rystalline solids are generally thought to adsorb water be-cause of minimal pathways for water to penetrate the particle
bulk. However, it is possible that some of the critical distinc-tions in crystalline materials arise from defects or imperfect
crystallinity, which leads to water absorption in addition to ad-sorption. In this context, the theoretical analysis should not be
limited to or assume only adsorption. It is in fact unnecessary and certainly undesirable to make such limiting assumptions in the theoretical analysis.
The chemical potential (μ) of water vapor can be readily calculated from its vapor pressure (p). The most common standard state for sorption studies is water vapor at its saturation vapor pressure p
0
. Using this standard state, the chemical potential