DIELECTRIC-RELAXATION OF ACETONITRILE-WATER MIXTURES

The dielectric relaxation of acetonitrile-water mixtures is measured a t 298.15 K. From the resulting complex permittivity spectra, two relax ation processes are found. The low-frequency process is attributed to water molecules that reside in a micro-phase of relatively stable clus ters. The high-frequency process is attributed to both acetonitrile an d water molecules in a second micro-phase. The divergence of the struc ture of the liquid, tile microheterogeneity, is at a maximum at mole f ractions x(w)=0.6-0.7. This is close to the composition at which the a cetonitrile-water mixture has an upper critical demixing point. albeit at much lower temperatures.