Sets of complex permittivity values for pure water are presented for nine temperatures between 0 and 50 °C and for microwave frequencies from 1.1 to 57 GHz. The data are analyzed together with static permittivity values and many sporadic microwave data found In the published literature. At all temperatures considered In this analysis (-4.1 °C < T < 60 °C) the frequency-dependent complex permittivities can be well described by a Debye-type relaxation spectral function reflecting one discrete relaxation time. The parameter values for this function as obtained by a nonlinear regression analysis of the measured dielectric spectra are displayed In tabular format. Also given are empirical correlations allowing these parameters to be Interpolated with respect to the temperature.

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The complex permittivity of ethylammonium nitrate has been measured as a function of frequency between 3 MHz and 40 GHz at eight temperatures between 288.15 and 353.15 K. The spectra are well represented by a sum of a conductivity term and a relaxation spectral function that reflects an unsymmetrical relaxation time distribution. Parameter values are given for the Cole−Davidson term and the Kohlrausch−Williams−Watts model. Molecular mechanisms in conformance with an unsymmetrical relaxation time distribution are discussed. The dominant relaxation process with a relaxation frequency in the accessible range can be explained by the formation of a small amount of dipolar ion complexes. The values for the extrapolated high-frequency permittivity indicate a further relaxation process, well above the frequency range of measurements, which is likely to reflect modes of motions of the cation and anion lattices relative to one another.

terminate errors in the complicated case, however, are bound to be larger since multiple measurements are often necessary to access the state of a particular exchanged ion. Consequently, deconvolution will yield poorer results, which may be improved only by improving the precision of the isotherm data obtained.At 25 °C the complex dielectric spectrum between 1 MHz and 40 GHz has been measured in the whole composition range for aqueous solutions of dimethyl sulfoxide. Different relaxation spectral functions have been fitted to the measured frequency-dependent permittivity data. It was found that the unsymmetrical continuous Davidson-Cole relaxation time distribution is appropriate to describe the spectra. The width of the distribution function is remarkably small. When plotted versus the mole fraction of dimethyl sulfoxide, the principal dielectric relaxation time in correspondence with other parameter exhibits a pronounced relative maximum. The static permittivity reflects some kind of antiparallel ordering of dipole moments.

At eight temperatures T between 0 and 60 °C and at five mole fractions x e of ethanol (0 < x e ≤ 1) the complex (electric) permittivity of ethanol/water mixtures has been measured as a function of frequency ν between 1 MHz and 24 GHz. At 25 °C the ethanol permittivities are completed by literature data for the frequency range 200 MHz to 90 GHz. The spectra for ethanol and for the ethanol/water mixtures are compared to permittivity spectra for water which, at some temperatures, are available up to 900 GHz. All spectra of the ethanol/water system can be well represented by the assumption of two relaxation regions. The relaxation time τ 1 of the dominating relaxation process varies between 4 ps (x e = 0, 60 °C) and 310 ps (x e = 1, 0 °C). The relaxation time τ 2 of the second relaxation process is smaller. Evaluation of the extrapolated low frequency (“static”) permittivity yields a minium in the effective dipole orientation correlation of the ethanol/water system at 0.2 ≤ x e ≤ 0.4. In this composition range, other parameters also exhibit extrema, indicating a microheterogeneous structure of the mixtures and the existence of precritical concentration fluctuations. Interesting, the activation enthalpy ΔH 1 ⧧ and entropy ΔS 1 ⧧ of the dominating dielectric relaxation process also display a distinct maximum at around x e = 0.22. These activation quantities have been obtained from Eyring plots of the relaxation time τ 1 at different mixture compositions. The relaxation parameters of the ethanol/water system are discussed in terms of a wait-and-switch model of dipole reorientation.