Abstract: Above the critical micelle concentration, sodium dodecyl sulfate (SDS) can aggregate and form micelle in aqueous solution. It will display its own conductance behavior different from that of general strong electrolyte solution. Therefore, we proposed a new model, named as micelle ionization model, where the micelle is treated as one kind of weak electrolyte and the molar conductivity is expressed by conductance equation of weak electrolyte. The formula for calculating the micelle ionization degree for SDS is deduced. According to the observed conductance data of SDS aqueous solutions in this work, the ionization degree of SDS micelle is determined. The calculated values of the ionization degree are in good agreement with those from literatures, which indicates that the new model can be used satisfactorily to describe the conductance behavior of ion-type surfactant SDS solution.

Key words: Sodium dodecyl sulfate(SDS), Weak electrolytes, Micelle ionization degree