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

At ''submicellar'' concentrations of cholate anions reaction with cadm ium(II) ions produces slightly soluble species involving small aggrega tes of bile salts. At large excess of cholate more soluble large aggre gates (''micelles'') are formed. Nature and concentration of an added neutral salt, initial concentration of Cd2+, and buffering do not affe ct qualitatively the pattern of observed processes. Quantitative chang es due to variations of reaction conditions result in the studied proc esses occurring at different concentrations of the bile salts. Composi tion of the reaction mixture affects the concentration above which pre cipitation occurs, the solubility of the compounds formed, and the com position and stability of the complexes formed, as well as the concent ration above which large aggregates are formed. Standard conditions, i nvolving 1 x 10(-4) M metal(II) ion, 0.15 M KNO3, bile salt concentrat ions varying from 5 x 10(-4) to 8 x 10(-2) M, and polarographic determ ination of the free metal ion concentration, proved to be most informa tive. (C) 1994 Academic Press, Inc.