'Many bodies ... have the property of exerting on other bodies an action which is very different from chemical affinity. By means of this action they produce decomposition in bodies, and form new compounds into the composition of which they do not enter. This new power, hitherto unknown, is common both in organic and inorganic nature ... I shall ... call it catalytic power. I shall also call catalysis the decomposition of bodies by this force. J. J. Berzelius (1836) Edinburgh New Philosophical Journal, XXI, 223. This quotation marks the origin of the term catalysis in a scientific context. The earlier literary meaning was 'the breakdown in law and order'. Perhaps Berzelius' train of thought was that catalytic action appeared to defy the scientific laws and principles as formulated in 1836. It is remarkable that this quotation, with some substitution of modern wording, can represent a fair summary of our present view of catalysis. There is now recognized a broad division of catalytic systems under the headings homogeneous and heterogeneous. In the former the catalyst is generally a dissolved species whilst in the latter it is usually an insoluble solid, with the action restricted to the surface. This book concerns hetero­ geneous catalysis, which is the more important for industrial applications.