Surface behavior of Triton X-165 and short chain alcohol mixtures

In this Article, the surface behavior of mixtures of nonionic Triton X-165 (TX-165) with methanol, ethanol, and propanol at constant Triton X-165 concentration in the range from 1 x 10(-7) to 10(-3) M in aqueous solutions was investigated by surface tension measurements of their solutions in a wide range of alcohol concentrations. The obtained values of the surface tension of solutions were compared with those calculated from Szyszkowski, Connors, and Fainerman and Miller equations. On the basis of the surface tension data, the Triton X-165 and alcohol concentrations at water-air interface and their standard free energy of adsorption as well as the composition of the monolayer at this interface were determined. Taking into account this composition and activity coefficient of Triton X-165 and alcohol, the free enthalpy of their mixing was also calculated. From the measurements and calculations, it results, among other things, that unexpectedly the Fainerman and Miller equation derived for ideal mixtures of homologous surfactant can be useful for the description of changes of the solution surface tension of the investigated mixtures and that the amount of short chain alcohols at the water-air interface at their low concentration in the bulk phase is proportional to the activity coefficient.