ABSTRACT
The distribution of both liquid and vapor within a porous body in equilibrium with its environment depends on the sizes and geometry of the porous space and the external conditions. The general condition for equilibrium is the balance of changes of chemical potential of molecules in liquid and vapor phases compared to the standard state of the bulk liquid at the same temperature. The content of liquid in a porous body W at rather high p/ps is determined by the condition of equilibrium between adsorption or wetting films and the capillary condensate. The reason for the hysteresis of capillary condensation, manifesting itself by the appearance of two branches of the isotherm W, is the possibility of metastable states for the condensate and films. Another reason for hysteresis of the capillary condensation may be the metastable state of wetting films. When a porous body contains cylindrical pores of various radii, a wide hysteresis loop of capillary condensation will arise.
