nitric acid

[xiāo suān]

Monobasic inorganic strong acid

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Nitric acid Oxidizability Corrosive monoinorganic strong acid 。 It is one of the six major inorganic strong acids, and also an important Chemical raw materials , chemical formula is HNO three Its molecular weight is 63.01, and its aqueous solution is commonly known as nitric acid water or ammonia nitrogen water. In industry, it can be used to produce chemical fertilizers, pesticides, explosives, dyes, etc; In organic chemistry, Concentrated nitric acid And concentrated sulfuric acid The mixed solution of N is an important nitrating agent. The hazard symbols are O (oxidizing agent) and C (corrosive). Nitric Acid anhydride yes Nitrogen pentoxide （N two O five ）。

In 2017, nitric acid was listed in the List of Explosive Hazardous Chemicals^[8] ， It shall be controlled in accordance with the Public Security Management Measures for Explosive Hazardous Chemicals^[9] 。

Chinese name: nitric acid
Foreign name: Nitric acid
chemical formula: HNO three
molecular weight: sixty-three point zero one
CAS login number: 7697-37-2
EINECS login number: 231-714-2
Melting point: -42 ℃
Boiling point: 83 ℃

Water solubility: Miscible with water
Density: 1.50 g/cm³^[10] (without water)
Appearance: Pure nitric acid is a colorless liquid
Application: For nitrogen fertilizer, aqua regia, nitrate, nitroglycerin, etc
Security description: S23；S26；S36；S45
Hazard symbol: O；C
Hazard description: R8；R35
UN dangerous goods number: two thousand and thirty-one

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A brief history of research

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History of Foreign Development

Jabir ibn Hayyan

Arab alchemists in the eighth century Jabir ibn Hayyan （ Jabir ibn Hayyan ）In dry distillation Saltpeter It is the earliest record of human beings about nitric acid^[7] 。

In 1905, a factory producing nitric acid by electric arc method appeared in Norway, which was the earliest attempt of nitric acid industrialization in history^[7] 。

In 1908, Germany built a nitric acid plant with a daily output of 3 tons using platinum mesh as catalyst^[7] 。

In 1913, synthetic ammonia The production of nitric acid by ammoxidation has entered the industrial stage since its inception, and this method is still the main method of producing nitric acid in the world more than 100 years later^[7] 。

Domestic development history

In 1935, a Chinese chemist Hou Debang Under the leadership of ammonium sulphate Yongli Ning Factory (now Nanjing Chemical Industry Company ）^[7] 。

In February 1937, Yongli Ning Plant produced high-quality nitric acid for the first time^[7] 。　

In May 1951, the production of coking, synthetic ammonia, nitric acid and sulfuric acid workshops of Dalian Chemical Plant was fully restored, and nitric acid products were produced.

From 1952 to 1958, China has successively built nitric acid plants with integrated process in Jilin, Lanzhou, Taiyuan, etc Concentrated nitric acid It has been the laurel of the largest device in China for decades before 1997^[7] 。

Since 1980, the development of China's domestic nitric acid industry has accelerated, with the total output increasing at the rate of 10%~15% every year. Especially in the late 1990s, China's Nitric acid industry Entering a period of vigorous development, the annual growth rate of total output reached 15%~20%. However, the nitric acid production technology in China was still relatively backward during this period. The early atmospheric pressure method and comprehensive method process units were mostly obsolete production lines, and the high-pressure method units were all imported second-hand equipment. Soon, Shanxi Fertilizer Plant (now Tianji Group ）The first double pressure nitric acid plant in China was introduced from abroad, and China's nitric acid industry began to march towards the international advanced ranks^[7] 。　

In 1999, Xi'an Shaangu Power Co., Ltd. successfully developed the first "four in one" unit in China and applied it to Yunnan Yunfeng Chemical Industry Co., Ltd. From then on, it accelerated the pace of China's domestic nitric acid double pressurization process equipment to the international advanced level. Yunnan Yunfeng Chemical Industry Co., Ltd., as the first nitric acid manufacturer to use domestic "four in one" units, has strengthened the confidence of domestic nitric acid manufacturers in selecting domestic equipment^[7] 。

After 2000, China's nitric acid industry entered a period of rapid development, with the total annual output growing at a rate of more than 18%. There are about 60 manufacturers of various types and scales^[7] 。

