Ahorption I Calorimetry I Kinetics I Metals I SurfacesAdsorption calorimetry, partially combined with thermal desorption spectroscopy and isotope exchange measurements, has been used to study the adsorption and coadsorption of gases on metal films under ultrahigh vacuum conditions. It has proved to be possible to get detailed information on both the primary adsorption step and the consecutive reaction in the adsorbed layer. Adsorption of CO and C 0 2 on Fe are treated as examples with subsequent decomposition reactions. In the case of the coadsorption of CO and O2 and of H2 and CO on Fe the mutual interaction of the gases including replacement processes are studied.E 8177