Electrical conductivity investigation of diluted potassium chloride solutions in binary mixture triethylamine–water near its consolute point

The binary liquid mixture of triethylamine + water (TEA–W) has a lower consolute point at a critical composition of 32.27 mass % triethylamine. Starting at a temperature within the one-phase region, the electrical conductivity of a sample of this mixture with addition of (K+, Cl−) ions was measured and found to be accurately described by the Vogel–Fulcher–Tammann (VFT) law. Before that, for the pure system, in a temperature range ΔT = Tc − T < 2 °C where Tc is the critical temperature, the electrical conductivity (σ) exhibits a monotonous deviation from the VFT behaviour. This anomaly is finite at Tc. The asymptotic behaviour of the electrical conductivity anomaly is described by a power law t1−α, where t   is the reduced temperature |(T−Tc)/Tc|(T−Tc)/Tc and α is the critical exponent of the specific heat anomaly at constant pressure. For the electrolyte mixtures, by combining the viscosity and the electrical conductivity data, the value of the computed Walden product has been determined and the salt dissociation degrees as well as the Debye screening length have been estimated.

► KCl salt as impurity in the near critical liquid mixture of triethylamine + water.
► Increasing the salt concentration decreases the degree of dissociation of solute.
► Values of the Debye screening length are about a few dozen Å.
► Restricted primitive model is inappropriate to describe the interaction potential.