ABSTRACT - Adsorption hysteresis exhibits a wide range of phenomena dependent on the
nature of both the adsorbent and the adsorptive, and on the tenperature. some of
these features are described and an outline is given of their interpretation in
terms of the physical processes involved. Particular attention is paid to the
changes in the size and shape of hysteresis loops brought about by changes in
tenperature, which are discussed in terms of hysteresis phase diagram . Hysteresis critical temperatures' are identified and linked to recent theories of
capillary condensation.