In November 2007, China's first domestic double pressure nitric acid plant, which can achieve self-sufficiency of by-product steam under full load production conditions and can also supply steam from outside, was born in Xinxiang Yongchang Chemical Co., Ltd., marking that China's self-developed domestic nitric acid plant can completely replace imports, and China's domestic nitric acid industry has freed itself from dependence on imported equipment^[7] 。

Physical and chemical properties

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physical property

Pure nitric acid is a colorless transparent liquid, and concentrated nitric acid is a light yellow liquid (dissolved with nitrogen dioxide). Normally, it is a colorless transparent liquid with a suffocating and irritating smell. The content of nitric acid in concentrated nitric acid is about 68%, which is volatile. White fog (the same as concentrated hydrochloric acid) is generated in the air. It is a small nitric acid droplet formed by the combination of nitric acid vapor (usually nitrogen dioxide decomposed from concentrated nitric acid) and water vapor. It is miscible with water. It can form azeotropic mixture with water. For dilute nitric acid, it is generally believed that the boundary between concentration and dilution is 6mol/L. The concentration of commercially available common reagent grade nitric acid is about 68%, while the concentration of industrial grade concentrated nitric acid is 98%. Generally, the concentration of fuming nitric acid is about 98%.

Relative density: 1.50 (without water)^[10]

Melting point: - 42 ℃ (without water)^[3]

Boiling point: 83 ℃ (without water)

Relative vapor density (air=1): 2~3

Saturated vapor pressure (kPa): 6.4 (20 ℃)

Critical pressure (MPa): 6.89

Octanol/water partition coefficient: 0.21

Solubility: miscible with water, soluble in ether.

Viscosity (mPa · s, 20 º C): 0.89

Specific heat capacity (kJ/(kg · K), 98.15%): 1.99

Specific heat capacity (kJ/(kg · K), 90.33%): 2.22

Specific heat capacity (kJ/(kg · K), 70.00%): 2.56

Specific heat capacity (kJ/(kg · K), 40.00%): 2.80

Conductivity (S/m, 30.42%): 7008

Conductivity (S/m, 51.78%): 5554.2

Conductivity (S/m, 78.96%): 1945.1

Conductivity (S/m, 98.50%): 167.8^[10]

molecular structure

Structure of nitric acid molecule (2 sheets)

Nitric acid molecule is a planar covalent molecule, with central nitrogen atom sp two Hybridization, one p orbital not involved in hybridization and two terminal oxygen formation Three center four electronic key^[1] 。 The hydroxyl hydrogen in nitric acid forms intramolecular hydrogen bonds with non hydroxylated oxygen atoms, which means that nitric acid is less acidic than sulfuric acid hydrochloric acid , the main reason why the melting and boiling points are lower than the first two^[2] 。

Key length:

O-N：119.9pm；O'-N：121.1pm；O-H：96.4pm；N-OH：140.6pm。

Bond angle ：

O'-N-O：130.27°； O-N-OH：113.85°； O'-N-OH：115.88°； N-O-H：102.2°。

1. Molar refractive index: 9.60

2. Molar volume (cm three /mol）：38.8

3. Isotonic specific volume (90.2K): 107.4

4. Surface tension (dyne/cm): 58.6

5. Polarization (10 -24 cm three ）：3.80^[10]

chemical property

Instability

Concentrated nitric acid is unstable and will decompose and release when exposed to light or heat Nitrogen dioxide The nitrogen dioxide generated from decomposition is dissolved in nitric acid, which makes the appearance light yellow^[2] 。 However, dilute nitric acid is relatively stable, 70%~90% nitric acid does not decompose in the dark at 0 ℃. Concentrated nitric acid has strong oxidizability and standard redox potential.^[10]

Reaction equation:

，

Strong acidity

It is generally believed that nitric acid can be completely ionized in aqueous solution to generate a large number of hydrogen ions:

As the highest valence (+5) hydrate of nitrogen element, nitric acid has strong acidity.

esterification

Nitric acid can react with alcohol to form corresponding nitrate ester. In mechanism, nitric acid participates in esterification It was thought that Carbocation Intermediates, many literatures describe the mechanism as Fischer esterification reaction（ Fischer esterification ）That is, "dehydrogenation of acid dehydroxylated alcohol" has the same esterification mechanism as carboxylic acid.^[5] The esterification reaction of nitric acid is used to produce nitrocellulose. The equation is as follows:

three n HNO three + [C six H seven O two (OH) three ] n ——→[C six H seven O two (O-NO two ) three ] n + 3 n H two O

