ELECTRICAL-PROPERTIES OF AN ETHANOL-DODECANE MIXTURE NEAR THE UPPER CRITICAL SOLUTION POINT

The electric permittivity and conductivity of an ethanol-dodecane crit ical mixture have been investigated as a function of frequency (100 Hz -1 MHz) and temperature. Dispersion of the electric permittivity and c onductivity were found and these phenomena were interpreted in terms o f Maxwell-Wagner polarization. The temperature dependence of E for hig h frequencies was described according to Senger's model and the theore tically predicted critical exponent (0.89) agrees with the experimenta l results. The temperature dependence of the conductivity was analysed both for low (f < f(r); f(r) is the characteristic frequency for Maxw ell-Wagner polarization) and high (f > f(r)) frequencies. The non-line ar temperature dependence of the background term makes the estimation of the conductivity critical exponent very difficult, but for low freq uencies the exponent phi = 1 - alpha is the most probable one. The Max well-Wagner permittivity increment defined as Delta epsilon(MW) = epsi lon(f < fr) - epsilon(f > fr) diverges in the vicinity of T-c with an exponent of -0.39. The conductivity increment defined as Delta sigma(M W) = sigma(f > fr ) - sigma(f < fr) diverges in the vicinity of T-c wi th an exponent of 0.22, close to the value predicted on the basis of t he Wagner model, beta-exponent value.