The process for fixing nitrogen from ammonia into nitric acid was a key development in the industrial production of fertilizers and explosives. It was patented in 1902 by Russian-German chemist Wilhelm Ostwald (1853-1932). One of the founders of the field of physical chemistry, Ostwald received the 1909 Nobel Prize in Chemistry for his work on catalysis, chemical equilibria, and reaction velocities. His process remains fundamental to the modern chemical industry.
During the Ostwald Process, ammonia is heated in the presence of a platinum-rhodium catalyst to form nitric oxide, which is then oxidized to yield nitrogen dioxide, which in turn reacts with water to produce nitric acid and nitric oxide.
Ostwald's major breakthrough was his .discovery that the length of time the reactants are in contact with the catalyst affects the yield of the ''reaction. Leave them there too long, and the nitric acid degrades back into nitrogen. Ostwald passed the ammonia and oxygen gases over the catalyst at a speed slow enough to allow the reaction to take place, but fast enough to protect the acid from degrading.
An earlier patent—by Kuhlmarm in 1838—had described the basic chemistry of the process, but was of purely academic interest because of the scarcity of ammonia from animal sources at the time. Once the Haber Process for producing ammonia was commercialized in the early twentieth century, the large-scale industrial manufacture of nitric acid could commence.
A negative effect of the development of the Ostwald and Haber processes is that it almost certainly prolonged World War I, allowing Germany to continue making explosives when its supplies of sodium nitrate from Chile were cut off.
