The Nobel Prize in Chemistry 1909 was awarded to Wilhelm Ostwald "in recognition of his work on catalysis and for his investigations into the fundamental principles governing chemical equilibria and rates of reaction".
 

As early as the first half of last century it had in certain cases been observed that chemical reactions could be induced by substances which did not appear to participate in the reaction themselves and which at all events were not altered in any way. Some 50 years later Wilhelm Ostwald carried out a number of studies to determine the relative strength of acids and bases. After Arrhenius had formulated his well-known theory that acids and bases in aqueous solution are separated into ions and that their strength depends on their electrical conductivity, or more accurately, on their degree of dissociation, Ostwald tested the correctness of this view by measuring the conductivity and hence the concentration of the hydrogen and hydroxyl ions with the acids and bases which he had used in his previous experiments. Ostwald was hence led to undertake a more thorough study of catalytic phenomena and he extended its scope to other catalysts, as they were called, as well. The rate of a reaction is a measurable parameter and hence all parameters affecting it are measurable as well. Catalysis, which formerly appeared to be a hidden secret, has thus become what is known as a kinetic problem and accessible to exact scientific study.