Ostwald Process

The Ostwald process is the industrial method used to manufacture nitric acid by catalytically oxidizing ammonia over a platinum-based catalyst at temperatures of roughly 900 degrees Celsius, converting it first to nitric oxide and then, through further oxidation and absorption in water, to nitric acid. The German chemist Wilhelm Ostwald developed the process at the start of the twentieth century and patented it in 1902, freeing nitric acid production from dependence on natural nitrate deposits. The process only became viable at large industrial scale once the Haber-Bosch process, put into industrial operation in 1913, supplied the continuous stream of synthetic ammonia it needed as a feedstock, and Germany relied on the two processes together during the First World War to keep making nitric acid for explosives and fertilizer after the Allied blockade cut off its imports of Chilean nitrate; later refinements added a secondary gauze of palladium or gold downstream of the platinum catalyst to recover metal that would otherwise be lost.