Absorption of NOx from aqueous solutions
NOx (Nitrogen oxides)

As already stated, according to the most commonly accepted reaction mechanisms of NO_x absorption in aqueous solutions, nitrogen oxides are made up of several species among which we distinguish, in ascending order of solubility in the aqueous phase, nitrogen monoxide NO, nitrogen dioxide NO₂ and nitrogen tetraoxide N₂O₄, nitrogen trioxide N₂O₃ and nitrous acid HNO₂ (which can form in the presence of water vapor).

• Absorption of NO_x from water or nitric acid solutions proceeds through a number of stages (see figure