Wilhelm Ostwald (1853-1933), German physical chemist. Ostwald is considered one of the founders of modern physical chemistry. He was instrumental in identifying the proper action of catalysts. He stated that although the overall energy change of a reaction remained unaltered, the catalyst lowered the activation energy. This concept made catalysis useful in industry, and is the view still held today. As a result, Ostwald was awarded the 1909 Nobel Prize in Chemistry. He spent the rest of his life studying thermodynamics, colour theory and the philosophy of science. This photograph, dating from the period before 1906, was published in 1905.