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Unformatted text preview: ophobic Sols
• Also called hydrophobic sols (if the dispersion medium is water).
• Relatively unstable.
• The addition of electrolytes to lyophobic sols frequently causes coagulation
and precipitation. 1 2. Lyophilic
• A liquid-loving sols
• Has strong affinity between the disperse phase and the molecules
comprising the dispersion mediu m.
• Much more stable and behave muc h more like true s o l u t i o n s .
PREPARATION OF COLLOIDAL DISPERSIONS
a) Intrinsic colloids
• Readily form sols when they are brought into contact with a suitable
dispersion medium (e.g. a colloidal solution of starch is easily prepared
by introducing starch into boiling water).
• Usually lyophilic macromolecules (such as proteins) or long-chain
molecules with polar end groups, which tend to aggregate and form particles of colloidal size, known as micelles.
b) Extrinsic colloids
• Do not form colloidal dispersions readily.
METHODS OF PREPARATION
1. Condensation Methods
The materials are initially in true solution. Chemical reactions are used to produce
the sol; care is taken by controll...
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