1. Scattering of light by the colloidal particles takes place and the path of light become illuminated. This is called Tyndall effect.
2. The positively charged colloidal particles of Fe(OH)3 sol get coagulated by the oppositely charged ion provided by the electrolyte.
3. On passing direct current, colloidal particles move towards the oppositely charged electrode where they lose their charge and get coagulated.