The complex dielectric permittivity spectra of butanenitrile(BN) with 1,2 Dichloroethane(DCE) mixture has been determined at temperature 250C in the frequency range of 10 MHz to 20 GHz using time domain reflectometry (TDR) for 11 different concentrations of the system. The dielectric parameters such as static permittivity ( e 0) and relaxation time (t) have been obtained by Fourier transform and the least squares fit method. The relaxation in this system can be described by a single relaxation time using the Debye model. The Excess parameters of the mixtures have been determined. In the mixtures excess permittivity is found to be positive in DCE rich region and negative in BN rich region. The excess inverse relaxation time is found to be negative. The investigation shows that there is systematic change in dielectric parameters of the system with change in concentration.
