Lyophobic sols also called hydrophobic sols if the

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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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This note was uploaded on 10/25/2012 for the course CHEMISTRY 570.448 taught by Professor Billball during the Fall '10 term at Johns Hopkins.

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