 Absorption, adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the adsorbate on the surface of the adsorbent. This process differs from absorption, in which a fluid the adsorbate is dissolved by more permi it's the liquid or solid the absorbent respectively. Absorption is a surface phenomenon, while absorption involves the whole volume of the material. The term absorption encompasses both processes, while desorption is the reverse of it. Similar to surface tension, adsorption is a consequence of surface energy. In a bulk material, all the bonding requirements be they ionic, covalent or metallic of the constituent atoms of the material are filled by other atoms in the material. However, atoms on the surface of the adsorbent are not wholly surrounded by other adsorbent atoms and therefore can attract adsorbates. The exact nature of the bonding depends on the details of the species involved, but the adsorption process is generally classified as FIS adsorption characteristic of weak van der Waals forces or chem adsorption characteristic of covalent bonding. It may also occur due to electrostatic attraction. Absorption is present in many natural, physical, biological and chemical systems and is widely used in industrial applications such as heterogeneous catalysts, activated charcoal, capturing and using waste heat to provide cold water for air conditioning and other process requirements. Absorption chillers synthetic resins, increasing storage capacity of carbide-derived carbons and water purification. Adsorption, ion exchange and chromatography are adsorption processes in which certain adsorbates are selectively transferred from the fluid phase to the surface of insoluble, rigid particles suspended in a vessel or packed in a column. Pharmaceutical industry applications, which use adsorption as a means to prolong neurological exposure to specific drugs or parts near rough, are lesser known. The word adsorption was coined in 1881 by German physicist Heinrich Kaiser 1853-1940.