Critical behavior of dielectric permittivity and electric conductivity in temperature and pressure studies above and below the critical consolute point

Abstract

Results of comprehensive temperature (T) and pressure (P) studies of static dielectric permittivity (ε′) and electric conductivity (σ) in the one- and two-phase regions of critical nitrobenzene–dodecane mixture are presented. A strong asymmetry of determined coexistence curves causes a strong violation of the law of rectilinear diameter. The obtained critical anomalies in the homogeneous phase [εhomo′(T),εhomo′(P),σhomo(P)] or the diameter of the binodal [εmean′(T),εmean′(P),σmean(T),σmean(P)] are associated with the same critical exponent φ=1−α ≈0.88, where α is the specific heat critical exponent. Critical anomalies for the isothermal, pressure path exhibit a set of favorite in comparison with results obtained in σ(T) and ε(T) tests. They are: the negligible influence of the critical Maxwell–Wagner effect, the hardly visible appearance of the correction-to-scaling term, a more pronounced manifestation of critical anomalies, and a reduced number of fitted parameters. Particularly noteworthy is the evidence for the σhomo(P) anomaly in the homogeneous phase, hardly obtained up to now in a mixture of a low electric conductivity. Results presented suggest the isomorphic behavior of ε′(T), σ(T) and ε′(P), σ(P) critical anomalies for the homogeneous phase and for the diameter of the binodal.