Applications of Colloidal Solutions

Colloids play a very important role in our daily life.

Sewage Disposal

Colloidal particles of dirt, etc. carry electric charge. When sewage is allowed to pass through metallic plates kept at a high potential, the colloidal particles move to the oppositely charged electrode and get precipitated there. Hence sewage water is purified.

Purification of Water in Wells

When alum is added to muddy water, the negatively charged particles of the colloid are neutralized by Al³⁺ ions. Hence, the mud particles settle down and the water can be filtered and used.

Smoke Precipitation

Smoke particles are actually electrically charged colloidal particles of carbon in air. Precipitation of this carbon is done in a Cottrell’s Precipitator. Smoke from chimneys is allowed to pass through a chamber having a number of metallic plates connected to a source of high potential. Charged particles of smoke get attracted to the oppositely charged electrode and get precipitated and hot purified air passes out.

Other Applications

Photography

A colloidal solution of silver bromide in gelatin is applied on glass plates or celluloid films to form photo-sensitive plates in photography.

Clotting of Blood

Blood is a colloidal solution and is negatively charged. On applying a solution of FeCl₃ bleeding stops and clotting of the colloidal particles of blood takes place.

Rubber Plating

Latex is a colloidal solution of negatively charged rubber particles. The object to be rubber plated is made the anode in the rubber plating bath. The negatively charged rubber particles move towards the anode and get deposited on it.

Blue Color of Sky

Sky is blue because the colloidal dust particles floating about in the sky scatter blue light, that makes the sky appear blue. In the absence of these colloidal particles the sky would have appeared dark throughout.