Silver chloride in methanol-water mixtures.

The thesis is divided into two parts, the development of a sensitive analytical technique for the estimation of silver and a study of the solubility of silver chloride in methanol-water mixtures. The analytical technique uses an ion exchange resin to concentrate labelled silver ions from a saturated solution of silver chloride, followed by gamma counting with a Nal(Tl) well-type crystal. In order to evaluate the procedure the solubility of silver chloride in water at various chloride concentrations at 25°C and 45°C was measured and the standard enthalpy of solution estimated from the temperature dependence of the solubility product. The results are in general agreement with published data. The adsorption of labelled silver on glassware has been examined and shown to be less significant at low specific activities. The solubility of silver chloride in 1%, 10% and 43.12% (w/w) methanol-water mixtures of various chloride concentrations and at 25°C, 35°C, 45°C and has been measured, solubility products calculated and from their dependence on temperature the standard enthalpies of solution estimated. These are all endothermic and decrease as methanol content of the solvent is increased. The standard Gibbs free energies of solution have a zero temperature coefficient. The standard entropies of solution decrease with increasing methanol content of the solvent. The free energies of transfer from water to the various methanol-water mixtures are, except for 1% methanol-water mixture, in reasonable agreement with the values obtained from the Born equation. Further agreement with the Born equation is shown by the linear dependence of logarithm of solubility product on the reciprocal of the dielectric constant at the different temperatures, although the results for pure water are inconclusive. The evidence provided by these thermodynamic quantities and the application of the Born equation has been shown to suggest strong bonding between the Ag+ and oxygen atoms in the methanol-water mixtures.