Dividing surface after Lucassen-Reynders

Here 6, = FitOi is the monolayer coverage, Fi is the adsorption, n = yo - y is the surface pressure, yo is the surface tension of solvent, n, = coj/too, and coo are the partial molar surface areas of the surfactant and solvent, respectively, bi is the adsorption constant, Cj is the surfactants concentration in the solution bulk. The Frumkin parameters ai and a2 represent the interactions of components 1 and 2 with the solvent, while the parameter ai2 accounts for interactions between the two surfactants 1 and 2 in the ternary regular mixture (see Eq. 2.32) a,=HJ,/RT aj=HJ2/RT a,2=(Ho,+Ho2-HJj)/2RT, where Hy=A,jRT. Choosing the dividing surface after Lucassen-Reynders (cf. Chapter 2), one can eliminate the contributions from the entropic non-ideality of the solvent, thus reducing Eq. (3.27) to a much simpler form... 

Note that, while the choice of the dividing surface after Lucassen-Reynders does not affect the form of the adsorption isotherm, Eqs. (3.28) and (3.29), the values of nj are now given by... 

All systems shown in these figures can be perfectly described by the model defined by Eqs. (3.28)-(3.31) which supports this theoretical model based on Butler s equation for the chemical potentials of the surface layer, and the regular solution theory. In addition, this agreement is due to the certain choice of the dividing surface after Lucassen-Reynders, and to the fact that Eq. (3.31) was used to calculate the mean molar area of the surfactants mixture. It is important to note that in some cases (for mixtures of normal alcohols. Fig. 3.62, and mixtures of sodium dodecyl sulphate (Ci2S04Na) with 1-butanol and 1-nonanol, Figs. 3.63 and... 

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