Colloids play a very significant role in nature and in our daily life. Some of the important applications of colloids are discussed below:
1) Medicines:
Medicines in colloidal form are easily adsorbed by the body tissues and hence are more effective.
2) Sewage disposal:
Colloidal particles of the dirt, mud etc. carry electric charge, hence when sewage water is passed through the plates kept at a high potential, the colloidal particles are coagulated due to electrophoresis and the suspended matter gets removed.
3) Purification of water:
The precipitation of colloidal impurities present in water can be done by adding certain electrolytes like alum etc. the negatively charged colloidal particles of impurities get neutralized by the Al3+ ions and settle down and pure water can be decanted off.
4) Cleansing action of soap:
Soap solution is colloidal in nature. It removes the dirt particles either by adsorption or by emulsifying the greasy matter sticking to the cloth.
5) Formation of Delta:
River water contains charged colloidal particles of clay, sand and many other materials. Sea water is very big store house of a variety of electrolytes dissolved in it. As soon as river water comes in contact with sea water coagulate the suspended colloidal particles which ultimately settle down at the point of contact. Thus the level of the river bed rises. As a result, water adopts a different course and delta is formed in due course of time.
6) Smoke precipitation:
Smoke particles are actually electrically charged colloidal particles of carbon in the air. Precipitation of smoke particles is carried out by Cottrell precipitator which is based on the principle of electrophoresis. Smoke is allowed to pass through a chamber having a number of metal plates attached to a metal wire connected to a source of high potential. Charged particles of smoke get attracted by oppositely charge electrode get precipitated after losing their charge and the hot air passes out through the chimney. The dust particles are also removed in this process. Thus the nuisance of smoke in big industrial cities can be avoided.
7) Photography:
A colloidal solution of silver bromide in gelatin is applied on glass plates or celluloid films or paper to from sensitive plates in photography.
8 ) Artificial rain:
Artificial rain can be caused by spraying oppositely charged colloidal dust or sand particles over a cloud. The colloidal water particles present in the cloud will be neutralized and coagulate to from bigger water drops causing artificial rain.
9) Rubber industry:
Latex is a colloidal solution of negatively charged rubber particles. From latex, rubber can be obtained by coagulation.
Rubber plated articles are prepared by depositing negatively charged rubber particles over the article to be rubber plated by making that article an anode in a rubber plating bath.
10) Smoke screen:
In warfare smoke screens are used which are nothing but colloidal dispersion of certain substances in the air.
11) Other applications:
a) Blue color of the sky is due to the scattering of light by colloidal dust particles in air (Tyndall effect). Similarly, sea water looks blue due to scattering of light by the colloidal impurities present in sea water.
b) Tail of comets is seen as a Tyndall cone due to the scattering of light by the tiny solid particles left by the comet in its path.
c) Blood is a colloidal solution and the stoppage of bleeding on applying ferric chloride solution is due to coagulation of blood forming a clot.
