Dinitrogen trioxide

Dinitrogen trioxide according to systematic nomenclature. Its chemical formula is (N 2 O 3 ) , also known by the stock nomenclature as nitrogen oxide (III), and by the traditional nomenclature as nitrogen sesquioxide, or nitrous anhydride, it exists at low temperatures as a blue solid, it has weak acid characteristic.


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  • 1 Physical properties
  • 2 Chemical properties
  • 3 Obtaining
    • 1 Industry
  • 4 Environmental pollution
  • 5 References
  • 6 Sources
  • 7 External link

Physical properties

Nitrogen trioxide is unstable above 3 ° C at normal pressure. Extremely poorly stable in the gaseous state, the gas condenses into a dark blue liquid that boils at 3.5 ° C and solidifies at –102 ° C to a pale blue solid. The liquid at 2 ° C has a density of 1.4 g / cm 3 .
The very low stability of nitrogen trioxide (at least in the liquid and gaseous states ), therefore it can be considered as an equimolar mixture of NO and NO 2 . For this reason its structure has not been determined, although some authors propose a structure like the following for the compound in the solid state :

Chemical properties

Dinitrogen trioxide, being not very stable to the gaseous state, is easily dissociated to monoxide and nitrogen oxide , in a disproportionation reaction:

2 O 3 (g) = NO (g) + NO 2 (g)

Indeed, under ordinary conditions, the chemistry of N 2 O 3 is the chemistry of an equimolar mixture of NO (g) and NO 2 (g).
Dinitrogen trioxide can be considered as nitrous acid anhydride (HNO 2 ). This acid is also very little stable in aqueous solution (and it has not been possible to isolate it as such), decomposing easily:

2 O 3 (g) + H 2 O = 2HNO 2 (ac)


3HNO 2 (ac) = 2HNO 3 (ac) + NO (g) + H 2 O

Notwithstanding this, the salts of this acid hydroxide have been isolated (they are nitrites ) and, for example, dinitrogen trioxide reacts slowly with alkalis with formation of the corresponding nitrites:

2 O 3 (g) + 2 NaOH (s) = 2 NaNO 2 (ac) + H 2 O

The other chemical properties of dinitrogen trioxide can be predicted based on knowledge of the chemistry of NO (g) and NO 2 (g).


Dinitrogen trioxide is produced by mixing equal parts of nitrogen monoxide (NO) and nitrogen dioxide (NO 2 ), and cooling the mixture below –21ºC. The resulting compound is only stable in the solid and liquid phases. When heated, it decomposes again.


It can be obtained by dripping nitric acid with a density of 1.3 g / cm3 on arsenic (III) oxide, a thick powder form:

2 HNO 3 (ac) + As 2 O 3 (s) = N 2 O 3 (g) + As 2 O 5 (s) + H 2 O


Environmental pollution

Dinitrogen trioxide (N 2 O 3 ) and dinitrogen tetroxide (N 2 O 4 ) exist in very low concentrations in the flue gas. However, they exist in such low concentrations in the atmosphere that both their presence and effect are often ignored


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