Variation of the Dielectric Relaxation Behaviour of Water by Added Alcohols

Lux, A.; Stockhausen, M.

doi:10.1515/zna-1990-0809

Cited by 6 publications

(2 citation statements)

References 8 publications

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“…We, therefore, decided to measure the complex dielectric spectra of mixtures of water with four linear diols of different lengths of their oleophilic part, hence varying ρ by the mole fraction of the organic constituent and also by the hydrophilic/hydrophobic balance of the alcohol molecules. These measurements complement some former studies of the dielectric properties of water/diol systems. − We predominantly aim at a comparison of the τ vs ρ relations of water/diol systems to those of mixtures of water with monohydric alcohols. In order to, in addition, look for structural properties of the liquids and for fine details of the relaxation process, attention has been also paid to the static permittivity and to the shape of the dielectric spectra under consideration.…”

Section: Introductionmentioning

confidence: 95%

Dielectric Properties of Alkanediol/Water Mixtures

1997

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At 25 °C the complex dielectric permittivity has been measured as a function of frequency ν (1 MHz ≤ ν ≤ 56 GHz) and mole fraction x (0 ≤ x ≤ 1) for mixtures of water with 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,7-heptanediol. Some parameters like the (extrapolated) static permittivity and the characteristic relaxation time can be directly taken from the spectra. But the spectra can be also analytically represented by semiempirical relaxation spectral functions. A function containing two relaxation terms, a high-frequency Cole−Cole term and a Debye term with smaller relaxation frequency, appears to be appropriate. The relaxation parameters of the water/diol mixtures have been evaluated and compared to other water/organic solvent systems to show that (i) a high degree of permanent electric dipole orientation correlation exists in the diols that is significantly reduced on addition of water, (ii) the characteristic relaxation time reflects a substantial effect of entropy in the mechanism of dielectric relaxation but exhibits also a significant difference from monohydric alcohol/water systems, and (iii) the subdivision of the spectra into two relaxation terms seems to be due to regions of different concentration of hydrogen-bonding sites within the mixtures.

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Section: Introductionmentioning

confidence: 95%

Dielectric Properties of Alkanediol/Water Mixtures

1997

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“…Residual water contents < 0.5 percent should, according to experiences with various alcohol-water systems [7], not yet significantly influence the relaxation parameters. The complex permittivity was determined by use of various Reprint requests to Prof. M. Stockhausen,…”

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confidence: 97%

Dielectric Relaxation of Liquid Alicyclic Alcohols

Stockhausen

Hornhardt

1992

Zeitschrift Für Naturforschung A

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The dielectric spectra of liquid cyclopentanol, cyclohexanol, cycloheptanol and cyclooctanol are reported for frequencies up to 72 GHz and temperature 20 (cyclohexanol solid), 30 and 40 °C. The absorption spectra are peculiar in exhibiting a remarkably developed high frequency shoulder which is attributed to single molecule and internal motion, while the principal absorption is due to association as with other alcohols.Although numerous dielectric relaxation studies on different kinds of liquid alcohols have been reported, alicyclic ones have received only little attention. Cyclohexanol has been examined in nonpolar solvents [1], which work was extended recently to some very high spot frequencies (< 670 GHz) [2], On ther other hand, the solid state dielectric properties have attracted attention. These, for example, have been measured at frequencies covering the solid state absorption region (at < 13 MHz [3, 4]) over a very broad temperature and pressure range. Those studies yielded also some results on the liquid state [5], An investigation of pure liquid cycloalcohols by Shinomiya [6] was restricted to frequencies covering the principal absorption region (< 4.5 GHz). It seems therefore worthwhile to reconsider the dielectric properties of pure cycloalcohols (at normal pressure) and to extend measurements over a broader frequency band in order to gain information also on possible higher frequency relaxation contributions. Here we report dielectric relaxation data of four alicyclic alcohols, cyclopentanol (C 5 ) to cyclooctanol (C 8 ), as measured up to 72 GHz. In relation to the literature quoted, our results complement the hitherto known lower frequency part of the dielectric spectrum of pure cycloalcohols [5,6] and also the solution results for cyclohexanol [2].Substances obtained from Fluka and Merck were used without further purification. Residual water contents < 0.5 percent should, according to experiences with various alcohol-water systems [7], not yet significantly influence the relaxation parameters. The complex permittivity was determined by use of various Reprint requests to Prof. M. Stockhausen,

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