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Monday, December 21, 2009

Adsorption at a Liquid Interface

1. Surfactants are substances, in molecular or ionic form which are strongly adsorbed at the interface of two liquids.

2. They are amphiphilic, meaning thereby that the molecule possesses both polar and non polar groups.

3. The polar groups as - OH, - COOH are adsorbed within the water phase where as the non-polar group is the hydrocarbon chain which is preferentially adsorbed in oil layer.

4. These are therefore referred to as hydrophilic and lipophilic groups, respectively.

5. Molecules which are not too large, e.g. methyl alcohol, ethyl alcohol stay wholly within the aqueous phase.

6. Similarly, wholly lipophilic molecules stay in oil phase.

7. More generally the hydrocarbon chain stays in oil phase and the polar groups in water phase.

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