SOLUBILITY AND COMPLEX FORMATION EQUILIBRIA OF SILVER CHLORIDE IN DIMETHYL SULFOXIDE-WATER MIXTURES

The equilibria of silver chloride in dimethyl sulfoxide-water solutions containing excess chloride have been studied potentiometrically in a constant ionic medium (0.1 M lithium perchlorate or tetraethylammonium perchlorate) at 25°. Equilibrium constants were fitted by a nonlinear least-squares pit-mapping technique. Mononuclear complexes AgCl, AgCl2-, and AgCl32- were found. The over-all formation constants for these complexes in anhydrous dimethyl sulfoxide are log β1 = 6.8 ± 0.7, log β2 = 11.73 ± 0.02, and log β3 = 13.1 ± 0.4. The solubility product of silver chloride is log Ks0 = -10.279 ± 0 003 (errors are statistical 95% confidence limits). With increasing water content, βn decreases and Ks0 increases. Discrepancies between previous results in the literature appear to be due to differences in ion pairing with the supporting electrolyte. Ion pairing is probably negligible in LiClO4 and Et4NClO4 medium. Estimates of the equilibrium constants at zero ionic strength are made, and the results are discussed in terms of ionic solvation.