059
1, 150	25, 48	292, 9	1, 435	74, 35	1081
1, 155	26, 24	303, 1	1, 440	76, 71	1105
1, 160	27, 00	313, 2	1, 445	78, 07	1128
1, 165	27, 26	323, 4	1, 450	79, 43	1152
1, 170	28, 51	333, 5	1, 455	80, 88	1177
1, 175	29, 25	343, 7	1, 460	82, 39	1203
1, 180	30, 00	354, 0	1, 465	83, 91	1229
1, 185	30, 74	364, 2	1, 470	8550	1257
1, 190	31, 47	374, 5	1, 475	87, 29	1287
1, 195	32, 21	385, 0	1, 480	89, 07	1318
1, 200	32, 94	395, 3	1, 485	91, 13	1353
1, 205	33, 68	405, 8	1, 490	93, 19	1393
1, 210	34, 41	416, 3	1, 495	95, 46	1427
1, 215	35, 16	427, 1	1, 500	96, 73	1450
1, 220	35, 93	438, 3	1, 501	96, 98	1456
1, 225	36, 70	449, 6	1, 502	97, 23	1461
1, 230	37, 48	460, 9	1, 503	97, 49	1465
1, 235	38, 25	472, 4	1, 504	97, 74	1470
1, 240	39, 02	483, 8	1, 505	97, 99	1474
1, 245	39, 80	495, 5	1, 506	98, 25	1479
1, 250	40, 58	505, 2	1, 507	98, 50	1485
1, 255	41, 36	519, 0	1, 508	98, 76	1490
1, 260	42, 14	530, 9	1, 509	99, 01	1494
1, 265	42, 92	542, 9	1, 510	99, 26	1499
1, 270	43, 70	555, 0	1, 511	99, 52	1503
1, 275	44, 48	567, 2	1, 512	99, 74	1508
1, 280	45, 27	579, 4	1, 513	100, 00	1513

One of the most important products used by man is nitrate acid. The formula of the substance is HNO 3, it also has a variety of physical and chemical characteristics that distinguish it from other inorganic acids. In our article, we will study the properties of nitric acid, get acquainted with the methods of its production, and also consider the scope of the substance in various industries, medicine and agriculture.

Features of physical properties

Laboratory-derived nitric acid, the structural formula of which is given below, is a colorless liquid with an unpleasant odor, heavier than water. It evaporates quickly and has a low boiling point of +83 °C. The compound is easily mixed with water in any proportions, forming solutions of various concentrations. Moreover, nitrate acid can absorb moisture from the air, that is, it is a hygroscopic substance. The structural formula of nitric acid is ambiguous, and can have two forms.

In molecular form, nitrate acid does not exist. In aqueous solutions of various concentrations, the substance has the form of the following particles: H 3 O + - hydronium ions and anions of the acid residue - NO 3 -.

Acid-base interaction

Nitric acid, which is one of the strongest acids, enters into exchange, neutralization. So, with basic oxides, the compound participates in metabolic processes, as a result of which salt and water are obtained. The neutralization reaction is the basic chemical property of all acids. The products of the interaction of bases and acids will always be the corresponding salts and water:

NaOH + HNO 3 → NaNO 3 + H 2 O

Reactions with metals

In the nitric acid molecule, the formula of which is HNO 3, nitrogen exhibits the highest oxidation state, equal to +5, therefore the substance has pronounced oxidizing properties. As a strong acid, it is able to interact with metals in the activity series of metals up to hydrogen. However, unlike other acids, it can also react with passive metal elements, such as copper or silver. Reagents and interaction products are determined both by the concentration of the acid itself and by the activity of the metal.

Dilute nitric acid and its properties

If the mass fraction of HNO 3 is 0.4-0.6, then the compound exhibits all the properties of a strong acid. For example, it dissociates into hydrogen cations and acid residue anions. Indicators in an acidic environment, for example, purple litmus, in the presence of an excess of H + ions, changes its color to red. The most important feature of the reactions of nitrate acid with metals is the impossibility of liberating hydrogen, which is oxidized to water. Instead, various compounds are formed - nitrogen oxides. For example, in the process of interaction of silver with molecules of nitric acid, the formula of which is HNO 3, nitrogen monoxide, water and salt - silver nitrate are found. The oxidation state of nitrogen in the complex anion decreases as three electrons are added.