Nitrification

Concentrated nitric acid or fuming nitric acid and dehydrating agent（ concentrated sulfuric acid 、 Phosphorus pentoxide ）The mixture can be used as a nitrating agent to initiate nitration of some compounds, which belongs to Electrophilic substitution reaction （ electrophilic substitution ）The electrophilic reagent in the reaction is nitrium ion, and the dehydrating agent is conducive to the production of nitrium ion.^[5]

The most common nitration reaction is the nitration of benzene:

Reaction equation

Redox reaction

Nitric acid can turn wool fabrics and animal tissues into bright yellow. Sulfur and phosphorus can be formed by nitric acid oxidation sulphuric acid and phosphoric acid 。 It can dissolve various metals to form nitrate solution. Iron, chromium, aluminum and other metals are inactive in concentrated nitric acid, but soluble in dilute nitric acid. Tin antimony 、 molybdenum And so on generate insoluble oxides.^[11]

Due to the strong oxidizing property of nitric acid, hydrogen cannot be produced by nitric acid. Hydrogen ions are oxidized by nitrate ions just after they are replaced by hydrogen from nitric acid. The strong oxidizability of nitric acid does not come from nitrate ion (nitrate ion itself has no oxidizability), but from nitrate ion under acidic conditions. Example: In Ferrous nitrate Add hydrochloric acid to the solution, and the color of the solution changes from green to yellow Potassium thiocyanide The solution turns blood red. Proof of ferrous ion

Is oxidized to iron ion again

。 The oxidizability of nitric acid is proportional to its concentration. Dilute nitric acid reacts with metal to generate nitric oxide, and concentrated nitric acid reacts with metal to generate nitric oxide as well. However, concentrated nitric acid is more oxidizing than dilute nitric acid. As soon as nitric oxide is reacted, it is oxidized to nitrogen dioxide by nitrate ions in the presence of hydrogen ions. The equation is as follows:

Hydrogen iodide React with nitric acid of different concentrations to oxidize iodine ions into iodine Simple substance and Iodate Root ion:

Nitric acid supports combustion and will explode when mixed with combustible materials.

The nitrogen element in the nitric acid molecule is the highest valence (+5), so nitric acid has strong oxidizability. Its reduction products vary with the concentration of nitric acid. In general, the higher the concentration of nitric acid, the fewer electrons are obtained per molecule of nitric acid. The reduction products of concentrated nitric acid are mainly Nitrogen dioxide ， Dilute nitric acid Mainly nitric oxide, more dilute nitric acid can be reduced to Nitrous oxide 、 nitrogen 、 ammonium nitrate It should be pointed out that the above is only the dominant product. In fact, as the reaction proceeds, the concentration of nitric acid gradually decreases, and all reduction products may appear^[2] 。

The potential diagram of nitric acid is as follows: (standard condition E/V)^[2]

HNO three — zero point eight zero three →NO two — one point zero seven →HNO two — zero point nine eight three →NO— one point five nine one →N two O— one point seven seven →N two — zero point two seven →NH four +

HNO three — zero point nine five seven →NO

HNO three — one point one one →N two O

HNO three — one point two four →N two

HNO three — zero point eight eight →NH four +

Typical reaction^[4]

Concentrated nitric acid:

Dilute nitric acid:

Pure nitric acid can undergo autoionization ：

Preparation method

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According to dilute nitric acid and concentrated nitric acid, they are described as follows: (1) The methods for preparing dilute nitric acid in dilute nitric acid industry include atmospheric pressure method, comprehensive method, medium pressure method and GP double pressure method. （2） There are indirect and direct methods for producing concentrated nitric acid in concentrated nitric acid industry (see fuming nitric acid ） And super azeotropic acid.^[11]

application area

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Nitric acid is an important chemical raw material, mainly used for manufacturing ammonium nitrate 、 Calcium ammonium nitrate 、 Nitrophosphate 、 Nitrogen, phosphorus and potassium And other compound fertilizers. It is used to produce nitrate nitrogen fertilizer (such as ammonium nitrate potassium nitrate Etc.) Aqua regia 、 Nitroglycerin 、 Nitrocellulose , nitrobenzene Picric acid It is also used to make explosives containing nitro group.

Organic industry

For manufacturing Tetranitromethane , nitrohexane, 1- Nitropropane , 2,4-dinitrophenoxyethanol and other nitro compounds.

