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.
Emulsions:-
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.
Example:-
·
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.
 |
| 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 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).
Coagulation in Chemistry:- In Chemical Science, coagulation is the process of setting of colloidal particles is called coagulation or precipitation of the sol.
 |
| Coagulation Process Diagram |
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).
