(i) Lyophilic sols:

The dispersed phase exhibits an affinity for the dispersion medium. For example,  dispersion of protein, starch & gum in water.

The affinity of sol particles for the medium occurs due to formation of H bond with water (dispersion medium). The particles might have small or no charge at all & they do not exhibit Tyndall effect. Lyophilic sols are reversible in nature, i.e., if two constituents of the sol are separated by evaporation, then the sol can be prepared again by mixing the dispersion medium with the dispersion phase and vigorous shaking the mixture.

(ii) Lyophobic sols:

The dispersed phase has no affinity for the dispersion medium or the solvent. For example. dispersion of iron, gold, & sulphur in water.  The particles carry positive or negative charge and do exhibit Tyndall effect. These sols are irreversible in nature.

 A lyophobic sol can be stabilized due to the adsorption of ions (positive  or negative) by the dispersed particles. As a result the repulsive forces between the charged particles do not allow them to settle. If the charge is removed, then it is possible to keep the particles apart from each other. Subsequently, they aggregate and precipitate. In lyophobic sols, they are not surrounded by adsorbed layer of dispersion medium, as a result they coagulate. So, an excess of electrolyte is added, the electrolyte contains both positive & negative charged ions in the medium & the sol particles adsorb oppositely charged ions and gets discharged. The electrically neutral particles then aggregate and precipitate.  The hydrophilic sols are stabilized depends on two things- the presence of a charge and the salvation of colloidal particles. On the other hand, the hydrophobic sols are stabilized due to the presence of a charge. Therefore, the hydrophobic sols is less stable than the hydrophilic sols.