Shape of the coexistence curve and electrical conductivity of fused KNO3+ TlBr mixtures

Abstract

A precise determination of the liquid–liquid coexistence curve has been made for fused KNO₃+ TlBr mixtures. The conductivities of these mixtures were measured as a function of temperature and the phase separation located by changes in slope of the conductivity curves. These solutions possess a parabolic curve when the temperature T is sufficiently different from the consolute temperature T_c for (T_c–T/T_c) > 4 × 10^–4. The temperature at which the change in shape, from a parabolic to a cubic curve occurs, is believed to depend on the nature of the cohesive energies, and extension of the nonclassical region may be prevented by long-range coulombic forces in the ionic liquid mixtures under consideration. The consolute concentration was 57.5 ± 0.5 mole % TlBr and the consolute temperature was 546.3 ± 1.1°C. Solutions near the consolute point show critical fluctuations demonstrated by the distinct composition dependence of the normalized temperature derivatives of resistivity at the critical temperature.