With active metal elements such as magnesium, zinc, calcium, nitrate acid reacts to form nitric oxide, the valence of which is the smallest, it is 1. Salt and water are also formed:

4Mg + 10HNO 3 \u003d NH 4 NO 3 + 4Mg (NO 3) 2 + 3H 2 O

If nitric acid, whose chemical formula is HNO 3 , is very dilute, in this case, the products of its interaction with active metals will be different. It can be ammonia, free nitrogen or nitric oxide (I). Everything depends on external factors, which include the degree of grinding of the metal and the temperature of the reaction mixture. For example, the equation for its interaction with zinc will look like this:

Zn + 4HNO 3 \u003d Zn (NO 3) 2 + 2NO 2 + 2H 2 O

Concentrated HNO 3 (96-98%) acid in reactions with metals is reduced to nitrogen dioxide, and this usually does not depend on the position of the metal in the N. Beketov series. This happens in the majority when interacting with silver.

Let's remember the exception to the rule: under normal conditions, concentrated nitric acid does not react with iron, aluminum and chromium, but passivates them. This means that a protective oxide film is formed on the metal surface, preventing further contact with acid molecules. A mixture of a substance with concentrated hydrochloric acid in a ratio of 3: 1 is called aqua regia. She has the ability to dissolve gold.

How nitrate acid reacts with non-metals

The strong oxidizing properties of a substance lead to the fact that in its reactions with non-metallic elements, the latter pass into the form of the corresponding acids. For example, sulfur is oxidized to sulfate, boron to boric, and phosphorus to phosphate acids. The reaction equations below confirm this:

S 0 + 2HN V O 3 → H 2 S VI O 4 + 2N II O

Obtaining nitric acid

The most convenient laboratory method for obtaining a substance is the interaction of nitrates with concentrated It is carried out with low heating, avoiding an increase in temperature, since in this case the resulting product decomposes.

In industry, nitric acid can be obtained in several ways. For example, obtained from air nitrogen and hydrogen. Acid production takes place in several stages. Nitrogen oxides will be intermediate products. First, nitrogen monoxide NO is formed, then it is oxidized with atmospheric oxygen to nitrogen dioxide. Finally, in reaction with water and excess oxygen, dilute (40-60%) nitrate acid is produced from NO 2 . If it is distilled with concentrated sulfate acid, the mass fraction of HNO 3 in solution can be increased to 98.

The above method for the production of nitrate acid was first proposed by the founder of the nitrogen industry in Russia, I. Andreev, at the beginning of the 20th century.

Application

As we remember, the chemical formula of nitric acid is HNO 3. What feature of chemical properties determines its use if nitrate acid is a large-tonnage product of chemical production? This is a high oxidizing ability of the substance. It is used in the pharmaceutical industry to produce drugs. The substance serves as a feedstock for the synthesis of explosive compounds, plastics, dyes. Nitrate acid is used in military technology as an oxidizing agent for rocket fuel. Its large volume is used in the production of the most important types of nitrogen fertilizers - saltpeter. They help to increase the yield of the most important crops and increase the content of protein in fruits and green mass.

Applications of nitrates

Having considered the main properties, production and use of nitric acid, we will focus on the use of its most important compounds - salts. They are not only mineral fertilizers, some of them are of great importance in the military industry. For example, a mixture of 75% potassium nitrate, 15% fine coal and 5% sulfur is called black powder. Ammonal, an explosive, is obtained from ammonium nitrate, as well as coal and aluminum powder. An interesting property of salts of nitrate acid is their ability to decompose when heated.

Moreover, the reaction products will depend on which metal ion is part of the salt. If the metal element is in the activity series to the left of magnesium, nitrites and free oxygen are found in the products. If the metal that is part of the nitrate is located from magnesium to copper inclusive, then when the salt is heated, nitrogen dioxide, oxygen and oxide of the metal element are formed. Salts of silver, gold or platinum at high temperature form the free metal, oxygen and nitrogen dioxide.

In our article, we found out what the chemical formula of nitric acid is in chemistry, and what features of its oxidizing properties are most important.

Nitric acid, HNO 3 , monobasic strong acid, colorless liquid under normal conditions; one of the most important products of the chemical industry.

Structural formula:

Physical and chemical properties.

Density of anhydrous nitric acid 1522 kg / m 3, t pl - 41.15 ° C, t bale 84 ° C. It mixes with water in all respects, and forms an azeotropic mixture containing 69.2% nitric acid with t bale 121.8 ° C.

