ammonia

hydride of nitrogen

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This entry is made by Compilation and application of scientific encyclopedia entries of "Science Popularization China" to examine.

Ammonia is a kind of inorganic compound , chemical formula is NH three , the molecular weight is 17.031. Under standard conditions, the density is 0.771g/L, and the relative density is 0.5971 (air=1.00). It is a colorless gas with strong pungent smell. Ammonia can make wet red Litmus paper It turns blue and can produce a small amount of hydroxyl ion in water, which is weakly alkaline. Pressurize at normal temperature to make it liquefaction (critical temperature 132.4 ℃, critical pressure 11.2 MPa, i.e. 112.2 atmospheric pressure), boiling point - 33.5 ℃, also easy to be solidified into snow like solid, melting point - 77.75 ℃, soluble in water ethanol and Ether 。 It will decompose into nitrogen and hydrogen , has reducing effect. yes catalyzer Ammonia can be oxidized into nitric oxide 。 Ammonia gas is commonly used to produce liquid nitrogen 、 ammonia 、 nitric acid 、 ammonium salt And amines, etc. Ammonia can be nitrogen It is directly synthesized with hydrogen and can burn skin, eyes and mucous membranes of respiratory organs. If people inhale too much, it can cause lung swelling and even death^[1] 。^[12]

Ammonia is listed in the List of Hazardous Chemicals,^[9] And according to《 Regulations on Safety Management of Hazardous Chemicals 》Control.^[10]

Chinese name: ammonia^[11]
Foreign name: Ammonia^[11]
Alias: ammonia^[11]
chemical formula: NH three^[4]
molecular weight: seventeen point zero three one^[11]
CAS login number: 7664-41-7^[11]
EINECS login number: 231-635-3^[11]
Melting point: -77.7 ℃ （101 KPa）

Boiling point: -33.5 ℃ （101 KPa）
Water solubility: Extremely soluble in water
Density: 0.771 kg/m³ （20℃，101 KPa）
Appearance: Colorless and pungent odor^[4]
Flash point: 11 ℃
Security description: S26；S7；S45；S36/37/39；S16；S9；S61^[11]
Hazard symbol: F^[11]
Hazard description: R10；R11；R36/37/38；R39/23/24/25^[11]
UN dangerous goods number: one thousand two hundred and nineteen^[11]

catalog

A brief history of research

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The smell of ammonia has been known since ancient times. In the 18th century, a famous chemist Joseph Black (Scotland), Peter Wolfe (Ireland) Carl Wilhelm Scheele (Sweden/Germany) and Joseph Priestley (England) found that nitrogen in the air can be formed by fixing calcium carbide Calcium cyanamide Ammonia produced by the reaction of calcium cyanamide with superheated water steam. In 1785, the French chemist Claude Louis Besole measured its elemental composition.^[8]

Due to the inactive chemical properties of nitrogen, the industrial production of ammonia from nitrogen and hydrogen was once a difficult subject. In 1909, German chemist Harper (E.Haber, 1868-1934) After repeated experimental studies, it was found that under the conditions of 500-600 ℃, 17.5~20.0 MPa and osmium as the catalyst, the ammonia content after reaction could reach more than 6%, which has the possibility of industrial production. In order to transform the laboratory method of Haber synthetic ammonia into large-scale industrial production, German engineers Bosch (C. Bosch，1874-1940) The high pressure ammonia synthesis initiated by Haber has been improved, and a suitable iron oxide catalyst has been found to industrialize the production of synthetic ammonia, which is called "Haber Bosch process".

In 1913, a synthetic ammonia plant with an annual output of 7000 tons was completed and put into operation, realizing the industrial production of synthetic ammonia. Since then, synthetic ammonia has become an important field of rapid development in the chemical industry. Both Haber and Bosch won the Nobel Prize in Chemistry because of the realization of the production of synthetic ammonia industry and the promotion of related research to the development of chemical theory and technology. synthetic ammonia It is a major achievement in the history of human science and technology development, has solved the problem of hunger caused by food shortage on the earth to a large extent, and is a great contribution of chemistry and technology to social development and progress.^[7]

In 2020, the global ammonia production capacity will be 224 million tons. The actual output is 187 million tons, ranking ninth among the chemicals produced in the world.^[8]

molecular structure

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There are five nitrogen atoms valence electron Three of them are unpaired. When it is combined with hydrogen atoms, each nitrogen atom can pass through with three hydrogen atoms Polar covalent bond Combine to form ammonia molecule.

