Note 53 — Chapter VI · TTHE COMPOUNDS OF NITROGEN WITH HYDROGEN AND OXYGEN

There are many researches which lead to the conclusion that the reaction N2O3 = NO2 - NO is reversible, i.e. resembles the conversion of N2O4 into NO2. The brown colour of the fumes of N2O3 is due to the formation of NO2.

If nitrogen peroxide be cooled to -20°, and half its weight of water be added to it drop by drop, then the peroxide is decomposed, as we have already said, into nitrous and nitric acids; the former does not then remain as a hydrate, but straightway passes into the anhydride, and, hence, if the resultant liquid be slightly warmed vapours of nitrous anhydride, N₂O₃, are evolved, and condense into a blue liquid, as Fritzsche showed. This method of preparing nitrous anhydride apparently gives the purest product, but it easily dissociates, forming NO and NO₂ (and therefore also nitric acid in the presence of water).