The surface activity of a mixture of Na perfluorooctanoate (C7F15CO2Na) and tetradecyltrimethylammonium bromide (TTAB) was studied. The surface tensions (g) of aqueous solns. of different ratio mixture were measured by the drop-vol. method. The crit. micelle concentration (cmc) and the surface tension at cmc (gcmc) were estimated from the g-log c (c = concn). curve. The Gibbs adsorption equation and the mol. interaction parameter method were used to calculate the total adsorption amount (Gt), the composition of adsorbed layer (xFs), and the micelle composition Synergism occurs in surface tension reduction effectiveness and efficiency, and in micelle formation in the C7F15CO2Na-TTAB system, as well as in other systems of cationic-anionic surfactants with different CH-chain or with equal CF-chain and CH-chain lengths. The max. adsorption is 7.7 ?10-10 mol cm-2, >1 monolayer, indicating multilayer character. The similarity to the C7F15CO2Na-C8H17N(CH3)3Br system indicates that this system should be characteristic of CF-chain and CH-chain surfactant mixed systems, but the surface tension reduction effectiveness is not as good as that of the C7F15CO2Na-C8H17N(CH3)3Br mixture (gcmc min. 15.1 mN m-1, vs. an expected 20.9 mN/m in this system), although the gcmc0 of aqueous TTAB alone solution is 6 mN/m lower than that of C8H17N(CH3)3Br. This can be interpreted crudely by extending the W. Zisman (1964) view of the relation between surface energy and surface composition from the solid to the liquid phase.

Key words: AQUEOUS SOLUTION, SODIUM COMPOUNDS, SURFACTANTS, TRIMETHYLALKYLAMMONIUM, BROMIDE, SURFACE ACTIVITY, C14 COMPOUNDS, CAPRYLIC ACID P, CHAIN LENGTH, PERFLUORO-HYDROCARBON