Ammonia molecule ball stick model

From the structure of ammonia, there is another nitrogen atom in the ammonia molecule Lone pair electron , can be combined into protons, showing alkalinity; Can be used as Lewis base to form Coordination compound (such as adducts); There are three active hydrogen on ammonia molecule, which can be replaced Substitution reaction ； The spatial structure of ammonia molecule is triangular cone, Polar molecule 。^[4]

Physical and chemical properties

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physical property

Density of ammonia under standard conditions	0.771g/L
critical point	132.4℃
Vapor pressure	506.62 kPa（4.7℃）
melting point	-77.7℃ (normal pressure)
boiling point	-33.5 ℃ (normal pressure)
Solubility	Extremely soluble in water (volume: 1:700 or mass: 53.97 g/100 g)
Autoignition point	651.1℃
critical pressure	11.2MPa
Critical volume	72.47cm three /mol
Critical density	0.235g/cm three
Critical compressibility	zero point two four two
Thermal expansion coefficient of liquid	0.00251/℃ at 25 ℃
surface tension	19.75×10 -3 N/m，19.75dyn/cm
Heat of vaporization	1336.97kJ/kg，574.9BTU/1b
Heat of fusion	332.16kJ/kg，142.83BTU/1b
Specific heat capacity of gas at constant pressure	2.112kJ/(kg·K)，0.505BTU/(1b·R)
Specific heat capacity of gas at constant volume	1.624kJ/(kg·K)，0.388BTU/(1b·R)
Specific heat capacity ratio of gas	one point three zero one
Gas molar entropy	192.67J/(mol·K)
Molar formation enthalpy of gas	-45.9kJ/mol
Gas viscosity	101.15×10 -7 Pa·s，101.15μPa
Liquid viscosity	0.135mPa·s
Heat of combustion	18603.1kJ/kg, 7999.3BTU/1 b at 25 ℃ (77 ℉) gaseous state
Low explosive content in air	16.1%
Upper explosive limit content in air	25%^[1]

Ammonia can be liquefied at 0.6~0.7MPa at room temperature（ critical temperature 132.5 ℃, critical pressure Is 11.23MPa). Ammonia is very soluble in water and ethanol. Liquid ammonia is inorganic protonic Nonaqueous solvent , with large dielectric constant dipole moment And hydrogen bonding energy. Molar volume Larger than water, but higher than HCN, H two S、SO two Other inorganic solvents are small, which is a kind of solvent with low self dissociation (pKa=34, - 33 ℃) and strong alkalinity. Therefore, liquid ammonia can be well dissolved Strong electrolyte 。 At the same time, because of the strong van der Waals force, it can also dissolve iodine ions, olefins Aromatic hydrocarbon And compounds containing hydroxyl and amino groups. The most special property of liquid ammonia is that it can dissolve alkali metals and alkaline-earth metal As a solvent for chemical reduction, it is used in many organic chemical reactions.^[13]

chemical property

1. React with water

Under normal temperature and pressure, 700 volumes of ammonia can be dissolved in one volume of water.

The reaction of ammonia in water can generate ammonia monohydrate:

Ammonia monohydrate Ammonia and water generated by unstable thermal decomposition:^[7]

Fountain experiment ：

Fountain experiment

Fill a dry round bottom flask with ammonia gas, and close the mouth of the flask with a plug with a glass tube and a dropper (the dropper absorbs water in advance). Immediately invert the flask, insert the glass tube into the beaker containing water (add a small amount of phenolphthalein test solution into the water in advance), and install the experimental device. Open the clamp of the rubber tube, squeeze the rubber head of the dropper, and let a small amount of water enter the flask, which can be observed Phenolphthalein The solution turns red and forms a fountain at the tip of the nozzle.

