two desorption mechanisms can be
distinguished: In pore blocking, the menisci retreat from
the ends of the pore, and the amount adsorbed decreases
gradually as pressure is reduced, until a point at which the
remaining concave lens breaks, and the amount adsorbed
decreases more rapidly, giving a knee in the isotherm. The
second mechanism is cavitation, where the adsorbed fluid
grows a vapour-like bubble which increases in size as
pressure is reduced, due to the stretching of the fluid
beyond its stability limit. In some cases, it is possible for
desorption to switch from pore blocking to cavitation as the
temperature is increased