Measurement of ionic mobilities in dielectric liquids by means of concentric cylindrical electrodes

Abstract

When a liquid, placed in an electric field between coaxial cylindrical electrodes, is ionized uniformly by a short pulse of x rays, the current resulting from the subsequent motion of the inward‐moving ions decays with time differently from that due to the outward‐moving ions. This effect provides a convenient method, here described in detail, for assigning mobilities to the positive and negative ions present. Mobilities were determined as a function of temperature for the ions formed in dilute solutions of the electron‐trapping molecules SF6, CH3I, CH3Br, CH3Cl, or O2 in cyclohexane or 2,2,4‐trimethylpentane. In all these cases the negative ions were more mobile than the positive. Only one major negative ion mobility and one major positive ion mobility was to be seen in the solutions, with the exception of O2 in 2,2,4‐trimethylpentane, which gave two negative ions of different mobilities.