The characteristics of various solid and liquid sorbents are outlined according to two classifications: absorbents and adsorbents. The properties of silica gel are described within the context of a discussion of the theory of adsorption, equilibrium capacity and reactivation. Examples of moisture load calculations for dehumidification equipment are also given. (Abstractor's note: A portion of the chapter explains some of the theory underlying the conditioning and regeneration of silica gel.) -- AATA