Crystalline hydrates HNO 3 ?H 2 O with t pl -37.85 ° С and HNO 3 ? 3H 2 O with t pl -18.5 ° С are known. In the absence of water Nitric acid unstable, decomposes in the light with the release of oxygen already at ordinary temperatures (4HNO 3 \u003d 4NO 2 + 2H 2 O + O 2), and the liberated nitrogen dioxide turns yellow, and at high concentrations of NO 2 - red.

Nitric acid- a strong oxidizing agent, oxidizes sulfur to sulfuric acid, phosphorus to phosphoric acid. Only gold, tantalum and some platinum metals do not react with nitric acid. With most metals Nitric acid interacts mainly with the release of nitrogen oxides: ZCu + 8HNO 3 \u003d 3Cu (NO 3) 2 + 2NO + 4H 2 O. Some metals, such as iron, chromium, aluminum, are easily soluble in dilute nitric acid, are resistant to concentrated nitric acid, which is explained by the formation of a protective oxide layer on the metal surface. This feature allows you to store and transport concentrated nitric acid in steel containers. A mixture of concentrated nitric acid and hydrochloric acid (1:3), called aqua regia, dissolves even gold and platinum. Organic compounds under the action nitric acid oxidized or nitrated, and in the latter case, the residue Nitric acid- nitro group - NO 2 + replaces hydrogen in organic compounds. salt nitric acid called nitrates, and salts with Na, K, Ca, NO 4 + are also saltpeters.

Receipt and application.

In the 13th century was described receiving nitric acid heating potassium nitrate with alum, iron sulfate and clay. In the middle of the 17th century. I. R. Glauber proposed to receive nitric acid with moderate (up to 150 ° C) heating of potassium nitrate with concentrated sulfuric acid: KNO 3 + H 2 SO 4 \u003d HNO 3 + KHSO 4 Until the beginning of the 20th century. this method was used in industry, replacing potassium nitrate with cheaper natural Chilean nitrate NaNO 3 .

Modern way of production nitric acid based on the catalytic oxidation of ammonia with oxygen in the air.

The main stages of the process:

Contact oxidation of ammonia to nitric oxide: 4NH 3 + 5O 2 = 4NO + 6H 2 O;

oxidation of nitric oxide to dioxide and absorption of a mixture of so-called "nitrous gases" by water: 2NO + O 2 = 2NO 2; 3NO 2 + H 2 O \u003d 2HNO 3 + NO.

A mixture of ammonia (10 - 12%) with air is passed through a catalyst mesh heated to 750 - 900 ° C, which is platinum alloys - triple (93% Pt, 3% Rh, 4% Pd) or double (90 - 95% Pt, 10 - 5% Rh).

A two-stage catalyst is also used (1st stage - platinoid mesh, 2nd - non-platinum catalyst), which allows to reduce the consumption of platinum by 25 - 30%. The contact time of the air-ammonia mixture with the catalyst should not exceed 1 ms, otherwise the formed nitric oxide decomposes.

The second stage of the process - the oxidation of NO to N0 2 and the dissolution of NO 2 in water - can be carried out at atmospheric pressure, under pressure up to 1 MN / m 2 (10 kgf / cm 2) or in a combined way, in which only the absorption of nitrous occurs under pressure gases with water.

receive nitric acid with concentrations of 45 - 49% or (when using pressure) 55 - 58%. Distillation of such solutions can be obtained Nitric acid azeotropic composition.

A more concentrated acid (up to 100%) is obtained by distillation of A.K. solutions. with concentrated H 2 SO 4 or direct synthesis - the interaction of N 2 O 4 with water (or dilute nitric acid) and oxygen: 2N 2 O 4 + 2H 2 O + O 2 \u003d \u003d 4HNO 3. 97 - 98% nitric acid is produced in the USSR

Key Applications nitric acid- production of nitrogen and combined fertilizers, explosives (trinitrotoluene, etc.), organic dyes. In organic synthesis, a mixture of concentrated nitric acid and sulfuric acid - "nitrating mixture".

Nitric acid used in the chamber method for the production of sulfuric acid, for the production of phosphoric acid from phosphorus, as an oxidizer for rocket fuel. In metallurgy nitric acid used for etching and dissolving metals, as well as for separating gold and silver.

Vapor inhalation nitric acid leads to poisoning nitric acid(especially concentrated) on the skin causes burns. Content limit nitric acid in the air of industrial premises is 50 mg / m 3 in terms of N 2 O 5. concentrated Nitric acid in contact with organic matter causes fires and explosions.