The critical micelle concentration (CMC) of surfactant-Cr(III)-dodecylamine complexes of the type cis-α-[Cr(trien)(C 12H 25NH 2)X] 2+ (where trien = triethylenetetramine; X = F -, Cl -, Br -) has been studied in n-alcohol and in formamide at different temperatures, by electrical conductivity measurements. From the CMC values as a function of temperature, various thermodynamic properties have been evaluated: standard Gibbs energy changes (Δ micG 0), standard enthalpy changes (Δ micH 0) and standard entropy changes (Δ micS 0) for micellization. Critical micelle concentrations have also been measured as a function of the percentage composition of alcohol added. The solvent composition dependences of these thermodynamic parameters were determined. It is suggested that alcohol addition leads to an increase in formamide penetration into the micellar interface that depends on the alcohol's chain length. The results are discussed in terms of an increased hydrophobic effect, dielectric constant of the medium, the chain length of the alcohols, and the surfactant in the solvent mixture. © Springer Science+Business Media, LLC 2011.