Editing Ostwald process (section)

===Conversion of nitric oxide ===
Stage two encompasses the absorption of nitrous oxides in water and is carried out in an [[absorption (chemistry)|absorption]] apparatus, a [[plate column]] containing water.{{Cn|date=May 2024}} This gas is then readily absorbed by the water, yielding the desired product (nitric acid in a dilute form), while [[redox|reducing]] a portion of it back to nitric oxide:<ref name="jones1" />
:{{chem2|3NO2 + H2O -> 2HNO3 + NO}} (Δ''H'' = −117 kJ/mol)
The NO is recycled, and the acid is concentrated to the required strength by [[distillation]].

This is only one of over 40 absorption reactions of nitrous oxides recorded,<ref name=":0" /> with other common reactions including:

:{{Chem2|3N2O4 + 2H2O -> 4HNO3 + 2NO}}

And, if the last step is carried out in air:
:{{chem2|4NO2 + O2  + 2H2O -> 4HNO3}} (Δ''H'' = −348 kJ/mol).