The Ostwald process is a commercial process, invented by Wilhelm Ostwald, used to produce nitric acid. Ammonia is heated with a catalyst (platinum) to form nitric oxide that is then oxidized to yield nitrogen dioxide, which in turn reacts with water to yield nitric acid and nitric oxide:

2 NH3 + 4 O2 --> 2 NO + 3 H2O

2 NO + O2 --> 2 NO2

4 NO2 + O2 + 2 H2O --> 4 HNO3(aq)