Dielectric relaxation and dispersion studies of mixtures of 1-propanol and benzonitrile in pure liquid state at radio and microwave frequencies

Complex permittivity of 1-propanol, benzonitrile and their binary mixtures over a range of concentrations was obtained in radio and microwave frequency range at various temperatures. Vector network analyzer (VNA) operating in the frequency range 0.3 MHz to 3.0 GHz was used to obtain complex permittivity spectra. Complex permittivity of the liquid samples at two spot frequencies 9.1 GHz and 19.61 GHz were also measured using standard microwave benches. Dielectric constant at optical frequency (∈∞) was measured using Abbe's refractometer. Measured values of the dielectric loss (∈″) have been plotted against dielectric constant (∈′) in a complex plane for 1-propanol, benzonitrile and their mixtures. Various dielectric relaxation parameters like relaxation time (τ), static dielectric constant (∈0) and high frequency limiting values of dielectric constant (∈∞1) were obtained from these curves. Dielectric relaxation parameters thus obtained were used to evaluate excess inverse relaxation time (1/τ)E, excess static permittivity (∈0E), Kirkwood correlation factor (g), angular correlation factor (geff) and thermodynamic parameters. Molecular interaction between the molecular species of the liquid mixtures was interpreted in terms of these parameters.