The basic principle of the experiment is to add water so that most of the ammonia gas in the flask is dissolved in water, which will produce a large pressure difference in a short time. The liquid in the beaker under the flask is pressed into the flask by using atmospheric pressure, thus forming a fountain at the nozzle.^[7]

2. React with acid

Ammonium ammonia reacts with acid to obtain ammonium salt, which is composed of Ammonium ion

and Acid radical ion Constituent compounds. Generally colorless crystal, soluble in water Strong electrolyte 。 In terms of structure,

and

Is generalized Isoelectronic body 。

Radius ratio of

Is large and close to

, so

With+1 price alkali metal The properties of ions are very similar in terms of crystal structure and solubility, except Ammonium hydrogen tartrate Most ammonium salts are soluble in water. But because

It is composed of 5 atoms and has different properties from ordinary alkali metal ions (such as easy decomposition, poor hydrolysis and thermal stability).^[4]

Reaction object	Reaction equation
Ammonia and nitric acid	NH three +HNO three =NH four NO three
Ammonia and sulphuric acid	2NH three +H two SO four =(NH four ) two SO four
Ammonia and hydrochloric acid	NH three +HCl=NH four Cl
Ammonia and phosphoric acid	3NH three +H three PO four =(NH four ) three PO four
Ammonia and acetic acid	NH three +CH three COOH=CH three COONH four
Ammonia and carbonic acid	NH three +H two CO three =NH four HCO three
Unstable thermal decomposition of ammonium bicarbonate

three Redox reaction

The oxidation number of N atom in ammonia molecule is - 3, which is the lowest oxidation state of nitrogen. Under certain conditions, it can be oxidized to form a substance with higher oxidation number two Mainly. For example, it can be oxidized by reacting with oxygen under the catalysis of hot platinum wire, burning in pure oxygen, or treating with chlorine or bromine:

In addition, ammonia can also reduce metal oxides to metal simple substances. For example, under heating conditions, ammonia will react with Cupric oxide React:^[4]

Ammonia burns in the air to produce a green flame. If the mixture of ammonia and air is ignited (volume ratio is 16%~25%), explosion can occur.^[13]

4. Addition reaction

Addition reaction (ammoniation reaction): as Lewis base , ammonia, with the lone pair electrons in its molecule and many metal ions（ Lewis acid ）Action to form ammonia complex ions, such as [Ag (NH three ) two ] + 、[Cu(NH three ) four ] 2+ 、[Cr(NH three ) six ] 3+ 、[Co(NH three ) six ] 3+ And [Pt (NH three ) four ] 2+ So as to dissolve many insoluble compounds.

Reaction of ammonia with Lewis acid with empty orbit^[4]

In addition, ammonia can also directly react with Lewis acid with empty orbit to form corresponding adducts, such as:^[4]

5. Substitution reaction

Substitution reaction (also called ammonolysis reaction): NH three As a ternary acid, its hydrogen atoms can be substituted to form amino, imino and nitrides A derivative of, the group that replaces hydrogen can be a metal, nonmetal or other group

On the other hand, it can also be regarded as the product generated by substituting amino and imino groups for atoms or groups in other compounds:^[4]

Preparation method

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1. There are pure synthetic ammonia in steel cylinders on the market, so ammonium salt is no longer used in the laboratory to prepare ammonia. Commercially available liquid ammonia in steel bottles (purity above 99.8%), with a pressure of about 0.8MPa at room temperature, can be directly used in general synthesis laboratories after being discharged at atmospheric pressure with the ammonia bottle pressure reducing valve, and some unimportant impurities such as oil and gas, trace CO two Ammonia can be heat treated Activated carbon except. For thorough drying, the bottled ammonia can be separately dried by Alkali lime Or solid KOH and Metallic sodium Two 0.5m long pipes of silk. Finally, you can make it in P two O five If ammonia and P two O five No reaction, indicating that the first two drying steps are effective. Refining method: Generally, the purity of commercially available liquid ammonia is very high, and the impurities are mainly water. Water was brought in during the pressure test of the cylinder. Secondly, there are traces of ferric oxide Etc. These impurities can be completely removed by repeated dehydration distillation. When metal sodium is put into the cylinder in advance, liquid ammonia can be distilled in the vacuum pressure resistant reaction tube, and water can be completely removed. The receiver shall be cooled sufficiently during distillation. It is obtained by repeatedly absorbing ammonia with water and cooling.^[13]

