1.2.2. Measurements
The surface tension of the aqueous solutions of the above men-tioned surfactant mixtures was measured at 293 K by a Krüss K9tensiometer according to the platinum ring detachment method(du Nouy’s method). Krüss K9 tensiometer was calibrated by takingthe procedure of C. Huh and S.G. Mason into account [15]. The ringwas cleaned with distilled water and heated to the red color witha Bunsen burner before each measurement. In all cases 10 or moresuccessive measurements were performed. The root-mean-squaredeviation of our surface tension data depending on the surfactantconcentration was in the range from ±0.1 to ±0.2 mN/m and thestandard uncertainty (standard deviation of the mean) was in therange from ±0.025 mN/m (calculated for 16 surface tension valuesfor each surfactant mixture concentration in the range of its lowconcentration) to ±0.063 mN/m (calculated for 10 surface tensionvalues for each surfactant mixture concentration in the range of itshigh concentration), respectively. The temperature was controlledby a jacketed vessel joined to the thermostatic water bath with the accuracy ±0.01 K.