Studies on imidazole derivatives as chelating agents-V Investigations of the applicabilities of the azoimidazoles as metallochromic indicators.
Applicabilities of several azoimidazoles as metallochromic indicators were investigated in the light of the general equations expressing the colour change of the visual chelatometric titrations. By using the stability constants of the nickel(II), copper(II), zinc(II) and cadmium(II) chelates, the useful pH ranges, titration errors and sharpness of colour changes were predicted theoretically and the usefulness of these reagents as indicators was established experimentally. The Cu(II)-EDTA-indicator system was also examined experimentally. The OH-containing azoimidazoles could be applied to the direct titration of copper, nickel, zinc, cadmium, lead and bismuth and to the titration of calcium and cobalt in the presence of Cu(II)-EDTA. Attempts were made to construct diagrams for the estimation of titration errors and sharpness of colour changes.
Yamauchi
O
O
Faculty of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto, Japan.
Tanaka
H
H
Uno
T
T