SURFACE FILMS OF SOLUBLE OR VOLATILE SUBSTANCES ADSORPTION ON LIQUID SURFACES

SURFACE FILMS OF SOLUBLE OR VOLATILE SUBSTANCES ADSORPTION ON LIQUID SURFACES 

Qualitatively, the rule for adsorption is that, if the solution has a smaller 

The quantitative relation between the amount of adsorption and the change in surface tension was first deduced thermodynamically by Gibbs in 187811 it was later calculated in a somewhat different form, by the methods of generalized dynamics, by J. J. Thomson.2 

Gibbs defined the superficial density , now more commonly called the adsorption or surface excess , for a solution, as follows. In Fig. 26, I, let the horizontal dotted lines represent approximately the limits of the transitional region, between the upper phase a and the lower phase p a normal to the surface is moved round so as to enclose a volume of cross-section A perpendicular to the surface. The volume is finally defined by drawing surfaces PaQa and PpQp parallel to the physical surface, in 

The surface excess of any component is defined as the amount by which the total quantity of that component in the actual system I exceeds that in the idealized system II. The symbols used are r1( r. .., r, for the surface excess of components 1, 2. i, per unit area raj, raj. raj, where ra = AVt, for the surface excess in the whole area A considered. Some of the quantities raj, rit will usually be positive, others negative. 

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