Josef Barthel

The dielectric relaxation of water between 0°C and 35°C

Abstract Precise complex permittivity data from our laboratory for pure water at temperatures 0.2⩽ϑ/°C⩽35 are combined with literature results to cover the frequency range 0.2⩽ν/GHz⩽410. A description of the e (ν) spectra requires the superposition of two Debye processes. Nonetheless, relaxation times and dispersion amplitudes discourage the discussion of the water structure in terms of a two-state model. The interpretation of the fast process with the relaxation time τ2 requires additional information, whereas it is possible to relate the relaxation time τ1 of the dominating slow process to the production rate of mobile water molecules. From the corresponding Eyring free energy, ΔG≠, hydrogen-bond probabilities are deduced, which are in good agreement with data from other methods.

Dielectric spectra of some common solvents in the microwave region. Water and lower alcohols

Abstract Precise complex permittivity spectra of the hydrogen-bonding liquids water, methanol, ethanol, 1-propanol, and 2-propanol have been determined in the frequency range 0.95-89 GHz. It is shown that the dielectric relaxation behaviour of water is governed by two exponentials, whereas three discrete dispersion steps are found for the alcohols.

Calibration of conductance cells at various temperatures

AbstractPrecise conductance measurements on aqueous potassium chloride solutions at 0, 10, 18, and 25°C have been made under various conditions over a concentration range 10−4<c<5×10−2 mole-dm−3, yielding the conductance equations

The dynamics of liquid formamide, N-methylformamide, N,N-dimethylformamide, and N,N-dimethylacetamide. A dielectric relaxation study

\begin{gathered} 25^\circ C:\Lambda = 149.873 - 95.01\sqrt c + 38.48c log c + 183.1c - 176.4c^{3/2} \hfill \\ 18^\circ C:\Lambda = 129.497 - 80.38\sqrt c + 32.87c log c + 154.3c - 143.0c^{3/2} \hfill \\ 10^\circ C:\Lambda = 107.359 - 64.98\sqrt c + 27.07c log c + 125.4c - 110.3c^{3/2} \hfill \\ 0^\circ C:\Lambda = 81.700 - 47.80\sqrt c + 20.60c log c + 93.8c - 79.3c^{3/2} \hfill \\ \end{gathered}

Conductance of 1,1-electrolytes in acetonitrile solutions from-40° to 35°C

which are proposed for calibration of conductance cells.

Conductivity of sodium chloride in water + 1,4-dioxane mixtures at temperatures from 5 to 35°C. I. Dilute solutions

Abstract Precise complex permittivity spectra of the amides formamide, N-methylformamide, N,N-dimethylformamide, and N,N-dimethylacetamide and of the dipolar aprotic solvents acetonitrile, propylene carbonate, and dimethylsulfoxide were determined in the frequency range 0.95-89 GHz. The dielectric relaxation of all liquids is non-exponential, ranging from a small symmetrical relaxation time distribution for acetonitrile to three discrete dispersion steps for NMF.

Dielectric relaxation of electrolyte solutions in acetonitrile

Dielec. relaxation was measured in liq. formamide (FA), N-methylformamide (NMF), DMF, and N,N-dimethylacetamide (DMA) 238.15-338.15 K in the frequency range from 0.2 to 89 GHz. Whereas the FA spectra can be formally fitted with a Davidson-Cole relaxation-time distribution, two relaxation process can be resolved for the other liqs. For DMF and DMA, the long relaxation time, τ1(T), follows the Vogel-Flucher-Tammann equation. For these liqs., τ1(T) probes the essentially isotropic rotational diffusion of the mol. dipole vector. For the hydrogen-bonding liqs. FA and NMF, a modified Eyring equation is more appropriate to describe τ1(T). From the parameters the av. no. of monomers in the chains of H-bonded NMF mols. is deduced, as well as the no. of hydrogen bonds which must be broken before relaxation in FA can occur. The data suggest that the obsd. high-frequency contribution in the spectra mainly reflects the onset of internal contributions.

Transport, Relaxation, and Kinetic Processes in Electrolyte Solutions

In this paper a brief survey is given of the properties of non-aqueous electrolyte solutions and their applications in chemistry and technology without going into the details of theory. Specific solvent-solute interactions and the role of the solvent beyond its function as a homogenous isotropic medium are stressed. Taking into account Parkers statement1) “Scientists nowadays are under increasing pressure to consider the relevance of their research, and rightly so” we have included examples showing the increasing industrial interest in non-aqueous electrolyte solutions.