Ostwald, Wilhelm (vĭlˈhĕlm ôstˈvält) [key], 1853–1932, German physical chemist and natural philosopher, b. Riga, Latvia. He was professor of chemistry and director of the chemical laboratory (1886–1906) at the Univ. of Leipzig. He received the 1909 Nobel Prize in Chemistry for his work on catalysis and his investigations into the fundamental principles governing equilibrium and rates of reaction. He also did outstanding work on color. He wrote Colour Science (1923, tr. 1931) and many textbooks. Ostwald originated the Ostwald process for preparing nitric acid. Ammonia mixed with air is heated and passed over a catalyst (platinum). It reacts with the oxygen to form nitric oxide, which is then oxidized to nitrogen dioxide; this in turn reacts with water to form nitric acid.