For lyophilic sols the charges on the particles often

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Unformatted text preview: called electrophoresis and it is one example of a transport property. • • • • • For lyophilic sols, the charges on the particles often result largely from the ionization of the material constituting the disperse phase. Protein molecules in general bear positive or negative charges because of the i onizations of -COOH, -NH 3 , -O H, and other groups. A t low pH value s t he protein bears a net positive charge because groups like NH3 are present but there are no negatively charged groups At high pH values negative groups like -COO and -O- are present but there are no positively charged groups and the molecule has a net negative charge. At the same time the charge is influenced by the specific Isoionic Point adsorption of ions. At some intermediate pH (the isoionic point) the protein does not migrate in an electric field. SCHULZE-HARDY RULE The precipitating action of ions of opposite sign to those on the surface of the particle is greater the higher the valence of the ion (Schulze-Hardy rule). • • • • Lyophilic sols differ from lyophobic so...
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