10.7 Various application of colloids

In every path of life, colloids play a great role. Human body contains the numerous colloidal solutions. The blood in our body, protoplasma of plant and animal cell, and fats in our intestines are in the form of emulsions. Synthetic polymers like polystyrene silicones and PVC are colloids.

Food Food stuffs like milk cream, butter, etc are present in colloidal form. Medicines Antibodies such as penicillin and streptomycin are produced in colloidal form for suitable injections. Colloidal gold and colloidal calcium are used as tonics. Milk of magnesia is used for stomach troubles.

Silver sol protected by gelatine known as Argyrol is used as eye lotion. In Industry Colloids find many applications in industries. (i) Water purification: Purification of drinking water is activated by coagulation of suspended impurities in water using alums containing Al + (ii) In washing: The cleansing action of soap is due to the formation of emulsion of soap molecules with dirt and grease. (iii) Tanning of leather Skin and hides are protein containing positively charged particles which are coagulated by adding tannin to give hardened leather for further application.

Chromium salts are used for the purpose. Chrome tanning can produce soft and polishable leather. (iv) Rubber industry: Latex is the emulsion of natural rubber with negative particles. By heating rubber with sulphur, vulcanized rubbers are produced for tyres, tubes, etc.

(v) Sewage disposal Sewage contains dirt, mud and wastes dispersed in water. The passage of electric current deposits the wastes materials which can be used as a manure. Primary treatment Screens Comminutor Primary effluent Primary clarifier Grit chamber Grit disposal Sludge treatment and disposal Raw of primary sludge Return sludge pump Activated sludge Discharge to surface water or tertiary treatment Disinfectant Secondary treatment Aeration tank Air compressor Return sludge Raw sewage Secondary clarifier Secondary effluent Figure . Sewage disposal Vi ) Cortrell’s precipitator Carbon dust in air is solidified by cortrell’s precipitator.

In it, a high potential difference of about ,000V is used. The charge on carbon is neutralized and solidified. Thus the air is free from carbon particles. Vii) The blue colour of the sky in nature is due to Tyndall effect of air particles.

Viii) Formation of delta: The electrolyte in sea and river water coagulates the solid particles in river water at their intersection. So, the earth becomes a fertile land. Ix) Analytical application Qualitative and quantitative analysis are based on the various properties of colloids. Hence we can conclude that in our life, there is hardly any field which is not including the applications of colloids.

Natural honey is a colloidal sol. It is distinguished from artificial one by adding ammoniacal AgNO In case of natural honey a metallic silver is produced, assumes a reddish yellow color due to traces of albumin or ethereal oil which acts as a protective colloid. In case of artificial honey a dark yellow or greenish yellow precipitate is formed.