2. The main raw materials for industrial production are coal (or coke, natural gas, etc.), air and water. The process of industrialized ammonia production is generally divided into gas production desulphurization Transformation, compression refining, synthesis and other processes. After the mixed gas of nitrogen and hydrogen is pressurized to 15MPa, it enters the synthesis tower from the upper part of the synthesis tower, passes through the heat exchanger, and enters from the central pipe Contact chamber Through the catalyst layer from top to bottom, the following reaction is carried out at 480~520 ℃: the gas after reaction (mixed gas containing 12%~16% ammonia) is led out from the tower bottom outlet after the temperature is reduced by the heat exchange gas. After leaving the tower, the water cooler will further cool down to liquefy the ammonia, and then the liquid ammonia will be separated through the ammonia separator. The unreacted nitrogen and hydrogen mixture is sent to the synthesis tower for recycling.^[13]

application area

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1. In the electronic industry, high-purity ammonia is used for modular integrated circuit decompression or plasma CVD to grow a silica film boiler feedwater pH regulator. Ammonia is used to neutralize the carbonic acid in feedwater, increase the pH value, and slow the corrosion of carbon dioxide in large-scale water. It is also a protective agent for boiler shutdown, and has a good protection effect for boilers with a small amount of water stored in the boiler that cannot be discharged.

3. It is used in food industry as alkaline agent, yeast nutrition, food pigment diluent, frozen tofu manufacturing agent and solvent. It can also be used for the processing of cocoa powder, sugar containing cocoa powder, cocoa bean powder, cocoa liquid block and cocoa oil cake, and edible caseinate, with the dosage according to GMP.

4. It is used as standard gas, standard mixture preparation, physical property determination, silicon or silicon oxide nitridation, etc. in chemical industry, scientific research and other fields. In inorganic chemical industry, it is used for manufacturing ammonium salt, nitric acid, hydrogen cyanide, hydrazine, hydroxylamine, thiamine, nitramine, phosphoramine, urea, etc. In the organic chemical industry, liquid ammonia can react with alkyl chloride or alcohol to prepare alkyl amine, such as 1,2-dichloroethane to prepare ethylenediamine, adiponitrile to prepare hexanediamine, propylene to prepare acrylonitrile, etc. Others can also be used in the manufacture of morpholine, piperazine, urotropine, picoline, 2-methyl-5-vinylpyridine, etc. and as refrigerants, etc. Ammonia can also be used as Biofuels To provide energy 。^[6]

5. It is used to manufacture ammonia and liquid ammonia. Ammonia is widely used, for example, it can test the existence of gases such as HCl and react with aluminum salt solution to produce Aluminium hydroxide 。 Preparation of silver ammonia solution for detection of organic molecules Aldehyde group The existence of. Liquid ammonia can be used to produce nitric acid, urea and other chemical fertilizers, as well as raw materials for medicine and pesticides. In the national defense industry, propellants are used to manufacture rockets and missiles. It can be used as the ammoniation raw material of organic chemical products. Because liquid ammonia can absorb a lot of heat by transforming into ammonia after gasification, it is known as "cryogen". At the same time, liquid ammonia has a certain bactericidal effect, so it is used for sterilization and cooling refrigeration in the poultry breeding industry. Liquid ammonia can also be used for mercerizing and finishing of textiles.

Calculate chemical data

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data^[11] ：

1. Reference value of drainage parameter calculation (XlogP): - 0.7

2. Number of hydrogen bond donors: 1

3. Number of hydrogen bond receptors: 1

4. Number of rotatable chemical bonds: 0

5. Number of tautomers: none

6. Topological molecular polar surface area 1

7. Number of heavy atoms: 1

8. Surface charge: 0

9. Complexity: 0

10. Number of isotope atoms: 0

11. Determine the number of atomic structure centers: 0

12. Number of uncertain atomic structure centers: 0

13. Determine the number of chemical bond structural centers: 0

14. Number of indeterminate chemical bond structure centers: 0

15. Number of covalent bond units: 1

Safety measures

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First aid measures

If the patient is simply exposed to ammonia and has no skin and eye irritation symptoms, it is not necessary to remove the pollution. If the contact is liquid ammonia , and the clothes have been contaminated, the clothes should be taken off and put into a double-layer plastic bag.

In case of eye contact or eye irritation, use plenty of water or normal saline Flush for more than 20 min. If the patient wears contact lenses that are easy to remove and will not damage the eyes, they should be removed.

