| Summary: | The measurement of conductivities of relatively concentrated electrolyte solutions using an annular glass cell, without contacting or dipping electrodes, is described. An electrolyte solution in the cell serves as a conductor linking the voltage and current transformers of a transformer ratio-arm bridge operating at audio-frequencies which is also described. The use of the transformer bridge for such measurements is discussed from a theoretical standpoint. Conductivity measurements were carried out on a series of aqueous solutions of uni-univalent salts and acids, bi-bi-, bi-uni-, uni-ter-, uni-tetra- and bi-tetravalent salts, and these are reported in terms of A and Vc. Where accurate data obtained using conventional apparatus are available agreement is good. Viscosity-corrected A, \/c curves obtained for uni-univalent electrolytes indicate, by their general similarity of shape, that the use of the approximate viscosity correction for conductivity, Anno, is justified. A method for the evaluation of the mean diameter of the ions of an electrolyte using a modification of the Onsager conductivity equation is discussed and applied to the conductivity data obtained for uni-univalent electrolytes and for barium chloride for a range of concentrations. With the exception of lithium chloride, the values are nearly constant for concentrations between 0.1 and 1.0 molar and are in striking agreement with those obtained from activity coefficient data. The results for lithium chloride are greatly improved for the higher concentrations when the conductivity data used are corrected for viscosity before substitution in the modified Onsager equation.
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