• Sorption is defined as the process by which one substance becomes attached to the surface of another substance. Specific cases of sorption are adsorption, absorption and ion-exchange.
• The reverse of sorption is called desorption.
(ii) Lyophilic colloids
• Based on the nature of interaction between the dispersed phase and dispersion medium colloids are classified as lyophilic and lyophobic colloids. Lyophilic means ‘liquid loving’.
• Colloids that are formed by the mixing of substances like gum, gelatine, rubber etc. with a suitable liquid are called lyophilic sols. These on separation can be reconstituted by mere mixing with the dispersion medium.
• Thus, they are also called reversible sols.
(iii) Associated colloids
• Based on the type of particles present in the dispersed phase, colloids are classified as multimolecular, macromolecular and associated colloids.
• Associated colloids are defined as those substances which behave as strong electrolytes at low concentration and have colloidal behaviour at high concentration due to formation of aggregates, also called micelles.
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