Determination of phase boundaries by electrical conductometry in multicomponent liquid mixtures

The detection of the phase boundaries by electrical conductometry was demonstrated with a ternary amphiphile/oil/water system with a view to developing the electrical method as a rapid and reliable one. The ternary 2-butoxyethanol/decane/water system was chosen because its tie triangle at 24 degrees C was already known. The electrical conductivity in terms of a component concentration in the single and two-phase regions was like a percolation curve. Hence, the phase boundary points between 1- and 2-phase regions could be determined by the measured electrical conductivities and percolation theory. These points are in excellent agreement with these obtained by flow calorimetry. When the phase boundaries between 2- and 3-phase regions was crossed, the conductivities exhibited a maximum or peculiar changes around the phase boundary points. The maximum corresponded to the phase boundary point. The peculiar changes appeared to correspond to the phase boundary points, but it was difficult to determine them Exactly, because of lack of an adequate theory or explanation for the conductivity behavior around these points.