A catalytic process used for the production of nitric acid by the oxidation of ammonia with air. The first step involves mixing air as a supply of oxygen and ammonia over a catalyst at a temperature of 700ºC:
The gases are then cooled in two towers and the oxidation is completed as:
The NO is in part reoxidized to form more nitric acid in successive repetitions of the process. It is named after German chemist Friedrich Wilhelm Ostwald (1853–1932).