Applications of Colloids

Colloids are put to use widely, in both industry and daily life. (i) Electrical precipitation of smoke: smoke is a colloidal dispersion of solid particles (carbon, arsenic compounds, dust, etc.) in air; passing the smoke through a chamber containing charged plates causes the charged smoke particles to lose their charge and precipitate onto the chamber floor -- this device is called a Cottrell precipitator. (ii) Purification of drinking water: water from natural sources contains colloidal impurities; adding alum coagulates these colloidal impurities so they settle out, making the water potable. (iii) Medicines: many medicines are colloidal in nature, and being colloidal makes them more effective because of the large surface-area-to-volume ratio of a colloidal particle and the resulting ease of assimilation into the body -- Argyrol, a silver sol, is used as an eye lotion, and milk of magnesia, an emulsion, is used for stomach disorders. (iv) Rubber industry: natural rubber is obtained by coagulating latex (a colloidal dispersion of rubber particles). (v) Cleansing action of soaps and detergents relies on their colloidal (micelle-forming) behaviour to …