Abstract: Surface tension[γ] of aqueous solutions of C_8H_(17)SO_4Na, C_8H_(17)N(CH_3)_3Br and the 1:1 mixture of them have been measured by drop volume method, and their contact angles [θ] on paraffin wax by a microseopefitted with a goniometer. According to Young equation, the L/S interface pressures were obtained from γ and θ data. Gibbs adsorption equation was applied for L/S interface to work out the adsorstion isotherms It is seen that the adsorption isotherms are of Langmuir type.
It would be the first time to calculate the molecular interacion parameter of mixed surfactants adsorption layer at L/S interface and to give β~σ values of the same pair of surfactants in A/L, L/L, L/S interface layers.
It has been pointed out that this method is simple, convenient and only a few ml solution is needed for obtaining more than ten different surface properties: surface tension of solution, adsorption at A/L interface, composition of the adsorbed layer at A/L interface, critical micelle concentration, contact angle, critical surface tension of solid, L/S interface pressure, adsorption at L/S interface, composition of the adsorbed layer at L/S interface, molecular interaction parameter in A/L and L/S interface adsorbed layer and in micelle, etc.