Dielectric relaxation in mixtures of some nitriles

Dielectric constant and loss have been measured at 10, 3, 2, and 1 cm at 30°C for pure acetonitrile, pure propionitrile, mixtures of acetonitrile and benzonitrile and propionitrile and benzonitrile. Also measured are the benzene solutions of acetonitrile and propionitrile at the same wavelengths over the temperature region 24 to 70°C. The far-infrared spectra between 10–150 cm⁻¹ of dilute benzene solutions of both the nitriles have also been investigated. The static dielectric constant has also been measured in all cases. A single relaxation time has been found for pure acetonitrile whereas the dielectric data of pure propionitrile indicate an unsymmetrical distribution of relaxation times. The dielectric data of the binary mixtures of acetonitrile and benzonitrile have been analyzed in terms of two partly superimposed Debye regions, whereas that of propionitrile and benzonitrile have been interpreted in terms of three partly overlapping Debye regions. The far-infrared absorption of propionitrile is similar to the one reported for acetonitrile in the literature. The contributions of the far-infrared absorptions to the microwave data were discussed. The thermodynamic quantities for each relaxation process have been estimated.