Esperimental techniques and of electrical properties of critical binary liquid systems

Abstract

A direct analysis of the resistance and capacitance data did not yield any unambiguous result on the value of the exponent ?. Both resistance and capacitance behave in a similar way, and the ? value seems to depend upon the range of reduced temperature (t) used. For dR/dt and dC/dt data with (1–?) fixed at 0.1 and 0.35, 0.1 is a preferred choice, i.e., the exponent fits well for both resistance and capacitance. Based on IPM, the assumed functional form yields ? = 0.65 for direct data analysis, but the validity of this functional form is under question. The poor state of analysis is attributed to several factors: (1) Correlations among parameters in non-linear curve fitting procedures. (2) Errors in (C–C?), which are large near Tc where the anomaly is observed, demanding higher resolution in temperature, resistance, and capacitance measurements. (3) Impurities in the liquid influencing results and drift problems in repeated runs. (4) IPM effect affecting data near Tc even at low frequencies, requiring further theoretical study. (5) Subtracted IPM data demands a new theory and functional form. (6) Thermal expansion contribution must be separated from the observed dielectric anomaly to obtain the true dielectric anomaly. Capacitance data show a 2.5% increase at low frequencies and virtually no increase at higher frequencies, indicating that part of the anomaly is due to a true dielectric term. Thus, the dielectric constant exhibits a singularity as T ? Tc. Directions for Future Work: Higher resolution in measurements is essential. Contributions like IPM, thermal expansion, and linear background must be separated. Electrode polarization and drift must be minimized. IPM effects should be probed over a wide frequency range, and new techniques for capacitance and resistance measurement are needed. Investigations at high frequencies and theoretical studies on droplet models may help understand the critical behavior of interfacial polarization and its functional form.