Wash the exposed skin and hair with plenty of water for more than 15 minutes. Protect eyes when washing skin and hair^[3] 。

Patient resuscitation

The patient should be immediately transferred out of the contaminated area to a fresh air place, and the three-step resuscitation method (airway, breathing, circulation) should be carried out for the patient.

Airway: ensure that the airway is not blocked by tongue or foreign matter.

Breathing: check whether the patient is breathing. If there is no breathing, the pocket mask can be used to provide ventilation.

Circulation: check the pulse, if there is no pulse, perform Cardiopulmonary resuscitation 。

Initial treatment

There is no specific antidote for ammonia poisoning, and supportive treatment should be adopted.

If the exposure concentration is ≥ 500 ppm and the symptoms of eye irritation and pulmonary edema appear, seek medical advice immediately.

For those who inhale ammonia, humidified air or oxygen should be given. if there be Anoxic symptom , humidified oxygen shall be supplied.

In case of respiratory distress, consider Tracheal intubation 。

If skin contact with ammonia will cause chemical burns, it can be treated as thermal burns: appropriate fluid infusion, pain killer, maintain body temperature, and cover the injured surface with disinfectant pads or clean sheets. If the skin is exposed to high-pressure liquid ammonia, pay attention to frostbite.

People who drink milk by mistake should avoid gastric lavage when they have corrosive symptoms^[3] 。

Leakage treatment

The influence of ammonia on human physiology Ammonia colorless has a strong irritating odor and is highly toxic to human body. Chronic ammonia poisoning can cause Chronic tracheitis , emphysema and other respiratory diseases, and acute ammonia poisoning is reflected in persistent cough and suffocation.

(1) A small amount of leakage.

Evacuate all personnel in the area. Prevent inhalation of vapor and contact with liquid or gas. The disposal personnel shall use respirators. Do not enter the confined space where ammonia may collect, and strengthen ventilation. Leakage can only be stopped under the condition of ensuring safety. The leaking container should be transferred to a safe place, and the valve can only be opened to relieve pressure when safety is ensured. Inert absorbing materials such as sand and vermiculite can be used to collect and absorb leakage. The collected leakage shall be placed in a closed container with corresponding labels for disposal.

(2) Large leakage.

Evacuate all unprotected personnel in the site and move upwind. The leakage disposal personnel shall wear fully enclosed heavy chemical protective clothing Air respirator After taking personal protective measures, dilute the leakage area with spray water flow. Dilute the water gun to gradually disperse the ammonia at the site, and seal the leakage point with non sparking tools.

Report to the local government, "119", local environmental protection department, public security and traffic police department, and the alarm shall include the accident unit; The time and place of the accident, the name of the chemicals, the amount of leakage and the degree of danger; Whether there are casualties and the name and telephone number of the police.

It is forbidden to contact or cross the leaked liquid ammonia, to prevent leakage from entering the sewer and drainage channel, and to enhance ventilation. Smoking and open fire are prohibited in the place. Under the condition of ensuring safety, the leaking container shall be plugged or turned over to avoid leakage of liquid ammonia. Spray water to restrain steam or change the flow direction of steam cloud, but it is forbidden to directly impact the leaked liquid ammonia or leakage source with water. Prevent leakage from entering water bodies, sewers, basements or confined spaces. It is forbidden to enter the confined space where ammonia may collect. After cleaning, all protective clothing and equipment shall be cleaned and disinfected before storage and reuse^[3] 。

Fire fighting measures

In case of fire during storage, transportation and use, the following measures shall be taken:

(1) Alarm: quickly report to the local 119 fire department and the government. The alarm shall include: accident unit, accident time, place, chemical name, danger degree, whether there are casualties, and the name and telephone number of the alarm person.

(2) Isolate, evacuate and transfer the people in distress to a safe area, establish an alert area of about 500 m, and implement traffic control on the main roads leading to the accident site. Except for fire fighting and emergency treatment personnel, other people are prohibited from entering the alert area, and quickly evacuate irrelevant people.

(3) Firefighters shall wear chemical protective clothing and positive pressure respirators before entering the fire site. Ammonia gas easily penetrates clothes and dissolves in water. Firefighters should pay attention to the protection of parts of the human body that sweat heavily, such as reproductive organs, armpits, anus and other parts.

