Polarographic behaviour of cobalt with 2,3-dimercapto-propanol

In ammonia buffer containing Co(II) and 2,3-dimercapto-propanol (2,3-DMP) s everal polarographic processes are produced:(i) catalytic cobalt prewave wi th E-1/2 about -0.93 V: (ii) catalytic hydrogen prewave with E-1/2 = -1.36 V; (iii) hydrogen diffusion wave superimposed on a Brdicka-type catalytic w ave at potential more negative than -1.87 V. Polarographic data show that c obalt complexes with 2,3-DMP are involved in the electrode reaction. The gi ven reaction mechanism explains the effects of the main parameters, taking into account the behaviour of the reducible species involved in chemical eq uilibrium as a function of potential.