Surfactant molecules at air-water

In contrast with inorganic salts whose adsorption at water-air interface is negative, surfactants are strongly adsorbed at water-air interface, and this results in depression of the surface tension. In very dilute solutions of surfactants, adsorption at water air interface can lead to substantial depletion of the solution. Orientation of surfactant molecules at air-water interface is illustrated in Fig. 4.64. 

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