The interactions of saturated fatty acids at the dodecane/water interface and their sodium salts at the air/water interface

The interfacial tension of lauric, myristic and palmitic acids at the dodecane/water interface and of their sodium salts at the air/water interface were measured using the Du Noüy (ring) method. On the basis of these results the standard free energies of adsorption (ΔG⁰_ad) and of micellization (ΔG⁰_mic) of the above mentioned systems were calculated. According to deviations of the Langmuir isotherm, the corresponding interactions were discussed from the dependence of the standard free energy of adsorption on the interface coverage (Θ).