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                    Absorption

                     Adsorption

1.  Absorption is a bulk phenomenon.

1.  Adsorption is a surface phenomenon.

2.  The substance getting absorbed is distributed uniformly throughout the bulk of the substance.

2.  The substance is accumulated at the surface of the solid. Thus, the concentration of the adsorbed substance is higher at the surface than in the bulk.     

3.  Absorption proceeds at a steady rate.

3.  The rate of adsorption is very rapid in the beginning. The rate, however, decreases gradually until equilibrium is reached