The behaviour of polar molecules in solid paraffin wax

Abstract
The idea that dielectric materials may contain minute electric dipoles, able to rotate under the action of an electric field, has been current for a very long time. Originally it provided simply a plausible explanation of the property which a dielectric has of increasing the capacity of a condenser into which it is introduced; later Hopkinson, Pellat, and others suggested that the “ anomalous ” after-effects of a condenser might be due to similar dipoles retarded by “ frictional” forces and able to rotate only slowly towards alignment with the external field. The quantity of electricity concerned in these effects is often approximately conserved, so that the explanation was an attractively simple one. With a growing knowledge of the time-scale of molecular processes, however, the notion that a molecular dipole might take seconds or minutes to take up an equilibrium position lost favour, while a quantitative theory of dipole effects was developed by Debye. From this it appeared that, for dilute solutions of polar substances in simple light liquids, the times involved would be of the order of 10 -9 sec. Measurements of dispersion and absorption in such liquids at frequencies up to the present limits of electrical measuring technique have largely confirmed Debye’s quantitative conclusions. More viscous liquids, many of which contain molecules of widely differing sizes, and which may possess quasi-crystalline structures, do not show such a satisfactory agreement with the simple theory. More recently Debye and Ramm (1937) have published a treatment in which viscous and crystalline forces are regarded as acting simultaneously. This seems to fit the facts in some cases, but its application is somewhat limited because of the complexity of the analytical expressions involved.

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