CATALYTIC POLAROGRAPHIC WAVES OF NICKEL AND HYDROGEN-IONS IN THE NICKEL-2-MERCAPTOBENZOTHIAZOLE SYSTEM - HIGH 2-MERCAPTOBENZOTHIAZOLE CONCENTRATION

At higher 2-mercaptobenzothiazole (MBT) concentration (over 1x10(-3) M ) in the presence of Ni2+ ions a hydrogen catalytic wave is formed at E(H)(1/2)- -1.48 V by a complex adsorbed on the mercury cathode surfac e. Around -1.55 V the catalytic current decreases sharply owing to the desorption of active complex, that loses its catalytic activity when it is in the bulb of solution only. The polarographic catalysis in the system Ni-MBT was explained as mediated by a zero charge complex of n ickel, formed after electrolytic discharge. This complex is protonated at the N-atom of the heterocycle and the deprotonation occurs by the charge transfer from Ni(O) to the protons. The catalytic waves height increases with the increase of both MBT and NH3 concentrations. This b ehaviour is a proof that in the structure of the Ni-MBT complex is bou nd also NH3 as ligand.