Surface tension of mixed surfactant solutions

Surface tension data for aqueous solutions of (N-n-dodecyl-N,Ndimethylammon io)-acetic acid bromide (BHB12), butanol and mixtures of butanol with BHB12 , BHB12 with BHB16, and C10EO5 with SDS in the presence of NaCl were analys ed on the basis of a simple thermodynamic approach. The thermodynamic equat ions describe the mixed adsorption layers very well and deviations between experiment and theory are within the limits of experimental accuracy. The o nly exception proved to be the results for the mixed adsorption layers of S DS and BHB12, which indicate that such anionic/cationic systems cannot be t reated like normal surfactant mixtures because a new surface-active compone nt with completely different surface properties is formed.