Temperature, isotope and solute effects on the non-linear electric field behaviour of water

Abstract

Measurements are reported on the non-linear electric field effect of the relative permittivity of aqueous systems at fields up to 10⁷ V m^–1. Over the range 273–293 K the Piekara factor (Δε/E²) for water has the Langevin anticipated negative values but shows a distinct pattern with a minimum near 277 K. H₂O and D₂O liquids give indistinguishable values.

Whilst acetone and pyridine show an essentially smooth variation of (Δε/E²) over their complete concentration ranges in water, dioxan and tetrahydrofuran show similar marked variations with a distinctive positive effect near the hemihydrate compositions. The influence of temperature on the sharp positive maxima with these two solutes is reported. t-Butyl alcohol, well known to give positive (Δε/E²) values in the pure liquid, does so at all concentrations above mole fraction 0.25. In many cases it is clear that the Piekara factor shows far more detail than the ε₀ against concentration plots as the measurements are sensitive to very small changes in permittivity due to the high fields.

The observations are discussed with the aim of identifying the principal factors contributing to the newly observed effects.