Ion-Pair Conductivity Theory Fitting Measured Data for Various Alcohol-Toluene Mixtures across Entire Concentration Range

We have measured the conductivity of binary alcohol-toluene mixtures (using 8 different alcohols) across the entire concentration range. The conductivity varies from 10 −11 up to 3.10 −4 S/m and, for a certain range decays rapidly and non-linearly with decreasing alcohol content. We assume that this range is associated with ion-pair formation due to decrease in dielectric constant. The Onsager-Fuoss conductivity theory is unable fit experimental conductivity across such wide range. Because of this we have suggested a more general conductivity theory that is based on the known expression for ionic strength, which has been derived directly from mass-action law for ion/ion-pair equilibrium (Aurbach [1999]). This theory fits experimental conductivity for all mixtures, for data which spans over 7 orders of magnitude. The adjustable parameters in this general theory are total ion concentration in the pure alcohol, the shortest distance of ion approach in the ion-pair, and hydrodynamic size of the ions.