Ammonium nitrite

Ammonium nitrite, NH4NO2, is the ammonium salt of nitrous acid. It is not used in pure isolated form since it is highly unstable and decomposes into water and nitrogen, even at room temperature.

Ammonium nitrite
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.033.257
EC Number
  • 236-598-7
UNII
Properties
NH4NO2
Molar mass 64.04 g/mol
Appearance pale yellow crystals, slowly decomposes to nitrogen and water
Density 1.69 g/cm3
Melting point Decomposes
118.3 g / 100mL
Explosive data
Shock sensitivity Low
Friction sensitivity Low
Detonation velocity >1000 m/s
Hazards
Main hazards Explosive
GHS pictograms
GHS Signal word Danger
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformReactivity code 3: Capable of detonation or explosive decomposition but requires a strong initiating source, must be heated under confinement before initiation, reacts explosively with water, or will detonate if severely shocked. E.g. hydrogen peroxideSpecial hazards (white): no code
0
2
3
Flash point Non-flammable
Non-flammable
Related compounds
Other anions
 Ammonium nitrate
Other cations
 Sodium nitrite
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Preparation

Ammonium nitrite forms naturally in the air and can be prepared by the absorption of equal parts nitrogen dioxide and nitric oxide in aqueous ammonia.[1]

It can also be synthesized by oxidizing ammonia with ozone or hydrogen peroxide, or in a precipitation reaction of barium or lead nitrite with ammonium sulfate, or silver nitrite with ammonium chloride, or ammonium perchlorate with potassium nitrite. The precipitate is filtered off and the solution concentrated. It forms colorless crystals which are soluble in water.

Physical and chemical properties

Ammonium nitrite may explode at a temperature of 60–70 °C,[1] and will decompose quicker when dissolved in a concentrated aqueous solution, than in the form of a dry crystal. Even in room temperature the compound decomposes into water and nitrogen;

It decomposes when heated or in the presence of acid into water and nitrogen.[2] Ammonium nitrite solution is stable at higher pH and lower temperature. If there is any decrease in pH lower than 7.0, it may lead to an explosion, since the nitrite can react to it. A safe pH can be maintained by adding an ammonia solution. The mole ratio of ammonium nitrite to ammonia must be above 10%.

References
  1. Thomas Scott; Mary Eagleson (1994). Concise encyclopedia chemistry. Walter de Gruyter. p. 66. ISBN 3-11-011451-8.
  2. "VIAS Encyclopedia: Ammonium Nitrite".


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