Dyestuff industry

Used for Nitroanisole , 4,4 '- dinitrodiphenyl ether P-Nitrophenol Synthesis of dye intermediates such as 2,5-dichloronitrobenzene.

Coating industry

Used to manufacture nitrocellulose varnish and nitrocellulose enamel.

Pharmaceutical industry

For manufacturing Nitroacetophenone 。

water treatment

Nitric acid can be used as carbon steel The cleaning and derusting agent for stainless steel equipment is used in the oxidation and reduction process of sewage and wastewater. In the process of biological treatment of sewage, it can be used as the nitrogen source of microbial nutrients.

Other roles

Nitric acid can oxidize alcohol aniline And other chemicals. It has been used as propellant for rockets. Nitric acid also makes calcium, copper, silver cobalt Strontium Nitrate Raw materials. Nitric acid is also used to refine metals (that is, to oxidize impure metals into nitrates, remove impurities, and then reduce them).

Nitric acid is corrosive to most metals. High concentration nitric acid has Passivation 。 For α - Fe two O three And magnetic Fe three O four Good solubility.

Nitric acid can be used as etchant and strong acid cleaning etchant Glacial acetic acid , hydrogen peroxide, etc.

Nitric acid is used as analytical reagent, such as solvent and oxidant. It is also used for organic synthesis to produce various kinds of Nitro chemical compound.

Natural distribution

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Nitric acid in nature is mainly generated in thunderstorms nitric oxide Or microbial life activities release nitrogen dioxide to form. Human activities also produce nitrogen oxides. The annual emissions of nitrogen oxides from man-made pollution sources around the world are about 53 million tons, and these nitrogen oxides also form nitric acid. Nitric acid is unstable, so it cannot exist in nature for a long time, but the formation of nitric acid is Nitrogen cycle A ring of.

Molecular structure data

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data^[11] ：

1. Molar refractive index: 9.60

2. Molar volume (cm three /mol）：38.8

3. Isotonic specific volume (90.2K): 107.4

4. Surface tension (dyne/cm): 58.6

5. Polarization (10 -24 cm three ）：3.80

Safety measures

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Environmental hazards

Harmful to the environment.

Health hazards

Nitric acid, whether concentrated or dilute, is oxidizing and corrosive, so it is very dangerous to people. If it is splashed on the skin, it will also cause serious burns. After contact with nitric acid, the skin will slowly turn yellow, and finally the yellowed epidermis will peel off (after contact with nitric acid and protein, it will cause the yellow protein reaction and denaturation). In addition, concentrated nitric acid needs to be packed in dark glass bottles to avoid toxic NO released by light reaction two^[6] 。

Inhalation of nitric acid aerosol can cause respiratory tract irritation and acute pulmonary edema. Oral administration may cause severe abdominal pain, and severe cases may include stomach perforation, peritonitis, laryngeal spasm, kidney damage, shock and asphyxia. Eye and skin contact may cause burns. Chronic effects: long-term contact can cause tooth erosion.

Contact with nitric acid vapor is very dangerous. Nitric acid solution and nitric acid vapor have strong irritating and corrosive effects on skin and mucosa.

Hazard prevention

First aid measures

Skin contact: Take off contaminated clothes immediately and wash with plenty of flowing water for 20-30 minutes. If you feel unwell, seek medical advice.

Eye contact: immediately lift the eyelid, and thoroughly flush it with a large amount of flowing water or physiological saline for 10-15 minutes. If you feel unwell, seek medical advice.

Inhalation: quickly leave the site to a place with fresh air. Keep the respiratory tract unobstructed. If breathing is difficult, give oxygen. If breathing and heartbeat stop, perform cardiopulmonary resuscitation immediately. Get medical attention.

Ingestion: Rinse with water and drink milk or egg white. Get medical attention.

Leakage emergency measures

Emergency treatment: the warning area shall be demarcated according to the influence area of liquid flow and vapor diffusion, and irrelevant personnel shall evacuate from crosswind and upwind to the safe area. It is recommended that emergency treatment personnel wear positive pressure self-contained breathing apparatus and acid and alkali resistant clothing. All equipment used in operation shall be grounded. Do not touch cracked containers and leaks before wearing appropriate protective clothing. Cut off the leakage source as much as possible. Prevent leakage from entering water bodies, sewers, basements or confined spaces. Spray water can restrain steam or change the flow direction of steam cloud, so as to avoid water flow contacting leakage. Do not allow water to enter the packaging container.

