Abstract
IT has been found that the molar electric susceptibility of liquids, P = (ɛ – 1) × M/d = 4πN(α + μ2/kT), where ε is the dielectric constant of the pure liquid and μ the moment. The derivation of this follows if we regard the dipole as needle-shaped. This assumption is inherent in the Debye equation for gases. In solids and liquids, owing to hindered rotation, molecular orientations are distributed according to the Boltzmann function µ2F/kT, because the dipoles can become oriented only in two directions, along and opposite to the direction of the electrical field. This relationship is found to hold good for all normal liquids from hydrogen bromide (0·8D) to nitrobenzene (4·2D), and for solids such as hydrogen chloride, hydrogen sulphide, hydrogen bromide and hydrogen iodide which show molecular rotation at low temperature. In the case of associated liquids and divalent salts, kT is ½. In ionic crystals the moment calculated from the dielectric constant has to be multiplied by the co-ordination number to give the same value as obtained by the molecular beam method. The results show that the alkali halides are 2/5 ionic or 'dipolar' in the gaseous and 1/15 in the solid state.
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JATKAR, S. Relationship between Dielectric Constant of Liquids and Solids and Dipole Moments. Nature 153, 222 (1944). https://doi.org/10.1038/153222a0
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DOI: https://doi.org/10.1038/153222a0
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