. Can. J. Chem. 61, 2151 (1983). The binary and ternary complexation in aqueous solution between coppcr(l1) ion, N,N1-dimethyltartramide (H2A) and mandelic acid (HB). were studied by potcntiornctric measurements in the 5-10 pH range at 25°C and p. = I M in NaCIOI. The titrations were analyzed using a pit-mapping method and the concentration distribution of the various simple and mixed compiexes were plotted versus a pH gradient. A significant stereoselective effect is displayed in the ternary complexes only.