ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 50, Number 3
JKCSEZ 50(3)
June 20, 2006 

The critical micelle concentrations (CMC) and the counter ion binding constants (B) in a micellar state of the mixed surfactant systems of sodium dodecylbenzenesulfonate (DBS) with polyoxyethylene(4) lauryl ether (Brij 30) in water were determined as a function of α₁ (the overall mole fraction of DBS) by the use of electric conductivity method and surface tensiometer method from 288 K to 308 K. Various thermodynamic parameters (ΔS_m^o, ΔH_m^o, and ΔG_m^o) for the micellization of DBS/Brij 30 mixtures were calculated and analyzed from the temperature dependence of CMC values. The measured values of ΔG^o_m are all negative but the values of ΔS_m^o are positive in the whole measured temperature region. On the other hand, the values of ΔH_m^o are positive or negative, depending on the measured temperature and α₁.