THE ROLE OF REACTION CONDITIONS IN THE INTERACTION OF CADMIUM(II) IONS WITH CHOLATE ANIONS

At ''submicellar'' concentrations of cholate anions reaction with cadmium(II) ions produces slightly soluble species involving small aggregates of bile salts. At large excess of cholate more soluble large aggregates (''micelles'') are formed. Nature and concentration of an added neutral salt, initial concentration of Cd2+, and buffering do not affect qualitatively the pattern of observed processes. Quantitative changes due to variations of reaction conditions result in the studied processes occurring at different concentrations of the bile salts. Composition of the reaction mixture affects the concentration above which precipitation occurs, the solubility of the compounds formed, and the composition and stability of the complexes formed, as well as the concentration above which large aggregates are formed. Standard conditions, involving 1 x 10(-4) M metal(II) ion, 0.15 M KNO3, bile salt concentrations varying from 5 x 10(-4) to 8 x 10(-2) M, and polarographic determination of the free metal ion concentration, proved to be most informative. (C) 1994 Academic Press, Inc.