The phenomenon of adsorption should not be confused with adsorption which refers to one material passing into the bulk of another. For example, water is adsorbed by a sponge and water vapours are adsorbed by anhydrous calcium chloride. The term Sorption is used which includes both adsorption and absorption like the process where water vapours are adsorbed by silica gel and acetic which is. adsorption or absorption. When solids are allowed to remain in contact with a gas, a film of gas molecules accummulates on the surface. Solid and liquid surfaces, therefore, have a tendency to satisfy their residual forces by attracting onto and retaining on their surfaces, molecules of gases or other substances with which they come in contact. This results in higher concentration of molecules on the surface of a solid or liquid than in the bulk of the medium. This phenomenon is known as ADSORPTION. The substance in which the adsorption takes place is know ADSORBENT and tye substance whic