Explain the coagulation of lyophilic sols and the protection of colloids.

(N/A) Coagulation of lyophilic sols: There are two factors responsible for the stability of lyophilic sols: the charge and the solvation of the colloidal particles. When these two factors are removed,a lyophilic sol can be coagulated. This is achieved by:
$(i)$ Adding an electrolyte.
$(ii)$ Adding a suitable solvent.
When solvents such as alcohol or acetone are added to hydrophilic sols,the dehydration of the dispersed phase occurs. Under these conditions,a small quantity of electrolyte can bring about coagulation.
Protection of colloids: Lyophilic sols are more stable than lyophobic sols because lyophilic colloids are extensively solvated; i.e.,the colloidal particles are covered by a sheath of the liquid in which they are dispersed.
Lyophilic colloids have a unique property of protecting lyophobic colloids. When a lyophilic sol is added to a lyophobic sol,the lyophilic particles form a layer around the lyophobic particles,protecting them from electrolytes. Lyophilic colloids used for this purpose are called protective colloids.