(4) Use dry powder or CO in case of small fire two Fire extinguisher, use water curtain, fog water or conventional foam in case of a big fire.

(5) In case of tank fire, put out the fire as far as possible or use remote water gun or water cannon.

(6) Do not spray water directly on the leakage port or safety valve to prevent freezing.

(7) When the safety valve makes a sound or changes color, evacuate as soon as possible, and do not stay at both ends of the tank^[3] 。

Hazard prevention

(1) Ammonia workers shall undergo pre operation physical examination, and suffer from serious chronic bronchitis 、 bronchiectasia 、 asthma And people with coronary heart disease should not be engaged in ammonia work.

(2) Corrosion resistant work clothes, alkali resistant gloves, glasses, rubber shoes, and gas masks should be selected during work. Gas masks should be checked regularly to prevent failure.

(3) When using ammonia water for operation, clear water should be kept with you in case; During the transportation of ammonia, 3% boric acid solution should be kept with you for first-aid washing; Wear goggles when preparing ammonia with a certain concentration; When using ammonia water, the operator shall stay upwind to prevent ammonia gas from stimulating the face; Do not rub your eyes with your hands during operation. Wash your hands after operation.

(4) Prevent skin contamination, optional boric acid Ointment.

(5) Provide good ventilation and exhaust facilities, appropriate explosion-proof and fire extinguishing devices.

(6) Eating, smoking, open flames and sparks are prohibited in the workplace.

(7) Air respirator must be worn during emergency rescue.

(8) In case of leakage, the leakage port of the leaking cylinder shall be upward to prevent liquid ammonia from overflowing.

(9) Strengthen the airtightness and automation of the production process to prevent leakage, bleeding, dripping and leakage.

(10) Safety shall be paid attention to during use, transportation and storage to prevent container from cracking and gassing.

(11) Ammonia gas monitor shall be installed on site to detect and alarm in time^[3] 。

Health hazards

inhalation

The irritation of ammonia is a reliable alarm signal of harmful concentration. However, due to olfactory fatigue, it is difficult to detect low concentrations of ammonia after long-term exposure. Inhalation is the main way of exposure, and the poisoning performance after inhalation of ammonia gas mainly includes the following aspects.

Mild ammonia inhalation poisoning rhinitis 、 pharyngitis , sore throat, hoarse voice. Ammonia ingress trachea 、 a bronchial tube It can cause coughing, expectoration and blood in sputum. Hemoptysis and pulmonary edema ， dyspnea , cough white or bloody foam sputum, both lungs are full of large, medium water bubble sound. The patient has sore throat, cough, expectoration or hemoptysis, chest tightness and Retrosternal pain Etc.

The occurrence of acute inhalation ammonia poisoning is mostly caused by accidents such as pipe rupture, valve burst, etc. The main manifestations of acute ammonia poisoning are respiratory tract mucosa irritation and burns. Symptoms vary according to ammonia concentration, inhalation time, and personal sensitivity.

Poisoning	symptom
Acute mild poisoning	Dry throat, sore throat hoarseness , cough, expectoration, chest tightness and mild headache, dizziness, fatigue, bronchitis And peribronchitis.
Acute moderate poisoning	The above symptoms are aggravated, with dyspnea, sometimes blood streak in sputum, mild cyanosis, obvious conjunctival congestion, laryngeal edema, and dry and wet arm sounds in the lungs.
Acute severe poisoning	Severe cough, a large amount of pink foamy sputum, shortness of breath, palpitations, dyspnea, laryngeal edema further aggravated, obvious cyanosis, or acute respiratory distress syndrome Severe pneumothorax and mediastinal emphysema.
Severe inhalation poisoning	There may be laryngeal edema, glottis stenosis and respiratory tract mucosa shedding, which may cause tracheal obstruction and asphyxia. Inhalation of high concentration ammonia can directly affect Pulmonary capillaries Pulmonary edema caused by permeability can induce convulsions, convulsions, lethargy, coma and other consciousness disorders. Breathing and cardiac arrest may occur in individual patients who inhale extremely thick ammonia.^[2]

Skin and eye contact

Low concentration ammonia can quickly stimulate eyes and wet skin. Exposure of moist skin or eyes to high concentrations of ammonia can cause serious Chemical burn 。 Acute mild poisoning: tearing, photophobia Blurred vision , Eye Conjunctival congestion 。

Skin contact can cause severe pain and burns, and coffee like coloration can occur. The corroded part is gelatinous and soft, which may cause deep tissue damage.

