Introduction It is widely accepted that the knowledge of adsorption heats is vital in the description of gas-solid interaction. is is particularly useful when adsorption heat measurements are combined with simultaneous measurement of the adsorption isotherm. ese measurements obviously may provide information about the energetic of surface processes. In some simple cases, even information on the structure of the surface itself, like for example the energetic topography, can be retrieved from adsorption heats and isotherms [1, 2]. Chemisorption and catalyzed reactions, like any chemical reaction, are associated with changes of enthalpy and can therefore be studied by means of calorimeters. Many calorimeters, operating on dierent principles, have indeed been used for this purpose [3-5]. Adsorption calorimeters are particularly convenient for these studies . ey oer a number of advantages which will be illustrated by means of selected examples.