Ammonium nitrite , thermal decomposition

Molecular nitrogen is obtained by fractional distillation of air (the boiling points of liquid nitrogen and liquid oxygen are -196°C and -183°C, respectively). In the laboratory, very pure nitrogen gas can be prepared by the thermal decomposition of ammonium nitrite ... 

The well-known old laboratory preparation of dinitrogen by thermal decomposition of solutions containing the ammonium and nitrite ions had been thought for decades to involve nitrosation of ammonia, but it was only much later that Olah et al. (1985 a) found experiment2il evidence for the intermediacy of the parent diazonium ion HN (protonated dinitrogen) thanks to the development of superacid media, a number of other simple diazonium compounds of type XNi were found in the 1980 s (see Sect. 3.1). 

A solution of ammonium nitrite is usually obtained by mixing equimolar solutions of ammonium chloride and sodium nitrite since the solid is not thermally stable. On heating the mixed solution, it decomposes to water and nitrogen. The kinetics of the thermal decomposition can be readily followed by measuring at intervals the volume of nitrogen evolved from a thermostatted solution. Since a solution of ammonium nitrite exhibits absorption peaks in the u.v., it is likely that u.v. irradiation may increase the rate of gas evolution i.e. the rate of decomposition. 

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