Ammonium nitrite

Ammonium nitrite is a chemical compound with the chemical formula [NH₄]NO₂. It is the ammonium salt of nitrous acid. It is composed of ammonium cations [NH₄]⁺ and nitrite anions NO−2. It is not used in pure isolated form since it is highly unstable and decomposes into water and nitrogen, even at room temperature.

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.

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.

2 NH₃ + O₃ → [NH₄]NO₂ + H₂O

Physical and chemical properties

Ammonium nitrite may explode at a temperature of 60–70 °C, 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 slowly decomposes into water and nitrogen:

[NH₄]NO₂ → N₂ + 2 H₂O

It decomposes when heated or in the presence of acid into water and nitrogen. 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. Nitrite
2. Prafulla Chandra Ray
3. Anammox
4. Thermal decomposition
5. Ammonium
6. Sodium nitrite
7. Nitrogen cycle
8. Ammonium nitrate
9. Dissimilatory nitrate reduction to ammonium
10. Raschig hydroxylamine process
11. Potassium nitrite
12. Nitrifying bacteria
13. Nitrous acid
14. Alkyl nitrite
15. Nitrification
16. Nitrite reductase (NAD(P)H)
17. Nitrate
18. Ammonium azide
19. Heterotroph
20. Ammonia