High concentration of vapor has strong irritation to eyes, which can cause pain and burns, leading to obvious inflammation and possible edema, epithelial tissue destruction, corneal opacity and iris inflammation. Mild cases will generally be relieved, while severe cases may last for a long time, and complications such as persistent edema, scar, permanent turbidity, eye bulge, cataract, eyelid and eyeball adhesion and blindness may occur. Repeated or continuous exposure to ammonia can cause conjunctivitis.

Toxicological data

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acute toxicity	LD fifty	350 mg/kg (rat oral)
	LC fifty	4230 ppm (mice inhaled, 1 h)
	LC fifty	2000 ppm (inhalation in rats, 4 h)
thrill	Rabbit transocular	100 mg, severe irritation
Subacute and chronic toxicity	——	Rats, 20 mg/m three , 24 hours a day, 84 days a day, or 5-6 hours a day, 7 months a day, nervous system dysfunction occurs.
Mutagenicity	Microbial mutagenicity	Escherichia coli 1500 ppm (3 h)
Mutagenicity	Cytogenetic analysis	Rats inhaled 19800 μ g/m three (16 weeks)
Ecotoxicity	LC fifty	＞ 3.58 mg/L (24 h) (color salmon, fertilized)
	LC fifty	＞ 3.58 mg/L (24 h) (color salmon, juvenile)
	LC fifty	0.068 mg/L (24 h) (colored salmon, 85 day fry)
	LC fifty	0.097 mg/L (24 h) (color salmon, adult)
	LC fifty	24 mg/L (48 h) (Daphnia)^[6]

Inspection method

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Neutralization method:

Dip with glass rod Concentrated hydrochloric acid When approaching, white smoke will be generated, which proves that there is ammonia gas.

(white solid)

Ion chromatography:

with Dilute sulfuric acid As the absorption solution, ammonia in the air is collected to convert ammonia into ammonium ion in the absorption solution. Inhibitory conductivity detector is selected, Dioex IonPac CS10 cation analysis column uses HCl as eluent, and the injection volume is 50 μ l. The concentration of ammonia in the air is calculated by measuring the ammonium ion in the absorption solution. Results: The sampling efficiency of ammonia in the air is more than 98%, the ammonium ion has good linearity in the range of 1~100 mg/L (r=0.9990), the method precision is high (RSD5%), and the detection limit for ammonium ion is 0.1 mg/L, The minimum sampling volume is 9.5 L; Compared with the national standard method Nessler's reagent spectrophotometry (GB/T14668), the determination results are consistent.^[5]

derivative

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Hydrazine

Hydrazine (NH two NH two ）Also known as hydrazine, Hydrazine is a colorless liquid with strong hygroscopicity and high dielectric constant. Its melting point is 275K and boiling point is 386.5K. In solid state, due to the formation of hydrogen bond, the two sides are linked polymers. Many salts are dissolved in liquid hydrazine, and the solution obtained has good conductivity. Hydrazine can be regarded as a derivative in which a hydrogen atom in the ammonia molecule is replaced by an amino group. Each nitrogen atom in hydrazine molecule is represented by sp three Heterogeneous hybridization forms σ bond, and each ammonia has a pair of Lone pair electron 。 In the past, it has been thought that due to the repulsion between the lone electron pairs on the nitrogen atom, the lone electrons correspond to be in the inverse position. Recently, considering that hydrazine molecule has strong polarity (μ=1.85D), it is considered that hydrazine molecule should be Cis structure 。^[4]

hydroxylamine

hydroxylamine (NH two OH) can be regarded as NH three One hydrogen in the molecule is OH - (hydroxy) substituted derivatives, N and O in hydroxylamine molecule are both characterized by three Hybrid orbitals form sigma bonds.

Hydroxylamine is a colorless solid with strong hygroscopicity. Its melting point is 305.5 K (2.93 kPa) and it is easily soluble in water and lower alcohols.^[4]

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