Conductivity measurements in single-phase microemulsions of the system sodium dodecyl sulfate/1-butanol/water/heptane

Abstract

Conductivity measurements have been performed in the single-phase region of the system sodium dodecyl sulfate (SDS)/1-butanol/water/heptane at 25°C. The applicability of the classical conductance theory for weak electrolytes, the semiempirical conductance theory for coarse emulsions, and the percolation theory has been examined. These measurements reveal that SDS micelles are converted into monomers in the presence of a sufficient amount of 1-butanol. In almost pure 1-butanol as a solvent, SDS behaves as a weak 1-1-electrolyte. At a certain water-to-heptane ratio at constant total amount of SDS and 1-butanol, the conductivity results indicate where a transition from water-in-oil to oil-in-water microemulsions takes place, and the transition can be described by the percolation theory.