Dielectric Relaxation Studies of Binary Mixtures of N-Methylformamide and Tetramethylurea in Benzene Using Microwave Absorption Data

The dielectric relaxation time (τ) and dipole moment (μ) of binary mixtures of different molar concentrations of N-methylformamide (NMF) in binary mixtures of NMF and tetramethylurea (TMU) in benzene have been calculated at 25, 30, 35 and 40 ◦C using standard standing wave microwave techniques and following the single frequency (9.885 GHz) concentration variational method of Gopala Krishna. The energy parameters (∆Hε , ∆Fε , ∆Sε ) for the dielectric relaxation process of binary mixtures containing 30 mol% of NMF have been calculated at different temperatures, and comparison has been made with the corresponding energy parameters (∆Hη , ∆Fη , ∆Sη ) for the viscous flow process. Based on these studies, it was inferred that the dielectric relaxation process can be treated as a rate process just like the viscous flow process. Solute-solvent and solute-solute molecular associations have been proposed.