Adsorption and Absorption
The phenomenon of adsorption is different from that of absorption. The latter term implies that a substance is uniformly distributed throughout the body of a solid, Fig. 17.2(b). If we leave a small lump of calcium chloride in open, it absorbs water vapour (moisture) from air and after some time even starts dissolving in it. On the other hand if we keep a sample of silica gel in open, it adsorbs water vapour on its surface as shown in Fig. 17.2 (a).