Give information about the applications of colloids.

(N/A) Colloids are widely used in the industry. Following are some examples:
$(i)$ Electrical precipitation of smoke: Smoke is a colloidal solution of solid particles such as carbon,arsenic compounds,dust,etc.,in air. The smoke,before it comes out from the chimney,is led through a chamber containing plates having a charge opposite to that carried by smoke particles. The particles,on coming in contact with these plates,lose their charge and get precipitated. The particles thus settle down on the floor of the chamber. The precipitator is called a Cottrell precipitator.
$(ii)$ Purification of drinking water: The water obtained from natural sources often contains suspended impurities. Alum is added to such water to coagulate the suspended impurities and make water fit for drinking purposes.
$(iii)$ Medicines: Most medicines are colloidal in nature. For example,argyrol is a silver sol used as an eye lotion.