Small amount of leakage: cover the leakage with dry sand or other incombustible materials.

Large amount of leakage: build a dike or dig a pit to receive. Absorb a large amount of liquid with flying dust or lime powder. Use agricultural lime (CaO), crushed stone limestone (CaCO three ）Or sodium bicarbonate (NaHCO three ）Neutralization. Cover with insoluble foam to reduce evaporation. Transfer to tank car or special collector with corrosion resistant pump^[3] 。

security information

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Safety terminology

S23：Do not breathe vapour.

Do not breathe vapor.

S26：In case of contact with eyes, rinse immediately with plenty of water and seek medical advice.

In case of contact with eyes, please immediately flush with plenty of water and seek medical advice.

S36：Wear suitable protective clothing.

Wear appropriate protective clothing.

S45：In case of accident or if you feel unwell, seek medical advice immediately (show the label whenever possible.)

In case of accident or discomfort, seek medical advice immediately (show the label if possible).

Risk terminology

R8：Contact with combustible material may cause fire.

Contact with combustible materials may cause fire.

R35：Causes severe burns.

Causes serious burns.

Toxicological data

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Concentrated nitric acid smoke can release nitrogen pentoxide (nitrate anhydride), which forms acid mist when encountering water vapor, and can quickly decompose to form nitrogen dioxide. Concentrated nitric acid generates nitric acid vapor when heated, and can also decompose to produce nitrogen dioxide, which can cause acute nitrogen oxide poisoning after inhalation. No obvious damage is found when the human body is below 12ppm (30mg/m ³). Inhalation can cause pneumonia. Rats inhaled LC fifty 49ppm/4 hours. It was reported that 3 cases had no respiratory symptoms after inhalation of nitric acid smoke. Progressive dyspnea after 4-6 hours. Cyanosis and foam liquid outflow from mouth and nose occurred after admission. Mechanical ventilation and 100% oxygen inhalation. Died within 24 hours. The autopsy, immunohistochemical analysis of lung tissue and electron microscope examination showed that the cell damage might be caused by the free radicals produced by the hydration of nitrogen dioxide, and this time-dependent effect might be part of the reason for the symptoms of delayed lung injury. Inhalation of nitric acid smoke may cause acute poisoning. Oral nitric acid can cause corrosive stomatitis and gastroenteritis, shock or renal failure.

Invasion route: inhalation and ingestion.

Storage and transportation

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Storage method

Store in a cool and ventilated warehouse. Keep away from kindling and heat sources. The storage temperature shall not exceed 30 ℃, and the relative humidity shall not exceed 80%. Keep container sealed. It shall be stored separately from reducing agents, alkalis, alcohols, alkali metals, etc., and mixed storage is strictly prohibited. The storage area shall be equipped with leakage emergency treatment equipment and appropriate materials^[6] 。

Transport method

Close operation and pay attention to ventilation. The operation shall be mechanized and automated as far as possible. Operators must be specially trained and strictly abide by the operating procedures. It is recommended that operators wear self-priming filter type gas mask (full mask), rubber acid and alkali resistant clothing, and rubber acid and alkali resistant gloves. Keep away from kindling and heat sources, and smoking is strictly prohibited in the workplace. Prevent vapor leakage into the air of the workplace. Avoid contact with reducing agents, alkalis, alcohols and alkali metals. Load and unload gently during transportation to prevent damage to packaging and containers. Fire fighting equipment and leakage emergency treatment equipment of corresponding types and quantities shall be provided. Empty containers may leave harmful substances. When diluting or preparing solution, add acid into water to avoid boiling and splashing^[6] 。

Railway tanker loading, of which lead tanker is used to transport 98% concentrated nitric acid, and dilute nitric acid shall be transported or stored by stainless steel or FRP reinforced plastic tanker or storage tank. A small amount is packed in acid resistant ceramic jars or glass bottles, with a net weight of 33-40kg per jar. Concentrated nitric acid is sealed with acid resistant mud, and dilute nitric acid is sealed with gypsum. Each jar is put into a solid wooden box lined with fine cinder or fine slag for transportation. The package shall be clearly marked with "corrosive articles". Because there is an oxide film on the surface of aluminum, which plays a passivating role and is economical, aluminum is an ideal container for nitric acid. Personal protection: direct contact with skin is prohibited. Wear acid and alkali resistant gloves, masks and other labor protection articles during operation^[6] 。

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