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Holt, Donald (1962) The conductance of lithium chloride in mixed solvents. Doctoral thesis, Northern Polytechnic.
The purpose of this study on the conductance behaviour of lithium chloride dissolved in acetone-water, dioxan-water and iso-propanol-water mixtures is to show the effect of varying dielectric constant and viscosity on the dissociation of the solute and the ionic radii of the lithium and chloride ions. The most satisfactory method of studying these relationships was to prepare a large number of solutions of lithium chloride dissolved in various organo-aqueous solvent mixtures. To obtain a large range of dielectric constants and viscosities the composition of the solvent mixtures varied from water-rich to organo-rich values. The method of measuring conductances required a modified Jones end Joseph’s bridge incorporating a visual aid detector unit, in preference to balancing the signal by means of earphones. The results obtained were not of a particularly high degree of precision, but this was not considered to be very serious, since our interest lay more in comparative results of the parameters of the solute in media of varying physical constants than in the determination of their absolute values. From the calculated values of the ionic radii and the dissociation constants for the various solutions studied, it was found that acetone molecules solvated the lithium cations, in large concentrations of the organic solvent, to form complex ions by means of coordinate links. This complex ion formation was possible because of the relatively large deforming power of the lithium ion. On the other hand, no solvation of the lithium ions, by dioxan molecules, occurred when lithium chloride solutions were studied in dioxan-water mixtures. Similarly, iso-propanol did not appear to solvate the solute ions (in contrast to ethanol), even in a largo concentration of the alcohol, because of preferential hydration by water molecules, which possessed greater electrostatic orientating power round the ions.
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