For modified acylglycerol emulsifiersstabilizing O/W emulsions, prepared from glycerol and C-12, C-14, C-16 and C-18 alkanoic acids and NaOH to yield in situ Na alkanoates, containing minor amounts of other acylglycerols and unconverted reactants, and for mixtures (9:1) pure monoacylglycerol and Na-alkanoate, interfacial tension (gamma) was measured at 45degreesC to evaluate critical micelle concentration (CMC), pC(30), CMC/C-30 and surfactant much less thans surface pressure D at CMC (D-CMC in relation to alkyl chain length. With ;C-18 MAG + KNa mixture, pC(30), CMC, CMC/C-30, gamma(CMC) and D-CMC were 3.28, 1.69 mmol/L, 3.21, 1.0 mN/m and 45.4 mN/m. resp. As emulsifier's C was raised, gamma fell. Na alkanoate as modifier increased CMC, hampered micellization and reduced (a) over tilde. On passing from C-12 to C-18, the efficiency to lower y diminished and the CMC/C-30 ratio and the IICMC decreased, Le., the tendency to micellization rose and that to adsorption fell.