EFFECT OF 1,4-DIOXANE ON THE MICELLAR PROPERTIES OF SOME SURFACTANT SOLUTIONS

From the observed conductivity data the values of critical micelle con centration (CMC), counter ion association constant (alpha) and, the li miting equivalent conductance (Lambda(0)) values have been obtained fo r the systems sodium dodecylsulphate (SDS) + 1,4-dioxane + H2O and dod ecyltrimethylammonium bromide (DTAB) + 1,4-dioxane + H2O. Thermodynami c properties of micellisation and transfer of surfactant from pure aqu eous solution to 1,4-dioxane + H2O have been obtained at 303.15 and 31 3.15 K. Whereas free energy of micellisation (Delta G(mic)(0)) values decrease with the addition of 1,4-dioxane to the aqueous SDS solution, such values, however, are found to increase when 1,4-dioxane is mixed with aqueous DTAB solutions. Micellisation process is favoured both b y energy effect as well as by entropy gain. The transfer of DTAB from water to 1,4-dioxane + H2O is accompanied by decrease of Gibb's free e nergy, such transfer of SDS, however, is found to be thermodynamically unfavoured.