what is coagulation


Coagulation: - The process of setting of colloidal particles is called coagulation or precipitation of the sol.
The coagulation of the lyophobic sols can be carried out in the following ways:-
1.      By electrophoresis: - The colloidal particles move towards oppositely changed electrodes get discharged and precipitate.
2.      By mixing two oppositely charged sols: - Oppositely charged sols when mixed almost equal proportional neutralise then changed and get partially or completely precipitated.
3.      By Boiling: - When a sol is boiled the adsorbed layer is disturbed due to increased collisions with the molecules of the dispersion medium. This reduces the charge on the particles and ultimately led to setting down in the form of a precipitate.
4.      By Persistent dialysis: - On prolonged dialysis, traces of the electrolyte present in the sol are removed almost completely collides become unstable and ultimately coagulate.
5.      By addition of electrolyte : -  When excess of electrolyte is added the colloidal particles precipitated, the reason is that colloids interact with ions carrying change opposite to that present on themselves, this causes neutralisation leading to their coagulation. 
Coagulation of Lyophilic Sols: - There are two factors which are responsible for stability or the lyophilic sols. These factors are change and salvation of the colloidal particles. When these two factors are removed, a lyophilic sol can be coagulated. This is done,
(i)     By addition of an electrolyte
(ii)   By adding a suitable solvent
Protection of Colloids:-
Lyophilic sols are more stable than lyophobic sols. Lyophilic colloids have a unique property of protecting lyophobic colloids. When a lyophilic sol is added to lyophobic sol, the lyophilic particles (colloids) covering up the particles of lyophobic sol.
An emulsion is a colloidal dispersion in which both the dispersion medium and dispersed phase are liquids generally; one of the two liquids is water. There are two types of emulsions.
1.      Oil dispersed in water (o/w type) and
2.      Water dispersed in oil (w/o type)
1.      O/W type – water act as a dispersion medium.
                                 Example: - Milk and vanishing cream.
2.      W/O type - oil act as dispersion medium.
                  Example: - Butter and cream.
Colloids Around Us: - Most of the substances all we come across in our daily life are colloids, for example meals, clothes, wooden, furniture, houses, newspaper are largely composed of colloids.
Application of Colloids: - Colloids are widely used in the industry.
·         Electro Precipitation of Smoke: - The smoke, before is comes out from the chimney, is led through a chamber containing plates having a charged opposite to that carried by smoke particles. The particles on coming in contact with these plates lose their charge get precipitated, the particles thus settle down on the floor of the chamber. The precipitator is called Cottrell precipitator.
Coagulation - Electro-Precipitation of Smoke at Power Station
Electroprecipitation at Power Station
·         Purification of Drinking Water: - Alum is added to water (that contain impurities) to coagulate the suspended impurities make water fit for colloidal in nature.
Example: - Argyrol is silver sol is used as an eye lotion.
·         Medicines :- Most of the medicines are colloidal in nature Ex:- Argirol is a silver sol used as an eye lotion.
·         Tanning  :- When a hide (Animal skin) , which has +ve  charged particles is soaked in tanning (or chromium salt) which contains – ve  charged particles , mutually coagulation take place. This result in the hardening of leather. This process is termed as tanning.
·         Photographic Plates and Films: - Photographic plates and films are prepared by coating an emulsion of the light sensitive silver bromide in gelatin over glass plates or celluloid films.
·         Rubber Industry: - Latex is a colloidal solution of rubber particles which are negative charged Rubber is obtained by coagulation of latex.
·         Industrial Products: - Paints inks, synthetic plastics, rubber, cement, graphite lubricants, etc. are all colloids solution.
      Coagulation in Chemistry:- In Chemical Science, coagulation is the process of setting of colloidal particles is called coagulation or precipitation of the sol. 
coagulation in chemistry
Coagulation Process Diagram

      Coagulation in Biology:- In Biological Science, coagulation is also called as clotting, means blood in body changes from liquid state to gel like state which further changes into blood clot.
      Daily Life Example Of Coagulation:- Curd (Dairy Product form by coagulating milk), Water Treatment (Coagulant is pour in water to destabilize the colloidal suspensions or impurities to take place coagulation).
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