2564
K. P. Anderson, E. A. Butler, and E. M. Woolley
The Complex Solubility of Silver Bromide in Ethanol- Water, Methanol-Water, Acetone-Water, and Dioxane-Water Mixtures Keith P. Anderson, Eliot A. Butler, and Earl M. Woolley* Department of Chemistry, Brigham Young University. Provo, Utah 84602
(Received January 29, 7973)
Publication costs assisted by the Department of Chemistry, Brigham Young University
Results of a study of the solubility of silver bromide a t 25" as a function of bromide ion concentration in water, in 10, 20, 30, 40, and 50% by weight methanol-water, ethanol-water, acetone-water, and dioxanewater mixtures, and in a 60% by weight dioxane-water mixture are presented. These results were obtained with previously established radiotracer techniques that are modified to include specific ion electrode measurements. All observed solubilities are interpreted in terms of the presence of silver ions, undissociated silver bromide molecules, dibromoargentate ions, and tribromoargentate ions. Values of the thermodynamic equilibrium constants relating the activities of these species to the bromide ion activity are obtained by a least-squares treatment of the solubility data for each solvent mixture. The observed changes in these equilibrium constants are discussed in terms of electrostatics theory, solvation theory, and other specific solvent effects.
Introduction The work reported in this paper is a continuation132 of our study of the solubilities of slightly soluble silver salts as functions of anion concentration in aqueous-nonaqueous mixtures. The solubility of silver bromide and the various equilibria involved have been investigated in 0, 10, 20, 30, 40, and 50% by weight ethanol-water, methanol-water, acetone-water, and dioxane-water mixtures and in a 60% dioxane-water mixture a t bromide ion concentrations between and 10-1M . A radiotracer technique described previously2 was used to determine total silver concentrations. Silver ion activities were measured with an Orion Model 94-16 silver-sulfide specific ion electrode. Our purpose was to determine quantitatively the effects of the composition of the solvent on the concentrations and equilibrium constants of the silver-containing species in solution and to interpret these effects.
Experimental Section All chemicals used were reagent grade. Solutions were prepared from doubly distilled water which had a specific conductance
